VHL suppresses autophagy and tumor growth through PHD1-dependent Beclin1 hydroxylation.

The Von Hippel-Lindau (VHL) protein, which is frequently mutated in clear-cell renal cell carcinoma (ccRCC), is a master regulator of hypoxia-inducible factor (HIF) that is involved in oxidative stresses. However, whether VHL possesses HIF-independent tumor-suppressing activity remains largely unclear. Here, we demonstrate that VHL suppresses nutrient stress-induced autophagy, and its deficiency in sporadic ccRCC specimens is linked to substantially elevated levels of autophagy and correlates with poorer patient prognosis. Mechanistically, VHL directly binds to the autophagy regulator Beclin1, after its PHD1-mediated hydroxylation on Pro54. This binding inhibits the association of Beclin1-VPS34 complexes with ATG14L, thereby inhibiting autophagy initiation in response to nutrient deficiency. Expression of non-hydroxylatable Beclin1 P54A abrogates VHL-mediated autophagy inhibition and significantly reduces the tumor-suppressing effect of VHL. In addition, Beclin1 P54-OH levels are inversely correlated with autophagy levels in wild-type VHL-expressing human ccRCC specimens, and with poor patient prognosis. Furthermore, combined treatment of VHL-deficient mouse tumors with autophagy inhibitors and HIF2α inhibitors suppresses tumor growth. These findings reveal an unexpected mechanism by which VHL suppresses tumor growth, and suggest a potential treatment for ccRCC through combined inhibition of both autophagy and HIF2α.

The moonlighting function of glycolytic enzyme enolase-1 promotes choline phospholipid metabolism and tumor cell proliferation.

Aberrantly upregulated choline phospholipid metabolism is a novel emerging hallmark of cancer, and choline kinase α (CHKα), a key enzyme for phosphatidylcholine production, is overexpressed in many types of human cancer through undefined mechanisms. Here, we demonstrate that the expression levels of the glycolytic enzyme enolase-1 (ENO1) are positively correlated with CHKα expression levels in human glioblastoma specimens and that ENO1 tightly governs CHKα expression via posttranslational regulation. Mechanistically, we reveal that both ENO1 and the ubiquitin E3 ligase TRIM25 are associated with CHKα. Highly expressed ENO1 in tumor cells binds to I199/F200 of CHKα, thereby abrogating the interaction between CHKα and TRIM25. This abrogation leads to the inhibition of TRIM25-mediated polyubiquitylation of CHKα at K195, increased stability of CHKα, enhanced choline metabolism in glioblastoma cells, and accelerated brain tumor growth. In addition, the expression levels of both ENO1 and CHKα are associated with poor prognosis in glioblastoma patients. These findings highlight a critical moonlighting function of ENO1 in choline phospholipid metabolism and provide unprecedented insight into the integrated regulation of cancer metabolism by crosstalk between glycolytic and lipidic enzymes.

Base editing of the mutated TERT promoter inhibits liver tumor growth.

BACKGROUND AND AIMS: Base editing has shown great potential for treating human diseases with mutated genes. However, its potential for treating HCC has not yet been explored. APPROACH AND RESULTS: We employed adenine base editors (ABEs) to correct a telomerase reverse transcriptase ( TERT ) promoter mutation, which frequently occurs in various human cancers, including HCC. The mutated TERT promoter -124 C>T is corrected to -124 C by a single guide (sg) RNA-guided and deactivated Campylobacter jejuni Cas9 (CjCas9)-fused adenine base editor (CjABE). This edit impairs the binding of the E-twenty six/ternary complex factor transcription factor family, including E-twenty six-1 and GABPA, to the TERT promoter, leading to suppressed TERT promoter and telomerase activity, decreased TERT expression and cell proliferation, and increased cell senescence. Importantly, injection of adeno-associated viruses expressing sgRNA-guided CjABE or employment of lipid nanoparticle-mediated delivery of CjABE mRNA and sgRNA inhibits the growth of liver tumors harboring TERT promoter mutations. CONCLUSIONS: These findings demonstrate that a sgRNA-guided CjABE efficiently converts the mutated TERT promoter -124 C>T to -124 C in HCC cells and underscore the potential to treat HCC by the base editing-mediated correction of TERT promoter mutations.

E3 ubiquitin ligases in cancer and implications for therapies.

E3 ligases are a class of enzymes that can transfer ubiquitin to substrates for their degradation, which are of importance in cellular homeostasis. Since many oncogenic or tumor-suppressive proteins are reported to be regulated by the ubiquitin-proteasome system (UPS), E3 ligases, which function as substrate interacting modules, have been attracting more and more attention as promising anticancer drug targets due to their pivotal role in conferring substrate specificity. Generally, based on their molecular structure and functional mechanism, E3 ligases can be divided into three major types: homologous to E6-associated protein C-terminus (HECT), really interesting new gene (RING), and RING-in-between-RING (RBR) E3 ligases. Based on the significance of their functions, more bioactive compounds targeting E3 ligases should be developed in the future. In this review, we discuss the important roles of E3 ligases involved in cancer as well as available bioactive compounds targeting various E3 ligases for potential anticancer activity.

ERK inhibition sensitizes cancer cells to oleanolic acid-induced apoptosis through ERK/Nrf2/ROS pathway.

Oleanolic acid (OA) is a natural triterpenoid that is widely distributed in edible and medicinal plants. OA exerts anti-tumor activity on a wide range of cancer cells primarily through inducing apoptosis. Dysregulated ERK signaling is closely complicated in the biology of cancer, such as metastasis, proliferation, and survival, and it can be activated by various stimuli. In this study, we found that OA induced the activation of ERK in cancer cells. ERK activation compromised the apoptosis induced by OA. Blocking ERK activation by U0126 or siRNAs was able to potentiate the pro-apoptotic activity of OA on cancer cells. OA was shown to promote ERK-dependent Nrf2 expression in cancer cells, and in turn, Nrf2 expression was able to suppress OA-induced ROS generation. Blockade of Nrf2 expression was able to increase ROS levels and apoptotic death in cancer cells. In conclusion, we provided evidences that ERK activation is a mechanism underlying the resistance of cancer cells to OA-induced apoptosis and targeting ERK is a promising strategy to enhance the anti-tumor efficacy of OA.

MAPK/ERK signaling pathway-induced hyper-O-GlcNAcylation enhances cancer malignancy.

Dysregulated MAPK/ERK signaling is implicated in one-third of human tumors and represents an attractive target for the development of anticancer drugs. Similarly, elevated protein O-GlcNAcylation and O-GlcNAc transferase (OGT) are detected in various cancers and serve as attractive novel cancer-specific therapeutic targets. However, the potential connection between them remains unexplored. Here, a positive correlation was found between the activated MAPK/ERK signaling and hyper-O-GlcNAcylation in various cancer types and inhibition of the MAPK/ERK signaling by 10 µM U0126 significantly decreased the expression of OGT and O-GlcNAcylation in H1299, BPH-1 and DU145 cells; then, the pathway analysis of the potential regulators of OGT obtained from the UCSC Genome Browser was done, and ten downstream targets of ERK pathway were uncovered; the following results showed that ELK1, one of the ten targets of ERK pathway, mediated ERK signaling-induced OGT upregulation; finally, the MTT assay and the soft agar assay showed that the inhibition of MAPK/ERK signaling reduced the promotion effect of hyper-O-GlcNAcylation on cancer cell proliferation and anchorage-independent growth. Taken together, our data originally provided evidence for the regulatory mechanism of hyper-O-GlcNAcylation in tumors, which will be helpful for the development of anticancer drugs targeting to hyper-O-GlcNAcylation. This study also provided a new mechanism by which MAPK/ERK signaling-enhanced cancer malignancy. Altogether, the recently discovered oncogenic factor O-GlcNAc was linked to the classical MAPK/ERK signaling which is essential for the maintenance of malignant phenotype of cancers.

Aplysin sensitizes cancer cells to TRAIL by suppressing P38 MAPK/survivin pathway.

TNF-related apoptosis-inducing ligand (TRAIL) is a tumor-selective apoptosis inducer and has been shown to be promising for treating various types of cancers. However, the application of TRAIL is greatly impeded by the resistance of cancer cells to its action. Studies show that overexpression of some critical pro-survival proteins, such as survivin, is responsible for TRAIL resistance. In this study, we found that Aplysin, a brominated compound from marine organisms, was able to restore the sensitivity of cancer cells to TRAIL both in vitro and in vivo. Aplysin was found to enhance the tumor-suppressing capacity of TRAIL on several TRAIL-resistant cancer cell lines. TRAIL-induced apoptosis was also potentiated in A549 and MCF7 cells treated with Aplysin. Survivin downregulation was identified as a mechanism by which Aplysin-mediated TRAIL sensitization of cancer cells. Furthermore, the activation of p38 MAPK was revealed in Aplysin-treated cancer cells, and its inhibitor SB203580 was able to abrogate the promoting effect of Aplysin on the response of cancer cells to TRAIL action, as evidenced by restored survivin expression, elevated cell survival and reduced apoptotic rates. In conclusion, we provided evidence that Aplysin acts as a sensitizer for TRAIL and its effect on p38 MAPK/survivin pathway may partially account for this activity. Considering its low cytotoxicity to normal cells, Aplysin may be a promising agent for cancer treatment in combination with TRAIL.

Lactylation: Linking the Warburg effect to DNA damage repair.

In this issue of Cell Metabolism, Li et al. report that the highly expressed aldehyde dehydrogenase 1 family member A3 interacts with pyruvate kinase M2 (PKM2) in glioblastoma cells. Consequently, PKM2 tetramerization and activation promote lactate production, leading to the lactylation and nuclear translocation of XRCC1 for DNA damage repair and therapeutic resistance.

Regulatory T cells and immune escape in HCC: understanding the tumor microenvironment and advancing CAR-T cell therapy.

Liver cancer, which most commonly manifests as hepatocellular carcinoma (HCC), is the sixth most common cancer in the world. In HCC, the immune system plays a crucial role in the growth and proliferation of tumor cells. HCC achieve immune escape through the tumor microenvironment, which significantly promotes the development of this cancer. Here, this article introduces and summarizes the functions and effects of regulatory T cells (Tregs) in the tumor microenvironment, highlighting how Tregs inhibit and regulate the functions of immune and tumor cells, cytokines, ligands and receptors, etc, thereby promoting tumor immune escape. In addition, it discusses the mechanism of CAR-T therapy for HCC and elaborate on the relationship between CAR-T and Tregs.

Trop2-targeted therapies in solid tumors: advances and future directions.

Trophoblast cell surface antigen 2 (Trop2) is overexpressed in a range of solid tumors and participants in multiple oncogenic signaling pathways, making it an attractive therapeutic target. In the past decade, the rapid development of various Trop2-targeted therapies, notably marked by the advent of the antibody-drug conjugate (ADC), revolutionized the outcome for patients facing Trop2-positive tumors with limited treatment opinions, such as triple-negative breast cancer (TNBC). This review provides a comprehensive summary of advances in Trop2-targeted therapies, including ADCs, antibodies, multispecific agents, immunotherapy, cancer vaccines, and small molecular inhibitors, along with in-depth discussions on their designs, mechanisms of action (MOAs), and limitations. Additionally, we emphasize the clinical research progress of these emerging Trop2-targeted agents, focusing on their clinical application and therapeutic efficacy against tumors. Furthermore, we propose directions for future research, such as enhancing our understanding of Trop2's structure and biology, exploring the best combination strategies, and tailoring precision treatment based on Trop2 testing methodologies.

Nanog regulates self-renewal of cancer stem cells through the insulin-like growth factor pathway in human hepatocellular carcinoma.

UNLABELLED: Hepatocellular carcinoma (HCC) exhibits cellular heterogeneity and embryonic stem-cell-related genes are preferentially overexpressed in a fraction of cancer cells of poorly differentiated tumors. However, it is not known whether or how these cancer cells contribute to tumor initiation and progression. Here, our data showed that increased expression of pluripotency transcription factor Nanog in cancer cells correlates with a worse clinical outcome in HCC. Using the Nanog promoter as a reporter system, we could successfully isolate a small subpopulation of Nanog-positive cells. We demonstrate that Nanog-positive cells exhibited enhanced ability of self-renewal, clonogenicity, and initiation of tumors, which are consistent with crucial hallmarks in the definition of cancer stem cells (CSCs). Nanog(Pos) CSCs could differentiate into mature cancer cells in in vitro and in vivo conditions. In addition, we found that Nanog(Pos) CSCs exhibited resistance to therapeutic agents (e.g., sorafenib and cisplatin) and have a high capacity for tumor invasion and metastasis. Knock-down expression of Nanog in Nanog(Pos) CSCs could decrease self-renewal accompanied with decreased expression of stem-cell-related genes and increased expression of mature hepatocyte-related genes. Overexpression of Nanog in Nanog(Neg) cells could restore self-renewal. Furthermore, we found that insulin-like growth factor (IGF)2 and IGF receptor (IGF1R) were up-regulated in Nanog(Pos) CSCs. Knock-down expression of Nanog in Nanog(Pos) CSCs inhibited the expression of IGF1R, and overexpression of Nanog in Nanog(Neg) cells increased the expression of IGF1R. A specific inhibitor of IGF1R signaling could significantly inhibit self-renewal and Nanog expression, indicating that IGF1R signaling participated in Nanog-mediated self-renewal. CONCLUSION: These data indicate that Nanog could be a novel biomarker for CSCs in HCC, and that Nanog could play a crucial role in maintaining the self-renewal of CSCs through the IGF1R-signaling pathway.

The interplay of the circadian clock and metabolic tumorigenesis.

The circadian clock and cell metabolism are both dysregulated in cancer cells through intrinsic cell-autonomous mechanisms and external influences from the tumor microenvironment. The intricate interplay between the circadian clock and cancer cell metabolism exerts control over various metabolic processes, including aerobic glycolysis, de novo nucleotide synthesis, glutamine and protein metabolism, lipid metabolism, mitochondrial metabolism, and redox homeostasis in cancer cells. Importantly, oncogenic signaling can confer a moonlighting function on core clock genes, effectively reshaping cellular metabolism to fuel cancer cell proliferation and drive tumor growth. These interwoven regulatory mechanisms constitute a distinctive feature of cancer cell metabolism.

FBXW7 attenuates tumor drug resistance and enhances the efficacy of immunotherapy.

FBXW7 (F-box and WD repeat domain containing 7) is a critical subunit of the Skp1-Cullin1-F-box protein (SCF), acting as an E3 ubiquitin ligase by ubiquitinating targeted protein. Through degradation of its substrates, FBXW7 plays a pivotal role in drug resistance in tumor cells and shows the potential to rescue the sensitivity of cancer cells to drug treatment. This explains why patients with higher FBXW7 levels exhibit higher survival times and more favorable prognosis. Furthermore, FBXW7 has been demonstrated to enhance the efficacy of immunotherapy by targeting the degradation of specific proteins, as compared to the inactivated form of FBXW7. Additionally, other F-box proteins have also shown the ability to conquer drug resistance in certain cancers. Overall, this review aims to explore the function of FBXW7 and its specific effects on drug resistance in cancer cells.

Glycolytic enzyme HK2 promotes PD-L1 expression and breast cancer cell immune evasion.

Immune therapies targeting the PD-1/PD-L1 pathway have been employed in the treatment of breast cancer, which requires aerobic glycolysis to sustain breast cancer cells growth. However, whether PD-L1 expression is regulated by glycolysis in breast cancer cells remains to be further elucidated. Here, we demonstrate that glycolytic enzyme hexokinase 2 (HK2) plays a crucial role in upregulating PD-L1 expression. Under high glucose conditions, HK2 acts as a protein kinase and phosphorylates IκBα at T291 in breast cancer cells, leading to the rapid degradation of IκBα and activation of NF-κB, which enters the nucleus and promotes PD-L1 expression. Immunohistochemistry staining of human breast cancer specimens and bioinformatics analyses reveals a positive correlation between HK2 and PD-L1 expression levels, which are inversely correlated with immune cell infiltration and survival time of breast cancer patients. These findings uncover the intrinsic and instrumental connection between aerobic glycolysis and PD-L1 expression-mediated tumor cell immune evasion and underscore the potential to target the protein kinase activity of HK2 for breast cancer treatment.

UBC9 stabilizes PFKFB3 to promote aerobic glycolysis and proliferation of glioblastoma cells.

Cancer cells prefer to utilizing aerobic glycolysis to generate energy and anabolic metabolic intermediates for cell growth. However, whether the activities of glycolytic enzymes can be regulated by specific posttranslational modifications, such as SUMOylation, in response to oncogenic signallings, thereby promoting the Warburg effect, remain largely unclear. Here, we demonstrate that phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key glycolytic enzyme, interacts with SUMO-conjugating enzyme UBC9 and is SUMOylated at K302 in glioblastoma cells. Expression of UBC9, which competitively prevents the binding of ubiquitin E3 ligase APC/C to PFKFB3 and subsequent PFKFB3 polyubiquitination, increases PFKFB3 stability and expression. Importantly, EGFR activation increases the interaction between UBC9 and PFKFB3, leading to increased SUMOylation and expression of PFKFB3. This increase is blocked by inhibition of EGFR-induced AKT activation whereas expression of activate AKT by itself was sufficient to recapitulate EGF-induced effect. Knockout of PFKFB3 expression decreases EGF-enhanced lactate production and GBM cell proliferation and this decrease was fully rescued by reconstituted expression of WT PFKFB3 whereas PFKFB3 K302R mutant expression abrogates EGF- and UBC9-regulated lactate production and GBM cell proliferation. These findings reveal a previously unknown mechanism underlying the regulation of the Warburg effect through the EGFR activation-induced and UBC9-mediated SUMOylation and stabilization of PFKFB3.

Creatine kinase B suppresses ferroptosis by phosphorylating GPX4 through a moonlighting function.

Activation of receptor protein kinases is prevalent in various cancers with unknown impact on ferroptosis. Here we demonstrated that AKT activated by insulin-like growth factor 1 receptor signalling phosphorylates creatine kinase B (CKB) T133, reduces metabolic activity of CKB and increases CKB binding to glutathione peroxidase 4 (GPX4). Importantly, CKB acts as a protein kinase and phosphorylates GPX4 S104. This phosphorylation prevents HSC70 binding to GPX4, thereby abrogating the GPX4 degradation regulated by chaperone-mediated autophagy, alleviating ferroptosis and promoting tumour growth in mice. In addition, the levels of GPX4 are positively correlated with the phosphorylation levels of CKB T133 and GPX4 S104 in human hepatocellular carcinoma specimens and associated with poor prognosis of patients with hepatocellular carcinoma. These findings reveal a critical mechanism by which tumour cells counteract ferroptosis by non-metabolic function of CKB-enhanced GPX4 stability and underscore the potential to target the protein kinase activity of CKB for cancer treatment.

Recent Advances of Degradation Technologies Based on PROTAC Mechanism.

PROTAC (proteolysis-targeting chimeras), which selectively degrades target proteins, has become the most popular technology for drug development in recent years. Here, we introduce the history of PROTAC, and summarize the recent advances in novel types of degradation technologies based on the PROTAC mechanism, including TF-PROTAC, Light-controllable PROTAC, PhosphoTAC, LYTAC, AUTAC, ATTEC, CMA, RNA-PROTAC and RIBOTACs. In addition, the clinical progress, current challenges and future prospects of degradation technologies based on PROTAC mechanism are discussed.

Myocyte enhancer factor 2D promotes hepatocellular carcinoma through AMOTL2/YAP signaling that inhibited by luteolin.

Hepatocellular carcinoma (HCC) is one of the deadliest malignancies in the world. There is a lack of effective treatment. Previous studies have shown that myocyte enhancer factor 2D (MEF2D) promotes the progression of HCC. Underlying mechanisms have not been fully elucidated. In this study, we reported experimental results obtained using double luciferase. Our results showed that AMOTL2, a negative regulator of Hippo/YAP signaling, and the MEF2 cis-acting element in the upstream region of its promoter bind to MEF2D, inhibiting its transcriptional expression. Studies confirmed that MEF2D affected the protein expression level of AMOTL2 and the YAP signaling activation. It promoted the migration and proliferation of hepatoma cells. We found that luteolin, a natural flavonoid, has anti-tumor activity in HCC cells by affecting YAP signaling transduction. In conclusion, we demonstrated that AMOTL2/YAP signaling is associated with MEF2D-related HCC progression. Luteolin is a promising anti-HCC compound for regulating this signaling.

CNNArginineMe: A CNN structure for training models for predicting arginine methylation sites based on the One-Hot encoding of peptide sequence.

Protein arginine methylation (PRme), as one post-translational modification, plays a critical role in numerous cellular processes and regulates critical cellular functions. Though several in silico models for predicting PRme sites have been reported, new models may be required to develop due to the significant increase of identified PRme sites. In this study, we constructed multiple machine-learning and deep-learning models. The deep-learning model CNN combined with the One-Hot coding showed the best performance, dubbed CNNArginineMe. CNNArginineMe performed best in AUC scoring metrics in comparisons with several reported predictors. Additionally, we employed CNNArginineMe to predict arginine methylation proteome and performed functional analysis. The arginine methylated proteome is significantly enriched in the amyotrophic lateral sclerosis (ALS) pathway. CNNArginineMe is freely available at https://github.com/guoyangzou/CNNArginineMe.

Bioinformatics analysis identified RGS4 as a potential tumor promoter in glioma.

Gliomas is the most common type of intracranial primary malignant tumor and it accounts for ∼80% of primary malignant tumors of the central nervous system. At present, surgical resection with adjuvant radiotherapy and temozolomide adjuvant chemotherapy combined with radiotherapy are the only standard treatments for glioma. However, but overall survival of patients is only 15 months. Glioma is resistant to radiotherapy and chemotherapy, and this malignant behavior leads to a high recurrence rate. Therefore, the use of therapeutics is usually ineffective. As a result, patients with glioma do not significantly benefit from standard treatment. There is therefore an urgent need to develop novel diagnostic approaches and, in particular, more effective treatment strategies. The application of gene expression microarrays provides a feasible and effective way to study gliomas. The present study therefore aimed to identify the key protein-coding genes of glioma using bioinformatics methods and thereby search, for novel biomarkers and therapeutic targets for the treatment of glioma. First, mRNA microarray datasets were selected and obtained from the Gene Expression Omnibus database to identify differentially expressed genes (DEGs) between gliomas and normal tissues. The DEGs were clarified using Gene Ontology (GO), the Kyoto Encyclopedia of Genes and Genomes (KEGG), Protein-Protein Interaction (PPI) network and statistical analysis. Subsequently, reverse transcription-quantitative PCR (RT-qPCR)and western blot were used to verify the results of the bioinformatics analysis. A total of 400 DEGs were identified in glioma and they were enriched in several cancer-related GO and KEGG pathways. In the PPI network, it was observed that G-protein signal regulatory protein 4 (RGS4), thymidine phosphorylase, collagen type VI alpha-1, Src homology 2 domain-containing transforming protein1(SHC1) and ring finger protein 135 exhibited a strong protein-protein interaction. Furthermore, . Subsequently, brain damaged tissues and glioma cell lines were selected for RT-qPCR and western blotting analysis. The results demonstrated that RGS4 was highly expressed in glioma cell lines. In conclusion, RGS4 may be a key protein-coding gene in glioma. RGS4 should therefore be studied further to verify its feasibility and effectiveness as a potential glioma biomarker and therapeutic target.