Gene expression profiles of rectal cancers with mutant or wild-type Kras.

414 Background: The Kras oncogene is one of the most common mutations in colorectal cancer. Kras mutations are associated with increased tumor aggressiveness, poor response to selected targeted therapies, and reduced patient survival. We have previously shown that rectal cancers carrying a Kras mutation were less likely to achieve a pathologic complete response to radiation compared to tumors with wild type Kras. Our objective was to compare the gene expression profiles of rectal cancers with mutant and wild type Kras to identify genes that could be related to the Kras–dependent aggressive phenotype. Methods: Pretreatment biopsy tissue was collected from 120 patients with stages I, II and III rectal cancer treated in two prospective trials (NCT00335816 and NCT00114231). DNA and total RNA were extracted from microdissected cancer cells. Mutations in codons 12, 13, and 61 of the Kras gene were detected by pCR. 50ng of total RNAs were amplified to generate cDNA libraries using Ovation FFPE WTA System (NuGEN ...