Circular RNA circ-Foxo3 inhibits esophageal squamous cell cancer progression via the miR-23a/PTEN axis.

Circ-Foxo3 is a circRNA encoded by the human FOXO3 gene and works as a sponge for potential microRNAs (miRNAs) to regulate cancer progression. However, the role of circ-Foxo3 in esophageal squamous cell cancer (ESCC) is not clear. In this study, circ-Foxo3 was lowly expressed in cell lines and ESCC tissues. Meanwhile, overexpression of circ-Foxo3 inhibited cell growth, migration, and invasion, whether in vivo or in vitro. Mechanically, we found a potential miRNA target, miR-23a, which negatively correlated with circ-Foxo3 in ESCC. Then, a luciferase assay confirmed the relationship between the circ-Foxo3 and miRNA. Moreover, circ-Foxo3 upregulation of PTEN occurred through "sponging" miR-23a. Taken together, these results indicated that the circ-Foxo3/miR-23a/PTEN pathway was critical for inhibiting the ESCC progression. This may provide a promising target for treat ESCC.

Circ-FOXO3 inhibits triple-negative breast cancer growth and metastasis via regulating WHSC1-H3K36me2-Zeb2 axis.

Circular RNAs (circRNAs), a subclass of non-coding RNAs characterized by covalently closed continuous loops, play a key role in tumorigenesis and aggressiveness. However, the potential molecular mechanism of circRNAs in triple-negative breast cancer (TNBC) remains largely unknown. Exploring their roles and mechanisms in TNBC progression may help identify new diagnostic markers and therapeutic targets. In this study, we found that circ-FOXO3 was dramatically downregulated in TNBC tissues and blood samples from patients with TNBC. Notably, low circ-FOXO3 expression in TNBC tissues and bloods was associated with lymph node metastasis and unfavorable outcomes in patients with TNBC. Overexpression of circ-FOXO3 significantly inhibited the growth, invasion, and metastasis of TNBC cells both in vitro and in vivo. Moreover, we demonstrated that circ-FOXO3 was predominantly expressed in the cytoplasm and directly interacted with Wolf-Hirschhorn syndrome candidate 1 (WHSC1), thereby inhibiting WHSC1 nuclear localization and activity, resulting in the inhibition of H3K36me2 modifications at the Zeb2 promoter, ultimately inhibiting Zeb2 expression and halting TNBC growth and metastasis. Taken together, these results reveal the tumor-suppressive functions of circ-FOXO3 in inhibiting WHSC1-mediated H3K36me2 modification of Zeb2, suggesting that circ-FOXO3 could serve as a potential novel predictive prognostic biomarker and therapeutic target for TNBC.

Downregulation of circ-Foxo3 in breast cancer stem-like cells.

OBJECTIVE: Cancer cells having stem cell characteristics are linked to metastasis and relapse in breast cancer. Circ-Foxo3, as a circular RNA, has been linked to the breast cancer lethal traits. This study's objective was to assess circ-Foxo3 expression in breast cancer stem-like cells. After isolation from tumor mass, breast cancer cells were subjected to the reliable in vitro assay of spheroid formation to determine the presence cancer stem cells (CSCs). We used a quantitative real-time polymerase chain reaction to examine circ-Foxo3 expression in spheroids. RESULTS: Circ-Foxo3 expression was significantly downregulated in spheroid-forming tumor cells, according to our data. This study demonstrated that breast CSCs have downregulated circ-Foxo3 expression, which may allow these cells to evade apoptosis. A precise analysis of this circRNA's role could be exploited to develop focused therapeutic approaches to fight breast CSCs.

Role of circ-FOXO3 and miR-23a in radiosensitivity of breast cancer.

Identifying the radiosensitivity of cells before radiotherapy (RT) in breast cancer (BC) patients allows appropriate switching between routinely used treatment regimens and reduces adverse side effects in exposed patients. In this study, blood was collected from 60 women diagnosed with Invasive Ductal Carcinoma (IDC) BC and 20 healthy women. To predict cellular radiosensitivity, a standard G2-chromosomal assay was performed. From these 60 samples, 20 BC patients were found to be radiosensitive based on the G2 assay. Therefore, molecular studies were finally performed on two equal groups (20 samples each) of patients with and without cellular radiosensitivity. QPCR was performed to examine the expression levels of circ-FOXO3 and miR-23a in peripheral blood mononuclear cells (PBMCs) and RNA sensitivity and specificity were determined by plotting Receiver Operating Characteristic (ROC) curves. Binary logistic regression was performed to identify RNA involvement in BC and cellular radiosensitivity (CR) in BC patients. Meanwhile, qPCR was used to compare differential RNA expression in the radiosensitive MCF-7 and radioresistant MDA-MB-231 cell lines. An annexin -V FITC/PI binding assay was used to measure cell apoptosis 24 and 48 h after 2 Gy, 4 Gy, and 8 Gy gamma-irradiation. Results indicated that circ-FOXO3 was downregulated and miR-23a was upregulated in BC patients. RNA expression levels were directly associated with CR. Cell line results showed that circ-FOXO3 overexpression induced apoptosis in the MCF-7 cell line and miR-23a overexpression inhibited apoptosis in the MDA-MB-231 cell line. Evaluation of the ROC curves revealed that both RNAs had acceptable specificity and sensitivity in predicting CR in BC patients. Binary logistic regression showed that both RNAs were also successful in predicting breast cancer. Although only circ-FOXO3 has been shown to predict CR in BC patients, circ-FOXO3 may function as a tumor suppressor and miR-23a may function as oncomiR in BC. Circ-FOXO3 and miR-23a may be promising potential biomarkers for BC prediction. Furthermore, Circ-FOXO3 could be a potential biomarker for predicting CR in BC patients.

Circular RNA FOXO3 regulates endometrial carcinoma progression through the microRNA-29a-3p/HDAC4 axis.

Previous studies determined that circular RNA FOXO3 (circ_FOXO3) plays a critical role in tumorigenesis. The definite molecular mechanism of cir_FOXO3 in endometrial carcinoma (EC), nevertheless, had not been fully explored. Circ_FOXO3 expression was determined using quantitative real-time polymerase chain reaction in human EC tissues and cell lines, whereas small interfering RNAs were used to specifically silence circ_FOXO3 expression in cultured EC cells. The cell counting kit-8 assay was employed to determine the effect of ectopic circ_FOXO3 expression on cell viability. Cell proliferation and apoptosis were evaluated by flow cytometry. Further, migration and invasion of EC cells were characterized using the Transwell assay. The interaction between microRNA (miR)-29a-3p and circ_FOXO3/histone deacetylase 4 (HDAC4) was validated using dual luciferase reporter assay. Additionally, qRT-PCR and WB were employed to determine HDAC4 levels. We found that circ_FOXO3 was highly expressed in EC cells and tissues. Moreover, suppressing circ_FOXO3 expression abrogated EC by regulating cell proliferation, apoptosis, migration, and invasion. Furthermore, circ_FOXO3 could act as a sponge for miR-29a-3p, and inhibition of miR-29a-3p expression reversed the effects of circ_FOXO3 suppression on EC progression. Overexpression of miR-29a-3p inhibited EC cell growth, migration, and invasion through the regulation of HDAC4, as it is a target of miR-29a-3p. In conclusion, circ_FOXO3 promotes EC progression by sponging miR-29a-3p and upregulating HDAC4, making it a promising therapeutic target in EC.

Circular RNA FOXO3 Suppresses Bladder Cancer Progression and Metastasis by Regulating MiR-9-5p/TGFBR2.

BACKGROUND: Increasing evidence indicates that the dysregulation of circular RNAs (circRNAs) plays important roles in tumor progressions. METHODS: In this study, we first analyzed circ-FOXO3 level in bladder cancers (BCs), and then BC cell lines were transfected with circ-FOXO3 expression vector, and cell proliferation, migration, and invasion abilities were analyzed. We also used bioinformatics tools to predict potential-binding miRNAs for circ-FOXO3, and luciferase reporter assay was used for the verification of binding miRNAs. For the further study, we analyzed potential downstream-binding mRNA for miRNA, and cell proliferation, migration and invasion abilities of it were also studied. RESULTS: We found that circ-FOXO3 was significantly down-regulated in bladder cancer (BC) tissues compared to normal bladder tissues. We also found that circ-FOXO3 overexpression inhibited cell proliferation, migration and invasion in BC cell lines. Moreover, we demonstrated that TGFBR2 was regulated by circ-FOXO3 through sponging miR-9-5p, the knockdown of TGFBR2 or the overexpression of miR-9-5p all related to the increased BC cell proliferation, migration, and invasion. DISCUSSION: In summary, our data showed that circ-FOXO3 was significantly down-regulated in bladder cancers. circ-FOXO3 overexpression inhibits BC cell progression and metastasis. Furthermore, circ-FOXO3 regulates TGFBR2 expression through sponging miR-9-5p in BC cell lines.

Circular RNA circ-Foxo3 induced cell apoptosis in urothelial carcinoma via interaction with miR-191-5p.

BACKGROUND: Circular RNAs (circRNAs) play a critical role in cancer. Emerging evidence has shown circ-Foxo3, a circRNA, was dysregulated in a variety of tumor types. However, the exact role of circ-Foxo3 in bladder cancer has never been studied. METHODS: We measured the expression level of circ-Foxo3 in human and murine bladder cancer tissues and in various human bladder cancer cell lines. We induced bladder cancer in mice by a carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). circ-Foxo3 was overexpressed in mice by lentiviral gene transfer and in cultured cells via overexpression plasmid. The effect of circ-Foxo3 on apoptosis was examined via apoptotic marker staining, Western blot, and flow cytometry. We further characterized the interaction between circ-Foxo3 and miR-191 and its functional impact on bladder cancer cells. RESULTS: circ-Foxo3 was downregulated in bladder cancer in vivo and in vitro, and was upregulated in response to apoptotic stress. Overexpression of circ-Foxo3 promoted bladder cancer cell apoptosis in BBN mice and in human bladder cancer cell lines. miR-191-5p suppressed circ-Foxo3 expression and the pro-apoptotic effect of circ-Foxo3 in bladder cancer cells via directly targeting the 3'-untranslated region (3'-UTR) of circ-Foxo3. CONCLUSION: circ-Foxo3 was downregulated in bladder cancer in vivo and in vitro, and promoted bladder cancer apoptosis via direct interaction with miR-191. circ-Foxo3 could be a potential therapeutic target for bladder cancer.

Circular RNA circ-FoxO3 Inhibits Myoblast Cells Differentiation.

CircRNA is a type of closed circular non-coding RNA formed by reverse splicing and plays an important role in regulating the growth and development of plants and animals. To investigate the function of circ-FoxO3 in mouse myoblast cells' (C2C12) differentiation and proliferation, we used RT-qPCR to detect the expression level of circ-FoxO3 in mouse myoblast cells at different densities and different differentiation stages, and the specific interference fragment was used to inhibit the expression level of circ-FoxO3 in myoblast cells to observe its effect on myoblast cells proliferation and differentiation. We found that the expression level of circ-FoxO3 in myoblast cells increased with the prolongation of myoblast cells differentiation time, and its expression level decreased with the proliferation of myoblast cells. At the same time, we found that the differentiation ability of the cells was significantly increased (p < 0.05), but the cell proliferation was unchanged (p > 0.05) after inhibiting the expression of circ-FoxO3 in myoblast cells. Combining the results of bioinformatics analysis and the dual luciferase reporter experiment, we found that circ-FoxO3 is a sponge of miR-138-5p, which regulates muscle differentiation. Our study shows that circ-FoxO3 can inhibit the differentiation of C2C12 myoblast cells and lay a scientific foundation for further study of skeletal muscle development at circRNA levels.