Antitumor, nephrotoxic and clastogenic effect of cis-DDP with DDTC or NAC

Diethyldithiocarbamate (DDTC) and N-acetylcysteine (NAC) are nucleophile sulfur-containing compounds which can protect the platinum-induced nephrotoxicity. Combinations of cis-diamminedichloroplatinum(II) (cis-DDP) and DDTC or NAC were tested on the leukemia L1210 and melanoma B 16 tumor models. Nephrotoxicity of cis-DDP alone and in combination with DDTC or NAC was evaluated. On both of the investigated tumor models clastogenic effects in bone marrow cells were detected. DNA synthetic and mitotic activity of L1210 cells in vivo were evaluated by 3H-thymidine incorporation and cytogenetic analysis. Amelioration of the platinum induced nephrotoxicity and preservation of the antitumor activity of cis-DDP through combined application with DDTC or NAC were obtained at the L1210 model. Maximal inhibition of the DNA synthesis in L1210 cells was detected with the cis-DDP treatment. The sulfurcontaining nucleophiles DDTC or NAC could modulate the inhibitory effect of cis-DDP on the incorporation of 3H-thymidine into the nuclei of L1210 cells. Enhanced mitotic activity was detected during cytotoxic therapy with cis-DDP. Cis-DDP alone and in combination with DDTC or NAC caused a significant growth inhibition on the s.c. tumor of the melanoma B16 bearing mice. Two times better therapeutic results at this model were obtained with cis-DDP alone (T/C = 234.09%, T/C = 136.36% for cis-DDP+DDTC and T/C = 151.14% for cis-DDP+NAC). The usefulness of DDTC or NAC as adjuvants in the platinum based chemotherapy of human cancers have been discussed. Clastogenic effect and antitumor activity are probably connected and it is supposed that the reduction of the genotoxicity could lead to a decreased antitumor activity of the platinum complex.