Correlation Between Abnormal Expression Of Ubiquitin-Conjugating Enzyme E2Q1(UBE2Q1) And The Development Of Hepatocellular Carcinoma

Objective:Hepatocellular carcinoma(HCC) is one of the most common cancer in the world. Ubiquitin-proteasome system(UPS) has been shown to play a pivotal role in the pathophysiology of hepatocellular carcinoma and other malignancies. Ubiquitin-conjugating enzyme E2Q1(UBE2Q1) is a putative E2 ubiquitin conjugating enzyme, and may be involved in the regulation of cancer-related proteins. In this study, the expression pattern of UBE2Q1 in HCC cell lines and human HCC specimens, and its potential clinical and biological significance in HCC were investigated.Methods:1. On the histological way, the expression of UBE2Q1 was detected in 8 cases of HCC and adjacent nontumorous liver tissues by Western blot analysis. Then, immunohistochemistry was used to find out UBE2Q1 and proliferation index Ki-67 expression in 86 human HCC specimens,and statistical methods was used to determine the correlationship between UBE2Q1 and Ki-67 expression with clinical pathological characteristics, such as age, gender, histological grade, tumor size, metastasis and so on. Survival curve was calculated in HCC cases using the Kaplan-Meier analysis, then the prognosis was analyzed by the univariate and Cox proportional hazards model.2. On the cellular way, BEL-7404、Hep G2 cells that with high UBE2Q1 expression level were selected as the research object, Western blot was used to test UBE2Q1 protein expression level changes after serum starvation and refeeding.3. On the molecular biology way, after knockdown of the expression of UBE2Q1 in BEL-7404、Hep G2 cells by small interfering RNAs, CCK-8 assay and flow cytometry analysis were adopted to explore cell proliferation and cell cycle progression respectively.Results:1. Both Western blot and immunohistochemistry analysis indicated that UBE2Q1 expression was higher in HCC tissues compared with adjacent nontumorous liver tissues. The expression of UBE2Q1 was only significantly associated with histological grade(P<0.001), and correlation analysis indicated that there was a positive correlation between UBE2Q1 expression and Ki-67-based proliferative activity(r= 0.639,P< 0.01); The Kaplan-Meier survival curves showed that high UBE2Q1 expression was correlated to a poor survival with statistical significance(P= 0.001). Unvaried analysis showed that UBE2Q1 expression was associated with a poor prognosis of HCC(P< 0.001). Multivariate Cox proportional hazards regression analysis showed that UBE2Q1 expression was an independent prognostic marker for HCC(P= 0.002).2. The cell cycle of BEL-7404、Hep G2 cells were blocked by serum starvation, reentering the cell cycle after serum addition. Western blot showed that the expression of UBE2Q1 and PCNA were increased, whereas the expression of p53 and p21 were inversely diminished after serum stimulation in BEL-7404、Hep G2 cells during cell cycle progression.3. Small interfering RNA analysis showed that UBE2Q1 depletion might inhibit cell proliferation and result in cell cycle arrest.Conclusions:1. Western blot and immunohistochemical analyses revealed that UBE2Q1 was significantly upregulated in HCC tumorous tissues compared with the adjacent noncancerous ones. Univariate and multivariate survival analyses were performed to determine the prognostic significance of UBE2Q1 in HCC. The results showed that upregulated expression of UBE2Q1 was positively correlated with high histological grades of HCC and predicted poor prognosis.2. The expression of UBE2Q1 was progressively increased in serum-referrd HCC cells. UBE2Q1 depletion by small interfering RNA inhibited cell proliferation and led to G1 phase arrest in Hep G2 and BEL-7404 cells. Cells transfected with UBE2Q1-targeting si RNA resulted in significant increase in the levels of p53, p21 in Hep G2 and BEL-7404 cells. These data imply that UBE2Q1 is upregulated in liver cancer cell lines and tumorous samples and may play a role in the development of HCC.