Dependence of MX69-induced cell death on MDM2 and XIAP expression and p53 status (A) Comparison of MX69 IC50 values in MDM2 KO (sgMDM2) EU-1 and SH-EP1 cells in presence or absence of sip53. IC50 values were measured by WST assay, *p<0.01, **p<0.05; Inserts, MDM2 and p53 expression in MDM2-silenced and MX69 and sip53-treated cells as detected by Western blot. (B) Comparison of MX69 IC50 values in SK-N-SH cells transfected with plasmids as indicated in presence or absence of sip53. IC50 values were measured by WST assay, *p<0.01, **p<0.05, ***p>0.5; Inserts, MDM2 expression in MDM2-transfected cells as detected by Western blot. (C) LA1-55N cells stably transfected with MDM2 in presence or absence of siXIAP were treated with MX69 (10 μM for 24 hr) and cell survival detected by WST assays; data represent mean ± SD of three independent experiments, *p<0.01; Insert, XIAP expression as detected by Western blot. (D) NB-1691 cells were treated with siMDM2, siXIAP (1), MX69 (10 μM for 24 hr) alone or their combinations as indicated and apoptotic cells quantitatively detected by flow cytometry, *p<0.05 (compared with siMDM2 or siXIAP alone); Insert, protein expression as detected by Western blot. Data in (A, B and D) represent mean ± SD of three independent experiments, bars ± SD. See also Figure S7.