semaxinib and orantinib

The vascularization is a very important part of a structure of each tissue both normal, including bone marrow stroma, and pathologically changed. Neoplastic tissues secure supplying in necessary substances for growth and expansion through regulated by its own cells neovasculation. Key role in multipotential cell's differentiation to endothelial cells plays regulatory system consisted of vascular-epithelial growth factor's family (VEGF B, C, D), receptors VEGFR-1, -2, -3, and system Tie2/angiopoetins. Stimulation and importance of angiogenesis for expansion of neoplastic diseases is a current problem in oncology. It is pointed to importance of neovascularization in pathogenesis of acute and chronic leukemias, lymphomas and multiple myeloma. The knowledge of the importance ofvascularization of neoplastic tissues is availing in therapy (researching of substances inhibiting angiogenesis--semaxinib, SU6668, ZD 6474, thalidomid, cetuximab, gefitinib, interferon-alpha, irradiation and others), in diagnostics as a monitoring of a success of the therapy, and in prognosis. Inhibitors ofangiogenesis are antineoplastic drugs with relatively lower toxicity, and lower risk of drug-resistance than conventional chemotherapy what has the importance especially during prolong administration, so they can be an alternative way of therapeutic process. During qualification for antiangiogenic therapy it is necessary to have a consciousness of its limited efficiency.

Topics: Angiogenesis Inducing Agents; Angiogenesis Inhibitors; Angiopoietin-1; Angiopoietin-2; Hematologic Neoplasms; Humans; Indoles; Leukemia, Lymphocytic, Chronic, B-Cell; Leukemia, Myeloid, Acute; Multiple Myeloma; Myelodysplastic Syndromes; Neoplasm Metastasis; Neovascularization, Pathologic; Oxindoles; Precursor Cell Lymphoblastic Leukemia-Lymphoma; Propionates; Pyrroles; Receptor, TIE-2; Receptors, Vascular Endothelial Growth Factor; Vascular Endothelial Growth Factors

Acute myelogenous leukemia (AML) is a difficult disease to treat. Novel treatment strategies, including molecular targeted therapy, are currently being explored. The c-kit receptor represents a potential therapeutic target for AML. The receptor is expressed on more than 10% of blasts in 64% of de novo AMLs and 95% of relapsed AMLs. C-kit mediates proliferation and anti-apoptotic effects in AML. This review will discuss the biology of c-kit in normal and malignant hematopoiesis, and the recent clinical trials targeting c-kit in AML.

Topics: Acute Disease; Angiogenesis Inhibitors; Animals; Antineoplastic Agents; Benzamides; Cell Line, Tumor; Clinical Trials as Topic; Hematopoiesis; Humans; Imatinib Mesylate; Indoles; Leukemia, Myeloid; Mice; Oxindoles; Piperazines; Propionates; Protein Kinase Inhibitors; Protein Processing, Post-Translational; Proto-Oncogene Proteins c-kit; Pyrimidines; Pyrroles; Stem Cell Factor

The realization that the growth and spread of tumors are dependent on angiogenesis has created new avenues of research designed to help us to better understand cancer biology and to facilitate the development of new therapeutic strategies. However, the process of angiogenesis consists of multiple sequential and interdependent steps with a myriad of positive and negative regulators of angiogenesis being involved. The survival of tumors and thus their metastases are dependent on the balance of endogenous angiogenic and antiangiogenic factors such that the outcome favors increased angiogenesis. Several growth factors have been identified that regulate angiogenesis in colon cancer; the most important of these is vascular endothelial growth factor. In addition, specific integrins such as alphavbeta3 and alpha5beta1 mediate endothelial cell survival and have been shown to be overexpressed on the endothelium of colon cancer. These angiogenic mediators thus serve as targets for therapy of metastatic colon cancer and have shown promise in preclinical trials.

Topics: Angiogenesis Inhibitors; Animals; Antibodies, Monoclonal; Colonic Neoplasms; Colorectal Neoplasms; Endothelial Growth Factors; Extracellular Matrix; Humans; Indoles; Integrins; Intercellular Signaling Peptides and Proteins; Lymphokines; Neovascularization, Pathologic; Oxindoles; Propionates; Pyrroles; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors

Activation of the KIT tyrosine kinase by somatic mutation has been documented in a number of human malignancies, including gastrointestinal stromal tumor (GIST), seminoma, acute myelogenous leukemia (AML), and mastocytosis. In addition, paracrine or autocrine activation of this kinase has been postulated in numerous other malignancies, including small-cell lung cancer and ovarian cancer. In this review, we discuss the rationale for and development of KIT tyrosine kinase inhibitors for the treatment of human malignancies.. Studies were identified through a MEDLINE search, review of bibliographies of relevant articles, and review of abstracts from national meetings.. Four tyrosine kinase inhibitors that have activity against KIT are currently being used in clinical trials, and one, STI571, has recently been approved by the United States Food and Drug Administration for treating patients with chronic myelogenous leukemia. The role of KIT inhibitors in treating KIT-positive malignancies is reviewed.. Targeted therapy to inhibit the kinase activity of KIT is a rational approach to the treatment of KIT-positive malignancies. Two key factors are the potency of a given inhibitor and the relative contribution of KIT activation to the growth of the tumor. Given our current understanding of KIT activity in human malignancy, the best candidate diseases for treatment with KIT inhibitors are GIST, mastocytosis, seminoma and possibly some cases of AML. Additionally, KIT inhibitors may play an adjunctive role in diseases such as small-cell lung cancer, in which KIT activation is secondary to ligand binding rather than an acquired mutation.

Topics: Angiogenesis Inhibitors; Benzamides; Enzyme Inhibitors; Humans; Imatinib Mesylate; Indoles; Mutation; Neoplasms; Oxindoles; Piperazines; Propionates; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-kit; Pyrimidines; Pyrroles

It is important to survey the molecular targets which are involved in tumor angiogenesis for the development of antiangiogenic agents as one of the cancer therapy. This article is meant to review the recent molecular targets of tumor angiogenesis and the molecular mechanism of antiangiogenic agents in human clinical trials.

Topics: Angiogenesis Inhibitors; Angiostatins; Animals; Antigens, CD; Antineoplastic Agents; Cadherins; ErbB Receptors; Gefitinib; Humans; Indoles; Mice; Neoplasms; Oxindoles; Peptide Fragments; Plasminogen; Propionates; Pyrroles; Quinazolines; Vascular Cell Adhesion Molecule-1

Photodynamic therapy (PDT) is a promising therapeutic modality using a tumor localizing photosensitizer and light to destroy tumor cells. A major limitation of PDT is tumor recurrence, which is partly due to neovascularization.. The objective of the present study was to determine whether combination therapy with PDT and antiangiogenic agents (i.e. SU5416 and SU6668) would be more effective in controlling tumor recurrence in a mouse model of human CNE2 poorly differentiated nasopharyngeal carcinoma compared with PDT or antiangiogenic agents administered alone.. Athymic mice bearing CNE2 tumor xenografts received daily i.p. injections of 20 mg/kg SU5416 or 100 mg/kg SU6668 for 28 consecutive days either alone or following a single hypericin-PDT treatment.. Significant inhibition of CNE2 tumor growth was observed in all treatment groups. Differences in 4x tumor growth time, the number of mice with 4x tumor growth, tumor growth inhibition as well as the percent of mice surviving were not statistically significant among individual treatment groups. However, the number of mice with 4x tumor growth observed in SU6668 monotherapy and combined PDT and SU6668 treatment groups was significantly less than that in the control group (P<0.05 and 0.01, respectively). Moreover, compared with the control group, only the combined PDT and SU6668 treatment significantly extended survival of tumor-bearing host mice (P<0.05). The semiquantitative RT-PCR results showed that the expression of HIF-1alpha, VEGF, COX-2 and bFGF were increased in PDT-treated tumor samples collected 24 h post-PDT, suggesting that PDT-induced damage to tumor microvasculature and the resultant hypoxia upregulate the expression of certain proangiogenic factors.. The effectiveness of PDT can be enhanced by antiangiogenic treatment with the synthetic RTK inhibitors. Of the two synthetic RTK inhibitors tested, SU6668 was more effective than SU5416 in enhancing tumor responsiveness to PDT.

Topics: Adenocarcinoma; Angiogenesis Inhibitors; Animals; Anthracenes; Antineoplastic Agents; Chemotherapy, Adjuvant; Drug Screening Assays, Antitumor; Gene Expression; Indoles; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Nasopharyngeal Neoplasms; Neoplasm Transplantation; Neoplasms, Experimental; Oxindoles; Perylene; Photochemotherapy; Propionates; Protein-Tyrosine Kinases; Proteins; Pyrroles; Survival Rate

With the goal of developing multitargeted receptor tyrosine kinase inhibitors that display potent inhibition against PDGFRβ and VEGFR-2 we designed and synthesized eleven N(4)-(3-bromophenyl)-7-(substitutedbenzyl) pyrrolo[2,3-d]pyrimidines 9a-19a. These compounds were obtained from the key intermediate N(4)-(3-bromophenyl)-7H-pyrrolo[2,3-d]pyrimidine-2,4-diamine 29. Various arylmethyl groups were regiospecifically attached at the N7 of 29 via sodium hydride induced alkylation with substituted arylmethyl halides. Compounds 11a and 19a were potent dual inhibitors of PDGFRβ and VEGFR-2. In a COLO-205, in vivo tumor mouse model 11a demonstrated inhibition of tumor growth, metastasis, and tumor angiogenesis that was better than or comparable to the standard compound TSU-68 (SU6668, 8).

Topics: Animals; Binding Sites; Cell Line, Tumor; Cell Movement; Cell Proliferation; Disease Models, Animal; Drug Design; Humans; Indoles; Mice; Mice, Nude; Molecular Dynamics Simulation; Neoplasms; Oxindoles; Propionates; Protein Kinase Inhibitors; Protein Structure, Tertiary; Pyrimidines; Pyrroles; Receptor, Platelet-Derived Growth Factor beta; Transplantation, Heterologous; Vascular Endothelial Growth Factor Receptor-2

Investigations on the combination of radiotherapy with vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) antiangiogenic agents, which has the potential to improve the clinical outcome in cancer patients.. Here, we analyze the combined VEGF (SU5416) and PDGF (SU6668) receptor tyrosine kinase inhibition with irradiation in human endothelium (HUVEC), prostate cancer (PC3), and glioblastoma (U87) in vitro and in vivo.. Combined inhibition of VEGF and PDGF signaling resulted in enhanced apoptosis, reduced cell proliferation, and clonogenic survival as well as reduced endothelial cell migration and tube formation compared with single pathway inhibition. These effects were further enhanced by additional irradiation. Likewise, in PC3 and U87 tumors growing s.c. on BALB/c nu/nu mice, dual inhibition of VEGF and PDGF signaling significantly increased tumor growth delay versus each monotherapy. Interestingly, radiation at approximately 20% of the dose necessary to induce local tumor control exerts similar tumor growth-inhibitory effects as the antiangiogenic drugs given at their maximum effective dose. Addition of radiotherapy to both mono- as well as dual-antiangiogenic treatment markedly increased tumor growth delay. With respect to tumor angiogenesis, radiation further decreased microvessel density (CD31 count) and tumor cell proliferation (Ki-67 index) in all drug-treated groups. Of note, the slowly growing PC3 tumor responded better to the antiangiogenic drug treatments than the faster-growing U87 tumor. In addition to the beneficial effect of abrogating VEGF survival signaling when combined with radiation, we identified here a novel mechanism for the tumor escape from radiation damage. We found that radiation induced up-regulation of all four isoforms of PDGF (A-D) in endothelial cells supporting adjacent smooth muscle cells resulting in a prosurvival effect of radiation. The addition of SU6668 attenuated this undesirable paracrine radiation effect, which may rationalize the combined application of radiation with PDGF signaling inhibition to increase antitumor effects.. A relative low radiation dose markedly enhances local antitumor effects of combined VEGF and PDGF signaling inhibition, suggesting a promising combination regimen for local tumor treatment with radiotherapy remaining an essential element.

Topics: Angiogenesis Inhibitors; Animals; Apoptosis; Cell Line, Tumor; Cell Proliferation; Combined Modality Therapy; Endothelial Cells; Flow Cytometry; Humans; Immunohistochemistry; Indoles; Mice; Mice, Nude; Neoplasms; Neovascularization, Pathologic; Oxindoles; Propionates; Protein Kinase Inhibitors; Pyrroles; Radiation-Sensitizing Agents; Radiotherapy; Receptors, Platelet-Derived Growth Factor; Receptors, Vascular Endothelial Growth Factor; Reverse Transcriptase Polymerase Chain Reaction; Xenograft Model Antitumor Assays

Angiogenesis represents the crucial step in the pathogenesis of endometriosis, because endometriotic lesions require neovascularization to establish, proliferate and invade inside the peritoneal cavity. To elucidate the role of angiogenic factors, we investigated in vivo whether blockade of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) affects angiogenesis of ectopic endometrium.. Mechanically isolated endometrial fragments were transplanted into the dorsal skinfold chamber of hormonally synchronized hamsters. Subsequently, we analysed the effect of the VEGF inhibitor SU5416 and the combined VEGF, FGF and PDGF inhibitor SU6668 on angiogenesis of the ectopic endometrium over a time-period of 14 days using intravital fluorescence microscopy.. Selective blockade of VEGF resulted in a slight reduction of microvessel density when compared to control animals. In contrast, combined inhibition of all three growth factors significantly suppressed angiogenesis of endometrial grafts, as indicated by a reduced size of the microvascular network and a decreased microvessel density. This was caused by an inhibition of blood vessel maturation.. Vascularization of endometriotic lesions is not solely driven by VEGF, but depends on the cross-talk between VEGF, FGF and PDGF. Thus, the combined inhibition of these growth factors may represent a novel therapeutic strategy in the treatment of endometriosis.

Topics: Angiogenesis Inhibitors; Animals; Capillaries; Cricetinae; Endometriosis; Endometrium; Female; Fibroblast Growth Factors; Indoles; Mesocricetus; Neovascularization, Pathologic; Oxindoles; Platelet-Derived Growth Factor; Propionates; Protein Kinase Inhibitors; Pyrroles; Uterine Diseases; Vascular Endothelial Growth Factor A

The oncogenic RET/PTC tyrosine kinase causes papillary thyroid cancer (PTC). The use of inhibitors specific for RET/PTC may be useful for targeted therapy of PTC.. The objective of the study was to evaluate the efficacies of the recently developed kinase inhibitors SU11248, SU5416, and SU6668 in inhibition of RET/PTC.. SU11248, SU5416, and SU6668 were synthesized, and their inhibitory potencies were evaluated using an in vitro RET/PTC kinase assay. The inhibitory effects of the compounds on RET/PTC were evaluated by quantifying the autophosphorylation of RET/PTC, signal transducer and activator of transcription (STAT)-3 activation, and the morphological reversal of RET/PTC-transformed cells.. An in vitro kinase assay revealed that SU5416, SU6668, and SU11248 inhibited phosphorylation of the synthetic tyrosine kinase substrate peptide E4Y by RET/PTC3 in a dose-dependent manner with IC(50) of approximately 944 nm for SU5416, 562 nm for SU6668, and 224 nm for SU11248. Thus, SU11248 effectively inhibits the kinase activity of RET/PTC3. RET/PTC-mediated Y705 phosphorylation of STAT3 was inhibited by addition of SU11248, and the inhibitory effects of SU11248 on the tyrosine phosphorylation and transcriptional activation of STAT3 were very closely correlated with decreased autophosphorylation of RET/PTC. SU11248 caused a complete morphological reversion of transformed NIH-RET/PTC3 cells and inhibited the growth of TPC-1 cells that have an endogenous RET/PTC1.. SU11248 is a highly effective tyrosine kinase inhibitor of the RET/PTC oncogenic kinase.

Topics: Administration, Oral; Animals; Antineoplastic Agents; Cell Proliferation; Humans; Indoles; Mice; NIH 3T3 Cells; Oxindoles; Phosphorylation; Propionates; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-ret; Pyrroles; STAT3 Transcription Factor; Sunitinib

To determine the effects of small molecule inhibitors of vascular endothelial growth factor receptor (VEGFR)-2 (SU5416 and SU6668) on receptor phosphorylation in tumor xenografts and in paired tumor biopsies obtained in three clinical trials in patients with advanced solid malignancies.. The dose-dependent effects of SU6668 on angiogenesis and tumor growth were investigated in orthotopic L3.6pl pancreatic tumors. Excisional or 18G core biopsies were obtained from patients before and after therapy with SU5416 or SU6668. Laser scanning cytometry-mediated analysis was used to quantify levels of phosphorylated and total VEGFRs and platelet-derived growth factor receptors (PDGFR), tumor microvessel densities, vessel sizes, and endothelial and tumor cell apoptosis.. Significant inhibition of tumor microvessel density and growth and increased apoptosis were observed at SU6668 maximum tolerated dose (100 mg/kg) in L3.6pl xenografts. At 6 hours post therapy, SU6668 reduced VEGFR and PDGFR phosphorylation in the tumors by 50% and 92%, respectively, but levels rebounded beyond the baselines by 24 hours. Levels of phosphorylated VEGFR-2 and PDGFR also decreased significantly ( approximately 50%) 6 hours after therapy in 1 of 6 primary human tumors treated with SU6668, but these effects were not associated with increased apoptosis. A significant increase in endothelial cell apoptosis was observed in one tumor exposed to SU5416 and was associated with an increase in vessel size, but these changes occurred without an increase in tumor cell death.. SU5416 and SU6668 displayed biological activity in xenografts. However, neither drug produced marked biological activity in primary patient tumors.

Topics: Adult; Aged; Aged, 80 and over; Animals; Apoptosis; Dose-Response Relationship, Drug; Endothelium, Vascular; Female; Humans; Indoles; Male; Mice; Mice, Nude; Middle Aged; Neovascularization, Pathologic; Oxindoles; Pancreatic Neoplasms; Phosphorylation; Propionates; Pyrroles; Receptor, Platelet-Derived Growth Factor beta; Transplantation, Heterologous; Vascular Endothelial Growth Factor Receptor-2

One of the emerging problems concerning the use of antiangiogenic drugs, when used in combination with certain chemotherapy regimens, is enhanced rates and severity of adverse clotting events. For as yet unknown reasons, certain drugs and particular combinations can induce an elevated incidence of thromboembolic events in treated cancer patients [e.g., SU5416, a vascular endothelial cell growth factor receptor-2 (VEGFR-2) antagonist, when combined with gemcitabine and cisplatin (CDDP)]. Such results highlight the need to develop assays capturing the essence of enhanced clot formation under such combination treatment and which may have predictive potential as well. Here, we report the possibility of such an assay (i.e., the ratio of tissue factor over tissue factor pathway inhibitor expression or activity in cultured human endothelial cells calculated as a coagulation index). A marked increase in coagulation index was observed after exposure to SU5416 and the CDDP/gemcitabine chemotherapy combination in contrast to either of these treatments used alone. Substitution of SU5416 with any one of ZD6474, SU6668, IMC-1121, a monoclonal antibody to VEGFR-2, or an antibody to VEGF (bevacizumab) did not cause a marked increase in the coagulation index, nor did the combination of SU5416 with 5-fluorouracil and leucovorin. Finally, we noted that reducing the concentrations of gemcitabine and CDDP (i.e., use of "metronomic dosing" in vitro) significantly attenuated the coagulation index increase induced by these drugs, suggesting that use of low-dose chemotherapy regimens might be an approach to consider for reducing the incidence of adverse clotting events associated with chemotherapy alone or in conjunction with antiangiogenic drug combination therapies.

Topics: Angiogenesis Inhibitors; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Combined Chemotherapy Protocols; Bevacizumab; Blood Coagulation; Cells, Cultured; Cisplatin; Deoxycytidine; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Synergism; Endothelial Cells; Gemcitabine; Humans; Indoles; Oxindoles; Piperidines; Propionates; Pyrroles; Quinazolines; Thromboplastin

Destruction of existing tumor blood vessels may be achieved by targeting vascular endothelial growth factor (VEGF) signaling, which mediates not only endothelial cell proliferation but also endothelial cell survival. In this study, however, intravital microscopy failed to demonstrate that targeting of VEGFR-2 (by the tyrosine kinase inhibitor SU5416) induces significant regression of experimental tumor blood vessels. Immunohistochemistry, electron microscopy, expression analyses, and in situ hybridization provide evidence that this resistance of tumor blood vessels to VEGFR-2 targeting is conferred by pericytes that stabilize blood vessels and provide endothelial cell survival signals via the Ang-1/Tie2 pathway. In contrast, targeting VEGFR-2 plus the platelet-derived growth factor receptor (PDGFR)-beta system (PDGFR-beta) signaling (by SU6668) rapidly forced 40% of tumor blood vessels into regression, rendering these tumors hypoxic as shown by phosphorescence quenching. TUNEL staining, electron microscopy, and apoptosis blocking experiments suggest that VEGFR-2 plus PDGFR-beta targeting enforced tumor blood vessel regression by inducing endothelial cell apoptosis. We further show that this is achieved by an interference with pericyte-endothelial cell interaction. This study provides novel insights into the mechanisms of how 1) pericytes may provide escape strategies to anti-angiogenic therapies and 2) novel concepts that target not only endothelial cells but also pericyte-associated pathways involved in vascular stabilization and maturation exert potent anti-vascular effects.

Topics: Animals; Apoptosis; Cell Survival; Hypoxia; Indoles; Microcirculation; Models, Biological; Neoplasms; Neovascularization, Pathologic; Oxindoles; Pericytes; Platelet-Derived Growth Factor; Propionates; Pyrroles; Receptor, Platelet-Derived Growth Factor beta; Signal Transduction; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-2

The proto-oncogene c-myc is involved in the regulation of cell proliferation, differentiation, and apoptosis. In this study, we used an inducible transgenic mouse model in which c-Myc was targeted to the epidermis and, after activation, gave rise to hyperplastic and dysplastic skin lesions and to dermal angiogenesis, involving both vascular endothelial growth factor (VEGF) receptor-1 and VEGF receptor-2. After c-Myc activation, VEGF mRNA was expressed in postmitotic keratinocytes where it colocalized with transgene expression and areas of tissue hypoxia, suggesting a role of hypoxia in VEGF induction. In vitro, c-Myc activation alone was able to induce VEGF protein release and in conjunction with hypoxia, c-Myc activation further increased VEGF protein. Blocking VEGF signaling in vivo significantly reduced dermal angiogenesis, demonstrating the importance of VEGF as a mediating factor for the c-Myc-induced angiogenic phenotype.

Topics: Animals; Cell Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Indoles; Keratinocytes; Mice; Neovascularization, Physiologic; Oxindoles; Papilloma; Precancerous Conditions; Propionates; Proto-Oncogene Proteins c-myc; Pyrroles; RNA, Messenger; Skin; Skin Neoplasms; Tamoxifen; Transcription Factors; Transgenes; Vascular Endothelial Growth Factor A

The cancer process in a combination of two kinds of events: a multistep cellular genetic defects giving cells independent growth and great adaptation capability, a multistep interactions profiles with what is called the stromal reaction from the original in situ tumor to the invasive metastatic and angiogenic tumor. The immune system plays an important role in the control of the cancer process but always must be seen as a part integrated in the stromal reaction. In order to boost the immune system capability to treat a cancer we must never forget these cellular and tissular dimensions. Interleukins, growth factors and monoclonal antibodies are new agents are able to bring immunotherapy of cancer to reality. Interleukin 2 did not match our dreams of the ideal factor which can stimulate the defective immune system and bring the cancer evolution to an end. The little but real remissions obtained with the IL-2 high dose protocols still sustains our trust of the immune system as a critical barrier to cancer evolution but the numerous side effects reminds us that cytokines are not to be used as antibiotics and hormones. IL-2 is a regulator of the immune system at the microenvironment level, therefore flooding the blood circulation with high IL-2 doses is not appropriate. We have also to understand that IL-2 can interact directly with cancer cells and also with stromal cells (endothelial and fibroblastic cells), the outcome of IL-2 immunotherapy is not restricted to the interactions with immune cells.

Topics: Cytokines; Humans; Immunotherapy; Indoles; Interleukin-2; Neoplasm Metastasis; Neoplasms; Neovascularization, Pathologic; Oxindoles; Propionates; Protein-Tyrosine Kinases; Pyrroles; Receptors, Interleukin-2

Functions of receptor tyrosine kinases implicated in angiogenesis were pharmacologically impaired in a mouse model of pancreatic islet cancer. An inhibitor targeting VEGFRs in endothelial cells (SU5416) is effective against early-stage angiogenic lesions, but not large, well-vascularized tumors. In contrast, a kinase inhibitor incorporating selectivity for PDGFRs (SU6668) is shown to block further growth of end-stage tumors, eliciting detachment of pericytes and disruption of tumor vascularity. Importantly, PDGFRs were expressed only in perivascular cells of this tumor type, suggesting that PDGFR(+) pericytes in tumors present a complimentary target to endothelial cells for efficacious antiangiogenic therapy. Therapeutic regimes combining the two kinase inhibitors (SU5416 and SU6668) were more efficacious against all stages of islet carcinogenesis than either single agent. Combination of the VEGFR inhibitor with another distinctive kinase inhibitor targeting PDGFR activity (Gleevec) was also able to regress late-stage tumors. Thus, combinatorial targeting of receptor tyrosine kinases shows promise for treating multiple stages in tumorigenesis, most notably the often-intractable late-stage solid tumor.

Topics: Angiogenesis Inhibitors; Animals; Antineoplastic Combined Chemotherapy Protocols; Blood Vessels; Carcinoma, Islet Cell; Endothelium, Vascular; Female; Indoles; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neovascularization, Pathologic; Oxindoles; Pericytes; Platelet-Derived Growth Factor; Propionates; Protein-Tyrosine Kinases; Pyrroles; Receptors, Platelet-Derived Growth Factor; Receptors, Vascular Endothelial Growth Factor

In recent decades, radiation research has concentrated primarily on the cancer cell compartment. Much less is known about the effect of ionizing radiation on the endothelial cell compartment and the complex interaction between tumor cells and their microenvironment. Here we report that ionizing radiation is a potent antiangiogenic agent that inhibits endothelial cell survival, proliferation, tube formation and invasion. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor were able to reduce the radiosensitivity of endothelial cells. Yet, it is also found that radiation induces angiogenic factor production by tumor cells that can be abrogated by the addition of antiangiogenic agents. Receptor tyrosine kinase inhibitors of Flk-1/KDR/VEGFR2, FGFR1 and PDGFR beta, SU5416, and SU6668 enhanced the antiangiogenic effects of direct radiation of the endothelial cells. In a coculture system of PC3 prostate cancer cells and endothelial cells, isolated irradiation of the PC3 cells enhanced endothelial cell invasiveness through a Matrigel matrix, which was inhibited by SU5416 and SU6668. Furthermore, ionizing radiation up-regulated VEGF and basic fibroblast growth factor in PC3 cells and VEGFR2 in endothelial cells. Together these findings suggest a radiation-inducible protective role for tumor cells in the support of their associated vasculature that may be down-regulated by coadministration of angiogenesis inhibitors. These results rationalize concurrent administration of angiogenesis inhibitors and radiotherapy in cancer treatment.

Topics: Angiogenesis Inhibitors; Cell Division; Cells, Cultured; Dose-Response Relationship, Radiation; Endothelial Growth Factors; Endothelium, Vascular; Fibroblast Growth Factor 2; Humans; Indoles; Intercellular Signaling Peptides and Proteins; Kinetics; Lymphokines; Male; Neoplasm Invasiveness; Neovascularization, Pathologic; Oxindoles; Particle Accelerators; Propionates; Prostatic Neoplasms; Pyrroles; Reverse Transcriptase Polymerase Chain Reaction; Tumor Cells, Cultured; Umbilical Veins; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors; X-Rays

A study designed to compare the effects on VEGF-induced angiogenesis of a number of known anti-angiogenic agents together with some novel derivatives thereof was undertaken. Thus the isoflavone biochanin A 1[structure: see text], indomethacin 2[structure: see text], the 3-arylquinoxaline SU1433 and its derivatives 3-6[structure: see text], the benzoic acid derivative 7[structure: see text], the oxindoles SU5416 8[structure: see text] and SU6668 11[structure: see text], together with their simple N-benzyl derivatives 9, 10, and 12[structure: see text] were selected for study. Using an in vitro assay the compounds were evaluated for their ability to inhibit VEGF-induced angiogenesis in HUVECs, and the cytotoxicity of representative compounds was also studied in tumour cell lines using 24-h exposure. The results indicate that the SU compounds, SU1433, SU 5416 and SU6668, are more potent inhibitors of VEGF-induced angiogenesis than indomethacin or the naturally occurring biochanin A, presumably because they inhibit VEGF receptor signalling. Blocking one of the phenolic OH groups of SU1433 reduced anti-angiogenic activity, as did blocking the NH groups of SU5416 and SU6668. Cytotoxicity studies indicate that none of the compounds examined exhibited cytotoxicity at anti-angiogenic concentrations.

Topics: Angiogenesis Inhibitors; Endothelium, Vascular; Humans; Indoles; Isoflavones; Neoplasms; Neovascularization, Pathologic; Oxindoles; Propionates; Pyrroles; Quinoxalines

SU5416 and SU6668 are potent antiangiogenic small-molecule inhibitors of receptor tyrosine kinases, including those of the vascular endothelial growth factor and platelet-derived growth factor receptor families. The stem cell factor (SCF) receptor, c-kit, is structurally related to these receptors and, although not expressed on mature peripheral blood cells, is expressed in leukemic blasts derived from 60% to 80% of acute myeloid leukemia (AML) patients. The c-kit kinase inhibitory activity of SU5416 and SU6668 was evaluated in MO7E cells, a human myeloid leukemia cell line. Tyrosine autophosphorylation of the receptor, induced by SCF, was inhibited in these cells by SU5416 and SU6668 in a dose-dependent manner (inhibitory concentration of 50% [IC(50)] 0.1-1 microM). Inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, a signaling event downstream of c-kit activation, was also inhibited in a dose-dependent manner. Both compounds also inhibited SCF-induced proliferation of MO7E cells (IC(50) 0.1 microM for SU5416; 0.29 microM for SU6668). Furthermore, both SU5416 and SU6668 induced apoptosis in a dose- and time-dependent manner as measured by the increase in activated caspase-3 and the enhanced cleavage of its substrate poly(ADP-ribose) polymerase. These findings with MO7E cells were extended to leukemic blasts from c-kit(+) patients. In patient blasts, both SU5416 and SU6668 inhibited SCF-induced phosphorylation of c-kit and ERK1/2 and induced apoptosis. These studies indicate that SU5416 and SU6668 inhibit biologic functions of c-kit in addition to exhibiting antiangiogenic properties and suggest that the combination of these activities may provide a novel therapeutic approach for the treatment of AML.

Topics: Angiogenesis Inhibitors; Apoptosis; Caspase 3; Caspases; Cell Division; Dose-Response Relationship, Drug; Humans; Indoles; Leukemia, Myeloid; Mitogen-Activated Protein Kinases; Oxindoles; Phosphorylation; Propionates; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-kit; Pyrroles; Stem Cell Factor; Tumor Cells, Cultured

Six indolinone tyrosine kinase inhibitors were characterized for their ability to inhibit Kit kinase and for their effects on the growth of small cell lung cancer (SCLC) cell lines. All of the six compounds were potent inhibitors of Kit kinase in a biochemical assay. A homology model of compound binding to the ATP binding site could account for the increased potency observed with the addition of a propionate moiety to the indolinone core but not the increase observed with addition of a chloride moiety. Although all of the compounds tested were potent in the biochemical assay, several exhibited significantly less potency in cellular kinase assays. Their effects on stem cell factor (SCF)-dependent Kit autophosphorylation and SCLC cell growth were also examined. Inhibition of SCF-stimulated Kit activation and cell growth in the H526 cell line was dose-dependent. At concentrations that inhibited SCF-stimulated H526 cell growth, there was little effect on insulin-like growth factor-1-stimulated growth, suggesting that these compounds exhibit reasonable selectivity for inhibition of Kit-mediated proliferation. Higher doses of the compounds were needed to inhibit serum-stimulated growth. Of the six compounds examined, SU5416 and SU6597 demonstrated the best cellular potency and, therefore, their effect on the growth of multiple SCLC cell lines in serum-containing media was examined. In addition to inhibiting proliferation, these compounds also induced significant cell death of several SCLC cell lines, but not of normal human diploid fibroblasts, in complete media. These observations suggest that Kit kinase inhibitors such as these may offer a new approach for inhibiting Kit-mediated proliferation of tumors such as SCLC, gastrointestinal stromal tumors, seminomas, and leukemias.

Topics: Animals; Carcinoma, Small Cell; Cell Division; CHO Cells; Cricetinae; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Inhibitors; Growth Inhibitors; Humans; Indoles; Lung Neoplasms; Models, Molecular; Oxindoles; Phosphorylation; Propionates; Proto-Oncogene Proteins c-kit; Pyrroles; Receptor Protein-Tyrosine Kinases; Receptors, Platelet-Derived Growth Factor; Stem Cell Factor; Structure-Activity Relationship; Tumor Cells, Cultured