NEAT expression is associated with tumor recurrence and unfavorable prognosis in colorectal cancer NEAT expression is associated with tumor recurrence and unfavorable prognosis in colorectal cancer

Background: Epigenetic alterations play an important role in hepatocellular carcinoma (HCC) development. Enhancer of zeste homolog 2 (EZH2) is a well-known epigenetic modifier that functions as an oncogene in tumors by promoting the H3K27me3-mediated transcriptional repression of tumor suppressor genes. “Senescent cells” has been proposed as a possible core component of the hallmarks of cancer conceptualization. Induction of cell senescence and targeted elimination of these senescent tumor cells are new strategies for tumor therapy. However, the role of EZH2 in regulating cellular senescence remains poorly understood. Methods: Bioinformatics analyses suggested that EZH2 and DNA topoisomerase II alpha (TOP2A) are coexpressed in tumors, including HCC. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analyses and gene set enrichment analyses (GSEA) suggests a correlation of EZH2 and TOP2A expression with cellular senescence in HCC. MicroRNA (miRNA) inhibitor and mimics, siRNA, PLKO-shRNA, and plenti6.3-miR-139 were used to upregulate or downregulate the expression of target genes. CCK8, EdU, clone formation, and senescence-associated β-galactosidase (SA-β-gal) staining assays were performed to assess cell proliferation and cellular senescence phenotypes. Dual-luciferase reporter and chromatin immunoprecipitation assays were performed to investigate the targeted binding and inhibition of TOP2A 3′ untranslated region (UTR) by miR-139-5p and the DNA enrichment of miR139-5p by EZH2 and H3K27me3. BALB/c nude mice were used to establish a xenograft tumor model and verify the phenotypes upon EZH2 and TOP2A silencing and miR-139 overexpression in vivo. In addition, tissue microarrays were used to analyze the expression patterns and correlations among EZH2, TOP2A, and miR-139-5p expression in HCC. Results: Bioinformatics analysis revealed that EZH2 and TOP2A are coexpressed in HCC. In vitro gain- and loss-of-function experiments showed that inhibition of EZH2 and TOP2A induces cellular senescence and inhibits proliferation of HCC cells. In vivo tumorigenesis assays indicated that EZH2 and TOP2A knockdown inhibits tumorigenesis by inducing cellular senescence. Mechanistically, EZH2 promotes TOP2A expression by regulating the H3K27me3-mediated epigenetic silencing of miR-139-5p. TOP2A is a direct target of miR-139-5p, and inhibition of miR-139-5p can reverse the promotion by EZH2 of TOP2A expression. The overexpression of miR-139-5p induces cellular senescence and inhibits proliferation of HCC cells both in vitro and in vivo. Clinically, expression of EZH2 and TOP2A are higher in HCC tissues than in normal tissues, and this high coexpression indicates a worse outcome of patients with HCC. Moreover, expression of EZH2 and TOP2A is significantly correlated with tumor differentiation grade, tumor invasion, and TNM stage in HCC. miR-139-5p expression is lower in HCC tumors than in normal tissues and is correlated with better prognosis of HCC patients. Conclusions: Our study revealed the role of the EZH2/miR-139-5p/TOP2A axis in regulating cellular senescence and cell proliferation in HCC, enriching the molecular mechanisms of EZH2-mediated epigenetic regulation in HCC. Therefore, our results provide insight into the therapeutic potential of targeting EZH2 to induce cellular senescence and then destroy senescent cells for HCC. Graphic

Fork-head box protein M1 (FoxM1) is a transcriptional factor which plays critical roles in cancer development and progression. However, the general regulatory mechanism of FoxM1 is still limited. STMN1 is a microtubule-binding protein which can inhibit the assembly of microtubule dimer or promote depolymerization of microtubules. It was reported as a major responsive factor of paclitaxel resistance for clinical chemotherapy of tumor patients. But the function of abnormally high level of STMN1 and its regulation mechanism in cancer cells remain unclear. In this study, we used public database and tissue microarrays to analyze the expression pattern of FoxM1 and STMN1 and found a strong positive correlation between FoxM1 and STMN1 in multiple types of cancer. Lentivirus-mediated FoxM1/STMN1-knockdown cell lines were established to study the function of FoxM1/STMN1 by performing cell viability assay, plate clone formation assay, soft agar assay in vitro and xenograft mouse model in vivo. Our results showed that FoxM1 promotes cell proliferation by upregulating STMN1. Further ChIP assay showed that FoxM1 upregulates STMN1 in a transcriptional level. Prognostic analysis showed that a high level of FoxM1 and STMN1 is related to poor prognosis in solid tumors. Moreover, a high co-expression of FoxM1 and STMN1 has a more significant correlation with poor prognosis. Our findings suggest that a general FoxM1-STMN1 axis contributes to cell proliferation and tumorigenesis in hepatocellular carcinoma, gastric cancer and colorectal cancer. The combination of FoxM1 and STMN1 can be a more precise biomarker for prognostic prediction.

The liver is the predominant metastatic site for several types of malignancies. Tumor-associated macrophages (TAMs) in the liver play crucial roles in the metastasis process. Shifting tumor-promoting M2-like TAMs toward the M1-like phenotype, which exerts tumor suppressor functions via phagocytosis and the secretion of inhibitory factors, may be a potential therapeutic strategy for liver cancer metastasis treatment.We first cloned NDRG2 (N-myc downstream-regulated gene 2) and verified its tumor suppressor role in multiple solid tumors, including colorectal cancer and hepatocellular carcinoma. However, its role in the tumor-associated liver microenvironment, especially in TAMs, has not been illustrated. By establishing a liver cancer metastasis model in wild-type (WT) and Ndrg2 knockout (Ndrg2−/−) mice, we found that the loss of the tumor suppressor Ndrg2 in liver microenvironment significantly suppressed the growth of liver colonies. In addition, this process was accompanied by a higher proportion of M1-like TAM infiltration in Ndrg2−/− mice. Interestingly, bone marrow (BM) transplantation revealed that BM-derived macrophages (BMDMs) rather than liver resident Kupffer cells were responsible for the inhibitory effect. We further demonstrated that loss of Ndrg2 influenced TAM polarization via the NF-κB pathway. Inhibition of IκBα phosphorylation in cancer cell-conditioned medium-stimulated BMDMs decreased M1 marker expression in Ndrg2−/− macrophages. Finally, in vitro, invasion, migration, and proliferation assays confirmed that NF-κB participated in the tumor suppressor function of Ndrg2−/− macrophages. Collectively, our findings highlight the role of NDRG2 in the regulation of TAM polarization and its function in promoting cancer liver metastasis.

Paracellular barriers play an important role in the pathogenesis of Inflammatory bowel disease (IBD) and maintain gut homeostasis. N-myc downstream-regulated gene 2 (NDRG2) has been reported to be a tumour suppressor gene and to inhibit colorectal cancer metastasis. However, whether NDRG2 affects colitis initiation and colitis-associated colorectal cancer is unclear. Intestine-specific Ndrg2 deficiency mice (Ndrg2ΔIEC) were subjected to DSS- or TNBS-induced colitis, and AOM-DSS-induced colitis-associated tumour. HT29 cells, Caco2 cells, primary intestinal epithelial cells (IECs) from Ndrg2ΔIEC mice, mouse embryo fibroblasts (MEFs) from systemic Ndrg2 knockout mice, HEK293 cells and human UC and DC specimens were used to investigate NDRG2 function in colitis and colitis-associated tumour. Ndrg2 loss led to adherens junction (AJ) structure destruction via E-cadherin expression attenuation, resulting in diminished epithelial barrier function and increased intestinal epithelial permeability. Mechanistically, NDRG2 enhanced the interaction of E3 ligase FBXO11 with Snail, the repressor of E-cadherin, to promote Snail degradation by ubiquitination and maintained E-cadherin expression. In human ulcerative colitis patients, reduced NDRG2 expression is positively correlated with severe inflammation. These findings demonstrate that NDRG2 is an essential colonic epithelial barrier regulator and plays an important role in gut homeostasis maintenance and colitis-associated tumour development. National Natural Science Foundation of China (No. 81770523, 31571437, 81672751), Creative Research Groups of China (No. 81421003), State Key Laboratory of Cancer Biology Project (CBSKL2019ZZ11, CBSKL201406, CBSKL2017Z08 and CBSKL2017Z11), Fund for Distinguished Young Scholars of ShaanXi province (2019JC-22).