ASPP2 suppresses invasion and TGF-β1-induced epithelial-mesenchymal transition by inhibiting Smad7 degradation mediated by E3 ubiquitin ligase ITCH in gastric cancer

GDF6 in gastric cancer upregulated by helicobacter pylori induces epithelial-mesenchymal translation via the TGF-β/SMAD3 signaling pathway

OBJECTIVE

To investigate the association between Helicobacter pylori infection and GDF6 expression in gastric cancer patients, and to determine its influence on prognosis and resistance to capecitabine.

METHODS

Tumor and adjacent non-tumor tissues were collected from 148 gastric cancer patients who underwent surgery in our department from October 2019 to June 2022. Of these patients, 78 tested positive for Helicobacter pylori and 70 tested negative. Hematoxylin-eosin (HE) and immunofluorescence staining were utilized to quantify GDF6 expression in cancerous and adjacent tissues. Patient prognosis was monitored via follow-up. Western blotting analyzed GDF6 expression in common gastric cancer cell lines. HGC27 cells exhibiting high GDF6 expression and BGC823 cells with low expression were used to create GDF6-silenced and overexpressed cell lines. The impact of GDF6 on the proliferation, migration, invasion, and cloning abilities of gastric cancer cells was evaluated using the CCK-8 assay, scratch test, Transwell assay, and plate colony formation assay. Fluorescent quantitative PCR and Western blotting assessed the effects of GDF6 levels on epithelial-mesenchymal transition (EMT) and tumor cell stemness.

RESULTS

GDF6 expression in gastric cancer tissues was significantly correlated with cancer grading and staging (P<0.05). Helicobacter pylori-positive tissues exhibited significantly higher GDF6 expression levels than negative samples (P<0.05). Kaplan-Meier survival analysis indicated that high GDF6 expression was associated with poor survival prognosis. Overexpressed GDF6 enhanced the proliferation, migration, and invasion abilities of gastric cancer cells, while silencing GDF6 yielded opposite results. Increased GDF6 expression upregulated TGF-β expression and the phosphorylation levels of SMAD3, leading to an elevation in mesenchymal cell markers N-cadherin, vimentin, and a reduction in epithelial cell markers cytokeratins, E-cadherin. Moreover, high GDF6 levels contributed to increased resistance to capecitabine and enhanced the expression of tumor stem cell markers Nanog, Sox-2, Oct-4, CD44, amplifying tumor cell stemness.

CONCLUSION

Helicobacter pylori infection is associated with increased GDF6 expression in gastric cancer tissue, correlating with poor survival prognosis. Elevated GDF6 expression promotes the proliferation, migration, and invasion abilities of gastric cancer cells, facilitates EMT via the TGF-β/SMAD3 pathway, and intensifies cell stemness and capecitabine resistance. Consequently, GDF6 presents itself as a potential new target for gastric cancer treatment.

DATA AVAILABILITY STATEMENT

The data that support the findings of this study are available from the corresponding author upon reasonable request.

SIVA-1 enhances acquired chemotherapeutic drug resistance of gastric cancer in vivo by regulating the ARF/MDM2/p53 pathway

SIVA-1 has been shown to affect apoptotic processes in various different cell lines, and SIVA-1 significantly contributes to the decreased responsiveness of cancer cells to some chemotherapy agents. However, whether SIVA-1 has potential application in gastric cancer remains unknown. Therefore, the objective of this investigation was to clarify the distinct function of SIVA-1 in chemotherapeutic drug resistance within a living murine model with gastric malignancy, and initially elucidate the underlying mechanisms. In an established multidrug-resistant gastric cancer xenograft mouse model, lentivirus, named Lv-SIVA-1, was injected into xenograft tumors, and increased the mRNA and protein expression of endogenous SIVA-1 in tumors. Immunohistochemical assays of xenograft tumor showed that SIVA-1 was significantly upregulated, and the protein expression levels of SIVA-1 were highly increased, as detected by Western blotting. In addition, we detected the role of SIVA-1 in cell proliferation and cell apoptosis in gastric cancer cells by TUNEL and found that SIVA-1 decreased tumor cell apoptosis and promoted tumor growth in vivo. Using a TMT assay between tumor tissues of experimental and control groups, differentially expressed proteins were examined and three potential biomarkers of multidrug resistance (ARF, MDM2, and p53) were screened. We further investigated the molecular mechanism by which SIVA-1 played an efficient role against chemotherapies and found that overexpressed SIVA-1 leads to increased ARF and MDM2 expression and suppressed expression of p53 in tumor tissue. In conclusion, SIVA-1 plays a significant role in the multidrug resistance of gastric tumors. In addition, overexpressed SIVA-1 positively regulates cell proliferation, adjusts cycle progression, and reduces the response to drug treatment for gastric cancer in an ARF/MDM2/p53-dependent manner. This novel research provides a basis for chemical management of gastric cancer through regulation of SIVA-1 expression.

ASPP2 Is Phosphorylated by CDK1 during Mitosis and Required for Pancreatic Cancer Cell Proliferation

(1) Background: pancreatic cancer is highly lethal. The role of apoptosis-stimulating protein of p53-2 (ASPP2) in this lethal disease remains unclear. This protein belongs to the ASPP family of p53 interacting proteins. Previous studies in this lab used phosphate-binding tag (Phos-tag) sodium dodecyl sulfate (SDS) polyacrylamide gels and identified a motility upshift of the ASPP family of proteins during mitosis. (2) Purpose: this study expands on previous findings to identify the detailed phosphorylation regulation of ASPP2 during mitosis, as well as the function of ASPP2 in pancreatic cancer. (3) Methods: the Phos-tag technique was used to investigate the phosphorylation mechanism of ASPP2 during mitosis. Phospho-specific antibodies were generated to validate the phosphorylation of ASPP2, and ASPP2-inducible expression cell lines were established to determine the role of ASPP2 in pancreatic cancer. RNA sequencing (RNA-Seq) was used to uncover the downstream targets of ASPP2. (4) Results: results demonstrate that ASPP2 is phosphorylated during mitosis by cyclin-dependent kinase 1 (CDK1) at sites S562 and S704. In vitro and in vivo results show that ASPP2 is required for pancreatic cancer growth. Furthermore, the expressions of yes-associated protein (YAP)-related genes are found to be dramatically altered by ASPP2 depletion. Together, these findings reveal the phosphorylation mechanism of ASPP2 during mitosis. Collectively, results strongly indicate that ASPP2 is a potential target for abating tumor cell growth in pancreatic cancer.

NEDD4 E3 ubiquitin ligases: promising biomarkers and therapeutic targets for cancer

Accumulating evidence has demonstrated that NEDD4 E3 ubiquitin ligase family plays a pivotal oncogenic role in a variety of malignancies via mediating ubiquitin dependent degradation processes. Moreover, aberrant expression of NEDD4 E3 ubiquitin ligases is often indicative of cancer progression and correlated with poor prognosis. In this review, we are going to address association of expression of NEDD4 E3 ubiquitin ligases with cancers, the signaling pathways and the molecular mechanisms by which the NEDD4 E3 ubiquitin ligases regulate oncogenesis and progression, and the therapies targeting the NEDD4 E3 ubiquitin ligases. This review provides the systematic and comprehensive summary of the latest research status of E3 ubiquitin ligases in the NEDD4 subfamily, and proposes that NEDD4 family E3 ubiquitin ligases are promising anti-cancer drug targets, aiming to provide research direction for clinical targeting of NEDD4 E3 ubiquitin ligase therapy.

UPS: Opportunities and challenges for gastric cancer treatment

Gastric cancer remains the fourth most frequently diagnosed malignancy and the fifth leading cause of cancer-related mortality worldwide owning to the lack of efficient drugs and targets for therapy. Accumulating evidence indicates that UPS, which consists of E1, E2, and E3 enzymes and proteasome, plays an important role in the GC tumorigenesis. The imbalance of UPS impairs the protein homeostasis network during development of GC. Therefore, modulating these enzymes and proteasome may be a promising strategy for GC target therapy. Besides, PROTAC, a strategy using UPS to degrade the target protein, is an emerging tool for drug development. Thus far, more and more PROTAC drugs enter clinical trials for cancer therapy. Here, we will analyze the abnormal expression enzymes in UPS and summarize the E3 enzymes which can be developed in PROTAC so that it can contribute to the development of UPS modulator and PROTAC technology for GC therapy.

Emerging roles of the HECT E3 ubiquitin ligases in gastric cancer

Gastric cancer (GC) is one of the most pernicious gastrointestinal tumors with extraordinarily high incidence and mortality. Ubiquitination modification of cellular signaling proteins has been shown to play important roles in GC tumorigenesis, progression, and prognosis. The E3 ubiquitin ligase is the crucial enzyme in the ubiquitination reaction and determines the specificity of ubiquitination substrates, and thus, the cellular effects. The HECT E3 ligases are the second largest E3 ubiquitin ligase family characterized by containing a HECT domain that has E3 ubiquitin ligase activity. The HECT E3 ubiquitin ligases have been found to engage in GC progression. However, whether HECT E3 ligases function as tumor promoters or tumor suppressors in GC remains controversial. In this review, we will focus on recent discoveries about the role of the HECT E3 ubiquitin ligases, especially members of the NEDD4 and other HECT E3 ligase subfamilies, in GC.

TP53BP2: Roles in suppressing tumorigenesis and therapeutic opportunities

Malignant tumor is still a major problem worldwide. During tumorigenesis or tumor development, tumor suppressor p53-binding protein 2 (TP53BP2), also known as apoptosis stimulating protein 2 of p53 (ASPP2), plays a critical role in p53 dependent and independent manner. Expression of TP53BP2 is highly correlated with the prognosis and survival rate of malignant tumor patients. TP53BP2 can interact with p53, NF-κB p65, Bcl-2, HCV core protein, PP1, YAP, CagA, RAS, PAR3, and other proteins to regulate cell function. Moreover, TP53BP2 can also regulate the proliferation, apoptosis, autophagy, migration, EMT and drug resistance of tumor cells through downstream signaling pathways, such as NF-κB, RAS/MAPK, mevalonate, TGF-β1, PI3K/AKT, aPKC-ι/GLI1 and autophagy pathways. As a potential therapeutic target, TP53BP2 has been attracted more attention. We review the role of TP53BP2 in tumorigenesis or tumor development and the signal pathway involved in TP53BP2, which may provide more deep insight and strategies for tumor treatment.

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.

Molecular Mechanisms and Potential Rationale of Immunotherapy in Peritoneal Metastasis of Advanced Gastric Cancer

Peritoneal metastasis (PM) is one of the most frequent metastasis patterns of gastric cancer (GC), and the prognosis of patients with PM is very dismal. According to Paget’s theory, disseminated free cancer cells are seeded and survive in the abdominal cavity, adhere to the peritoneum, invade the subperitoneal tissue, and proliferate through angiogenesis. In these sequential processes, several key molecules are involved. From a therapeutic point of view, immunotherapy with chemotherapy combination has become the standard of care for advanced GC. Several clinical trials of newer immunotherapy agents are ongoing. Understanding of the molecular process of PM and the potential rationale of immunotherapy for PM treatment is necessary. Beyond understanding of the molecular aspect of PM, many studies have been conducted on the modality of treatment of PM. Notably, intraperitoneal approaches, including chemotherapy or immunotherapy, have been conducted, because systemic treatment of PM has limitations. In this study, we reviewed the molecular mechanisms and immunologic aspects of PM, and intraperitoneal approaches under investigation for treating PM.

Reticulon 2 promotes gastric cancer metastasis via activating endoplasmic reticulum Ca2+ efflux-mediated ERK signalling

Gastric cancer ranks fourth for mortality globally among various malignant tumours, and invasion and metastasis are the major reason leading to its poor prognosis. Recently, accumulating studies revealed the role of reticulon proteins in cell growth and transmigration. However, the expression and biological function of reticulon proteins in human gastric cancer remain largely unclear. Herein, we explored the potential role of reticulon 2 (RTN2) in the progression of gastric cancer. Tissue microarray was used to determine the expression levels of RTN2 in 267 gastric cancer patients by immunohistochemistry. Gastric cancer cell lines were utilised to examine the influences of RTN2 on cellular migration and invasion abilities, epithelial-to-mesenchymal transition (EMT) and signalling pathway. In vivo studies were also performed to detect the effect of RTN2 on tumour metastasis. We found that RTN2 expression was notably upregulated in tumour tissues compared to pericarcinomatous tissues. High RTN2 expression was positively correlated with patients’ age, vessel invasion, tumour invasion depth, lymph node metastasis and TNM stage. Besides, high RTN2 staining intensity was associated with adverse survival which was further identified as an independent prognostic factor for gastric cancer patients by multivariate analysis. And the predictive accuracy was also improved when incorporated RTN2 into the TNM-staging system. RTN2 could promote the proliferation, migration and invasion of gastric cancer cells in vitro and lung metastasis in vivo. Mechanistically, RTN2 interacted with IP3R, and activated ERK signalling pathway via facilitating Ca²⁺ release from the endoplasmic reticulum, and subsequently drove EMT in gastric cancer cells. These results proposed RTN2 as a novel promotor and potential molecular target for gastric cancer therapies.

A CD44 variant is essential for Slug-dependent vimentin gene expression to acquire TGF-β1-induced tumor cell motility

CD44 is a widely expressed polymorphic adhesion molecule that has pleiotropic functions in development and tumor progression. Its mRNA undergoes alternative splicing to generate multiple variant (CD44v) isoforms, although the function of each CD44v isoform is not fully elucidated. Here, we show that CD44v plays an important role in the induction of vimentin expression upon transforming growth factor‐β1 (TGF‐β1)‐induced epithelial–mesenchymal transition (EMT). Among multiple CD44v isoforms expressed in NUGC3 gastric cancer cells, CD44v8‐10 and CD44v3,8‐10 are involved in the acquisition of migratory and invasive properties associated with TGF‐β1‐induced EMT, and only CD44v3,8‐10 induces the transcription of vimentin mediated by the EMT transcription factor Slug. In primary tumor specimens obtained from patients with gastric cancer, CD44‐containing variant exon 9 (CD44v9) expression and EMT features [E‐cadherin(−)vimentin(+)] were significantly correlated, and EMT features in the cells expressing CD44v9 were associated with tumor invasion depth, lymph node metastasis, and pStage, which indicate invasive and metastatic properties, and poor prognosis. These results indicate that certain CD44v isoforms promote tumor cell motility and metastasis in gastric cancer in association with EMT features, and CD44v3,8‐10 may contribute to these clinical characteristics.

Concurrent targeting of MAP3K3 and BRD4 by miR-3140-3p overcomes acquired resistance to BET inhibitors in neuroblastoma cells

Neuroblastoma (NB) harboring MYCN amplification is a refractory disease with a poor prognosis. As BRD4, an epigenetic reader belonging to the bromodomain and extra terminal domain (BET) family, drives transcription of MYCN in NB cells, BET inhibitors (BETis) are considered useful for NB therapy. However, clinical trials of BETis suggested that early acquired resistance to BETis limits their therapeutic benefit. MicroRNAs are small non-coding RNAs that mediate post-transcriptional silencing of target genes. We previously identified miR-3140-3p as a potent candidate for nucleic acid therapeutics for cancer, which directly targets BRD4. We demonstrated that miR-3140-3p suppresses tumor cell growth in MYCN-amplified NB by downregulating MYCN and MYC through BRD4 suppression. We established BETi-acquired resistant NB cells to evaluate the mechanism of resistance to BETi in NB cells. We revealed that activated ERK1/2 stabilizes MYCN protein by preventing ubiquitin-mediated proteolysis via phosphorylation of MYCN at Ser62 in BETi-acquired resistant NB cells, thereby attenuating the effects of BETi in these cells. miR-3140-3p efficiently downregulated MYCN expression by directly targeting the MAP3K3-ERK1/2 pathway in addition to BRD4 suppression, inhibiting tumor cell growth in BETi-acquired resistant NB cells. This study suggests that miR-3140-3p has the potential to overcome resistance to BETi in NB.

Exploring the Roles of HERC2 and the NEDD4L HECT E3 Ubiquitin Ligase Subfamily in p53 Signaling and the DNA Damage Response

Cellular homeostasis is governed by the precise expression of genes that control the translation, localization, and termination of proteins. Oftentimes, environmental and biological factors can introduce mutations into the genetic framework of cells during their growth and division, and these genetic abnormalities can result in malignant transformations caused by protein malfunction. For example, p53 is a prominent tumor suppressor protein that is capable of undergoing more than 300 posttranslational modifications (PTMs) and is involved with controlling apoptotic signaling, transcription, and the DNA damage response (DDR). In this review, we focus on the molecular mechanisms and interactions that occur between p53, the HECT E3 ubiquitin ligases WWP1, SMURF1, HECW1 and HERC2, and other oncogenic proteins in the cell to explore how irregular HECT-p53 interactions can induce tumorigenesis.

Knockout of ASPP2 promotes DEN-induced hepatocarcinogenesis via the NF-κB pathway in mice

Apoptosis-stimulating protein p53 2 (ASPP2) is a member of the p53-binding protein family, which is closely related to tumor development. However, the precise mechanism of ASPP2 in liver inflammation and tumorigenesis remains largely unclear. We aimed to characterize the mechanistic significance and clinical implication of ASPP2 in hepatitis and hepatocellular carcinoma (HCC). In this study, ASPP2 knockout (APKO) mice were generated to confirm the role of ASPP2 in the development of hepatitis and HCC. Liver tissues from mice were analyzed by immunohistochemistry, Western blotting, proteomic analysis, ChIP-Seq, and qRT-PCR to evaluate the role of ASPP2 in DEN-induced hepatitis and HCC. We found that APKO promoted the formation of hepatitis/hepatocarcinoma and the increased expression of proinflammatory factors. The proteomics and Western blotting results showed that APKO activated the NF-κB signaling pathway. Further, ChIP-Seq results revealed that NF-κB target genes were dramatically increased in APKO mice. In contrast, blockade of the NF-κB pathway by QNZ reduced the expression of proinflammatory factors and the susceptibility of APKO mice to DEN-induced hepatocarcinogenesis. These results suggested that the absence of ASPP2 activates the NF-κB pathway to promote the occurrence of DEN-induced hepatocarcinogenesis, indicating that ASPP2 may be a potential target for the treatment of hepatocarcinoma.

Itch regulation of innate and adaptive immune responses in mice and humans

The E3 ubiquitin ligase Itch has long been appreciated to be a critical suppressor of inflammation, first identified as a regulator of Th2 differentiation and lung inflammation. Recent studies have revealed novel roles for this protein in mouse and human disease, and it is now clear that Itch also limits the function of other lymphocytes, innate immune cells, and nonhematopoietic cells to regulate immunity. In addition to Th2 cells, Itch also regulates Th17 and regulatory T cells. Itch regulates humoral immunity through direct roles in T follicular helper cells and T follicular regulatory cells, and B cells. Furthermore, Itch limits innate immune responses, such as macrophage cytokine production. Through these cell-intrinsic functions, Itch regulates the interplay between innate and adaptive immune cells, resulting in profound autoinflammation in Itch-deficient mice. Whereas Itch deficiency was previously thought to be an extremely rare occurrence humans, whole exome sequencing of patients with unexplained autoimmune disease has revealed at least two additional cases of Itch deficiency in the last year alone, each caused by distinct mutations within the Itch gene. The recent identification of these patients suggests that Itch mutations may be more common than previously thought, and demonstrates the need to understand how this protein regulates inflammation and autoimmune disease.

Mir-30b-5p Promotes Proliferation, Migration, and Invasion of Breast Cancer Cells via Targeting ASPP2

Triple-negative breast cancer (TNBC) is the most aggressive subtypes of breast cancer, which has few effective targeted therapies. Various sources of evidence confirm that microRNAs (miRNAs) contribute to the progression and metastasis of human breast cancer. However, the molecular mechanisms underlying the changes in miRNAs expression and the regulation of miRNAs functions have not been well clarified. In this study, we found that the expression of miR-30b-5p was upregulated in breast cancer tissues and breast cancer cell lines, compared to paracancer tissues and normal breast cell lines. Moreover, induced overexpression of miR-30b-5p promoted the MDA-MB-231 and HCC 1937 cell growth, migration, and invasion and reduced the cellular apoptosis. Further studies confirmed that miR-30b-5p could directly target ASPP2 and then activate the AKT signaling pathway. Our results suggested that miR-30b-5p could act as a tumor promoter in TNBC. The newly identified miR-30b-5p/ASPP2/AKT axis represents a novel therapeutic strategy for treating TNBC.

miR-1293, a Candidate for miRNA-Based Cancer Therapeutics, Simultaneously Targets BRD4 and the DNA Repair Pathway

BRD4, a member of the bromodomain and extra-terminal domain (BET) protein family, plays a role in the organization of super-enhancers and transcriptional activation of oncogenes in cancer and is recognized as a promising target for cancer therapy. microRNAs (miRNAs), endogenous small noncoding RNAs, cause mRNA degradation or inhibit protein translation of their target genes by binding to complementary sequences. miRNA mimics simultaneously targeting several tumor-promoting genes and BRD4 may be useful as therapeutic agents of tumor-suppressive miRNAs (TS-miRs) for cancer therapy. To investigate TS-miRs for the development of miRNA-based cancer therapeutics, we performed function-based screening in 10 cancer cell lines with a library containing 2,565 human miRNA mimics. Consequently, miR-1293, miR-876-3p, and miR-6571-5p were identified as TS-miRs targeting BRD4 in this screening. Notably, miR-1293 also suppressed DNA repair pathways by directly suppressing the DNA repair genes APEX1 (apurinic-apyrimidinic endonuclease 1), RPA1 (replication protein A1), and POLD4 (DNA polymerase delta 4, accessory subunit). Concurrent suppression of BRD4 and these DNA repair genes synergistically inhibited tumor cell growth in vitro. Furthermore, administration of miR-1293 suppressed in vivo tumor growth in a xenograft mouse model. These results suggest that miR-1293 is a candidate for the development of miRNA-based cancer therapeutics.

CagA-ASPP2 complex mediates loss of cell polarity and favors H. pylori colonization of human gastric organoids

The main risk factor for stomach cancer, the third most common cause of cancer death worldwide, is infection with Helicobacter pylori bacterial strains that inject cytotoxin-associated gene A (CagA). As the first described bacterial oncoprotein, CagA causes gastric epithelial cell transformation by promoting an epithelial-to-mesenchymal transition (EMT)-like phenotype that disrupts junctions and enhances motility and invasiveness of the infected cells. However, the mechanism by which CagA disrupts gastric epithelial cell polarity to achieve its oncogenicity is not fully understood. Here we found that the apoptosis-stimulating protein of p53 2 (ASPP2), a host tumor suppressor and an important CagA target, contributes to the survival of cagA-positive H. pylori in the lumen of infected gastric organoids. Mechanistically, the CagA-ASPP2 interaction is a key event that promotes remodeling of the partitioning-defective (PAR) polarity complex and leads to loss of cell polarity of infected cells. Blockade of cagA-positive H. pylori ASPP2 signaling by inhibitors of the EGFR (epidermal growth factor receptor) signaling pathway-identified by a high-content imaging screen-or by a CagA-binding ASPP2 peptide, prevents the loss of cell polarity and decreases the survival of H. pylori in infected organoids. These findings suggest that maintaining the host cell-polarity barrier would reduce the detrimental consequences of infection by pathogenic bacteria, such as H. pylori, that exploit the epithelial mucosal surface to colonize the host environment.

RASSF10 Is a TGFβ-Target That Regulates ASPP2 and E-Cadherin Expression and Acts as Tumor Suppressor That Is Epigenetically Downregulated in Advanced Cancer

The Ras Association Domain Family (RASSF) encodes members of tumor suppressor genes which are frequently inactivated in human cancers. Here, the function and the regulation of RASSF10, that contains a RA (Ras-association) and two coiled domains, was investigated. We utilized mass spectrometry and immuno-precipitation to identify interaction partners of RASSF10. Additionally, we analyzed the up- and downstream pathways of RASSF10 that are involved in its tumor suppressive function. We report that RASSF10 binds ASPP1 (Apoptosis-stimulating protein of p53) and ASPP2 through its coiled-coils. Induction of RASSF10 leads to increased protein levels of ASPP2 and acts negatively on cell cycle progression. Interestingly, we found that RASSF10 is a target of the EMT (epithelial mesenchymal transition) driver TGFβ (Transforming growth factor beta) and that negatively associated genes of RASSF10 are significantly over-represented in an EMT gene set collection. We observed a positive correlation of RASSF10 expression and E-cadherin that prevents EMT. Depletion of RASSF10 by CRISPR/Cas9 technology induces the ability of lung cancer cells to proliferate and to invade an extracellular matrix after TGFβ treatment. Additionally, knockdown of RASSF10 or ASPP2 induced constitutive phosphorylation of SMAD2 (Smad family member 2). Moreover, we found that epigenetic reduction of RASSF10 levels correlates with tumor progression and poor survival in human cancers. Our study indicates that RASSF10 acts a TGFβ target gene and negatively regulates cell growth and invasion through ASPP2. This data suggests that epigenetic loss of RASSF10 contributes to tumorigenesis by promoting EMT induced by TGFβ.

miR-34b/c regulates doxorubicin-induced myocardial cell injury through ITCH

Objective: To determine the underlying mechanism of miR-34b/c in regulating doxorubicin (Dox)-induced myocardial cell injury.Methods: The viability of mouse myocardial cells HL-1 was detected by MTT assay. The apoptosis of HL-1 cells was detected by TUNEL assay. mRNA expressions of ITCH, TNF-α and IL-6 were measured by qRT-PCR. Protein levels of ITCH, NF-κB, TNF-α and IL-6 were measured by western blot. Dual luciferase assay was performed to detect the regulation of miR-34b/c on ITCH. Mouse model of cardiomyopathy was induced by intraperitoneal injection of Dox.Results: Dox reduced HL-1 cell viability and activated NF-κB pathway in HL-1 cells. miR-34b/c expressions were gradually up-regulated and ITCH expression was gradually down-regulated in Dox-treated HL-1 cells. miR-34b/c expression had negative correlation with the mRNA expression of ITCH. Besides, ITCH was a target of miR-34b/c. miR-34b/c mimic reduced cell viability, suppressed ITCH expression, increased TNF-α and IL-6 level, and promoted NF-κB expression in nucleus and cytoplasm of HL-1 cells. Whereas silencing miR-34 protected HL-1 cells through regulating ITCH. Finally, we demonstrated miR-34 antagomir-protected myocardial cells in mouse model of cardiomyopathy.Conclusion: miR-34b/c decreased HL-1 cell viability and promoted the secretion of proinflammatory cytokines in Dox-induced myocardial cells through ITCH/NF-κB pathway.

A Multidimensional Characterization of E3 Ubiquitin Ligase and Substrate Interaction Network

E3 ubiquitin ligases (E3s) play a critical role in molecular and cellular mechanisms. However, a large number of E3-substrate interactions (ESIs) remain unrevealed. Here, we integrated the increasing omics data with biological knowledge to characterize and identify ESIs. Multidimensional features were computed to obtain the association patterns of ESIs, and an ensemble prediction model was constructed to identify ESIs. Comparison with non-ESI cases revealed the specific association patterns of ESIs, which provided meaningful insights into ESI interpretation. Reliability of the prediction model was confirmed from various perspectives. Notably, our evaluations on leucine-rich repeat family of F box (FBXL) family were consistent with a proteomic study, and several substrates for SKP2 and an orphan E3 FBXL6 were experimentally verified. Moreover, a cancer hallmark ESI landscape was studied. Taken together, our study catches a glimpse at the omics-driven ESI association patterns and provides a valuable resource (http://www.esinet.dicp.ac.cn/home.php) to assist ubiquitination research.

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Systematically describe E3 ligase and substrate association patterns

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Build a computational model for predicting E3 ligase and substrate interactions

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Predict and validate promising substrates for F box family E3 ligases

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Construct a valuable data resource on potential E3-substrate interactions

Regulation of autoimmune disease by the E3 ubiquitin ligase Itch

Itch is a HECT type E3 ubiquitin ligase that is required to prevent the development of autoimmune disease in both mice and humans. Itch is expressed in most mammalian cell types, and, based on published data, it regulates many cellular pathways ranging from T cell differentiation to liver tumorigenesis. Since 1998, when Itch was first discovered, hundreds of publications have described mechanisms through which Itch controls various biologic activities in both immune and non-immune cells. Other studies have provided insight into how Itch catalytic activity is regulated. However, while autoimmunity is the primary clinical feature that occurs in both mice and humans lacking Itch, and Itch control of immune cell function has been well-studied, it remains unclear how Itch prevents the emergence of autoimmune disease. In this review, we explore recent discoveries that advance our understanding of how Itch regulates immune cell biology, and the extent to which these clarify how Itch prevents autoimmune disease. Additionally, we discuss how molecular regulators of Itch impact its ability to control these processes, as this may provide clues on how to therapeutically target Itch to treat patients with autoimmune disease.

The Role of TGF-β and Its Receptors in Gastrointestinal Cancers

Early detection of gastrointestinal tumors improves patient survival. However, patients with these tumors are typically diagnosed at an advanced stage and have poor prognosis. The incidence and mortality of gastrointestinal cancers, including esophageal, gastric, liver, colorectal, and pancreatic cancers, are increasing worldwide. Novel diagnostic and therapeutic agents are required to improve patient survival and quality of life. The tumor microenvironment, which contains nontumor cells, signaling molecules such as growth factors and cytokines, and extracellular matrix proteins, plays a critical role in cancer cell proliferation, invasion, and metastasis. Transforming growth factor beta (TGF-β) signaling has dual roles in gastrointestinal tumor development and progression as both a tumor suppressor and tumor promoter. Here, we review the dynamic roles of TGF-β and its receptors in gastrointestinal tumors and provide evidence that targeting TGF-β signaling may be an effective therapeutic strategy.

MFAP2 promotes epithelial-mesenchymal transition in gastric cancer cells by activating TGF-β/SMAD2/3 signaling pathway

Introduction

Microfibril-associated protein 2 (MFAP2) is an extracellular matrix protein that interacts with fibrillin to modulate the function of microfibrils. MFAP2 has been reported to play a significant role in obesity, diabetes, and osteopenia, and has been shown to be upregulated in head and neck squamous cell carcinoma. However, the molecular function and prognostic value of MFAP2 have never been reported in gastric cancer (GC) or any other tumors.

Methods

The current study investigated the expression patterns, prognostic significance, functional role, and possible mechanisms of MFAP2 in GC.

Results

We demonstrated that MFAP2 was overexpressed in GC tissues, and its overexpression was significantly correlated with poor overall and disease-free survival in patients with GC. Moreover, we found that MFAP2 promoted the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) phenotype in GC cells. MFAP2 might modulate EMT of GC cells by activating the TGF-β/SMAD2/3 signaling pathway.

Conclusion

These findings provide novel evidence that MFAP2 plays a crucial role in the progression of GC. Therefore, MFAP2 may be a promising prognostic marker and a potent anticancer agent.