Hsa_circRNA_000166 Promotes Cell Proliferation, Migration and Invasion by Regulating miR-330-5p/ELK1 in Colon Cancer

Hsa_circ_0101050 accelerates the progression of Colon cancer by targeting the miR-140-3 p/MELK axis

BACKGROUND

Circular RNAs (circRNAs) are involved in the progression of colon cancer (CC). This study aimed to examine the role of a new circRNA circ_0101050 in CC.

METHODS

Dual-luciferase reporter and RNA immunoprecipitation analyses were performed to validate the target relationships among maternal embryonic leucine zipper kinase (MELK), microRNA (miR)-140-3 p, and circ_0101050. Expression levels were calculated using western blotting and/or quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Western blotting was performed to evaluate the relative expression of Bcl-2 and Bax proteins to determine cell death. Cell Counting Kit-8 (CCK-8) and colony formation assays were performed to determine the proliferative potential of CC cells. The migration rate of CC cells was evaluated using wound healing assays. Tumor formation tests were performed to determine the effect of circ_0101050 on tumor development in vivo.

RESULTS

Elevated levels of circ_0101050 and MELK were observed in CC. By inhibiting circ 0,101,050 or MELK, CC cell proliferation and migration were inhibited, but CC cell apoptosis was promoted. Silencing circ_0101050 also inhibited CC growth in vivo. We also found that miR-140-3 p was downregulated, which alleviated the repressive effects of circ_0101050 knockdown on proliferating and migrating CC cells, as well as the stimulating effect on apoptosis. In addition, the absence of MELK alleviated the effects of miR-140-3 p downregulation, which enhanced CC cell malignancy.

CONCLUSIONS

Circ_0101050 exacerbates malignant phenotypes in CC by targeting the miR-140-3 p/MELK axis. These findings suggested that the circ_0101050/miR-140-3 p/MELK network may be a prospective target for CC treatment.

LncRNA AGAP2 antisense RNA 1 stabilized by insulin-like growth factor 2 mRNA binding protein 3 promotes macrophage M2 polarization in clear cell renal cell carcinoma through regulation of the microRNA-9-5p/THBS2/PI3K-Akt pathway

BACKGROUND

Increasing evidence highlights the potential role of long non-coding RNAs (lncRNAs) in the biological behaviors of renal cell carcinoma (RCC). Here, we explored the mechanism of AGAP2-AS1 in the occurrence and development of clear cell RCC (ccRCC) involving IGF2BP3/miR-9-5p/THBS2.

METHODS

The expressions of AGAP2-AS1, IGF2BP3, miR-9-5p, and THBS2 and their relationship were analyzed by bioinformatics. The targeting relationship between AGAP2-AS1 and miR-9-5p and between miR-9-5p and THBS2 was evaluated with their effect on cell biological behaviors and macrophage polarization assayed. Finally, we tested the effect of AGAP2-AS1 on ccRCC tumor formation in xenograft tumors.

RESULTS

IGF2BP3 could stabilize AGAP2-AS1 through m6A modification. AGAP2-AS1 was highly expressed in ccRCC tissues and cells. The lentivirus-mediated intervention of AGAP2-AS1 induced malignant behaviors of ccRCC cells and led to M2 polarization of macrophages. In addition, THBS2 promoted M2 polarization of macrophages by activating the PI3K/AKT signaling pathway. AGAP2-AS1 could directly bind with miR-9-5p and promote the expression of THBS2 downstream of miR-9-5p. These results were further verified by in vivo experiments.

CONCLUSION

AGAP2-AS1 stabilized by IGF2BP3 competitively binds to miR-9-5p to up-regulate THBS2, activating the PI3K/AKT signaling pathway and inducing macrophage M2 polarization, thus facilitating the development of RCC.

CircSHKBP1 regulates colon cancer cell proliferation and apoptosis by targeting miR-125a-5p

BACKGROUND

Colon cancer is a common malignant tumor in clinical practice. It has been reported that circular RNAs (circRNAs) are involved in the occurrence and development of cancer. Among them, circSHKBP1 acts as an oncogene to promote cancer progression. Thus, we hypothesized that circSHKBP1 might be also implicated in the development of colon cancer.

AIM

To explore the role of circSHKBP1 in colon cancer cell proliferation and apoptosis and the possible mechanism involved.

METHODS

Sixty-nine cancer tissues and matched adjacent normal tissues were selected from March 2020 to July 2020 at our hospital. The expression of circSHKBP1 and miR-125a-5p was detected by qRT-PCR. Human colon cancer cells (HT29) cultured in vitro were randomly divided into sh-NC group, sh-circSHKBP1 group, miR-NC group, miR-125a-5p group, sh-circSHKBP1 + anti-miR-NC group, and sh-circSHKBP1 + anti-miR-125a-5p group. MTT assay, colony formation experiment, and flow cytometry were used to detect cell proliferation, colony formation, and apoptosis, respectively. The dual luciferase reporter experiment was used to detect the impact of miR-125a-5p overexpression on the luciferase activity of the wild-type vector wt-circSHKBP1. Western blot was used to detect the protein expression of Bax and Bcl-2.

RESULTS

Compared with adjacent tissues, the expression of circSHKBP1 in colon cancer tissues was increased (P < 0.05), while the expression of miR-125a-5p was decreased (P < 0.05). Cell proliferation inhibition rate, apoptosis rate, and Bax protein level in the sh-circSHKBP1 group were increased (P < 0.05), while the number of cell colonies (P < 0.05) and Bcl-2 protein level were decreased (P < 0.05). Overexpression of miR-125a-5p could reduce the luciferase activity of wt-circSHKBP1 (P < 0.05). Relative to the miR-NC group, miR-125a-5p reduced cell proliferation, increased apoptosis rate and Bax protein level (P < 0.05), decreased the number of cell colonies (P < 0.05), and reduced Bcl-2 protein level (P < 0.05). Compared with the sh-circSHKBP1 + anti-miR-NC group, cell proliferation inhibition rate, apoptosis, and the protein level of Bax in the sh-circSHKBP1 + anti-miR-125a-5p group were decreased (P < 0.05), while the number of cell colonies and Bcl-2 protein level were increased (P < 0.05).

CONCLUSION

Knockdown of circSHKBP1 could inhibit colon cancer cell proliferation and promote apoptosis via up-regulating miR-125a-5p expression.

circ-0000512 inhibits PD-L1 ubiquitination through sponging miR-622/CMTM6 axis to promote triple-negative breast cancer and immune escape

BACKGROUND

This study reported the function and mechanism of circ-0000512 in the progression of triple-negative breast cancer (TNBC).

METHODS

circ-0000512 expression in TNBC tissues and paired adjacent normal tissues and cells was examined by qRT-PCR. Moreover, circ-0000512 expression in TNBC cells was modulated by transfection. Thereafter, colony formation assay, Transwell assay and flow cytometry were conducted to observe cell proliferation, migration and apoptosis. TNBC cells were treated with cycloheximide and the protease inhibitor MG132. Later, ubiquitination assay was performed to detect programmed cell death ligand 1 (PD-L1) ubiquitination in TNBC cells. The T cell killing ability was assessed by the T cell-mediated tumor cell killing assay. IFNγ and IL-2 levels were detected by ELISA. The percentage of activated T cells was detected with a flow cytometer. In addition, dual luciferase reporter gene assay and RNA immunoprecipitation assay were carried out to evaluate the binding between two genes. In vivo study was conducted on mice. CD8+ T cells in xenograft tumors were detected by immunohistochemistry.

RESULTS

circ-0000512 was upregulated in patients with TNBC. circ-0000512 knockdown attenuated the proliferation and migration of TNBC cells and enhanced their apoptosis. circ-0000512 overexpression had opposite effects. circ-0000512 knockdown enhanced the PD-L1 protein ubiquitination in TNBC cells by inhibiting CMTM6. Meanwhile, circ-0000512 promoted CMTM6 expression by sponging miR-622. circ-0000512 knockdown increased the ratio of CD8+T cells and the lethality of T cells against TNBC cells. Besides, circ-0000512 knockdown inhibited the growth of TNBC cells in immunodeficient nude mice and normal immune mice and increased the ratio of CD8+T cells in xenograft tumors of normal immune mice.

CONCLUSIONS

circ-0000512 inhibited PD-L1 ubiquitination by sponging the miR-622/CMTM6 axis, thus promoting TNBC progression and immune escape.

CircRNA RNA hsa_circ_0008234 Promotes Colon Cancer Progression by Regulating the miR-338-3p/ETS1 Axis and PI3K/AKT/mTOR Signaling

Circular RNAs (circRNAs) have been shown to play a crucial role in cancer occurrence and progression. This present work investigated the link between hsa_circ_0008234 and colon cancer. Data retrieved from GSE172229 was used to compare the circRNA profiles of colon cancer and surrounding non-tumorous tissues. The amount of RNA and protein in the molecules was determined using quantitative real-time PCR (qRT-PCR) and Western blot analysis, respectively. The cell proliferation ability was assessed using CCK8, EdU, colon formation, and nude mice tumorigenesis tests. Cell invasion and migration abilities were evaluated using transwell wound healing and mice lung metastasis model. Hsa_circ_0008234 piqued our interest because bioinformatics and qRT-PCR analyses revealed that it is upregulated in colon cancer tissue. Cell phenotypic studies suggest that hsa_circ_0008234 may significantly increase colon cancer cell aggressiveness. Mice experiments revealed that inhibiting hsa_circ_0008234 significantly reduced tumor growth and metastasis. Moreover, the fluorescence in situ hybridization experiment demonstrated that hsa_circ_0008234 is primarily found in the cytoplasm, implying that it potentially functions via a competitive endogenous RNA pathway. These findings indicated that hsa_circ_0008234 may act as a “molecular sponge” for miR-338-3p, increasing the expression of miR-338-target 3p’s ETS1. In addition, the traditional oncogenic pathway PI3K/AKT/mTOR signaling was found to be the potential downstream pathway of the hsa_circ_0008234/miR-338-3p/ETS1 axis. In conclusion, hsa_circ_0008234 increases colon cancer proliferation, infiltration, and migration via the miR-338-3p/ETS1/PI3K/AKT axis; therefore, it could serve as a target and a focus for colon cancer therapy.

Circ_0000467 Exerts an Oncogenic Role in Colorectal Cancer via miR-330-5p-Dependent Regulation of TYRO3

Colorectal cancer (CRC) remains one of the most frequent neoplasms of digestive tract worldwide. Circular RNAs (circRNAs) have been identified to serve crucial regulatory roles in the pathogenesis of human cancers. However, the role and regulatory mechanism of circ_0000467 in the progression of CRC are still unclear. The expression levels of circ_0000467, microRNA-330-5p (miR-330-5p), and tyrosine receptor kinase 3 (TYRO3) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The interaction between miR-330-5p and circ_0000467 or TYRO3 was validated by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Xenograft tumor assay and Immunohistochemistry (IHC) assay were implemented to analyze CRC tumor growth in vivo. Circ_0000467 was a stable circRNA and was highly expressed in CRC tumor tissues and cells. Silencing of circ_0000467 could inhibit the proliferation, migration, invasion, and glycolysis and accelerated the apoptosis of CRC cells in vitro and hindered tumor growth in vivo. Mechanistically, circ_0000467 directly interacted with miR-330-5p and circ_0000467 depletion inhibited CRC cell malignant progression by regulating miR-330-5p. Furthermore, TYRO3 was a target of miR-330-5p and circ_0000467 upregulated TYRO3 expression by sponging miR-330-5p. Moreover, TYRO3 overexpression counteracted the inhibitory effect of miR-330-5p overexpression or circ_0000467 knockdown on CRC cell progression. Altogether, circ_0000467 knockdown suppressed CRC cell malignant development through modulating the miR-330-5p/TYRO3 network, providing a novel molecular target of CRC therapy.

Circ_0058063 promotes progression of thyroid cancer by sponging miR-330-3p/SDC4 axis

Circular RNA takes a crucial part in carcinogenesis. Circ_0058063 has been found to act as an oncogene in esophageal cancer and bladder cancer, but its role in thyroid cancer (TC) is still under investigation. Therefore, we carried out a study to understand its role in TC and its association with miR-330-3p. The circ_0058063 and miR-330-3p in TC tissues and cells were quantified by quantitative reverse transcription PCR, and cell counting kit-8 and scratch adhesion test were conducted for evaluation of cell proliferation and migration. In addition, a dual luciferase reporter assay and RNA immunoprecipitation assay were conducted for interaction analysis between circ_0058063 and miR-330-3p. Circ_0058063 was upregulated in TC tissues and cells, but miR-330-3p expression showed an opposite trend. Both silencing circ_0058063 and upregulating miR-330-3p can suppress the proliferation and migration of TC cells, upregulate Bax, and downregulate Bcl-2. In addition, circ_0058063 is able to target miR-330-3p that is also able to target syndecan 4 (SDC4). circ_0058063 can act as a carcinogen in cases with TC via the miR-330-3p/SDC4 axis.

Long Noncoding RNA HAGLROS Promotes the Malignant Progression of Bladder Cancer by Regulating the miR-330-5p/SPRR1B Axis

Bladder cancer (BC) is the most common genitourinary malignancy worldwide, and its aetiology and pathogenesis remain unclear. Accumulating evidence has shown that HAGLROS is closely related to the occurrence and progression of various cancers. However, the biological functions and underlying mechanisms of HAGLROS in BC remain unknown. In the present study, the expression of HAGLROS in BC was determined by public dataset analysis, transcriptome sequencing analysis, qRT–PCR and ISH assays. Gain- or loss-of-function assays were performed to study the biological roles of HAGLROS in BC cells and nude mouse xenograft model. Bioinformatic analysis, qRT–PCR, western blot, immunohistochemistry, FISH assays, subcellular fractionation assays and luciferase reporter assays were performed to explore the underlying molecular mechanisms of HAGLROS in BC. Here, we found that HAGLROS expression is significantly upregulated in BC tissues and cells, and elevated HAGLROS expression was related to higher pathologic grade and advanced clinical stage, which is significant for BC diagnosis. HAGLROS can enhance the growth and metastasis of BC in vitro and in vivo. Furthermore, miR-330-5p downregulation reversed the BC cells proliferation, migration and invasion inhibited by silencing HAGLROS. SPRR1B silencing restored the malignant phenotypes of BC cells promoted by miR-330--5p inhibitor. Mechanistically, we found that HAGLROS functions as a microRNA sponge to positively regulate SPRR1B expression by sponging miR-330-5p. Together, these results demonstrate that HAGLROS plays an oncogenic role and may serve as a potential biomarker for the diagnosis and treatment of BC.

circ_000166/miR-296 Aggravates the Process of Diabetic Renal Fibrosis by Regulating the SGLT2 Signaling Pathway in Renal Tubular Epithelial Cells

Diabetic renal fibrosis is a common cause of end-stage renal disease, and the circRNA-miRNA-mRNA network may play an important role in the progression of diabetic nephropathy- (DN-) induced renal fibrosis. In this study, the role of circ_000166/miR-296/SGLT2 in the process of DN-related renal fibrosis was studied by constructing an animal model of DN renal fibrosis via lentiviral transfection, plasmid transfection, and dual-luciferase reporting techniques. Compared with that of normal controls, the expression of circ_000166 in the kidney tissues of DN renal fibrosis mice substantially increased. Silencing circ_000166 could minimize kidney damage and decrease urine protein levels, thereby inhibiting the progression of renal fibrosis. Moreover, circ_000166 could act as the ceRNA of miR-296 and competitively bind to miR-296, leading to an increase in the expression of the SGLT2 gene regulated by miR-296. Through mutual verification via in vivo and in vitro experiments, miR-296 was overexpressed and SGLT2 was silenced. Results showed that DN renal fibrosis and cell apoptosis were considerably reduced. We postulate that circ_000166/miR-296/SGLT2 may become a new target in the progression of DN renal fibrosis, and the regulation of this pathway may be a promising strategy for clinical treatment of DN renal fibrosis.

Circ_RPPH1 regulates glioma cell malignancy by binding to miR-627-5p/miR-663a to induce SDC1 expression

BACKGROUND

Recent studies revealed the key role of circular RNA (circRNA) in glioma progression. However, the effect of circ_0000520, also named as circRNA ribonuclease P RNA component H1 (circ_RPPH1), in glioma development was unknown. The study aimed to reveal the role of circ_RPPH1 in glioma cell malignancy.

METHODS

Human astrocytes (NHA) and glioma cell lines (A172 and U251) were employed in this study. Quantitative real-time polymerase chain reaction and western blot were used to check the expression of circ_RPPH1, microRNA-627-5p (miR-627-5p), miR-663a and syndecan 1 (SDC1). Immunohistochemistry assay was conducted to assess the protein expression of nuclear proliferation marker ki67 and matrix metalloprotein 9 (MMP9). Cell viability was assessed by 3-(4,5-Dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation and apoptosis were investigated by flow cytometry analysis, 5-Ethynyl-29-deoxyuridine, or cell colony formation assay. Cell migration and invasion were evaluated by transwell assays. The interaction between miRNAs (miR-627-5p and miR-663a) and circ_RPPH1 or SDC1 was identified by a dual-luciferase reporter assay. A mouse model assay was performed to reveal the impact of circ_RPPH1 knockdown on glioma cell malignancy in vivo by analyzing neoplasm volume and weight.

RESULTS

Circ_RPPH1 and SDC1 expression were significantly increased, whereas miR-627-5p and miR-663a expression were decreased in glioma tissues and cells in comparison with healthy brain tissues or human astrocytes. Circ_RPPH1 depletion led to the decreased cell proliferation, migration and invasion, and the increased cell apoptosis. Additionally, circ_RPPH1 bound to miR-627-5p/miR-663a and mediated glioma cell processes by interacting with them. SDC1 overexpression attenuated miR-627-5p/miR-663a-mediated actions. Moreover, circ_RPPH1 regulated SDC1 expression through interaction with miR-627-5p and/or miR-663a. Furthermore, circ_RPPH1 knockdown inhibited glioma cell malignancy in vivo, accompanied by the decreases of ki67 and MMP9 expression.

CONCLUSION

Circ_RPPH1 knockdown inhibited glioma tumorigenesis by downregulating SDC1 by binding to miR-627-5p/miR-663a, showing that circ_RPPH1 might be an effective therapeutic target for glioma.

Role of hsa_circ_0066966 in proliferation and migration of hepatitis B virus-related liver cancer cells

A large proportion of liver cancer cases is caused by hepatitis B virus (HBV) infection. In recent years, an increasing number of reports have indicated that circular RNAs (circRNAs) exert regulatory effects in cancer development, whereas the role of circRNAs in HBV-positive liver cancer requires further investigation. In the present study, abnormally expressed circRNAs were identified in HBV-positive liver cancer cells through microarray analysis. A total of 1,493 differentially expressed circRNAs [absolute fold-change (FC) ≥2] in HBV-positive liver cancer cells were detected, of which 171 were upregulated and 1,322 were downregulated. Subsequently, Gene Ontology enrichment analysis indicated that the genes of dysregulated circRNAs were mainly involved in regulating Sertoli cell differentiation and development, as well as telomeric DNA binding. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that most of these genes were enriched in cancer-related signaling pathways, including the MAPK and Hippo signaling pathways. Next, the expression levels of the top-10 dysregulated circRNAs were verified in HBV-positive liver cancer cells through reverse transcription-quantitative PCR. Among them, hsa_circ_0066966 had the highest absolute Log₂FC value and was abnormally increased in HBV-positive liver cancer cells. Functional experiments further verified that knockdown of hsa_circ_0066966 had a significant inhibitory effect on the proliferation and migration of HBV-positive liver cancer cells. By contrast, overexpression of hsa_circ_0066966 in HBV-negative liver cancer cells resulted in the opposite effect. In conclusion, in the present study, comprehensive circRNA profiling in HBV-positive liver cancer cells indicated that hsa_circ_0066966 may regulate the progression of HBV-positive liver cancer.

Dysregulated expression and functions of microRNA-330 in cancers: A potential therapeutic target

As small non-coding RNAs, MicroRNAs (miRNAs) bind to the 3' untranslated region (3'-UTR) of mRNA targets to control gene transcription and translation. The gene of miR-330 has two miRNA products, including miR-330-3p and miR-330-5p, which exhibit anti-tumorigenesis and/or pro-tumorigenesis effects in many kinds of malignancies. In cancers, miR-330-3p and miR-330-5p aberrant expression can influence many malignancy-related processes such as cell proliferation, migration, invasion, apoptosis and epithelial-mesenchymal transition, as well as angiogenesis and responsiveness to treatment. In many cancer types (such as lung, prostate, gastric, breast, bladder, ovarian, colorectal, and pancreatic cancer, and osteosarcoma), miR-330-5p acts as an anti-tumor agent. These cancers have low levels of miR-330-5p that leads to the upregulation of the tumor promotor target genes leading to tumor progression. Here, overexpression of miR-330-5p using miRNA inducers can prevent tumor development. Dual roles of miR-330-5p have been also indicated in the thyroid, liver and cervical cancers. Moreover, miR-330-3p exhibits pro-tumorigenesis effects in lung cancer, pancreatic cancer, osteosarcoma, bladder cancer, and cervical cancer. Here, downregulation of miR-330-3p using miRNA inhibitors can prevent tumor development. Demonstrated in breast and liver cancers, miR-330-3p also has dual roles. Importantly, the activities of miR-330-3p and/or miR-330-5p are regulated by upstream regulators long non-coding RNAs (lncRNAs), including circular and linear lncRNAs. This review comprehensively explained miR-330-3p and miR-330-5p role in development of cancers, while highlighting their downstream target genes and upstream regulators as well as possible therapeutic strategies.

The Dual Role of Circular RNAs as miRNA Sponges in Breast Cancer and Colon Cancer

Breast cancer (BC) and colon cancer (CRC) are the two most deadly cancers in the world. These cancers partly share the same genetic background and are partially regulated by the same genes. The outcomes of traditional chemoradiotherapy and surgery remain suboptimal, with high postoperative recurrence and a low survival rate. It is, therefore, urgent to innovate and improve the existing treatment measures. Many studies primarily reported that the microRNA (miRNA) sponge functions of circular RNA (circRNA) in BC and CRC have an indirect relationship between the circRNA–miRNA axis and malignant behaviors. With a covalent ring structure, circRNAs can regulate the expression of target genes in multiple ways, especially by acting as miRNA sponges. Therefore, this review mainly focuses on the roles of circRNAs as miRNA sponges in BC and CRC based on studies over the last three years, thus providing a theoretical reference for finding new therapeutic targets in the future.

A novel circular RNA circPPFIA1 promotes laryngeal squamous cell carcinoma progression through sponging miR-340-3p and regulating ELK1 expression

Abnormal expression of circular RNA (circRNA) is closely related to the occurrence and development of many cancers. By screening the expression of circRNA, we identified a novel circRNA termed as has_circ_0023326 in laryngeal squamous cell carcinoma (LSCC). We verified the expression of circPPFIA1 and found that it was upregulated in LSCC tissues compared to the adjacent normal tissues. Functional studies were carried out to detect the effect of circPPFIA1 expression on the phenotype of LSCC cells. These results suggest that circPPFIA1 knockdown can suppress the proliferation, migration, and invasion of LSCC cells, while circPPFIA1 overexpression can promote these processes. Mechanistically, miR-340-3p was predicted to be the target miRNA sponged by circPPFIA1 as confirmed through the luciferase assay and rescue experiments. In addition, miR-340-3p was found to target ELK1 and inhibit its expression. Taken together, circPPFIA1 promotes the progression of LSCC via the miR-340-3p/ELK1 signaling axis, which may serve as a novel prognostic or therapeutic target for LSCC.

Oncogenic Functions and Clinical Significance of Circular RNAs in Colorectal Cancer

Colorectal cancer (CRC) is ranked as the second most commonly diagnosed disease in females and the third in males worldwide. Therefore, the finding of new more reliable biomarkers for early diagnosis, for prediction of metastasis, and resistance to conventional therapies is an important challenge in overcoming the disease. The current review presents circular RNAs (circRNAs) with their unique features as potential prognostic and diagnostic biomarkers in CRC. The review highlights the mechanism of action and the role of circRNAs with oncogenic functions in the CRC as well as the association between their expression and clinicopathological characteristics of CRC patients. The comprehension of the role of oncogenic circRNAs in CRC pathogenesis is growing rapidly and the next step is using them as suitable new drug targets in the personalized treatment of CRC patients.

CircPPP1R12A promotes the progression of colon cancer through regulating CTNNB1 via sponging miR-375

Circular RNAs (circRNAs) have been identified as potential biomarkers for many cancer, including colon cancer (CC). However, the function and mechanism of circPPP1R12A in CC have not been fully elucidated. Quantitative real-time PCR was employed to assess the expression of circPPP1R12A, microRNA (miR)-375 and catenin beta-1 (CTNNB1). The proliferation, apoptosis, migration and invasion of cells were determined using colony formation assay, flow cytometry, wound healing assay and transwell assay. The protein levels of cell cyclin-related markers and CTNNB1 were detected by western blot analysis. The interaction between miR-375 and circPPP1R12A or CTNNB1 was verified by dual-luciferase reporter assay. Xenograft models were built to evaluate the effect of circPPP1R12A silencing and CTNNB1 overexpression on CC tumor growth in vivo. Our results showed that circPPP1R12A was a highly expressed circRNA in CC tissues and cells. Silenced circPPP1R12A suppressed the proliferation, promoted the apoptosis, and inhibited the migration and invasion of CC cells. MiR-375 could be sponged by circPPP1R12A, and its inhibitor could reverse the inhibition of circPPP1R12A silencing on CC progression. Furthermore, CTNNB1 was a target of miR-375, and its overexpression also abolished the suppression of miR-375 on CC progression. Moreover, circPPP1R12A indirectly regulated CTNNB1 expression by sponging miR-375. Importantly, circPPP1R12A knockdown reduced the tumor growth of CC in vivo, and this effect also could be reversed by overexpressing CTNNB1. Our study proposed that circPPP1R12A might play an oncogenic role in CC, which could act as a potential therapeutic target for CC.

hsa_circRNA_000166 Facilitated Cell Growth and Limited Apoptosis through Targeting miR-326/LASP1 Axis in Colorectal Cancer

Circular RNAs (circRNAs) belong to noncoding RNAs and are widely expressed in a variety of cell species, including cancers. However, the function and mechanism of circRNAs in colorectal cancer (CRC) has not been well investigated. Here, we firstly downloaded and analyzed the circRNA expression profile of CRC from the Gene Expression Omnibus (GEO) database. And we identified 181 differentially expressed circRNAs between 10 pairs of CRC and adjacent normal tissues. Interestingly, we observed that the expression of hsa_circRNA_000166 was the top increased among these circRNAs. Then, we confirmed an upregulation of hsa_circRNA_000166 in CRC tissues and cell lines and observed that higher expression of hsa_circRNA_000166 was associated with poor 5-year survival rate of patients with CRC. Next, we investigated the function of hsa_circRNA_000166 during CRC progression by knocking down its expression. Cell growth and apoptosis assay revealed that hsa_circRNA_000166 regulated the cell growth and apoptosis in CRC cell lines. Furthermore, we identified that hsa_circRNA_000166 targeted the miR-326/LASP1 pathway using bioinformatics analysis and luciferase reporter assay. Finally, suppression of miR-326 or overexpression of LASP1 could sufficiently rescue the aberrant cell growth and apoptosis in CRC cell lines. Taken together, our results indicated that downregulation of hsa_circRNA_000166 inhibited the cell growth and facilitated apoptosis during CRC development by sponging the miR-326/LASP1 pathway.

Overexpression of circRNA circUCK2 Attenuates Cell Apoptosis in Cerebral Ischemia-Reperfusion Injury via miR-125b-5p/GDF11 Signaling

Circular RNAs (circRNAs) are expressed at high levels in the brain and are involved in various central nervous system diseases. However, the potential role of circRNAs in ischemic stroke-associated neuronal injury remains largely unknown. Herein, we uncovered the function and underlying mechanism of the circRNA UCK2 (circUCK2) in ischemia stroke. The oxygen-glucose deprivation model in HT-22 cells was used to mimic ischemia stroke in vitro. Neuronal viability and apoptosis were determined by Cell Counting Kit-8 (CCK-8) assays and TUNEL (terminal deoxynucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling) staining, respectively. Middle cerebral artery occlusion was conducted to evaluate the function of circUCK2 in mice. The levels of circUCK2 were significantly decreased in brain tissues from a mouse model of focal cerebral ischemia and reperfusion. Upregulated circUCK2 levels significantly decreased infarct volumes, attenuated neuronal injury, and improved neurological deficits. circUCK2 reduced oxygen glucose deprivation (OGD)-induced cell apoptosis by regulating transforming growth factor β (TGF-β)/mothers against decapentaplegic homolog 3 (Smad3) signaling. Furthermore, circUCK2 functioned as an endogenous miR-125b-5p sponge to inhibit miR-125b-5p activity, resulting in an increase in growth differentiation factor 11 (GDF11) expression and a subsequent amelioration of neuronal injury. Consequently, these findings showed that the circUCK2/miR-125b-5p/GDF11 axis is an essential signaling pathway during ischemia stroke. Thus, the circRNA circUCK2 may serve as a potential target for novel treatment in patients with ischemic stroke.

Bioinformatics Analysis of Key Genes and circRNA-miRNA-mRNA Regulatory Network in Gastric Cancer

Gastric cancer (GC) is one of the most common malignancies in the world, with morbidity and mortality ranking second among all cancers. Accumulating evidences indicate that circular RNAs (circRNAs) are closely correlated with tumorigenesis. However, the mechanisms of circRNAs still remain unclear. This study is aimed at determining hub genes and circRNAs and analyzing their potential biological functions in GC. Expression profiles of mRNAs and circRNAs were downloaded from the Gene Expression Omnibus (GEO) data sets of GC and paracancer tissues. Differentially expressed genes (DEGs) and differentially expressed circRNAs (DE-circRNAs) were identified. The target miRNAs of DE-circRNAs and the bidirectional interaction between target miRNAs and DEGs were predicted. Functional analysis was performed, and the protein-protein interaction (PPI) network and the circRNA-miRNA-mRNA network were established. A total of 456 DEGs and 2 DE-circRNAs were identified with 3 mRNA expression profiles and 2 circRNA expression profiles. GO analysis indicated that DEGs were mainly enriched in extracellular matrix and cell adhesion, and KEGG confirmed that DEGs were mainly associated with focal adhesion, the PI3K-Akt signaling pathway, extracellular matrix- (ECM)- receptor interaction, and gastric acid secretion. 15 hub DEGs (BGN, COL1A1, COL1A2, FBN1, FN1, SPARC, SPP1, TIMP1, UBE2C, CCNB1, CD44, CXCL8, COL3A1, COL5A2, and THBS1) were identified from the PPI network. Furthermore, the survival analysis indicate that GC patients with a high expression of the following 9 hub DEGs, namely, BGN, COL1A1, COL1A2, FBN1, FN1, SPARC, SPP1, TIMP1, and UBE2C, had significantly worse overall survival. The circRNA-miRNA-mRNA network was constructed based on 1 circRNA, 15 miRNAs, and 45 DEGs. In addition, the 45 DEGs included 5 hub DEGs. These results suggested that hub DEGs and circRNAs could be implicated in the pathogenesis and development of GC. Our findings provide novel evidence on the circRNA-miRNA-mRNA network and lay the foundation for future research of circRNAs in GC.