CDKN1B and colorectal carcinoma: Given the increase in expression levels of p27Kip1 following Brachyury-knockdown, and the reported ability of p27Kip1 to regulate self-renewal of human (h)ES cells [39], we carried out the cell proliferation assay on CRC cells (grown from single cells) under conditions of Brachyury and p27Kip1 double knockdown, to determine whether simultaneous p27Kip1 reduction could rescue the inhibition of proliferation observed in single Brachyury-knockdown cells.