NDRG2 facilitates colorectal cancer differentiation through the regulation of Skp2-p21/p27 axis

E3 ubiquitin ligases and deubiquitinases in colorectal cancer: Emerging molecular insights and therapeutic opportunities

Colorectal cancer (CRC) presents ongoing challenges due to limited treatment effectiveness and a discouraging prognosis, underscoring the need for ground-breaking therapeutic approaches. This review delves into the pivotal role of E3 ubiquitin ligases and deubiquitinases (DUBs), underscoring their role as crucial regulators for tumor suppression and oncogenesis in CRC. We spotlight the diverse impact of E3 ligases and DUBs on CRC's biological processes and their remarkable versatility. We closely examine their specific influence on vital signaling pathways, particularly Wnt/β-catenin and NF-κB. Understanding these regulatory mechanisms is crucial for unravelling the complexities of CRC progression. Importantly, we explore the untapped potential of E3 ligases and DUBs as novel CRC treatment targets, discussing aspects that may guide more effective therapeutic strategies. In conclusion, our concise review illuminates the E3 ubiquitin ligases and deubiquitinases pivotal role in CRC, offering insights to inspire innovative approaches for transforming the treatment landscape in CRC.

NDRG2 Deficiency Exacerbates UVB-Induced Skin Inflammation and Oxidative Stress Damage

UVB radiation induces inflammatory and oxidative stress responses, contributing to skin damage, yet the underlying mechanisms are not fully understood. N-Myc downstream-regulated gene 2 (NDRG2), an emerging stress-associated gene, remains unexplored in UVB-induced skin injury. In this study, we detected skin NDRG2 expression after UVB irradiation for the first time and further used Ndrg2 knockout mice to clarify the role of NDRG2 in UVB-induced skin injury. Three-month-old male Ndrg2+/+ and Ndrg2-/- mice (16-18g) were exposed to UVB to induce acute skin damage, and then dorsal skin samples were collected for subsequent analyses. UVB-induced skin damage was scored. Western Blot Analysis, immunofluorescence (IF) double labeling, and immunohistochemistry (IHC) were employed to assess NDRG2 expression and/or distribution. The concentrations of TNF-α, IL-6, IL-1β, MPO, MMP8, superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) were quantitatively assessed using enzyme-linked immunosorbent assay (ELISA). Hematoxylin and eosin (HE) staining were employed to determine pathological changes. RNA sequencing and analysis were performed to estimate transcript expression levels and analyze mRNA expression. DESeq2 software was employed to identify differentially expressed genes (DEGs). DEGs were visualized using volcanic and heat maps. Gene Ontology (GO) functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were analyzed to identify primary biological functions, metabolic pathways, or signal transduction pathways associated with DEGs. UVB-challenged Ndrg2-/- mice exhibited significantly exacerbated skin damage (erythema, edema, and erosion), neutrophil infiltration, and apoptosis compared to Ndrg2+/+ mice. Furthermore, UVB-challenged Ndrg2-/- mice displayed significantly elevated pro-inflammatory cytokines, myeloperoxidase (MPO), matrix metalloproteinase-8 (MMP8), and reduced antioxidant expression. RNA sequencing identified 1091 significantly differentially expressed genes enriched in inflammation, immune response, and oxidative stress pathways. In conclusion, the deficiency of Ndrg2 markedly exacerbated UVB-induced skin damage by promoting inflammatory responses and inhibiting antioxidant responses. This suggests that stabilizing NDRG2 expression holds promise as a therapeutic strategy for protecting against UVB-induced skin damage.

NDRG1 acts as an oncogene in triple-negative breast cancer and its loss sensitizes cells to mitochondrial iron chelation

Multiple studies indicate that iron chelators enhance their anti-cancer properties by inducing NDRG1, a known tumor and metastasis suppressor. However, the exact role of NDRG1 remains controversial, as newer studies have shown that NDRG1 can also act as an oncogene. Our group recently introduced mitochondrially targeted iron chelators deferoxamine (mitoDFO) and deferasirox (mitoDFX) as effective anti-cancer agents. In this study, we evaluated the ability of these modified chelators to induce NDRG1 and the role of NDRG1 in breast cancer. We demonstrated that both compounds specifically increase NDRG1 without inducing other NDRG family members. We have documented that the effect of mitochondrially targeted chelators is at least partially mediated by GSK3α/β, leading to phosphorylation of NDRG1 at Thr346 and to a lesser extent on Ser330. Loss of NDRG1 increases cell death induced by mitoDFX. Notably, MDA-MB-231 cells lacking NDRG1 exhibit reduced extracellular acidification rate and grow slower than parental cells, while the opposite is true for ER+ MCF7 cells. Moreover, overexpression of full-length NDRG1 and the N-terminally truncated isoform (59112) significantly reduced sensitivity towards mitoDFX in ER+ cells. Furthermore, cells overexpressing full-length NDRG1 exhibited a significantly accelerated tumor formation, while its N-terminally truncated isoforms showed significantly impaired capacity to form tumors. Thus, overexpression of full-length NDRG1 promotes tumor growth in highly aggressive triple-negative breast cancer.

T2-weighted imaging-based radiomic-clinical machine learning model for predicting the differentiation of colorectal adenocarcinoma

BACKGROUND

The study on predicting the differentiation grade of colorectal cancer (CRC) based on magnetic resonance imaging (MRI) has not been reported yet. Developing a non-invasive model to predict the differentiation grade of CRC is of great value.

AIM

To develop and validate machine learning-based models for predicting the differentiation grade of CRC based on T2-weighted images (T2WI).

METHODS

We retrospectively collected the preoperative imaging and clinical data of 315 patients with CRC who underwent surgery from March 2018 to July 2023. Patients were randomly assigned to a training cohort (n = 220) or a validation cohort (n = 95) at a 7:3 ratio. Lesions were delineated layer by layer on high-resolution T2WI. Least absolute shrinkage and selection operator regression was applied to screen for radiomic features. Radiomics and clinical models were constructed using the multilayer perceptron (MLP) algorithm. These radiomic features and clinically relevant variables (selected based on a significance level of P < 0.05 in the training set) were used to construct radiomics-clinical models. The performance of the three models (clinical, radiomic, and radiomic-clinical model) were evaluated using the area under the curve (AUC), calibration curve and decision curve analysis (DCA).

RESULTS

After feature selection, eight radiomic features were retained from the initial 1781 features to construct the radiomic model. Eight different classifiers, including logistic regression, support vector machine, k-nearest neighbours, random forest, extreme trees, extreme gradient boosting, light gradient boosting machine, and MLP, were used to construct the model, with MLP demonstrating the best diagnostic performance. The AUC of the radiomic-clinical model was 0.862 (95%CI: 0.796-0.927) in the training cohort and 0.761 (95%CI: 0.635-0.887) in the validation cohort. The AUC for the radiomic model was 0.796 (95%CI: 0.723-0.869) in the training cohort and 0.735 (95%CI: 0.604-0.866) in the validation cohort. The clinical model achieved an AUC of 0.751 (95%CI: 0.661-0.842) in the training cohort and 0.676 (95%CI: 0.525-0.827) in the validation cohort. All three models demonstrated good accuracy. In the training cohort, the AUC of the radiomic-clinical model was significantly greater than that of the clinical model (P = 0.005) and the radiomic model (P = 0.016). DCA confirmed the clinical practicality of incorporating radiomic features into the diagnostic process.

CONCLUSION

In this study, we successfully developed and validated a T2WI-based machine learning model as an auxiliary tool for the preoperative differentiation between well/moderately and poorly differentiated CRC. This novel approach may assist clinicians in personalizing treatment strategies for patients and improving treatment efficacy.

Elucidating Differences in Early-Stage Centrosome Amplification in Primary and Immortalized Mouse Cells

The centrosome is involved in cytoplasmic microtubule organization during interphase and in mitotic spindle assembly during cell division. Centrosome amplification (abnormal proliferation of centrosome number) has been observed in several types of cancer and in precancerous conditions. Therefore, it is important to elucidate the mechanism of centrosome amplification in order to understand the early stage of carcinogenesis. Primary cells could be used to better understand the early stage of carcinogenesis rather than immortalized cells, which tend to have various genetic and epigenetic changes. Previously, we demonstrated that a poly(ADP-ribose) polymerase (PARP) inhibitor, 3-aminobenzamide (3AB), which is known to be nontoxic and nonmutagenic, could induce centrosome amplification and chromosomal aneuploidy in CHO-K1 cells. In this study, we compared primary mouse embryonic fibroblasts (MEF) and immortalized MEF using 3AB. Although centrosome amplification was induced with 3AB treatment in immortalized MEF, a more potent PARP inhibitor, AG14361, was required for primary MEF. However, after centrosome amplification, neither 3AB in immortalized MEF nor AG14361 in primary MEF caused chromosomal aneuploidy, suggesting that further genetic and/or epigenetic change(s) are required to exhibit aneuploidy. The DNA-damaging agents doxorubicin and γ-irradiation can cause cancer and centrosome amplification in experimental animals. Although doxorubicin and γ-irradiation induced centrosome amplification and led to decreased p27Kip protein levels in immortalized MEF and primary MEF, the phosphorylation ratio of nucleophosmin (Thr199) increased in immortalized MEF, whereas it decreased in primary MEF. These results suggest that there exists a yet unidentified pathway, different from the nucleophosmin phosphorylation pathway, which can cause centrosome amplification in primary MEF.

The involvement of E3 ubiquitin ligases in the development and progression of colorectal cancer

To date, colorectal cancer (CRC) still has limited therapeutic efficacy and poor prognosis and there is an urgent need for novel targets to improve the outcome of CRC patients. The highly conserved ubiquitination modification mediated by E3 ubiquitin ligases is an important mechanism to regulate the expression and function of tumor promoters or suppressors in CRC. In this review, we provide an overview of E3 ligases in modulating various biological processes in CRC, including proliferation, migration, stemness, metabolism, cell death, differentiation and immune response of CRC cells, emphasizing the pluripotency of E3 ubiquitin ligases. We further focus on the role of E3 ligases in regulating vital cellular signal pathways in CRC, such as Wnt/β-catenin pathway and NF-κB pathway. Additionally, considering the potential of E3 ligases as novel targets in the treatment of CRC, we discuss what aspects of E3 ligases can be utilized and exploited for efficient therapeutic strategies.

MYOD-SKP2 axis boosts tumorigenesis in fusion negative rhabdomyosarcoma by preventing differentiation through p57Kip2 targeting

Rhabdomyosarcomas (RMS) are pediatric mesenchymal-derived malignancies encompassing PAX3/7-FOXO1 Fusion Positive (FP)-RMS, and Fusion Negative (FN)-RMS with frequent RAS pathway mutations. RMS express the master myogenic transcription factor MYOD that, whilst essential for survival, cannot support differentiation. Here we discover SKP2, an oncogenic E3-ubiquitin ligase, as a critical pro-tumorigenic driver in FN-RMS. We show that SKP2 is overexpressed in RMS through the binding of MYOD to an intronic enhancer. SKP2 in FN-RMS promotes cell cycle progression and prevents differentiation by directly targeting p27Kip1 and p57Kip2, respectively. SKP2 depletion unlocks a partly MYOD-dependent myogenic transcriptional program and strongly affects stemness and tumorigenic features and prevents in vivo tumor growth. These effects are mirrored by the investigational NEDDylation inhibitor MLN4924. Results demonstrate a crucial crosstalk between transcriptional and post-translational mechanisms through the MYOD-SKP2 axis that contributes to tumorigenesis in FN-RMS. Finally, NEDDylation inhibition is identified as a potential therapeutic vulnerability in FN-RMS.

Characterization and therapeutic perspectives of differentiation-inducing therapy in malignant tumors

Cancer is a major public health issue globally and is one of the leading causes of death. Although available treatments improve the survival rate of some cases, many advanced tumors are insensitive to these treatments. Cancer cell differentiation reverts the malignant phenotype to its original state and may even induce differentiation into cell types found in other tissues. Leveraging differentiation-inducing therapy in high-grade tumor masses offers a less aggressive strategy to curb tumor progression and heightens chemotherapy sensitivity. Differentiation-inducing therapy has been demonstrated to be effective in a variety of tumor cells. For example, differentiation therapy has become the first choice for acute promyelocytic leukemia, with the cure rate of more than 90%. Although an appealing concept, the mechanism and clinical drugs used in differentiation therapy are still in their nascent stage, warranting further investigation. In this review, we examine the current differentiation-inducing therapeutic approach and discuss the clinical applications as well as the underlying biological basis of differentiation-inducing agents.

The ndrg2 Gene Regulates Hair Cell Morphogenesis and Auditory Function during Zebrafish Development

Damages of sensory hair cells (HCs) are mainly responsible for sensorineural hearing loss, however, its pathological mechanism is not yet fully understood due to the fact that many potential deafness genes remain unidentified. N-myc downstream-regulated gene 2 (ndrg2) is commonly regarded as a tumor suppressor and a cell stress-responsive gene extensively involved in cell proliferation, differentiation, apoptosis and invasion, while its roles in zebrafish HC morphogenesis and hearing remains unclear. Results of this study suggested that ndrg2 was highly expressed in the HCs of the otic vesicle and neuromasts via in situ hybridization and single-cell RNA sequencing. Ndrg2 loss-of-function larvae showed decreased crista HCs, shortened cilia, and reduced neuromasts and functional HCs, which could be rescued by the microinjection of ndrg2 mRNA. Moreover, ndrg2 deficiency induced attenuated startle response behaviors to sound vibration stimuli. Mechanistically, there were no detectable HC apoptosis and supporting cell changes in the ndrg2 mutants, and HCs were capable of recovering by blocking the Notch signaling pathway, suggesting that ndrg2 was implicated in HC differentiation mediated by Notch. Overall, our study demonstrates that ndrg2 plays crucial roles in HC development and auditory sensory function utilizing the zebrafish model, which provides new insights into the identification of potential deafness genes and regulation mechanism of HC development.

BCR-ABL triggers a glucose-dependent survival program during leukemogenesis through the suppression of TXNIP

Imatinib is highly effective in the treatment of chronic myelogenous leukemia (CML), but the primary and acquired imatinib resistance remains the big hurdle. Molecular mechanisms for CML resistance to tyrosine kinase inhibitors, beyond point mutations in BCR-ABL kinase domain, still need to be addressed. Here, we demonstrated that thioredoxin-interacting protein (TXNIP) is a novel BCR-ABL target gene. Suppression of TXNIP was responsible for BCR-ABL triggered glucose metabolic reprogramming and mitochondrial homeostasis. Mechanistically, Miz-1/P300 complex transactivates TXNIP through the recognition of TXNIP core promoter region, responding to the c-Myc suppression by either imatinib or BCR-ABL knockdown. TXNIP restoration sensitizes CML cells to imatinib treatment and compromises imatinib resistant CML cell survival, predominantly through the blockage of both glycolysis and glucose oxidation which results in the mitochondrial dysfunction and ATP production. In particular, TXNIP suppresses expressions of the key glycolytic enzyme, hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), potentially through Fbw7-dependent c-Myc degradation. In accordance, BCR-ABL suppression of TXNIP provided a novel survival pathway for the transformation of mouse bone marrow cells. Knockout of TXNIP accelerated BCR-ABL transformation, whereas TXNIP overexpression suppressed this transformation. Combination of drug inducing TXNIP expression with imatinib synergistically kills CML cells from patients and further extends the survival of CML mice. Thus, the activation of TXNIP represents an effective strategy for CML treatment to overcome resistance.

Intact regulation of G1/S transition renders esophageal squamous cell carcinoma sensitive to PI3Kα inhibitors

Phosphatidylinositol 3-kinase alpha (PI3Kα) inhibitors are currently evaluated for the therapy of esophageal squamous cell carcinoma (ESCC). It is of great importance to identify potential biomarkers to predict or monitor the efficacy of PI3Kα inhibitors in an aim to improve the clinical responsive rate in ESCC. Here, ESCC PDXs with CCND1 amplification were found to be more sensitive to CYH33, a novel PI3Kα-selective inhibitor currently in clinical trials for the treatment of advanced solid tumors including ESCC. Elevated level of cyclin D1, p21 and Rb was found in CYH33-sensitive ESCC cells compared to those in resistant cells. CYH33 significantly arrested sensitive cells but not resistant cells at G1 phase, which was associated with accumulation of p21 and suppression of Rb phosphorylation by CDK4/6 and CDK2. Hypo-phosphorylation of Rb attenuated the transcriptional activation of SKP2 by E2F1, which in turn hindered SKP2-mediated degradation of p21 and reinforced accumulation of p21. Moreover, CDK4/6 inhibitors sensitized resistant ESCC cells and PDXs to CYH33. These findings provided mechanistic rationale to evaluate PI3Kα inhibitors in ESCC patients harboring amplified CCND1 and the combined regimen with CDK4/6 inhibitors in ESCC with proficient Rb.

MESP2 binds competitively to TCF4 to suppress gastric cancer progression by regulating the SKP2/p27 axis

Gastric cancer (GC) is a major cause of human deaths worldwide, and is notorious for its high incidence and mortality rates. Mesoderm Posterior Basic Helix-loop-helix (bHLH) transcription factor 2 (MESP2) acts as a transcription factor with a conserved bHLH domain. However, whether MESP2 contributes to tumorigenesis and its potential molecular mechanisms, remain unexplored. Noticeably, MESP2 expression levels are decreased in GC tissues and cell lines compared to those in normal tissue. Further, in vitro and in vivo experiments have confirmed that MESP2 overexpression suppresses GC cell growth, migration, and invasion, whereas MESP2 knockdown results in the exact opposite. Here, we present the first report that MESP2 binds to transcription factor 7-like 2 (TCF7L2/TCF4) to inhibit the activation of the TCF4/beta-catenin transcriptional complex, decrease the occupancy of the complex on the S-phase kinase Associated Protein 2 (SKP2) promoter, and promote p27 accumulation. MESP2 knockdown facilitated tumorigenesis, which was partially suppressed by SKP2 knockdown. Taken together, we conclude that MESP2 binds competitively to TCF4 to suppress GC progression by regulating the SKP2/p27 axis, thus offering a potential therapeutic strategy for future treatment.

Platycodin D suppresses proliferation, migration, and invasion of human glioblastoma cells through regulation of Skp2

BACKGROUND

Platycodin D (PD) is a major bioactive component of Platycodon grandiflorum, a medicinal herb that is widely used in China, and is effective against various human cancers, including glioblastoma multiforme (GBM). S phase kinase-related protein 2 (Skp2) is oncogenic and overexpressed in various human tumors. It is highly expressed in GBM and its expression is correlated with tumor growth, drug resistance and poor prognosis. In this study, we investigated whether inhibition of glioma progression by PD is mediated by decreasing expression of Skp2.

METHODS

Cell Counting Kit-8 (CCK-8) and Transwell assays were used to determine the effects of PD on GBM cell proliferation, migration, and invasion in vitro. mRNA and protein expression were determined by real time polymerase chain reaction (RT-PCR) and western blotting, respectively. The U87 xenograft model was used to verify the anti-glioma effect of PD in vivo. Expression levels of Skp2 protein were analyzed by immunofluorescence staining.

RESULTS

PD suppressed proliferation and motility of GBM cells in vitro. The expression of Skp2 in U87 and U251 cells was significantly reduced by PD. PD mainly decreased the cytoplasmic expression of Skp2 in glioma cells. Skp2 protein expression was downregulated by PD, resulting in upregulation of its downstream targets, p21and p27. The inhibitory effect of PD was enhanced by Skp2 knockdown in GBM cells and reversed in cells with Skp2 overexpression.

CONCLUSION

PD suppresses glioma development by regulation of Skp2 in GBM cells.

N-Myc transcriptionally activates Skp2 to suppress p27 expression in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is characterized by a high proliferative rate, a strong predilection for early metastasis and poor prognosis. Novel SCLC biomarkers are urgently required to improve current diagnostic and treatment modalities. MYCN encodes the proto-oncogene N-Myc that is overexpressed in SCLC, but its downstream effectors are poorly characterized. Here, we investigated the role of the N-Myc/Skp2/p27 axis during SCLC progression.

METHODS

Immunohistochemistry (IHC) and western blotting were performed to evaluate N-Myc/Skp2/p27 expression. SCLC cell apoptosis was investigated through TUNEL staining. Wound healing and transwell assays were performed to detect the migratory and invasive potential of SCLC cells. N-Myc and Skp2 binding was confirmed through luciferase reporter and ChIP assays. Xenograft models were developed to investigate the function of Skp2 during SCLC tumor growth in vivo.

RESULTS

N-Myc and Skp2 were overexpressed in SCLC, whilst p27 expression was suppressed. Skp2 facilitated SCLC progression by protecting cells from apoptosis and facilitating cell migration and invasion. N-Myc was found to bind to the promoter region of Skp2 to enhance its expression. Skp2 enhanced tumor growth in vivo through the suppression of p27. Skp2 silencing reversed the pro-oncogenic effects of N-myc in SCLC tumors.

CONCLUSION

We show that N-Myc enhances Skp2 to regulate p27 expression during SCLC progression. We therefore highlight the N-Myc/Skp2/p27 axis as a novel diagnostic and much-needed therapeutic target in SCLC.

NDRG2 inhibits pyruvate carboxylase-mediated anaplerosis and combines with glutamine blockade to inhibit the proliferation of glioma cells

Due to the rapid proliferation, cancer cells have increased anabolic biosynthesis, which requires anaplerosis to replenish precursor intermediates. The major anaplerotic sources are pyruvate and glutamine, which require the catalysis of pyruvate carboxylase (PC) and glutaminase (GLS) respectively. In GLS-suppressed cancer cells, the PC-mediated pathway for anaplerosis is crucial to maintain cell growth and proliferation. Here, we investigated the regulatory role and molecular mechanism of N-myc downstream-regulated gene 2 (NDRG2) in PC and PC-mediated anaplerosis. NDRG2 interacted with PC and induced the degradation of PC in glutamine-deprived cells. NDRG2 also inhibited the activity of PC and PC-mediated anaplerosis. As a result, NDRG2 significantly inhibited the malignant growth and proliferation of glioma cells in combination with a glutamine antagonist. In addition, NDRG2 more significantly inhibited the protein level of PC in isocitrate dehydrogenase 1 (R132H)-mutant glioma cells than in wild-type glioma cells. These findings indicate that the molecular mechanism of NDRG2 inhibits PC-mediated anaplerosis and collaborates with glutamine antagonist to inhibit the malignant proliferation of glioma cells, thus providing a theoretical and experimental basis for targeting anaplerosis in glioma therapy.

Colorectal Cancer Cell Differentiation Is Dependent on the Repression of Aerobic Glycolysis by NDRG2-TXNIP Axis

BACKGROUND

Poorly differentiated colorectal cancers are more aggressive. Metabolism reprogramming is a significant hallmark in cancer, and aerobic glycolysis is common. However, how cancer cells reprogramming glucose metabolism contributes to cell differentiation was largely unknown. Previous studies have reported that tumor suppressor NDRG2 could promote colorectal cancers differentiation.

AIMS

This study aims to demonstrate that NDRG2 promotes the differentiation of colorectal cancers, potentially through the inhibition of aerobic glycolysis via TXNIP induction.

METHODS

Western blotting, qRT-PCR and immunohistochemical staining were used to detect the expression of related molecules. MTT assay was used to reflect cell viability and proliferation. Immunofluorescent assay was performed to identify the expression and distribution of molecules. Luciferase analysis and CHIP assays were used to investigate the mechanism. Bioinformatic analysis was performed to predict the relevance.

RESULTS

In colorectal cancers, NDRG2 could inhibit cell proliferation, reduce glucose uptake and decrease expression of key glycolysis enzymes. Upregulated NDRG2 is associated with differentiated cancer. However, deletion of TXNIP, a classic glucose metabolism inhibitor, could obviously alter the function of NDRG2 in differentiation, glucose uptake, expression of key glycolysis enzymes and proliferation. Mechanistically, high glucose flux promotes the activity of TXNIP promoter. And NDRG2 promotes the occupancy of transcription factor Mondo A on TXNIP promoter, predominantly through the suppression of c-myc, which could complete with Mondo A binding to TXNIP promoter. In clinical samples, high expression of TXNIP indicates good prognosis and outcome.

CONCLUSIONS

NDRG2-dependent induction of TXNIP is critical for the aerobic glycolysis during colorectal cancers differentiation.

Skp2 promotes APL progression through the stabilization of oncoprotein PML-RARα and the inhibition of JunB expression

AIMS

To investigate the role of Skp2 and JunB on acute promyelocytic leukemia (APL) progression and the related mechanism.

MATERIALS AND METHODS

The expression of Skp2 in NB4 cell line was depleted to explore its effect on proliferation and differentiation both in vitro and in vivo assays. Western blot and quantitative RT-PCR analysis were performed to explore Skp2-regulated downstream target genes. Luciferase and co-immunoprecipitation analysis indicated that PML-RARα inhibited the transactivation of JunB by interacting with the PU.1 protein. The western blot analysis confirmed that Skp2 could maintain the stability of PML-RARα.

KEY FINDINGS

We report that the progression of APL and the attenuation of APL sensitivity to ATRA are positively associated with Skp2. Elevated Skp2 expression promotes APL progression by decreasing the expression of lncRNA HOTAIRM1 and inactivation of GSK3β, causing autophagy inhibition followed by the suppression of PML-RARα ubiquitylation and degradation, which represses JunB transcriptional activation through PU.1/PML-RARα transcriptional complex to block cell differentiation. Coupled with ATRA or GSK3β inhibitor treatment, genetic or pharmacological inhibition of Skp2 strikingly induces JunB expression by accelerating the degradation of PML-RARα, which contributes to the eradication of APL. Additionally, the expressions of Skp2 and JunB are negatively correlated in mice subcutaneous leukemia xenograft tumors.

SIGNIFICANCE

Collectively, this study uncovers the roles of Skp2 in PML-RARα stabilization and in APL oncogenic functions. We reveal a novel mechanism of PML-RARα degradation and JunB regulation that constitute an important signaling network of Skp2-GSK3β-PML/RARα-JunB.

Long noncoding RNA MIR22HG promotes Leydig cell apoptosis by acting as a competing endogenous RNA for microRNA-125a-5p that targets N-Myc downstream-regulated gene 2 in late-onset hypogonadism

Leydig cells (LCs) apoptosis is responsible for the deficiency of serum testosterone in Late-onset hypogonadism (LOH), while its specific mechanism is still unknown. This study focuses on the role of long noncoding RNA (lncRNA) MIR22HG in LC apoptosis and aims to elaborate its regulatory mechanism. MIR22HG was up-regulated in the testicular tissues of mice with LOH and H2O2-treated TM3 cells (mouse Leydig cell line). Interference of MIR22HG ameliorated cell apoptosis and upregulated miR-125a-5p expression in H2O2-treated TM3 cells. Then, the interaction between MIR22HG and miR-125a-5p was confirmed with RIP and RNA pull-down assay. Further study showed that miR-125a-5p downregulated N-Myc downstream-regulated gene 2 (NDRG2) expression by targeting its 3'-UTR of mRNA. What's more, MIR22HG overexpression aggravated cell apoptosis and reduced testosterone production in TM3 cells via miR-125a-5p/NDRG2 pathway. MIR22HG knockdown elevated testosterone levels in LOH mice. In conclusion, MIR22HG up-regulated NDRG2 expression through targeting miR-125a-5p, thus promoting LC apoptosis in LOH.

CD147 confers temozolomide resistance of glioma cells via the regulation of β-TrCP/Nrf2 pathway

Background: Drug resistance is one of the biggest challenges in cancer therapy. temozolomide (TMZ) represents the most important chemotherapeutic option for glioma treatment. However, the therapeutic efficacy of TMZ remains very limited due to its frequent resistance in glioma, and the underlying mechanisms were not fully addressed. Herein, we demonstrate that the elevated expression of CD147 contributes to TMZ resistance in glioma cells, potentially through the post-translational regulation of Nrf2 expression. Methods: Cell-based assays of CD147 triggered drug resistance were performed through Edu-incorporation assay, CCK8 assay, TUNEL staining assay and flow cytometric assay. Luciferase reporter assay, protein stability related assays, co-immunoprecipitation assay were used to determine CD147 induction of Nrf2 expression through β-TrCP dependent ubiquitin system. Finally, the effect of the CD147/Nrf2 signaling on glioma progression and TMZ resistance were evaluated by functional experiments and clinical samples. Results: Based on the analysis of clinical glioma tissues, CD147 is highly expressed in glioma tissues and positively associated with tumor malignancy. Suppression of CD147 expression increased the inhibitory effect of TMZ on cell survival in both U251 and T98G cells, whereas the gain of CD147 function blocked TMZ-induced ROS production and cell death. Mechanistic study indicates that CD147 inhibited GSK3β/β-TrCP-dependent Nrf2 degradation by promoting Akt activation, and subsequently increased Nrf2-mediated anti-oxidant gene expressions. Supporting the biological significance, the reciprocal relationship between CD147 and Nrf2 was observed in glioma tissues, and associated with patient outcome. Conclusions: Our data provide the first evidence that glioma resistance to TMZ is potentially due to the activation of CD147/Nrf2 axis. CD147 promotes Nrf2 stability through the suppression of GSK3β/β-TrCP dependent Nrf2 protein degradation, which results in the ablation of TMZ induced ROS production. As such, we point out that targeting CD147/Nrf2 axis may provide a new strategy for the treatment of TMZ resistant gliomas.

Activated macrophages promote invasion by early colorectal cancer via an interleukin 1β-serum amyloid A1 axis

Submucosal invasion and lymph node metastasis are important issues affecting treatment options for early colorectal cancer (CRC). In this study, we aimed to unravel the molecular mechanism underlying the invasiveness of early CRCs. We performed RNA‐sequencing (RNA‐seq) with poorly differentiated components (PORs) and their normal counterparts isolated from T1 CRC tissues and detected significant upregulation of serum amyloid A1 (SAA1) in PORs. Immunohistochemical analysis revealed that SAA1 was specifically expressed in PORs at the invasive front of T1b CRCs. Upregulation of SAA1 in CRC cells promoted cell migration and invasion. Coculture experiments using CRC cell lines and THP‐1 cells suggested that interleukin 1β (IL‐1β) produced by macrophages induces SAA1 expression in CRC cells. Induction of SAA1 and promotion of CRC cell migration and invasion by macrophages were inhibited by blocking IL‐1β. These findings were supported by immunohistochemical analysis of primary T1 CRCs showing accumulation of M1‐like/M2‐like macrophages at SAA1‐positive invasive front regions. Moreover, SAA1 produced by CRC cells stimulated upregulation of matrix metalloproteinase‐9 in macrophages. Our data suggest that tumor‐associated macrophages at the invasive front of early CRCs promote cancer cell migration and invasion through induction of SAA1 and that SAA1 may be a predictive biomarker and a useful therapeutic target.

FAM60A promotes cisplatin resistance in lung cancer cells by activating SKP2 expression

Cisplatin is a widely used chemotherapeutic drug in lung cancer treatment. Most cancer patients eventually develop cisplatin resistance, resulting in a poor prognosis. Previously, we identified a novel marker, family with sequence similarity 60A (FAM60A), that was responsible for resistance in cisplatin-resistant human lung adenocarcinoma A549 (A549/DDP) cells. Here, we investigated the biological effects of FAM60A in A549/DDP cells and explored the underlying molecular mechanisms to understand its functional role in cisplatin resistance. Real-time quantitative PCR and western blot analysis were used to determine the expression levels of FAM60A in A549/DDP cells. FAM60A and SKP2 were knockdown with small-interfering RNA (siRNA). Cancer cell viability was analyzed with flow cytometry. The mRNA and protein expression levels of FAM60A increased significantly and dose-dependently in A549/DDP cells following cisplatin treatment. FAM60A overexpression up-regulated MDR1 expression, inhibited caspase 3, cleaved-caspase 3, and caspase 8 expression, and prevented cancer cell death. Microarray analysis of cells transfected with siRNA against the FAM60A transcript and control samples showed that SKP2 expression was positively regulated by FAM60A. SKP2 knockdown using a short-hairpin RNA reversed the functions induced by FAM60A. These results suggest that overexpression of FAM60A in A549/DDP cells led to SKP2 upregulation and enhanced cisplatin resistance in cancer cells. These provide new insights into chemoresistance and may contribute to reversing cisplatin resistance during lung cancer treatment.

Nicotine-derived NNK induces the stemness enrichment of CRC cells through regulating the balance of DUSP4-ERK1/2 feedback loop

Cigarette smoking has been considered as an independent risk factor for colorectal cancer (CRC) initiation and progression. In this study, we found that cigarette smoking was significantly associated with poor CRC differentiation (P = 0.040). Since studies have indicated that poorly differentiated tumors are more aggressive and metastasize earlier, leading to poorer prognosis; and cancer stem cells (CSCs) are largely responsible for tumor differentiation state, here we observed that the exposure of nicotine-derived 4-(methylnitrosamino)- 1-(3-pyridyl)- 1-butanone (NNK) promoted cell sphere formation and the expression of the stem cell markers, CD44, OCT4, C-MYC and NANOG in HCT8 and DLD-1 cells. Further colony formation assay, CCK-8 assay and tumor-bearing experiment showed that NNK exposure significantly increased the proliferative and growth ability of CRC cells. In mechanism, we found that NNK-activated ERK1/2 played an important role in enrichment of CRC stem cells and the up-regulation of DUSP4, a major negative regulator of ERK1/2. Moreover, DUSP4 up-regulation was essential for maintaining NNK-activated ERK1/2 in an appropriate level, which was an required event for NNK-induced stemness enrichment of CRC cells. Taken together, our findings provided a possible mechanistic insight into cigarette smoking-induced CRC progression.

Isoalantolactone inhibits pancreatic cancer proliferation by regulation of PI3K and Wnt signal pathway

BACKGROUND/AIMS

Isoalantolactone (IATL) is one of multiple isomeric sesquiterpene lactones and is isolated from inula helenium. IATL has multiple functions such as antibacterial, antihelminthic and antiproliferative activities. IATL also inhibits pancreatic cancer proliferation and induces apoptosis by increasing ROS production. However, the detailed mechanism of IATL-mediated pancreatic cancer apoptosis remains largely unknown.

METHODS

In current study, pancreatic carcinoma cell lines (PANC-1, AsPC-1, BxPC-3) and a mouse xenograft model were used to determine the mechanism of IATL-mediated toxic effects.

RESULTS

IATL (20μM) inhibited pancreatic adenocarcinoma cell lines proliferation in a time-dependent way; while scratch assay showed that IATL significantly inhibited PANC-1 scratch closure (P<0.05); Invasion assays indicated that IATL significantly attenuated pancreatic adenocarcinoma cell lines invasion on matrigel. Signal analysis showed that IATL inhibited pancreatic adenocarcinoma cell proliferation by blocking EGF-PI3K-Skp2-Akt signal axis. Moreover, IATL induced pancreatic adenocarcinoma cell apoptosis by increasing cytosolic Caspase3 and Box expression. This apoptosis was mediated by inhibition of canonical wnt signal pathway. Finally, xenograft studies showed that IATL also significantly inhibited pancreatic adenocarcinoma cell proliferation and induced pancreatic adenocarcinoma cell apoptosis in vivo.

CONCLUSIONS

IATL inhibits pancreatic cancer proliferation and induces apoptosis on cellular and in vivo models. Signal pathway studies reveal that EGF-PI3K-Skp2-Akt signal axis and canonical wnt pathway are involved in IATL-mediated cellular proliferation inhibition and apoptosis. These studies indicate that IATL may provide a future potential therapy for pancreatic cancer.

The differentiation of colorectal cancer is closely relevant to m6A modification

The occurrence and development of tumors cannot be separated from the influence of differentiation at different stages and levels. Our study found that E-cadherin was significantly increased in cell model induced by sodium butyrate and cell density, while METTL3, METTL16 and WTAP were decreased during the differentiation of cells. In the clinicopathological tissues, E-cadherin was low expressed in poorly differentiated tumor tissues and above three regulators were highly expressed in poorly differentiated tissues. At the levels of clinicopathological differentiation, tissue differentiation and cell differentiation, the result indicated that the poor prognosis of colorectal cancer (CRC) may be closely related to high expression of total m6A level and high expression of METTL3, METTL16 and WTAP.

Radiation-induced gastrointestinal syndrome is alleviated in NDRG2-deficient mice

Background

Radiation-induced gastrointestinal syndrome (GIS) often occurs after therapeutic or accidental exposure to high doses of radiation. Unfortunately, there are still no effective medical treatments for GIS. N-Myc downstream regulated gene 2 (NDRG2), is a tumor suppressor gene and promotes cell apoptosis and differentiation. The aim of our study was to identify the role of NDRG2 in the progression of GIS and explore the potential mechanism.

Methods

We generated Ndrg2^ΔG mice, lacking NDRG2 specifically in the intestinal epithelium. Survival analysis was performed to validate the effect of NDRG2 on GIS, and other common indicators (body weight loss and diarrhea) were used for the assessment of GIS. Enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) were conducted to obtain the expression of pro-inflammatory interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α). TUNNEL and western blotting were further adopted to determine the relationship between NDRG2 and apoptosis. Finally, we performed histology and immunohistochemistry assays to explore the morphological alternations and changes of proliferation-related molecules, including Ki-67 and proliferating cell nuclear antigen (PCNA).

Results

We found that after 8 gray of total body ɤ-irradiation (TBI), the deletion of NDRG2 in the intestine revealed longer survival time, considerably milder symptoms of GIS, and milder damage to jejunal tissue, compared with the WT mice. Moreover, the Ndrg2^ΔG mice significantly inhibited the expression of pro-inflammatory IL-1β, IL-6, and TNF-α, which were typically increased by irradiation. Apoptosis of the epithelial cells in the Ndrg2^ΔG mice was significantly milder while the ratio of proliferation cells was larger in the epithelium of mice 8 days after TBI when compared with the WT mice.

Conclusions

These findings all indicated that NDRG2 deficiency in the intestine protects mice against radiation-induced GIS mainly through promoting proliferation and suppressing apoptosis of epithelial cells.

LncRNA RAD51-AS1/miR-29b/c-3p/NDRG2 crosstalk repressed proliferation, invasion and glycolysis of colorectal cancer

LncRNAs are recently increasingly emerging as molecules that take its part in human carcinogenesis. A large body of literature has identified the functional roles of lncRNAs in the pathophysiology of CRC. The current study was intended to provide new ideas and perspectives for the functional role of lncRNA RAD51-AS1 in regulating CRC progression. Herein, a survey of RAD51-AS1 expression profile in The Cancer Genome Atlas (TCGA)-colon adenocarcinoma (COAD) dataset revealed that RAD51-AS1 was downregulated in COAD specimens. Consistently, RAD51-AS1 expression was observed to be lower in CRC cell lines compared with normal cell line (NCM460). In the meanwhile, both the levels of miR-29b-3p and miR-29c-3p were prominently elevated in CRC cells. Functionally, administration of RAD51-AS1 refrained growth, invasion and migration of CRC cells. Additionally, accumulation of RAD51-AS1 hampered glucose consumption and lactate production, as well as the restraint of hexokinase 2 (HK2) and glucose transporter 1 (GLUT1) levels. More important, RAD51-AS1 functioned as a competing endogenous RNA (ceRNA) for sponging miR-29b-3p and miR-29c-3p, leading to enhancement of their common target N-myc downstream-regulated gene 2 (NDRG2). Mechanistically, the delivery of miR-29b/c-3p mimics or ablation of NDRG2 effectively blunted the salutary effects of RAD51-AS1 on CRC cell behaviors. Moreover, augmentation of RAD51-AS1 inhibited the tumorigenesis of CRC cells in vivo. Collectively, these findings provide comprehensive evidence that RAD51-AS1 repressed cell proliferation, migration, invasion and glycolysis process, ultimately contributing to the progression of CRC by repressing the miR-29b/c-3p/NDRG2 signaling axis, insinuating the putative potential of RAD51-AS1/miR-29b/c-3p/NDRG2 interaction network in unraveling CRC pathology and hopefully contributed to the treatment of CRC patients.

N-myc downstream-regulated gene 2 promotes the protein stability of estrogen receptor beta via inhibition of ubiquitin-protein ligase E3A to suppress colorectal cancer

Background

N-myc downstream-regulated gene 2 (NDRG2) and estrogen receptor beta (ERβ) both play key roles in cellular differentiation in colorectal cancer (CRC). Previous studies have demonstrated that ERβ co-locates with and directly transactivates NDRG2. However, the effect of NDRG2 on ERβ and its underlying mechanism remain largely unknown. Our aim of the study is to explore the effect of NDRG2 on ERβ and their contributions to progression of CRC.

Methods

The Cancer Genome Atlas (TCGA) database was first utilized to validate the clinical significance of ERβ and NDRG2 in CRC. MTT and scratch migration assays were carried out to verify the role of ERβ and NDRG2 in CRC cells. Western blotting and polymerase chain reaction were performed to analyze the effect of NDRG2 on ERβ, and an immunoprecipitation assay was conducted to explore the protein-protein interaction.

Results

ERβ and NDRG2 were both found to be significantly down-regulated in tumor tissues from the TCGA-CRC database. NDRG2 was also observed to enhance the protein stability of ERβ while could not change messenger RNA (mRNA) level of ESR2 (encoding ERβ). A positive relationship was found to exist between the two proteins in CRC cells, with NDRG2 prolonging the half-life of ERβ and improving its nuclear translocation. Through detecting expression of ERβ downstream genes (such as TP53 and JNK) and performing related function experiment, we demonstrated that NDRG2 could promote transcriptional activation of ERβ target genes and enhance the function of tumor suppressors when the ERβ agonist diarylpropionitrile (DPN). The immunoprecipitation assay showed that NDRG2 could affect the complex components of ubiquitin-protein ligase E3A (UBE3A, known as E6AP) and ERβ, reducing the ubiquitin-mediated proteasome degradation of ERβ.

Conclusions

In the current study, we found that NDRG2 could bind with UBE3A to hinder the binding of UBE3A with ERβ. Moreover, a positive feedback loop was discovered between NDRG2 and ERβ, which provides a novel insight and therapeutic target for CRC.

Roles of N-myc downstream-regulated gene 2 in the central nervous system: molecular basis and relevance to pathophysiology

N-myc downstream-regulated gene 2 (NDRG2) is a member of the NDRG family, whose members have multiple functions in cell proliferation, differentiation, and stress responses. NDRG2 is widely distributed in the central nervous system and is uniquely expressed by astrocytes; however, its role in brain function remains elusive. The clinical relevance of NDRG2 and the molecular mechanisms in which it participates have been reported by studies using cultured cells and specimens of patients with neurological disorders. In recent years, genetic tools, including several lines of Ndrg2-knockout mice and virus-mediated gene transfer, have improved understanding of the roles of NDRG2 in vivo. This review aims to provide an update of recent growing in vivo evidence that NDRG2 is involved in brain function, focusing on research of Ndrg2-knockout mice with neurological disorders such as brain tumors, chronic neurodegenerative diseases, and acute brain insults including brain injury and cerebral stroke. These studies demonstrate that NDRG2 plays diverse roles in the regulation of astrocyte reactivity, blood-brain barrier integrity, and glutamate excitotoxicity. Further elucidation of the roles of NDRG2 and their molecular basis may provide novel therapeutic approaches for various neurological disorders.

The Active Constituent From Gynostemma Pentaphyllum Prevents Liver Fibrosis Through Regulation of the TGF-β1/NDRG2/MAPK Axis

Liver fibrosis resulting from chronic liver damage constitutes a major health care burden worldwide; however, no antifibrogenic agents are currently available. Our previous study reported that the small molecule NPLC0393 extracted from the herb Gynostemma pentaphyllum exerts efficient antifibrotic effects both in vivo and in vitro. In this study, a TMT-based quantitative proteomic study using a carbon tetrachloride (CCl₄)-induced mouse model of liver fibrosis was performed to identify the potential target of NPLC0393. Combining this study with bioinformatic analysis of differentially expressed proteins between the CCl₄ model and NPLC0393 treatment groups, we focused on the function of N-myc downstream-regulated gene 2 (NDRG2) involved in cell differentiation. In vitro studies showed that NPLC0393 prevented the TGF-β1 stimulation-induced decrease in the NDRG2 level in hepatic stellate cells (HSCs). Functional studies indicated that NDRG2 can inhibit the activation of HSCs by preventing the phosphorylation of ERK and JNK. Furthermore, knockdown of NDRG2 abolished the ability of NPLC0393 to inhibit HSC activation. In conclusion, these results provide information on the mechanism underlying the antifibrotic effect of NPLC0393 and shed new light on the potential therapeutic function of the TGF-β1/NDRG2/MAPK signaling axis in liver fibrosis.

NDRG2 regulates adherens junction integrity to restrict colitis and tumourigenesis

BACKGROUND

Paracellular barriers play an important role in the pathogenesis of Inflammatory bowel disease (IBD) and maintain gut homeostasis. N-myc downstream-regulated gene 2 (NDRG2) has been reported to be a tumour suppressor gene and to inhibit colorectal cancer metastasis. However, whether NDRG2 affects colitis initiation and colitis-associated colorectal cancer is unclear.

METHODS

Intestine-specific Ndrg2 deficiency mice (Ndrg2^ΔIEC) were subjected to DSS- or TNBS-induced colitis, and AOM-DSS-induced colitis-associated tumour. HT29 cells, Caco2 cells, primary intestinal epithelial cells (IECs) from Ndrg2^ΔIEC mice, mouse embryo fibroblasts (MEFs) from systemic Ndrg2 knockout mice, HEK293 cells and human UC and DC specimens were used to investigate NDRG2 function in colitis and colitis-associated tumour.

FINDINGS

Ndrg2 loss led to adherens junction (AJ) structure destruction via E-cadherin expression attenuation, resulting in diminished epithelial barrier function and increased intestinal epithelial permeability. Mechanistically, NDRG2 enhanced the interaction of E3 ligase FBXO11 with Snail, the repressor of E-cadherin, to promote Snail degradation by ubiquitination and maintained E-cadherin expression. In human ulcerative colitis patients, reduced NDRG2 expression is positively correlated with severe inflammation.

INTERPRETATION

These findings demonstrate that NDRG2 is an essential colonic epithelial barrier regulator and plays an important role in gut homeostasis maintenance and colitis-associated tumour development.

FUNDING

National Natural Science Foundation of China (No. 81770523, 31571437, 81672751), Creative Research Groups of China (No. 81421003), State Key Laboratory of Cancer Biology Project (CBSKL2019ZZ11, CBSKL201406, CBSKL2017Z08 and CBSKL2017Z11), Fund for Distinguished Young Scholars of ShaanXi province (2019JC-22).

NDRG2 ablation reprograms metastatic cancer cells towards glutamine dependence via the induction of ASCT2

Background: Metastasis is the most common cause of lethal outcome in various types of cancers. Although the cell proliferation related metabolism rewiring has been well characterized, less is known about the association of metabolic changes with tumor metastasis. Herein, we demonstrate that metastatic tumor obtained a mesenchymal phenotype, which is obtained by the loss of tumor suppressor NDRG2 triggered metabolic switch to glutamine metabolism.

Methods: mRNA-seq and gene expression profile analysis were performed to define the differential gene expressions in primary MEC1 and metastatic MC3 cells and the downstream pathways of NDRG2. NDRG2 regulation of Fbw7-dependent c-Myc stability were determined by immunoprecipitation and protein half-life assay. Luciferase reporter and ChIP assays were used to determine the roles of Akt and c-Myc in mediating NDRG2-dependent regulation of ASCT2 in in both tumor and NDRG2-knockout MEF cells. Finally, the effect of the NDRG2/Akt/c-Myc/ASCT2 signaling on glutaminolysis and tumor metastasis were evaluated by functional experiments and clinical samples.

Results: Based on the gene expression profile analysis, we identified metastatic tumor cells acquired the mesenchymal-like characteristics and displayed the increased dependency on glutamine utilization. Further, the gain of NDRG2 function blocked epithelial-mesenchymal transition (EMT) and glutaminolysis, potentially through suppression of glutamine transporter ASCT2 expression. The ASCT2 restoration reversed NDRG2 inhibitory effect on EMT program and tumor metastasis. Mechanistic study indicates that NDRG2 promoted Fbw7-dependent c-Myc degradation by inhibiting Akt activation, and subsequently decreased c-Myc-mediated ASCT2 transcription, in both tumor and NDRG2-knockout MEF cells. Supporting the biological significance, the reciprocal relationship between NDRG2 and ASCT2 were observed in multiple types of tumor tissues, and associated with tumor malignancy.

Conclusions: NDRG2-dependent repression of ASCT2 presumably is the predominant route by which NDRG2 rewires glutaminolysis and blocks metastatic tumor survival. Targeting glutaminolytic pathway may provide a new strategy for the treatment of metastatic tumors.

Low NDRG2 expression predicts poor prognosis in solid tumors: A meta-analysis of cohort study

BACKGROUND

As a member of the N-myc down-regulated gene family, N-Myc downstream-regulated gene 2 (NDRG2) contributes to the tumorigenesis of various types of cancers. However, the correlation between NDRG2 expression and the prognosis of solid tumor remains to be elucidated because of small sample sizes and inconsistent results in previous studies. In the present study, we conducted a systematic review and meta-analysis to explore the prognostic significance of NDRG2 in human solid tumors.

METHODS

PubMed, Web of Science, Embase, Chinese National Knowledge Infrastructure, and WanFang databases (up to April 2020) were searched for relevant studies that evaluated the impact of NDRG2 on clinical outcomes, including overall survival (OS), and disease-free survival (DFS), in solid tumors. Hazard ratios (HRs) with 95% confidence intervals (CIs) were pooled to assess the association between NDRG2 expression and the survival of patients with solid tumors. Odds ratios (ORs) with 95% CIs were pooled to estimate the correlation between NDRG2 expression and clinicopathologic characteristics in the patients.

RESULTS

A total of 13 eligible studies with 1980 patients were included in this meta-analysis. Low NDRG2 expression was significantly associated with poor OS (HR = 1.96, 95% CI: 1.60-2.40, P < .001) and DFS (HR = 2.70, 95% CI: 1.42-5.13, P = .002) in solid tumor. Furthermore, low NDRG2 expression was related to some phenotypes of tumor aggressiveness, such as clinical stage (OR = 3.21, 95% CI: 1.96-5.26, P < .001), lymph node metastasis (OR = 2.14, 95% CI: 1.49-3.07, P < .001), and degree of differentiation (OR = 0.60, 95% CI: 0.45-0.81, P = .001).

CONCLUSIONS

NDRG2 may be a meaningful biomarker of poor prognosis and a potential therapeutic target for human solid tumors.

MiR-130a/Ndrg2 Axis Inhibits the Proliferation of Fibroblast-Like Synoviocytes in Rheumatoid Arthritis

Studies have found that N-myc downstream-regulated gene 2 (Ndrg2) is involved in the progression of rheumatoid arthritis (RA); however, the specific mechanism still remains unclear. Gene expression profiles in the tibial joints of the collagen-induced rheumatoid arthritis model were obtained using Gene Expression Omnibus database. Western blot and real-time PCR were respectively performed to determine the expression of Ndrg2 and gene messenger RNA. Cell viability was measured by Cell Counting Kit-8 (CCK-8) method, and cell cycle was detected by flow cytometry. Cell scratch assays were carried out to detect migration. The binding ability of miR-130a to Ndrg2-3'-UTR was predicted by TargetScan website and confirmed by dual luciferase assay. A collagen-induced arthritis rat model was constructed to observe the effects of miR-130a on arthritis index, hind limb swelling, volume of rat hind paw, and inflammation. Ndrg2 was found downregulated in RA tissues, and knockdown of Ndrg2 promoted fibroblast-like synoviocytes (FLS) proliferation and inflammation, while overexpressed Ndrg2 produced opposite results. Ndrg2 was predicted as a target gene for miR-130a, and miR-130a mimic promoted FLS proliferation, while miR-130a inhibitor suppressed FLS proliferation. Moreover, we found that miR-130a antagomir could significantly reduce the arthritis index, swelling degree, foot volume, and inflammatory factor levels; inhibit the expression of miR-130a; and promote the expression of Ndrg2. The miR-130a/Ndrg2 axis signaling pathway is involved in the progression of RA. Our findings provide a theoretical basis for the clinical treatment of RA.

NDRG2 attenuates ischemia-induced astrocyte necroptosis via the repression of RIPK1

Cerebral ischemia results in severe brain damage, and is a leading cause of death and long-term disability. Previous studies have investigated methods to activate astrocytes in order to promote repair in injured brain tissue and inhibit cell death. It has previously been shown that N-myc downstream-regulated gene 2 (NDRG2) was highly expressed in astrocytes and associated with cell activity, but the underlying mechanism is largely unknown. The present study generated NDRG2 conditional knockout (Ndrg2-/-) mice to investigate whether NDRG2 can block ischemia-induced astrocyte necroptosis by suppressing receptor interacting protein kinase 1 (RIPK1) expression. This study investigated astrocyte activity in cerebral ischemia, and identified that ischemic brain injuries could trigger RIP-dependent astrocyte necroptosis. The depletion of NDRG2 was found to accelerate permanent middle cerebral artery occlusion-induced necroptosis in the brain tissue of Ndrg2-/- mice, indicating that NDRG2 may act as a neuroprotector during cerebral ischemic injury. The present study suggested that NDRG2 attenuated astrocytic cell death via the suppression of RIPK1. The pharmacological inhibition of astrocyte necroptosis by necrostatin-1 provided neuroprotection against ischemic brain injuries after NDRG2 knockdown. Therefore, NDRG2 could be considered as a potential target for the treatment of cerebral ischemia.

Differential Expression of HER2 and SKP2 in Benign and Malignant Colorectal Lesions

Background:

Colorectal cancer (CRC) is the fourth most common cancer worldwide. Both HER2 and SKP2 have a carcinogenic role in CRC making them attractive targets for tailored treatment. This work aims to correlate HER2 and SKP2 protein expression as well as HER2 gene amplification with clinicopathological parameters aiming at identifying potential candidates for targeted therapy.

Methods:

This Study was conducted on 127 paraffin-embedded tissue samples of different colorectal lesions [controls, chronic colitis, ulcerative colitis (UC), hyperplastic polyps (HPs), adenomas and CRCs] to investigate HER2 and SKP2 expression by immunohistochemistry (IHC), Selected CRC cases [equivocal (2+) and positive (3+) by IHC] were further evaluated by ISH (CISH and SISH ) to assess HER2 gene amplification.

Results:

Chronic colitis, UC, HPs and adenomas were HER2-negative. HER2 positivity (scores 2+ and 3+) was found only in15% of CRCs. Both SISH and CISH showed the same results with high concordance as 66.7% of equivocal and 100% of positive cases showed amplification of HER2 gene. SKP2 positivity was detected in 26.7% and 45% of adenomas and CRCs respectively, while other studied groups were negative. A significant correlation was noted between HER2 and SKP2 expression.

Conclusion:

A small percent of CRCs exhibited HER2 gene amplification, which would be potential candidates for anti HER2 therapy whereas IHC could be a primary screening test for patient selection. A potential carcinogenic role of SKP2 was suggested by the findings that SKP2 expression was undetectable in normal colonic mucosa but significantly increases from adenoma to carcinoma, hoping adenoma patients to get benefit from targeted therapy.

Astrocyte-specific NDRG2 gene: functions in the brain and neurological diseases

In recent years, the roles of astrocytes of the central nervous system in brain function and neurological disease have drawn increasing attention. As a member of the N-myc downstream-regulated gene (NDRG) family, NDRG2 is principally expressed in astrocytes of the central nervous system. NDRG2, which is involved in cell proliferation and differentiation, is commonly regarded as a tumor suppressor. In astrocytes, NDRG2 affects the regulation of apoptosis, astrogliosis, blood-brain barrier integrity, and glutamate clearance. Several preclinical studies have revealed that NDRG2 is implicated in the pathogenesis of many neurological diseases not limited to tumors (mostly glioma in the nervous system), such as stroke, neurodegeneration (Alzheimer's disease and Parkinson's disease), and psychiatric disorders (depression and attention deficit hyperactivity disorder). This review summarizes the biological functions of NDRG2 under physiological and pathological conditions, and further discusses the roles of NDRG2 during the occurrence and development of neurological diseases.

Cell Survival Is Regulated via SOX9/BCL2L1 Axis in HCT-116 Colorectal Cancer Cell Line

Colorectal cancer (CRC) is one of the most frequent types of malignancies and one of the major causes of cancer-related death worldwide. Sex-determining region Y (SRY)-box 9 protein (SOX9) is a member of the SOX family of transcription factors which are involved in the regulation of differentiation and development. Recently, several reports suggest an important role of SOX9 in tumorigenesis since its overexpression correlates with tumor progression and poor outcome in several types of cancer; however, its role in CRC is not clear until now. Therefore, in this work, we searched for novel SOX9-regulated genes involved in cell survival of CRC. We silenced SOX9 in the poorly differentiated HCT-116 cell line, using a specific siRNA, to identify differential expressed genes by DNA microarrays and analyzed the role or candidate genes in apoptosis and autophagy. Transcriptome analysis showed that diverse cellular pathways, associated with CRC carcinogenesis such as Wnt/β-catenin, MAPK, TGF-β, and mTOR, were modulated after SOX9 silencing. Interestingly, we found that SOX9 silencing promotes downregulation of BCL2L1 and overexpression of CASP3, proteins related to apoptosis, which was further confirmed in SW-480, a moderated-differentiated cell line, but not in HT-29, well-differentiated cell line. Moreover, inhibition of BCL2L1 by ABT-737 (BH3 mimetic) in SOX9-silenced HCT-116 cells resulted in an increased apoptosis percentage. However, downregulation of BCL2L1 was not enough to induce autophagy. This is the first report, suggesting that cell survival in poorly and moderated-differentiated CRC cells lines is regulated by SOX9/BCL2L1 axis, but not in well-differentiated cell lines.

Dp44mT, an iron chelator, suppresses growth and induces apoptosis via RORA-mediated NDRG2-IL6/JAK2/STAT3 signaling in glioma

PURPOSE

The iron-chelating agent di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) has been found to inhibit cell growth and to induce apoptosis in several human cancers. However, its effects and mechanism of action in glioma are unknown.

METHODS

Human glioma cell line LN229 and patient-derived glioma stem cells GSC-42 were applied for both in vitro and in vivo xenograft nude mouse experiments. The anti-tumor effects of Dp44mT were assessed using MTS, EdU, TUNEL, Western blotting, qRT-PCR, luciferase reporter, chromatin immunoprecipitation and immunohistochemical assays.

RESULTS

We found that Dp44mT can upregulate the expression of the anti-oncogene N-myc downstream-regulated gene (NDRG)2 by directly binding to and activating the RAR-related orphan receptor (ROR)A. In addition, we found that NDRG2 overexpression suppressed inflammation via activation of interleukin (IL)-6/Janus kinase (JAK)2/signal transducer and activator of transcription (STAT)3 signaling.

CONCLUSIONS

Our data indicate that Dp44mT may serve as an effective drug for the treatment of glioma by targeting RORA and enhancing NDRG2-mediated IL-6/JAK2/STAT3 signaling.

N-myc Downstream-Regulated Gene 2 (NDRG2) Promotes Bone Morphogenetic Protein 2 (BMP2)-Induced Osteoblastic Differentiation and Calcification by Janus Kinase 3 (JAK3)/Signal Transducer and Activator of Transcription 3 (STAT3) Signaling Pathway

Background

Osteoporosis is an osteolytic disease resulted from imbalance in bone homeostasis. Studies indicated that N-myc downstream-regulated gene 2 (NDRG2) could affect the osteoclast differentiation. However, the effect of NDRG2 on osteoblastic differentiation and calcification remains unknown. Hence, we aimed to analyze the effect of NDRG2 on the proliferation and differentiation of osteoblasts.

Material/Methods

The differentiation of bone morphogenetic protein 2 (BMP2) induced MC3T3-E1 cells was observed by the microscope. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blot analysis detected the expression of BMP2, NDRG2, runt-related transcription factor 2 (Runx2), osteoprotegerin (OPG), osterix (OSX), and osteocalcin (OCN). Alkaline phosphatase (ALP) activity assay was detecting the ALP activity and alizarin red staining assay was analyzing intracellular calcium salt deposition. The cell transfection was also verified by RT-qPCR analysis.

Results

The results demonstrated that BMP2 promoted the osteoblastic differentiation with the increasing expression of Runx2, OPG, OSX, and OCN. NDRG2 expression was upregulated during osteogenic differentiation. NDRG2 overexpression promoted the expression of Runx2, OPG, OSX, and OCN, and increased the ALP activity while NDRG2 inhibition reversed the changes. NDRG2 overexpression increased the intracellular calcium salt deposition and NDRG2 inhibition reversed the changes. The role of NDRG2 in osteoblastic differentiation and calcification was played through the JAK3/STAT3 signal pathway.

Conclusions

The presented data indicated that NDRG2 promoted BMP2-induced osteoblastic differentiation and calcification by activating the JAK3/STAT3 signal pathway.

Cdh1-mediated Skp2 degradation by dioscin reprogrammes aerobic glycolysis and inhibits colorectal cancer cells growth

BACKGROUND

The F-box protein S-phase kinase-associated protein 2 (Skp2) is overexpressed and correlated with poor prognosis in human malignancies, including colorectal cancer (CRC).

METHODS

A natural product library was used for natural compound screening through glycolysis analysis. The expression of Skp2 in CRCs and the inhibitory effect of dioscin on glycolysis were examined through methods of immunoblot, immunofluorescence, immunohistochemical staining, anchorage-dependent and -independent growth assays, EdU incorporation assay, ubiquitination analysis, co-immunoprecipitation assay, CRISPR-Cas9-based gene knockout, and xenograft experiment.

FINDINGS

We demonstrated that Skp2 was highly expressed in CRC tissues and cell lines. Knockout of Skp2 inhibited HK2 and glycolysis and decreased CRC cell growth in vitro and in vivo. We screened 88 commercially available natural products and found that dioscin, a natural steroid saponin derived from several plants, significantly inhibited glycolysis in CRC cells. Dioscin decreased the protein level of Skp2 by shortening the half-life of Skp2. Further study showed that dioscin attenuated Skp2 phosphorylation on S72 and promoted the interaction between Skp2 and Cdh1, which eventually enhanced Skp2 lysine 48 (K48)-linked polyubiquitination and degradation. Depletion of Cdh1 impaired dioscin-induced Skp2 reduction, rescued HK2 expression, and glycolysis in CRC cells. Finally, dioscin delayed the in vivo tumor growth, promoted Skp2 ubiquitination, and inhibited Skp2 expression in a mouse xenograft model.

INTERPRETATION

This study suggests that in addition to pharmacological inactivation of Skp2, enhancement of ubiquitination-dependent Skp2 turnover is a promising approach for cancer treatment.

WNT7A Overexpression Inhibits Growth and Migration of Hepatocellular Carcinoma via the β-Catenin Independent Pathway

Background/Aims. Hepatocellular carcinoma (HCC) is the lethal digestive cancer and the second leading cause of cancer death in men worldwide. Wnt7a, a 39Kd secreted glycoprotein composed of 349 amino acids, was reported to be related to various diseases. However, its role in HCC has not been studied yet. In this study, using gene expression data and clinical information obtained from the Oncomine and KMplot database, we acknowledged that WNT7A was underexpressed in HCC cancer tissue compared with normal tissue, and WNT7A underexpression was correlated with the decreased survival rate of HCC patients. The function of Wnt7a in cell viability, apoptosis, and migration was evaluated by biological behavior assay and molecular analysis. The findings revealed that WNT7A overexpression significantly restrained cell viability and migration while enhancing apoptosis. In addition, WNT7A overexpression promoted cell apoptosis by strengthening Caspase-3 activity and inhibited migration by downregulating EMT transcriptional factor Snail. Furthermore, the expression level of SKP2 was significantly downregulating in the WNT7A overexpression group. In conclusion, this study illustrated that overexpression of WNT7A inhibited cell viability and migration, which was likely attributed to the regulation of SKP2/P21.

Truncated TEAD-binding protein of TAZ inhibits glioma survival through the induction of apoptosis and repression of epithelial-mesenchymal transition

Transcriptional coactivator with PDZ-binding motif (TAZ), a Hippo pathway downstream effector, promotes tumor progression by serving as a transcriptional coactivator with TEAD. Here, we introduced a new construct which can express the TEAD-binding domain of TAZ protein (TAZBD), and determined its antitumor effect in malignant glioma both in vitro and in vivo. We first observed that TAZ was upregulated in glioma tissues and related to malignant clinicopathologic characteristic, indicating the crucial role of TAZ during glioma progression. In U87 and U251 cells, TAZBD expression increased the proportion of apoptotic cells, and suppressed the colony formation and tumorigenicity. Further, TAZBD also decreased cell metastasis through the repression of epithelial-mesenchymal transition. The mechanistic study showed that TAZBD suppression of glioma cells was predominantly through blocking the TAZ-TEAD complex formation by competing with endogenous TAZ. Thus, the gene therapy of malignant glioma through blocking TAZ-TEAD complex by TAZBD may provide a new way for the targeted therapy of glioma.

Expression of NDRG2 in Human Colorectal Cancer and its Association with Prognosis

Objective: As a member of the N-myc downregulated gene family, N-Myc downstream-regulated gene 2 (NDRG2) contributes to tumorigenesis of various types of cancer. The expression status of NDRG2 in colorectal cancer (CRC) and its prognostic value remain to be elucidated. The goal of this study was to determine the expression pattern of NDRG2 in human CRC and its association of NDRG2 expression with prognosis.

Methods: Immunohistochemistry was used to determine the level of NDRG2 expressions in 316 CRC tissues. The medical records of consecutive CRC patients undergoing primary tumor resection from September 2000 to February 2015 were retrospectively selected. Then, we compared to specific clinicopathological features in patients with different level of NDRG2 expressions. The correlation of NDRG2 expression with 3-year survival rate was assessed by Kaplan-Meier method and Cox regression modeling.

Results: NDRG2 was expressed in 94.6% (299/316) of CRC tissues. The median IHC score of NDRG2 expression was significantly lower in tumor tissues compared with that of tumor-adjacent normal tissues [4.50(range 0.00-12.00) vs. 10.00 (range 0.00-12.00), P < 0.001].Survival analysis indicated that patients with low NDRG2 expression had poorer 3-year OS than those with high NDRG2 expression (59.9% vs. 76.6%, P = 0.017). Low NDRG2 expression also presented a significantly poorer 3-year OS rate in patient with stage IV disease (29.4% vs. 56.5%, P = 0.002), liver metastasis(32.2% vs. 54.7%, P = 0.005) and those receiving liver resection(56.5% vs. 71.9% , P = 0.012). Multivariate analysis indicated that high NDRG2 expression was independently associated with poor OS (hazard ratio [HR]: 1.499; 95% confidence interval [CI]: 1.037-2.165; P = 0.031).

Conclusions: Low expression of NDRG2 was associated with unfavorable prognosis in CRC patients with primary tumor resection. Detection of NDRG2 expression might be useful for providing valuable information of individualized therapy for CRC patients.

Effect of silencing S-phase kinase-associated protein 2 on chemosensitivity to temozolomide of human glioma cells U251

OBJECTIVE

To examine the effect of silencing SKP2 on chemosensitivity of human glioma cells U251 to temozolomide (TMZ).

METHODS

Adenoviruses harbouring shRNA targeting SKP2 (i.e. Ad-shSKP2) and non-targeting scrambled shRNA (i.e. Ad-shNC) were used to infect U251 cells. The transduced cells were then treated with TMZ. Cell viability after treatment was assayed using CCK8; while cell cycle and apoptosis were examined using flow cytometry. To study the effect of silencing SKP2 on autophagy in U251, we co-transduced the cells with Ad-mRFP-LC3 and Ad-shSKP2/Ad-shNC. The expression of autophagy marker LC3 after TMZ treatment was studied using microscopy and Western blotting assays.

RESULTS

The cytotoxicity of TMZ (i.e. 20-100 µM) was more significantly seen in Ad-shSKP2-transduced U251 cells than in the Ad-shNC-transduced U251 cells. The IC₅₀ values in shSKP2-U251 were significantly lower than those of the shNC-U251 (P < 0.05). Both TMZ and Ad-shSKP2 alone increased apoptosis and promoted expression of LC3 in U251. Combined treatment of Ad-shSKP2 and TMZ further elevated apoptosis and LC3 expression.

CONCLUSION

Silencing SKP2 in U251 cells increased chemosensitivity to TMZ that was accompanied with enhanced apoptosis and autophagy. Targeting SKP2 may be a potential approach to potentiate TMZ treatment in patients with glioma.

NDRG3 overexpression is associated with a poor prognosis in patients with hepatocellular carcinoma

N-myc downstream-regulated gene 3 (NDRG3), an important member of the NDRG family, is involved in cell proliferation, differentiation, and other biological processes. The present study analyzed NDRG3 expression in hepatocellular carcinoma (HCC) and explored the relationship between expression of NDRG3 in HCC patients and their clinicopathological characteristics. We performed quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) analysis and immunohistochemistry (IHC) analyses on HCC tissues to elucidate NDRG3 expression characteristics in HCC patients. Kaplan-Meier survival curve and Cox regression analyses were used to evaluate the prognoses of 102 patients with HCC. The results revealed that compared with non-tumor tissues, HCC tissues showed significantly higher NDRG3 expression. In addition, our analyses showed that NDRG3 expression was statistically associated with tumor size (P=0.048) and pathological grade (P=0.001). Survival analysis and Kaplan-Meier curves revealed that NDRG3 expression is an independent prognostic indicator for disease-free survival (P=0.002) and overall survival (P=0.005) in HCC patients. The data indicate that NDRG3 expression may be considered as a oncogenic biomarker and a novel predictor for HCC prognosis.

Burkholderia Lethal Factor 1, a Novel Anti-Cancer Toxin, Demonstrates Selective Cytotoxicity in MYCN-Amplified Neuroblastoma Cells

Immunotoxins are being investigated as anti-cancer therapies and consist of a cytotoxic enzyme fused to a cancer targeting antibody. All currently used toxins function via the inhibition of protein synthesis, making them highly potent in both healthy and transformed cells. This non-specific cell killing mechanism causes dose-limiting side effects that can severely limit the potential of immunotoxin therapy. In this study, the recently characterised bacterial toxin Burkholderia lethal factor 1 (BLF1) is investigated as a possible alternative payload for targeted toxin therapy in the treatment of neuroblastoma. BLF1 inhibits translation initiation by inactivation of eukaryotic initiation translation factor 4A (eIF4A), a putative anti-cancer target that has been shown to regulate a number of oncogenic proteins at the translational level. We show that cellular delivery of BLF1 selectively induces apoptosis in neuroblastoma cells that display MYCN amplification but has little effect on non-transformed cells. Future immunotoxins based on this enzyme may therefore have higher specificity towards MYCN-amplified cancer cells than more conventional ribosome-inactivating proteins, leading to an increased therapeutic window and decreased side effects.

Computer-aided drug design and inhibitive effect of a novel nitrogenous heterocyclic compound and its mechanism on glioma U251 cells and breast cancer MCF-7 cells

Background

Glioma and breast cancer are severe malignant cancerous tumors that highlight the importance of developing new anti-cancer drugs. The aim of this study was to explore the effects of a novel nitrogenous heterocyclic compound on glioma and breast cancer cells and to determine its mechanism of action.

Methods

We designed and synthesized a novel nitrogenous heterocyclic compound, 3-(4-amino-1H-benzo[d]imidazole-2-carboxamido)-4-oxo-3,4-dihydroimidazo[5,1-d][1,2,3,5] tetrazine-8-carboxamide, based on alkylglycerone phosphate synthase (AGPS) using computer-aided drug design (CADD), and we measured its effect on the proliferation, invasion, cell cycle and apoptosis of U251 glioma and MCF-7 breast cancer cells. In addition, the compound’s effect on the expression of tumor-related mRNA, circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs) was explored.

Results

It was found that the nitrogenous heterocyclic compound could induce cell cycle arrest at the G2/M phase of U251/MCF-7 cells and activate apoptosis. Real-time PCR showed that the expression levels of tumor-related mRNA, circRNAs and lncRNAs were impacted.

Conclusion

We concluded that the nitrogenous heterocyclic compound inhibits the proliferation and invasion of U251 glioma and MCF-7 breast cancer cells through the induction of apoptosis and cell cycle arrest by regulating tumor-related genes.