TGFB1 and glioblastoma: Moreover, a positive correlation was seen between endoglin and TGF-β1 protein (r = 0.453, p = 0.006) and PAI-1 protein (r = 0.350, p = 0.036) in tumor cells of newly diagnosed glioblastoma, as well as a positive significant correlation of endoglin and pSmad1/5 levels in the tumor cells of the newly diagnosed and recurrent patients (r = 0.479, p = 0.004 and r = 0.885, p = 0.019, respectively) (Table 2).