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Metastasis accounts for the major cause of cancer-related mortality. How disseminated tumor cells survive under suspension conditions and avoid anoikis is largely unknown. Here, using a metabolic enzyme-centered CRISPR-Cas9 genetic screen, we identified methylenetetrahydrofolate dehydrogenase, cyclohydrolase and formyltetrahydrofolate synthetase 1 (MTHFD1) as a novel suppressor of anoikis. MTHFD1 depletion obviously restrained the capacity of cellular antioxidant defense and inhibited tumor distant metastasis. Mechanistically, MTHFD1 was found to bind the protein arginine methyltransferase 5 (PRMT5) and then undergo symmetric dimethylation on R173 by PRMT5. Under suspension conditions, the interaction between MTHFD1 and PRMT5 was strengthened, which increased the symmetric dimethylation of MTHFD1. The elevated methylation of MTHFD1 largely augmented its metabolic activity to generate NADPH, therefore leading to anoikis resistance and distant organ metastasis. Therapeutically, genetic depletion or pharmacological inhibition of PRMT5 declined tumor distant metastasis. And R173 symmetric dimethylation status was associated with metastasis and prognosis of ESCC patients. In conclusion, our study uncovered a novel regulatory role and therapeutic implications of PRMT5/MTHFD1 axis in facilitating anoikis resistance and cancer metastasis.

Background: Epstein‒Barr virus-associated gastric cancer (EBVaGC) is regarded as a distinct molecular subtype of GC, accounting for approximately 9% of all GC cases, and it often exhibits unique molecular features and clinicopathological characteristics. Clinically, EBVaGC patients are found to have a significantly lower frequency of lymph node metastasis and better prognosis than uninfected individuals. RNA N6-methyladenosine (m6A) modification has an indispensable role in modulating tumour progression in various cancer types. However, its impact on EBVaGC remains unclear. Methods: Methylated RNA immunoprecipitation sequence (MeRIP-seq) and m6A dot blot were conducted to compare the m6A modification levels between EBVaGC and EBV-negative GC (EBVnGC) cells. Western blot, real-time quantitative PCR (RT-qPCR) and immunohistochemistry were applied to explore the underlying mechanism of the reduced m6A modification in EBVaGC. The biological function of FTO was determined in vivo and in vitro. The target genes of FTO were screened by MeRIP-seq, RT-qPCR and Western blot. The m6A binding proteins of target genes were verified by RNA pulldown and RNA immunoprecipitation assay. Chromatin immunoprecipitation and Luciferase report assay were performed to investigate the mechanism how EBV upregulated FTO expression. Results: Here, we found that m6A demethylase fat mass and obesity associated protein (FTO) was notably increased in EBVaGC, leading to a reduction in m6A modification, and higher FTO expression was associated with better clinical outcomes. Our findings revealed that FTO depressed EBVaGC cell metastasis and aggressiveness both in vitro and in vivo by controlling the expression of its downstream target gene AP-1 transcription factor subunit (FOS). Methylated FOS mRNA was specifically recognized by the m6A “reader” insulin-like growth factor 2 mRNA binding protein 1/2 (IGF2BP1/2), which enhanced its transcript stability. Moreover, we demonstrated that MYC activated by EBV in EBVaGC elevated FTO expression by binding to a specific region of the FTO promoter. Conclusions: Mechanistically, our work uncovered a crucial suppressive role of FTO in EBVaGC metastasis and invasiveness via an m6A-FOS-IGF2BP1/2-dependent manner, suggesting a promising biomarker panel for GC metastatic prediction and therapy.

Fat mass and obesity-associated protein (FTO), an N6-methyladenosine (m6A) demethylase, participates in tumor progression and metastasis in many malignancies, but its role in colorectal cancer (CRC) is still unclear. Here, we found that FTO protein levels, but not RNA levels, were downregulated in CRC tissues. Reduced FTO protein expression was correlated with a high recurrence rate and poor prognosis in resectable CRC patients. Moreover, we demonstrated that hypoxia restrained FTO protein expression, mainly due to an increase in ubiquitin-mediated protein degradation. The serine/threonine kinase receptor associated protein (STRAP) might served as the E3 ligase and K216 was the major ubiquitination site responsible for hypoxia-induced FTO degradation. FTO inhibited CRC metastasis both in vitro and in vivo. Mechanistically, FTO exerted a tumor suppressive role by inhibiting metastasis-associated protein 1 (MTA1) expression in an m6A-dependent manner. Methylated MTA1 transcripts were recognized by an m6A “reader”, insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2), which then stabilized its mRNA. Together, our findings highlight the critical role of FTO in CRC metastasis and reveal a novel epigenetic mechanism by which the hypoxic tumor microenvironment promotes CRC metastasis.

Nicotinamide adenine dinucleotide phosphate (NADPH) is an essential electron donor in all organisms, and provides the reducing power for anabolic reactions and redox balance. NADPH homeostasis is regulated by varied signaling pathways and several metabolic enzymes that undergo adaptive alteration in cancer cells. The metabolic reprogramming of NADPH renders cancer cells both highly dependent on this metabolic network for antioxidant capacity and more susceptible to oxidative stress. Modulating the unique NADPH homeostasis of cancer cells might be an effective strategy to eliminate these cells. In this review, we summarize the current existing literatures on NADPH homeostasis, including its biological functions, regulatory mechanisms and the corresponding therapeutic interventions in human cancers, providing insights into therapeutic implications of targeting NADPH metabolism and the associated mechanism for cancer therapy.

Altered metabolism is a hallmark of cancer, and the reprogramming of energy metabolism has historically been considered a general phenomenon of tumors. It is well recognized that long noncoding RNAs (lncRNAs) regulate energy metabolism in cancer. However, lncRNA‐mediated posttranslational modifications and metabolic reprogramming are unclear at present. In this review, we summarized the current understanding of the interactions between the alterations in cancer‐associated energy metabolism and the lncRNA‐mediated posttranslational modifications of metabolic enzymes, transcription factors, and other proteins involved in metabolic pathways. In addition, we discuss the mechanisms through which these interactions contribute to tumor initiation and progression, and the key roles and clinical significance of functional lncRNAs. We believe that an in‐depth understanding of lncRNA‐mediated cancer metabolic reprogramming can help to identify cellular vulnerabilities that can be exploited for cancer diagnosis and therapy.

The acidic tumor microenvironment provides an energy source driving malignant tumor progression. Adaptation of cells to an acidic environment leads to the emergence of cancer stem cells. The expression of the vitamin D receptor (VDR) is closely related to the initiation and development of colorectal carcinoma (CRC), but its regulatory mechanism in CRC stem cells is still unclear. Our study revealed that acidosis reduced VDR expression by downregulating peroxisome proliferator-activated receptor delta (PPARD) expression. Overexpression of VDR effectively suppressed the stemness and oxaliplatin resistance of cells in acidosis. The nuclear export signal in VDR was sensitive to acidosis, and VDR was exported from the nucleus. Chromatin immunoprecipitation (ChIP) and assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) analyses showed that VDR transcriptionally repressed SRY-box 2 (SOX2) by binding to the vitamin D response elements in the promoter of SOX2, impairing tumor growth and drug resistance. We demonstrated that a change in the acidic microenvironment combined with overexpression of VDR substantially restricted the occurrence and development of CRC in vivo. These findings reveal a new mechanism by which acidosis could affect the stemness of CRC cells by regulating the expression of SOX2 and show that abnormal VDR expression leads to ineffective activation of vitamin D signaling, resulting in a lack of efficacy of vitamin D in antineoplastic process.

Background RNA N6-methyladenosine (m6A) is an emerging regulatory mechanism for gene expression and participates in tumor progression in several cancer types. M6A ‘readers’ were reported to be involved in controlling the fate of mRNA, and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) was reported to be associated with methylated mRNA stability and promote tumor progress However, its role in colorectal carcinoma (CRC) and its target m6A-specific target genes remains unexplored. Methods Western blot, real-time quantitative PCR and immunohistochemical (IHC) analysis were used to detect IGF2BP2 expression in cell lines and patient‘s tissues. The MTS assay, migration assay, sphere formation assay was performed to detect the function of IGF2BP2. Cell-based xenograft model and PDX model revealed the clinical benefits of target IGF2BP2 in vivo. RNA immunoprecipitation (RIP) sequence was used to screen the target genes of IGF2BP2 and RNA pull-down assay was used to verify the direct binding of IGF2BP2 and targets genes. Results IGF2BP2 was significantly upregulated in human CRC tumor tissues and CRC cell lines and high expression of IGF2BP2 was associated with poor prognosis of CRC patients. Knockdown of IGF2BP2 in CRC cell lines drastically suppressed cellular proliferation and stemness phenotype in vitro. IGF2BP2 inhibition suppresses CRC tumorigenesis and metastasis in both cell models and PDX models in vivo. RIP-seq analysis and RIP-qPCR revealed that SOX2 mRNA was the potential target gene of IGF2BP2. RNA pull-down assay showed the direct binding of IGF2BP2 and SOX2 transcripts which could be impaired by mutating m6a site of SOX2 transcripts. After IGF2BP2 inhibition, the RNA and protein level of SOX2 were downregulated due to the half-life of SOX2 mRNA decreased. Moreover, the downstream genes of SOX2 showed a positive correlation with IGF2BP2 expression in CRC patients. Conclusions In summary, we demonstrated that IGF2BP2 was frequently upregulated in human CRC and contributing to CRC malignancy. IGF2BP2 maintained methylated SOX2 mRNA stability to facilitate cellular stemness features through the m6A-dependent mechanism. Thus, our findings reveal an important role of IGF2BP2 and provide a potential target of treatment in colorectal carcinoma.

Background Glutamate-cysteine ligase modifier (GCLM) subunits, combined with catalytic (GCLC) subunits, has been known for the first rate-limiting enzyme for glutathione (GSH) synthesis. Increasing studies have shown that the non-metabolic functions of many metabolic enzymes also play a crucial role in tumor progress. However, the non-metabolic functions of GCLM remain unexplored. Hence, we wonder if there are unorthodox functions of GCLM under redox stress participating colorectal Carcinoma(CRC) tumorigenesis. Methods Western blot, real-time quantitative PCR and immunohistochemical analysis were used to detect the relative expression of GCLM in cell lines and patients‘ specimens. The MTS assay, migration and invasion assay, sphere formation assay were performed to detect the functions of GCLM in vitro, and the xenograft models and PDX models in nude mice in vivo. Cytosolic and nuclear extraction, immunofluorescent analysis were used to show the location of GCLM. Chromatin immunoprecipitation (ChIP) assay was used to screen and verify the GCLM target genes. Results We found that glucose deprivation condition upregulated the expression of GCLM rather than hypoxia or H2O2. Compared to adjacent tumor tissues, the expression of GCLM was upregulated in CRC tumor tissues. The high expression of GCLM predicted poor prognosis in CRC patients. Inhibition of GCLM results in decreased proliferation rate, migration and invasion ability and sphere formation in HCT116 and DLD1 in vitro. Similarly, GCLM inhibition suppressed CRC tumorigenesis and metastasis in xenograft models and PDX models in vivo. The cancer cell stem cell markers were also downregulated after GCLM inhibition. Interestingly, we found that glucose starvation could rescue the anti-cancer phenotypes of GCLM inhibition and led to nucleus-translocation and accumulation of GCLM. ChIP assay showed GCLM could interact with octamer-binding transcription factor 4 (OCT4) promoter, a cancer stem cell marker, to increase its expression, and the target gene of OCT4 showed a positive correlation with GCLM expression in CRC patients. Conclusions Our data showed that GCLM displayed nucleus accumulation in the condition of glucose deprivation which increased the transcription of OCT4. This study revealed an unorthodox oncogenic function of GCLM in colorectal carcinoma and suggested GCLM as a potential therapeutic target in CRC.

Background Deregulation of protein translation control is a hallmark of cancers. Eukaryotic initiation factor 4A2 (EIF4A2) is required for mRNA binding to ribosome and plays an important role in translation initiation. However, little is known about its functions in colorectal cancer (CRC). Methods Analysis of CRC transcriptome data from TCGA identified that EIF4A2 was associated with poor prognosis. Immunohistochemistry study of EIF4A2 was carried out in 297 paired colorectal tumor and adjacent normal tissue samples. In vitro and in vivo cell-biological assays were performed to study the biological functions of EIF4A2 on experimental metastasis and sensitivity to oxaliplatin treatment. Bioinformatic prediction, chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assay were carried out to unveil the transcription factor of EIF4A2 regulation. Results EIF4A2 Expression is significantly higher in colorectal tumors. Multivariate analysis suggests EIF4A2 as an independent predictor of overall, disease-free and progression-free survival. Dysfunction of EIF4A2 by genetic knock-down or small-molecule inhibitor silvestrol dramatically inhibited CRC invasion and migration, sphere formation and enhanced sensitivity to oxaliplatin treatment in vitro and in vivo. Notably, EIF4A2 knock-down also suppressed lung metastasis in vivo. qRT-PCR and immunoblotting analyses identified c-Myc as a downstream target and effector of EIF4A2. ChIP and dual-luciferase reporter assays validated the bioinformatical prediction of ZNF143 as a specific transcription factor of EIF4A2. Conclusions EIF4A2 promotes experimental metastasis and oxaliplatin resistance in CRC. Silvestrol inhibits tumor growth and has synergistic effects with oxaliplatin to induce apoptosis in cell-derived xenograft (CDX) and patient-derived xenograft (PDX) models. Electronic supplementary material The online version of this article (10.1186/s13046-019-1178-z) contains supplementary material, which is available to authorized users.

Recently, it is unclear about the mechanism of notable regenerated ability of adult zebrafish after spinal cord injury. To investigate the effects of brain on restoration from spinal cord injury, adult zebrafish spinal cord injury model was built and brain samples were dissected at different time points after the injury. Real-time quantitative PCR and in situ hy- bridization were applied to reveal the dynamics of glial cell line-derived neurotrophic factor (gdnf) and nitric oxide synthases (nos) mRNA expression in various regions of zebrafish brain. The results showed that, compared to sham group at each time points separately, the expression of gdnf mRNA in adult zebrafish brain during both acute phase (4 h and 12 h) and chronic phase of neuroregeneration (6 d and 11 d) increased significantly (P

Adult zebrafish has a remarkable capability to recover from spinal cord injury, providing an excellent model for studying neuroregeneration. Here we list equipment and reagents, and give a detailed protocol for complete transection of the adult zebrafish spinal cord. In this protocol, potential problems and their solutions are described so that the zebrafish spinal cord injury model can be more easily and reproducibly performed. In addition, two assessments are introduced to monitor the success of the surgery and functional recovery: one test to assess free swimming capability and the other test to assess extent of neuroregeneration by in vivo anterograde axonal tracing. In the swimming behavior test, successful complete spinal cord transection is monitored by the inability of zebrafish to swim freely for 1 week after spinal cord injury, followed by the gradual reacquisition of full locomotor ability within 6 weeks after injury. As a morphometric correlate, anterograde axonal tracing allows the investigator to monitor the ability of regenerated axons to cross the lesion site and increasingly extend into the gray and white matter with time after injury, confirming functional recovery. This zebrafish model provides a paradigm for recovery from spinal cord injury, enabling the identification of pathways and components of neuroregeneration.

Recently, it is unclear about the mechanism of notable regenerated ability of adult zebrafish after spinal cord injury. To investigate the effects of brain on restoration from spinal cord injury, adult zebrafish spinal cord injury model was built and brain samples were dissected at different time points after the injury. Real-time quantitative PCR and in situ hybridization were applied to reveal the dynamics of glial cell line-derived neurotrophic factor (gdnf) and nitric oxide synthases (nos) mRNA expression in various regions of zebrafish brain. The results showed that, compared to sham group at each time points separately, the expression of gdnf mRNA in adult zebrafish brain during both acute phase (4 h and 12 h) and chronic phase of neuroregeneration (6 d and 11 d) increased significantly (P0.05). The expression of nos mRNA in zebrafish brain enhanced during acute phase, and then reduced to the level lower than the sham group during the chronic phase of neuroregeneration (11 d) (P0.05). This suggests that brain may promote neural axons regeneration in spinal cord via a more beneficial microenvironment which retains higher level of gdnf and lower level of nos.

In contrast to mammals, adult zebrafish recover locomotor functions after spinal cord injury (SCI), in part due to axonal regrowth and regeneration permissivity of the central nervous system. Upregulation of major vault protein (MVP) expression after spinal cord injury in the brainstem of the adult zebrafish prompted us to probe for its contribution to recovery after SCI. MVP is a multifunctional protein expressed not only in many types of tumours but also in the nervous system, where its importance for regeneration is, however, unclear. Using an established zebrafish SCI model, we found that MVP mRNA and protein expression levels were increased in ependymal cells in the spinal cord caudal to the lesion site at 6 and 11 days after SCI. Double immunolabelling showed that MVP was co-localised with Islet-1 or tyrosine hydroxylase around the central canal of the spinal cord in sham-injured control fish and injured fish 11 days after surgery. MVP co-localised with the neural stem cell marker nestin in ependymal cells after injury. By using an in vivo morpholino-based knock-down approach, we found that the distance moved by MVP morpholino-treated fish was reduced at 4, 5 and 6 weeks after SCI when compared to fish treated with standard control morpholino. Knock-down of MVP resulted in reduced regrowth of axons from brainstem neurons into the spinal cord caudal to the lesion site. These results indicate that MVP supports locomotor recovery and axonal regrowth after SCI in adult zebrafish.

The cell neural adhesion molecule contactin-2 plays a key role in axon extension and guidance, fasciculation, and myelination during development. We thus asked, whether contactin-2 is also important in nervous system regeneration after trauma. In this study, we used an adult zebrafish spinal cord transection model to test the functions of contactin-2 in spinal cord regeneration. The expression patterns of contactin-2 at different time points after spinal cord injury were studied at the mRNA level by qPCR and in situ hybridization, and contactin-2 protein levels and immunohistological localization were detected by Western blot and immunofluorescence analyses, respectively. Contactin-2 mRNA and protein levels were increased along the central canal at 6 days and 11 days after spinal cord injury, suggesting a requirement for contactin-2 in spinal cord regeneration. Co-localization of contactin-2 and islet-1 (a motoneuron marker) was observed in spinal cords before and after injury. To further explore the functions of contactin-2 in regeneration, an anti-sense morpholino was used to knock down the expression of contactin-2 protein by application at the time of injury. Motion analysis showed that inhibition of contactin-2 retarded the recovery of swimming functions when compared to standard control morpholino. Anterograde and retrograde tracing at 6 weeks after injury showed that knock down of contactin-2 inhibited axonal regrowth from NMLF neurons beyond lesion site. The combined observations indicate that contactin-2 contributes to locomotor recovery and successful regrowth of axons after spinal cord injury in adult zebrafish.