Ex Vivo Anti-Tumor Activity of Rosiglitazone on Multiple Myeloma Cells.

Peroxisome proliferation activated receptor-g (PPAR-g) belongs to the family of nuclear hormone receptors (NHRs), it is normally expressed in adipocytes, adrenal gland, spleen and liver. Recently it was reported that PPAR-g can also be found in tumor tissues. Activation of PPAR-g by its ligands has potential anti-neoplastic effects in a variety of human malignancies, including leukemia through inhibition of cell proliferation, induction of apoptosis and terminal differentiation. The ligands of PPAR-g may represent a promising, novel therapeutic approach for certain human malignancies.

The thiazolidinedione (TZD) class drug rosiglitazone (RGZ), one of synthetic ligands of PPAR-g, is currently used for the treatment of type 2 diabetes. In this study, we cultured myeloma cell line U266 with different concentration of rosiglitazone, as well as combined with dexamethasone. Cell proliferation was measured by [3H] thymidine incorporation after 48h incubation. Rosiglitazone was found to generate inhibition of cell proliferation on U266 cells in a dose-dependent manner. Cell cycle analysis by flow cytometry showed that rosiglitazone can arrested U266 cells in G0/G1 phase and the G2/M phase cells were significantly decreased compared to controls. We also studied the effect of rosiglitazone on expression of different anti-apoptosis protein FLIP and survivin by RT-PCR, the result revealed that rosiglitazone can also decrease the FLIP and survivin expression. Furthermore, exposure to rosiglitazone can induce the decreased caspase-3 activity in U266 cells, which was associated with apoptosis induction. When rosiglitazone was combined with dexamethasone, the data demonstrated that cell growth inhibition and apoptosis they exerted was much greater than they were used alone, the decreased expression of FLIP and survivin and decreased caspase-3 activity were also greater than when rosiglitazone was used alone. Based on these findings, we suppose that rosiglitazone alone and in combination with dexamethasone holds promise as novel therapy for myeloma.