Molecular phylogenetic analysis of the human endogenous retrovirus E (HERV-E) family in human tissues and human cancers

The human genome is estimated to contain up to 50 copies of full-length and truncated members of HERV-E family. They are thought to be involved in human gene transcription. Here we examine the expression pattern and phylogenetic relationships of the HERV-E in diverse human tissues and cancer cells using RT-PCR amplification and bioinformatic tools. The env gene was expressed in many human tissues (brain, prostate, testis, kidney, placenta, spleen, thymus and uterus) but not in heart, liver, lung and skeletal muscle, importantly, HERV-E expression was detected in all cancer cell lines examined (RT4, PFSK-1, BT-474, HCT-116, TE-1, UO-31, Jurkat, HepG2, A549, MCF7, OVCAR-3, MIA-PaCa-2, PC3, LOX-IMVI, AZ521, 2F7, U-937 and C-33A), suggesting that HERV-E family are expressed corresponding to the transcriptional program of human tissues and human cancer cells. Phylogenetic analysis of HERV-E env family from human tissues, cancer cells and our previous data identify two groups (I and II) through evolutionary divergence. Taken together, HERV-E family expression in human tissues and human cancer cells exhibited close relationships of the env gene sequences across human chromosomes. These active HERV-E elements deserve further investigation as potential pathogenic factors in human diseases such as cancers.