Mechanisms Of Notch Signaling Inhibitors In Proliferating Inhibition Of Multiple Myeloma Cells

Objective: To investigate the effects of cell proliferation and apoptosis with PHI on myeloma cells, Notch signaling and PI3K/Akt/Bcl-2 signaling pathways were analyzed and the potential mechenisam was further discussed.Methods: Western blot and immuocytochemistry were used to detect the expression and localization of Notch proteins on RPMI8226 cells and U266 cells cultured in vitro. RPMI8226 cells were treated with various concentrations of PHI for 24h,48h and 72h and then trypan blue and MTT test were used to measure cell viability and inhibition ratio. Apoptotic cells were determined by the characteristic morphology via DAPI dye, and the cell cycle were detected by flow cytometry. The Notch proteins (Notch1, Jagged1/2), Bcl-2 and Akt signaling pathway proteins (Akt, p-akt) were detected by Western blot. The production of VEGF from MM cells were detected by Elisa.Results: Compared to normal lymphocyte, the expression of Notch receptors Notch 1, Notch2 and the Notch ligands Jagged1 , Jagged2 are higher in MM cells. The apoptotic cells appeared to have condensed chromatin, plasma membrane blebbing and cell shrinkage, apoptotic body. On Myeloma cells ,PHI caused a concentration- and time-dependent growth inhibition and G0/G1 arrest followed treated by PHI. PHI mediated a significant decrease of the expression of Notch1, Jagged1,Jagged2, p-Akt and Bcl-2 and the suppression of VEGF production. Conclusions: (1). The proteins of Notch signaling are overexpressed in MM cells RPMI8226 and U266. (2).PHI and GSI inhibit the proliferation ,induce apoptosis and cause G0/G1 arrest of multiple myeloma cells. (3). PHI inhibits the expression of Notch1,Jagged1/2 and downstream proteins p-Akt and Bcl-2 ,and induce the decrease of VEGF level from multiple myeloma cells. (4).The inhibitors of Notch signaling is a promising strategy for multiple myeloma. PHI,as a natural compound,is the inhibitor of Notch signaling.