CIT knockdown of MM cells reduced tumor growth in vivo. SCID/Beige mice were injected subcutaneously with OPM2 CIT-knockdown cells (n = 8) or scramble cells (n = 7) (5 × 10⁶ per mouse) to establish an MM xenograft model. Tumor growth was measured, and volume was calculated as (length [mm] × width2 [mm²])/2. (A) CIT-knockdown cells showed reduced tumor growth in vivo (P < .001). (B) Mice bearing CIT-knockdown cells exhibited significantly prolonged survival (P < .001). (C) CIT expression of tumors collected from mice injected with scramble or CIT-knockdown cells. Decrease in CIT expression was confirmed ex vivo on harvested tumors using qRT-PCR. K.D, knockdown; Scr, scramble control.