SKP1 and esophageal squamous cell carcinoma: As reported previously, SKP2 containing SCF (SKP1-cullin1-F-box protein) E3 ubiquitin ligase is able to degrade P27 through polyubiquitination.56 We thus measured the level of SKP2 in RBM4 stably depleted KYSE150 and KYSE450 ESCC cells, and revealed that the expression of SKP2 was evidently decreased by RBM4-depletion (Fig. 3e).