Characterization of adrenocortical cell lines produced by genetically targeted tumorigenesis in transgenic mice
N A Compagnone1, S R Bair, S H Mellon
1Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Francisco 94143-0556, USA.
Abstract:
Using transgenic mice, we targeted SV40 T antigen and the bacterial neomycin resistance gene to steroidogenic tissues using a human P450 cholesterol side-chain cleavage promoter. Expression of SV40 T antigen resulted in adrenocortical tumors. Adrenocortical cell lines from one of these tumors (ST5R) was previously characterized. We have now obtained clonal lines from the second more differentiated tumor. After dispersion 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 the right adrenal tumor (ST5R). ST5L cell lines secrete progesterone and corticosterone to varying degrees, whereas ST5R cells secrete only progesterone. One of the clonal cell lines, ST5Lc16, expresses both P450c11 beta and P450c11AS mRNAs, which normally are regionally distributed in different zones of the adrenal cortex. Thus, ST5Lc16 cells may be progenitor cells for both glomerulosa and fasciculata cells and may provide clues to the cellular and molecular events leading to the differentiation of the glomerulosa and the fasciculata-reticularis. Other ST5Lc cell lines are more representative of the fasciculata-reticularis, because they express P450c11 beta mRNA and secrete corticosterone, and they neither express P450c11AS mRNA nor do they secrete aldosterone. All cell lines also have 21-hydroxylase activity, but none express P450c21, indicating that some other, as yet unidentified, enzyme has this activity. In all cell lines, steroid secretion is regulable by cAMP stimulation but not by ACTH stimulation. All ST5L cell lines also express mouse renin-1 mRNA. In addition to their utility in studies of adrenal steroidogenesis, these cell lines may also be useful in studying the etiology of adrenocortical tumors.
Insights
Transgenic mice developed adrenocortical tumors, yielding new cell lines (ST5L) that better model adrenal steroidogenesis and differentiation. These cell lines offer insights into glomerulosa and fasciculata cell development and adrenocortical tumor origins.
Area of Science:
- Endocrinology
- Molecular Biology
- Oncology
Background:
- Transgenic mice were engineered to express SV40 T antigen in steroidogenic tissues.
- This led to the development of adrenocortical tumors, from which cell lines were derived.
- Previous work characterized ST5R cell lines from one tumor; this study focuses on lines from a second, more differentiated tumor.
Purpose of the Study:
- To establish and characterize novel adrenocortical cell lines from a more differentiated tumor.
- To investigate the differentiation potential and steroidogenic capabilities of these new cell lines.
- To explore their utility in understanding adrenal cell differentiation and the etiology of adrenocortical tumors.
Main Methods:
- Adrenal tumors from transgenic mice were dispersed to obtain parental cells (ST5L).
- Cells were selected with G418 and subcloned to generate clonal cell lines.
- Steroid secretion, gene expression (P450s, renin), and responsiveness to cAMP and ACTH were analyzed.
Main Results:
- ST5L cell lines exhibited higher differentiation than ST5R lines, secreting progesterone and corticosterone.
- One line, ST5Lc16, expressed P450c11 beta and P450c11AS mRNAs, suggesting progenitor capacity for glomerulosa and fasciculata cells.
- Other ST5L lines mimicked fasciculata-reticularis cells, secreting corticosterone but not aldosterone.
- All lines possessed 21-hydroxylase activity without P450c21 expression, indicating an unknown enzyme.
- Steroid secretion was regulated by cAMP but not ACTH; renin-1 mRNA was expressed.
Conclusions:
- The novel ST5L cell lines represent valuable tools for studying adrenal steroidogenesis and differentiation.
- ST5Lc16 cells may serve as progenitors for distinct adrenal cortex zones.
- These cell lines can elucidate molecular events in adrenal cell differentiation and adrenocortical tumor development.
