Lactate Is a Natural Suppressor of RLR Signaling by Targeting MAVS.

RLR-mediated type I IFN production plays a pivotal role in elevating host immunity for viral clearance and cancer immune surveillance. Here, we report that glycolysis, which is inactivated during RLR activation, serves as a barrier to impede type I IFN production upon RLR activation. RLR-triggered MAVS-RIG-I recognition hijacks hexokinase binding to MAVS, leading to the impairment of hexokinase mitochondria localization and activation. Lactate serves as a key metabolite responsible for glycolysis-mediated RLR signaling inhibition by directly binding to MAVS transmembrane (TM) domain and preventing MAVS aggregation. Notably, lactate restoration reverses increased IFN production caused by lactate deficiency. Using pharmacological and genetic approaches, we show that lactate reduction by lactate dehydrogenase A (LDHA) inactivation heightens type I IFN production to protect mice from viral infection. Our study establishes a critical role of glycolysis-derived lactate in limiting RLR signaling and identifies MAVS as a direct sensor of lactate, which functions to connect energy metabolism and innate immunity.

Tiam1 methylation by NSD2 promotes Rac1 signaling activation and colon cancer metastasis.

Metastasis is a major cause of cancer therapy failure and mortality. However, targeting metastatic seeding and colonization remains a significant challenge. In this study, we identified NSD2, a histone methyltransferase responsible for dimethylating histone 3 at lysine 36, as being overexpressed in metastatic tumors. Our findings suggest that NSD2 overexpression enhances tumor metastasis both in vitro and in vivo. Further analysis revealed that NSD2 promotes tumor metastasis by activating Rac1 signaling. Mechanistically, NSD2 combines with and activates Tiam1 (T lymphoma invasion and metastasis 1) and promotes Rac1 signaling by methylating Tiam1 at K724. In vivo and in vitro studies revealed that Tiam1 K724 methylation could be a predictive factor for cancer prognosis and a potential target for metastasis inhibition. Furthermore, we have developed inhibitory peptide which was proved to inhibit tumor metastasis through blocking the interaction between NSD2 and Tiam1. Our results demonstrate that NSD2-methylated Tiam1 promotes Rac1 signaling and cancer metastasis. These results provide insights into the inhibition of tumor metastasis.

Sirtuin 2 Prevents Liver Steatosis and Metabolic Disorders by Deacetylation of Hepatocyte Nuclear Factor 4α.

BACKGROUND AND AIMS: Sirtuin 2 (SIRT2), an NAD+ -dependent deacetylase, is involved in various cellular processes regulating metabolic homeostasis and inflammatory responses; however, its role in hepatic steatosis and related metabolic disorders is unknown. APPROACH AND RESULTS: Integrating the published genomic data on NAFLD samples from humans and rodents available in the Gene Expression Omnibus, we found that SIRT2 was significantly down-regulated in livers from patients with advanced NAFLD and high-fat diet (HFD)-induced NAFLD mice. This study further revealed that SIRT2 was markedly decreased in obese (ob/ob) mice and in palmitate-treated HepG2 cells. Restoration of hepatic SIRT2 expression in ob/ob or HFD-fed mice largely alleviated insulin resistance, hepatic steatosis, and systematic inflammation, whereas SIRT2 liver-specific ablation exacerbated these metabolic dysfunctions in HFD-fed C57BL/6J mice. Mechanistically, SIRT2 stabilized the hepatocyte nuclear factor 4α (HNF4α) protein by binding to and deacetylating HNF4α on lysine 458. Furthermore, HNF4α was sufficient to mediate SIRT2 function, and SIRT2-HNF4α interaction was required for SIRT2 function both in vivo and in vitro. CONCLUSIONS: Collectively, the present study provided evidence that SIRT2 functions as a crucial negative regulator in NAFLD and related metabolic disorders and that targeting the SIRT2-HNF4α pathway may be a promising strategy for NAFLD treatment.

SIX4 activates Akt and promotes tumor angiogenesis.

Angiogenesis plays important roles in solid tumors progression. Growth factors such as vascular endothelial growth factors (VEGFs) can induce angiogenesis and hypoxia promotes the expression of VEGFs through activating hypoxia-inducible factor 1 (HIF-1α). However, the regulation of HIF-1α still not been fully understood. Here, we demonstrate that the Sine Oculis Homeobox Homolog 4 (SIX4) is up-regulated in colorectal cancer (CRC) and high expression of SIX4 predicts a poor prognosis. Overexpression of SIX4 enhances tumor growth and angiogenesis in vitro and in vivo, while knockdown of SIX4 inhibits tumor growth and angiogenesis. Furthermore, we show that SIX4 increases the expression of VEGF-A by coordinating with the HIF-1α. Mechanically, we explore that SIX4 up-regulates the expression of HIF-1α depending on Akt activation. Collectively, we demonstrate that SIX4 is functional in regulating tumor angiogenesis and SIX4 might be used as anti-angiogenic therapy in CRC.

Histone demethylase KDM4D promotes gastrointestinal stromal tumor progression through HIF1ß/VEGFA signalling.

BACKGROUND: Gastrointestinal stromal tumour (GIST) is the most common soft tissue sarcoma. The identification of the molecular mechanisms regulating GIST progression is vital for its treatment and prevention. Increasing reports have demonstrated that epigenetic alterations play critical roles in GIST development. However, the role of the histone demethylase KDM4D in GIST progression is poorly understood. METHODS: In clinically matched GIST tissues, KDM4D protein levels were measured by Western blot and immunohistochemical (IHC) staining. KDM4D mRNA levels were examined by quantitative real-time PCR (qRT-PCR). Bioinformatics analysis was used to examine KDM4D expression. The biological effects of KDM4D were investigated in vitro using CCK-8, BrdU/PI, wound healing, colony formation, tube formation and Transwell assays and in vivo using a xenograft mice model. Luciferase assays were used to assess regulation of HIF1ß gene promoter activity by KDM4D. ChIP assays were performed to assess KDM4D, H3K36me3 and H3K9me3 occupancy on the HIF1ß gene promoter. RESULTS: We observed a significant upregulation of KDM4D in GIST tissue compared with matched normal tissue and further explored the oncogenic function of KDM4D both in vitro and in vivo. Furthermore, we demonstrated that KDM4D directly interacted with the HIF1ß gene promoter and regulated its activity, promoting tumour angiogenesis and GIST progression both in vitro and in vivo. Finally, we demonstrated that KDM4D transcriptionally activates HIF1ß expression via H3K9me3 and H3K36me3 demethylation at the promoter region. CONCLUSIONS: Our findings reveal the important roles of the KDM4D/HIF1ß/VEGFA signalling pathway in GIST progression, and this pathway may act as a potential therapeutic target for GIST patients.

TRIB2 functions as novel oncogene in colorectal cancer by blocking cellular senescence through AP4/p21 signaling.

BACKGROUND: Cellular senescence is a state of irreversible cell growth arrest and senescence cells permanently lose proliferation potential. Induction of cellular senescence might be a novel therapy for cancer cells. TRIB2 has been reported to participate in regulating proliferation and drug resistance of various cancer cells. However, the role of TRIB2 in cellular senescence of colorectal cancer (CRC) and its molecular mechanism remains unclear. METHODS: The expression of TRIB2 in colorectal cancer tissues and adjacent tissues was detected by immunohistochemistry and RT-PCR. The growth, cell cycle distribution and cellular senescence of colorectal cancer cells were evaluated by Cell Counting Kit-8 (CCK8) assay, flow cytometry detection and senescence-associated ß-galactosidase staining, respectively. Western blot, RT-PCR and luciferase assay were performed to determine how TRIB2 regulates p21. Immunoprecipitation (IP) and chromatin-immunoprecipitation (ChIP) were used to investigate the molecular mechanisms. RESULTS: We found that TRIB2 expression was elevated in CRC tissues compared to normal adjacent tissues and high TRIB2 expression indicated poor prognosis of CRC patients. Functionally, depletion of TRIB2 inhibited cancer cells proliferation, induced cell cycle arrest and promoted cellular senescence, whereas overexpression of TRIB2 accelerated cell growth, cell cycle progression and blocked cellular senescence. Further studies showed that TRIB2 physically interacted with AP4 and inhibited p21 expression through enhancing transcription activities of AP4. The rescue experiments indicated that silencing of AP4 abrogated the inhibition of cellular senescence induced by TRIB2 overexpression. CONCLUSION: These data demonstrate that TRIB2 suppresses cellular senescence through interaction with AP4 to down-regulate p21 expression. Therefore, TRIB2 could be a potential target for CRC treatment.

Correction to: Histone demethylase KDM4D promotes gastrointestinal stromal tumor progression through HIF1ß/VEGFA signalling.

After the publication of this work [1] an error was noticed in Fig. 7e, in which the incorrect information is shown. The updated figure included in this correction now shows the quantification of tumor microvessel density. This correction does not affect the findings or conclusions of the article. Nevertheless, we apologize for the inconvenience.

ETHE1 dampens colorectal cancer angiogenesis by promoting TC45 Dephosphorylation of STAT3 to inhibit VEGF-A expression.

Angiogenesis is critical for colorectal cancer (CRC) progression, but its mechanisms remain unclear. Here, we reveal that ethylmalonic encephalopathy protein 1 (ETHE1), an essential enzyme in hydrogen sulfide catabolism, inhibits VEGF-A expression and tumor angiogenesis in vitro and in vivo. Moreover, we find that this biological function of ETHE1 depends on the STAT3/VEGF-A pathway. Further investigation demonstrates that ETHE1 promotes the interaction between T cell protein tyrosine phosphatase (TC45) and STAT3, resulting in decreased STAT3 phosphorylation and inhibition of the STAT3 signaling pathway. In clinical samples, we find that ETHE1 is downregulated in CRC and positively correlates with survival outcomes of CRC patients. Meanwhile, the negative correlation of ETHE1 and VEGF-A expression is verified in CRC specimens, and the patients with low ETHE1 and high VEGF-A expression exhibits poorer prognosis. Collectively, our study identifies ETHE1 as a novel regulator of tumor angiogenesis, implying its potential as a prognostic biomarker and promising antiangiogenic target for CRC patients.

USP26 promotes colorectal cancer tumorigenesis by restraining PRKN-mediated mitophagy.

Deubiquitinating enzymes (DUBs) are promising targets for cancer therapy because of their pivotal roles in various physiological and pathological processes. Among these, ubiquitin-specific peptidase 26 (USP26) is a protease with crucial regulatory functions. Our study sheds light on the upregulation of USP26 in colorectal cancer (CRC), in which its increased expression correlates with an unfavorable prognosis. Herein, we evidenced the role of USP26 in promoting CRC tumorigenesis in a parkin RBR E3 ubiquitin-protein ligase (PRKN) protein-dependent manner. Our investigation revealed that USP26 directly interacted with PRKN protein, facilitating its deubiquitination, and subsequently reducing its activity. Additionally, we identified the K129 site on PRKN as a specific target for USP26-mediated deubiquitination. Our research highlights that a K-to-R mutation at the site on PRKN diminishes its potential for activation and ability to mediate mitophagy. In summary, our findings underscore the significance of USP26-mediated deubiquitination in restraining the activation of the PRKN-mediated mitophagy pathway, ultimately driving CRC tumorigenesis. This study not only elucidated the multifaceted role of USP26 in CRC but also introduced a promising avenue for therapeutic exploration through the development of small molecule inhibitors targeting USP26. This strategy holds promise as a novel therapeutic approach for CRC.

PRMT5 methylating SMAD4 activates TGF-ß signaling and promotes colorectal cancer metastasis.

Perturbations in transforming growth factor-ß (TGF-ß) signaling can lead to a plethora of diseases, including cancer. Mutations and posttranslational modifications (PTMs) of the partner of SMAD complexes contribute to the dysregulation of TGF-ß signaling. Here, we reported a PTM of SMAD4, R361 methylation, that was critical for SMAD complexes formation and TGF-ß signaling activation. Through mass spectrometric, co-immunoprecipitation (Co-IP) and immunofluorescent (IF) assays, we found that oncogene protein arginine methyltransferase 5 (PRMT5) interacted with SMAD4 under TGF-ß1 treatment. Mechanically, PRMT5 triggered SMAD4 methylation at R361 and induced SMAD complexes formation and nuclear import. Furthermore, we emphasized that PRMT5 interacting and methylating SMAD4 was required for TGF-ß1-induced epithelial-mesenchymal transition (EMT) and colorectal cancer (CRC) metastasis, and SMAD4 R361 mutation diminished PRMT5 and TGF-ß1-induced metastasis. In addition, highly expressed PRMT5 or high level of SMAD4 R361 methylation indicated worse outcomes in clinical specimens analysis. Collectively, our study highlights the critical interaction of PRMT5 and SMAD4 and the roles of SMAD4 R361 methylation for controlling TGF-ß signaling during metastasis. We provided a new insight for SMAD4 activation. And this study indicated that blocking PRMT5-SMAD4 signaling might be an effective targeting strategy in SMAD4 wild-type CRC.

PD-L1 methylation restricts PD-L1/PD-1 interactions to control cancer immune surveillance.

Immune checkpoint inhibitors targeting programmed cell death protein 1 (PD-1) or programmed cell death 1 ligand 1 (PD-L1) have enabled some patients with cancer to experience durable, complete treatment responses; however, reliable anti-PD-(L)1 treatment response biomarkers are lacking. Our research found that PD-L1 K162 was methylated by SETD7 and demethylated by LSD2. Furthermore, PD-L1 K162 methylation controlled the PD-1/PD-L1 interaction and obviously enhanced the suppression of T cell activity controlling cancer immune surveillance. We demonstrated that PD-L1 hypermethylation was the key mechanism for anti-PD-L1 therapy resistance, investigated that PD-L1 K162 methylation was a negative predictive marker for anti-PD-1 treatment in patients with non-small cell lung cancer, and showed that the PD-L1 K162 methylation:PD-L1 ratio was a more accurate biomarker for predicting anti-PD-(L)1 therapy sensitivity. These findings provide insights into the regulation of the PD-1/PD-L1 pathway, identify a modification of this critical immune checkpoint, and highlight a predictive biomarker of the response to PD-1/PD-L1 blockade therapy.

EZH2-triggered methylation of SMAD3 promotes its activation and tumor metastasis.

SMAD3 plays a central role in cancer metastasis, and its hyperactivation is linked to poor cancer outcomes. Thus, it is critical to understand the upstream signaling pathways that govern SMAD3 activation. Here, we report that SMAD3 underwent methylation at K53 and K333 (K53/K333) by EZH2, a process crucial for cell membrane recruitment, phosphorylation, and activation of SMAD3 upon TGFB1 stimulation. Mechanistically, EZH2-triggered SMAD3 methylation facilitated SMAD3 interaction with its cellular membrane localization molecule (SARA), which in turn sustained SMAD3 phosphorylation by the TGFB receptor. Pathologically, increased expression of EZH2 expression resulted in the accumulation of SMAD3 methylation to facilitate SMAD3 activation. EZH2-mediated SMAD3 K53/K333 methylation was upregulated and correlated with SMAD3 hyperactivation in breast cancer, promoted tumor metastasis, and was predictive of poor survival outcomes. We used 2 TAT peptides to abrogate SMAD3 methylation and therapeutically inhibit cancer metastasis. Collectively, these findings reveal the complicated layers involved in the regulation of SMAD3 activation coordinated by EZH2-mediated SMAD3 K53/K333 methylation to drive cancer metastasis.

IL-6 regulates autophagy and chemotherapy resistance by promoting BECN1 phosphorylation.

Extracellular cytokines are enriched in the tumor microenvironment and regulate various important properties of cancers, including autophagy. However, the precise molecular mechanisms underlying the link between autophagy and extracellular cytokines remain to be elucidated. In the present study, we demonstrate that IL-6 activates autophagy through the IL-6/JAK2/BECN1 pathway and promotes chemotherapy resistance in colorectal cancer (CRC). Mechanistically, IL-6 triggers the interaction between JAK2 and BECN1, where JAK2 phosphorylates BECN1 at Y333. We demonstrate that BECN1 Y333 phosphorylation is crucial for BECN1 activation and IL-6-induced autophagy by regulating PI3KC3 complex formation. Furthermore, we investigate BECN1 Y333 phosphorylation as a predictive marker for poor CRC prognosis and chemotherapy resistance. Combination treatment with autophagy inhibitors or pharmacological agents targeting the IL-6/JAK2/BECN1 signaling pathway may represent a potential strategy for CRC cancer therapy.

The autophagy-independent role of BECN1 in colorectal cancer metastasis through regulating STAT3 signaling pathway activation.

BECN1 is a critical regulator of autophagy, which plays important roles in tumor formation and metastasis. However, the autophagy-independent role of BECN1 and the clinical prediction value of BECN1 still need to be explored. Here, we observed significantly lower expression of BECN1 in colorectal cancers (CRCs) compared with adjacent normal colon tissue, and downregulation of BECN1 was positively related to poor prognosis in CRC patients. In addition, we found that knockdown of BECN1 markedly promoted CRC cell motility and invasion. Bioinformatics gene set enrichment analysis (GSEA) revealed that low levels of BECN1 were significantly correlated with the STAT3 signaling pathway in CRC. Consistently, knockdown of BECN1 increased the phosphorylation of STAT3 and activated the STAT3 signaling pathway in CRC cells. Furthermore, we demonstrated that STAT3 was involved in the CRC metastasis mediated by knockdown of BECN1 in vitro and in vivo. Mechanistically, knockdown of BECN1 promoted the phosphorylation of STAT3 via regulation of the interaction between STAT and JAK2 but did not inhibit autophagy. Our study revealed that BECN1 served as a negative regulator of CRC metastasis by regulating STAT3 signaling pathway activation in an autophagy-independent manner. The BECN1/JAK2/STAT3 signaling pathway can be used as a potential therapeutic target for metastatic CRC.

Blocking histone methyltransferase SETDB1 inhibits tumorigenesis and enhances cetuximab sensitivity in colorectal cancer.

The histone methyltransferase SETDB1 catalyzes the addition of methyl groups to histone H3 at lysine 9, and upregulation of SETDB1 is associated with poor prognosis in cancer patients. Here, we describe how overexpression of SETDB1 contributes to colorectal cancer (CRC) tumorigenesis and drug resistance. We show that SETDB1 is upregulated in CRC, and its level correlates with poor clinical outcome. SETDB1 attenuation inhibits CRC cell proliferation Mechanistically, SETDB1 promotes cell proliferation by upregulating Akt activation. Further, SETDB1 is essential for the tumorigenic activity of Akt. Functional characterization revealed that inhibition of SETDB1 reduces cell growth in CRC resistant to targeted treatments in vitro and in vivo, KRAS-mutated CRC included. Taken together, our results indicate that SETDB1 is a major driver of CRC and may serve as a potential target for the treatment of KRAS-mutated CRC.

M2 Macrophage-Derived Exosomes Promote Cell Migration and Invasion in Colon Cancer.

Clinical and experimental evidence has shown that tumor-associated macrophages promote cancer initiation and progression. However, the macrophage-derived molecular determinants that regulate colorectal cancer metastasis have not been fully characterized. Here, we demonstrate that M2 macrophage-regulated colorectal cancer cells' migration and invasion is dependent upon M2 macrophage-derived exosomes (MDE). MDE displayed a high expression level of miR-21-5p and miR-155-5p, and MDE-mediated colorectal cancer cells' migration and invasion depended on these two miRNAs. Mechanistically, miR-21-5p and miR-155-5p were transferred to colorectal cancer cells by MDE and bound to the BRG1 coding sequence, downregulating expression of BRG1, which has been identified as a key factor promoting the colorectal cancer metastasis, yet is downregulated in metastatic colorectal cancer cells. Collectively, these findings show that M2 macrophages induce colorectal cancer cells' migration and invasion and provide significant plasticity of BRG1 expression in response to tumor microenvironments during malignant progression. This dynamic and reciprocal cross-talk between colorectal cancer cells and M2 macrophages provides a new opportunity for the treatment of metastatic colorectal cancer. SIGNIFICANCE: These findings report a functional role for miRNA-containing exosomes derived from M2 macrophages in regulating migration and invasion of colorectal cancer cells.

PIK3R3 regulates PPARα expression to stimulate fatty acid ß-oxidation and decrease hepatosteatosis.

Phosphatidylinositol 3-kinase (PI3K) signaling plays an important role in the regulation of cellular lipid metabolism and non-alcoholic fatty liver disease (NAFLD). However, little is known about the role of the regulatory subunits of PI3K in lipid metabolism and NAFLD. In this study, we characterized the functional role of PIK3R3 in fasting-induced hepatic lipid metabolism. In this study, we showed that the overexpression of PIK3R3 promoted hepatic fatty acid oxidation via PIK3R3-induced expression of PPARα, thus improving the fatty liver phenotype in high-fat diet (HFD)-induced mice. By contrast, hepatic PIK3R3 knockout in normal mice led to increased hepatic TG levels. Our study also showed that PIK3R3-induced expression of PPARα was dependent on HNF4α. The novel PIK3R3-HNF4α-PPARα signaling axis plays a significant role in hepatic lipid metabolism. As the activation of PIK3R3 decreased hepatosteatosis, PIK3R3 can be considered a promising novel target for developing NAFLD and metabolic syndrome therapies.

Inhibition of SIRT2 limits tumour angiogenesis via inactivation of the STAT3/VEGFA signalling pathway.

Mounting evidence has demonstrated that angiogenesis plays an important role in tumour progression. However, the key regulators in tumour angiogenesis remain unclear. Recently, emerging reports have indicated that SIRT2 plays critical roles in proliferation, metastasis and tumourigenesis in diverse tumours. However, the function of SIRT2 in tumour angiogenesis and the mechanism underlying the regulation of angiogenesis by SIRT2 are still unknown. Here, we found that SIRT2 was upregulated in colorectal cancer tissues compared to that in normal samples and that the elevated SIRT2 was associated with poor prognosis in patients with colorectal cancer. In addition, a series of in vitro and in vivo experiments were performed to demonstrate the role of SIRT2 in tumour angiogenesis. We showed that silencing SIRT2 significantly suppressed tumour angiogenesis. Mechanistically, the knockdown of SIRT2 inhibited STAT3 phosphorylation, causing decreased secretion of VEGFA. Notably, we found that SIRT2 directly interacted with STAT3 and affected the phosphorylation of STAT3 and the translocation of phosphorylated STAT3 to the nucleus. Importantly, a series of rescue experiments suggested that the function of SIRT2 in tumour angiogenesis depends on the STAT3/VEGFA signalling pathway. Our findings provide insight into the important role of SIRT2 in colon tumour angiogenesis and suggest that SIRT2/STAT3/VEGFA might be a novel prognostic biomarker and a potential therapeutic target for patients with colorectal cancer.

PIK3R3 promotes chemotherapeutic sensitivity of colorectal cancer through PIK3R3/NF-kB/TP pathway.

Phosphoinositide-3-kinase regulatory subunit 3(PIK3R3) is overexpressed in different types of human cancer. We previously reported the important role of PIK3R3 in colorectal cancer (CRC). However, the prognosis effect of PIK3R3 in CRC is still remaining unclear. In this study, we explored online clinical databases to analyze the prognosis differences between higher and lower expression of PIK3R3 in CRC patients. Interestingly, we found that better disease-free survival (DFS) were occurred in patients with higher expression of PIK3R3, but there is no significant difference in overall survival (OS). For further, we showed that PIK3R3 could enhance 5-FU induced apoptosis by regulating the expression of thymmidine phosphorylase (TP). In conclusion, PIK3R3 could be considered as a predictor of 5-FU sensitivity for personalized treatment, and a therapeutic target for colorectal cancer.

SIX4 promotes metastasis via activation of the PI3K-AKT pathway in colorectal cancer.

BACKGROUND: Several studies report aberrant expression of sine oculis homeobox (SIX) homolog family members during cancer development and progression. SIX4 participates in organ development, such as myogenesis and neurogenesis. However, the expression and clinical implication of SIX4 in colorectal cancer (CRC) remains unclear. METHODS: The SIX4 expression levels in colorectal patients were assessed in nine different human cancer arrays and compared using patient survival data. SIX4 expression was silenced in two cell culture lines for invasion and wound healing assessment. Finally, bioinformatics assessments ascertained the pathways impacted by SIX4. RESULTS: SIX4 was upregulated in The Cancer Genome Atlas CRC cohort and other gene expression omnibus (GEO) cohorts. In addition, SIX4 expression significantly correlated with lymph node metastasis and advanced Tumor Node Metastasis (TNM) stages. Moreover, SIX4 overexpression was related to unfavorable prognosis in CRC patients. Silencing SIX4 inhibited CRC cell metastasis by surpressing AKT phosphorylation. DISCUSSION: SIX4 is upregulated in CRC and can be used as a prognosis biomarker.