Induction of drug-resistant bladder carcinoma cells in vitro: impact on polychemotherapy with cisplatin, methotrexate and vinblastine (CMV).

Residual tumor, tumor progression or relapse after chemotherapy of patients with advanced or metastasized transitional cell carcinoma of the bladder (TCCB) are suggested to reflect intrinsic drug resistance of cancer cells, or the development of chemotherapy-resistant tumor cell populations. The present study aimed to establish drug-resistant subculture cell lines from human TCCB, selected for anticancer drugs, administered in the cisplatin, methotrexate and vinblastine (CMV) polychemotherapy protocol. Tumor cells from chemonaive cell lines of human TCCB (HT1376, TCCSUP) have been exposed to progressively increasing concentrations of cis-diamminedichloroplatinum (II) (CDDP), methotrexate (MTX), vinblastine (VBL) or etoposide (VP16). The resulting drug-resistant subculture cell lines (HT1376-CDDP, HT1376-MTX, HT1376-VBL, HT1376-VP, TCCSUP-CDDP, TCCSUP-MTX, TCCSUP-VBL, TCCSUP-VP) were analyzed with regard to the achieved resistance factor (RF) for the inductive anticancer agent, the acquisition of cross-resistance, DNA content, cell cycle distribution and cellular morphology. Parental HT1376 cells were intrinsically less sensitive to all anticancer drugs (1.7-50x), compared with TCCSUP cells. Relative resistance against the inductive anticancer agents was similar for the final drug-resistant subculture cell lines of both parental cell lines concerning CDDP and VP-16 (RF: 4-5x), but were reciprocal for MTX and VBL, respectively. MTX led to much stronger resistance (RF > 200) than the other drugs (RF < 10). Pleiotropic cross-resistances were observed in six out of eight (75%) drug-resistant subculture cell lines. Highest RF (50-500x) and frequency of cross-resistance (five of six cell lines) occured for MTX, and the least from exposure to CDDP (one of six cell lines). Overall, the results corroborated the central role of CDDP against urothelial carcinoma whereas repetitive applications of MTX appeared to be a doubtful strategy. Moreover, the experiments provide the largest panel so far of drug-resistant cell lines of human TCCB. They represent an appropriate tool for basic research on drug-resistance mechanisms, for the development and screening of future anticancer drugs or to elaborate strategies to overcome drug resistance for those patients who ultimately fail to respond to standard chemotherapy.