Expression profiles of HERV-K Env protein in normal and cancerous tissues

Human endogenous retroviruses (HERVs) have been proposed as etiological cofactors in chronic diseases such as cancer, autoimmunity and neurological disease. HERV RNA expression is also increased in several autoimmune diseases and cancers. However, only a few studies have analyzed the expression levels of HERV-derived proteins in normal and diseased tissues. Here, we investigated the expression profiles of HERV-K Env protein, which is the most well-known pathogen, from normal and cancer tissue microarray. Normal and cancer tissue microarray slides containing 59 normal or 60 tumor surgical specimens, respectively were immunostained with mouse monoclonal antibody to HERV-K and staining intensity was scored. The expression of HERV-K Env protein is generally low in normal tissues but high in specific tissues including bronchus submucosal gland, salivary gland acini, pancreas acini, testis seminiferous tubule, uterine cervix epithelium, ovary stroma, skin epidermis, and heart. The expression of HERV-K Env protein in tumors was usually higher than normal tissues and specifically high in breast, liver, stomach, prostate, and ovarian cancer. This study provides protein expression profiles of HERV-K Env protein in human normal and cancer tissues and provides a good reference for further studies on the expression patterns and roles of HERV-K Env protein in normal organs and various cancers. Further studies with specific organs or cancers and a statistically significant numbers of samples are necessary.