Human JC polyomavirus in normal colorectal mucosa, hyperplastic polyps, sporadic adenomas, and adenocarcinomas in Portugal.

John Cunningham virus (JCV) infects chronically human populations worldwide and probably might confer a higher risk for colorectal cancer (CRC). The prevalence of JCV DNA has been determined in normal colon mucosa and compared it with different degrees of colorectal lesions, as well as viral presence in the urine of the individuals in the study. JCV DNA was detected by a nested-PCR approach targeting the JCV small-t antigen in 100 healthy controls, and 100 patients undergoing biopsy for diagnosis of colorectal disorders. JCV DNA was detected in 40% of normal mucosa from controls and patients. JCV DNA presence in urine was also similar in controls and patients (37-41% range). JCV DNA detection in normal mucosa and urine reflects the infected population in Portugal. However, in cases with colorectal tumor lesions, JCV DNA was detected in 90% cases, independently of histological type or grade, and this increase was significantly higher with respect to its normal surrounding mucosa. This higher detection of JCV DNA in tumor lesions with respect to its own normal mucosa suggested that a selection for virus containing cells has occurred at some early stage in tumor initiation or progression. JCV may have a specific tropism for colon epithelial cells with some inherent predisposition that makes them more prone to oncogenic transformation, with selection of infected cells. Several p53 polymorphisms in intron 2, common to both groups, were more frequently detected in colorectal pathology cases. A novel p53 mutation in the 3' untranslated region (exon 11) was identified in 10 patients.