Antitumor drug cross-resistance in vivo in a cisplatin-resistant murine P388 leukemia

Synergistic binding of actinomycin D and echinomycin to DNA mismatch sites and their combined anti-tumour effects

Combination cancer chemotherapy is one of the most useful treatment methods to achieve a synergistic effect and reduce the toxicity of dosing with a single drug. Here, we use a combination of two well-established anticancer DNA intercalators, actinomycin D (ActD) and echinomycin (Echi), to screen their binding capabilities with DNA duplexes containing different mismatches embedded within Watson-Crick base-pairs. We have found that combining ActD and Echi preferentially stabilised thymine-related T:T mismatches. The enhanced stability of the DNA duplex-drug complexes is mainly due to the cooperative binding of the two drugs to the mismatch duplex, with many stacking interactions between the two different drug molecules. Since the repair of thymine-related mismatches is less efficient in mismatch repair (MMR)-deficient cancer cells, we have also demonstrated that the combination of ActD and Echi exhibits enhanced synergistic effects against MMR-deficient HCT116 cells and synergy is maintained in a MMR-related MLH1 gene knockdown in SW620 cells. We further accessed the clinical potential of the two-drug combination approach with a xenograft mouse model of a colorectal MMR-deficient cancer, which has resulted in a significant synergistic anti-tumour effect. The current study provides a novel approach for the development of combination chemotherapy for the treatment of cancers related to DNA-mismatches.

The 6π-azaelectrocyclization of azatrienes. Synthetic applications in natural products, bioactive heterocycles, and related fields

Covering: 2006 to 2018 The application of the 6π-azaelectrocyclization of azatrienes as a key strategy for the synthesis of natural products, their analogs and related bioactive or biomedically-relevant compounds (from 2006 to date) is comprehensively reviewed. Details about reaction optimization studies, relevant reaction mechanisms and conditions are also discussed.

One-pot three-component selective synthesis of isoindolo[2,1-a]quinazoline derivatives via a palladium-catalyzed cascade cyclocondensation/cyclocarbonylation sequence

A practical and highly efficient procedure for the selective preparation of 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones through a palladium-catalyzed one-pot three-component cascade reaction of 2-aminobenzamides with 2-bromobenzaldehydes and carbon monoxide under atmospheric pressure has been developed. This cascade reaction, in which four new C-C/C-N bonds and two new rings are simultaneously constructed, is triggered by a cyclocondensation of 2-aminobenzamides with 2-bromobenzaldehydes, followed by a Pd-catalyzed cyclocarbonylation of the in situ formed 2,3-dihydroquinazolin-4(1H)-ones with CO (1 atm). Compared with the existing methods, the present protocol has the advantages of readily available starting materials, broad substrate scope, structural diversity of products, and free of high-pressure equipment.

Synthesis and biological evaluation of novel analogues of batracylin with synthetic amino acids and adenosine: an unexpected effect on centromere segregation in tumor cells through a dual inhibition of topoisomerase IIα and Aurora B

In the search for new anticancer agents we designed and synthesized batracylin derivatives with linking synthetic amino acid side chains of different lengths and adenosine.

Synthesis of functionalized new conjugates of batracylin with tuftsin/retro-tuftsin derivatives and their biological evaluation

New batracylin conjugates with tuftsin/retro-tuftsin derivatives were designed and synthesized using T3P as a coupling agent. The conjugates possess an amide bond formed between the carboxyl group of heterocyclic molecule and the N-termini of the tuftsin/retro-tuftsin chain. The in vitro cytotoxic activity of the new analogues and their precursors was evaluated using a series of human and murine tumor cells. BAT conjugates containing retro-tuftsin with branched side aminoacid chain, in particular with leucine or isoleucine, were about 10-fold more cytotoxic toward two human tumor cell lines (lung adenocarcinoma (A549) and myeloblastic leukemia (HL-60)). These compounds showed about 10-fold increased cytotoxicity against the two types of tumor cells compared to parent BAT. We have not observed important differences in the mechanism of action between BAT and its cytotoxic tuftsin/retro-tuftsin conjugates. We propose that high biological activity of the most active BAT conjugates is a result of their greatly increased intracellular accumulation.

A combined experiment and computation study of the fused polycyclic benzimidazole derivatives

Novel fused polycyclic benzimidazole derivatives were synthesized from dimethyl 4,5-diaminophthalate/dimethyl 3,4-diaminophthalate with aromatic anhydride (a-b) by condensation. The UV-Visible absorption and fluorescence emission spectra of the dyes were studied in solvents of differing polarity. The dyes were characterized by the spectral analysis. Density Functional Theory computations have been used to derive more understanding of structural, molecular, electronic and photophysical parameters of the push-pull dyes. The computed absorption wavelength values were observed to be in good agreement with the experimental results. The second order hyperpolarizability (β(o)) values were computed by Density Functional Theory and found to be in the range of 67.16 × 10(-31) to 107.76 × 10(-31) e.s.u.

Pharmacogenetically driven patient selection for a first-in-human phase I trial of batracylin in patients with advanced solid tumors and lymphomas

PURPOSE

Batracylin (daniquidone), an ATP-insensitive topoisomerase I/II inhibitor, demonstrated wide interspecies variation in preclinical models consistent with formation of a toxic metabolite, N-acetyl-batracylin, following metabolism by N-acetyl-transferase 2 (NAT2). To minimize exposure to this toxic metabolite, this first-in-human study was conducted in patients with advanced refractory solid tumors or lymphomas demonstrated to have a slow NAT2 acetylator genotype. The objectives were to determine the safety, maximum tolerated dose (MTD), and pharmacokinetics of batracylin and its metabolites.

METHODS

Based on the MTD for rats, the most sensitive species, the starting dose was 5 mg/day for 7 days in 28-day cycles. Dose escalation followed accelerated titration design 4B, with restaging performed every 2 cycles.

RESULTS

Thirty-one patients were enrolled. Treatment was well tolerated; one patient experienced grade 3 toxicity (lymphopenia). Dose escalation was stopped at 400 mg/day due to grade 1 and 2 hemorrhagic cystitis. No objective responses were observed, but prolonged disease stabilization was observed in 2 patients, one with peritoneal mesothelioma (8 cycles) and another with adrenocortical cancer (18 cycles). Across an 80-fold range of doses, the ratios of systemic exposures for batracylin and N-acetyl batracylin were near 1.

CONCLUSIONS

Pharmacogenetically selected patients reached a dose that was 20-fold higher than the MTD in rats and 70 % of the MTD in mice. This genotype-guided strategy was successful in safely delivering batracylin to patients. However, due to unexpected cystitis, not preventable by hydration, and in the absence of a stronger signal for antitumor activity, further development of batracylin has been stopped.

Establishment of three cisplatin-resistant endometrial cancer cell lines using two methods of cisplatin exposure

Using the endometrial cancer cell line EI established in our department, we attempted to establish cisplatin (CDDP)-resistant cell lines by incremental exposure and high concentration exposure methods. Three CDDP-resistant cell lines were isolated, which could be distinguished by morphological differences. 1. Upon acquiring CDDP resistance, the cells tended to become small and grow in a floating state. This tendency was especially marked when using incremental exposure method. Using the incremental exposure method, a cell line obtained by isolating and culturing only adherent cells was designated EICR-Ia, and a cell line established by culturing only floating cells was designated EICR-If. A cell line obtained by the high concentration exposure method was designated EICR-II. 2. Upon acquiring CDDP resistance, tumor markers such as TPA and LDH increased, while proliferative capability of the cells was lowered. 3. The invasion capability was diminished in EICR-If cells, but was increased in EICR-Ia and EICR-II cells. 4. Following exposure to CDDP, the intracellular platinum concentrations were markedly elevated in EI and EICR-If cells, whereas the increase was mild in EICR-Ia and EICR-II cells and the concentration was lower than that in parent EI cells. 5. Studies of drug resistance gene expression revealed increased expression of MDR1, GSTπ, and Topo-II in EICR-If cells; increased expression of GSTπ in EICR-II cells; but no expression of any of the genes in EICR-Ia cells. 6. Analyses of cancer- and apoptosis-related genes showed increased expressions of Bcl-2, c-Myc, p53, and ICE in EICR-If cells. 7. Upon acquiring CDDP resistance, sensitivity to mitomycin and adriamycin decreased, but sensitivity to etoposide and 5-fluorouracil increased. The findings indicate that the mechanisms of CDDP resistance are different in the three cell lines.

cis-Dichloroplatinum(II) complexes tethered to 9-aminoacridine-4-carboxamides: synthesis and action in resistant cell lines in vitro

A series of intercalator-tethered platinum(II) complexes PtLCl(2) have been prepared where L are the diamine ligands N-[2-[(aminoethyl)amino]ethyl]-9-aminoacridine-4-carboxamide, N-[3-[(2-aminoethyl)amino]propyl]-9-aminoacridine-4-carboxamide, N-[4-[(2-aminoethyl)amino]butyl]-9-aminoacridine-4-carboxamide and N-[5-[(aminoethyl)amino]pentyl]-9-aminoacridine-4-carboxamide and N-[6-[(aminoethyl)amino]hexyl]-9-aminoacridine-4-carboxamide. The activity of the complexes was assessed in the CH-1, CH-1cisR, 41M, 41McisR and SKOV-3 cell lines. The compounds with the shorter linker chain lengths are generally the most active against these cell lines and are much more toxic than Pt(en)C1(2). For example, for the n=2 compound the IC(50) values are 0.017 microM (CH-1), 1.7 microM (41M), 1.4 microM (SKOV-3) and the resistance ratios are 51 (CH-1cisR) and 1.6 (41McisR). For the untethered analogue Pt(en)C1(2) the IC(50) values are 2.5 microM (CH-1), 2.9 microM (41M), 45 microM (SKOV-3) and the resistance ratios are 2.8 (CH-1cisR) and 4.1 (41McisR). The very large differential in IC(50) values between the CH-1 and CH-1cisR pair of cell lines for the 9-aminoacridine-4-carboxamide tethered platinum complexes indicates that repair of platinum-induced DNA damage may be a major determinant of the activity of these compounds.

Altered expression of gamma-glutamylcysteine synthetase, metallothionein and topoisomerase I or II during acquisition of drug resistance to cisplatin in human ovarian cancer cells

This study was designed to elucidate the mechanisms of cisplatin (CDDP) resistance using two human ovarian cancer cell lines, KF and TYK, and two CDDP-resistant lines, KFr and TYK/R, derived from the former lines. KFr and TYK/R showed about 3-fold higher resistance to the cytotoxic effects of CDDP than their parental lines. They also showed a significant increase in sensitivity to not only etoposide, but also (+)-(4S)-4, 11-diethyl-4-hydroxy-9-[(4-piperidino -piperidino)carbonyloxy]-1H -pyrano[3',4':6,7]inodolizino[1,2-b]quinoline-3,14(4H, 12H)-dione hydrochloride trihydrate (CPT-11). Cellular CDDP accumulation levels in KFr and TYK/R were decreased from those of the parental cells. By contrast, the cellular glutathione (GSH) content in KFr cells was 1.7-fold higher than that in KF, whereas TYK/R cells had a 40% lower content than TYK cells. Cellular mRNA levels of drug-resistance-related genes, such as DNA topoisomerase (topo) I and topo II, glutathione S-transferase-pi (GST-pi), gamma-glutamylcysteine synthetase (gamma-GCS), and metallothionein (hMT) genes, were compared between drug-sensitive KF or TYK and KFr or TYK/R. KFr cells had 8.5- and 24.7-fold higher mRNA levels of gamma-GCS and topo II genes than KF cells while KFr had only a slight increase in GST-pi mRNA level as compared with KF. By contrast, TYK/R cells had 2.9- and 1.7-fold higher hMT and topo I mRNA levels than TYK cells. Acquisition of CDDP resistance in human ovarian cancer cells thus appeared to be related mainly to expression of gamma-GCS, topo II and hMT genes, and partly to that of topo I and GST-pi genes, in addition to a decrease in CDDP accumulation.

In vitro and in vivo modulation by rhizoxin of non-P-glycoprotein-mediated vindesine resistance

Rhizoxin is an antineoplastic drug that inhibits tubulin polymerization. In this study, we demonstrated that rhizoxin was approximately twice as active in vitro against a human small-cell lung cancer cell line with non-P-glycoprotein-mediated resistance to vindesine, H69/VDS, as against its parental line, H69. Tubulin polymerization in H69/VDS, demonstrated by Western blot analysis, was inhibited markedly by rhizoxin compared with that in H69, in a concentration-dependent manner. A drug-accumulation study showed that the intracellular rhizoxin level in H69/VDS was 15% lower than that in H69, whereas efflux from H69/VDS was enhanced slightly. These results indicate that enhanced inhibition of tubulin polymerization rather than increased intracellular drug concentration accounted for the higher sensitivity of H69/VDS to rhizoxin. In an experiment using mice with severe combined immunodeficiency and inoculated subcutaneously with H69/VDS, in vivo tumor growth was reduced markedly by three intermittent intraperitoneal doses of rhizoxin compared with that in mice inoculated with H69. Three weeks after the last rhizoxin dose, the relative treated/untreated tumor volumes were 0.29 for H69, but only 0.06 for H69/VDS, indicating that H69/VDS regrowth was minimal even after a 3-week treatment-free period. In conclusion, rhizoxin conquers vindesine resistance of a human small-cell lung cancer cell line in vitro and in vivo.

Determinants of cellular sensitivity to topoisomerase-targeting antitumor drugs

It is now clear that topoisomerase activity level is an important determinant of sensitivity to topo drugs. The regulation of topoisomerases is no doubt complex and multifaceted and is probably accomplished through redundancy at many control levels. The mechanism(s) of altered topo I expression in certain tumor types is unknown, but may be related to the central importance of topoisomerases in proliferating cell functions (transcription, replication, etc.), and the aberrant and chronic activation of these functions as a result of specific tumorigenic alterations. Small differences in sensitivity to chemotherapy can have a dramatic effect on cure rates, and therefore subtle cell type-specific differences may be important determinants of drug sensitivity. Whether abnormal topoisomerase quantity and specific activity are associated with resistance or sensitivity to topoisomerase-targeted chemotherapy in the clinic is now being studied. Determinants downstream of cleavable complex formation that affect the sensitivity of tumor versus normal cells to topo drugs in particular and DNA-damaging agents in general are little known. The goal of enhancing selective tumor cell killing relative to the normal cells that are dose limiting may be achieved either by overcoming tumor cell resistance or by protecting normal cells. Both of these strategies will become more feasible as specific molecular differences between tumor and normal cells are being rapidly identified and new combination therapies that take advantage of these differences are being designed and tested.

Anti-leukaemic action of RuCl2 (DMSO)4 isomers and prevention of brain involvement on P388 leukaemia and on P388/DDP subline

Two ruthenium(II) complexes, characterised by the presence of dimethylsulphoxide ligands, were investigated in comparison to cisplatin on mouse P388 leukaemia and on a subline made resistant to cisplatin (P388/DDP). Both cis- and trans-RuCl2(DMSO)4 significantly prolonged the survival time of leukaemic mice, independently of the tumour line used. Unlike cisplatin, the prolongation of life-span of tumour-bearing hosts caused by ruthenium complexes was not supported by a parallel inhibition of the number of tumour cells in the treated hosts, as evidenced by tumour cell count in the peritoneal cavity and by vivo-vivo bioassays of blood samples and of whole brains. Thus, cis- and trans-RuCl2(DMSO)4 appear capable of preventing leukaemic spread into the central nervous system also when the number of tumour cells in the peritoneal cavity and in the blood stream is as high as in untreated controls. When the drug-induced DNA damage was investigated by modifying double stranded DNA and identifying the lesions able to inhibit DNA synthesis in vitro, trans-RuCl2(DMSO)4 and, to a lesser extent, cis-RuCl2(DMSO)4 formed blocking lesions at the same sites of cisplatin; nevertheless, the mechanism of antitumour activity of ruthenium complexes appears to be different from that of cisplatin for the absence of any relationship between cytotoxicity and prevention of leukaemic dissemination into the central nervous system. These data indicate that the activity of cis- and trans-RuCl2(DMSO)4 on the P388 leukaemia is characterised by the lack of cross-resistance with cisplatin and by the alteration of the metastasising behaviour of leukaemic cells which lose their natural capacity to invade the central nervous system.

Acquisition of platinum drug resistance and platinum cross resistance patterns in a panel of human ovarian carcinoma xenografts

In vivo models of acquired resistance to the platinum-based agents cisplatin (CDDP), carboplatin (CBDCA), iproplatin (CHIP) and tetraplatin have been established using a panel of six parent human ovarian carcinoma lines, two (HX/110 and PXN/87) being derived from previously untreated patients. Resistance has been generated to CDDP (three lines), CBDCA (one line), CHIP (three lines) and tetraplatin (one line) either by treatment in vivo or (for one line to CDDP) through exposure in vitro and subsequent transfer to mice. With the four tumours where resistance was generated using CDDP or CBDCA, a complete cross-resistance to the remaining platinum agents studied was observed. In contrast, in one of three lines with derived resistance to the platinum (IV) agent, CHIP, (PXN/951) a retention in sensitivity was observed with CDDP and CBDCA. Only one of the six parent tumour lines (PXN/100) was markedly sensitive to tetraplatin. Where resistance was generated to tetraplatin (PXN/100T) there was some retention of activity by CDDP. For the CDDP-resistant line established in vitro, there was a close agreement between the cross-resistance profile obtained in vitro vs that obtained in vivo. This tumour panel may be useful in the elucidation of cellular and molecular resistance mechanisms to platinum drugs operative in vivo. Moreover, as they appear to mimic the clinical observations of shared cross-resistance between CDDP, CBDCA and CHIP, they may represent valuable preclinical evaluation models for the discovery of drugs capable of conferring responses in CDDP-refractory ovarian cancer.

Pharmacologic validation of human tumor clonogenic assays based on pleiotropic drug resistance: implications for individualized chemotherapy and new drug screening programs

Because of the bias toward successful cloning of human tumor cells from more advanced malignancies, alternative approaches to clinical correlations of drug resistance are needed to determine the validity of the human tumor clonogenic assay (HTCA) as a clinically useful test. Capitalizing on the prevalence of clinical drug resistance among these advanced malignancies, we have taken an independent approach to testing the validity of HTCAs based upon pharmacologic principles rather than tumor response. A database of results from drug sensitivity/resistance testing in 1,777 HTCAs has been examined retrospectively for specimens exhibiting either the MDR1 or Topo-II pleiotropic drug resistance phenotype. Twenty specimens were identified as MDR1 based upon test results showing resistance to adriamycin, vinca alkaloid, and etoposide. Test results with mitomycin-c confirmed the MDR1 phenotype in eight out of nine of these specimens. Seven out of eight of the confirmed MDR1 samples were resistant to either cis-platinum or alkylating agents or to both. There was no significant difference in the 5-fluorouracil resistance of these MDR1 specimens and the database as a whole, demonstrating the specific nature of this drug resistance phenotype in vitro. One specimen, a squamous carcinoma of the lung, was mitomycin-c sensitive, even though it exhibited all the other drug resistances characteristic of the MDR1 phenotype. Six specimens with the Topo-II phenotype were identified based upon resistance to adriamycin and etoposide with sensitivity to vinca alkaloids. Surprisingly, the Topo-II phenotype showed a strong association with increased cis-platinum resistance and a weaker one with decreased 5-fluorouracil resistance. Thus, 26/30 (87%) of analyzable specimens showed some form of clinically characterized multidrug resistance, illustrating how easily one can obtain 90% accuracy in predicting clinical drug resistance with HTCAs that are heavily biased by a disproportionate number of successful cloning assays with advanced malignancies. The data analysis also shows that prediction of adriamycin resistance based on lack of Topoisomerase II expression will not be very accurate, in contrast to a previous claim. Until cell culture technology can facilitate frequent successes in the cloning of early detected, drug-sensitive lesions, this bias will remain in HTCA databases, and studies comparing HTCA results with clinical response will continue to be uninformative. However, the in vitro identification of pleiotropic drug resistance phenotypes exactly analogous to those previously observed in patients provides pharmacologic validation at least for the prediction of drug resistance as measured by current HTCAs using suprapharmacologic drug concentrations.

Cross-resistance of drug-resistant murine P388 leukemias to toxol in vivo

The antimicrotubule agent taxol (NSC 125973) has shown clinical antitumor activity against several classically refractory tumors. We developed a drug-resistance profile for taxol using ten drug-resistant P388 leukemias to identify potentially useful guides for patient selection for further clinical trials of taxol and possible non-cross-resistant drug combinations with taxol. Multidrug-resistant P388 leukemias exhibited either clear (leukemia resistant to amsacrine) or marginal cross-resistance (leukemias resistant to doxorubicin, actinomycin D, and mitoxantrone) to taxol. Leukemias resistant to vincristine (non-multidrug-resistant leukemia), camptothecin, melphalan, cisplatin, 1-beta-D-arabinofuranosylcytosine, and methotrexate were not cross-resistant to taxol. The data suggest that (1) it may be important to exclude or to monitor with extra care patients who have previously been treated with amsacrine, doxorubicin, actinomycin D, or mitoxantrone and (2) a combination of one of the non-cross-resistant drugs and taxol might exhibit therapeutic synergism.

Antitumor drug cross-resistance in vivo in a murine P388 leukemia resistant to ethyl 5-amino-1,2-dihydro-2-methyl-3-phenylpyrido[3,4-b]pyrazin-7 - ylcarbamate 2-hydroxyethanesulfonate hydrate (NSC 370,147) 370147

Ethyl 5-amino-1,2-dihydro-2-methyl-3-phenylpyrido[3,4-b]pyrazin-7- ylcarbamate 2-hydroxyethane-sulfonate hydrate (NSC 370147) is a potent mitotic inhibitor, which has provided the basis for a candidate for clinical trial. As observed with clinically useful drugs, the development of clinical resistance to NSC 370147 will probably be encountered. Information concerning resistance to NSC 370147 should aid in the design of strategies for the optimal clinical use of the drug. A P388 leukemia resistant to NSC 370147 (P388/NSC 370147) was isolated and its in vivo cross-resistance profile was determined. The P388/NSC 370147 line was cross-resistant to vincristine but was not cross-resistant to doxorubicin, etoposide, cisplatin, melphalan, methotrexate, or 5-fluorouracil. This information plus other in vivo cross-resistance data [Waud et al. (1990) Cancer Res 50: 3239] suggests that NSC 370147 may be useful in non-cross-resistant combinations with doxorubicin, melphalan, cisplatin, or methotrexate. The lack of cross-resistance of P388/NSC 370147 to doxorubicin and etoposide shows that resistance to NSC 370147 does not involve multidrug resistance and suggests that the mdr1 gene is not involved in resistance to NSC 370147.