The association of clinicopathological features of colorectal cancers with RAS/RAF/MAPK pathway

Background: Mutations in KRAS gene are validated biomarkers of failure to anti-epidermal growth factor receptor (EGFR) therapeutic agents like cetuximab in metastatic colorectal cancer. Many studies have confirmed cooperations of mutations of other genes like as NRAS and BRAF with resistance anagainst anti-EGFR monoclonal therapies. However, the association of PIK3CA mutations on the efficacy of those approaches remains controversial. Objective: Purpose of this study was to determine the association of clinicopathologic features in colorectal cancer patients with mutation in RAS/RAF/MAPK pathway related genes KRAS, NRAS, BRAF and PIK3CA. Method: colorectal cancer diagnosed patients between 2009-2014 years in Dokuz Eylül University Hospital enrolled to this study. Genomic DNA was isolated from formalin fixed paraffin embedded blocks with spin column base DNA isolation method. Collected samples were used to determination of mutation status of KRAS, NRAS, BRAF and PIK3CA by using QIAGEN Pyrosequencing Q24 and AmoyDx Real-time PCR methods. Results: Forty four point seven percent of patients were sixty years or older and %34.8 were women. Ninety point six percent of them had at least one site of metastasis. KRAS, NRAS, BRAF and PIK3CA mutation were %21.2, %12.5, %4.2 and %46.9 respectively. G13D with %32.1 of mutation was the most observed mutation of KRAS. Mutation of women in KRAS was significantly more than men's with KRAS mutation (p=0.02). NRAS mutation of colon was significantly more in comparison to primary tumors of rectum (p=0.08). Q61K was the only detected substitution at codon 61 at NRAS. PIK3CA-H1047R was the most recurrent mutation while other mutations detected were E545D, E542K, E545K and H1047L. Except the ones which mentioned no significant association of detected genes mutation with age, gender, tumor differentiation, stage and metastases site was noted. Conclusion: In conclusion, to our knowledge this was the first retrospective study to evaluate the NRAS and PIK3CA mutation in Turkish metastatic colorectal cancer patients to make clinical correlations. Mutations of PIK3CA in KRAS, NRAS and BRAF wild type patients have been observed. Although there were no statistical relations between mutations and clinicopathologic features in our cohort, these markers have important role in selection of suitable therapies for patients. Knowledge of multiple gene mutation patterns could give useful information in predicting benefit of patients from anti-EGFR treatment. Key Words: Colorectal cancer, KRAS, NRAS, BRAF, PIK3CA