No abstract

SummaryA link between elevated luteinizing hormone (LH) levels, GATA-4 and LH receptor (LHCGR) expression and gonadotropin-dependent adrenocortical tumorigenesis in humans and mice has been shown. To assess the mechanistic tumorigenic interrelationships between these factors, we transgenically expressed Gata4 under the 21-hydroxylase promoter (Cyp21a1, 21-OH) in C57Bl/6N mice. There was a gradual age-dependent increase of GATA-4 expression only in 21-OH-GATA-4 (TG) female adrenals, in association with slowly progressing neoplasia of non-steroidogenic spindle-shaped A cells in the subcapsular cortex. Gonadectomy (GDX), apparently through direct action of elevated serum LH, markedly enhanced the adrenocortical neoplasia, which now also appeared in GDX TG males. The neoplastic areas of the post-GDX TG adrenals contained, besides A cells, larger lipid-laden, steroidogenically active and LHCGRpositive B cells. Prolonged (.10 months) exposure to elevated post-GDX LH levels resulted in formation of adrenocortical adenomas in the TG mice. Intact and GDX TG mouse adrenals displayed elevated FOG-2 and decreased GATA-6 expression. Additionally, increased expression/activation of components of the Inhbb-Acvr2a-Acvr1c-Smad2/3 signaling system was observed in 12-month-old GDX TG adrenals. Our findings show that two distinct GATA-4-dependent populations of neoplastic adrenocortical cells form: non-steroidogenic LH-independent A cells and steroidogenic LH-dependent B cells.

Novel strategies are needed for the treatment of adrenocortical tumors that are usually resistant to chemotherapy. Hecate, a 23-amino acid lytic peptide, was conjugated to the 15-amino acid (81-95) fragment of the human chorionic gonadotropin b (CGb) chain, which would selectively kill cancer cells expressing the LH receptor (LHR) sparing the normal ones with LHR. To prove the principle that Hecate-CGb conjugate may eradicate tumors ectopically expressing plasma membrane receptors, transgenic (TG) inhibin a-subunit promoter (inha)/Simian Virus 40 Tantigen mice, expressing LHR in their adrenal gland tumors, were used as the experimental model. Wild-type control littermates and TG mice with adrenal tumors were treated with either Hecate or Hecate-CGb conjugate at the age of 6.5 months for 3 weeks and killed 7 days after the last treatment. The Hecate-CGb conjugate reduced the adrenal tumor burden significantly in TG male but not in female mice, in comparison with Hecate-treated mice. Hecate-CGb conjugate treatment did not affect normal adrenocortical function as the serum corticosterone level between Hecate and Hecate-CGb conjugate groups were similar. The mRNA and protein expressions of GATA-4 and LHR colocalized only in tumor area, and a significant downregulation of gene expression was found after the Hecate-CGb conjugate in comparison with Hecate-and/or non-treated adrenal tumors by western blotting. This finding provides evidence for a selective destruction of the tumor cells by the Hecate-CGb conjugate. Hereby, our findings support the principle that Hecate-CGb conjugate is able to specifically destroy tumor cells that ectopically express LHR.

Specific inbred strains and transgenic inhibin-α Simian Virus 40 T antigen (inhα/Tag) mice are genetically susceptible to gonadectomy-induced adrenocortical neoplasias. We identified altered gene expression in prepubertally gonadectomized (GDX) inhα/Tag and wild-type (WT) mice. Besides earlier reported Gata4 and Lhcgr, we found up-regulated Esr1, Prlr-rs1, and down-regulated Grb10, Mmp24, Sgcd, Rerg, Gnas, Nfatc2, Gnrhr, Igf2 in inhα/Tag adrenal tumors. Sex-steroidogenic enzyme genes expression (Srd5a1, Cyp19a1) was up-regulated in tumors, but adrenal-specific steroidogenic enzyme (Cyp21a1, Cyp11b1, Cyp11b2) down-regulated. We localized novel Lhcgr transcripts in adrenal cortex parenchyma and in non-steroidogenic A cells, in GDX WT and in intact WT mice. We identified up-regulated Esr1 as a potential novel biomarker of gonadectomy-induced adrenocortical tumors in inhα/Tag mice presenting with an inverted adrenal-to-gonadal steroidogenic gene expression profile. A putative normal adrenal remodeling or tumor suppressor role of the down-regulated genes (e.g. Grb10, Rerg, Gnas, and Nfatc2) in the tumors remains to be addressed.