CIT silencing decreases MM tumor growth in vitro and induces cytokinesis failure. (A) Depletion of CIT induced by shRNA (F5 and F10) in OPM2 and MM.1s cells was validated using qRT-PCR. (B) OPM2 and MM.1s CIT-knockdown cells were cultured for 48 hours. Cell proliferation was measured using [³H]-thymidine uptake assay. CIT silencing led to significant inhibition of MM cell proliferation (P < .001 and P < .02, respectively). (C) Immunofluorescence of OPM2 and MM.1s cells transfected with scramble or CIT shRNA (F5). Green arrows in enlarged images (magnification ×200) of original magnifications (×100) show nuclei; DAPI (blue) and α-tubulin (red). (D) Multinucleated OPM2 cells were quantified by immunofluorescence. Random fields were analyzed. A significant increase in multinucleated cells in short hairpin (sh)–CIT (F5)-knockdown cells was observed compared with scramble control. (E) The cell cycle of CIT-knockdown OPM2 and MM.1s cells was assessed by propidium iodide (PI) staining and flow cytometric analysis. Although silencing of CIT increased the G2-phase population in OPM2 cells, it did not have any effect on the G2-phase population in MM.1s cells. K.D., knockdown; scr/Scr, scramble.