URG11 mediates hypoxia-induced epithelial-to-mesenchymal transition by modulation of E-cadherin and β-catenin

Insight into the mechanisms regulating liver cancer stem cells by hepatitis B virus X protein

Hepatocellular carcinoma (HCC) is a heterogeneous disease with high recurrence and mortality. It is well known that a large proportion of HCCs are caused by hepatitis B virus (HBV) infection. In particular, the HBV X protein (HBX), a multifunctional molecule produced by the virus, plays a leading role in hepatocarcinogenesis. However, the molecular mechanisms underlying HBX-mediated HCC remain not fully elucidated. Recently, liver cancer stem cells (LCSCs), a unique heterogeneous subpopulation of the malignancy, have received particular attention owing to their close association with tumorigenesis. Especially, the modulation of LCSCs by HBX by upregulating CD133, CD44, EpCAM, and CD90 plays a significant role in HBV-related HCC development. More importantly, not only multiple signaling pathways, including Wnt/β-catenin signaling, transforming growth factor-β (TGF-β) signaling, phosphatidylinositol-3-kinase (PI-3 K)/AKT signaling, and STAT3 signaling pathways, but also epigenetic regulation, such as DNA and histone methylation, and noncoding RNAs, including lncRNA and microRNA, are discovered to participate in regulating LCSCs mediated by HBX. Here, we summarized the mechanisms underlying different signaling pathways and epigenetic alterations that contribute to the modulation of HBX-induced LCSCs to facilitate hepatocarcinogenesis. Because LCSCs are important in hepatic carcinogenesis, understanding the regulatory factors controlled by HBX might open new avenues for HBV-associated liver cancer treatment.

Expression Analysis of Early Metastatic Seeding of Colorectal Cancer

BACKGROUND

Distant metastasis is the leading cause of death in patients with colorectal cancer (CRC). Tumor dissemination for metastasis formation occurs in advanced cancers and also during early stages of tumorigenesis. Here, we investigated the genes involved in early metastatic seeding of CRC using gene expression analysis.

PATIENTS AND METHODS

We performed a cDNA microarray using specimens resected from stages I-II CRC with and without metachronous metastatic recurrence. For the candidate genes, we immunohistochemically validated protein expression using a tissue microarray of stages I-III CRC.

RESULTS

The expression of TROP2, VWCE, and BMP7 was upregulated in the recurrence group rather than in the non-recurrence group. Protein expression analysis revealed significant association of these genes with distant metastatic recurrence. The specimens with high expression of BMP7 showed worse recurrence-free survival (RFS; p = 0.02). Those with high expression of TROP2 and VWCE showed worse overall survival (OS) and RFS (TROP2: p = 0.01 and p = 0.03; VWCE: p < 0.05 and p < 0.001, respectively). In the multivariate analysis, high expression of VWCE and BMP7 was an independent predictor of recurrence [VWCE: hazard ratio (HR) 3.41, p < 0.001; BMP7: HR 2.93, p = 0.005]. In contrast, TROP2 was an independent prognostic factor for OS (HR 4.58, p = 0.03).

CONCLUSIONS

Gene expression analysis revealed that TROP2, VWCE, and BMP7 were involved in early metastatic seeding. The high expression of these genes may warrant careful surveillance or adjuvant therapy, even in stages I-II CRC cases.

The Role of HBx Protein in Diseases Beyond the Liver

HBX gene is essential for HBV replication, evading the surveillance of the immune system by integrating its sequence into the human genome. It also exists stably in human cells by inhibiting the expression and activity of mismatch repair-related pathway genes. Previous reviews have comprehensively summarized the role of HBx in liver-related diseases. Our article complements the summary of research on HBx in diseases other than liver disease. Through a comprehensive literature search and reading, we found that HBx is expressed in the kidney, placenta, lung and other organs of HBV-infected patients, and is closely related to the occurrence and development of diseases such as nephritis, diffuse large B-cell lymphoma, and gastric cancer. However, in the clinical treatment of these diseases, HBV infection and the role of HBx have not attracted sufficient attention, and there is no corresponding treatment strategy. Therefore, more research on HBx in diseases other than the liver is particularly necessary, and we hope that our article can provide some insight into the treatment of related diseases.

URG11 promotes proliferation and induced apoptosis of LNCaP cells

von Willebrand factor C and EGF domain-containing protein (URG11), a cell growth regulator, is involved in the progression of a variety of types of cancer, including prostate cancer (Pca). However, the functions of the URG11 gene in Pca cells require in-depth investigation. The mRNA and protein levels of URG11 were measured by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Cell Counting kit-8 (CCK-8), wound-healing and Transwell assays were used to detect cell viability, migration and invasion, respectively. Apoptosis and cell cycle analyses were performed using flow cytometry. The mRNA and protein expression levels of epithelial (E)-cadherin, vimentin, α-smooth muscle actin (α-SMA), cyclin D1 and MYC proto-oncogene protein (c-Myc) were analyzed by RT-qPCR and western blot analysis. In the present study, the mRNA and protein levels of URG11 were markedly upregulated in Pca cell lines compared with those in the normal prostate epithelial cell line. With functional experiments, the cell viability, migration and invasion of Pca cells were markedly promoted by URG11 overexpression. The cell cycle was effectively induced by URG11 and apoptosis was inhibited by the overexpression of URG11. Concomitantly, the epithelial marker E-cadherin was downregulated, and the mesenchymal markers vimentin and α-SMA were upregulated following URG11 overexpression. By contrast, genetic knockout of URG11 elicited the opposite effects. The present study also identified that the downstream effector genes of the Wnt/β-catenin signal pathway, cyclin D1 and c-Myc, were increased following the overexpression of endogenous URG11, which are known to regulate cell proliferation. In addition, the Wnt/β-catenin inhibitor FH535 ameliorated the promotive effects of URG11 on LNCaP cells viability, migration and invasion, and the Wnt/β-catenin agonist LiCl reversed the inhibitory effects of siURG11 in LNCaP cells on cell viability, migration and invasion. The present study demonstrated that URG11 served an oncogenic role in the development of Pca cells and provided evidence that URG11 has potential as a novel therapeutic target in Pca.

Macrophages induce EMT to promote invasion of lung cancer cells through the IL-6-mediated COX-2/PGE2/β-catenin signalling pathway

Infiltration of macrophages plays a critical role in the connection between inflammation and cancer invasion; however, the molecular mechanism that enables this crosstalk remains unclear. This paper investigates a molecular link between infiltration of macrophages and metastasis of lung cancer cells. In this study, the macrophage density and cyclooxygenase-2 (COX-2) protein were examined in surgical specimens by immunohistochemistry (IHC), and the prostaglandin E₂ (PGE₂) levels were determined in the blood of 30 non-small cell lung cancer (NSCLC) patients using enzyme-linked immunosorbent assay (ELISA). We demonstrated that macrophage infiltration was significantly associated with elevated tumour COX-2 expression and serum PGE₂ levels in NSCLC patients. Interestingly, the COX-2 and PGE₂ levels as well as macrophages were poor predictors of NSCLC patient survival. THP-1-derived macrophages were co-cultured in vitro with A549 and H1299 lung cancer cells. In the co-culture process, interleukin-6 (IL-6) induced the COX-2/PGE₂ pathway in lung cancer cells, which subsequently promoted β-catenin translocation from the cytoplasm to the nucleus, resulting in epithelial-mesenchymal transition (EMT) and lung cancer cell invasion. Our findings show that the IL-6-dependent COX-2/PGE₂ pathway induces EMT to promote invasion of tumour cells through β-catenin activation during the interaction between macrophages and lung cancer cells, which suggests that inhibition of COX-2/PGE₂ or macrophages has the potential to suppress metastasis of lung cancer cells.

E‑cadherin involvement in human lens epithelial cell transdifferentiation may be associated with N‑cadherin

E-cadherin, β-catenin and N‑cadherin serve key roles in the epithelial‑to‑mesenchymal transition (EMT) that leads to human lens epithelial cell (LEC) transdifferentiation and subsequent cataract formation. The present study aimed to investigate the role of E‑cadherin in LEC transdifferentiation. SRA01/04 human LECs were transfected with E‑cadherin short interfering (si)RNA (E‑cadherin siRNA group), negative control siRNA (NC group) or the transfection regent Lipofectamine 2000 (blank group). Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was used to detect mRNA expression levels of E‑cadherin, N‑cadherin and β‑catenin, and western blot analysis was performed to measure the protein expression levels in the three groups. SRA01/04 cells transfected with E‑cadherin siRNA exhibited a significant decrease in the mRNA expression level of E‑cadherin (P<0.05) and N‑cadherin (P<0.05), whereas no significant changes were identified for β‑catenin expression (P>0.05). Consistent with the results of RT‑qPCR, western blotting demonstrated that the protein expression levels of E‑cadherin and N‑cadherin were notably decreased in E‑cadherin siRNA‑transfected cells, whereas the protein expression level of β‑catenin remained unchanged. Results from the present study indicated that E‑cadherin may be involved in human LEC transdifferentiation by affecting N‑cadherin expression.

The regulation of proteins associated with the cytoskeleton by hepatitis B virus X protein during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is a major malignant disease worldwide, and chronic hepatitis B virus (HBV) infection is one of the primary causes for this type of cancer. Hepatitis B virus X protein (HBx) is a non-structural protein encoded by the viral genome that has significant effects on the pathogenesis of HCC. With the development of high-throughput assays and technologies, the abnormal HBx-induced expression of certain cellular proteins with assorted biological functions has been investigated. These target proteins identified by various methods include specific proteins associated with the cellular cytoskeleton, which contribute to HBx-induced hepatocarcinogenesis. In addition, the cytoskeletal proteins deregulated by HBx are involved in cell morphogenesis, adhesion, migration and proliferation. This review aims to summarize the current understanding of the expression profiles of HBx-associated cytoskeletal proteins, as well as their complex functions and underlying mechanisms in hepatocarcinogenesis. Considering that the potential therapeutics for various types of tumors may function through the stabilization of cytoskeletal proteins in order to restrict cellular movement and limit intracellular processes, clarifying the mechanisms underlying protein-associated cytoskeleton dysregulation by HBx may provide novel possibilities and potent therapeutic targets for HBV-associated HCC.

Signalling pathways involved in hypoxia-induced renal fibrosis

Renal fibrosis is the common pathological hallmark of progressive chronic kidney disease (CKD) with diverse aetiologies. Recent researches have highlighted the critical role of hypoxia during the development of renal fibrosis as a final common pathway in end‐stage kidney disease (ESKD), which joints the scientist's attention recently to exploit the molecular mechanism underlying hypoxia‐induced renal fibrogenesis. The scaring formation is a multilayered cellular response and involves the regulation of multiple hypoxia‐inducible signalling pathways and complex interactive networks. Therefore, this review will focus on the signalling pathways involved in hypoxia‐induced pathogenesis of interstitial fibrosis, including pathways mediated by HIF, TGF‐β, Notch, PKC/ERK, PI3K/Akt, NF‐κB, Ang II/ROS and microRNAs. Roles of molecules such as IL‐6, IL‐18, KIM‐1 and ADO are also reviewed. A comprehensive understanding of the roles that these hypoxia‐responsive signalling pathways and molecules play in the context of renal fibrosis will provide a foundation towards revealing the underlying mechanisms of progression of CKD and identifying novel therapeutic targets. In the future, promising new effective therapy against hypoxic effects may be successfully translated into the clinic to alleviate renal fibrosis and inhibit the progression of CKD.

Hypoxia inducible factor-1α-dependent epithelial to mesenchymal transition under hypoxic conditions in prostate cancer cells

Prostate cancer is the most commonly diagnosed cancer in men and the second leading cause of cancer death. Hypoxia is an environmental stimulus that plays an important role in the development and cancer progression especially for solid tumors. The key regulator under hypoxic conditions is stabilized hypoxia-inducible factor (HIF)-1α. In the present study, immune-fluorescent staining, siRNAs, qRT-PC, immunoblotting, cell migration and invasion assays were carried out to test typical epithelial to mesenchymal transition under hypoxia and the key regulators of this process in PC3, a human prostate cancer cell line. Our data demonstrated that hypoxia induces diverse molecular, phenotypic and functional changes in prostate cancer cells that are consistent with EMT. We also showed that a cell signal factor such as HIF-1α, which might be stabilized under hypoxic environment, is involved in EMT and cancer cell invasive potency. The induced hypoxia could be blocked by HIF-1α gene silencing and reoxygenation of EMT in prostate cancer cells, hypoxia partially reversed accompanied by a process of mesenchymal-epithelial reverting transition (MErT). EMT might be induced by activation of HIF-1α-dependent cell signaling in hypoxic prostate cancer cells.

COX-2 promotes metastasis in nasopharyngeal carcinoma by mediating interactions between cancer cells and myeloid-derived suppressor cells

The expansion of myeloid-derived suppressor cells (MDSCs) is a common feature of cancer, but its biological roles and molecular mechanism remain unclear. Here, we investigated a molecular link between MDSC expansion and tumor cell metastasis in nasopharyngeal carcinoma (NPC). We demonstrated that MDSCs expanded and were positively correlated with the elevated tumor COX-2 expression and serum IL-6 levels in NPC patients. Importantly, COX-2 and MDSCs were poor predictors of patient disease-free survival (DFS). Knocking down tumor COX-2 expression hampered functional TW03-mediated-MDSC cell (T-MDSC) induction with IL-6 blocking. We identified that T-MDSCs promoted NPC cell migration and invasion by triggering the epithelial-mesenchymal transition (EMT) on cell-to-cell contact, and T-MDSCs enhanced tumor experimental lung metastasis in vivo. Interestingly, the contact between T-MDSCs and NPC cells enhanced tumor COX-2 expression, which subsequently activated the β-catenin/TCF4 pathway, resulting in EMT of the cancer cells. Blocking transforming growth factor β (TGFβ) or inducible nitric oxide synthase (iNOS) significantly abolished the T-MDSC-induced upregulation of COX-2 and EMT scores in NPC cells, whereas the administration of TGFβ or L-arginine supplements upregulated COX-2 expression and EMT scores in NPC cells. These findings reveal that COX-2 is a key factor mediating the interaction between MDSCs and tumor cells, suggesting that the inhibition of COX-2 or MDSCs has the potential to suppress NPC metastasis.

URG11 predicts poor prognosis of pancreatic cancer by enhancing epithelial-mesenchymal transition-driven invasion

The poor prognosis and high recurrent rate of pancreatic cancer (PC) necessitates the discovery of new predictive markers of PC invasion and prognosis. In this study, we evaluated the expression pattern of up-regulated gene 11 (URG11) in a tissue microarray with 18 pairs of PC and adjacent normal tissues. It was shown that URG11 was significantly up-regulated in PC tissues. High expression levels of URG11 were detected in all PC specimens, but were rarely detected in adjacent non-tumorous tissues. In addition, high expression of URG11 was correlated to poor prognosis. Furthermore, it was discovered that URG11 was correlated to epithelial-mesenchymal transition (EMT) markers and clinical pathological parameters indicative of high PC invasion, while knockdown of URG11 significantly changed the expression pattern of EMT markers and decreased the invasion of PC cells. These findings indicate that URG11 might enhance the invasion of PC by inducing EMT and thus lead to poor PC prognosis. Thus, URG11 has the potential to be a new predictive biomarker of PC invasion and prognosis, which may help in the diagnosis and treatment of PC patients.

Association of URG11 and Twist with clinical pathological characteristics and prognosis in patients with IgA nephropathy

BACKGROUND

Our previous studies demonstrated that URG11 is involved in hypoxia-induced tubular epithelial-mesenchymal transition and the development of kidney fibrosis in cellular and animal models. The objective of this study was to determine the expression levels of URG11 in kidneys with IgA nephropathy (IgAN), and the association of URG11 with various clinical parameters.

METHODS

We analysed the degree of expression and localization of URG11 in biopsies from kidneys with IgAN, and correlated their immunostaining levels with various clinical and histological parameters. We also analysed the correlation between the expression of URG11 and Twist in the renal interstitium with renal survival.

RESULTS

URG11 was strongly expressed in the cytoplasm of tubular epithelial cells obtained from kidneys of patients with IgAN. However, there was little positive staining for URG11 in the renal tubules of normal kidneys (P = 0.024). URG11 protein levels in the tubulointerstitium were inversely correlated with estimated glomerular filtration rates (eGFRs) (r = -0.305, P = 0.038) and the percentage of tubulointerstitial fibrosis (r = 0.350, P = 0.023). Moreover, a high level of URG11 correlated with the activation of Twist expression and E-cadherin repression in patients with IgAN (P = 0.000 and 0.041, respectively). Multivariate analyses indicated that a combination of high URG11 and Twist expression was an independent prognostic factor [relative ratio, RR 4.738 (95% CI: 1.040, 21.591), P = 0.044] of IgAN.

CONCLUSIONS

Our findings suggest that URG11 staining in renal biopsy specimens might be a novel histological marker for progression in IgAN patients.

Functional implications of microRNA-215 in TGF-β1-induced phenotypic transition of mesangial cells by targeting CTNNBIP1

Mesangial cell (MC) phenotypic transition is crucial for the progression of diabetic nephropathy. A major stimulus mediating high glucose-induced MC phenotypic transition is TGF-β1. Our current study focuses on microRNA-215 (miR-215) and investigates its role in TGF-β1-mediated MC phenotypic transition. Using real-time quantitative PCR (qRT-PCR) and northern blotting, we determined that the miR-192/215 family is dramatically upregulated under diabetic conditions both in vitro and in vivo. Gain- and loss-of-function approaches demonstrated that miR-215 inhibition significantly inhibited TGF-β1-induced mouse mesangial cell (MMC) phenotypic transition, whereas miR-215 upregulation promoted MMC phenotypic transition. Interestingly, these changes were not detected in cells that were treated with TGF-β1 and miR-192 mimics or inhibitors. These results suggest that miR-215 participates in TGF-β1-induced MMC phenotypic transition. Luciferase reporter assays were used to identify whether catenin-beta interacting protein 1 (CTNNBIP1) is a direct target of miR-215, which was predicted by bioinformatic analysis. Mechanistic studies revealed that CTNNBIP1 suppresses Wnt/β-catenin signaling and that miR-215 promotes β-catenin activation and upregulates α-SMA and fibronectin expression in TGF-β1-treated MMCs by targeting CTNNBIP1. In addition, in vivo miR-215 silencing with a specific antagomir significantly increased CTNNBIP1 protein expression, resulting in reduced β-catenin activity and decreased α-SMA and fibronectin expression in db/db mouse kidney glomeruli. Taken together, our findings indicate that miR-215 plays an essential role in MC phenotypic transition by regulating the CTNNBIP1/β-catenin pathway, which is related to the pathogenesis of diabetic nephropathy.

Wnt5a inhibits hypoxia-induced pulmonary arterial smooth muscle cell proliferation by downregulation of β-catenin

Chronic hypoxia-induced pulmonary arterial hypertension (HPH) is closely associated with profound vascular remodeling, especially pulmonary arterial medial hypertrophy and muscularization due to hyperplasia of pulmonary artery smooth muscle cells (PASMCs). Aberrant Wnt signaling has been associated with lung diseases, but its role in pulmonary hypertension is unclear. This study evaluated the effect of Wnt5a on hypoxia-induced proliferation of human PASMCs and its possible mechanism. The results show that hypoxia (3% O2, 48 h) induced proliferation of human PASMCs, accompanied with a significant decrease in Wnt5a gene expression, increase in β-catenin and Cyclin D1 expression, as well as β-catenin nuclear translocation. Treatment with recombinant mouse Wnt5a significantly inhibited hypoxia-induced proliferation of human PASMCs, upregulation of Cyclin D1 and β-catenin expression, as well as the nuclear translocation of β-catenin. These effects were inhibited by Wnt5a antibody. Knocking down β-catenin or Cyclin D1 gene expression inhibited hypoxia-induced human PASMC proliferation, whereas overexpression of β-catenin increased hypoxia-induced human PASMC proliferation and counteracted the inhibitory effect of Wnt5a. These results suggest that Wnt5a has an antiproliferative effect on hypoxia-induced human PASMC proliferation by downregulation of β-catenin and its target gene Cyclin D1. Hypoxia-induced downregulation of Wnt5a may be a way to facilitate hypoxia-induced human PASMC proliferation. The results of this study will help to understand the novel strategies for PH treatment involving Wnt signaling.

Upregulator of cell proliferation predicts poor prognosis in hepatocellular carcinoma and contributes to hepatocarcinogenesis by downregulating FOXO3a

Objective

The goal of the present study was to investigate the potential correlation between the expression level of upregulator of cell proliferation (URGCP/URG4) and the prognosis of hepatocellular carcinoma (HCC), and to examine the biological function of URGCP/URG4 in the progression of HCC, to better understand its underlying molecular mechanism in hepatic tumorigenesis.

Design

URGCP/URG4 expression was analyzed in 15 HCC cell lines, in 278 archived paraffin-embedded HCC sections, and in 10 pairs of fresh HCC tumor and para-tumor non-cancerous tissues using immunohistochemistry (IHC) and Western blotting analysis (WB). The effect of URGCP/URG4 on cell proliferation and tumorigenesis was examined in vitro and in vivo. WB and luciferase reporter analyses were performed to identify the effects of URGCP/URG4-overexpression or -knockdown on expression of cell cycle regulators and transcriptional activity of FOXO3a.

Results

IHC results revealed an upregulation of URGCP/URG4 in all HCC cell lines and fresh HCC samples as compared with normal liver cells and para-tumor tissues, respectively. URGCP/URG4 was also expressed at a high level in 122 of the 278 (43.8%) archived HCC specimens. The expression level of URGCP/URG4 was significantly correlated with clinical staging and poor patient survival of HCC in the study cohort, and in various clinical subgroups. Strikingly, ectopic expression of URGCP/URG4 induced proliferation and anchorage-independent growth of HCC cells, while silencing of URGCP/URG4 had the opposite effect. Furthermore, URGCP/URG4 overexpression in HCC cells increased cellular entry into the G1/S transitional phase, associated with downregulation of p27^Kip1 and p21^Cip1 and upregulation of cyclin D1. These effects were accompanied by enhanced Akt activity and reduced FOXO3a transcriptional activity.

Conclusions

URGCP/URG4 plays an important role in promoting proliferation and tumorigenesis of HCC and may represent a novel prognostic biomarker and therapeutic target for this disease.

Generation of genetically modified mice by oocyte injection of androgenetic haploid embryonic stem cells

Haploid cells are amenable for genetic analysis. Recent success in the derivation of mouse haploid embryonic stem cells (haESCs) via parthenogenesis has enabled genetic screening in mammalian cells. However, successful generation of live animals from these haESCs, which is needed to extend the genetic analysis to the organism level, has not been achieved. Here, we report the derivation of haESCs from androgenetic blastocysts. These cells, designated as AG-haESCs, partially maintain paternal imprints, express classical ESC pluripotency markers, and contribute to various tissues, including the germline, upon injection into diploid blastocysts. Strikingly, live mice can be obtained upon injection of AG-haESCs into MII oocytes, and these mice bear haESC-carried genetic traits and develop into fertile adults. Furthermore, gene targeting via homologous recombination is feasible in the AG-haESCs. Our results demonstrate that AG-haESCs can be used as a genetically tractable fertilization agent for the production of live animals via injection into oocytes.

Hypoxia-induced down-regulation of microRNA-34a promotes EMT by targeting the Notch signaling pathway in tubular epithelial cells

Background

Hypoxia-induced renal tubular cell epithelial–mesenchymal transition (EMT) is an important event leading to renal fibrosis. MicroRNAs (miRNAs) are small non-coding RNA molecules that bind to their mRNA targets, thereby leading to translational repression. The role of miRNA in hypoxia-induced EMT is largely unknown.

Methodology/Principal Findings

miRNA profiling was performed for the identification of differentially expressed miRNAs in HK-2 cells under normal and low oxygen, and the results were then verified by quantitative real time RT-PCR (qRT-PCR). The function of miRNAs in hypoxia-induced renal tubular cell EMT was assessed by the transfection of specific miRNA inhibitors and mimics. Luciferase reporter gene assays and western blot analysis were performed to validate the target genes of miR-34a. siRNA against Jagged1 was designed to investigate the role of the miR-34a-Notch pathway in hypoxia induced renal tubular cell EMT. miRNA-34a was identified as being downregulated in hypoxic renal tubular epithelial cells. Inhibition of miR-34a expression in HK-2 cells, which highly express endogenous miR-34a, promoted a mesenchymal phenotype accompanied by reduced expression of the epithelial marker Z0-1, E-cadherin and increased expression of the mesenchymal markers α-SMA and vimentin. Conversely, miR-34a mimics effectively prevented hypoxia-induced EMT. Transfection of miRNA-34a in HK-2 cells under hypoxia abolished hypoxia-induced expression of Notch1 and Jagged1 as well as Notch downstream signals, such as snail. Western blot analysis and luciferase reporter gene assays showed direct evidence for miR-34a targeting Notch1 and Jagged1. siRNAs against Jagged1 or Notch1 effectively prevented miR-34a inhibitor-induced tubular epithelial cell EMT.

Conclusions/Significance

Our study provides evidence that the hypoxia-induced decrease of miR-34a expression could promote EMT in renal tubular epithelial cells by directly targeting Notch1 and Jagged1, and subsequently, Notch downstream signaling.

Expression, purification, and functional characterization of recombinant PTD-SARA

The Smad anchor for receptor activation (SARA) protein is a binding partner for Smad2/3 that plays an important role in the fibrotic promoting signaling pathway initiated by transforming growth factor-β1 (TGF-β1). The C-terminal 665-750 aa of SARA comprises the Smad-binding domain (SBD). By direct interaction through the SBD, SARA inhibits Smad2/3 phosphorylation and blocks the interaction between Smad2/3 and Smad4, thereby restrains the process of fibrosis. In this study, we constructed a SARA peptide aptamer based on the SBD sequence. The recombinant SARA aptamer, fused with a protein transduction domain (PTD-SARA), was cloned, purified from E. coli, and characterized for the first time. The full-length PTD-SARA coding sequence, created with E. coli favored codons, was cloned into a pQE-30 vector, and the recombinant plasmid was transformed into an M15 strain. After Isopropyl β-D-1-Thiogalactopyranoside (IPTG) induction and Ni(2+) affinity purification, recombinant PTD-SARA was further identified by immunoblotting and protein N-terminal sequencing. Epifluorescence microscopy revealed that the recombinant PTD-SARA was transferred into the cytoplasm and nucleus more efficiently than SARA. Moreover, the recombinant PTD-SARA was found to up-regulate the level of E-cadherin and down-regulate the levels of α-SMA and phospho-Smad3 more efficiently than SARA (P < 0.05). Our work explored a method to obtain recombinant PTD-SARA protein. The recombinant PTD-SARA fusion protein could enter HK2 cells (an immortalized proximal tubule epithelial cell line) more efficiently than the SARA protein and reverse the renal epithelial-to-mesenchymal transdifferentiation process that was induced by TGF-β1 more effectively than the SARA protein. Recombinant PDT-SARA is likely to be a potential candidate for clinical prevention and treatment of renal fibrosis.