Genome-wide transcriptome analysis of prostate cancer tissue identified overexpression of specific members of the human endogenous retrovirus-K family

Aim: Human endogenous retroviruses (HERVs) are integrated into the human genome and represent 8% of the total genome. A retrovirus is the most complete retroelement and is characterized by three defined sets of regions of genes: gag, pol, and env, flanking by long terminal repeats. Among different HERVs, the K family is one of those that have been most recently integrated into the human genome. Activation and expression of members of this family are shown to be connected with some human diseases including prostate cancer. Here, we showed the global expression pattern of HERV-K (HML-2) in prostate cancer tissue. Methods: Samples from 14 patients were subjected to whole transcriptome sequencing on rRNA-depleted samples. This analysis was performed through a distinct bioinformatics method and confirmed through a series of quantitative polymerase chain reaction and immunoblotting experiments. Results: For the first time, we showed the expression of gag protein in prostate cancer tissue both in sequencing results and also immunoblotting. This showed a higher expression of the gag protein in the tumor samples relative to benign samples. Conclusion: Overexpression of gag in the tumor can implicate a role within its overexpression in tumor tissue, either by acting on neighboring genes or through the activation of promoter transcription factors.