The level of phosphorylated Smad2 (P-Smad2) and total Smad2 (Smad2) was assessed by immunoblotting and β-actin was used as a loading control. Lower bar graphs show WB quantification of P-Smad2 (P-S2) normalized to β-actin. (C) Conditioned media experiments were performed on the HDMB03 MB cell line. Phosphorylation of Smad2 was analyzed by immunoblot upon treatment with either non conditioned media (NCM), media conditioned with HDMB03 cells (CM-HDMB03) or media conditioned with 1603MED cells (CM-1603). Pre-incubation with blocking antibody against ActivinB (Ab α-ActB) or vehicule (PBS) was performed before HDMB03 cell-line treatment as indicated. Relative level of P-Smad2 (P-S2) were quantified to β-actin (below). 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. 