Fas and Fas ligand analysis in multiple myeloma cells and mesenchymal stem cells under co-culture. (A) Multiplication of multiple myeloma (MM) cells under different co-culture conditions with mesenchymal stem cells (MSCs) (Cont., MM single culture; C-medium, MM culture with conditioned medium from MSC culture; Trans-well, indirect co-culture between MM and MSC; Co-cul, direct culture between MM and MSC). Each data point represents the mean ± standard deviation (SD) of two parallel experiments. #P <0.05 versus the control group (Cont.). (B) Western blotting analyses of the expression levels of Fas and Fas ligand (Fas-L) in MM cells and MSCs under co-culture condition for 0, 6, 12, and 24 hours. (C), (D) The rates of Fas-positive or Fas-L-positive cells were determined through immunofluorescence staining. (C) MM cells were prestained for carboxyfluorescein diacetate, succinimidyl ester (CFSE; green) and then post-stained for Fas (red). (D) MSCs were stained for Scar-1 (green) and subsequently stained for Fas-L (red). Bar = 300 μm. Numbers of Fas-positive MM cells and Fas-L-positive MSCs are shown. Data presented as the mean ± SD for two parallel experiments. #P <0.05 versus the control group (Cont.). DAPI, 4′,6-diamidino-2-phenylindole.