PRKN and esophageal squamous cell carcinoma: Besides, cox analysis showed that several risk factors related to poor prognosis in ESCC patients, including poor differentiation (P = 0.015), tumor invasion depth (P = 0.001), lymph node metastasis (P < 0.001), distant metastasis (P < 0.001) and low PARK2 expression (P < 0.001) (Table 2).