Inhibition of USP2 eliminates cancer stem cells and enhances TNBC responsiveness to chemotherapy

The PIK3CA gene and its pivotal role in tumor tropism of triple-negative breast cancer

The PIK3CA gene is a linchpin in the intricate molecular network governing triple-negative breast cancer (TNBC) tumor tropism, serving as a focal point for understanding this aggressive disease. Anchored within the PI3K/AKT/mTOR signaling axis, PIK3CA mutations exert substantial influence, driving cellular processes that highlight the unique biology of TNBC. This review meticulously highlights the association between PIK3CA mutations and distinct TNBC subtypes, elucidating the gene's multifaceted contributions to tumor tropism. Molecular dissection reveals how PIK3CA mutations dynamically modulate chemokine responses, growth factor signaling, and extracellular matrix interactions, orchestrating the complex migratory behaviour characteristic of TNBC cells. A detailed exploration of PIK3CA-targeted strategies in the therapeutic arena is presented, outlining the current landscape of clinical trials and precision medicine approaches. As the scientific narrative converges, this review underscores the critical role of PIK3CA in shaping the molecular intricacies of TNBC tumor tropism and illuminates pathways toward tailored interventions, promising a paradigm shift in the clinical management of TNBC.

The role of deubiquitinase USP2 in driving bladder cancer progression by stabilizing EZH2 to epigenetically silence SOX1 expression

BACKGROUND

The Ubiquitin-proteasome system (UPS) is known to participate in multiple cellular events. The deubiquitinating enzyme USP2 (ubiquitin-specific protease 2) is involved in the vasculature remodeling process associated with bladder cancer (BLCA). However, the role of USP2 in BLCA progression has not been clearly defined and whether its regulatory mechanism involving EZH2 (Enhancer of Zeste Homolog 2) remains elusive yet.

METHODS

Differential expression patterns of USP2 and EZH2 were examined in 46 pairs of BLCA and adjacent normal tissues. USP2 knockdown plasmids were transfected into 5637 and J82 cells to detect its impact on cell proliferation, migration and invasion using CCK-8, EdU, wound healing and transwell assays. The USP2-EZH2-SOX1 cascade was confirmed through Co-immunoprecipitation (Co-IP) and chromatin immunoprecipitation (ChIP) assays. An in vivo verification was conducted using a xenograft model of nude mice.

RESULTS

USP2 was significantly upregulated in BLCA tissues and cells, which was associated with poor clinical prognosis in BLCA patients. USP2 depletion resulted in decreased cell proliferation, migration and invasion in BLCA cells. USP2 stabilized the EZH2 protein by directly binding to it, thereby reducing its ubiquitination. Ectopic introduction of EZH2 restored cell growth and invasion of BLCA cells, which had been inhibited by USP2 silencing. USP2-mediated stabilization of EZH2 promoted the enrichment of histone H3K27me3 and repression of SOX1. Involvement of the USP2-EZH2-SOX1 axis in tumor formation was ultimately verified in vivo.

CONCLUSION

Our findings reveal that a USP2-EZH2-SOX1 axis orchestrates the interplay between dysregulated USP2 and EZH2-mediated gene epigenetic silencing in BLCA progression.

Emerging roles of deubiquitinating enzymes in actin cytoskeleton and tumor metastasis

BACKGROUND

Metastasis accounts for the majority of cancer-related deaths. Actin dynamics and actin-based cell migration and invasion are important factors in cancer metastasis. Metastasis is characterized by actin polymerization and depolymerization, which are precisely regulated by molecular changes involving a plethora of actin regulators, including actin-binding proteins (ABPs) and signalling pathways, that enable cancer cell dissemination from the primary tumour. Research on deubiquitinating enzymes (DUBs) has revealed their vital roles in actin dynamics and actin-based migration and invasion during cancer metastasis.

CONCLUSION

Here, we review how DUBs drive tumour metastasis by participating in actin rearrangement and actin-based migration and invasion. We summarize the well-characterized and essential actin cytoskeleton signalling molecules related to DUBs, including Rho GTPases, Src kinases, and ABPs such as cofilin and cortactin. Other DUBs that modulate actin-based migration signalling pathways are also discussed. Finally, we discuss and address therapeutic opportunities and ongoing challenges related to DUBs with respect to actin dynamics.

The ubiquitin-proteasome system in the regulation of tumor dormancy and recurrence

Tumor recurrence is a mechanism triggered in sparse populations of cancer cells that usually remain in a quiescent state after strict stress and/or therapeutic factors, which is affected by a variety of autocrine and microenvironmental cues. Despite thorough investigations, the biology of dormant and/or cancer stem cells is still not fully elucidated, as for the mechanisms of their reawakening, while only the major molecular patterns driving the relapse process have been identified to date. These molecular patterns profoundly interfere with the elements of cellular proteostasis systems that support the efficiency of the recurrence process. As a major proteostasis machinery, we review the role of the ubiquitin-proteasome system (UPS) in tumor cell dormancy and reawakening, devoting particular attention to the functions of its components, E3 ligases, deubiquitinating enzymes and proteasomes in cancer recurrence. We demonstrate how UPS components functionally or mechanistically interact with the pivotal proteins implicated in the recurrence program and reveal that modulators of the UPS hold promise to become an efficient adjuvant therapy for eradicating refractory tumor cells to impede tumor relapse.

Chemoresistance to additive PARP/PI3K dual inhibition in triple-negative breast cancer cell lines is associated with adaptive stem cell-like prevalence

Cancer stem-like cells (CSCs) are posited to exhibit specialized oncogenic capacity to drive malignancies. CSCs are distinguished by enhanced hallmarks of cancer, including apoptosis avoidance, phenotypic plasticity and aberrant growth pathway signaling. Standard-of-care chemotherapies targeted to rapidly cycling cells routinely fail to eliminate this resistant subpopulation, leading to disease recurrence and metastasis. Triple-negative breast cancer (TNBC), a highly aggressive subtype of breast cancer, is enriched for tumor-propagating CD44+/CD24-/low CSCs, which are poorly ablated by chemotherapeutics and are associated with poor prognosis. CD44 governs sustained PI3K signaling in breast cancer, which is essential for CSC maintenance. PI3K inhibition can elicit DNA damage and down-regulate BRCA1 expression, which in turn enhance the synthetic lethality of PARP inhibitors. Here, we examined a dual chemotherapeutic approach targeting these pathways by combining a pan-PI3K inhibitor (Buparlisib) and a PARP1 inhibitor (Olaparib) on a panel of TNBC cell lines with distinct mutational profiles and proportions of CSCs. We observed differential sensitivity to this dual inhibition strategy and varying cellular stress and resistance responses across eight TNBC lines. The dual chemotherapeutic effect is associated with a reduction in S-phase cells, an increased in apoptotic cells and elevated expression of cleaved PARP, indicating a provoked replicative stress response. We observed that PARP/PI3K inhibition efficacy was potentiated by repeated administration in some TNBC lines and identified critical treatment schedules, which further potentiated the dual chemotherapeutic effect. Dual inhibition induced small but significant increases in CSC relative abundance as marked by CD44+/CD24-/low or ALDH1+ cells and increased stress and survival signaling in multiple TNBC cell lines, suggesting this sub-population contributes to TNBC chemoresistance. These results suggest the additive effects of PARP and PI3K inhibition against CSC phenotypes may be enhanced by temporally-staged administration in TNBC cells.

Structural optimization and biological evaluation of ML364 based derivatives as USP2a inhibitors

Ubiquitination is a representative post-translational modification that tags target proteins with ubiquitin to induce protein degradation or modify their functions. Deubiquitinating enzymes (DUBs) play a crucial role in reversing this process by removing ubiquitin from target proteins. Among them, USP2a has emerged as a promising target for cancer therapy due to its oncogenic properties in various cancer types, but its inhibitors have been limited. In this study, our aim was to optimize the structure of ML364, a USP2a inhibitor, and synthesize a series of its derivatives to develop potent USP2a inhibitors. Compound 8v emerged as a potential USP2a inhibitor with lower cytotoxicity compared to ML364. Cellular assays demonstrated that compound 8v effectively reduced the levels of USP2a substrates and attenuated cancer cell growth. We confirmed its direct interaction with the catalytic domain of USP2a and its selective inhibitory activity against USP2a over other USP subfamily proteins (USP7, 8, or 15). In conclusion, compound 8v has been identified as a potent USP2a inhibitor with substantial potential for cancer therapy.

OTUD7B knockdown inhibits the proliferation and stemness of breast cancer cells by destabilizing FOXM1

Breast cancer is a leading cause of cancer-related death in women worldwide; therefore, there is an urgent need to develop novel therapies and drugs that prolong the survival and improve the quality of life of patients with breast cancer. In the present study, the effects and underlying mechanisms of OTU domain-containing 7B (OTUD7B) knockdown on breast cancer were investigated using MDA-MB-468, MDA-MB-453 and MCF7 cell lines. The results of Cell Counting Kit 8, colony formation and tumor sphere formation experiments showed that OTUD7B knockdown caused a significant decrease in the proliferation and sphere formation ability of MDA-MB-468, MDA-MB-453 and MCF7 cells in vitro. Moreover, western blotting results showed that CD44, EpCAM, SOX2 and Nanog protein levels were significantly decreased following OTUD7B knockdown. These findings indicated that OTUD7B knockdown reduced the proliferation and stemness of breast cancer cells. Co-immunoprecipitation assays demonstrated that OTUD7B interacted with forkhead box protein M1 (FOXM1) and reduced the polyubiquitylation of FOXM1 in breast cancer cells; accordingly, FOXM1 protein levels were significantly decreased by OTUD7B knockdown. Furthermore, the overexpression of FOXM1 reduced the inhibitory effects of OTUD7B knockdown on breast cancer cells. The findings of the present study provide new insights into the oncogenic role of OTUD7B in breast cancer and indicate that OTUD7B may serve as a therapeutic target for breast cancer.

Ubiquitin-specific protease 5 promotes bladder cancer progression through stabilizing Twist1

Aberrant activation of the epithelial-mesenchymal transition (EMT) pathway drives the development of solid tumors, which is precisely regulated by core EMT-related transcription factors, including Twist1. However, the expression pattern and regulatory mechanism of Twist1 in the progression of bladder cancer is still unclear. In this study, we explore the role of Twist1 in the progression of bladder cancer. We discovered that the EMT regulon Twist1 protein, but not Twist1 mRNA, is overexpressed in bladder cancer samples using RT-qPCR, western blot and immunohistochemistry (IHC). Mechanistically, co-immunoprecipitation (Co-IP) coupled with liquid chromatography and tandem mass spectrometry identified USP5 as a binding partner of Twist1, and the binding of Twist1 to ubiquitin-specific protease 5 (USP5) stabilizes Twist through its deubiquitinase activity to activate the EMT. Further studies found that USP5 depletion reduces cell proliferation, invasion and the EMT in bladder cancer cells, and ectopic expression of Twist1 rescues the adverse effects of USP5 loss on cell invasion and the EMT. A xenograft tumor model was used to reconfirmed the inhibitor effect of silencing USP5 expression on tumorigenesis in vivo. In addition, USP5 protein levels are significantly elevated and positively associated with Twist1 levels in clinical bladder cancer samples. Collectively, our study revealed that USP5-Twist1 axis is a novel regulatory mechanism driving bladder cancer progression and that approaches targeting USP5 may become a promising cancer treatment strategy.

Sphingomyelin synthase 2 promotes the stemness of breast cancer cells via modulating NF-κB signaling pathway

OBJECTIVES

Multi-drug resistance (MDR) to chemotherapy is the main obstacle influencing the anti-tumor effect in breast cancer, which might lead to the metastasis and recurrence of cancer. Until now, there are still no effective methods that can overcome MDR. In this study, we aimed to investigate the role of sphingomyelin synthase 2 (SMS2) in breast cancer resistance.

METHODS

Quantitative RT-PCR analysis was performed to assess changes in mRNA expression. Western blot analysis was performed to detect protein expression. Inhibitory concentration value of adriamycin (ADR) was evaluated using CCK 8 assay. The stemness ability of breast cancer cells was assessed by spheroid-formation assay. Immunofluorescence staining was conducted to show the cellular distribution of proteins. Breast tumor masses were harvested from the xenograft tumor mouse model.

RESULTS

SMS2 overexpression increased the IC50 values of breast cancer cells. SMS2 decreased the CD24 transcription level but increased the transcription levels of stemness-related genes including CD44, ALDH, OCT 4 and SOX2 in breast cancer cells. SMS2 overexpression promoted the nuclear translocation of phosphorylated NF-κB, while suppression of SMS2 could inhibit the NF-κB pathway.

CONCLUSIONS

SMS2 increased the stemness of breast cancer cells via NF-κB signaling pathway, leading to resistance to the chemotherapeutic drug ADR. Thus, SMS2 might play a critical role in the development of breast cancer resistance, which is a previously unrecognized mechanism in breast cancer MDR development.

LncRNA USP2-AS1 facilitates the osteogenic differentiation of bone marrow mesenchymal stem cells by targeting KDM3A/ETS1/USP2 to activate the Wnt/β-catenin signaling pathway

Human bone marrow mesenchymal stem cells (HBMSCs) can promote new bone formation. Previous studies have proven the ability of long non-coding RNAs (lncRNAs) to modulate the osteogenic differentiation of mesenchymal stem cells. However, the molecular mechanism modulated by lncRNAs in affecting the osteogenic differentiation of HBMSCs remains largely unknown. Thus, this study aims to reveal the role of lncRNA ubiquitin-specific peptidase 2 antisense RNA 1 (USP2-AS1) in regulating the osteogenic differentiation of HBMSCs and investigate its regulatory mechanism. Through bioinformatics analysis and RT-qPCR, we confirmed that USP2-AS1 expression was increased in HBMSCs after culturing in osteogenic differentiation medium (OM-HBMSCs). Moreover, we uncovered that knockdown of USP2-AS1 inhibited the osteogenic differentiation of HBMSCs. Further exploration indicated that USP2-AS1 positively regulated the expression of its nearby gene USP2. Mechanistically, USP2-AS1 recruited lysine demethylase 3A (KDM3A) to stabilize ETS proto-oncogene 1 (ETS1), transcription factor that transcriptionally activated USP2. Additionally, USP2-induced Wnt/β-catenin signalling pathway activation via deubiquitination of β-catenin protein. In summary, our study proved that lncRNA USP2-AS1 facilitates the osteogenic differentiation of HBMSCs by targeting KDM3A/ETS1/USP2 axis to activate the Wnt/β-catenin signalling pathway.

Deubiquitinases in cancer

Ubiquitination is an essential regulator of most, if not all, signalling pathways, and defects in cellular signalling are central to cancer initiation, progression and, eventually, metastasis. The attachment of ubiquitin signals by E3 ubiquitin ligases is directly opposed by the action of approximately 100 deubiquitinating enzymes (DUBs) in humans. Together, DUBs and E3 ligases coordinate ubiquitin signalling by providing selectivity for different substrates and/or ubiquitin signals. The balance between ubiquitination and deubiquitination is exquisitely controlled to ensure properly coordinated proteostasis and response to cellular stimuli and stressors. Not surprisingly, then, DUBs have been associated with all hallmarks of cancer. These relationships are often complex and multifaceted, highlighted by the implication of multiple DUBs in certain hallmarks and by the impact of individual DUBs on multiple cancer-associated pathways, sometimes with contrasting cancer-promoting and cancer-inhibiting activities, depending on context and tumour type. Although it is still understudied, the ever-growing knowledge of DUB function in cancer physiology will eventually identify DUBs that warrant specific inhibition or activation, both of which are now feasible. An integrated appreciation of the physiological consequences of DUB modulation in relevant cancer models will eventually lead to the identification of patient populations that will most likely benefit from DUB-targeted therapies.

Function, mechanism and drug discovery of ubiquitin and ubiquitin-like modification with multiomics profiling for cancer therapy

Ubiquitin (Ub) and ubiquitin-like (Ubl) pathways are critical post-translational modifications that determine whether functional proteins are degraded or activated/inactivated. To date, >600 associated enzymes have been reported that comprise a hierarchical task network (e.g., E1-E2-E3 cascade enzymatic reaction and deubiquitination) to modulate substrates, including enormous oncoproteins and tumor-suppressive proteins. Several strategies, such as classical biochemical approaches, multiomics, and clinical sample analysis, were combined to elucidate the functional relations between these enzymes and tumors. In this regard, the fundamental advances and follow-on drug discoveries have been crucial in providing vital information concerning contemporary translational efforts to tailor individualized treatment by targeting Ub and Ubl pathways. Correspondingly, emphasizing the current progress of Ub-related pathways as therapeutic targets in cancer is deemed essential. In the present review, we summarize and discuss the functions, clinical significance, and regulatory mechanisms of Ub and Ubl pathways in tumorigenesis as well as the current progress of small-molecular drug discovery. In particular, multiomics analyses were integrated to delineate the complexity of Ub and Ubl modifications for cancer therapy. The present review will provide a focused and up-to-date overview for the researchers to pursue further studies regarding the Ub and Ubl pathways targeted anticancer strategies.

DUBing Primary Tumors of the Central Nervous System: Regulatory Roles of Deubiquitinases

The ubiquitin proteasome system (UPS) utilizes an orchestrated enzymatic cascade of E1, E2, and E3 ligases to add single or multiple ubiquitin-like molecules as post-translational modification (PTM) to proteins. Ubiquitination can alter protein functions and/or mark ubiquitinated proteins for proteasomal degradation but deubiquitinases (DUBs) can reverse protein ubiquitination. While the importance of DUBs as regulatory factors in the UPS is undisputed, many questions remain on DUB selectivity for protein targeting, their mechanism of action, and the impact of DUBs on the regulation of diverse biological processes. Furthermore, little is known about the expression and role of DUBs in tumors of the human central nervous system (CNS). In this comprehensive review, we have used publicly available transcriptional datasets to determine the gene expression profiles of 99 deubiquitinases (DUBs) from five major DUB families in seven primary pediatric and adult CNS tumor entities. Our analysis identified selected DUBs as potential new functional players and biomarkers with prognostic value in specific subtypes of primary CNS tumors. Collectively, our analysis highlights an emerging role for DUBs in regulating CNS tumor cell biology and offers a rationale for future therapeutic targeting of DUBs in CNS tumors.

Revolutionizing treatment for triple-negative breast cancer: Harnessing the power of exosomal miRNAs for targeted therapy

Triple-negative breast cancer (TNBC) represents a challenging and aggressive form of breast cancer associated with limited treatment options and poor prognosis. Although chemotherapy is a primary therapeutic approach, drug resistance often hinders treatment success. However, the expanding knowledge of TNBC subtypes and molecular biology has paved the way for targeted therapies. Notably, exosomes (extracellular vesicles) have emerged as crucial carriers of tumorigenic factors involved in oncogenesis and drug resistance, facilitating cell-to-cell communication and offering potential as self-delivery systems. Among the cargo carried by exosomes, microRNAs (miRNAs) have gained attention due to their ability to mediate epigenetic changes in recipient cells upon transfer. Research has confirmed dysregulation of exosomal miRNAs in breast cancer cells compared to healthy cells, establishing them as promising biomarkers for cancer diagnosis and prognosis. In this comprehensive review, we summarize the latest research findings that underscore the diagnostic and prognostic significance of exosomal miRNAs in TNBC treatment. Furthermore, we explore contemporary therapeutic approaches utilizing these exosomal miRNAs for the benefit of TNBC patients, shedding light on potential breakthroughs in TNBC management.

Targeting the deubiquitinase USP2 for malignant tumor therapy (Review)

The ubiquitin‑proteasome system is a major degradation pathway for >80% of proteins in vivo. Deubiquitylases, which remove ubiquitinated tags to stabilize substrate proteins, are important components involved in regulating the degradation of ubiquitinated proteins. In addition, they serve multiple roles in tumor development by participating in physiological processes such as protein metabolism, cell cycle regulation, DNA damage repair and gene transcription. The present review systematically summarized the role of ubiquitin‑specific protease 2 (USP2) in malignant tumors and the specific molecular mechanisms underlying the involvement of USP2 in tumor‑associated pathways. USP2 reverses ubiquitin‑mediated degradation of proteins and is involved in aberrant proliferation, migration, invasion, apoptosis and drug resistance of tumors. Additionally, the present review summarized studies reporting on the use of USP2 as a therapeutic target for malignancies such as breast, liver, ovarian, colorectal, bladder and prostate cancers and glioblastoma and highlights the current status of pharmacological research on USP2. The clinical significance of USP2 as a therapeutic target for malignant tumors warrants further investigation.

USP2 promotes tumor immune evasion via deubiquitination and stabilization of PD-L1

The abnormal upregulation of programmed death ligand-1 (PD-L1) on tumor cells impedes T-cell mediated cytotoxicity through PD-1 engagement, and further exploring the mechanisms regulation of PD-L1 in cancers may enhance the clinical efficacy of PD-L1 blockade. Here, using single-guide RNAs (sgRNAs) screening system, we identify ubiquitin-specific processing protease 2 (USP2) as a novel regulator of PD-L1 stabilization for tumor immune evasion. USP2 directly interacts with and increases PD-L1 abundance in colorectal and prostate cancer cells. Our results show that Thr288, Arg292 and Asp293 at USP2 control its binding to PD-L1 through deconjugating the K48-linked polyubiquitination at lysine 270 of PD-L1. Depletion of USP2 causes endoplasmic reticulum (ER)-associated degradation of PD-L1, thus attenuates PD-L1/PD-1 interaction and sensitizes cancer cells to T cell-mediated killing. Meanwhile, USP2 ablation-induced PD-L1 clearance enhances antitumor immunity in mice via increasing CD8+ T cells infiltration and reducing immunosuppressive infiltration of myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs), whereas PD-L1 overexpression reverses the tumor growth suppression by USP2 silencing. USP2-depletion combination with anti-PD-1 also exhibits a synergistic anti-tumor effect. Furthermore, analysis of clinical tissue samples indicates that USP2 is positively associated with PD-L1 expression in cancer. Collectively, our data reveal a crucial role of USP2 for controlling PD-L1 stabilization in tumor cells, and highlight USP2 as a potential therapeutic target for cancer immunotherapy.

USP2 promotes cell proliferation and metastasis in choroidal melanoma via stabilizing Snail

BACKGROUND

Choroidal melanoma (CM) is an intraocular tumor that arises from melanocytes. While ubiquitin-specific protease 2 (USP2) modulates the progression of numerous diseases, its role in CM is not known. This study aimed to determine the role of USP2 in CM and elucidate its molecular mechanisms.

METHODS

MTT, Transwell, and wound-scratch assays were used to investigate the function of USP2 in the proliferation and metastasis of CM. Western blotting and qRT-PCR were used to analyze the expression of USP2, Snail, and factors associated with the epithelial-mesenchymal transition (EMT). The relationship between USP2 and Snail was explored by co-immunoprecipitation and in vitro ubiquitination assays. A nude mouse model of CM was established for verifying the role of USP2 in vivo.

RESULTS

USP2 overexpression promoted proliferation and metastasis, and induced the EMT in CM cells in vitro, while specific inhibition of USP2 by ML364 produced the opposite effects. ML364 also suppressed CM tumor growth in vivo. Mechanistically, USP2 is known to deubiquitinate Snail, stabilizing the latter through the removal of its K48 poly-ubiquitin chains. However, a catalytically inactive form of USP2 (C276A) had no effect on Snail ubiquitination and failed to increase Snail protein expression. The C276A mutant was also unable to promote CM cell proliferation, migration, and invasion, as well as EMT progression. Furthermore, Snail overexpression partly counteracted the effects of ML364 on proliferation and migration, while rescuing the effects of the inhibitor on the EMT.

CONCLUSIONS

The findings demonstrated that USP2 modulated CM development through the stabilization of Snail and suggest that USP2 may be a useful target for the development of novel treatments for CM.

Induction of Aryl Hydrocarbon Receptor-Mediated Cancer Cell-Selective Apoptosis in Triple-Negative Breast Cancer Cells by a High-Affinity Benzimidazoisoquinoline

Triple-negative breast cancer (TNBC) remains a disease with a paucity of targeted treatment opportunities. The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that is involved in a wide range of physiological processes, including the sensing of xenobiotics, immune function, development, and differentiation. Different small-molecule AhR ligands drive strikingly varied cellular and organismal responses. In certain cancers, AhR activation by select small molecules induces cell cycle arrest or apoptosis via activation of tumor-suppressive transcriptional programs. AhR is expressed in triple-negative breast cancers, presenting a tractable therapeutic opportunity. Here, we identify a novel ligand of the aryl hydrocarbon receptor that potently and selectively induces cell death in triple-negative breast cancer cells and TNBC stem cells via the AhR. Importantly, we found that this compound, Analog 523, exhibits minimal cytotoxicity against multiple normal human primary cells. Analog 523 represents a high-affinity AhR ligand with potential for future clinical translation as an anticancer agent.

The ubiquitin-proteasome system in breast cancer

Ubiquitin-proteasome system (UPS) is a selective proteolytic system that is associated with the expression or function of target proteins and participates in various physiological and pathological processes of breast cancer. Inhibitors targeting the 26S proteasome in combination with other drugs have shown promising therapeutic effects in the clinical treatment of breast cancer. Moreover, several inhibitors/stimulators targeting other UPS components are also effective in preclinical studies, but have not yet been applied in the clinical treatment of breast cancer. Therefore, it is vital to comprehensively understand the functions of ubiquitination in breast cancer and to identify potential tumor promoters or tumor suppressors among UPS family members, with the aim of developing more effective and specific inhibitors/stimulators targeting specific components of this system.

Synthesis and structure-activity relationships of USP48 deubiquitinylase inhibitors

Ubiquitin-specific proteases represent a family of enzymes that catalyze the cleavage of ubiquitin from specific substrate proteins to regulate their activity. USP48 is a rarely studied USP, which has recently been linked to inflammatory signaling via regulation of the transcription factor nuclear factor kappa B. Nonetheless, a crystal structure of USP48 has not yet been resolved and potent inhibitors are not known. We screened a set of 14 commercially available USP inhibitors for their activity against USP48 and identified the USP2 inhibitor "ML364" as a candidate for further optimization. Using a ligand-based approach, we derived and synthesized a series of ML364 analogs. The IC₅₀ concentrations of the new compounds to inhibit USP48 were determined in a deubiquitinylase activity assay by measuring the fluorescence intensity using tetra-ubiquitin rhodamine110 as substrate. A compound containing a carboxylic acid functionalization (17e) inhibited USP48 activity toward tetra-ubiquitin rhodamine110 with an IC₅₀ of 12.6 µM. Further structure-based refinements are required to improve the inhibition activity and specificity.

Angiotensin II-induced calcium overload affects mitochondrial functions in cardiac hypertrophy by targeting the USP2/MFN2 axis

Ubiquitination, a common type of post-translational modification, is known to affect various diseases, including cardiac hypertrophy. Ubiquitin-specific peptidase 2 (USP2) plays a crucial role in regulating cell functions, but its role in cardiac functions remains elusive. The present study aims to investigate the mechanism of USP2 in cardiac hypertrophy. Animal and cell models of cardiac hypertrophy were established using Angiotensin II (Ang II) induction. Our experiments revealed that Ang II induced USP2 downregulation in the in vitro and in vivo models. USP2 overexpression suppressed the degree of cardiac hypertrophy (decreased ANP, BNP, and β-MHC mRNA levels, cell surface area, and ratio of protein/DNA), calcium overload (decreased Ca²⁺ concentration and t-CaMKⅡ and p-CaMKⅡ, and increased SERCA2), and mitochondrial dysfunction (decreased MDA and ROS and increased MFN1, ATP, MMP, and complex Ⅰ and II) both in vitro and in vivo. Mechanically, USP2 interacted with MFN2 and improved the protein level of MFN2 through deubiquitination. Rescue experiments confirmed that MFN2 downregulation neutralized the protective role of USP2 overexpression in cardiac hypertrophy. Overall, our findings suggested that USP2 overexpression mediated deubiquitination to upregulate MFN2, thus alleviating calcium overload-induced mitochondrial dysfunction and cardiac hypertrophy.

Dynamic tumor microenvironment, molecular heterogeneity, and distinct immunologic portrait of triple-negative breast cancer: an impact on classification and treatment approaches

Heterogeneity of the tumor microenvironment (TME) and the lack of a definite targetable receptor in triple-negative breast cancer (TNBC) has carved a niche for this cancer as a particularly therapeutically challenging form of breast cancer. However, recent advances in high-throughput genomic analysis have provided new insights into the unique microenvironment and defining characteristics of various subsets of TNBC. This improved understanding has contributed to the development of novel therapeutic strategies including targeted therapies such as PARP inhibitors and CDK inhibitors. Moreover, the recent FDA approval of the immune checkpoint inhibitor against programmed cell death protein 1 (PD-1), pembrolizumab and atezolizumab, holds the promise of improving the quality of life and increasing the overall survival of TNBC patients. This recent approval is one of the many therapeutically novel strategies that are currently being exploited in clinical trials toward eventual contribution to the oncologist's toolbox against TNBC. In this review, we comprehensively discuss TNBC's distinct TME and its immunophenotype. Furthermore, we highlight the histological and molecular classification of this cancer. More importantly, we describe how these characteristics and classifications contribute to the current standards of care and how they steer the development of newer and more targeted therapies toward achieving peak therapeutic goals in the treatment of TNBC.

The Potential of PSMA as a Vascular Target in TNBC

Recent studies proving prostate-specific membrane antigen (PSMA) expression on triple-negative breast cancer (TNBC) cells and adjacent endothelial cells suggest PSMA as a promising target for therapy of until now not-targetable cancer entities. In this study, PSMA and its isoform expression were analyzed in different TNBC cells, breast cancer stem cells (BCSCs), and tumor-associated endothelial cells. PSMA expression was detected in 91% of the investigated TNBC cell lines. The PSMA splice isoforms were predominantly found in the BCSCs. Tumor-conditioned media from two TNBC cell lines, BT-20 (high full-length PSMA expression, PSMAΔ18 expression) and Hs578T (low full-length PSMA expression, no isoform expression), showed significant pro-angiogenic effect with induction of tube formation in endothelial cells. All TNBC cell lines induced PSMA expression in human umbilical vein endothelial cells (HUVEC). Significant uptake of radiolabeled ligand [⁶⁸Ga]Ga-PSMA was detected in BCSC1 (4.2%), corresponding to the high PSMA expression. Moreover, hypoxic conditions increased the uptake of radiolabeled ligand [¹⁷⁷Lu]Lu-PSMA in MDA-MB-231 (0.4% vs. 3.4%, under hypoxia and normoxia, respectively) and MCF-10A (0.3% vs. 3.0%, under normoxia and hypoxia, respectively) significantly (p < 0.001). [¹⁷⁷Lu]Lu-PSMA-induced apoptosis rates were highest in BT-20 and MDA-MB-231 associated endothelial cells. Together, these findings demonstrate the potential of PSMA-targeted therapy in TNBC.

Glutamine synthetase regulates the immune microenvironment and cancer development through the inflammatory pathway

Although adjuvant tamoxifen therapy is beneficial to estrogen receptor-positive (ER⁺) breast cancer patients, a significant number of patients still develop metastasis or undergo recurrence. Therefore, identifying novel diagnostic and prognostic biomarkers for these patients is urgently needed. Predictive markers and therapeutic strategies for tamoxifen-resistant ER⁺ breast cancer are not clear, and micro (mi)RNAs have recently become a focal research point in cancer studies owing to their regulation of gene expressions, metabolism, and many other physiological processes. Therefore, systematic investigation is required to understand the modulation of gene expression in tamoxifen-resistant patients. High-throughput technology uses a holistic approach to observe differences among expression profiles of thousands of genes, which provides a comprehensive level to extensively investigate functional genomics and biological processes. Through a bioinformatics analysis, we revealed that glutamine synthetase/glutamate-ammonia ligase (GLUL) might play essential roles in the recurrence of tamoxifen-resistant ER⁺ patients. GLUL increases intracellular glutamine usage via glutaminolysis, and further active metabolism-related downstream molecules in cancer cell. However, how GLUL regulates the tumor microenvironment for tamoxifen-resistant ER⁺ breast cancer remains unexplored. Analysis of MetaCore pathway database demonstrated that GLUL is involved in the cell cycle, immune response, interleukin (IL)-4-induced regulators of cell growth, differentiation, and metabolism-related pathways. Experimental data also confirmed that the knockdown of GLUL in breast cancer cell lines decreased cell proliferation and influenced expressions of specific downstream molecules. Through a Connectivity Map (CMap) analysis, we revealed that certain drugs/molecules, including omeprazole, methacholine chloride, ioversol, fulvestrant, difenidol, cycloserine, and MK-801, may serve as potential treatments for tamoxifen-resistant breast cancer patients. These drugs may be tested in combination with current therapies in tamoxifen-resistant breast cancer patients. Collectively, our study demonstrated the crucial roles of GLUL, which provide new targets for the treatment of tamoxifen-resistant breast cancer patients.

USP2 Inhibits Lung Cancer Pathogenesis by Reducing ARID2 Protein Degradation via Ubiquitination

Background

Ubiquitination is an important regulator in physiological and pathological conditions. Ubiquitin-specific protease 2 (USP2), as a member of the USP family, exhibits oncogenic effects in multiple malignancies. However, the exact role of USP2 has not been well clarified in lung cancer pathogenesis and progression. Therefore, we aimed to further investigate the regulatory roles of USP2 in lung cancer in this study.

Methods

Firstly, immunoprecipitation-Mass Spectrometry (IP-MS), Co-immunoprecipitation (Co-IP), combined with immunofluorescent colocalization method, was conducted for USP2 protein interaction analysis in lung cancer cell lines. qRT-PCR, Western blot, and immunohistochemistry assays explored the USP2 expression pattern and USP2/ARID2- (AT-rich interactive domain 2-) specific shRNAs and overexpression vectors. Co-IP assays were designed to validate USP2-ARID2 protein interaction. Further functional studies including CHX chase assay, transwell assay, and wound healing assay were subsequently applied to evaluate the impact of USP2 modulation on lung cancer cells.

Results

USP2 suppression was characteristic in lung cancer cell line models and lung cancer samples. USP2 and ARID2 demonstrated protein-protein interaction and overlapping localization in cancer cell models. Functional experiments suggested USP2 inhibited lung cancer cell invasion and migration by reducing ARID2 protein degradation. Subsequent ubiquitination assays indicated ARID2 protein degradation via the ubiquitination was significantly reduced by USP2 interaction.

Conclusions

Our study provided novel insight that USP2 might suppress lung cancer by reducing ARID2 protein degradation via ubiquitination.

The deubiquitinating enzyme STAMBP is a newly discovered driver of triple-negative breast cancer progression that maintains RAI14 protein stability

Triple-negative breast cancer (TNBC) is a heterogeneous malignancy in women. It is associated with poor prognosis, aggressive malignant behavior, and limited treatment options. In the ubiquitin‒proteasome system (UPS), deubiquitinases (DUBs) are potential therapeutic targets for various tumors. In this study, by performing unbiased siRNA screening, we identified STAMBP, a JAMM metalloprotease in the DUB family, as a driver of human TNBC tumor growth. Functionally, the knockdown of STAMBP inhibited the proliferation, migration, and invasion of multiple TNBC cell lines. Immunoprecipitation-mass spectrometry combined with functional and morphological analysis verified the interaction between STAMBP and the actin-binding protein RAI14. Mechanistically, STAMBP stabilized the RAI14 protein by suppressing the K48-linked ubiquitination of RAI14 and thus prevented its proteasomal degradation. Therefore, knocking down STAMBP resulted in the reduction in RAI14 protein levels and suppression of tumor growth in vitro and in vivo. Importantly, high levels of STAMBP were correlated with poor prognosis in TNBC patients. In summary, we reveal a previously unrecognized DUB pathway that promotes TNBC progression and provides a rationale for potential therapeutic interventions for the treatment of TNBC.

Mitochondria, mitophagy, and the role of deubiquitinases as novel therapeutic targets in liver pathology

Liver diseases such as nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), fibrosis, and hepatocellular carcinoma (HCC) have increased over the past few decades due to the absence or ineffective therapeutics. Recently, it has been shown that inappropriate regulation of hepatic mitophagy is linked to the pathogenesis of the above-mentioned liver diseases. As mitophagy maintains cellular homeostasis by removing damaged and nonfunctional mitochondria from the cell, the proper function of the molecules involved are of utmost importance. Thereby, mitochondrial E3 ubiquitin ligases as well as several deubiquitinases (DUBs) appear to play a unique role for the degradation of mitochondrial proteins and for proper execution of the mitophagy process by either adding or removing ubiquitin chains from target proteins. Therefore, these enzymes could be considered as valuable liver disease biomarkers and also as novel targets for therapy. In this review, we focus on the role of different DUBs on mitophagy and their contribution to NAFLD, NASH, alcohol-related liver disease, and especially HCC.

Integrative bioinformatics analysis to identify the effects of circadian rhythm on Crohn’s disease

Background: Crohn’s disease (CD) is a multifactorial inflammatory bowel disease characterized by complex aberrant autoimmune disorders. Currently, the involvement of the circadian rhythm in the pathogenesis of CD is unknown.

Methods: Bulk and single-cell RNA-seq data and associated clinical data from patients with CD were downloaded from the Gene Expression Omnibus (GEO). Single-sample gene set enrichment analysis was performed to calculate the enrichment score (ES) of circadian rhythm-related genes. Differential expression analysis was used to identify differentially expressed genes. Functional enrichment analysis was used to explore potential disease mechanisms. CIBERSORT was used to estimate immune cell abundance. Single-cell RNA-seq data were analyzed using the R package “Seurat.”

Results: The ES of circadian rhythm-related genes was lower in the CD tissue than in the normal tissue. Ubiquitin-specific protease 2 (USP2), a circadian rhythm-related gene, was identified as a potential modulator of CD pathogenesis. USP2 expression was reduced in CD and was associated with disease severity. Moreover, the analysis of bulk RNA-seq and single-cell RNA-seq data showed that monocyte and neutrophil abundance was elevated in CD and was negatively correlated with USP2 expression. It should be noted that USP2 expression in acinar cells was negatively correlated with monocyte and neutrophil abundance. Functional enrichment analysis revealed several canonical pathways to be enriched in CD, including the interleukin-17 signaling pathway, tumor necrosis factor signaling pathway, cytokine–cytokine receptor interaction, toll-like receptor signaling pathway, and nod-like receptor signaling pathway.

Conclusion: Aberrant expression of circadian rhythm-related genes is correlated with CD pathogenesis. USP2 might be related to crosstalk among the different cell types in CD. These findings provide insights into future chronotherapy for CD.

Triple-negative breast cancer drug resistance, durable efficacy, and cure: How advanced biological insights and emerging drug modalities could transform progress

INTRODUCTION

Triple-negative breast cancer (TNBC) is a heterogeneous disease characterized by the lack of estrogen receptor (ER), progesterone receptor (PR) and epidermal growth factor receptor 2 (HER2) and often associated with poor survival outcomes. The backbone of current treatments for TNBC relies on chemotherapy; however, resistance to cytotoxic agents is a commonly encountered hurdle to overcome.

AREAS COVERED

: Current understanding on the mechanisms involved in TNBC chemoresistance is evaluated and novel potential actionable targets and recently explored modalities for carrying and delivering chemotherapeutics are highlighted.

EXPERT OPINION

: A comprehensive identification of both genomic and functional TNBC signatures is required for a more definite categorization of the patients in order to prevent insensitivity to chemotherapy and therefore realize the full potential of precision-medicine approaches. In this scenario, cell-line-derived xenografts (CDX), patient-derived xenografts (PDX), patient-derived orthotopic xenografts (PDOX) and patient-derived organoids (PDO) are indispensable experimental models for evaluating the efficacy of drug candidates and predicting the therapeutic response. The combination of increasingly sensitive "omics" technologies, computational algorithms and innovative drug modalities may accelerate the successful translation of novel candidate TNBC targets from basic research to clinical settings, thus contributing to reach optimal clinical output, with lower side effects and reduced resistance.

Ubiquitin-Specific Protease 2 in the Ventromedial Hypothalamus Modifies Blood Glucose Levels by Controlling Sympathetic Nervous Activation

Ubiquitin-specific protease 2 (USP2) participates in glucose metabolism in peripheral tissues such as the liver and skeletal muscles. However, the glucoregulatory role of USP2 in the CNS is not well known. In this study, we focus on USP2 in the ventromedial hypothalamus (VMH), which has dominant control over systemic glucose homeostasis. ISH, using a Usp2-specific probe, showed that Usp2 mRNA is present in VMH neurons, as well as other glucoregulatory nuclei, in the hypothalamus of male mice. Administration of a USP2-selective inhibitor ML364 (20 ng/head), into the VMH elicited a rapid increase in the circulating glucose level in male mice, suggesting USP2 has a suppressive role on glucose mobilization. ML364 treatment also increased serum norepinephrine concentration, whereas it negligibly affected serum levels of insulin and corticosterone. ML364 perturbated mitochondrial oxidative phosphorylation in neural SH-SY5Y cells and subsequently promoted the phosphorylation of AMP-activated protein kinase (AMPK). Consistent with these findings, hypothalamic ML364 treatment stimulated AMPKα phosphorylation in the VMH. Inhibition of hypothalamic AMPK prevented ML364 from increasing serum norepinephrine and blood glucose. Removal of ROS restored the ML364-evoked mitochondrial dysfunction in SH-SY5Y cells and impeded the ML364-induced hypothalamic AMPKα phosphorylation as well as prevented the elevation of serum norepinephrine and blood glucose levels in male mice. These results indicate hypothalamic USP2 attenuates perturbations in blood glucose levels by modifying the ROS-AMPK-sympathetic nerve axis.SIGNIFICANCE STATEMENT Under normal conditions (excluding hyperglycemia or hypoglycemia), blood glucose levels are maintained at a constant level. In this study, we used a mouse model to identify a hypothalamic protease controlling blood glucose levels. Pharmacological inhibition of USP2 in the VMH caused a deviation in blood glucose levels under a nonstressed condition, indicating that USP2 determines the set point of the blood glucose level. Modification of sympathetic nervous activity accounts for the USP2-mediated glucoregulation. Mechanistically, USP2 mitigates the accumulation of ROS in the VMH, resulting in attenuation of the phosphorylation of AMPK. Based on these findings, we uncovered a novel glucoregulatory axis consisting of hypothalamic USP2, ROS, AMPK, and the sympathetic nervous system.

Ribonucleotide reductase holoenzyme inhibitor COH29 interacts with deubiquitinase ubiquitin-specific protease 2 and downregulates its substrate protein cyclin D1

USP2 contributes to the quality control of multiple oncogenic proteins including cyclin D1, Mdm2, Aurora-A, etc., and it is a potential target for anti-cancer drug development. However, currently only a few inhibitors with moderate inhibition activities against USP2 have been discovered. USP2-targeted active compounds with either new scaffolds or enhanced activities are in need. Here in this study, Ub-AMC hydrolysis assay-based screening against ~4000 commercially available drugs and drug candidates was performed to identify USP2-targeted inhibitors. COH29, which was originally developed as an anti-cancer agent by blocking the function of human ribonucleotide reductase (RNR, IC₅₀  = 16 µM), was found to exhibit an inhibition activity against USP2 with the IC₅₀ value at 2.02 ± 0.16 µM. The following conducted biophysical and biochemical experiments demonstrated that COH29 could specifically interact with USP2 and inhibit its enzymatic activity in a noncompetitive inhibition mode (K_i  = 1.73 ± 0.14 µM). Since COH29 shows similar inhibitory potencies against RNR (RRM2) and USP2, USP2 inhibition-dependent cellular consequences of COH29 are expected. The results of cellular assays confirmed that the application of COH29 could downregulate the level of cyclin D1 by enhancing its degradation via ubiquitin-proteasome system (UPS), and the modulation effect of COH29 on cyclin D1 is independent of RRM2. Since cyclin D1 acts as an oncogenic driver in human cancer, our findings suggest that USP2 might be a promising therapeutic target for cyclin D1-addicted cancers, and COH29 could serve as a starting compound for high selectivity inhibitor development against USP2.

Ubiquitin-specific protease 1 acts as an oncogene and promotes lenvatinib efficacy in hepatocellular carcinoma by stabilizing c-kit

INTRODUCTION AND OBJECTIVES

Ubiquitin-specific proteases (USPs) act as proto-oncogenes or tumor suppressors in a wide variety of cancers. In this study, we intended to explore the role of USP1 in hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

The clinical significance of USP1 in HCC was analyzed based on The Cancer Genome Atlas (TCGA) data and immunohistochemical staining. siRNAs and lentivirus were used to knock down and overexpress indicated genes, respectively. qRT-PCR and immunoblotting were performed to examine mRNA and protein expression, respectively. CCK8, colony formation and PI/Annexin V-APC staining were performed to examine cellular function. Immunoprecipitation, coomassie blue staining, mass spectrum and immunoblotting were conducted to evaluate the interaction between USP1 and c-kit.

RESULTS

USP1 was over-expressed in HCC patients. Patients with high expression of USP1 had shorter overall and disease free survival than those with low expression of USP1. Functional results showed that USP1 was critical for HCC cell growth and proliferation. Immunoprecipitation and immunoblotting results suggested that USP1 interacted with c-kit and promoted the stability of c-kit, which is an important target of lenvatinib in HCC. Knockdown of c-kit reversed the oncogenic function of USP1 on HCC cell growth. Lastly, USP1 upregulation conferred higher sensitivity of HCC cells to lenvatinib treatment.

CONCLUSIONS

Our study demonstrated that USP1 acted as an oncogene in HCC. It also promoted lenvatinib efficacy by stabilizing c-kit.

Targeting regulated cell death (RCD) with small-molecule compounds in triple-negative breast cancer: a revisited perspective from molecular mechanisms to targeted therapies

Triple-negative breast cancer (TNBC) is a subtype of human breast cancer with one of the worst prognoses, with no targeted therapeutic strategies currently available. Regulated cell death (RCD), also known as programmed cell death (PCD), has been widely reported to have numerous links to the progression and therapy of many types of human cancer. Of note, RCD can be divided into numerous different subroutines, including autophagy-dependent cell death, apoptosis, mitotic catastrophe, necroptosis, ferroptosis, pyroptosis and anoikis. More recently, targeting the subroutines of RCD with small-molecule compounds has been emerging as a promising therapeutic strategy, which has rapidly progressed in the treatment of TNBC. Therefore, in this review, we focus on summarizing the molecular mechanisms of the above-mentioned seven major RCD subroutines related to TNBC and the latest progress of small-molecule compounds targeting different RCD subroutines. Moreover, we further discuss the combined strategies of one drug (e.g., narciclasine) or more drugs (e.g., torin-1 combined with chloroquine) to achieve the therapeutic potential on TNBC by regulating RCD subroutines. More importantly, we demonstrate several small-molecule compounds (e.g., ONC201 and NCT03733119) by targeting the subroutines of RCD in TNBC clinical trials. Taken together, these findings will provide a clue on illuminating more actionable low-hanging-fruit druggable targets and candidate small-molecule drugs for potential RCD-related TNBC therapies.

High Ubiquitin-Specific Protease 2a Expression Level Predicts Poor Prognosis in Upper Tract Urothelial Carcinoma

BACKGROUND

Ubiquitin-mediated protein degradation has been reported to be involved in regulating the activity of oncoproteins and tumor suppressors. Dysfunction or dysregulation of the ubiquitin-proteasome system may induce tumorigenesis. Deubiquitinase ubiquitin-specific protease 2a (USP2a) has been reported to regulate cell growth or death and is involved in the pathogenesis of various diseases, including cancers. However, the role of USP2a in upper tract urothelial carcinoma (UTUC) has not been investigated yet. The goal of this study was to evaluate the clinical significance of USP2a expression in UTUC.

MATERIALS AND METHODS

A total of 110 UTUC cases were included in this study. USP2a expression level was evaluated through immunohistochemistry staining, and the correlation of USP2a expression level with both clinical and pathologic variables was analyzed.

RESULTS

High USP2a expression level was observed in 48 (43.6%) cancer specimens. USP2a expression level was significantly correlated with tumor stage (P=0.001), grade (P=0.033), and tumor recurrence (P=0.008). High USP2a expression level was correlated with poor disease-free survival (P=0.005) and cancer-specific survival (P<0.001). In addition, high USP2a expression level was an independent predictor of poor disease-free survival (hazard ratio=2.31; P=0.007) and cancer-specific survival (hazard ratio=5.49; P=0.009).

CONCLUSIONS

This study indicated that USP2a protein expression level may be a potential biomarker for predicting UTUC patient survival. Further prospective studies are needed to investigate the role of USP2a in UTUC progression.

Loss of deubiquitylase USP2 triggers development of glioblastoma via TGF-β signaling

Glioblastoma (GBM) is the most aggressive primary brain tumor as one of the deadliest cancers. The TGF-β signaling acts as an oncogenic factor in GBM, and plays vital roles in development of GBM. SMAD7 is a major inhibitor of TGF-β signaling, while the deubiquitination of SMAD7 has been poorly studied in GBM. Here, we found USP2 as a new prominent candidate that could regulate SMAD7 stability. USP2 was lost in GBM, leading to the poor prognosis in patients. Moreover, aberrant DNA methylation mediated by DNMT3A induced the low expression of USP2 in GBM. USP2 depletion induced TGF-β signaling and progression of GBM. In contrast, overexpressed USP2 suppressed TGF-β signaling and GBM development. Specifically, USP2 interacted with SMAD7 and prevented SMAD7 ubiquitination. USP2 directly cleaved Lys27- and Lys48-linked poly-ubiquitin chains of SMAD7, and Lys27-linked poly-ubiquitin chains of SMAD7 K185 mediated the recruitment of SMAD7 to HERC3, which regulated Lys63-linked poly-ubiquitination of SMAD7. Moreover, we demonstrated that the DNMT3A inhibitor SGI-1027 induced USP2, suppressed TGF-β signaling and GBM development. Thus, USP2 repressed development of GBM by inhibition TGF-β signaling pathway via the deubiquitination of SMAD7.

Piperlongumine loaded PLGA nanoparticles inhibit cancer stem-like cells through modulation of STAT3 in mammosphere model of triple negative breast cancer

TNBC exhibits higher rate of chemoresistance, metastasis, and relapse among all subtypes of breast cancer. This malignant statein TNBC is due to self-renewing sub-population of cells called cancer stem cells (CSCs). They are major caveats in TNBC treatment and need to be obliterated. In this regard, we explored piperlongumine (PL) that has remarkable anti-cancerous property but poor pharmacokinetics limits its application. So, to enhance its biological activity we developed PLGA based nanoformulation for PL (PL-NPs) and examined anti-CSCs effects of PL and PL-NPs in mammospheres. Results indicated that PL-NPs have higher cellular uptake than PL in mammospheres. Further, we demonstrated that PL-NPs remarkably inhibit various characteristics of CSCs like expression of ALDH, self-renewability, chemoresistance, and EMT in mammopsheres. We next investigated the possible mechanism underlying these multi-modal effects, and found that inhibition of STAT3 might be the driving force. In order to confirm this, we used colivelin a potent synthetic peptide activator of STAT3 in combination with treatments and found that anti-CSCs effects of PL and PL-NPs were reversed. Taken together, our data indicates that PL-NPs show enhanced inhibition of CSCs through downregulation of STAT3 and provides insight into development of PL based nanomedicine for targeting CSCs in TNBC.

Tight junction protein 1 promotes vasculature remodeling via regulating USP2/TWIST1 in bladder cancer

Bladder cancer (BLCA) is the most common malignant tumor of the urinary system and is characterized by high metastatic rates and poor prognosis. The expression of tight junction protein 1 (TJP1) is associated with bladder cancer invasion; however, the mechanism by which TJP1 affects vasculature remodeling remains unknown. In this study, we found that TJP1 expression correlated with tumor angiogenesis and poor overall survival in clinical samples. Furthermore, TJP1 overexpression promoted tumor angiogenesis in BLCA cells and stimulated recruitment of macrophages to tumors by upregulating CCL2 expression. Mechanistically, TJP1 interacted with TWIST1 and enhanced the transcriptional activity of CCL2. The impairment of tumor angiogenesis caused by knockdown of TJP1 was dramatically rescued by overexpression of TWIST1. Furthermore, TJP1 recruited USP2, which deubiquitinated TWIST1, thereby protecting TWIST1 from proteasome-mediated protein degradation. In conclusion, our results suggest that TJP1 controls angiogenesis in BLCA via TWIST1-dependent regulation of CCL2. We demonstrate that TJP1 functions as a scaffold for the interaction between USP2 and TWIST1 and this may provide potential therapeutic targets in bladder cancer.

The role of RNA processing and regulation in metastatic dormancy

Tumor dormancy is a major contributor to the lethality of metastatic disease, especially for cancer patients who develop metastases years-to-decades after initial diagnosis. Indeed, tumor cells can disseminate during early disease stages and persist in new microenvironments at distal sites for months, years, or even decades before initiating metastatic outgrowth. This delay between primary tumor remission and metastatic relapse is known as "dormancy," during which disseminated tumor cells (DTCs) acquire quiescent states in response to intrinsic (i.e., cellular) and extrinsic (i.e., microenvironmental) signals. Maintaining dormancy-associated phenotypes requires DTCs to activate transcriptional, translational, and post-translational mechanisms that engender cellular plasticity. RNA processing is emerging as an essential facet of cellular plasticity, particularly with respect to the initiation, maintenance, and reversal of dormancy-associated phenotypes. Moreover, dysregulated RNA processing, particularly that associated with alternative RNA splicing and expression of noncoding RNAs (ncRNAs), can occur in DTCs to mediate intrinsic and extrinsic metastatic dormancy. Here we review the pathophysiological impact of alternative RNA splicing and ncRNAs in promoting metastatic dormancy and disease recurrence in human cancers.

The involvement of epithelial-to-mesenchymal transition in doxorubicin resistance: Possible molecular targets

Considering the fact that cancer cells can switch among various molecular pathways and mechanisms to ensure their progression, chemotherapy is no longer effective enough in cancer therapy. As an anti-tumor agent, doxorubicin (DOX) is derived from Streptomyces peucetius and can induce cytotoxicity by binding to topoisomerase enzymes to suppress DNA replication, leading to apoptosis and cell cycle arrest. However, efficacy of DOX in suppressing cancer progression is restricted by development of drug resistance. Cancer cells elevate their metastasis in triggering DOX resistance. The epithelial-to-mesenchymal transition (EMT) mechanism participates in transforming epithelial cells into mesenchymal cells that have fibroblast-like features. The EMT diminishes intercellular adhesion and enhances migration of cells that are necessary for carcinogenesis. Various oncogenic molecular pathways stimulate EMT in cancer. EMT can induce DOX resistance, and in this way, upstream mediators such as ZEB proteins, microRNAs, Twist1 and TGF-β play a significant role. Identification of molecular pathways involved in EMT regulation and DOX resistance has resulted in using gene therapy such as microRNA transfection and siRNA in overcoming chemoresistance. Furthermore, curcumin and formononetin, owing to their cytotoxicity against cancer cells, can suppress EMT in mediating DOX sensitivity. For promoting efficacy in DOX sensitivity, nanoparticles have been developed for boosting ability in EMT inhibition.

EVs delivery of miR-1915-3p improves the chemotherapeutic efficacy of oxaliplatin in colorectal cancer

PURPOSE

Oxaliplatin is a crucial component of the combinatorial chemotherapeutic standard of care for advanced colorectal cancer (CRC). Unfortunately, a serious barrier to effective oxaliplatin treatment is drug resistance due to epithelial-mesenchymal transitioning (EMT). Interestingly, stable oxaliplatin-resistant CRC cell lines show differential expression of miR-1915-3p; thus, this microRNA may represent a potential modifier of oxaliplatin resistance in CRC cells.

METHODS

miR-1915-3p was over-expressed in oxaliplatin-resistant CRC cells and a non-tumorigenic intestinal cell line (FHC) via lentiviral transduction. Extracellular vesicles (EVs) were purified from transduced FHC cells and co-incubated with CRC cells. Expression levels of miR-1915-3p and other RNA species were assessed by RT-qPCR, while protein expression levels were assessed by Western blotting. The effects of miR-1915-3p on CRC viability were evaluated by proliferation, apoptosis assays, and Transwell assays. Effects of miR-1915-3p over-expression on in vivo oxaliplatin sensitivity was tested via murine xenograft models.

RESULTS

miRNA-1915-3p decreased EMT marker expression in oxaliplatin-resistant CRC cell lines and in vivo. FHC cells were able to produce and secrete miR-1915-3p-containing EVs, which we employed to mediate miR-1915-3p delivery to oxaliplatin-resistant CRC cells and increase their oxaliplatin sensitivity in vivo and in vitro. Mechanistically, miR-1915-3p overexpression downregulated the EMT-promoting oncogenes 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) and ubiquitin carboxyl-terminal hydrolase 2 (USP2) as well as upregulated E-cadherin (a cell adhesion mediator). miR-1915-3p's effects on chemosensitivity and EMT were mediated by its regulation of PFKFB3 and USP2.

CONCLUSION

Exosomal delivery of miR-1915-3p can improve the chemotherapeutic efficacy of oxaliplatin in CRC cells by suppressing the EMT-promoting oncogenes PFKFB3 and USP2.

Roles and Mechanisms of Deubiquitinases (DUBs) in Breast Cancer Progression and Targeted Drug Discovery

Deubiquitinase (DUB) is an essential component in the ubiquitin—proteasome system (UPS) by removing ubiquitin chains from substrates, thus modulating the expression, activity, and localization of many proteins that contribute to tumor development and progression. DUBs have emerged as promising prognostic indicators and drug targets. DUBs have shown significant roles in regulating breast cancer growth, metastasis, resistance to current therapies, and several canonical oncogenic signaling pathways. In addition, specific DUB inhibitors have been identified and are expected to benefit breast cancer patients in the future. Here, we review current knowledge about the effects and molecular mechanisms of DUBs in breast cancer, providing novel insight into treatments of breast cancer-targeting DUBs.

USP2 is an SKP2 deubiquitylase that stabilizes both SKP2 and its substrates

The stability of a protein is regulated by a balance between its ubiquitylation and deubiquitylation. S-phase kinase-associated protein 2 (SKP2) is an oncogenic F-box protein that recognizes tumor suppressor substrates for targeted ubiquitylation by the E3 ligase SKP1-Cullin1-F-box and degradation by proteasome. SKP2 is itself ubiquitylated by the E3 ligases APC/C^CDH1 and SCF^FBXW2, and deubiquitylated by deubiquitylases (DUBs) USP10 and USP13. Given the biological significance of SKP2, it is likely that the other E3s or DUBs may also regulate its stability. Here, we report the identification and characterization of USP2 as a new DUB. We first screened a panel of DUBs and found that both USP2 and USP21 bound to endogenous SKP2, but only USP2 deubiquitylated and stabilized SKP2 protein. USP2 inactivation via siRNA knockdown or small-molecule inhibitor treatment remarkably shortened SKP2 protein half-life by enhancing its ubiquitylation and subsequent degradation. Unexpectedly, USP2-stabilized SKP2 did not destabilize its substrates p21 and p27. Mechanistically, USP2 bound to SKP2 via the leucine-rich repeat substrate-binding domain on SKP2 to disrupt the SKP2-substrate binding, leading to stabilization of both SKP2 and these substrates. Biologically, growth suppression induced by USP2 knockdown or USP2 inhibitor is partially mediated via modulation of SKP2 and its substrates. Our study revealed a new mechanism of the cross-talk among the E3–DUB substrates and its potential implication in targeting the USP2–SKP2 axis for cancer therapy.

Triple Negative Breast Cancer: A Mountain Yet to Be Scaled Despite the Triumphs

Metastatic progression and tumor recurrence pertaining to TNBC are certainly the leading cause of breast cancer-related mortality; however, the mechanisms underlying TNBC chemoresistance, metastasis, and tumor relapse remain somewhat ambiguous. TNBCs show 77% of the overall 4-year survival rate compared to other breast cancer subtypes (82.7 to 92.5%). TNBC is the most aggressive subtype of breast cancer, with chemotherapy being the major approved treatment strategy. Activation of ABC transporters and DNA damage response genes alongside an enrichment of cancer stem cells and metabolic reprogramming upon chemotherapy contribute to the selection of chemoresistant cells, majorly responsible for the failure of anti-chemotherapeutic regime. These selected chemoresistant cells further lead to distant metastasis and tumor relapse. The present review discusses the approved standard of care and targetable molecular mechanisms in chemoresistance and provides a comprehensive update regarding the recent advances in TNBC management.

ALKBH5-mediated m6A-demethylation of USP1 regulated T-cell acute lymphoblastic leukemia cell glucocorticoid resistance by Aurora B

Recent studies evidence that ubiquitin-specific proteases (USPs) are associated with the occurrence and chemoresistance of T-cell acute lymphoblastic leukemia (T-ALL). N⁶ -methyladenosine (m6A) demethylase AlkB homolog 5 (ALKBH5) exerts a carcinogenic effect in human cancers and improves the mRNA stability of USPs. Whether ubiquitin-specific protease 1 (USP1) controls chemoresistance of T-ALL is unknown. Our study demonstrated that USP1 expression was upregulated in glucocorticoid (GC)-resistant T-ALL patients and cells (CEM-C1). High expression of USP1 was correlated to the poor prognosis in T-ALL patients. Silencing USP1 increased CEM-C1 cell sensitivity to dexamethasone (Dex), reduced cell invasion, promoted cell apoptosis, and ameliorated glucocorticoid receptor (GR) expression. USP1 mediated T-ALL chemoresistance by interacting with and deubiquitination of Aurora B. Overexpression of USP1 reversed the amelioration effect of Aurora B inhibitor on CEM-C1 cell resistance to Dex. Mechanistically, ALKBH5 enhanced USP1 expression by reducing m6A level and mRNA stability in USP1 mRNA transcript. Downregulation of ALKBH5 reduced the levels of USP1 and Aurora B, facilitated CEM-C1 cell sensitivity to Dex, apoptosis, and GR expression, suppressed cell invasion. However, overexpression of USP1 reversed all the effects of ALKBH5 on CEM-C1 cells. In vivo results showed that tail vein injection of sh-USP1 resulted in a significant prolongation of mouse survival, suppressed tumor growth, maintained the normal weight of mice, reduced USP1 expression and facilitated GR expression. In conclusion, inhibition of ALKBH5-mediated m6A modification decreased USP1 expression and downregulation of USP1 ameliorated GC resistance of T-ALL through suppressing Aurora B expression and elevating GR level.

Regulation of cancer stem cells in triple negative breast cancer

Triple Negative Breast Cancer (TNBC) is the most lethal subtype of breast cancer. Despite the successes of emerging targeted therapies, relapse, recurrence, and therapy failure rates in TNBC significantly outpace other subtypes of breast cancer. Mounting evidence suggests accumulation of therapy resistant Cancer Stem Cell (CSC) populations within TNBCs contributes to poor clinical outcomes. These CSCs are enriched in TNBC compared to non-TNBC breast cancers. The mechanisms underlying CSC accumulation have been well-characterized and discussed in other reviews. In this review, we focus on TNBC-specific mechanisms that allow the expansion and activity of self-renewing CSCs. We highlight cellular signaling pathways and transcription factors, specifically enriched in TNBC over non-TNBC breast cancer, contributing to stemness. We also analyze publicly available single-cell RNA-seq data from basal breast cancer tumors to highlight the potential of emerging bioinformatic approaches in identifying novel drivers of stemness in TNBC and other cancers.

Anlotinib exerts anti-cancer efficiency on lung cancer stem cells in vitro and in vivo through reducing NF-κB activity

Anlotinib is a multi-target tyrosine kinase inhibitor. Previous studies confirmed that anlotinib exerts anti-cancer efficiency. However, the functional roles of anlotinib on cancer stem cells (CSCs) are yet to be elucidated. In this study, lung CSCs were isolated and identified in vitro, and mouse xenografts were established in vivo. MTT assays, tumour sphere formation assays, TdT-mediated dUTP nick-end labelling (TUNEL) staining, Annexin V-FITC/PI staining, immunofluorescence analysis and Western blot were performed to investigate the anti-cancer effects of anlotinib on lung CSCs. The results showed that anlotinib inhibits the growth of lung CSCs in vitro and in vivo. In addition, anlotinib induced apoptosis of these cells along with down-regulated expression level of Bcl-2 whereas up-regulated Bax and cleaved caspase-3 expression. It also sensitized lung CSCs to the cytotoxicity of cisplatin and paclitaxel; the tumour sphere formation and expression levels of multiple stemness-associated markers, such as ALDH1 and CD133, were also decreased. Furthermore, the underlying mechanism indicated that anlotinib reduces the phosphorylated levels of NF-κB p65 and IκB-α in lung CSCs. Taken together, these findings suggested that anlotinib exerts potent anti-cancer effects against lung CSCs through apoptotic induction and stemness phenotypic attenuation. The mechanism could be associated with the suppression of NF-κB activity.

Loss of CBX2 induces genome instability and senescence-associated chromosomal rearrangements

The polycomb group protein CBX2 is an important epigenetic reader involved in cell proliferation and differentiation. While CBX2 overexpression occurs in a wide range of human tumors, targeted deletion results in homeotic transformation, proliferative defects, and premature senescence. However, its cellular function(s) and whether it plays a role in maintenance of genome stability remain to be determined. Here, we demonstrate that loss of CBX2 in mouse fibroblasts induces abnormal large-scale chromatin structure and chromosome instability. Integrative transcriptome analysis and ATAC-seq revealed a significant dysregulation of transcripts involved in DNA repair, chromocenter formation, and tumorigenesis in addition to changes in chromatin accessibility of genes involved in lateral sclerosis, basal transcription factors, and folate metabolism. Notably, Cbx2^−/− cells exhibit prominent decondensation of satellite DNA sequences at metaphase and increased sister chromatid recombination events leading to rampant chromosome instability. The presence of extensive centromere and telomere defects suggests a prominent role for CBX2 in heterochromatin homeostasis and the regulation of nuclear architecture.

Disulfiram and 6-Thioguanine synergistically inhibit the enzymatic activities of USP2 and USP21

Disulfiram is a promising repurposed drug that, combining with radiation and chemotherapy, exhibits effective anticancer activities in several preclinical models. The cellular metabolites of disulfiram have been established, however, the intracellular targets of disulfiram remain largely unexplored. We have previously reported that disulfiram suppresses the coronaviral papain-like proteases through attacking their zinc-finger domains, suggesting an inhibitory function potentially on other proteases with similar catalytic structures. Ubiquitin-specific proteases (USPs) share a highly-conserved zinc-finger subdomain that structurally similar to the papain-like proteases and are attractive anticancer targets as upregulated USPs levels are found in a variety of tumors. Here, we report that disulfiram functions as a competitive inhibitor for both USP2 and USP21, two tumor-related deubiquitinases. In addition, we also observed a synergistic inhibition of USP2 and USP21 by disulfiram and 6-Thioguanine (6TG), a clinical drug for acute myeloid leukemia. Kinetic analyses revealed that both drugs exhibited a slow-binding mechanism, moderate inhibitory parameters, and a synergistically inhibitory effect on USP2 and USP21, suggesting the potential combinatory use of these two drugs for USPs-related tumors. Taken together, our study provides biochemical evidence for repurposing disulfiram and 6TG as a combinatory treatment in clinical applications.

USP2-Related Cellular Signaling and Consequent Pathophysiological Outcomes

Ubiquitin specific protease (USP) 2 is a multifunctional deubiquitinating enzyme. USP2 modulates cell cycle progression, and therefore carcinogenesis, via the deubiquitination of cyclins and Aurora-A. Other tumorigenic molecules, including epidermal growth factor and fatty acid synthase, are also targets for USP2. USP2 additionally prevents p53 signaling. On the other hand, USP2 functions as a key component of the CLOCK/BMAL1 complex and participates in rhythmic gene expression in the suprachiasmatic nucleus and liver. USP2 variants influence energy metabolism by controlling hepatic gluconeogenesis, hepatic cholesterol uptake, adipose tissue inflammation, and subsequent systemic insulin sensitivity. USP2 also has the potential to promote surface expression of ion channels in renal and intestinal epithelial cells. In addition to modifying the production of cytokines in immune cells, USP2 also modulates the signaling molecules that are involved in cytokine signaling in the target cells. Usp2 knockout mice exhibit changes in locomotion and male fertility, which suggest roles for USP2 in the central nervous system and male genital tract, respectively. In this review, we summarize the cellular events with USP2 contributions and list the signaling molecules that are upstream or downstream of USP2. Additionally, we describe phenotypic differences found in the in vitro and in vivo experimental models.