2010 Papers - Chun

The WRN-encoded RecQ helicase as a potential tumor suppressor gene in pancreatic adenocarcinoma

Stephen Chun Department of Surgery, University of Hawaii

Background: The vast majority of pancreatic adenocarcinoma is diagnosed in the geriatric population, and genes involved in cellular senescence such as the WRN-encoded RecQ helicase/exonuclease may be involved in pancreatic oncogenesis. Accumulating evidence suggests that WRN is a tumor suppressor gene (TSG), as a variety of cancers including pancreatic adenocarcinoma are associated with its epigenetic silencing or loss-of-function mutations. We hypothesize that wild-type WRN protects pancreatic epithelia from malignant transformation by regulating cell cycle progression and cell growth.

Methodology: We characterized a pancreatic adenocarcinoma cell line established from a human cadaver with Werner’s syndrome (WS-Panc).

Results: WS-Panc had two loss-of-function mutations of WRN, formed adherent colonies in vitro, and expressed the pancreatic ductal epithelial marker cytokeratin 7. No oncogenic mutations of the epidermal growth factor receptor (EGFR), K-Ras nor B-Raf were detected by polymerase chain reaction (PCR), and immunologic assays revealed over-expression of lysyl oxidase-like 2, p53, and ß-catenin in WS-Panc. Fluorescent in situ hybrdization showed that WS-Panc over-expresses EGFR. Cytogenetic analyses showed normal karyotype. Strong telomerase activity was detected in WS-Panc by the Telomere Repeat Amplification Protocol. To test the hypothesis that WRN is a TSG, we forced ectopic expression of wild-type WRN in WS-Panc and are analyzing the biologic properties and molecular phenotype of transfected cells. Consistent with an anti-proliferative effect, wild-type WRN mRNA levels are uniformly repressed in a panel of sporadic pancreatic cancer cell lines from the American Type Culture Collection as shown by quantitative real-time PCR.

Discussion: In summary, we provide evidence that WRN is a TSG in pancreatic epithelia using WS-Panc and other pancreatic cancer cell lines. WS-Panc is the first cancer cell line carrying WRN loss-of-function mutations that represents a unique translational resource to elucidate WRN in the neoplastic state. Ongoing investigation of WRN in primary pancreatic cancer tissue and tumor models in vivo are expected to elucidate mechanistic links between aging and pancreatic cancer for the purpose of developing efficacious interventional strategies.