TGF-beta1 and type III Deiodinase are involved in the mechanism of action of HCB in the generation of preneoplastic foci in rat liver

ANA CLARA DEL TOMASO PORTAZ; DIANA L. KLEIMAN DE PISAREV; EZEQUIEL RIDRUEJO; FLORENCIA CHIAPPINI; MAR¨ªA JES¨²S OBREG¨®N; CAROLINA PONTILLO; HILDA BURGOS; ANDREA RANDI; OSCAR MANDO; LAURA ALVAREZ

Boston

Congreso; The 63rd anual Meeting of the American Association for the Study and Liver Diseases; 2012

AASLD

Experimental studies suggest that deregulation of the homeostasis of thyroid hormones (TH) would be an important physiological process for early neoplastic transformations. Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death; however there are no biochemical and molecular markers of early HCC expression. Certain environmental toxins are capable of inducing HCC. Hexachlorobenzene (HCB), a pesticide, is an endocrine disruptor and a promoter of liver cancer in rats. TGF-¦Â is a regulator of liver cell growth. Upregulation of type III deiodinase (DIII), by TGF- ¦Â has been demonstrated in various tissues. We have demonstrated that HCB alters thyroid hormone (TH) homeostasis, and induces cell proliferation and apoptosis in rat liver. Objective: 1-To study whether TGF-¦Â is involved in the generation of preneoplastic foci in an initiation-promotion model in rat liver, [diethylnitrosamine (DEN) (50 mg / kg) and HCB (100 mg / kg bw)]; to analyze if TH homeostasis is altered; to analyze the effect of HCB on proliferation and apoptosis. 2- To evaluate TGF-¦Â1 levels, cell proliferation and cD1 in Hep-G2 cells. 3- TGF- ¦Â in human HCC samples. Methods: PCNA, TGF-¦Â1 and D1 cicline (cD1) protein levels, by Westerblot; Expression of TGF-¦Â1, DIII and CYP1A1, by RT-PCR; tissue levels of TH, by RIA; and TGF-¦Â1 and GST-P levels in focal and non focal areas by immunohistochemistry. Results: PCNA protein levels increased 60% (¡Ü 0.001) and cD1 36% (p ¡Ü 0.01) in (DEN + HCB) compared to their respective control (DEN).  TGF-¦Â1 protein levels increased 50% (p ¡Ü 0.01), TGF-¦Â1 mRNA 45% (p ¡Ü 0.01) and CYP1A1 38% (p ¡Ü 0.01) in the (DEN + HCB) compared to their control DEN. T4 levels were increased 35% (p ¡Ü 0.01), T3 levels were reduced 37% (p ¡Ü 0.01) and DIII mRNA levels increased 30% (p ¡Ü 0.01) in (DEN + HCB) compared to DEN group. TGF-¦Â1 protein levels were increased in focal compared with non-focal area 62% (p ¡Ü 0.001). In Hep-G2, PCNA, TGF-¦Â1 and cD1 were increased depending on the dose of HCB (5, 50, 500 and 5000 nM). TGF-¦Â1 protein levels increased 43% (p ¡Ü 0.01) in HCC biopsies compared with normal human liver tissue. Conclusion: HCB alters homeostasis of cell growth in the induction-promotion model, towards proliferation. TGF- ¦Â1 and DIII might be involved in this effect in this model. HCB increases cell proliferation and TGF- ¦Â1 levels in Hep-G2 cells. Likewise, these cytokine levels are increased in human HCC samples, and may have a prognostic value.