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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
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.