p16INK4a is a Prognostic Marker in Resected Ductal Pancreatic Cancer

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Abstract
To identify the prognostic relevance of the G1/S cell cycle regulator genes p16 INK4a, p53, MDM2, and Rb in patients with resected ductal pancreatic cancer (PC). The tumor suppressor genes p16 INK4a, p53, and Rb are altered in PC in 27% to 95%, 40% to 70%, and 5%, respectively. The role of MDM2 is not clearly defined in PC. The prognostic value of these cell cycle regulators has not been clarified. Sixty-two patients with PC with complete follow-up who underwent potentially curative resections were included in the study. An extreme group analysis was performed including the 20 patients with the shortest survival and the 20 patients with the longest survival. Protein expression of p16, p53, MDM2, and Rb was investigated, and mutation analysis of p16 INK4a and p53 was performed. p16 INK4a promoter hypermethylation was examined by methylation-specific polymerase chain reaction. Significantly more tumors in the shortest-surviving patients had p16 INK4a alterations compared with tumors of the longest-surviving patients. In contrast, the frequency of p53 alterations was not significantly higher in the shortest-surviving versus the longest-surviving groups. Stabilization of MDM2 and loss of Rb expression were identified in a minority of tumors, independent of survival length. The presence of p16 INK4a alterations in resected tumors of patients with PC is connected with a worse prognosis, indicating patients that might benefit from adjuvant therapy regimens. p53 alterations, MDM2 overexpression, and loss of Rb expression could not be identified as prognostic markers from this study, but a larger study with greater statistical power might show a different result with regard to p53.