Prognostic significance of USP22 as an oncogene in papillary thyroid carcinoma

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 papillary thyroid carcinoma (PTC) samples and to evaluate its clinical significance in PTC patients. USP22 expression was examined in 30 fresh PTC tissues and paired adjacent noncancerous tissues by real-time quantitative RT-PCR. Immunohistochemistry for USP22 was performed on additional 156 PTC tissues. The clinical significance of USP22 expression was analyzed. We found that the expression levels of USP22 mRNA and protein in PTC tissues were both significantly higher than those in noncancerous tissues. Clinicopathological analysis showed that USP22 expression was significantly correlated with tumor size (p=0.036), extracapsular invasion (p=0.012), multifocality (p=0.014), lymph node metastasis (p=0.022), distant metastasis (p=0.005), and TNM stage (p=0.002). The Kaplan-Meier survival curves revealed that USP22 expression was associated with poor prognosis in PTC patients. USP22 expression was an independent prognostic marker of overall patient survival in a multivariate analysis. Our findings suggest that USP22 is an independent predictor of poor prognosis of PTC patients.