Development and application of RT-PCR systems to determine HERV expression in astrocytoma cell lines

Abstract

Human endogenous retroviruses (HERVs) belong to the family of transposable elements that make up 8% of the human genome. Unlike exogenous retrovirus (e.g., HIV and HTLV), HERVs are inherited in a Mendelian manner. More than 22 families of HERVs have been identified over the past two decades. Importantly, some HERVs have been found to possess large open reading frames and produce viral like particles. More latterly, these viruses have been linked with certain autoimmune diseases and cancers. Indeed, HERVs may contribute toward carcinogenesis through retrotransposition, promoter insertion, immunomodulation, disruption of normal HERV-related functions, recombination, or by the production of fusion proteins. Of importance, HERV-K, HERV-W, and HERV-H have the potential to be transcriptionally active in the brain. We have developed robust RT-PCR systems using primers/probes specific to HERV-K and HERV-W to assess mRNA expression in conjunction with the house keeping gene, histidyl tRNA synthetase. In employing a gel-documentation system, we are able to provide semiquantitative levels of HERV expression in cell lines. Pilot data shows markedly enhanced expression of HERV-K in the cell line U251-MG (derived from a glioblastoma multiforme; WHO grade IV astrocytoma) as compared to a control cell line SW480 (colon adenocarcinoma): RT-PCR values; 1.0 and 0.42, respectively. This observation raises an intriguing possibility that HERV-K expression may be elevated in malignant brain tumors. In addition, this approach provides a useful approach to optimize primers and probes prior to using real-time quantitative PCR.