Yan-Mei Yang

Aberrant expression of USP22 is associated with liver metastasis and poor prognosis of colorectal cancer.

The present study was aimed at clarifying the expression of ubiquitin carboxyl‐terminal hydrolase 22 (USP22), a novel deubiquitinating enzyme gene, in colorectal cancer (CRC) and its clinical significance.

USP22 acts as an oncogene by the activation of BMI-1-mediated INK4a/ARF pathway and Akt pathway.

Recent studies provided strong support for the view that ubiquitin-specific protease 22 (USP22) plays a central role in cell-cycle progression and also in pathological processes such as oncogenesis. We have recently shown that USP22 levels are elevated in colorectal carcinoma with associated increase in the expression of several cell-cycle-related genes. However, the precise mechanism for these functions of USP22 at molecular level has not been fully elucidated. Currently, we investigated the role of USP22 in human colorectal cancer (CRC). We observed that USP22 expression was statistically significantly correlated positively with that of BMI-1, c-Myc and both, pAkt (Ser473), and pAkt (Thr308), in primary tumor tissues from 43 CRC patients. Down-regulation of USP22 expression in HCT116 colorectal cancer cells by siRNA resulted in the accumulation of cells in the G1 phase of the cell cycle. RNAi-knockdown of USP22 in HCT16 cells also led to the repression of BMI-1 and was accompanied by the up-regulation of p16INK4a and p14ARF, with a consequent decrease in E2F1 and p53 levels. In addition, down-regulation of c-Myc-targeted cyclin D2 was also noticed in cells treated with USP22-siRNA. Furthermore, our results showed that USP22 deletion also caused down-regulation of Akt/GSK3β activity, which can also contribute to the reduction of cyclin D2. Collectively, our current results suggest that USP22 may act as an oncogene in CRC as it positively regulates cell cycle via both BMI-1-mediated INK4a/ARF pathway and Akt signaling pathway.

Knock-down of ubiquitin-specific protease 22 by micro-RNA interference inhibits colorectal cancer growth

PurposeIncreasing experimental evidences suggest that ubiquitin-specific protease 22 (USP22), a cancer stem cell marker, plays a crucial role in pathological processes of epithelial malignancies and other solid tumors, which makes it a potential target for cancer therapy. The aim of this study was to study the roles of USP22 in human colorectal cancer cell line HCT116 by suppressing USP22 expression with micro-interfering RNA (miRNA).MethodsWith the knock-down of USP22, the changes of cellular proliferation, cell cycle, cell apoptosis, and major vault protein (MVP) expression were investigated. Furthermore, a tumor xenograft model in nude mice was injected with USP22 miRNA silencing vector and the immunohistochemical staining was performed to evaluate the USP22 expression in the tumor.ResultsThe knock-down of USP22 protein expression by miRNA resulted in the inhibition of cellular proliferation, the accumulation of cells in the G1 phase, the reduction of apoptosis, and the down-regulation of MVP expression. Furthermore, with orthotopic mice as a model, tumor growth was suppressed when USP22 miRNA silencing vector was injected. Immunohistochemical analyses of tumor sections revealed that USP22 expression in animals decreased when USP22 expression was inhibited by miRNA.ConclusionThese results support the hypothesis that USP22 plays a crucial role in tumor formation and growth by regulating cell proliferation with USP22-dependent signaling pathway. Furthermore, USP22 acts as a major transcriptional factor to regulate MVP drug resistant gene. Taken together, targeting USP22 may offer additional possibilities in cancer therapy.

Implication of USP22 in the regulation of BMI-1, c-Myc, p16INK4a, p14ARF, and cyclin D2 expression in primary colorectal carcinomas.

BackgroundIncreasing experimental evidence suggests that USP22 plays a crucial role in the pathologic processes of epithelial malignancies and other solid tumors. BMI-1, p16INK4a, p14ARF, cyclin D2, and c-Myc have been implicated in the regulation of the cell cycle mediated by USP22 in cell culture experiments. In this study, we examined whether these in vitro findings can be extrapolated to the in vivo situation. MethodsWe measured the expression of USP22 and the candidate targets such as BMI-1, c-Myc, cyclin D2, p16INK4a, p14ARF by quantitative real time-polymerase chain reaction, Western blotting, and immunostaining in a series of 43 colorectal carcinomas (CRCs) and correlated the data with several clinicopathologic variables. ResultsThe frequency of overexpression (4-fold expression analysis) was 37.0% for USP22, 48.9% for BMI-1, 48.9% for c-Myc, and 58.0% for cyclinD2, respectively. Statistical correlation analysis at the mRNA level showed USP22 to be significantly correlated with BMI-1 (r=0.889, P<0.0001), c_Myc (r=0.573, P<0.0001), and cyclin D2 (r=0.872, P<0.0001), but not p16IN K4a (r=0.222, P=0.153) or p14Are (r=−0.154, P=0.325) by quantitative real time-polymerase chain reaction. These findings were confirmed by the Western blotting assay. Furthermore, the k-means cluster analysis showed that CRCs with high mRNA expression of USP22, BMI-1, c-Myc, and cyclin D2 were significantly correlated with the advanced AJCC stage (P=0.01) associated with poor prognosis. ConclusionsThe findings of this study supported dysregulation of a proposed functional pathway by upregulation of gene products in primary CRC.

Expression and clinicopathological significance of EED, SUZ12 and EZH2 mRNA in colorectal cancer.

AbstractBackground and objectivesEnhancer of zeste 2 (EZH2), embryonic ectoderm development (EED), and suppressor of zeste 12 homolog (SUZ12), the key component of polycomb repressive complex 2, are of great importance in human cancer pathogenesis. This study was designed to investigate the clinical and prognostic significances of EZH2, EED and SUZ12 in colorectal cancer (CRC) patients.nMethodsThe expression of EZH2, EED and SUZ12 mRNA was evaluated in 82 primary CRC and paired non-cancerous mucosa samples by qRT-PCR.nResultsWe found that overall EZH2, EED and SUZ12 mRNA expression in the CRC tissues was significantly increased than in the non-cancerous tissue (pxa0<xa00.05). Increased EZH2, EED and SUZ12 mRNA expression was directly correlated with primary tumor size, regional lymph node metastases, distant metastasis and AJCC stage. Furthermore, CRC patients with higher level of EED, SUZ12 or EZH2 showed a worse disease-free survival (DFS) (pxa0<xa00.01). In multivariate analysis, the increased EZH2 expression may be a risk factor for the patients’ 3-year DFS (HR 2.517; 95xa0% CI 1.104, 5.736; pxa0=xa00.028). Furthermore, the k-means cluster analysis showed that high mRNA expression of EED, SUZ12 and EZH2 was significantly correlated with the aggressive clinical behavior and poor prognosis.ConclusionsHigh expression of EED, SUZ12 and EZH2 might contribute to the CRC development/progression.

Studies on the expression patterns of class I PI3K catalytic subunits and its prognostic significance in colorectal cancer.

The phosphatidylinositol 3-kinase/AKT (PI3K/AKT) pathway plays a critical role in human cancer. We determined the expression patterns of class I PI3K catalytic subunits and evaluated their importance in the development or progression of colorectal cancer (CRC). For this purpose, expression of class I PI3K isoforms was evaluated in 82 primary CRC and paired non-cancerous mucosa samples by qRT-PCR. P-AKT-Ser473 and P-AKT-Thr308 expression were measured by western blot. We found that, compared with paired non-cancerous mucosa samples, mRNA expression of p110α and p110β in CRCs was significantly increased to 2.02-fold (95% confidence interval [CI] 1.25–3.28 fold) and 1.76-fold (95% CI 1.19–2.60 fold), respectively; while slight differences were found regarding the expression of p110δ (0.57-fold; 95% CI 0.31–1.07 fold) and p110γ (0.97-fold; 95% CI 0.50–1.88 fold). Increased p110α and p110β expression correlated with primary tumor size, regional lymph node metastases, and AJCC stage. Increased p110β expression also correlated with distant metastasis. P-AKT-Thr308 and P-AKT-Ser473 expression showed significant direct correlations with p110α and p110β mRNA expression. Besides, CRC patients with p110β mRNA overexpression had a worse disease-free survival after radical surgery compared with those with normal or decreased levels (Pxa0=xa00.043). It was, therefore, concluded that the altered p110α and p110β expression might contribute to the CRC development or progression.

USP22 drives colorectal cancer invasion and metastasis via epithelial-mesenchymal transition by activating AP4

Ubiquitin specific peptidase 22 (USP22), a putative cancer stem cell marker, is overexpressed in liver metastases of colorectal cancer (CRC). However, the mechanism by which USP22 promotes CRC metastasis remains largely unknown. Here, we report that USP22 and AP4 are simultaneously overexpressed during TGF-β1-induced CRC cell epithelial-mesenchymal transition (EMT). USP22 up-regulation enhances CRC cell migration and invasion and EMT-related marker and AP4 expression, but these effects are partly blocked by AP4 knockdown. In addition, USP22 binds to the promoter region of AP4 to activate its transcription. In vivo, elevated USP22 expression promotes CRC cell metastasis to the lungs in nude mice, as evidenced by the fact that CRC metastatic nodules stain deeply positive for USP22 and AP4. In human CRC tissues, the genes encoding USP22 and AP4 are overexpressed in metastatic liver lesions compared with primary cancer tissues, and their overexpression is significantly associated with poor CRC patient survival. These findings indicate that USP22 and AP4 may serve as prognostic markers for predicting the risk of developing distant metastases in CRC.

Expression and clinicopathological significance of Mel-18 mRNA in colorectal cancer.

Mel-18 is a member of the polycomb group (PcG) of proteins, which are chromatin regulatory factors that play an important role in oncogenesis. This study was designed to investigate the clinical and prognostic significance of Mel-18 in colorectal cancer (CRC) patients. For this purpose, expression of Mel-18 mRNA was evaluated in 82 primary CRC and paired noncancerous mucosa samples by qRT-PCR and Western blotting. We found that overall Mel-18 mRNA expression in the CRC tissue was significantly lower than in the noncancerous mucosal tissue (pu2009=u20090.007, Wilcoxon matched-pairs signed-ranks test). Mel-18 was conversely correlated with the pathological classifications (pu2009=u20090.003 for T, pu2009<u20090.001 for N, and pu2009=u20090.015 for M classifications, respectively) and clinical AJCC stage (pu2009<u20090.001). Furthermore, CRC patients with a higher level of Mel-18 showed prolonged disease-free survivals (DFS) (pu2009<u20090.001). In multivariate analysis, the diminished Mel-18 expression may be a risk factor for the patients’ 3-year DFS (HRu2009=u20091.895; 95xa0% CI 1.032, 3.477; pu2009=u20090.039). It was therefore concluded that the lower Mel-18 expression might contribute to the CRC development/progression.

Prognostic significance of lymph node status in patients with metastatic colorectal carcinoma treated with lymphadenectomy

To test prognostic significance of lymph node status in patients with metastatic colorectal carcinoma (mCRC).