DNA methylating activity in murine lymphoma cells treated with xenogenizing chemicals.

We investigated whether epigenetic rather than mutational events might be involved in the induction of immunogenicity by the triazene derivative 1-(p-chlorophenyl)-3,3-dimethyltriazene (DM-Cl). To this purpose, we assessed the DNA methylation pattern of murine lymphoma cells xenogenized by DM-Cl and compared it with the changes induced by the DNA hypomethylating agent 5-azacytidine (5-Aza), which is also capable of affecting tumor cell immunogenicity. Both agents were found to increase the immunogenic potential of the treated tumor but according to different modalities. In particular, the novel immunogenicity conferred by 5-Aza treatment correlated well with the extent of hypomethylation induced, as opposed to what was observed for tumor xenogenization by DM-Cl.