NUMB and breast cancer: To this end, we compared the expression levels of talin, MARK2, and clathrin adaptor proteins ARH, Numb and Dab2, and phosphorylation of myosin light chain on serine 19 [phospho-myosin light chain 2 (MCL2)] as an indicator of cellular tension, by western blot in keratinocytes and several colorectal and breast cancer cell lines (Fig. 5A,B).