NOTCH1 activation in breast cancer confers sensitivity to inhibition of SUMOylation

UBA2 SUMOylates NQO1 and promotes the proliferation of hepatocellular carcinoma by modulating the MAPK pathway

In our previous study, we found that small ubiquitin-related modifier (SUMO)-activating enzyme ubiquitin-associated-2 domain (UBA2) was upregulated in hepatocellular carcinoma (HCC) patients who were insensitive to chemoembolization. In this study, we aimed to investigate the role of UBA2 in HCC progression. Three cohorts were used to evaluate the efficacy of UBA2 as a prognostic factor for HCC. Our results indicated that UBA2 was associated with aggressive clinical behaviors and was a strong indicator of poor prognosis in HCC. In vitro experiments demonstrated that UBA2 accelerated cell growth, invasion, and migration. These results were further supported by in vivo experiments. RNA-sequencing analysis indicated NQO1 as a target of UBA2, with its levels altering following UBA2 manipulation. The results were verified by western blotting (WB) and quantitative PCR. The SUMOplot Analysis Program predicted lysine residue K240 as a modification target of UBA2, which was confirmed by immunoprecipitation (IP) assays. Subsequent mutation of NQO1 at K240 in HCC cell lines and functional assays revealed the significance of this modification. In addition, the oncogenic effect of UBA2 could be reversed by the SUMO inhibitor ML792 in vivo and in vitro. In conclusion, our study elucidated the regulatory mechanism of UBA2 in HCC and suggested that the SUMO inhibitor ML792 may be an effective combinatory treatment for patients with aberrant UBA2 expression.

SUMO2/3 promotes the progression and oxaliplatin resistance of colorectal cancer through facilitating the SUMOylation at Ku80-K307

Colorectal cancer (CRC) is one of the most prevalent cancers worldwide and is typically treated with the FOLFOX regimen (folinic acid, 5-fluorouracil, and oxaliplatin). However, oxaliplatin resistance remains a serious clinical problem. In the present study, we found that SUMO2/3 was overexpressed in CRC tissues and exogenous overexpression of SUMO2/3 promoted CRC cell proliferation, extension, and invasion and positively regulated the cell cycle. In contrast, SUMO2/3 gene knockdowns inhibited migration and repressed cell viability in vitro and in vivo. In addition, we found that SUMO2/3 was recruited to the cell nucleus and suppressed oxaliplatin-induced apoptosis of CRC cells. Moreover, Ku80, a DNA-binding protein essential for the repair of DNA double-strand breaks, was confirmed to bind with SUMO2/3. Notably, Ku80 undergoes SUMOylation at K307 by SUMO2/3 and this correlated with apoptosis in CRC cells suffering oxaliplatin stress. Collectively, we found that SUMO2/3 plays a specific role in CRC tumorigenesis and acts through Ku80 SUMOylation which is linked with the development of CRC-oxaliplatin resistance.

Lycorine inhibits pancreatic cancer cell growth and neovascularization by inducing Notch1 degradation and downregulating key vasculogenic genes

Pancreatic cancer is highly metastatic and lethal with an increasing incidence globally and a 5-year survival rate of only 8%. One of the factors contributing to the high mortality is the lack of effective drugs in the clinical setting. We speculated that effective compounds against pancreatic cancer exist in natural herbs and explored active small molecules among traditional Chinese medicinal herbs. The small molecule lycorine (MW: 323.77) derived from the herb Lycoris radiata inhibited pancreatic cancer cell growth with an IC50 value of 1 μM in a concentration-dependent manner. Lycorine markedly reduced pancreatic cancer cell viability, migration, invasion, neovascularization, and gemcitabine resistance. Additionally, lycorine effectively suppressed tumor growth in mouse xenograft models without obvious toxicity. Pharmacological studies revealed that the levels and half-life of Notch1 oncoprotein in the pancreatic cancer cells Panc-1 and Patu8988 were notably reduced. Moreover, the expression of the key vasculogenic genes Semaphorin 4D (Sema4D) and angiopoietin-2 (Ang-2) were also significantly inhibited by lycorine. Mechanistically, lycorine strongly triggered the degradation of Notch1 oncoprotein through the ubiquitin-proteasome system. In conclusion, lycorine effectively inhibits pancreatic cancer cell growth, migration, invasion, neovascularization, and gemcitabine resistance by inducing degradation of Notch1 oncoprotein and downregulating the key vasculogenic genes Sema4D and Ang-2. Our findings provide a new therapeutic candidate and treatment strategy against pancreatic cancer.

The era of high-quality chemical probes

Small-molecule chemical probes are among the most important tools to study the function of proteins in cells and organisms. Regrettably, the use of weak and non-selective small molecules has generated an abundance of erroneous conclusions in the scientific literature. More recently, minimal criteria have been outlined for investigational compounds, encouraging the selection and use of high-quality chemical probes. Here, we briefly recall the milestones and key initiatives that have paved the way to this new era, illustrate examples of recent high-quality chemical probes and provide our perspective on future challenges and developments.

Targeting pancreatic cancer by TAK-981: a SUMOylation inhibitor that activates the immune system and blocks cancer cell cycle progression in a preclinical model

OBJECTIVE

Pancreatic ductal adenocarcinoma (PDAC) has the characteristics of high-density desmoplastic stroma, a distinctive immunosuppressive microenvironment and is profoundly resistant to all forms of chemotherapy and immunotherapy, leading to a 5-year survival rate of 9%. Our study aims to add novel small molecule therapeutics for the treatment of PDAC.

DESIGN

We have studied whether TAK-981, a novel highly selective and potent small molecule inhibitor of the small ubiquitin like modifier (SUMO) activating enzyme E1 could be used to treat a preclinical syngeneic PDAC mouse model and we have studied the mode of action of TAK-981.

RESULTS

We found that SUMOylation, a reversible post-translational modification required for cell cycle progression, is increased in PDAC patient samples compared with normal pancreatic tissue. TAK-981 decreased SUMOylation in PDAC cells at the nanomolar range, thereby causing a G2/M cell cycle arrest, mitotic failure and chromosomal segregation defects. TAK-981 efficiently limited tumour burden in the KPC3 syngeneic mouse model without evidence of systemic toxicity. In vivo treatment with TAK-981 enhanced the proportions of activated CD8 T cells and natural killer (NK) cells but transiently decreased B cell numbers in tumour, peripheral blood, spleen and lymph nodes. Single cell RNA sequencing revealed activation of the interferon response on TAK-981 treatment in lymphocytes including T, B and NK cells. TAK-981 treatment of CD8 T cells ex vivo induced activation of STAT1 and interferon target genes.

CONCLUSION

Our findings indicate that pharmacological inhibition of the SUMO pathway represents a potential strategy to target PDAC via a dual mechanism: inhibiting cancer cell cycle progression and activating anti-tumour immunity by inducing interferon signalling.

SUMOylation Pattern Predicts Prognosis and Indicates Tumor Microenvironment Infiltration Characterization in Bladder Cancer

Background

SUMOylation is an important component of post-translational protein modifications (PTMs), and bladder cancer (BCa) is the ninth most common cancer around the world. But the comprehensive role of SUMOylation in shaping tumor microenvironment (TME) and influencing tumor clinicopathological features and also the prognosis of patients remains unclear.

Methods

Using the data downloaded from The Cancer Genome Atlas (TCGA) and the Gene Expression Omnibus (GEO), we comprehensively evaluated the SUMOylation patterns of 570 bladder cancer samples, and systematically correlated these SUMOylation patterns with TME immune cell infiltrating characteristics. The SUMO score was constructed to quantify SUMOylation patterns of individuals using principal component analysis (PCA) algorithms.

Results

Two distinct SUMOylation patterns and gene clusters were finally determined. Significant differences in the prognosis of patients were found among two different SUMOylation patterns and gene clusters, so were in the mRNA transcriptome and the landscape of TME immune cell infiltration. We also established a set of scoring system named SUMO score to quantify the SUMOylation pattern of individuals with BCa, which was discovered to be tightly connected with tumor clinicopathological characteristics and could predict the prognosis of patients with BCa. Moreover, SUMO score was a considerable predictive indicator for the survival outcome independent of tumor mutation burden (TMB) and low SUMO score was related to better response to immunotherapy using PD-1 blockade. We also found that there existed a significant relationship between sensitivity to commonly used chemotherapy drugs and SUMO score. Finally, a nomograph based on five features, namely, SUMO score, age, gender, T category, and M category was constructed to predict the survival probability of patients with BCa in 1, 3, and 5 years, respectively.

Conclusions

Our work demonstrated and overviewed the complicated regulation mechanisms of SUMOylation in bladder cancer, and better understanding and evaluating SUMOylation patterns could be helpful in guiding clinical therapeutic strategy and improving the prognosis of patients with BCa.

SUMOylation and NEDDylation in Primary and Metastatic Cancers to Bone

Post-translational modifications comprise series of enzymatically-driven chemical modifications, virtually involving the entire cell proteome, that affect the fate of a target protein and, in turn, cell activity. Different classes of modifications can be established ranging from phosphorylation, glycosylation, ubiquitination, acetylation, methylation, lipidation and their inverse reactions. Among these, SUMOylation and NEDDylation are ubiquitin-like multi-enzymatic processes that determine the bound of SUMOs and NEDD8 labels, respectively, on defined amino acidic residues of a specific protein and regulate protein function. As fate-determinants of several effectors and mediators, SUMOylation and NEDDylation play relevant roles in many aspects of tumor cell biology. Bone represents a preferential site of metastasis for solid tumors (e.g., breast and prostate cancers) and the primary site of primitive tumors (e.g., osteosarcoma, chondrosarcoma). Deregulation of SUMOylation and NEDDylation affects different aspects of neoplastic transformation and evolution such as epithelial-mesenchymal transition, adaptation to hypoxia, expression and action of tumor suppressors and oncogenic mediators, and drug resistance. Thereby, they represent potential therapeutic targets. This narrative review aims at describing the involvement and regulation of SUMOylation and NEDDylation in tumor biology, with a specific focus on primary and secondary bone tumors, and to summarize and highlight their potentiality in diagnostics and therapeutic strategies.

Osteopontin is required for the maintenance of leukemia stem cells in acute myeloid leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematopoietic disorder with a poor prognosis. The clinical significance of Leukemia stem cells (LSCs) plays an important role in the generation of AML and is the main cause of the recurrence after remission. Osteopontin (OPN), an extracellular matrix protein, has been implicated in hematopoietic malignancies. However, the specific role and the underlying mechanism of AML cell autocrined OPN in leukemia maintenance remain unknown. Here, we showed that knockdown of Opn expression significantly prolonged the survival of mice with MLL-AF9 cell-induced AML and markedly reduced the tumor burden. The LSCs from the Opn-knockdown groups exhibited decreased numbers and impaired function as determined by immunophenotype, colony-forming and limiting dilution assays. Further analysis revealed that Opn prevents LSCs from undergoing apoptosis and cell cycle arrest. Repression of OPN in human AML cell lines in vitro mimics the phenotypes observed in the mouse model. Overall, our data indicated that OPN is a potent therapeutic target for eradicating LSCs in AML.

Novel insights into the impact of the SUMOylation pathway in hematological malignancies (Review)

The small ubiquitin-like modifier (SUMO) system serves an important role in the regulation of protein stability and function. SUMOylation sustains the homeostatic equilibrium of protein function in normal tissues and numerous types of tumor. Accumulating evidence has revealed that SUMO enzymes participate in carcinogenesis via a series of complex cellular or extracellular processes. The present review outlines the physiological characteristics of the SUMOylation pathway and provides examples of SUMOylation participation in different cancer types, including in hematological malignancies (leukemia, lymphoma and myeloma). It has been indicated that the SUMO pathway may influence chromosomal instability, cell cycle progression, apoptosis and chemical drug resistance. The present review also discussed the possible relationship between SUMOylation and carcinogenic mechanisms, and evaluated their potential as biomarkers and therapeutic targets in the diagnosis and treatment of hematological malignancies. Developing and investigating inhibitors of SUMO conjugation in the future may offer promising potential as novel therapeutic strategies.

SLX4IP promotes RAP1 SUMOylation by PIAS1 to coordinate telomere maintenance through NF-κB and Notch signaling

The maintenance of telomere length supports repetitive cell division and therefore plays a central role in cancer development and progression. Telomeres are extended by either the enzyme telomerase or the alternative lengthening of telomeres (ALT) pathway. Here, we found that the telomere-associated protein SLX4IP dictates telomere proteome composition by recruiting and activating the E3 SUMO ligase PIAS1 to the SLX4 complex. PIAS1 SUMOylated the telomere-binding protein RAP1, which disrupted its interaction with the telomere-binding protein TRF2 and facilitated its nucleocytoplasmic shuttling. In the cytosol, RAP1 bound to IκB kinase (IKK), resulting in activation of the transcription factor NF-κB and its induction of Jagged-1 expression, which promoted Notch signaling and the institution of ALT. This axis could be targeted therapeutically in ALT-driven cancers and in tumor cells that develop resistance to antitelomerase therapies. Our results illuminate the mechanisms underlying SLX4IP-dependent telomere plasticity and demonstrate the role of telomere proteins in directly coordinating intracellular signaling and telomere maintenance dynamics.

Poly-SUMO-2/3 chain modification of Nuf2 facilitates CENP-E kinetochore localization and chromosome congression during mitosis

SUMO modification is required for the kinetochore localization of the kinesin-like motor protein CENP-E, which subsequently mediates the alignment of chromosomes to the spindle equator during mitosis. However, the underlying mechanisms by which sumoylation regulates CENP-E kinetochore localization are still unclear. In this study, we first elucidate that the kinetochore protein Nuf2 is not only required for CENP-E kinetochore localization but also preferentially modified by poly-SUMO-2/3 chains. In addition, poly-SUMO-2/3 modification of Nuf2 is significantly upregulated during mitosis, which is temporally correlated to the kinetochore localization of CENP-E during mitosis. We further show that the mitotic defects in CENP-E kinetochore localization and chromosome congression caused by global inhibition of sumoylation can be rescued by expressing a fusion protein between Nuf2 and the SUMO-conjugating enzyme Ubc9 for stimulating Nuf2 SUMO-2/3 modification. Moreover, the expression of another fusion protein between Nuf2 and three SUMO-2 moieties (SUMO-2 trimer), which mimics the trimeric SUMO-2/3 chain modification of Nuf2, can also rescue the mitotic defects due to global inhibition of sumoylation. Conversely, expressing the other forms of Nuf2-SUMO fusion proteins, which imitate Nuf2 modifications by SUMO-2/3 monomer, SUMO-2/3 dimer, and SUMO-1 trimer, respectively, cannot rescue the same mitotic defects. Lastly, compared to Nuf2, the fusion protein simulating the trimeric SUMO-2 chain-modified Nuf2 exhibits a significantly higher binding affinity to CENP-E wild type containing a functional SUMO-interacting motif (SIM) but not the CENP-E SIM mutant. Hence, our results support a model that poly-SUMO-2/3 chain modification of Nuf2 facilitates CENP-E kinetochore localization and chromosome congression during mitosis.Abbreviations: CENP-E, centromere-associated protein E; SUMO, small ubiquitin-related modifier; SIM, SUMO-interacting motif.

E1 Enzymes as Therapeutic Targets in Cancer

Post-translational modifications of cellular substrates with ubiquitin and ubiquitin-like proteins (UBLs), including ubiquitin, SUMOs, and neural precursor cell-expressed developmentally downregulated protein 8, play a central role in regulating many aspects of cell biology. The UBL conjugation cascade is initiated by a family of ATP-dependent enzymes termed E1 activating enzymes and executed by the downstream E2-conjugating enzymes and E3 ligases. Despite their druggability and their key position at the apex of the cascade, pharmacologic modulation of E1s with potent and selective drugs has remained elusive until 2009. Among the eight E1 enzymes identified so far, those initiating ubiquitylation (UBA1), SUMOylation (SAE), and neddylation (NAE) are the most characterized and are implicated in various aspects of cancer biology. To date, over 40 inhibitors have been reported to target UBA1, SAE, and NAE, including the NAE inhibitor pevonedistat, evaluated in more than 30 clinical trials. In this Review, we discuss E1 enzymes, the rationale for their therapeutic targeting in cancer, and their different inhibitors, with emphasis on the pharmacologic properties of adenosine sulfamates and their unique mechanism of action, termed substrate-assisted inhibition. Moreover, we highlight other less-characterized E1s-UBA6, UBA7, UBA4, UBA5, and autophagy-related protein 7-and the opportunities for targeting these enzymes in cancer. SIGNIFICANCE STATEMENT: The clinical successes of proteasome inhibitors in cancer therapy and the emerging resistance to these agents have prompted the exploration of other signaling nodes in the ubiquitin-proteasome system including E1 enzymes. Therefore, it is crucial to understand the biology of different E1 enzymes, their roles in cancer, and how to translate this knowledge into novel therapeutic strategies with potential implications in cancer treatment.

Transcriptome-wide analysis and modelling of prognostic alternative splicing signatures in invasive breast cancer: a prospective clinical study

Aberrant alternative splicing (AS) has been highly involved in the tumorigenesis and progression of most cancers. The potential role of AS in invasive breast cancer (IBC) remains largely unknown. In this study, RNA sequencing of IBC samples from The Cancer Genome Atlas was acquired. AS events were screened by conducting univariate and multivariate Cox analysis and least absolute shrinkage and selection operator regression. In total, 2146 survival-related AS events were identified from 1551 parental genes, of which 93 were related to prognosis, and a prognostic marker model containing 14 AS events was constructed. We also constructed the regulatory network of splicing factors (SFs) and AS events, and identified DDX39B as the node SF gene, and verified the accuracy of the network through experiments. Next, we performed quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) in triple negative breast cancer patients with different responses to neoadjuvant chemotherapy, and found that the exon-specific expression of EPHX2, C6orf141, and HERC4 was associated with the different status of patients that received neoadjuvant chemotherapy. In conclusion, this study found that DDX39B, EPHX2 (exo7), and HERC4 (exo23) can be used as potential targets for the treatment of breast cancer, which provides a new idea for the treatment of breast cancer.

Antitumor potential of dark sweet cherry sweet (Prunus avium) phenolics in suppressing xenograft tumor growth of MDA-MB-453 breast cancer cells

This study investigated in vivo the antitumor activity of dark sweet cherry (DSC) whole extracted phenolics (WE) and fractions enriched in anthocyanins (ACN) or proanthocyanidins (PCA) in athymic mice xenografted with MDA-MB-453 breast cancer cells. Mice were gavaged with WE, ACN or PCA extracts (150 mg/kg body weight/day) for 36 days. Results showed that tumor growth was suppressed at similar levels by WE, ACN and PCA compared to control group (C) without signs of toxicity or significant changes in mRNA oncogenic biomarkers in tumors or mRNA invasive biomarker in distant organs. Tumor protein analyses showed that WE, ACN and PCA induced at similar levels the stress-regulated ERK1/2 phosphorylation, known to be linked to apoptosis induction. However, ACN showed enhanced antitumor activity through down-regulation of total oncogenic and stress-related Akt, STAT3, p38, JNK and NF-kB proteins. In addition, immunohistochemistry analysis of Ki-67 revealed inhibition of tumor cell proliferation with potency WE ≥ ACN ≥ PCA. Differential quantitative proteomic high-resolution nano-HPLC tandem mass spectrometry analysis of tumors from ACN and C groups revealed the identity of 66 proteins associated with poor breast cancer prognosis that were expressed only in C group (61 proteins) or differentially up-regulated (P<.05) in C group (5 proteins). These findings revealed ACN-targeted proteins associated to tumor growth and invasion and the potential of DSC ACN for breast cancer treatment. Results lead to a follow-up study with highly immunodeficient mice/invasive cell line subtype and advanced tumor development to validate the anti-invasive activity of DSC anthocyanins.

The implication of the SUMOylation pathway in breast cancer pathogenesis and treatment

Breast cancer is the most commonly diagnosed malignancy in woman worldwide, and is the second most common cause of death in developed countries. The transformation of a normal cell into a malignant derivate requires the acquisition of diverse genomic and proteomic changes, including enzymatic post-translational modifications (PTMs) on key proteins encompassing critical cell signaling events. PTMs occur on proteins after translation, and regulate several aspects of proteins activity, including their localization, activation and turnover. Deregulation of PTMs can potentially lead to tumorigenesis, and several de-regulated PTM pathways contribute to abnormal cell proliferation during breast tumorigenesis. SUMOylation is a PTM that plays a pivotal role in numerous aspects of cell physiology, including cell cycle regulation, protein trafficking and turnover, and DNA damage repair. Consistently with this, the deregulation of the SUMO pathway is observed in different human pathologies, including breast cancer. In this review we will describe the role of SUMOylation in breast tumorigenesis and its implication for breast cancer therapy.

The SUMO Pathway in Hematomalignancies and Their Response to Therapies

SUMO (Small Ubiquitin-related MOdifier) is a post-translational modifier of the ubiquitin family controlling the function and fate of thousands of proteins. SUMOylation is deregulated in various hematological malignancies, where it participates in both tumorigenesis and cancer cell response to therapies. This is the case for Acute Promyelocytic Leukemias (APL) where SUMOylation, and subsequent destruction, of the PML-RARα fusion oncoprotein are triggered by arsenic trioxide, which is used as front-line therapy in combination with retinoic acid to cure APL patients. A similar arsenic-induced SUMO-dependent degradation was also documented for Tax, a human T-cell lymphotropic virus type I (HTLV1) viral protein implicated in Adult T-cell Leukemogenesis. SUMOylation also participates in Acute Myeloid Leukemia (AML) response to both chemo- and differentiation therapies, in particular through its ability to regulate gene expression. In Multiple Myeloma, many enzymes of the SUMO pathway are overexpressed and their high expression correlates with lower response to melphalan-based chemotherapies. B-cell lymphomas overexpressing the c-Myc oncogene also overexpress most components of the SUMO pathway and are highly sensitive to SUMOylation inhibition. Targeting the SUMO pathway with recently discovered pharmacological inhibitors, alone or in combination with current therapies, might therefore constitute a powerful strategy to improve the treatment of these cancers.

Additive Pharmacological Interaction between Cisplatin (CDDP) and Histone Deacetylase Inhibitors (HDIs) in MDA-MB-231 Triple Negative Breast Cancer (TNBC) Cells with Altered Notch1 Activity-An Isobolographic Analysis

The aim of this study was to investigate the influence of the Notch1 activity level on the pharmacological interaction between cisplatin (CDDP) and two histone deacetylase inhibitors (HDIs)-valproic acid (VPA) and vorinostat (SAHA) in the triple negative breast cancer (TNBC) cells. Stable breast cancer (BC) cell lines with increased and decreased activity of Notch1 were generated using a transfection method. The type of interaction between CDDP and the HDIs was determined by isobolographic analysis of cell proliferation in MDA-MB-231 cells with differential levels of Notch1 activity in vitro. The combination of CDDP/SAHA and CDDP/VPA in the MDA-MB-231 triple negative breast cancer (TNBC) cells with increased activity of Notch1, as well as CDDP/VPA in the MDA-MB-231 cells with decreased activity of Notch1, yielded an additive interaction, whereas additivity with a tendency towards antagonism was observed for the combination of CDDP/SAHA in MDA-MB-231 cells with the decreased activity of Notch1. Our studies demonstrated that SAHA and VPA might be considered as potential therapeutic agents in combination therapy with CDDP against TNBC with altered Notch1 activity.

Decoding the PTM-switchboard of Notch

The developmentally indispensable Notch pathway exhibits a high grade of pleiotropism in its biological output. Emerging evidence supports the notion of post-translational modifications (PTMs) as a modus operandi controlling dynamic fine-tuning of Notch activity. Although, the intricacy of Notch post-translational regulation, as well as how these modifications lead to multiples of divergent Notch phenotypes is still largely unknown, numerous studies show a correlation between the site of modification and the output. These include glycosylation of the extracellular domain of Notch modulating ligand binding, and phosphorylation of the PEST domain controlling half-life of the intracellular domain of Notch. Furthermore, several reports show that multiple PTMs can act in concert, or compete for the same sites to drive opposite outputs. However, further investigation of the complex PTM crosstalk is required for a complete understanding of the PTM-mediated Notch switchboard. In this review, we aim to provide a consistent and up-to-date summary of the currently known PTMs acting on the Notch signaling pathway, their functions in different contexts, as well as explore their implications in physiology and disease. Furthermore, we give an overview of the present state of PTM research methodology, and allude to a future with PTM-targeted Notch therapeutics.

2-D08 as a SUMOylation inhibitor induced ROS accumulation mediates apoptosis of acute myeloid leukemia cells possibly through the deSUMOylation of NOX2

Acute myeloid leukemia (AML) is a heterogeneous clonal hematopoietic malignancy with poor survival and frequent relapse. Recently, a posttranslational modification of proteins with small ubiquitin-like modifiers (SUMO) has been notably implicated in a wide spectrum of diseases, especially cancers. Ubc9, as the sole E2-conjugating enzyme in SUMOylation cascade, particularly has been associated with adverse clinical outcomes. 2-D08, a small molecular agent, functions by blocking the transfer of SUMO from the Ubc9 thioester to SUMO substrates without any effects on other individual steps in this process. However, both the effects and mechanisms of 2-D08 on AML cells are still unknown. In this study, we found that 2-D08 significantly suppressed cell viability and colony formation ability. Additionally, it induced mitochondrial-mediated apoptosis with dramatic accumulation of the reactive oxygen species (ROS), which could be almost completely rescued by the ROS scavenger N-acetylcysteine (NAC). Furthermore, we confirmed that the fatal accumulation of ROS was due to its aberrant generation instead of defective scavenging. In summary, our results suggest that 2-D08, as a specific SUMOylation inhibitor, induces ROS accumulation-mediated intrinsic apoptosis of AML cells possibly through deSUMOylation of NOX2. Therefore, 2-D08 might be a promising therapeutic agent for the treatment of AML in the future.

The deSUMOylase SENP2 coordinates homologous recombination and nonhomologous end joining by independent mechanisms

SUMOylation (small ubiquitin-like modifier) in the DNA double-strand break (DSB) response regulates recruitment, activity, and clearance of repair factors. However, our understanding of a role for deSUMOylation in this process is limited. Here we identify different mechanistic roles for deSUMOylation in homologous recombination (HR) and nonhomologous end joining (NHEJ) through the investigation of the deSUMOylase SENP2. We found that regulated deSUMOylation of MDC1 prevents excessive SUMOylation and its RNF4-VCP mediated clearance from DSBs, thereby promoting NHEJ. In contrast, we show that HR is differentially sensitive to SUMO availability and SENP2 activity is needed to provide SUMO. SENP2 is amplified as part of the chromosome 3q amplification in many cancers. Increased SENP2 expression prolongs MDC1 focus retention and increases NHEJ and radioresistance. Collectively, our data reveal that deSUMOylation differentially primes cells for responding to DSBs and demonstrates the ability of SENP2 to tune DSB repair responses.

Altered Expression Patterns of the Sumoylation Enzymes E1, E2 and E3 Are Associated with Glucose Oxidase- and UVA-Induced Cataractogenesis

PURPOSE

Protein sumoylation is a well established regulatory mechanism that regulates chromatin structure and dynamics, cell proliferation and differentiation, stress response and cell apoptosis. In the vertebrate eye, we and others have shown that sumoylation plays an indispensable role in regulating eye development. During stress induction and aging process, the ocular tissues gradually loss their normality and develop major ocular diseases such as cataract and aging-related macular degeneration. We have recently demonstrated that sumoylation actively regulates differentiation of lens cells, whether this process is implicated in lens pathogenesis remains to be investigated. In this study, we have demonstrated that transparent mouse lenses treated with glucose oxidase and UVA irradiation undergo in vitro cataract formation, and associated with this process, the expression patterns of the 3 sumoylation enzymes have been found significantly altered.

METHODS

Four-week-old C57BL/6J mice were used in our experiment. Lenses were carefully excised from eyes and cultured in M199 medium (Sigma 3769) for at least 12 hours. Transparent lenses (without surgical damage) were selected for experimentation. The lenses were exposed to UVA for 60 min or treated with 30 mU/mL glucose oxidase (GO, MP Biomedicals, 1673) to induce cataract formation. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J.

RESULTS

we have obtained the following results: 1) Both GO treatment and UVA irradiation can induce cataract formation in the in vitro cultured mouse lenses; 2) With GO treatment, the mRNAs and proteins for the 5 sumoylation enzymes were all significantly downregulated; 3) With UVA irradiation, the changes in the expression patterns of the mRNAs and proteins for the SAE1, UBA2 , UBC9 and PIAS1 were opposite, while the mRNAs were upregulated either significantly (for SAE1, UBA2 and UBC9) or slightly (PIAS1), the proteins for all 4 sumoylation enzymes were downregulated; For RanBP2, the UVA induced changes in both mRNA and protein are consist with the GO treatment.

CONCLUSION

Under GO and UVA irradiation conditions, the expression levels of both mRNA and protein for the three major sumoylation enzymes were significantly changed. Our results suggest that altered expression patterns of the sumoylation enzymes are associated with oxidative stressinduced cataractogenesis.

Developing Practical Therapeutic Strategies that Target Protein SUMOylation

Post-translational modification by small ubiquitin-like modifier (SUMO) has emerged as a global mechanism for the control and integration of a wide variety of biological processes through the regulation of protein activity, stability and intracellular localization. As SUMOylation is examined in greater detail, it has become clear that the process is at the root of several pathologies including heart, endocrine, and inflammatory disease, and various types of cancer. Moreover, it is certain that perturbation of this process, either globally or of a specific protein, accounts for many instances of congenital birth defects. In order to be successful, practical strategies to ameliorate conditions due to disruptions in this post-translational modification will need to consider the multiple components of the SUMOylation machinery and the extraordinary number of proteins that undergo this modification.

Moving Breast Cancer Therapy up a Notch

Breast cancer is the second most common malignancy, worldwide. Treatment decisions are based on tumor stage, histological subtype, and receptor expression and include combinations of surgery, radiotherapy, and systemic treatment. These, together with earlier diagnosis, have resulted in increased survival. However, initial treatment efficacy cannot be guaranteed upfront, and these treatments may come with (long-term) serious adverse effects, negatively affecting a patient's quality of life. Gene expression-based tests can accurately estimate the risk of recurrence in early stage breast cancers. Disease recurrence correlates with treatment resistance, creating a major need to resensitize tumors to treatment. Notch signaling is frequently deregulated in cancer and is involved in treatment resistance. Preclinical research has already identified many combinatory therapeutic options where Notch involvement enhances the effectiveness of radiotherapy, chemotherapy or targeted therapies for breast cancer. However, the benefit of targeting Notch has remained clinically inconclusive. In this review, we summarize the current knowledge on targeting the Notch pathway to enhance current treatments for breast cancer and to combat treatment resistance. Furthermore, we propose mechanisms to further exploit Notch-based therapeutics in the treatment of breast cancer.

The significance of SUMOylation of angiogenic factors in cancer progression

Angiogenesis is the process of endothelial cell migration and proliferation induced by angiogenic factors, which is essential for the development of tumors. In recent years, studies have reported that SUMOylation acts on tumor angiogenesis by targeting angiogenic factors as one of post-translational modifications of proteins. Anti-angiogenic therapy is a new treatment method for tumor treatment following radiotherapy and chemotherapy, and it inhibits tumor growth by blocking tumor blood vessels. Therefore, SUMOylation may become a potential target for anti-angiogenesis therapy. This article focuses on the effect of SUMOylation on vascular growth factors, important signaling pathways proteins, and the migration and function of endothelial cells, in order to provide a new research idea for the anti-angiogenic therapy of tumors.

NICD-mediated notch transduction regulates the different fate of chicken primordial germ cells and spermatogonial stem cells

Background

Notch signaling is mainly regulated by Notch1 during development of chicken germ stem cells; however, the molecular mechanisms that contribute to generation of these germ stem cells have not been thoroughly investigated.

Results

In our studies, Overexpression of the Notch1 NICD promoted development of the reproductive ridge, but inhibited the formation of seminiferous tubules. The formation efficiency of PGCs in the reproductive ridge following overexpression of NICD (7.5% ± 0.11) was significantly higher than that (4.9% ± 0.17, p < 0.05) following inhibition of NICD, While the formation efficiency of spermatogonial stem cells (SSCs) in the testes (12.7% ± 0.08) was significantly lower after NICD overexpression than that after inhibition of NICD (16.3% ± 0.16, p < 0.05). Using co-immunoprecipitation, we found that this anomaly stemmed from the reversal of dissociation of the Notch-regulated transcription factor CBF-1/RBP co-suppression complex during the differentiation of PGCs into SSCs. This dissociation of the CBF-1/RBP co-suppressing complex during the differentiation of ESCs into PGCs resulted in the release of HDAC1 and HDAC2 and the recruitment of mastermind-like 1 to form a coactive complex to promote the expression of the downstream transcription suppressor hairy/enhancer of split-1. Dynamic expression of transducin-like enhancer of split 3, TLE4, and C-terminal binding protein 2 during further differentiation of PGCs inhibited the dissociation of the CBF-1/RBP co-suppression complex and inhibited the expression of the downstream genes.

Conclusions

In summary, Notch signaling plays diametrically opposing roles during normal development of chicken PGCs and SSCs, and these functions was determined by the expression of NICD, changes in the CBF-1/RBP complex composition, and histone modification.

Heterozygous IDH1R132H/WT created by "single base editing" inhibits human astroglial cell growth by downregulating YAP

Mutations in the isocitrate dehydrogenase 1 (IDH1) gene have been identified in a number of cancer types, including brain cancer. The Cancer Genome Atlas project has revealed that IDH1 mutations occur in 70-80% of grade II and grade III gliomas. Until recently, most of the functional studies of IDH1 mutations in cellular models have been conducted in overexpression systems with the IDH1 wild type background. In this study, we employed a modified CRISPR/Cas9 genome editing technique called "single base editing", and efficiently introduced heterozygous IDH1 R132H mutation (IDH1^R132H/WT) in human astroglial cells. Global DNA methylation profiling revealed hypermethylation as well as hypomethylation induced by IDH1^R132H/WT. Global gene expression analysis identified molecular targets and pathways altered by IDH1^R132H/WT, including cell proliferation, extracellular matrix (ECM), and cell migration. Our phenotype analysis indicated that compared with IDH1 wild type cells, IDH1^R132H/WT promoted cell migration by upregulating integrin β4 (ITGB4); and significantly inhibited cell proliferation. Using our mutated IDH1 models generated by "single base editing", we identified novel molecular targets of IDH1^R132H/WT, namely Yes-associated protein (YAP) and its downstream signaling pathway Notch, to mediate the cell growth-inhibiting effect of IDH1^R132H/WT. In summary, the "single base editing" strategy has successfully created heterozygous IDH1 R132H mutation that recapitulates the naturally occurring IDH1 mutation. Our isogenic cellular systems that differ in a single nucleotide in one allele of the IDH1 gene provide a valuable model for novel discoveries of IDH1^R132H/WT-driven biological events.

Sumoylation of Notch1 represses its target gene expression during cell stress

The Notch signaling pathway is a key regulator of stem cells during development, and its deregulated activity is linked to developmental defects and cancer. Transcriptional activation of Notch target genes requires cleavage of the Notch receptor in response to ligand binding, production of the Notch intracellular domain (NICD1), NICD1 migration into the nucleus, and assembly of a transcriptional complex. Post-translational modifications of Notch regulate its trafficking, turnover, and transcriptional activity. Here, we show that NICD1 is modified by small ubiquitin-like modifier (SUMO) in a stress-inducible manner. Sumoylation occurs in the nucleus where NICD1 is sumoylated in the RBPJ-associated molecule (RAM) domain. Although stress and sumoylation enhance nuclear localization of NICD1, its transcriptional activity is attenuated. Molecular modeling indicates that sumoylation can occur within the DNA-bound ternary transcriptional complex, consisting of NICD1, the transcription factor Suppressor of Hairless (CSL), and the co-activator Mastermind-like (MAML) without its disruption. Mechanistically, sumoylation of NICD1 facilitates the recruitment of histone deacetylase 4 (HDAC4) to the Notch transcriptional complex to suppress Notch target gene expression. Stress-induced sumoylation decreases the NICD1-mediated induction of Notch target genes, which was abrogated by expressing a sumoylation-defected mutant in cells and in the developing central nervous system of the chick in vivo. Our findings of the stress-inducible sumoylation of NICD1 reveal a novel context-dependent regulatory mechanism of Notch target gene expression.

CBX4 exhibits oncogenic activities in breast cancer via Notch1 signaling

Polycomb chromobox (CBX) proteins are involved in gene silencing to function as oncogenes or tumor suppressors through the polycomb repressive complex (PRC1). CBX4 has been implicated in the progression of human cancers, but its role and clinical significance in breast cancer remain unclear. Here, we show that CBX4 is up-regulated in breast cancer and exerts oncogenic activities via miR-137-mediated activation of Notch1 signaling pathway. CBX4 expression was increased in breast cancer, compared with the nontumorous tissues. High CBX4 expression was closely correlated with tumor metastasis, advanced clinical stage and poor overall survival in a cohort of 179 patients with breast cancer. In vitro studies demonstrated that CBX4 overexpression enhanced, whereas CBX4 knockdown inhibited cell growth and migration. Mechanistically, in a PRC1-dependent manner, CBX4 inhibited the promoter activity of miR-137 and suppressed its expression. miR-137 decreased the expression of Notch1, Jag1 and Hey2 via targeting their 3'-UTRs. The suppression of Notch1 by siRNA or overexpression of miR-137 markedly attenuated CBX4-promoted phenotypes. Collectively, these findings indicate that CBX4 promotes breast cancer via miR-137-mediated Notch1 signaling. Our data, therefore, suggest that CBX4 serve as a prognostic biomarker and that targeting CBX4/miR-137 axis may provide therapeutic potent in the treatment of breast cancer.

Mesenchymal Stem Cell Migration and Proliferation Are Mediated by Hypoxia-Inducible Factor-1α Upstream of Notch and SUMO Pathways

Mesenchymal stem cells (MSCs) are effective in treating several pathologies. We and others have demonstrated that hypoxia or hypoxia-inducible factor 1 alpha (HIF-1α) stabilization improves several MSC functions, including cell adhesion, migration, and proliferation, thereby increasing their therapeutic potential. To further explore the mechanisms induced by HIF-1α in MSCs, we studied its relationship with Notch signaling and observed that overexpression of HIF-1α in MSCs increased protein levels of the Notch ligands Jagged 1-2 and Delta-like (Dll)1, Dll3, and Dll4 and potentiated Notch signaling only when this pathway was activated. Crosstalk between HIF and Notch resulted in Notch-dependent migration and spreading of MSCs, which was abolished by γ-secretase inhibition. However, the HIF-1-induced increase in MSC proliferation was independent of Notch signaling. The ubiquitin family member, small ubiquitin-like modifier (SUMO), has important functions in many cellular processes and increased SUMO1 protein levels have been reported in hypoxia. To investigate the potential involvement of SUMOylation in HIF/Notch crosstalk, we measured general SUMOylation levels and observed increased SUMOylation in HIF-1-expressing MSCs. Moreover, proliferation and migration of MSCs were reduced in the presence of a SUMOylation inhibitor, and this effect was particularly robust in HIF-MSCs. Immunoprecipitation studies demonstrated SUMOylation of the intracellular domain of Notch1 (N1ICD) in HIF-1-expressing MSCs, which contributed to Notch pathway activation and resulted in increased levels of N1ICD nuclear translocation as assessed by subcellular fractionation. SUMOylation of N1ICD was also observed in HEK293T cells with stabilized HIF-1α expression, suggesting that this is a common mechanism in eukaryotic cells. In summary, we describe, for the first time, SUMOylation of N1ICD, which is potentiated by HIF signaling. These phenomena could be relevant for the therapeutic effects of MSCs in hypoxia or under conditions of HIF stabilization.

SUMO and the robustness of cancer

Post-translational protein modification by small ubiquitin-like modifier (SUMO), termed sumoylation, is an important mechanism in cellular responses to stress and one that appears to be upregulated in many cancers. Here, we examine the role of sumoylation in tumorigenesis as a possibly necessary safeguard that protects the stability and functionality of otherwise easily misregulated gene expression programmes and signalling pathways of cancer cells.

Missense variant in UBA2 associated with aplasia cutis congenita, duane anomaly, hip dysplasia and other anomalies: A possible new disorder involving the SUMOylation pathway

We report a patient with aplasia cutis congenita, Duane anomaly, hip dysplasia, and other anomalies who had a de novo missense variant in UBA2, which encodes for a protein involved in the SUMOylation pathway. It has previously been suggested that UBA2 haploinsufficiency underlies scalp defects in the 19q13.11 deletion syndrome. We propose that disturbance of the SUMOylation pathway, mediated by pathogenic variants in UBA2, is a novel mechanism for aplasia cutis congenita and other phenotypic abnormalities. © 2017 Wiley Periodicals, Inc.

SUMOylation-Mediated Regulation of Cell Cycle Progression and Cancer

Protein conjugation with Small ubiquitin-like modifier (SUMOylation) has critical roles during cell cycle progression. Many important cell cycle regulators, including many oncogenes and tumor suppressors, are functionally regulated via SUMOylation. The dynamic SUMOylation pattern observed throughout the cell cycle is ensured via distinct spatial and temporal regulation of the SUMO machinery. Additionally, SUMOylation cooperates with other post-translational modifications to mediate cell cycle progression. Deregulation of these SUMOylation and deSUMOylation enzymes causes severe defects in cell proliferation and genome stability. Different types of cancer were recently shown to be dependent on a functioning SUMOylation system, a finding that could be exploited in anticancer therapies.

Roles of ubiquitination and SUMOylation on prostate cancer: mechanisms and clinical implications

The initiation and progression of human prostate cancer are highly associated with aberrant dysregulations of tumor suppressors and proto-oncogenes. Despite that deletions and mutations of tumor suppressors and aberrant elevations of oncogenes at the genetic level are reported to cause cancers, emerging evidence has revealed that cancer progression is largely regulated by posttranslational modifications (PTMs) and epigenetic alterations. PTMs play critical roles in gene regulation, cellular functions, tissue development, diseases, malignant progression and drug resistance. Recent discoveries demonstrate that ubiquitination and SUMOylation are complicated but highly-regulated PTMs, and make essential contributions to diseases and cancers by regulation of key factors and signaling pathways. Ubiquitination and SUMOylation pathways can be differentially modulated under various stimuli or stresses in order to produce the sustained oncogenic potentials. In this review, we discuss some new insights about molecular mechanisms on ubiquitination and SUMOylation, their associations with diseases, oncogenic impact on prostate cancer (PCa) and clinical implications for PCa treatment.