RBM39 is required for MM cell survival and tumor growth. (A) Knockdown of RBM39 in H929 cells was verified, and the modulation of apoptotic and cell cycle related proteins in RBM39-silenced H929 cells was detected by western blotting. (B) Knockdown of RBM39 induced apoptosis in H929 and MM.1S cells. Apoptosis was detected by annexin V/PI 48 hours after infection. (C) Knockdown of RBM39 inhibited the proliferation of H929. Cell viability was detected using CCK-8 at the indicated time points and the growth curve was calculated. (D) Knockdown of RBM39 induced cell cycle of H929 arrest at the G2/M phase, which was detected 48 hours after infection. (E) Images of subcutaneous tumor tissues of H929-shRBM39 cells. RBM39-knockdown H929 cells were subcutaneously inoculated into the hind flank of 6-week-old female NOG mice. The mice were euthanized 5 weeks after inoculation. (F) Tumor volume of subcutaneous tumors in panel E after mice sacrificed. (G) Images of subcutaneous tumor tissue with U266-inducible RBM39-knockdown cells. U266 cells with dox-inducible shRBM39 2 were subcutaneously inoculated into the hind flank of 6-week-old female NOG mice. The mice were euthanized 20 days after inoculation. dox− group: mice were treated with 5% sugar in water. dox+ group: mice were treated with 5% sugar plus 2 mg/mL dox. (H) Tumor sizes were measured every 4 days. ∗∗P < .01, ∗∗∗P < .001, ∗∗∗∗P < .0001. CCK-8, Cell Counting Kit-8; ns, no significant; PI, propidium iodide; scr, scrambled.