Therapeutic potential of antiviral drugs targeting chemorefractory XXXX cells overexpressing endogenous retroviral elements.

@entity1 @entity694 @entity2879 @entity72086 @entity98 @entity14 @entity105
BACKGROUND: Endoretroviruses account for circa 8  % of all transposable elements found in the genome of @entity1 and other animals. They represent a genetic footprint of ancestral germ-cell infections of exoviruses that is transmittable to the progeny by Mendelian segregation. Traces of @entity1 endogenous retroviruses are physiologically expressed in ovarial, testicular and placental tissues as well as in stem cells. In addition, a number of these fossil viral elements have also been related to @entity105 . However, a relation between endoretroviruses expression and chemoresistance has not been reported yet. METHODS: Twenty @entity14 @entity1 samples were scrutinized for HERV-WE1 and HERV-FRD1 endoretroviruses using immunohistochemical approaches. In order to search for differential expression of these elements in chemotherapy refractory cells, a resistant HCT8 @entity694 subline was developed by serial @entity2879 exposure. Endoretroviral elements were detected by immunocytochemical staining, qPCR and ELISA. IC50-values of antiviral and cytostatic drugs in HCT8 cells were determined by @entity98 proliferation assay. The antivirals-cytostatics interaction was evaluated by the isobologram method. RESULTS: In this work, we show for the first time that HERV-WE1, HERV-FRD1, HERV-31, and @entity72086 are a) simultaneously expressed in treatment-na  ve @entity694 cells and b) upregulated after cytostatic exposure, suggesting that these retroviral elements are intimately related to chemotherapy resistance. We found a number of antiviral drugs to have cytotoxic activity and the ability to force the downregulation of HERV proteins in vitro. We also demonstrate that the use of different antiviral compounds alone or in combination with anticancer agents results in a synergistic antiproliferative effect and downregulation of different endoretroviral elements in highly chemotherapy-resistant @entity14 cells. CONCLUSIONS: Enhanced HERV-expression is associated with chemoresistance in @entity694 which can be overcome by antiviral drugs alone or in combination with anticancer drugs. Therefore, the introduction of antiviral compounds to the current chemotherapy regimens potentially improves @entity1 outcomes.
