Preliminary exploration of the effects of environmental factors on the microsatellite status of BRAF mutated colorectal cancer

Background: To investigate the expression of EBV products and incidence of Gallstone disease (GD) among different microsatellite status in colorectal cancer (CRC) with BRAF V600E mutation. Methods: We collected 30 CRC patients with BRAF V600E mutation and 10 BRAF (-) CRC patients as well as 54 healthy subjects. Tumor tissue samples were collected to detect the mutation of BRAF, KRAS, and TP53. Microsatellite status was determined by immunohistochemistry and PCR. EBER in situ hybridization was performed to detect EBV. In addition, we also collected clinical information about the patients. Results: We found that although EBV products were detected in CRC, there were no significant differences in the EBV distribution between the different BRAF groups. Our study demonstrated that BRAF V600E mutation and BRAF V600E with MSI were significantly more frequent in the right CRC. Furthermore, the KRAS mutation rate in the BRAF-wild type group was proved to be significantly higher than that in the BRAF mutation group. In addition, we revealed that BRAF mutation and MSI were independent risk factors of TNM stage. The incidence of GD was higher in CRC patients than in general population, and although there was no significant difference between CRC with or without BRAF V600E mutation, the highest incidence of GD was found in MSS CRC with BRAF V600E mutation. Conclusions: EBV plays a role in CRC, but is not a determinant of different microsatellite status in CRC with BRAF V600E mutation. The incidence of GD in MSS CRC with BRAF V600E mutation is significantly higher than that in the general population.