Construction and identification of lncRNA/circRNA-coregulated ceRNA networks in gemcitabine-resistant bladder carcinoma.

OBJECTIVES: To explore the regulatory networks that underlie the development of chemoresistance in bladder cancer. METHODS: We analyzed profiles of differentially expressed long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), microRNAs (miRNAs) and messenger RNA (mRNAs) in gemcitabine-resistant/sensitive bladder cancer cells using next-generation sequencing data. RESULTS: Hundreds of differentially expressed lncRNAs and miRNAs and thousands of circRNAs and mRNAs were identified. Bioinformatics analysis revealed the chromosomal localizations, classification and coexpression of mRNAs, as well as candidates for cis and trans regulation by lncRNAs. Furthermore, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis of differentially expressed mRNAs and circRNAs indicated important functional roles of coregulated RNAs, thus establishing competing endogenous RNA (ceRNA) and protein-protein interactions networks that may underlie chemoresistance in bladder cancer. We demonstrated that lncRNA LINP1 can act as a ceRNA by inhibiting miR-193a-5p to increase TP73 expression; and that lncRNA ESRG and hsa_circ_0075881 can simultaneously bind miR-324-3p to increase ST6GAL1 expression. Modulation of ceRNA network components using ablation and overexpression approaches contributed to gemcitabine resistance in bladder cancer cells. CONCLUSIONS: These results elucidate mechanisms by which lncRNAs and circRNAs coregulate the development of bladder cancer cell resistance to gemcitabine, thus laying the foundation for future research to identify biomarkers and disease targets.

High-fructose corn syrup aggravates colitis via microbiota dysbiosis-mediated Th17/Treg imbalance.

Dietary fructose is widely used in beverages, processed foods, and Western diets as food additives, and is closely related to the increased prevalence of multiple diseases, including inflammatory bowel disease (IBD). However, the detailed mechanism by which high fructose disrupts intestinal homeostasis remains elusive. The present study showed that high-fructose corn syrup (HFCS) administration exacerbated intestinal inflammation and deteriorated barrier integrity. Several in vivo experimental models were utilized to verify the importance of gut microbiota and immune cells in HFCS-mediated dextran sulfate sodium (DSS)-induced colitis. In addition, untargeted metabolomics analysis revealed the imbalance between primary bile acids (PBAs) and secondary bile acids (SBAs) in feces. Hence, high fructose was speculated to modulate gut microbiota community and reduced the relative abundance of Clostridium and Clostridium scindens at genus and species level respectively, followed by a decrease in SBAs, especially isoalloLCA, thereby affecting Th17/Treg cells equilibrium and promoting intestinal inflammation. These findings provide novel insights into the crosstalk between gut flora, bile acids, and mucosal immunity, and highlight potential strategies for precise treatment of IBD.

Long non-coding RNA BBOX1-AS1 exacerbates esophageal squamous cell carcinoma development by regulating HOXB7/ß-catenin axis.

Mounting evidence suggests that long non-coding RNAs play a critical role in the occurrence and development of human malignancies. Nonetheless, it remains unknown whether Gamma-Butyrobetaine Hydroxylase 1-Antisense RNA 1 (BBOX1-AS1) participates in the regulation of esophageal squamous cell carcinoma (ESCC) carcinogenesis. Herein, we validated that BBOX1-AS1 was notably overexpressed in ESCC tissues compared to the adjacent non-tumor tissues and significantly correlated with tumor sizes. BBOX1-AS1 enhanced the malignant behavior of ESCC cells in vitro, such as cell proliferation, migration, and invasion. In addition, knockdown of BBOX1-AS1 augmented the proportion of apoptotic cells in ESCC cells. Mechanistically, BBOX1-AS1 regulated HOXB7 expression, and rescue experiments indicated that silencing of HOXB7 could abolish the malignant phenotypes mediated by BBOX1-AS1 to a certain extent. Moreover, HOXB7 participated in the activation of the Wnt/ß-catenin signaling pathway. In summary, our findings substantiated that BBOX1-AS1 could activate the Wnt/ß-catenin pathway by upregulating HOXB7 expression to promote ESCC progression, providing a rationale to develop novel therapeutic approaches.

METTL1-mediated tRNA m7G methylation and translational dysfunction restricts breast cancer tumorigenesis by fueling cell cycle blockade.

BACKGROUND: RNA modifications of transfer RNAs (tRNAs) are critical for tRNA function. Growing evidence has revealed that tRNA modifications are related to various disease processes, including malignant tumors. However, the biological functions of methyltransferase-like 1 (METTL1)-regulated m7G tRNA modifications in breast cancer (BC) remain largely obscure. METHODS: The biological role of METTL1 in BC progression were examined by cellular loss- and gain-of-function tests and xenograft models both in vitro and in vivo. To investigate the change of m7G tRNA modification and mRNA translation efficiency in BC, m7G-methylated tRNA immunoprecipitation sequencing (m7G tRNA MeRIP-seq), Ribosome profiling sequencing (Ribo-seq), and polysome-associated mRNA sequencing were performed. Rescue assays were conducted to decipher the underlying molecular mechanisms. RESULTS: The tRNA m7G methyltransferase complex components METTL1 and WD repeat domain 4 (WDR4) were down-regulated in BC tissues at both the mRNA and protein levels. Functionally, METTL1 inhibited BC cell proliferation, and cell cycle progression, relying on its enzymatic activity. Mechanistically, METTL1 increased m7G levels of 19 tRNAs to modulate the translation of growth arrest and DNA damage 45 alpha (GADD45A) and retinoblastoma protein 1 (RB1) in a codon-dependent manner associated with m7G. Furthermore, in vivo experiments showed that overexpression of METTL1 enhanced the anti-tumor effectiveness of abemaciclib, a cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor. CONCLUSION: Our study uncovered the crucial tumor-suppressive role of METTL1-mediated tRNA m7G modification in BC by promoting the translation of GADD45A and RB1 mRNAs, selectively blocking the G2/M phase of the cell cycle. These findings also provided a promising strategy for improving the therapeutic benefits of CDK4/6 inhibitors in the treatment of BC patients.

When N7-methyladenosine modification meets cancer: Emerging frontiers and promising therapeutic opportunities.

N7-methylguanosine (m7G) methylation, one of the most common RNA modifications in eukaryotes, has recently gained considerable attention. The biological functions of m7G modification in RNAs, including tRNA, rRNA, mRNA, and miRNA, remain largely unknown in human diseases. Owing to rapid advances in high-throughput technologies, increasing evidence suggests that m7G modification plays a critical role in cancer initiation and progression. As m7G modification and hallmarks of cancer are inextricably linked together, targeting m7G regulators may provide new possibilities for future cancer diagnoses and potential intervention targets. This review summarizes various detection methods for m7G modification, recent advances in m7G modification and tumor biology regarding their interplay and regulatory mechanisms. We conclude with an outlook on the future of diagnosing and treating m7G-related diseases.

EIF4A3-mediated circ_0042881 activates the RAS pathway via miR-217/SOS1 axis to facilitate breast cancer progression.

Breast cancer (BC) is one of the most frequent cancer-related deaths in women worldwide. Studies have shown the potential impact of circRNAs in multiple human tumorigeneses. Research on the vital signaling pathways and therapeutic targets of circRNAs is indispensable. Here, we aimed to investigate the clinical implications and underlying mechanisms of circ_0042881 in BC. RT-qPCR validated circ_0042881 was notably elevated in BC tissues and plasma, and closely associated with BC clinicopathological features. Functionally, circ_0042881 significantly accelerated the proliferation, migration, and invasion of BC cells in vitro and tumor growth and metastasis in vivo. Mechanistically, circ_0042881 promoted BC progression by sponging miR-217 to relieve its inhibition effect in son of sevenless 1 (SOS1), which further activated RAS protein and initiated downstream signaling cascades, including MEK/ERK pathway and PI3K/AKT pathway. We also demonstrated that treatment of BAY-293, an inhibitor of SOS1 and RAS interaction, attenuated BC progression induced by circ_0042881 overexpression. Furthermore, Eukaryotic initiation factor 4A-III (EIF4A3) could facilitate circ_0042881 circularization. Altogether, we proposed a novel signaling network in which circ_0042881, induced by EIF4A3, influences the process of BC tumorigenesis and metastasis by miR-217/SOS1 axis.

N6-methyladenosine modification of REG1α facilitates colorectal cancer progression via ß-catenin/MYC/LDHA axis mediated glycolytic reprogramming.

Aerobic glycolysis has been considered as a hallmark of colorectal cancer (CRC). However, the potential functional regulators of glycolysis in CRC remains to be elucidated. In the current study, we found that Regenerating islet-derived protein 1-alpha (REG1α) was significantly increased in both CRC tissues and serum, and positively associated with CRC patients' lymph node metastasis, advanced tumor stage, and unfavorable prognosis. Ectopic expression of REG1α contributed to various tumorigenic properties, including cell proliferation, cell cycle, migration, invasion, and glycolysis. In contrast, REG1α deficiency in CRC cells attenuated malignant properties and glucose metabolism. Mechanically, REG1α promoted CRC proliferation and metastasis via ß-catenin/MYC axis-mediated glycolysis upregulation. Moreover, the malignant behaviors governed by REG1α could be effectively abolished by silencing of Wnt/ß-catenin/MYC axis or glycolysis process using specific inhibitors. Besides, REG1α expression was mediated by METTL3 in an m6A-dependent manner. Overall, our work defines a novel regulatory model of the METTL3/REG1α/ß-catenin/MYC axis in CRC, which indicates that REG1α could function as a novel biomarker and a potential therapeutic target for patients with CRC.

Novel insights into m6A modification of coding and non-coding RNAs in tumor biology: From molecular mechanisms to therapeutic significance.

Accumulating evidence has revealed that m6A modification, the predominant RNA modification in eukaryotes, adds a novel layer of regulation to the gene expression. Dynamic and reversible m6A modification implements sophisticated and crucial functions in RNA metabolism, including generation, splicing, stability, and translation in messenger RNAs (mRNAs) and non-coding RNAs (ncRNAs). Furthermore, m6A modification plays a determining role in producing various m6A-labeling RNA outcomes, thereby affecting several functional processes, including tumorigenesis and progression. Herein, we highlighted current advances in m6A modification and the regulatory mechanisms underlying mRNAs and ncRNAs in distinct cancer stages. Meanwhile, we also focused on the therapeutic significance of m6A regulators in clinical cancer treatment.

Current advances and future perspectives on the functional roles and clinical implications of circular RNAs in esophageal squamous cell carcinoma: more influential than expected.

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive gastrointestinal cancers with high incidence and mortality. Therefore, it is necessary to identify novel sensitive and specific biomarkers for ESCC detection and treatment. Circular RNAs (circRNAs) are a type of noncoding RNAs featured by their covalently closed circular structure. This special structure makes circRNAs more stable in mammalian cells, coupled with their great abundance and tissue specificity, suggesting circRNAs may present enormous potential to be explored as valuable prognostic and diagnostic biomarkers for tumor. Mounting studies verified the critical roles of circRNAs in regulating ESCC cells malignant behaviors. Here, we summarized the current progresses in a handful of aberrantly expressed circRNAs, and elucidated their biological function and clinical significance in ESCC, and introduced a series of databases for circRNA research. With the improved advancement in high-throughput sequencing and bioinformatics technique, new frontiers of circRNAs will pave the path for the development of precision treatment in ESCC.

IGF2BP2-induced circRUNX1 facilitates the growth and metastasis of esophageal squamous cell carcinoma through miR-449b-5p/FOXP3 axis.

BACKGROUND: Esophageal squamous cell carcinoma (ESCC) is one of the most common digestive malignancies with relatively high morbidity and mortality. Emerging evidence suggests circular RNAs (circRNAs) play critical roles in tumor cell malignancy. However, the biological function and clinical significance of many circRNAs in ESCC remain elusive. METHODS: The expression level and clinical implication of circRUNX1 in ESCC tissues were evaluated using qRT-PCR. In vitro and in vivo functional studies were conducted to investigate the underlying biological effects of circRUNX1 on ESCC cell growth and metastasis. Moreover, bioinformatics analysis, RNA sequencing (RNA-seq), RNA immunoprecipitation (RIP) assays, dual-luciferase reporter assays, and rescue experiments were performed to explore the relationships between circRUNX1, miR-449b-5p, Forkhead box protein P3 (FOXP3), and insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). RESULTS: CircRUNX1 was found to be significantly up-regulated in ESCC tissues and associated with TNM stage and differentiation grade. Functionally, circRUNX1 promoted ESCC cell proliferation and metastasis in vitro and in vivo. CircRUNX1 enhanced FOXP3 expression by competitively sponging miR-449b-5p. Notably, both miR-449b-5p mimics and FOXP3 knockdown restored the effects of circRUNX1 overexpression on cell proliferation and metastasis. Furthermore, IGF2BP2 binding to circRUNX1 prevented its degradation. CONCLUSIONS: IGF2BP2 mediated circRUNX1 functions as an oncogenic factor to facilitate ESCC progression through the miR-449b-5p/FOXP3 axis, implying that circRUNX1 has the potential to be a promising diagnostic marker and therapeutic target for ESCC patients.