Emerging landscape of circFNDC3B and its role in human malignancies

Prospects for the clinical application of exosomal circular RNA in squamous cell carcinoma

Squamous cell carcinoma (SCC) is a prevalent malignancy affecting multiple organs in the human body, including the oral cavity, esophagus, cervix, and skin. Given its significant incidence and mortality rates, researchers are actively seeking effective diagnostic and therapeutic strategies. In recent years, exosomes and their molecular cargo, particularly circular RNA (circRNA), have emerged as promising areas of investigation in SCC research. Exosomes are small vesicles released into the extracellular environment by cells that contain biomolecules that reflect the physiological state of the cell of origin. CircRNAs, known for their unique covalently closed loop structure and stability, have garnered special attention in oncology and are closely associated with tumorigenesis, progression, metastasis, and drug resistance. Interestingly, exosomal circRNAs have been identified as ideal biomarkers for noninvasive cancer diagnosis and prognosis assessment. This article reviews the progress in research on exosomal circRNAs, focusing on their expression patterns, functions, and potential applications as biomarkers in SCC, aiming to provide new insights and strategies for the diagnosis and treatment of SCC.

A novel protein FNDC3B-267aa encoded by circ0003692 inhibits gastric cancer metastasis via promoting proteasomal degradation of c-Myc

BACKGROUND

Gastric cancer (GC) ranks fifth in global cancer incidence and third in mortality rate among all cancer types. Circular RNAs (circRNAs) have been extensively demonstrated to regulate multiple malignant biological behaviors in GC. Emerging evidence suggests that several circRNAs derived from FNDC3B play pivotal roles in cancer. However, the role of circFNDC3B in GC remains elusive.

METHODS

We initially screened circFNDC3B with translation potential via bioinformatics algorithm prediction. Subsequently, Sanger sequencing, qRT-PCR, RNase R, RNA-FISH and nuclear-cytoplasmic fractionation assays were explored to assess the identification and localization of circ0003692, a circRNA derived from FNDC3B. qRT-PCR and ISH were performed to quantify expression of circ0003692 in human GC tissues and adjacent normal tissues. The protein-encoding ability of circ0003692 was investigated through dual-luciferase reporter assay and LC/MS. The biological behavior of circ0003692 in GC was confirmed via in vivo and in vitro experiments. Additionally, Co-IP and rescue experiments were performed to elucidate the interaction between the encoded protein and c-Myc.

RESULTS

We found that circ0003692 was significantly downregulated in GC tissues. Circ0003692 had the potential to encode a novel protein FNDC3B-267aa, which was downregulated in GC cells. We verified that FNDC3B-267aa, rather than circ0003692, inhibited GC migration in vitro and in vivo. Mechanistically, FNDC3B-267aa directly interacted with c-Myc and promoted proteasomal degradation of c-Myc, resulting in the downregulation of c-Myc-Snail/Slug axis.

CONCLUSIONS

Our study revealed that the novel protein FNDC3B-267aa encoded by circ0003692 suppressed GC metastasis through binding to c-Myc and enhancing proteasome-mediated degradation of c-Myc. The study offers the potential applications of circ0003692 or FNDC3B-267aa as therapeutic targets for GC.

Emerging roles of circular RNAs in tumorigenesis, progression, and treatment of gastric cancer

With an estimated one million new cases reported annually, gastric cancer (GC) ranks as the fifth most diagnosed malignancy worldwide. The early detection of GC remains a major challenge, and the prognosis worsens either when patients develop resistance to chemotherapy or radiotherapy or when the cancer metastasizes. The precise pathogenesis underlying GC is not well understood, which further complicates its treatment. Circular RNAs (circRNAs), a recently discovered class of noncoding RNAs that originate from parental genes through "back-splicing", have been shown to play a key role in various biological processes in both eukaryotes and prokaryotes. CircRNAs have been linked to cardiovascular diseases, diabetes, hypertension, Alzheimer's disease, and the occurrence and progression of tumors. Prior studies have established that circRNAs play a crucial role in GC, impacting tumorigenesis, diagnosis, progression, and therapy resistance. This review aims to summarize how circRNAs contribute to GC tumorigenesis and progression, examine their roles in the development of drug resistance, discuss their potential as biotechnological drugs, and summarize their response to therapeutic drugs and microorganism in GC.

Identification of miRNA, lncRNA and circRNA associated with gastric cancer metabolism through sequencing and bioinformatics analysis

Gastric cancer remains a highly prevalent malignancy worldwide with its molecular features poorly understood. To gain full insight into its genetic landscape, we performed whole-transcriptome sequencing on human tumors and adjacent non-tumors to predict the function of microRNA, long coding RNA, circular RNA, and mRNA, as well as estimate their correlation with gastric cancer characteristics through construction of ceRNA, WGCNA and PPI network. Functional enrichment analysis annotated nucleic acid binding, enzyme activity and binding related to differentially expressed miRNAs (dif-miRNAs); energy binding and enzyme binding related to dif-lncRNAs; protein binding and enzyme activity related to dif-circRNAs; protein digestion and absorption related to dif-mRNAs. The expression of key miR-135a-5p, lncRNAs-MSTRG.48856.1, ENST00000569981, MSTRG.22826.1, ENST00000564492, circRNAs-CCSER2, FNDC3B, CORO1C, FAM214A were validated by real-time PCR. The ceRNA network filtered 14 miRNAs, 30 lncRNAs, and 6 mRNA in the lncRNA-ceRNA axis and 8 miRNAs, 9 circRNAs, and 3 mRNA in the circRNA-ceRNA axis. Genes involved in ceRNA were annotated to be closely related to tumor material synthesis and metabolism. The WGCNA network filtered gene clusters related to TNM traits and extracted the hub genes CLDN10, CD177, newGene_35523, newGene_51201, CEACAM7, and newGene_46634. These genes were associated with cell proliferation, metabolism, and enzyme activity regulation. The PPI network analyzed the stable interaction relationships of the hub genes. Our research provides a valuable resource for understanding the molecular mechanisms of gastric cancer from the perspective of tumor metabolism.