Regulatory mechanism and promising clinical application of exosomal circular RNA in gastric cancer

Hsa_circ_0008667 promotes progression and improves the prognosis of gastric cancer by inhibiting miR-9-5p

BACKGROUND AND STUDY AIM

Gastric cancer (GC) is one of the most common gastrointestinal tumors characterized by aggressive development and poor prognosis. Circular RNAs (circRNAs) have been used as prognostic biomarkers and therapeutic targets in many cancers, including GC. Hsa_circ_0008667 is differentially expressed in GC; however, its function and clinical significance remained unelucidated. Therefore, this study aimed to investigate the role and significance of hsa_circ_0008667 in GC and its potential as a biomarker and therapeutic target of GC.

PATIENTS AND METHODS

Through quantitative reverse-transcription real-time PCR, hsa_circ_0008667 expression in GC tissues and cells were analyzed, followed by statistical analyses to assess the clinical significance. Cell Counting Kit-8 and Transwell assays were performed to examine the effects of hsa_circ_0008667 silencing on GC cell growth and metastasis. Additionally, correlation analysis was performed to assess the relationship between hsa_circ_0008667 and miR-9-5p, which was further validated through luciferase reporter assay.

RESULTS

Hsa_circ_0008667 was considerably upregulated and tightly correlated with lymph node metastasis and the tumor-node-metastasis stage, which was predictive of poor prognosis in patients with GC. Hsa_circ_0008667 silencing suppressed GC cell proliferation, migration, and invasion. Furthermore, hsa_circ_0008667 negatively regulated miR-9-5p expression. MiR-9-5p downregulation enhanced GC malignancy and reversed hsa_circ_0008667 knockdown-mediated GC suppression.

CONCLUSION

The findings of this study suggest hsa_circ_0008667 to be a prognostic biomarker and tumor promoter of GC via miR-9-5p modulation.

Circular RNA in cancer

Over the past decade, circular RNA (circRNA) research has evolved into a bona fide research field shedding light on the functional consequence of this unique family of RNA molecules in cancer. Although the method of formation and the abundance of circRNAs can differ from their cognate linear mRNA, the spectrum of interacting partners and their resultant cellular functions in oncogenesis are analogous. However, with 10 times more diversity in circRNA variants compared with linear RNA variants, combined with their hyperstability in the cell, circRNAs are equipped to influence every stage of oncogenesis. This is an opportune time to address the breadth of circRNA in cancer focused on their spatiotemporal expression, mutations in biogenesis factors and contemporary functions through each stage of cancer. In this Review, we highlight examples of functional circRNAs in specific cancers, which satisfy critical criteria, including their physical co-association with the target and circRNA abundance at stoichiometrically valid quantities. These considerations are essential to develop strategies for the therapeutic exploitation of circRNAs as biomarkers and targeted anticancer agents.

The Importance of Extracellular Vesicle Screening in Gastric Cancer: A 2024 Update

Extracellular vesicles, or EVs, are membrane-bound nanocompartments produced by tumor cells. EVs carry proteins and nucleic acids from host cells to target cells, where they can transfer lipids, proteomes, and genetic material to change the function of target cells. EVs serve as reservoirs for mobile cellular signals. The collection of EVs using less invasive processes has piqued the interest of many researchers. Exosomes carry substances that can suppress the immune system. If the results of exosome screening are negative, immunotherapy will be beneficial for GC patients. In this study, we provide an update on EVs and GC based on ongoing review papers and clinical trials.

Exosomal circ50547 as a potential marker and promotor of gastric cancer progression via miR-217/HNF1B axis

BACKGROUND

Exosomes, one of small extracellular vesicles, play a vital role in cell to cell communication and contribute to the advancement of tumors through their cargo molecules. Exosomal circRNAs have emerged as significant players in various types of tumors. Thus, this study aimed to investigate how exosomal circRNAs are involved in the diagnosis and progression of gastric cancer (GC).

METHODS

Serum exosomes were characterized using transmission electron microscopy, nanoparticle tracking analysis and Western blot. CCK-8, colony formation and transwell assays were conducted to study the function of hsa_circ_0050547 (named as circ50547). qRT-PCR was used to quantify the expression of circ50547 in GC tissues and serum exosomes. Fluorescence in situ hybridization was applied to detect the cellular distribution of circ50547. Stemness and drug-resistance were detected by sphere formation, WB, flow cytometry and half-maximal inhibitory concentration analyses. Bioinformatic analyses, luciferase experiments, qRT-PCR and WB were used to investigate molecular mechanisms.

RESULTS

We discovered for the first time a new type of GC-derived exosomal circRNA, circ50547. We found that circ50547 is highly expressed in both GC tissues and serum exosomes. Interestingly, we observed that the diagnostic value of exosomal circ50547 is superior to that of serum circ50547. Circ50547 overexpression enhanced the proliferation, migration, invasion, stemness and drug resistance of GC cells, while knockdown of circ50547 showed the opposite effect. Mechanistically, circ50547 acted as a sponge for miR-217 to regulate the expression of HNF1B, which promoted gastric cancer progression.

CONCLUSION

Exosomal circ50547 may be a promising marker for the diagnosis and prognosis prediction of GC. These findings suggest that it plays an oncogenic role through miR-217/HNF1B signaling pathway in GC.

Circular RNA Circ_0000119 promotes gastric cancer progression via circ_0000119/miR-502-5p/MTBP axis

Dysregulated circular RNAs (circRNAs) are significantly related with tumor initiation and progression. However, biological activity and potential molecular mechanism of circRNAs in gastric cancer (GC) deserve further exploration. We carried out total RNA sequencing and acquired the expression profiles of circRNAs. Quantitative real-time PCR as well as RNA in situ hybridization helped to validate circ_0000119 dysregulation. Various in vitro experiments were utilized to investigate the biological activities of circ_0000119 in GC, and the clinical relation of circ_0000119 in vivo was identified through nude mouse xenograft models. Finally, the molecular mechanism of circ_0000119 was clarified via luciferase assays, western blot, and rescue experiments. Compared with adjacent normal tissues, the study found an increase in the expression of circ_0000119 as well as its host linear gene MAN1A2 in GC tissues. Circ_0000119 overexpression promoted proliferation and migration of GC cells in vitro and in vivo, whereas circ_0000119 suppression had the opposite effect. Mechanistically, circ_0000119 sponged miR-502-5p which played an inhibitory role in tumors. Furthermore, we found that miR-502-5p alleviated GC progression through targeting MTBP and downregulating its expression at mRNA and protein levels. In conclusion, our findings reveal a new regulatory mechanism for circ_0000119, which sponges the miR-502-5p, suppresses MTBP expression, and finally promotes GC progression.