Role of CIP4 in high glucose induced epithelial--mesenchymal transition of rat peritoneal mesothelial cells

Regulation of epithelial-mesenchymal transition via sonic hedgehog/glioma-associated oncogene homolog 1 signaling pathway in peritoneal mesothelial cells

Sonic hedgehog (Shh) signaling regulating epithelial-mesenchymal transition (EMT) in cultured rat peritoneal mesothelial cells (PMCs) remains an under-investigated topic. The current study aimed to elucidate the role of Shh signaling in the regulation of EMT in PMCs to attenuate peritoneal injury, with the view of enhancing the efficacy of peritoneal dialysis (PD). PMCs were initially extracted from male Wistar rats using pancreatic enzyme digestion. The expression of Shh and glioma-associated oncogene homolog (Gli1) was quantitatively analyzed using the reverse-transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Migration of PMCs was determined using Transwell assay. The expression of Shh, Gli1, and EMT markers including α-smooth muscle actin (α-SMA), fibronectin, collagen I, snail1, and E-cadherin was examined by RT-qPCR, western blot analysis, and immunofluorescence respectively. High glucose induction was identified to promote cell migration and increase the expression of Shh and Gli1 in a dose- and time-dependent manner in rat PMCs. Cyclopamine (CPN) was observed to block the Shh signaling induced by high glucose, accompanied by cell migration inhibition, decreased expression of α-SMA, fibronectin, collagen I and snail1 as well as increased expression of E-cadherin. Altogether, overexpression of Gli1 by transfected Gli1 plasmid promotes cell migration and upregulates α-SMA, fibronectin, Snail1, and collagen I expression, while downregulating E-cadherin expression. Shh/Gli1 signaling is important in mediating EMT in rat PMCs, which provides a potential novel therapeutic approach for clinical investigation on renal failure treatment.

Cdc42-interacting protein 4 silencing relieves pulmonary fibrosis in STZ-induced diabetic mice via the Wnt/GSK-3β/β-catenin pathway

Cdc42-interacting protein-4 (CIP4) has been reported to be closely associated with diabetic nephropathy in rat. However, little is known about the correlation between CIP4 and diabetic pulmonary fibrosis (PF) in mice. Here, diabetes was induced by streptozotocin (STZ), and later lung tissue was collected and subjected to hematoxylin and eosin (H & E) staining for morphological examination. The distinct up-regulation of CIP4 was observed in diabetic PF mice. CIP4 silencing increased overall weight and decreased lung weight. Simultaneously, levels of TGF-β1, collagen-1, collagen-3 and hydroxyproline were down-regulated by CIP4 silencing, accompanied by an increase in MMP-9 expression and a decrease in TIMP-1 expression. Down-regulation of CIP4 suppressed EMT by decreasing the expression of vimentin and α-SMA as well as augmenting E-cadherin expression. Mechanistic analysis confirmed that CIP4 silencing inhibited p-GSK-3β and β-catenin expression, indicating that CIP4 down-regulation attenuated the activation of Wnt/GSK-3β/β-catenin signaling. However, β-catenin overexpression ameliorated the inhibitory effect of CIP4 down-regulation on lung tissue damage, fibrosis-related cytokines and EMT. These results suggest that CIP4 silencing can efficiently alleviate STZ-induced PF in mice, perhaps through suppressing Wnt/GSK-3β/β-catenin signaling.

Rapamycin inhibits epithelial-to-mesenchymal transition of peritoneal mesothelium cells through regulation of Rho GTPases

Epithelial-mesenchymal transition (EMT) of peritoneal mesothelial cells (PMCs) is a key process of peritoneal fibrosis. Rapamycin has been previously shown to inhibit EMT of PMCs and prevent peritoneal fibrosis. In this study, we investigated the undefined molecular mechanisms by which rapamycin inhibits EMT of PMCs. To define the protective effect of rapamycin, we initially used a rat PD model which was daily infused with 20 mL of 4.25% high glucose (HG) dialysis solution for 6 weeks to induce fibrosis. The HG rats showed decreased ultrafiltration volume and obvious fibroproliferative response, with markedly increased peritoneal thickness and higher expression of α-smooth muscle actin (α-SMA) and transforming growth factor-β1. Rapamycin significantly ameliorated those pathological changes. Next, we treated rat PMCs with HG to induce EMT and/or rapamycin for indicated time. Rapamycin significantly inhibited HG-induced EMT, which manifests as increased expression of α-SMA, fibronectin, and collagen I, decreased expression of E-cadherin, and increased mobility. HG increased the phosphorylation of PI3K, Akt, and mTOR. Importantly, rapamycin inhibits the RhoA, Rac1, and Cdc42 activated by HG. Moreover, rapamycin repaired the pattern of F-actin distribution induced by HG, reducing the formation of stress fiber, focal adhesion, lamellipodia, and filopodia. Thus, rapamycin shows an obvious protective effect on HG-induced EMT, by inhibiting the activation of Rho GTPases (RhoA, Rac1, and Cdc42).

AKAP-9 promotes colorectal cancer development by regulating Cdc42 interacting protein 4

Our previous studies have shown that PRKA kinase anchor protein 9 (AKAP-9) is involved in colorectal cancer (CRC) cell proliferation and migration in vitro. However, whether or not AKAP-9 is important for CRC development or metastasis in vivo remains unknown. In the present study, we found that AKAP-9 expression was significantly higher in human colorectal cancer tissues than the paired normal tissues. In fact, AKAP-9 level correlated with the CRC infiltrating depth and metastasis. Moreover, the higher AKAP-9 expression was associated with the lower survival rate in patients. In cultured CRC cells, knockdown of AKAP-9 inhibited cell proliferation, invasion, and migration. AKAP-9 deficiency also attenuated CRC tumor growth and metastasis in vivo. Mechanistically, AKAP-9 interacted with cdc42 interacting protein 4 (CIP4) and regulated its expression. CIP4 levels were interrelated to the AKAP-9 level in CRC cells. Functionally, AKAP-9 was essential for TGF-β1-induced epithelial-mesenchymal transition of CRC cells, and CIP4 played a critical role in mediating the function of AKAP-9. Importantly, CIP4 expression was significantly up-regulated in human CRC tissues. Taken together, our results demonstrated that AKAP-9 facilitates CRC development and metastasis via regulating CIP4-mediated epithelial-mesenchymal transition of CRC cells.

Centrosomal AKAP350 and CIP4 act in concert to define the polarized localization of the centrosome and Golgi in migratory cells

The acquisition of a migratory phenotype is central in processes as diverse as embryo differentiation and tumor metastasis. An early event in this phenomenon is the generation of a nucleus-centrosome-Golgi back-to-front axis. AKAP350 (also known as AKAP9) is a Golgi and centrosome scaffold protein that is involved in microtubule nucleation. AKAP350 interacts with CIP4 (also known as TRIP10), a cdc42 effector that regulates actin dynamics. The present study aimed to characterize the participation of centrosomal AKAP350 in the acquisition of migratory polarity, and the involvement of CIP4 in the pathway. The decrease in total or in centrosomal AKAP350 led to decreased formation of the nucleus-centrosome-Golgi axis and defective cell migration. CIP4 localized at the centrosome, which was enhanced in migratory cells, but inhibited in cells with decreased centrosomal AKAP350. A decrease in the CIP4 expression or inhibition of the CIP4-AKAP350 interaction also led to defective cell polarization. Centrosome positioning, but not nuclear movement, was affected by loss of CIP4 or AKAP350 function. Our results support a model in which AKAP350 recruits CIP4 to the centrosome, providing a centrosomal scaffold to integrate microtubule and actin dynamics, thus enabling centrosome polarization and ensuring cell migration directionality.

CIP4 promotes lung adenocarcinoma metastasis and is associated with poor prognosis

Aberrant Epidermal growth factor receptor (EGFR) signaling in non-small cell lung cancer (NSCLC) is linked to tumor progression, metastasis, and poor survival rates. Here, we report the role of Cdc42-interacting protein 4 (CIP4) in the regulation of NSCLC cell invasiveness and tumor metastasis. CIP4 was highly expressed in a panel of NSCLC cell lines and normal lung epithelial cell lines. Stable knock-down (KD) of CIP4 in lung adenocarcinoma H1299 cells, expressing wild-type EGFR, led to increased EGFR levels on the cell surface, and defects in sustained activation of Erk kinase in H1299 cells treated with EGF. CIP4 localized to leading edge projections in NSCLC cells, and CIP4 KD cells displayed defects in EGF-induced cell motility and invasion through extracellular matrix. This correlated with reduced expression and activity of matrix metalloproteinase-2 (MMP-2) in CIP4 KD cells compared to control. In xenograft assays, CIP4 silencing had no effect on tumor growth, but resulted in significant defects in spontaneous metastases to the lungs from these subcutaneous tumors. This correlated with reduced expression of the Erk target gene Zeb1, and the Zeb1 target gene MMP-2 in CIP4 KD tumors compared to control. CIP4 also enhanced rates of metastasis to the liver and lungs in an intrasplenic experimental metastasis model. In human NSCLC tumor sections, CIP4 expression was elevated ≥ 2-fold in 43% of adenocarcinomas and 32% of squamous carcinomas compared to adjacent normal lung tissues. Analysis of microarray data for NSCLC patients also revealed that high CIP4 transcript levels correlated with reduced overall survival. Together, these results identify CIP4 as a positive regulator of NSCLC metastasis, and a potential poor prognostic biomarker in lung adenocarcinoma.

Targeting EGFR signalling in chronic lung disease: therapeutic challenges and opportunities

Chronic respiratory diseases, including pulmonary fibrosis, chronic obstructive pulmonary disease (COPD) and lung cancer, are the second leading cause of death among Europeans. Despite this, there have been only a few therapeutic advances in these conditions over the past 20 years. In this review we provide evidence that targeting the epidermal growth factor receptor (EGFR) signalling pathway may represent a novel therapeutic panacea for treating chronic lung disease. Using evidence from human patient samples, transgenic animal models, and cell and molecular biology studies we highlight the roles of this signalling pathway in lung development, homeostasis, repair, and disease ontogeny. We identify mechanisms underlying lung EGFR pathway regulation and suggest how targeting these mechanisms using new and existing therapies has the potential to improve future lung cancer, COPD and pulmonary fibrosis patient outcomes.