The NKG2D receptor in the border of immune surveillance and carcinogenesis
The immune system is able to perform the detection and elimination of transformed cells by a mechanism known as physiological immune surveillance. This process involves the NKG2D receptor activator present in T lymphocytes and NK cells, both of paramount importance in the immune surveillance against cancer. To recognize the receptor NKG2D ligands (NKG2DLs) in cells that experience retransformation triggers the specific lithic response of the cytotoxic lymphoid cells. Also, soluble forms of NKG2DLs have been described in various types of cancer that have proven to be used for tumor evasion by saturating the NKG2D receptors present in the effectorlymphoid cells thus avoiding their recognition and elimination, which makes them escape immune surveillance. Although this phenomenon of immune evasion, where some NKG2DLs participate, has already been described and corroborated, clinically, it has not been studied whether the receptor NKG2DL is present in the tumor cells per se because it could also be involved in reversing immune surveillance. This paper analyzes recent evidence that the expression of the NKG2D receptor is not lymphocyte T and NK exclusive it is already expressed by tumor epithelial cells in vitro and in vivo. Consequences of this anomalous expression in non-lymphoid cells have widespread implications in carcinogenesis, which will be revised. Recent clinical studies to prove the participation of NKG2D receptor in several tumor pathologies are analyzed.
