Microcell-mediated transfer of carcinogen-induced ouabain resistance from C3H/10T1/2 Cl 8 mouse fibroblasts to human cells.

We previously developed a quantitative assay for measuring the induction of ouabain-resistant (Ouar) variants in transformable C3H/20T1/2 Cl 8 mouse fibroblasts following treatment of the cells with chemical carcinogens. To further define the nature of the Ouar phenotype, we conducted microcell-mediated chromosome transfer studies using Ouar cell lines induced by chemical carcinogens in C3H/10T1/2 Cl 8 cells as donors and 8-azaguanine-resistant (Azgr) derivatives of the human cell lines, D98/AH2 and HT 1080, as recipients. Microcells prepared from one spontaneous and two carcinogen-induced Ouar mouse cell lines were able to transfer resistance to 0.01 and 1 mM Oua to ouabain-sensitive D98 and HT 1080 cells. The frequency of microcell hybrid formation ranged from 10(-6) to 10(-5). Karyotypic analysis of the microcell hybrids indicated that the Ouar phenotype of C3H/10T1/2 Cl 8 derivatives mapped to mouse chromosome 3, the chromosome to which the wild-type murine Oua-1 allele had previously been assigned. These studies show that both spontaneous and chemically induced high level Ouar phenotypes of C3H/10T1/2 Cl 8 mouse fibroblasts can be transferred via microcell-mediated chromosome transfer, and provide strong genetic evidence that chemically induced Ouar phenotypes of C3H/10T1/2 Cl 8 cells arise from mutations at Oua-1. In addition, this study sufficiently standardizes microcell-mediated chromosome transfer in the C3H/10T1/2 Cl 8 cell line so that this technique can be used to investigate the nature of other phenotypic changes in these cells, such as the chemically transformed phenotype.