SUMOylation in carcinogenesis

PIAS family in cancer: from basic mechanisms to clinical applications

Protein inhibitors of activated STATs (PIAS) are proteins for cytokine signaling that activate activator-mediated gene transcription. These proteins, as versatile cellular regulators, have been described as regulators of approximately 60 proteins. Dysregulation of PIAS is associated with inappropriate gene expression that promotes oncogenic signaling in multiple cancers. Multiple lines of evidence have revealed that PIAS family members show modulated expressions in cancer cells. Most frequently reported PIAS family members in cancer development are PIAS1 and PIAS3. SUMOylation as post-translational modifier regulates several cellular machineries. PIAS proteins as SUMO E3 ligase factor promotes SUMOylation of transcription factors tangled cancer cells for survival, proliferation, and differentiation. Attenuated PIAS-mediated SUMOylation mechanism is involved in tumorigenesis. This review article provides the PIAS/SUMO role in the modulation of transcriptional factor control, provides brief update on their antagonistic function in different cancer types with particular focus on PIAS proteins as a bonafide therapeutic target to inhibit STAT pathway in cancers, and summarizes natural activators that may have the ability to cure cancer.

From the regulatory mechanism of TFEB to its therapeutic implications

Transcription factor EB (TFEB), known as a major transcriptional regulator of the autophagy-lysosomal pathway, regulates target gene expression by binding to coordinated lysosomal expression and regulation (CLEAR) elements. TFEB are regulated by multiple links, such as transcriptional regulation, post-transcriptional regulation, translational-level regulation, post-translational modification (PTM), and nuclear competitive regulation. Targeted regulation of TFEB has been victoriously used as a treatment strategy in several disease models such as ischemic injury, lysosomal storage disorders (LSDs), cancer, metabolic disorders, neurodegenerative diseases, and inflammation. In this review, we aimed to elucidate the regulatory mechanism of TFEB and its applications in several disease models by targeting the regulation of TFEB as a treatment strategy.

ROS-mediated up-regulation of SAE1 by Helicobacter pylori promotes human gastric tumor genesis and progression

Helicobacter pylori (H. pylori) is a major risk factor of gastric cancer (GC). The SUMO-activating enzyme SAE1(SUMO-activating enzyme subunit 1), which is indispensable for protein SUMOylation, involves in human tumorigenesis. In this study, we used the TIMER and TCGA database to explore the SAE1 expression in GC and normal tissues and Kaplan-Meier Plotter platform for survival analysis of GC patients. GC tissue microarray and gastric samples from patients who underwent endoscopic treatment were employed to detect the SAE1expression. Our results showed that SAE1 was overexpressed in GC tissues and higher SAE1 expression was associated with worse clinical characteristics of GC patients. Cell and animal models showed that H. pylori infection upregulated SAE1, SUMO1, and SUMO2/3 protein expression. Functional assays suggested that suppression of SAE1 attenuated epithelial-mesenchymal transition (EMT) biomarkers and cell proliferation abilities induced by H. pylori. Cell and animal models of ROS inhibition in H. pylori showed that ROS could mediate the H. pylori-induced upregulation of SAE1, SUMO1, and SUMO2/3 protein. RNA sequencing was performed and suggested that knockdown of SAE1 could exert an impact on IGF-1 expression. General, increased SUMOylation modification is involved in H. pylori-induced GC.

Profile analysis of N4-acetylcytidine (ac4C) on mRNA of human lung adenocarcinoma and paired adjacent non-tumor tissues

BACKGROUND

RNA modification, a major component of post-transcriptional modification, plays an essential role in tumor initiation and progression. N4-acetylcytidine (ac4C) present in different species as a highly conserved RNA modification. ac4C on mRNA increases the stability of mRNA and the efficiency of protein translation. However, the mRNA profiling of ac4C in lung adenocarcinoma (LUAD) is unknown.

METHODS

NAT10 expression was tested using immunohistochemistry in tissue microarray (TMA). The ac4C peaks on mRNA were identified through acetylated RNA immunoprecipitation sequencing in both human LUAD tissues and adjacent non-tumor tissues, and differences of acetylation and mRNA between the two groups were analyzed. Furthermore, the function of AC4C-specific acetylated transcripts was analyzed bioinformatically. And a ac-RIP-PCR was used to verify the ac4C acetylation sites of TFAP2A.

RESULTS

The expression of acetylated key enzyme NAT10 was obviously increased in LUAD group. Then we found noticeable differences in ac4C mRNA modification between LUAD and adjacent non-tumor tissues. In addition, bioinformatics analysis showed that the distinctive distribution pattern of mRNA ac4C in LUAD affects a variety of cellular functions, such as protein sumoylation and transmembrane transporter activity. Importantly, we verified the ac4C level of TFAP2A was up-regulated in LUAD.

CONCLUSIONS

Our study revealed that the degree of ac4C in mRNA in LUAD was significantly higher than in adjacent tissues and was concentrated mainly in the coding sequences with a implications in a wide range of cellular functions. The ac4C may become a new molecular marker and treatment target for lung cancer.

Enhancing Sumoylation Site Prediction: A Deep Neural Network with Discriminative Features

Sumoylation is a post-translation modification (PTM) mechanism that involves many critical biological processes, such as gene expression, localizing and stabilizing proteins, and replicating the genome. Moreover, sumoylation sites are associated with different diseases, including Parkinson's and Alzheimer's. Due to its vital role in the biological process, identifying sumoylation sites in proteins is significant for monitoring protein functions and discovering multiple diseases. Therefore, in the literature, several computational models utilizing conventional ML methods have been introduced to classify sumoylation sites. However, these models cannot accurately classify the sumoylation sites due to intrinsic limitations associated with the conventional learning methods. This paper proposes a robust computational model (called Deep-Sumo) for predicting sumoylation sites based on a deep-learning algorithm with efficient feature representation methods. The proposed model employs a half-sphere exposure method to represent protein sequences in a feature vector. Principal Component Analysis is applied to extract discriminative features by eliminating noisy and redundant features. The discriminant features are given to a multilayer Deep Neural Network (DNN) model to predict sumoylation sites accurately. The performance of the proposed model is extensively evaluated using a 10-fold cross-validation test by considering various statistical-based performance measurement metrics. Initially, the proposed DNN is compared with the traditional learning algorithm, and subsequently, the performance of the Deep-Sumo is compared with the existing models. The validation results show that the proposed model reports an average accuracy of 96.47%, with improvement compared with the existing models. It is anticipated that the proposed model can be used as an effective tool for drug discovery and the diagnosis of multiple diseases.

SUMOylation indirectly suppresses activity of the HIF-1α pathway in intestinal epithelial cells

The hypoxia-inducible factor (HIF) is a master regulator of the cellular transcriptional response to hypoxia. While the oxygen-sensitive regulation of HIF-1α subunit stability via the ubiquitin-proteasome pathway has been well described, less is known about how other oxygen-independent post-translational modifications impact the HIF pathway. SUMOylation, the attachment of SUMO (small ubiquitin-like modifier) proteins to a target protein, regulates the HIF pathway, although the impact of SUMO on HIF activity remains controversial. Here, we examined the effects of SUMOylation on the expression pattern of HIF-1α in response to pan-hydroxylase inhibitor dimethyloxalylglycine (DMOG) in intestinal epithelial cells. We evaluated the effects of SUMO-1, SUMO-2, and SUMO-3 overexpression and inhibition of SUMOylation using a novel selective inhibitor of the SUMO pathway, TAK-981, on the sensitivity of HIF-1α in Caco-2 intestinal epithelial cells. Our findings demonstrate that treatment with TAK-981 decreases global SUMO-1 and SUMO-2/3 modification and enhances HIF-1α protein levels, whereas SUMO-1 and SUMO-2/3 overexpression results in decreased HIF-1α protein levels in response to DMOG. Reporter assay analysis demonstrates reduced HIF-1α transcriptional activity in cells overexpressing SUMO-1 and SUMO-2/3, whereas pretreatment with TAK-981 increased HIF-1α transcriptional activity in response to DMOG. In addition, HIF-1α nuclear accumulation was decreased in cells overexpressing SUMO-1. Importantly, we showed that HIF-1α is not directly SUMOylated, but that SUMOylation affects HIF-1α stability and activity indirectly. Taken together, our results indicate that SUMOylation indirectly suppresses HIF-1α protein stability, transcriptional activity, and nuclear accumulation in intestinal epithelial cells.

PIAS1 impedes vascular endothelial injury and atherosclerotic plaque formation in diabetes by blocking the RUNX3/TSP-1 axis

The protein PIAS1 functions as a type of ubiquitin-protease, which is known to play an important regulatory role in various diseases, including cardiovascular diseases and cancers. Its mechanism of action primarily revolves around regulating the transcription, translation, and modification of target proteins. This study investigates role and mechanism of PIAS1 in the RUNX3/TSP-1 axis and confirms its therapeutic effects on diabetes-related complications in animal models. A diabetic vascular injury was induced in human umbilical vein endothelial cells (HUVECs) by stimulation with H2O2 and advanced glycation end product (AGE), and a streptozotocin (STZ)-induced mouse model of diabetes was constructed, followed by detection of endogenous PIAS1 expression and SUMOylation level of RUNX3. Effects of PIAS1 concerning RUNX3 and TSP-1 on the HUVEC apoptosis and inflammation were evaluated using the ectopic expression experiments. Down-regulated PIAS1 expression and SUMOylation level of RUNX3 were identified in the H2O2- and AGE-induced HUVEC model of diabetic vascular injury and STZ-induced mouse models of diabetes. PIAS1 promoted the SUMOylation of RUNX3 at the K148 site of RUNX3. PIAS1-mediated SUMOylation of RUNX3 reduced RUNX3 transactivation activity, weakened the binding of RUNX3 to the promoter region of TSP-1, and caused downregulation of TSP-1 expression. PIASI decreased the expression of TSP-1 by inhibiting H2O2- and AGE-induced RUNX3 de-SUMOylation, thereby arresting the inflammatory response and apoptosis of HUVECs. Besides, PIAS1 reduced vascular endothelial injury and atherosclerotic plaque formation in mouse models of diabetes by inhibiting the RUNX3/TSP-1 axis. Our study proved that PIAS1 suppressed vascular endothelial injury and atherosclerotic plaque formation in mouse models of diabetes via the RUNX3/TSP-1 axis.

Deletion of protein tyrosine phosphatase SHP-1 restores SUMOylation of podocin and reverses the progression of diabetic kidney disease

Both clinical and experimental data suggest that podocyte injury is involved in the onset and progression of diabetic kidney disease (DKD). Although the mechanisms underlying the development of podocyte loss are not completely understood, critical structural proteins such as podocin play a major role in podocyte survival and function. We have reported that the protein tyrosine phosphatase SHP-1 expression increased in podocytes of diabetic mice and glomeruli of patients with diabetes. However, the in vivo contribution of SHP-1 in podocytes is unknown. Conditional podocyte-specific SHP-1-deficient mice (Podo-SHP-1-/-) were generated to evaluate the impact of SHP-1 deletion at four weeks of age (early) prior to the onset of diabetes and after 20 weeks (late) of diabetes (DM; Ins2+/C96Y) on kidney function (albuminuria and glomerular filtration rate) and kidney pathology. Ablation of the SHP-1 gene specifically in podocytes prevented and even reversed the elevated albumin/creatinine ratio, glomerular filtration rate progression, mesangial cell expansion, glomerular hypertrophy, glomerular basement membrane thickening and podocyte foot process effacement induced by diabetes. Moreover, podocyte-specific deletion of SHP-1 at an early and late stage prevented diabetes-induced expression of collagen IV, fibronectin, transforming growth factor-β, transforming protein RhoA, and serine/threonine kinase ROCK1, whereas it restored nephrin, podocin and cation channel TRPC6 expression. Mass spectrometry analysis revealed that SHP-1 reduced SUMO2 post-translational modification of podocin while podocyte-specific deletion of SHP-1 preserved slit diaphragm protein complexes in the diabetic context. Thus, our data uncovered a new role of SHP-1 in the regulation of cytoskeleton dynamics and slit diaphragm protein expression/stability, and its inhibition preserved podocyte function preventing DKD progression.

Circ-RAPGEF5 promotes intrahepatic cholangiocarcinoma progression by stabilizing SAE1 to facilitate SUMOylation

BACKGROUND

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy with a poor prognosis. The underlying functions and mechanisms of circular RNA and SUMOylation in the development of ICC remain poorly understood.

METHODS

Circular RNA hsa_circ_0001681 (termed Circ-RAPGEF5 hereafter) was identified by circular RNA sequencing from 19 pairs of ICC and adjacent tissue samples. The biological function of Circ-RAPGEF5 in tumor proliferation and metastasis was examined by a series of in vitro assays. A preclinical model was used to validate the therapeutic effect of targeting Circ-RAPGEF5. RNA pull-down and dual-luciferase reporter assays were used to access the RNA interactions. Western blot and Co-IP assays were used to detect SUMOylation levels.

RESULTS

Circ-RAPGEF5, which is generated from exons 2 to 6 of the host gene RAPGEF5, was upregulated in ICC. In vitro and in vivo assays showed that Circ-RAPGEF5 promoted ICC tumor proliferation and metastasis, and inhibited apoptosis. Additionally, high Circ-RAPGEF5 expression was significantly correlated with a poor prognosis. Further investigation showed that SAE1, a potential target of Circ-RAPGEF5, was also associated with poor oncological outcomes. RNA pull-down and dual-luciferase reporter assays showed an interaction of miR-3185 with Circ-RAPGEF5 and SAE1. Co-IP and western blot assays showed that Circ-RAPGEF5 is capable of regulating SUMOylation.

CONCLUSION

Circ-RAPGEF5 promotes ICC tumor progression and SUMOylation by acting as a sponge for miR-3185 to stabilize SAE1. Targeting Circ-RAPGEF5 or SAE1 might be a novel diagnostic and therapeutic strategy in ICC.

Unraveling the Post-Translational Modifications and therapeutical approach in NSCLC pathogenesis

Non-Small Cell Lung Cancer (NSCLC) is the most prevalent kind of lung cancer with around 85% of total lung cancer cases. Despite vast therapies being available, the survival rate is low (5 year survival rate is 15%) making it essential to comprehend the mechanism for NSCLC cell survival and progression. The plethora of evidences suggests that the Post Translational Modification (PTM) such as phosphorylation, methylation, acetylation, glycosylation, ubiquitination and SUMOylation are involved in various types of cancer progression and metastasis including NSCLC. Indeed, an in-depth understanding of PTM associated with NSCLC biology will provide novel therapeutic targets and insight into the current sophisticated therapeutic paradigm. Herein, we reviewed the key PTMs, epigenetic modulation, PTMs crosstalk along with proteogenomics to analyze PTMs in NSCLC and also, highlighted how epi‑miRNA, miRNA and PTM inhibitors are key modulators and serve as promising therapeutics.

A novel risk model of three SUMOylation genes based on RNA expression for potential prognosis and treatment sensitivity prediction in kidney cancer

Introduction: Kidney cancer is one of the most common and lethal urological malignancies. Discovering a biomarker that can predict prognosis and potential drug treatment sensitivity is necessary for managing patients with kidney cancer. SUMOylation is a type of posttranslational modification that could impact many tumor-related pathways through the mediation of SUMOylation substrates. In addition, enzymes that participate in the process of SUMOylation can also influence tumorigenesis and development. Methods: We analyzed the clinical and molecular data which were obtanied from three databases, The Cancer Genome Atlas (TCGA), the National Cancer Institute's Clinical Proteomic Tumor Analysis Consortium (CPTAC), and ArrayExpress. Results: Through analysis of differentially expressed RNA based on the total TCGA-KIRC cohort, it was found that 29 SUMOylation genes were abnormally expressed, of which 17 genes were upregulated and 12 genes were downregulated in kidney cancer tissues. A SUMOylation risk model was built based on the discovery TCGA cohort and then validated successfully in the validation TCGA cohort, total TCGA cohort, CPTAC cohort, and E-TMAB-1980 cohort. Furthermore, the SUMOylation risk score was analyzed as an independent risk factor in all five cohorts, and a nomogram was constructed. Tumor tissues in different SUMOylation risk groups showed different immune statuses and varying sensitivity to the targeted drug treatment. Discussion: In conclusion, we examined the RNA expression status of SUMOylation genes in kidney cancer tissues and developed and validated a prognostic model for predicting kidney cancer outcomes using three databases and five cohorts. Furthermore, the SUMOylation model can serve as a biomarker for selecting appropriate therapeutic drugs for kidney cancer patients based on their RNA expression.

Post-Translational Modification of ZEB Family Members in Cancer Progression

Post-translational modification (PTM), the essential regulatory mechanisms of proteins, play essential roles in physiological and pathological processes. In addition, PTM functions in tumour development and progression. Zinc finger E-box binding homeobox (ZEB) family homeodomain transcription factors, such as ZEB1 and ZEB2, play a pivotal role in tumour progression and metastasis by induction epithelial-mesenchymal transition (EMT), with activation of stem cell traits, immune evasion and epigenetic reprogramming. However, the relationship between ZEB family members' post-translational modification (PTM) and tumourigenesis remains largely unknown. Therefore, we focussed on the PTM of ZEBs and potential therapeutic approaches in cancer progression. This review provides an overview of the diverse functions of ZEBs in cancer and the mechanisms and therapeutic implications that target ZEB family members' PTMs.

Natural Products Against Renal Fibrosis via Modulation of SUMOylation

Renal fibrosis is the common and final pathological process of kidney diseases. As a dynamic and reversible post-translational modification, SUMOylation and deSUMOylation of transcriptional factors and key mediators significantly affect the development of renal fibrosis. Recent advances suggest that SUMOylation functions as the promising intervening target against renal fibrosis, and natural products prevent renal fibrosis via modulating SUMOylation. Here, we introduce the mechanism of SUMOylation in renal fibrosis and therapeutic effects of natural products. This process starts by summarizing the key mediators and enzymes during SUMOylation and deSUMOylation and its regulation role in transcriptional factors and key mediators in renal fibrosis, then linking the mechanism findings of SUMOylation and natural products to develop novel therapeutic candidates for treating renal fibrosis, and concludes by commenting on promising therapeutic targets and candidate natural products in renal fibrosis via modulating SUMOylation, which highlights modulating SUMOylation as a promising strategy for natural products against renal fibrosis.

Epigenetic modifications from arsenic exposure: A comprehensive review

Arsenic is a notorious element with the potential to harm exposed individuals in ways that include cancerous and non-cancerous health complications. Millions of people across the globe (especially in South and Southeast Asian countries including China, Vietnam, India and Bangladesh) are currently being unknowingly exposed to precarious levels of arsenic. Among the diverse effects associated with such arsenic levels of exposure is the propensity to alter the epigenome. Although a large volume of literature exists on arsenic-induced genotoxicity, cytotoxicity, and inter-individual susceptibility due to active research on these subject areas from the last millennial, it is only recently that attention has turned on the ramifications and mechanisms of arsenic-induced epigenetic changes. The present review summarizes the possible mechanisms involved in arsenic induced epigenetic alterations. It focuses on the mechanisms underlying epigenome reprogramming from arsenic exposure that result in improper cell signaling and dysfunction of various epigenetic components. The mechanistic information articulated from the review is used to propose a number of novel therapeutic strategies with a potential for ameliorating the burden of worldwide arsenic poisoning.

Bioinformatic reanalysis of public proteomics data reveals that nuclear proteins are recurrent in cancer secretomes

Proteins secreted by tumoral cells (cancer secretomes) have been continuously associated with cancer development and progression processes. In this context, secreted proteins contribute to the signaling mechanisms related to tumor growth and spreading and studies on tumor secretomes provide valuable clues on putative tumor biomarkers. Although the in vitro identification of intracellular proteins in cancer secretome studies has usually been associated with contamination derived from cell lysis or fetal bovine serum, accumulated evidence reports on intracellular proteins with moonlighting functions in the extracellular environment. In this study, we performed a systematic reanalysis of public proteomics data regarding different cancer secretomes, aiming to identify intracellular proteins potentially secreted by tumor cells via unconventional secretion pathways. We found a similar repertoire of unconventionally secreted proteins, including the recurrent identification of nuclear proteins secreted by different cancer cells. In addition, in some cancer types, immunohistochemical data were in line with proteomics identifications and suggested that nuclear proteins might relocate from the nucleus to the cytoplasm. Both the presence of nuclear proteins and the likely unconventional secretion of such proteins may comprise biological signatures of malignant transformation in distinct cancer types and may be targeted for further analysis aiming at the prognostic/therapeutic value of such features.

Knockdown of ubiquitin-like modifier-activating enzyme 2 promotes apoptosis of clear cell renal cell carcinoma cells

Small ubiquitin-related modifier (SUMO) proteins are involved in the development of tumors. Ubiquitin-like modifier-activating enzyme 2 (UBA2) is an important member of the SUMO modification system; however, its role in clear cell renal cell carcinoma (ccRCC) is unclear. Therefore, we investigated the expression and function of UBA2 in ccRCC. Both mRNA and protein expression levels of UBA2 were found to be higher in ccRCC than in normal renal tissues and significantly related to the tumor size, Fuhrman grade, and tumor stage. UBA2 knockdown inhibited ccRCC cell growth, promoted apoptosis in vitro and in vivo, and decreased the abundance of a p53 mutant, c-Myc, and key enzymes of the SUMO modification system. Meanwhile, overexpression of UBA2 had the opposite effects. Overexpression of the p53 mutant or c-Myc alleviated the effects of UBA2 knockdown on ccRCC cell proliferation and apoptosis. In conclusion, targeting UBA2 may have a therapeutic potential against ccRCC.

Cleavage of Syndecan-1 Promotes the Proliferation of the Basal-Like Breast Cancer Cell Line BT-549 Via Akt SUMOylation

Basal-like breast cancer is characterized by an aggressive clinical outcome and presence of metastasis, for which effective therapies are unavailable. We have previously shown that chondroitin 4-O-sulfotransferase-1 (C4ST-1) controls the invasive properties of the basal-like breast cancer cell line BT-549 by inducing matrix metalloproteinase (MMP) expression through the N-cadherin/β-catenin pathway. Here we report that C4ST-1 controls the proliferation of BT-549 cells via the MMP-dependent cleavage of syndecan-1. Syndecan-1 is a membrane-bound proteoglycan associated with an aggressive phenotype and poor prognosis in breast cancer. In addition, the cleavage of syndecan-1 at a specific juxtamembrane cleavage site is implicated in the pathophysiological response in breast cancer. Knockout of C4ST-1 remarkably suppressed both the cleavage of syndecan-1 and proliferation of BT-549 cells. Kinases (AKT1, ERK1/2, PI3K, and STAT3) comprising cancer proliferative pathways are phosphorylated in C4ST-1 knockout cells at a level similar to that in parental BT-549 cells, whereas levels of phosphorylated S6 kinase and SUMOylated AKT (hyperactivated AKT observed in breast cancer) decreased in C4ST-1 knockout cells. An MMP inhibitor, GM6001, suppressed the small ubiquitin-like modifier (SUMO) modification of AKT, suggesting that cleavage of syndecan-1 by MMPs is involved in the SUMO modification of AKT. Forced expression of the cytoplasmic domain of syndecan-1, which is generated by MMP-dependent cleavage, increased the SUMO modification of AKT and global protein SUMOylation. Furthermore, syndecan-1 C-terminal domain-expressing BT-549 cells were more proliferative and sensitive to a potent SUMOylation inhibitor, tannic acid, compared with BT-549 cells transfected with an empty expression vector. These findings assign new functions to the C-terminal fragment of syndecan-1 generated by MMP-dependent proteolysis, thereby broadening our understanding of their physiological importance and implying that the therapeutic inhibition of syndecan-1 cleavage could affect the progression of basal-like breast cancer.

Downregulation of SUMO2 inhibits hepatocellular carcinoma cell proliferation, migration and invasion

This study aimed to evaluate the prognostic value and biological function of small ubiquitin‐like modifier 2 (SUMO2) in hepatocellular carcinoma (HCC). SUMO2 expression in HCC tissues was markedly higher than that in normal liver tissues, and patients with high SUMO2 expression had significantly shorter median overall survival than those with low SUMO2 expression. Furthermore, SUMO2 expression was closely correlated with lymph node metastasis and vascular invasion and was a predictor of poor prognosis. The knockdown of SUMO2 in two HCC cell lines (SMMC‐7721 and Bel‐7404) dramatically suppressed their proliferation, migration and invasion. Western blot analysis showed that the downregulation of SUMO2 significantly reduced the expression of Ki‐67, matrix metalloproteinase‐9 (MMP‐9) and vascular endothelial growth factor (VEGF) in SMMC‐7721 and Bel‐7404 cells. Similarly, quantitative reverse transcription–PCR revealed consistently decreased expression of MMP‐9 and VEGF. Our data suggest that SUMO2 promotes proliferation, migration and invasion of HCC cells via mechanisms involving MMP‐9 and VEGF. Therefore, SUMO2 may be a prognostic factor and a promising therapeutic target for patients with HCC.

Platinum Drug Sensitivity Polymorphisms in Stage III Non-small Cell Lung Cancer With Invasion of Mediastinal Lymph Nodes

BACKGROUND/AIM

Patients with stage IIIA (N2) non-small cell lung cancer (NSCLC) with no progression after induction chemotherapy are usually selected for surgery. Nowadays, response to chemotherapy is not predictable. We aimed to identify genomic predictive markers for response to induction chemotherapy in stage IIIA (N2) NSCLC patients.

PATIENTS AND METHODS

Whole-exome sequencing (WES) was performed on samples from 11 patients with no response after induction chemotherapy and 6 patients with documented pathological response, admitted to the Hotel Dieu Hospital, Paris or Allegemeines Krakenhaus University, Vienna.

RESULTS

A higher alternative allele frequency was found on SENP5, rs63736860, rs1602 and NCBP2, rs553783 in the non-responder group, and on RGP1, rs1570248, SLFN12L, rs2304968, rs9905892, and GBA2, rs3833700 in the responder group.

CONCLUSION

These polymorphisms contribute to inter-individual sensibility to chemotherapy response. Interrogation of these genetic variations may have potential applicability when deciding the treatment strategy for patients with stage III NSCLC (N2).

The Function of SUMOylation and Its Role in the Development of Cancer Cells under Stress Conditions: A Systematic Review

Malignant tumors still pose serious threats to human health due to their high morbidity and mortality. Recurrence and metastasis are the most important factors affecting patient prognosis. Chemotherapeutic drugs and radiation used to treat these tumors mainly interfere with tumor metabolism, destroy DNA integrity, and inhibit protein synthesis. The upregulation of small ubiquitin-like modifier (SUMO) is a prevalent posttranslational modification (PTM) in various cancers and plays a critical role in tumor development. The dysregulation of SUMOylation can protect cancer cells from stresses exerted by external or internal stimuli. SUMOylation is a dynamic process finely regulated by SUMOylation enzymes and proteases to maintain a balance between SUMOylation and deSUMOylation. An increasing number of studies have reported that SUMOylation imbalance may contribute to cancer development, including metastasis, angiogenesis, invasion, and proliferation. High level of SUMOylation is required for cancer cells to survive internal or external stresses. Downregulation of SUMOylation may inhibit the development of cancer, making it an important potential clinical therapeutic target. Some studies have already begun to treat tumors by inhibiting the expression of SUMOylation family members, including SUMO E1 or E2. The tumor cells become more aggressive under internal and external stresses. The prevention of tumor development, metastasis, recurrence, and radiochemotherapy resistance by attenuating SUMOylation requires further exploration. This review focused on SUMOylation in tumor cells to discuss its effects on tumor suppressor proteins and oncoproteins as well as classical tumor pathways to identify new insights for cancer clinical therapy.

An unanticipated tumor-suppressive role of the SUMO pathway in the intestine unveiled by Ubc9 haploinsufficiency

Sumoylation is an essential posttranslational modification in eukaryotes that has emerged as an important pathway in oncogenic processes. Most human cancers display hyperactivated sumoylation and many cancer cells are remarkably sensitive to its inhibition, thus supporting application of chemical sumoylation inhibitors in cancer treatment. Here we show, first, that transformed embryonic fibroblasts derived from mice haploinsufficient for Ubc9, the essential and unique gene encoding the SUMO E2 conjugating enzyme, exhibit enhanced proliferation and transformed phenotypes in vitro and as xenografts ex vivo. To then evaluate the possible impact of loss of one Ubc9 allele in vivo, we used a mouse model of intestinal tumorigenesis. We crossed Ubc9+/- mice with mice harboring a conditional ablation of Apc either all along the crypt-villus axis or only in Lgr5+ crypt-based columnar (CBC) cells, the cell compartment that includes the intestinal stem cells proposed as cells-of-origin of intestinal cancer. While Ubc9+/- mice display no overt phenotypes and no globally visible hyposumoylation in cells of the small intestine, we found, strikingly, that, upon loss of Apc in both models, Ubc9+/- mice develop more (>2-fold) intestinal adenomas and show significantly shortened survival. This is accompanied by reduced global sumoylation levels in the polyps, indicating that Ubc9 levels become critical upon oncogenic stress. Moreover, we found that, in normal conditions, Ubc9+/- mice show a moderate but robust (15%) increase in the number of Lgr5+ CBC cells when compared to their wild-type littermates, and further, that these cells display higher degree of stemness and cancer-related and inflammatory gene expression signatures that, altogether, may contribute to enhanced intestinal tumorigenesis. The phenotypes of Ubc9 haploinsufficiency discovered here indicate an unanticipated tumor-suppressive role of sumoylation, one that may have important implications for optimal use of sumoylation inhibitors in the clinic.

PIAS1 and TIF1γ collaborate to promote SnoN SUMOylation and suppression of epithelial-mesenchymal transition

SUMO E3 ligases specify protein substrates for SUMOylation. The SUMO E3 ligases PIAS1 and TIF1γ target the transcriptional regulator SnoN for SUMOylation leading to suppression of epithelial-mesenchymal transition (EMT). Whether and how TIF1γ and PIAS1 might coordinate SnoN SUMOylation and regulation of EMT remained unknown. Here, we reveal that SnoN associates simultaneously with both TIF1γ and PIAS1, leading to a trimeric protein complex. Hence, PIAS1 and TIF1γ collaborate to promote the SUMOylation of SnoN. Importantly, loss of function studies of PIAS1 and TIF1γ suggest that these E3 ligases act in an interdependent manner to suppress EMT of breast cell-derived tissue organoids. Collectively, our findings unveil a novel mechanism by which SUMO E3 ligases coordinate substrate SUMOylation with biological implications.

Benzothiophene-2-carboxamide derivatives as SENPs inhibitors with selectivity within SENPs family

The SUMO (small ubiquitin-related modifier)-specific proteases (SENPs) are responsible for the cleavage of SUMO from its target proteins, thus play important roles in the dynamic SUMOylation and deSUMOylation processes. SENPs are related to a variety of human diseases including cancer and represent a new class of potential therapeutic targets with mechanism of action that is likely to be different from that of current clinically used drugs. However, potent inhibitors that are selective within the SENPs family members still remain a challenge due to their high homology. In order to demonstrate the feasibility of developing selective inhibitors within the SENPs family, we chose SENP1/2/5 as representatives, aiming to identify inhibitors with selectivity among the members. Starting from a hit compound ZCL951 from virtual screening, a series of benzothiophene-2-carboxamide inhibitors were designed based on the protein structures of SENP1, 2, and 5. First, an unoccupied hydrophobic pocket was first identified which led to IC₅₀ as low as 0.56 μM. Furthermore, the ethylacetate 77 gave both submicromolar inhibitory activity and 33-fold selectivity for SENP2 versus SENP5. They are the most potent and selective nonpeptidic inhibitor reported so far for the SENPs family, as far as we are aware. Their structure-activity relationship was also discussed.

Cell transformation by the adenovirus oncogenes E1 and E4

Extensive studies on viral-mediated oncogenic transformation by human adenoviruses have revealed much of our current understanding on the molecular mechanisms that are involved in the process. To date, these studies have shown that cell transformation is a multistep process regulated by the cooperation of several adenoviral gene products encoded in the early regions 1 (E1) and 4 (E4). Early region 1A immortalizes primary rodent cells, whereas co-expression of early region protein 1B induces full manifestation of the transformed phenotype. Beside E1 proteins, also some E4 proteins have partial transforming activities through regulating many cellular pathways. Here, we summarize recent data of how adenoviral oncoproteins may contribute to viral transformation and discuss the challenge of pinpointing the underlying mechanisms.

Post-translational Mechanisms Regulating NK Cell Activating Receptors and Their Ligands in Cancer: Potential Targets for Therapeutic Intervention

Efficient clearance of transformed cells by Natural Killer (NK) cells is regulated by several activating receptors, including NKG2D, NCRs, and DNAM-1. Expression of these receptors as well as their specific “induced self” ligands is finely regulated during malignant transformation through the integration of different mechanisms acting on transcriptional, post-transcriptional, and post-translational levels. Among post-translational mechanisms, the release of activating ligands in the extracellular milieu through protease-mediated cleavage or by extracellular vesicle secretion represents some relevant cancer immune escape processes. Moreover, covalent modifications including ubiquitination and SUMOylation also contribute to negative regulation of NKG2D and DNAM-1 ligand surface expression resulting either in ligand intracellular retention and/or ligand degradation. All these mechanisms greatly impact on NK cell mediated recognition and killing of cancer cells and may be targeted to potentiate NK cell surveillance against tumors. Our mini review summarizes the main post-translational mechanisms regulating the expression of activating receptors and their ligands with particular emphasis on the contribution of ligand shedding and of ubiquitin and ubiquitin-like modifications in reducing target cell susceptibility to NK cell-mediated killing. Strategies aimed at inhibiting shedding of activating ligands and their modifications in order to preserve ligand expression on cancer cells will be also discussed.

Noncovalent structure of SENP1 in complex with SUMO2

SUMOylation is a post-translational modification in which a small ubiquitin-like molecule (SUMO) is appended to substrate proteins and is known to influence myriads of biological processes. A delicate interplay between several families of SUMOylation proteins and their substrates ensures the proper level of SUMOylation required for normal cell function. Among the SUMO proteins, SUMO2 is known to form mono-SUMOylated proteins and engage in poly-SUMO chain formation, while sentrin-specific protease 1 (SENP1) is a key enzyme in regulating both events. Determination of the SENP1-SUMO2 interaction is therefore necessary to better understand SUMOylation. In this regard, the current paper reports the noncovalent structure of SENP1 in complex with SUMO2, which was refined to a resolution of 2.62 Å with R and Rfree values of 22.92% and 27.66%, respectively. The structure shows that SENP1-SUMO2 complex formation is driven largely by polar interactions and limited hydrophobic contacts. The essential C-terminal motif (QQTGG) of SUMO2 is stabilized by a number of specific bonding interactions that enable it to protrude into the catalytic triad of SENP1 and provide the arrangement necessary for maturation of SUMO and deSUMOylation activity. Overall, the structure shows a number of structural details that pinpoint the basis of SENP1-SUMO2 complex formation.

Fish SUMO3 functions as a critical antiviral molecule against iridovirus and nodavirus

Protein SUMOylation (SUMO is small ubiquitin-related modifier) is a dynamic process that is strictly regulated under physiological and pathological conditions. We previously cloned and characterized two SUMO homologue genes (EcSUMO1 and EcSUMO2) from orange-spotted grouper (Epinephelus coioides). In the present study, the SUMO3 homologue from E. coioides (EcSUMO3) was cloned and its possible roles in fish immunity were analyzed. The open reading frame of EcSUMO3 contains 285 base pairs encoding a 94 amino acid protein with a predicted molecular mass of 10.73 kDa. The protein sequence of EcSUMO3 revealed similar domains with mammals, including the UBQ (ubiquitin-like proteins) domain, the hydrophobic surface, the Ulp1-Smt3 interaction sites, a VKTE motif and the C-terminal Gly residues. EcSUMO3 shares 46.83% and 89.58% identity with EcSUMO1 and EcSUMO2, respectively, and it shares 94%, 98%, and 98% identity with SUMO3 from Oreochromis niloticus, Danio rerio, and Homo sapiens, respectively. Quantitative real-time polymerase chain reaction analysis indicated that EcSUMO3 was constitutively expressed in all of the analyzed tissues in healthy grouper. EcSUMO3 expression levels were remarkably (p < 0.01) up-regulated in grouper spleen (GS) cells in response to stimulation with red-spotted grouper nervous necrosis virus (RGNNV) and Singapore grouper iridovirus (SGIV). EcSUMO3 was distributed in both the cytoplasm and nucleus in GS cells. EcSUMO3 enhanced SGIV and RGNNV replication during viral infection in vitro. These results are important for better understanding of the SUMO pathway in fish and provide insights into the regulatory mechanism of viral infection in E. coioides under farmed conditions.

Association of SENPs single-nucleotide polymorphism and breast cancer in Chinese population

SUMO-specific Cysteine Proteases (SENPs) have involvement in the initiation and progression of human cancers. In the present study, we evaluated the association of SENPs polymorphism with susceptibility as well as clinicopathologic features and patients' response of breast cancer (BC) in a Chinese population.We genotyped SENP1 (rs61918808), SENP2 (rs6762208), SENP7 (rs61697963) by sequencing in a case-control study including 210 BC patients and 225 healthy volunteers. Odds ratios (ORs) and 95% confidence intervals (CIs) were used to assume the association strength.No significant association was found between polymorphism of the 3 SENPs and BC susceptibility. However, SENP1 rs61918808 (C>T) and SENP7 rs61697963 (A>C) was associated with HER-2 expression (P < .05). SENP2 rs6762208(C>A) was correlated with increasing risk of lymph node metastases (P < .05). Among the patients who received neoadjuvant chemotherapy, T allele and TT genotype of SENP1 rs61918808 were less likely to achieve pCR (P < .05).We first reported SENPs variants were not associated with BC risk in Chinese population, but presented specific effect on clinicopathological features of BC. Moreover, SENP1 rs61918808 may be a predictor for the clinical response in local advanced BC patients who received neoadjuvant chemotherapy.

Progression on Citrullination of Proteins in Gastrointestinal Cancers

The citrullination modification (Cit) of proteins has received increasing attention in recent years. This kind of protein modification was first discovered in autoimmune diseases such as rheumatoid arthritis. The citrullination modification process is catalyzed by the peptidyl arginine deiminases (PADIs) family. A well-known citrullination of histone involves the key mechanism of neutrophil extracellular traps (NETs) of inflammation in the peripheral blood. Further studies revealed that citrullination modification of proteins also involves in carcinogenesis in human being. Citrullinated proteins disturbed the stability of proteins and caused DNA damages. There is increasing evidence that citrullinated proteins can be used as potential targets for cancer diagnosis or treatment. This review introduces the concept of citrullination modification of proteins, substrate proteins, examining methods and biological significances.

Sumoylation of Flotillin-1 promotes EMT in metastatic prostate cancer by suppressing Snail degradation

Flotillin-1 (Flot-1) has been shown to regulate cancer progression, but the regulatory role of post-translational modifications of Flot-1 on cancers remains elusive. Herein, we show that up-regulated E2 conjugating enzyme UBC9 sumoylates Flot-1 at Lys-51 and Lys-195 with small ubiquitin-like modifier (SUMO)-2/3 modification in metastatic prostate cancer. Mitogen induced the sumoylation and nuclear translocation of Flot-1. The nuclear-targeted Flot-1 physically interacted with Snail, and inhibited Snail degradation through the proteasome in a sumoylation-dependent manner, thereby promoting epithelial-to-mesenchymal transition (EMT). Sumoylation of Flot-1 by up-regulated UBC9 in human metastatic prostate cancer tissues and prostate cancer cells with high metastatic potential positively correlated with the stabilization of Snail and the induction of Snail-mediated EMT genes in the metastatic prostate cancer. Our study reveals a new mechanism of sumoylated Flot-1-mediating Snail stabilization, and identifies a novel sumoylated Flot-1-Snail signaling axis in EMT of metastatic prostate cancer.

SENP1 Interacts with HIF1α to Regulate Glycolysis of Prostatic Carcinoma Cells

Background: Hypoxic microenvironment inside the tumor forces tumor cells to up-regulate the glycolytic pathway to maintain a sufficient energy supply for tumor growth. Activation of HIF1α under hypoxia condition is able to regulate the expression of glycolysis-related genes, and results in the proliferation and metastasis of cancer cells. However, the mechanism underlying HIF1α activation and glycolysis induction by hypoxia remains unclear. The present study is aimed to test if SENP1 regulates the glycolysis of prostate cancer cells (CaP) by improving stability of HIF1α protein.

Methods: We employed qPCR and western blotting assay to analyze expression of HIF1α and SENP1. Glucose uptake assay, lactate production assay, LDH release assay and ATP production assay were utilized to evaluate cell glycolysis. The interaction between SENP1 and HIF1α was verified by co-immunoprecipitation assay.

Results: We found that hypoxia condition improves glucose uptake and lactate production to sustain sufficient ATP for cellular activity in prostatic carcinoma cells. The expression of SENP1 mRNA was significantly increased in human prostatic carcinoma cell lines after exposure to hypoxia, accompanied by the up-regulation of HIF1α. Furthermore, forced expression of SENP1 was shown to regulate the glycolysis in prostatic carcinoma cells by stabilizing HIF1α. The up-regulation of SENP1 promotes tumor cell proliferation and tumorgenesis by interacting with HIF1α which was deSUMOylated and sequentially leading to a “Warburg effect”.

Conclusion: SENP1 interacts with HIF1α to regulate glycolysis and proliferation of prostatic carcinoma cells under hypoxia condition, which provides new insights into prostatic carcinoma therapy.

Deciphering the SUMO code in the kidney

SUMOylation of proteins is an important regulatory element in modulating protein function and has been implicated in the pathogenesis of numerous human diseases such as cancers, neurodegenerative diseases, brain injuries, diabetes, and familial dilated cardiomyopathy. Growing evidence has pointed to a significant role of SUMO in kidney diseases such as DN, RCC, nephritis, AKI, hypertonic stress and nephrolithiasis. Recently, emerging studies in podocytes demonstrated that SUMO might have a protective role against podocyte apoptosis. However, the SUMO code responsible for beneficial outcome in the kidney remains to be decrypted. Our recent experiments have revealed that the expression of both SUMO and SUMOylated proteins is appreciably elevated in hypoxia‐induced tubular epithelial cells (TECs) as well as in the unilateral ureteric obstruction (UUO) mouse model, suggesting a role of SUMO in TECs injury and renal fibrosis. In this review, we attempt to decipher the SUMO code in the development of kidney diseases by summarizing the defined function of SUMO and looking forward to the potential role of SUMO in kidney diseases, especially in the pathology of renal fibrosis and CKD, with the goal of developing strategies that maximize correct interpretation in clinical therapy and prognosis.

Direct SUMOylation of M1 muscarinic acetylcholine receptor increases its ligand-binding affinity and signal transduction

SUMOylation is a significant post-translational modification (PTM) by the small ubiquitin-related modifier (SUMO). Increasing evidence shows SUMOylation regulates GPCR signaling; however, very few GPCRs have been shown to be SUMOylation targets to date. In this study, we identified M1 muscarinic acetylcholine receptor (M1 mAChR), a member of the GPCRs, as a new SUMO substrate. When the mAChR was activated by the agonist carbachol, the colocalization of the M1 mAChR and SUMO-1 protein markedly decreased in immunoprecipitation and immunofluorescence assays. SUMOylation of the M1 mAChR played an important role in increasing the ligand-binding affinity to M1 mAChR, signaling efficiencies, and receptor endocytosis. Through the site-directed mutagenesis approach, K327 was identified as the SUMOylation site of the M1 mAChR. Mutation of the consensus SUMOylation site of the M1 mAChR reduces not only the colocalization of SUMO-1, but also the ligand-binding affinity and signal transduction. The function of M1 mAChR was regulated by SUMOylation through the stabilization of active-state conformation revealed by molecular dynamics simulations. Our results provide evidence that M1 SUMOylation is an important PTM involved in regulation of the affinity for agonists and for activation of signaling pathways.-Xu, J., Tan, P., Li, H., Cui, Y., Qiu, Y., Wang, H., Zhang, X., Li, J., Zhu, L., Zhou, W., Chen, H. Direct SUMOylation of M1 muscarinic acetylcholine receptor increases its ligand-binding affinity and signal transduction.

The SUMO System and TGFβ Signaling Interplay in Regulation of Epithelial-Mesenchymal Transition: Implications for Cancer Progression

Protein post-translational modification by the small ubiquitin-like modifier (SUMO), or SUMOylation, can regulate the stability, subcellular localization or interactome of a protein substrate with key consequences for cellular processes including the Epithelial-Mesenchymal Transition (EMT). The secreted protein Transforming Growth Factor beta (TGFβ) is a potent inducer of EMT in development and homeostasis. Importantly, the ability of TGFβ to induce EMT has been implicated in promoting cancer invasion and metastasis, resistance to chemo/radio therapy, and maintenance of cancer stem cells. Interestingly, TGFβ-induced EMT and the SUMO system intersect with important implications for cancer formation and progression, and novel therapeutics identification.

The SUMO protease SENP1 and the chromatin remodeler CHD3 interact and jointly affect chromatin accessibility and gene expression

The small ubiquitin-like modifier (SUMO) post-translationally modifies lysine residues of transcription factors and co-regulators and thereby contributes to an important layer of control of the activities of these transcriptional regulators. Likewise, deSUMOylation of these factors by the sentrin-specific proteases (SENPs) also plays a role in gene regulation, but whether SENPs functionally interact with other regulatory factors that control gene expression is unclear. In the present work, we focused on SENP1, specifically, on its role in activation of gene expression investigated through analysis of the SENP1 interactome, which revealed that SENP1 physically interacts with the chromatin remodeler chromodomain helicase DNA-binding protein 3 (CHD3). Using several additional methods, including GST pulldown and co-immunoprecipitation assays, we validated and mapped this interaction, and using CRISPR-Cas9-generated CHD3- and SENP1-KO cells (in the haploid HAP1 cell line), we investigated whether these two proteins are functionally linked in regulating chromatin remodeling and gene expression. Genome-wide ATAC-Seq analysis of the CHD3- and SENP1-KO cells revealed a large degree of overlap in differential chromatin openness between these two mutant cell lines. Moreover, motif analysis and comparison with ChIP-Seq profiles in K562 cells pointed to an association of CHD3 and SENP1 with CCCTC-binding factor (CTCF) and SUMOylated chromatin-associated factors. Lastly, genome-wide RNA-Seq also indicated that these two proteins co-regulate the expression of several genes. We propose that the functional link between chromatin remodeling by CHD3 and deSUMOylation by SENP1 uncovered here provides another level of control of gene expression.

Control of SUMO and Ubiquitin by ROS: Signaling and disease implications

Reversible post-translational modifications (PTMs) ensure rapid signal transmission from sensors to effectors. Reversible modification of proteins by the small proteins Ubiquitin and SUMO are involved in virtually all cellular processes and can modify thousands of proteins. Ubiquitination or SUMOylation is the reversible attachment of these modifiers to lysine residues of a target via isopeptide bond formation. These modifications require ATP and an enzymatic cascade composed of three classes of proteins: E1 activating enzymes, E2 conjugating enzymes and E3 ligases. The reversibility of the modification is ensured by specific isopeptidases. E1 and E2 enzymes, some E3 ligases and most isopeptidases have catalytic cysteine residues, which make them potentially susceptible for oxidation. Indeed, an increasing number of examples reveal regulation of ubiquitination and SUMOylation by reactive oxygen species, both in the context of redox signaling and in severe oxidative stress. Importantly, ubiquitination and SUMOylation play essential roles in the regulation of ROS homeostasis, participating in the control of ROS production and clearance. In this review, we will discuss the interplay between ROS homeostasis, Ubiquitin and SUMO pathways and the implications for the oxidative stress response and cell signaling.

Small ubiquitin-like modifier/sentrin-specific peptidase 1 associates with chemotherapy and is a risk factor for poor prognosis of non-small cell lung cancer

BACKGROUND

SUMO/sentrin-specific peptidase 1 (SENP1) was associated with radioresistance of cancer cells and was upregulated in non-small cell lung cancer (NSCLC). This study was to investigate the association of SENP1 with resistance of NSCLC tumor to chemoradiotherapy.

METHODS

Sentrin-specific peptidase 1 expression profile was detected using the immunohistochemistry and quantitative real-time PCR (qRT-PCR) analyses. The relative expression level of SENP1 mRNA was detected using qRT-PCR. The response to chemoradiotherapy was evaluated according to the Response Evaluation Criteria in Solid Tumors.

RESULTS AND CONCLUSION

When compared with adjacent non-tumor tissues, the overexpression of SENP1 mRNA and protein in NSCLC tumor tissues was determined using qRT-PCR and immunochemistry. Based on the chemoradiotherapy response rate, we found that NSCLC patients with higher SENP1 expression showed lower rates of complete response and higher partial and non-response rate to chemoradiotherapy. In the overall survival analysis, we found patients with high SENP1 expression showed significant shorter survival time compared with those with low SENP1 expression. In the multivariate Cox regression model, we found SENP1 overexpression, TNM stage, and lymph metastasis were independent risk factors for poor prognosis of NSCLC. SENP1 overexpression contributed to chemoradiotherapy resistance of NSCLC. The overexpression of SENP1 could be used as a risk factor for the poor prognosis of NSCLC.

Knockdown of SUMO1P3 represses tumor growth and invasion and enhances radiosensitivity in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common types of malignant tumors with high recurrence and metastasis rates. Radiotherapy represents a major therapeutic option for HCC patients. However, the efficacy of radiotherapy has been limited due to the development of intrinsic radioresistance of the tumor cells. Small ubiquitin-like modifier 1 pseudogene 3 (SUMO1P3), one member of SUMO pseudogene family, is a novel identified lncRNA that was originally identified to be upregulated in gastric cancer. However, the detailed roles of SUMO1P3 in HCC development remain to be elucidated. Here, the expression of SUMO1P3 in HCC tissues and cells was examined by qRT-PCR. Cell proliferation, colony formation ability, invasion ability, apoptosis, and radiosensitivity were detected by MTT assay, colony formation assay, cell invasion assay, flow cytometry analysis, and survival fraction assay, respectively. We found that SUMO1P3 was significantly upregulated in HCC tissues and cells. Besides, SUMO1P3 was highly expressed in HCC patients with higher TNM stage. Furthermore, SUMO1P3 knockdown markedly suppressed cell proliferation, colony formation ability, and cell invasiveness, promoted apoptosis, and enhanced radiosensitivity of HCC cells. We concluded that the knockdown of SUMO1P3 repressed tumor growth, invasion, promoted apoptosis, and enhanced radiosensitivity in HCC, providing evidence that SUMO1P3 might be a potential novel biomarker and a therapeutic target for HCC.

Small-Molecule Inhibitors Targeting Protein SUMOylation as Novel Anticancer Compounds

SUMOylation, one of post-translational modifications, is covalently modified on lysine residues of a target protein through an enzymatic cascade reaction similar to protein ubiquitination. Along with identification of many SUMOylated proteins, protein SUMOylation has been proven to regulate multiple biologic activities including transcription, cell cycle, DNA repair, and innate immunity. The dysregulation of protein SUMOylation and deSUMOylation modification is linked with carcinogenesis and tumor progression. The SUMOylation-associated enzymes are usually elevated in various cancers, which function as cancer biomarkers to relate to poor outcomes for patients. Considering the significance of protein SUMOylation in regulating diverse biologic functions in cancer progression, numerous small-molecule inhibitors targeting protein SUMOylation pathway are developed as potentially clinical anticancer therapeutics. Here, we systematically summarize the latest progresses of associations of small ubiquitin-like modifier (SUMO) enzymes with cancers and small-molecular inhibitors against human cancers by targeting SUMOylation enzymes. We also compared the pros and cons of several special anticancer inhibitors targeting SUMO pathway. As more efforts are invested in this field, small-molecule inhibitors targeting the SUMOylation modification pathway are promising for development into novel anticancer drugs.

Wnt signaling in multiple myeloma: a central player in disease with therapeutic potential

Multiple myeloma is the second most frequent hematological malignancy in the western world and remains incurable, predominantly due to acquired drug resistance and disease relapse. The highly conserved Wnt signal transduction pathway, which plays a key role in regulating cellular processes of proliferation, differentiation, migration, and stem cell self-renewal, is associated with multiple aspects of disease. Bone homeostasis is severely disturbed by Wnt antagonists that are secreted by the malignant plasma cells in the bone marrow. In the vast majority of patients, this results in osteolytic bone disease, which is associated with bone pain and pathological fractures and was reported to facilitate disease progression. More recently, cumulative evidence also indicates the importance of intrinsic Wnt signaling in the survival of multiple myeloma cells. However, Wnt pathway-activating gene mutations could not be identified. The search for factors or processes responsible for Wnt pathway activation currently focuses on aberrant ligand levels in the bone marrow microenvironment, increased expression of Wnt transcriptional co-factors and associated micro-RNAs, and disturbed epigenetics and post-translational modification processes. Furthermore, Wnt pathway activation is associated with acquired cell adhesion-mediated resistance of multiple myeloma cells to conventional drug therapies, including doxorubicin and lenalidomide. In this review, we present an overview of the relevance of Wnt signaling in multiple myeloma and highlight the Wnt pathway as a potential therapeutic target for this disease.

Quantitative SUMO proteomics reveals the modulation of several PML nuclear body associated proteins and an anti-senescence function of UBC9

Several regulators of SUMOylation have been previously linked to senescence but most targets of this modification in senescent cells remain unidentified. Using a two-step purification of a modified SUMO3, we profiled the SUMO proteome of senescent cells in a site-specific manner. We identified 25 SUMO sites on 23 proteins that were significantly regulated during senescence. Of note, most of these proteins were PML nuclear body (PML-NB) associated, which correlates with the increased number and size of PML-NBs observed in senescent cells. Interestingly, the sole SUMO E2 enzyme, UBC9, was more SUMOylated during senescence on its Lys-49. Functional studies of a UBC9 mutant at Lys-49 showed a decreased association to PML-NBs and the loss of UBC9’s ability to delay senescence. We thus propose both pro- and anti-senescence functions of protein SUMOylation.

SUMOylated MAFB promotes colorectal cancer tumorigenesis

The transcription factor, v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB), promotes tumorigenesis in some cancers. In this study, we found that MAFB levels were increased in clinical colorectal cancer (CRC) samples, and higher expression correlated with more advanced TNM stage. We identified MAFB amplifications in a majority of tumor types in an assessment of The Cancer Genome Atlas database. Altered MAFB levels due to gene amplification, deletion, mutation, or transcription upregulation occurred in 9% of CRC cases within the database. shRNA knockdown experiments demonstrated that MAFB deficiency blocked CRC cell proliferation by arresting the cell cycle at G0/G1 phase in vitro. We found that MAFB could be SUMOylated by SUMO1 at lysine 32, and this modification was critical for cell cycle regulation by MAFB in CRC cells. SUMOylated MAFB directly regulated cyclin-dependent kinase 6 transcription by binding to its promoter. MAFB knockdown CRC cell xenograft tumors in mice grew more slowly than controls, and wild-type MAFB-overexpressing tumors grew more quickly than tumors overexpressing MAFB mutated at lysine 32. These data suggest that SUMOylated MAFB promotes CRC tumorigenesis through cell cycle regulation. MAFB and its SUMOylation process may serve as novel therapeutic targets for CRC treatment.

The post-translational modification, SUMOylation, and cancer (Review)

SUMOylation is a reversible post-translational modification which has emerged as a crucial molecular regulatory mechanism, involved in the regulation of DNA damage repair, immune responses, carcinogenesis, cell cycle progression and apoptosis. Four SUMO isoforms have been identified, which are SUMO1, SUMO2/3 and SUMO4. The small ubiquitin-like modifier (SUMO) pathway is conserved in all eukaryotes and plays pivotal roles in the regulation of gene expression, cellular signaling and the maintenance of genomic integrity. The SUMO catalytic cycle includes maturation, activation, conjugation, ligation and de-modification. The dysregulation of the SUMO system is associated with a number of diseases, particularly cancer. SUMOylation is widely involved in carcinogenesis, DNA damage response, cancer cell proliferation, metastasis and apoptosis. SUMO can be used as a potential therapeutic target for cancer. In this review, we briefly outline the basic concepts of the SUMO system and summarize the involvement of SUMO proteins in cancer cells in order to better understand the role of SUMO in human disease.

Role of novel histone modifications in cancer

Oncogenesis is a multistep process mediated by a variety of factors including epigenetic modifications. Global epigenetic post-translational modifications have been detected in almost all cancers types. Epigenetic changes appear briefly and do not involve permanent changes to the primary DNA sequence. These epigenetic modifications occur in key oncogenes, tumor suppressor genes, and transcription factors, leading to cancer initiation and progression. The most commonly observed epigenetic changes include DNA methylation, histone lysine methylation and demethylation, histone lysine acetylation and deacetylation. However, there are several other novel post-translational modifications that have been observed in recent times such as neddylation, sumoylation, glycosylation, phosphorylation, poly-ADP ribosylation, ubiquitination as well as transcriptional regulation and these have been briefly discussed in this article. We have also highlighted the diverse epigenetic changes that occur during the process of tumorigenesis and described the role of histone modifications that can occur on tumor suppressor genes as well as oncogenes, which regulate tumorigenesis and can thus form the basis of novel strategies for cancer therapy.

Connexin 43 SUMOylation improves gap junction functions between liver cancer stem cells and enhances their sensitivity to HSVtk/GCV

Connexin 43 (Cx43) can be modified and regulated by small ubiquitin-like modifier (SUMO)1; however, its role in liver cancer stem cells is poorly understood. In this study, we found a significant difference in the expression of Cx43 and SUMO1 between cancer stem cells and non-cancer stem cells in liver cancer. In liver cancer stem cells, Cx43 was almost absent, although the level of SUMO1 was significantly higher than that in non-cancer stem cells. Further experiments confirmed that the conjugated site of Cx43 by SUMO1 was located in Lys-144 and Lys-237, both of which are highly conserved among species. By the co-expression of Cx43 and SUMO1 in cancer stem cells, the gap junction intercellular communication (GJIC) of liver cancer stem cells was obviously improved. Using this feature, we verified whether it could effectively increase the sensitivity of cancer stem cells to the herpes simplex virus 1 thymidine kinase (HSVtk) gene in combination with ganciclovir (GCV), a conventional chemotherapeutic drug, in vitro and in vivo. As expected, increasing the expression of Cx43 SUMOylation in liver cancer stem cells effectively enhanced their sensitivity to HSVtk/GCV. On the whole, this study revealed a novel method which may be used to effectively restore GJIC in cancer stem cells in liver cancer, which enhances their sensitivity to conventional chemotherapeutic drugs.

In silico structure-based approaches to discover protein-protein interaction-targeting drugs

A core concept behind modern drug discovery is finding a small molecule that modulates a function of a target protein. This concept has been successfully applied since the mid-1970s. However, the efficiency of drug discovery is decreasing because the druggable target space in the human proteome is limited. Recently, protein-protein interaction (PPI) has been identified asan emerging target space for drug discovery. PPI plays a pivotal role in biological pathways including diseases. Current human interactome research suggests that the number of PPIs is between 130,000 and 650,000, and only a small number of them have been targeted as drug targets. For traditional drug targets, in silico structure-based methods have been successful in many cases. However, their performance suffers on PPI interfaces because PPI interfaces are different in five major aspects: From a geometric standpoint, they have relatively large interface regions, flat geometry, and the interface surface shape tends to fluctuate upon binding. Also, their interactions are dominated by hydrophobic atoms, which is different from traditional binding-pocket-targeted drugs. Finally, PPI targets usually lack natural molecules that bind to the target PPI interface. Here, we first summarize characteristics of PPI interfaces and their known binders. Then, we will review existing in silico structure-based approaches for discovering small molecules that bind to PPI interfaces.

SUMOylation Promotes Nuclear Import and Stabilization of Polo-like Kinase 1 to Support Its Mitotic Function

As a pivotal mitotic regulator, polo-like kinase 1 (PLK1) is under highly coordinated and multi-layered regulation. However, the pathways that control PLK1's activity and function have just begun to be elucidated. PLK1 has recently been shown to be functionally modulated by post-translational modifications (PTMs), including phosphorylation and ubiquitination. Herein, we report that SUMOylation plays an essential role in regulating PLK1's mitotic function. We found that Ubc9 was recruited to PLK1 upon initial phosphorylation and activation by CDK1/cyclin B. By in vivo and in vitro SUMOylation assays, PLK1 was identified as a physiologically relevant small ubiquitin-related modifier (SUMO)-targeted protein, preferentially modified by SUMO-1. We further showed that K492 on PLK1 is essential for SUMOylation. SUMOylation causes PLK1's nuclear import and significantly increases its protein stability, both of which are critical for normal mitotic progression and genomic integrity. Our findings suggest that SUMOylation is an important regulatory mechanism governing PLK1's mitotic function.

PML nuclear bodies, membrane-less domains acting as ROS sensors?

PML Nuclear bodies (PML NBs) are spherical domains associated with a broad range of activities upon stress responses such as apoptosis, senescence DNA repair, epigenetic control, as well as control of oncogenesis. These bodies are considered as privileged sites for post-translational modifications, where sumoylation plays a key role. Here we summarize recent in vitro and in vivo findings on the link between PML NBs and ROS, in particular PML contributions to oxidative stress response. We discuss how it may regulate switch from cell protection against stress to cell arrest/cell death.

Inhibitors targeting the SUMOylation pathway: A patent review 2012‑2015 (Review)

Small ubiquitin‑related modifier (SUMO) proteins bind to the lysine residue of target proteins to produce functionally mature proteins. The abnormal SUMOylation of certain target proteins is associated with diseases including cancer, heart disease, diabetes, arthritis, degenerative diseases and brain ischemia/stroke. Thus, there has been growing appreciation for the potential importance of the SUMO conjugation pathway as a target for treating these diseases. This review introduces the important steps in the reversible SUMOylation pathway. The SUMO inhibitors disclosed in the patents between 2012 and 2015 are divided into different categories according to their mechanisms of action. Certain compounds disclosed in this review have also been reported in other articles for their inhibition of the SUMOylation pathway following screening in cell lines. Although there are few studies using animal models or clinical trials that have used these compounds, the application of bortezomin, a ubiquitylation inhibitor, for treating cancer indicates that SUMO inhibitors may be clinically successful.