Implicación del gen Wilms\'Tumor 1 (WT1) en la desdiferenciación y la transformación neoplásica del hígado. Papel de su diana anfirregulina (AR) en el daño hepático crónico

Resumen

The Wilms tumor 1 gene (WT1) encodes a transcription factor involved in cell growth and development. WT1 expression is hardly detectable in normal liver but is induced in cirrhosis. Although WT1 is overexpressed in a number of malignancies, the role of WT1 in hepatocarcinogenesis is unknown. We found that WT1 is expressed in several human hepatocellular carcinoma (HCC) cell lines, and in HCC tumor tissue in 42% of patients. Transcriptome analysis of PLC/PRF/5 cells after WT1 knockdown demonstrated upregulation of 251 genes and downregulation of 321. Ninety per cent of the former corresponded to metabolic genes characteristic of the mature hepatocyte. Opposedly, genes that decreased upon WT1 inhibition were mainly related to cell survival, cell cycle and tumor progression. Accordingly, WT1 expression increased the resistance of HCC cells to the cytotoxic doxorubicin. Interestingly, doxorubicin strongly enhanced WT1 expression in HCC cells and normal human hepatocytes. Among different chemotherapeutics, WT1 upregulation was restricted to topoisomerase-2 inhibitors. When WT1 expression was prohibited doxorubicin increased caspase-3 activation. In conclusion, expression of WT1 in HCC contributes to tumor progression and chemoresistance, therefore WT1 may be an important target for HCC treatment. One of the best-characterized targets directly induced by WT1 is amphirregulin (AR), a member of the epidermal growth factor (EGF) family and ligand of the EGF receptor (EGFR). AR gene expression in the healthy liver is very low, however it is significantly elevated in acute and chronic injury. We have addressed the role of AR in experimental liver fibrosis. We found that among the different EGFR ligands AR plays a specific role in liver fibrosis. AR may contribute to the expression of fibrogenic mediators and to the growth and survival of fibrogenic cells. Our findings suggest that the AR/EGFR signalling system could be a new target in the prevention of liver fibrosis. Cirrhosis is the background on which most liver tumors develop. We have studied the expression and role of AR in human HCC. AR is expressed in HCC tissues and cell lines, and behaves as a mitogenic and antiapoptotic growth factor for HCC cells. We provide several lines of evidence, including AR silencing by siRNAs and inhibition of AR by neutralizing antibodies, demonstrating the existence of a pro-tumorigenic AR-mediated autocrine loop. Interference with endogenous AR production resulted in inhibition of cell proliferation, anchorage-independent growth, and enhanced apoptosis. Moreover, knockdown of AR potentiated TGF-β and doxorubicin-induced apoptosis. These observations suggest that AR is involved in the acquisition of neoplastic traits in the liver, and thus constitutes a novel therapeutic target in human HCC.