Inhibition of PLK4 might enhance the anti-tumour effect of bortezomib on glioblastoma via PTEN/PI3K/AKT/mTOR signalling pathway

Glioblastoma (GBM) is one of the most common aggressive cancers of the central nervous system in adults with a high mortality rate. Bortezomib is a boronic acid–based potent proteasome inhibitor that has been actively studied for its anti-tumour effects through inhibition of the proteasome. The proteasome is a key component of the ubiquitin-proteasome pathway that is critical for protein homeostasis, regulation of cellular growth, and apoptosis. Overexpression of polo-like kinase 4 (PLK4) is commonly reported in tumour cells and increases their invasive and metastatic abilities. In this study, we established a cell model of PLK4 knockdown and overexpression in LN-18, A172 and LN-229 cells and found that knockdown of PLK4 expression enhanced the anti-tumour effect of bortezomib. We further found that this effect may be mediated by the PTEN/PI3K/AKT/mTOR signalling pathway and that the apoptotic and oxidative stress processes were activated, while the expression of matrix metalloproteinases (MMPs) was down-regulated. Similar phenomenon was observed using in vitro experiments. Thus, we speculate that PLK4 inhibition may be a new therapeutic strategy for GBM.     

Polymyxin B exerts nephrotoxicity effects via inhibition of the Nrf2/NQO1 pathway-mediated antioxidant response

Polymyxin B (PMB) is a polypeptide antibiotic widely used in treating multidrug-resistant Gram-negative bacteria. However, nephrotoxicity is a serious adverse effect that limits its clinical use. Therefore, clarification of the molecular mechanism of PMB-induced renal injury is essential. Our study aimed to explore possible mechanisms of PMB-induced nephrotoxicity in vivo and in vitro. Mice were treated with PMB to construct the kidney injury model. The antioxidant capacity was assessed by measuring the superoxide dismutase (SOD) and catalase (CAT) activities and the glutathione (GSH) and malondialdehyde (MDA) contents. The pathway of the nuclear factor erythroid 2-related factor 2/NADH quinone oxidoreductase 1 (Nrf2/NQO1) was examined after PMB treatment in NRK-52E cells and mice. Finally, the expressions of genes and proteins (Bax, Bcl-2, Caspase-3, Caspase-9) related to apoptosis were evaluated through quantitative polymerase chain reaction and western blot assay. The study verified PMB-induced nephrotoxicity in mice and NRK-52E cells in a dose- and time-dependent manner. PMB treatment significantly decreased the expression of Nrf2 and its downstream target gene NQO1 and increased the apoptosis-related proteins expression. In summary, our results suggested that PMB-induced oxidative stress damage by inhibiting the Nrf2/NQO1 pathway and promoting apoptosis in kidney tissues.     

MicroRNA-10a promotes epithelial-to-mesenchymal transition and stemness maintenance of pancreatic cancer stem cells via upregulating the Hippo signaling pathway through WWC2 inhibition

MicroRNAs (miRNAs)-mediated cancer stem cells (CSCs) have drawn wide attention. This study aimed to probe the role of miR-10a in epithelial–mesenchymal transition (EMT) and stemness maintenance of pancreatic CSCs (PCSCs). Differentially expressed miRs and genes in pancreatic cancer (PC) were predicted via an online database, and the miR-10a and WW and C2 domain containing 2 (WWC2) expression were identified via a comparative study in PC and pancreatitis tissues. PCNCs were isolated and identified, and then the functional roles of miR-10a and WWC2 in proliferation, invasion, migration, self-renewal, colony formation abilities, EMT, and stemness maintenance of PCNCs were determined. The effects of miR-10a on tumor growth in vivo were studied by performing a xenograft tumor in nude mice. Consequently, miR-10a was highly expressed while WWC2 was lowly expressed in PC tissues. miR-10a could target WWC2 expression. miR-10a inhibition reduced EMT and stemness maintenance of PCSCs via enhancing WWC2 expression. The in vitro results were reproduced in in vivo studies. miR-10a promoted EMT and stemness maintenance of PCSCs via activating the Hippo signaling pathway. Our study provided evidence that miR-10a inhibition reduced EMT and stemness maintenance of PCSCs via upregulating WWC2 expression and inhibiting the Hippo signaling pathway.     

MicroRNA‐351 eases insulin resistance and liver gluconeogenesis via the PI3K/AKT pathway by inhibiting FLOT2 in mice of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is known as different degree glucose intolerance that is initially identified during pregnancy. MicroRNAs (miRs) may be a potential candidate for treatment of GDM. Herein, we suggested that miR‐351 could be an inhibitor in the progression of GDM via the phosphoinositide 3‐kinase/protein kinase B (PI3K/AKT) pathway. Microarray analysis was used to identify differentially expressed genes and predict miRs regulating flotillin 2 (FLOT2). Target relationship between miR‐351 and FLOT2 was verified. Gestational diabetes mellitus mice were treated with a series of mimic, inhibitor and small interfering RNA to explore the effect of miR‐351 on insulin resistance (IR), cell apoptosis in pancreatic tissues and liver gluconeogenesis through evaluating GDM‐related biochemical indexes, as well as expression of miR‐351, FLOT2, PI3K/AKT pathway‐, IR‐ and liver gluconeogenesis‐related genes. MiR‐351 and FLOT2 were reported to be involved in GDM. FLOT2 was the target gene of miR‐351. Gestational diabetes mellitus mice exhibited IR and liver gluconeogenesis, up‐regulated FLOT2, activated PI3K/AKT pathway and down‐regulated miR‐351 in liver tissues. Additionally, miR‐351 overexpression and FLOT2 silencing decreased the levels of FLOT2, phosphoenolpyruvate carboxykinase, glucose‐6‐phosphatase, fasting blood glucose, fasting insulin, total cholesterol, triglyceride, glyeosylated haemoglobin and homeostasis model of assessment for IR index (HOMA‐IR), extent of PI3K and AKT phosphorylation, yet increased the levels of HOMA for islet β‐cell function, HOMA for insulin sensitivity index and glucose transporter 2 expression, indicating reduced cell apoptosis in pancreatic tissues and alleviated IR and liver gluconeogenesis. Our results reveal that up‐regulation of miR‐351 protects against IR and liver gluconeogenesis by repressing the PI3K/AKT pathway through regulating FLOT2 in GDM mice, which identifies miR‐351 as a potential therapeutic target for the clinical management of GDM.     

Inhibition of fatty acid synthase suppresses U-2 OS cell invasion and migration via downregulating the activity of HER2/PI3K/AKT signaling pathway in vitro

FASN plays an important role in the malignant phenotype of various tumors. Our previous studies show that inhibition FASN could induce apoptosis and inhibit proliferation in human osteosarcoma (OS) cell in vivo and vitro. The aim in this study was to investigate the effect of inhibition FASN on the activity of HER2/PI3K/AKT axis and invasion and migration of OS cell. The expression of FASN, HER2 and p-HER2(Y1248) proteins was detected by immunohistochemistry in OS tissues from 24 patients with pulmonary metastatic disease, and the relationship between FASN and p-HER2 as well as HER2 was investigated. The results showed that there was a positive correlation between FASN and HER2 as well as p-HER2 protein expression. The U-2 OS cells were transfected with either the FASN specific RNAi plasmid or the negative control RNAi plasmid. FASN mRNA was measured by RT-PCR. Western blot assays was performed to examine the protein expression of FASN, HER2, p-HER2(Y1248), PI3K, Akt and p-Akt (Ser473). Migration and invasion of cells were investigated by wound healing and transwell invasion assays. The results showed that the activity of HER2/PI3K/AKT signaling pathway was suppressed by inhibiting FASN. Meanwhile, the U-2OS cells migration and invasion were also impaired by inhibiting the activity of FASN/HER2/PI3K/AKT. Our results indicated that inhibition of FASN suppresses OS cell invasion and migration via down-regulation of the “HER2/PI3K/AKT” axis in vitro. FASN blocker may be a new therapeutic strategy in OS management.     

Retracted: Downregulated microRNA-135a ameliorates rheumatoid arthritis by inactivation of the phosphatidylinositol 3-kinase/AKT signaling pathway via phosphatidylinositol 3-kinase regulatory subunit 2

Synovial fibroblasts (SFs) of rheumatoid arthritis (RA) are phenotypically aggressive, typically progressing into arthritic cartilage degradation. Throughout our study, we made explorations into the effects of microRNA-135a (miR-135a) on the SFs involved in RA by mediating the phosphatidylinositol 3-kinase (PI3K)/AKT signaling pathway via regulation of phosphatidylinositol 3-kinase regulatory subunit 2 (PIK3R2). The expression of PI3K was higher, the expression of PIK3R2 was lower, and AKT was phosphorylated in the RA synovial tissues, relative to the levels found in the normal synovial tissues. We predicted miR-135a to be a candidate miR targeting PIK3R2 using an online website, microRNA.org, which was verified with a dual-luciferase reporter gene assay. Subsequently, high miR-135a expression was observed in RA synovial tissues. To study the effect of the interaction between miR-135a and PIK3R2 in RA, the SFs isolated from RA samples were cultured and transfected with mimic, inhibitor, and small interfering RNA. The proliferation, invasion, and apoptosis of the SFs were detected after the transfection. The cells transfected with miR-135a inhibitor showed inhibited cell proliferation, migration, and invasion, while also displaying promoted cell apoptosis, G0/G1 cell ratio, and decreased S cell ratio, through upregulation of PIK3R2 and inactivation of the PI3K/AKT signaling pathway. These findings provided evidence that downregulation of miR-135a inhibits proliferation, migration, and invasion and promotes apoptosis of SFs in RA by upregulating the PIK3R2 coupled with inactivating the PI3K/AKT signaling pathway. The downregulation of miR-135a might be a potential target in the treatment of RA.     

ASIC1a stimulates the resistance of human hepatocellular carcinoma by promoting EMT via the AKT/GSK3β/Snail pathway driven by TGFβ/Smad signals

Multidrug resistance is the main obstacle to curing hepatocellular carcinoma (HCC). Acid‐sensing ion channel 1a (ASIC1a) has critical roles in all stages of cancer progression, especially invasion and metastasis, and in resistance to therapy. Epithelial to mesenchymal transition (EMT) transforms epithelial cells into mesenchymal cells after being stimulated by extracellular factors and is closely related to tumour infiltration and resistance. We used Western blotting, immunofluorescence, qRT‐PCR, immunohistochemical staining, MTT, colony formation and scratch healing assay to determine ASIC1a levels and its relationship to cell proliferation, migration and invasion. ASIC1a is overexpressed in HCC tissues, and the amount increased in resistant HCC cells. EMT occurred more frequently in drug‐resistant cells than in parental cells. Inactivation of ASIC1a inhibited cell migration and invasion and increased the chemosensitivity of cells through EMT. Overexpression of ASIC1a upregulated EMT and increased the cells’ proliferation, migration and invasion and induced drug resistance; knocking down ASIC1a with shRNA had the opposite effects. ASIC1a increased cell migration and invasion through EMT by regulating α and β‐catenin, vimentin and fibronectin expression via the AKT/GSK‐3β/Snail pathway driven by TGFβ/Smad signals. ASIC1a mediates drug resistance of HCC through EMT via the AKT/GSK‐3β/Snail pathway.