DIFFERENTIAL INDUCTION OF EGR-1 EXPRESSION IN WEHI-231 SUBLINES DOES NOT CORRELATE WITH APOPTOSIS

To determine whether the absence of inducible Egr-1 expression correla tes with apoptosis and growth arrest, we compared the inducible expres sion of two Egr family members (Egr-1 and Egr-2) in three sublines of WEHI-231. Expression of Egr-2 is induced in all sublines of WEHI-231 f ollowing surface immunoglobulin (sIg) cross-linking, but Egr-1 express ion is induced in only two. We find that the lack of inducible Egr-1 e xpression corresponded to an increase in the methylation pattern of th e Egr-1 gene. In spite of these differences in Egr-1 expression, all t he sublines demonstrate similar inhibition of [H-3] thymidine incorpor ation following anti-Ig treatment. Growth arrest leads to apoptosis in only two of the sublines. but apoptosis does not correlate with the a bsence of inducible Egr-1 expression. Demethylation, by treatment with 5-azacytidine, in the Egr-1 non-expressing subline allows for inducti on of Egr-1 expression by anti-Ig, but fails to prevent growth arrest and apoptosis. Therefore, we conclude that the lack of Egr-1 expressio n is not responsible for either the apoptotic response or growth arres t induced by anti-Ig in WEHI-231.