A, Immunoblot of p-NRF2, ATF4 and TXNRD1 expression in GILM2 (left) and MDA-MB-468 (right) cells cultured in control or MR media for 24 hours in the presence or absence of NAC (2 mM). B, Immunoblot of p-NRF2, ATF4 and TXNRD1 expression in WT, ATF4−/− and NRF2−/− MEFs grown in MR media for the indicated number of hours. C, TXNRD activity (expressed as percentage of time t=0) was determined in the indicated MEFs cultured in control or MR media for 48 hours (mean ± SEM, n = 3). ***, P < 0.001 vs. control