Abstract 1726: Estrogen implication in human hepatocellular carcinoma is associated with changes in estrogen receptors and aromatase expression

Abstract

Abstract There is evidence that hints at a potential role of sex steroids in development and progression of human hepatocellular carcinoma (HCC). Previous studies have revealed that estrogen receptors (ER) are expressed in primary HCC. However, the use of antiestrogens has failed to improve disease-free and overall survival of patients. In the present study we have investigated aromatase-driven estrogen formation in nontumoral and malignant human liver tissues and cells, also in relation to the expression of ERα, ERβ, and their splicing variants, aiming to get insights into the potential role of estrogens and the underlying mechanism(s) in human HCC. Chromatographic and exon-specific RT-PCR analyses were used to respectively assess activity and expression the aromatase enzyme and the expression of wild-type (hERα66, hERβ1) and variant (hERα46, hERα36; hERβ2/Cx, hERβ5) ER, both in vivo and in vitro. Following 24h and 72h incubation of tissue minces or hepatic cell lines, with either testosterone (T) or androstenedione (Ad) being used as tritiated androgen precursor, human HCC tissues and HepG2 hepatoma cells showed elevated aromatase activity, with estrogen formation rates respectively of 20% at 24h and >95% at 72h. By contrast, no aromatase activity could be detected in nontumoral hepatic tissues and HA22T liver cancer cells at any incubation time. Cirrhotic samples exhibited intermediate enzyme activity, with average estrogen formation rates of nearly 4%, while Huh7 HCC cells gave rise to 34% estrogen formation by 72h. Markedly lower aromatase mRNA levels were observed in HA22T cells and nontumoral liver tissues, as compared to HepG2 cells and HCC samples. Cirrhotic specimens displayed variable transcript levels, comparable in turn to those observed in nontumoral or HCC tissues. Interestingly, no or low expression of both wild type ERα and ERβ could be detected in liver cancer cells and malignant tissues. Conversely, equivalent amounts of the hERα46 variant were observed in both cells and tissues, while hERα36 expression was highest in HepG2 cells and HCC samples, intermediate in Huh7 cells and cirrhotic tissues, and very low in HA22T cells and nontumoral liver. On the other hand, only occasional expression of the two ERβ variants was observed in liver cancer cells and tissues. It is noteworthy that the pattern of hERα36 expression was strictly related to that of the aromatase enzyme, suggesting that this ERα variant may be primarily implicated as a mediator of estrogen action in the malignant liver. The above evidence may advance the current appraisal of the endocrine status of human liver tumors and represent an experimental basis to develop novel, personalized, endocrine therapeutic strategies for HCC patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1726.