Apoptosis of Lung Cancer Cells Caused by Some Anti-cancer Agents (MMC, CPT-11, ADM) is Inhibited by BCL-2

To determine whether the apoptotic cell death induced by anti-cancer agents could be inhibited by bcl-2, we established a bcl-2-transfected human small cell lung cancer cell line, SBC-3/Bcl2. SBC-3/Bcl2 showed higher resistance to ADM, CPT-11 and MMC compared with the parental line SBC-3, with relative resistance values of 3.4, 7.6 and 5.7, respectively. However, there was no difference in sensitivity to CDDP, VP16, ACNU, MTX and taxol between SBC-3 and SBC-3/Bcl2. Agarose gel electrophoresis showed typical DNA fragmentation of SBC-3 following treatment with CPT-11 or MMC, in a concentration-dependent manner. In contrast, the same concentration of the drugs did not induce DNA fragmentation in SBC-3/Bcl2. Treatment with CDDP resulted in the same degree of DNA fragmentation in SBC-3 and SBC-3/Bcl2. These studies indicate that bcl-2 can modulate the cytotoxicity of some anti-cancer agents by inhibiting the process of apoptosis.