Roxarsone induces angiogenesis via PI3K/Akt signaling

A Recombinant Lentiviral Vegfr2-Silencing Vector Attenuates Roxarsone-Promoted Growth of Rat Vascular Endothelial Cells and Angiogenesis in Matrigel Plug and B16F10 Xenograft Models

Roxarsone (ROX) is widely used as a feed addictive for livestock and poultry. ROX promotes angiogenesis, which can lead to health problems, and it is necessary to identify methods to counter this angiogenic effect of ROX. The VEGF/VEGFR2 signaling pathway is involved in the growth and reconstruction of new blood vessels during angiogenesis. In this study, a recombinant lentiviral vector encoding Vegfr2 shRNA was transfected into rat vascular endothelial cells and used in mouse matrigel plug and melanoma xenograft models to investigate its potential to regulate ROX-induced angiogenesis and tumor growth. Treating endothelial cells with ROX increased cell proliferation, migration, and a tube-like structure of growth relative to the control group. The addition of the lentiviral Vegfr2-silencing vector significantly attenuated the effects of ROX on endothelial cells. The hemoglobin content of mouse matrigel plugs treated with ROX was increased significantly. This effect was dramatically attenuated by the co-administration of shRNA targeting Vegfr2. The volume, weight and CD34 staining of the melanoma xenograft tumors increased by ROX were also attenuated by Vegfr2 silence. These results indicate that the down-regulation of VEGFR2 protein plays an inhibitory role in the ROX-promoted angiogenesis in vivo and in vitro. These data support the targeting of Vegfr2 gene as an effective means to treat ROX-induced angiogenesis and tumor growth.

A Versatile Chitosan-Based Hydrogel Accelerates Infected Wound Healing via Bacterial Elimination, Antioxidation, Immunoregulation, and Angiogenesis

Drug-resistant bacterial infection of cutaneous wounds causes great harm to the human body. These infections are characterized by a microenvironment with recalcitrant bacterial infections, persistent oxidative stress, imbalance of immune regulation, and suboptimal angiogenesis. Treatment strategies available to date are incapable of handling the healing dynamics of infected wounds. A Schiff base and borate ester cross-linked hydrogel, based on phenylboronic acid-grafted chitosan (CS-PBA), dibenzaldehyde-grafted poly(ethylene glycol), and tannic acid (TA), is fabricated in the present study. Customized phenylboronic acid-modified zinc oxide nanoparticles (ZnO) are embedded in the hydrogel prior to gelation. The CPP@ZnO-P-TA hydrogel effectively eliminates methicillin-resistant Staphylococcus aureus (MRSA) due to the pH-responsive release of Zn2+ and TA. Killing is achieved via membrane damage, adenosine triphosphate reduction, leakage of intracellular components, and hydrolysis of bacterial o-nitrophenyl-β-d-galactopyranoside. The CPP@ZnO-P-TA hydrogel is capable of scavenging reactive oxygen and nitrogen species, alleviating oxidative stress, and stimulating M2 polarization of macrophages. The released Zn2+ and TA also induce neovascularization via the PI3K/Akt pathway. The CPP@ZnO-P-TA hydrogel improves tissue regeneration in vivo by alleviating inflammatory responses, stimulating angiogenesis, and facilitating collagen deposition. These findings suggest that this versatile hydrogel possesses therapeutic potential for the treatment of MRSA-infected cutaneous wounds.

Pharmacological modulation of Sonic Hedgehog signaling pathways in Angiogenesis: A mechanistic perspective

The Sonic hedgehog (SHh) signaling pathway is an imperative operating network that helps in regulates the critical events during the development processes like multicellular embryo growth and patterning. Disruptions in SHh pathway regulation can have severe consequences, including congenital disabilities, stem cell renewal, tissue regeneration, and cancer/tumor growth. Activation of the SHh signal occurs when SHh binds to the receptor complex of Patch (Ptc)-mediated Smoothened (Smo) (Ptc-smo), initiating downstream signaling. This review explores how pharmacological modulation of the SHh pathway affects angiogenesis through canonical and non-canonical pathways. The canonical pathway for angiogenesis involves the activation of angiogenic cytokines such as fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), placental growth factor (PGF), hepatocyte growth factor (HGF), platelet-derived growth factor (PDGF), stromal cell-derived factor 1α, transforming growth factor-β1 (TGF-β1), and angiopoietins (Ang-1 and Ang-2), which facilitate the process of angiogenesis. The Non-canonical pathway includes indirect activation of certain pathways like iNOS/Netrin-1/PKC, RhoA/Rock, ERK/MAPK, PI3K/Akt, Wnt/β-catenin, Notch signaling pathway, and so on. This review will provide a better grasp of the mechanistic approach of SHh in mediating angiogenesis, which can aid in the suppression of certain cancer and tumor growths.

Candesartan protects against unilateral peripheral limb ischemia in type-2 diabetic rats: Possible contribution of PI3K-Akt-eNOS-VEGF angiogenic signaling pathway

Type-2 diabetes (T2DM) is known to be highly associated with increased risk for vascular complications including peripheral arterial diseases (PAD). Critical limb ischemia (CLI) is the most advanced stage of PAD. Current therapeutic options for diabetic patients experiencing vascular complications are limited to surgical revascularization with no effective pharmacotherapy available for clinical settings. This study is dedicated to evaluate the angiogenic potential of candesartan an angiotensin-II receptor blocker in an experimental model of vascular complications associating T2DM. T2DM was induced in rats through feeding with high fat diet for 6 weeks, followed by injection with streptozotocin (STZ, 30 mg/kg; i.p). After establishment of T2DM, unilateral CLI was induced through the ligation and excision of superficial femoral artery. Candesartan treatment (10 or 30 mg/kg; orally) was initiated one day post CLI and thereafter once daily for up to 14 days. T2DM rats that underwent CLI demonstrated impaired angiogenic signaling, increased inflammation and apoptosis in gastrocnemius muscle (GC). Candesartan reversed ischemic insult in T2DM rats subjected to unilateral CLI and induced reparative angiogenesis that was evident by increase in p-PI3K/PI3K, p-Akt/Akt, p-eNOS/eNOS, p-VEGFR2/VEGFR2 ratios, and VEGF levels. Candesartan treatment also increased levels of HO-1; while decreased caspase-3 apoptotic marker and levels of inflammatory markers; NF-κB and TNF-α, all of which were accompanied by preserved histological manifestations of GC muscles. Candesartan was able to combat limb ischemia under diabetic conditions which could pave the way for its therapeutic utility for diabetic patients experiencing vascular complications in clinical setting.

Strontium and simvastatin dual loaded hydroxyapatite microsphere reinforced poly(ε-caprolactone) scaffolds promote vascularized bone regeneration

The promotion of vascular network formation in the early stages of implantation is considered a prerequisite for successful functional bone regeneration. In this study, we successfully constructed 3D printed scaffolds with strong mechanical strength and a controllable pore structure that can sustainably release strontium (Sr) ions and simvastatin (SIM) for up to 28 days by incorporation of Sr²⁺ and SIM-loaded hydroxyapatite microspheres (MHA) into a poly(ε-caprolactone) (PCL) matrix. In vitro cell experiments showed that Sr-doped scaffolds were beneficial to the proliferation and osteogenic differentiation of bone mesenchymal stem cells (BMSCs), an appropriate dose of SIM was beneficial to cell proliferation and angiogenesis, and a high dose of SIM was cytotoxic. The Sr- and SIM-dual-loaded scaffolds with an appropriate dose significantly induced osteogenic differentiation of BMSCs and tube formation of human umbilical vein endothelial cells (HUVECs) in vitro and promoted vascular network and functional bone formation in vivo. Ribose nucleic acid (RNA) sequencing analysis suggested that the mechanism of promotion of vascularized bone regeneration by fabricated scaffolds is that dual-loaded Sr²⁺ and SIM can upregulate osteogenic and vasculogenic-related genes and downregulate osteoclast-related genes, which is beneficial for vascular and new bone regeneration. The 3D printed composite scaffolds loaded with high-stability and low-cost inorganic Sr²⁺ ions and SIM small-molecule drugs hold great promise in the field of promoting vascularized bone regeneration.

Roxarsone inhibits hepatic stellate cell activation and ameliorates liver fibrosis by blocking TGF-β1/Smad signaling pathway

Hepatic fibrosis is a pathological change caused by chronic liver injury and self-repair, and it is the inevitable stage of the development of chronic liver disease to cirrhosis or even liver cancer. Activation of hepatic stellate cells (HSCs) is a core event in the development of liver fibrosis and blockage of the activation of HSCs has been shown to alleviate liver fibrosis. Roxarsone, an organoarsenic additive, with antibiotic effect, growth promotion and improving feed efficiency, is widely used in livestock and animal production. The purpose of this study was to evaluate the therapeutic effect of Roxarsone on liver fibrosis and explore the possible mechanism. We found that Roxarsone could inhibit transforming growth factor-β1 (TGF-β1) induced the activation of HSCs and weaken the migration ability. Moreover, Roxarsone administration significantly ameliorated CCl₄-induced liver fibrosis in mice with improvement of liver function and decreases of deposition of extracellular matrix (ECM). Mechanism investigations revealed that Roxarsone specifically inhibited the activation of TGF-β1/Smad signaling pathway, but had no effect on MAPK and PI3K/AKT pathways. These results suggest that Roxarsone has a protective effect on liver fibrosis which provides a new candidate for the treatment of liver fibrosis.

The absence of cellular glucose triggers oncogene AEG-1 that instigates VEGFC in HCC: A possible genetic root cause of angiogenesis

BACKGROUND AND OBJECTIVE

Astrocyte Elevated Gene-1 (AEG-1) is the master and multi-regulator of the various transcriptional factor primarily regulating chemoresistance, angiogenesis, metastasis, and invasion under the pathological condition, including liver cancer. This study was focused on investigating the process of tumor angiogenesis in liver carcinoma by studying the role of AEG-1 under GD/2DG conditions.

METHOD AND RESULTS

The PCR and western blot analysis revealed that glucose depletion (GD) induces the overexpression of AEG-1. Further, it leads to the constant expression of VEGFC through the activation of HIF-1α/CCR7 via the stimulations of PI3K/Akt signaling pathways. GLUT2 is the major transporter of a glucose molecule that is highly participating under GD through the expression of AEG-1 and constantly expresses glucokinase (GCK). The obtained data suggest that AEG-1 act as an angiogenesis and glycolysis regulator by modulating the expression of GCK through HIF-1α and GLUT2. 2-deoxy-D-glucose (2DG) is a glycolysis inhibitor that induces impaired glycolysis and cellular apoptosis by cellular oxidative stress. The administration of 2DG has led to the chemoresistance of AEG-1.

CONCLUSION

The total findings of the study judged that disruption of cellular energy metabolism induced by the absence of glucose or the presence of mutant glucose moiety (2DG) promotes the overexpression of AEG-1. The GD/2DG activates the VEGFC by inducing the HIF-1α and CCR7. Moreover, AEG-1 induces the expression of OPN, which regulates metastasis, angiogenesis, and actively participates in protective autophagy by promoting LC3 a/b.

Roxarsone Promotes Glycolysis and Angiogenesis by Inducing Hypoxia-Inducible Factor-1α In Vitro and In Vivo

Roxarsone (Rox) is an organic arsenic compound used as a feed additive to promote animal growth. The release of Rox into the environment poses risks to human health. Rox demonstrated tumor-promoting and proangiogenic effects in xenograft models. Increasing studies revealed the tight relationship among angiogenesis, carcinogenesis, tumorigenesis, and glycolysis. Glycolysis, via hypoxia-inducible factor-1α (HIF-1α), controls vascular endothelial cell (VEC) growth. To date, there has been no literature report on the effect of Rox on HIF-1α-dependent glycolysis. Herein, we report that Rox promoted glycolysis in rat VECs, as shown by the increased adenosine triphosphate production, the lactic acid release, the activity and content of aldolase (ALD), and the expression levels of ALD A and glucose transporter 1 (GLUT1). Rox also increased the cellular levels of HIF-1α. Treatment with the HIF-1α inhibitor YC-1 reversed Rox-increased ALD A and GLUT1 levels and attenuated Rox-induced VEC viability, suggesting that Rox-induced HIF-1α contributes to the glycolytic and angiogenic effects of Rox. Rox also promoted tumor growth and angiogenesis and increased the levels of ALD A, GLUT1, and HIF-1α in the tumor tissue of a mouse xenograft model, whereas these effects were abolished using YC-1. Our findings indicated that Rox induces HIF-1α in VECs to promote glycolysis and angiogenesis thus enhancing the tumor growth.

Human adipose-derived stem cells promote seawater-immersed wound healing via proangiogenic effects

Seawater immersion can increase the damage to skin wounds and produce chronic wounds, and the application of human adipose-derived stem cells can significantly promote healing. However, the mechanism underlying angiogenesis is currently unclear. In this study, we investigated the vascularization effect of human adipose-derived stem cells on the repair of seawater-treated skin wounds and explored the underlying mechanisms using bioinformatics. The results showed that human adipose-derived stem cells differentiated into vascular endothelial cells and promoted seawater-immersed wound vascularization by promoting vascular endothelial cell proliferation and migration. The differentially expressed genes between human adipose-derived stem cells and fibroblasts were identified and analyzed (including via gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment, protein–protein interaction network, and correlation analyses). The genes may promote wound healing by regulating the mechanisms of extracellular matrix remodeling, programmed cell death, inflammation, and vascularization. In conclusion, this study provides novel insights into the use of human adipose-derived stem cells in the regeneration of seawater-immersed skin wounds and chronic wounds.

Role of receptor tyrosine kinases mediated signal transduction pathways in tumor growth and angiogenesis-New insight and futuristic vision

In the past two decades, significant progress has been made in the past two decades towards the understanding of the basic mechanisms underlying cancer growth and angiogenesis. In this context, receptor tyrosine kinases (RTKs) play a pivotal role in cell proliferation, differentiation, growth, motility, invasion, and angiogenesis, all of which contribute to tumor growth and progression. Mutations in RTKs lead to abnormal signal transductions in several pathways such as Ras-Raf, MEK-MAPK, PI3K-AKT and mTOR pathways, affecting a wide range of biological functions including cell proliferation, survival, migration and vascular permeability. Increasing evidence demonstrates that multiple kinases are involved in angiogenesis including RTKs such as vascular endothelial growth factor, platelet derived growth factor, epidermal growth factor, insulin-like growth factor-1, macrophage colony-stimulating factor, nerve growth factor, fibroblast growth factor, Hepatocyte Growth factor, Tie 1 & 2, Tek, Flt-3, Flt-4 and Eph receptors. Overactivation of RTKs and its downstream regulation is implicated in tumor initiation and angiogenesis, representing one of the hallmarks of cancer. This review discusses the role of RTKs, PI3K, and mTOR, their involvement, and their implication in pro-oncogenic cellular processes and angiogenesis with effective approaches and newly approved drugs to inhibit their unrestrained action.

Crocetin attenuates the oxidative stress, inflammation and apoptosisin arsenic trioxide-induced nephrotoxic rats: Implication of PI3K/AKT pathway

Arsenic trioxide (ATO)-induced renal toxicity through oxidative stress and apoptosis restricts the therapeutic action of acute myelogenous leukemia. Crocetin (Crt) possesses antioxidant and antiapoptosis properties, and has certain renal protective effects, but it has not been reported that it has protective effect on renal injury caused by ATO. The current study explored the effects and mechanisms of Crt on kidney damage induced by ATO. Fifty Sprague-Dawley rats were randomly divided into five groups. Adult rats were given Crt concurrently with ATO for 1 week. On the 8th day, rats were killed and blood and kidney tissues were collected. Histopathological changes were measured, and kidneytissues and serum were used to determine renal function and antioxidant enzyme activity. In addition, the protein expression levels of P-PI3K, PI3K, P-AKT, AKT, CytC, Bax, Bcl-2 and Caspase-3 were determined via western blot analysis. Results revealed ATO induced renal morphological alterations and activated serum BUN and CRE. Compared with the control group, ROS, MDA, IL-1β, TNF-α, protein carbonyls (PC), lipid hydroperoxides (LOOH) and arsenic concentration levels were found to be significantly increased and SOD, CAT, GSH-Px, GSH and total sulphydryl groups (TSH) levels were attenuated in the ATO group. Crt markedly reduced oxidative stress in ATO-induced nephrotoxicity. Further, ATO induced apoptosis by significantly enhancing CytC, Bax and Caspase-3 and inhibiting Bcl-2. Administration with Crt markedly improved the expression of apoptosis factor. Moreover, Crt treatment stimulated the expressions of P-PI3K, PI3K, P-AKT, AKT induced by ATO. This study indicates Crt could prevent renal injury caused by ATO through inhibiting oxidative stress, inflammation and apoptosis, and its mechanism may be related to activation of PI3K/Akt signaling pathway.

VEGF/Flk1 Mechanism is Involved in Roxarsone Promotion of Rat Endothelial Cell Growth and B16F10 Xenograft Tumor Angiogenesis

The potential angiogenic effect of roxarsone, a feed additive widely used to promote animal growth worldwide, was demonstrated recently. We explored the mechanism of vascular endothelial growth factor (VEGF) and its receptor (VEGFR) in roxarsone promotion of rat vascular endothelial cells (ECs) and B16F10 mouse xenografts. ECs were treated with 0.1–50 μM roxarsone or with roxarsone plus 10 ng/mL VEGF, VEGFR1 (Flt1), or VEGFR2 (Flk1) antibodies for 12–48 h to examine their role in cell growth promotion. Small interfering RNA (siRNA) targeting Vegf, Flt1, and Flk1 were transfected in the ECs, and we measured the expression level, cell proliferation, migration, and tube formation ability. The siRNA targeting Vegf or Flk1 were injected intratumorally in the B16F10 xenografts of mice that received 25 mg/kg roxarsone orally. Cell viability and VEGF expression following roxarsone treatment were significantly higher than that of the control (P < 0.05), peaking following treatment with 1.0 μM roxarsone. Compared to roxarsone alone, the VEGF antibody decreased cell promotion by roxarsone (P < 0.05), and the Flk1 antibody greatly reduced cell viability compared to the Flt1 antibody (P < 0.01). Roxarsone and Flk1 antibody co-treatment increased supernatant VEGF significantly, while cellular VEGF was obviously decreased (P < 0.01), whereas there was no significant difference following Flt1 antibody blockade. The siRNA against Vegf or Flk1 significantly attenuated the roxarsone promotion effects on EC proliferation, migration, and tube-like formation (P < 0.01), whereas the siRNA against Flt1 effected no obvious differences. Furthermore, the RNA interference significantly weakened the roxarsone-induced increase in xenograft weight and volume, and VEGF and Flk1 expression. Roxarsone promotion of rat EC growth, migration, and tube-like formation in vitro and of B16F10 mouse xenograft model tumor growth and angiogenesis involves a VEGF/Flk1 mechanism.

Role of the P2X7 receptor in inflammation-mediated changes in the osteogenesis of periodontal ligament stem cells

Accumulating evidence indicates that the pluripotency of periodontal ligament stem cells (PDLSCs) is compromised under inflammatory conditions; however, the underlying mechanisms remain largely unexplored. In this study, we hypothesize that the P2X7 receptor (P2X7R) is a key molecule linked to inflammation-associated impairment of PDLSCs. We first investigated P2X7R expression in PDLSCs under normal and inflammatory conditions and then determined the effect of a P2X7R agonist (BzATP) or antagonist (BBG) on PDLSC osteogenesis under various conditions. Gene-modified PDLSCs were used to further examine the role of P2X7R and the signaling pathway underlying P2X7R-enhanced osteogenesis. We found that inflammatory conditions decreased P2X7R expression in PDLSCs and reduced osteogenesis in these cells. In addition, activation of P2X7R by BzATP or overexpression of P2X7R via gene transduction reversed the inflammation-mediated decrease in PDLSC osteogenic differentiation. When selected osteogenesis-related signaling molecules were screened, the PI3K-AKT-mTOR pathway was identified as potentially involved in P2X7R-enhanced PDLSC osteogenesis. Our data reveal a crucial role for P2X7R in PDLSC osteogenesis under inflammatory conditions, suggesting a new therapeutic target to reverse or rescue inflammation-mediated changes in PDLSCs for future mainstream therapeutic uses.

MicroRNA-204 deregulation in lung adenocarcinoma controls the biological behaviors of endothelial cells potentially by modulating Janus kinase 2-signal transducer and activator of transcription 3 pathway

MicroRNAs (miRNAs) have been implicated in a wide range of biological processes including angiogenesis. MiR-204 was identified as a tumor suppressor in multiple cancer types, including lung adenocarcinoma. However, the function of miR-204 in lung tumor angiogenesis remains unknown. In this study, we found that the miR-204 expression was decreased in lung adenocarcinoma based on the cancer genome atlas (TCGA) analysis and gain-of-function experiment showed that miR-204 promoted cancer cell apoptosis and suppressed cell proliferation, migration in vitro and tumor growth in vivo. Functionally, both the tube formation and migration abilities of human umbilical vein endothelial cells (HUVECs) were suppressed by conditioned media from lung cancer A549 cells with miR-204 overexpression. Meanwhile, these conditioned media inhibited proliferation and promoted apoptosis in HUVECs. The key angiogenesis inducer hypoxia inducible factor-1α (HIF1α) and the pro-angiogenic mediators vascular endothelial growth factor and platelet-derived growth factor were decreased in A549 cells transfected with miR-204 mimics. Mechanistically, miR-204 could target Janus kinase 2 (JAK2) and further impaired signal transducer and activator of transcription 3 both in vitro and in vivo. Inhibition of JAK2 or signal transducer and activator of transcription 3 (STAT3) activity with small chemical inhibitors in A549 cells impaired lung adenocarcinoma angiogenesis in vitro. Meanwhile, conditional media from interleukin 6-treated lung normal epithelial cells significantly promoted tube formation of HUVEC, which was disturbed by miR-204 overexpression. Taken together, our findings demonstrate that miR-204 attenuates angiogenesis in lung adenocarcinoma potentially via JAK2-STAT3 pathway. Clinically, the miR-204/JAK2/STAT3 signaling pathway is a putative therapeutic target in lung adenocarcinoma. © 2017 IUBMB Life, 70(1):81-91, 2018.

MicroRNA-9 modified bone marrow-derived mesenchymal stem cells (BMSCs) repair severe acute pancreatitis (SAP) via inducing angiogenesis in rats

Background

Severe acute pancreatitis (SAP) is an acute abdominal disease characterized by pancreatic necrosis and systemic disease. In a previous study, we showed that bone marrow-derived mesenchymal stem cells (BMSCs) can reduce SAP by secreting microRNA (miR)-9; however, the underlying mechanism remains unclear. The present study investigated the mechanism underlying BMSC-induced pancreatic regeneration.

Methods

BMSCs were isolated, and miR-9 modified/antagonized BMSCs (pri-miR-9-BMSCs/TuD-BMSCs) were generated and injected into SAP rats. The levels of inflammatory cytokines and histopathologic changes were examined using ELISA and H&E staining. Angiogenesis was analyzed by qRT-PCR, western blotting, and immunohistochemistry. Cell function tests, dual luciferase reporter assays, cell co-culture, western blotting, and cell tracing were used to explore the mechanisms underlying miR-9 induced angiogenesis.

Results

Pri-miR-9-BMSCs induced angiogenesis in SAP rats (Ang-1↑, TIE-2↑, and CD31↑) and repaired damaged vascular endothelial cells (VECs) in vitro, promoting angiogenesis (Ang-1↑, TIE-2↑, PI3K↑, AKT↑, p-AKT↑, CD31↑, and CD34↑). Pri-miR-9-BMSCs released miR-9 into VECs or injured pancreatic tissue, targeting the VE-cadherin gene and promoting PI3K/AKT signaling to treat SAP (VE-cadherin↓, β-catenin↓, PI3K↑, p-AKT↑), whereas antagonizing miR-9 in BMSCs did not alleviate or aggravated SAP.

Conclusions

Pri-miR-9-BMSCs can repair injured pancreatic tissue by secreting miR-9 and promoting angiogenesis.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-1022-y) contains supplementary material, which is available to authorized users.

Tumor-promoting and pro-angiogenic effects of roxarsone via VEGFR2/PLCγ/PKC signaling

Roxarsone is an organoarsenic feed additive used in livestock and poultry production that is released into the environment, where it poses a risk to human health. It is known to have a tumor-promoting effect that is brought about by pro-angiogenic factors such as vascular endothelial growth factor (VEGF) and it receptors (VEGFR). However, little information is available about the other signaling molecules that could be involved. This study aims to investigate the role of PLCγ/PKC signaling in roxarsone-induced angiogenesis in a mouse B16-F10 melanoma xenograft model and rat vascular endothelial cells (ECs). Results showed treatment with 5 mg/kg and 25 mg/kg roxarsone resulted in an obvious increase in the weight and volume of B16-F10 xenografts and PLCγ/PKC phosphorylation in a dose-dependent manner in C57BL/6 mice. SU5416, a VEGFR2 inhibitor, significantly attenuated the tumor growth induced by roxarsone. Further, 1.0 μmol/L roxarsone treatment in rat ECs was observed to significantly increase the optical density rate in the MTT assay, the number of BrdU-positive cells in the proliferation assay, the migration distance in the scratch test, and the number of meshes formed in the tube formation assay. In addition, treatment with 1.0 μmol/L roxarsone was associated with significantly higher phosphorylation of PLCγ/PKC than the control treatment. U73122, a PLCγ inhibitor, was found significantly to combat the effects of 1.0 μmol/L roxarsone on the ECs. Roxarsone is capable of promoting the growth of mouse B16-F10 xenografts and tube formation in vascular ECs. Moreover, VEGFR2/PLCγ/PKC signaling may play a regulatory role in in vivo and in vitro roxarsone-induced angiogenesis.

PI3K/Akt/mTOR Signaling Pathway and the Biphasic Effect of Arsenic in Carcinogenesis

Arsenic is a naturally occurring, ubiquitous metalloid found in the Earth's crust. In its inorganic form, arsenic is highly toxic and carcinogenic and is widely found across the globe and throughout the environment. As an International Agency for Research on Cancer-defined class 1 human carcinogen, arsenic can cause multiple human cancers, including liver, lung, urinary bladder, skin, kidney, and prostate. Mechanisms of arsenic-induced carcinogenesis remain elusive, and this review focuses specifically on the role of the PI3K/AKT/mTOR pathway in promoting cancer development. In addition to exerting potent carcinogenic responses, arsenic is also known for its therapeutic effects against acute promyelocytic leukemia. Current literature suggests that arsenic can achieve both therapeutic as well as carcinogenic effects, and this review serves to examine the paradoxical effects of arsenic, specifically through the PI3K/AKT/mTOR pathway. Furthermore, a comprehensive review of current literature reveals an imperative need for future studies to establish and pinpoint the exact conditions for which arsenic can, and through what mechanisms it is able to, differentially regulate the PI3K/AKT/mTOR pathway to maximize the therapeutic and minimize the carcinogenic properties of arsenic.