Enhanced expression of early mitotic inhibitor-1 predicts a poor prognosis in esophageal squamous cell carcinoma patients

Early mitotic inhibitor-1 (Emi1), as a key cell cycle regulatory gene, induces S phase and mitotic entry by controlling anaphase-promoting complex substrates. Emi1 overexpression may be a prognostic factor for patients with invasive breast cancer. However, its expression and clinical significance in esophageal squamous cell carcinoma (ESCC) remain unknown. In the present study, Emi1 was overexpressed in ESCC samples, contrarily to their neighboring normal tissues. The expression of Emi1 was correlated with histological differentiation (P=0.032), lymphatic metastasis (P=0.006) and Ki-67 expression (P=0.028). Multivariate analysis indicated that the presence of lymphatic metastasis and the protein expression levels of Emi1 and Ki-67 were all independent prognostic factors for ESCC patients (P=0.042, 0.018 and 0.001, respectively). In vitro, however, the expression of Emi1 was upregulated in the ECA109 cell line following release from serum starvation. In addition, depletion of endogenous Emi1 by small interfering RNA could effectively reduce cell proliferation. Thus, the present data indicated that Emi1 expression was upregulated in ESCC tissues and correlated with poor survival in ESCC patients, and suggested that Emi1 may be an independent prognostic factor for ESCC patients.