Résumé
FAM110B was first identified in a functional screen using genetic suppressor elements to identify new genes involved in the sensitivity to topoisomerase II poisons (Gros et al. Cancer Res, 2003 63: 164-71). FAM110B is extremely conserved in vertebrates. It shares strong sequence homologies with the two other members of this new family (FAM110A & C), but has no known functional domains. We generated a polyclonal antibody and showed that endogenous FAM110B had a MW of ≈40 kDa and was expressed in various cancer cell lines with a predominant cytoplasmic localization. To identify its biological function, we evaluate the different genes/pathways that it could modulate, using specific lentiviral shRNA to target FAM110B in HeLa cells. We found that transient downregulation of FAM110B induced a net decrease in cell proliferation and cell survival. It also induced a change in cell morphology which was accompanied by an increase in E-cadherin and a decrease in N-cadherin expression which are two markers of a reverse epithelial to mesenchymal (EMT) transition phenotype. We also measured the levels of SNAIL and SLUG protein levels, two known repressors of E-cadherin expression and found that only SLUG was decreased in shFAM110B-transfected cells, suggesting that regulation of E-cadherin expression by FAM110B involves, at least in part, its transcriptional repression by SLUG. Increased expression of E-cadherin was confirmed at the mRNA level by microarray analyses comparing control cells to shFAM110B-transfected cells. This analysis also revealed the presence of various genes involved in EMT among the 1000 most differentially expressed genes (adjusted t-value > 7 or < -7) such as Twist2, fibronectin 1, Collagen 1A1 & 4, MMP2, PAI-1, claudin1 & 4, integrin α4, Nestin, interleukin 8, MUC1, or MUC16. Our data were confirmed at the functional level by analyzing the effects of FAM110B repression on the motility/migratory behaviour of HeLa cells using the wound model. While cells expressing control shRNA were able to invade the wound within 7-10h, cells with reduced levels of FAM110B had barely started to move towards the wound. Similarly, shFAM110B-transfected cells displayed a 2-fold decrease in their capacity to invade and migrate through collagen gels as compared to control cells. Using the Cignal Finder Cancer 10-Pathway Reporter Assay, we assess whether other signalling pathways could be deregulated following FAM110B downregulation. We found that Wnt, TGF-β and the Notch pathways, which are all involved in EMT, were significantly downregulated in shFAM110B-transfected cells, which is in accordance with our previous observations. Together, our results provide new evidences on the potential role of FAM110B in the regulation of E-cadherin expression and more generally in crucial cellular processes such as cell motility, migration, invasion and metastasis which makes it a new potential target for cancer therapy. Citation Format: Authors. Abstract title [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2332. doi:10.1158/1538-7445.AM2011-2332