CSNK1A1 and neoplasm: Importantly, we demonstrate that CK1α phosphorylates and primes the less well-characterized FOXO4 tumour suppressor for proteolytic degradation, suggesting that RAS-mutant cancer cells have evolved to use CK1α phosphorylation-driven proteolysis as a general mechanism to specifically eradicate the FOXO family of tumour suppressors in their nuclei (Figure 7).