The co-expression of USP22 and BMI-1 may promote cancer progression and predict therapy failure in gastric carcinoma.

Recent experimental evidence support the model in which the simultaneous induction of BMI-1 and USP22 is critical during cancer progression. Whether this model may affect gastric cancer (GC) progression is worthy of additional study. In this study, we examined the significance of the USP22 and BMI-1 expression in GC (n = 219), non-cancerous mucosa (n = 37), and lymph node metastasis (n = 37). The protein expression level of USP22 and BMI-1 were concomitantly up-regulated from non-cancerous mucosa to primary carcinoma and from carcinomas to lymph node metastasis (P < 0.001). A statistical correlation was observed between USP22 and BMI-1 expression in GC tissues (n = 219, r = 0.634, P < 0.001) and in lymph node metastasis (n = 37, r = 0.689, P < 0.001). The incidence of positive expression was 57.08% for USP22, 49.32% for BMI-1, and 45.21% for USP22/BMI-1 in 219 GC tissues, respectively. Co-positive of USP22/BMI-1 was significantly correlated with gross features (x(2) = 14.256, P < 0.001), differentiation (x(2) = 5.872, P = 0.015), pT classification (x(2) = 18.486, P < 0.001), pN classification (x(2) = 9.604, P = 0.002), pM classification (x(2) = 32.766, P < 0.001), and AJCC stage (x(2) = 58.278, P < 0.001). Notably, high USP22/BMI-1 expression was significantly associated with shorter disease-specific survival (P < 0.001). By Cox regression analysis, co-positive of USP22/BMI-1 was found to be an independent prognostic factor (P = 0.002). Our results indicated the simultaneous activation of USP22 and BMI-1 may associate with GC progression and therapy failure.