Etodolac Induces Apoptosis and Inhibits Cell Adhesion to Bone Marrow Stromal Cells in Human Myeloma Cells.

Cyclooxygenase-2 (COX-2) is reported to regulate apoptosis and to be an important cellular target for therapy. In this study, we demonstrated that etodolac, a COX-2 inhibitor, inhibited proliferation and induced apoptosis in myeloma cell lines (RPMI 8226 and MC/CAR cells), expressing the COX-2 enzyme. In both cell lines, etodolac more strongly induced apoptosis compared with thalidomide or meloxicam. Etodolac induced down-regulation of bcl-2 protein and mRNA, activation of caspase-9, -7 and -3, down-regulation of caspase inhibitors, cIAP-1 and survivin, and loss of mitochondrial membrane potential in a dose-dependent manner. In addition, our data demonstrated that when myeloma cells were coincubated with 50 mM etodolac on bone marrow stromal cells (BMSC), myeloma cell adhesion to BMSC was significantly inhibited compared with thalidomide or meloxicam coincubation, and the adhesion molecules VLA-4, LFA-1 (CD11a), CXCX4, and CD44 were suppressed on myeloma cells treated with etodolac. Moreover, we found that 100 mM R-etodolac, S-etodolac, and the combination of R- and S-etodolac, which are the stereoisomers of etodolac, slightly inhibited the proliferation of myeloma cells, while 50 to 100 mM etodolac significantly inhibited the proliferation of myeloma cells. In conclusion, our findings indicate that etodolac induced apoptosis via a bcl-2 dependent pathway, suppressed the expression of adhesion molecules, and inhibited myeloma cell adhesion to BMSC compared with thalidomide or meloxicam. Thus, the activities of etodolac potentially extend to the treatment of patients with myeloma resistant to standard chemotherapy, including thalidomide.