Roles of Arf6 in cancer cell invasion, metastasis and proliferation

Protein S-glutathionylation confers cellular resistance to ferroptosis induced by glutathione depletion

Ferroptosis is one of the most critical biological consequences of glutathione depletion. Excessive oxidative stress, indicated by an elevated oxidized glutathione (GSSG)/reduced glutathione (GSH) ratio, is recognized as a key driver of ferroptosis. However, in glutathione depletion-induced ferroptosis, a marked decrease in total glutathione levels (including both GSH and GSSG) is frequently observed, yet its significance remains understudied. Protein S-glutathionylation (protein-SSG) levels are closely linked to the redox state and cellular glutathione pools including GSH and GSSG. To date, the role of protein-SSG during cell ferroptosis induced by glutathione depletion remains poorly understood. Here, we demonstrated that upregulation of CHAC1, a glutathione-degrading enzyme, acted as a key regulator of protein-SSG formation and exacerbated glutathione depletion-induced ferroptosis. This effect was observed in both in vitro and in vivo models, including erastin-induced ferroptosis across multiple cell lines and acetaminophen overdose-triggered ferroptosis in hepatocytes. Deficiency of CHAC1 resulted in increased glutathione pools, enhanced protein-SSG, improved liver function, and attenuation of hepatocyte ferroptosis upon acetaminophen challenge. These protective effects were reversed by CHAC1 overexpression. Using quantitative redox proteomics, we identified glutathione pool-sensitive S-glutathionylated proteins. As an important example, we discovered that ADP-ribosylation factor 6 (ARF6) was regulated by S-glutathionylation during glutathione depletion-induced ferroptosis. Our findings revealed that CHAC1 upregulation reduced the S-glutathionylation of ARF6, resulting in decreased ARF6 levels in lysosomes. This, in turn, enhanced the localization of the transferrin receptor (TFRC) on the cell membrane and increased transferrin uptake, ultimately compromising the protective role of ARF6 in ferroptosis induced by glutathione depletion. Targeting TFRC using GalNAc-siTfrc mitigated acetaminophen-induced liver injury in vivo. In conclusion, our study provide evidence that availability of glutathione pools affects protein S-glutathionylation and regulates protein functions to influence the process of ferroptosis, which opens an avenue to understanding the cell ferroptosis induced by glutathione depletion.

Methuosis key gene ARF6 as a diagnostic, prognostic and immunotherapeutic marker for prostate cancer: based on a comprehensive pan-cancer multi-omics analysis

BACKGROUND

Prostate cancer (PCa) is a leading cause of cancer-related mortality among men worldwide. Despite progress in the understanding of tumor biology, the prognosis for advanced prostate cancer remains poor, necessitating the identification of novel diagnostic, prognostic, and therapeutic biomarkers. Methuosis, a recently identified form of programmed cell death (PCD), is characterized by cytoplasmic vacuole accumulation and subsequent cell rupture, distinct from classical apoptosis and necrosis. The key regulatory gene in Methuosis, ARF6 (ADP-ribosylation factor 6), has emerged as a potential marker for cancer diagnosis and treatment. However, its role in prostate cancer and other malignancies remains insufficiently understood.

METHODS

In this study, we performed a comprehensive pan-cancer multi-omics analysis to investigate the role of ARF6 in Methuosis across multiple cancer types, with a specific focus on PCa as the primary context. Using data from public databases, including RNA sequencing, gene expression profiling, and clinical outcomes, we assessed the association between ARF6 expression and patient prognosis in PCa within this broader pan-cancer framework. Additionally, we employed functional enrichment analyses and survival analysis to explore the potential of ARF6 as a diagnostic and prognostic marker for prostate cancer. Immunotherapy-related gene expression signatures were also evaluated to determine the therapeutic relevance of ARF6.

RESULTS

ARF6 was significantly overexpressed in PCa tissues compared to normal tissues and was associated with poor prognosis (p < 0.05), particularly in advanced and metastatic stages. Receiver operating characteristic (ROC) analysis revealed a diagnostic AUC of 0.792 for ARF6. Functional analyses indicated that ARF6 regulates pathways critical to cell migration, invasion, and drug resistance. Moreover, ARF6 expression showed a strong negative correlation with immune checkpoint markers, such as PD-L1 (r = - 0.74), suggesting its potential as an immunotherapy target. These findings underscore ARF6's pivotal role in Methuosis and its promise as a biomarker in PCa.

CONCLUSION

ARF6 is a key regulator of Methuosis in prostate cancer, contributing to tumor progression, metastasis, and resistance to treatment. Our findings support the potential of ARF6 as a diagnostic, prognostic, and immunotherapeutic target in prostate cancer. Further experimental validation is needed to confirm these observations and to explore the therapeutic implications of targeting ARF6 in cancer treatment.

The calcium pump PMCA4b promotes epithelial cell polarization and lumen formation

Loss of epithelial cell polarity and tissue disorganization are hallmarks of carcinogenesis, in which Ca2+ signaling plays a significant role. Here we demonstrate that the plasma membrane Ca2+ pump PMCA4 (ATP2B4) is downregulated in luminal breast cancer, and this is associated with shorter relapse-free survival in patients with luminal A and B1 subtype tumors. Using the MCF-7 breast cancer cell model we show that PMCA4 silencing results in the loss of cell polarity while a forced increase in PMCA4b expression induces cell polarization and promotes lumen formation. We identify Arf6 as a regulator of PMCA4b endocytic recycling essential for PMCA4-mediated lumen formation. Silencing of the single pmca gene in Drosophila melanogaster larval salivary gland destroys lumen morphology suggesting a conserved role of PMCAs in lumen morphogenesis. Our findings point to a role of PMCA4 in controlling epithelial cell polarity, and in the maintenance of normal glandular tissue architecture.

Construction of T-Cell-Related Prognostic Risk Models and Prediction of Tumor Immune Microenvironment Regulation in Pancreatic Adenocarcinoma via Integrated Analysis of Single-Cell RNA-Seq and Bulk RNA-Seq

Pancreatic adenocarcinoma (PAAD) is a fatal malignant tumor of the digestive system, and immunotherapy has currently emerged as a key therapeutic approach for treating PAAD, with its efficacy closely linked to T-cell subsets and the tumor immune microenvironment. However, reliable predictive markers to guide clinical immunotherapy for PAAD are not available. We analyzed the single-cell RNA sequencing (scRNA-seq) data focused on PAAD from the GeneExpressionOmnibus (GEO) database. Then, the information from the Cancer Genome Atlas (TCGA) database was integrated to develop and validate a prognostic risk model derived from T-cell marker genes. Subsequently, the correlation between these risk models and the effectiveness of immunotherapy was explored. Analysis of scRNA-seq data uncovered six T-cell subtypes and 1837 T-cell differentially expressed genes (DEGs). Combining these data with the TCGA dataset, we constructed a T-cell prognostic risk model containing 16 DEGs, which can effectively predict patient survival and immunotherapy outcomes. We have found that patients in the low-risk group had better prognostic outcomes, increased immune cell infiltration, and signs of immune activation compared to those in the high-risk group. Additionally, analysis of tumor mutation burden showed higher mutation rates in patients with PAAD in the high-risk group. Risk scores with immune checkpoint gene expression and drug sensitivity analysis provide patients with multiple therapeutic targets and drug options. Our study constructed a prognostic risk model for PAAD patients based on T-cell marker genes, providing valuable insights into predicting patient prognosis and the effectiveness of immunotherapy.

Altered expression of vesicular trafficking machinery in prostate cancer affects lysosomal dynamics and provides insight into the underlying biology and disease progression

BACKGROUND

This study focuses on the role of lysosomal trafficking in prostate cancer, given the essential role of lysosomes in cellular homoeostasis.

METHODS

Lysosomal motility was evaluated using confocal laser scanning microscopy of LAMP-1-transfected prostate cells and spot-tracking analysis. Expression of lysosomal trafficking machinery was evaluated in patient cohort databases and through immunohistochemistry on tumour samples. The roles of vesicular trafficking machinery were evaluated through over-expression and siRNA. The effects of R1881 treatment on lysosome vesicular trafficking was evaluated by RNA sequencing, protein quantification and fixed- and live-cell microscopy.

RESULTS

Altered regulation of lysosomal trafficking genes/proteins was observed in prostate cancer tissue, with significant correlations for co-expression of vesicular trafficking machinery in Gleason patterns. The expression of trafficking machinery was associated with poorer patient outcomes. R1881 treatment induced changes in lysosomal distribution, number, and expression of lysosomal vesicular trafficking machinery in hormone-sensitive prostate cancer cells. Manipulation of genes involved in lysosomal trafficking events induced changes in lysosome positioning and cell phenotype, as well as differential effects on cell migration, in non-malignant and prostate cancer cells.

CONCLUSIONS

These findings provide novel insights into the altered regulation and functional impact of lysosomal vesicular trafficking in prostate cancer pathogenesis.

Metabolic regulation of neutrophil functions in homeostasis and diseases

Neutrophils are the most abundant leukocytes in humans and play a role in the innate immune response by being the first cells attracted to the site of infection. While early studies presented neutrophils as almost exclusively glycolytic cells, recent advances show that these cells use several metabolic pathways other than glycolysis, such as the pentose phosphate pathway, oxidative phosphorylation, fatty acid oxidation, and glutaminolysis, which they modulate to perform their functions. Metabolism shifts from fatty acid oxidation-mediated mitochondrial respiration in immature neutrophils to glycolysis in mature neutrophils. Tissue environments largely influence neutrophil metabolism according to nutrient sources, inflammatory mediators, and oxygen availability. Inhibition of metabolic pathways in neutrophils results in impairment of certain effector functions, such as NETosis, chemotaxis, degranulation, and reactive oxygen species generation. Alteration of these neutrophil functions is implicated in certain human diseases, such as antiphospholipid syndrome, coronavirus disease 2019, and bronchiectasis. Metabolic regulators such as AMPK, HIF-1α, mTOR, and Arf6 are linked to neutrophil metabolism and function and could potentially be targeted for the treatment of diseases associated with neutrophil dysfunction. This review details the effects of alterations in neutrophil metabolism on the effector functions of these cells.

Golgi apparatus targeted therapy in cancer: Are we there yet?

Membrane trafficking within the Golgi apparatus plays a pivotal role in the intracellular transportation of lipids and proteins. Dysregulation of this process can give rise to various pathological manifestations, including cancer. Exploiting Golgi defects, cancer cells capitalise on aberrant membrane trafficking to facilitate signal transduction, proliferation, invasion, immune modulation, angiogenesis, and metastasis. Despite the identification of several molecular signalling pathways associated with Golgi abnormalities, there remains a lack of approved drugs specifically targeting cancer cells through the manipulation of the Golgi apparatus. In the initial section of this comprehensive review, the focus is directed towards delineating the abnormal Golgi genes and proteins implicated in carcinogenesis. Subsequently, a thorough examination is conducted on the impact of these variations on Golgi function, encompassing aspects such as vesicular trafficking, glycosylation, autophagy, oxidative mechanisms, and pH alterations. Lastly, the review provides a current update on promising Golgi apparatus-targeted inhibitors undergoing preclinical and/or clinical trials, offering insights into their potential as therapeutic interventions. Significantly more effort is required to advance these potential inhibitors to benefit patients in clinical settings.

Targeting guanine nucleotide exchange factors for novel cancer drug discovery

INTRODUCTION

Guanine nucleotide exchange factors (GEFs) regulate the activation of small GTPases (G proteins) of the Ras superfamily proteins controlling cellular functions. Ras superfamily proteins act as 'molecular switches' that are turned 'ON' by guanine exchange. There are five major groups of Ras family GTPases: Ras, Ran, Rho, Rab and Arf, with a variety of different GEFs regulating their GTP loading. GEFs have been implicated in various diseases including cancer. This makes GEFs attractive targets to modulate signaling networks controlled by small GTPases.

AREAS COVERED

In this review, the roles and mechanisms of GEFs in malignancy are outlined. The mechanism of guanine exchange activity by GEFs on a small GTPase is illustrated. Then, some examples of GEFs that are significant in cancer are presented with a discussion on recent progress in therapeutic targeting efforts using a variety of approaches.

EXPERT OPINION

Recently, GEFs have emerged as potential therapeutic targets for novel cancer drug development. Targeting small GTPases is challenging; thus, targeting their activation by GEFs is a promising strategy. Most GEF-targeted drugs are still in preclinical development. A deeper biological understanding of the underlying mechanisms of GEF activity and utilizing advanced technology are necessary to enhance drug discovery for GEFs in cancer.

Membrane trafficking alterations in breast cancer progression

Breast cancer (BC) is the most common type of cancer in women, and remains one of the major causes of death in women worldwide. It is now well established that alterations in membrane trafficking are implicated in BC progression. Indeed, membrane trafficking pathways regulate BC cell proliferation, migration, invasion, and metastasis. The 22 members of the ADP-ribosylation factor (ARF) and the >60 members of the rat sarcoma (RAS)-related in brain (RAB) families of small GTP-binding proteins (GTPases), which belong to the RAS superfamily, are master regulators of membrane trafficking pathways. ARF-like (ARL) subfamily members are involved in various processes, including vesicle budding and cargo selection. Moreover, ARFs regulate cytoskeleton organization and signal transduction. RABs are key regulators of all steps of membrane trafficking. Interestingly, the activity and/or expression of some of these proteins is found dysregulated in BC. Here, we review how the processes regulated by ARFs and RABs are subverted in BC, including secretion/exocytosis, endocytosis/recycling, autophagy/lysosome trafficking, cytoskeleton dynamics, integrin-mediated signaling, among others. Thus, we provide a comprehensive overview of the roles played by ARF and RAB family members, as well as their regulators in BC progression, aiming to lay the foundation for future research in this field. This research should focus on further dissecting the molecular mechanisms regulated by ARFs and RABs that are subverted in BC, and exploring their use as therapeutic targets or prognostic markers.

Splenic proteome profiling in response to Marek's disease virus strain GX0101 infection

Marek's disease virus (MDV) strain GX0101 was the first reported field strain of recombinant gallid herpesvirus type 2 (GaHV-2). However, the splenic proteome of MDV-infected chickens remains unclear. In this study, a total of 28 1-day-old SPF chickens were intraperitoneally injected with chicken embryo fibroblast (CEF) containing 2000 PFU GX0101. Additionally, a control group, consisting of four one-day-old SPF chickens, received intraperitoneal equal doses of CEF. Blood and various tissue samples were collected at different intervals (7, 14, 21, 30, 45, 60, and 90 days post-infection; dpi) for histopathological, real-time PCR, and label-free quantitative analyses. The results showed that the serum expressions of MDV-related genes, meq and gB, peaked at 45 dpi. The heart, liver, and spleen were dissected at 30 and 45 dpi, and their hematoxylin-eosin staining indicated that virus infection compromised the normal organizational structure at 45 dpi. Particularly, the spleen structure was severely damaged, and the lymphocytes in the white medulla were significantly reduced. Furthermore, liquid chromatography-mass spectrometry (LC-MS) and label-free techniques were used to analyze the difference in splenic proteome profiles of the experimental and control groups at 30 and 45 dpi. Proteomic analysis identified 1660 and 1244 differentially expressed proteins (DEPs) at 30 and 40 dpi, respectively, compared with the uninfected spleen tissues. According to GO analysis, these DEPs were involved in processes such as organelle organization, cellular component biogenesis, cellular component assembly, anion binding, small molecule binding, metal ion binding, cation binding, cytosol, nuclear part, etc. Additionally, KEGG analysis indicated that the following pathways were linked to MDV-induced inflammation, apoptosis, and tumor: Wnt, Hippo, AMPK, cAMP, Notch, TGF-β, PI3K-Akt, Rap1, Ras, Calcium, NF-κB, PPAR, cGMP-PKG, Apoptosis, VEGF, mTOR, FoxO, TNF, JAK-STAT, MAPK, Prion disease, T cell receptor, and B cell receptor. We finally screened 674 DEPs that were linked to MDV infection in spleen tissue. This study improves our understanding of the MDV response mechanism in the spleen.

The Sclerotinia sclerotiorum ADP-Ribosylation Factor 6 Plays an Essential Role in Abiotic Stress Response and Fungal Virulence to Host Plants

The ADP-ribosylation factor 6 (Arf6), as the only member of the Arf family III protein, has been extensively studied for its diverse biological functions in animals. Previously, the Arf6 protein in Magnaporthe oryzae was found to be crucial for endocytosis and polarity establishment during asexual development. However, its role remains unclear in S. sclerotiorum. Here, we identified and characterized SsArf6 in S. sclerotiorum using a reverse genetic approach. Deletion of SsArf6 impaired hyphal growth and development and produced more branches. Interestingly, knockout of SsArf6 resulted in an augmented tolerance of S. sclerotiorum towards oxidative stress, and increased its sensitivity towards osmotic stress, indicative of the different roles of SsArf6 in various stress responses. Simultaneously, SsArf6 deletion led to an elevation in melanin accumulation. Moreover, the appressorium formation was severely impaired, and fungal virulence to host plants was significantly reduced. Overall, our findings demonstrate the essential role of SsArf6 in hyphal development, stress responses, appressorium formation, and fungal virulence to host plants.

A prognostic model based on prognosis-related ferroptosis genes for patients with acute myeloid leukemia

Background: Acute myeloid leukemia (AML) is a heterogeneous disorder with an unpredictable prognosis. Ferroptosis, the iron-dependent cell death program, could serve as an alternative for overcoming drug resistance. However, its effect on AML remains largely unclear. Methods: We collected RNA sequencing data and relevant clinical information of AML patients from The Cancer Genome Atlas to construct a prognosis prediction model. Risk score was calculated with eight prognosis-related ferroptosis genes (PRFGs) discovered through univariate analysis and Least Absolute Shrinkage and Selection Operator (LASSO) Cox regression. A nomogram was constructed by incorporating LASSO risk score, age, and cytogenetic risk based on univariate/multivariate Cox regression. Results: Of the 33 AML PRFGs identified from the TCGA-derived dataset, 8 genes were used to construct a gene signature to predict AML prognosis. Principal component analysis and heatmap showed significant differences between the low and high risk score groups. Next, LASSO risk score, age, and cytogenetic risk were incorporated into the nomogram to predict the overall survival (OS) of AML patients. According to survival analysis, patients with a low risk score had markedly increased OS as compared to those with a high risk score. Based on the results of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, the differences between the two risk groups showed a close relationship with immune-related pathways and membrane transportation. The analysis of tumor-infiltrating immune cells and immune checkpoints revealed that the immunosuppressive tumor microenvironment possibly facilitated different prognostic outcomes between the two groups. Gene expression analyses showed that the mRNA expression levels of PARP1 and PARP3 (PARPs) were closely related to the different clinical subgroups and the analyzed OS in AML patients. Finally, the PARP inhibitor talazoparib and the ferroptosis inducer erastin exerted a synergistic anti-proliferative effect on AML cells. Conclusion: We constructed a nomogram by incorporating PRFGs, and the constructed nomogram showed a good performance in AML patient stratification and prognosis prediction. The combination of PARP inhibitors with ferroptosis inducers could be a novel treatment strategy for treating AML patients.

Arf6 is required for endocytosis and filamentous actin assembly during angiogenesis in vitro

OBJECTIVE

Endocytosis is a process vital to angiogenesis and vascular homeostasis. In pathologies where supraphysiological growth factor signaling underlies disease etiology, such as in diabetic retinopathy and solid tumors, strategies to limit chronic growth factor signaling by way of blunting endocytic processes have been shown to have tremendous clinical value. ADP ribosylation factor 6 (Arf6) is a small GTPase that promotes the assembly of actin necessary for clathrin-mediated and clathrin-independent endocytosis. In its absence, growth factor signaling is greatly diminished, which has been shown to ameliorate pathological signaling input in diseased vasculature. However, it is less clear if there are bystander effects related to loss of Arf6 on angiogenic behaviors. Our goal was to provide an analysis of Arf6's function in angiogenic endothelium, focusing on its role in actin and endocytosis as well as sprouting morphogenesis.

METHODS

Primary endothelial cells were cultured in both 2D and 3D environments. Here, endothelial cells were fixed and stained for various proteins or transfected with fluorescently-tagged constructs for live-cell imaging.

RESULTS

We found that Arf6 localized to both filamentous actin and sites of endocytosis in two-dimensional culture. Loss of Arf6 distorted both apicobasal polarity and reduced the total cellular filamentous actin content, which may be the primary driver underlying gross sprouting dysmorphogenesis in its absence.

CONCLUSIONS

Our findings highlight that endothelial Arf6 is a potent mediator of both actin regulation and endocytosis and is required for proper sprout formation.

Arf6 as a therapeutic target: Structure, mechanism, and inhibitors

ADP-ribosylation factor 6 (Arf6), a small G-protein of the Ras superfamily, plays pivotal roles in multiple cellular events, including exocytosis, endocytosis, actin remodeling, plasma membrane reorganization and vesicular transport. Arf6 regulates the progression of cancer through the activation of cell motility and invasion. Aberrant Arf6 activation is a potential therapeutic target. This review aims to understand the comprehensive function of Arf6 for future cancer therapy. The Arf6 GEFs, protein structure, and roles in cancer have been summarized. Comprehending the mechanism underlying Arf6-mediated cancer cell growth and survival is essential. The structural features of Arf6 and its efforts are discussed and may be contributed to the discovery of future novel protein-protein interaction inhibitors. In addition, Arf6 inhibitors and mechanism of action are listed in the table. This review further emphasizes the crucial roles in drug resistance and attempts to offer an outlook of Arf6 in cancer therapy.

The emerging roles of MAPK-AMPK in ferroptosis regulatory network

Ferroptosis, a newform of programmed cell death, driven by peroxidative damages of polyunsaturated-fatty-acid-containing phospholipids in cellular membranes and is extremely dependent on iron ions, which is differs characteristics from traditional cell death has attracted greater attention. Based on the curiosity of this new form of regulated cell death, there has a tremendous progress in the field of mechanistic understanding of ferroptosis recent years. Ferroptosis is closely associated with the development of many diseases and involved in many diseases related signaling pathways. Not only a variety of oncoproteins and tumor suppressors can regulate ferroptosis, but multiple oncogenic signaling pathways can also have a regulatory effect on ferroptosis. Ferroptosis results in the accumulation of large amounts of lipid peroxides thus involving the onset of oxidative stress and energy stress responses. The MAPK pathway plays a critical role in oxidative stress and AMPK acts as a sensor of cellular energy and is involved in the regulation of the energy stress response. Moreover, activation of AMPK can induce the occurrence of autophagy-dependent ferroptosis and p53-activated ferroptosis. In recent years, there have been new advances in the study of molecular mechanisms related to the regulation of ferroptosis by both pathways. In this review, we will summarize the molecular mechanisms by which the MAPK-AMPK signaling pathway regulates ferroptosis. Meanwhile, we sorted out the mysterious relationship between MAPK and AMPK, described the crosstalk among ferroptosis and MAPK-AMPK signaling pathways, and summarized the relevant ferroptosis inducers targeting this regulatory network. This will provide a new field for future research on ferroptosis mechanisms and provide a new vision for cancer treatment strategies. Video Abstract.

Activation of NFAT by HGF and IGF-1 via ARF6 and its effector ASAP1 promotes uveal melanoma metastasis

Preventing or effectively treating metastatic uveal melanoma (UM) is critical because it occurs in about half of patients and confers a very poor prognosis. There is emerging evidence that hepatocyte growth factor (HGF) and insulin-like growth factor 1 (IGF-1) promote metastasis and contribute to the striking metastatic hepatotropism observed in UM metastasis. However, the molecular mechanisms by which HGF and IGF-1 promote UM liver metastasis have not been elucidated. ASAP1, which acts as an effector for the small GTPase ARF6, is highly expressed in the subset of uveal melanomas most likely to metastasize. Here, we found that HGF and IGF-1 hyperactivate ARF6, leading to its interaction with ASAP1, which then acts as an effector to induce nuclear localization and transcriptional activity of NFAT1. Inhibition of any component of this pathway impairs cellular invasiveness. Additionally, knocking down ASAP1 or inhibiting NFAT signaling reduces metastasis in a xenograft mouse model of UM. The discovery of this signaling pathway represents not only an advancement in our understanding of the biology of uveal melanoma metastasis but also identifies a novel pathway that could be targeted to treat or prevent metastatic uveal melanoma.

Preclinical-to-clinical Anti-cancer Drug Response Prediction and Biomarker Identification Using TINDL

Prediction of the response of cancer patients to different treatments and identification of biomarkers of drug response are two major goals of individualized medicine. Here, we developed a deep learning framework called TINDL, completely trained on preclinical cancer cell lines (CCLs), to predict the response of cancer patients to different treatments. TINDL utilizes a tissue-informed normalization to account for the tissue type and cancer type of the tumors and to reduce the statistical discrepancies between CCLs and patient tumors. Moreover, by making the deep learning black box interpretable, this model identifies a small set of genes whose expression levels are predictive of drug response in the trained model, enabling identification of biomarkers of drug response. Using data from two large databases of CCLs and cancer tumors, we showed that this model can distinguish between sensitive and resistant tumors for 10 (out of 14) drugs, outperforming various other machine learning models. In addition, our small interfering RNA (siRNA) knockdown experiments on 10 genes identified by this model for one of the drugs (tamoxifen) confirmed that tamoxifen sensitivity is substantially influenced by all of these genes in MCF7 cells, and seven of these genes in T47D cells. Furthermore, genes implicated for multiple drugs pointed to shared mechanism of action among drugs and suggested several important signaling pathways. In summary, this study provides a powerful deep learning framework for prediction of drug response and identification of biomarkers of drug response in cancer. The code can be accessed at https://github.com/ddhostallero/tindl.

Prognostic impact of MICALL1 and associates with immune infiltration in liver hepatocellular carcinoma patients

BACKGROUND

Liver hepatocellular carcinoma (LIHC) is one of the most malignancy over the world. Previous studies have proven that Molecules Interacting with CasL-Like 1 (MICALL1) participated in cellular trafficking cascades, while there has no study to explore the function and carcinogenic mechanism MICALL1 in LIHC.

METHODS

We aimed to investigate the relationship between MICALL1 mRNA expression and LIHC using TCGA database. The expression of MICALL1 protein in clinic samples were examined by UALCAN database. Kaplan-Meier method was used for survival analysis. Logistic regression and Cox regression were performed to evaluate the prognostic significance of MICALL1. The MICALL1-binding protein were built by the STRING tool. Enrichment analysis by GO, KEGG and GSEA was used to explore possible function of MICALL1. The ssGSEA method was used to investigate the association between MICALL1 expression and the immune infiltration level in LIHC.

RESULTS

The expression and prognostic value of different MICAL family members in LIHC were evaluated. The expression of MICALL1 was significantly increased at both the transcript and protein levels in LIHC tissues. Further, the LIHC patients with high MICALL1 levels showed a worse OS, DSS and PFI. Some clinicopathologic features were identified to be related to MICALL1 expression in LIHC included clinical T stage, pathologic stage, histologic grade and AFP concentration. Univariate and multivariate survival analysis showed that MICALL1 was an independent prognostic marker for OS and DSS. Further enrichment analysis revealed that the K-RAS, TNFα/NF-κB and inflammatory response were significantly enriched in the high MICALL1 expression group. Immune infiltration analysis showed that high MICALL1 expression was correlated with infiltration level of macrophage cells, Th2 cells and some other immune cell types, including TFH.

CONCLUSIONS

MICALL1 expression was significantly associated with immune cell infiltration and may regarded as a promising prognostic biomarker for LIHC patients.

Arf6 Regulates Endocytosis and Angiogenesis by Promoting Filamentous Actin Assembly

Clathrin-mediated endocytosis (CME) is a process vital to angiogenesis as well as general vascular homeostasis. In pathologies where supraphysiological growth factor signaling underlies disease etiology, such as in diabetic retinopathy and solid tumors, strategies to limit chronic growth factor signaling by way of CME have been shown to have tremendous clinical value. ADP ribosylation factor 6 (Arf6) is a small GTPase that promotes the assembly of actin necessary for CME. In its absence, growth factor signaling is greatly diminished, which has been shown to ameliorate pathological signaling input in diseased vasculature. However, it is less clear if there are bystander effects related to loss of Arf6 on angiogenic behaviors. Our goal was to provide a analysis of Arf6’s function in angiogenic endothelium, focusing on its role in lumenogenesis as well as its relation to actin and CME. We found that Arf6 localized to both filamentous actin and sites of CME in 2-dimensional culture. Loss of Arf6 distorted both apicobasal polarity and reduced the total cellular filamentous actin content, and this may be the primary driver underlying gross dysmorphogenesis during angiogenic sprouting in its absence. Our findings highlight that endothelial Arf6 is a potent mediator of both actin regulation and CME.

Extracellular vesicles and particles impact the systemic landscape of cancer

Intercellular cross talk between cancer cells and stromal and immune cells is essential for tumor progression and metastasis. Extracellular vesicles and particles (EVPs) are a heterogeneous class of secreted messengers that carry bioactive molecules and that have been shown to be crucial for this cell-cell communication. Here, we highlight the multifaceted roles of EVPs in cancer. Functionally, transfer of EVP cargo between cells influences tumor cell growth and invasion, alters immune cell composition and function, and contributes to stromal cell activation. These EVP-mediated changes impact local tumor progression, foster cultivation of pre-metastatic niches at distant organ-specific sites, and mediate systemic effects of cancer. Furthermore, we discuss how exploiting the highly selective enrichment of molecules within EVPs has profound implications for advancing diagnostic and prognostic biomarker development and for improving therapy delivery in cancer patients. Altogether, these investigations into the role of EVPs in cancer have led to discoveries that hold great promise for improving cancer patient care and outcome.

A positive feedback loop of ARF6 activates ERK1/2 signaling pathway via DUSP6 silencing to promote pancreatic cancer progression

ERK1/2 are essential proteins mediating mitogen-activated protein kinase signaling downstream of RAS in pancreatic adenocarcinoma (PDAC). Our previous study reveals that ARF6 plays a positive regulatory role in ERK1/2 pathway in a feedback loop manner. A significant part of the literature on ARF6 has emphasized its oncogenic effect as an essential downstream molecule of ERK1/2, and no research has been done on the regulation mechanisms of the feedback loop between ARF6 and the ERK1/2 signaling pathway. In the present study, we explore the gene network downstream of ARF6 and find that DUSP6 may be the critical signal molecule in the positive feedback loop between ARF6 and ERK1/2. Specifically, to elucidate the negative correlations between ARF6 and DUSP6 in pancreatic cancer, we examine their expressions in pancreatic cancer tissues by immunohistochemical staining. Then the impact of DUSP6 on the proliferation and apoptosis of PDAC cells are investigated by gain-of-function and loss-of-function approaches. Mechanism explorations uncover that ARF6 suppresses the expression of DUSP6, which is responsible for the dephosphorylation of ERK1/2. Altogether, these results indicate that DUSP6 plays a tumor-suppressive role and acts as an intermediate molecule between ARF6 and ERK1/2 in PDAC cells, thereby forming a positive feedback loop.

XIST sponges miR-320d to promote chordoma progression by regulating ARF6

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XIST was highly expressed in chordoma tissues.

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XIST knockdown inhibited chordoma progression by downregulating ARF6.

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MiR-320d inhibited the malignant behaviors of chordoma cells.

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XIST positively upregulated ARF6 expression via sponging miR-320d in chordoma cells.

Background

Long non-coding RNAs (lncRNAs) have been demonstrated to play important roles in various tumors, including chordoma. The purpose of this study was to investigate the role and mechanism of lncRNA X-inactive specific transcript (XIST) in chordoma.

Methods

RNA levels and protein levels were measured by real-time quantitative polymerase chain reaction (RT‑qPCR) and western blot assay, respectively. Cell proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, 5-ethynyl-2′-deoxyuridine (EdU) assay and colony formation assay. Tanswell assay was used to examine cell migration and invasion. Cellular glycolysis was examined via the measurement of extracellular acidification rate (ECAR) and lactate production. The interaction between microRNA-320d (miR-320d) and XIST or ADP-ribosylation factor 6 (ARF6) was predicted by bioinformatics analysis and verified by a dual-luciferase reporter and RNA-pull down assays. The xenograft tumor model was used to explore the biological function of XIST in vivo.

Results

XIST was overexpressed in chordoma tissues. XIST knockdown suppressed chordoma cell proliferation, migration, invasion, and glycolysis. XIST acted as a sponge of miR-320d. Moreover, miR-320d overexpression inhibited the proliferation, migration, invasion, and glycolysis of chordoma cells. ARF6 was a direct target of miR-320d, and XIST upregulated ARF6 expression via sponging miR-320d. Furthermore, overexpression of ARF6 reversed the inhibitory effects of XIST knockdown on chordoma cell proliferation, migration, invasion, and glycolysis. Importantly, XIST silencing blocked xenograft tumor growth in vivo.

Conclusion

XIST knockdown inhibited chordoma progression via regulating the miR-320d/ARF6 axis, providing a novel insight into chordoma pathogenesis.

Site-Specific 19F NMR Method for Detecting Arf6 GEF Activity

Guanine nucleotide exchange factors (GEFs) of small GTPase (sGTPase) coordinate signal networks in normal cells and dysfunction in cancer. Therefore, effective monitoring of GEF activity is very important for studying the regulation of sGTPase signal transduction. In this study, we developed a 1D ¹⁹F NMR-based method for rapid detection of the GEF activity of sGTPases. The activity of Arf6GEF in vitro and cell lysate environment can be conveniently detected by tracking the conformational changes of the Arf6 switch region where a tfmF site-specific ¹⁹F labeling at Phe47 was introduced. This strategy could potentially be applied to monitor the conformational change of Arf6 or other sGTPase and detect the activities of sGTPase regulatory proteins in physiology and pathology environments.

Construction of a Signature Model to Predict the Radioactive Iodine Response of Papillary Thyroid Cancer

Papillary thyroid cancer (PTC) accounts for about 90% of thyroid cancer. There are approximately 20%-30% of PTC patients showing disease persistence/recurrence and resistance to radioactive iodine (RAI) treatment. For these PTC patients with RAI refractoriness, the prognosis is poor. In this study, we aimed to establish a comprehensive prognostic model covering multiple signatures to increase the predictive accuracy for progression-free survival (PFS) of PTC patients with RAI treatment. The expression profiles of mRNAs and miRNAs as well as the clinical information of PTC patients were extracted from TCGA and GEO databases. A series of bioinformatics methods were successfully applied to filtrate a two-RNA model (IPCEF1 and hsa-mir-486-5p) associated with the prognosis of RAI-therapy. Finally, the RNA-based risk score was calculated based on the Cox coefficient of the individual RNA, which achieved good performances by the time-dependent receiver operating characteristic (tROC) curve and PFS analyses. Furthermore, the predictive power of the nomogram, integrated with the risk score and clinical parameters (age at diagnosis and tumor stage), was assessed by tROC curves. Collectively, our study demonstrated high precision in predicting the RAI response of PTC patients.

Genetic Influence on Frequencies of Myeloid-Derived Cell Subpopulations in Mouse

Differences in frequencies of blood cell subpopulations were reported to influence the course of infections, atopic and autoimmune diseases, and cancer. We have discovered a unique mouse strain B10.O20 containing extremely high frequency of myeloid-derived cells (MDC) in spleen. B10.O20 carries 3.6% of genes of the strain O20 on the C57BL/10 genetic background. It contains much higher frequency of CD11b⁺Gr1⁺ cells in spleen than both its parents. B10.O20 carries O20-derived segments on chromosomes 1, 15, 17, and 18. Their linkage with frequencies of blood cell subpopulations in spleen was tested in F₂ hybrids between B10.O20 and C57BL/10. We found 3 novel loci controlling MDC frequencies: Mydc1, 2, and 3 on chromosomes 1, 15, and 17, respectively, and a locus controlling relative spleen weight (Rsw1) that co-localizes with Mydc3 and also influences proportion of white and red pulp in spleen. Mydc1 controls numbers of CD11b⁺Gr1⁺ cells. Interaction of Mydc2 and Mydc3 regulates frequency of CD11b⁺Gr1⁺ cells and neutrophils (Gr1⁺Siglec-F^- cells from CD11b⁺ cells). Interestingly, Mydc3/Rsw1 is orthologous with human segment 6q21 that was shown previously to determine counts of white blood cells. Bioinformatics analysis of genomic sequence of the chromosomal segments bearing these loci revealed polymorphisms between O20 and C57BL/10 that change RNA stability and genes’ functions, and we examined expression of relevant genes. This identified potential candidate genes Smap1, Vps52, Tnxb, and Rab44. Definition of genetic control of MDC can help to personalize therapy of diseases influenced by these cells.

Arf6 anchors Cdr2 nodes at the cell cortex to control cell size at division

Fission yeast cells prevent mitotic entry until a threshold cell surface area is reached. The protein kinase Cdr2 contributes to this size control system by forming multiprotein nodes that inhibit Wee1 at the medial cell cortex. Cdr2 node anchoring at the cell cortex is not fully understood. Through a genomic screen, we identified the conserved GTPase Arf6 as a component of Cdr2 signaling. Cells lacking Arf6 failed to divide at a threshold surface area and instead shifted to volume-based divisions at increased overall size. Arf6 stably localized to Cdr2 nodes in its GTP-bound but not GDP-bound state, and its guanine nucleotide exchange factor (GEF), Syt22, was required for both Arf6 node localization and proper size at division. In arf6Δ mutants, Cdr2 nodes detached from the membrane and exhibited increased dynamics. These defects were enhanced when arf6Δ was combined with other node mutants. Our work identifies a regulated anchor for Cdr2 nodes that is required for cells to sense surface area.

Development of a NanoBRET assay to validate dual inhibitors of Sirt2-mediated lysine deacetylation and defatty-acylation that block prostate cancer cell migration

Sirtuin2 (Sirt2) with its NAD⁺-dependent deacetylase and defatty-acylase activities plays a central role in the regulation of specific cellular functions. Dysregulation of Sirt2 activity has been associated with the pathogenesis of many diseases, thus making Sirt2 a promising target for pharmaceutical intervention. Herein, we present new high affinity Sirt2 selective Sirtuin-Rearranging Ligands (SirReals) that inhibit both Sirt2-dependent deacetylation and defatty-acylation in vitro and in cells. We show that simultaneous inhibition of both Sirt2 activities results in strongly reduced levels of the oncoprotein c-Myc and an inhibition of cancer cell migration. Furthermore, we describe the development of a NanoBRET-based assay for Sirt2, thereby providing a method to study cellular target engagement for Sirt2 in a straightforward and accurately quantifiable manner. Applying this assay, we could confirm cellular Sirt2 binding of our new Sirt2 inhibitors and correlate their anticancer effects with their cellular target engagement.

Sirt2 inhibitors that show simultaneous inhibition of Sirt2 deacetylase and defatty-acylase activity block prostate cancer cell migration and their target engagement is shown by a newly developed NanoBRET assay.

A polymer‑calcium phosphate nanocapsule for RNAi-induced oxidative stress and cascaded chemotherapy

As most of intracellular reactive oxygen species (ROS) is produced in the mitochondria, mitochondrial modulation of cancer cell is a promising strategy for maximizing the in situ-activable combination therapy of oxidative catastrophe and cascaded chemotherapy. Herein, a serum-stable polymer‑calcium phosphate (CaP) hybrid nanocapsule carrying siRNA against ADP-ribosylation factor 6 (Arf6) overexpressed in cancer cells and parent drug camptothecin (CPT), designated as PTkCPT/siRNA, was developed for the RNAi-induced oxidative catastrophe and cascaded chemotherapy. A copolymer of mPEG-P(Asp-co-TkCPT), covalently tethered with chemotherapeutic CPT via a ROS-labile dithioketal (Tk) linker, was synthesized and self-assembled into a PTkCPT micelle as a nanotemplate for the CaP mineralization. The as-prepared PTkCPT/siRNA nanoparticle showed a core-shell-distinct nanocapsule which was consisted of a spherical polymeric core enclosed within a CaP shell capable of releasing siRNA in response to lysosomal acidity. Blocking Arf6 signal pathway of cancer cells led to their mitochondrial aggregation and subsequently induced a burst of ROS for oxidative catastrophe, which further triggered the cascaded CPT chemotherapy via the breakage of ROS-labile dithioketal linker. This strategy of RNAi-induced oxidative catastrophe and cascaded chemotherapy resulted in a significant combination effect on cancer cell killing and tumor growth inhibition in mice with low side effects, and provided a promising paradigm for precise cancer therapy.

Long Non-Coding RNA MDFIC-7 Promotes Chordoma Progression Through Modulating the miR-525-5p/ARF6 Axis

Background

Chordoma, an extremely rare malignant tumor, remains difficult to be cured because of its strong local invasiveness and high recurrence rate. Long non-coding RNAs (lncRNAs) have been demonstrated to play multiple roles in various cancers. The purpose of this study was to investigate the modulatory function of lncRNA MDFIC-7 in chordoma and to elucidate its underlying mechanisms.

Methods

Quantitative real-time polymerase chain reaction was performed to detect the expression of lncRNA MDFIC-7 in tumor tissues and adjacent nontumorous tissues collected from 15 chordoma patients, as well as in chordoma cell lines. Gene silencing and overexpression experiments were carried out by RNA interference and lentiviral transduction. The effect of lncRNA MDFIC-7 on the proliferation of chordoma cells was evaluated by cell counting kit-8 assay, colony formation assay and xenograft tumor experiments. RNA immunoprecipitation and dual luciferase reporter assays were conducted to evaluate the binding between lncRNA MDFIC-7 and miRNA-525-5p and the interaction between miR-525-5p and the 3′ untranslated region of ADP-ribosylation factor 6 (ARF6) mRNA. The glycolytic capacity and mitochondrial function of chordoma cells were measured by the Seahorse Bioscience XF96 Extracellular Flux Analyzer.

Results

The expression of lncRNA MDFIC-7 was higher in chordoma tumor tissues than in adjacent non-tumor tissues. Downregulation of lncRNA MDFIC-7 reduced colony formation and cell proliferation in chordoma cells and decreased xenograft tumor growth in a nude mouse model. Moreover, lncRNA MDFIC-7 knockdown attenuated the Warburg effect in chordoma cells and xenograft tumors. LncRNA MDFIC-7 knockdown elevated miR-525-5p levels and decreased ARF6 expressions. Overexpression of ARF6 reversed the inhibitory effect of lncRNA MDFIC-7 knockdown on cell proliferation and the Warburg effect in chordoma cells and xenograft tumors. Mechanistically, lncRNA MDFIC-7, as a molecular sponge of miR-525-5p, negatively regulated miR-525-5p expression and promoted the gene expression of ARF6, a miR-525-5p target.

Conclusion

Our findings demonstrate that lncRNA MDFIC-7 acts as a molecular sponge to competitively bind to miR-525-5p and promote expression of ARF6. The lncRNA MDFIC-7/miR-525-5p/ARF6 axis regulates chordoma progression and the Warburg effect in chordoma, suggesting that lncRNA MDFIC-7 and miR-525-5p could be promising therapeutic targets for the treatment of chordoma.

ADP Ribosylation Factor 6 Promotes Contraction and Proliferation, Suppresses Apoptosis and Is Specifically Inhibited by NAV2729 in Prostate Stromal Cells

The presumed ADP ribosylation factor (ARF) 6 inhibitor NAV2729 inhibits human prostate smooth muscle contraction and proliferation of stromal cells, which are driving factors of voiding symptoms in benign prostatic hyperplasia (BPH). However, its specificity and a confirmed role of ARF6 for smooth muscle contraction are still pending. Here, we generated monoclonal ARF6 knockouts in human prostate stromal cells (WPMY-1), and characterized phenotypes of contractility, growth-related functions, and susceptibility to NAV2729 in knockout and control clones. ARF6 knockout was verified by Western blot. Knockout clones showed impaired contraction and actin organization, reduced proliferation and viability, and increased apoptosis and cell death. In ARF6-expressing control clones, NAV2729 (5 µM) strongly inhibited contraction (67% inhibition across all three control clones), actin organization (72%), proliferation (97%), and viability (up to 82%), and increased apoptosis (5-fold) and cell death (6-fold). In ARF6 knockouts, effects of NAV2729 (5 µM) were widely reduced, including lacking or minor effects on contractions (0% inhibition across all three knockout clones), actin (18%) and proliferation (13%), and lacking increases of apoptosis and cell death. Viability was reduced by NAV2729 with an IC50 of 3.3 µM across all three ARF6 control clones, but of 4.5-8.2 µM in ARF6 knockouts. In conclusion, ARF6 promotes prostate smooth muscle contraction and proliferation of stromal cells. Both are inhibited by NAV2729, which showed high specificity for ARF6 up to 5 µM and represents an attractive compound in the context of BPH. Considering the relevance of smooth muscle-based diseases, shared roles of ARF6 in other smooth muscle types merit further investigation. SIGNIFICANCE STATEMENT: By knockout of ARF6 in prostate stromal cells, this study demonstrates the involvement of ARF6 in promotion of prostate smooth muscle contraction and stromal growth, and defines concentration ranges for their ARF6-specific inhibition by NAV2729. Besides the context of benign prostatic hyperplasia and lower urinary tract symptoms, analog ARF6 functions in contraction and growth appear possible in other smooth muscle-rich organs, which merits further attention considering the high clinical relevance of smooth muscle-based diseases.

miR-28-3p inhibits prostate cancer cell proliferation, migration and invasion, and promotes apoptosis by targeting ARF6

Previous studies have reported that the expression levels of microRNA (miR)-28-3p are downregulated in prostate cancer (PCa) compared with those in adjacent normal tissues. However, to the best of our knowledge, the function and underlying mechanisms of miR-28-3p in PCa have not been reported. The present study aimed to explore the role of miR-28-3p and its mechanism in the development of PCa. In the present study, miR-28-3p and ADP-ribosylation factor 6 (ARF6) expression levels were analyzed using reverse transcription-quantitative PCR (RT-qPCR). Cell proliferation, colony formation, apoptosis, migration and invasion were determined using Cell Counting Kit-8, colony forming, flow cytometry and Transwell assays, respectively. The association between miR-28-3p and ARF6 was investigated using a dual luciferase reporter assay. ARF6, Rac1, Erk1/2 and phosphorylated (p)-Erk1/2 protein expression levels were analyzed using western blotting. The results of the present study revealed that miR-28-3p expression levels were downregulated, whereas ARF6 expression levels were upregulated in PCa cell lines (LNCaP, 22Rv-1, PC-3 and DU145) compared with those in the normal prostate line RWPE-1. The overexpression of miR-28-3p promoted cell apoptosis, and inhibited cell proliferation, colony formation, migration and invasion. However, the knockdown of miR-28-3p exerted the opposite results. The results of the dual luciferase reporter assays, RT-qPCR and western blotting indicated that ARF6 was a target gene of miR-28-3p. Finally, rescue experiments demonstrated that ARF6 overexpression attenuated the effects of the miR-28-3p mimic by upregulating Rac1 and p-Erk1/2 expression in PCa cells. In conclusion, these findings indicated that miR-28-3p may inhibit the biological behaviors of PCa cells by targeting ARF6, and therefore may represent a novel therapeutic candidate for PCa.

Profiling of 3D Genome Organization in Nasopharyngeal Cancer Needle Biopsy Patient Samples by a Modified Hi-C Approach

Nasopharyngeal cancer (NPC), a cancer derived from epithelial cells in the nasopharynx, is a cancer common in China, Southeast Asia, and Africa. The three-dimensional (3D) genome organization of nasopharyngeal cancer is poorly understood. A major challenge in understanding the 3D genome organization of cancer samples is the lack of a method for the characterization of chromatin interactions in solid cancer needle biopsy samples. Here, we developed Biop-C, a modified in situ Hi-C method using solid cancer needle biopsy samples. We applied Biop-C to characterize three nasopharyngeal cancer solid cancer needle biopsy patient samples. We identified topologically associated domains (TADs), chromatin interaction loops, and frequently interacting regions (FIREs) at key oncogenes in nasopharyngeal cancer from the Biop-C heatmaps. We observed that the genomic features are shared at some important oncogenes, but the patients also display extensive heterogeneity at certain genomic loci. On analyzing the super enhancer landscape in nasopharyngeal cancer cell lines, we found that the super enhancers are associated with FIREs and can be linked to distal genes via chromatin loops in NPC. Taken together, our results demonstrate the utility of our Biop-C method in investigating 3D genome organization in solid cancers.

Integrated analysis of Solute carrier family-2 members reveals SLC2A4 as an independent favorable prognostic biomarker for breast cancer

Most of Solute carrier family-2 (SLC2) members play a key role of facilitative transporters, and glucose transporter (GLUT) proteins encoded by SLC2s can transport hexoses or polyols. However, the function and mechanism of SLC2s remain unclear in human cancers. Here, we explored the dysregulated expression, prognostic values, epigenetic, genetic alterations, and biomolecular network of SLC2s in human cancers. According to the data from public-omicsrepository, SLC2A4 (GLUT4) was found to be significantly downregulated in most cancers, and higher messenger RNA (mRNA) expression of SLC2A4 significantly associated with better prognosis of breast cancer (BRCA) patients. Moreover, DNA hypermethylation in the promoter of SLC2A4 may affect the regulation of its mRNA expression, and SLC2A4 was strongly correlated with pathways, including the translocation of SLC2A4 to the plasma membrane and PID INSULIN PATHWAY. In conclusion, these results provide insight into SLC2s in human cancers and suggest that SLC2A4 could be an unfavorable prognostic biomarker for the survival of BRCA patients.

Discovery of a dual Ras and ARF6 inhibitor from a GPCR endocytosis screen

Internalization and intracellular trafficking of G protein-coupled receptors (GPCRs) play pivotal roles in cell responsiveness. Dysregulation in receptor trafficking can lead to aberrant signaling and cell behavior. Here, using an endosomal BRET-based assay in a high-throughput screen with the prototypical GPCR angiotensin II type 1 receptor (AT1R), we sought to identify receptor trafficking inhibitors from a library of ~115,000 small molecules. We identified a novel dual Ras and ARF6 inhibitor, which we named Rasarfin, that blocks agonist-mediated internalization of AT1R and other GPCRs. Rasarfin also potently inhibits agonist-induced ERK1/2 signaling by GPCRs, and MAPK and Akt signaling by EGFR, as well as prevents cancer cell proliferation. In silico modeling and in vitro studies reveal a unique binding modality of Rasarfin within the SOS-binding domain of Ras. Our findings unveil a class of dual small G protein inhibitors for receptor trafficking and signaling, useful for the inhibition of oncogenic cellular responses.

While Ras is a promising target for cancer therapy, development of inhibitors targeting Ras signaling has proven challenging. Here, the authors report the discovery of Rasarfin, a small molecule from a phenotypic screen on G protein-coupled receptor (GPCR) endocytosis that acts as a dual Ras and ARF6 inhibitor.

Over-expressed RHEB promotes the progression of pancreatic adenocarcinoma

AIMS

Mammalian/mechanistic target of rapamycin (mTOR) is essential in the progression of pancreatic adenocarcinoma (PAAD). But the role of Ras homolog enriched in brain (RHEB), a key activator of mTORC1, is unclear in this disease. This work aims to clarify the function of RHEB in PAAD.

MATERIALS AND METHODS

A pan-cancer analysis of RHEB was conducted by using data from several public available databases. Immunohistochemical (IHC) staining on a tissue microarray was used to validate the expression of RHEB in PAAD. In vitro experiments were conducted to explore the function of RHEB in the disease. An integrated bioinformatics tools were used to understand the mechanism of RHEB and construct a RHEB-related prognostic signature.

KEY FINDINGS

RHEB was significantly overexpressed in PAAD and high expression of the gene was associated with poor prognosis. RHEB promoted proliferation, migration and invasion of pancreatic cancer cells. Gene set enrichment analysis (GSEA) showed that RHEB participated in cell cycle progression and WNT signaling pathway. A RHEB-related prognostic signature was developed, and PAAD patients with high risk score had a significantly shorter overall survival.

SIGNIFICANCE

RHEB was up-regulated in PAAD and might be a useful therapeutic target.

Construction and Analysis of the Dysregulated ceRNA Network and Identification of Risk Long Noncoding RNAs in Breast Cancer

Breast cancer (BRCA) is the second leading cause of cancer-related mortality in women worldwide. However, the molecular mechanism involved in the development of BRCA is not fully understood. In this study, based on the miRNA-mediated long non-coding RNA (lncRNA)-protein coding gene (PCG) relationship and lncRNA-PCG co-expression information, we constructed and analyzed a specific dysregulated lncRNA-PCG co-expression network in BRCA. Then, we performed the random walk with restart (RWR) method to prioritize BRCA-related lncRNAs through comparing their RWR score and significance. As a result, we identified 30 risk lncRNAs for BRCA, which can distinguish normal and tumor samples. Moreover, through gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis, we found that these risk lncRNAs mainly synergistically exerted functions related to cell cycle and DNA separation and replication. At last, we developed a four-lncRNA prognostic signature (including AP000851.1, LINC01977, MAFG-DT, SIAH2-AS1) and assessed the survival accuracy of the signature by performing time-dependent receiver operating characteristic (ROC) analysis. The areas under the ROC curve for 1, 3, 5, and 10 years of survival prediction were 0.68, 0.61, 0.62, and 0.63, respectively. The multivariable Cox regression results verified that the four-lncRNA signature could be used as an independent prognostic biomarker in BRCA. In summary, these results have important reference value for the study of diagnosis, treatment, and prognosis evaluation of BRCA.

The ins and outs of microvesicles

Microvesicles are a heterogeneous group of membrane-enclosed vesicles that are released from cells into the extracellular space by the outward budding and pinching of the plasma membrane. These vesicles are loaded with multiple selectively sorted proteins and nucleic acids. Although interest in the clinical potential of microvesicles is increasing, there is only limited understanding of different types of microvesicles and the mechanisms involved in their formation. Here, we describe what is presently known about this expanding and complex field of research focusing on the mechanism of biogenesis, cargo loading, and release of microvesicles.

Chlortetracycline, a Novel Arf Inhibitor That Decreases the Arf6-Dependent Invasive Properties of Breast Cancer Cells

Breast cancer is a major disease for women worldwide, where mortality is associated with tumour cell dissemination to distant organs. While the number of efficient anticancer therapies increased in the past 20 years, treatments targeting the invasive properties of metastatic tumour cells are still awaited. Various studies analysing invasive breast cancer cell lines have demonstrated that Arf6 is an important player of the migratory and invasive processes. These observations make Arf6 and its regulators potential therapeutic targets. As of today, no drug effective against Arf6 has been identified, with one explanation being that the activation of Arf6 is dependent on the presence of lipid membranes that are rarely included in drug screening. To overcome this issue we have set up a fluorescence-based high throughput screening that follows overtime the activation of Arf6 at the surface of lipid membranes. Using this unique screening assay, we isolated several compounds that affect Arf6 activation, among which the antibiotic chlortetracycline (CTC) appeared to be the most promising. In this report, we describe CTC in vitro biochemical characterization and show that it blocks both the Arf6-stimulated collective migration and cell invasion in a 3D collagen I gel of the invasive breast cancer cell line MDA-MB-231. Thus, CTC appears as a promising hit to target deadly metastatic dissemination and a powerful tool to unravel the molecular mechanisms of Arf6-mediated invasive processes.

Circ_0105346 Knockdown Inhibits Osteosarcoma Development via Regulating miR-1182/WNT7B Axis

Background

Osteosarcoma (OS) is a common bone malignancy in children and adolescents. Circular RNAs (circRNAs) have been reported to affect OS progression. This paper mainly delineated the role of circRNA circ_0105346 in OS development and the potential mechanism.

Methods

Quantitative reverse transcription PCR (qRT-PCR) and Western blot assays were applied to detect the expression of circ_0105346, microRNA (miR)-1182 and wingless-type MMTV integration site family 7B (WNT7B). 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay was conducted to evaluate cell viability, and flow cytometry was performed to monitor cell apoptosis and cycle. In addition, cell migration and invasion were determined via transwell assay. Wound healing assay was also employed to evaluate the migrated capacity of OS cells. Western blot assay was also employed to examine the levels of protein markers. Additionally, the interaction between miR-1182 and circ_0105346 or WNT7B was confirmed by the dual-luciferase reporter, RNA immunoprecipitation (RIP) and pull-down assays. Mouse xenograft model was constructed to clarify the effect of circ_0105346 on tumor growth in vivo.

Results

Circ_0105346 and WNT7B were upregulated, while miR-1182 was downregulated in OS tissues and cells. Circ_0105346 knockdown suppressed OS cell proliferation, cell cycle, migration, invasion and glycolysis, as well as accelerated apoptosis, which was attenuated by miR-1182 inhibition. Interestingly, circ_0105346 targeted miR-1182, and miR-1182 interacted with WNT7B. Circ_0105346 could upregulate WNT7B by downregulating miR-1182 expression. Furthermore, circ_0105346 knockdown blocked tumor growth in vivo.

Conclusion

Circ_0105346 knockdown repressed OS progression by regulating miR-1182/WNT7B axis, at least in part.

Serine-Threonine Kinase TAO3-Mediated Trafficking of Endosomes Containing the Invadopodia Scaffold TKS5α Promotes Cancer Invasion and Tumor Growth

Invadopodia are actin-based proteolytic membrane protrusions required for invasive behavior and tumor growth. In this study, we used our high-content screening assay to identify kinases whose activity affects invadopodia formation. Among the top hits selected for further analysis was TAO3, an STE20-like kinase of the GCK subfamily. TAO3 was overexpressed in many human cancers and regulated invadopodia formation in melanoma, breast, and bladder cancers. Furthermore, TAO3 catalytic activity facilitated melanoma growth in three-dimensional matrices and in vivo. A novel, potent catalytic inhibitor of TAO3 was developed that inhibited invadopodia formation and function as well as tumor cell extravasation and growth. Treatment with this inhibitor demonstrated that TAO3 activity is required for endosomal trafficking of TKS5α, an obligate invadopodia scaffold protein. A phosphoproteomics screen for TAO3 substrates revealed the dynein subunit protein LIC2 as a relevant substrate. Knockdown of LIC2 or expression of a phosphomimetic form promoted invadopodia formation. Thus, TAO3 is a new therapeutic target with a distinct mechanism of action. SIGNIFICANCE: An unbiased screening approach identifies TAO3 as a regulator of invadopodia formation and function, supporting clinical development of this class of target.

miR‑7/SP1/TP53BP1 axis may play a pivotal role in NSCLC radiosensitivity

MicroRNA‑7 (miR‑7) has been identified as a tumor suppressor in non‑small cell lung cancer (NSCLC) and a radiosensitivity regulator. Numerous studies have revealed that specific protein 1 (SP1) plays a critical role in the tumorigenesis of various types of cancers and regulates radiosensitivity and tumor suppressor p53‑binding protein 1 (TP53BP1), which plays an essential role in DNA repair. However, it is not clear whether miR‑7 has a regulatory effect on SP1 and TP53BP1 in NSCLC. In the present study it was revealed that miR‑7 directly binds to the 3'UTR of SP1, thereby suppressing SP1 expression to regulate radiosensitivity. Overexpression of miR‑7 and SP1 and knockdown of miR‑7 and SP1 were performed using lentiviral transfection. Protein and mRNA abundance of SP1 and TP53BP1 were determined using western blotting and RT‑qPCR, respectively, while miR‑7 binding to SP1 was validated using a luciferase reporter assay. Biological function analysis indicated that miR‑7 negatively regulated SP1 and inhibited cell proliferation, migration, and invasion when combined with radiation. It was also revealed that the expression of TP53BP1 was positively regulated by SP1 or negatively regulated by miR‑7. In conclusion, SP1 was a target of miR‑7, and the decreased expression of SP1 resulting from miR‑7 overexpression in NSCLC was vital for improving radiosensitivity in NSCLC cells. Moreover, SP1 expression was detected in 95 paired NSCLC and adjacent normal tissues, and it was determined that SP1 was significantly upregulated in NSCLC tissues and that its upregulation was correlated with the degree of tissue differentiation. Thus, SP1 and/or miR‑7 may be potential molecular targets in NSCLC radiotherapy.

Overexpression of SEZ6L2 predicts poor prognosis in patients with cholangiocarcinoma

Background

With the feature of destructive and biliary malignancy, intrahepatic cholangiocarcinoma (ICC), presents unclear molecular mechanisms which contributes to typically poor prognosis for patients. Seizure-related 6 homolog-like 2 (SEZ6L2) is a gene that encodes for a seizure-associated protein localized on the cell surface. Thus far, the function of SEZ6L2 in ICC has not been reported.

Methods

We used data from The Cancer Genome Atlas and the Gene Expression Omnibus to analyze dynamics behind and levels of expression of SEZ6L2 in ICC. Then we used qRT-PCR and Immunohistochemical staining to detect levels of expression of SEZ6L2 and thereby determined the potential clinical significance of this protein in ICC.

Results

According to qRT-PCR and immunohistochemical analysis results, SEZ6L2 was overexpressed in ICC. Kaplan-Meier and Cox proportional hazard analyses indicated that patients afflicted by ICC with high levels of relative expression of SEZ6L2 have a poorer prognosis and that SEZ6L2 may be an independent prognostic factor which enables to the accurate prediction of overall survival (OS) and disease-free survivals’ (DFS) expected rates. Subcutaneous xenograft models used to explore the role of SEZ6L2 in tumor formation in vivo. The dynamics of the SEZ6L2 gene being promote angiogenesis in cholangiocarcinoma are related to increasing expressive growth factors which include EGF, VEGF, PDGF and the activation of the P38-MAPK pathway.

Conclusions

Our findings suggest that SEZ6L2 can serve as an advanced biomarker that can be used to accurately predict a patient prognosis and be used as a target for ICC treatment.

Sevoflurane Suppresses the Migration, Invasion, and Epithelial-Mesenchymal Transition of Breast Cancer Cells Through the miR-139-5p/ARF6 Axis

BACKGROUND

Breast cancer (BC) is common cancer in female globally. Sevoflurane (SEV) has been reported to inhibit the metastasis of multiple cancers, including glioma, colorectal cancer, and hepatocellular carcinoma. However, the role of SEV in the metastasis of BC cells remains poorly understood.

METHODS

Transwell migration and invasion assays were performed to detect the migration and invasion of BC cells. Western blot assay was carried out to measure epithelial-mesenchymal transition (EMT)-related proteins in BC cells, including E-cadherin, N-cadherin, and fibronectin. Quantitative real-time polymerase chain reaction was conducted to determine the enrichment of miR-139-5p and ADP-ribosylation factor 6 (ARF6) in BC tissues and cells. The protein expression of ARF6 in BC tissues and cells was measured by western blot assay. The target of miR-139-5p was predicted by starBase software, and the target relationship between miR-139-5p and ARF6 in BC cells was confirmed by dual-luciferase reporter assay.

RESULTS

SEV suppressed the migration, invasion, and EMT of BC cells, especially in the high-concentration SEV group. The level of miR-139-5p was lower in BC tissues and cells than that in paired normal tissues and normal mammary epithelial cells MCF-10A. MiR-139-5p was upregulated in BC cells treated with SEV. ARF6 was upregulated in BC tissues and cells compared with that in corresponding normal tissues and normal mammary epithelial cells MCF-10A. SEV reduced the mRNA and protein expression of ARF6 in BC cells. The accumulation of ARF6 or the interference of miR-139-5p reversed the suppressive effects of SEV treatment on the migration, invasion, and EMT of BC cells. MiR-139-5p bound to ARF6 and inversely modulated the level of ARF6 in BC cells. The transfection of si-ARF6 attenuated the promoting effects of miR-139-5p depletion on the migration, invasion, and EMT of BC cells treated with SEV.

CONCLUSIONS

SEV suppressed the migration, invasion, and EMT of BC cells through downregulating the abundance of ARF6 by upregulating miR-139-5p. The miR-139-5p/ARF6 axis might be a promising target for the treatment of BC.

Development and validation of a robust immune-related prognostic signature in early-stage lung adenocarcinoma

Background

The incidence of stage I and stage II lung adenocarcinoma (LUAD) is likely to increase with the introduction of annual screening programs for high-risk individuals. We aimed to identify a reliable prognostic signature with immune-related genes that can predict prognosis and help making individualized management for patients with early-stage LUAD.

Methods

The public LUAD cohorts were obtained from the large-scale databases including 4 microarray data sets from the Gene Expression Omnibus (GEO) and 1 RNA-seq data set from The Cancer Genome Atlas (TCGA) LUAD cohort. Only early-stage patients with clinical information were included. Cox proportional hazards regression model was performed to identify the candidate prognostic genes in GSE30219, GSE31210 and GSE50081 (training set). The prognostic signature was developed using the overlapped prognostic genes based on a risk score method. Kaplan–Meier curve with log-rank test and time-dependent receiver operating characteristic (ROC) curve were used to evaluate the prognostic value and performance of this signature, respectively. Furthermore, the robustness of this prognostic signature was further validated in TCGA-LUAD and GSE72094 cohorts.

Results

A prognostic immune signature consisting of 21 immune-related genes was constructed using the training set. The prognostic signature significantly stratified patients into high- and low-risk groups in terms of overall survival (OS) in training data set, including GSE30219 (HR = 4.31, 95% CI 2.29–8.11; P = 6.16E−06), GSE31210 (HR = 11.91, 95% CI 4.15–34.19; P = 4.10E−06), GSE50081 (HR = 3.63, 95% CI 1.90–6.95; P = 9.95E−05), the combined data set (HR = 3.15, 95% CI 1.98–5.02; P = 1.26E−06) and the validation data set, including TCGA-LUAD (HR = 2.16, 95% CI 1.49–3.13; P = 4.54E−05) and GSE72094 (HR = 2.95, 95% CI 1.86–4.70; P = 4.79E−06). Multivariate cox regression analysis demonstrated that the 21-gene signature could serve as an independent prognostic factor for OS after adjusting for other clinical factors. ROC curves revealed that the immune signature achieved good performance in predicting OS for early-stage LUAD. Several biological processes, including regulation of immune effector process, were enriched in the immune signature. Moreover, the combination of the signature with tumor stage showed more precise classification for prognosis prediction and treatment design.

Conclusions

Our study proposed a robust immune-related prognostic signature for estimating overall survival in early-stage LUAD, which may be contributed to make more accurate survival risk stratification and individualized clinical management for patients with early-stage LUAD.

Effects of Arf6 downregulation on biological characteristics of human prostate cancer cells

Objective

To evaluate the effects of Arf6 downregulation on human prostate cancer cells.

Materials and Methods

The effects of Arf6 downregulation on cell proliferation, migration, invasion and apoptosis were assessed by MTT, BrdU, scratch, Transwell assays and flow cytometry respectively. AKT, p-AKT, ERK1/2, p-ERK1/2 and Rac1 protein expressions were detected by Western blot.

Results

Downregulating Arf6 by siRNA interference suppressed the mRNA and protein expressions of Arf6. The proliferation capacities of siRNA group at 48h, 72h, and 96h were significantly lower than those of control group (P <0.05). The migration distance of siRNA group at 18h was significantly shorter than that of control group (P <0.01). The number of cells penetrating Transwell chamber membrane significantly decreased in siRNA group compared with that of control group (P <0.01). After 24h, negative control and normal control groups had similar apoptotic rates (P >0.05) which were both significantly lower than that of siRNA group (P <0.01). After Arf6 expression was downregulated, p-ERK1/2 and Rac1 protein expressions were significantly lower than those of control group (P <0.05).

Conclusion

Downregulating Arf6 expression can inhibit the proliferation, migration and invasion of prostate cancer cells in vitro, which may be related to ERK1/2 phosphorylation and Rac1 downregulation.

ARF family GTPases with links to cilia

The ADP-ribosylation factor (ARF) superfamily of regulatory GTPases, including both the ARF and ARF-like (ARL) proteins, control a multitude of cellular functions, including aspects of vesicular traffic, lipid metabolism, mitochondrial architecture, the assembly and dynamics of the microtubule and actin cytoskeletons, and other pathways in cell biology. Considering their general utility, it is perhaps not surprising that increasingly ARF/ARLs have been found in connection to primary cilia. Here, we critically evaluate the current knowledge of the roles four ARF/ARLs (ARF4, ARL3, ARL6, ARL13B) play in cilia and highlight key missing information that would help move our understanding forward. Importantly, these GTPases are themselves regulated by guanine nucleotide exchange factors (GEFs) that activate them and by GTPase-activating proteins (GAPs) that act as both effectors and terminators of signaling. We believe that the identification of the GEFs and GAPs and better models of the actions of these GTPases and their regulators will provide a much deeper understanding and appreciation of the mechanisms that underly ciliary functions and the causes of a number of human ciliopathies.

miR-744-5p inhibits cellular proliferation and invasion via targeting ARF1 in epithelial ovarian cancer

miR-744-5p has been demonstrated to play an important role in cancer progression. However, the functions of miR-744-5p in epithelial ovarian cancer (EOC) are not well clarified. In this study, our aim was to investigate the role of miR-744-5p and its underlying molecular mechanism in cell progression of EOC. EOC clinical tissues and matched adjacent ovarian epithelial tissues were collected from 18 patients. Tissues and cell lines were analyzed by qPCR or Western blot to investigate the expression of miR-744-5p and ARF1 in EOC. Cell proliferative capacity was assessed by CCK8 and colony formation assays. Wound healing and transwell assays were performed to evaluate cell migration and invasion. The potential binding relation between miR-744-5p and IRF1 was demonstrated by dual luciferase report assay. The results showed that expression of miR-744-5p was low in EOC clinical tissues and cells. Overexpression of miR-744-5p inhibited proliferation, migration, and invasion of EOC cells. Further mechanistic study identified that ARF1 is a target of miR-744-5p, which is negatively correlated with the expression of miR-744-5p, and overexpression of ARF1 could reverse the inhibition of miR-744-5p on the proliferation, migration, and invasion of EOC cells. Taken together, our results indicated that miR-744-5p attenuated EOC progression via targeting IRF1, providing potential guidance for the clinical treatment of ovarian cancer.

P53: A Guardian of Immunity Becomes Its Saboteur through Mutation

Awareness of the importance of immunity in controlling cancer development triggered research into the impact of its key oncogenic drivers on the immune response, as well as their value as targets for immunotherapy. At the heart of tumour suppression is p53, which was discovered in the context of viral infection and now emerges as a significant player in normal and cancer immunity. Wild-type p53 (wt p53) plays fundamental roles in cancer immunity and inflammation. Mutations in p53 not only cripple wt p53 immune functions but also sinisterly subvert the immune function through its neomorphic gain-of-functions (GOFs). The prevalence of mutant p53 across different types of human cancers, which are associated with inflammatory and immune dysfunction, further implicates mutant p53 in modulating cancer immunity, thereby promoting tumorigenesis, metastasis and invasion. In this review, we discuss several mutant p53 immune GOFs in the context of the established roles of wt p53 in regulating and responding to tumour-associated inflammation, and regulating innate and adaptive immunity. We discuss the capacity of mutant p53 to alter the tumour milieu to support immune dysfunction, modulate toll-like receptor (TLR) signalling pathways to disrupt innate immunity and subvert cell-mediated immunity in favour of immune privilege and survival. Furthermore, we expose the potential and challenges associated with mutant p53 as a cancer immunotherapy target and underscore existing therapies that may benefit from inquiry into cancer p53 status.

The Role of ARF Family Proteins and Their Regulators and Effectors in Cancer Progression: A Therapeutic Perspective

The Adenosine diphosphate-Ribosylation Factor (ARF) family belongs to the RAS superfamily of small GTPases and is involved in a wide variety of physiological processes, such as cell proliferation, motility and differentiation by regulating membrane traffic and associating with the cytoskeleton. Like other members of the RAS superfamily, ARF family proteins are activated by Guanine nucleotide Exchange Factors (GEFs) and inactivated by GTPase-Activating Proteins (GAPs). When active, they bind effectors, which mediate downstream functions. Several studies have reported that cancer cells are able to subvert membrane traffic regulators to enhance migration and invasion. Indeed, members of the ARF family, including ARF-Like (ARL) proteins have been implicated in tumorigenesis and progression of several types of cancer. Here, we review the role of ARF family members, their GEFs/GAPs and effectors in tumorigenesis and cancer progression, highlighting the ones that can have a pro-oncogenic behavior or function as tumor suppressors. Moreover, we propose possible mechanisms and approaches to target these proteins, toward the development of novel therapeutic strategies to impair tumor progression.

Angiotensin II promotes podocyte injury by activating Arf6-Erk1/2-Nox4 signaling pathway

Angiotensin II (Ang II) is a key contributor to glomerular disease by predominantly resulting in podocyte injury, whereas the underlying molecular mechanisms has not been fully understood. This study aimed to investigate if and how ADP-ribosylation factor 6 (Arf6), a small GTP-binding protein, involves Ang II-induced cellular injury in cultured human podocytes. Cellular injury was evaluated with caspase 3 activity, reactive oxygen species (ROS) level and TUNEL assay. Arf6 activity was measured using an Arf6-GTP Pull-Down Assay. Ang II significantly enhanced Arf6 expressions accompanied by increase of Arf6-GTP. The TUNEL-positive cells as well as activated caspase 3, NADPH oxidase 4 protein (Nox4) and ROS levels were dramatically increased in Ang II-treated podocytes, which was prevented by secinH3, an Arf6 activity inhibitor. Induction of ROS by Ang II was inhibited in podocytes with Nox4 knockdown. Ang II-induced elevation of Nox4 and ROS was prevented by Arf6 knockdown. Phpspho-Erk1/2^{Thr202/Tyr204} levels were upregulated remarkably following Ang II treatment, and Erk inhibitor LY3214996 significantly downregulated Nox4 expression. In addition, Ang II decreased CD2AP expression. Overexpression of CD2AP prevented Ang II-induced upregulation of Arf6-GTP. Our data demonstrated that Ang II promotes ROS production and podocytes injury through activation of Arf6-Erk1/2-Nox4 signaling. We also provided evidence that Ang II activates Arf6 by degradation of CD2AP.