Aberrant methylation of Reprimo correlates with genetic instability and predicts poor prognosis in pancreatic ductal adenocarcinoma

BACKGROUND. The p53-dependent G2/M checkpoint plays a key role in the maintenance of genomic integrity, thereby protecting cells from neoplastic progression. Reprimo, a gene involved in the p53-induced G2 cell cycle arrest, has been recently identified as a novel target for aberrant methylation in pancreatic and other cancers. The biological and clinical relevance of Reprimo methylation in pancreatic cancer was investigated. METHODS. The methylation status of Reprimo CpG island was analyzed by methylation-specific polymerase chain reaction in a large series of pancreatic cancers and was correlated with p53 mutation status, genetic instability (as measured by the fractional allelic loss), and clinicopathologic features. RESULTS. Aberrant methylation of Reprimo was identified in 60% (75 of 125) of pancreatic cancer xenografts and primary pancreatic adenocarcinomas. Reprimo methylation was also detectable in 30% (19 of 63) of pancreatic intraepithelial neoplasias (PanIN), known precursors to infiltrating carcinoma. Reprimo methylation was unrelated to the p53 mutation status and associated with the increased degree of genetic instability (P=.04). Furthermore, we found that patients with Reprimo methylation in their primary pancreatic cancers have significantly worse prognosis than those without Reprimo methylation (P=.007). In contrast, other methylation targets in pancreatic cancers (SPARC and CXCR4) did not correlate with prognosis. CONCLUSIONS. These results suggest that aberrant methylation of Reprimo is a common event in pancreatic carcinogenesis and is associated with genetic instability and unfavorable outcome after surgical resection.