Promotion of Morphological Transformation by di-n-butyltin Dichloride in C3H/10T1/2 Cells: Prediction by Prior Expression of Tumour Promoter-Responsive Genes

Previous studies in our laboratory have shown that chemical treatments may induce increases in proliferin gene family mRNA accumulation in cultured murine embryonic cells. Proliferin inductions are highly correlated with subsequent promotional outcomes during two-stage focus-formation assays in C3H/10T1/2 cell cultures. In work reported here, the strong affiliation between these two responses was further validated after treating cells with di-n-butyltin dichloride which is a polyvinyl chloride (PVC) plastic additive that often contaminates food and water. Increased proliferin expression and promotion of morphological transformation occurred at similar concentrations. Promotion of transformation was detected at di-n-butyltin dichloride concentrations of 80 n m (24 ng/ml) and above, if added to initiated cultures before confluent monolayers had formed. Proliferin induction and morphological transformation were both reduced in confluent cultures treated with di-n-butyltin dichloride, as compared to subconfluent cultures. Proliferin expression measured in near-confluent cultures was induced up to 10-fold during the 36-hr period following di-n-butyltin dichloride exposure and was accompanied by increased accumulation of transcripts from many genes regulated by oxidative stresses, growth-inducing agents, and/or other promoting agents (asbestos, superoxide radicals ). Di-n-butyltin dichloride-induced mRNA species included members of the fos and jun proto-oncogene families, c-myc, egr1, ribonucleotide reductase (R2 subunit), odc, macrophage chemotactic protein/je, hsp70, metallothionine IIA, c-sod and mn-sod. The observed patterns of RNA accumulation suggested that a small subset of mRNA species, including proliferin, exhibit regulatory behaviour as a response to dissimilar agents or conditions that promote focus-formation in C3H/10T1/2 cultures. Plausible predictions of promotional effects in two-stage morphological transformation assays can be made from gene-expression responses to test agents.