Knockdown of REG gamma inhibits the proliferation and migration and promotes the apoptosis of multiple myeloma cells by downregulating NF-kappa B signal pathway

Objectives: This study aimed to evaluate the effects of REG gamma knockdown on the proliferation, apoptosis and migration of multiple myeloma (MM) cells, and reveal the potential regulatory mechanisms. Methods: The expression of REG gamma on myeloma cells of 28 MM patients was detected by Western blot. shRNA-REG gamma-1 and shRNA-REG gamma-2 were constructed to downregulate REG gamma in RPMI-8226 cells. The proliferation, apoptosis and migration of transfected cells were analyzed by Cell Counting Kit 8 (CCK8), flow cytometry and transwell chamber, respectively. The expression of phosphorylated p65 (p-p65), p65, NF-kappa-B inhibitor epsilon (IkB epsilon), matrix metalloproteinase 2 (MMP2), B-cell lymphoma xL (Bcl-xL) and X-linked inhibitor of apoptosis protein (XIAP) in transfected cells was detected by Western blot. Using cycloheximide (CHX), the half-life period of IkB epsilon was detected by Western blot. Results: The expression of REG gamma was positive in myeloma cells. The proliferation and migration of RPMI-8226 cells were significantly inhibited by shRNA-REG gamma-1/shRNA-REG gamma-2, while the apoptosis rates were significantly increased (p < 0.05). The expression of p-p65 and IkB epsilon was significantly reduced in RPMI-8226 cells transfected with shRNA-REG gamma-1/shRNA-REG gamma-2. The degradation of IkB epsilon was significantly lower in RPMI-8226 cells transfected with shRNA-REG gamma-1 than the control (longer half-life period). Besides, the expression of MMP2, Bcl-xL and XIAP in RPMI-8226 cells was significantly inhibited by shRNA-REG gamma-1/shRNA-REG gamma-2. Discussion: Knockdown of REG gamma may inhibit the proliferation and migration, and promote the apoptosis of RPMI-8226 cells possibly by downregulating NF-kappa B signal pathway.