Comparison of the response of synchronized HeLa cells to talisomycin and bleomycin.

The cytotoxic activities of the antitumor antibiotics talisomycin (TLM) and bleomycin (BLM), were compared with asynchronous and synchronous populations of HeLa cells. The sensitivities of asynchronous and synchronous cells to TLM and BLM were expressed as biphasic dose-response survival curves. Of the cell cycle populations investigated, mitotic phase cells were the most sensitive and G1 phase cells the most resistant to tLM and BLM cytotoxic activity. A significantly greater portion of mid-G1 cells was more resistant to TLM than to BLM. Mid-S-phase cells showed greater resistance to TLM than to BLM in the initial portion (primary slope) of the dose-response curve.