BMP-2 is present in MM sera. (A) MM sera (n = 3) were immunodepleted with anti–BMP-2/4 or isotype-control antibody. Depleted sera were used to treat HuH7 cells that had been transfected with WT-HAMP promoter-luciferase construct. After treatment, cells were lysed and luciferase activity was measured. Bars represent mean ± SD. Statistical significance was determined with the Student t test; *P < .001. (B) ELISA assay was used to measure BMP-2 values in normal (n = 9) and MM sera (n = 23). As expected, MM sera contained higher amounts of BMP-2, then normal sera. Bars represent mean ± SD. The Mann-Whitney rank-sum test was used to determine statistical significance, and *P < .001.