SMAD2 and cancer: miR-140 inhibits breast or colorectal CSC survival and cancer invasive phenotype via downregulation of SOX2/9 or Smad2 [17–21], whereas, during embryonic bone development, miR-140 drives chondrocyte cell proliferation [8, 9] by targeting HDAC4 and the subsequent transcription of Runx2 [9].