Oxidative stress induces the expression of the Major Histocompatibility Complex in murine tumor cells

The effect of t-butyl hydroperoxide (t-BOOH) on the induction of the Major Histocompatibility Complex (MHC) class I genes has been studied in two cell clones (B9 and G2) of the methylcholanthrene-induced murine fibrosarcoma G R9. These two clones were selected based on their different biological and biochemical behavior specially related to their tumor induction capability when injected into a BALB/c mouse. t-BOOH (0.125mM) induced the expression of H-2 molecules in both cell clones. In B9 cell clone, in which MHC basal expression is very low or absent, t-BOOH significantly induced H-2K(d), H-2 D(d) and H-2L(d) molecules. In G2 cell clone the expression of MHC class I genes was also enhanced by the xenobiotic, the effect being especially sign ificant on the H-2L(d) molecule which is not expressed under basal conditio ns. H-2 molecules expression was accompanied by the activation of the trans activator factor NF kappaB. These results suggest that oxidative stress may modulate the antigen expression of tumor cells and thus the immune respons e of the host organism. Basal levels of oxidative parameters, such as antioxidant enzymes, malondia ldehyde (MDA) and the DNA damaged base 8-hydroxy-2 ' -deoxyguanosme (8-OHdG ), showed differences between the two fibrosarcoma cell clones.