Human papillomavirus does not have a causal role in colorectal carcinogenesis

AIM: To investigate the presence of human papillomavirus(HPV) DNA along with the integration,the quantification and the expression of the HPV16 in colorectal cancers.METHODS: A prospective series of colorectal tumors were genotyped for HPV DNA.The clinical and pathological variables of the HPV-positive tumors were compared to those of HPV-negative samples.The integration status of HPV16 was evaluated by calculating E2/E6 ng ratios.HPV16-positive tumors were also evaluated for(1) E2,E4,E5,E6 and E7 viral gene ng quantification;(2) relative quantification compared to W12 cells; and(3) viral E2,E4,E5,E6 and E7 mR NA transcripts by real-time polymerase chain reaction.RESULTS: HPV infection was detected in 16.9% of all tumors examined,and HPV16 was the most frequent type detected(63.6% of positive tissues).Notably,the clinical and pathological features of HPV-positive colorectal cancers were not significantly different than those of HPV-negative cancers(χ2 and t-test for all clinical and pathological features of HPV-positive vs HPV-negative colorectal cancers: p ns).HPV16 DNA was present exclusively in episomal form,and the HPV16 E2,E4,E5,E6 and E7 genes were detected in tracenanogram quantities.Furthermore,the HPV16 genes ranged from 10-3 to 10-9 compared to W12 cells at an episomal stage.Although the extractions were validated by housekeeping gene expression,all the HPV16 positive tissues were transcriptionally inactive for the E2,E4,E5,E6 and E7 mR NAs.CONCLUSION: Based on our results,HPV is unlikely involved in colorectal carcinogenesis.