The most important and useful property of stem cells is that of self-renewal. Through this property, striking parallels can be found between stem cells and cancer cells. Natural killer (NK) cells play a key role in inflammation and tumor regression through their ability to cytotoxicity. The infiltrating NK cells are thought to kill cancer cells independently of major histocompatibility complex (MHC). Generally, NK cells are unable to exhibit their cytotoxicity unless adhering to target cells via an adhesion molecule. In order to clarify part of the mechanism for the killing of cancer cells by NK cells, we investigated the adhesion molecule between two cell types, i.e., NK92 MI cells and WM35 cells, and evaluated the effect of the cell adhesion on the manifestation of the cytotoxicity of NK cells. We used NK92 MI cells, which were obtained by non-viral transfection of NK92 cells with the cDNA for human IL-2.
It was confirmed that NK92 MI cells kill WM35 cells. We proceeded to investigate the effect of the adhesion molecule CD54 on the killing of WM35 cells by IL-2 activated NK92 MI cells. After a reaction with anti-CD54 antibody, WM35 cells were subjected to a cytotoxicity experiment with NK92 MI cells. The anti-CD54 antibody significantly suppressed the killing of WM35 cells by IL-2 activated NK92 MI cells.
These results suggest that the killing of CD54 expressed melanoma cells by IL-2 activated CD56 positive NK cells might be CD54-dependent.