(D) Conditioned media experiments were performed on HDMB03 MB cell line. Phosphorylation of Smad2 (P-Smad2) was analyzed by immunoblot upon treatment with either non-conditioned media (NCM), media conditioned with HDMB03 cells (CM-HDMB03) or media conditioned on PDX4 cells (CM-PDX4). Pre-incubation with blocking antibody against ActivinB (Ab α-ActB) or with vehicle was performed before HDMB03 cell-line treatment as indicated. lower panels represent the relative quantification of P-Smad2 normalized to β-actin. The p-values were determined by unpaired t-test. *p < 0.05, **p < 0.01, ***p < 0.001. Bars represent the mean ± SD. Number of replicates is n≥3. 