Targeting TBL1X results in the degradation of RAD51, DNA damage, and MCL cell death. Immunoblot analyses for RAD51 protein expression in (A) MCL cell lines (n = 9) and (B) primary MCL patient samples (n = 10) as compared with normal B cells. RAD51 protein levels by immunoblot and RAD51 transcript levels by qPCR in MCL cell lines (n = 2) (C-D) treated with tegavivint (IC₅₀, 12-18 hours) vs DMSO control or (E-F) subjected to TBL1X KD with specific constructs (n = 2; sh425 and sh525) vs EV control. (G) RAD51 protein levels in MCL cell lines (n = 2) treated with proteasome inhibitor Mg132 or translation inhibitor cycloheximide combined with tegavivint compared with tegavivint-only treated cells. Cells were first treated with tegavivint (IC₅₀), then MG132 (10 μM) or cycloheximide (10 μg/mL) was added for the last 1.5 or 3 hours, respectively, for a total incubation time of 18 hours. RAD51 shRNA KD in MCL cell lines (n = 2) with specific constructs (sh77 and sh79) compared with an EV control: (H) RAD51 transcript levels by qPCR, (I) RAD51/γH2AX protein levels by immunoblot, and (J) cell viability. (K) Cell viability and (L) γH2AX levels by immunoblot in MCL cell lines (n = 2) with targeting RAD51 pharmacologically with small molecule inhibitor RI-1 (72-hour incubation). Cell viability was determined for all experiments by annexin-V/PI staining and flow cytometry. Tegavivint IC₅₀ concentrations = 95 nM for JeKo-1 and 65 nM for SP-53. Ann, annexin-V; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; hr, hour; ns, not significant; NT, no treatment; FC, flow cytometry; PI, propidium iodide; qPCR, quantitative polymerase chain reaction. ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001.