tirapazamine and Carcinoma--Non-Small-Cell-Lung

The role of chemotherapy in the treatment of advanced non-small cell lung cancer (NSCLC) has been debated over three decades, but it is only relatively recently that chemotherapy has become a standard of care for this disease. In addition to prolonging survival, chemotherapy can palliate distressing symptoms. Concerns that the adverse effects of chemotherapy are likely to outweigh its benefits have largely not been confirmed by quality-of-life data reported among patients with good performance status. Platinum-based chemotherapy regimens in which cisplatin or carboplatin are partnered by a third-generation cytotoxic drug such as gemcitabine, paclitaxel or vinorelbine, have similar activity and efficacy, but differ in adverse effect profiles. Response rates of 30-40% should be expected with median and 1-year survival of 8-10 months and 30-40%, respectively. In the second-line setting chemotherapy with docetaxel has been shown to be significantly superior to best supportive care alone. In a recent trial that compared docetaxel to the novel antifolate, pemetrexed the response rates and survival rates did not differ, but the toxicity profile favored pemetrexed. Overall, these data demonstrate that progress has been made in the use of chemotherapy to improve survival in patients with NSCLC without increasing the incidence of further toxicity. In the past, the potential to survive 1 year was extremely small, whereas now many more patients reach this milestone as well as the 2-year point. However, a plateau has probably been reached with existing cytotoxic drugs and there is a general belief that the next significant advance in the treatment of NSCLC will come from the addition of drugs that target specific molecular pathways in sequence with standard chemotherapy regimens.

Topics: Antimetabolites, Antineoplastic; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cisplatin; Drug Delivery Systems; Humans; Lung Neoplasms; Microtubules; Quality of Life; Survival Analysis; Tirapazamine; Treatment Outcome; 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

Chemotherapeutic regimens containing new anticancer agents in combination with cisplatin and carboplatin have been demonstrated to be equivalently active against advanced non-small cell lung cancer. The choice of a chemotherapeutic regimen depends on differences in time to progression, response rate, toxicity profile, cost and symptom relief. Several other strategies, such as three-drug combinations, sequential use of a third drug, weekly administration, etc., have been evaluated to improve the chemotherapeutic effect. The sequencing of the human genome may permit targeting of specific abnormalities related to each lung cancer with target-based drugs. This should increase the possibility of application of individualized therapy and, we would hope, improve survival.

Topics: Antineoplastic Combined Chemotherapy Protocols; Camptothecin; Carcinoma, Non-Small-Cell Lung; Cisplatin; Deoxycytidine; Drug Administration Schedule; Etoposide; Gemcitabine; Humans; Irinotecan; Lung Neoplasms; Randomized Controlled Trials as Topic; Survival Rate; Tirapazamine; Triazines; Vinblastine; Vinorelbine

Treatment of stage IV NSCLC has been a controversial issue during the last decade. However, there is now clear evidence that cisplatin-containing chemotherapy regimens lead to prolonged survival with an increase of the 1-year survival rates at about 10%. New drugs like gemcitabine, the taxanes (paclitaxel, docetaxel), and vinorelbine have shown very promising single-agent activity and have been included into modern combination chemotherapy regimens achieving response rates of 40 to 50% and 1-year survival rates of between 30 and 40%. In comparison to single-agent cisplatin or cisplatin/etoposide as 'standard treatment approaches', most of these modern combinations could demonstrate advantages in terms of response, survival and improved QOL. Patients with favourable prognostic factors are at the moment frequently treated with platinum-based combination chemotherapy often including one of these newer active drugs. Patients with adverse prognostic factors such as elderly or stage IV patients with a reduced performance status are preferably treated with single agents such as gemcitabine, paclitaxel or vinorelbine.

Topics: Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Deoxycytidine; Docetaxel; Gemcitabine; Humans; Lung Neoplasms; Neoplasm Staging; Paclitaxel; Prognosis; Survival Rate; Taxoids; Tirapazamine; Triazines; Vinblastine; Vinorelbine

Over the last decade, a group of new agents with differing mechanisms of action have shown great promise in early clinical studies in non-small-cell lung cancer (NSCLC). These include the taxanes docetaxel (Taxotere) and paclitaxel (Taxol); the nucleoside analog gemcitabine (Gemzar); the vinca alkaloid vinorelbine (Navelbine); the topoisomerase-I inhibitor irinotecan (Camptosar, CPT-11); and the bioreductive agent tirapazamine. Cisplatin (Platinol), which has been the "backbone" of combination chemotherapy in patients with NSCLC because of its proven single-agent activity, has been examined in combination with these agents as well as radiation and surgery in numerous trials. This article summarizes trials of these combination therapies in the treatment of NSCLC.

Topics: Antineoplastic Combined Chemotherapy Protocols; Camptothecin; Carboplatin; Carcinoma, Non-Small-Cell Lung; Cisplatin; Clinical Trials as Topic; Deoxycytidine; Docetaxel; Gemcitabine; Humans; Ifosfamide; Irinotecan; Lung Neoplasms; Mitomycin; Paclitaxel; Taxoids; Tirapazamine; Triazines; Vinblastine; Vinorelbine

The last decade has seen the introduction of several new chemotherapeutic agents that have activity against non-small cell lung cancer (NSCLC) and produce single-agent response rates of > or = 20% in previously untreated patients with advanced tumors. Furthermore, the results of phase I-II trials have shown that the agents can be combined safely with cisplatin or carboplatin and that most combinations result in response rates of 35% to 40% or more. Gemcitabine, paclitaxel, vinorelbine, and tirapazamine have all been studied in combination with cisplatin in trials that compared the combinations with cisplatin alone. All trials reported response rates that were significantly higher for the combination arm and, with the exception of the paclitaxel trial, median and 1-year survival rates were also significantly greater. Vinorelbine as a single agent was compared with vinorelbine in combination with cisplatin in three studies. Although response and survival rates were longer for the combination arms, single-agent vinorelbine produced median survivals of longer than 30 weeks in all trials and a 1-year survival rate of 30% in one study. Single-agent gemcitabine was compared with the combination of etoposide and cisplatin in two trials. In each study, the response to gemcitabine was equal to that of the combination arm, and the 1-year survival rate was actually superior for the single-agent gemcitabine arm. Combinations of the new agents with cisplatin or carboplatin also have been evaluated in randomized phase III trials and compared with standard chemotherapy regimens for the treatment of NSCLC. The vinorelbine/cisplatin combination was found to be superior to vindesine/cisplatin. Paclitaxel/cisplatin and gemcitabine/cisplatin were both found to be superior to etoposide/cisplatin. Survival gains have been modest, with median survival ranging from approximately 8 to 10 months and 1-year survival rates with the new regimens ranging from 32% to 41%. The new chemotherapy regimens have resulted in modest benefit and have set a new standard for the treatment of advanced NSCLC.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Camptothecin; Carcinoma, Non-Small-Cell Lung; Deoxycytidine; Enzyme Inhibitors; Gemcitabine; Humans; Lung Neoplasms; Paclitaxel; Palliative Care; Randomized Controlled Trials as Topic; Tirapazamine; Triazines; Vinblastine; Vinorelbine

Tirapazamine is a novel bioreductive agent with selective cytotoxicity against hypoxic tumour cells. Synergy with cisplatin and other chemotherapeutic agents has been shown in preclinical trials. Pharmacokinetic studies of tirapazamine have revealed that exposure increases with dose over the range of 18-450 mg m(-2) for a single dose and of 9-390 mg m(-2) for multiple doses. Plasma clearance is high. Tirapazamine has been clinically tested in combination with cisplatin at escalating doses in a phase I trial and at therapeutic doses in three separate phase II trials in patients with advanced non-small-cell lung cancer (NSCLC) in 11 study centres. Limiting toxicity for tirapazamine at an intravenous dose of 390 mg m(-2) was acute, reversible hearing loss. Other frequently observed side-effects included muscle cramping and gastrointestinal symptoms. Tirapazamine did not cause myelosuppression, and no toxic deaths were reported in these trials. The anti-tumour efficacy against previously untreated, advanced NSCLC was evaluated by cumulative intent-to-treat analysis of 132 patients. The objective response rate (confirmed by two independent measurements) was 25% [confidence interval (CI) 17.8-33.33], with a median survival of 38.9 weeks (CI 29.4-49.9). The efficacy of tirapazamine plus cisplatin shown in these trials was better than that of historical controls with cisplatin monotherapy. Two large-scale international trials have been conducted, involving more than 70 centres, to confirm these results. The CATAPULT I trial compares tirapazamine plus cisplatin with cisplatin and has finished accrual with 446 patients. The CATAPULT II trial, which is comparing tirapazamine plus cisplatin with etoposide plus cisplatin, had enrolled 550 patients by June 1997. Follow-up is ongoing. Tirapazamine is the promising first drug from a new class of cytotoxic agents with a novel mechanism of action. It can be effectively combined with cisplatin, and possibly with other agents, because of its safety profile and lack of overlapping dose-limiting toxicity, such as myelosuppression. The combination of tirapazamine and cisplatin appears to be safe and effective in the treatment of NSCLC.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cisplatin; Clinical Trials, Phase I as Topic; Clinical Trials, Phase II as Topic; Drug Synergism; Humans; Lung Neoplasms; Multicenter Studies as Topic; Tirapazamine; Triazines

S0003 was a phase III trial of carboplatin/paclitaxel with or without the hypoxic cytotoxin tirapazamine in patients with advanced or metastatic non-small-cell lung cancer (NSCLC). We investigated the relationship between clinical outcomes and plasma levels of the hypoxia-associated protein osteopontin (OPN) in patients on this protocol.. Baseline plasma was obtained from 172 patients. In 56 patients, sequential plasma was obtained after one or two cycles. Concentrations of OPN, as well as plasminogen activator inhibitor-1 (PAI-1) and vascular endothelial growth factor (VEGF), were measured using enzyme-linked immunosorbent assay. Tumor expression of OPN was assessed by immunohistochemistry in 61 matched archival specimens.. Patients with lower OPN levels (below the median) had a significantly superior overall survival compared with patients with higher levels, regardless of treatment arm (hazard ratio [HR] = 0.60, P = .002). A similar correlation was observed for progression-free survival (HR = 0.69, P = .02). When examined as a continuous variable, OPN maintained its significant association with both progression-free (HR = 1.05, P = .01) and overall survival (HR = 1.09, P < .0001). Patients with lower plasma OPN levels were significantly more likely to have tumor response (P = .03). No differences were observed between treatment arms. Tumor OPN levels did not correlate with patient outcomes or with plasma levels. No associations were observed between patient outcomes and VEGF or PAI-1 levels; however, plasma concentrations of these markers were significantly interrelated (P < .0001) and significantly decreased after treatment (P = .0002 and P = .03, respectively).. Pretreatment plasma levels of OPN are significantly associated with patient response, progression-free survival, and overall survival in chemotherapy-treated patients with advanced NSCLC.

Topics: Aged; Antineoplastic Agents; Biomarkers, Tumor; Carboplatin; Carcinoma, Non-Small-Cell Lung; Female; Humans; Lung Neoplasms; Male; Middle Aged; Osteopontin; Survival Analysis; Tirapazamine; Treatment Outcome; Triazines

This phase I/II study was conducted to evaluate the safety and efficacy of tirapazamine in combination with cisplatin and vinorelbine for patients with advanced-stage IIIB/IV chemonaive non-small-cell lung cancer. Seventy patients with a Karnofsky performance status of > or = 60% were included. In the phase I part of the study, 21 patients were treated on day 1 with tirapazamine (escalating doses of 260, 330, or 390 mg/m(2)), cisplatin (75 or 100 mg/m(2)), and vinorelbine (25 or 30 mg/m(2)) for a maximum of 6 cycles every 4 weeks. Vinorelbine was repeated every week. In the phase II part of the study, 49 patients were treated on day 1 with tirapazamine 390 mg/m(2), cisplatin 100 mg/m(2), and vinorelbine 30 mg/m(2). The maximum tolerated dose was not reached. Muscle cramps, vomiting, nausea, tinnitus, neutropenia, and diarrhea were the most frequently reported adverse events in the phase I part of the study. Most of these events were grade 1 or 2. In the phase II part of the study, response rate was 47%, and median survival was 50 weeks. The most frequently reported adverse event was neutropenia. Asthenia, fever, anemia, vomiting, weight decrease, nausea, and muscle cramps were also noted. For patients treated at the maximum dose, dose reductions occurred 14% of tirapazamine cycles and in 4% of cisplatin cycles. The median number of cycles was 3. This regimen has a manageable toxicity profile. Response rate and median survival suggest that this combination might be more active than the cisplatin/vinorelbine combination. This triplet is currently being evaluated in a phase III study.

Topics: Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cisplatin; Female; Humans; Lung Neoplasms; Male; Maximum Tolerated Dose; Middle Aged; Neoplasm Staging; Survival Analysis; Tirapazamine; Treatment Outcome; Triazines; Vinblastine; Vinorelbine

Tumor hypoxia confers chemotherapy resistance. Tirapazamine is a cytotoxin that selectively targets hypoxic cells. We conducted a phase III clinical trial to determine whether the addition of tirapazamine to paclitaxel and carboplatin offered a survival advantage when used in the treatment of patients with advanced non-small-cell lung cancer (NSCLC).. Of 396 patients registered, 367 eligible patients were randomly assigned to either arm 1 (n = 181), which consisted of treatment every 21 days with paclitaxel 225 mg/m2/3 h, carboplatin (area under the curve = 6), and tirapazamine 260 mg/m2 in cycle 1 (which was escalated, if tolerable, to 330 mg/m(2) in cycle 2), or arm 2 (n = 186), which consisted of paclitaxel and carboplatin as in arm 1 with no tirapazamine.. Patient characteristics were similar between the two arms. There were no statistically significant differences in response rates, progression-free survival, or overall survival. Patients on arm 1 had significantly (P < .05) more abdominal cramps, fatigue, transient hearing loss, febrile neutropenia, hypotension, myalgias, and skin rash and were removed from treatment more often as a result of toxicity than patients in arm 2 (26% v 13%, respectively; P = .003). More than 40% of patients did not have the tirapazamine dose escalated, primarily because of toxicity. The trial was closed early after an interim analysis demonstrated that the projected 37.5% improvement in survival (8 v 11 months median survival) in arm 1 was unachievable (P = .003).. The addition of tirapazamine to paclitaxel and carboplatin does not result in improved survival in advanced NSCLC compared with paclitaxel and carboplatin alone but substantially increases toxicity.

Topics: Antineoplastic Combined Chemotherapy Protocols; Carboplatin; Carcinoma, Non-Small-Cell Lung; Cell Hypoxia; Drug Administration Schedule; Female; Humans; Lung Neoplasms; Male; Middle Aged; Paclitaxel; Survival Analysis; Tirapazamine; Treatment Outcome; Triazines

Despite improvements in chemotherapy of advanced and metastatic Non-Small-Cell-Lung-Cancer (NSCLC) the prognosis of these patients still remains poor with a 5-year-survival of 2 to 5 %. Due to the high level of hypoxic cells in solid tumors agents with activity in hypoxic milieu as the Benzotriazine compound Tirapazamine (SR 259 075) might improve the therapeutic results. We treated 45 patients with advanced or metastatic Non-Small-Cell-Lung-Cancer (stage IIIb: 20 patients, stage IV: 25 patients) with the combination TPZ 330 mg/m (2) (day 1), Cisplatin 75 mg/m (2) (day 1) and Gemcitabine 1250 mg/m (2) (day 1 and 8) every 3 weeks. With a response rate of 40 % median progression free survival was 6.7 months (4.8 - 8.1 months) and median survival was 8.1 months (7.5 - 12.5 months), (1-year-survival: 35 %). Hematologic and non-hematologic toxicity was moderate (neutropenia CTC grade 3 and 4: 20 %, thrombocytopenia CTC grade 3 and 4: 16 %, nausea and vomiting CTC 3: 5 %). Treatment of advanced and metastatic NSCLC with TPZ in combination with Gemcitabine/Cisplatin was well feasible and showed results recording to currently published data. The results of a following phase III-trial are awaited.

Topics: Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cisplatin; Deoxycytidine; Disease-Free Survival; Female; Gemcitabine; Humans; Lung Neoplasms; Male; Middle Aged; Neoplasm Staging; Neutropenia; Survival Analysis; Thrombocytopenia; Tirapazamine; Triazines

A phase III trial, Cisplatin and Tirapazamine in Subjects with Advanced Previously Untreated Non-Small-Cell Lung Tumors (CATAPULT I), was designed to determine the efficacy and safety of tirapazamine plus cisplatin for the treatment of non-small-cell lung cancer (NSCLC).. Patients with previously untreated NSCLC were randomized to receive either tirapazamine (390 mg/m(2) infused over 2 hours) followed 1 hour later by cisplatin (75 mg/m(2) over 1 hour) or 75 mg/m(2) of cisplatin alone, every 3 weeks for a maximum of eight cycles.. A total of 446 patients with NSCLC (17% with stage IIIB disease and pleural effusions; 83% with stage IV disease) were entered onto the study. Karnofsky performance status (KPS) was >/= 60 for all patients (for 10%, KPS = 60; for 90%, KPS = 70 to 100). Sixty patients (14%) had clinically stable brain metastases. The median survival was significantly longer (34.6 v 27. 7 weeks; P =.0078) and the response rate was significantly greater (27.5% v 13.7%; P <.001) for patients who received tirapazamine plus cisplatin (n = 218) than for those who received cisplatin alone (n = 219). The tirapazamine-plus-cisplatin regimen was associated with mild to moderate adverse events, including acute, reversible hearing loss, reversible, intermittent muscle cramping, diarrhea, skin rash, nausea, and vomiting. There were no incremental increases in myelosuppression, peripheral neuropathy, or renal, hepatic, or cardiac toxicity and no deaths related to tirapazamine.. The CATAPULT I study shows that tirapazamine enhances the activity of cisplatin in patients with advanced NSCLC and confirms that hypoxia is an exploitable therapeutic target in human malignancies.

Topics: Adult; Aged; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cell Hypoxia; Cisplatin; Drug Synergism; Female; Humans; Lung Neoplasms; Male; Middle Aged; Survival Analysis; Tirapazamine; Triazines

A phase II study was conducted to evaluate the safety and efficacy of tirapazamine combined with cisplatin for the treatment of patients with advanced non-small-cell lung cancer (NSCLC).. Forty-four patients with stage IIIB/IV NSCLC were treated with a combination of tirapazamine and cisplatin. Patients received tirapazamine 260 mg/m2 administered intravenously over 2 hours, followed 1 hour later by cisplatin 75 mg/m2 administered over an additional hour, repeated every 21 days. The duration of therapy was meant to be limited to four cycles for nonresponders and eight cycles for responders.. Ten of 44 patients (23%) showed a partial response. The estimated median survival for all patients was 37 weeks. Toxicities were treatable and included grade 3 nausea or vomiting (25%), fatigue (27.3%), and muscle cramps (4.5%). No dose reductions were necessary.. The results show that tirapazamine can safely be added to cisplatin. Both the median survival and response rate observed strongly suggest that tirapazamine with cisplatin is more active than cisplatin alone.

Topics: Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cisplatin; Drug Administration Schedule; Female; Humans; Lung Neoplasms; Male; Middle Aged; Survival Analysis; Tirapazamine; Treatment Outcome; Triazines

Tirapazamine is a bioreductive compound synergistic with cisplatin in preclinical testing. This phase II study was conducted to evaluate the efficacy and toxicity of tirapazamine with cisplatin in patients with advanced non-small-cell lung cancer.. Twenty patients with unresectable stage III-B and IV non-small-cell lung cancer who had not received prior chemotherapy were given tirapazamine (390 mg/m2) intravenously (i.v.) over two hours followed one hour later by cisplatin (75 mg/m2) i.v. over one hour every 21 days.. Five of 20 patients (25%) had major objective responses (95% confidence interval, 11%-50%). Median duration of response was eight months with a one-year survival of 40%. Toxicities included temporary hearing loss (25%), muscle cramping, diarrhea, skin rash and nausea/vomiting. No grade 3 or 4 hematologic or renal toxicity was observed.. The combination of tirapazamine plus cisplatin appears to be safe and active in the treatment of advanced non-small lung cancer without a substantial increase in toxicity compared to cisplatin alone. A phase III randomized study compared the combination to cisplatin alone has completed accrual. Further evaluation of tirapazamine with other active agents and in multi-modality therapy is warranted.

Topics: Antineoplastic Combined Chemotherapy Protocols; Carcinoma, Non-Small-Cell Lung; Cisplatin; Drug Synergism; Humans; Lung Neoplasms; Tirapazamine; Treatment Outcome; Triazines

Hypoxia is one of the inevitable circumstances of various tumors. It controls various levels of regulation in tumor progression and results in tumor resistance to radiotherapy and chemotherapy. Here we investigated a synthetic TPZ derivative, N-ethoxymethyl-3-amino-1,2,4-benzotriazine-1,4-dioxide (XQ2), a novel compound that induced anti-cancer effects both in normoxia and in hypoxia, cell proliferation assay found that XQ2 exhibited a potent inhibitory effect on the tested cancer cell lines both in normoxia and in hypoxia. Flow cytometry and western blot studies indicated that XQ2 induces G2/M arrest and a caspase-dependent apoptosis in A549 cells. Additionally, intracellular reactive oxygen species (ROS) appear to play a key role in the anticancer effect of XQ2 in hypoxia. Taken together, our data suggest that XQ2 exerted anticancer action by suppressing the ROS level and triggering cell-cycle arrest and the caspase-dependent pathway, which is associated with apoptosis.

Topics: Antineoplastic Agents; Apoptosis; bcl-2-Associated X Protein; Carcinoma, Non-Small-Cell Lung; Caspase 3; Caspase 9; Cell Division; Cell Hypoxia; Cell Line, Tumor; Cell Proliferation; Cyclic N-Oxides; G2 Phase; Gene Expression Regulation, Neoplastic; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Mitochondria; Poly(ADP-ribose) Polymerases; Proto-Oncogene Proteins c-bcl-2; Reactive Oxygen Species; Signal Transduction; Tirapazamine; Triazines

The diaziridiny/benzoquinone RH1 is shortly to enter a phase I clinical trial. The drug was originally designed as a substrate for the enzyme DT-diaphorase (DTD) such that metabolic activation of the drug would lead to toxicity. To evaluate this, we have measured the toxicity of RH1 in a pair of non-small cell lung cancer (NSCLC) cell lines of widely differing levels of DTD and in MDA231 breast cancer cells which have been engineered to overexpress DTD. In addition, we have explored the importance of the putative one-electron reductase, P450 reductase, by assessing the toxicity of RH1 in MDA231 cells engineered to overexpress the enzyme. All drug exposures were carried out under hypoxic and aerobic conditions. Those cells with the highest levels of DTD, i.e. D7 versus MDA231 wt and H460 versus H596, are substantially more sensitive to RH1 than the cell lines expressing low DTD activity. Those cells with the lowest levels of DTD activity, i.e. MDA231 wt, R4 and H596, show much greater sensitivity to RH1 under hypoxic conditions compared to aerobic conditions. Finally, overexpression of P450 reductase, i.e. comparing MDA231 wt with R4, has little, if any, impact on the toxicity of RH1 under hypoxic or aerobic conditions. In summary, RH1 can be effective in killing cells containing high levels of DTD and may be useful in treating tumors expressing this enzyme.

Topics: Aerobiosis; Antineoplastic Agents; Aziridines; Benzoquinones; Breast Neoplasms; Carcinoma, Non-Small-Cell Lung; Cell Hypoxia; Cell Line, Tumor; Cell Survival; Colony-Forming Units Assay; Humans; Inhibitory Concentration 50; Lung Neoplasms; NAD(P)H Dehydrogenase (Quinone); NADPH-Ferrihemoprotein Reductase; Spectrophotometry; Tirapazamine; Transfection; Triazines

Tirapazamine (TPZ), a hypoxia-selective cytotoxin, has demonstrated activity in cancer clinical trials. Under hypoxic conditions, TPZ is reduced to a radical that leads to DNA double-strand breaks (DSBs), single-strand breaks, and base damage. A previous finding of an association of the DSBs with protein led us to investigate the involvement of topoisomerase II (topo II) in their formation. Nuclear extracts from human lung cancer cells treated with either the topo II poison etoposide or TPZ under hypoxic conditions had markedly reduced topo II activity as judged by an inability to convert kinetoplast DNA from the catenated to the decatenated form. Because topo II poisons, such as etoposide, cause DNA DSBs, we hypothesized that pretreatment of cells with merbarone or aclarubicin, known catalytic inhibitors of topo II, would abrogate DNA DSBs caused by topo II. Cells pretreated with these catalytic inhibitors abrogated both DNA DSBs and cell kill induced by etoposide or by TPZ. Etoposide- and TPZ-mediated DSBs were also greatly reduced in a small cell lung cancer cell line with low levels of nuclear topo IIalpha. We also showed that topo IIalpha becomes covalently bound to DNA after TPZ treatment under hypoxic conditions, and that the cleavable complexes formed by TPZ are more stable over time than those formed by etoposide. Taken together, these data suggest that TPZ exerts its cytotoxic effect at least in part through poisoning topo II. Because TPZ is activated only under hypoxic conditions, which are characteristic of solid tumors, these data implicate TPZ as a tumor-specific topo II poison.

Topics: Antineoplastic Agents; Carcinoma, Non-Small-Cell Lung; Carcinoma, Small Cell; Cell Hypoxia; DNA Damage; DNA Topoisomerases, Type II; DNA, Neoplasm; Enzyme Inhibitors; Etoposide; HeLa Cells; Humans; Lung Neoplasms; Tirapazamine; Topoisomerase II Inhibitors; Triazines

Tirapazamine (TPZ) is a new anticancer drug that is activated specifically at the low oxygen level typically found in solid tumours. It exhibits preferential cytotoxicity towards hypoxic cells and has been shown in preclinical studies with transplanted tumours and in phase II and III clinical trials to potentiate the anti-tumour efficacy of cisplatin without increasing its systemic toxicity. At present, the mechanism for this potentiation is unknown. Here we show that there is a schedule-dependent enhancement of cisplatin cytotoxicity by TPZ for cells in vitro that is similar to that seen with transplanted murine tumours. This cisplatin potentiation depends on the TPZ exposure being at oxygen concentrations below 1%, which are typical of many cells in tumours but not in normal tissues. Also, the interaction between TPZ and cisplatin does not occur in cells mutant in ERCC4, a protein essential for repair of DNA interstrand cross-links. Incubation of the cells with TPZ under hypoxia prior to cisplatin treatment increases cisplatin-induced DNA interstrand cross-links with kinetics suggesting that TPZ inhibits or delays repair of the DNA cross-links. In conclusion, we show that the tumour-specific potentiation of cisplatin cytotoxicity is likely the result of an interaction between TPZ and cisplatin at the cellular level that requires the low oxygen levels typical of those in solid tumours. The mechanism of the interaction appears to be through a potentiation of cisplatin-induced DNA interstrand cross-links, possibly as a result of a diminished or delayed repair of these lesions

Topics: 3T3 Cells; Animals; Antineoplastic Agents; Carcinoma, Non-Small-Cell Lung; Cell Hypoxia; CHO Cells; Cisplatin; Cricetinae; Cross-Linking Reagents; DNA Damage; DNA Repair; Drug Interactions; Humans; Lung Neoplasms; Mice; Tirapazamine; Triazines

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

The bioreductive drug tirapazamine (TPZ, SR 4233, WIN 59075) is a lead compound in a series of potent cytotoxins that selectively kill hypoxic rodent and human solid tumour cells in vitro and in vivo. Phases II and III trials have demonstrated its efficacy in combination with both fractionated radiotherapy and some chemotherapy. We have evaluated the generality of an enzyme-directed approach to TPZ toxicity by examining the importance of the one-electron reducing enzyme NADPH:cytochrome P450 reductase (P450R) in the metabolism and toxicity of this lead prodrug in a panel of seven human non-small-cell lung cancer cell lines. We relate our findings on TPZ sensitivity in these lung lines with our previously published results on TPZ sensitivity in six human breast cancer cell lines (Patterson et al (1995) Br J Cancer 72: 1144-1150) and with the sensitivity of all these cell types to eight unrelated cancer chemotherapeutic agents with diverse modes of action. Our results demonstrate that P450R plays a significant role in the activation of TPZ in this panel of lung lines, which is consistent with previous observations in a panel of breast cancer cell lines (Patterson et al (1995) Br J Cancer 72: 1144-1150; Patterson et al (1997) Br J Cancer 76: 1338-1347). However, in the lung lines it is likely that it is the inherent ability of these cells to respond to multiple forms of DNA damage, including that arising from P450R-dependent TPZ metabolism, that underlies the ultimate expression of toxicity.

Topics: Antineoplastic Agents; Breast Neoplasms; Carcinoma, Non-Small-Cell Lung; Drug Screening Assays, Antitumor; Female; Humans; Lung Neoplasms; Tirapazamine; Triazines; Tumor Cells, Cultured