BAG3 directly stabilizes Hexokinase 2 mRNA and promotes aerobic glycolysis in pancreatic cancer cells

Exosomal circSIPA1L3-mediated intercellular communication contributes to glucose metabolic reprogramming and progression of triple negative breast cancer

BACKGROUND

Breast cancer is the most common malignant tumor, and metastasis remains the major cause of poor prognosis. Glucose metabolic reprogramming is one of the prominent hallmarks in cancer, providing nutrients and energy to support dramatically elevated tumor growth and metastasis. Nevertheless, the potential mechanistic links between glycolysis and breast cancer progression have not been thoroughly elucidated.

METHODS

RNA-seq analysis was used to identify glucose metabolism-related circRNAs. The expression of circSIPA1L3 in breast cancer tissues and serum was examined by qRT-PCR, and further assessed its diagnostic value. We also evaluated the prognostic potential of circSIPA1L3 by analyzing a cohort of 238 breast cancer patients. Gain- and loss-of-function experiments, transcriptomic analysis, and molecular biology experiments were conducted to explore the biological function and regulatory mechanism of circSIPA1L3.

RESULTS

Using RNA-seq analysis, circSIPA1L3 was identified as the critical mediator responsible for metabolic adaption upon energy stress. Gain- and loss-of-function experiments revealed that circSIPA1L3 exerted a stimulative effect on breast cancer progression and glycolysis, which could also be transported by exosomes and facilitated malignant behaviors among breast cancer cells. Significantly, the elevated lactate secretion caused by circSIPA1L3-mediated glycolysis enhancement promoted the recruitment of tumor associated macrophage and their tumor-promoting roles. Mechanistically, EIF4A3 induced the cyclization and cytoplasmic export of circSIPA1L3, which inhibited ubiquitin-mediated IGF2BP3 degradation through enhancing the UPS7-IGF2BP3 interaction. Furthermore, circSIPA1L3 increased mRNA stability of the lactate export carrier SLC16A1 and the glucose intake enhancer RAB11A through either strengthening their interaction with IGF2BP3 or sponging miR-665, leading to enhanced glycolytic metabolism. Clinically, elevated circSIPA1L3 expression indicated unfavorable prognosis base on the cohort of 238 breast cancer patients. Moreover, circSIPA1L3 was highly expressed in the serum of breast cancer patients and exhibited high diagnostic value for breast cancer patients.

CONCLUSIONS

Our study highlights the oncogenic role of circSIPA1L3 through mediating glucose metabolism, which might serve as a promising diagnostic and prognostic biomarker and potential therapeutic target for breast cancer.

IGF2BPs as novel m6A readers: Diverse roles in regulating cancer cell biological functions, hypoxia adaptation, metabolism, and immunosuppressive tumor microenvironment

m6A methylation is the most frequent modification of mRNA in eukaryotes and plays a crucial role in cancer progression by regulating biological functions. Insulin-like growth factor 2 mRNA-binding proteins (IGF2BP) are newly identified m6A 'readers'. They belong to a family of RNA-binding proteins, which bind to the m6A sites on different RNA sequences and stabilize them to promote cancer progression. In this review, we summarize the mechanisms by which different upstream factors regulate IGF2BP in cancer. The current literature analyzed here reveals that the IGF2BP family proteins promote cancer cell proliferation, survival, and chemoresistance, inhibit apoptosis, and are also associated with cancer glycolysis, angiogenesis, and the immune response in the tumor microenvironment. Therefore, with the discovery of their role as 'readers' of m6A and the characteristic re-expression of IGF2BPs in cancers, it is important to elucidate their mechanism of action in the immunosuppressive tumor microenvironment. We also describe in detail the regulatory and interaction network of the IGF2BP family in downstream target RNAs and discuss their potential clinical applications as diagnostic and prognostic markers, as well as recent advances in IGF2BP biology and associated therapeutic value.

BAG3 as a novel prognostic biomarker in kidney renal clear cell carcinoma correlating with immune infiltrates

PURPOSE

BCL-2-associated athanogene 3 (BAG3) is an anti-apoptotic protein that plays an essential role in the onset and progression of multiple cancer types. However, the clinical significance of BAG3 in kidney renal clear cell carcinoma (KIRC) remains unclear.

METHODS

Using Tumor IMmune Estimation Resource (TIMER), The Cancer Genome Atlas (TCGA), and Gene Expression Omnibus (GEO) database, we explored the expression, prognostic value, and clinical correlations of BAG3 in KIRC. In addition, immunohistochemistry (IHC) of HKH cohort further validated the expression of BAG3 in KIRC and its impact on prognosis. Gene Set Cancer Analysis (GSCA) was utilized to scrutinize the prognostic value of BAG3 methylation. Gene Ontology (GO) term analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene set enrichment analysis (GSEA) were used to identify potential biological functions of BAG3 in KIRC. Single-sample gene set enrichment analysis (ssGSEA) was performed to confirm the correlation between BAG3 expression and immune cell infiltration.

RESULTS

BAG3 mRNA expression and protein expression were significantly downregulated in KIRC tissues compared to normal kidney tissues, associated with adverse clinical-pathological factors and poor clinical prognosis. Multivariate Cox regression analysis indicated that low expression of BAG3 was an independent prognostic factor in KIRC patients. GSEA analysis showed that BAG3 is mainly involved in DNA methylation and the immune-related pathways in KIRC. In addition, the expression of BAG3 is closely related to immune cell infiltration and immune cell marker set.

CONCLUSION

BAG3 might be a potential therapeutic target and valuable prognostic biomarker of KIRC and is closely related to immune cell infiltration.

Bioinformatics analysis of the clinicopathological and prognostic significance of BAG3 mRNA in gynecological cancers

BAG3 is a co-chaperone BAG family protein that plays important roles in protein homeostasis, cell survival, cell motility, and tumour metastasis. This study aimed to clarify the clinicopathological and prognostic implications of BAG3 mRNA expression in tumours. We performed bioinformatics analysis on BAG3 mRNA expression using TCGA, XIANTAO, UALCAN, and Kaplan-Meier plotter databases. BAG3 mRNA expression was downregulated in breast and endometrial cancers and positively correlated with favourable PAM50 subtyping in breast cancer，clinical stage and short overall survival in ovarian cancer and negatively correlated with T stage, clinical stage, and histological grade in cervical and endometrial cancers. The top BAG3-related pathways included ligand-receptor interactions and activity, DNA packaging and nucleosomes, hormonal responses, membrane regions, microdomains and rafts, and endosomes in breast cancer; ligand-receptor interactions, transmembrane transporters and channels, cell adhesion, and keratinisation in cervical cancer; ligand-receptor interactions, anion transmembrane transporters, lipoproteins, keratinisation, cell adhesion, and protein processing in endometrial cancer; metabolism of porphyrin, chlorophyll, pentose, uronic acid, ascorbate, and alternate and cell adhesion in ovarian cancer. BAG3 expression could represent a potential marker for carcinogenesis, histogenesis, aggressive behaviours, and prognosis in gynecological cancers.IMPACT STATEMENTWhat is already known on this subject? BAG3 regulates cell activity, autophagy, and resistance to apoptosis through multiple domains and plays an important role in tumour development. BAG3 positively regulates tumour cell invasion and migration in cervical and ovarian cancers.What do the results of this study add? BAG3 expression is closely associated with histogenesis, clinicopathology, and prognosis in gynecological cancers and is involved in signalling pathways associated with the control of cell proliferation, migration, invasion, and drug resistance in tumours.What are the implications of these findings for clinical practice and/or further research? Abnormal BAG3 expression can be employed as a possible marker of tumour development, invasion, and prognosis, providing new ideas for treating cancer.

The roles and implications of RNA m6A modification in cancer

N6-Methyladenosine (m6A), the most prevalent internal modification in eukaryotic mRNA, has been extensively and increasingly studied over the past decade. Dysregulation of RNA m6A modification and its associated machinery, including writers, erasers and readers, is frequently observed in various cancer types, and the dysregulation profiles might serve as diagnostic, prognostic and/or predictive biomarkers. Dysregulated m6A modifiers have been shown to function as oncoproteins or tumour suppressors with essential roles in cancer initiation, progression, metastasis, metabolism, therapy resistance and immune evasion as well as in cancer stem cell self-renewal and the tumour microenvironment, highlighting the therapeutic potential of targeting the dysregulated m6A machinery for cancer treatment. In this Review, we discuss the mechanisms by which m6A modifiers determine the fate of target RNAs and thereby influence protein expression, molecular pathways and cell phenotypes. We also describe the state-of-the-art methodologies for mapping global m6A epitranscriptomes in cancer. We further summarize discoveries regarding the dysregulation of m6A modifiers and modifications in cancer, their pathological roles, and the underlying molecular mechanisms. Finally, we discuss m6A-related prognostic and predictive molecular biomarkers in cancer as well as the development of small-molecule inhibitors targeting oncogenic m6A modifiers and their activity in preclinical models.

Role of exosomes in the development of the immune microenvironment in hepatocellular carcinoma

Despite numerous improved treatment methods used in recent years, hepatocellular carcinoma (HCC) is still a disease with a high mortality rate. Many recent studies have shown that immunotherapy has great potential for cancer treatment. Exosomes play a significant role in negatively regulating the immune system in HCC. Understanding how these exosomes play a role in innate and adaptive immunity in HCC can significantly improve the immunotherapeutic effects on HCC. Further, engineered exosomes can deliver different drugs and RNA molecules to regulate the immune microenvironment of HCC by regulating the aforementioned immune pathway, thereby significantly improving the mortality rate of HCC. This study aimed to declare the role of exosomes in the development of the immune microenvironment in HCC and list engineered exosomes that could be used for clinical transformation therapy. These findings might be beneficial for clinical patients.

Hsa_circ_0084003 modulates glycolysis and epithelial-mesenchymal transition in pancreatic ductal adenocarcinoma through targeting hsa-miR-143-3p/DNMT3A axis

Pancreatic ductal adenocarcinoma, one of the deadliest tumors of the digestive tract, is a difficult and invasive malignancy. Current treatment for pancreatic ductal adenocarcinoma mainly depends on surgery combined with radiotherapy and chemotherapy, which, however, often resulting in questionable curative effect. Therefore, new targeted therapies are needed in future treatment. We first interfered with hsa_circ_0084003 expression in pancreatic ductal adenocarcinoma cells, and further studied how hsa_circ_0084003 functioned in regulating pancreatic ductal adenocarcinoma cell aerobic glycolysis and epithelial-mesenchymal transition, and also evaluated the regulatingeffect of hsa_circ_0084003 on hsa-miR-143-3p and its target DNA methyltransferase 3A. Hsa_circ_0084003 knockdown could notably inhibit the aerobic glycolysis and epithelial-mesenchymal transition of pancreatic ductal adenocarcinoma cells. Mechanistically, hsa_circ_0084003 could regulate its downstream target DNA methyltransferase 3A by binding to hsa-miR-143-3p, and overexpression of hsa_circ_0084003 could reverse the anticarcinogenic effect of hsa-miR-143-3p on aerobic glycolysis and epithelial-mesenchymal transition in pancreatic ductal adenocarcinoma cells. Hsa_circ_0084003, as a carcinogenic circular RNA, regulated its downstream target DNA methyltransferase 3A to promote pancreatic ductal adenocarcinoma cell aerobic glycolysis and epithelial-mesenchymal transition through sponging hsa-miR-143-3p. Therefore, hsa_circ_0084003 could be studied as a possible therapeutic target regarding pancreatic ductal adenocarcinoma.

Skeletal Muscle-Specific Bis Depletion Leads to Muscle Dysfunction and Early Death Accompanied by Impairment in Protein Quality Control

Bcl-2-interacting cell death suppressor (BIS), also called BAG3, plays a role in physiological functions such as anti-apoptosis, cell proliferation, autophagy, and senescence. Whole-body Bis-knockout (KO) mice exhibit early lethality accompanied by abnormalities in cardiac and skeletal muscles, suggesting the critical role of BIS in these muscles. In this study, we generated skeletal muscle-specific Bis-knockout (Bis-SMKO) mice for the first time. Bis-SMKO mice exhibit growth retardation, kyphosis, a lack of peripheral fat, and respiratory failure, ultimately leading to early death. Regenerating fibers and increased intensity in cleaved PARP1 immunostaining were observed in the diaphragm of Bis-SMKO mice, indicating considerable muscle degeneration. Through electron microscopy analysis, we observed myofibrillar disruption, degenerated mitochondria, and autophagic vacuoles in the Bis-SMKO diaphragm. Specifically, autophagy was impaired, and heat shock proteins (HSPs), such as HSPB5 and HSP70, and z-disk proteins, including filamin C and desmin, accumulated in Bis-SMKO skeletal muscles. We also found metabolic impairments, including decreased ATP levels and lactate dehydrogenase (LDH) and creatine kinase (CK) activities in the diaphragm of Bis-SMKO mice. Our findings highlight that BIS is critical for protein homeostasis and energy metabolism in skeletal muscles, suggesting that Bis-SMKO mice could be used as a therapeutic strategy for myopathies and to elucidate the molecular function of BIS in skeletal muscle physiology.

Sestrin2-mediated disassembly of stress granules dampens aerobic glycolysis to overcome glucose starvation

Sestrins are a small gene family of pleiotropic factors whose actions promote cell adaptation to a range of stress conditions. In this report we disclose the selective role of Sestrin2 (SESN2) in dampening aerobic glycolysis to adapt to limiting glucose conditions. Removal of glucose from hepatocellular carcinoma (HCC) cells inhibits glycolysis associated with the downregulation of the rate-limiting glycolytic enzyme hexokinase 2 (HK2). Moreover, the accompanying upregulation of SESN2 through an NRF2/ATF4-dependent mechanism plays a direct role in HK2 regulation by destabilizing HK2 mRNA. We show SESN2 competes with insulin like growth factor 2 mRNA binding protein 3 (IGF2BP3) for binding with the 3'-UTR region of HK2 mRNA. Interactions between IGF2BP3 and HK2 mRNA result in their coalescence into stress granules via liquid-liquid phase separation (LLPS), a process which serves to stabilize HK2 mRNA. Conversely, the enhanced expression and cytoplasmic localization of SESN2 under glucose deprivation conditions favors the downregulation of HK2 levels via decreases in the half-life of HK2 mRNA. The resulting dampening of glucose uptake and glycolytic flux inhibits cell proliferation and protect cells from glucose starvation-induced apoptotic cell death. Collectively, our findings reveal an intrinsic survival mechanism allowing cancer cells to overcome chronic glucose shortages, also providing new mechanistic insights into SESN2 as an RNA-binding protein with a role in reprogramming of cancer cell metabolism.

BAG3: Nature's Quintessential Multi-Functional Protein Functions as a Ubiquitous Intra-Cellular Glue

BAG3 is a 575 amino acid protein that is found throughout the animal kingdom and homologs have been identified in plants. The protein is expressed ubiquitously but is most prominent in cardiac muscle, skeletal muscle, the brain and in many cancers. We describe BAG3 as a quintessential multi-functional protein. It supports autophagy of both misfolded proteins and damaged organelles, inhibits apoptosis, maintains the homeostasis of the mitochondria, and facilitates excitation contraction coupling through the L-type calcium channel and the beta-adrenergic receptor. High levels of BAG3 are associated with insensitivity to chemotherapy in malignant cells whereas both loss of function and gain of function variants are associated with cardiomyopathy.

Lactate, histone lactylation and cancer hallmarks

Histone lactylation, an indicator of lactate level and glycolysis, has intrinsic connections with cell metabolism that represents a novel epigenetic code affecting the fate of cells including carcinogenesis. Through delineating the relationship between histone lactylation and cancer hallmarks, we propose histone lactylation as a novel epigenetic code priming cells toward the malignant state, and advocate the importance of identifying novel therapeutic strategies or dual-targeting modalities against lactylation toward effective cancer control. This review underpins important yet less-studied area in histone lactylation, and sheds insights on its clinical impact as well as possible therapeutic tools targeting lactylation.

Tumor associated macrophages-derived exosomes facilitate hepatocellular carcinoma malignance by transferring lncMMPA to tumor cells and activating glycolysis pathway

Background

Tumor-associated macrophages (TAMs), which form a large part of the tumor microenvironment, are normally regulated by metabolic reprogramming. However, the potential mechanisms of the immune-metabolism interaction between hepatocellular carcinoma (HCC) cells and TAMs remain unclear.

Methods

The candidate long non-coding RNAs (lncRNAs) were screened by Smart-seq based scRNA-seq method and then validated by qPCR. Immunostaining analysis was done to examine the levels of markers for TAMs and glycolysis. Exosomes from primary TAMs of human HCC tissues were isolated by centrifugation, and their internalization with lncRNAs was confirmed by immunofluorescence. The underlying mechanism of TAMs-derived exosomal lncRNA to HCC was confirmed by luciferase reporter assay and RNA immunoprecipitation. Metabolism regulation was evaluated through glucose consumption, lactate productions and extracellular acidification rates (ECARs). Mouse xenograft models were used to elucidate the in vivo effect of candidate lncRNAs on tumor growth.

Results

TAMs augment the aerobic glycolysis in HCC cells and their proliferation by the extracellular exosome transmission of a myeloid-derived lncRNA, M2 macrophage polarization associated lncRNA (lncMMPA). Mechanistically, lncMMPA not only could polarize M2 macrophage, but also could act as an microRNA sponge to interact with miR-548 s and increase the mRNA level of ALDH1A3, then further promote glucose metabolism and cell proliferation in HCC. Moreover, lncMMPA increased HCC cell multiplication through interacting with miR-548 s in vivo. Clinically, lncMMPA expression associates with glycolysis in TAMs and reduced survival of HCC patients.

Conclusion

LncMMPA plays an important role in regulating HCC malignancy and metabolic reprogramming of miR-548 s/ALDH1A3 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02458-3.

Glycolysis-Related LINC02432/Hsa-miR-98–5p/HK2 Axis Inhibits Ferroptosis and Predicts Immune Infiltration, Tumor Mutation Burden, and Drug Sensitivity in Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is a malignant cancer with high incidence and mortality. Glycometabolic rearrangements (aerobic glycolysis) is a hallmark of PAAD and contributes to tumorigenesis and progression through numerous mechanisms. This study aimed to identify a novel glycolysis-related lncRNA-miRNA-mRNA ceRNA signature in PAAD and explore its potential molecular function. We first calculated the glycolysis score for each PAAD patient by the ssGSEA algorithm and found that patients with higher hallmark glycolysis scores had poorer prognosis. Subsequently, we obtained a novel glycolysis-related LINC02432/hsa-miR-98–5p/HK2 axis from the TCGA and GEO databases using comprehensive bioinformatics analysis and developed a nomogram to predict overall survival. Furthermore, functional characterization analysis revealed that LINC02432/hsa-miR-98–5p/HK2 axis risk score was negatively correlated with ferroptosis. The tumor immune infiltration analysis suggested positive correlations between ceRNA risk score and infiltrated M0 macrophage levels in PAAD. Correlation analysis found that ceRNA risk scores were positively correlated with four chemokines (CXCL3, CXCL5, CXCL8 and CCL20) and one immune checkpoint gene (SIGLEC15). Meanwhile, tumor mutation burden (TMB), an indicator for predicting response to immunotherapy, was positively correlated with ceRNA risk score. Finally, the drug sensitivity analysis showed that the high-risk score patients might be more sensitive to EGFR, MEK and ERK inhibitors than low-risk score patients. In conclusion, our study suggested that LINC02432/hsa-miR-98–5p/HK2 axis may serve as a novel diagnostic, prognostic, and therapeutic target in PAAD treatment.

Long non-coding RNA CYTOR modulates cancer progression through miR-136-5p/MAT2B axis in renal cell carcinoma

BACKGROUND

To explore the role of long noncoding RNAs (lncRNAs) cytoskeleton regulator RNA (CYTOR) in renal cell carcinoma (RCC).

METHODS

The levels of CYTOR in RCC tissues and cell lines were detected by RT-qPCR. 786-O and Caki-1 cells were transfected with CYTOR-shRNA or pcDNA-CYTOR respectively, or co-transfected with CYTOR-shRNA and miR-136-5p inhibitor, or co-transfected with miR-136-5p mimic and pcDNA-MAT2B. MTT assay, Transwell assay and flow cytometry were used to evaluate cell proliferation, invasion and apoptosis. The relationship between lncRNA CYTOR and miRNA-136-5p was detected by dual luciferase reporter gene and RNA pull down assays, and the targeted relationship between miRNA-136-5p and MAT2B was verified by dual luciferase reporter gene assay. The interaction between MAT2B and BAG3 protein was verified by co-IP experiment. The role of lncRNA CYTOR in vivo was also examined.

RESULTS

LncRNA CYTOR was up-regulated in RCC tissues and cell lines, and miR-136-5p was down-regulated in renal carcinoma cell lines and tissues. Downregulation of CYTOR inhibited cell proliferation and invasion and promoted apoptosis. miR-136-5p was sponged by lncRNA CYTOR, which negatively regulated the development of RCC. MAT2B was a target gene of miR-136-5p. MAT2B protein interacted directly with BAG3 protein to affect the proliferation, invasion and apoptosis of RCC cells. In vivo experiments showed that the expression level of miR-136-5p was increased, and MAT2B expression was decreased after CYTOR knockdown, thereby inhibiting the development of RCC.

CONCLUSIONS

LncRNA CYTOR promoted the progression of RCC by targeting miR-136-5p to regulate the target gene MAT2B, which interacted with BAG3 protein.

Proteomics Approach Highlights Early Changes in Human Fibroblasts-Pancreatic Ductal Adenocarcinoma Cells Crosstalk

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer mortality worldwide. Non-specific symptoms, lack of biomarkers in the early stages, and drug resistance due to the presence of a dense fibrous stroma all contribute to the poor outcome of this disease. The extracellular matrix secreted by activated fibroblasts contributes to the desmoplastic tumor microenvironment formation. Given the importance of fibroblast activation in PDAC pathology, it is critical to recognize the mechanisms involved in the transformation of normal fibroblasts in the early stages of tumorigenesis. To this aim, we first identified the proteins released from the pancreatic cancer cell line MIA-PaCa2 by proteomic analysis of their conditioned medium (CM). Second, normal fibroblasts were treated with MIA-PaCa2 CM for 24 h and 48 h and their proteostatic changes were detected by proteomics. Pathway analysis indicated that treated fibroblasts undergo changes compatible with the activation of migration, vasculogenesis, cellular homeostasis and metabolism of amino acids and reduced apoptosis. These biological activities are possibly regulated by ITGB3 and TGFB1/2 followed by SMAD3, STAT3 and BAG3 activation. In conclusion, this study sheds light on the crosstalk between PDAC cells and associated fibroblasts. Data are available via ProteomeXchange with identifier PXD030974.

FTO suppresses glycolysis and growth of papillary thyroid cancer via decreasing stability of APOE mRNA in an N6-methyladenosine-dependent manner

Background

N6-methyladenosine (m⁶A) modification is the most common chemical modification in mammalian mRNAs, and it plays important roles by regulating several cellular processes. Previous studies report that m⁶A is implicated in modulating tumorigenesis and progression. However, dysregulation of m⁶A modification and effect of m⁶A demethylase fat-mass and obesity-associated protein (FTO) on glucose metabolism has not been fully elucidated in papillary thyroid cancer (PTC).

Methods

Quantitative real-time PCR (qRT-PCR), western blotting and immunohistochemistry were performed to explore the expression profile of FTO in PTC tissues and adjacent non-cancerous thyroid tissues. Effects of FTO on PTC glycolysis and growth were investigated through in vitro and in vivo experiments. Mechanism of FTO-mediated m⁶A modification was explored through transcriptome-sequencing (RNA-seq), methylated RNA immunoprecipitation sequencing (MeRIP-seq), MeRIP-qPCR, luciferase reporter assays, RNA stability assay and RNA immunoprecipitation assay.

Results

FTO expression was significantly downregulated in PTC tissues. Functional analysis showed that FTO inhibited PTC glycolysis and growth. Further analyses were conducted to explore FTO-mediated m⁶A modification profile in PTC cells and Apolipoprotein E (APOE) was identified as the target gene for FTO-mediated m⁶A modification using RNA-seq and MeRIP-seq. FTO knockdown significantly increased APOE mRNA m⁶A modification and upregulated its expression. FTO-mediated m⁶A modification of APOE mRNA was recognized and stabilized by the m⁶A reader IGF2BP2. The findings showed that APOE also promoted tumor growth through glycolysis in PTC. Analysis showed that FTO/APOE axis inhibits PTC glycolysis by modulating IL-6/JAK2/STAT3 signaling pathway.

Conclusion

FTO acts as a tumor suppressor to inhibit tumor glycolysis in PTC. The findings of the current study showed that FTO inhibited expression of APOE through IGF2BP2-mediated m⁶A modification and may inhibit glycolytic metabolism in PTC by modulating IL-6/JAK2/STAT3 signaling pathway, thus abrogating tumor growth.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02254-z.

The role of BAG3 in health and disease: A "Magic BAG of Tricks"

The multi-domain structure of Bcl-2-associated athanogene 3 (BAG3) facilitates its interaction with many different proteins that participate in regulating a variety of biological pathways. After revisiting the BAG3 literature published over the past ten years with Citespace software, we classified the BAG3 research into several clusters, including cancer, cardiomyopathy, neurodegeneration, and viral propagation. We then highlighted recent key findings in each cluster. To gain greater insight into the roles of BAG3, we analyzed five different published mass spectrometry data sets of proteins that co-immunoprecipitate with BAG3. These data gave us insight into universal, as well as cell-type-specific BAG3 interactors in cancer cells, cardiomyocytes, and neurons. Finally, we mapped variable BAG3 SNPs and also mutation data from previous publications to further explore the link between the domains and function of BAG3. We believe this review will provide a better understanding of BAG3 and direct future studies towards understanding BAG3 function in physiological and pathological conditions.

MIR210HG regulates glycolysis, cell proliferation, and metastasis of pancreatic cancer cells through miR-125b-5p/HK2/PKM2 axis

Pancreatic cancer has the worst prognosis of all common cancers. Pancreatic cancer cells have a metabolic advantage due to their swiftly adaptive responses to hypoxic and low-nutrient medium. This advantage contributes to the aggressivity of pancreatic cancer. In this study, lncRNA MIR210HG was abnormally upregulated within pancreatic cancer. It acted as a key oncogenic regulator of pancreatic cancer aggressiveness and glycolysis. Knockdown of MIR210HG significantly inhibited the aggressive phenotype of pancreatic cancer cells and inhibited the growth of xenograft tumours. More importantly, MIR210HG knockdown inhibited pancreatic cancer cell glycolysis via regulating the glycolysis-related hexokinase 2 (HK2) and Pyruvate kinase muscle isozyme M2 (PKM2) expression. Compared with the MIR210HG knockdown group, miR-125b-5p inhibition promoted the aggressive phenotypes and glycolysis of pancreatic cancer cells. Furthermore, the effects of MIR210HG knockdown on HK2 and PKM2 expression, pancreatic cancer cell aggressive phenotypes, and glycolysis were significantly reversed by miR-125b-5p inhibition. In tissue samples, MIR210HG expression was negatively correlated with miR-125b-5p levels and positively correlated with HK2 and PKM2 expression. miR-125b-5p expression was negatively correlated with HK2 and PKM2 expression. In conclusion, MIR210HG affected the phenotypes of pancreatic cancer cells, including proliferation, invasion, migration, and glycolysis, via modulating the miR-125b-5p/HK2/PKM2 axis.

Lutein induces an inhibitory effect on the malignant progression of pancreatic adenocarcinoma by targeting BAG3/cholesterol homeostasis

Pancreatic adenocarcinoma (PDAC) is a fatal malignancy and patients with PDAC are mostly diagnosed at advanced stages. Lutein is a natural compound that belongs to the non-vitamin A carotenoids family and has presented antitumor effects on multiple cancer types. However, the function of lutein in PDAC and the mechanisms are not reported. Here, we explored the role of lutein in PDAC progression. Bioinformatic analysis identified that lutein is correlated with PDAC. Lutein suppressed the proliferation, migration, and invasion of PANC-1 cells. The upregulated genes in PDAC patients were identified and the overlap analysis predicted BAG3 as one target of lutein. Lutein repressed BAG3 expression and bioinformatics analysis predicted the interaction between lutein and BAG3. The inhibitory effects of lutein on PANC-1 cell proliferation, migration, and invasion are reversed by overexpression of BAG3. GSEA analysis identified that cholesterol homeostasis as one of the downstream signaling pathways of BAG3. In conclusion, lutein induced an inhibitory effect on the malignant progression of PDAC by targeting BAG3/cholesterol homeostasis. Lutein may be applied as a promising candidate for PDAC therapy.

Knockdown of Bcl-2-Associated Athanogene-3 Can Enhance the Efficacy of BGJ398 via Suppressing Migration and Inducing Apoptosis in Gastric Cancer

BACKGROUND

Gastric cancer (GC) is one of the most common malignancies of the digestive tract worldwide, and cancer cell resistance against anticancer drugs remains a major challenge for GC treatment. Nvp-BGJ398 (BGJ398) is considered as a common drug for cancer treatment; however, Bcl-2-associated athanogene-3 (BAG3) plays an important role in drug resistance.

AIMS

To investigate the function of BAG3 on the sensitivity of GC cells to BGJ398.

METHODS

The expression of BAG3 in GC cells and GC resistance cells was examined by qRT-PCR and western blot. The resistance to BGJ398 was detected by viability assay, and a half-maximal inhibitory concentration (IC50) was calculated. The cell migration and apoptosis were determined by wound-healing assay and flow cytometry assay.

RESULTS

BAG3 was highly expressed in drug-resistant cells Fu97R and Snu16R. BAG3 was also associated with sensitivity of Snu16 cells to BGJ398, promoting migration but inhibiting apoptosis. However, knockdown of heat shock transcription factor 1 (HSF1) suppressed BAG3 expression and lowered the sensitivity to BGJ398 in Snu16R cells. Knockdown of BAG3 inhibited tumor growth and cell apoptosis but induced cell apoptosis and amplified the sensitivity to BGJ398 in Snu16R cells, followed by enhancing BGJ398-induced antitumor function in a Snu16R-derived xenograft mouse model.

CONCLUSION

The mechanism of resistance to BGJ398 in GC is mediated by BAG3/HSF1, and combined treatment with shBAG3 could improve the efficacy of BGJ398 in GC. Thus, BAG3-targeted therapy improves the antitumor efficacy of BGJ398, which might provide a novel therapeutic strategy for GC.

BAG3 epigenetically regulates GALNT10 expression via WDR5 and facilitates the stem cell-like properties of platin-resistant ovarian cancer cells

Ovarian cancer is the most lethal gynecologic malignant cancer, frequently due to its late diagnosis and high recurrence. Cancer stem cells (CSCs) from different malignancies including ovarian cancer have been linked to chemotherapy resistance and poor prognosis. Therefore, identifying the molecular mechanisms mediating therapy resistance is urgent to finding novel targets for therapy-resistant tumors. Aberrant O-glycosylation ascribed to subtle alteration of GALNT family members during malignant transformation facilitate metastasis in various cancers. The current study demonstrated that BAG3 was upregulated in platin-resistant ovarian cancer tissues and cells, and high BAG3 predicted dismal disease-free survival of patients with ovarian cancer. In addition, the current study showed that BAG3 facilitated CSC-like properties of ovarian cancer cells via regulation of GALTN10. In a term of mechanism, BAG3 epigenetically regulated GALNT10 transactivation via histone H3 lysine 4 (H3K4) presenter WDR5. We demonstrated that WDR5 increased H3K4 trimethylation (H3K4me3) modification at the promoter regions of GALNT10, facilitating recruitment of transcription factor ZBTB2 to the GALNT10 promoter. Collectively, our study uncovers an epigenetic upregulation of GALNT10 by BAG3 via WDR5 to facilitate CSCs of platin-resistant ovarian cancers, providing additional information for further identification of attractive targets with therapeutic significance in platin-resistant ovarian cancer.

MicroRNA-216b targets HK2 to potentiate autophagy and apoptosis of breast cancer cells via the mTOR signaling pathway

Patients suffering from breast cancer (BC) still have a poor response to treatments, even though early detection and improved therapy have contributed to a reduced mortality. Recent studies have been inspired on the association between microRNAs (miRs) and therapies of BC. The current study set out to investigate the role of miR-216b in BC, and further analyze the underlining mechanism. Firstly, hexokinase 2 (HK2) and miR-216b were characterized in BC tissues and cells by RT-qPCR and Western blot assay. In addition, the interaction between HK2 and miR-216b was analyzed using dual luciferase reporter assay. BC cells were further transfected with a series of miR-126b mimic or inhibitor, or siRNA targeting HK2, so as to analyze the regulatory mechanism of miR-216b, HK2 and mammalian target of rapamycin (mTOR) signaling pathway, and to further explore their regulation in BC cellular behaviors. The results demonstrated that HK2 was highly expressed and miR-216b was poorly expressed in BC cells and tissues. HK2 was also verified as a target of miR-216b with online databases and dual luciferase reporter assay. Functionally, miR-216b was found to be closely associated with BC progression via inactivating mTOR signaling pathway by targeting HK2. Moreover, cell viability, migration and invasion were reduced as a result of miR-216b upregulation or HK2 silencing, while autophagy, cell cycle arrest and apoptosis were induced. Taken together, our findings indicated that miR-216 down-regulates HK2 to inactivate the mTOR signaling pathway, thus inhibiting the progression of BC. Hence, this study highlighted a novel target for BC treatment.

JAK2V617F Mutation Promoted IL-6 Production and Glycolysis via Mediating PKM1 Stabilization in Macrophages

A substitution mutation of valine to phenylalanine at codon encoding position 617 of the Janus kinase 2 (JAK2) gene (JAK2^V617F) has been detected in myeloid cells of some individuals with higher levels of proinflammatory cytokine production such as interleukin (IL)-6. However, the mechanisms by which JAK2^V617F mutation mediating those cytokines remain unclear. We, therefore, established JAK2^V617F-expressing murine macrophages (JAK2^V617F macrophages) and found that the levels of p-STAT3 were markedly elevated in JAK2^V617F macrophages in association with an increase in IL-6 production. However, inhibition of STAT3 by C188-9 significantly decreased the production of IL-6. Furthermore, the JAK2^V617F mutation endowed macrophages with an elevated glycolytic phenotype in parallel with aberrant expression of PKM1. Interestingly, silencing of PKM1 inactivated STAT3 in parallel with reduced IL-6 production. In contrast, ectopic expression of PKM1 elevated IL-6 production via STAT3 activation. Importantly, the JAK2^V617F mutation contributed to PKM1 protein stabilization via blockade of lysosomal-dependent degradation via chaperone-mediated autophagy (CMA), indicating that the JAK2^V617F mutation could protect PKM1 from CMA-mediated degradation, leading to activation of STAT3 and promoting IL-6 production.

Stellate Cells Aid Growth-Permissive Metabolic Reprogramming and Promote Gemcitabine Chemoresistance in Pancreatic Cancer

Simple Summary

The great majority, more than 90%, of patients with pancreatic ductal adenocarcinoma (PDAC) die within less than five years after detection of the disease, despite recent treatment advances. The poor prognosis is related to late diagnosis, aggressive disease progression, and tumor resistance to conventional chemotherapy. PDAC tumor tissue is characterized by dense fibrosis and poor nutrient availability. A large portion of the tumor is made up of stromal fibroblasts, the pancreatic stellate cells (PSCs), which are known to contribute to tumor progression in several ways. PSCs have been shown to act as an alternate energy source, induce drug resistance, and inhibit drug availability in tumor cells, however, the underlying exact molecular mechanisms remain unknown. In this literature review, we discuss recent available knowledge about the contributions of PSCs to the overall progression of PDAC via changes in tumor metabolism and how this is linked to therapy resistance.

Abstract

Pancreatic ductal adenocarcinoma (PDAC), also known as pancreatic cancer (PC), is characterized by an overall poor prognosis and a five-year survival that is less than 10%. Characteristic features of the tumor are the presence of a prominent desmoplastic stromal response, an altered metabolism, and profound resistance to cancer drugs including gemcitabine, the backbone of PDAC chemotherapy. The pancreatic stellate cells (PSCs) constitute the major cellular component of PDAC stroma. PSCs are essential for extracellular matrix assembly and form a supportive niche for tumor growth. Various cytokines and growth factors induce activation of PSCs through autocrine and paracrine mechanisms, which in turn promote overall tumor growth and metastasis and induce chemoresistance. To maintain growth and survival in the nutrient-poor, hypoxic environment of PDAC, tumor cells fulfill their high energy demands via several unconventional ways, a process generally referred to as metabolic reprogramming. Accumulating evidence indicates that activated PSCs not only contribute to the therapy-resistant phenotype of PDAC but also act as a nutrient supplier for the tumor cells. However, the precise molecular links between metabolic reprogramming and an acquired therapy resistance in PDAC remain elusive. This review highlights recent findings indicating the importance of PSCs in aiding growth-permissive metabolic reprogramming and gemcitabine chemoresistance in PDAC.

CircCDKN2B-AS1 interacts with IMP3 to stabilize hexokinase 2 mRNA and facilitate cervical squamous cell carcinoma aerobic glycolysis progression

Background

Circular RNAs (circRNAs) have been reported to play key roles in the development of various cancers. However, the biological functions and clinical significance of most circRNAs are still elusive. The purpose of this study was to explore the function and mechanism of a certain circRNA named circCDKN2B-AS1 in cervical cancer development and its potential value in the clinic.

Methods

qRT-PCR was used to verify the expression level of circCDKN2B-AS1. CCK-8, Transwell, and flow cytometry (FCM) assays were performed to detect cellular proliferation, migration, and apoptosis, respectively. A Seahorse XFe96 Analyzer was used to measure glycolysis metabolism level. RNA pull-down, RNA immunoprecipitation (RIP), actinomycin-D addition assays and Western blotting were used to screen and elucidate the potential mechanisms involved. BALB/c nude mice and zebrafish embryos (AB, WT) were used as animal models to investigate tumorigenesis capability. ¹⁸FDG-microPET/CT imaging and lactic acid (LA) and pyruvic acid (PA) content detection assays were used to detect the level of glucose metabolism in subcutaneous tumors from nude mice.

Results

CircCDKN2B-AS1, a circular isoform of the long noncoding RNA (lncRNA) CDKN2B-AS1, was upregulated in cervical cancer and precancerous tissues. We found that circCDKN2B-AS1 associated with the IMP3 protein depending on a specific binding site and regulated the stability of Hexokinase 2 (HK2) mRNA, the rate-limiting enzyme of the aerobic glycolysis pathway. The expression level of circCDKN2B-AS1 fated the binding of IMP3 to the 3′ untranslated region (UTR) of HK2 mRNA, consequently affecting the malignant cell phenotype and aerobic glycolysis in cervical cancer in vitro and in vivo. Mutant circCDKN2B-AS1, lacking the IMP3 binding site, did not have such effects. Utilization of an inhibitory peptide to block the interaction between circCDKN2B-AS1 and the IMP3 protein impeded the binding of IMP3 to the 3’UTR of HK2 mRNA and suppressed aerobic glycolysis in cervical cancer cells.

Conclusions

Our findings demonstrate that circCDKN2B-AS1 facilitates aerobic glycolysis by sponging the IMP3 protein to stabilize HK2 mRNA, consequently promoting the malignant phenotype in cervical cancer, which may provide a potential approach for cervical cancer therapeutics.

Targets (Metabolic Mediators) of Therapeutic Importance in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), an extremely aggressive invasive cancer, is the fourth most common cause of cancer-related death in the United States. The higher mortality in PDAC is often attributed to the inability to detect it until it has reached advanced stages. The major challenge in tackling PDAC is due to its elusive pathology, minimal effectiveness, and resistance to existing therapeutics. The aggressiveness of PDAC is due to the capacity of tumor cells to alter their metabolism, utilize the diverse available fuel sources to adapt and grow in a hypoxic and harsh environment. Therapeutic resistance is due to the presence of thick stroma with poor angiogenesis, thus making drug delivery to tumor cells difficult. Investigating the metabolic mediators and enzymes involved in metabolic reprogramming may lead to the identification of novel therapeutic targets. The metabolic mediators of glucose, glutamine, lipids, nucleotides, amino acids and mitochondrial metabolism have emerged as novel therapeutic targets. Additionally, the role of autophagy, macropinocytosis, lysosomal transport, recycling, amino acid transport, lipid transport, and the role of reactive oxygen species has also been discussed. The role of various pro-inflammatory cytokines and immune cells in the pathogenesis of PDAC and the metabolites involved in the signaling pathways as therapeutic targets have been previously discussed. This review focuses on the therapeutic potential of metabolic mediators in PDAC along with stemness due to metabolic alterations and their therapeutic importance.

BAG3 Proteomic Signature under Proteostasis Stress

The multifunctional HSP70 co-chaperone BAG3 (BCL-2-associated athanogene 3) represents a key player in the quality control of the cellular proteostasis network. In response to stress, BAG3 specifically targets aggregation-prone proteins to the perinuclear aggresome and promotes their degradation via BAG3-mediated selective macroautophagy. To adapt cellular homeostasis to stress, BAG3 modulates and functions in various cellular processes and signaling pathways. Noteworthy, dysfunction and deregulation of BAG3 and its pathway are pathophysiologically linked to myopathies, cancer, and neurodegenerative disorders. Here, we report a BAG3 proteomic signature under proteostasis stress. To elucidate the dynamic and multifunctional action of BAG3 in response to stress, we established BAG3 interactomes under basal and proteostasis stress conditions by employing affinity purification combined with quantitative mass spectrometry. In addition to the identification of novel potential BAG3 interactors, we defined proteins whose interaction with BAG3 was altered upon stress. By functional annotation and protein-protein interaction enrichment analysis of the identified potential BAG3 interactors, we confirmed the multifunctionality of BAG3 and highlighted its crucial role in diverse cellular signaling pathways and processes, ensuring cellular proteostasis and cell viability. These include protein folding and degradation, gene expression, cytoskeleton dynamics (including cell cycle and transport), as well as granulostasis, in particular.

Glycolysis inhibition and apoptosis induction in human prostate cancer cells by FV-429-mediated regulation of AR-AKT-HK2 signaling network

Prostate cancer (PCa) depends on androgen receptor (AR) signaling to regulate cell metabolism, including glycolysis, and thereby promotes tumor growth. Glycolysis is overactive in PCa and associated with poor prognosis, but the therapeutic efficacy of glycolysis inhibitors has thus far been limited by their inability to induce cell death. FV-429, a flavonoid derivative of Wogonin, is a glycolysis inhibitor that has shown anti-cancer promise. In this study, we used FV-429 as an anti-PCa agent and investigated its mechanisms of action. In vitro, both the glycolytic ability and the viability of PCa cells were inhibited by FV-429. We found that FV-429 could induce mitochondrial dysfunction and apoptosis, with AKT-HK2 signaling pathway playing a key role. In addition, FV-429 had a pro-apoptotic effect on human prostate cancer cells that relied on the inhibition of AR expression and activity. In vivo, FV-429 exerted significant tumor-repressing activity with high safety in the xenograft model using LNCaP cells. In summary, we demonstrated that FV-429 induced glycolysis inhibition and apoptosis in human prostate cancer cells by downregulating the AR-AKT-HK2 signaling network, making FV-429 a promising candidate as one therapeutic agent for advanced PCa.

ALDH1A3 Accelerates Pancreatic Cancer Metastasis by Promoting Glucose Metabolism

Background: The aldehyde dehydrogenase 1 family member A3 (ALDH1A3) is a key enzyme associated with a variety of metabolic processes, including glucose metabolism. We recently uncovered that glucose metabolism played an essential role in promoting metastasis of pancreatic ductal adenocarcinoma (PDAC). As ALDH1A3 labels an aggressive subtype of PDAC, we hypothesized that ALDH1A3 functionally promoted PDAC metastasis via its metabolic effect on glucose metabolism.

Methods: Expression of ALDH1A3 was detected in human PDAC tissues by immunohistochemistry. ALDH1A3 was knocked down or overexpressed in PDAC cells by either shRNA or overexpression vector. The functional roles of ALDH1A3 were characterized in vitro and in vivo. Transcriptional profiling via RNA-sequencing was used to explore the possible underlying molecular mechanisms. Glucose uptake, extracellular lactate, and ATP production were measured to access the metabolic influence of ALDH1A3 on PDAC cells.

Results: ALDH1A3 was associated with poor prognosis in PDAC patients. Functionally, ALDH1A3 promoted PDAC metastasis in vitro and in vivo. Further studies revealed that ALDH1A3 activated PI3K/AKT/mTOR signaling pathway and its downstream target-PPARγ (peroxisome proliferator-activated receptor gamma). This led to increase the expression of HK2 (hexokinase 2), which subsequently enhanced the glycolysis in PDAC cells. Additionally, the pharmacological inhibition of PPARγ activity in ALDH1A3-positive cells impaired glycolytic genes expression, PI3K/AKT/mTOR activity and cellular glycolysis.

Conclusions: ALDH1A3 promotes PDAC metastasis via its metabolic influence on glucose metabolism. PPARγ and its downstream PI3K/AKT/mTOR signaling pathway maybe involved in this process.

YAP1 Inhibition in HUVECs Is Associated with Released Exosomes and Increased Hepatocarcinoma Invasion and Metastasis

Hepatocellular carcinoma is one of the most common gastrointestinal malignancies. Anti-angiogenesis therapies have recently demonstrated promise in the treatment of malignancies, although early treatment benefits may be accompanied by metastasis over time. Additional and more effective anti-angiogenic treatment modalities are therefore needed. We previously found that Yes-associated protein 1 (YAP1) expression is increased in hepatocellular carcinoma (HCC), particularly around tumor-associated blood vessels, suggesting a role in angiogenesis. The YAP1 inhibitor verteporfin is presently in anti-angiogenic clinical trials for the treatment of various cancers. Depleted YAP1 from vascular endothelial cells effectively reduced proliferation and tube formation, validating its utility as an anti-angiogenesis target. We also showed that YAP1 depletion or inhibition in vascular endothelial cells leads to increased release of exosomes containing the long non-coding RNA (lncRNA) MALAT1 into the tumor microenvironment. Direct exosomal transfer of MALAT1 to hepatic cells leads to increased hepatic cell invasion and migration via activation of extracellular signal-regulated kinase 1/2 (ERK1/2) signaling. These observations may explain the occurrence of distant tumor metastasis with YAP1-associated anti-angiogenic therapy over time. It provides insight into new pathways and treatment paradigms that may be targeted to increase the long-term success of anti-angiogenic therapies.

Cyclin-Dependent Kinase 5-Dependent BAG3 Degradation Modulates Synaptic Protein Turnover

BACKGROUND

Synaptic protein dyshomeostasis and functional loss is an early invariant feature of Alzheimer's disease (AD), yet the unifying etiological pathway remains largely unknown. Knowing that cyclin-dependent kinase 5 (CDK5) plays critical roles in synaptic formation and degeneration, its phosphorylation targets were reexamined in search of candidates with direct global impacts on synaptic protein dynamics, and the associated regulatory network was also analyzed.

METHODS

Quantitative phosphoproteomics and bioinformatics analyses were performed to identify top-ranked candidates. A series of biochemical assays was used to investigate the associated regulatory signaling networks. Histological, electrochemical, and behavioral assays were performed in conditional knockout, small hairpin RNA-mediated knockdown, and AD-related mice models to evaluate the relevance of CDK5 to synaptic homeostasis and functions.

RESULTS

Among candidates with known implications in synaptic modulations, BAG3 ranked the highest. CDK5-mediated phosphorylation on S297/S291 (mouse/human) destabilized BAG3. Loss of BAG3 unleashed the selective protein degradative function of the HSP70 machinery. In neurons, this resulted in enhanced degradation of a number of glutamatergic synaptic proteins. Conditional neuronal knockout of Bag3 in vivo led to impairment of learning and memory functions. In human AD and related mouse models, aberrant CDK5-mediated loss of BAG3 yielded similar effects on synaptic homeostasis. Detrimental effects of BAG3 loss on learning and memory functions were confirmed in these mice, and such effects were reversed by ectopic BAG3 reexpression.

CONCLUSIONS

Our results highlight that the neuronal CDK5-BAG3-HSP70 signaling axis plays a critical role in modulating synaptic homeostasis. Dysregulation of the signaling pathway directly contributes to synaptic dysfunction and AD pathogenesis.

At the Crossroads of Apoptosis and Autophagy: Multiple Roles of the Co-Chaperone BAG3 in Stress and Therapy Resistance of Cancer

BAG3, a multifunctional HSP70 co-chaperone and anti-apoptotic protein that interacts with the ATPase domain of HSP70 through its C-terminal BAG domain plays a key physiological role in cellular proteostasis. The HSP70/BAG3 complex determines the levels of a large number of selective client proteins by regulating their turnover via the two major protein degradation pathways, i.e. proteasomal degradation and macroautophagy. On the one hand, BAG3 competes with BAG1 for binding to HSP70, thereby preventing the proteasomal degradation of its client proteins. By functionally interacting with HSP70 and LC3, BAG3 also delivers polyubiquitinated proteins to the autophagy pathway. BAG3 exerts a number of key physiological functions, including an involvement in cellular stress responses, proteostasis, cell death regulation, development, and cytoskeletal dynamics. Conversely, aberrant BAG3 function/expression has pathophysiological relevance correlated to cardiomyopathies, neurodegeneration, and cancer. Evidence obtained in recent years underscores the fact that BAG3 drives several key hallmarks of cancer, including cell adhesion, metastasis, angiogenesis, enhanced autophagic activity, and apoptosis inhibition. This review provides a state-of-the-art overview on the role of BAG3 in stress and therapy resistance of cancer, with a particular focus on BAG3-dependent modulation of apoptotic signaling and autophagic/lysosomal activity.

CSN5 upregulates glycolysis to promote hepatocellular carcinoma metastasis via stabilizing the HK2 protein

Aerobic glycolysis promotes metastasis and correlates with poorer clinical outcomes in hepatocellular carcinoma (HCC), but the controllers and mechanisms of abnormally activated glycolysis remain unclear. Herein, we demonstrated that the fifth component of the constitutive photomorphogenic 9 (COP9) signalosome complex (COPS5/CSN5) was a controller of glycolysis. For the first time, we found that CSN5 could influence the expression of glycolytic metabolism-associated proteins, especially hexokinase 2 (HK2), a glycolytic rate-limiting enzyme. In addition, we found that CSN5 was associated with HK2 overexpression in HCC tissues. Silencing CSN5 expression caused a decrease in the level of the HK2 protein, glucose uptake, glycolysis capacity and the production of glycolytic intermediates in HCC cells. Re-expression of HK2 rescued the decreased glycolytic flux induced by CSN5 knockdown, whereas inhibition of HK2 alleviated CSN5-enhanced glycolysis. Functionally, CSN5 regulated HCC cell invasion and metastasis via HK2-mediated glycolysis. Mechanistically, we demonstrated that CSN5 attenuated the ubiquitin-proteasome system-mediated degradation of HK2 through its deubiquitinase function. Inhibition of CSN5 kinase activity by curcumin decreased HK2 protein expression and glycolysis, repressed the metastasis of HCC cells in vitro and in vivo, and prolonged the survival time of tumor-bearing nude mice. Overall, our study identified CSN5 as a controller of glycolysis, and it may be a potential treatment target for HCC.

Glycolysis promotes the progression of pancreatic cancer and reduces cancer cell sensitivity to gemcitabine

Previous studies have reported that increased glycolytic activity enhances chemotherapy resistance in some types of malignancies. However, whether glycolysis influences the curative effect of gemcitabine (GEM) on pancreatic cancer (PC) cells remains unclear. The aim of this study was to investigate the status of glycolysis in PC and its association with tolerance to GEM. Data from The Cancer Genome Atlas (TCGA) were used to analyze the correlation between glycolysis-related gene (GRG) expression and PC progression and prognosis. 2-Deoxy-D-glucose (2-DG) was applied to assess the effect of glycolysis inhibition on PC cell death and GEM tolerance. Expression of some GRGs, such as HK1, GAPDH, PKM2, and LDHA, was significantly associated with the prognosis of PC. Furthermore, HK1, PKLR, and LDHA expression correlated positively with PC progression. Further analysis revealed that cancer cell death was markedly enhanced following glycolysis inhibition and that the sensitivity of cancer cells to GEM was notably increased in the presence of 2-DG. Our findings indicate that abnormally increased glycolytic activity promotes the development of PC and enhances drug tolerance to GEM. 2-DG combined with GEM is a potential therapy for PC.

p53-dependent transcriptional suppression of BAG3 protects cells against metabolic stress via facilitation of p53 accumulation

Solid tumour frequently undergoes metabolic stress during tumour development because of inadequate blood supply and the high nutrient expenditure. p53 is activated by glucose limitation and maintains cell survival via triggering metabolic checkpoint. However, the exact downstream contributors are not completely identified. BAG3 is a cochaperone with multiple cellular functions and is implicated in metabolic reprogramming of pancreatic cancer cells. The current study demonstrated that glucose limitation transcriptionally suppressed BAG3 expression in a p53‐dependent manner. Importantly, hinderance of its down‐regulation compromised cellular adaptation to metabolic stress triggered by glucose insufficiency, supporting that BAG3 might be one of p53 downstream contributors for cellular adaptation to metabolic stress. Our data showed that ectopic BAG3 expression suppressed p53 accumulation via direct interaction under metabolic stress. Thereby, the current study highlights the significance of p53‐mediated BAG3 suppression in cellular adaptation to metabolic stress via facilitating p53 accumulation.

Glucose Metabolism in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal cancers, with a five-year survival rate of around 5% to 8%. To date, very few available drugs have been successfully used to treat PDAC due to the poor understanding of the tumor-specific features. One of the hallmarks of pancreatic cancer cells is the deregulated cellular energetics characterized by the “Warburg effect”. It has been known for decades that cancer cells have a dramatically increased glycolytic flux even in the presence of oxygen and normal mitochondrial function. Glycolytic flux is the central carbon metabolism process in all cells, which not only produces adenosine triphosphate (ATP) but also provides biomass for anabolic processes that support cell proliferation. Expression levels of glucose transporters and rate-limiting enzymes regulate the rate of glycolytic flux. Intermediates that branch out from glycolysis are responsible for redox homeostasis, glycosylation, and biosynthesis. Beyond enhanced glycolytic flux, pancreatic cancer cells activate nutrient salvage pathways, which includes autophagy and micropinocytosis, from which the generated sugars, amino acids, and fatty acids are used to buffer the stresses induced by nutrient deprivation. Further, PDAC is characterized by extensive metabolic crosstalk between tumor cells and cells in the tumor microenvironment (TME). In this review, we will give an overview on recent progresses made in understanding glucose metabolism-related deregulations in PDAC.

Identification of new high affinity targets for Roquin based on structural conservation

Post-transcriptional gene regulation controls the amount of protein produced from a specific mRNA by altering both its decay and translation rates. Such regulation is primarily achieved by the interaction of trans-acting factors with cis-regulatory elements in the untranslated regions (UTRs) of mRNAs. These interactions are guided either by sequence- or structure-based recognition. Similar to sequence conservation, the evolutionary conservation of a UTR’s structure thus reflects its functional importance. We used such structural conservation to identify previously unknown cis-regulatory elements. Using the RNA folding program Dynalign, we scanned all UTRs of humans and mice for conserved structures. Characterizing a subset of putative conserved structures revealed a binding site of the RNA-binding protein Roquin. Detailed functional characterization in vivo enabled us to redefine the binding preferences of Roquin and identify new target genes. Many of these new targets are unrelated to the established role of Roquin in inflammation and immune responses and thus highlight additional, unstudied cellular functions of this important repressor. Moreover, the expression of several Roquin targets is highly cell-type-specific. In consequence, these targets are difficult to detect using methods dependent on mRNA abundance, yet easily detectable with our unbiased strategy.

BAG3-positive pancreatic stellate cells promote migration and invasion of pancreatic ductal adenocarcinoma

BAG3 is constitutively expressed in multiple types of cancer cells and its high expression is associated with tumour progression and poor prognosis of PDAC. However, little is known about the role of BAG3 in the regulation of stromal microenvironment of PDAC. The current study demonstrated that beside PDAC tumour cells, BAG3 was also expressed in some activated stroma cells in PDAC tissue, as well as in activated PSCs. In addition, the current study demonstrated that BAG3 expression in PSCs was involved in maintenance of PSCs activation and promotion of PDACs invasion via releasing multiple cytokines. The current study demonstrated that BAG3‐positive PSCs promoted invasion of PDACs via IL‐8, MCP1, TGF‐β2 and IGFBP2 in a paracrine manner. Furthermore, BAG3 sustained PSCs activation through IL‐6, TGF‐β2 and IGFBP2 in an autocrine manner. Thereby, the current study provides a new insight into the involvement of BAG3 in remodelling of stromal microenvironment favourable for malignant progression of PDAC, indicating that BAG3 might serve as a potential target for anti‐fibrosis of PDAC.

BAG3 Suppresses Loading of Ago2 to IL6 mRNA in Pancreatic Ductal Adenocarcinoma

Pancreatic stellate cells (PSCs) are a subset of pancreatic cancer-associated fibroblasts, which play a critical role in pancreatic fibrosis, a characteristic feature of pancreatic cancer. The interplay between PSCs and pancreatic cancer cells is vital for promotion of tumor progression and metastasis. BAG3 is correlated with poor prognostics in patients with pancreatic ductal adenocarcinoma (PDAC), however, the exact mechanisms remain largely unknown. In this study, we demonstrated that BAG3 downregulation decreased IL6 release by PDACs, and IL6 reduction was, at least partially, responsible for suppression of PSCs activation by PDACs with BAG3 downmodulation. Importantly, BAG3 expression positively correlated with fibrosis in pancreatic cancer tissue. With regard to the underlying mechanism, we demonstrated that BAG3 knockdown facilitated recruitment of Agonaute 2 (Ago2) to IL6 mRNA, resulting in destabilization of IL6 mRNA. In addition, the current study demonstrated that phosphorylation at Serine (Ser) 387 site was required for recruitment of Ago2-containing miRISC to IL6 mRNA and BAG3 knockdown facilitated Ago2 loading to IL6 mRNA via increasing its phosphorylation at Ser 387. This study shed new light on the tumor-promoting role of BAG3 in PDAC tumors, suggesting BAG3 might represent an interesting therapeutic opportunity to PDAC patients.

Crucial role of the pentose phosphate pathway in malignant tumors

Interest in cancer metabolism has increased in recent years. The pentose phosphate pathway (PPP) is a major glucose catabolism pathway that directs glucose flux to its oxidative branch and leads to the production of a reduced form of nicotinamide adenine dinucleotide phosphate and nucleic acid. The PPP serves a vital role in regulating cancer cell growth and involves many enzymes. The aim of the present review was to describe the recent discoveries associated with the deregulatory mechanisms of the PPP and glycolysis in malignant tumors, particularly in hepatocellular carcinoma, breast and lung cancer.

Tristetraprolin-mediated hexokinase 2 expression regulation contributes to glycolysis in cancer cells

Hexokinase 2 (HK2) catalyzes the first step of glycolysis and is up-regulated in cancer cells. The mechanism has not been fully elucidated. Tristetraprolin (TTP) is an AU-rich element (ARE)-binding protein that inhibits the expression of ARE-containing genes by enhancing mRNA degradation. TTP expression is down-regulated in cancer cells. We demonstrated that TTP is critical for down-regulation of HK2 expression in cancer cells. HK2 mRNA contains an ARE within its 3'-UTR. TTP binds to HK2 3'-UTR and enhances degradation of HK2 mRNA. TTP overexpression decreased HK2 expression and suppressed the glycolytic capacity of cancer cells, measured as glucose uptake and production of glucose-6-phosphate, pyruvate, and lactate. TTP overexpression reduced both the extracellular acidification rate (ECAR) and the oxygen consumption rate (OCR) of cancer cells. Ectopic expression of HK2 in cancer cells attenuated the reduction in glycolytic capacity, ECAR, and OCR from TTP. Taken together, these findings suggest that TTP acts as a negative regulator of HK2 expression and glucose metabolism in cancer cells.

Targeting Pancreatic Stellate Cells in Cancer

Pancreatic stellate cells (PSCs) are the major contributor to the aggressive, metastatic, and resilient nature of pancreatic ductal adenocarcinoma (PDAC), which has a poor prognosis with a 5-year survival rate of 8%. PSCs constitute more than 50% of the tumor stroma in PDAC, where they induce extensive desmoplasia by secreting abundant extracellular matrix (ECM) proteins. In addition, they establish dynamic crosstalk with cancer cells and other stromal cells, which collectively supports tumor progression via various inter- and intracellular pathways. These cellular interactions and associated pathways may reveal novel therapeutic opportunities against this unmet clinical problem. In this review article, we discuss the role of PSCs in inducing tumor progression, their crosstalk with other cells, and therapeutic strategies to target PSCs.

BAG3 regulates stability of IL-8 mRNA via interplay between HuR and miR-4312 in PDACs

Bcl-2 associated athanogene 3 (BAG3) is highly expressed in pancreatic ductal adenocarcinoma (PDAC), and its high expression appears to be a poor prognostic factor for patients with PDAC. In this study, we show that BAG3 knockdown significantly decreases migration and invasion of PDACs via reduction of interleukine-8 (IL-8) production. BAG3 knockdown regulates IL-8 expression at the posttranscriptional levels via interplay between recruitment of RNA-binding protein HuR and miR-4312. HuR binds to the cis-elements located in the 3'-untranslational region (UTR) of the IL-8 transcript to stabilize it, whereas miR-4312-containing miRNA-induced silencing complex (miRISC) is recruited to the adjacent seed element to destabilize it. The binding of HuR prevents the recruitment of Argonaute (Ago2), overriding miR-4312-mediated translation inhibition of IL-8. BAG3 knockdown decreases cytoplasmic distribution of HuR via increasing its phosphorylation at Ser202, therefore compromising its recruitment while promoting recruitment of miR-4312 containing miRISC to IL-8 transcript. Furthermore, our data indicate that only phosphorylated Ago2 at Ser387 interacts with IL-8 transcript. BAG3 knockdown increases phosphorylation of Ago2 at Ser387, thereby further promoting loading of miR-4312 containing miRISC to IL-8 transcript. Taken together, we propose that BAG3 promotes invasion by stabilizing IL-8 transcript via HuR recruitment, and subsequently suppressing the loading of miR-4312 containing miRISC in PDACs. Our results reveal a novel pathway linking BAG3 expression to enhanced PDAC metastasis, thus making BAG3 a potential target for intervention in pancreatic cancer.

CBX3 promotes proliferation and regulates glycolysis via suppressing FBP1 in pancreatic cancer

More and more evidence has demonstrated that Chromobox protein homolog 3(CBX3) has an important role in carcinogenesis by regulating several mechanisms, such as heterochromatin formation, gene silencing, DNA replication and repair. However, its role in pancreatic cancer has seldom been discussed. In the present study, we silenced CBX3 expression in pancreatic cancer cell lines and identified the positive roles of CBX3 in cancer cell proliferation. Furthermore, we demonstrated that silencing CBX3 in pancreatic cancer cells inhibited aerobic glycolysis, the basis for providing cancer cells with building blocks for macromolecule synthesis and ATP that required. To search for the underlying molecular mechanism, we turned to examine the impact of CBX3 on the expression of FBP1, a negative regulator of aerobic glycolysis in pancreatic cancer and indicated that CBX3 negatively regulated FBP1 expression. Silencing FBP1 expression attenuated the decrease in glycolytic capacity that caused by CBX3 knockdown in pancreatic cancer cells. Taken together, these data reveal that CBX3 serves as a positive regulator of aerobic glycolysis via suppressing of the FBP1 in pancreatic cancer cells. Disrupting the CBX3-FBP1 signaling axis would be effective to treat pancreatic cancer and prevent aerobic glycolysis.

The critical roles of activated stellate cells-mediated paracrine signaling, metabolism and onco-immunology in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignant diseases worldwide. It is refractory to conventional treatments, and consequently has a documented 5-year survival rate as low as 7%. Increasing evidence indicates that activated pancreatic stellate cells (PSCs), one of the stromal components in tumor microenvironment (TME), play a crucial part in the desmoplasia, carcinogenesis, aggressiveness, metastasis associated with PDAC. Despite the current understanding of PSCs as a "partner in crime" to PDAC, detailed regulatory roles of PSCs and related microenvironment remain obscure. In addition to multiple paracrine signaling pathways, recent research has confirmed that PSCs-mediated tumor microenvironment may influence behaviors of PDAC via diverse mechanisms, such as rewiring metabolic networks, suppressing immune responses. These new activities are closely linked with treatment and prognosis of PDAC. In this review, we discuss the recent advances regarding new functions of activated PSCs, including PSCs-cancer cells interaction, mechanisms involved in immunosuppressive regulation, and metabolic reprogramming. It's clear that these updated experimental or clinical studies of PSCs may provide a promising approach for PDAC treatment in the near future.