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 correlates with apoptosis and growth arrest, we compared the inducible expression 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 following surface immunoglobulin (sIg) cross-linking, but Egr-1 expression is induced in only two. We find that the lack of inducible Egr-1 expression corresponded to an increase in the methylation pattern of the Egr-1 gene. In spite of these differences in Egr-1 expression, all the sublines demonstrate similar inhibition of [3H] thymidine incorporation following anti-Ig treatment. Growth arrest leads to apoptosis in only two of the sublines, but apoptosis does not correlate with the absence of inducible Egr-1 expression. Demethylation, by treatment with 5-azacytidine, in the Egr-1 non-expressing subline allows for induction of Egr-1 expression by anti-Ig, but fails to prevent growth arrest and apoptosis. Therefore, we conclude that the lack of Egr-1 expression is not responsible for either the apoptotic response or growth arrest induced by anti-Ig in WEHI-231.