The expression of human endogenous retrovirus env-gene product as a hallmark of sidedness in operable colorectal cancer.

e15632 Background: Human Endogenous Retroviruses (HERV) constitute 8% of the human genome, where they are integrated, and usually not expressed. Despite their inactivation, many retroviral sequences present an intact ORF capable of producing retroviral transcripts and/or proteins, which can be detected in colorectal cancer. Methods: Three different cohorts of patients who underwent surgery at three different hospitals, comprising 167 Italian and Tunisian colon cancer patients, were analyzed. HERV-H, -K, -P env gene, and HERV-K pol gene expression levels were analyzed in tumor and adjacent healthy tissues by qPCR. Associations between clinicopathological features, such as tumor position and stage, patient age, lymphocyte infiltration and vascular/perineural invasion, and HERV gene expression levels were analyzed by correlative analysis. Results: HERV gene expression level was similar between tumor and adjacent healthy tissue samples. Significant (p < 0.05) higher expression of HERV-P and -R env was observed in tumor tissues from the right colon than from the left colon, while HERV-H env was more (p < 0.05) expressed in the left colon than in the right colon. A significant increase in the expression of HERV-H and -K env was observed in tumor tissue with increasing tumor grade. HERV-H and -P env genes were more expressed in patients under 73 and over 73 years old, respectively, in the tumor tissue Conclusions: in colorectal cancer HERV env gene expression seems to represent a specific signature in tumor and/or adjacent healthy tissues, based on tumor location and patients’ age. Analysis of differential HERV expression and its association with clinicopathological patients’ features might be useful to evaluate novel biomarkers for colon cancer and to address novel therapeutic options.