Bim downregulation by activation of NF-κB p65, Akt, and ERK1/2 is associated with adriamycin and dexamethasone resistance in multiple myeloma cells

Multiple myeloma (MM) frequently acquires multidrug resistance (MDR), which is due to poor prognosis. Our previous study indicated that high expression of Survivin and multidrug resistance protein 1 (MDR1) and decreased expression of Bim are associated with MDR in adriamycin- and dexamethasone-resistant cells. However, the fundamental mechanism of MDR in adriamycin- and dexamethasone-resistant MM cells is still unidentified. In this study, we examined the MDR mechanism in adriamycin- and dexamethasone-resistant cells. RPMI8226/ADM, ARH-77/ADM, RPMI8226/DEX, and ARH-77/DEX cells exhibited enhanced nuclear factor kappa B (NF-kappa B) p65, Akt, and extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Combination treatment with NF-kappa B p65, phosphoinositide 3-kinase (PI3K), and mitogen-activated protein kinase 1/2 (MEK1/2) inhibitors resensitized to adriamycin and dexamethasone via increased Bim expression. Although treatment with MDR1 or Survivin siRNA did not overcome adriamycin and dexamethasone resistance in RPMI8226/ADM and RPMI8226/DEX cells, administration of Bim siRNA induced adriamycin and dexamethasone resistance in RPMI8226 cells. Moreover, low expression of Bim was related to poor prognosis in MM patients. These results indicate that activation of NF-kappa B p65, Akt, and ERK1/2 is associated with adriamycin and dexamethasone resistance via decreasing Bim expression, and these signal inhibitor combinations overcome drug resistance in MM. These findings suggest that combination treatment with these inhibitors and adriamycin or dexamethasone may be a promising therapy for adriamycin- and dexamethasone-resistant MM.

Automated summary

Activation of NF-kappa B p65, Akt, and ERK1/2 is associated with adriamycin and dexamethasone resistance via decreasing Bim expression. Combination treatment with NF-kappa B p65, PI3K, and MEK1/2 inhibitors can overcome drug resistance by increasing Bim expression. Low expression of Bim is related to poor prognosis in multiple myeloma patients.