MCL1 and esophageal squamous cell carcinoma: Since protein phosphatase 2A (PP2A) was reported to dephosphorylate MCL1 at Ser159 and Thr163 in its PEST region and prevent its rapid degradation in lymphoma cells [26], we hypothesized that PP2A may participate in MCL1 stabilization during nab-PTX resistance in ESCC.