Figure 7

ER stress and ATO exhibit synergic toxicity in RA-resistant NB4-R4 cells. NB4-R4 cells were treated with 10 nM RA and/or 50 ng/ml Tm and/or 500 nM ATO as indicated, in the absence (nil) or presence of the PERK inhibitor GSK (300 nM), or of the GADD34 inhibitor Guanabenz (17 μM) for the indicated time points. (a) Morphological analysis of cells treated for 72 h. (b) Quantitative reverse transcriptase-PCR (qRT-PCR) analysis for the expression of the UPR genes CHOP, BiP and sXBP1 in samples treated for 24 h. (c) Propidium iodide (PI) uptake analysis following 72 h of treatment (n=2±s.e.m.; Student’s T-test **P-value<0.02, ***P-value<0.005; analysis of variance (ANOVA) in Supplementary Table 1, see results for Supplementary Figure S6b). (d) qRT-PCR for the expression of the Heme-Oxigenase-1 (HO-1) in the same samples. (e) PI uptake analysis of cells treated with the addition of 20 mM N-acetyl-cysteine (NAC) for 72 h.