Silencing USP22 by asymmetric structure of interfering RNA inhibits proliferation and induces cell cycle arrest in bladder cancer cells. Mol Cell Biochem. 2011;346:11-21. [PMID: 20824490 DOI: 10.1007/s11010-010-0585-4]

USP22 is useful as a novel molecular marker for predicting disease progression and patient prognosis of oral squamous cell carcinoma

BACKGROUND AND OBJECTIVE

The significance of ubiquitin-specific protease 22 (USP22) as a potential marker has been growing in the field of oncology. The aim of this study was to investigate the role of USP22 and the association with its potential targets in oral squamous cell carcinoma (OSCC).

METHODS

Immunohistochemistry was used to determine the expression of USP22 protein in 319 OSCC patients in comparison with 42 healthy controls. The clinical correlations and prognostic significance of the aberrantly expressed protein was evaluated to identify novel biomarker of OSCC.

RESULTS

The incidence of positive USP22 expression was 63.32% in 319 conventional OSCC tissues. The protein expression level of USP22 was concomitantly up-regulated from non-cancerous mucosa to primary carcinoma and from carcinomas to lymph node metastasis (P<0.001). Moreover, statistical analysis showed that positive USP22 expression was positively related to lymph node metastasis, Ki67, Cox-2 and recurrence. Furthermore, it was shown that patients with positive USP22 expression had significantly poorer outcome compared with patients with negative 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<0.001 and P<0.001, respectively). Cancer cells with reduced USP22 expression exhibited reduced proliferation and colony formation evaluated by MTT and soft agar assays.

CONCLUSION

To our knowledge, this is the first study that determines the relationship between USP22 expression and prognosis in OSCC. We found that increased expression of USP22 is associated with poor prognosis in OSCC. USP22 may represent a novel and useful prognostic marker for OSCC.

USP22 nuclear expression is significantly associated with progression and unfavorable clinical outcome in human esophageal squamous cell carcinoma

PURPOSE

To detect the expression levels of ubiquitin-specific protease 22 (USP22) in human esophageal squamous cell carcinoma (ESCC) and to correlate it with clinicopathologic and prognostic data.

METHODS

The immunoreactivity of USP22 protein was analyzed in 157 pathologically characterized ESCC tissues by immunohistochemistry. All statistical analyses were performed with SPSS statistical software to evaluate the association of USP22 protein with clinicopathologic factors and survival.

RESULTS

High expression of USP22 protein was detected in 50.96 % of 157 ESCC tissues and significantly associated with invasion depth, lymph node metastasis, pathologic stage and tumor relapse (P < 0.05, respectively). Univariate survival analysis showed that patients with high expression of USP22 protein had a significantly poorer 5-year disease-specific survival (P = 0.002), and multivariate survival analysis showed that high expression of USP22 protein was an independent prognosticator for unfavorable disease-specific survival (P = 0.039). Further survival analysis stratified by pathologic stage demonstrated that high expression of USP22 protein significantly predicted unfavorable clinical outcome (P = 0.029) among patients with pathologic stage II(b)-III diseases.

CONCLUSION

USP22 protein plays an essential role in ESCC progression and has clinical potentials not only as a promising biomarker to identify the subgroup of patients with more aggressive tumors and poor prognostic potential but also as an attractively therapeutic target for ESCC.

Expression patterns of USP22 and potential targets BMI-1, PTEN, p-AKT in non-small-cell lung cancer

BACKGROUND

Recent researches document that an oncogenic role of USP22 activation may contribute to progression and predict the prognosis. We have reported that USP22 mediates cell survival and proliferation by promoting the expression of BMI-1 and upregulation of activated AKT pathway in colon cancer cells. However, little is known about its mechanisms in non-small-cell lung cancer (NSCLC). Here the authors investigated the significance of activation of USP22 and potential targets BMI-1, PTEN and phospho-AKT (p-AKT) in NSCLC.

METHODS

Expression levels of USP22, BMI-1, PTEN and p-AKT in samples from 114 patients with NSCLC were evaluated immunohistochemically using the tissue microarray method. Clinical significance was analyzed by multivariate Cox regression analysis, Kaplan-Meier curves and the log-rank test.

RESULTS

Immunohistochemically, USP22, BMI-1, p-AKT and PTEN were positive in 66.66%, 78.07%, 71.92% and 43.85% of NSCLC samples, respectively. Statistical correlation analysis showed USP22 to be significantly correlated with BMI-1 (r=0.315, P=0.001), p-AKT (r=0.271, P=0.003), and PTEN (r=-0.384, P<0.0001). NSCLCs with positive expression of USP22, BMI-1, p-AKT, and negative expression of PTEN were significantly correlated to tumor size (P=0.0240), differentiation (P=0.0457), pT classification (P=0.0077), pN classification (P=0.0064), and AJCC stage (P=0.0363) and poor overall survival (P<0.001). Multivariate Cox proportional hazards model analysis showed that the combined 4 markers was the independent prognostic indicator of overall survival (P<0.001; HR, 5.974; 95% CI, 3.307-10.791).

CONCLUSIONS

The simultaneous targeting of USP22, and its downstream signal transduction molecules seem highly informative in stratification of the cancer into subgroups with distinct likelihood of therapy failure, which contribute to make decision process regarding the individualized therapy selection and optimization.

The enigmatic role of H2Bub1 in cancer

The post-translational modification of histone proteins plays an important role in controlling cell fate by directing essentially all DNA-associated nuclear processes. Misregulation and mutation of histone modifying enzymes is a hallmark of tumorigenesis. However, how these different epigenetic modifications lead to tumor initiation and/or progression remains poorly understood. Recent studies have uncovered a potential tumor suppressor role for histone H2B monoubiquitination (H2Bub1). Like many other histone modifications, H2Bub1 has diverse functions and plays roles both in transcriptional activation and repression as well as in controlling mRNA processing and directing DNA repair processes. Notably, H2Bub1 has been linked to transcriptional elongation and is preferentially found in the transcribed region of active genes. Its activity is intimately connected to active transcription and the transcriptional elongation regulatory protein cyclin-dependent kinase-9 (CDK9) and the facilitates chromatin transcription (FACT) complex. This review provides an overview of the current understanding of H2Bub1 function in mammalian systems with a particular emphasis on its role in cancer and potential options for exploiting this knowledge for the treatment of cancer.

Histone ubiquitination and deubiquitination in transcription, DNA damage response, and cancer

Histone post-transcriptional modifications play essential roles in regulation of all DNA related processes. Among them, histone ubiquitination has been discovered for more than three decades. However, its functions are still less well understood than other histone modifications such as methylation and acetylation. In this review, we will summarize our current understanding of histone ubiquitination and deubiquitination. In particular, we will focus on how they are regulated by histone ubiquitin ligases and deubiquitinating enzymes. We will then discuss the roles of histone ubiquitination in transcription and DNA damage response and the crosstalk between histone ubiquitination and other histone modifications. Finally, we will review the important roles of histone ubiquitination in stem cell biology and cancer.

Plumbagin inhibits cell growth and potentiates apoptosis in human gastric cancer cells in vitro through the NF-κB signaling pathway

AIM

To investigate the effects and underlying mechanisms of plumbagin, a naphthoquinone derived from medicinal plant Plumbago zeylanica, on human gastric cancer (GC) cells.

METHODS

Human gastric cancer cell lines SGC-7901, MKN-28, and AGS were used. The cell viability was examined using CCK-8 viability assay. Cell proliferation rate was determined using both clonogenic assay and EdU incorporation assay. Apoptosis was detected via Annexin V/propidium iodide double-labeled flow cytometry. Western blotting was used to assess the expression of both NF-κB-regulated gene products and TNF-α-induced activation of p65, IκBα, and IKK. The intracellular location of NF-κB p65 was detected using confocal microscopy.

RESULTS

Plumbagin (2.5-40 μmol/L) concentration-dependently reduced the viability of the GC cells. The IC(50) value of plumbagin in SGC-7901, MKN-28, and AGS cells was 19.12, 13.64, and 10.12 μmol/L, respectively. The compound (5-20 μmol/L) concentration-dependently induced apoptosis of SGC-7901 cells, and potentiated the sensitivity of SGC-7901 cells to chemotherapeutic agents TNF-αand cisplatin. The compound (10 μmol/L) downregulated the expression of NF-κB-regulated gene products, including IAP1, XIAP, Bcl-2, Bcl-xL, tumor factor (TF), and VEGF. In addition to inhibition of NF-κB p65 nuclear translocation, the compound also suppressed TNF-α-induced phosphorylation of p65 and IKK, and the degradation of IκBα.

CONCLUSION

Plumbagin inhibits cell growth and potentiates apoptosis in human GC cells through the NF-κB pathway.

Flickin' the ubiquitin switch: the role of H2B ubiquitylation in development

The reversible ubiquitylation of histone H2B has long been implicated in transcriptional activation and gene silencing. However, many questions regarding its regulation and effects on chromatin structure remain unanswered. In addition, while several studies have uncovered an involvement of this modification in the control of certain developmental processes, a more general understanding of its requirement is lacking. Herein, we present a broad overview of the pathways known to be regulated by H2B ubiquitylation, while drawing parallels between findings in disparate organisms, in order to facilitate continued delineation of its spatiotemporal role in development. Finally, we integrate the findings of recent studies into how H2B ubiquitylation affects chromatin, and cast an eye over emerging areas for future research.

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.

An atlas of altered expression of deubiquitinating enzymes in human cancer

Background

Deubiquitinating enzymes (DUBs) are proteases that process ubiquitin (Ub) or ubiquitin-like gene products, remodel polyubiquitin(-like) chains on target proteins, and counteract protein ubiquitination exerted by E3 ubiquitin-ligases. A wealth of studies has established the relevance of DUBs to the control of physiological processes whose subversion is known to cause cellular transformation, including cell cycle progression, DNA repair, endocytosis and signal transduction. Altered expression of DUBs might, therefore, subvert both the proteolytic and signaling functions of the Ub system.

Methodology/Principal Findings

In this study, we report the first comprehensive screening of DUB dysregulation in human cancers by in situ hybridization on tissue microarrays (ISH-TMA). ISH-TMA has proven to be a reliable methodology to conduct this kind of study, particularly because it allows the precise identification of the cellular origin of the signals. Thus, signals associated with the tumor component can be distinguished from those associated with the tumor microenvironment. Specimens derived from various normal and malignant tumor tissues were analyzed, and the “normal” samples were derived, whenever possible, from the same patients from whom tumors were obtained. Of the ∼90 DUBs encoded by the human genome, 33 were found to be expressed in at least one of the analyzed tissues, of which 22 were altered in cancers. Selected DUBs were subjected to further validation, by analyzing their expression in large cohorts of tumor samples. This analysis unveiled significant correlations between DUB expression and relevant clinical and pathological parameters, which were in some cases indicative of aggressive disease.

Conclusions/Significance

The results presented here demonstrate that DUB dysregulation is a frequent event in cancer, and have implications for therapeutic approaches based on DUB inhibition.