Jianqi Liu

Transcription factors GATA-6, SF-1, and cell proliferation in human adrenocortical tumors.

Transcription factor GATA-6 is expressed in fetal and adult human adrenal cortex and has been suggested to have a role in adrenal androgen synthesis. In other tissues GATA-6 has been linked to the cell cycle regulation and the dedifferentiation of carcinoma cells. GATA-6 has been shown to be downregulated in mouse adrenocortical tumors, but has not been studied in human adrenocortical tumors in detail. We have now analyzed GATA-6 expression in 20 human adrenocortical adenomas and 16 carcinomas using Northern blot analysis and immunohistochemistry. GATA-6 mRNA and protein expression was remarkably diminished in adrenocortical carcinomas as compared to normal adrenal cortex and adenomas (p<0.05). In opposite to other tumor types GATA-6 expression was, however, high in virilizing carcinomas. Steroidogenic factor 1 (SF-1) has been functionally linked to GATA-6, and the expression of these two factors correlated in the adrenal tumors. Furthermore, GATA-6 immunoreactivity was linked to P450c17 expression. In contrast to GATA-6, we found upregulated cyclin-dependent kinase inhibitor p21 and proliferation marker Ki67 in adrenocortical carcinomas indicating that GATA-6 is not linked to cell proliferation in human adrenal tumors. Taken together, the present and earlier results link GATA-6 to adrenocortical steroidogenesis and to the benign adrenocortical phenotype.

Expression of inhibin α in the human adrenal gland and adrenocortical tumors

We studied the expression of inhibin α-subunit in normal and hyperplastic adrenal glands, as well as in various adrenocortical tumors. The protein expression of inhibin α was performed by immunohistochemistry. Virilizing adenomas showed strong immunoreactivity against monoclonal inhibin α-subunit antibody, whereas other adenomas were only weakly positive or completely negative. In the adrenal cortex no inhibin α immunoreactivity was detected in the zona glomerulosa. Zona fasciculata showed weak staining for inhibin α, however, strong immunostaining was detected in zona reticularis both in normal and hyperplastic adrenal glands. Adrenal medulla was negative for inhibin α. In conclusion, we show high expression of inhibin α subunit in zona reticularis of normal and hyperplastic adrenal glands as well as strong expression in virilizing adenomas.

Transcription factors GATA-4 and GATA-6 during mouse and human adrenocortical development.

Our earlier work implicates transcription factors GATA-4 and GATA-6 in the murine adrenal. We have now studied their expression during mouse and human adrenal development in detail. GATA-4 and GATA-6 mRNAs are readily detectable from embryonic day 15 in mouse and gestational week 19 in human adrenal cortex. In postnatal adrenal, GATA-4 expression is down-regulated, whereas GATA-6 mRNA and protein continue to be abundantly present. In a human adrenocortical cell line NCI-H295R, GATA-6 mRNA is up-regulated by cAMP. This cell line does not express GATA-4. Our findings suggest that GATA-6 expression is hormonally controlled, and required throughout adrenal development from fetal to adult age. GATA-4, on the other hand, may serve a role in fetal adrenal gene regulation.

Acth regulates ldl receptor and CLA-1 mRNA in the rat adrenal cortex

Rat adrenocortical cells utilize both low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol for steroid hormone production. In addition to exogenous lipoprotein-derived cholesterol, cells produce cholesterol de novo. Adrenocorticotropin (ACTH) increases both steroid hormone secretion and uptake of LDL and HDL. We studied the expression of LDL receptor mRNA and CLA-1 (a putative HDL receptor) mRNA in cultured rat adrenocortical cells. ACTH increased the amounts of LDL receptor mRNA during 2 to 48 h of stimulation, the highest levels being detected after 2-4 h. Similar results were obtained with cyclic AMP (cAMP) derivatives, 8-bromo cAMP (8-Br cAMP) or dibutyryl cAMP. ACTH increased CLA-1 mRNA during 2 to 24 h of stimulation, the highest levels being detected after 4 h. In conclusion, ACTH up regulates both LDL and HDL receptor mRNA in rat adrenocortical cells.

Expression of adrenomedullin in human ovaries, ovarian sex cord–stromal tumors and cultured granulosa–luteal cells

The aim of the present study was to characterise the expression pattern of the multifunctional vasoactive peptide adrenomedullin (ADM) in human ovarian tumors, and to find hormonal regulators of ADM expression in human ovaries. The expression of ADM messenger RNA (mRNA) was higher in granulosa cell tumors than in fibrothecomas and normal ovaries, as analysed by Northern blots. In normal ovaries, ADM immunoreactivity was localised in both granulosa and thecal cells. Eight of the 90 granulosa cell tumors (9%) showed moderate and 53 (59%) weak ADM immunoreactivity, whereas 27% (11/41) of the fibrothecomas displayed weak ADM staining. FSH, protein kinase A activator (Bu)2cAMP, prostaglandin E2 (PGE2), activin A and the broad protein kinase regulator staurosporine decreased ADM mRNA accumulation in cultured granulosa–luteal cells time- and dose-dependently. FSH, (Bu)2cAMP and PGE2 increased progesterone secretion and the accumulation of the steroidogenic acute regulatory protein mRNA in these cells. In conclusion, ADM is expressed in normal human ovaries and sex cord–stromal tumors, particularly in those of granulosa cell origin. FSH, PGE2, (Bu)2cAMP and activin A suppress ADM gene expression in granulosa–luteal cells. Expression of ADM in human ovaries and its hormonal regulation in granulosa cells suggests a paracrine role for ADM in ovarian function.