Z Gastroenterol 2015; 53 - KG230
DOI: 10.1055/s-0035-1559256

Cofilin-1-mediated growth regulation in pancreatic cancer cells is associated with downregulation of Gli1 and increased activity of the MAL/SRF transcription factor complex

B Kaistha 1, S Kirchhoff 1, H Schmidt 1, M Lauth 2, R Singh 2, B Sipos 3, T Gress 1, M Buchholz 1
  • 1Philipps-Universität Marburg, Klinik für Gastroenterologie, Zentrum für Tumor- und Immunbiologie (ZTI), Marburg, Deutschland
  • 2Philipps-Universität Marburg, Institute of Molecular Biology and Tumor Research (IMT), Zentrum für Tumor- und Immunbiologie (ZTI), Marburg, Deutschland
  • 3Universität Tübingen, Institute of Pathology, Tübingen, Deutschland

Introduction: We have previously described a multi-step high-content screening approach to identify novel functionally relevant target genes in pancreatic ductal adenocarcinoma (Buchholz et al., PLoS-One, in press). The results of these analyses predicted an unexpected and previously undocumented role for the small actin-binding protein cofilin-1 in growth control of pancreatic cancer cells.

Methods: Multiple tissue arrays, RNAi, cell proliferation and viability assays, FACS analysis, Western blot, inducible shRNA clones, reporter gene assays.

Results: Cofilin-1 is strongly overexpressed in human pancreatic ductal adenocarcinoma both at the mRNA and at the protein level. RNAi-mediated knockdown of cofilin-1 gene expression in four different pancreatic cancer cell lines resulted in significantly reduced cell viability and proliferation rates, while apoptosis was not induced. Further, the capacity for anchorage-independent growth was strongly reduced in the absence of cofilin-1 expression. Moreover, stable repression of cofilin-1 expression in pancreatic cancer cell clones significantly decreased the growth of xenograft tumors in vivo. Flow cytometric analyses indicated that these effects were primarily mediated by attenuation of G1/S transition during cell cycle. Mechanistically, CFL1 knockdown resulted in simultaneous overactivation of the MAL/SRF transcription factor complex and downregulation of expression of the Hedgehog pathway effector Gli1, which is well known to regulate pancreatic cancer cell growth.

Conclusions: In addition to its previously known roles in actin dynamics and cell motility, cofilin-1 has a direct and essential role in growth regulation of pancreatic cancer cells. The clinical significance of this observation is emphasized by the strong and widespread overexpression of cofilin-1 in human PDAC.