Etodolac induces apoptosis and inhibits cell adhesion to bone marrow stromal cells in human myeloma cells.

Objectives: Cyclooxygenase-2 (COX-2) is reported to regulate apoptosis and to be an important cellular target for therapy.

Methods: We examined whether etodolac, meloxicam, and thalidomide inhibited proliferation and induced apoptosis in myeloma cell lines (RPMI 8226 and MC/CAR cells).

Results: Etodolac induced apoptosis more strongly compared with thalidomide or meloxicam. Etodolac induced down-regulation of Bcl-2 protein and mRNA, activation of Caspase-9, -7 and -3, cIAP-1 and Survivin, and loss of mitochondrial membrane potential in a dose-dependent manner. In addition, when myeloma cells were coincubated with 50 microM etodolac on bone marrow stromal cells (BMSCs), myeloma cell adhesion to BMSCs 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, 50-100 microM racemate of etodolac significantly inhibited the proliferation of myeloma cells compared to 100 microM R-etodolac or S-etodolac.

Conclusions: Etodolac induced loss of mitochondrial membrane potential and apoptosis via a COX-2-independent pathway, suppressed the expression of adhesion molecules, and inhibited myeloma cell adhesion to BMSCs compared with thalidomide or meloxicam. The activities of etodolac potentially extend to the treatment of patients with myeloma resistant to standard chemotherapy, including thalidomide.