The influence of TNF on the membrane fluidity of tumor cells.

Possible TNF (tumor necrosis factor) effects on the membrane fluidity of tumor cells were investigated. Viable tumor cells, TNF sensitive, were obtained from the ascitic form of the SA-1 tumor bearing mice. The influence of in vitro and in vivo treatment of cells with the TNF analog was investigated by EPR (electron paramagnetic resonance). SA-1 cells were spin labeled with the methylester of 5-doxylpalmitate, which primarily dissolves in the membranes. The maximal hyperfine splitting was determined and the empirical correlation time calculated. The results show that TNF significantly decreases the correlation time, i.e. it increases the fluidity of SA-1 cell membranes. Such alteration could contribute to the cytotoxicity of TNF.