CHARACTERIZATION OF ADRENOCORTICAL CELL-LINES PRODUCED BY GENETICALLYTARGETED TUMORIGENESIS IN TRANSGENIC MICE

Using transgenic mice, we targeted SV40 T antigen and the bacterial ne omycin resistance gene to steroidogenic tissues using a human P450 cho lesterol side-chain cleavage promoter. Expression of SV40 T antigen re sulted in adrenocortical tumors. Adrenocortical cell lines from one of these tumors (ST5R) was previously characterized. We have now obtaine d clonal lines from the second more differentiated tumor. After disper sion of the left adrenal tumor, ST5L parental cells were selected with G418 and subcloned. The resulting adrenocortical subcloned cell lines are more highly differentiated than those cell lines resulting from t he right adrenal tumor (ST5R). ST5L cell lines secrete progesterone an d corticosterone to varying degrees, wheres ST5R cells secrete only pr ogesterone. One of the clonal cell lines, ST5Lc16, expresses both P450 c11 beta and P450c11AS mRNAs, which normally are regionally distribute d in different zones of the adrenal cortex. Thus, ST5Lc16 cells may be progenitor cells for both glomerulosa and fasciculata cells and may p rovide clues to the cellular and molecular events leading to the diffe rentiation of the glomerulosa and the fasciculata-reticularis. Other S T5Lc cell lines are more representative of the fasciculata-reticularis , because they express P450c11 beta mRNA and secrete corticosterone, a nd they neither express P450c11AS mRNA nor do they secrete aldosterone . All cell lines also have 21-hydroxylase activity, but none express P 450c21, indicating that some other, as yet unidentified, enzyme has th is activity. In all cell lines, steroid secretion is regulable by cAMP stimulation but not by ACTH stimulation. All ST5L cell lines also exp ress mouse renin-1 mRNA. In addition to their utility in studies of ad renal steroidogenesis, these cell lines may also be useful in studying the etiology of adrenocortical tumors. (C) 1997 by Elsevier Science I nc.