Human polyomaviruses genomes in clinical specimens of colon cancer patients.

Colon cancer is the third cause of cancer death in the developed countries. Some environmental factors are involved in its pathogenesis, including viral infections. The possible involvement of human polyomaviruses (HPyVs) in colon cancer pathogenesis has been previously reported, leading to inconsistent conclusions. Clinical specimens were collected from 125 colon cancer patients. Specifically, 110 tumor tissues, 55 negative surgical margins, and 39 peripheral blood samples were analyzed for the presence of six HPyVs: JC polyomavirus (JCPyV), BK polyomavirus (BKPyV), Merkel cell PyV (MCPyV), HPyV -6, -7, and -9 by means of DNA isolation and subsequent duplex Real Time quantitative polymerase chain reaction. HPyVs genome was detected in 33/204 samples (16.2%): the significant higher positivity was found in tumor tissues (26/110, 23.6%), followed by negative surgical margins (3/55, 5.5%, p < .05), and peripheral blood mononuclear cells (PBMCs) (4/39; 10.3%). HPyVs load was statistically higher only in the tumor tissues compared to negative surgical margins (p < .05). Specifically, MCPyV was detected in 19.1% (21/110) of tumor tissues, 3.6% (2/55) of negative surgical margins (p < .05), and 7.7% (3/39) of PBMCs; HPyV-6 in 2.7% (3/110) of tumor tissues, and 1.8% (1/55) of negative surgical margins; one tumor tissue (1/110, 0.9%) and one PBMCs sample (1/39, 2.6%) were positive for BKPyV; JCPyV was present in 0.9% (1/110) of tumor tissues. HPyV-7 and 9 were not detected in any sample. High prevalence and load of MCPyV genome in the tumor tissues might be indicative of a relevant rather than bystander role of the virus in the colon tumorigenesis.

Detection of a new JCV strain of genotype A in a subpopulation of colorectal adenocarcinomas in Tunisia

The etiology of colorectal cancer (CRC) remains elusive in spite of major advances in knowledge of this disease and related risk factors. Several studies report the detection of human polyomavirus JC (JCV) in colorectal tumors and some suggest its association with CRC. Since many known human virus associations with cancer are linked to factors such as ethnic and geographical origin, it is interesting to search for the postulated association of JCV with CRC in different populations and regions. In this perspective, the present work was undertaken to assess the presence of JCV in CRC tumors in Tunisia. Fresh biopsies were obtained from both colorectal tumors and adjacent normal tissues of 47 CRC patients. Only tumors diagnosed as adenocarcinomas were included in the present study. Twenty patients with other gastroenterological disorders were taken as controls. DNA was extracted from fresh biopsies or formalin-fixed, paraffin-embedded tissue sections. A region of the viral T-Ag gene was amplified by PCR and the DNA amplicons were subjected to automated sequencing. JCV DNA was found in 22 (46%) of the adenocarcinomas but in none of the normal mucosa biopsies of either CRC or control patients. Sequence analysis indicated that the amplified DNA belonged to a new JCV variant of genotype A. The presence of JCV DNA was correlated with tumor location and grade. The data obtained suggest that JCV may be associated either with a subpopulation of colorectal tumors or with CRC in general, possibly through a hit and run mechanism.

Human Endogenous Retroviruses Long Terminal Repeat Methylation, Transcription, and Protein Expression in Human Colon Cancer.

Colon cancer is the fourth most common malignancy in both incidence and mortality in developed countries. Infectious agents are among the risk factors for colon cancer. Variations in human endogenous retrovirus (HERV) transcript and protein levels are associated with several types of cancers, but few studies address HERV expression in colon cancer. Fifty-eight patients with advanced-stage colon cancer were enrolled in this study. HERV-H, -K (HML-2), -P LTRs, Alu, and LINE-1 methylation levels and transcription of HERV-H, -K (HML-2), and -P env and HERV-K pol genes in normal adjacent and tumor tissues were investigated by pyrosequencing and RT-qPCR, respectively. Expression of the HERV-K (HML-2) Pol and Env proteins in selected tissues was examined by Western blotting. Associations between HERV transcript expression and methylation levels and between clinical characteristics and HERV expression were evaluated. Compared to adjacent normal tissues, LINE-1 was hypomethylated in tumor tissues (p < 0.05), whereas Alu, HERV-K (HML-2), and -H LTRs showed a decreasing trend in tumor tissue compared to normal tissue, though without a significant difference. The transcription levels of HERV env and pol genes were similar. However, the HERV-K (HML-2) Pol protein was more highly expressed (p < 0.01) in surrounding normal tissues, but the HERV-K (HML-2) Env protein was only expressed in tumor tissues. Although HERV LTR methylation and gene expression did not show significant differences between tumor and normal tissues, HERV protein expression differed greatly. Pol protein expression in normal cells may induce reverse transcription and subsequent integration into the host genome, likely favoring cell transformation; in contrast, the Env protein in tumor tissue may contribute to cancer progression through cell-to-cell fusion.