Co-existence of BRAF V600E Gene Mutation in Tumor and Non-tumoral Surrounding Tissues in Colorectal Cancer

Background/aim: The murine sarcoma viral (V-Raf) oncogene homolog B (BRAF) V600E mutation, which increases protein kinase activity in BRAF-mitogen-activated protein kinase kinase (MEK) - extracellular signal-regulated kinases (ERK) (mitogen-activated protein kinase (MAPK)) signaling, is found in 5-40% of all colorectal carcinoma cases. Proteins with this mutation are reported to be 130-fold more active, which results in induced proliferation, differentiation, cellular survival, and angiogenesis. The aim of the present study was to investigate tumor tissues, together with the surrounding non-tumoral tissues, for BRAF mutation presence, which may be an indicator for possible recurrence or prognosis as in the 'field carcinogenesis' model.

Materials and methods: The BRAF V600E genotype of 152 colorectal adenocarcinoma paraffin-embedded specimens were determined by mutant-allele-specific amplification-polymerase chain reaction.

Results: According to our results, the presence of BRAF mutation increases risk of lymph node invasion by 1.55-fold [χ(2)=3.83, p=0.05, odds ratio (OR)=1.55, 95% confidence interval (CI)=1.00-2.42], histologically medium or high-grade tumor by 1.60-fold (χ(2)=4.34, p=0.030, OR=1.60, 95% CI=1.03-2.48), vascular invasion by 1.55-fold (χ(2)=3.55, p=0.05, OR=1.55, 95% CI=0.99-2.42), perineural invasion by 1.50-fold (χ(2)=3.16, p=0.07, OR=1.5, 95% CI=0.96-2.33) and the combination of these poor prognostic features by 1.54-fold (χ(2)=2.47, p=0.11, OR=1.54, 95% CI=0.93-2.53). We also found that females are more prone to having the mutation and that being female increases the risk of having this mutation by 1.54-fold (χ(2)=3.58, p=0.05, OR=1.54, 95% CI=0.97-2.44).

Conclusion: BRAF V600E mutation in non-tumoral surrounding tissue in patients with colorectal cancer may be used as a valuable marker to foresee clinical outcome or a possible recurrence. To our knowledge, this was the first study to take into consideration the non-tumoral surrounding tissues in addition to the tumor tissue.