Fig. 2.

tmTNF-α is required for DOX-resistance of breast cancer. a Primary human breast cancer cells were isolated from patients with low (n = 5) or high (n = 15) expression of tmTNF-α and incubated with DOX for 72 h. IC50 values of DOX-mediated cytotoxicity was determined by ATP-TCA. b, c Primary breast cancer cells from three patients were transfected with control or tmTNF-α shRNA for 48 h. DOX was added in indicated concentrations and incubated for 72 h. b Dose dependent DOX-induced cytotoxicity determined by ATP-TCA. c IC50 values of DOX to primary cancer cells or those transfected with shRNA. d FACS analysis of tmTNF-α expression in parental or shRNA stably transfected MDA-MB-231 cells. e, f Cytotoxicity and DNA fragmentation of parental or shRNA-transfected MDA-MB-231 cells treated with 3 μM DOX for 24 h detected by MTT assay and ELISA, respectively. g Scheme of NTF-tmTNF-α-mediated reverse signaling without delivering forward signaling. h FACS analysis of NTF expression in parental, or empty vector or NTF-transfected MCF-7 cells. i and j Cytotoxicity and DNA fragmentation of parental or NTF-transfected MCF-7 cells treated with 3 μM DOX for 24 h. Data are represented as mean ± SEM of three independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001