A keratinocyte-mediated mutagenesis assay, and the murine skin multistage
carcinogenesis tumor model were used to survey the chemopreventive properties of Cu(II)(3,5-diisopropylsalicylate)2 [
CuDIPS] and its analogs. Supplementation of cocultures of newborn SENCAR keratinocytes and Chinese hamster lung fibroblasts (V79 cells) with
CuDIPS, 3,5-diisopropylsalicylate (
DIPS), and CuSO4 resulted in dose-dependent killings of V79 cells (LD50 of 34, 75, 960 microM, respectively), and inhibitions of
benzo[a]pyrene (BP) and 7,12-dimethylbenz[a]
anthracene (DMBA) mutagenesis (ED50 of 13, 95, 80 microM, and 40, 125, 110 microM, respectively). Analyses of dose-response curves suggest (i)
CuDIPS preferentially inhibits BP mutagenesis; (ii) the antimutagenic activity of
CuDIPS towards DMBA and the cytotoxicity of the
copper complex are derived from the
DIPS component of the chelate; (iii) the antimutagenic activity of
CuDIPS towards BP requires both
copper and
DIPS; and (iv)
DIPS and
CuDIPS induced cytotoxicity is required for inhibition of mutagenesis. Inhibition of mutagenesis by
CuDIPS was not mediated by modulation of promutagen metabolism because antimutagenic concentrations of the chelate had no significant effects on DMBA- and BP-dependent cytotoxicities. Topical pretreatment of SENCAR mice with
CuDIPS (100-4000 nmol) 15 min prior to initiation with DMBA or BP resulted in small (38% maximum) non-dose-responsive reductions of
papillomas/mouse following 20 weeks of promotion.