We have generated temperature-sensitive (ts) mutants for
steroid-regulated anchorage-independent cell growth.
Androgen-responsive S115+A mouse mammary
tumor cells were mutagenized with ethyl methane sulfonate and the variants which were growth-arrested in
suspension at the nonpermissive temperature of 41 degrees C were selected by killing dividing wild-type cells with the
DNA synthesis inhibitors 5-fluoro-2'-deoxyuridine or
cytosine arabinoside. Fifteen clones were isolated and characterized for morphology and growth properties. Three (ts21, ts27, ts33) of the phenotypic variants were ts for
androgen-maintained anchorage-independent growth, two of them (ts27 and ts33) also for growth in monolayer. Growth arrest at 41 degrees C was not due to a defect in
androgen receptor function in any of the mutant cell lines as shown by
steroid binding assays and by the
androgen-stimulated expression of both endogenous MMTV
RNA and the transiently transfected LTR-CAT gene at the nonpermissive temperature. It remains to be determined for clone ts33 whether the defect is in postreceptor events of
steroid action or in genes affecting general mechanisms of cell growth. However, since in clones ts21 and ts27 general cell growth remains functional at 41 degrees C under serum stimulation, defects may be in postreceptor
steroid-related pathways. It is hoped that these mutants will provide a useful tool for study of
steroid regulation of cell growth and in particular of the property of anchorage-independent growth.