Differential response to mitomycin-C- and cis-diamminedichloroplatinum(II)-induced damage in normal human fibroblasts during confluent holding.

Confluent cultures of normal human fibroblasts were treated with the chemotherapeutic agents, mitomycin C (MMC) and cis-diamminedichloroplatinum(II) (cis-Pt(II]. This treatment induced a decrease in clonogenic cell survival. Recovery of the cytotoxic effect was observed in the case of cis-Pt(II)-treated cultures maintained at confluence for 1-5 days. No such recovery was observed after treatment with MMC. These data suggest that contrary to potential lethal damage induced by cis-Pt(II) which is repaired in confluent cells, DNA damage induced by MMC is not repaired in confluent cells.