Global identification of phospho-dependent SCF substrates reveals a FBXO22 phosphodegron and an ERK-FBXO22-BAG3 axis in tumorigenesis

USP32 facilitates non-small cell lung cancer progression via deubiquitinating BAG3 and activating RAF-MEK-ERK signaling pathway

The regulatory significance of ubiquitin-specific peptidase 32 (USP32) in tumor is significant, nevertheless, the biological roles and regulatory mechanisms of USP32 in non-small cell lung cancer (NSCLC) remain unclear. According to our research, USP32 was strongly expressed in NSCLC cell lines and tissues and was linked to a bad prognosis for NSCLC patients. Interference with USP32 resulted in a significant inhibition of NSCLC cell proliferation, migration potential, and EMT development; on the other hand, USP32 overexpression had the opposite effect. To further elucidate the mechanism of action of USP32 in NSCLC, we screened H1299 cells for interacting proteins and found that USP32 interacts with BAG3 (Bcl2-associated athanogene 3) and deubiquitinates and stabilizes BAG3 in a deubiquitinating activity-dependent manner. Functionally, restoration of BAG3 expression abrogated the antitumor effects of USP32 silencing. Furthermore, USP32 increased the phosphorylation level of the RAF/MEK/ERK signaling pathway in NSCLC cells by stabilizing BAG3. In summary, these findings imply that USP32 is critical to the development of NSCLC and could offer a theoretical framework for the clinical diagnosis and management of NSCLC patients in the future.

Promotion of stem cell-like phenotype of lung adenocarcinoma by FAM83A via stabilization of ErbB2

Lung cancer stands as the leading cause of mortality among all types of tumors, with over 40% of cases being lung adenocarcinoma (LUAD). Family with sequence similarity 83 member A (FAM83A) emerges as a notable focus due to its frequent overexpression in LUAD. Despite this, the precise role of FAM83A remains elusive. This study addresses this gap by unveiling the crucial involvement of FAM83A in maintaining the cancer stem cell-like (CSC-like) phenotype of LUAD. Through a global proteomics analysis, the study identifies human epidermal growth factor receptor 2 (HER2 or ErbB2) as a crucial target of FAM83A. Mechanistically, FAM83A facilitated ErbB2 expression at the posttranslational modification level via the E3 ubiquitin ligase STUB1 (STIP1-homologous U-Box containing protein 1). More importantly, the interaction between FAM83A and ErbB2 at Arg241 promotes calcineurin (CALN)-mediated dephosphorylation of ErbB2, followed by inhibition of STUB1-mediated ubiquitin-proteasomal ErbB2 degradation. The maintenance of the CSC-like phenotype by FAM83A, achieved through the posttranslational regulation of ErbB2, offers valuable insights for identifying potential therapeutic targets for LUAD.

Cross-talk between BCKDK-mediated phosphorylation and STUB1-dependent ubiquitination degradation of BCAT1 promotes GBM progression

Branched-chain amino acid transferase 1 (BCAT1) is highly expressed in multiple cancers and is associated with poor prognosis, particularly in glioblastoma (GBM). However, the post-translational modification (PTM) mechanism of BCAT1 is unknown. Here, we investigated the cross-talk mechanisms between phosphorylation and ubiquitination modifications in regulating BCAT1 activity and stability. We found that BCAT1 is phosphorylated by branched chain ketoacid dehydrogenase kinase (BCKDK) at S5, S9, and T312, which increases its catalytic and antioxidant activity and stability. STUB1 (STIP1 homology U-box-containing protein 1), the first we found and reported E3 ubiquitin ligase of BCAT1, can also be phosphorylated by BCKDK at the S19 site, which disrupts the interaction with BCAT1 and inhibits its degradation. In addition, we demonstrate through in vivo and in vitro experiments that BCAT1 phosphorylation inhibiting its ubiquitination at multiple sites is associated with GBM proliferation and that inhibition of the BCKDK-BCAT1 axis enhances the sensitivity to temozolomide (TMZ). Overall, we identified novel mechanisms for the regulation of BCAT1 modification and elucidated the importance of the BCKDK-STUB1-BCAT1 axis in GBM progression.

Substrate and Functional Diversity of Protein Lysine Post-translational Modifications

Lysine post-translational modifications (PTMs) are widespread and versatile protein PTMs that are involved in diverse biological processes by regulating the fundamental functions of histone and non-histone proteins. Dysregulation of lysine PTMs is implicated in many diseases, and targeting lysine PTM regulatory factors, including writers, erasers, and readers, has become an effective strategy for disease therapy. The continuing development of mass spectrometry (MS) technologies coupled with antibody-based affinity enrichment technologies greatly promotes the discovery and decoding of PTMs. The global characterization of lysine PTMs is crucial for deciphering the regulatory networks, molecular functions, and mechanisms of action of lysine PTMs. In this review, we focus on lysine PTMs, and provide a summary of the regulatory enzymes of diverse lysine PTMs and the proteomics advances in lysine PTMs by MS technologies. We also discuss the types and biological functions of lysine PTM crosstalks on histone and non-histone proteins and current druggable targets of lysine PTM regulatory factors for disease therapy.

BAG3 promotes proliferation and migration of arterial smooth muscle cells by regulating STAT3 phosphorylation in diabetic vascular remodeling

BACKGROUND

Diabetic vascular remodeling is the most important pathological basis of diabetic cardiovascular complications. The accumulation of advanced glycation end products (AGEs) caused by elevated blood glucose promotes the proliferation and migration of vascular smooth muscle cells (VSMCs), leading to arterial wall thickening and ultimately vascular remodeling. Therefore, the excessive proliferation and migration of VSMCs is considered as an important therapeutic target for vascular remodeling in diabetes mellitus. However, due to the lack of breakthrough in experiments, there is currently no effective treatment for the excessive proliferation and migration of VSMCs in diabetic patients. Bcl-2-associated athanogene 3 (BAG3) protein is a multifunctional protein highly expressed in skeletal muscle and myocardium. Previous research has confirmed that BAG3 can not only regulate cell survival and apoptosis, but also affect cell proliferation and migration. Since the excessive proliferation and migration of VSMCs is an important pathogenesis of vascular remodeling in diabetes, the role of BAG3 in the excessive proliferation and migration of VSMCs and its molecular mechanism deserve further investigation.

METHODS

In this study, BAG3 gene was manipulated in smooth muscle to acquire SM22αCre; BAG3FL/FL mice and streptozotocin (STZ) was used to simulate diabetes. Expression of proteins and aortic thickness of mice were detected by immunofluorescence, ultrasound and hematoxylin-eosin (HE) staining. Using human aorta smooth muscle cell line (HASMC), cell viability was measured by CCK-8 and proliferation was measured by colony formation experiment. Migration was detected by transwell, scratch experiments and Phalloidin staining. Western Blot was used to detect protein expression and Co-Immunoprecipitation (Co-IP) was used to detect protein interaction.

RESULTS

In diabetic vascular remodeling, AGEs could promote the interaction between BAG3 and signal transducer and activator of transcription 3 (STAT3), leading to the enhanced interaction between STAT3 and Janus kinase 2 (JAK2) and reduced interaction between STAT3 and extracellular signal-regulated kinase 1/2 (ERK1/2), resulting in accumulated p-STAT3(705) and reduced p-STAT3(727). Subsequently, the expression of matrix metallopeptidase 2 (MMP2) is upregulated, thus promoting the migration of VSMCs.

CONCLUSIONS

BAG3 upregulates the expression of MMP2 by increasing p-STAT3(705) and decreasing p-STAT3(727) levels, thereby promoting vascular remodeling in diabetes. This provides a new orientation for the prevention and treatment of diabetic vascular remodeling.

Post-translational regulation of the mTORC1 pathway: A switch that regulates metabolism-related gene expression

The mechanistic target of rapamycin complex 1 (mTORC1) is a kinase complex that plays a crucial role in coordinating cell growth in response to various signals, including amino acids, growth factors, oxygen, and ATP. Activation of mTORC1 promotes cell growth and anabolism, while its suppression leads to catabolism and inhibition of cell growth, enabling cells to withstand nutrient scarcity and stress. Dysregulation of mTORC1 activity is associated with numerous diseases, such as cancer, metabolic disorders, and neurodegenerative conditions. This review focuses on how post-translational modifications, particularly phosphorylation and ubiquitination, modulate mTORC1 signaling pathway and their consequential implications for pathogenesis. Understanding the impact of phosphorylation and ubiquitination on the mTORC1 signaling pathway provides valuable insights into the regulation of cellular growth and potential therapeutic targets for related diseases.

AZD7762 induces CRBN dependent BAG3 degradation through ubiquitin-proteasome pathway

Protein degraders are currently under rapid development as a promising modality for drug discovery. They are compounds that orchestrate interactions between a target protein and an E3 ubiquitin ligase, prompting intracellular protein degradation through proteasomal pathway. More protein degraders identification will greatly promote the development of this field. BAG3 is widely recognized as an excellent therapeutic target in cancer treatments. Exploring protein degraders that target BAG3 degradation has profound implications. Herein, molecular docking was applied to assess binding energy between 81 clinical phase I kinase inhibitors and BAG3. BAG3 protein and mRNA level were detected by western blot and quantitative real-time PCR. CCK8 assay and colony formation assay were applied to detect the cell viability and proliferation rate. Cell death was accessed using flow cytometry combined with PI and Annexin V double staining. AZD7762, a Chk1 kinase inhibitor, was identified to induce BAG3 degradation in a ubiquitin-proteasome pathway. AZD7762-induced BAG3 degradation was not dependent on Chk1 expression or activity. CRBN, an E3 ligase, was identified to bind to BAG3 and mediated BAG3 ubiquitination in the presence of AZD7762. By targeting Chk1 and BAG3, two ideal therapeutic targets in cancer treatment, AZD7762 would be a powerful chemotherapy agent in the future.

Proteomics and β-hydroxybutyrylation Modification Characterization in the Hearts of Naturally Senescent Mice

Aging is widely accepted as an independent risk factor for cardiovascular disease (CVD), which contributes to increasing morbidity and mortality in the elderly population. Lysine β-hydroxybutyrylation (Kbhb) is a novel post-translational modification (PTM), wherein β-hydroxybutyrate is covalently attached to lysine ε-amino groups. Recent studies have revealed that histone Kbhb contributes to tumor progression, diabetic cardiomyopathy progression, and postnatal heart development. However, no studies have yet reported a global analysis of Kbhb proteins in aging hearts or elucidated the mechanisms underlying this modification in the process. Herein, we conducted quantitative proteomics and Kbhb PTM omics to comprehensively elucidate the alterations of global proteome and Kbhb modification in the hearts of aged mice. The results revealed a decline in grip strength and cardiac diastolic function in 22-month-old aged mice compared to 3-month-old young mice. High-throughput liquid chromatogram-mass spectrometry analysis identified 1710 β-hydroxybutyrylated lysine sites in 641 proteins in the cardiac tissue of young and aged mice. Additionally, 183 Kbhb sites identified in 134 proteins exhibited significant differential modification in aged hearts (fold change (FC) > 1.5 or <1/1.5, p < 0.05). Notably, the Kbhb-modified proteins were primarily detected in energy metabolism pathways, such as fatty acid elongation, glyoxylate and dicarboxylate metabolism, tricarboxylic acid cycle, and oxidative phosphorylation. Furthermore, these Kbhb-modified proteins were predominantly localized in the mitochondria. The present study, for the first time, provides a global proteomic profile and Kbhb modification landscape of cardiomyocytes in aged hearts. These findings put forth novel possibilities for treating cardiac aging and aging-related CVDs by reversing abnormal Kbhb modifications.

Serial and multi-level proteome analysis for microscale protein samples

Post-translational modifications (PTMs), such as phosphorylation and ubiquitination, play key roles in signal transduction and protein homeostasis. The crosstalk of PTMs greatly expands the components of proteome and protein functions. Multi-level proteome analysis, which involves proteome investigations of total lysate and PTMs in this context, provides a comprehensive approach to explore the PTM crosstalk of a biological system under diverse disturbances. However, multi-level proteome practice remains technically challenging. Here we intended to build a strategy for multi-level proteome analysis, in which we focus on the serial profiling the total proteome, ubiquitinome and phosphoproteome from the microscale of starting material. We started by evaluating five common lysis buffers and found that the sodium deoxycholate buffer provided the best overall performance. We then developed an approach for serial enrichment and profiling of the multi-level proteome. To expand the depth of identification, we customized the variable windows to perform data-independent acquisition (DIA) sequencing for each proteome. In total, we identified 6465 proteins, ∼20,000 GlyGly sites (class 1), and ∼ 19,000 phosphosites (class 1) sequentially using 1 mg of HeLa digest by three DIA measurements. We applied this strategy to analyze MG132-treated HeLa cells and observed the crosstalk between ubiquitination and phosphorylation. Our method can be referenced for other multi-level proteome studies with microscale samples. SIGNIFICANCE: Lysis buffer containing sodium deoxycholate provided the best overall performance in multi-level proteome analysis. One step of ubiquitination enrichment before phosphorylation enrichment does not reduce the reproducibility of phosphoproteome. Customized isolation windows were established for DIA analysis on each level of proteome. Combined the serial enrichment approach and the customized single-shot DIA method enabled the multi-level proteome of microscale protein samples.

Inhibition of CDK1 Overcomes Oxaliplatin Resistance by Regulating ACSL4-mediated Ferroptosis in Colorectal Cancer

Oxaliplatin is a widely used chemotherapy drug for patients with advanced colorectal cancer (CRC); however, frequent drug resistance limits its therapeutic efficacy in patients. Here, this work identifies cyclin-dependent kinase 1 (CDK1) as a critical contributor to oxaliplatin resistance via in vitro and in vivo CRISPR/Cas9 screening. CDK1 is highly expressed in oxaliplatin-resistant cells and tissues due to the loss of N6-methyladenosine modification. Genetic and pharmacological blockade of CDK1 restore the susceptibility of CRC cells to oxaliplatin in vitro and in cell/patient-derived xenograft models. Mechanistically, CDK1 directly binds to and phosphorylates Acyl-CoA synthetase long-chain family 4 (ACSL4) at S447, followed by recruitment of E3 ubiquitin ligase UBR5 and polyubiquitination of ACSL4 at K388, K498, and K690, which leads to ACSL4 protein degradation. Reduced ACSL4 subsequently blocks the biosynthesis of polyunsaturated fatty acid containing lipids, thereby inhibiting lipid peroxidation and ferroptosis, a unique iron-dependent form of oxidative cell death. Moreover, treatment with a ferroptosis inhibitor nullifies the enhancement of CRC cell sensitivity to oxaliplatin by CDK1 blockade in vitro and in vivo. Collectively, the findings indicate that CDK1 confers oxaliplatin resistance to cells by suppressing ferroptosis. Therefore, administration of a CDK1 inhibitor may be an attractive strategy to treat patients with oxaliplatin-resistant CRC.

Exploiting E3 ubiquitin ligases to reeducate the tumor microenvironment for cancer therapy

Tumor development relies on a complex and aberrant tissue environment in which cancer cells receive the necessary nutrients for growth, survive through immune escape, and acquire mesenchymal properties that mediate invasion and metastasis. Stromal cells and soluble mediators in the tumor microenvironment (TME) exhibit characteristic anti-inflammatory and protumorigenic activities. Ubiquitination, which is an essential and reversible posttranscriptional modification, plays a vital role in modulating the stability, activity and localization of modified proteins through an enzymatic cascade. This review was motivated by accumulating evidence that a series of E3 ligases and deubiquitinases (DUBs) finely target multiple signaling pathways, transcription factors and key enzymes to govern the functions of almost all components of the TME. In this review, we systematically summarize the key substrate proteins involved in the formation of the TME and the E3 ligases and DUBs that recognize these proteins. In addition, several promising techniques for targeted protein degradation by hijacking the intracellular E3 ubiquitin-ligase machinery are introduced.

Sirt3 mediates the benefits of exercise on bone in aged mice

Exercise in later life is important for bone health and delays the progression of osteoporotic bone loss. Osteocytes are the major bone cells responsible for transforming mechanical stimuli into cellular signals through their highly specialized lacunocanalicular networks (LCN). Osteocyte activity and LCN degenerate with aging, thus might impair the effectiveness of exercise on bone health; however, the underlying mechanism and clinical implications remain elusive. Herein, we showed that deletion of Sirt3 in osteocytes could impair the formation of osteocyte dendritic processes and inhibit bone gain in response to exercise in vivo. Mechanistic studies revealed that Sirt3 regulates E11/gp38 through the protein kinase A (PKA)/cAMP response element-binding protein (CREB) signaling pathway. Additionally, the Sirt3 activator honokiol enhanced the sensitivity of osteocytes to fluid shear stress in vitro, and intraperitoneal injection of honokiol reduced bone loss in aged mice in a dose-dependent manner. Collectively, Sirt3 in osteocytes regulates bone mass and mechanical responses through the regulation of E11/gp38. Therefore, targeting Sirt3 could be a novel therapeutic strategy to prevent age-related bone loss and augment the benefits of exercise on the senescent skeleton.

Signaling pathways governing glioma cancer stem cells behavior

Glioma is the most common malignant brain tumor that develops in the glial tissue. Several studies have identified that glioma cancer stem cells (GCSCs) play important roles in tumor-initiating features in malignant gliomas. GCSCs are a small population in the brain that presents an essential role in the metastasis of glioma cells to other organs. These cells can self-renew and differentiate, which are thought to be involved in the pathogenesis of glioma. Therefore, targeting GCSCs might be a novel strategy for the treatment of glioma. Accumulating evidence revealed that several signaling pathways, including Notch, TGF-β, Wnt, STAT3, AKT, and EGFR mediated GCSC growth, proliferation, migration, and invasion. Besides, non-coding RNAs (ncRNAs), including miRNAs, circular RNAs, and long ncRNAs have been found to play pivotal roles in the regulation of GCSC pathogenesis and drug resistance. Therefore, targeting these pathways could open a new avenue for glioma management. In this review, we summarized critical signaling pathways involved in the stimulation or prevention of GCSCs tumorigenesis and invasiveness.

Proteomic characterization of post-translational modifications in drug discovery

Protein post-translational modifications (PTMs), which are usually enzymatically catalyzed, are major regulators of protein activity and involved in almost all celluar processes. Dysregulation of PTMs is associated with various types of diseases. Therefore, PTM regulatory enzymes represent as an attractive and important class of targets in drug research and development. Inhibitors against kinases, methyltransferases, deacetyltransferases, ubiquitin ligases have achieved remarkable success in clinical application. Mass spectrometry-based proteomics technologies serve as a powerful approach for system-wide characterization of PTMs, which facilitates the identification of drug targets, elucidation of the mechanisms of action of drugs, and discovery of biomakers in personalized therapy. In this review, we summarize recent advances of proteomics-based studies on PTM targeting drugs and discuss how proteomics strategies facilicate drug target identification, mechanism elucidation, and new therapy development in precision medicine.

Role of SARS-CoV-2-induced Cytokine Storm in Multi-Organ Failure: Molecular Pathways and Potential Therapeutic Options

Coronavirus disease 2019 (COVID-19) outbreak has become a global public health emergency and has led to devastating results. Mounting evidence proposes that the disease causes severe pulmonary involvement and influences different organs, leading to a critical situation named multi-organ failure. It is yet to be fully clarified how the disease becomes so deadly in some patients. However, it is proven that a condition called “cytokine storm” is involved in the deterioration of COVID-19. Although beneficial, sustained production of cytokines and overabundance of inflammatory mediators causing cytokine storm can lead to collateral vital organ damages. Furthermore, cytokine storm can cause post-COVID-19 syndrome (PCS), an important cause of morbidity after the acute phase of COVID-19. Herein, we aim to explain the possible pathophysiology mechanisms involved in COVID-19-related cytokine storm and its association with multi-organ failure and PCS. We also discuss the latest advances in finding the potential therapeutic targets to control cytokine storm wishing to answer unmet clinical demands for treatment of COVID-19.

Targeting matrix metalloproteinases by E3 ubiquitin ligases as a way to regulate the tumor microenvironment for cancer therapy

The tumor microenvironment (TME) plays an important role in neoplastic development. Matrix metalloproteinases (MMPs) are critically involved in tumorigenesis by modulation of the TME and degradation of the extracellular matrix (ECM) in a large variety of malignancies. Evidence has revealed that dysregulated MMPs can lead to ECM damage, the promotion of cell migration and tumor metastasis. The expression and activities of MMPs can be tightly regulated by TIMPs, multiple signaling pathways and noncoding RNAs. MMPs are also finely controlled by E3 ubiquitin ligases. The current review focuses on the molecular mechanism by which MMPs are governed by E3 ubiquitin ligases in carcinogenesis. Due to the essential role of MMPs in oncogenesis, they have been considered the attractive targets for antitumor treatment. Several strategies that target MMPs have been discovered, including the use of small-molecule inhibitors, peptides, inhibitory antibodies, natural compounds with anti-MMP activity, and RNAi therapeutics. However, these molecules have multiple disadvantages, such as poor solubility, severe side-effects and low oral bioavailability. Therefore, it is necessary to discover the novel inhibitors that suppress MMPs for cancer therapy. Here, we discuss the therapeutic potential of targeting E3 ubiquitin ligases to inhibit MMPs. We hope this review will stimulate the discovery of novel therapeutics for the MMP-targeted treatment of a variety of human cancers.

FBXO2 targets glycosylated SUN2 for ubiquitination and degradation to promote ovarian cancer development

SAD1/UNC84 domain protein-2 (SUN2) plays a tumor suppressor role in various types of cancer by inhibiting cancer cell proliferation, migration and promoting apoptosis. However, the post-translational regulation of SUN2 and the cellular mechanism responsible for its proteasomal degradation remains largely unknown. Here, we show that FBXO2, an E3 ubiquitin ligase of the F-box proteins (FBPs) family targets glycosylated SUN2 for ubiquitination and degradation via the ubiquitin-proteasome system (UPS). By integrating the Cancer Genome Atlas (TCGA), Gene Expression Omnibus (GEO), and the Encyclopedia of Cancer Cell Lines (CCLE) databases, we revealed that FBXO2 was selectively highly expressed in ovarian cancer (OV) tissues and cells. Patients with relatively high FBXO2 expression levels were associated with worse prognosis. Manipulation of the expression of FBXO2 affecting ovarian cancer cell proliferation, migration/invasion in vitro, and tumor growth in mice in vivo. The transcription factor SOX6 promoted FBXO2 expression by recognizing a putative response element localized on the promoter region of FBXO2. Abnormally highly expressed FBXO2 recognized and targeted glycosylated SUN2 protein for ubiquitination-depended degradation to prevent cell apoptosis, promote cell proliferation, and ultimately promote the progression of OV. Thus, we revealed a new SOX6-FBXO2-SUN2 axis that contributed to the development of OV, and targeting this axis may represent an effective OV treatment strategy.

Valganciclovir as Add-on to Second-Line Therapy in Patients with Recurrent Glioblastoma

Simple Summary

Patients with glioblastoma have a dismal prognosis. The major challenge with this disease is that it recurs despite aggressive first-line therapy and rapidly becomes therapy resistant. Cytomegalovirus has been found in most glioblastoma tumors and may contribute to tumor aggressiveness. Antiviral therapy may thus represent a novel therapeutic strategy and has shown promising results in patients with newly diagnosed glioblastoma. We performed a retrospective analysis of survival data of 29 patients with recurrent glioblastoma receiving the antiviral drug valganciclovir as an add-on to second-line therapy and of 109 contemporary controls treated at our institution. Valganciclovir was well tolerated and seemed to improve survival after tumor recurrence in patients with recurrent disease both in re-operated and non-re-operated patients and in patients with unmethylated and methylated MGMT promoter status. Prospective controlled clinical studies on patients with recurrent glioblastoma are warranted to evaluate if valganciclovir treatment offers a novel therapeutic option.

Abstract

Glioblastoma invariably recurs despite aggressive and multimodal first-line treatment and no standardized second-line therapy exists. We previously reported that treatment with the antiviral drug valganciclovir as an add-on to standard therapy significantly prolonged overall survival in 102 patients with newly diagnosed glioblastoma compared to contemporary controls. Here we present the results of retrospective survival analyses including patients with glioblastoma that initiated valganciclovir therapy after recurrence. Twenty-nine patients with recurrent glioblastoma received valganciclovir as an add-on to second-line therapy at Karolinska University Hospital. Contemporary controls were 109 patients with glioblastoma who received similar second-line therapy at our institution. We retrospectively analyzed survival data of these patients. Patients with recurrent glioblastoma who received valganciclovir had longer median overall survival after recurrence than controls (12.1 vs. 7.4 months, respectively, p = 0.0028). The drug was well tolerated. Both patients who underwent re-operation and patients that were not re-operated after recurrence benefitted significantly from valganciclovir therapy. Valganciclovir prolonged survival after recurrence both in patients with an unmethylated and methylated MGMT promoter gene. Valganciclovir was safe to use and prolonged median survival after recurrence for patients with recurrent glioblastoma, re-operated or not after recurrence, and with methylated or unmethylated MGMT promoter gene.

Insights in Post-Translational Modifications: Ubiquitin and SUMO

Both ubiquitination and SUMOylation are dynamic post-translational modifications that regulate thousands of target proteins to control virtually every cellular process. Unfortunately, the detailed mechanisms of how all these cellular processes are regulated by both modifications remain unclear. Target proteins can be modified by one or several moieties, giving rise to polymers of different morphology. The conjugation cascades of both modifications comprise a few activating and conjugating enzymes but close to thousands of ligating enzymes (E3s) in the case of ubiquitination. As a result, these E3s give substrate specificity and can form polymers on a target protein. Polymers can be quickly modified forming branches or cleaving chains leading the target protein to its cellular fate. The recent development of mass spectrometry(MS) -based approaches has increased the understanding of ubiquitination and SUMOylation by finding essential modified targets in particular signaling pathways. Here, we perform a concise overview comprising from the basic mechanisms of both ubiquitination and SUMOylation to recent MS-based approaches aimed to find specific targets for particular E3 enzymes.

Pan-Cancer Analyses Reveal Oncogenic Role and Prognostic Value of F-Box Only Protein 22

The F-box protein 22 (FBXO22), an F-box E3 ligase, has been identified to be critically involved in carcinogenesis. However, a systematic assessment of the role of FBXO22 across human cancers is lacking. Here, we performed a pan-cancer analysis to explore the role of FBXO22 in 33 cancer types using multiomic data from The Cancer Genome Atlas (TCGA). First, we found that high FBXO22 expression in multiple cancers was closely associated with poor overall survival and relapse-free survival. Next, we identified ten proteins that interact with FBXO22 and 13 of its target substrates using the STRING database and a literature search to explore the regulatory role of FBXO22 in tumorigenesis. Genes encoding these proteins were found to be significantly enriched in cell cycle negative regulation and ubiquitination pathways. This was confirmed in nonsmall cell lung cancer A549 cells, where FBXO22 overexpression enhanced cyclin-dependent kinase 4 (CDK4) protein levels and promoted cell proliferation. Similarly, overexpression or interference of FBXO22 changed the protein level of one of its substrates, PTEN. Additionally, we found that FBXO22 mutations were accompanied by altered substrate expression, especially in uterine corpus endometrial carcinoma and lung adenocarcinoma; endometrial carcinoma patients with FBXO22 genetic alterations also had better overall and relapse-free survival. Notably, FBXO22 methylation levels were also decreased in most tumors, and hypomethylation of FBXO22 was associated with poor overall survival, relapse-free interval, and progression-free interval in pancreatic adenocarcinoma. Finally, we analyzed the correlation between the abundance of tumor infiltrating lymphocytes (TILs) and FBXO22 expression, copy number variation, and methylation. Multiple algorithms revealed that high FBXO22 expression was associated with lower TIL levels, especially in lung adenocarcinoma, lung squamous cell carcinoma, and sarcoma. Taken together, our findings demonstrate that FBXO22 degrades tumor suppressor genes by ubiquitination and inhibits the cell cycle to promote nonsmall cell lung cancer progression. Our study also provides a relatively comprehensive understanding of the oncogenic role of FBXO22 in different tumors.