THBS1 and central nervous system cancer: In addition, PPAR-γ expression in the gliomas was negatively correlated with TGF-β (r=−0.38, P=0.002), but positively correlated with TSP-1 (r=0.37, P=0.003) (data not shown), suggesting that PPAR-γ inhibits angiogenesis by regulating TSP-1 and TGF-β expression.