FIGURE 6.

Critical role of the TAM family receptor Mer in Gas6-related signaling pathways in the pathogenesis of MM. A, the lysates were immunoprecipitated (IP) with anti-Mer monoclonal antibody, and immunoprecipitates were analyzed by Western blotting with anti-Gas6 antibody. Gas6 expression was detected in the subsequent immunoprecipitation with anti-Mer antibody in MM cells treated with HS-5 cell-CM, whereas very little or no Gas6 expression was detectable in the immunoprecipitated proteins with anti-Axl or anti-Tyro3 antibody in MM cells. B, RPMI-8226 cells were transfected with siRNA to Mer. siRNA-mediated knockdown of Mer reduced the protein levels of Mer as compared with the scrambled negative control. C and D, MM cells were incubated in serum-free X-VIVO medium for 48 h at 37 °C in the presence of Gas6 (100 ng/ml) or 50% (v/v) HS-5 cell-CM with or without the silencing of Mer with siRNA, followed by an MTT assay. Data are expressed as means ± S.D. (error bars) (n = 8, each group). *, p < 0.05. E, MM cells were incubated in serum-free X-VIVO medium in the presence of Gas6 (100 ng/ml) or 50% (v/v) HS-5 cell-CM for 24 h with or without the silencing of Mer with siRNA, and cell apoptosis was analyzed by FCM after staining with Annexin V and 7-AAD. Representative data are from three independent experiments. Data shown are representative of three independent experiments. F, RPMI-8226 cells were incubated in serum-free X-VIVO medium in the presence of Gas6 (100 ng/ml) or 50% (v/v) HS-5 cell-CM for 24 h with or without the silencing of Mer with siRNA, followed by Western blotting. Representative immunoblots are from three similar experiments are shown.