shRNA-mediated silencing of sorcin increases drug chemosensitivity in myeloma KM3/DDP and U266/ADM cell lines.

Sorcin is a penta-EF hand calcium binding protein, which is involved in the resistance to chemotherapeutics in cancer cells, and is overexpressed in various cancer cells. However, tumor relapse combined with the development of drug resistance remains a significant problem. Here, we demonstrated that silencing of Sorcin in chemotherapy resistance myeloma U266/ADM and KM3/DDP cell lines resulted in reduced cell proliferation, cell cycle arrest and cell apoptosis. Sorcin siRNA successfully silenced Sorcin mRNA and protein expression. Silencing of Sorcin also significantly reduced the mRNA and protein expression levels of MDR1, MRP1, GST-π, Survinvin, Livin, Bcl-2, Cyclin-D1, phospho-Src, C-myc, p21, NF-κB and phospho-AKT, while p53 expression and caspase-3 and caspase-8 activity significantly increased when compared with control group. Silencing of Sorcin significantly increased the sensitivity of KM3/DDP cells to cisplatin and the sensitivity of U266/ADM to adriamycin, compared to cells untransfected and transfected with negative control shRNA. In addition, intracellular accumulation of Rhodamine 123 significantly increased in KM3/DDP and U266/ADM cells. In summary, our studies indicate that drug resistance can be effectively reversed in cisplatin-resistance and adriamycin-resistant myeloma cells through delivery of siRNAs targeting Sorcin. Assessment of potential as a target for human myeloma treatment is clearly warranted.