Bortezomib promotes apoptosis of multiple myeloma cells by regulating HSP27.

The aim of the present study was to investigate the effect of bortezomib on heat shock protein 27 (HSP27) in multiple myeloma (MM) and provide a potential new target for clinical treatment. Peripheral blood was collected from 50 normal subjects and 50 patients with newly diagnosed MM and the expression of HSP27 was detected by ELISA. The changes of HSP27 after conventional vincristine, doxorubicin and dexamethasone (VAD) chemotherapy, and bortezomib plus VAD were compared. The effect of bortezomib on U266 cell proliferation and apoptosis was detected using a Cell Counting Kit‑8 assay and Annexin V‑FITC/propidium iodide double staining with flow cytometry. The content of HSP27 following bortezomib treatment was determined by ELISA. Western blot analysis and reverse transcription‑quantitative PCR were used to detect the mRNA and protein expression of HSP27, Bax and Bcl‑2. HSP27 expression was increased in patients with MM compared with healthy control subjects, and the expression was increased as the cancer progressed (P<0.05). Compared with the VAD chemotherapy group, the bortezomib plus VAD chemotherapy regimen significantly inhibited the expression of HSP27 (P<0.05), and the content of HSP27 was decreased in patients in which treatment was effective compared to those patients that exhibited disease progression (P<0.05). The efficacy of the treatment regimes was not associated with age or gender. Compared with the control group, bortezomib or OGX‑427 (HSP27 inhibitor) treatment inhibited U266 cell proliferation, promoted U266 cell apoptosis (P<0.05) and significantly decreased HSP27 expression (P<0.05). Furthermore, the expression of HSP27 and Bcl‑2 was significantly decreased, while the expression of Bax was increased by bortezomib and OGX‑427 (P<0.05). There was no significant difference between the bortezomib and OGX‑427 group in the in vitro analysis. HSP27 was positively correlated with Bcl‑2 expression and negatively correlated with Bax expression in U266 cells. In conclusion, bortezomib promotes the apoptosis of MM cells, potentially by downregulating the expression of HSP27, providing a potential novel target for the clinical treatment of multiple myeloma.