ERAP1 promotes Hedgehog-dependent tumorigenesis by controlling USP47-mediated degradation of βTrCP

Combining ERAP1 silencing and entinostat therapy to overcome resistance to cancer immunotherapy in neuroblastoma

BACKGROUND

Checkpoint immunotherapy unleashes tumor control by T cells, but it is undermined in non-immunogenic tumors, e.g. with low MHC class I expression and low neoantigen burden, such as neuroblastoma (NB). Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an enzyme that trims peptides before loading on MHC class I molecules. Inhibition of ERAP1 results in the generation of new antigens able of inducing potent anti-tumor immune responses. Here, we identify a novel non-toxic combinatorial strategy based on genetic inhibition of ERAP1 and administration of the HDAC inhibitor (HDACi) entinostat that increase the immunogenicity of NB, making it responsive to PD-1 therapy.

METHODS

CRISPR/Cas9-mediated gene editing was used to knockout (KO) the ERAP1 gene in 9464D NB cells derived from spontaneous tumors of TH-MYCN transgenic mice. The expression of MHC class I and PD-L1 was evaluated by flow cytometry (FC). The immunopeptidome of these cells was studied by mass spectrometry. Cocultures of splenocytes derived from 9464D bearing mice and tumor cells allowed the assessment of the effect of ERAP1 inhibition on the secretion of inflammatory cytokines and activation and migration of immune cells towards ERAP1 KO cells by FC. Tumor cell killing was evaluated by Caspase 3/7 assay and flow cytometry analysis. The effect of ERAP1 inhibition on the immune content of tumors was analyzed by FC, immunohistochemistry and multiple immunofluorescence.

RESULTS

We found that inhibition of ERAP1 makes 9464D cells more susceptible to immune cell-mediated killing by increasing both the recall and activation of CD4+ and CD8+ T cells and NK cells. Treatment with entinostat induces the expression of MHC class I and PD-L1 molecules in 9464D both in vitro and in vivo. This results in pronounced changes in the immunopeptidome induced by ERAP1 inhibition, but also restrains the growth of ERAP1 KO tumors in vivo by remodelling the tumor-infiltrating T-cell compartment. Interestingly, the absence of ERAP1 in combination with entinostat and PD-1 blockade overcomes resistance to PD-1 immunotherapy and increases host survival.

CONCLUSIONS

These findings demonstrate that ERAP1 inhibition combined with HDACi entinostat treatment and PD-1 blockade remodels the immune landscape of a non-immunogenic tumor such as NB, making it responsive to checkpoint immunotherapy.

Exploiting the potential of the ubiquitin-proteasome system in overcoming tyrosine kinase inhibitor resistance in chronic myeloid leukemia

The advent of tyrosine kinase inhibitors (TKI) targeting BCR-ABL has drastically changed the treatment approach of chronic myeloid leukemia (CML), greatly prolonged the life of CML patients, and improved their prognosis. However, TKI resistance is still a major problem with CML patients, reducing the efficacy of treatment and their quality of life. TKI resistance is mainly divided into BCR-ABL-dependent and BCR-ABL-independent resistance. Now, the main clinical strategy addressing TKI resistance is to switch to newly developed TKIs. However, data have shown that these new drugs may cause serious adverse reactions and intolerance and cannot address all resistance mutations. Therefore, finding new therapeutic targets to overcome TKI resistance is crucial and the ubiquitin-proteasome system (UPS) has emerged as a focus. The UPS mediates the degradation of most proteins in organisms and controls a wide range of physiological processes. In recent years, the study of UPS in hematological malignant tumors has resulted in effective treatments, such as bortezomib in the treatment of multiple myeloma and mantle cell lymphoma. In CML, the components of UPS cooperate or antagonize the efficacy of TKI by directly or indirectly affecting the ubiquitination of BCR-ABL, interfering with CML-related signaling pathways, and negatively or positively affecting leukemia stem cells. Some of these molecules may help overcome TKI resistance and treat CML. In this review, the mechanism of TKI resistance is briefly described, the components of UPS are introduced, existing studies on UPS participating in TKI resistance are listed, and UPS as the therapeutic target and strategies are discussed.

ERAP Inhibitors in Autoimmunity and Immuno-Oncology: Medicinal Chemistry Insights

Endoplasmic reticulum aminopeptidases ERAP1 and 2 are intracellular aminopeptidases that trim antigenic precursors and generate antigens presented by major histocompatibility complex class I (MHC-I) molecules. They thus modulate the antigenic repertoire and drive the adaptive immune response. ERAPs are considered as emerging targets for precision immuno-oncology or for the treatment of autoimmune diseases, in particular MHC-I-opathies. This perspective covers the structural and biological characterization of ERAP, their relevance to these diseases and the ongoing research on small-molecule inhibitors. We describe the chemical and pharmacological space explored by medicinal chemists to exploit the potential of these targets given their localization, biological functions, and family depth. Specific emphasis is put on the binding mode, potency, selectivity, and physchem properties of inhibitors featuring diverse scaffolds. The discussion provides valuable insights for the future development of ERAP inhibitors and analysis of persisting challenges for the translation for clinical applications.

Exploring the neuropharmacological properties of scopoletin-rich Evolvulus alsinoides extract using in-silico and in-vitro methods

OBJECTIVES

This study investigates the neuropharmacologic properties of Scopoletin, a bioactive compound in Evolvulus alsinoides (EA) extract, for managing cognitive impairment using in-vitro, in-silico, and zebrafish embryo toxicity assays.

METHODS

The study estimates Scopoletin concentration in EA extract using HPTLC, assesses antioxidant properties using 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing ability of plasma (FRAP) assays, and uses bioinformatic tools for scopoletin targets. Zebrafish embryo toxicity (ZET) is used to assess its toxicological profile.

RESULTS

0.0076% w/w Scopoletin in the samples was quantified using HPTLC, further studies on the DPPH (0.5 mM) and FRAP gave EC50 at 440.0 μg/ml and 84.29 μg/ml respectively. Twelve common targets associated with cognitive impairment (CI) were identified, along with possible pathways and molecular interactions. Our results indicate significant binding affinities of Scopoletin with ERAP1, SCN3A, and COMT. Molecular dynamics simulations further confirm the stability of these interactions. ZET assessment demonstrated mortality after 450 µg/ml concentration of EA extract.

CONCLUSION

The study verifies the presence of Scopoletin in EA, along with their targets playing a crucial role in neurogenesis and neuroplasticity. The ZET demonstrated concentration-dependent effects, emphasizing the importance of dosage considerations in developing new formulations or therapeutics. This comprehensive study contributes valuable insight into the therapeutic potential of Scopoletin from EA for cognitive impairment, paving the way for further research.

Human umbilical cord mesenchymal stem cell-derived exosomes ameliorate renal fibrosis in diabetic nephropathy by targeting Hedgehog/SMO signaling

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease globally. Currently, there are no effective drugs for the treatment of DN. Although several studies have reported the therapeutic potential of mesenchymal stem cells, the underlying mechanisms remain largely unknown. Here, we report that both human umbilical cord MSCs (UC-MSCs) and UC-MSC-derived exosomes (UC-MSC-exo) attenuate kidney damage, and inhibit epithelial-mesenchymal transition (EMT) and renal fibrosis in streptozotocin-induced DN rats. Strikingly, the Hedgehog receptor, smoothened (SMO), was significantly upregulated in the kidney tissues of DN patients and rats, and positively correlated with EMT and renal fibrosis. UC-MSC and UC-MSC-exo treatment resulted in decrease of SMO expression. In vitro co-culture experiments revealed that UC-MSC-exo reduced EMT of tubular epithelial cells through inhibiting Hedgehog/SMO pathway. Collectively, UC-MSCs inhibit EMT and renal fibrosis by delivering exosomes and targeting Hedgehog/SMO signaling, suggesting that UC-MSCs and their exosomes are novel anti-fibrotic therapeutics for treating DN.

Friend or foe? Reciprocal regulation between E3 ubiquitin ligases and deubiquitinases

Protein ubiquitination is a post-translational modification that entails the covalent attachment of the small protein ubiquitin (Ub), which acts as a signal to direct protein stability, localization, or interactions. The Ub code is written by a family of enzymes called E3 Ub ligases (∼600 members in humans), which can catalyze the transfer of either a single ubiquitin or the formation of a diverse array of polyubiquitin chains. This code can be edited or erased by a different set of enzymes termed deubiquitinases (DUBs; ∼100 members in humans). While enzymes from these distinct families have seemingly opposing activities, certain E3-DUB pairings can also synergize to regulate vital cellular processes like gene expression, autophagy, innate immunity, and cell proliferation. In this review, we highlight recent studies describing Ub ligase-DUB interactions and focus on their relationships.

A genetic variant in the immune-related gene ERAP1 affects colorectal cancer prognosis

BACKGROUND

Findings on the association of genetic factors and colorectal cancer (CRC) survival are limited and inconsistent, and revealing the mechanism underlying their prognostic roles is of great importance. This study aimed to explore the relationship between functional genetic variations and the prognosis of CRC and further reveal the possible mechanism.

METHODS

We first systematically performed expression quantitative trait locus (eQTL) analysis using The Cancer Genome Atlas (TCGA) dataset. Then, the Kaplan-Meier analysis was used to filter out the survival-related eQTL target genes of CRC patients in two public datasets (TCGA and GSE39582 dataset from the Gene Expression Omnibus database). The seven most potentially functional eQTL single nucleotide polymorphisms (SNPs) associated with six survival-related eQTL target genes were genotyped in 907 Chinese CRC patients with clinical prognosis data. The regulatory mechanism of the survival-related SNP was further confirmed by functional experiments.

RESULTS

The rs71630754 regulating the expression of endoplasmic reticulum aminopeptidase 1 ( ERAP1 ) was significantly associated with the prognosis of CRC (additive model, hazard ratio [HR]: 1.43, 95% confidence interval [CI]: 1.08-1.88, P = 0.012). The results of dual-luciferase reporter assay and electrophoretic mobility shift assay showed that the A allele of the rs71630754 could increase the binding of transcription factor 3 (TCF3) and subsequently reduce the expression of ERAP1 . The results of bioinformatic analysis showed that lower expression of ERAP1 could affect the tumor immune microenvironment and was significantly associated with severe survival outcomes.

CONCLUSION

The rs71630754 could influence the prognosis of CRC patients by regulating the expression of the immune-related gene ERAP1 .

TRIAL REGISTRATION

No. NCT00454519 ( https://clinicaltrials.gov/ ).

SALL4 is a CRL3REN/KCTD11 substrate that drives Sonic Hedgehog-dependent medulloblastoma

The Sonic Hedgehog (SHH) pathway is crucial regulator of embryonic development and stemness. Its alteration leads to medulloblastoma (MB), the most common malignant pediatric brain tumor. The SHH-MB subgroup is the best genetically characterized, however the molecular mechanisms responsible for its pathogenesis are not fully understood and therapeutic benefits are still limited. Here, we show that the pro-oncogenic stemness regulator Spalt-like transcriptional factor 4 (SALL4) is re-expressed in mouse SHH-MB models, and its high levels correlate with worse overall survival in SHH-MB patients. Proteomic analysis revealed that SALL4 interacts with REN/KCTD11 (here REN), a substrate receptor subunit of the Cullin3-RING ubiquitin ligase complex (CRL3REN) and a tumor suppressor lost in ~30% of human SHH-MBs. We demonstrate that CRL3REN induces polyubiquitylation and degradation of wild type SALL4, but not of a SALL4 mutant lacking zinc finger cluster 1 domain (ΔZFC1). Interestingly, SALL4 binds GLI1 and cooperates with HDAC1 to potentiate GLI1 deacetylation and transcriptional activity. Notably, inhibition of SALL4 suppresses SHH-MB growth both in murine and patient-derived xenograft models. Our findings identify SALL4 as a CRL3REN substrate and a promising therapeutic target in SHH-dependent cancers.

The strategies to cure cancer patients by eradicating cancer stem-like cells

Cancer stem-like cells (CSCs), a subpopulation of cancer cells, possess remarkable capability in proliferation, self-renewal, and differentiation. Their presence is recognized as a crucial factor contributing to tumor progression and metastasis. CSCs have garnered significant attention as a therapeutic focus and an etiologic root of treatment-resistant cells. Increasing evidence indicated that specific biomarkers, aberrant activated pathways, immunosuppressive tumor microenvironment (TME), and immunoevasion are considered the culprits in the occurrence of CSCs and the maintenance of CSCs properties including multi-directional differentiation. Targeting CSC biomarkers, stemness-associated pathways, TME, immunoevasion and inducing CSCs differentiation improve CSCs eradication and, therefore, cancer treatment. This review comprehensively summarized these targeted therapies, along with their current status in clinical trials. By exploring and implementing strategies aimed at eradicating CSCs, researchers aim to improve cancer treatment outcomes and overcome the challenges posed by CSC-mediated therapy resistance.

Structural and functional characterization of USP47 reveals a hot spot for inhibitor design

USP47 is widely involved in tumor development, metastasis, and other processes while performing a more regulatory role in inflammatory responses, myocardial infarction, and neuronal development. In this study, we investigate the functional and biochemical properties of USP47, whereby depleting USP47 inhibited cancer cell growth in a p53-dependent manner-a phenomenon that enhances during the simultaneous knockdown of USP7. Full-length USP47 shows higher deubiquitinase activity than the catalytic domain. The crystal structures of the catalytic domain, in its free and ubiquitin-bound states, reveal that the misaligned catalytic triads, ultimately, become aligned upon ubiquitin-binding, similar to USP7, thereby becoming ready for catalysis. Yet, the composition and lengths of BL1, BL2, and BL3 of USP47 differ from those for USP7, and they contribute to the observed selectivity. Our study provides molecular details of USP47 regulation, substrate recognition, and the hotspots for drug discovery by targeting USP47.

Beta-Transducin Repeats-Containing Proteins as an Anticancer Target

Beta-transducin repeat-containing proteins (β-TrCPs) are E3-ubiquitin-ligase-recognizing substrates and regulate proteasomal degradation. The degradation of β-TrCPs' substrates is tightly controlled by various external and internal signaling and confers diverse cellular processes, including cell cycle progression, apoptosis, and DNA damage response. In addition, β-TrCPs function to regulate transcriptional activity and stabilize a set of substrates by distinct mechanisms. Despite the association of β-TrCPs with tumorigenesis and tumor progression, studies on the mechanisms of the regulation of β-TrCPs' activity have been limited. In this review, we studied publications on the regulation of β-TrCPs themselves and analyzed the knowledge gaps to understand and modulate β-TrCPs' activity in the future.

All-Trans Retinoic Acid Promotes a Tumor Suppressive OTUD6B-β-TrCP-SNAIL Axis in Esophageal Squamous Cell Carcinoma and Enhances Immunotherapy

β-TrCP is an E3 ubiquitin ligase that plays important roles in multiple human cancers including esophageal squamous cell carcinoma (ESCC). Analysis of ESCC patient samples reveal that only protein level but not transcript level of β-TrCP associated with patient prognosis, suggesting regulators of β-TrCP protein stability play an essential role in ESCC progression and may be novel targets to develop ESCC therapies. Although β-TrCP stability is known to be mediated by the ubiquitin-proteasome system, it is unclear which enzymes play a major role to determine β-TrCP stability in the context of ESCC. In this study, OTUD6B is identified as a potent deubiquitinase of β-TrCP that suppress ESCC progression through the OTUD6B-β-TrCP-SNAIL axis. Low OTUD6B expression is associated with a poor prognosis of ESCC patients. Importantly, all-trans retinoic acid (ATRA) is found to promote OTUD6B translation and thus suppress ESCC tumor growth and enhance the response of ESCC tumors to anti-PD-1 immunotherapies. These findings demonstrate that OTUD6B is a crucial deubiquitinase of β-TrCP in ESCC and suggest combination of ATRA and anti-PD-1 immune checkpoint inhibitor may benefit a cohort of ESCC patients.

GLI1, a novel target of the ER stress regulator p97/VCP, promotes ATF6f-mediated activation of XBP1

Upon accumulation of improperly folded proteins in the Endoplasmic Reticulum (ER), the Unfolded Protein Response (UPR) is triggered to restore ER homeostasis. The induction of stress genes is a sine qua non condition for effective adaptive UPR. Although this requirement has been extensively described, the mechanisms underlying this process remain in part uncharacterized. Here, we show that p97/VCP, an AAA+ ATPase known to contribute to ER stress-induced gene expression, regulates the transcription factor GLI1, a primary effector of Hedgehog (Hh) signaling. Under basal (non-ER stress) conditions, GLI1 is repressed by a p97/VCP-HDAC1 complex while upon ER stress GLI1 is induced through a mechanism requiring both USF2 binding and increase histone acetylation at its promoter. Interestingly, the induction of GLI1 was independent of ligand-regulated Hh signaling. Further analysis showed that GLI1 cooperates with ATF6f to induce promoter activity and expression of XBP1, a key transcription factor driving UPR. Overall, our work demonstrates a novel role for GLI1 in the regulation of ER stress gene expression and defines the interplay between p97/VCP, HDAC1 and USF2 as essential players in this process.

USP47 deubiquitylates Groucho/TLE to promote Wnt-β-catenin signaling

The Wnt-β-catenin signal transduction pathway is essential for embryonic development and adult tissue homeostasis. Wnt signaling converts TCF from a transcriptional repressor to an activator in a process facilitated by the E3 ligase XIAP. XIAP-mediated monoubiquitylation of the transcriptional corepressor Groucho (also known as TLE) decreases its affinity for TCF, thereby allowing the transcriptional coactivator β-catenin to displace it on TCF. Through a genome-scale screen in cultured Drosophila melanogaster cells, we identified the deubiquitylase USP47 as a positive regulator of Wnt signaling. We found that USP47 was required for Wnt signaling during Drosophila and Xenopus laevis development, as well as in human cells, indicating evolutionary conservation. In human cells, knockdown of USP47 inhibited Wnt reporter activity, and USP47 acted downstream of the β-catenin destruction complex. USP47 interacted with TLE3 and XIAP but did not alter their amounts; however, knockdown of USP47 enhanced XIAP-mediated ubiquitylation of TLE3. USP47 inhibited ubiquitylation of TLE3 by XIAP in vitro in a dose-dependent manner, suggesting that USP47 is the deubiquitylase that counteracts the E3 ligase activity of XIAP on TLE. Our data suggest a mechanism by which regulated ubiquitylation and deubiquitylation of TLE enhance the ability of β-catenin to cycle on and off TCF, thereby helping to ensure that the expression of Wnt target genes continues only as long as the upstream signal is present.

Emerging Roles of Hedgehog Signaling in Cancer Immunity

Hedgehog-GLI (HH) signaling plays an essential role in embryogenesis and tissue homeostasis. Aberrant activation of the pathway through mutations or other mechanisms is involved in the development and progression of numerous types of cancer, including basal cell carcinoma, medulloblastoma, melanoma, breast, prostate, hepatocellular and pancreatic carcinomas. Activation of HH signaling sustains proliferation, suppresses cell death signals, enhances invasion and metastasis, deregulates cellular metabolism and promotes angiogenesis and tumor inflammation. Targeted inhibition of the HH pathway has therefore emerged as an attractive therapeutic strategy for the treatment of a wide range of cancers. Currently, the Smoothened (SMO) receptor and the downstream GLI transcriptional factors have been investigated for the development of targeted drugs. Recent studies have revealed that the HH signaling is also involved in tumor immune evasion and poor responses to cancer immunotherapy. Here we focus on the effects of HH signaling on the major cellular components of the adaptive and innate immune systems, and we present recent discoveries elucidating how the immunosuppressive function of the HH pathway is engaged by cancer cells to prevent immune surveillance. In addition, we discuss the future prospect of therapeutic options combining the HH pathway and immune checkpoint inhibitors.

A high-throughput MALDI-TOF MS biochemical screen for small molecule inhibitors of the antigen aminopeptidase ERAP1

MALDI-TOF MS is a powerful analytical technique that provides a fast and label-free readout for in vitro assays in the high-throughput screening (HTS) environment. Here, we describe the development of a novel, HTS compatible, MALDI-TOF MS-based drug discovery assay for the endoplasmic reticulum aminopeptidase 1 (ERAP1), an important target in immuno-oncology and auto-immune diseases. A MALDI-TOF MS assay was developed beginning with an already established ERAP1 RapidFire MS (RF MS) assay, where the peptide YTAFTIPSI is trimmed into the product TAFTIPSI. We noted low ionisation efficiency of these peptides in MALDI-TOF MS and hence incorporated arginine residues into the peptide sequences to improve ionisation. The optimal assay conditions were established with these new basic assay peptides on the MALDI-TOF MS platform and validated with known ERAP1 inhibitors. Assay stability, reproducibility and robustness was demonstrated on the MALDI-TOF MS platform. From a set of 699 confirmed ERAP1 binders, identified in a prior affinity selection mass spectrometry (ASMS) screen, active compounds were determined at single concentration and in a dose-response format with the new MALDI-TOF MS setup. Furthermore, to allow for platform performance comparison, the same compound set was tested on the established RF MS setup, as the new basic peptides showed fragmentation in ESI-MS. The two platforms showed a comparable performance, but the MALDI-TOF MS platform had several advantages, such as shorter sample cycle times, reduced reagent consumption, and a lower tight-binding limit.

Research Progress for Targeting Deubiquitinases in Gastric Cancers

Gastric cancers (GCs) are malignant tumors with a high incidence that threaten global public health. Despite advances in GC diagnosis and treatment, the prognosis remains poor. Therefore, the mechanisms underlying GC progression need to be identified to develop prognostic biomarkers and therapeutic targets. Ubiquitination, a post-translational modification that regulates the stability, activity, localization, and interactions of target proteins, can be reversed by deubiquitinases (DUBs), which can remove ubiquitin monomers or polymers from modified proteins. The dysfunction of DUBs has been closely linked to tumorigenesis in various cancer types, and targeting certain DUBs may provide a potential option for cancer therapy. Multiple DUBs have been demonstrated to function as oncogenes or tumor suppressors in GC. In this review, we summarize the DUBs involved in GC and their associated upstream regulation and downstream mechanisms and present the benefits of targeting DUBs for GC treatment, which could provide new insights for GC diagnosis and therapy.

Discovery of Selective Nanomolar Inhibitors for Insulin-Regulated Aminopeptidase Based on α-Hydroxy-β-amino Acid Derivatives of Bestatin

The oxytocinase subfamily of M1 zinc aminopeptidases comprises emerging drug targets, including the ER-resident aminopeptidases 1 and 2 (ERAP1 and ERAP2) and insulin-regulated aminopeptidase (IRAP); however, reports on clinically relevant inhibitors are limited. Here we report a new synthetic approach of high diastereo- and regioselectivity for functionalization of the α-hydroxy-β-amino acid scaffold of bestatin. Stereochemistry and mechanism of inhibition were investigated by a high-resolution X-ray crystal structure of ERAP1 in complex with a micromolar inhibitor. By exploring the P1 side-chain functionalities, we achieve significant potency and selectivity, and we report a cell-active, low-nanomolar inhibitor of IRAP with >120-fold selectivity over homologous enzymes. X-ray crystallographic analysis of IRAP in complex with this inhibitor suggest that interactions with the GAMEN loop is an unappreciated key determinant for potency and selectivity. Overall, our results suggest that α-hydroxy-β-amino acid derivatives may constitute useful chemical tools and drug leads for this group of aminopeptidases.

Ubiquitin specific peptidase 47 promotes proliferation of lung squamous cell carcinoma

BACKGROUND

Ubiquitin specific peptidase 47 (USP47) is a kind of deubiquitinase, which has been reported to play oncogenic roles in several malignancies including colorectal cancer and breast cancer.

OBJECTIVE

Here we aimed to investigate the clinical significance of USP47 in lung squamous cell carcinoma (LUSC).

METHODS

We retrospectively enrolled a cohort of LUSC patients who underwent surgical resection in our hospital (n = 280) and conducted immunohistochemistry staining for their tumor tissues targeting USP47. The correlations between USP47 expression and clinicopathological characteristics were evaluated by Chi-square test. Univariate and multivariate analyses were conducted to assess the prognostic predictive role of USP47 in LUSC. Cell lines and mice models were utilized to explore the tumor-related functions of USP47 in vitro and in vivo, respectively.

RESULTS

Among the 280 cases, there were 127 cases classified as high-USP47 expression and 153 cases with low-USP47 expression. Statistical analyses revealed that higher USP47 expression was independently correlated with larger tumor size, advanced T stage, and unfavorable prognosis. Knockdown of USP47 by shRNA resulted in impaired proliferation of LUSC cell lines and reduced nucleus beta-catenin level. Furthermore, xenograft assays demonstrated that silencing USP47 can inhibit LUSC tumor growth in vivo.

CONCLUSION

Our research established a novel tumor-promoting effect and prognostic predictive role of USP47 in LUSC, thereby providing evidence for further therapeutic development.

Hepatokine ERAP1 Disturbs Skeletal Muscle Insulin Sensitivity Via Inhibiting USP33-Mediated ADRB2 Deubiquitination

Chronic inflammation in liver induces insulin resistance systemically and in other tissues, including the skeletal muscle (SM); however, the underlying mechanisms remain largely unknown. RNA sequencing of primary hepatocytes from wild-type mice fed long-term high-fat diet (HFD), which have severe chronic inflammation and insulin resistance revealed that the expression of hepatokine endoplasmic reticulum aminopeptidase 1 (ERAP1) was upregulated by a HFD. Increased ERAP1 levels were also observed in interferon-γ-treated primary hepatocytes. Furthermore, hepatic ERAP1 overexpression attenuated systemic and SM insulin sensitivity, whereas hepatic ERAP1 knockdown had the opposite effects, with corresponding changes in serum ERAP1 levels. Mechanistically, ERAP1 functions as an antagonist-like factor, which interacts with β2 adrenergic receptor (ADRB2) and reduces its expression by decreasing ubiquitin-specific peptidase 33-mediated deubiquitination and thereby interrupts ADRB2-stimulated insulin signaling in the SM. The findings of this study indicate ERAP1 is an inflammation-induced hepatokine that impairs SM insulin sensitivity. Its inhibition may provide a therapeutic strategy for insulin resistance-related diseases, such as type 2 diabetes.

Sonic Hedgehog Signaling in Cerebellar Development and Cancer

The sonic hedgehog (SHH) pathway regulates the development of the central nervous system in vertebrates. Aberrant regulation of SHH signaling pathways often causes neurodevelopmental diseases and brain tumors. In the cerebellum, SHH secreted by Purkinje cells is a potent mitogen for granule cell progenitors, which are the most abundant cell type in the mature brain. While a reduction in SHH signaling induces cerebellar structural abnormalities, such as hypoplasia in various genetic disorders, the constitutive activation of SHH signaling often induces medulloblastoma (MB), one of the most common pediatric malignant brain tumors. Based on the existing literature on canonical and non-canonical SHH signaling pathways, emerging basic and clinical studies are exploring novel therapeutic approaches for MB by targeting SHH signaling at distinct molecular levels. In this review, we discuss the present consensus on SHH signaling mechanisms, their roles in cerebellar development and tumorigenesis, and the recent advances in clinical trials for MB.

ERAP1 as an emerging therapeutic target for medulloblastoma

Endoplasmic reticulum aminopeptidase 1 (ERAP1) is a multifunctional enzyme that shapes the peptide repertoire presented by major histocompatibility complex class I (MHC-I) molecules, thereby affecting tumor immunogenicity. ERAP1 is altered in many tumors, including medulloblastoma (MB). We review the role of ERAP1 in MB development and the possibility of targeting this enzyme for MB treatment.

USP47-Mediated Deubiquitination and Stabilization of TCEA3 Attenuates Pyroptosis and Apoptosis of Colorectal Cancer Cells Induced by Chemotherapeutic Doxorubicin

The ubiquitin–proteasome system regulates a variety of cellular processes including growth, differentiation and apoptosis. While E1, E2, and E3 are responsible for the conjugation of ubiquitin to substrates, deubiquitinating enzymes (DUBs) reverse the process to remove ubiquitin and edit ubiquitin chains, which have profound effects on substrates’ degradation, localization, and activities. In the present study, we found that the deubiquitinating enzyme USP47 was markedly decreased in primary colorectal cancers (CRC). Its reduced expression was associated with shorter disease-free survival of CRC patients. In cultured CRC cells, knockdown of USP47 increased pyroptosis and apoptosis induced by chemotherapeutic doxorubicin. We found that USP47 was able to bind with transcription elongation factor a3 (TCEA3) and regulated its deubiquitination and intracellular level. While ectopic expression of USP47 increased cellular TCEA3 and resistance to doxorubicin, the effect was markedly attenuated by TCEA3 knockdown. Further analysis showed that the level of pro-apoptotic Bax was regulated by TCEA3. These results indicated that the USP47-TCEA3 axis modulates cell pyroptosis and apoptosis and may serve as a target for therapeutic intervention in CRC.

Role of Ubiquitin-Specific Peptidase 47 in Cancers and Other Diseases

Deubiquitination is the reverse process of ubiquitination, which is catalyzed by deubiquitinase enzymes. More than 100 deubiquitinases have been identified. Ubiquitin-specific peptidase 47 (USP47), a member of the ubiquitin-specific protease family with high homology to USP7, is an active molecule with a wide range of functions and is closely associated with cancer and other diseases. However, no systematic summary exists regarding the functions of USP47. Here, we summarize the functions and expression regulation of USP47. USP47 is highly expressed in many tumors and is widely involved in tumor development, metastasis, drug resistance, epithelial-mesenchymal transition, and other processes. Targeted inhibition of USP47 can reverse malignant tumor behavior. USP47 also plays a role in inflammatory responses, myocardial infarction, and neuronal development. USP47 is involved in multiple levels of expression-regulating mechanisms, including transcriptional, post-transcriptional, and post-translational modifications. Development of targeted inhibitors against USP47 will provide a basis for studying the mechanisms of USP47 and developing therapeutic strategies for cancers and other diseases.

Molecular and functional diversity of the oxytocinase subfamily of M1 aminopeptidases

The placental leucine aminopeptidase/insulin-regulated aminopeptidase, endoplasmic reticulum aminopeptidase 1 and endoplasmic reticulum aminopeptidase 2 are part of a distinct subfamily of M1 aminopeptidases termed the 'oxytocinase subfamily'. The subfamily members show molecular diversity due to differential usage of translation initiation sites, alternative splicing and multiple single nucleotide polymorphisms. It is becoming evident that, depending on their intracellular or extracellular location, members of the oxytocinase subfamily play important roles in the maintenance of homeostasis, including the regulation of blood pressure, maintenance of normal pregnancy, retention of memory and trimming of antigenic peptides presented to major histocompatibility complex class I molecules, by acting as either aminopeptidases or binding partners of specific functional proteins in the cells. Based on their molecular diversity and moonlighting protein-like properties, it is conceivable that the subfamily members exert pleiotropic effects during evolution, to become important players in the regulation of homeostasis.

USP47 maintains the stemness of colorectal cancer cells and is inhibited by parthenolide

Colorectal cancer stem cells (CCSCs) are implicated in colorectal tumor initiation, invasion, recurrence and treatment resistance, so elucidation of the mechanism underlying the cancer stem cells induction and development of drugs targeting CCSCs are vital for cancer treatment. Growing evidence shows that dysregulated deubiquitinase (DUBs) expression is frequently associated with stemness and maintenance of cancer stem cells (CSCs). In the current study, we found that upregulation of USP47 is associated with tumorigenesis and poor prognosis in clinical patients with colorectal cancer (CRC). Besides, USP47 was highly expressed in CCSCs enriched by serum-free culture. Further investigation showed that USP47 is closely involved in the maintenance of the stemness of CCSCs. USP47 silencing reduces proliferation and migration of colorectal cancer cells and suppresses the self-renewal of CCSCs by downregulating the expression of cancer stem cell markers, including CD44, CD133, CD166, OCT4 and NANOG. Furthermore, we identified Parthenolide (PTL), a natural sesquiterpene lactone, as a novel USP47 inhibitor. PTL diminishes CCSCs self-renewal and induces apoptosis of CCSCs. Taken together, our findings highlighted a novel DUB involved in the modulation of CCSCs stemness and the potential of PTL in the CRC treatment by targeting CCSCs as the USP47 inhibitor.

Targeting USP47 overcomes tyrosine kinase inhibitor resistance and eradicates leukemia stem/progenitor cells in chronic myelogenous leukemia

Identifying novel drug targets to overcome resistance to tyrosine kinase inhibitors (TKIs) and eradicating leukemia stem/progenitor cells are required for the treatment of chronic myelogenous leukemia (CML). Here, we show that ubiquitin-specific peptidase 47 (USP47) is a potential target to overcome TKI resistance. Functional analysis shows that USP47 knockdown represses proliferation of CML cells sensitive or resistant to imatinib in vitro and in vivo. The knockout of Usp47 significantly inhibits BCR-ABL and BCR-ABLT315I-induced CML in mice with the reduction of Lin-Sca1+c-Kit+ CML stem/progenitor cells. Mechanistic studies show that stabilizing Y-box binding protein 1 contributes to USP47-mediated DNA damage repair in CML cells. Inhibiting USP47 by P22077 exerts cytotoxicity to CML cells with or without TKI resistance in vitro and in vivo. Moreover, P22077 eliminates leukemia stem/progenitor cells in CML mice. Together, targeting USP47 is a promising strategy to overcome TKI resistance and eradicate leukemia stem/progenitor cells in CML.

β-TrCP1 facilitates cell cycle checkpoint activation, DNA repair, and cell survival through ablation of β-TrCP2 in response to genotoxic stress

F-box proteins β-TrCP1 and β-TrCP2 are paralogs present in the human genome. They control several cellular processes including cell cycle and DNA damage signaling. Moreover, it is reported that they facilitate DNA damage-induced accumulation of p53 by directing proteasomal degradation of MDM2, a protein that promotes p53 degradation. However, the individual roles of β-TrCP1 and β-TrCP2 in the genotoxic stress-induced activation of cell cycle checkpoints and DNA damage repair remain largely unknown. Here, using biochemical, molecular biology, flow cytometric, and immunofluorescence techniques, we show that β-TrCP1 and β-TrCP2 communicate during genotoxic stress. We found that expression levels of β-TrCP1 are significantly increased while levels of β-TrCP2 are markedly decreased upon induction of genotoxic stress. Further, our results revealed that DNA damage-induced activation of ATM kinase plays an important role in maintaining the reciprocal expression levels of β-TrCP1 and β-TrCP2 via the phosphorylation of β-TrCP1 at Ser158. Phosphorylated β-TrCP1 potently promotes the proteasomal degradation of β-TrCP2 and MDM2, resulting in the activation of p53. Additionally, β-TrCP1 impedes MDM2 accumulation via abrogation of its lysine 63-linked polyubiquitination by β-TrCP2. Thus, β-TrCP1 helps to arrest cells at the G2/M phase of the cell cycle and promotes DNA repair upon DNA damage through attenuation of β-TrCP2. Collectively, our findings elucidate an intriguing posttranslational regulatory mechanism of these two paralogs under genotoxic stress and revealed β-TrCP1 as a key player in maintaining the genome integrity through the attenuation of β-TrCP2 levels in response to genotoxic stress.

A Dynamic Role of Mastermind-Like 1: A Journey Through the Main (Path)ways Between Development and Cancer

Major signaling pathways, such as Notch, Hedgehog (Hh), Wnt/β-catenin and Hippo, are targeted by a plethora of physiological and pathological stimuli, ultimately resulting in the modulation of genes that act coordinately to establish specific biological processes. Many biological programs are strictly controlled by the assembly of multiprotein complexes into the nucleus, where a regulated recruitment of specific transcription factors and coactivators on gene promoter region leads to different transcriptional outcomes. MAML1 results to be a versatile coactivator, able to set up synergistic interlinking with pivotal signaling cascades and able to coordinate the network of cross-talking pathways. Accordingly, despite its original identification as a component of the Notch signaling pathway, several recent reports suggest a more articulated role for MAML1 protein, showing that it is able to sustain/empower Wnt/β-catenin, Hh and Hippo pathways, in a Notch-independent manner. For this reason, MAML1 may be associated to a molecular “switch”, with the function to control the activation of major signaling pathways, triggering in this way critical biological processes during embryonic and post-natal life. In this review, we summarize the current knowledge about the pleiotropic role played by MAML proteins, in particular MAML1, and we recapitulate how it takes part actively in physiological and pathological signaling networks. On this point, we also discuss the contribution of MAML proteins to malignant transformation. Accordingly, genetic alterations or impaired expression of MAML proteins may lead to a deregulated crosstalk among the pathways, culminating in a series of pathological disorders, including cancer development. Given their central role, a better knowledge of the molecular mechanisms that regulate the interplay of MAML proteins with several signaling pathways involved in tumorigenesis may open up novel opportunities for an attractive molecular targeted anticancer therapy.

Glabrescione B delivery by self-assembling micelles efficiently inhibits tumor growth in preclinical models of Hedgehog-dependent medulloblastoma

Aberrant activation of the Hedgehog (Hh) pathway leads to the development of several tumors, including medulloblastoma (MB), the most common pediatric brain malignancy. Hh inhibitors acting on GLI1, the final effector of Hh signaling, offer a valuable opportunity to overcome the pitfalls of the existing therapies to treat Hh-driven cancers. In this study, the toxicity, delivery, biodistribution, and anticancer efficacy of Glabrescione B (GlaB), a selective GLI1 inhibitor, were investigated in preclinical models of Hh-dependent MB. To overcome its poor water solubility, GlaB was formulated with a self-assembling amphiphilic polymer forming micelles, called mPEG_5kDa-cholane. mPEG_5kDa-cholane/GlaB showed high drug loading and stability, low cytotoxicity, and long permanence in the bloodstream. We found that mPEG_5kDa-cholane efficiently enhanced the solubility of GlaB, thus avoiding the use of organic solvents. mPEG_5kDa-cholane/GlaB possesses favorable pharmacokinetics and negligible toxicity. Remarkably, GlaB encapsulated in mPEG_5kDa-cholane micelles was delivered through the blood-brain barrier and drastically inhibited tumor growth in both allograft and orthotopic models of Hh-dependent MB. Our findings reveal that mPEG_5kDa-cholane/GlaB is a good candidate for the treatment of Hh-driven tumors and provide relevant implications for the translation of GlaB into clinical practice.

The characteristics and roles of β-TrCP1/2 in carcinogenesis

β-transducin repeat-containing protein (β-TrCP), one of the well-characterized F-box proteins, acts as a substrate receptor and constitutes an active SCF^β-TrCP E3 ligase with a scaffold protein CUL1, a RING protein RBX1, and an adaptor protein SKP1. β-TrCP plays a critical role in the regulation of various physiological and pathological processes, including signal transduction, cell cycle progression, cell migration, DNA damage response, and tumorigenesis, by governing burgeoning amounts of key regulators for ubiquitination and proteasomal degradation. Given that a variety of β-TrCP substrates are well-known oncoproteins and tumor suppressors, and dysregulation of β-TrCP is frequently identified in human cancers, β-TrCP plays a vital role in carcinogenesis. In this review, we first briefly introduce the characteristics of β-TrCP1, β-TrCP2, and SCF^β-TrCP ubiquitin ligase, and then discuss SCF^β-TrCP ubiquitin ligase regulated biological processes by targeting its substrates for degradation. Moreover, we summarize the regulation of β-TrCP1 and β-TrCP2 at multiple layers and further discuss the various roles of β-TrCP1 and β-TrCP2 in human cancer, functioning as either an oncoprotein or a tumor suppressor in a manner dependent of cellular context. Finally, we provide novel insights for future perspectives on the potential of targeting β-TrCP1 and β-TrCP2 for cancer therapy.

The SHH/GLI signaling pathway: a therapeutic target for medulloblastoma

INTRODUCTION

Medulloblastoma (MB) is a heterogeneous tumor of the cerebellum that is divided into four main subgroups with distinct molecular and clinical features. Sonic Hedgehog MB (SHH-MB) is the most genetically understood and occurs predominantly in childhood. Current therapies consist of aggressive and non-targeted multimodal approaches that are often ineffective and cause long-term complications. These problems intensify the need to develop molecularly targeted therapies to improve outcome and reduce treatment-related morbidities. In this scenario, Hedgehog (HH) signaling, a developmental pathway whose deregulation is involved in the pathogenesis of several malignancies, has emerged as an attractive druggable pathway for SHH-MB therapy.

AREAS COVERED

This review provides an overview of the advancements in the HH antagonist research field. We place an emphasis on Smoothened (SMO) and glioma-associated oncogene homolog (GLI) inhibitors and immunotherapy approaches that are validated in preclinical SHH-MB models and that have therapeutic potential for MB patients. Literature from Pubmed and data reported on ClinicalTrial.gov up to August 2020 were considered.

EXPERT OPINION

Extensive-omics analysis has enhanced our knowledge and has transformed the way that MB is studied and managed. The clinical use of SMO antagonists has yet to be determined, however, future GLI inhibitors and multitargeting approaches are promising.

Impact of Natural Occurring ERAP1 Single Nucleotide Polymorphisms within miRNA-Binding Sites on HCMV Infection

Human cytomegalovirus (HCMV) is a β-herpesvirus that causes serious problems in people with a compromised immune system, whereas it coexists asymptomatically within the host with a healthy immune system. Like other viruses, HCMV has adopted multiples strategies to manipulate the host’s immune responses. Among them, expression of viral microRNAs (miRNAs) is one of the most intriguing. HCMV miR-UL112-5p and miR-US4-1 have been found to contribute to immune evasion by targeting the endoplasmic reticulum aminopeptidase 1 (ERAP1), a highly polymorphic key component of antigen processing. The current incomplete picture on the interplay between viral miRNAs and host immunity implies the need to better characterize the host genetic determinants. Naturally occurring single nucleotide polymorphisms (SNPs) within the miRNA binding sites of target genes may affect miRNA–target interactions. In this review, we focus on the relevance of 3′ untranslated region (3′UTR) ERAP1 SNPs within miRNA binding sites in modulating miRNA–mRNA interactions and the possible consequent individual susceptibility to HCMV infection. Moreover, we performed an in silico analysis using different bioinformatic algorithms to predict ERAP1 variants with a putative powerful biological function. This evidence provides a basis to deepen the knowledge on how 3′UTR ERAP1 variants may alter the mechanism of action of HCMV miRNAs, in order to develop targeted antiviral therapies.

DUBs Activating the Hedgehog Signaling Pathway: A Promising Therapeutic Target in Cancer

The Hedgehog (HH) pathway governs cell proliferation and patterning during embryonic development and is involved in regeneration, homeostasis and stem cell maintenance in adult tissues. The activity of this signaling is finely modulated at multiple levels and its dysregulation contributes to the onset of several human cancers. Ubiquitylation is a coordinated post-translational modification that controls a wide range of cellular functions and signaling transduction pathways. It is mediated by a sequential enzymatic network, in which ubiquitin ligases (E3) and deubiquitylase (DUBs) proteins are the main actors. The dynamic balance of the activity of these enzymes dictates the abundance and the fate of cellular proteins, thus affecting both physiological and pathological processes. Several E3 ligases regulating the stability and activity of the key components of the HH pathway have been identified. Further, DUBs have emerged as novel players in HH signaling transduction, resulting as attractive and promising drug targets. Here, we review the HH-associated DUBs, discussing the consequences of deubiquitylation on the maintenance of the HH pathway activity and its implication in tumorigenesis. We also report the recent progress in the development of selective inhibitors for the DUBs here reviewed, with potential applications for the treatment of HH-related tumors.

Embryonic Barcoding of Equipotent Mammary Progenitors Functionally Identifies Breast Cancer Drivers

Identification of clinically relevant drivers of breast cancers in intact mammary epithelium is critical for understanding tumorigenesis yet has proven challenging. Here, we show that intra-amniotic lentiviral injection can efficiently transduce progenitor cells of the adult mammary gland and use that as a platform to functionally screen over 500 genetic lesions for functional roles in tumor formation. Targeted progenitors establish long-term clones of both luminal and myoepithelial lineages in adult animals, and via lineage tracing with stable barcodes, we found that each mouse mammary gland is generated from a defined number of ∼120 early progenitor cells that expand uniformly with equal growth potential. We then designed an in vivo screen to test genetic interactions in breast cancer and identified candidates that drove not only tumor formation but also molecular subtypes. Thus, this methodology enables rapid and high-throughput cancer driver discovery in mammary epithelium.

The roles of ERAP1 and ERAP2 in autoimmunity and cancer immunity: New insights and perspective

Autoimmunity and cancer affect millions worldwide and both, in principal, result from dysregulated immune responses. There are many well-known molecules involved in immunological process playing as a double-edged sword, by which associating autoimmune diseases and cancer. In this regard, Endoplasmic reticulum aminopeptidases (ERAP) 1, which belongs to the M1 family of aminopeptidases, plays a central role as a "molecular ruler", proteolyzing of N-terminal of the antigenic peptides before their loading onto HLA-I molecules for antigen presentation in the Endoplasmic Reticulum (ER). Several genome-wide association studies (GWAS) highlighted the significance of ERAP1 and ERAP2 in autoimmune diseases, including Ankylosing spondylitis, Psoriasis, Bechet's disease, and Birdshot chorioretinopathy, as well as in cancers. The expression of ERAP1/2 is mostly altered in different cancers compared to normal cells, but how this affects anti-cancer immune responses and cancer growth has been little explored. Recent studies on the immunological outcomes and the catalytic functions of ERAP1 and ERAP2 have provided a better understanding of their potential pathogenetic role in autoimmunity and cancer. In this review, we summarize the role of ERAP1 and ERAP2 in the autoimmune diseases and cancer immunity based on the recent advances in GWAS studies.

Hedgehog signaling pathway inhibitors: an updated patent review (2015-present)

Introduction: Hedgehog (Hh) signaling plays a pivotal role in tissue development and stemness, and its deregulation is found in many different tumors. Several efforts have been devoted to discovery of Hh inhibitors, including three drugs approved by the Food and Drug Administration (FDA), targeting the upstream receptor smoothened (SMO). However, SMO mutations or SMO-independent Hh pathway activation raise the need for novel Hh inhibitors.Areas covered: This review describes Hh inhibitors with anticancer potential patented in the period 2015-present.Expert opinion: Despite the initial enthusiasm in SMO antagonists, drug-resistant mutations, and SMO-independent Hh activation limited their clinical application. A growing number of therapeutic strategies are currently focusing on downstream Hh effectors (i.e. glioma-associate oncogenes (GLI) proteins) or other signaling pathways related to Hh, in addition to drug repositioning. Given the heterogenic nature of cancers, a terrific clinical impact is expected by multi-targeting approaches able to modulate simultaneously SMO and GLI, and/or additional targets that act as regulators of Hh signaling. It is expected that these alternative strategies might be investigated in clinical trials in the next years against a wide variety of tumor types, and that they provide improved outcomes compared to current SMO antagonists or other single-agent anticancer drugs.

A Smo/Gli Multitarget Hedgehog Pathway Inhibitor Impairs Tumor Growth

Pharmacological Hedgehog (Hh) pathway inhibition has emerged as a valuable anticancer strategy. A number of small molecules able to block the pathway at the upstream receptor Smoothened (Smo) or the downstream effector glioma-associated oncogene 1 (Gli1) has been designed and developed. In a recent study, we exploited the high versatility of the natural isoflavone scaffold for targeting the Hh signaling pathway at multiple levels showing that the simultaneous targeting of Smo and Gli1 provided synergistic Hh pathway inhibition stronger than single administration. This approach seems to effectively overcome the drug resistance, particularly at the level of Smo. Here, we combined the pharmacophores targeting Smo and Gli1 into a single and individual isoflavone, compound 22, which inhibits the Hh pathway at both upstream and downstream level. We demonstrate that this multitarget agent suppresses medulloblastoma growth in vitro and in vivo through antagonism of Smo and Gli1, which is a novel mechanism of action in Hh inhibition.