SMAD4 and colorectal cancer: Although in certain circumstance BMPR2 may be dispensable for some developmental process, such as the formation of the limb skeleton,32 it has important roles in the oncogenesis and development of some malignant tumors.10, 11, 14, 31 Voorneveld et al.33 showed that BMPR2 increased migration and invasion of Smad4-negtive colorectal cancer cells, and the presence of normal BMPR expression in the Smad4-negative colorectal cancer tumors was associated with a poor prognosis.