Smad2 is overactivated in BM cells and HSPCs of MM patients. BM biopsy sections from patients with MM and healthy controls were fixed and immunostained with an Ab against phospho-smad2, the activated form of the downstream mediator of TGFβ receptor I kinase (TBRI) activation. (A) Four representative samples of healthy donors and MM patients, respectively. P-smad2 staining was quantified by counting the total number of positively stained cells in 3 hot fields for each patient sample under ×200 magnification aided by Motic Image Plus software. (B) The bar chart shows the mean percentage of phospho-smad2–positive BM cells in healthy donors and MM patients. HSPCs from the BM of healthy donors and MM patients were assessed for smad2 phosphorylation by immunoblotting. (C) One representative of 4 experiments is shown. TGFβ1 concentrations were assessed by ELISA. (D) The bar charts display the mean TGFβ1 concentration in the BMEF. The Student t test was used to detect statistically significant differences. *P < .05.