tirapazamine and Hypoxia

The occurrence of hypoxic cells in solid tumors, and their resistance to radiotherapy and many chemotherapeutic drugs, has engendered an interest in non-toxic prodrugs that can be activated selectively under hypoxic conditions. Despite this, no such compounds are yet registered for clinical use, due to the difficulty of their design and of measuring the extent of hypoxia clinically, and the failure of early examples. A new appreciation of the critical importance of the extravascular diffusion of the parent prodrug from the blood vessels to the remote hypoxic cells, and the back-diffusion of the activated cytotoxin from the hypoxic cells to surrounding tumor cells, is now guiding drug design in this area. New principles for the selective activation of prodrugs have also been reported, including using the reducing species generated in cells by radiotherapy itself, and using non-pathogenic anaerobic bacteria as a hypoxia-dependent vector for the delivery of prodrug-activating enzymes in a suicide gene therapy context.

Topics: Antineoplastic Agents; Diffusion; Drug Design; Humans; Hypoxia; Models, Biological; Models, Chemical; Prodrugs; Tirapazamine; Triazines

Preclinical models in vitro and in vivo have shown that tumor hypoxia alters the malignant cell phenotype, selecting for p53 mutations, stimulating angiogenesis and metastasis, and markedly reducing the efficacy of both radiotherapy and chemotherapy. Similarly, clinical studies measuring pretreatment tumor oxygen status confirm that the presence of hypoxia confers a negative impact on local control, disease-free survival, and overall survival. Despite these data and extensive past research efforts, the promise of developing selective hypoxic-cell sensitizers has been largely unfulfilled. In contrast, tirapazamine is the rationally designed prototype for a new class of therapeutic agents targeting tumor hypoxia: hypoxic cytotoxins. Tirapazamine is bioreductively activated in hypoxic cells and has been shown to potentiate the cytotoxicity of radiation and a number of chemotherapeutic drug classes, in particular platinum compounds and taxanes. This article reviews the preclinical and clinical development of tirapazamine, as well as current trials in non-small cell lung cancer designed to provide proof of principle for this new category of cancer therapeutics.

Topics: Carcinoma, Non-Small-Cell Lung; Clinical Trials as Topic; Drug Interactions; Drug Resistance, Neoplasm; Humans; Hypoxia; Lung Neoplasms; Phenotype; Radiation-Sensitizing Agents; Tirapazamine; Triazines

Hypoxia is a feature of some regions of many tumours, ischaemic events, and arthritis. Drugs activated in hypoxia have wide potential application, particularly in overcoming the resistance of hypoxic tumour cells to radiotherapy. Key features of such drugs include redox properties appropriate for activation by reductase enzymes (typically flavoproteins), and oxygen-sensitive reduction chemistry such that normal levels of oxygen inhibit or reverse reduction. In many cases this selectivity is achieved by a fast, free-radical reaction in which the drug radical (often an obligate intermediate in drug reduction) reduces oxygen to form superoxide radicals and thus 'futile cycles' the drug in normoxic tissues. However, this enhances cellular oxidative stress, which may be linked to normal tissue toxicity. Appropriate redox properties are found with nitroarene, quinone, or aromatic N-oxide moieties. A particularly promising and versatile exploitation of bioreductive activation is for reduction of such 'triggers' to activate release of an 'effector', an agent that can obviously be active against diverse conditions associated with hypoxia. The same approach can also be used in diagnosis of hypoxia. Much information concerning the reactions of intermediates in drug action and the quantitative prediction of redox properties of analogues has been accrued. Drug design can be mechanism-led, with the wealth of literature quantifying redox properties of drug candidates a rich source of potential new leads. There is a clear appreciation of the kinetic factors that limit drug efficacy or selectivity. Thus the potential for rapid expansion of these concepts to diverse diseases is considerable.

Topics: Drug Delivery Systems; Drug Design; Electron Transport; Enzyme Activation; Flavoproteins; Free Radical Scavengers; Humans; Hypoxia; Neoplasms; Oxidation-Reduction; Oxidative Stress; Quinones; Tirapazamine; Triazines

The idea of 'targeting' hypoxia stems from recognition of the fact that oxygen (or its lack) is central to the practice of radiation oncology. Targeting embraces the alternative goals of trying to overcome hypoxia on the one hand and trying to exploit it on the other. This presentation briefly reviews these two approaches with major emphasis on the latter.

Topics: Cell Survival; Combined Modality Therapy; Head and Neck Neoplasms; Humans; Hypoxia; Radiation Oncology; Radiation-Sensitizing Agents; Regional Blood Flow; Tirapazamine; Triazines

As a currently common strategy to treat cancer, surgical resection may cause tumor recurrence and metastasis due to residual postoperative tumors. Herein, an implantable sandwich-structured dual-drug depot is developed to trigger a self-intensified starvation therapy and hypoxia-induced chemotherapy sequentially. The two outer layers are 3D-printed using a calcium-crosslinked mixture ink containing soy protein isolate, polyvinyl alcohol, sodium alginate, and combretastatin A4 phosphate (CA4P). The inner layer is one patch of poly (lactic-co-glycolic acid)-based electrospun fibers loaded with tirapazamine (TPZ). The preferentially released CA4P destroys the preexisting blood vessels and prevents neovascularization, which obstructs the external energy supply to cancer cells but aggravates hypoxic condition. The subsequently released TPZ is bioreduced to cytotoxic benzotriazinyl under hypoxia, further damaging DNA, generating reactive oxygen species, disrupting mitochondria, and downregulating hypoxia-inducible factor 1α, vascular endothelial growth factor, and matrix metalloproteinase 9. Together these processes induce apoptosis, block the intracellular energy supply, counteract the disadvantage of CA4P in favoring intratumor angiogenesis, and suppress tumor metastasis. The in vivo and in vitro results and the transcriptome analysis demonstrate that the postsurgical adjuvant treatment with the dual-drug-loaded sandwich-like implants efficiently inhibits tumor recurrence and metastasis, showing great potential for clinical translation.

Topics: Antineoplastic Agents; Cell Line, Tumor; Humans; Hypoxia; Neoplasm Recurrence, Local; Tirapazamine; Vascular Endothelial Growth Factor A

Inducing immunogenic cell death (ICD) by sonodynamic therapy (SDT) is promising for cancer immunotherapy, which however is inefficient due to oxygen depletion that compromises SDT effect and mediates recruitment of immunosuppressive myeloid-derived suppressor cells (MDSCs). The fabrication of sono-activatable semiconducting polymer nanopartners (SPN

Topics: Animals; Cell Line, Tumor; Hypoxia; Immunogenic Cell Death; Immunotherapy; Mice; Myeloid-Derived Suppressor Cells; Neoplasms; Oxygen; Polymers; Tirapazamine; Tumor Microenvironment

Blockage of blood supply while administering chemotherapy to tumors, using trans-arterial chemoembolization (TACE), is the most common treatment for intermediate and advanced-stage unresectable Hepatocellular carcinoma (HCC). However, HCC is characterized by a poor prognosis and high recurrence rates (≈30%), partly due to a hypoxic pro-angiogenic and pro-cancerous microenvironment. This study investigates how modifying tissue stress while improving drug exposure in target organs may maximize the therapeutic outcomes. Porous degradable polymeric microspheres (MS) are designed to obtain a gradual occlusion of the hepatic artery that nourishes the liver, while enabling efficient drug perfusion to the tumor site. The fabricated porous MS are introduced intrahepatically and designed to release a combination therapy of Doxorubicin (DOX) and Tirapazamine (TPZ), which is a hypoxia-activated prodrug. Liver cancer cell lines that are treated with the combination therapy under hypoxia reveal a synergic anti-proliferation effect. An orthotopic liver cancer model, based on N1-S1 hepatoma in rats, is used for the efficacy, biodistribution, and safety studies. Porous DOX-TPZ MS are very effective in suppressing tumor growth in rats, and induction tissue necrosis is associated with high intratumor drug concentrations. Porous particles without drugs show some advantages over nonporous particles, suggesting that morphology may affect the treatment outcomes.

Topics: Animals; Carcinoma, Hepatocellular; Chemoembolization, Therapeutic; Doxorubicin; Hypoxia; Liver Neoplasms; Microspheres; Porosity; Rats; Tirapazamine; Tissue Distribution; Tumor Microenvironment

The efficacy of photodynamic therapy (PDT) is severely limited by the hypoxic tumor microenvironment (TME), while the performance of PDT-aroused antitumor immunity is frustrated by the immunosuppressive TME and deficient immunogenic cell death (ICD) induction. To simultaneously tackle these pivotal problems, we herein create an albumin-based nanoplatform co-delivering IR780, NLG919 dimer and a hypoxia-activated prodrug tirapazamine (TPZ) as the dual enhancer for synergistic cancer therapy. Under NIR irradiation, IR780 generates

Topics: Cell Line, Tumor; Humans; Hypoxia; Immunotherapy; Nanoparticles; Neoplasm Recurrence, Local; Neoplasms; Photochemotherapy; Photosensitizing Agents; Tirapazamine; Tumor Microenvironment

Photodynamic therapy (PDT) has a promising application prospect in Echinococcus granulosus (Egs), however, the hypoxic environment of Egs and the hypoxia associated with PDT will greatly limit its effects. As a hypoxic-activated pre-chemotherapeutic drug, tirapazamine (TPZ) can be only activated and produce cytotoxicity under hypoxia environment. Albendazole sulfoxide (ABZSO) is the first choice for the treatment of Egs. This study aimed to explore the effects of ABZSO nanoparticles (ABZSO NPs), TPZ combined with PDT on the activity of Egs in vitro and in vivo.. The Egs were divided into control, ABZSO NPs, ABZSO NPs + PDT, and ABZSO NPs + TPZ + PDT groups, and the viability of Egs was determined using methylene blue staining. Then, the ROS, LDH and ATP levels were measured using their corresponding assay kit, and H2AX and TopoI protein expression was detected by western blot. The morphology of Egs with different treatments was observed using hematoxylin eosin (HE) staining and scanning electron microscopy (SEM). After that, the in vivo efficacy of ABZSO NPs, TPZ and PDT on Egs was determined in a Egs infected mouse model.. In vitro experiments showed that the combined treatment of TPZ, ABZSO NPs and PDT significantly inhibited Egs viability; and significantly increased ROS levels and LDH contents, while decreased ATP contents in Egs; as well as up-regulated H2AX and down-regulated TopoI protein expression. HE staining and SEM results showed that breaking-then-curing treatment seriously damaged the Egs wall. Additionally, in vivo experiments found that the combination of ABZSO NPs, PDT and TPZ had more serious calcification and damage of the wall structure of cysts.. ABZSO NPs combined with TPZ and PDT has a better inhibitory effect on the growth of Egs in vitro and in vivo based on the strategy of "breaking-then-curing".

Topics: Adenosine Triphosphate; Animals; Echinococcosis; Echinococcus granulosus; Hypoxia; Mice; Nanoparticles; Photochemotherapy; Reactive Oxygen Species; Tirapazamine

Tirapazamine (TPZ) and its derivatives (TPZD) have shown their great potential for efficiently killing hypoxic cancer cells. However, unsatisfactory clinical outcomes resulting from the low bioavailability of the low-molecular TPZ and TPZD limited their further applications. Precise delivery and release of these prodrugs via functional nanocarriers can significantly improve the therapeutic effects due to the targeted drug delivery and enhanced permeability and retention (EPR) effect. Herein, zwitterionic block copolymer (BCP) micelles with aldehyde functional groups are prepared from the self-assembly of poly(2-methacryloyloxyethyl phosphorylcholine-

Topics: Doxorubicin; Humans; Hydrogen-Ion Concentration; Hypoxia; Imines; Methacrylates; Micelles; Polymers; Prodrugs; Tirapazamine

Photodynamic therapy (PDT) has been applied in cancer treatment by utilizing reactive oxygen species (ROS) to kill cancer cells. However, the effectiveness of PDT is greatly reduced due to local hypoxia. Hypoxic activated chemotherapy combined with PDT is expected to be a novel strategy to enhance anti-cancer therapy. Herein, a novel liposome (LCT) incorporated with photosensitizer (PS) and bioreductive prodrugs was developed for PDT-activated chemotherapy. In the design, CyI, an iodinated cyanine dye, which could simultaneously generate enhanced ROS and heat than other commonly used cyanine dyes, was loaded into the lipid bilayer; while tirapazamine (TPZ), a hypoxia-activated prodrug was encapsulated in the hydrophilic nucleus. Upon appropriate near-infrared (NIR) irradiation, CyI could simultaneously produce ROS and heat for synergistic PDT and photothermal therapy (PTT), as well as provide fluorescence signals for precise real-time imaging. Meanwhile, the continuous consumption of oxygen would result in a hypoxia microenvironment, further activating TPZ free radicals for chemotherapy, which could induce DNA double-strand breakage and chromosome aberration. Moreover, the prepared LCT could stimulate acute immune response through PDT activation, leading to synergistic PDT/PTT/chemo/immunotherapy to kill cancer cells and reduce tumor metastasis. Both

Topics: Animals; Antineoplastic Agents; Cell Survival; Chemistry, Pharmaceutical; Chromosome Aberrations; DNA Damage; Drug Carriers; Drug Liberation; Hypoxia; Liposomes; Mice; Mice, Inbred BALB C; Nanoparticle Drug Delivery System; Particle Size; Photosensitizing Agents; Phototherapy; Reactive Oxygen Species; Surface Properties; Tirapazamine; Xenograft Model Antitumor Assays

Employing hypoxia-activated prodrugs is an appealing oncotherapy strategy, but limited by insufficient tumor hypoxia. Moreover, a standalone prodrug fails to treat tumors satisfactorily due to tumor complexity. Herein, a nanosystem (TPZ@FeMSN-GOX) was established for triple synergetic cancer starvation therapy, hypoxia-activated chemotherapy and chemodynamic therapy (CDT). TPZ@FeMSN-GOX was prepared by synthesizing iron-doped mesoporous silica nanoparticles (FeMSNs) followed by surface conjugation with glucose oxidase (GOX), and then loading with hypoxia-activated prodrug tirapazamine (TPZ). When TPZ@FeMSN-GOX entered the tumor cells, GOX could not only exhaust glucose to starve cancer cells and concomitantly produce H

Topics: Cell Line, Tumor; Glucose; Glucose Oxidase; Humans; Hydrogen Peroxide; Hypoxia; Nanoparticles; Neoplasms; Prodrugs; Tirapazamine

With the advantages of deep tissue penetration and controllability, external X-ray-induced photodynamic therapy (X-PDT) is highly promising for combined cancer therapy. In addition to the low efficiency of photosensitizer (PS) delivery to tumor sites, however, the radiation- and drug-resistance of hypoxic cells inside the tumor after X-PDT also limit its benefits. Herein, we develop a combined therapeutic modality based on an intelligent nanosized platform (

Topics: Antineoplastic Agents; Cell Line, Tumor; Humans; Hypoxia; Nanoparticles; Oxidation-Reduction; Photochemotherapy; Tirapazamine; X-Rays

Tirapazamine (TPZ) is a promising hypoxia-selective cytotoxic agent that may exert synergistic tumor-killing activity with transcatheter arterial embolization (TAE) for liver cancer. To investigated whether TPZ-loaded microspheres enhance the synergy between TPZ and TAE in liver cancer, we prepared TPZ-loaded CalliSpheres microspheres (CSMTPZs) and characterized their properties as a chemoembolization agent in vitro. Tumor hypoxia after TAE was detected in the rabbit VX2 model of liver cancer using a modified Clark-type microelectrode research system. CSMTPZ therapy was performed in the animal model. The plasma and tumor concentrations of TPZ and its metabolites were measured, and the efficacy and safety of CSMTPZ therapy were evaluated and compared with those of the conventional combination of intraarterial TPZ injection and embolization. The results showed that CSMTPZs displayed favorable in vitro properties including drug loading and release and microsphere size, shape, and surface profiles. TAE induced acute tumor hypoxia, but residual tumor cells responded to hypoxia through hypoxia-inducible factor 1α. CSMTPZ therapy improved TPZ delivery into tumor tissue with minimal systemic exposure. Accordingly, CSMTPZ therapy exhibited advantages in terms of hypoxia-selected cytotoxicity, tumor apoptosis and necrosis, animal survival, and safety over the conventional combination of TPZ and TAE. We revealed the improved synergistic anti-tumor effects of CSMTPZ therapy in the rabbit VX2 liver cancer model. Our data support the clinical evaluation of CSMTPZs in the treatment of hepatocellular carcinoma, and CSMTPZ administration might serve as a successful therapeutic strategy for this malignancy.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Disease Models, Animal; Embolization, Therapeutic; Hypoxia; Liver Neoplasms; Microspheres; Rabbits; Tirapazamine

The treatment efficacy of anticancer drugs in complex physiological environments is still restricted by multi-drug resistance. To overcome this issue, a nanodrug system of HA-SS@CuS@ZIF-8@TPZ&TBMACN (HSCZTT) that breaks through the detoxification barrier for tirapazamine (TPZ) delivery was developed in this manuscript. In addition to the photothermal effect aroused by CuS in HSCZTT, which can damage tumour cells, TBMACN with photostable fluorescence in the aggregate state can also generate sufficient reactive oxygen species (ROS) to destroy tumour cells. The continuous consumption of oxygen in PDT aggravates the hypoxic environment of tumours, which further activates the TPZ released in the acidic microenvironment of the tumour to achieve apoptosis of the tumour cells. The HSCZTT can not only target the CD44 receptor overexpressed on the surface of the cancer cell, but can also effectively consume a large amount of glutathione (GSH) through the disulphide bond-modified hyaluronic acid, which serves as a targeted disulphide bond, interfering with the detoxification barrier. Our finding presents a rational strategy to overcome multidrug resistance for the improved efficacy of anticancer drugs by the targeting of Hyaluronic acid (HA), release of the drug by the acid response of ZIF-8, breakthrough of the detoxification barrier, precise positioning of the drug release and combined treatment with phototherapy and hypoxia-activated chemotherapy.

Topics: Antineoplastic Agents; Cell Line, Tumor; Disulfides; Humans; Hyaluronic Acid; Hypoxia; Nanoparticles; Neoplasms; Photochemotherapy; Photosensitizing Agents; Tirapazamine; Tumor Microenvironment

Hypoxia is one of the prominent features of solid tumors. Hypoxia activated prodrugs (HAPs), selectively killing hypoxic cells, possess the potential to transform hypoxia from a nuisance to an advantage in precision therapy. Exhibiting a more significant hypoxic microenvironment, gliomas, as the most frequent and incurable neurological tumors, provide HAPs a more attractive therapeutic prospect. However, the insufficient hypoxia and the obstruction of the blood-brain barrier (BBB) severely limit the activation and bio-availability of HAPs. Herein, a novel nanoparticle iRGD@ZnPc + TPZ was designed and synthesized to achieve gliomas inhibition by encapsulating tirapazamine (TPZ) as a HAP and zinc phthalocyanine (ZnPc) as a photosensitizer to enhance hypoxia. iRGD@ZnPc + TPZ can realize breakthrough BBB, deep penetration, and significant retention in gliomas, which is attributed to the iRGD-mediated receptor targeting and active transport. After being internalized by tumor cells and radiated, ZnPc efficiently consumes intratumoral O

Topics: Antineoplastic Agents; Cell Line, Tumor; Glioma; Humans; Hypoxia; Indoles; Isoindoles; Neoplasms; Organometallic Compounds; Photosensitizing Agents; Prodrugs; Reactive Oxygen Species; Tirapazamine; Tumor Microenvironment; Zinc Compounds

Photodynamic therapy (PDT) can produce a large amount of reactive oxygen species (ROS) in the radiation field to kill tumor cells. However, the sustainable anti-tumor efficacy of PDT is limited due to the hypoxic microenvironment of tumor. In this study, classic PDT agent indocyanine green (ICG) and hypoxia-activated chemotherapeutic drug tirapazamine (TPZ) were loaded on mesoporous polydopamine (PDA) to construct PDA@ICG-TPZ nanoparticles (PIT). Then, PIT was camouflaged with cyclic arginine-glycine-aspartate (cRGD) modified tumor cell membranes to obtain the engineered membrane-coated nanoreactor (cRGD-mPIT). The nanoreactor cRGD-mPIT could achieve the dual-targeting ability via tumor cell membrane mediated homologous targeting and cRGD mediated active targeting. With the enhanced tumor-targeting and penetrating delivery system, PIT could efficiently accumulate in hypoxic tumor cells and the loaded drugs were quickly released in response to near-infrared (NIR) laser. The nanoreactor might produce cytotoxic ROS under NIR and further enhance hypoxia within tumor to activate TPZ, which efficiently inhibited hypoxic tumor by synergistic photodynamic-chemotherapy. Mechanically, hypoxia-inhibitory factor-1α (HIF-1α) was down-regulated by the synergistic therapy. Accordingly, the cRGD-mPIT nanoreactor with sustainable and cascade anti-tumor effects and satisfied biosafety might be a promising strategy in hypoxic tumor therapy.

Topics: Biomimetics; Cell Line, Tumor; Humans; Hypoxia; Indocyanine Green; Nanoparticles; Nanotechnology; Neoplasms; Photochemotherapy; Photosensitizing Agents; Reactive Oxygen Species; Tirapazamine; Tumor Microenvironment

With the advantages of high safety and selectivity, photodynamic therapy (PDT) has been widely used for cancer treatments, while the anticancer efficacy is often limited because of its relying on oxygen concentrations. Therefore, sole PDT fails to achieve the desired therapeutic effect for hypoxic tumors. To address this issue, we herein report the construction of prodrug and glucose oxidase (GOx) coloaded alginate (ALG) hydrogels for PDT-combined chemotherapy of melanoma. The hydrogels are in situ formed in tumor sites after injection of ALG solution containing semiconducting polymer nanoparticles, hypoxia-responsive prodrug tirapazamine (TPZ), and GOx, which is based on chelation of ALG by endogenous Ca

Topics: Glucose Oxidase; Humans; Hydrogels; Hypoxia; Melanoma; Oxygen; Polymers; Prodrugs; Tirapazamine; Tumor Microenvironment

The selective anti-tumor activity and less toxic nature of hypoxia-activated prodrugs including tirapazamine (TPZ) are harbored by hypoxia levels in tumors, the inadequacy of which leads to failure in clinical trials. Thus, the development of effective clinical applications of TPZ requires advanced strategies to intensify hypoxia levels in tumors effectively and safely. In this study, we designed and fabricated a paclitaxel (PTX)-loaded dual-response delivery system with a low dose (

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Drug Delivery Systems; Hypoxia; Mice; Neoplasms; Paclitaxel; Reactive Oxygen Species; Tirapazamine; Tumor Hypoxia; X-Rays

Effective therapy for rheumatoid arthritis (RA) keeps a challenge due to the complex pathogenesis of RA. It is not enough to completely inhibit the process of RA with any single therapy method. The purpose of the research is to compensate for the insufficiency of monotherapy using multiple treatment regimens with different mechanisms.. In this study, we developed a new method to synthesize mesoporous silica nanoparticles hybridized with photosensitizer PCPDTBT (HNs). Branched polyethyleneimine-folic acid (PEI-FA) could be coated on the surface of HNs through electrostatic interactions. It simultaneously blocked the hypoxia-activated prodrug tirapazamine loaded into the mesopores and binded with Mcl-1 siRNA (siMcl-1) that interfered with the expression of the anti-apoptotic protein Mcl-1. Released from the co-delivery nanoparticles (PFHNs/TM) Tirapazamine and siMcl-1 upon exposure to acidic conditions of endosomes/lysosomes in activated macrophages. Under NIR irradiation, photothermal therapy and photodynamic therapy derived from PCPDTBT, hypoxia-activated chemotherapy derived from tirapazamine, and RNAi derived from siMcl-1 were used for the combined treatment for RA by killing activated macrophages. PEI-FA-coated PFHNs/TM exhibited activated macrophage-targeting characteristics, thereby enhancing the in vitro and in vivo NIR-induced combined treatment of RA.. The prepared PFHNs/TM have high blood compatibility (far below 5% of hemolysis) and ideal in vitro phototherapy effect while controlling the TPZ release and binding siMcl-1. We prove that PEI-FA-coated PFHNs/TM not only protect the bound siRNA but also are selectively uptaked by activated macrophages through FA receptor-ligand-mediated endocytosis, and effectively silence the target anti-apoptotic protein by siMcl-1 transfection. In vivo, PFHNs/TM have also been revealed to be selectively enriched at the inflammatory site of RA, exhibiting NIR-induced anti-RA efficacy.. Overall, these FA-functionalized, pH-responsive PFHNs/TM represent a promising platform for the co-delivery of chemical drugs and nucleic acids for the treatment of RA cooperating with NIR-induced phototherapy.

Topics: Arthritis, Rheumatoid; Folic Acid; Humans; Hypoxia; Myeloid Cell Leukemia Sequence 1 Protein; Nanoparticle Drug Delivery System; Nanoparticles; Phototherapy; RNA Interference; RNA, Small Interfering; Tirapazamine

Various cancers treated with cisplatin almost invariably develop drug resistance that is frequently caused by substantial DNA repair. We searched for acquired vulnerabilities of cisplatin-resistant cancers to identify undiscovered therapy. We herein found that cisplatin resistance of cancer cells comes at a fitness cost of increased intracellular hypoxia. Then, we conceived an inspired strategy to combat the tumor drug resistance by exploiting the increased intracellular hypoxia that occurs as the cells develop drug resistance. Here, we constructed a hypoxia-amplifying DNA repair-inhibiting liposomal nanomedicine (denoted as HYDRI NM), which is formulated from a platinum(IV) prodrug as a building block and payloads of glucose oxidase (GOx) and hypoxia-activatable tirapazamine (TPZ). In studies on clinically relevant models, including patient-derived organoids and patient-derived xenograft tumors, the HYDRI NM is able to effectively suppress the growth of cisplatin-resistant tumors. Thus, this study provides clinical proof of concept for the therapy identified here.

Topics: Antineoplastic Agents; Cell Line, Tumor; Cisplatin; DNA Repair; Humans; Hypoxia; Nanomedicine; Neoplasms; Tirapazamine

Photodynamic therapy (PDT) efficacy has been severely limited by the hypoxia in tumor microenvironment. A multitherapy modality was developed, integrating the advantages of each therapy and a nanocarrier: PDT and PDT-induced hypoxia-activated chemotherapy. Following PDT-induced hypoxia augmented in the periphery of the tumors, chemotherapy was locally activated. To this end, new indocyanine green (IR820) and a hypoxia-activated prodrug tirapazamine (TPZ) were loaded in glutathione (GSH) decomposable mesoporous organic silica nanoparticles (GMONs), tethered by hyaluronic acid (HA). This nanohybrid showed a tendency to accumulate and be retained in tumors, due to passive and active targeting. The IR820 produced singlet oxygen (

Topics: Cell Line, Tumor; Glutathione; Humans; Hypoxia; Nanoparticles; Neoplasms; Photochemotherapy; Photosensitizing Agents; Tirapazamine; Tumor Microenvironment

A zinc(ii) phthalocyanine (ZnPc) was conjugated to doxorubicin (Dox) via an acid-labile hydrazone linker. The resulting ZnPc-Dox conjugate was then encapsulated into polymeric micelles formed through self-assembly of a block copolymer of poly(ethylene glycol) and poly(d,l-lactide) both in the absence and presence of the hypoxia-activated prodrug tirapazamine (TPZ) to give ZnPc-Dox@micelles and ZnPc-Dox/TPZ@micelles respectively. These polymeric micelles exhibited an excellent stability in aqueous media, but underwent disassembly in an acidic environment. Upon internalisation into HT29 human colorectal carcinoma cells, fluorescence due to ZnPc and Dox could be observed in the cytoplasm and nucleus respectively for both nanosystems. This observation suggested the disassembly of the polymeric micelles and the cleavage of the hydrazone linker in ZnPc-Dox in the acidic intracellular compartments. These micelles were slightly cytotoxic against HT29 cells in the dark due to the chemotherapeutic effect of Dox and/or TPZ. Upon light irradiation, ZnPc-Dox@micelles showed higher cytotoxicity. The IC50 value under a normoxic condition (0.35 μM based on ZnPc-Dox) was significantly lower than that under hypoxia (>1 μM). With an additional therapeutic component, ZnPc-Dox/TPZ@micelles exhibited higher photocytotoxicity with IC50 values of 0.20 μM and 0.78 μM under normoxia and hypoxia respectively. It is believed that the photodynamic action of this nanosystem consumed the intracellular oxygen and hence triggered the hypoxia-mediated chemotherapeutic action of TPZ. The multimodal antitumor effects of these polymeric micelles were also validated on HT29 tumour-bearing nude mice.

Topics: Animals; Doxorubicin; Hypoxia; Indoles; Isoindoles; Mice; Mice, Nude; Micelles; Neoplasms; Polyethylene Glycols; Tirapazamine

Combination therapy provides significantly better outcomes than a single drug treatment and becomes an efficient strategy for cancer therapy at present. Owing to the advantages of improved drug bioavailability, decreased side effects, and drug codelivery properties, polymeric carrier-based nanodrugs show great application potential in combination therapy. In this study, a pH-responsive block polymer consisting of polyethylene glycol (mPEG) and poly(asparagyl diisopropylethylenediamine-co-phenylalanine) (P(Asp(DIP)-co-Phe)) is synthesized for drug delivery. The polymer self-assembles into nanovesicles and simultaneously encapsulates the hydrophilic hypoxia-activated prodrug tirapazamine (TPZ) and the hydrophobic photosensitizer dihydrogen porphin (chlorin e6, Ce6). The formed nanodrug can be triggered by near infrared irradiation to induce photodynamic therapy (PDT), resulting in a hypoxic tumor environment to activate the prodrug TPZ to achieve efficient chemotherapy. The cascade synergistic therapeutic effect is evaluated both in vitro and in vivo in a breast cancer mice model. This study reveals a potential strategy for efficient cancer therapy by using Ce6 and TPZ co-encapsulated nanovesicles.

Topics: Animals; Cell Line, Tumor; Hypoxia; Mice; Nanoparticles; Neoplasms; Photochemotherapy; Photosensitizing Agents; Porphyrins; Tirapazamine

For cancer treatment, the traditional monotherapy has the problems of low drug utilization rate, poor efficacy and easy recurrence of the cancer. Herein, nanoparticles (NPs) based on a novel semiconducting molecule (ITTC) are developed with excellent photostability, high photothermal conversion efficiency and good 1O2 generation ability. The chemotherapy of the hypoxia-activated prodrug tirapazamine (TPZ) was improved accordingly after oxygen consumption by the photodynamic therapy of ITTC NPs. Additionally, the metabolic process of ITTC NPs in vivo could be monitored in real time for fluorescence imaging guided phototherapy, which presented great passive targeting ability to the tumor site. Remarkably, both in vitro and in vivo experiments demonstrated that the combination of ITTC NPs and TPZ presented excellent synergistic tumor ablation through photothermal therapy, photodynamic therapy and hypoxia-activated chemotherapy with great potential for clinical applications in the future.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Cell Survival; Drug Screening Assays, Antitumor; Humans; Hypoxia; Injections, Intraperitoneal; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Molecular Structure; Nanoparticles; Neoplasms, Experimental; Optical Imaging; Photosensitizing Agents; Semiconductors; Tirapazamine

In this study, novel cupric-tirapazamine [Cu(TPZ)

Topics: Humans; Hypoxia; Liposomes; Male; Prostatic Neoplasms; Solubility; Tirapazamine

Tumor cell populations are highly heterogeneous, which limit the homogeneous distribution and optimal delivery of nanomedicines, thereby inducing insufficient therapeutic benefits. We develop tumor microenvironment activatable and external stimuli-responsive drug delivery system (

Topics: Cell Hypoxia; Cell Line, Tumor; Humans; Hypoxia; Nanoparticles; Photochemotherapy; Photosensitizing Agents; Tirapazamine

In the present work, a copper-tirapazamine (TPZ) nanocomplex [Cu(TPZ)

Topics: Antineoplastic Agents; Biological Transport; Copper; DNA; Humans; Hypoxia; Male; Nanoparticles; Prostatic Neoplasms; Radiation-Sensitizing Agents; Spheroids, Cellular; Tirapazamine; Tumor Cells, Cultured

The reduction potentials of bioreductively-activated drugs represent an important design parameter to be accommodated in the course of creating lead compounds and improving the efficacy of older generation drugs.  Reduction potentials are traditionally reported as single-electron reduction potentials, E(1), measured against reference electrodes under strictly defined experimental conditions.  More recently, computational chemists have described redox properties in terms of a molecule's highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), in electron volts (eV).  The relative accessibility of HOMO/LUMO data through calculation using today's computer infrastructure and simplified algorithms make the calculated value (LUMO) attractive in comparison to the accepted but rigorous experimental determination of E(1).  This paper describes the correlations of eV (LUMO) to E(1) for three series of bioreductively-activated benzotriazine di-N-oxides (BTDOs), ring-substituted BTDOs, ring-added BTDOs and a selection of aromatic nitro compounds. The current computational approach is a closed-shell calculation with a single optimization.  Gas phase geometry optimization was followed by a single-point DFT (Density Functional Theory) energy calculation in the gas phase or in the presence of polar solvent.  The resulting DFT-derived LUMO energies (eV) calculated for BTDO analogues in gas phase and in presence of polar solvent (water) exhibited very strong linear correlations with high computational efficiency (r2 = 0.9925) and a very high predictive ability (MAD = 7 mV and RMSD = 9 mV) when compared to reported experimentally determined single-electron reduction potentials.

Topics: Density Functional Theory; Electrons; Hypoxia; Oxidation-Reduction; Tirapazamine

Hypoxia is an adverse prognostic feature of solid cancers that may be overcome with hypoxia-activated prodrugs (HAPs). Tirapazamine (TPZ) is a HAP which has undergone extensive clinical evaluation in this context and stimulated development of optimized analogues. However the subcellular localization of the oxidoreductases responsible for mediating TPZ-dependent DNA damage remains unclear. Some studies conclude only nuclear-localized oxidoreductases can give rise to radical-mediated DNA damage and thus cytotoxicity, whereas others identify a broader role for endoplasmic reticulum and cytosolic oxidoreductases, indicating the subcellular location of TPZ radical formation is not a critical requirement for DNA damage. To explore this question in intact cells we engineered MDA-231 breast cancer cells to express the TPZ reductase human NADPH: cytochrome P450 oxidoreductase (POR) harboring various subcellular localization sequences to guide this flavoenzyme to the nucleus, endoplasmic reticulum, cytosol or inner surface of the plasma membrane. We show that all POR variants are functional, with differences in rates of metabolism reflecting enzyme expression levels rather than intracellular TPZ concentration gradients. Under anoxic conditions, POR expression in all subcellular compartments increased the sensitivity of the cells to TPZ, but with a fall in cytotoxicity per unit of metabolism (termed 'metabolic efficiency') when POR is expressed further from the nucleus. However, under aerobic conditions a much larger increase in cytotoxicity was observed when POR was directed to the nucleus, indicating very high metabolic efficiency. Consequently, nuclear metabolism results in collapse of hypoxic selectivity of TPZ, which was further magnified to the point of reversing O

Topics: Antineoplastic Agents; Cell Engineering; Cell Hypoxia; Cell Line, Tumor; Cell Membrane; Cell Nucleus; Cell Survival; Copper; DNA Damage; Humans; Hypoxia; Models, Biological; NADPH-Ferrihemoprotein Reductase; Oxygen; Prodrugs; Tirapazamine

Photodynamic therapy (PDT) as a promising noninvasive and effective treatment modality has been clinically approved for cancer therapy. However, the poor selectivity of tumor and hypoxia-induced resistance constrain PDT efficacy immensely. To further enhance PDT's potency, we developed a drug delivery system based on liposome combining PDT and chemotherapeutics. The lipophilic IR780 was loaded into the lipid bilayer while hydrophilic chemotherapeutic agent tirapazamine (TPZ) was encapsulated in the hydrophilic core. IR780 could generate reactive oxygen species and hypoxic microenvironment in local site because of the continuous consumption of oxygen, resulting in the TPZ encapsulated in the aqueous liposome chamber brings out TPZ radicals to cause DNA double-strand breaks and chromosome aberrations. In vivo studies demonstrated that the liposomes which encapsulate IR780 and TPZ showed great antitumor efficacy via combining photodynamic therapy with chemotherapy. Therefore, the investigation combines PDT and hypoxia-activated chemotherapy from the TPZ. It is a simple but effective liposome platform to achieve multiple synergistic antitumor efficacy and shows potential for clinical use.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Combined Modality Therapy; Drug Compounding; Drug Liberation; Female; Hypoxia; Indoles; Infrared Rays; Injections, Subcutaneous; Kinetics; Liposomes; Mammary Glands, Animal; Mice; Neoplasms; Photochemotherapy; Radiation-Sensitizing Agents; Reactive Oxygen Species; Tirapazamine; Tumor Burden

The hypoxic microenvironment induced by sonodynamic therapy (SDT) via sonochemical oxygen consumption usually triggered tumor resistance to SDT, impeding therapeutic efficacy. In this sense, it was highly desired to tackle the hypoxia-related negative issues. Here we provide the therapeutic agents delivery system, TPZ/HMTNPs-SNO, which was constructed by loading tirapazamine (TPZ) into hollow mesoporous titanium dioxide nanoparticles (HMTNPs) with modification of S-nitrosothiol (R-SNO). Upon encountering ultrasound waves, the HMTNPs as sonosensitizers would generate reactive oxygen species (ROS) for SDT. In a sequential manner, the followed SDT-induced hypoxia further activated the "hypoxic cytotoxin", TPZ, for hypoxia-specific killing effect. Meanwhile, the generated ROS could sensitize -SNO groups for on-demand nitric oxide (NO) release in an "anticancer therapeutic window", resulting in the NO sensitized SDT effect. This study confirmed that the TPZ/HMTNPs-SNO with multi-mechanisms exploited the merits of synergistic combination of the three therapeutic modes, consequently potentiating the anticancer efficacy of SDT. Moreover, the echogenic property of NO made the nanoplatform as an ultrasound contrast agent to enhance ultrasound imaging. In this sense, we developed a sequential strategy for ultrasound mediated all-in-one nanotheranostic platform of TPZ/HMTNPs-SNO, which highlighted new possibilities of advancing cancer theranostics in biomedical fields.

Topics: Animals; Antineoplastic Agents; Humans; Hypoxia; MCF-7 Cells; Mice, Inbred BALB C; Mice, Nude; Nanoparticles; Neoplasms; S-Nitrosothiols; Theranostic Nanomedicine; Tirapazamine; Titanium; Tumor Burden; Ultrasonography

Photodynamic therapy (PDT) induced hypoxia can significantly upregulate the expression of vascular endothelial growth factor (VEGF) at the tumor-stromal interface, resulting in a promoted angiogenesis. Thus, an angiogenesis vessel-targeting nanoparticle (AVT-NP) consisting of photosensitizer, angiogenic vessel-targeting peptide, and bioreductive prodrug is developed for a chemo-photo synergistic cancer therapy, with which anti-cancer effect is achieved first by PDT and immediately followed with hypoxia-activated cytotoxic free radicals. With targeting capability, the AVT-NPs can effectively accumulate at the tumor site due to the promoted angiogenesis in response to PDT-induced hypoxia. The more nanoparticles delivered to the tumor tissue, the higher efficacy of PDT can be achieved, resulting in a more severe hypoxia and increased angiogenesis. Therefore, the prodrug embedded AVT-NP functions as a positive feedback amplifier in the combinational chemo-photo treatment and indeed achieves an enhanced anti-tumor effect in both in vitro and in vivo studies.

Topics: 3T3 Cells; Animals; Antineoplastic Agents; Cell Line, Tumor; Drug Delivery Systems; Human Umbilical Vein Endothelial Cells; Humans; Hypoxia; Male; Mice; Mice, Inbred BALB C; Mice, Inbred ICR; Mice, Nude; Nanoparticles; Neoplasms; Neovascularization, Pathologic; Photochemotherapy; Photosensitizing Agents; Prodrugs; Reactive Oxygen Species; Tirapazamine; Triazines; Vascular Endothelial Growth Factor A

Anaerobic bacteria, such as Clostridium and Salmonella, can selectively invade and colonize in tumor hypoxic regions (THRs) and deliver therapeutic products to destroy cancer cells. Herein, we present an anaerobe nanovesicle mimic that can not only be activated in THRs but also induce hypoxia in tumors by themselves. Moreover, inspired by the oxygen metabolism of anaerobes, we construct a light-induced hypoxia-responsive modality to promote dissociation of vehicles and activation of bioreductive prodrugs simultaneously. In vitro and in vivo experiments indicate that this anaerobe-inspired nanovesicle can efficiently induce apoptotic cell death and significantly inhibit tumor growth. Our work provides a new strategy for engineering stimuli-responsive drug delivery systems in a bioinspired and synergistic fashion.

Topics: Antineoplastic Agents; Cell Death; Cell Proliferation; Clostridium; Drug Carriers; Drug Delivery Systems; Drug Screening Assays, Antitumor; Humans; Hypoxia; Imidazoles; Nanoparticles; Prodrugs; Salmonella; Tirapazamine

Poor tumor penetration is a major challenge for the use of nanoparticles in anticancer therapy. Moreover, the inability to reach hypoxic tumor cells that are distant from blood vessels results in inadequate exposure to antitumor therapeutics and contributes to development of chemoresistance and increased metastasis. In the present study, we developed iRGD-modified nanoparticles for simultaneous tumor delivery of a photosensitizer indocyanine green (ICG) and hypoxia-activated prodrug tirapazamine (TPZ). The iRGD-modified nanoparticles loaded with ICG and TPZ showed significantly improved penetration in both 3D tumor spheroids in vitro and orthotopic breast tumors in vivo. ICG-mediated photodynamic therapy upon irradiation with a near-IR laser induced hypoxia, which activated antitumor activity of the codelivered TPZ for synergistic cell-killing effect. In vivo studies demonstrated that the nanoparticles could efficiently deliver the drug combination in 4T1 orthotopic tumors. Primary tumor growth and metastasis were effectively inhibited by the iRGD-modified combination nanoparticles with minimal side effects. The results also showed the anticancer benefits of codelivering ICG and TPZ in a single nanoparticle formulation in contrast to a mixture of nanoparticles containing individual drugs. The study demonstrates the benefits of combining tumor-penetrating nanoparticles with hypoxia-activated drug treatment and establishes a delivery platform for PDT and hypoxia-activated chemotherapy.

Topics: Animals; Antineoplastic Agents; Apoptosis; Cell Proliferation; Drug Delivery Systems; Drug Screening Assays, Antitumor; Hypoxia; Indocyanine Green; Injections, Intravenous; Mice; Molecular Structure; Nanoparticles; Photochemotherapy; Photosensitizing Agents; Prodrugs; Reactive Oxygen Species; Tirapazamine; Tissue Distribution; Tumor Cells, Cultured

Tumor resistance to ionizing irradiation and cancer cell's metastasis stimulated by radiation often lead to anti-cancer failure, and can be negatively caused by a key role--cellular hypoxia. In this regard, the exploitation of hypoxia-specific cytotoxic agents which assist to potentiate the anti-tumor effect of radiotherapy (RT) as well as efficiently counteract radiation-/hypoxia-induced cancer cell metastasis, becomes especially important, but has been widely overlooked. Herein, a core/shell-structured multifunctional nanoradiosensitizer with upconversion nanoparticle (UCNP) as an inside core, mesoporous silica as the shell and a cavity in between, has been constructed, in which UCNP core serves as radiation dose amplifiers and bio-reductive pro-drug--tirapazamine (TPZ) loaded in cavity is an hypoxia-selective cytotoxin and the silica shell provides the protection and diffusion path for TPZ. Such nanoradiosensitizer has been employed to inhibit the hypoxia-reoxygenation and the subsequent replication of cancer cells that often occurs after a single unaccompanied RT at low doses, and to silence the expression of transcription factors that support the progression of malignancy in cancer. This study confirms the radiotherapeutic benefits of utilizing nanoradiosensitizer as adjuvant to low-dose RT, and the results demonstrate the highly efficient hypoxia-specific killing in oxygen-dependent anti-tumor therapies.

Topics: Animals; Cell Death; Cell Proliferation; Cell Survival; Extracellular Matrix; Female; Fluorescent Antibody Technique; HeLa Cells; Humans; Hypoxia; Mice, Inbred BALB C; Mice, Nude; Nanoparticles; Neoplasm Metastasis; Neoplasms; Oxygen; Radiation-Sensitizing Agents; Tirapazamine; Triazines

To assess the contribution of hypoxia and bone marrow-derived cells to aggressive outgrowth of micrometastases after liver surgery.. Liver surgery generates a microenvironment that fosters aggressive tumor recurrence. These areas are characterized by chronic hypoxia and influx of bone marrow-derived cells.. The contribution of hematopoietic cell types was studied in mice lacking specific components of the immune system and in irradiated mice lacking all bone marrow-derived cells. Tumor cells were derived from colorectal cancer patients and from a metastatic tumor cell line. Hypoxia-induced changes in stem cell and differentiation marker expression, clone-forming potential, and metastatic capacity were assessed. The effect of vascular clamping on cancer stem cell (CSC) characteristics was performed in mice bearing patient-derived liver metastases.. Immune cells and bone marrow-derived cells were not required for aggressive outgrowth of micrometastases in livers treated with surgery. Rather, hypoxia was sufficient to promote invasion and accelerate metastatic outgrowth. This was associated with a rapid loss of differentiation markers and increased expression of CSC markers and clone-forming capacity. Likewise, metastases residing in ischemia-reperfusion-injured liver lobes acquired CSC characteristics. Despite their renowned general resistance to chemotherapy, clone-forming CSCs were readily killed by the hypoxia-activated prodrug tirapazamine.. Surgery-generated hypoxia in the liver causes rapid dedifferentiation of tumor cells into immature CSCs with high clone- and metastasis-forming capacity. The results help explain the phenomenon of aggressive local tumor recurrence after liver surgery and offer a potential strategy to kill aggressive CSCs by hypoxia-activated prodrugs.

Topics: Animals; Antineoplastic Agents; Biomarkers, Tumor; Blotting, Western; Catheter Ablation; Cell Line, Tumor; Colorectal Neoplasms; Flow Cytometry; Hematopoietic Stem Cells; Hepatectomy; Humans; Hypoxia; Immunohistochemistry; Liver Neoplasms, Experimental; Male; Mice; Mice, Inbred BALB C; Mice, Inbred NOD; Mice, Nude; Mice, SCID; Neoplasm Invasiveness; Neoplasm Micrometastasis; Neoplasm Recurrence, Local; Neoplasm, Residual; Neoplastic Stem Cells; Phenotype; Postoperative Complications; Real-Time Polymerase Chain Reaction; Reperfusion Injury; Tirapazamine; Triazines

Tirapazamine (3-amino-1,2,4-benzotriazine 1,4-dioxide) is a heterocyclic di-N-oxide that undergoes enzymatic deoxygenation selectively in the oxygen-poor (hypoxic) cells found in solid tumors to generate a mono-N-oxide metabolite. This work explored the idea that the electronic changes resulting from the metabolic deoxygenation of tirapazamine analogues might be exploited to activate a DNA-alkylating species selectively in hypoxic tissue. Toward this end, tirapazamine analogues bearing nitrogen mustard units were prepared. In the case of the tirapazamine analogue 18a bearing a nitrogen mustard unit at the 6-position, it was found that removal of the 4-oxide from the parent di-N-oxide to generate the mono-N-oxide analogue 17a did indeed cause a substantial increase in reactivity of the mustard unit, as measured by hydrolysis rates and DNA-alkylation yields. Hammett sigma values were measured to quantitatively assess the magnitude of the electronic changes induced by metabolic deoxygenation of the 3-amino-1,2,4-benzotriazine 1,4-dioxide heterocycle. The results provide evidence that the 1,2,4-benzotiazine 1,4-dioxide unit can serve as an oxygen-sensing prodrug platform for the selective unmasking of bioactive agents in hypoxic cells.

Topics: Alkylating Agents; Antineoplastic Agents; Cyclic N-Oxides; DNA Damage; Gas Chromatography-Mass Spectrometry; Hypoxia; Mechlorethamine; Molecular Structure; Oxidation-Reduction; Prodrugs; Tirapazamine; Triazines

Many cancer research efforts focus on exploiting genetic-level features that may be targeted for therapy. Tissue-level features of the tumour microenvironment also represent useful therapeutic targets. Here we investigate the presence of low oxygen tension and sensitivity to NOS inhibition of tumour vasculature as potential tumour-specific features that may be targeted by hypoxic cytotoxins, a class of therapeutics currently under investigation. We have previously demonstrated that tirapazamine (TPZ) mediates central vascular dysfunction in tumours. TPZ is a hypoxic cytotoxin that is also a competitive inhibitor of NOS. Here we further investigated the vascular-targeting activity of TPZ by combining it with NOS inhibitor L-NNA, or with low oxygen content gas breathing. Tumours were analyzed via multiplex immunohistochemical staining that revealed irreversible loss of perfusion and enhanced tumour cell death when TPZ was combined with either low oxygen or a NOS inhibitor. Tumour growth rate was reduced by TPZ + NOS inhibition, and tumours previously resistant to TPZ-mediated vascular dysfunction were sensitized by low oxygen breathing. Additional mapping analysis suggests that tumours with reduced vascular-associated stroma may have greater sensitivity to these effects. These results indicate that poorly oxygenated tumour vessels, also being abnormally organized and with inadequate smooth muscle, may be successfully targeted for significant anti-cancer effects by inhibition of NOS and hypoxia-activated prodrug toxicity. This strategy illustrates a novel use of hypoxia-activated cytotoxic prodrugs as vascular targeting agents, and also represents a novel mechanism for targeting tumour vessels.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cytotoxins; Female; HCT116 Cells; HT29 Cells; Humans; Hypoxia; Immunohistochemistry; Mice; Mice, Inbred C3H; Mice, Inbred NOD; Mice, SCID; Neoplasms; Neovascularization, Pathologic; Nitric Oxide Synthase; Nitroarginine; Tirapazamine; Treatment Outcome; Triazines; Tumor Burden; Xenograft Model Antitumor Assays

What's known on the subject? and What does the study add? Castration therapy has rather modest effects on cell death in tumours but can be enhanced by other treatments targeting tumour stroma and vasculature. This study shows that the prostate becomes hypoxic following castration and that targeting hypoxic cells during castration therapy potently enhances the effects of castration.. To explore the effects of castration therapy, the standard treatment for advanced prostate cancer, in relation to tumour hypoxia and to elicit its importance for the short- and long-term therapeutic response.. We used the androgen-sensitive rat Dunning H prostate tumour model that transiently responds to castration treatment followed by a subsequent relapse, much like the scenario in human patients. Tumour tissues were analysed using stereological methods in intact, 1 and 7 days after castration therapy.. Hypoxia was transiently up-regulated after castration therapy and correlated with the induction of tumour cell apoptosis. When castration therapy was combined with tirapazamine (TPZ), a drug that targets hypoxic cells and the vasculature, the effects on tumour cell apoptosis and tumour volume were enhanced in comparison to either castration or TPZ alone.. The present study suggests that castration-induced tumour hypoxia is a novel target for therapy.

Topics: Animals; Apoptosis; Cell Hypoxia; Disease Models, Animal; Hypoxia; Immunohistochemistry; Male; Orchiectomy; Organ Culture Techniques; Oxygen Consumption; Prostatic Neoplasms; Random Allocation; Rats; Rats, Inbred Strains; Statistics, Nonparametric; Tirapazamine; Triazines

Bioreductive drugs can cause retinal toxicity, mediated by extensive apoptosis in the outer retina of rodents and monkeys. In the present study, we have investigated whether or not the novel and promising hypoxia-selective cytotoxin 4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinoline hydrochloride (NLCQ-1, NSC 709257) can cause hypoxia-dependent retinal toxicity in BALB/c mice alone or in combination with cyclophosphamide (CPM), one of the anti-cancer agents that acts synergistically with NLCQ-1 against mouse tumours and human xenografts. The bioreductive agent tirapazamine (TPZ) was included for comparison purposes. Retinal damage was quantified by morphometric analysis of histological sections following IP treatment of female BALB/c mice. No retinal toxicity was observed with 10 or 22 mg/kg of NLCQ-1 or 23 mg/kg TPZ alone, whereas statistically significant retinal toxicity was observed with the higher TPZ dose of 52 mg/kg (p < 0.001). Thus, a normalized photoreceptor layer thickness (NPT) value of 0.50 ± 0.04, 0.48 ± 0.03 and 0.33 ± 0.06 was determined for untreated, NLCQ-1 and TPZ-treated mice at the highest dose, respectively. Marginal retinal toxicity was observed with the lower dose of TPZ in combination with CPM.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Cyclophosphamide; Cytotoxins; Dose-Response Relationship, Drug; Drug Synergism; Female; Humans; Hypoxia; Imidazoles; Mice; Mice, Inbred BALB C; Neoplasms; Quinolines; Retina; Tirapazamine; Triazines

The heterocyclic N-oxide, 3-amino-1,2,4-benzotriazine 1,4-dioxide (tirapazamine, 1), shows promising antitumor activity in preclinical studies, but there is a continuing need to explore new compounds in this general structural category. In the work described here, we examined the properties of 7-chloro-2-thienylcarbonyl-3-trifluoromethylquinoxaline 1,4-dioxide (9h). We find that 9h causes redox-activated, hypoxia-selective DNA cleavage that mirrors the lead compound, tirapazamine, in both mechanism and potency. Furthermore, we find that 9h displays hypoxia-selective cytotoxicity against human cancer cell lines.

Topics: Antineoplastic Agents; Chromatography, High Pressure Liquid; Cytochrome P-450 Enzyme System; DNA; DNA Cleavage; Humans; Hypoxia; Molecular Structure; NADP; Oxidation-Reduction; Quinoxalines; Tirapazamine; Triazines

Metronomic cyclophosphamide treatment is associated with anti-angiogenic activity and is anticipated to generate exploitable hypoxia using hypoxia-activated prodrugs. Weekly administration of tirapazamine (TPZ; 5 mg/kg body weight i.p.) failed to inhibit the growth of 9L gliosarcoma tumors grown s.c. in scid mice. However, the anti-tumor effect of weekly cyclophosphamide (CPA) treatment (140 mg/kg BW i.p.) was substantially enhanced by weekly TPZ administration. An extended tumor free period and increased frequency of tumor eradication without overt toxicity were observed when TPZ was given 3, 4 or 5 days after each weekly CPA treatment. Following the 2(nd) CPA injection, Electron Paramagnetic Resonance (EPR) Oximetry indicated significant increases in tumor pO(2), starting at 48 hr, which further increased after the 3(rd) CPA injection. pO(2) levels were, however, stable in growing untreated tumors. A strong negative correlation (-0.81) between tumor pO(2) and tumor volume during 21 days of weekly CPA chemotherapy was observed, indicating increasing tumor pO(2) with decreasing tumor volume. Furthermore, CPA treatment resulted in increased tumor uptake of activated CPA. CPA induced increases in VEGF RNA, which reached a maximum on day 1, and in PLGF RNA which was sustained throughout the treatment, while anti-angiogenic host thrombospondin-1 increased dramatically through day 7 post-CPA treatment. Weekly cyclophosphamide treatment was anticipated to generate exploitable hypoxia. However, our findings suggest that weekly CPA treatment induces a functional improvement of tumor vasculature, which is characterized by increased tumor oxygenation and drug uptake in tumors, thus counter-intuitively, benefiting intratumoral activation of TPZ and perhaps other bioreductive drugs.

Topics: Angiogenesis Inducing Agents; Angiogenesis Inhibitors; Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cyclophosphamide; Drug Administration Schedule; Humans; Hypoxia; Mice; Mice, SCID; NADPH-Ferrihemoprotein Reductase; Neoplasms; Oxygen; Time Factors; Tirapazamine; Triazines; Xenograft Model Antitumor Assays

The interaction of stem cells with their bone marrow microenvironment is a critical process in maintaining normal hematopoiesis. We applied an approach to resolve the spatial organization that underlies these interactions by evaluating the distribution of hematopoietic cell subsets along an in vivo Hoechst 33342 (Ho) dye perfusion gradient. Cells isolated from different bone marrow regions according to Ho fluorescence intensity contained the highest concentration of hematopoietic stem cell (HSC) activity in the lowest end of the Ho gradient (i.e., in the regions reflecting diminished perfusion). Consistent with the ability of Ho perfusion to simulate the level of oxygenation, bone marrow fractions separately enriched for HSCs were found to be the most positive for the binding of the hypoxic marker pimonidazole. Moreover, the in vivo administration of the hypoxic cytotoxic agent tirapazamine exhibited selective toxicity to the primitive stem cell subset. These data collectively indicate that HSCs and the supporting cells of the stem cell niche are predominantly located at the lowest end of an oxygen gradient in the bone marrow with the implication that regionally defined hypoxia plays a fundamental role in regulating stem cell function.

Topics: Animals; Benzimidazoles; Bone Marrow Cells; Cell Differentiation; Hematopoietic Stem Cells; Hematopoietic System; Hypoxia; Mice; Mice, Inbred C57BL; Nitroimidazoles; Oxygen; Perfusion; Stem Cells; Tirapazamine; Triazines

A series of 3-amino-1,2,4-benzotriazine-1,4-dioxide derivatives 1 have been synthesized and evaluated for their cytotoxic activity in vitro against human leukemia cell lines: Molt-4, K562, HL60, human liver cancer cell Hep-G2, human prostate cancer cell PC-3 in hypoxia. Most of the compounds showed more potent activity than TPZ. Compounds 1i and 1m displayed encouraging superior activity against Molt-4 and HL-60 cell lines. Three potential derivatives received the test of the activity in hypoxia and in normoxia against Molt-4 and HL-60 cell lines and showed obvious hypoxia selectivity. Further mechanism study revealed that the cytotoxic activities of compounds 1i and 1k in Molt-4 cells might be mediated by modulation of p53 protein expression and mitochondrial membrane potential (DeltaPsi(m)).

Topics: Antineoplastic Agents; Cell Line, Tumor; Drug Screening Assays, Antitumor; HL-60 Cells; Humans; Hypoxia; Inhibitory Concentration 50; K562 Cells; Membrane Potentials; Models, Chemical; Tirapazamine; Triazines; Tumor Suppressor Protein p53

Because of the inefficient vasculature of solid tumors, anticancer drugs must penetrate relatively long distances through the extravascular compartment. The requirement for such diffusion may limit their activity, especially that of hypoxia-targeted drugs. We tested whether a three-dimensional pharmacokinetic/pharmacodynamic (PK/PD) model based on a representative mapped tumor microvascular network could predict the therapeutic activity of anticancer drugs in mouse xenograft tumors.. Diffusion coefficients of the hypoxia-activated anticancer drug tirapazamine (TPZ) and of 15 TPZ analogs were estimated by measuring their transport through HT29 colon cancer multicellular layers (MCLs). Anoxic cytotoxic potency (by clonogenic assay) and metabolism of the TPZ analogs were measured in HT29 cell suspensions, and their plasma pharmacokinetics was measured in CD-1 nude mice. This information was used to create a spatially resolved PK/PD model for the tumor microvascular network. Model predictions were compared with actual hypoxic cell kill as measured by clonogenic assays on HT29 xenograft tumors 18 hours after treatment with each TPZ analog.. Modeling TPZ transport in the tumor microvascular network showed substantial drug depletion in the most hypoxic regions, with predicted maximum cell kill of only 3 logs, compared with more than 10 logs if there were no transport impediment. A large range of tissue diffusion coefficients (0.027 x 10(-6)-1.87 x 10(-6) cm2/s) was observed for the TPZ analogs. There was a strong correlation between model-predicted and measured hypoxic cell kill (R2 = 0.89) but a poor correlation when the model did not include extravascular transport (R2 = 0.32).. Extravascular transport in tumors, and its consequences for tumor cell killing, can be predicted by measuring drug penetration through MCLs in vitro and modeling pharmacokinetics at each position in three-dimensional microvascular networks.

Topics: Analysis of Variance; Animals; Antineoplastic Agents; Biological Transport, Active; Chromatography, High Pressure Liquid; Colonic Neoplasms; Disease Models, Animal; Humans; Hypoxia; Mice; Radiation-Sensitizing Agents; Reproducibility of Results; Tirapazamine; Transplantation, Heterologous; Triazines; Tumor Cells, Cultured; Tumor Stem Cell Assay

To investigate potential synergistic interactions between bioreductive agents, either NLCQ-1 or tirapazamine (TPZ) and two alkylating chemotherapeutic drugs, and how such interactions compare in vitro and in vivo.. V79 cells (in vitro studies) and the SCCVII/C3H murine tumor model (in vivo studies) were used. The alkylating chemotherapeutic agents examined were cisplatin (cisDDP) and melphalan (L-PAM). In vivo, all agents were administered by i.p. injection wherein NLCQ-1 and TPZ were given at equitoxic doses of 10 and 23 mg/kg, respectively. Optimal administration schedules and dose modification factors (DMF) were determined in vivo for the antitumor effect or bone marrow toxicity by using the in vivo-in vitro clonogenic assay as the endpoint.. A schedule-dependent synergistic interaction was observed between NLCQ-1/TPZ and each alkylating agent, both in vitro and in vivo, and an optimal potentiation was obtained when each bioreductive agent was administered prior to each chemotherapeutic drug. However, significant DMF values and an in vivo therapeutic index (TI) was obtained only with NLCQ-1. Limited mechanistic studies in V79 cells by using the alkaline comet assay demonstrated that hypoxic preincubation with NLCQ-1 increases the cross-links induced by subsequent aerobic exposure to cisDDP.. These results verify our previous observations in EMT6 tumors and suggest a potential clinical use of NLCQ-1 as a synergistic adjuvant to chemotherapy with alkylating agents against solid tumors possessing hypoxic regions.

Topics: Animals; Antineoplastic Agents; Antineoplastic Agents, Alkylating; Cisplatin; Comet Assay; Cricetinae; Drug Synergism; Female; Hypoxia; Imidazoles; In Vitro Techniques; Melphalan; Mice; Mice, Inbred C3H; Neoplasm Transplantation; Quinolines; Tirapazamine; Triazines

The level of hypoxia in primary tumors has been linked both clinically and experimentally to the incidence of metastases. This study was designed to address the effect of selectively targeting hypoxic cells in primary tumors on subsequent presentation of metastasis.. The murine KHT model was used as a reproducible temporal and spatial onset of metastases is revealed following treatment of primary ( approximately 400 mm(3)) s.c. tumors with a 25 Gy radiation dose. The bioreductive drugs tirapazamine and RB6145 were administered in multiple doses before radiotherapy.. Fractionated treatment with both tirapazamine and RB6145 significantly reduced the hypoxic fraction of the primary tumor, as assessed by pimonidazole binding, and had no effect on the overall growth rate of the primary tumor. Excision assays showed an increased level of cell kill in tirapazamine-treated versus RB6145-treated tumors consistent with tirapazamine targeting hypoxic cells at a broader range of oxygen tensions than RB6145. Tirapazamine treatment significantly reduced the presentation of metastases following radiotherapy (P = 0.003 versus saline controls) whereas RB6145 had no effect. Local control rates increased from 20% to 32% and 50% when radiation was combined with RB6145 and tirapazamine, respectively.. These data provide direct evidence that selective targeting of hypoxic cells in primary tumors is a viable approach in the control of metastatic disease. The enhanced efficacy of tirapazamine versus RB6145 suggests that the radioresistant cells at intermediate oxygen tensions, conducive to targeting with tirapazamine but not with the more stringent bioreductive RB6145, predominate in terms of linking primary tumor hypoxia and metastases.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Combined Modality Therapy; Female; Hypoxia; Mice; Mice, Inbred C3H; Neoadjuvant Therapy; Neoplasm Metastasis; Neoplasm Transplantation; Neovascularization, Pathologic; Nitroimidazoles; Radiation-Sensitizing Agents; Sarcoma, Experimental; Tirapazamine; Treatment Outcome; Triazines

We reported recently that exposure of hamster V79 fibroblasts to 6 drugs that varied in their ability to produce DNA double-strand breaks stimulated formation of phosphorylated histone H2AX (serine 139 phosphorylated histone H2AX; gammaH2AX). Using flow cytometry to analyze gammaH2AX antibody-stained cells 1 h after a 30-min drug treatment, the fraction of cells that showed the control levels of gammaH2AX correlated well with the fraction of cells that survived to form colonies. This observation is now extended to V79 and SiHa human cervical carcinoma cells grown as multicell spheroids and SiHa xenografts and SCCVII tumors in mice. Animals were injected with etoposide, a topoisomerase-II inhibitor that targets proliferating cells or 3-amino-1,2,4-benzotriazine-1,3-dioxide (tirapazamine), a bioreductive cytotoxin that targets hypoxic cells. For spheroids, gammaH2AX intensity predicted clonogenic cell survival for cells recovered 90 min after drug injection, regardless of position of the cells within the spheroid. Similar results were obtained for etoposide in tumors; however, the gammaH2AX signal for tirapazamine was smaller than expected for the observed amount of cell killing. Frozen sections of tumors confirmed the greater intensity of gammaH2AX staining in cells close to blood vessels of tumors soon after treatment with etoposide and the opposite pattern for tumors exposed to tirapazamine. Analysis of cells or frozen sections from mouse spleen and kidney suggests that information can also be obtained on initial damage in normal tissues. These results support the possibility of using gammaH2AX antibody staining as a method to aid in prediction of tumor and normal tissue response to treatment.

Topics: Animals; Antineoplastic Agents; Cell Survival; DNA Damage; Etoposide; Female; Flow Cytometry; Histones; Humans; Hypoxia; Kidney; Mice; Mice, Inbred NOD; Mice, SCID; Phosphorylation; Spheroids, Cellular; Spleen; Tirapazamine; Transplantation, Heterologous; Triazines; Tumor Stem Cell Assay; Uterine Cervical Neoplasms

To improve the potency of the hypoxic cytotoxin tirapazamine (TPZ), we have constructed an analog, SN26955, with the TPZ moiety attached to an acridine chromophore to target the drug to DNA. The underlying reason for this is our previous finding that the hypoxic cytotoxicity of TPZ is a result of its ability to produce DNA double-strand breaks, whereas many of the toxicities of the drug in clinical use are likely the result of its metabolism in the cytoplasm and effects on mitochondria. We found that the DNA-targeted TPZ analog was more potent than TPZ in killing hypoxic cells by 1-2 orders of magnitude, yet it retained the hypoxic selectivity for cell killing of TPZ. We show that SN26955 is only active in producing DNA damage when it is enzymatically reduced while bound to, or in close association with, the DNA. We also show that it has a different cofactor dependence than TPZ for reduction leading to DNA double-strand breaks, suggesting the involvement of a different reductase for production of the lethal lesion than for TPZ. These results show the promise of DNA-targeting of TPZ to produce a DNA compound with greater clinical efficacy than TPZ itself.

Topics: Acridines; Antineoplastic Agents; Cell Survival; DNA Damage; DNA, Neoplasm; Drug Screening Assays, Antitumor; Free Radicals; HeLa Cells; Humans; Hypoxia; Oxygen; Tirapazamine; Triazines; Tumor Cells, Cultured

Targeting the anticancer compound tirapazamine (3-amino-1,2,4-benzotriazine 1,4-dioxide; TPZ) to DNA by appended binding units has been found to greatly increase the free radical-induced production of both single and double strand breaks under hypoxia compared to TPZ itself. The (*)OH radical, produced upon the radiolysis of aqueous solutions, was used to damage plasmid DNA, and both types of strand breaks were quantified in the absence and presence of TPZ and analogues. Targeted analogues of TPZ show increases of 12-18-fold in single strand breaks, and 60-110-fold in double strand breaks, as compared with TPZ itself. The observed increased formation of double strand breaks under hypoxia is the likely mechanism for the large increase in potency previously demonstrated for a similarly targeted analogue of TPZ as a bioreductive drug (Delahoussaye et al. (2003) Biochem. Pharmacol. 65, 1807-1815). The one-electron reduction potential of the two-electron reduced metabolite of TPZ (the 1-oxide, SR 4317) has been measured as -568 +/- 9 mV, which is sufficiently high to oxidize carbon-centered radicals such as those formed on the sugar moiety of DNA. Targeting the 1-oxide moiety to DNA resulted in a ca. 50% increase in single strand breaks over that seen for TPZ without the dramatic increase in double strand breaks seen for the similarly targeted benzotriazine 1,4-dioxides. These studies support the mechanism by which the reduction of TPZ to an oxidizing radical leads to free radical damage on DNA that can be further oxidized by TPZ or SR4317 (and especially well by DNA-targeted analogues) to yield lesions resulting in strand breakage. The targeting of benzotriazine 1,4-dioxide analogues to DNA by appending binding units to the compounds thus represents an efficient system for inducing strand breaks in DNA.

Topics: Acridines; Animals; Binding Sites; DNA; DNA Adducts; DNA Damage; Dose-Response Relationship, Drug; Dose-Response Relationship, Radiation; Drug Delivery Systems; Free Radical Scavengers; Free Radicals; Hydroxyl Radical; Hypoxia; Plasmids; Pulse Radiolysis; Solutions; Structure-Activity Relationship; Tirapazamine; Triazines; Water

The antitumor effect and bone marrow toxicity of 5-fluorouracil (5FU) in combination with the hypoxia-selective cytotoxins NLCQ-1 or tirapazamine (TPZ) were investigated in vivo.. Using appropriate intraperitoneal administration schedules for optimal synergistic interactions, the antitumor effect and the bone marrow toxicity of combinations of NLCQ-1 or TPZ and 5FU were determined in EMT6/BALB/c and SCCVII/C3H models in terms of dose modification factors (DMF) using the in vivo-in vitro clonogenic assay as endpoint. Bone marrow toxicity studies were performed in parallel using a modified CFU-GM assay. The antitumor efficacies of each combination treatment under optimal administration conditions were evaluated in the SCCVII/C3H model using also the tumor regrowth assay as endpoint.. A schedule-dependent and tumor-specific synergistic interaction was observed for NLCQ-1 plus 5FU and DMFs of 2.0-2.3 and 1.0 were obtained for the antitumor effect and bone marrow toxicity, respectively, in both tumor models. The antitumor effect of 5FU was slightly potentiated (DMF 1.2) by TPZ in the EMT6/BALB/c model but not in the SCCVII/C3H model when the in vivo-in vitro assay was used as the endpoint. Significant additional tumor regrowth delays (about 11 and 6 days for NLCQ-1 and TPZ, respectively) were observed, compared to the effect of 5FU alone, when an equitoxic dose of NLCQ-1 (10 mg/kg) or TPZ (23 mg/kg) was administered 1 h before 5FU (50 mg/kg) twice a day at 4-h intervals on days 0 and 9.. These results corroborate the therapeutic advantage of combining hypoxia-selective cytotoxins such as NLCQ-1 and TPZ with chemotherapy.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Bone Marrow; Drug Synergism; Female; Fluorouracil; Hypoxia; Imidazoles; Mice; Mice, Inbred BALB C; Quinolines; Tirapazamine; Triazines; Tumor Cells, Cultured; Tumor Stem Cell Assay

Combined radioimmunotherapy (RAIT) and hypoxic cytotoxin therapy (SR4233 or NLCQ-1) have been evaluated with both modalities administered on the same day with only moderate improvement compared with the effects of RAIT alone. In a series of studies using oxygen electrodes, immunohistochemistry and radiotracers, we have demonstrated that RAIT induces a prolonged state of hypoxia in most tumors, without affecting the pO(2) levels in normal tissues. Using serial microelectrode measurements through subcutaneous (s.c.) GW-39 human colonic xenografts, we established that the median pO(2) was unrelated to the initial size of the tumor, over a range of sizes from 1.0 to 4.0 cm. Fourteen days after mice were given a 240-microCi dose of (131)I-MN-14 anti-carcinoembryonic antigen immunoglobulin G, their median pO(2) declined from 26.1 +/- 9.6 mmHg to 9.8 +/- 3.9 mmHg (p < 0.001). Using the radiotracer (3)H-MISO that accumulates in hypoxic regions, uptake in GW-39, LoVo and LS174T s.c. human colonic tumors increased 3.0- to 4.2-fold from day 14 through day 28 post-RAIT, but uptake of (3)H-MISO in CALU-3 tumors remained unchanged after RAIT. Normal tissue (liver, kidney, lung) uptake of (3)H-MISO did not exhibit significant changes. The increase in tumor hypoxia was also demonstrated visually using anti-PIMO staining of tumor sections. We postulated that sequential delivery of the 2 therapeutic agents, with the hypoxic cytotoxin given 2 weeks after RAIT when tumor pO(2) levels were at their nadir, would improve the therapeutic response above either modality alone or above the 2 agents delivered on the same day. Tumor growth was compared in mice given either RAIT or cytotoxin alone, the combined treatment on the same day or with the cytotoxin delivered 14 days after RAIT. Tumor size on day 35 for RAIT-treated and SR4233-treated GW-39 were 3.56 +/- 0.40 and 7.98 +/- 2.50 cm(3). When RAIT + SR4233 were delivered on the same day, tumor size dropped to 2.78 +/- 0.80 cm(3). If RAIT was given on day 0 and SR4233 on day 14, size further declined further to 1.74 +/- 0.32 cm(3) (p < 0.05 compared with same day delivery). For LS174T, tumor size on day 28 for RAIT-treated and SR4233-treated tumors were 1.14 +/- 0.36 cm(3) and 3.65 +/- 0.78 cm(3), respectively. When RAIT + SR4233 were delivered on the same day, size was 0.51 +/- 0.174 cm(3). If RAIT was dosed on day 0 and SR4233 was given on day 14, tumor size was 0.13 +/- 0.07 cm(3) (p < 0.05). Similar results were obtained for L

Topics: Animals; Antineoplastic Agents; Carcinoembryonic Antigen; Cell Hypoxia; Combined Modality Therapy; Cytotoxins; Drug-Related Side Effects and Adverse Reactions; Female; Humans; Hypoxia; Imidazoles; Immunoglobulin G; Mice; Mice, Nude; Microelectrodes; Neoplasm Transplantation; Neoplasms; Oxygen; Quinolines; Radiation-Sensitizing Agents; Radioimmunotherapy; Time Factors; Tirapazamine; Triazines; Tumor Cells, Cultured

The bioreductive anticancer prodrug CI-1010 ((2R)-1-[(2-bromoethyl)amino]-3-(2-nitro-1H-imidazol-1-yl)-2-propanol hydrobromide) is an alkylating nitroimidazole which shows selective toxicity against hypoxic cells in murine tumors, but causes extensive apoptosis in the outer retina in rodents and monkeys. This irreversible retinal toxicity has terminated preclinical development of CI-1010. We have investigated whether such toxicity is due to physiological hypoxia in the retina, and whether it is a general feature of hypoxia-selective bioreductive drugs. Retinal damage was quantified by morphometric analysis of histological sections following treatment of female C57Bl6 mice. Both CI-1010 and tirapazamine (TPZ, 1,2,4-benzotriazin-3-amine 1,4-dioxide), a bioreductive drug in Phase III clinical trial, caused a time and dose-dependent loss of photoreceptor cells of the outer retina following administration of single intraperitoneal doses. The lesion caused by TPZ was qualitatively similar to that with CI-1010, but was less severe at equivalent fractions of the maximum tolerated dose (as defined by lethality). With both bioreductive drugs, lesion severity was increased if animals breathed 10% O(2) for 3 h after drug administration, while breathing 95% O(2)/5% CO(2) was protective. Other hypoxia-selective bioreductive drugs tested (the quinone porfiromycin, the anthraquinone N-oxide AQ4N and the nitrogen mustard prodrugs SN 23816 and SN 25341) did not cause retinal damage at their maximum tolerated doses. This study suggests that the retinal toxicity of bioreductive drugs might be avoided by manipulation of tissue hypoxia using 95% O(2)/5% CO(2), although this intervention could suppress antitumor activity. The finding that not all bioreductive drugs cause retinal toxicity suggests this toxicity can be avoided through appropriate drug design.

Topics: Animals; Antineoplastic Agents; Dose-Response Relationship, Drug; Female; Hypoxia; Light; Mice; Mice, Inbred C57BL; Nitroimidazoles; Oxidation-Reduction; Prodrugs; Radiation-Sensitizing Agents; Retina; Tirapazamine; Triazines

Tirapazamine (TPZ) is a bioreductive drug that exhibits greatly enhanced cytotoxicity in hypoxic tumor cells, which are frequently radiation-resistant and chemoresistant. TPZ exhibits particularly good activity when combined with alkylating agents such as cyclophosphamide (CPA). The present study examines the potential of combining TPZ with CPA in a cytochrome P450-based prodrug activation gene therapy strategy. Recombinant retroviruses were used to transduce 9L gliosarcoma cells with the genes encoding P450 2B6 and NADPH-P450 reductase. Intratumoral coexpression of P450 2B6 with P450 reductase sensitized 9L tumor cells to CPA equally well under normoxic (19.6% O2) and hypoxic (1% O2) conditions. The P450 2B6/P450 reductase combination also sensitized 9L tumor cells to TPZ under both culture conditions. Interestingly, bystander cytotoxic effects were observed for both CPA and TPZ under hypoxia. Furthermore, TPZ exerted a striking growth-inhibitory effect on CPA-treated 9L/2B6/P450 reductase cells under both normoxia and hypoxia, which suggests the utility of this drug combination for P450-based gene therapy. To evaluate this possibility, 9L tumor cells were transduced in culture with P450 2B6 and P450 reductase and grown as solid tumors in severe combined immune deficient mice in vivo. Although these tumors showed little response to TPZ treatment alone, tumor growth was significantly delayed, by up to approximately four doubling times, when TPZ was combined with CPA. Some toxicity from the drug combination was apparent, however, as indicated by body weight profiles. These findings suggest the potential benefit of incorporating TPZ, and perhaps other bioreductive drugs, into a P450/P450 reductase-based gene therapy strategy for cancer treatment.

Topics: Animals; Antineoplastic Agents; Antineoplastic Agents, Alkylating; Antineoplastic Combined Chemotherapy Protocols; Body Weight; Cell Division; Cyclophosphamide; Cytochrome P-450 Enzyme System; Dose-Response Relationship, Drug; Gene Transfer Techniques; Genetic Vectors; Gliosarcoma; Humans; Hypoxia; Mice; Mice, SCID; NADH, NADPH Oxidoreductases; NADPH-Ferrihemoprotein Reductase; Neoplasm Transplantation; Oxygen; Prodrugs; Retroviridae; Time Factors; Tirapazamine; Transduction, Genetic; Triazines; Tumor Cells, Cultured

Tirapazamine (TPZ), a new anti-cancer drug activated to a toxic free radical under hypoxic conditions, produces a tumor specific potentiation of cell kill by cisplatin. In the present study we discuss the mechanism and clinical potential of this effect, as well as investigate the influence of p53 mutations on the activity of TPZ.. For in vitro experiments we have used mouse SCCVII tumor cells, minimally transformed mouse embryo fibroblasts (MEFs) from wild-type and p53 knockout mice, and several human NSCLC cell lines. For in vivo experiments we have used RIF-1 tumors implanted subcutaneously into C3H mice.. Prior injection of TPZ into tumor-bearing mice markedly potentiated tumor cell kill by cisplatin, but produced no effect on systemic toxicity. The maximum potentiation occurred when TPZ was injected two to three hours prior to cisplatin administration. Experiments performed with cells in vitro showed a similar synergistic interaction between the two drugs when cells were exposed to TPZ under hypoxic conditions prior to exposure to cisplatin. Experiments with MEFs from either p53 wild-type or p53-knockout mice showed no influence of p53 on the sensitivity of cells to killing by TPZ under hypoxia. A similar lack of influence of p53 on the toxicity to TPZ was obtained for a panel of NSCLC cell lines.. TPZ is a novel anticancer drug that produces tumor selective potentiation of cisplatin and carboplatin in both pre-clinical and clinical studies. The fact that the drug produces no potentiation of the systemic side effects of these drugs, or of other anticancer drugs used in combination with platinum in NSCLC, suggests that TPZ could become a useful agent in the treatment of lung cancer.

Topics: Animals; Antineoplastic Agents; Carboplatin; Carcinoma, Non-Small-Cell Lung; Cell Death; Cisplatin; Drug Interactions; Genes, p53; Humans; Hypoxia; Lung Neoplasms; Mice; Mice, Knockout; Tirapazamine; Transplantation, Heterologous; Triazines; Tumor Cells, Cultured

Interleukin-1 (IL-1) has radioprotective activity in hematopoietic lineages and in other normal cell renewal systems, but little is known about the effects of IL-1 alpha on the radiosensitivity of tumor cell populations. The present studies were conducted to investigate the effects of IL-1 alpha on the radiosensitivity of clonogenic cells in RIF-1 and SCC-7 tumors. Radioresistance was detected within 2-4 after administration of IL-1 alpha (0.5 micrograms/mouse, ip) and characterized by increases in D(o), Dq, alpha/beta and SF2. This radioresistance was similar to that seen in tumors rendered totally hypoxic before X irradiation. Tirapazamine, a hypoxic cell cytotoxin, and IL-1 alpha had synergistic schedule-dependent antitumor activity in vivo, suggesting that IL-1-induced radioresistance in vivo is due to hypoxia. Radioresistance induced by IL-1 alpha was transient, and the data suggested reoxygenation within 12 h. In vitro, IL-1 alpha had no direct effect on the radiosensitivity of SCC-7 cells in tissue culture under aerobic conditions. However, an increase in D(o), alpha/beta and SF2 was seen in clonogenic tumor cells from primary cultures treated with IL-1 alpha under aerobic conditions. Superoxide dismutase and catalase prevented the induction of radioresistance by IL-1 alpha in vitro, suggesting that oxidative responses from tumor macrophages after administration of IL-1 alpha may be responsible for induced radioresistance by IL-1 in vitro. Although oxidant stress induced by IL-1 and in vitro in our models, the mechanisms by which such responses modulate tumor radiosensitivity in vivo and in vitro are likely quite different.

Topics: Animals; Catalase; Cell Survival; Clone Cells; Drug Synergism; Hypoxia; Interleukin-1; Mice; Neoplasms, Experimental; Radiation Injuries, Experimental; Radiation-Protective Agents; Radiation-Sensitizing Agents; Recombinant Proteins; Superoxide Dismutase; Tirapazamine; Triazines; Tumor Cells, Cultured; Whole-Body Irradiation

Topics: Animals; Antineoplastic Agents; Carcinoma; Combined Modality Therapy; Female; Hypoxia; Male; Mice; Mice, Inbred C3H; Radiation-Sensitizing Agents; Tirapazamine; Triazines

The effects of SR-4233 (3-amino-1,2,4-benzotriazine-1,4-dioxide), a hypoxic cell cytotoxic agent, were assayed against the FSaIIC murine fibrosarcoma in vitro and in vivo alone and in conjunction with hyperthermia and radiation. In vitro, a concentration of 500 microM of SR-4233 upon exposure of the cells for 1 h decreased the survival of hypoxic cells by about 1 log more than euoxic cells at 37 degrees C and pH 7.40. At the same concentration at pH 6.45, this difference in cytotoxicity increased to about 3 logs. In conjunction with 42 or 43 degrees C hyperthermia at pH 7.40, the killing of both euoxic and hypoxic cells was markedly increased (hypoxic greater than oxic), and the effect of hyperthermia on SR-4233 cytotoxicity was further increased at pH 6.45. SR-4233 proved to be an effective radiosensitizer of hypoxic cells in vitro, producing an enhancement ratio of 2.6 +/- 0.2 at pH 7.40 and 2.7 +/- 0.2 at pH 6.45. In vivo, however, SR-4233 (50 mg/kg) used with single dose radiation (10, 20, or 30 Gy) did not alter the slope of the radiation dose-dependent tumor growth delay curve but did produce a significant additive increase in tumor growth delay. Local hyperthermia (43 degrees C, 30 min) plus SR-4233 (30 mg/kg) produced a tumor growth delay of 9.1 +/- 2.2 days, whereas SR-4233 alone caused a tumor growth delay of only 1.7 +/- 0.9 days and the hyperthermia, only 1.4 +/- 0.7 days. The tumor growth delay increased to 28.2 +/- 4.4 days with the addition of daily radiation (3 Gy for 5 days) to SR-4233 and hyperthermia given on treatment day 1 only. Hoechst 33342 dye-selected tumor subpopulation analysis at 24 h following treatment demonstrated that SR-4233 (30 mg/kg) was more toxic to dim (presumably hypoxic) cells by about 1.8-fold. The addition of hyperthermia to treatment with SR-4233 increased the killing of dim cells by about 5-fold but of bright cells by only 2-fold. Trimodality treatment with SR-4233, hyperthermia, and radiation increased the killing of bright cells by about 6.5-fold and of dim cells by about 16.5-fold as compared with radiation alone. These results indicate that SR-4233 might be used quite effectively with radiation and/or hyperthermia to treat tumors with significant hypoxic subpopulations.

Topics: Animals; Antineoplastic Agents; Cell Division; Cell Line; Cell Survival; Combined Modality Therapy; Female; Fibrosarcoma; Flow Cytometry; Hot Temperature; Hydrogen-Ion Concentration; Hyperthermia, Induced; Hypoxia; Kinetics; Mice; Mice, Inbred C3H; Sarcoma, Experimental; Tirapazamine; Triazines; Tumor Cells, Cultured

SR 4233 (3-amino-1,2,4-benzotriazine-1,4-dioxide) is presently undergoing investigation as an antitumor agent because of its high selective toxicity for hypoxic cells in vitro and in vivo. It has been found to be 15 to 200 times more toxic to hypoxic rodent and human cell lines than their normoxic counterparts. We investigated the toxicity of SR 4233 in primary cultures of hepatocytes under various oxygen tensions, ranging from 1% to 20% oxygen. The 50% lethal dose of SR 4233 was found to be 50 times lower in hepatocyte monolayers at 1% O2 versus 20% O2. Even at 4% O2, a concentration that prevails in the pericentral area of the liver under conditions of normal blood flow, SR 4233 was an order of magnitude more toxic than at 20% O2. All samples were analyzed for metabolites, and metabolism was found to be dependent on both the SR 4233 concentration and the oxygen tension. Formation of the major metabolite SR 4317 occurred to the greatest extent at the lowest oxygen concentration and the highest SR 4233 concentration. Very little metabolism occurred at 10 to 20% O2, which is in agreement with data in Chinese hamster ovary cells under aerobic conditions.

Topics: Animals; Antineoplastic Agents; Cell Survival; Cells, Cultured; Hypoxia; Kinetics; Liver; Male; Oxygen; Rats; Rats, Inbred F344; Tirapazamine; Triazines