RLIP76 regulates HIF-1 activity, VEGF expression and secretion in tumor cells, and secretome transactivation of endothelial cells

Physiological and tumor-associated angiogenesis: Key factors and therapy targeting VEGF/VEGFR pathway

Cancer remains one of the leading causes of death worldwide and poses a significant challenge to effective treatment due to its complexity. Angiogenesis, the formation of new blood vessels, is one of the cancer hallmarks and is a critical process in tumor growth and metastasis. The pivotal role of angiogenesis in cancer development has made antiangiogenic treatment a promising strategy for cancer therapy. To develop an effective therapy, it is essential to understand the basics of the physiological and tumor angiogenesis process. This review presents the primary factors related to physiological and tumor angiogenesis and the mechanisms of angiogenesis in tumors. We summarize potential molecular targets for cancer treatment by focusing on the vasculature, with the VEGF/VEGFR pathway being one of the most important and well-studied. Additionally, we present the advantages and limitations of currently used clinical protocols for cancer treatment targeting the VEGF/VEGFR pathway.

The potential role of Ral-interacting protein 76 and vascular endothelial growth factor on angiogenesis in the tumor and ovarian corpus luteum microenvironment

Tumors and the ovarian corpus luteum have complex mechanisms in the growth microenvironment. Angiogenesis is especially important for demonstrating the molecular mechanism of dynamic cellular function in tumors and corpus luteum. Angiogenesis in tumors and corpus luteum seems to have a similar function, and Ral-interacting protein 76 (RLIP76) and vascular endothelial growth factor (VEGF) are expressed in the tissues of tumors and ovarian corpus luteum. RLIP76 is a potential factor with VEGF in the tumor and corpus luteum angiogenesis. RLIP76 regulates a small GTPase (R-Ras) in cell survival, spreading, and migration. VEGF activates angiogenic functions in tumor and endothelial cells. Hypoxia-inducible factor-1 (HIF-1) is important in tumor growth, tumor angiogenesis, and corpus luteum. VEGF and HIF-1 regulate the angiogenic function of RLIP76, and RLIP76 controls vascular growth in endothelial and tumor cells. RLIP76, R-Ras, VEGF, and HIF-1 may be useful in the research of corpus luteum and cancer therapy and the study of mechanisms of tumor and corpus luteum angiogenesis. This review will help to elucidate the roles of RLIP76 and VEGF in tumor and corpus luteum angiogenesis, tumorigenesis, and the specific regulation of RLIP76 and VEGF. Thus, we reviewed the potential role of RLIP76 and VEGF in the angiogenesis of the tumor and corpus luteum in the tumor and ovarian microenvironment.

Crucial Role of RLIP76 in Promoting Glycolysis and Tumorigenesis by Stabilization of HIF-1α in Glioma Cells Under Hypoxia

Hypoxia is intimately associated with enhanced glycolysis in gliomas, and hypoxia-inducible factor 1α (HIF-1α) plays a critical role in this process. RLIP76 (Ral-interacting protein 76) functions as a multifunctional mediator and is aberrantly expressed in various malignant tumors, including glioma. However, the underlying mechanism of RLIP76 and HIF-1α in glioma glycolysis remains largely unclear. In the present study, we demonstrated that RLIP76 is a hypoxia-inducible molecule that contributes to facilitating glycolysis in glioma cells under hypoxic conditions. In addition, hypoxia-induced RLIP76 is a novel target of HIF-1α and enhances the two important HIF-1α-target glycolytic proteins glucose transporter type 1 (GLUT1) and lactate dehydrogenase A (LDHA) in hypoxia. Mechanistically, RLIP76 can directly bind to HIF-1α in the nucleus and regulate the stability of HIF-1α by alleviating HIF-1α ubiquitination and therefore activates GLUT1 and LDHA to accelerate glycolysis in hypoxia. Furthermore, the enhanced glycolysis is necessary for the role of RLIP76 to promote glioma development in vivo, confirming the ability of RLIP76 to regulate tumor cell glycolysis. Collectively, our results demonstrate a previously unappreciated function of RLIP76 in hypoxia-mediated glycolytic metabolism and implicate that RLIP76 might be a valuable therapeutic target for gliomas.

Haploinsufficiency Interactions between RALBP1 and p53 in ERBB2 and PyVT Models of Mouse Mammary Carcinogenesis

Simple Summary

Rlip knockout has been reported to prevent cancer in highly cancer-susceptible mice lacking p53, and Rlip knockdown kills many types of cancer cells. In humans, breast cancer shows diverse characteristics, including HER2-driven subtypes and viral-driven subtypes. HER2 can be targeted; however, escape of the cancer from targeted therapies remains a problem. In this work we evaluated the capacity of Rlip knockout to prevent breast cancer in genetically engineered mouse models of HER2-driven breast cancer (Erbb2 model) and polyomavirus-driven breast cancer (PyVT model). We found that in Erbb2 mice, Rlip knockout significantly delayed oncogenesis and reduced the expression of genes associated with poor prognosis in patients. In PyVT mice, Rlip knockout did not delay oncogenesis or tumor growth, but Rlip knockdown reduced tumor metastasis to the lung. We conclude that Rlip inhibitors may significantly improve survival in HER2-positive patients, but are unlikely to offer benefits to patients with polyomavirus-associated tumors.

Abstract

We recently reported that loss of one or both alleles of Ralbp1, which encodes the stress-protective protein RLIP76 (Rlip), exerts a strong dominant negative effect on both the inherent cancer susceptibility and the chemically inducible cancer susceptibility of mice lacking one or both alleles of the tumor suppressor p53. In this paper, we examined whether congenital Rlip deficiency could prevent genetically-driven breast cancer in two transgenic mouse models: the MMTV-PyVT model, which expresses the polyomavirus middle T antigen (PyVT) under control of the mouse mammary tumor virus promoter (MMTV) and the MMTV-Erbb2 model which expresses MMTV-driven erythroblastic leukemia viral oncogene homolog 2 (Erbb2, HER2/Neu) and frequently acquires p53 mutations. We found that loss of either one or two Rlip alleles had a suppressive effect on carcinogenesis in Erbb2 over-expressing mice. Interestingly, Rlip deficiency did not affect tumor growth but significantly reduced the lung metastatic burden of breast cancer in the viral PyVT model, which does not depend on either Ras or loss of p53. Furthermore, spontaneous tumors of MMTV-PyVT/Rlip+/+ mice showed no regression following Rlip knockdown. Finally, mice lacking one or both Rlip alleles differentially expressed markers for apoptotic signaling, proliferation, angiogenesis, and cell cycling in PyVT and Erbb2 breast tumors. Our results support the efficacy of Rlip depletion in suppressing p53 inactivated cancers, and our findings may yield novel methods for prevention or treatment of cancer in patients with HER2 mutations or tumor HER2 expression.

The complexity of tumour angiogenesis based on recently described molecules

Tumour angiogenesis is a crucial factor associated with tumour growth, progression, and metastasis. The whole process is the result of an interaction between a wide range of different molecules, influencing each other. Herein we summarize novel discoveries related to the less known angiogenic molecules such as galectins, pentraxin-3, Ral-interacting protein of 76 kDa (RLIP76), long non-coding RNAs (lncRNAs), B7-H3, and delta-like ligand-4 (DLL-4) and their role in the process of tumour angiogenesis. These molecules influence the most important molecular pathways involved in the formation of blood vessels in cancer, including the vascular endothelial growth factor (VEGF)-vascular endothelial growth factor receptor interaction (VEGFR), HIF1-a activation, or PI3K/Akt/mTOR and JAK-STAT signalling pathways. Increased expression of galectins, RLIP76, and B7H3 has been proven in several malignancies. Pentraxin-3, which appears to inhibit tumour angiogenesis, shows reduced expression in tumour tissues. Anti-angiogenic treatment based mainly on VEGF inhibition has proved to be of limited effectiveness, leading to the development of drug resistance. The newly discovered molecules are of great interest as a potential source of new anti-cancer therapies. Their role as targets for new drugs and as prognostic markers in neoplasms is discussed in this review.

Hypoxia and Extracellular Acidification as Drivers of Melanoma Progression and Drug Resistance

Hypoxia and elevated extracellular acidification are prevalent features of solid tumors and they are often shown to facilitate cancer progression and drug resistance. In this review, we have compiled recent and most relevant research pertaining to the role of hypoxia and acidification in melanoma growth, invasiveness, and response to therapy. Melanoma represents a highly aggressive and heterogeneous type of skin cancer. Currently employed treatments, including BRAF V600E inhibitors and immune therapy, often are not effective due to a rapidly developing drug resistance. A variety of intracellular mechanisms impeding the treatment were discovered. However, the tumor microenvironment encompassing stromal and immune cells, extracellular matrix, and physicochemical conditions such as oxygen level or acidity, may also influence the therapy effectiveness. Hypoxia and acidification are able to reprogram the metabolism of melanoma cells, enhance their survival and invasiveness, as well as promote the immunosuppressive environment. For this reason, these physicochemical features of the melanoma niche and signaling pathways related to them emerge as potential therapeutic targets.

Physcion and Physcion 8-O-β-D-glucopyranoside: Natural Anthraquinones with Potential Anticancer Activities

Nature has provided prodigious reservoirs of pharmacologically active compounds for drug development since times. Physcion and physcion 8-O-β-D-glucopyranoside (PG) are bioactive natural anthraquinones which exert anti-inflammatory and anticancer properties with minimum or no adverse effects. Moreover, physcion also exhibits anti-microbial and hepatoprotective properties, while PG is known to have anti-sepsis as well as ameliorative activities against dementia. This review aims to highlight the natural sources and anticancer activities of physcion and PG, along with associated mechanisms of actions. On the basis of the literature, physcion and PG regulate multitudinous cell signaling pathways through the modulation of various regulators of cell cycle, protein kinases, microRNAs, transcriptional factors, and apoptosis linked proteins resulting in the effective killing of cancerous cells in vitro as well as in vivo. Both compounds effectively suppress metastasis, furthermore, physcion acts as an inhibitor of 6PGD and also plays an important role in chemosensitization. This review article suggests that physcion and PG are potent anticancer drug candidates, but further investigations on their mechanism of action and pre-clinical trials are mandatory in order to comprehend the full potential of these natural cancer killers in anticancer remedies.

Houshiheisan promotes angiogenesis via HIF-1α/VEGF and SDF-1/CXCR4 pathways: in vivo and in vitro

Rationale: Houshiheisan (HSHS), a classic prescription in traditional Chinese medicine (TCM), has remarkable efficacy in the treatment of ischemic stroke.

Objective: To investigate the pro-angiogenic effect and molecular mechanism of HSHS for stroke recovery.

Methods and results: The rat permanent middle cerebral artery occlusion (pMCAO) model was constructed by suture method, HSHS (5.25 or 10.5 g/kg) and Ginaton (28 mg/kg) treatment was intragastrically administrated at 6 h after modeling which remained for 7 consecutive days. Pathological evaluation conducted by Hematoxylin–Eosin (HE) staining and the results showed that HSHS alleviated blood vessel edema, reduced the damage to blood vessels and neurons in the ischemic areas. Immunostaining, quantitative real-time fluorescence PCR results showed that HSHS up-regulated pro-angiogenic factors including platelet endothelial cell adhesion molecule-1 (cluster of differentiation 31 (CD31)), vascular endothelial growth factor (VEGF), vascular endothelial growth factor A (VEGFA), VEGF receptor 2 (VEGFR2), angiopoietin-1 (Ang-1), while down-regulated angiopoietin-2 (Ang-2), stromal cell derived factor-1 (SDF-1), and cxc chemokine receptor 4 (CXCR4) expression in infarct rat cortex, and similar results were obtained in subsequent Western blot experiment. Furthermore, CCK8 assay and transwell migration assay were performed to assess cell proliferation, migration, and tube formation. The medicated serum (MS) of HSHS appeared to have beneficial effects for immortalized human umbilical vein cells (Im-HUVECs) on proliferation and migration after persistence hypoxia. Western blot analysis revealed that the expression of hypoxia inducible factor-1α (HIF-1α), VEGFA, Ang-1, Ang-2, and CXCR4 were significantly up-regulated while Ang-2 was down-regulated by HSHS MS treatment compared with vehicle group in vitro.

Conclusion: The present study suggests a novel application of HSHS as an effective angiogenic formula for stroke recovery.

Implications of flavonoids as potential modulators of cancer neovascularity

PURPOSE

The formation of new blood vessels from previous ones, angiogenesis, is critical in tissue repair, expansion or remodeling in physiological processes and in various pathologies including cancer. Despite that, the development of anti-angiogenic drugs has great potential as the treatment of cancer faces many problems such as development of the resistance to treatment or an improperly selected therapy approach. An evaluation of predictive markers in personalized medicine could significantly improve treatment outcomes in many patients.

METHODS

This comprehensive review emphasizes the anticancer potential of flavonoids mediated by their anti-angiogenic efficacy evaluated in current preclinical and clinical cancer research.

RESULTS AND CONCLUSION

Flavonoids are important groups of phytochemicals present in common diet. Flavonoids show significant anticancer effects. The anti-angiogenic effects of flavonoids are currently a widely discussed topic of preclinical cancer research. Flavonoids are able to regulate the process of tumor angiogenesis through modulation of signaling molecules such as VEGF, MMPs, ILs, HIF or others. However, the evaluation of the anti-angiogenic potential of flavonoids within the clinical studies is not frequently discussed and is still of significant scientific interest.

Roles of microRNA-186 and vascular endothelial growth factor in hepatocellular carcinoma complicated with portal vein tumor thrombus

The present study aims to investigate the role and underlying mechanism of microRNA (miR)-186 in patients with hepatocellular carcinoma (HCC) complicated with portal vein tumor thrombus. Blood samples from 29 HCC patients with portal vein tumor thrombus were collected between January 2014 and September 2015 in Huai'an First People's Hospital, while blood from 36 HCC patients without vein tumor thrombus was also collected in the same period. In addition, tumor thrombus specimens were collected from the HCC patients with portal vein tumor thrombus, and peritumoral tissues of the tumor thrombus were used as the control. Reverse transcription-quantitative polymerase chain reaction, ELISA and western blot analyses were applied to detect vascular endothelial growth factor (VEGF) expression at the mRNA and protein levels. Bioinformatics prediction was used to predict the target of miR-186, and then miR-186 expression was detected. Furthermore, dual-luciferase reporter assay was used to validate whether miR-186 directly targeted VEGF. Following transfection with agomiR-186, the expression levels of miR-186 and VEGF were detected, while MTT assay was used to detect EA.hy926 cell proliferation subsequent to small interfering RNA (siRNA) silencing. The results identified that VEGF was significantly increased in the tumor thrombus and blood samples of HCC patients with vein tumor thrombus at the mRNA and protein levels, while miR-186 expression was significantly decreased (P<0.05). Following silencing VEGF by siRNA transfection, the proliferation of EA.hy926 cells was inhibited. In addition, VEGF expression was significantly decreased and cell proliferation was reduced when upregulating miR-186. Dual-luciferase reporter assay demonstrated that miR-186 regulated VEGF expression through complementary binding to 3'-untranslated region. In conclusion, VEGF was significantly increased in tumor thrombus and blood samples from HCC patients with vein tumor thrombus, which may be associated with the downregulation of miR-186. Thus, miR-186 may promote the development and progression of vein tumor thrombus in HCC.

Cellular Interactions in the Tumor Microenvironment: The Role of Secretome

Over the past years, it has become evident that cancer initiation and progression depends on several components of the tumor microenvironment, including inflammatory and immune cells, fibroblasts, endothelial cells, adipocytes, and extracellular matrix. These components of the tumor microenvironment and the neoplastic cells interact with each other providing pro and antitumor signals. The tumor-stroma communication occurs directly between cells or via a variety of molecules secreted, such as growth factors, cytokines, chemokines and microRNAs. This secretome, which derives not only from tumor cells but also from cancer-associated stromal cells, is an important source of key regulators of the tumorigenic process. Their screening and characterization could provide useful biomarkers to improve cancer diagnosis, prognosis, and monitoring of treatment responses.

A potential function of RLIP76 in the ovarian corpus luteum

Ral interacting protein of 76 kDa (RLIP76) is multifunctional protein localized and distributed in the plasma membrane, cytosol, and nucleus of the cell. In tumorigenesis, RLIP76 emerges as a common feature for the solid tumor growth. RLIP76 is ubiquitously expressed in various tissues including the ovary. Interestingly, the similar physiological events in obtaining an adequate supply of nutrient by gaining access to the host vascular system are required either for corpus luteum formation or tumor development. In addition, the identical angiogenesis modulators were found in neoplastic and normal ovaries. Our previous study involving RLIP76−/− mice implanted with melanoma or carcinoma cell conclusively demonstrated that RLIP76 is necessary for angiogenesis and neovascularization of primary solid tumors. RLIP76 plays an essential role in tumor angiogenesis through the regulation of pro-angiogenic factors such as vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1 (HIF-1). In certain previous studies, those pro-angiogenic factors were found significantly to be upregulated during the corpus luteum formation. To that, the following review will discuss the likelihood of RLIP76 role in ovarian corpus luteum.

RLIP: An existential requirement for breast carcinogenesis

Breast cancer (BC) is the most common cancer among women worldwide. Due to its complexity in nature, effective BC treatment can encounter many challenges. The human RALBP1 gene encodes a 76-kDa splice variant protein, RLIP (ral-binding protein1, RalBP1), a stress-protective mercapturic acid pathway (MAP) transporter protein, that also plays a key role in regulating clathrin-dependent endocytosis (CDE) as a Ral effector. Growing evidence shows that targeting RLIP may be an effective strategy in cancer therapy, as RLIP is over-expressed in multiple cancers and is known to induce resistance to apoptosis and chemotherapeutic drugs. Recent studies demonstrated that RLIP is expressed in human BC tissues, as well as BC cell lines. Knockdown of RLIP resulted in apoptotic death of BC cells in vitro, and targeted inhibition and depletion of RLIP resulted in regression of BC in xenograft studies of nude mice. Signaling studies showed that RLIP depletion inhibited endocytosis and differentially regulated signaling to Akt, Myc, and ERK1/2. However, the proliferation and multi-specific transport mechanisms that promote RLIP-mediated cell death in BC are not well understood. In this review, we will discuss a missing but an essentially determining and connecting piece of the puzzle on the understanding of proliferation and transport mechanisms by focused analyses of the apoptotic, drug- and radiation-sensitivity regulated by RLIP, a stress-responsive non-ATP-binding cassette (ABC), high capacity MAP transporter, in breast cancer.

An-te-xiao capsule inhibits tumor growth in non-small cell lung cancer by targeting angiogenesis

An-te-xiao capsule consists of total alkaloids from the dried whole plantof Solanum lyratum, and showed antitumor effects in our previous study. However, its inhibitory effect on multiple non-small cell lung cancer (NSCLC) cell lines and the underlying mechanisms have not been elucidated clearly. This study sought to investigate the inhibitory effects of An-te-xiao capsule on three main types of NSCLC cell lines (A549, NCI-H460, and NCI-H520) in vitro and in vivo and the underlying mechanisms of action including its potential anti-angiogenesis effects. An-te-xiao capsule showed no acute oral toxicity in mice, and significantly prolonged survival time in a mouse model of Lewis tumor xenograft. The inhibition of A549, NCI-H460, and NCI-H520 cells by An-te-xiao capsule was reflected in its effects on tumor growth, histopathological changes, tumor microvessel density (MVD), cell cycle regulatory proteins, and cell apoptosis. In vitro, An-te-xiao capsule repressed migration, invasion, and tube formation of tumor-derived vascular endothelial cells (Td-ECs), which were obtained using a co-culture system, in the presence or absence of vascular endothelial growth factor (VEGF) at safe concentrations selected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, An-te-xiao capsule inhibited the secretion of VEGF by A549 cells in the co-culture system and suppressed the phosphorylation of VEGF receptor 2 (VEGFR2). Taken together, An-te-xiao capsule has potential for treating NSCLC.

2'-Hydroxyflavanone inhibits in vitro and in vivo growth of breast cancer cells by targeting RLIP76

Consumption of citrus-fruits is associated with reduced incidence of breast cancer (BC), the most common cancer diagnosed in women across the globe. In this study, we investigated the anticancer potential of 2-Hydroxyflavanone (2HF) in BC. 2HF, a citrus-bioflavonoid, has demonstrated anticancer properties in various cancers, but its anticancer role in BC has not been well studied. We investigated the in vitro and in vivo growth inhibitory effects of 2HF in an array of BC lines and in xenograft mouse models of ER-positive and HER2-positive BC cells. Compared to control, 2HF treatment reduced cell viability and suppressed migratory and invasive potential of BC cells, while, no growth inhibitory effects were observed in non-tumorigenic breast epithelial cells. Further, 2HF inhibited the expression of RLIP76, a stress-defensive and anti-apoptotic protein, which is over-expressed in BC cells and simultaneously reduced proliferation of BC cells. Nude mice bearing MCF7 or SKBR3 BC cells xenografts treated with either 2HF or targeting RLIP76 by RLIP76-antisense or RLIP76-antibody treatment had significantly lower tumor-weight as compared to corresponding controls. In addition, Western-blotting and immunohistochemical analysis of tumor tissue from control and treatment group mice showed that 2HF decreased protein expression levels of RLIP76, and the decrease was similar to those seen following RLIP76-antisense treatment. Furthermore, 2HF decreased expression of Ki67, CD31, vimentin, inhibited phosphorylation of Akt and expression of survivin and Bcl2, and increased levels of Bax, E-cadherin, and cleaved-PARP. Therefore, our results indicate that 2HF may suppress BC growth in vitro and in vivo by targeting RLIP76, and may serve as a potential adjuvant treatment in BC patients.

Rlip depletion prevents spontaneous neoplasia in TP53 null mice

Mice that have homozygous deletion of the p53 tumor suppressor protein universally die of malignancy, generally before 6 months of age. We show that hemizygous deficiency of RALBP1 (RLIP76 or Rlip) confers a degree of protection from spontaneous malignancy that has never previously been observed. This discovery introduces a paradigm for p53 function, in which Rlip plays a central role as an effector that appears necessary for the cancer susceptibility of p53 null mice. Because p53 loss has a powerful effect on genomic instability that contributes to the initiation and promotion of cancers and to drug and radiation resistance in humans, our findings provide a method for prevention and therapy of p53-deficient cancer.

TP53 (p53) is a tumor suppressor whose functions are lost or altered in most malignancies. p53 homozygous knockout (p53^−/−) mice uniformly die of spontaneous malignancy, typically T-cell lymphoma. RALBP1 (RLIP76, Rlip) is a stress-protective, mercapturic acid pathway transporter protein that also functions as a Ral effector involved in clathrin-dependent endocytosis. In stark contrast to p53^−/− mice, Rlip^−/− mice are highly resistant to carcinogenesis. We report here that partial Rlip deficiency induced by weekly administration of an Rlip-specific phosphorothioate antisense oligonucleotide, R508, strongly inhibited spontaneous as well as benzo(a)pyrene-induced carcinogenesis in p53^−/− mice. This treatment effectively prevented large-scale methylomic and transcriptomic abnormalities suggestive of inflammation found in cancer-bearing p53^−/− mice. The remarkable efficiency with which Rlip deficiency suppresses spontaneous malignancy in p53^−/− mice has not been observed with any previously reported pharmacologic or genetic intervention. These findings are supported by cross-breeding experiments demonstrating that hemizygous Rlip deficiency also reduces the spontaneous malignancy phenotype of p53^+/− mice. Rlip is found on the cell surface, and antibodies directed against Rlip were found to inhibit growth and promote apoptosis of cell lines as effectively as Rlip siRNA. The work presented here investigates several features, including oxidative DNA damage of the Rlip–p53 association in malignant transformation, and offers a paradigm for the mechanisms of tumor suppression by p53 and the prospects of suppressing spontaneous malignancy in hereditary cancer syndromes such as Li-Fraumeni.

Metastasis-Associated Protein 1 Deficiency Results in Compromised Pulmonary Alveolar Capillary Angiogenesis in Mice

Background

The aim of this study was to investigate the effects of metastasis-associated protein 1 (MTA1) deficiency during angiogenesis of pulmonary alveolar capillaries in mice and to determine the molecular mechanisms involved.

Material/Methods

The expressions of MTA1, CD34, vascular endothelial growth factor (VEGF), alpha smooth muscle actin (α-SMA), and HIF-1α were analyzed in the lungs of MTA1-knockout (KO) and wild-type mice at embryonic day 18.5 and 2 months by quantitative PCR, immunoblotting, and immunohistochemistry. The morphological changes were investigated during pulmonary alveolar capillary formation. The heart weight/body weight (HW/BW) ratio and the size of the right ventricular wall cardiomyocytes were also measured. Regulation of MTA1 on HIF-1α was determined in vitro.

Results

MTA1 deficiency reduced the number of pulmonary alveolar capillaries compared to the wild-type mice. MTA1-KO mice exhibited a decreased expression of HIF-1α and VEGF in the lungs. The retarded growth of the MTA1-KO mice was also noticed during the first week after birth. Accordingly, MTA1 deficiency resulted in increased infant mortality. In surviving adult mice, MTA1 deficiency induced myocardial hypertrophy, highlighted by an increased heart weight/body weight ratio and larger cardiomyocytes. In cultured cells, HIF-1α and VEGF levels were significantly upregulated upon MTA1 overexpression, suggesting a close relationship between all 3 molecules.

Conclusions

MTA1 participates in the formation of pulmonary capillaries via stabilization of HIF-1α. This finding sheds new light on the function of MTA1 in lung development, opening new avenues for the diagnosis/treatment of related pulmonary diseases.

Proteomic profiling of the cancer cell secretome: informing clinical research

INTRODUCTION

Cancer represents one of the major causes of human deaths. Identification of proteins as biomarkers for early detection of cancer and therapeutic targets for cancer treatment are important issues in precision medicine. Secretome of cancer cells represents the collection of proteins secreted or shed from cancer cells. Proteomic profiling of the cancer cell secretome has been proven to be a convenient and efficient way to discover cancer biomarker and/or therapeutic targets. Areas covered: There have been numerous reviews describing the history and application of secretome analysis in cancer biomarker/therapeutic target research. The present review focuses on the technological advancement for profiling low-molecular-mass proteins in secretome, the latest information regarding the new candidate biomarkers and molecular mechanisms discovered on the basis of cancer cell secretome analysis, as well as the previously discovered candidate biomarkers that enter into clinical trials. Expert commentary: Current technologies for protein sample preparation/separation and MS-based protein identification have allowed in-depth analysis of cancer cell secretome. Future efforts should focus on the comprehensiveness of cancer cell secretome, meta-analysis of different secretome datasets and integrated analysis via combining other omics datasets, as well as the incorporation of MS-based biomarker verification pipeline into both preclinical studies and clinical trials.

Upregulation of miR-124 by physcion 8-O-β-glucopyranoside inhibits proliferation and invasion of malignant melanoma cells via repressing RLIP76

Melanoma is the most malignant type of skin cancer. In recent years, mounting studies have evidenced the involvement of miRNAs in melanoma. One of these miRNAs, miR-124 has been found aberrantly downregulated in a variety of human malignancies. In this study, our results showed that the expression of miR-124 was significantly lower in malignant melanoma tissues and cell lines and miR-124 functioned as a tumor suppressor in melanoma. Moreover, our findings showed that miR-124 exerted anti-tumor effect by directly targeting RLIP76, a stress-inducible non-ABC transporter that plays a crucial role in the development of melanoma. Furthermore, our study also showed that physcion 8-O-β-glucopyranoside, a natural compound from medicinal plant, could inhibit the proliferation and invasion of melanoma cells by targeting miR-124/RLIP76 signaling.

Inflammation Modulates RLIP76/RALBP1 Electrophile-Glutathione Conjugate Transporter and Housekeeping Genes in Human Blood-Brain Barrier Endothelial Cells

Endothelial cells are often present at inflammation sites. This is the case of endothelial cells of the blood-brain barrier (BBB) of patients afflicted with neurodegenerative disorders such as Alzheimer's, Parkinson's, or multiple sclerosis, as well as in cases of bacterial meningitis, trauma, or tumor-associated ischemia. Inflammation is a known modulator of gene expression through the activation of transcription factors, mostly NF-κB. RLIP76 (a.k.a. RALBP1), an ATP-dependent transporter of electrophile-glutathione conjugates, modulates BBB permeability through the regulation of tight junction function, cell adhesion, and exocytosis. Genes and pathways regulated by RLIP76 are transcriptional targets of tumor necrosis factor alpha (TNF-α) pro-inflammatory molecule, suggesting that RLIP76 may also be an inflammation target. To assess the effects of TNF-α on RLIP76, we faced the problem of choosing reference genes impervious to TNF-α. Since such genes were not known in human BBB endothelial cells, we subjected these to TNF-α, and measured by quantitative RT-PCR the expression of housekeeping genes commonly used as reference genes. We find most to be modulated, and analysis of several inflammation datasets as well as a metaanalysis of more than 5000 human tissue samples encompassing more than 300 cell types and diseases show that no single housekeeping gene may be used as a reference gene. Using three different algorithms, however, we uncovered a reference geneset impervious to TNF-α, and show for the first time that RLIP76 expression is induced by TNF-α and follows the induction kinetics of inflammation markers, suggesting that inflammation can influence RLIP76 expression at the BBB. We also show that MRP1 (a.k.a. ABCC1), another electrophile-glutathione transporter, is not modulated in the same cells and conditions, indicating that RLIP76 regulation by TNF-α is not a general property of glutathione transporters. The reference geneset uncovered herein should aid in future gene expression studies in inflammatory conditions of the BBB.

The RLIP76 N-terminus binds ARNO to regulate PI 3-kinase, Arf6 and Rac signaling, cell spreading and migration

RLIP76 is a multifunctional protein involved in tumor growth and angiogenesis, and a promising therapeutic target in many cancers. RLIP76 harbors docking sites for many proteins, and we have found that it interacts with ARNO, a guanine nucleotide exchange factor for Arf6, and that RLIP76 regulates activation of Rac1 via Arf6, and regulates cell spreading and migration in an ARNO and Arf6-dependent manner. Here we show that ARNO interacts with the RLIP76 N-terminal domain, and this domain was required for RLIP76-dependent cell spreading and migration. We identified two sites in the RLIP76 N-terminus with differential effects on ARNO binding and downstream signaling: Ser29/Ser30 and Ser62. Ser29/30 mutation to Alanine inhibited ARNO interaction and was sufficient to block RLIP76-dependent cell spreading and migration, as well as RLIP76-dependent Arf6 activation. In contrast, RLIP76(S62A) interacted with ARNO and supported Arf6 activation. However, both sets of mutations blocked Rac1 activation. RLIP76-mediated Rac and Arf6 activation required PI3K activity. S29/30A mutations inhibited RLIP76-dependent PI3K activation, but S62A mutation did not. Together these results show that ARNO interaction with the RLIP76 N-terminus regulates cell spreading and motility via PI3K and Arf6, independent of RLIP76 control of Rac.