Increased expression of USP22 is associated with disease progression and patient prognosis of salivary duct carcinoma

Abstract

Ubiquitin-specific protease 22 (USP22) could exhibit a critical function in pathological processes, including oncogenesis and cell cycle progression. This study examines the protein expression of USP22 in salivary duct carcinoma (SDC) in association with patient survival and other clinicopathologic parameters. Quantitative RT-PCR and immunohistochemistry (IHC) were used to determine the expression of USP22 protein in 44 SDCs in comparison with 20 non-cancerous salivary tissues. Furthermore, we analyzed the correlation between the expression of the USP22 protein and various clinicopathologic factors including survival status of patients with SDC. The incidence of positive USP22 expression was 63.7% in 44 SDC tissues. The mRNA level of USP22 expression in SDC samples was significantly higher than that in non-cancerous salivary tissues (P < 0.001), which was consistent with the IHC result (P < 0.001). Moreover, statistical analysis showed that positive USP22 expression was positively related to pT classification, pN classification and AJCC stage. Notably, high USP22 expression was significantly associated with shorter overall survival (P = 0.023) and disease-specific survival (P = 0.019). Multivariate Cox regression analysis revealed that USP22 expression level was an independent prognostic factor for both overall survival (P < 0.001) and disease-free survival (P < 0.001). Our results indicate that activation of USP22 correlates with SDC progression and therapy failure. Overexpression of USP22 may contribute to the progression of SDC and thus may serve as a new molecular marker to predict the prognosis of SDC patients.