Loss of TRAF3 confers resistance of lymphoma cells to bendamustine. (A) Cell death rates of HBL1 induced by etoposide, 4-OHCP, and bendamustine treatment in the absence of feeder cells, in the presence of L cells or CD40L⁺ L cells. Caspase-positive and dead cells were assessed by flow cytometry. Error bars indicate the SEM of duplicate samples. (B) Western blot analysis for TRAF2, TRAF3, and β-actin (loading control) of HBL1, FL18, and FL318 cells cultured in the absence of feeder cells or in the presence of L cells or CD40L⁺ L cells. (C) Western blot analysis for TRAF3, cFLIP, and β-actin (loading control) of mock or TRAF3-KO FL18 cells cocultured with L cells or CD40L⁺ L cells. (D) Cell death rates of mock or TRAF3-KO FL18 cells induced by bendamustine at the indicated concentrations in the presence of L cells or CD40L⁺ L cells. Caspase-positive and dead cells were assessed by flow cytometry. Error bars indicate the SEM of duplicate samples. Statistical significance was evaluated by 2-way analysis of variance (ANOVA), followed by Tukey-Kramer test for multiple comparisons. The results are indicated as: n.s., P > .05; ∗P < .05; ∗∗P < .01; ∗∗∗P < .001. n.s., not significant.