NK314, a novel topoisomerase II inhibitor, induces rapid DNA double-strand breaks and exhibits superior antitumor effects against tumors resistant to other topoisomerase II inhibitors

NK314 is a novel synthetic benzo[c]phenanthridine alkaloid that shows strong antitumor activity. It inhibited topoisomerase II activity and stabilized topoisomerase II-DNA cleavable complexes. The DNA breaks occurred within 1h after treatment with NK314 even without digestion of topoisomerase II by proteinase K, whereas etoposide required digestion of the enzyme protein in cleavable complex to detect DNA breaks. Pretreatment with topoisomerase II catalytic inhibitors, ICRF-193 and suramin, reduced both cleavable complex-mediated DNA breaks and proteinase K-independent DNA breaks, but protease inhibitors and nuclease inhibitors only decreased the latter. These results indicate that NK314 might affect topoisomerase II in the different manner from cleavable complex formation and activate intracellular proteinase and nuclease to produce DNA fragmentation. As a result of this unique mechanism of DNA breakage, NK314 showed substantial growth inhibition of topoisomerase II inhibitor-resistant tumors.     

In vivo inhibition of etoposide-mediated apoptosis,toxicity, and antitumor effect by the topoisomerase II-uncoupling anthracycline aclarubicin

A number of clinically important drugs such as the epipodophyllotoxins etoposide (VP-16) and teniposide (VM-26), the anthracyclines daunorubicin and doxorubicin (Adriamycin), and the aminoacridine amsacrine exert their cytotoxic action by stabilizing the cleavable complex formed between DNA and the nuclear enzyme topoisomerase II. We have previously demonstrated in several in vitro assays that the anthracycline aclarubicin (aclacinomycin A) inhibits cleavable-complex formation and thus antagonizes the action of drugs such as VP-16 and daunorubicin. The present study was performed to validate these in vitro data in an in vivo model. At nontoxic doses of 6 and 9 mg/kg, aclarubicin yielded a marked increase in the survival of non-tumor-bearing mice given high doses of VP-16 (80–90 mg/kg) in six separate experiments. In therapy experiments on mice inoculated with Ehrlich ascites tumor cells, aclarubicin given at 6 mg/kg roughly halved the increase in median life span induced by VP-16 at doses ranging from 22 to 33 mg/kg. An attempt to determine a more favorable combination of VP-16 and aclarubicin by increasing VP-16 doses failed, as the two drugs were always less effective than VP-16 alone. The way in which VP-16-induced DNA strand breaks lead to cell death remains unknown. However, VP-16 has been reported to cause apoptosis (programmed cell death) in several cell lines. To ascertain whether the protection given by aclarubicin could have a disruptive effect on the apoptotic process, we used the small intestine as an in vivo model. Whereas VP-16-induced apoptosis in crypt stem cells was detectable at a dose as low as 1.25 mg/kg, aclarubicin given at up to 20 mg/kg did not cause apoptosis. Indeed, aclarubicin caused a statistically significant reduction in the number of cells rendered apoptotic by VP-16. The present study thus confirms the previous in vitro experiments and indicates the value of including an in vivo model in a preclinical evaluation of drug combinations.This work was supported by the Danish Cancer Society     

Menogaril, an Anthracycline Derivative, Inhibits DNA Topoisomerase II by Stabilizing Cleavable Complexes

Menogaril, an anthracycline derivative, has been shown to possess antitumor activity in experimental animal systems, and is now under phase II clinical studies. However, its mechanism of action has not been elucidated. We have found that it inhibits the decatenation activity of purified DNA topoisomerase II using kinetoplast DNA from Crithidia fasciculata , its IC50 being 10 μM, which is comparable to that of etoposide. It does not, however, inhibit topoisomerase I activity at concentrations of up to 400 μM. Binding of topoisomerase II with DNA is not affected, but cleavable complex formation is stimulated by the drug. Cleavage site specificity differes from that of 4'-(9-acridinylamino)methanesulfon- m -anisidide. Menogaril was shown to possess a weak double-helix unwinding activity. These findings allow us to classify menogaril as a cleavable complex-stabilizing topoisomerase II inhibitor.     

The effect of 9-β-D-arabinofuranosyl-2-fluoroadenine and 1-β-D-arabinofuranosylcytosine on the cell cycle phase distribution,topoisomerase II level,mitoxantrone cytotoxicity,and DNA strand break production in K562 human leukemia cells

 Antimetabolites and topoisomerase (topo) II-reactive drugs are frequently combined in the therapy of acute leukemia. The two types of agents are thought to be synergistic in their actions against malignant blasts but the mechanism for this synergism is incompletely described. This study sought to determine whether the combination of two rather than one antimetabolite with the topo II-reactive intercalator mitoxantrone would be greater than the effect of the single antimetabolite ara-C on mitoxantrone’s cytotoxic actions. We also aimed to determine a mechanism for synergism should it occur. The model system used was K562 human leukemia cells. The second antimetabolite selected was F-ara-A, the active form of fludarabine. The resultant combination (F-ara-A, ara-C, and a topo II-reactive drug) is one currently being tested against acute myelogenous leukemia in clinical trials. F-ara-A itself had little effect on the cytotoxicity or the topo II-mediated DNA cleaving actions of mitoxantrone, while ara-C potentiated these actions as it does those of other topo II-reactive drugs. Surprisingly F-ara-A enhanced the actions of ara-C on mitoxantrone-associated cytotoxicity by at least an order of magnitude. The effect of the addition of F-ara-A to ara-C on mitoxantrone-induced DNA cleavage was considerably smaller, but present. Antimetabolite treatment did not increase the amount of topo II within cells measured directly by immunoblotting or indirectly by quantifying the maximum number of topo II – DNA complexes stabilized by mitoxantrone. Rather, the antimetabolites altered the distribution of the cells in the cell cycle. Antimetabolite treatment caused a large increase in S-phase cells, a phase in which cells are more sensitive to topo II-reactive drugs than the associated topo II-mediated DNA cleavage would predict. Therefore, it is likely that this shift in the distribution of the cells within the cell cycle accounts for both the enhanced cytotoxicity of mitoxantrone in antimetabolite pretreated cells and the discrepancy between the magnitude of antimetabolite action on topo II-mediated DNA cleavage. Received: 11 April 1995/Accepted: 20 October 1995     

Topoisomerase IIα content and topoisomerase II catalytic activity cannot explain drug sensitivities to topoisomerase II inhibitors in lung cancer cell lines

 Purpose: Topoisomerase IIα content, topoisomerase II catalytic activity and drug sensitivities to the topoisomerase II inhibitors, doxorubicin and etoposide, were examined in a panel of 14 unselected human lung cancer cell lines in order to determine the relationship between topoisomerase II and drug sensitivities to the topoisomerase II inhibitors. Methods: Drug sensitivities were determined using a microculture tetrazolium assay. The topoisomerase IIα levels were determined by Western blot analysis and the topoisomerase II catalytic activity was determined using a decatenation assay of kinetoplast DNA, using nuclear protein from cells of each cell line. Results: Drug sensitivity tests revealed that small-cell lung cancer (SCLC) cell lines were more sensitive to drugs than non-small-cell lung cancer (NSCLC) cell lines. The relative topoisomerase IIα levels and relative topoisomerase II catalytic activity from SCLC cell lines (mean± SD 0.89±0.54 and 5.3±3.4, respectively) were slightly higher than those from NSCLC cell lines (0.78±0.56 and 4.0±2.8, respectively), but the differences were not statistically significant, and not sufficient to account for the variation in drug sensitivities. Moreover, no clear association was observed between the topoisomerase IIα levels or the topoisomerase II catalytic activity and drug sensitivities in the cell lines studied. Conclusions: These findings suggest that the difference in drug sensitivities to doxorubicin and etoposide in human lung cancer cell lines might not be explainable by the topoisomerase IIα levels and topoisomerase II catalytic activity. Moreover, our results suggest that the topoisomerase IIα levels and topoisomerase II catalytic activity may play a minor role in the determination of clinical drug resistance of human lung cancers. Received: 11 July 1995/Accepted: 18 May 1996     

In vivo antitumor activity of S 16020-2, a new olivacine derivative

 The antitumor activity of S 16020-2, a new olivacine derivative, was investigated in vivo and compared with that of Adriamycin and elliptinium acetate in a panel of murine (P388 leukemia, M5076 sarcoma, Lewis lung carcinoma, and B16 melanoma) and human (NCI-H460 non-small-cell lung and MCF7 breast carcinomas) tumor models. S 16020-2 given i.v. was active against P388 leukemia implanted i.p., s.c., or intracerebrally. The therapeutic effect of an intermittent schedule (administration on days 1, 5, 9) was superior to that of single-dose treatment, allowing the i.v. administration of high total doses of S 16020-2 and resulting in the cure of 60% of mice in the i.p. P388 model. In this model, S 16020-2 was more active than elliptinium acetate and showed a better therapeutic index than Adriamycin:≥8 versus 2. A good therapeutic effect of S 16020-2 was also observed in three P388 leukemia sublines displaying the classic multidrug-resistance phenotype, namely, P388/VCR, P388/VCR-20, and P388/MDRC.04, the latter being totally insensitive to vincristine and Adriamycin. However, S 16020-2 was not active against the P388/ADR leukemia, a model highly resistant to adriamycin in vivo. S 16020-2 was both more active than Adriamycin and curative in the M5076 sarcoma and Lewis lung carcinoma implanted s.c. In the B16 melanoma implanted i.p. or s.c., S 160202 was less active than Adriamycin. Against the NCI-H460 human tumor xenograft, S 16020-2 demonstrated activity superior to that of Adriamycin (T/C=20% versus 43% on day 21). Against the MCF7 breast cancer xenograft, S 16020-2 was active, but less so than Adriamycin (T/C=23% versus 9% on day 21), whereas elliptinium acetate was marginally active (T/C=49% on day 24). The hematological toxicity of S 16020-2 given to B6D2F1 mice at pharmacological dose appeared to be less severe than that of Adriamycin, particularly in bone-marrow stem cells. These results demonstrate that S 16020-2 is a highly active antitumor drug in various experimental tumor models and is markedly more efficient than elliptinium acetate. Because of its pharmacological profile, which is globally different from that of Adriamycin, S 16020-2 is considered an interesting candidate for clinical trials. Received: 21 October 1995/Accepted: 4 March 1996     

ICRF-187 rescue in etoposide treatment in vivo. A model targeting high-dose topoisomerase II poisons to CNS tumors

 The catalytic cycle of topoisomerase II is the target of some of the most successful antitumor agents used today, e.g., etoposide (VP-16), in the treatment of testicular cancer and small-cell lung cancer. The cell kill mediated by topoisomerase II poisons can be antagonized by distinct drug types. Thus, we have demonstrated etoposide antagonism with the type-II anthracycline aclarubicin, the antimalarial drug chloroquine, and the cardioprotective agent ICRF-187. In other setups, combinations of agonist and antagonists have led to high-dose regimens for counteracting drug resistance. Thus, the exploitation of folinic acid rescue for methotrexate toxicity and the use of mesna to protect against cyclophosphamide toxicity have enabled the use of high-dose methotrexate and cyclophosphamide protocols. Using a similar approach, we have studied possible ways to apply antagonists to topoisomerase II poisons. NDF1-hybrid female mice were treated with the various drugs and drug combinations. Lethality (LD₁₀ and LD₅₀ values) was computed by use of the maximum-likelihood method, and the antitumor effect of the drugs was compared in mice inoculated i.p. with either L1210 cells or Ehrlich ascites tumor cells. In addition, the compounds were tested on L1210 cells inoculated intracranially. The toxicity of the various drugs was evaluated by weight and leukocyte counts. ICRF-187 rescues healthy mice from lethal doses of topoisomerase II poisons. In mice the ICRF-187 LD₁₀ was 500 mg/kg. Within a wide nontoxic dose range (50–250 mg/kg) of ICRF-187 we found protection against m-AMSA and etoposide lethality. Thus, the LD₁₀ of etoposide increased from 34 mg/kg for the single agent to 122 mg/kg for its combination with ICRF-187, corresponding to a 3.6-fold etoposide dose escalation. In contrast, ICRF-187 did not protect against lethal doses of the non-topoisomerase II-directed drug paclitaxel. We further investigated the antitumor effect of equitoxic schedules in mice inoculated i.p. with L1210 or Ehrlich ascites tumor cells. The L1210-bearing mice appeared to obtain a larger increase in life span from the etoposide and ICRF-187 combination as compared with etoposide alone, whereas this was not the case in mice inoculated with Ehrlich ascites tumor cells. As the hydrophilic ICRF-187 is not expected to cross the blood-brain barrier, in contrast to the lipophilic etoposide, we investigated the effect of the drug combination in mice inoculated intracranially with L1210 cells. We obtained a significant increase in life span in mice treated with ICRF-187 + etoposide as compared with mice treated with an equitoxic dose of etoposide alone. Thus, there appear to be potential routes by which one can benefit from this antagonism. ICRF-187 is a powerful nontoxic protector against the lethality of the topoisomerase II-directed drugs etoposide and m-AMSA in vivo. A brain tumor model demonstrates the superiority of high-dose etoposide treatment with ICRF-187 protection as compared with etoposide treatment alone. This implies that tumors in the brain can be reached by cytotoxic drug doses and that normal tissues can be protected due to differences in drug transport across the blood-brain barrier. ICRF-187 is therefore a promising lead compound for the development of schedules using high-dose topoisomerase II poisons in the treatment of brain tumors and metastases. Received: 15 June 1995/Accepted: 16 November 1995     

A Topoisomerase II Inhibitor, NK109, Induces DNA Single- and Double-strand Breaks and Apoptosis

2,3-(Methylenedioxy)-5-methyl-7-hydroxy-8-methoxybenzo[ c ]phenanthridinium hydrogensulfate di-hydrate, called NK109, is a benzo[ c ]phenanthridine derivative, which inhibits DNA topoisomerase II activity by stabilizing the DNA-enzyme-drug complex, and shows strong growth-inhibitory effects on several human cancer cells. In the present study, NK109 treatment induced DNA fragmentation and a rise in the level of cytoplasmic nucleosomes, which are markers of apoptosis, in human small-cell lung carcinoma SBC-3 cells. These effects were inhibited by zinc ions and enhanced by cycloheximide or actinomycin D. Dose-dependent single- and double-strand DNA breaks were observed, using alkaline and neutral elution assays, in SBC-3 cells treated with more than 0.2 μM NK109 for 4 h. Treatment with NK109 caused more DNA single- and double-strand breaks than treatment with an equimolar amount of VP-16. These results suggest that NK109 induces DNA strand breaks and apoptosis. In addition, it appears that this process does not require protein or RNA synthesis, but involves a specific endonuclease which is inhibited by zinc ions.     

Potentiation of antitumor and antimetastatic activities of adriamycin by a novel N-alkylated dihydropyridine,AC394, and its enantiomers in colon cancer-bearing mice

 Purpose: We have previously shown that a series of N-alkylated 1,4-dihydropyridines potentiate the therapeutic efficacy of vincristine in vincristine-resistant P388 leukemia. The purpose of this study was to investigate the ability of one of the compounds, AC394, and its enantiomers to potentiate the antitumor activity of adriamycin against colon cancer cells in vitro and in vivo. Methods: The effects of AC394 on potentiation of adriamycin cytotoxicity and enhancement of its accumulation were evaluated using colon 26, HCT-15 and MCF-7 cells. Furthermore, the activities of AC394 and its enantiomers were compared. We also studied the combined effects of (+)-AC394 and adriamycin on subcutaneously (s.c.)-implanted and liver metastasis tumor models. Results: AC394 potentiated the cytotoxicity of adriamycin and enhanced its accumulation in colon cancer cells (colon 26 and HCT-15), which are known to express P-GP (P-glycoprotein) intrinsically. Enhancement of adriamycin accumulation by AC394 was found in s.c.-implanted colon 26 cells in vivo. Although both enantiomers of AC394 showed equal activity in vitro, (+)-AC394 was more effective than (−)-AC394 given orally. (−)-AC394 was found to be cleared more rapidly from the plasma than (+)-AC394. Thus, (+)-AC394 was evaluated for further study. Administration of (+)-AC394 significantly potentiated the antitumor activities of adriamycin in human colon cancer HCT-15 cells implanted s.c. Furthermore, in the liver metastasis model using colon 26 cells, a model completely resistant to adriamycin, the combination therapy of adriamycin with (+)-AC394 produced superior antitumor effects over adriamycin alone. Conclusions: A newly synthesized N-alkylated 1,4-dihydropyridine derivative, (+)-AC394, showed superior effects on the potentiation of adriamycin antitumor and antimetastatic activities in vivo. These results suggest that this combination may have therapeutic efficacy not only against primary colon cancers but also against metastatic liver cancer. Received: 19 June 1995/accepted: 6 December 1995     

Preclinical pharmacology and antitumour activity of the novel sequence-selective DNA minor-groove cross-linking agent DSB-120

 We examined the in vitro cytotoxicity, antitumour activity and preclinical pharmacokinetics of the novel sequence-selective, bifunctional alkylating agent DSB-120, a synthetic pyrrolo[1, 4][2, 1-c]benzodiazepine dimer. DSB-120 was shown to be a potent cytotoxic agent in vitro against a panel of human colon carcinomas [50% growth-inhibitory concentration (IC₅₀) 42±7.9 nM, mean±SE, n=7] and two rodent tumours (L1210 and ADJ/PC6). Antitumour activity was assessed in the bifunctional alkylating-agent-sensitive murine plasmacytoma ADJ/PC6 using a variety of administration protocols. The maximal antitumour eff- ects were observed following a single i.v. dose but the therapeutic index was only 2.6. DSB-120 was less effective when given i.p. either singly or by a daily+5 schedule. After a single i.v. dose at the maximum tolerated dose (MTD, 5 mg kg⁻¹) the plasma elimination was biphasic, with a short distribution phase (t _1/2α 4 min) being followed by a longer elimination phase (t _1/3β 38 min). Peak plasma concentrations were 25 μg ml⁻¹, the clearance was 1.3 ml g⁻¹ h⁻¹ and the AUC_0-∞ was 230 μg ml⁻¹ min. Concentrations of DSB-120 in ADJ/PC6 tumours were very low, showing a peak of 0.4 μg g⁻¹at 5 min. The steady-state tumour/plasma ratio was about 5% and the AUC was only 2.5% of that occurring in the plasma. DSB-120 appeared to be unstable in vivo, with only 1% of an administered dose being recovered unchanged in 24-h urine samples. Plasma protein binding was extensive at 96.6%. In conclusion, the poor antitumour activity of DSB-120 may be a consequence of low tumour selectivity and drug uptake as a result of high protein binding and/or extensive drug metabolism in vivo. Received: 5 November 1995/Accepted: 30 January 1996     

A novel in vitro model system for studying the action of ara-C

 The antimetabolite 1-β-D-arabinofuranosylcytosine (ara-C) has proven to be one of the most effective agents available for the treatment of acute leukemia. While ara-C has been implicated as a potent inhibitor of mammalian cell DNA replication, the specific mechanism by which ara-C kills cells is not known. In this report we describe the development of an in vitro model system to study the molecular mechanism of ara-CMP incorporation into DNA. This model system makes use of a recently described human cell multiprotein DNA replication complex (MRC) that is competent to replicate DNA in vitro. The MRC can successfully incorporate ara-CMP into replicating DNA at internucleotide positions. These results are similar to those described for studies using intact cells. This MRC-driven in vitro replication system may therefore serve as a powerful model for the study of anticancer agents that directly affect human cell DNA synthesis. Received: 31 March 1995/Accepted: 9 October 1995     

TW01001, a novel piperazinedione compound,induces mitotic arrest and autophagy in non-small cell lung cancer A549 cells

Here, we report that TW01001, a novel piperazinedione compound, could be a new mitotic inhibitor for the treatment of non-small cell lung cancer by the following observations in A549 cells: (1) induction of cells to accumulate at G2/M phase, which ultimately led to cell apoptotic death, (2) accumulation of p53 and inhibition of survival signalings, and (3) induction of p53-independent autophagy. Taken together, our data suggested that TW01001 induces autophagy-p53-signaling pathway to cause mitotic arrest and cell growth inhibition in A549 cells and provides the framework for further development as a novel therapeutic agent for lung cancer treatment.     

A novel synthetic DNA minor groove binder, MS-247: antitumor activity and cytotoxic mechanism

Purpose: MS-247 is a novel synthetic compound possessing a DNA-binding moiety and a DNA-alkylating residue, chlorambucil. In this study, we evaluated the antitumor activity of MS-247 against murine tumor cell lines and its effects on DNA molecules in both cell-free and cellular systems. Methods: The in vitro cytotoxic activity of MS-247 was evaluated against four murine tumor cell lines, P388, L1210, Colon26 and B16, and its in vivo antitumor activity was also tested in comparison with Adriamycin (ADM), cisplatin (CDDP) and paclitaxel. The ability of MS-247 to associate with the DNA minor groove was assessed by measuring quenching of Hoechst 33342 fluorescence. DNA-DNA interstrand crosslinks (ICL) were detected by an alkaline elution assay for cellular DNA and a band-shift assay using the plasmid pBR322. The effects of MS-247 on macromolecule synthesis (DNA, RNA and proteins) were examined by measuring incorporation of the radiolabeled precursors. Results: MS-247 exhibited in vitro cytotoxicity with IC₅₀ values ranging 11 to 500 nM, and MS-247 given i.v. showed strong in vivo antitumor activity against i.p.-implanted L1210 leukemia cells and s.c.-implanted Colon26 carcinoma cells, and moderate activity against i.p.-implanted P388 leukemia cells but no apparent activity against s.c.-implanted B16 melanoma cells. MS-247 reversibly displaced Hoechst 33342 bound to DNA within a few minutes, and irreversibly formed ICL within 1–6 h in both the cell-free system and the cellular system. These results suggest that an association of MS-247 with the DNA minor groove occurred more quickly than ICL formation. The inhibition of DNA synthesis was more prominent than the inhibition of RNA and protein synthesis in L1210 cells exposed to MS-247, and a 6-h incubation with MS-247, which formed apparent ICL in the cellular system, strongly inhibited DNA synthesis. This result suggests that impairment of DNA replication preceded the inhibition of RNA and protein synthesis and that ICL formation greatly contributed to the inhibition of macromolecule synthesis. Conclusion: The results of this study suggest that MS-247 exerts its cytotoxic effect through impairment of DNA function by getting into the minor groove of DNA and subsequently forming ICL. MS-247 has potent antitumor activity with a different spectrum from the activity of clinically proven antitumor agents such as paclitaxel, ADM and CDDP against several murine tumor cell lines. This result suggests that MS-247 may be useful for the treatment of human cancers. Received: 6 July 1999 / Accepted: 14 February 2000     

A phase I/II study of high-dose cyclophosphamide,cisplatin, and thioTEPA followed by autologous bone marrow and granulocyte colony-stimulating factor-primed peripheral-blood progenitor cells in patients with advanced malignancies

 The purpose of the present study was to determine the maximally tolerated dose of thioTEPA given with fixed high-dose cyclophosphamide (CPA) and cisplatin (cDDP) followed by autologous bone marrow (ABM) with or without granulocyte colonystimulating factor (G-CSF)-primed peripheral-blood progenitor cells (PBPCs) in patients with advanced malignancies. Patients were required to have histologically documented malignancies and adequate renal, hepatic, pulmonary, and cardiac function. CPA was given at 1,875 mg/m² per day as a 1-h i.v. infusion for 3 consecutive days, and cDDP was given at 55 mg/m² per day as a 24-h continuous i.v. infusion over 3 days concurrently with CPA. ThioTEPA was given once as a 1-h i.v. infusion (300–900 mg/m²) either following (the first 13 patients) or prior to CPA and cDDP. In all, 31 patients received PBPCs. A total of 46 patients were treated. There were 6 deaths among the 15 patients who did not receive PBPCs (13 received thioTEPA following CPA and cDDP). Among the other 31 patients who received PBPCs (all of whom also received thioTEPA prior to CPA and cDDP), there were 4 deaths, all involving patients with refractory ovarian carcinoma. The main toxicities were mucositis, esophagitis, hepatotoxicity, and nephrotoxicity. The median time required to achieve an absolute neutrophil count of 500 μl was 10 days (range, 9–12 days) for those who received PBPCs and 15 days (range, 15–34 days) for those who did not receive PBPCs. Altogether, 47% of the major organ toxicities (grades 3 and 4 renal, hepatic, and cardiac toxicities) occurred among the 15 patients who did not receive PBPCs, although these patients received thioTEPA at the lowest 2 dose levels. There were 3 complete responses and 22 partial responses among 35 evaluable patients (overall response rate, 71%), with the median duration of response being 3.5 months (range, 2–17 months). The maximally tolerated dose of thioTEPA was 600 mg/m² given as a 1-h i.v. infusion on the day prior to CPA and cDDP administration. The combination of high-dose CPA, cDDP, and thioTEPA is a well-tolerated regimen when thioTEPA is given prior to CPA and cDDP and when the combination also includes PBPCs in addition to ABM. This regimen is active in a variety of malignancies. Received: 15 February 1995/Accepted: 22 May 1995     

A novel DNA intercalator, 8‐methoxy pyrimido[4′,5′:4,5]thieno (2,3‐b)quinoline‐4(3H)‐one induces apoptosis in cancer cells,inhibits the tumor progression and enhances lifespan in mice with tumor

Polycyclic aromatic molecules such as ellipticine intercalate into double‐stranded DNA and interfere with physiological functions. In the present study, we evaluate the chemotherapeutic potential of MPTQ on animal models and its mode of action. In order to test the antitumor activity, monohydrochloride of MPTQ was orally administered in mice bearing tumor. Results showed a significant inhibition of tumor growth compared to that of untreated controls. More importantly, mean lifespan of tumor bearing animals treated with MPTQ was significantly higher as compared to that of untreated tumor bearing mice suggesting that the treatment affected viability of cancerous cells, but not of normal cells. Consistent with this, we find that administration of MPTQ to normal mice did not cause any major side effects as observed upon hematological and serum profiling. We also found that MPTQ induces cytotoxicity in cancer cell lines, by activating apoptosis both by intrinsic and extrinsic pathways. Thus, MPTQ could be used as a potential cancer therapeutic agent. © 2011 Wiley Periodicals, Inc.