Circ_SNX27 regulates hepatocellular carcinoma development via miR-637/FGFR1 axis

Emerging roles of CircRNA-miRNA networks in cancer development and therapeutic response

The complex interplay of epigenetic factors is essential in regulating the hallmarks of cancer and orchestrating intricate molecular interactions during tumor progression. Circular RNAs (circRNAs), known for their covalently closed loop structures, are non-coding RNA molecules exceptionally resistant to enzymatic degradation, which enhances their stability and regulatory functions in cancer. Similarly, microRNAs (miRNAs) are endogenous non-coding RNAs with linear structures that regulate cellular biological processes akin to circRNAs. Both miRNAs and circRNAs exhibit aberrant expressions in various cancers. Notably, circRNAs can function as sponges for miRNAs, influencing their activity. The circRNA/miRNA interaction plays a pivotal role in the regulation of cancer progression, including in brain, gastrointestinal, gynecological, and urological cancers, influencing key processes such as proliferation, apoptosis, invasion, autophagy, epithelial-mesenchymal transition (EMT), and more. Additionally, this interaction impacts the response of tumor cells to radiotherapy and chemotherapy and contributes to immune evasion, a significant challenge in cancer therapy. Both circRNAs and miRNAs hold potential as biomarkers for cancer prognosis and diagnosis. In this review, we delve into the circRNA-miRNA circuit within human cancers, emphasizing their role in regulating cancer hallmarks and treatment responses. This discussion aims to provide insights for future research to better understand their functions and potentially guide targeted treatments for cancer patients using circRNA/miRNA-based strategies.

Circ-EIF3I Promotes Hepatocellular Carcinoma Progression Through Modulating miR-361-3p/DUSP2 Axis

Hepatocellular carcinoma (HCC) is one of the most common malignant cancers globally. Circular RNAs (circRNAs) have been implicated in the development of HCC. Previous studies have confirmed that circ-EIF3I plays an important role in the progress of lung cancer. Nevertheless, the biological functions of circ-EIF3I and the underlying mechanisms by which they regulate HCC progression remain unclear. In this study, the regulatory mechanism and targets were studied with bioinformatics analysis, luciferase reporting analysis, transwell migration, Cell Counting Kit-8, and 5-Ethynyl-2'-deoxyuridine analysis. In addition, in vivo tumorigenesis and metastasis assays were employed to evaluate the roles of circ-EIF3I in HCC. The result shows that the circ-EIF3I expression was increased in HCC cell line, which means that circ-EIF3I plays a role in the progression of HCC. Downregulation of circ-EIF3I suppressed HCC cells' proliferation and migration in both in vivo and in vitro experiments. Bioinformatics and luciferase report analysis confirmed that both miR-361-3p and Dual-specificity phosphatase 2 (DUSP2) were the downstream target of circ-EIF3I. The overexpression of DUSP2 or inhibition of miR-361-3p restored HCC cells' proliferation and migration ability after silence circ-EIF3I. Taken together, our study found that downregulation of circ-EIF3I suppressed the progression of HCC through miR-361-3p/DUSP2 Axis.

A novel intronic circular RNA circFGFR1int2 up-regulates FGFR1 by recruiting transcriptional activators P65/FUS and suppressing miR-4687-5p to promote prostate cancer progression

Fibroblast growth factor receptor 1 (FGFR1) is a core component of the FGFs/FGFR pathway that activates multiple signalling pathways, including ERK1/2, PI3K/AKT, PLCγ, and NF-κB. Aberrant expression of FGFR1 due to gene amplification, chromosome rearrangement, point mutation, and epigenetic deregulations, have been reported in various cancers. FGFR1 overexpression has also been reported in prostate cancer (PCa), but the underlining mechanisms are not clear. Here we report a novel circular RNA, circFGFR1int2, derived from intron 2 of FGFR1 gene, which is overexpressed in PCa and associated with tumor progression. Importantly, we show that circFGFR1int2 facilitates FGFR1 transcription by recruiting transcription activators P65/FUS and by interacting with FGFR1 promoter. Moreover, we show that circFGFR1int2 suppresses post-transcriptional inhibitory effects of miR-4687-5p on FGFR1 mRNA. These mechanisms synergistically promote PCa cell growth, migration, and invasion. Overexpression of circFGFR1int2 is significantly correlated with higher tumor grade, Gleason score, and PSA level, and is a significant unfavorable prognosticator for CRPC-free survival (CFS) (RR = 3.277, 95% confidence interval: 1.192-9.009; P = 0.021). These findings unravelled novel mechanisms controlling FGFR1 gene expression by intronic circRNA and its potential clinicopathological utility as a diagnostic or therapeutic target.

Exosomal ZFPM2-AS1 contributes to tumorigenesis, metastasis, stemness, macrophage polarization, and infiltration in hepatocellular carcinoma through PKM mediated glycolysis

BACKGROUND

With high morbidity and mortality, hepatocellular carcinoma (HCC) deserves further exploration in its pathogenesis mechanisms for promising prognostic and therapeutic markers. This research was conducted to dig out roles of exosomal ZFPM2-AS1 in HCC.

METHODS

The level of exosomal ZFPM2-AS1 in HCC tissue and cells was determined by Real-time fluorescence quantitative PCR. Pull-down assay and dual-luciferase reporter assay were performed to identify interactions between ZFPM2-AS1 and miRNA-18b-5p, as well as miRNA-18b-5p and PKM. Western blotting was employed to explore the potential regulatory mechanism. Several in vitro assays were conducted in mice xenograft and orthotopic transplantation models to investigate impacts of exosomal ZFPM2-AS1 on HCC development, metastasis, and macrophage infiltration.

RESULTS

ZFPM2-AS1 was activated in HCC tissue and cells, with high enrichment in HCC-derived exosomes. Exosomal ZFPM2-AS1 enhances the cell abilities and stemness of HCC. MiRNA-18b-5p was directly targeted by ZFPM2-AS1 which triggered PKM expression via sponging miR-18b-5p. Exosomal ZFPM2-AS1 modulated glycolysis via PKM in an HIF-1α dependent way in HCC, promoting M2 polarization, and macrophage recruitment. Furthermore, exosomal ZFPM2-AS1 enhanced HCC cell growth, metastasis, and M2 infiltration in vivo.

CONCLUSIONS

Exosomal ZFPM2-AS1 exerted regulatory function on the progression of HCC via miR-18b-5p/PKM axis. ZFPM2-AS1 could be promising biomarker for the diagnosis and therapies of HCC.

Splicing factor SNRPA associated with microvascular invasion promotes hepatocellular carcinoma metastasis through activating NOTCH1/Snail pathway and is mediated by circSEC62/miR-625-5p axis

Microvascular invasion (MVI) is a crucial risk factor related to the metastasis of hepatocellular carcinoma (HCC), but the underlying mechanisms remain to be revealed. Characterizing the inherent mechanisms of MVI may aid in the development of effective treatment strategies to improve the prognosis of HCC patients with metastasis. Through the Gene Expression Omnibus (GEO) database, we identified that small nuclear ribonucleoprotein polypeptide A (SNRPA) was related to MVI in HCC. SNRPA was overexpressed in MVI-HCC and correlated with poor patient survival. Mechanistically, SNRPA promoted the epithelial-mesenchymal transition (EMT)-like process for HCC cells to accelerate metastasis by activating the NOTCH1/Snail pathway in vitro and in vivo. Importantly, circSEC62 upregulated SNRPA expression in HCC cells via miR-625-5p sponging. Taking these results together, our study identified a novel regulatory mechanism among SNRPA, miR-625-5p, circSEC62 and the NOTCH1/Snail pathway in HCC, which promoted metastasis of HCC and may provide effective suggestions for improving the prognosis of HCC patients with metastasis.