Elevated expression of USP22 in correlation with poor prognosis in patients with invasive breast cancer

Purpose Ubiquitin-specific protease 22 (USP22), a novel deubiquitinating enzyme, has been associated with metastasis, therapy resistance, and cell-cycle progression. The purpose of this study was to investigate the expression level of USP22 in breast samples and to evaluate its clinical significance in breast cancer patients. Methods Immunohistochemistry was used to determine the expression of USP22 protein in 31 breast fibroadenoma and 100 breast cancer patients in comparison with 34 normal breast specimens. Furthermore, we analyzed the correlation between the expression of the USP22 protein and various clinicopathologic factors including survival status of patients with breast cancer. Results The immunohistochemistry results showed that the expression level of USP22 protein in breast cancer samples was significantly higher than that in breast fibroadenoma and normal breast tissues (P = 0.003 and P = 0.021). Moreover, statistical analysis showed that high USP22 expression was positively related to lymph node metastasis, Her-2, Ki67, and recurrence. Furthermore, it was shown that patients with high USP22 expression had significantly poorer outcome compared with patients with low expression of USP22 for patients with positive lymph nodes. Multivariate Cox regression analysis revealed that USP22 expression level was an independent prognostic factor for both overall survival and disease-free survival (P = 0.039 and P = 0.041, respectively). Conclusion Overexpression of USP22 may contribute to the progression of breast cancer and thus may serve as a new molecular marker to predict the prognosis of breast cancer patients.