In vitro chemosensitivity and radiosensitivity of an adriamycin-resistant subline of human small cell lung cancer cells

Using a cell line (SBC-3/ADM) of human small cell lung cancer, which is 30-fold more resistant to adriamycin than the parent cell line (SBC-3), the activity of a variety of anticancer agents was analyzed by soft agar clonogenic assay to search for a means of circumventing drug resistance. The SBC-3/ADM cells were markedly resistant to some anthracycline antibiotics in comparison with the SBC-3 cells: 28-fold for daunomycin, 26-fold for 4'-epiadriamycin, 18-fold for THP-adriamycin, and 8.4-fold for aclarubicin. However, the cells were as sensitive to mitoxantrone, one of the anthraquinone derivatives, as the parent cells. The cells were resistant to structurally or pharmacodynamically unrelated compounds such as vincristine, mitomycin C, and an active form of ifosfamide, whereas they were susceptible to cisplatin to some extent. The in vitro radiosensitivity of both cell lines was also evaluated, and they were found to be equally sensitive to X-ray. These results suggest that mitoxantrone and cisplatin may exert sufficient activity for small cell lung cancer which has acquired resistance to adriamycin, and that consolidative chest irradiation may be clinically useful after combination chemotherapy including adriamycin.