Mutational Profiling in Ampullary Adenocarcinomas Using the 'SNaPSHOT' Platform
Maressa T Pollen, Cindy L Vnencak-Jones, Kaidi Mikhitarian, Nipun Merchant, Chanjuan Shi. Vanderbilt University, Nashville, TN
Background: The ampulla of Vater is at the union of the pancreaticobiliary tree and the duodenum. Both pancreaticobiliary and intestinal epithelia may contribute to the development of ampullary carcinoma. However, genetic alterations underlying ampullary carcinogenesis have not been well established. In addition, there are no effective adjuvant therapies available for patients with ampullary carcinoma. Molecular targeted therapies can potentially provide more effective and less toxic treatment options for these patients. To gain insights into the genetic basis of this tumor type, we analyzed 63 possible gene mutations in 7 cancer genes using multiplex mutational profiling.
Design: Twenty surgically resected ampullary carcinomas were included in the study and their histopathology reviewed. 5 unstained slides from each sample were prepared from formalin fixed paraffin embedded tissue. Microdissection was performed to achieve a neoplastic cellularity of >20%. DNA from the enriched neoplastic samples was screened for 63 mutations in 7 cancer genes (AKT1, BRAF, KRAS, NRAS, PIK3CA, PTEN and SMAD4) using the SNaPSHOT single base extension assay (Applied Biosystems).
Results: Eighteen of the 20 cases had intestinal type morphology. Among the intestinal type tumors, 9 (50%) displayed mutations in the genes analyzed. Seven of the 9 cases had a mutation solely in the KRAS2 gene, including 6 at codon 12 and one at codon 61. One had a lone mutation in codon 545 of the PIK3CA gene. Only one case harbored 2 driver mutations with one in KRAS2 at codon 13 and one in SMAD4 at codon 361. Two cases included in the study had pancreaticobiliary histology. One of these possessed a KRAS2 gene mutation at codon 12. Overall the KRAS2 mutations were detected in 9 of 20 (45%) cases. PIK3CA and SMAD4 mutations were present in a single specimen each.
Conclusions: KRAS2 gene mutations are common in ampullary adenocarcinoma. Other genes associated with ampullary carcinoma include SMAD4 and PIK3CA. We have utilized a reproducible and sensitive multigene assay for mutational screening in ampullary carcinoma. Accurate prognostication and therapeutic choice for these neoplasms may be driven by the results of these studies.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 77, Wednesday Morning