BMP signaling and SMURF1 are differentially regulated in HNSCC CSC-like sphere cells. (A) Summary of qRT-PCR array data showing relative expression of BMP signaling inhibitors (SMURF1, BMPER, and BAMBI) and BMP signaling target genes ID1 and ID2 in sphere cell cultures compared to the monolayer cell cultures. Data are shown as mean ± SE with n ≥ 3. (B) Immunoblotting of SMURF1 in monolayer cells and spheres cells from 7-day and 14-day sphere cell culture, shown as a representative of at least three independent repeats. (C) Immunoblotting of pSMAD1/5/8 and total SMAD1 in monolayer (Mo) and three independent, 14-day sphere cultures. β-actin was used as total protein loading control for all samples.