Casein kinase 1 (CK1) family members are serine/threonine kinases that are ubiquitously expressed and that play different roles in regulating a variety of cellular processes, including apoptosis, proliferation, DNA repair, differentiation, and cellular trafficking [73]; furthermore, activating mutations and the overexpression of several CK1 isoforms have been implicated in cancer [74]. Here, MARK2 is linked to cancer.