538 Nuclear Translocation of FGFR1 and FGF2 in Pancreatic Stellate Cells Is Necessary for Pancreatic Cancer Cell Invasion

Abstract

Background: It is now appreciated that, in pancreatic cancer, transformed cells interact with stromal cells, extracellular matrix proteins, and neighboring normal epithelial cells to exploit feedback mechanisms and facilitate tumour progression. Studies have shown that overexpression of FGF2 in pancreatic cancer correlates with poor patient survival and nuclear FGF2 has been observed in pancreatic cancer patient tissue but not in normal patient samples (Yamanka et al 1993). A number of mechanisms have been proposed for the nuclear accumulation of FGFR1 and its ligand; however, the role of intracrine FGF2 signalling in tumour invasion remains poorly understood. We investigated whether nuclear translocation of FGFR1 with FGF2 plays a role in pancreatc stellate cell (PSC) behaviour. Design: FGF2 and FGFR1 RNAi, together with an FGFR inhibitor (PD173074) were used on pancreatic cancer cell lines PSCs and in organotypic cultures to assess their effect on cell behaviour and to assess the effects of blocking FGF signalling on cancer cell behaviour and invasion. Nuclear FGFR1 and FGF2 expression were also studied in vivo. Results: FGF2 and FGFR1 localised to the nucleus in stromal fibroblasts at the invasive front of human pancreatic cancer tissue. In vitro, FGFR1 and FGF2 co-localised to the nucleus in PSCs but not in cancer or normal ductal epithelial cell lines. PSCs but not cancer cells secrete both HMW and LMW FGF2 isoforms. Abolishing nuclear FGFR1 and FGF2 in PSCs using either RNAi or FGFR inhibitor resulted in a significant reduction in cell proliferation which correlated with a G1 cell-cycle block and reduction in the G1 cyclin, cyclin D1. In an organotypic model, nuclear FGFR1 and FGF2 were significantly greater in PSCs invading into the matrix. When treated with FGFR inhibitor, PSCs were unable to invade into the extra-cellular matrix and FGFR1 and FGF2 remained cytoplasmic. Effective blockade of nuclear FGFR1 signalling in PSCs abolished cancer cell invasion. Conclusion: These studies show for the first time that nuclear FGFR1 and FGF2 plays a role in driving pancreatic stellate cell proliferation. Preventing nuclear FGF/FGFR mediated proliferation in PSCs leads to disruption of the tumour microenvironment, thus preventing pancreatic cancer cell invasion.