Reduction of Akt2 inhibits migration and invasion of glioma cells

Malignant gliomas have a tendency to invade diffusely into surrounding healthy brain tissues, thereby precluding their successful surgical removal. The serine/threonine kinase Akt2 is well known as an important regulator of cell survival and growth. In this study, we show that siRNA-mediated depletion of Akt2 inhibited migration and invasion of glioma cells. In addition, we demonstrate the mechanisms by which Akt2 functions to promote cell migration and invasion. Phosphorylation of cofilin, a critical step of actin polymerization, and phosphorylation of Girdin, essential for the integrity of the actin cytoskeleton and cell migration, were impaired. Furthermore, epidermal growth factor-induced ACAP1 phosphorylation and integrin beta1 phosphorylation were also blocked, consistent with defects in adhesion. Thus, Akt2 regulates both cell adhesion and cytoskeleton rearrangement during migration. Decreased MMP-9 expression in Akt2 knocked-down glioma cells was subsequently confirmed by Western blotting, consistent with the decreased invasion in vitro and in vivo. These results suggest that Akt2 contributes to glioma cells migration and invasion by regulating the formation of cytoskeleton, influencing adhesion and increasing expression of MMP-9. Our immunohistochemistry results by using human gliomas tissue sections also indicated that Akt2 expression was closely related with the malignancy of gliomas. This is coincident with our in vivo and in vitro results from cell lines. All of these results indicate that Akt2 is a critical factor in gliomas invasion. This study identifies that Akt2 is a potentially antiinvasion target for therapeutic intervention in gliomas.

Nir1 promotes invasion of breast cancer cells by binding to chemokine (C-C motif) ligand 18 through the PI3K/Akt/GSK3β/Snail signalling pathway

Chemokine (C-C motif) ligand 18 (CCL18), which is derived from tumour-associated macrophages (TAMs), plays a critical role in promoting breast cancer metastasis via its receptor, PYK2 N-terminal domain interacting receptor 1 (Nir1). However, the molecular mechanism by which Nir1 promotes breast cancer metastasis by binding to CCL18 remains elusive. In this study, Nir1 expression was associated with lymph node and distant metastasis in patients with invasive ductal carcinoma. For the first time, we report that Nir1 binding to CCL18 promotes the phosphorylation of Akt, LIN-11, Isl1 and MEC-3 protein domain kinase (LIMK), and cofilin, which is a critical step in cofilin recycling and actin polymerisation. Interestingly, Nir1 binding to CCL18 can enhance cell mesenchymal properties and induce epithelial-mesenchymal transition (EMT). Mechanistically, Nir1 binding to CCL18 stabilises Snail via the Akt/GSK3β signalling pathway. In support of these observations, Nir1 binding to CCL18 promoted lung metastasis and LY294002 could inhibit it in vivo. In summary, our in vitro and in vivo results indicate that Nir1 binding to CCL18 plays an important role in breast cancer invasion/metastasis. This study identified both Nir1 and CCL18 as potential anti-invasion targets for therapeutic intervention in breast cancer.

Autocrine IL-8 promotes F-actin polymerization and mediate mesenchymal transition via ELMO1-NF-κB-Snail signaling in glioma

Glioma is the most common form of primary malignant brain cancers. Tumor cell invasiveness is a critical challenge in the clinical management of glioma patients. The invasive biological feature of glioma cell is stimulated by both autocrine and paracrine factors including chemokine IL-8. In this study, we report that the production of IL-8 is higher in glioma tissues and cells than adjacent nontumor tissues (ANT) and normal glial cells. Autocrine IL-8 can increase the invasive ability of glioma cells by binding to CXCR1. In addition, high expression of IL-8 indicates poor prognosis of glioma patients. Furthermore, IL-8 is capable of modulating cell migration and invasion by regulating the activation of RAC1 which resulted in cytoskeletal reorganisation in an ELMO1 dependent manner. Finally, we found that IL-8 could enhance mesenchymal transition(MT) of glioma cells by activating ELMO1-NF-κB-Snail signaling. Our data indicate that IL-8 autocrine is responsible for the invasive phenotype of glioma and IL-8 may be a useful prognostic marker for glioma and novel therapeutic target for glioma invasion intervention.

Akt2 is required for macrophage chemotaxis

Tumor-associated macrophages play an important role in tumorigenesis and metastasis. Trafficking of macrophages to the proximity of tumors is mediated by CSF-1, a growth factor. In this study, we investigated the role of PKB/Akt in CSF-1-induced macrophage migration. Disruption of Akt2 expression by small interference RNA impaired chemotaxis of both THP-1 cells and mouse peritoneal macrophages. Phosphorylation of PKCzeta, an essential component in chemotaxis signaling pathway, was reduced. LIMK/Cofilin, downstream of PKCzeta, regulated cytoskeleton rearrangement during cell migration. Disruption of Akt2 expression inhibited CSF-1-induced LIMK/Cofilin phosphorylation, which contributed to defects in actin polymerization and chemotaxis. Furthermore, MCP-1, a chemokine, -induced macrophage chemotaxis was also impaired. Taken together, our results demonstrated that Akt2 plays an essential role in both CSF-1- and chemokine-induced chemotaxis of macrophages.

The effects of STAT3 and Survivin silencing on the growth of human bladder carcinoma cells

Despite accumulating evidence suggesting a critical role of signal transducer and activator of transcription 3 (STAT3) and Survivin in human bladder cancer, the effects of silencing these genes on the proliferation of T24 bladder carcinoma cells remain unknown. Here, we investigated the inhibitory effects of STAT3 or Survivin silencing on the in vitro and in vivo growth of human T24 bladder carcinoma cells. Small interfering RNA (siRNA) vectors targeting STAT3, Survivin, or both genes were designed and synthesized. The recombinant plasmid DNA constructs were confirmed by DNA sequencing. They were then transiently transfected into T24 cells, and the mRNA and protein expressions of STAT3 and Survivin were determined using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot, respectively. Cell proliferation was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The in vivo growth-inhibition effects of the siRNA vectors were assessed using a bladder cancer mouse model. The tumor weight and size was recorded 4 weeks post-inoculation. We successfully synthesized four siRNA vectors targeting STAT3 and four vectors targeting Survivin. The STAT3-3 and Survivin-4 siRNA constructs were most efficient in reducing STAT3 or Survivin expression, respectively. We then constructed a vector containing these two sequences together (STAT3-Survivin siRNA) and found that the single vector efficiently silenced STAT3 and Survivin expression. Moreover, silencing of STAT3 or Survivin significantly suppressed the in vitro and in vivo proliferation of T24 cells compared to the controls (P<0.05). Our findings indicated that the downregulation of STAT3 or Survivin can suppress the proliferation of T24 bladder cancer cells. Moreover, no additive effects were observed when STAT3 and Survivin were knocked down together, suggesting that they work in the same signaling pathway in T24 cells. These results provide valuable insights into understanding the pathways involved during the tumorigenesis of bladder cancer.

Dock1 promotes the mesenchymal transition of glioma and is modulated by MiR-31

AIMS

This research aimed to examine the relationship between Dock1 and miR-31 and to determine the effect of miR-31 on the mesenchymal transition and invasiveness of glioma.

METHODS

Real-time PCR was used to measure the expression of miR-31 and other RNAs. The transfection was used to manipulate the expression levels of Dock1 and miR-31 in cancer cells. Western blot was used to detect the expression of Dock1 and other related proteins. Wound healing, Matrigel invasion and chemotaxis assays were performed to detect the invasion and migration of glioma cell lines. The actual binding site of miR-31 to the 3'-untranslated region of Dock1 was confirmed through luciferase assay and RNA immunoprecipitation. Methylation-specific PCR was performed to detect the methylation level of miR-31 in both glioma cell lines and tissues.

RESULTS

Dock1 can promote the IL8-induced chemotaxis and mesenchymal transition of glioma cells through the NF-κB/Snail signalling pathway. The protein levels of Dock1 in glioma cell lines and clinical specimens were negatively correlated with miR-31 expression, and Dock1 was directly targeted by miR-31. Animal experiments showed that Dock1 downregulation and miR-31 overexpression reduced glioma cell invasion. Investigation of the underlying molecular mechanism revealed that miR-31 downregulation was attributable to the hypermethylation of the promoter region of miR-31 in glioma cells.

CONCLUSION

Dock1 modulation by miR-31 plays an important function in glioma invasion both in vitro and in vivo. This study provides new insights into the invasion of glioma cells and might therefore contribute to the development of new antiglioma strategies.

Slippery liquid-infused porous surface (SLIPS) with super-repellent and contact-killing antimicrobial performances

Slippery liquid-filled porous surfaces (SLIPS) have attracted extensive research attention for their unique repellent properties, but such surfaces typically lack essential bactericidal activity and cannot defend against the spread of bacteria once bacterial contamination occurs. Herein, a slippery liquid-infused porous surface (SLIPS), endowed with both super-repellent and contact-killing antimicrobial performances is reported. Firstly, polystyrene (PS) based porous structures are developed via a facile microphase separation technique with poly(ethylene glycol) (PEG) as the sacrifice template. The porous surface was then covalently modified by 3-(trimethoxysilyl)propyl dimethyl undecyl ammonium chloride (QAC-Silane) to get the contact-killing antimicrobial performances. After lubricant (silicone oil) is introduced to the porous structure, the SLIPS surface demonstrates remarkably high super-repellence against both Gram-positive and negative bacteria, and also maintains essential contact-killing antimicrobial activities from the fixed QAC-11 groups, once the infused lubricant was depleted. Also, this surface demonstrates a reduced coefficient of friction (COF) of ∼56% as compared to that of the control flat surface. Moreover, this SLIPS surface can be easily realized on various substrates, such as silica glass, polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE) and silicone catheter tube. Owing to its simple, low-cost and fast fabrication approach, this kind of surface may find unique biomedical applications where an effective antibacterial performance and lubricity are highly needed.