Fig. 4

TGF-β2 secreted by MSC may have induced drug resistance in GIST cells. TGF-β inhibitors but not CXCR4 and TNF-α inhibitors antagonize co-culture-induced GIST resistance (A–C). When cultured alone, there was no significant increase in TGF-β in both MSC or GIST cell media after cultured 8 days. However, there was a significant increase in TGF-β2 in the medium of the co-culture system (D–F). MSC and GIST cells were isolated after 2–8 days of co-culture, and their mRNA and protein expression were examined. Only the mRNA (G–I) and protein (J–M) expression of TGF-β2 was consistently increased in MSC cells. All experiments were repeated at least thrice. Data are means ± SEM (n = 3 in each group) *p < 0.05; **p < 0.01