Abstract 1035: hMENA splicing program and TGF-β1-mediated EMT in pancreatic cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background Epithelial to mesenchymal transition (EMT) is an early event in pancreatic cancer and has been involved in cancer invasiveness. An intense stromal reaction, peculiar to the pancreatic tumor microenvironment, includes cancer-associated fibroblasts(CAFs), abundant cells in the tumor stroma, recently linked to the induction of EMT. On the other hand, the EMT process requires a dynamic remodeling of the actin cytoskeleton, and the splicing program of hMENA, a regulator of actin, has been associated with the EMT process. We have described two alternatively expressed isoforms, hMENA11a and hMENAΔv6, with opposite functions in invasiveness in breast cancer (1). hMENA expression was detected in human pancreatic ductal adenocarcinoma samples (PDAC) (2), but no data are available on the alternative isoform expression in this neoplasia. The aim of this study is to investigate the role of hMENA splicing in TGF-β -mediated EMT in pancreatic cancer, the mechanisms involved in hMENA induction in PDAC and the role of CAFs in this process. Methods hMENA isoform expression was evaluated in PDAC tissues by immunohistochemistry using isoform-specific antibodies. Human PDAC cell lines, untreated or TGF-β treated, were characterized for the expression of hMENA isoforms and markers of EMT by qRT-PCR and WB analysis. The effects of both hMENAΔv6 knockdown or overexpression were also evaluated. Pancreatic cancer associated-fibroblasts were isolated from primary PDAC tissues. To study the role of fibroblast-cancer cell interactions on hMENA expression, a noncontact coculture system was used. Results IHC analysis of PDAC tissues revealed that epithelial hMENA11a is rarely expressed in primary pancreatic tumors that express a high level of hMENA and hMENAΔv6 isoforms. In a panel of pancreatic cancer cell lines, hMENA11a expression correlates with an epithelial phenotype, wherea hMENAΔv6 expression is associated with a mesechymal phenotype. TGF-β treatment specifically upregulated the invasive hMENAΔv6 isoform expression. Knockdown of endogenous hMENA/hMENAΔv6 isoform reduced cell invasiveness, reverted cells to an epithelial -“like” phenotype with an increased E-cadherin expression and impaired the TGF-β-mediated vimentin up-regulation. Conversely, overexpression of hMENAΔv6 increased the expression of the mesenchymal marker vimentin. Freshly explanted CAFs expressed the “mesenchymal” hMENAΔv6, and not hMENA11a and produced paracrine factors involved in the induction of hMENA isoforms in tumor cells. Conclusions These data provide new and critical insights into the role of hMENA splicing in TGF-β mediated EMT and identify the hMENA splicing program as a promising pathway for the development of new diagnostics and therapeutics in PDAC. (1) Di Modugno F. et al PNAS 2012 (2) Pino S. et al Clin Cancer Res 2008 Citation Format: Roberta Melchionna, Pierluigi Iapicca, Francesca Di Modugno, Paola Trono, Novella Gualtieri, Maria Grazia Diodoro, Sheila Spada, Giuliana Falasca, Gian Luca Grazi, Mina J Bissell, Paola Nistico. hMENA splicing program and TGF-β1-mediated EMT in pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1035. doi:10.1158/1538-7445.AM2014-1035