G1 PHASE CHINESE-HAMSTER V79-379A CELLS ARE INHERENTLY MORE SENSITIVE TO PLATINUM BOUND TO THEIR DNA THAN MID S-PHASE OR ASYNCHRONOUSLY TREATED-CELLS

The importance of expressing cell sensitivity in terms of extent of platinum bound to DNA is demonstrated using HeLa and Chinese hamster V79-379A cells. HeLa cells were found to be slightly more sensitive to cis platinum{II} diammine dichloride (cis Pt{II}) for a given extent of platinum binding to DNA compared with Chinese hamster V79-379A cells, although the difference between the two cell lines was less than that indicated by dose-survival data. Chinese hamster cells in the G1 phase of their cell cycles were more sensitive to treatment with cis Pt{II} than cells in other phases of the cell cycle or than cells in an asynchronous cell culture. This sensitivity of G1 phase cells was not due to an increased uptake of platinum into the cells but rather reflected an inherent increase in sensitivity of these cells to a given binding of cis Pt{II} to their DNA. Chinese hamster cells were inherently more sensitive to the drug when they were treated in a stationary growth phase followed by dilution as compared with treatment in an exponential growth phase. © 1979.