Accumulation of cis-diamminedichloroplatinum (II) and its analogues in sensitive and resistant human ovarian carcinoma cells

Microphthalmia-Associated Transcription Factor-Dependent Melanoma Cell Adhesion Molecule Activation Promotes Peritoneal Metastasis of Ovarian Cancer

Ovarian cancer (OvCa) is one of the leading causes of death due to its high metastasis rate to the peritoneum. Recurrent peritoneal tumors also develop despite the use of conventional platinum-based chemotherapies. Therefore, it is still important to explore the factors associated with peritoneal metastasis, as these predict the prognosis of patients with OvCa. In this study, we investigated the function of microphthalmia-associated transcription factor (MITF), which contributes to the development of melanoma, in epithelial ovarian cancer (OvCa). High MITF expression was significantly associated with a poor prognosis in OvCa. Notably, MITF contributed to the motility and invasion of OvCa cells, and specifically with their peri-mesothelial migration. In addition, MITF-positive cells expressed the melanoma cell adhesion molecule (MCAM/CD146), which was initially identified as a marker of melanoma progression and metastasis, and MCAM expression was regulated by MITF. MCAM was also identified as a significant prognostic factor for poor progression-free survival in patients with OvCa. Collectively, our results suggest that MITF is a novel therapeutic target that potentially promotes peritoneal metastasis of OvCa.

Combination of tunicamycin with anticancer drugs synergistically enhances their toxicity in multidrug-resistant human ovarian cystadenocarcinoma cells

BACKGROUND

The pharmacologic modulatory effects of the antibiotic, tunicamycin (TM), on multidrug-resistant human UWOV2 ovarian cancer cells are reported. The UWOV2 cell line was derived from a cystadenocarcinoma in a patient refractory to combination chemotherapy with actinomycin D, vincristine (VCR), cis-diaminedichloroplatinum (II) (CDDP) and doxorubicin (DXR). In an attempt to explain drug resistance in this cell line, we examined the effects of TM on their sensitivity to various anticancer drugs, the uptake, efflux and retention of [3H]VCR, and their ability to bind [14C]DXR and [3H]azidopine (AZD), a photoaffinity label of the multidrug transporter, P-glycoprotein (Pgp).

RESULTS

TM effectively decreased the EC50 for DXR, EXR, VCR and CDDP, thus enhancing their cytotoxicity. The antibiotic also prolonged the intracellular retention time of [3H]VCR and increased the binding of both [14C]DXR and [3H]AZD to the cells.

CONCLUSION

It is concluded that the pharmacomodulatory effects of TM in these cells are mediated by global inhibition of protein and glycoprotein synthesis and synergistic interaction with antineoplastic drugs. The ability of TM to enhance the sensitivity of drug resistant tumour cells may have impact on the design and optimization of novel resistance modifiers to improve the efficacy of combination treatment of intractable neoplasms.

Tunicamycin potentiates drug cytotoxicity and vincristine retention in multidrug resistant cell lines

Tunicamycin (TM), an inhibitor of glycoprotein processing, was investigated for its potential to reverse the multiple drug resistance (MDR) phenotype. When TM was added in vitro to drug-resistant NIH-3T3-MDR and KB-8-5-11 cells, they developed an increased sensitivity to doxorubicin, epirubicin, vincristine and colchicine. Similarly, the sensitivity of NIH-3T3-MDR cells to cisplatin was also enhanced by TM. In the presence of TM, drug-sensitive NIH-3T3-parental cells exhibited greater susceptibility to the toxic effects of doxorubicin, epirubicin, vincristine (marginally significant), and colchicine, but not to cisplatin. Tunicamycin-treated drug-sensitive KB-3-1 cells showed an increased response to vincristine, but not to the other anticancer drugs. Pretreatment with TM inhibited glycoprotein synthesis in all the cell lines. Neither prior exposure to, nor co-incubation with TM, influenced the uptake of vincristine (VCR) in the various cell lines. However, NIH-3T3-MDR cells accumulated less VCR than their drug-sensitive controls and also exhibited reduced efflux of the drug when treated with TM. There were no significant differences in the levels of intracellular VCR uptake between drug-sensitive KB-3-1 and KB-8-5-11 cells. Tunicamycin increased intracellular VCR retention in KB-8-5-11 and NIH-3T3-MDR cells, but not in NIH-3T3-parental cells. However, drug-sensitive KB-3-1 cells expressed reduced VCR retention in response to TM exposure, indicating that correlations between VCR toxicity and its retention in the presence of TM should be made with caution. The results suggest that the enhancement of intracellular VCR retention in MDR cells lines caused by TM is likely to be the result of inhibition of VCR efflux. Inhibition of glycoprotein synthesis during TM exposure may account for the changes in VCR efflux and retention observed in the MDR cell lines. The enhancement of cisplatin cytotoxicity in NIH-3T3-MDR cells after exposure to TM is an interesting observation, since it is generally believed that agents which modify the MDR phenotype do not show a sensitising effect to cisplatin. These findings may have applications in the reversal of drug resistance.

Synergistic enhancement of cisplatin cytotoxicity by SN-38, an active metabolite of CPT-11, for cisplatin-resistant HeLa cells

A cisplatin (cis-diamminedichloroplatinum(II); CDDP)-resistant HeLa cell line (HeLa/CDDP cells), which showed more than 8-fold resistance to CDDP compared to the parent cells, was newly established for this study. HeLa/CDDP cells accumulated 50% less platinum than the parent cells. There was no difference in intracellular glutathione (GSH) content between the parent and HeLa/CDDP cells. The dose modification factor by DL-buthionine-S,R-sulfoximine (BSO) pretreatment was similar in both cell lines. HeLa/CDDP cells had cross-resistance to diammine(1,1-cyclobutanedicarboxylato)platinum(II) (CBDCA), (cis-diammine(glycolato)platinum (254-S), but not to (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato++ +)platinum(II) (DWA2114R), adriamycin, or VP-16. HeLa/CDDP cells showed a collateral sensitivity to 7-ethyl-10-hydroxycamptothecin (SN-38), an active metabolite of 7-ethyl-10-[4-(1-piperidino)-1-piperidino]carbonyloxycamptothecin (CPT-11). Furthermore, isobologram analysis indicated synergistic interaction of CDDP and SN-38 only for HeLa/CDDP cells. The present study suggests that combination therapy with CDDP and CPT-11 may be potentially useful in the treatment of some patients with CDDP-resistant cancer.

Drug accumulation and DNA platination in cells exposed to aquated cisplatin species

Since CP always exists in aqueous solution as a mixture of native drug and various aqua and hydroxo species, it is conceivable that one or more of these aquated species is the main form of the drug that enters the cell. To test this hypothesis, we examined the accumulation by 2008 human ovarian carcinoma cells of CP and aquated CP in Cl-, deficient medium. After 24 h in 150 mM NaNO3, HPLC analysis indicated that 54% of the platinum in solution was accounted for by aquated species. Immediately following addition of this solution to Cl- deficient RPMI 1640 medium, the initial concentrations of the aqua and hydroxo species were calculated to be 34-2400-fold higher with pre-aquated CP than with native CP. The cellular platinum accumulation, however, was the same under both conditions and was also identical to that of native CP in normal RPMI. To confirm that aquated species were actually entering the cell, the amount of platinum reaching the DNA was determined. The total platinum levels on DNA were 1.9-fold higher when cells were exposed to pre-aquated CP in Cl- deficient medium compared to CP in regular medium. We conclude that 2008 cells do not preferentially transport an aquated form of CP under these conditions compared to native CP.

Antitumor activity and cellular accumulation of a new platinum complex, (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato)platinum( II) monohydrate, in cisplatin-sensitive and -resistant murine P388 leukemia cells

We have examined the cytotoxicity and accumulation of (-)-(R)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato++ +)platinum(II) monohydrate (DWA2114R) in parent and cisplatin-resistant mouse P388 leukemia cells (P388 and P388/DDP), in comparison with those of cisplatin (CDDP) and carboplatin (CBDCA). The degrees of resistance to CDDP and CBDCA, expressed as the ratio of IC50 for P388/DDP cells to IC50 for P388 cells, were 75-33 and 100-27, respectively, under the conditions of 2-24 h exposure to each drug at a density of 10(6) cells/ml. The corresponding values (25-7) for DWA2114R were relatively low. Accumulations of CDDP and CBDCA were reduced in P388/DDP cells; however, no reduction in accumulation of DWA2114R was observed at various exposure periods and concentrations of the drugs. The accumulations of CDDP in P388 and P388/DDP cells at drug concentrations corresponding to the IC50 values for drug exposure periods of 2-24 h were 0.41-0.97 and 13.1-33.7 ng Pt/10(7) cells, respectively, suggesting that an intracellular mechanism of resistance against CDDP could be activated in P388/DDP cells. P388/DDP cells also showed relatively low resistance to DWA2114R via this mechanism in comparison with CDDP and CBDCA. From the relationship between structure and activity of several Pt-complexes, these different properties of DWA2114R compared with CDDP and CBDCA could be due not only to the differences in carrier ligand structure but also to the properties of the whole molecule associated with the carrier ligand and leaving group.