Expression Profile of KRAS and p16 in Periampullary Cancer.

Activating point mutations in codons 12, 13, and 61 of the KRAS gene and loss of p16 expression, a tumor suppressor gene, are common genetic alterations in periampullary cancer (PAC). The present study explores expression profile of KRAS and p16 genes in PAC and its prognostic relevance. A total of 50 patients with PAC who underwent potentially curative pancreaticoduodenectomy were included in the study. Formalin-fixed, paraffin-embedded tissue samples were analyzed for point mutations in codons 12 and 13 of KRAS and codon 9 of p16 using polymerase chain reaction. KRAS mutation in codon 12/13 was found in 32 (64%) and loss of p16 expression in 36 (72%) cases. KRAS mutation was significantly associated with higher grade, higher pathological tumor (pT) stage, lymphovascular invasion (LVI), perineural invasion (PNI), and pathological lymph nodes (pN) involvement on univariate analysis. On multivariate analysis, significant association of KRAS remained with higher grade (p = 0.031), pT stage (p = 0.09), and LVI (p = 0.028). On univariate analysis, loss of p16 expression was significantly associated with higher grade, pN involvement, LVI, PNI, and pT stage whereas on multivariate analysis, statistical significant association of p16 was found with higher grade of tumor only (p = 0.04). Patients with KRAS mutation had significantly (p = 0.018) worse disease-free survival (DFS) whereas no significant association was found in overall survival (OS). Loss of p16 expression had no association with either DFS or OS. The presence of p16 and KRAS alterations in patients with PAC suggests aggressive tumor biology. KRAS mutations confer a significantly poor DFS in PAC.

Molecular Aberrations in Periampullary Carcinoma.

Periampullary carcinomas are a group of rare lesions around the ampulla of Vater including distal bile duct and duodenum and are very different from pancreatic ductal adenocarcinoma clinically and pathologically, but the molecular alterations in these tumours are less known. Genetic alterations of the KRAS oncogenes, tumour suppressor genes p53, p16 and MADH4 (SMAD4/DPC4) and genome maintenance genes (MLHI, MSH2) are commonly altered in pancreatic adenocarcinoma and have also been described in periampullary cancers, although at lower frequencies. To understand the molecular characteristics of non-pancreatic periampullary carcinomas, ampullary cancers can now be further defined accurately into their intestinal and pancreatobiliary subtypes using histomolecular profiling. KRAS mutation, which occurs in most pancreatic cancers, is found to occur less frequently in ampullary (42-52%), biliary (22-23%) and duodenal cancers (32-35%). Mutations are also found in tumour suppressor genes (p53) and are associated with transformation of adenomas and low-grade carcinomas into high-grade carcinomas. Loss of DPC4 occurs late in ampullary carcinogenesis. This study summarizes the current knowledge in molecular aberrations in non-pancreatic periampullary cancers.