Evidence for an association of human papillomavirus infection and colorectal cancer

Aim To investigate the presence of human papillomavirus (HPV) in colorectal carcinomas and the correlation of the viral infection with prognostic factors for the disease outcome. Methods Seventy-two patients with primary colorectal adenocarcinoma were studied. From each patient two tissue samples were collected: one sample of the tumor and one sample of normal colorectal tissue from an area located 15 cm away from the tumor. Samples of colorectal mucosa obtained from 30 individuals without malignant disease were also studied as control group. Tissues were initially analyzed through MY/GP nested polymerase chain reaction (PCR) and through GP5+/GP6+ auto-nested PCR. Specific primer sets targeting the E6/E7 region of the HPVs 6, 11, 16, 18, 31, 33, 45 were used for typing. Direct DNA sequencing was conducted to confirm positive PCR results. Results HPV DNA was detected in colorectal specimens of 60 patients with cancer (83.3%), but in none of the tissues from the non-malignant control group (p < 0.001). Twenty-three cancer patients had HPV DNA detected in both the tumor and the matched normal tissue, 23 had HPV only in the tumor, and 14 had HPV only in the normal colorectal tissue. HPV16 was the viral type most frequently detected, being present in 41 out of 60 positive cases (68.3%). No correlation between the presence of the virus and specific prognostic predictors for the disease outcome was observed. Conclusion HPV is present in the colon and rectum of most patients with colorectal adenocarcinoma, suggesting that this virus may be related to the pathogenesis of colorectal cancer.