Restoration of ELOVL6 levels in BTZ-resistant cells sensitizes them to bortezomib. (A) Parental (P) and BTZ-resistant (R) MM cells were transduced with empty vector (V) or ELOVL6 cDNA-expressing vector (E6) followed by immunoblotting with indicated antibodies 48 hours postinfection. (B) BTZ-resistant MM.1S and RPMI8226 cells described in panel A were treated or not with 6 nM BTZ or 3 nM BTZ, respectively, for 16 hours followed by immunoblotting with the indicated antibodies. (C) MM cells described in panel A were treated or not with the indicated amounts of BTZ for 24 hours and probed in trypan blue cell viability assay. Shown immunoblots are representative images of at least 2 independent experiments with no tangible experimental variability. Viability data of parental MM.1S and RPMI8226 cells treated under the same conditions as BTZ-resistant cells are shown for comparison. The viability data are presented as the mean values of triplicates ± standard errors of the mean. (D) BTZ-resistant MM.1S or RPMI8226 cells transduced with empty vector or ELOVL6 cDNA-expressing vector (as in panel A) and inoculated subcutaneously into both flanks of 4- to 6-week-old female NOG mice. Mice with similar tumor burden were randomized into 2 groups (n = 5 animals per group) and treated on days 0, 3, 6, and 9 via intraperitoneal injections with vehicle (PBS) or BTZ in vehicle (0.5 mg/kg). Tumor volumes were recorded on the indicated dates. (E) At the end of the experiments, mice were euthanized, and tumors were excised, fixed in formaldehyde solution, and photographed. Data are presented as the mean values ± standard errors of the mean. P values were determined by Student t test. *P < .05, **P < .01, ***P < .001, ****P < .0001.