Role of metformin in functional endometrial hyperplasia and polycystic ovary syndrome involves the regulation of MEG3/miR‑223/GLUT4 and SNHG20/miR‑4486/GLUT4 signaling

Metformin (MET) can effectively treat endometrial hyperplasia (EH), and the expression of glucose transporter type 4 insulin-responsive (GLUT4) is closely associated with the development of EH. The present study aimed to verify the effect of MET in functional EH and polycystic ovary syndrome (PCOS). H&E staining was performed to analyze the severity of EH, and immunohistochemistry was performed to evaluate the expression of GLUT4 in the endometrium of PCOS rats. Reverse transcription-quantitative PCR was used to calculate the expression of long non-coding (lnc)RNA-maternally expressed gene 3 (MEG3), lncRNA-small nucleolar RNA host gene 20 (SNHG20), GLUT4 mRNA, microRNA (miR)-223 and miR-4486. Sequence analysis and luciferase assays were performed to explore the regulatory relationship among certain lncRNAs, miRNAs and target genes. EH in PCOS rats was efficiently inhibited by MET administration. The increased expression of GLUT4 in PCOS rats was attenuated by MET treatment. Moreover, the expression levels of lncRNA-MEG3 and lncRNA-SNHG20 were significantly inhibited in the endometrium of PCOS rats. MET treatment also showed remarkable efficiency in restoring the expression of lncRNA-MEG3 and lncRNA-SNHG20. Meanwhile, the expression levels of miR-223 and miR-4486 were notably elevated in the endometrium of PCOS rats, while MET treatment reduced the expression of miR-223 and miR-4486 in PCOS rats. Furthermore, a luciferase assay confirmed the inhibitory relationship between miR-223 and lncRNA-MEG3/GLUT4 expression, as well as between miR-4486 and lncRNA-SNHG20/GLUT4 expression. GLUT4 knockdown restored the decreased viability of HCC-94 cells induced by overexpression of lncRNA-MEG3. To conclude, MET exhibited a therapeutic effect in the treatment of EH by modulating the lncRNA-MEG3/miR-223/GLUT4 and lncRNA-SNHG20/miR-4486/GLUT4 signaling pathways. This work provides mechanistic insight into the development of EH.

Regulatory roles of miRNAs 16, 133a, and 223 on osteoclastic bone destruction caused by breast cancer metastasis

Osteolytic bone metastasis leads to skeletal-related events, resulting in a decline in the patient activities and survival; therefore, it is important to understand the mechanism underlying bone metastasis. Recent studies have suggested that microRNAs (miRNAs or miRs) are involved in osteoclast differentiation and/or osteolytic bone metastasis; however, the roles of miRNAs have not been elucidated. In the present study, the roles of miRNAs in bone destruction caused by breast cancer metastasis were investigated in vitro and in vivo. miR-16, miR-133a and miR-223 were transfected into a human breast cancer cell line, MDA-MB-231. The expression of osteolytic factors in conditioned medium (miR-CM) collected from the culture of transfected cells was assessed. To evaluate the effects of miRNAs on osteoclast differentiation and activities, tartrate-resistant acid phosphatase (TRAP) staining and bone resorptive assays were performed in osteoclasts following miR-CM treatment. To create in vivo bone metastasis models for histological and morphometric evaluation, miRNA-transfected MDA-MB-231 cells were transplanted into the proximal tibia of nude mice. Expression of osteolytic factors, including receptor activator for nuclear factor-κB ligand (RANKL), interleukin (IL)-1β, IL-6, parathyroid hormone-related protein (PTHrP), and tumor necrosis factor (TNF), was increased in miR-16-CM, whereas it was decreased in both miR-133a-CM and miR-223-CM. TRAP staining and bone resorptive assays revealed that osteoclast function and activities were promoted by miR-16-CM treatment, whereas they were suppressed by miR-133a-CM and miR-223-CM. Consistent with in vitro findings, in vivo experiments revealed that the overexpression of miR-16 increased osteoclast activities and bone destruction in MDA-MB-231 cells, whereas the opposite results were observed in both miR-133a- and miR-223-transfected MDA-MB-231 cells. Our results indicated that miR-16 promoted osteoclast activities and bone destruction caused by breast cancer metastasis in the bone microenvironment, whereas miR-133a and miR-223 suppressed them. These miRNAs could be potential biomarkers and therapeutic targets for breast cancer bone metastasis.

Treatment with melatonin ameliorates febrile convulsion via modulating the MEG3/miR‑223/PTEN/AKT signaling pathway

The PTEN/AKT signaling pathway is involved in the pathogenesis of febrile convulsion (FC), a convulsion caused by abnormal electrical activity in the brain. The objective of the present study was to evaluate the therapeutic effect of melatonin (MT) on FC and the according underlying molecular mechanisms. Reverse transcription‑quantitative PCR and western blot analysis were used to explore the effects of MT on the expression levels of MEG3, microRNA (miRNA/miR)‑223, phosphatase and tensin homolog (PTEN) and protein kinase B (AKT). Luciferase assay was performed to verify the downstream targets of MEG3 and miR‑223. An animal model was established to evaluate the effects of MT on the MEG3/miR‑223/PTEN/AKT pathway. TUNEL staining was carried out to assess the effect of MT on neuronal apoptosis. Finally, the duration of seizure/convulsion was recorded to determine the effect of MT on FC. In both cell and animal models, mRNA levels of MEG3 and PTEN increased in the apoptosis group, while treatment with MT decreased the expression levels of MEG3 and PTEN. miR‑223 expression was decreased in the apoptosis group, whereas treatment with MT increased the expression level of miR‑223. Protein levels of PTEN and cleaved caspase‑3 increased in the apoptosis group, whereas treatment with MT decreased the protein level of PTEN. Phosphorylated (p)‑AKT expression was decreased in the apoptosis group and treatment with MT reversed this effect. miR‑223 could directly bind to MEG3, and PTEN was a direct target of miR‑223. MT could decrease the duration of seizure/convulsion. In all experimental groups, treatment with MT could decrease the ratio of β waves, while increasing the ratios of α, θ and δ waves. Therefore, the results from the present study collectively suggested that treatment with MT alleviated FC via the MEG3/miR‑223/PTEN/AKT pathway, which also indicated that MT could be considered as a novel strategy for the treatment of FC disease.

MicroRNA‑223‑induced inhibition of the FBXW7 gene affects the proliferation and apoptosis of colorectal cancer cells via the Notch and Akt/mTOR pathways

The tumour suppressor gene F-box and WD repeat domain-containing 7 (FBXW7) plays an important role in human cancer by regulating cell division, proliferation and differentiation. However, the exact regulatory mechanisms of microRNA (miR)-223 in colorectal cancer (CRC) cells are still unknown. The present study aimed to investigate the effect and mechanism of miR-223 inhibiting FBXW7 on the proliferation and apoptosis of CRC cells. HCT116 cells were transfected with miR-223 mimics or small interfering RNA (siRNA) targeting FBXW7 (siFBXW7), and the effects of these treatments on cell proliferation and apoptosis were examined. The downstream Notch and Akt/mTOR pathways were also assessed. Following miR-223 overexpression, the mRNA and protein expression levels of FBXW7 were downregulated. Transfection with miR-223 mimics or siFBXW7 promoted the proliferation of HCT116 cells and inhibited apoptosis by promoting the Notch and Akt/mTOR signalling pathways. Conversely, miR-223 mimics transfection with FBXW7 overexpression inhibited cell viability and restored apoptosis. Thus, the present study demonstrated that miR-223 could bind to the FBXW7 gene and inhibit its expression, ultimately increasing the proliferation and preventing the apoptosis of CRC cells through the Notch and Akt/mTOR signalling pathways.