PDGF promotes VEGF production in CLL MSCs in a PI3K-dependent manner. (A) Addition of PDGF to MSC culture promotes VEGF production (n = 6; mean increase, 3.3-fold; P = .03). TSP-1 and bFGF production in MSCs were not altered by addition of PDGF. (B) PI3K blockade with LY294002 was able to reduce the increased production of VEGF in MSCs mediated by PDGF (P = .04, PDGF versus PDGF+LY; P = .25, PDGF versus PDGF+SB). SB, SB202190; LY, LY294002. Six MSCs derived from the marrow biopsies of 6 different patients were tested in 6 individual experiments shown in the bar graph.