Bortezomib prevents oncogenesis and bone metastasis of prostate cancer by inhibiting WWP1, Smurf1 and Smurf2

The role of WWP1 and WWP2 in bone/cartilage development and diseases

Bone and cartilage diseases are often associated with trauma and senescence, manifested as pain and limited mobility. The repair of bone and cartilage lesion by mesenchymal stem cells is regulated by various transcription factors. WW domain-containing protein 1 (WWP1) and WW domain-containing protein 2 (WWP2) are named for WW domain which recognizes PPXY (phono Ser Pro and Pro Arg) motifs of substrate. WWP1and WWP2 are prominent components of the homologous to the E6-AP carboxyl terminus (HECT) subfamily, a group of the ubiquitin ligase. Recently, some studies have found that WWP1 and WWP2 play an important role in the pathogenesis of bone and cartilage diseases and regulate the level and the transactivation of various transcription factors through ubiquitination. Therefore, this review summarizes the distribution and effects of WWP1 and WWP2 in the development of bone and cartilage, discusses the potential mechanism and therapeutic drugs in bone and cartilage diseases such as osteoarthritis, fracture, and osteoporosis.

Immunohistochemical Expression and Clinical Significance of WWP1 Protein in Nasopharyngeal Cancer

Nasopharyngeal carcinoma (NPC) is a common malignant tumor of the head and neck. Its pathogenesis is complicated and needs further investigation. The aim of this study was to investigate the expression and clinical significance of WWP1 in NPC. Bioinformatics approaches were used to evaluate the expression and functions of WWP1 in NPC. WWP1 protein expression was then detected by immunohistochemistry on a tissue microarray in an NPC cohort and its association with clinical features and prognosis was determined. In addition, WWP1 expression was knocked down in NPC cells using RNA interference, and their colony formation and invasion abilities were assessed. A total of 25 genes closely related to WWP1, which may be enriched in different pathways, were filtered out. WWP1 expression was significantly higher in NPC cells than in normal controls. High WWP1 expression was correlated with lymph node metastasis, tumor recurrence, clinical stage and poor prognosis. Knockdown of WWP1 resulted in attenuated proliferation and invasion of NPC cells. The results suggest that WWP1 may serve as a novel biomarker and prognostic factor for NPC and a potential therapeutic target worthy of further investigation.

WWP1 E3 ligase at the crossroads of health and disease

The E3 ubiquitin ligase WWP1 (WW Domain-containing E3 Ubiquitin Protein Ligase 1) is a member of the HECT (Homologous to the E6-associated protein Carboxyl Terminus) E3 ligase family. It is conserved across several species and plays crucial roles in various physiological processes, including development, cell growth and proliferation, apoptosis, and differentiation. It exerts its functions through ubiquitination or protein-protein interaction with PPXY-containing proteins. WWP1 plays a role in several human diseases, including cardiac conditions, neurodevelopmental, age-associated osteogenic disorders, infectious diseases, and cancers. In solid tumors, WWP1 plays a dual role as both an oncogene and a tumor suppressor, whereas in hematological malignancies such as AML, it is identified as a dedicated oncogene. Importantly, WWP1 inhibition using small molecule inhibitors such as Indole-3-Carbinol (I3C) and Bortezomib or siRNAs leads to significant suppression of cancer growth and healing of bone fractures, suggesting that WWP1 might serve as a potential therapeutic target for several diseases. In this review, we discuss the evolutionary perspective, structure, and functions of WWP1 and its multilevel regulation by various regulators. We also examine its emerging roles in cancer progression and its therapeutic potential. Finally, we highlight WWP1's role in normal physiology, contribution to pathological conditions, and therapeutic potential for cancer and other diseases.

NEDD4 E3 ubiquitin ligases: promising biomarkers and therapeutic targets for cancer

Accumulating evidence has demonstrated that NEDD4 E3 ubiquitin ligase family plays a pivotal oncogenic role in a variety of malignancies via mediating ubiquitin dependent degradation processes. Moreover, aberrant expression of NEDD4 E3 ubiquitin ligases is often indicative of cancer progression and correlated with poor prognosis. In this review, we are going to address association of expression of NEDD4 E3 ubiquitin ligases with cancers, the signaling pathways and the molecular mechanisms by which the NEDD4 E3 ubiquitin ligases regulate oncogenesis and progression, and the therapies targeting the NEDD4 E3 ubiquitin ligases. This review provides the systematic and comprehensive summary of the latest research status of E3 ubiquitin ligases in the NEDD4 subfamily, and proposes that NEDD4 family E3 ubiquitin ligases are promising anti-cancer drug targets, aiming to provide research direction for clinical targeting of NEDD4 E3 ubiquitin ligase therapy.

The intricate interplay between HIFs, ROS, and the ubiquitin system in the tumor hypoxic microenvironment

Alterations in protein ubiquitination and hypoxia-inducible factor (HIF) signaling both contribute to tumorigenesis and tumor progression. Ubiquitination is a dynamic process that is coordinately regulated by E3 ligases and deubiquitinases (DUBs), which have emerged as attractive therapeutic targets. HIF expression and transcriptional activity are usually increased in tumors, leading to poor clinical outcomes. Reactive oxygen species (ROS) are upregulated in tumors and have multiple effects on HIF signaling and the ubiquitin system. A growing body of evidence has shown that multiple E3 ligases and UBDs function synergistically to control the expression and activity of HIF, thereby allowing cancer cells to cope with the hypoxic microenvironment. Conversely, several E3 ligases and DUBs are regulated by hypoxia and/or HIF signaling. Hypoxia also induces ROS production, which in turn modulates the stability or activity of HIF, E3 ligases, and DUBs. Understanding the complex networks between E3 ligase, DUBs, ROS, and HIF will provide insights into the fundamental mechanism of the cellular response to hypoxia and help identify novel molecular targets for cancer treatment. We review the current knowledge on the comprehensive relationship between E3 ligase, DUBs, ROS, and HIF signaling, with a particular focus on the use of E3 ligase or DUB inhibitors in cancer.

Leucine zipper protein 2 serves as a prognostic biomarker for prostate cancer correlating with immune infiltration and epigenetic regulation

Background

We sought to determine whether leucine zipper protein 2 (LUZP2) could benefit men with prostate cancer (PCa) undergoing radical radiotherapy (RT) or prostatectomy (RP).

Methods

Analysis was done on differentiating expression, clinical prognosis, co-expressed genes, immune infiltration, and epigenetic changes. All of our analyses were done using the R software (version 3.6.3) and the appropriate packages.

Results

In terms of PCa, tumor samples expressed LUZP2 more than normal samples did. In the TCGA database and GSE116918, we found that LUZP2 was the only independent risk factor for PCa. The shared enriched pathways for patients undergoing RP or RT were cell-cell adhesion, regulation of filopodium assembly, and extracellular matrix containing collagen. With the exception of TNFRSF14, we discovered that LUZP2 was negatively correlated with 21 immune checkpoints in PCa patients receiving RT. We found a significant inverse relationship between LUZP2 expression and the tumor immune environment, which included B cells, CD4+ T cells, neutrophils, macrophages, dendritic cells, stromal score, immune score, and estimate score, in patients receiving RP or RT. Additionally, tumor purity was positively correlated with LUZP2. We found that the drug bortezomib may be susceptible to the LUZP2. DNA methylation was significantly associated with the mRNA expression of LUZP2 in PCa patients from the TCGA database, and LUZP2 methylation was positively correlated with immune cells. The proliferative activity of various PCa cells, which correlated to different stages of this disease, was also found to be significantly reduced by LUZP2 reduction, according to the results of our experimental work.

Conclusions

We proposed a relatively comprehensive understanding of the roles of LUZP2 on PCa from the fresh perspective of senescence.

Smurf2 inhibition enhances chemotherapy and radiation sensitivity in non-small-cell lung cancer

Lung cancer has been the most common cancer worldwide for several decades. The outcomes of patients with locally advanced lung cancer remain dismal, and only a minority of patients survive more than 5 years. However, tumor therapeutic resistance mechanisms are poorly studied. Identification of therapeutic resistance pathways in lung cancer in order to increase the sensitivity of lung tumor cells to therapeutic agents is a crucial but challenging need. To identify novel genes that modulate the response to platinum-based therapy, we performed a genome-wide high-throughput ribonucleic acid interference (RNAi) screen via transfection of human lung cancer (PC9) cells with a viral short hairpin RNA (shRNA) library. We further validated a potential target via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and clonogenic survival assays on PC9 and A549 lung tumor cells transfected with small interfering RNAs (siRNAs) to successfully downregulate protein expression and then treated with increasing doses of cisplatin or X-ray radiation. We determined protein expression by immunohistochemistry (IHC) after chemoradiotherapy and analyzed gene expression-based survival outcomes in two cohorts of human non-small-cell lung cancer (NSCLC) patients. The screen identified several targets involved in epithelial-to-mesenchymal transition (EMT), including Smurf1, Smurf2, YAP1, and CEBPZ, and glycolytic pathway proteins, including PFKFB3. Furthermore, we found that the small molecule proteasome inhibitor bortezomib significantly downregulated Smurf2 in lung cancer cells. The addition of bortezomib in combination with cisplatin and radiation therapy in PC9 and A549 cells led to an increase in deoxyribonucleic acid (DNA) double-strand breaks with increased numbers of γ-H2AX-positive cells and upregulation of apoptosis. Finally, we found that Smurf2 protein expression was upregulated in situ after treatment with cisplatin and radiation therapy in a relevant cohort of patients with stage III NSCLC. Additionally, Smurf2 gene expression was the strongest predictor of survival in patients with squamous NSCLC after chemotherapy or chemoradiotherapy. We successfully identified and validated Smurf2 as both a common modulator of resistance and an actionable target in lung cancer. These results suggest the urgent need to investigate clinical Smurf2 inhibition via bortezomib in combination with cisplatin and radiation for patients with locally advanced NSCLC.

Translational Strategies to Target Metastatic Bone Disease

Metastatic bone disease is a common and devastating complication to cancer, confounding treatments and recovery efforts and presenting a significant barrier to de-escalating the adverse outcomes associated with disease progression. Despite significant advances in the field, bone metastases remain presently incurable and contribute heavily to cancer-associated morbidity and mortality. Mechanisms associated with metastatic bone disease perpetuation and paralleled disruption of bone remodeling are highlighted to convey how they provide the foundation for therapeutic targets to stem disease escalation. The focus of this review aims to describe the preclinical modeling and diagnostic evaluation of metastatic bone disease as well as discuss the range of therapeutic modalities used clinically and how they may impact skeletal tissue.

Smurf2 suppresses the metastasis of hepatocellular carcinoma via ubiquitin degradation of Smad2

Purpose

Smurf2, one of C2-WW-HECT domain E3 ubiquitin ligases, is closely related to the development and progression in different cancer types, including hepatocellular carcinoma (HCC). This study aims to illustrate the expression and molecular mechanism of Smurf2 in regulating the progression of HCC.

Methods

The expression of Smurf2 in human HCC and adjacent non-tumor liver specimens was detected using tissue microarray studies from 220 HCC patients who underwent curative resection. The relationships of Smurf2 and HCC progression and survival were analyzed using the chi-square test, Kaplan–Meier analysis, and Cox proportional hazards model. For Smurf2 was low expression in HCC cell lines, Smurf2 overexpression cell lines were established. The effect of Smurf2 on cell proliferation and migration was detected by Cell Counting Kit-8 and colony formation assay, and the epithelial–mesenchymal transition (EMT) markers and its transcription factors were tested by immunoblotting. The interaction and ubiquitination of Smad2 by Smurf2 were detected by co-immunoprecipitation and immunoprecipitation assay. Finally, the effect of Smurf2 on HCC was verified using the mouse lung metastasis model.

Results

Smurf2 was downregulated in HCC tissues compared to that of corresponding non-tumor liver specimens. The low expression of Smurf2 in HCC was significantly associated with macrovascular or microvascular tumor thrombus and the impairment of overall survival and disease-free survival. In vitro and in vivo analysis showed that Smurf2 overexpression decreased the EMT potential of HCC cells by promoting the ubiquitination of Smad2 via the proteasome-dependent degradation pathway.

Conclusion

The expression of Smurf2 was downregulated in HCC specimens and affected the survival of patients. Smurf2 inhibited the EMT of HCC by enhancing Smad2 ubiquitin-dependent proteasome degradation.

Bortezomib Rescues Ovariectomy-Induced Bone Loss via SMURF-Mediated Ubiquitination Pathway

A balance between bone formation by osteoblasts and bone resorption by osteoclasts is necessary to maintain bone health and homeostasis. As a cancer of plasma cells, multiple myeloma (MM) is accompanied with rapid bone loss and fragility fracture. Bortezomib has been used as a first-line for treating MM for decades. Recently, the potential protection of bortezomib on osteoporosis (OP) is reported; however, the specific mechanism involving bortezomib-mediated antiosteoporotic effect is undetermined. In the present study, we assessed the effects of in vitro bortezomib treatment on osteogenesis and osteoclastogenesis and the protective effect on bone loss in ovariectomized (OVX) mice. Our results indicated that bortezomib treatment increased osteogenic differentiation of MC3T3-E1 cells as evidenced by increased levels of matrix mineralization and osteoblast-specific markers. In bortezomib-treated bone marrow monocytes (BMMs), osteoclast differentiation was suppressed, substantiated by downregulated tartrate-resistant acid phosphatase- (TRAP-) positive multinucleated cells, areas of actin rings, pit formation, and osteoclast-specific genes. Mechanistically, bortezomib exerted a protective effect against OP through the Smad ubiquitination regulatory factor- (SMURF-) mediated ubiquitination pathway. Furthermore, in vivo intraperitoneal injection of bortezomib attenuated the bone microarchitecture in OVX mice. Accordingly, our findings corroborated that bortezomib might have future applications in the treatment of postmenopausal OP.

The efficacy and mechanism of proteasome inhibitors in solid tumor treatment

BACKGROUND

The ubiquitin-proteasome system (UPS) is critical in cellular protein degradation and widely involved in the regulations of cancer hallmarks. Targeting the UPS pathway has emerged as a promising novel treatment in hematological malignancies and solid tumors.

OBJECTIVE

This review mainly focuses on the preclinical results of proteasome inhibitors in solid tumors.

METHODS

We analyzed the published articles associated with the anticancer results of proteasome inhibitors alone or combination chemotherapy in solid tumors. Important data presented in abstract form were also discussed in this review.

RESULTS/CONCLUSION

Proteasome inhibitors, such as bortezomib and carfilzomib, are highly effective in treating solid tumors. The anticancer efficacy is not limited to affect the proteasomal inhibition-associated signaling pathways but also widely involves the signaling pathways related to cell cycle, apoptosis, and epithelial-mesenchymal transition (EMT). In addition, proteasome inhibitors overcome the conventional chemo-resistance of standard chemotherapeutics by inhibiting signaling pathways, such as NF-κB or PI3K/Akt. Combination chemotherapy of proteasome inhibitors and standard chemotherapeutics are widely investigated in multiple relapsed or chemo-resistant solid tumor types, such as breast cancer and pancreatic cancer. The proteasome inhibitors re-sensitize the standard chemotherapeutic regimens and induce synergistic anticancer effects. The development of novel proteasome inhibitors and delivery systems also improves the proteasome inhibitors' anticancer efficacy in solid tumors. This review summarizes the current preclinical results of proteasome inhibitors in solid tumors and reveals the potential anticancer mechanisms.

Potential of E3 Ubiquitin Ligases in Cancer Immunity: Opportunities and Challenges

Cancer immunotherapies, including immune checkpoint inhibitors and immune pathway–targeted therapies, are promising clinical strategies for treating cancer. However, drug resistance and adverse reactions remain the main challenges for immunotherapy management. The future direction of immunotherapy is mainly to reduce side effects and improve the treatment response rate by finding new targets and new methods of combination therapy. Ubiquitination plays a crucial role in regulating the degradation of immune checkpoints and the activation of immune-related pathways. Some drugs that target E3 ubiquitin ligases have exhibited beneficial effects in preclinical and clinical antitumor treatments. In this review, we discuss mechanisms through which E3 ligases regulate tumor immune checkpoints and immune-related pathways as well as the opportunities and challenges for integrating E3 ligases targeting drugs into cancer immunotherapy.

Mechanisms, Diagnosis and Treatment of Bone Metastases

Bone and bone marrow are among the most frequent metastatic sites of cancer. The occurrence of bone metastasis is frequently associated with a dismal disease outcome. The prevention and therapy of bone metastases is a priority in the treatment of cancer patients. However, current therapeutic options for patients with bone metastatic disease are limited in efficacy and associated with increased morbidity. Therefore, most current therapies are mainly palliative in nature. A better understanding of the underlying molecular pathways of the bone metastatic process is warranted to develop novel, well-tolerated and more successful treatments for a significant improvement of patients' quality of life and disease outcome. In this review, we provide comparative mechanistic insights into the bone metastatic process of various solid tumors, including pediatric cancers. We also highlight current and innovative approaches to biologically targeted therapy and immunotherapy. In particular, we discuss the role of the bone marrow microenvironment in the attraction, homing, dormancy and outgrowth of metastatic tumor cells and the ensuing therapeutic implications. Multiple signaling pathways have been described to contribute to metastatic spread to the bone of specific cancer entities, with most knowledge derived from the study of breast and prostate cancer. However, it is likely that similar mechanisms are involved in different types of cancer, including multiple myeloma, primary bone sarcomas and neuroblastoma. The metastatic rate-limiting interaction of tumor cells with the various cellular and noncellular components of the bone-marrow niche provides attractive therapeutic targets, which are already partially exploited by novel promising immunotherapies.

The emerging role of WWP1 in cancer development and progression

Emerging evidence demonstrates that WW domain-containing E3 ubiquitin protein ligase 1 (WWP1) participates into carcinogenesis and tumor progression. In this review article, we will describe the association between dysregulated WWP1 expression and clinical features of cancer patients. Moreover, we summarize the both oncogenic and tumor suppressive functions of WWP1 in a variety of human cancers. Furthermore, we briefly describe the downstream substrates of WWP1 and its upstream factors to regulate the expression of WWP1. Notably, targeting WWP1 by its inhibitors or natural compounds is potentially useful for treating human malignancies. Finally, we provide the perspectives regarding WWP1 in cancer development and therapies. We hope this review can stimulate the research to improve our understanding of WWP1-mediated tumorigenesis and accelerate the discovery of novel therapeutic strategies via targeting WWP1 expression in cancers.

Exploring the Roles of HERC2 and the NEDD4L HECT E3 Ubiquitin Ligase Subfamily in p53 Signaling and the DNA Damage Response

Cellular homeostasis is governed by the precise expression of genes that control the translation, localization, and termination of proteins. Oftentimes, environmental and biological factors can introduce mutations into the genetic framework of cells during their growth and division, and these genetic abnormalities can result in malignant transformations caused by protein malfunction. For example, p53 is a prominent tumor suppressor protein that is capable of undergoing more than 300 posttranslational modifications (PTMs) and is involved with controlling apoptotic signaling, transcription, and the DNA damage response (DDR). In this review, we focus on the molecular mechanisms and interactions that occur between p53, the HECT E3 ubiquitin ligases WWP1, SMURF1, HECW1 and HERC2, and other oncogenic proteins in the cell to explore how irregular HECT-p53 interactions can induce tumorigenesis.

SMURF1, a promoter of tumor cell progression?

Overexpression of HECT-type E3 ubiquitin ligase SMURF1 is correlated with poor prognosis in patients with various cancers, such as glioblastoma, colon cancer, and clear cell renal cell carcinoma. SMURF1 acts as a tumor promoter by ubiquitination modification and/or degradation of tumor-suppressing proteins. Combined treatment of Smurf1 knockdown with rapamycin showed collaborative antitumor effects in mice. This review described the role of HECT, WW, and C2 domains in regulating SMURF1 substrate selection. We summarized up to date SMURF1 substrates regulating different type cell signaling, thus, accelerating tumor progression, invasion, and metastasis. Furthermore, the downregulation of SMURF1 expression, inhibition of its E3 activity and regulation of its specificity to substrates prevent tumor progression. The potential application of SMURF1 regulators, specifically, wisely choose certain drugs by blocking SMURF1 selectivity in tumor suppressors, to develop novel anticancer treatments.

PSMA5 promotes the tumorigenic process of prostate cancer and is related to bortezomib resistance

Proteasome α5 subunit (PSMA5) is related to poor prognosis in various cancers. The first therapeutic proteasome inhibitor, bortezomib, induces apoptosis, suppressing cell growth in many tumor types. However, the effects of PSMA5 and bortezomib in prostate cancer (PCa) are still unknown. In this study, we investigated whether PSMA5 is associated with the tumorigenic progression and the interaction of PSMA5 with bortezomib in PCa. We knocked down PSMA5 with siRNA and studied the changes in cell viability and motility with Cell Counting Kit-8, quantitative PCR, fluorescence-activated cell sorting, scratch, and invasion assays. We also investigated the effect of PSMA5 in PCa cells treated with bortezomib and in those that are resistant to bortezomib. We found that silencing PSMA5 inhibited cell proliferation, induced apoptosis, restricted cell migration and invasion, and demonstrated a coordinated effect with bortezomib. Cells resistant to bortezomib gained sensitivity to bortezomib after PSMA5 was knocked down. Our results show, for the first time, that PSMA5 promotes the tumorigenic process of PCa and is linked to bortezomib resistance.

IMP3 accelerates the progression of prostate cancer through inhibiting PTEN expression in a SMURF1-dependent way

BACKGROUND

Insulin-like growth factor 2 (IGF2) messenger RNA binding protein 3 (IMP3) has been testified to be overexpressed in prostate cancer and strongly related to patients' poor prognosis. However, the functions of IMP3 and the underlying mechanisms in prostate cancer still remain unknown. Therefore, the current study was carried out to reveal the role and molecular mechanism of IMP3 in prostate cancer progression.

METHODS

The expression levels of IMP3 in prostate cancer tissues and cells were detected by immunohistochemistry (IHC), western blotting and RT-PCR. CCK-8, clone formation, flow cytometry and in vivo tumor formation assays were used to determine cell growth, clone formation apoptosis and tumorigenesis, respectively. The effect of IMP3 on the expression levels of the key proteins in PI3K/AKT/mTOR signaling pathway, including PIP2, PIP3, p-AKT, AKT, p-mTOR, mTOR, PTEN and BAD activation of was determined by western blotting. IP (Immunoprecipitation) assay was used to evaluate the effects of IMP3 and SMURF1 (SMAD specific E3 ubiquitin protein ligase 1) on the ubiquitination of PTEN protein.

RESULTS

IMP3 expression level was significantly increased in prostate cancer tissues and cell lines (LNCap, PC3 and DU145) as compared with the paracancerous normal tissues and cells (RWPE-1), respectively. High expression of IMP3 apparently promoted cell viability, tumorigenesis and inhibited cell apoptosis in prostate cancer LNCap, DU145 and PC3 cell lines. In mechanism, IMP3 upregulation significantly increased the phosphorylation levels of AKT and mTOR, and elevated PIP3 expression level, while induced significant reductions in the expression levels of BAD, PTEN and PIP2. And, IMP3 overexpression increased SMURF1 expression, which facilitated PTEN ubiquitination. In addition, SMURF1 overexpression enhanced prostate cancer cell viability and inhibited cell apoptosis. Silence of SMURF1 rescued the enhancements in cell proliferation and tumorigenesis and the inhibition in cell apoptosis rates induced by IMP3 in prostate cancer DU145 and LNCap cells.

CONCLUSION

This study reveals that IMP3 is overdressed in prostate cancer, which accelerates the progression of prostate cancer through activating PI3K/AKT/mTOR signaling pathway via increasing SMURF1-mediated PTEN ubiquitination.

[Abnormal expression of WWP1 in chronic lymphocytic leukemia and its clinical significance]

Objective: This study aims to investigate the expression of E3 ubiquitin-ligase (WWP1) in chronic lymphocytic leukemia (CLL) patients and analyze its correlation with clinical prognostic indicators (TP53, CD38, IGHV mutation) and its prognostic value. Methods: A total of 48 CLL patients and 9 age-matched normal subjects were enrolled in the study. The WWP1 expression was detected by SYBR Green-based real-time PCR, and the clinical relationship was analyzed by GraphPad Prism software. Results: The WWP1 median expression was 0.007 (95% CI 0.005-0.010) in the normal control group and 0.031 (95% CI 0.019-0.044) in the CLL group (P<0.001) . A sub-groups analysis implicated a statistically significant result (P=0.022) , showing that the median time from a relatively high and low transcription level of WWP1 to the first treatment was 24 months and 35 months, respectively. Positive CD38 and ZAP-70 expressions were associated with a higher WWP1 expression (P=0.012 and 0.029, respectively) . Conclusion: An abnormal WWP1 mRNA expression was found in CLL patients with significant correlation with ZAP-70 and CD38 expressions, and WWP1 may become a new supplement of CLL prognostic markers.

Divergent Modulation of Proteostasis in Prostate Cancer

Proteostasis regulates key cellular processes such as cell proliferation, differentiation, transcription, and apoptosis. The mechanisms by which proteostasis is regulated are crucial and the deterioration of cellular proteostasis has been significantly associated with tumorigenesis since it specifically targets key oncoproteins and tumor suppressors. Prostate cancer (PCa) is the second most common cause of cancer death in men worldwide. Androgens mediate one of the most central signaling pathways in all stages of PCa via the androgen receptor (AR). In addition to their regulation by hormones, PCa cells are also known to be highly secretory and are particularly prone to ER stress as proper ER function is essential. Alterations in various complex signaling pathways and cellular processes including cell cycle control, transcription, DNA repair, apoptosis, cell adhesion, epithelial-mesenchymal transition (EMT), and angiogenesis are critical factors influencing PCa development through key molecular changes mainly by posttranslational modifications in PCa-related proteins, including AR, NKX3.1, PTEN, p53, cyclin D1, and p27. Several ubiquitin ligases like MDM2, Siah2, RNF6, CHIP, and substrate-binding adaptor SPOP; deubiquitinases such as USP7, USP10, USP26, and USP12 are just some of the modifiers involved in the regulation of these key proteins via ubiquitin-proteasome system (UPS). Some ubiquitin-like modifiers, especially SUMOs, have been also closely associated with PCa. On the other hand, the proteotoxicity resulting from misfolded proteins and failure of ER adaptive capacity induce unfolded protein response (UPR) that is an indispensable signaling mechanism for PCa development. Lastly, ER-associated degradation (ERAD) also plays a crucial role in prostate tumorigenesis. In this section, the relationship between prostate cancer and proteostasis will be discussed in terms of UPS, UPR, SUMOylation, ERAD, and autophagy.

The functions and regulation of Smurfs in cancers

Smad ubiquitination regulatory factor 1 (Smurf1) and Smurf2 are HECT-type E3 ubiquitin ligases, and both Smurfs were initially identified to regulate Smad protein stability in the TGF-β/BMP signaling pathway. In recent years, Smurfs have exhibited E3 ligase-dependent and -independent activities in various kinds of cells. Smurfs act as either potent tumor promoters or tumor suppressors in different tumors by regulating biological processes, including metastasis, apoptosis, cell cycle, senescence and genomic stability. The regulation of Smurfs activity and expression has therefore emerged as a hot spot in tumor biology research. Further, the Smurf1- or Smurf2-deficient mice provide more in vivo clues for the functional study of Smurfs in tumorigenesis and development. In this review, we summarize these milestone findings and, in turn, reveal new avenues for the prevention and treatment of cancer by regulating Smurfs.

Resveratrol induces depletion of TRAF6 and suppresses prostate cancer cell proliferation and migration

Although the early diagnosis of prostate cancer (PCa) enhances life expectancy with a 5-year survival rate of 100 %, metastasized-PCa is the fundamental reason for death by PCa, hence requires an advanced and target-directed treatment strategy. Metastasis is considered to be initiated with the epithelial-mesenchymal transition (EMT) event in which tumor cells change their epithelial characteristics into mesenchymal form and exacerbates the cancer progression. Herein, we investigated the effect and mechanism of resveratrol function in PCa cell proliferation and migration and reported that TNF-receptor associated factor 6 (TRAF6), an unconventional E3 ligase, is a key mediator of resveratrol function to inhibit PCa cell growth and proliferation and targeted for lysosomal degradation by resveratrol. MTT and cell counting demonstrated that resveratrol inhibited the viability and proliferation in DU145 and PC3 cells. Resveratrol (50 μM) mediated the degradation of TRAF6 which in turn facilitated repression of the NF-κB pathway. Also, wound healing and transwell migration assays and level of EMT-related proteins showed that resveratrol used TRAF6, at least in part to inhibit cell migration. Overexpression of TRAF6 augmented EMT in PCa by upregulating the expression of transcription factor SLUG. Moreover, TRAF6 overexpression was closely associated with EMT process through the NF-κB pathway. Our exploration exhibited that resveratrol may inhibit EMT through the TRAF6/NF-κB/SLUG axis. Altogether, this study represents that TRAF6 acts as an intermediary of resveratrol action to suppress PCa cell proliferation and migration, and concerns future attention to obtain as a therapeutic target for the treatment of PCa.

Bortezomib attenuates renal interstitial fibrosis in kidney transplantation via regulating the EMT induced by TNF-α-Smurf1-Akt-mTOR-P70S6K pathway

Allograft interstitial fibrosis was characterized by massive extracellular matrix deposition caused by activated fibroblasts and myofibroblasts. Epithelial‐mesenchymal transition (EMT) is recognized as an important source of myofibroblasts contributing to the pathogenesis of allograft interstitial fibrosis. Smad ubiquitination regulatory factor 1 (Smurf1) has been recently reported to be involved in the progression of EMT. Our study was to detect the effect of Bortezomib and Smurf1 in the EMT and allograft interstitial fibrosis. Biomarkers of EMT, as well as Smurf1, were examined in human proximal tubular epithelial cells (HK‐2) treated with tumour necrosis factor‐alpha (TNF‐α) in various doses or at various time points by Western Blotting or qRT‐PCR. We knockdown or overexpressed Smurf1 in HK‐2 cells. Furthermore, rat renal transplant model was established and intervened by Bortezomib. Allograft tissues from human and rats were also collected and prepared for HE, Masson's trichrome, immunohistochemical staining and western blotting assays. As a result, we found that TNF‐α significantly promoted the development of EMT in a time‐dependent and dose‐dependent manner through Smurf1/Akt/mTOR/P70S6K signalling pathway. More importantly, Bortezomib alleviated the progression of EMT and allograft interstitial fibrosis in vivo and in vitro by inhibiting the production of TNF‐α and expression of Smurf1. In conclusion, Smurf1 plays a critical role in the development of EMT induced by TNF‐α. Bortezomib can attenuate the Sumrf1‐mediated progression of EMT and renal allograft interstitial fibrosis, which could be suggested as a novel choice for the prevention and treatment of renal allograft interstitial fibrosis.

WW domain-containing E3 ubiquitin protein ligase 1 depletion evokes antitumor effect in cutaneous squamous cell carcinoma by inhibiting signal transducer and activator of transcription 3 signaling pathway

Objectives

WW domain-containing E3 ubiquitin protein ligase 1 (WWP1) has been implicated in tumor progression. We aimed to investigate the role of WWP1 in cutaneous squamous cell carcinoma (CSCC).

Methods

WWP1 gene and protein levels were detected using semi-quantitative reverse transcription-polymerase chain reaction, immunohistochemistry and western blotting. The effects of WWP1 on cell cycle, apoptosis, cell migration and invasion were examined by flow cytometry, wound healing and Transwell assays, respectively. The antitumor efficacy of WWP1 small interfering RNA was determined in CSCC tumor xenografts in mice.

Results

WWP1 expression was significantly higher in CSCC tissues and cells than in normal skin and cells, respectively. WWP1 expression was significantly associated with histological grade, invasion depth and lymph node metastasis in patients with CSCC. High expression predicted metastatic potential and an unfavorable prognosis. WWP1 downregulation suppressed tumor growth in vitro and in vivo, reduced cell migration and invasion, arrested the cell cycle in G0/G1 and induced apoptosis in A431 cells. WWP1 depletion also decreased phosphorylated signal transducer and activator of transcription 3 (STAT3), matrix metalloproteinase-2, cyclin D1 and Bcl-2, but did not affect total STAT3.

Conclusions

WWP1 is a potential target for the diagnosis, prognosis and therapy of patients with CSCC.

The Proteasome and Myeloma-Associated Bone Disease

Bone disease is the hallmark of multiple myeloma (MM), a hematological malignancy characterized by osteolytic lesions due to a severe uncoupled and unbalanced bone remodeling with pronounced osteoblast suppression. Bone metastasis is also a frequent complication of solid tumors including advanced breast or prostate cancer. In the past years, the ubiquitin-proteasome pathway has been proved critical in regulating the balance between bone formation and bone resorption. Proteasome inhibitors (PIs) are a new class of drugs, currently used in the treatment of MM, that affect both tumor cells and bone microenvironment. Particularly, PIs stimulate osteoblast differentiation by human mesenchymal stromal cells and increase bone regeneration in mice. Interestingly, in vitro data indicate that PIs block MM-induced osteoblast and osteocyte cell death by targeting both apoptosis and autophagy. The preclinical data are supported by the following effects observed in MM patients treated with PIs: increase of bone alkaline phosphatase levels, normalization of the markers of bone turnover, and reduction of the skeletal-related events. Moreover, the histomorphometric data indicate that the treatment with bortezomib stimulates osteoblast formation and maintains osteocyte viability in MM patients. This review updates the evidence on the effects of PIs on bone remodeling and on cancer-induced bone disease while focusing on MM bone disease.

Suppression of the Smurf1 Expression Inhibits Tumor Progression in Gliomas

Glioblastoma, one of the common malignant brain tumors, results in the highly death, but its underlying molecular mechanisms remain unclear. Smurf1, a member of Nedd4 family of HECT-type ligases, has been reported to contribute to tumorigenicity through several important biological pathways. Recently, it was also found to participate in modulate cellular processes, including morphogenesis, autophagy, growth, and cell migration. In this research, we reported the clinical guiding significance of the expression of Smurf1 in human glioma tissues and cell lines. Western blotting analysis discovered that the expression of Smurf1 was increased with WHO grade. Immunohistochemistry levels discovered that high expression of Smurf1 is closely consistent with poor prognosis of glioma. In addition, suppression of Smurf1 can reduce cell invasion and increase the E-cadherin expression, which is a marker of invasion. Our study firstly demonstrated that Smurf1 may promote glioma cell invasion and suppression of the Smurf1 may provide a novel treatment strategy for glioma.

Regulation of E3 ubiquitin ligase-1 (WWP1) by microRNA-452 inhibits cancer cell migration and invasion in prostate cancer

Background:

MicroRNA-224 (miR-224) and microRNA-452 (miR-452) are closely located on the human chromosome Xq28 region. miR-224 functions as a tumour suppressor by targeting tumour protein D52 (TPD52) in prostate cancer (PCa). Here, we aimed to investigate the functional significance of miR-452 in PCa cells.

Methods:

Functional studies of PCa cells were performed using transfection with mature miRNAs or siRNAs. Genome-wide gene expression analysis, in silico analysis, and dual-luciferase reporter assays were applied to identify miRNA targets. The association between miR-452 levels and overall patient survival was estimated by the Kaplan–Meier method.

Results:

Expression of miR-452 was significantly downregulated in PCa tissues. Transfection with mature miR-452 inhibited the migration and invasion of PCa cells. Kaplan–Meier survival curves showed that low expression of miR-452 predicted a short duration of progression to castration-resistant PCa. WW domain-containing E3 ubiquitin protein ligase-1 (WWP1) was a direct target of miR-452, and knockdown of WWP1 inhibited the migration and invasion of PCa cells. WWP1 was upregulated in PCa clinical specimens.

Conclusions:

Regulation of the miR-452–WWP1 axis contributed to PCa cell migration and invasion, and elucidation of downstream signalling of this axis will provide new insights into the mechanisms of PCa oncogenesis and metastasis.