Objective To investigate the in vitro cytotoxic effects of targeted silencing of long non-coding RNA colorectal cancer associated transcripts 2(CCAT2)by siRNA on multiple myeloma cell RPMI 8226 and U266.Methods Two strands of siRNA targeting at CCAT2,including siCCAT2-1 and siCCAT2-2,were transfected into RPMI 8226 and U266 cells at logarith-mic growth phase by liposome.The siRNA with the best silencing efficiency was screened for the subsequent experiments as ex-periment group by real-time fluorescence quantitative PCR(qPCR).The cells transfected with scramble sequence served as nega-tive control group and cells without transfection as blank control group.The cell proliferation rates were measured by cell count-ing kit-8.The apoptotic rates were measured by Annexin Ⅴ-FITC/PI double staining via flow cytometry.The mRNA levels of apoptosis related genes were detected by qPCR method.The numbers of invasive and metastatic cells were detected by Tran-swell method.Results The CCAT2 levels of multiple myeloma cell lines were reduced after transfection with siCCAT 2-1 and siCCAT2-2 in comparison with cells of negative control group and blank control group(P<0.05).The inhibition rates of RPMI 8226 and U266 cells were higher by transfection with siCCAT 2-2 than transfection with siCCAT2-1(P<0.05),and siCCAT2-2 was chosen to verify the cytology function.The inhibitory rates of RPMI 8226 and U266 cells in the experimental group was higher than those in the control group and the negative control group in a time dependent manner(P<0.05).Compared with RPMI 8226 cells of other two groups,the apoptotic rates and mRNA levels of Bax and Bad were increased but number of trans-membrane cells and mRNA level of Bcl-2 were decreased in experimental group(P<0.05).There was no significant difference between the control group and the negative control group on the above indices(P>0.05).Conclusion In multiple myeloma cell lines,siRNA targeting CCAT2 expression can inhibit the proliferation,invasion and metastasis and induce apoptosis of CCAT2, which may be valuable in the prevention and treatment of multiple myeloma.