BACKGROUND: The improvement of treatment outcome of small-cell lung cancer (SCLC), and search for new effective drugs and to overcome drug-resistance are essential. MATERIALS AND METHODS: We evaluated the cytotoxicity of antimicrotubule agents to seven human SCLC cell lines consisting of one cell line (SBC-3) established from a previously untreated patient as a representative of drug-sensitive cell line, three cell lines (SBC-2, SBC-4, and -7) derived from treated patients as representatives of intrinsic drug-resistance cell lines, and three drug-resistant sublines (SBC-3/ADM, SBC-3/ETP, and SBC-3/CDDP) selected by continuous exposure of the SBC-3 cell line to increasing concentrations of doxorubicin, etoposide, or cisplatin as representatives of acquired drug-resistant cell lines. RESULTS: IC50 values for SBC-2, -3, -4, and -7 cells of antimicrotubule agents were markedly lower than those of doxorubicin, etoposide, and cisplatin. Both SBC-3/ADM and SBC-3/ETP subline were highly resistant to paclitaxel, docetaxel, vinorelbine, vincristine, vindesine, and vinblastine. However, an SBC-3/ADM subline was not fully cross-resistant to rhizoxin, and an SBC-3/ETP subline was as sensitive to rhizoxin as an SBC-3 cell line. A cisplatin-resistant subline, SBC-3/CDDP, showed no cross-resistance to the antimicrotubule agents. CONCLUSION: These results suggest that antimicrotubule agents are useful for SCLC, and rhizoxin may be particularly effective in the salvage treatment of refractory or relapsed patients.
BACKGROUND: The improvement of treatment outcome of small-cell lung cancer (SCLC), and search for new effective drugs and to overcome drug-resistance are essential. MATERIALS AND METHODS: We evaluated the cytotoxicity of antimicrotubule agents to seven humanSCLC cell lines consisting of one cell line (SBC-3) established from a previously untreated patient as a representative of drug-sensitive cell line, three cell lines (SBC-2, SBC-4, and -7) derived from treated patients as representatives of intrinsic drug-resistance cell lines, and three drug-resistant sublines (SBC-3/ADM, SBC-3/ETP, and SBC-3/CDDP) selected by continuous exposure of the SBC-3 cell line to increasing concentrations of doxorubicin, etoposide, or cisplatin as representatives of acquired drug-resistant cell lines. RESULTS: IC50 values for SBC-2, -3, -4, and -7 cells of antimicrotubule agents were markedly lower than those of doxorubicin, etoposide, and cisplatin. Both SBC-3/ADM and SBC-3/ETP subline were highly resistant to paclitaxel, docetaxel, vinorelbine, vincristine, vindesine, and vinblastine. However, an SBC-3/ADM subline was not fully cross-resistant to rhizoxin, and an SBC-3/ETP subline was as sensitive to rhizoxin as an SBC-3 cell line. A cisplatin-resistant subline, SBC-3/CDDP, showed no cross-resistance to the antimicrotubule agents. CONCLUSION: These results suggest that antimicrotubule agents are useful for SCLC, and rhizoxin may be particularly effective in the salvage treatment of refractory or relapsed patients.