Regulation of the chemokine receptor CXCR4 by hypoxia

Uncovering the mystery of opposite circadian rhythms between mouse and human leukocytes in humanized mice

Many immune parameters show circadian rhythms during the 24-hour day in mammals. The most striking circadian oscillation is the number of circulating immune cells that display an opposite rhythm between humans and mice. The physiological roles and mechanisms of circadian variations in mouse leukocytes are well studied, whereas for humans they remain unclear because of the lack of a proper model. In this study, we found that consistent with their natural host species, mouse and human circulating leukocytes exhibited opposite circadian oscillations in humanized mice. This cyclic pattern of trafficking correlated well with the diurnal expression levels of C-X-C chemokine receptor 4, which were controlled by the intracellular hypoxia-inducible factor 1α/aryl hydrocarbon receptor nuclear translocator-like heterodimer. Furthermore, we also discovered that p38 mitogen-activated protein kinases/mitogen-activated 2 had opposite effects between mice and humans in generating intracellular reactive oxygen species, which subsequently regulated HIF-1α expression. In conclusion, we propose humanized mice as a robust model for human circadian studies and reveal insights on a novel molecular clock network in the human circadian rhythm.

The role of vitamin D in hepatic metastases from colorectal cancer

Colorectal cancer (CRC) represents a significant health burden worldwide, comprising approximately 10% of annual cancer cases globally. Hepatic metastases are the most common site of CRC metastasis, and are the leading cause of death in CRC patients. There is strong epidemiologic evidence for an inverse association between vitamin D status and risk of CRC; however, the role of vitamin D in the natural history of liver metastases has not yet been investigated. Several researchers have proposed hallmarks of metastases; crucially, metastases can be blocked by interrupting just one rate-limiting step. Vitamin D status has been implicated in each proposed hallmark of metastasis. The aim of this review is to examine the potential role for vitamin D in reducing the development of hepatic metastases from CRC and outline the candidate mechanisms by which vitamin D may mediate these effects. The results of ongoing randomised intervention trials are eagerly awaited to determine whether addressing vitamin D insufficiency in CRC patients could reduce the occurrence of liver metastases, and the consequent morbidity and mortality.

Tumor-associated myeloid cells as guiding forces of cancer cell stemness

Due to their ability to differentiate into various cell types and to support tissue regeneration, stem cells simultaneously became the holy grail of regenerative medicine and the evil obstacle in cancer therapy. Several studies have investigated niche-related conditions that favor stemness properties and increasingly emphasized their association with an inflammatory environment. Tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs) are major orchestrators of cancer-related inflammation, able to dynamically express different polarized inflammatory programs that promote tumor outgrowth, including tumor angiogenesis, immunosuppression, tissue remodeling and metastasis formation. In addition, these myeloid populations support cancer cell stemness, favoring tumor maintenance and progression, as well as resistance to anticancer treatments. Here, we discuss inflammatory circuits and molecules expressed by TAMs and MDSCs as guiding forces of cancer cell stemness.

Hypoxia-Inducible Factor 1α Signaling Promotes Repair of the Alveolar Epithelium after Acute Lung Injury

During the acute respiratory distress syndrome, epithelial cells, primarily alveolar type (AT) I cells, die and slough off, resulting in enhanced permeability. ATII cells proliferate and spread onto the denuded basement membrane to reseal the barrier. Repair of the alveolar epithelium is critical for clinical recovery; however, mechanisms underlying ATII cell proliferation and spreading are not well understood. We hypothesized that hypoxia-inducible factor (HIF)1α promotes proliferation and spreading of ATII cells during repair after lung injury. Mice were treated with lipopolysaccharide or hydrochloric acid. HIF activation in ATII cells after injury was demonstrated by increased luciferase activity in oxygen degradation domain-Luc (HIF reporter) mice and expression of the HIF1α target gene GLUT1. ATII cell proliferation during repair was attenuated in ATII cell-specific HIF1α knockout (SftpcCreERT2+/-;HIF1αf/f) mice. The HIF target vascular endothelial growth factor promoted ATII cell proliferation in vitro and after lung injury in vivo. In the scratch wound assay of cell spreading, HIF stabilization accelerated, whereas HIF1α shRNA delayed wound closure. SDF1 and its receptor, CXCR4, were found to be HIF1α-regulated genes in ATII cells and were up-regulated during lung injury. Stromal cell-derived factor 1/CXCR4 inhibition impaired cell spreading and delayed the resolution of permeability after lung injury. We conclude that HIF1α is activated in ATII cells after lung injury and promotes proliferation and spreading during repair.

The chemokinome superfamily: II. The 64 CC chemokines in channel catfish and their involvement in disease and hypoxia responses

Chemokines are a superfamily of structurally related chemotactic cytokines exerting significant roles in regulating cell migration and activation. Based on the arrangement of the first four cysteine residues, they are classified into CC, CXC, C and CX3C subfamilies. In this study, a complete set of 64 CC chemokine ligand (CCL) genes was systematically identified, annotated, and characterized from the channel catfish genome. Extensive phylogenetic and comparative genomic analyses supported their annotations, allowing establishment of their orthologies, revealing fish-specific CC chemokines and the expansion of CC chemokines in the teleost genomes through lineage-specific tandem duplications. With 64 genes, the channel catfish genome harbors the largest numbers of CC chemokines among all the genomes characterized to date, however, they fall into 11 distinct CC chemokine groups. Analysis of gene expression after bacterial infections indicated that the CC chemokines were regulated in a gene-specific and time-dependent manner. While only one member of CCL19 (CCL19a.1) was significantly up-regulated after Edwardsiella ictaluri infection, all CCL19 members (CCL19a.1, CCL19a.2 and CCL19b) were significantly induced after Flavobacterium columnare infection. In addition, CCL19a.1, CCL19a.2 and CCL19b were also drastically up-regulated in ESC-susceptible fish, but not in resistant fish, suggesting potential significant roles of CCL19 in catfish immune responses. High expression levels of certain CC appeared to be correlated with susceptibility to diseases and intolerance to hypoxia.

SDF1-CXCR4 Signaling Maintains Central Post-Stroke Pain through Mediation of Glial-Neuronal Interactions

Central post-stroke pain (CPSP) is an intractable central neuropathic pain that has been poorly studied mechanistically. Here we showed that stromal cell-derived factor 1 (SDF1 or CXCL12), a member of the CXC chemokine family, and its receptor CXCR4 played a key role in the development and maintenance of thalamic hemorrhagic CPSP through hypoxia inducible factor 1α (HIF-1α) mediated microglial-astrocytic-neuronal interactions. First, both intra-thalamic collagenase (ITC) and SDF1 injections could induce CPSP that was blockable and reversible by intra-thalamic administration of both AMD3100 (a selective CXCR4 antagonist) and inhibitors of microglial or astrocytic activation. Second, long-term increased-expression of SDF1 and CXCR4 that was accompanied by activations of both microglia and astrocytes following ITC could be blocked by both AMD-3100 and YC-1, a selective inhibitor of HIF-1α. AMD-3100 could also inhibit release of proinflammatory mediators (TNFα, IL1β and IL-6). Increased-expression of HIF-1α, SDF1, CXCR4, Iba1 and GFAP proteins could be induced by both ITC and intra-thalamic CoCl₂, an inducer of HIF-1α that was blockable by both HIF-1α inhibition and CXCR4 antagonism. Finally, inhibition of HIF-1α was only effective in prevention, but not in treatment of ITC-induced CPSP. Taken together, the present study demonstrated that in the initial process of thalamic hemorrhagic state HIF-1α up-regulated SDF1-CXCR4 signaling, while in the late process SDF1-CXCR4 signaling-mediated positive feedback plays more important role in glial-glial and glial-neuronal interactions and might be a novel promising molecular target for treatment of CPSP in clinic.

Hypoxia inhibits growth, proliferation, and increases response to chemotherapy in retinoblastoma cells

Retinoblastoma is a malignant tumor of the retina and the most frequent intraocular cancer in children. Low oxygen tension (hypoxia) is a common phenomenon in advanced retinoblastomas, but its biological effect on retinoblastoma growth is not clearly understood. Here we studied how hypoxia altered retinoblastoma gene expression and modulated growth and response to chemotherapy. The hypoxic marker lysyl oxidase (LOX) was expressed in 8 of 12 human retinoblastomas analyzed by immunohistochemistry, suggesting that a hypoxic microenvironment is present in up to two thirds of the cases. WERI Rb1 and Y79 retinoblastoma lines were exposed to 1% or 5% pO₂, cobalt chloride (CoCl₂), or to normoxia (21% pO₂) for up to 8 days. Both 1% and 5% pO₂ inhibited growth of both lines by more than 50%. Proliferation was reduced by 25-50% when retinoblastoma cells were exposed to 1% vs 21% pO₂, as determined by Ki67 assay. Surprisingly, Melphalan, Carboplatin, and Etoposide produced greater reduction in growth and survival of hypoxic cells than normoxic ones. Gene expression profile analysis of both lines, exposed for 48 h to 1%, 5%, or 21% pO₂, showed that glycolysis and glucose transport were the most up-regulated pathways, whereas oxidative phosphorylation was the most down-regulated pathway in hypoxia as compared to normoxia. These data support a role for hypoxia in suppressing growth, proliferation, and enhancing response of retinoblastoma cells to chemotherapy, possibly by impairing energy production through activation of glycolysis and inhibition of mitochondrial respiration. Targeting glucose metabolism or enhancing delivery of chemotherapeutic agents to hypoxic regions may improve treatment of advanced retinoblastomas.

Apelin modulates pathological remodeling of lymphatic endothelium after myocardial infarction

Lymphatic endothelium serves as a barrier to control fluid balance and immune cell trafficking to maintain tissue homeostasis. Long-term alteration of lymphatic vasculature promotes edema and fibrosis, which is an aggravating factor in the onset of cardiovascular diseases such as myocardial infarction. Apelin is a bioactive peptide that plays a central role in angiogenesis and cardiac contractility. Despite an established role of apelin in lymphangiogenesis, little is known about its function in the cardiac lymphatic endothelium. Here, we show that apelin and its receptor APJ were exclusively expressed on newly formed lymphatic vasculature in a pathological model of myocardial infarction. Using an apelin-knockout mouse model, we identified morphological and functional defects in lymphatic vasculature associated with a proinflammatory status. Surprisingly, apelin deficiency increased the expression of lymphangiogenic growth factors VEGF-C and VEGF-D and exacerbated lymphangiogenesis after myocardial infarction. Conversely, the overexpression of apelin in ischemic heart was sufficient to restore a functional lymphatic vasculature and to reduce matrix remodeling and inflammation. In vitro, the expression of apelin prevented the alteration of cellular junctions in lymphatic endothelial cells induced by hypoxia. In addition, we demonstrated that apelin controls the secretion of the lipid mediator sphingosine-1-phosphate in lymphatic endothelial cells by regulating the level of expression of sphingosine kinase 2 and the transporter SPNS2. Taken together, our results show that apelin plays a key role in lymphatic vessel maturation and stability in pathological settings. Thus, apelin may represent a novel candidate to prevent pathological lymphatic remodeling in diseases.

Effects of conditioned medium from LL-37 treated adipose stem cells on human fibroblast migration

Adipose stem cell-conditioned medium may promote human dermal fibroblast (HDF) proliferation and migration by activating paracrine peptides during the re-epithelization phase of wound healing. Human antimicrobial peptide LL-37 is upregulated in the skin epithelium as part of the normal response to injury. The effects of conditioned medium (CM) from LL-37 treated adipose stem cells (ASCs) on cutaneous wound healing, including the mediation of fibroblast migration, remain to be elucidated, therefore the aim of the present study was to determine how ASCs would react to an LL-37-rich microenvironment and if CM from LL-37 treated ASCs may influence the migration of HDFs. The present study conducted migration assays with HDFs treated with CM from LL-37 treated ASCs. Expression of CXC chemokine receptor 4 (CXCR4), which controls the recruitment of HDFs, was analyzed at the mRNA and protein levels. To further characterize the stimulatory effects of LL-37 on ASCs, the expression of stromal cell-derived factor-1α (SDF-1α), a CXC chemokine, was investigated. CM from LL-37-treated ASCs induced migration of HDFs in a time- and dose-dependent manner, with a maximum difference in migration observed 24 h following stimulation with LL-37 at a concentration of 10 µg/ml. The HDF migration and the expression of CXCR4 in fibroblasts was markedly increased upon treatment with CM from LL-37-treated ASCs compared with CM from untreated ASCs. SDF-1α expression was markedly increased in CM from LL-37 treated ASCs. It was additionally observed that SDF-1α blockade significantly reduced HDF migration. These findings suggest the feasibility of CM from LL-37-treated ASCs as a potential therapeutic for human dermal fibroblast migration.

Chemokines and their receptors in lung cancer progression and metastasis

Lung cancer is the leading cause of cancer-related mortality around the world. Despite advancements in diagnosis, surgical techniques, and neoadjuvant chemoradiotherapy over the last decade, the mortality rate is still high and the 5-year survival is a dismal 15%. Fortunately, early detection by low-dose computed tomography (LDCT) scans has reduced mortality by 20%; yet, overall, 5-year-survival remains low at less than 20%. Therefore, in order to ameliorate this situation, a thorough understanding of the underlying molecular mechanisms is urgently needed. Chemokines and their receptors, crucial microenvironmental factors, play important roles in lung tumor genesis, progression, and metastasis, and exploring the mechanisms of this might bring new insights into early diagnosis and precisely targeted treatment. Consequently, this review will mainly focus on recent advancements on the axes of chemokines and their receptors of lung cancer.

Chemokines in the cancer microenvironment and their relevance in cancer immunotherapy

The tumour microenvironment is the primary location in which tumour cells and the host immune system interact. Different immune cell subsets are recruited into the tumour microenvironment via interactions between chemokines and chemokine receptors, and these populations have distinct effects on tumour progression and therapeutic outcomes. In this Review, we focus on the main chemokines that are found in the human tumour microenvironment; we elaborate on their patterns of expression, their regulation and their roles in immune cell recruitment and in cancer and stromal cell biology, and we consider how they affect cancer immunity and tumorigenesis. We also discuss the potential of targeting chemokine networks, in combination with other immunotherapies, for the treatment of cancer.

Prolyl-hydroxylase inhibition induces SDF-1 associated with increased CXCR4+/CD11b+ subpopulations and cardiac repair

SDF-1/CXCR4 activation facilitates myocardial repair. Therefore, we aimed to activate the HIF-1α target genes SDF-1 and CXCR4 by dimethyloxalylglycine (DMOG)-induced prolyl-hydroxylase (PH) inhibition to augment CXCR4+ cell recruitment and myocardial repair. SDF-1 and CXCR4 expression was analyzed under normoxia and ischemia ± DMOG utilizing SDF-1-EGFP and CXCR4-EGFP reporter mice. In bone marrow and heart, CXCR4-EGFP was predominantly expressed in CD45+/CD11b+ leukocytes which significantly increased after myocardial ischemia. PH inhibition with 500 μM DMOG induced upregulation of SDF-1 mRNA in human microvascular endothelial cells (HMEC-1) and aortic vascular smooth muscle cells (HAVSMC). CXCR4 was highly elevated in HMEC-1 but almost no detectable in HAVSMC. In vivo, systemic administration of the PH inhibitor DMOG without pretreatment upregulated nuclear HIF-1α and SDF-1 in the ischemic mouse heart associated with increased recruitment of CD45+/CXCR4-EGFP+/CD11b+ cell subsets. Enhanced PH inhibition significantly upregulated reparative M2 like CXCR4-EGFP+ CD11b+/CD206+ cells compared to inflammatory M2-like CXCR4-EGFP+ CD11b+/CD86+ cells associated with reduced apoptotic cell death, increased neovascularization, reduced scar size, and an improved heart function after MI. In summary, our data suggest increased PH inhibition as a promising tool for a customized upregulation of SDF-1 and CXCR4 expression to attract CXCR4+/CD11b+ cells to the ischemic heart associated with increased cardiac repair.

KEY MESSAGES

DMOG-induced prolyl-hydroxylase inhibition upregulates SDF-1 and CXCR4 in human endothelial cells. Systemic application of DMOG upregulates nuclear HIF-1α and SDF-1 in vivo. Enhanced prolyl-hydroxylase inhibition increases mainly CXCR4+/CD11b+ cells. DMOG increased reparative M2-like CD11b+/CD206+ cells compared to M1-like cells after MI. Enhanced prolyl-hydroxylase inhibition improved cardiac repair and heart function.

Uremic Toxins Affect the Imbalance of Redox State and Overexpression of Prolyl Hydroxylase 2 in Human Adipose Tissue-Derived Mesenchymal Stem Cells Involved in Wound Healing

Chronic kidney disease (CKD) results in a delay in wound healing because of its complications such as uremia, anemia, and fluid overload. Mesenchymal stem cells (MSCs) are considered to be a candidate for wound healing because of the ability to recruit many types of cells. However, it is still unclear whether the CKD-adipose tissue-derived MSCs (CKD-AT-MSCs) have the same function in wound healing as healthy donor-derived normal AT-MSCs (nAT-MSCs). In this study, we found that uremic toxins induced elevated reactive oxygen species (ROS) expression in nAT-MSCs, resulting in the reduced expression of hypoxia-inducible factor-1α (HIF-1α) under hypoxic conditions. Consistent with the uremic-treated AT-MSCs, there was a definite imbalance of redox state and high expression of ROS in CKD-AT-MSCs isolated from early-stage CKD patients. In addition, a transplantation study clearly revealed that nAT-MSCs promoted the recruitment of inflammatory cells and recovery from ischemia in the mouse flap model, whereas CKD-AT-MSCs had defective functions and the wound healing process was delayed. Of note, the expression of prolyl hydroxylase domain 2 (PHD2) is selectively increased in CKD-AT-MSCs and its inhibition can restore the expression of HIF-1α and the wound healing function of CKD-AT-MSCs. These results indicate that more studies about the functions of MSCs from CKD patients are required before they can be applied in the clinical setting.

Hif-1α regulates macrophage-endothelial interactions during blood vessel development in zebrafish

Macrophages are known to interact with endothelial cells during developmental and pathological angiogenesis but the molecular mechanisms modulating these interactions remain unclear. Here, we show a role for the Hif-1α transcription factor in this cellular communication. We generated hif-1aa;hif-1ab double mutants in zebrafish, hereafter referred to as hif-1α mutants, and find that they exhibit impaired macrophage mobilization from the aorta-gonad-mesonephros (AGM) region as well as angiogenic defects and defective vascular repair. Importantly, macrophage ablation is sufficient to recapitulate the vascular phenotypes observed in hif-1α mutants, revealing for the first time a macrophage-dependent angiogenic process during development. Further substantiating our observations of vascular repair, we find that most macrophages closely associated with ruptured blood vessels are Tnfα-positive, a key feature of classically activated macrophages. Altogether, our data provide genetic evidence that Hif-1α regulates interactions between macrophages and endothelial cells starting with the mobilization of macrophages from the AGM.

The molecular mechanism regulating macrophage interaction with endothelial cells during development is unclear. Here, the authors show that in zebrafish mutation of hypoxia-inducible factor-1α impairs macrophage mobilization from the aorta-gonad-mesonephros, causing defects in angiogenesis and vessel repair.

Trimming the Vascular Tree in Tumors: Metabolic and Immune Adaptations

Angiogenesis, the formation of new blood vessels, has become a well-established hallmark of cancer. Its functional importance for the manifestation and progression of tumors has been further validated by the beneficial therapeutic effects of angiogenesis inhibitors, most notably ones targeting the vascular endothelial growth factor (VEGF) signaling pathways. However, with the transient and short-lived nature of the patient response, it has become evident that tumors have the ability to adapt to the pressures of vascular growth restriction. Several escape mechanisms have been described that adapt tumors to therapy-induced low-oxygen tension by either reinstating tumor growth by vascular rebound or by altering tumor behavior without the necessity to reinitiate revascularization. We review here two bypass mechanisms that either instigate angiogenic and immune-suppressive polarization of intratumoral innate immune cells to facilitate VEGF-independent angiogenesis or enable metabolic adaptation and reprogramming of endothelial cells and tumor cells to adapt to low-oxygen tension.

Preconditioning-induced CXCL12 upregulation minimizes leukocyte infiltration after stroke in ischemia-tolerant mice

Repetitive hypoxic preconditioning creates long-lasting, endogenous protection in a mouse model of stroke, characterized by reductions in leukocyte-endothelial adherence, inflammation, and infarct volumes. The constitutively expressed chemokine CXCL12 can be upregulated by hypoxia and limits leukocyte entry into brain parenchyma during central nervous system inflammatory autoimmune disease. We therefore hypothesized that the sustained tolerance to stroke induced by repetitive hypoxic preconditioning is mediated, in part, by long-term CXCL12 upregulation at the blood-brain barrier (BBB). In male Swiss Webster mice, repetitive hypoxic preconditioning elevated cortical CXCL12 protein levels, and the number of cortical CXCL12+ microvessels, for at least two weeks after the last hypoxic exposure. Repetitive hypoxic preconditioning-treated mice maintained more CXCL12-positive vessels than untreated controls following transient focal stroke, despite cortical decreases in CXCL12 mRNA and protein. Continuous administration of the CXCL12 receptor (CXCR4) antagonist AMD3100 for two weeks following repetitive hypoxic preconditioning countered the increase in CXCL12-positive microvessels, both prior to and following stroke. AMD3100 blocked the protective post-stroke reductions in leukocyte diapedesis, including macrophages and NK cells, and blocked the protective effect of repetitive hypoxic preconditioning on lesion volume, but had no effect on blood-brain barrier dysfunction. These data suggest that CXCL12 upregulation prior to stroke onset, and its actions following stroke, contribute to the endogenous, anti-inflammatory phenotype induced by repetitive hypoxic preconditioning.

Phase I study of pazopanib plus TH-302 in advanced solid tumors

PURPOSE

To define the maximum tolerated dose (MTD), recommended phase II dose (RPTD), and assess safety and tolerability for the combination of pazopanib plus TH-302, an investigational hypoxia-activated prodrug (HAP), in adult patients with advanced solid tumors.

METHODS

This was an open-label, non-randomized, single-center, phase I trial consisting 2 stages. Stage 1 was a standard "3 + 3" dose escalation design to determine safety and the RPTD for TH-302 plus pazopanib combination. Stage 2 was an expanded cohort to better describe the tolerability and toxicity profile at the MTD. Pazopanib was orally dosed at 800 mg daily on days 1-28 for all cohorts. TH-302 was administered intravenously on days 1, 8 and 15 of a 28-day cycle at doses of 340 mg/m² (cohort 1) or 480 mg/m² (cohort 2). Dose limiting toxicity (DLT) was assessed in the first 28-day cycle. Efficacy was assessed every 2 cycles.

RESULTS

Thirty patients were enrolled between December 2011 and September 2013. In the dose escalation stage, 7 patients were enrolled in the 340 mg/m² TH-302 cohort and 6 patients in the 480 mg/m² TH-302 cohort. Ten patients were evaluable for DLT. DLTs included grade 2 intolerable esophagitis (n = 1) in the 340 mg/m² TH-302 cohort, and grade 3 vaginal inflammation (n = 1) and grade 3 neutropenia with grade 3 thrombocytopenia (n = 1, same patient) in the 480 mg/m² TH-302 cohort. The 340 mg/m² TH-302 cohort was determined to be MTD and RPTD. The most common treatment-related adverse events were hematologic (anemia, neutropenia, and thrombocytopenia), nausea/vomiting, palmar-plantar erythrodysesthesia syndrome, constipation, fatigue, mucositis, anorexia, pain, and hypertension. Partial response (PR) was observed in 10% (n = 3) of patients, stable disease (SD) in 57% (n = 17), and progressive disease (PD) in 23% (n = 7). Due to toxicity, 3 patients were discontinued from study drug prior to first radiographic assessment but were included in these calculations. Disease control ≥6 months was observed in 37% of patients (n = 11).

CONCLUSIONS

The RPTD for this novel combination is pazopanib 800 mg daily on days 1-28 plus TH-302 340 mg/m² on days 1, 8 and 15 of each 28-day cycle. Preliminary activity was seen in treatment-refractory cancers and supports potential value of co-targeting tumor angiogenesis and tumor hypoxia.

Hypoxia and hyperoxia differentially control proliferation of rat neural crest stem cells via distinct regulatory pathways of the HIF1α-CXCR4 and TP53-TPM1 proteins

BACKGROUND

Neural crest stem cells (NCSCs) are a population of adult multipotent stem cells. We are interested in studying whether oxygen tensions affect the capability of NCSCs to self-renew and repair damaged tissues. NCSCs extracted from the hair follicle bulge region of the rat whisker pad were cultured in vitro under different oxygen tensions.

RESULTS

We found significantly increased and decreased rates of cell proliferation in rat NCSCs (rNCSCs) cultured, respectively, at 0.5% and 80% oxygen levels. At 0.5% oxygen, the expression of both hypoxia-inducible factor (HIF) 1α and CXCR4 was greatly enhanced in the rNCSC nuclei and was suppressed by incubation with the CXCR4-specific antagonist AMD3100. In addition, the rate of cell apoptosis in the rNCSCs cultured at 80% oxygen was dramatically increased, associated with increased nuclear expression of TP53, decreased cytoplasmic expression of TPM1 (tropomyosin-1), and increased nuclear-to-cytoplasmic translocation of S100A2. Incubation of rNCSCs with the antioxidant N-acetylcysteine (NAC) overcame the inhibitory effect of 80% oxygen on proliferation and survival of rNCSCs.

CONCLUSIONS

Our results show for the first time that extreme oxygen tensions directly control NCSC proliferation differentially via distinct regulatory pathways of proteins, with hypoxia via the HIF1α-CXCR4 pathway and hyperoxia via the TP53-TPM1 pathway. Developmental Dynamics 246:162-185, 2017. © 2016 Wiley Periodicals, Inc.

All-trans retinoic acid preconditioning enhances proliferation, angiogenesis and migration of mesenchymal stem cell in vitro and enhances wound repair in vivo

OBJECTIVES

Stem cell therapy is considered to be a suitable alternative in treatment of a number of diseases. However, there are challenges in their clinical application in cell therapy, such as to reduce survival and loss of transplanted stem cells. It seems that chemical and pharmacological preconditioning enhances their therapeutic efficacy. In this study, we investigated effects of all-trans retinoic acid (ATRA) on survival, angiogenesis and migration of mesenchymal stem cells (MSCs) in vitro and in a wound-healing model.

MATERIALS AND METHODS

MSCs were treated with a variety of concentrations of ATRA, and mRNA expression of cyclo-oxygenase-2 (COX-2), hypoxia-inducible factor-1 (HIF-1), C-X-C chemokine receptor type 4 (CXCR4), C-C chemokine receptor type 2 (CCR2), vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2) and Ang-4 were examined by qRT-PCR. Prostaglandin E2 (PGE2) levels were measured using an ELISA kit and MSC angiogenic potential was evaluated using three-dimensional tube formation assay. Finally, benefit of ATRA-treated MSCs in wound healing was determined with a rat excisional wound model.

RESULTS

In ATRA-treated MSCs, expressions of COX-2, HIF-1, CXCR4, CCR2, VEGF, Ang-2 and Ang-4 increased compared to control groups. Overexpression of the related genes was reversed by celecoxib, a selective COX-2 inhibitor. Tube formation and in vivo wound healing of ATRA-treated MSCs were also significantly enhanced compared to untreated MSCs.

CONCLUSION

Pre-conditioning of MSCs with ATRA increased efficacy of cell therapy by activation of survival signalling pathways, trophic factors and release of pro-angiogenic molecules.

Inflammation and Cancer: Extra- and Intracellular Determinants of Tumor-Associated Macrophages as Tumor Promoters

One of the hallmarks of cancer-related inflammation is the recruitment of monocyte-macrophage lineage cells to the tumor microenvironment. These tumor infiltrating myeloid cells are educated by the tumor milieu, rich in cancer cells and stroma components, to exert functions such as promotion of tumor growth, immunosuppression, angiogenesis, and cancer cell dissemination. Our review highlights the ontogenetic diversity of tumor-associated macrophages (TAMs) and describes their main phenotypic markers. We cover fundamental molecular players in the tumor microenvironment including extra- (CCL2, CSF-1, CXCL12, IL-4, IL-13, semaphorins, WNT5A, and WNT7B) and intracellular signals. We discuss how these factors converge on intracellular determinants (STAT3, STAT6, STAT1, NF-κB, RORC1, and HIF-1α) of cell functions and drive the recruitment and polarization of TAMs. Since microRNAs (miRNAs) modulate macrophage polarization key miRNAs (miR-146a, miR-155, miR-125a, miR-511, and miR-223) are also discussed in the context of the inflammatory myeloid tumor compartment. Accumulating evidence suggests that high TAM infiltration correlates with disease progression and overall poor survival of cancer patients. Identification of molecular targets to develop new therapeutic interventions targeting these harmful tumor infiltrating myeloid cells is emerging nowadays.

Disrupting Tumor Angiogenesis and "the Hunger Games" for Breast Cancer

Angiogenesis, one of the hallmarks of cancers, has become an attractive target for cancer therapy since decades ago. It is broadly thought that upregulation of angiogenesis is involved in tumor progression and metastasis. Though tumor vessels are tortuous, disorganized, and leaky, they deliver oxygen and nutrients for tumor development. Based on this knowledge, many kinds of drugs targeting angiogenesis pathways have been developed, such as bevacizumab. However, the clinical outcomes of anti-angiogenesis therapies are moderate in metastatic breast cancer as well as in metastatic colorectal cancer and non-small cell lung cancer, even combined with traditional chemotherapy. In this chapter, the morphologic angiogenesis patterns and the key molecular pathways regulating angiogenesis are elaborated. The FDA-approved anti-angiogenesis drugs and current challenges of anti-angiogenesis therapy are described. The strategies to overcome the barriers will also be elucidated.

The chemokinome superfamily in channel catfish: I. CXC subfamily and their involvement in disease defense and hypoxia responses

Chemokines are a superfamily of structurally related chemotactic cytokines exerting significant roles in regulating cell migration and activation. They are defined by the presence of four conserved cysteine residues and are divided into four subfamilies depending on the arrangement of the first two conserved cysteines residues: CXC, CC, C and CX3C. In this study, a complete set of 17 CXC chemokine ligand (CXCL) genes was systematically identified and characterized from channel catfish genome through data mining of existing genomic resources. Phylogenetic analysis allowed annotation of the 17 CXC chemokines. Extensive comparative genomic analyses supported their annotations and orthologies, revealing the existence of fish-specific CXC chemokines and the expansion of CXC chemokines in the teleost genomes. The analysis of gene expression after bacterial infection indicated the CXC chemokines were expressed in a gene-specific manner. CXCL11.3 and CXCL20.3 were expressed significantly higher in resistant fish than in susceptible fish after ESC infection, while CXCL20.2 were expressed significantly higher in resistant fish than in susceptible fish after columnaris infection. The expression of those CXC chemokines, therefore can be a useful indicator of disease resistance. A similar pattern of expression was observed between resistant and susceptible fish with biotic and abiotic stresses, ESC, columnaris and hypoxia, suggesting that high levels of expression of the majority of CXC chemokines, with exception of CXC11 and CXC20, are detrimental to the host.

Sildenafil attenuates hypoxic pulmonary remodelling by inhibiting bone marrow progenitor cells

The recruitment of bone marrow (BM)-derived progenitor cells to the lung is related to pulmonary remodelling and the pathogenesis of pulmonary hypertension (PH). Although sildenafil is a known target in PH treatment, the underlying molecular mechanism is still elusive. To test the hypothesis that the therapeutic effect of sildenafil is linked to the reduced recruitment of BM-derived progenitor cells, we induced pulmonary remodelling in rats by two-week exposure to chronic hypoxia (CH, 10% oxygen), a trigger of BM-derived progenitor cells. Rats were treated with either placebo (saline) or sildenafil (1.4 mg/kg/day ip) during CH. Control rats were kept in room air (21% oxygen) with no treatment. As expected, sildenafil attenuated the CH-induced increase in right ventricular systolic pressure and right ventricular hypertrophy. However, sildenafil suppressed the CH-induced increase in c-kit⁺ cells in the adventitia of pulmonary arteries. Moreover, sildenafil reduced the number of c-kit⁺ cells that colocalize with tyrosine kinase receptor 2 (VEGF-R2) and CD68 (a marker for macrophages), indicating a positive effect on moderating hypoxia-induced smooth muscle cell proliferation and inflammation without affecting the pulmonary levels of hypoxia-inducible factor (HIF)-1α. Furthermore, sildenafil depressed the number of CXCR4⁺ cells. Collectively, these findings indicate that the improvement in pulmonary haemodynamic by sildenafil is linked to decreased recruitment of BM-derived c-kit⁺ cells in the pulmonary tissue. The attenuation of the recruitment of BM-derived c-kit⁺ cells by sildenafil may provide novel therapeutic insights into the control of pulmonary remodelling.

Hypoxia-induced CCL28 promotes recruitment of regulatory T cells and tumor growth in liver cancer

Tumor cells craft microenvironment to overcome growth disadvantages and adjust to escape the immunosurveillance during tumorigenesis and metastasis. The evolving adaption to the changing microenvironment is exemplified by the development of strategies to deal with hypoxia resulted from fast proliferation of the tumor cells. In this study, we found that hypoxia hepatocellular carcinoma (HCC) cells recruited Regulatory T cells (Tregs) and expressed more Chemokine (C-C motif) ligand 28 (CCL28). Deletion of CCL28 inhibited Treg recruitment. Furthermore, overexpression of CCL28 promoted tumor growth and Treg infiltration in vivo. Enhanced angiogenesis and VEGF expression was also observed. Moreover, inhibition of HIF1α reversed hypoxia-induced CCL28 upregulation. Taken together, our results demonstrate that HCC recruits Tregs to promote angiogenesis under hypoxic condition by upregulating CCL28 expression. These findings establish a link between Tregs and hypoxia in HCC growth and may provide a new potential therapeutic target for treating HCC.

Radioresistant human lung adenocarcinoma cells that survived multiple fractions of ionizing radiation are sensitive to HSP90 inhibition

Despite the common usage of radiotherapy for the treatment of NSCLC, outcomes for these cancers when treated with ionizing radiation (IR) are still unsatisfactory. A better understanding of the mechanisms underlying resistance to IR is needed to design approaches to eliminate the radioresistant cells and prevent tumor recurrence and metastases. Using multiple fractions of IR we generated radioresistant cells from T2821 and T2851 human lung adenocarcinoma cells. The radioresistant phenotypes present in T2821/R and T2851/R cells include multiple changes in DNA repair genes and proteins expression, upregulation of EMT markers, alterations of cell cycle distribution, upregulation of PI3K/AKT signaling and elevated production of growth factors, cytokines, important for lung cancer progression, such as IL-6, PDGFB and SDF-1 (CXCL12). In addition to being radioresistant these cells were also found to be resistant to cisplatin.

HSP90 is a molecular chaperone involved in stabilization and function of multiple client proteins implicated in NSCLC cell survival and radioresistance. We examined the effect of ganetespib, a novel HSP90 inhibitor, on T2821/R and T2851/R cell survival, migration and radioresistance. Our data indicates that ganetespib has cytotoxic activity against parental T2821 and T2851 cells and radioresistant T2821/R and T2851/R lung tumor cells. Ganetespib does not affect proliferation of normal human lung fibroblasts. Combining IR with ganetespib completely abrogates clonogenic survival of radioresistant cells.

Our data show that HSP90 inhibition can potentiate the effect of radiotherapy and eliminate radioresistant and cisplatin -resistant residual cells, thus it may aid in reducing NSCLC tumor recurrence after fractionated radiotherapy.

Pharmacological targeting of CXCL12/CXCR4 signaling in prostate cancer bone metastasis

Background

The CXCL12/CXCR4 axis transactivates HER2 and promotes intraosseous tumor growth. To further explore the transactivation of HER2 by CXCL12, we investigated the role of small GTP protein G_αi2 in Src and HER2 phosphorylation in lipid raft membrane microdomains and the significance of CXCR4 in prostate cancer bone tumor growth.

Methods

We used a variety of methods such as lipid raft isolation, invasion assays, an in vivo model of intratibial tumor growth, bone histomorphometry, and immunohistochemistry to determine the role of CXCR4 signaling in lipid raft membrane microdomains and effects of targeting of CXCR4 for bone tumor growth.

Results

We determined that (a) CXCL12/CXCR4 transactivation of EGFR and HER2 is confined to lipid raft membrane microdomains, (b) CXCL12 activation of HER2 and Src is mediated by small GTP proteins in lipid rafts, (c) inhibition of the CXCL12/CXCR4 axis through plerixafor abrogates the initial establishment of tumor growth without affecting the growth of established bone tumors, and (d) inhibition of EGFR signaling through gefitinib leads to inhibition of established bone tumor growth.

Conclusions

These data suggest that lipid raft membrane microdomains are key sites for CXCL12/CXCR4 transactivation of HER2 via small GTP binding protein G_αi2 and Src kinase. The initial establishment of prostate cancer is supported by the endosteal niche, and blocking the CXCL12/CXCR4 axis of this niche along with its downstream signaling severely compromises initial establishment of tumors in the bone microenvironment, whereas expanding bone tumors are sensitive only to the members of growth factor receptor inhibition.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0552-0) contains supplementary material, which is available to authorized users.

Imaging the Cytokine Receptor CXCR4 in Atherosclerotic Plaques with the Radiotracer 68Ga-Pentixafor for PET

⁶⁸Ga-pentixafor is a radiotracer for PET that binds with nanomolar affinity to CXCR4. The CXCR4 receptor is expressed at the surface of inflammatory cells. The objective of the study was to analyze the ability of radiolabeled pentixafor to detect CXCR4 expression on inflammatory cells present in atherosclerotic plaques of an experimental rabbit model. Methods: Atherosclerotic plaques were induced by endothelial abrasion of the right carotid artery and abdominal aorta of 7 rabbits fed an atherogenic diet. Five noninjured rabbits fed a chow diet were used as controls. Rabbits were imaged on a PET/MR system after injection of ⁶⁸Ga-pentixafor (15 MBq/kg). Vascular signal was quantified as tissue-to-background ratio (TBR). Biodistribution and autoradiographic studies were performed 1 h after injection of ¹²⁵I-pentixafor (7.5 MBq/kg). In addition, blocking studies were performed in 2 atherosclerotic rabbits with preinjection of the CXCR4 inhibitor AMD3100. Tracer uptake was quantified on arterial cryosections using autoradiography and compared with CXCR4 and RAM-11 (macrophage) expression on adjacent histologic sections. Results: One hour after injection of ⁶⁸Ga-pentixafor, strong signals were detected in vivo with PET/MR imaging in atherosclerotic plaques of the abdominal aorta and right carotid artery as compared with normal control arteries (mean TBR = 1.95 ± 0.51 vs. 1.22 ± 0.25 and mean TBR = 1.24 ± 0.38 vs. 0.96 ± 0.37, respectively; P < 0.05 for both). Blocking studies with preinjection of a CXCR4 inhibitor reduced ¹²⁵I-pentixafor uptake in atherosclerotic plaques by approximately 40%. ¹²⁵I-pentixafor uptake in the vessel wall on autoradiographies was located in macrophage-rich regions of atherosclerotic plaques and correlated with the intensity of CXCR4 expression on corresponding cryosections (r² = 0.61; P < 0.05). Conclusion:⁶⁸Ga-pentixafor allows for the noninvasive detection of CXCR4 expression in the vessel wall with PET and emerges as a potential alternative to ¹⁸F-FDG for the assessment of macrophage infiltration in atherosclerotic plaques.

CXCL1-Mediated Interaction of Cancer Cells with Tumor-Associated Macrophages and Cancer-Associated Fibroblasts Promotes Tumor Progression in Human Bladder Cancer

Tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) are reported to be associated with poor prognosis, depending on their pro-tumoral roles. Current knowledge of TAMs and CAFs in the tumor microenvironment of urothelial cancer of the bladder (UCB) is limited. Therefore, we investigated the paracrine effect induced by TAMs and CAFs in the tumor microenvironment of human UCB. For this, we first carried out immunohistochemical analysis for CXCL1, CD204 (TAM marker), αSMA (CAF marker), E-cadherin, and MMP2 using 155 UBC tissue samples. Next, CXCL1-overexpressing clones of THP-1-derived TAMs and NIH3T3-derived CAFs were developed by lentiviral vector infection. The immunohistochemical study showed high CXCL1 levels in UCB cells to be associated with enhanced recruitment of TAMs/CAFs, higher metastatic potential, and poor prognosis. Three-dimensional (3D) co-culture of UCB cells and TAMs/CAFs suggested that CXCL1 production in TAMs/CAFs play an important role in cell-to-cell adhesion and interaction among cancer cells and these stromal cells. CXCL1-expressing TAMs/CAFs enhanced tumor growth of subcutaneous UCB tumors in nude mice when injected together. In addition, an experiment using the orthotopic bladder cancer model revealed that CXCL1 production in TAMs/CAFs supported tumor implantation into the murine bladder wall and UCB growth when injected together, which was confirmed by clinical data of patients with bladder cancer. Thus, CXCL1 signaling in the tumor microenvironment is highly responsible for repeated intravesical recurrence, disease progression, and drug resistance through enhanced invasion ability. In conclusion, disrupting CXCL1 signaling to dysregulate this chemokine is a promising therapeutic approach for human UCB.

Chemokines, cytokines and exosomes help tumors to shape inflammatory microenvironment

Relationship between inflammation and cancer is now well-established and represents a paradigm that our immune response does not necessarily serves solely to protect us from infections and cancer. Many specific mechanisms that link chronic inflammation to cancer promotion and metastasis have been uncovered in the recent years. Here we are focusing on the effects that tumors may exert on inflammatory cascades, tuning the immune system ability to cause tumor promotion or regression. In particular, we discuss the contributions of chemokines, cytokines and exosomes to the processes such as induction of inflammation and tumorigenesis. Overall, tumor-elicited inflammation is a key driver of tumor progression and an essential component of tumor microenvironment.

Hypoxia-inducible factors: key regulators of myeloid cells during inflammation

Hypoxia is a prominent characteristic of many acute or chronic inflammatory diseases, and exerts significant influence on their progression. Macrophages and neutrophils are major cellular components of innate immunity and contribute not only to O2 deprivation at the site of inflammation, but also alter many of their functions in response to hypoxia to either facilitate or suppress inflammation. Hypoxia stabilizes HIF-αs in macrophages and neutrophils, and these O2-sensitive transcription factors are key regulators of inflammatory responses in myeloid cells. In this review, we will summarize our current understanding of the role of HIF-αs in shaping macrophage and neutrophil functions in the pathogenesis and progression of multiple inflammatory diseases.

The P-Rex1/Rac signaling pathway as a point of convergence for HER/ErbB receptor and GPCR responses

Guanine nucleotide Exchange Factors (GEFs) are responsible for mediating GDP/GTP exchange for specific small G proteins, such as Rac. There has been substantial evidence for the involvement of Rac-GEFs in the control of cancer cell migration and metastatic progression. We have previously established that the Rac-GEF P-Rex1 is a mediator of actin cytoskeleton rearrangements and cell motility in breast cancer cells downstream of HER/ErbB receptors and the G-Protein Coupled Receptor (GPCR) CXCR4. P-Rex1 is highly expressed in luminal A and B breast cancer compared to normal mammary tissue, whereas expression is very low in basal breast cancer, and its expression correlates with the appearance of metastasis in patients. Here, we discuss the involvement of P-Rex1 as an effector of oncogenic/metastatic receptors in breast cancer and underscore its relevance in the convergence of receptor-triggered motile signals. In addition, we provide an overview of our recent findings describing a cross-talk between HER/ErbB receptors and CXCR4, and how this impacts on the activation of P-Rex1/Rac1 signaling, as well as highlight challenges that lie ahead. We propose a model in which P-Rex1 acts as a crucial node for the integration of upstream inputs from HER/ErbB receptors and CXCR4 in luminal breast cancer cells.

The ever-expanding role of HIF in tumour and stromal biology

Low oxygen tension (hypoxia) is a hallmark of cancer that influences cancer cell function, but is also an important component of the tumour microenvironment as it alters the extracellular matrix, modulates the tumour immune response and increases angiogenesis. Here we discuss the regulation and role of hypoxia and its key transcriptional mediators, the hypoxia-inducible factor (HIF) family of transcription factors, in the tumour microenvironment and stromal compartments.

Hypoxia-inducible factors: a central link between inflammation and cancer

The tumor immune response is in a dynamic balance between antitumor mechanisms, which serve to decrease cancer growth, and the protumor inflammatory response, which increases immune tolerance, cell survival, and proliferation. Hypoxia and expression of HIF-1α and HIF-2α are characteristic features of all solid tumors. HIF signaling serves as a major adaptive mechanism in tumor growth in a hypoxic microenvironment. HIFs represent a critical signaling node in the switch to protumorigenic inflammatory responses through recruitment of protumor immune cells and altered immune cell effector functions to suppress antitumor immune responses and promote tumor growth through direct growth-promoting cytokine production, angiogenesis, and ROS production. Modulating HIF function will be an important mechanism to dampen the tumor-promoting inflammatory response and inhibit cancer growth.

CXCR4 polymorphism predicts progression-free survival in metastatic colorectal cancer patients treated with first-line bevacizumab-based chemotherapy

We analyzed associations between CXCR4/CXCL12 single-nucleotide polymorphisms and outcomes in metastatic colorectal cancer (mCRC) patients who underwent first-line bevacizumab-based chemotherapy. A total of 874 patients were included in this study: 144 treated with bevacizumab and FOLFOX or XELOX (training cohort), 653 treated with bevacizumab and FOLFIRI or FOLFOXIRI (validation cohort A or B) and 77 treated with cetuximab- and oxaliplatin-based regimens (control cohort). One CXCR4 polymorphism (rs2228014) and two CXCL12 polymorphisms (rs1801157 and rs3740085) were analyzed by PCR-based direct sequencing. Patients with a C/C genotype had a prolonged progression-free survival (PFS) compared with those with any T allele (P=0.030) in the training cohort. Similarly, patients with the C/C genotype had a superior PFS in the validation cohorts, but not in the control cohort. Our findings suggest that a common genetic variant, CXCR4 rs2228014, could predict PFS and may guide therapeutic decisions in mCRC patients receiving first-line bevacizumab-based chemotherapy.

Blockade of hypoxia-induced CXCR4 with AMD3100 inhibits production of OA-associated catabolic mediators IL-1β and MMP-13

Binding of the chemokine stromal cell-derived factor-1 (SDF-1) to its receptor C-X-C chemokine receptor type 4 (CXCR4) results in receptor activation and the subsequent release of matrix metalloproteinases (MMPs) that contribute to osteoarthritis (OA) cartilage degradation. As hypoxia is a defining feature of the chondrocyte microenvironment, the present study investigated the possible mechanism through which SDF‑1 induces cartilage degradation under hypoxic conditions. To do this, OA chondrocyte cultures and patient tissue explants pretreated with the CXCR4 inhibitor, AMD3100 were incubated with SDF‑1. It was identified that hypoxic conditions significantly elevated the expression of CXCR4 in osteoarthritic chondrocytes relative to normoxic conditions. Furthermore, SDF‑1 elevated MMP‑13 mRNA levels and proteinase activity. It also elevated the mRNA and protein levels of runt‑related transcription factor 2, and induced the release of glycosaminoglycans and the inflammatory cytokine, interleukin‑1β. By contrast, such changes did not occur to an appreciable degree in cells that were pretreated with AMD3100. The results of the present study demonstrate that even under hypoxic conditions, where CXCR4 expression is significantly elevated in chondrocytes, AMD3100 effectively blocks this receptor and protects chondrocytes from OA‑induced catabolism, suggesting that the successful inhibition of CXCR4 may be an effective approach for OA treatment.

Stromal cell-derived factor-1 (SDF-1) as a target in liver diseases

The chemokine stromal cell-derived factor-1 (SDF-1) or CXCL12 is constitutively expressed in healthy liver. However, its expression increases following acute or chronic liver injury. Liver sinusoidal endothelial cells (LSEC), hepatic stellate cells (HSC), and malignant hepatocytes are important sources of SDF-1/CXCL12 in liver diseases. CXCL12 is able to activate two chemokine receptors with different downstream signaling pathways, CXCR4 and CXCR7. CXCR7 expression is relevant on LSEC, while HSC, mesenchymal stem cells, and tumor cells mainly respond via CXCR4. Here, we summarize recent developments in the field of liver diseases involving this chemokine and its receptors. SDF-1-dependent signaling contributes to modulating acute liver injury and subsequent tissue regeneration. By activating HSC and recruiting mesenchymal cells from bone marrow, CXCL12 can promote liver fibrosis progression, while CXCL12-CXCR7 interactions endorse proregenerative responses in chronic injury. Moreover, the SDF-1 pathway is linked to development of hepatocellular carcinoma (HCC) by promoting tumor growth, angiogenesis, and HCC metastasis. High hepatic CXCR4 expression has been suggested as a biomarker indicating poor prognosis of HCC patients. Tumor-infiltrating myeloid-derived suppressor cells (MDSC) also express CXCR4 and migrate toward CXCL12. Thus CXCL12 inhibition might not only directly block HCC growth but also modulate the tumor microenvironment (angiogenesis, MDSC), thereby sensitizing HCC patients to conventional or emerging novel cancer therapies (e.g., sorafenib, regorafenib, nivolumab, pembrolizumab). We herein summarize the current knowledge on the complex interplay between CXCL12 and CXCR4/CXCR7 in liver diseases and discuss approaches on the therapeutic targeting of these axes in hepatitis, fibrosis, and liver cancer.

Hypoxia-inducible factor-1 expression predicts osteosarcoma patients' survival: a meta-analysis

Osteosarcoma, the most common primary bone malignancy, is characterized by easily relapsing and metastasizing. Hypoxia-inducible factor-1 (HIF-1) plays an essential role in tumorigenesis, affecting tumor metabolism, differentiation, angiogenesis, proliferation and metastasis, and has been found to be associated with survival in patients with osteosarcoma. The possible prognostic value of HIF-1 was investigated in many studies, but the results were inconsistent. We therefore conducted a meta-analysis to elucidate the correlation of HIF-1 expression, analyzed by immunohistochemistry in osteosarcoma tissues, with prognosis. The association degree was assessed by calculation of the hazard ratio (HR) and risk ratio (RR) with corresponding 95% confidence intervals (CIs). Follow-up information was available for 486 patients from 7 studies. The results showed that high HIF-1 expression was associated with a worse prognosis when compared to low or undetectable HIF-1 expression, with an HR of 3.67 (95% CI 2.24-5.99; p<0.001) for overall survival (OS) and an RR of 3.72 (95% CI 2.26-6.13; p<0.001) for OS. The RR of 2.55 for disease-free survival (DFS) did not show any obvious relationship between a high level of HIF-1 and DFS (95% CI 0.95-6.87; p = 0.064). The stability of this result was tested by sensitivity analysis and no significant change was detected. This meta-analysis suggests that HIF-1 is an effective prognostic biomarker to predict OS in patients with osteosarcoma.

Heregulin/ErbB3 Signaling Enhances CXCR4-Driven Rac1 Activation and Breast Cancer Cell Motility via Hypoxia-Inducible Factor 1α

The growth factor heregulin (HRG), a ligand of ErbB3 and ErbB4 receptors, contributes to breast cancer development and the promotion of metastatic disease, and its expression in breast tumors has been associated with poor clinical outcome and resistance to therapy. In this study, we found that breast cancer cells exposed to sustained HRG treatment show markedly enhanced Rac1 activation and migratory activity in response to the CXCR4 ligand SDF-1/CXCL12, effects mediated by P-Rex1, a Rac-guanine nucleotide exchange factor (GEF) aberrantly expressed in breast cancer. Notably, HRG treatment upregulates surface expression levels of CXCR4, a G protein-coupled receptor (GPCR) implicated in breast cancer metastasis and an indicator of poor prognosis in breast cancer patients. A detailed mechanistic analysis revealed that CXCR4 upregulation and sensitization of the Rac response/motility by HRG are mediated by the transcription factor hypoxia-inducible factor 1α (HIF-1α) via ErbB3 and independently of ErbB4. HRG caused prominent induction in the nuclear expression of HIF-1α, which transcriptionally activates the CXCR4 gene via binding to a responsive element located in positions -1376 to -1372 in the CXCR4 promoter, as revealed by mutagenesis analysis and chromatin immunoprecipitation (ChIP). Our results uncovered a novel function for ErbB3 in enhancing breast cancer cell motility and sensitization of the P-Rex1/Rac1 pathway through HIF-1α-mediated transcriptional induction of CXCR4.

Chemokines accentuating protumoral activities in oral cancer microenvironment possess an imperious stratagem for therapeutic resolutions

Chemokines, the chemotactic cytokines have established their role in tumorigenesis and tumor progression. Studies, which explored their role in oral cancer for protumoral activity, point towards targeting chemokines for oral squamous cell carcinoma therapy. The need of the hour is to emphasize/divulge in the activities of chemokine ligands and their receptors in the tumor microenvironment for augmentation of such stratagems. This progressing sentience of chemokines and their receptors has inspired this review which is an endeavour to comprehend their role as an aid in accentuating hallmarks of cancer and targeted therapy.

Harnessing mesenchymal stem cell homing as an anticancer therapy

INTRODUCTION

Mesenchymal stromal cells (MSCs) are non-hematopoietic progenitor cells that have been exploited as vehicles for cell-based cancer therapy. The general approach is based on the innate potential of adoptively applied MSC to undergo facilitated recruitment to malignant tissue. MSC from different tissue sources have been engineered using a variety of therapy genes that have shown efficacy in solid tumor models.

AREAS COVERED

In this review we will focus on the current developments of MSC-based gene therapy, in particular the diverse approaches that have been used for MSCs-targeted tumor therapy. We also discuss some outstanding issues and general prospects for their clinical application.

EXPERT OPINION

The use of modified mesenchymal stem cells as therapy vehicles for the treatment of solid tumors has progressed to the first generation of clinical trials, but the general field is still in its infancy. There are many questions that need to be addressed if this very complex therapy approach is widely applied in clinical settings. More must be understood about the mechanisms underlying tumor tropism and we need to identify the optimal source of the cells used. Outstanding issues also include the therapy transgenes used, and which tumor types represent viable targets for this therapy.

Polarized CD163+ tumor-associated macrophages are associated with increased angiogenesis and CXCL12 expression in gastric cancer

PURPOSE

Tumor-associated macrophages (TAMs) play a significant role in tumor progression and angiogenesis. However, the prognostic value of TAMs in different histologic locations of gastric cancer (GC) is still unknown. We evaluated the distribution of TAMs in different histologic locations to investigate its importance in predicting prognosis and the relationship with angiogenesis and CXCL12 expression in GC.

METHODS AND MATERIALS

The distribution of TAMs and microvessel density (MVD) in 113 GC samples were evaluated by immunohistochemical staining of CD163 and CD105, respectively. The extent of TAM distribution in the tumor was categorized into three groups: infiltrated TAMs in the tumor nest (TN), tumor stroma (TS) and invasive tumor margin (TM). The expression of CXCL12 in GC were evaluated by immunohistochemical staining of tissues from 88 GC samples.

RESULTS

The increased CD163+ TAMs in TS and TM were closely correlated with tumor size, depth of invasion, TNM stage, lymph node metastasis, and lymphovascular invasion. TAMs in TN was not related with any clinicopathologic characteristics except histologic differentiation. The high infiltration of CD163+ TAMs in TS and TM were significantly correlated with poor overall survival. Regardless of location, CD163+ TAMs were significantly correlated with increased MVD. CXCL12 expression was significantly associated with increased CD163+ TAMs in TS and TM.

CONCLUSIONS

TAMs in different histologic locations in GC were related to distinct aspects of tumor progression. CD163+ TAMs in TS and TM are associated with tumor progression and CXCL12 expression in GC. TAMs may be involved in tumor progression through the angiogenesis.

Targeting chemokine receptor CXCR4 for treatment of HIV-1 infection, tumor progression, and metastasis

The chemokine receptor CXCR4 is required for the entry of human immunodeficiency virus type 1 (HIV-1) into target cells and for the development and dissemination of various types of cancers, including gastrointestinal, cutaneous, head and neck, pulmonary, gynecological, genitourinary, neurological, and hematological malignancies. The T-cell (T)-tropic HIV-1 strains use CXCR4 as the entry coreceptor; consequently, multiple CXCR4 antagonistic inhibitors have been developed for the treatment of acquired immune deficiency syndrome (AIDS). However, other potential applications of CXCR4 antagonists have become apparent since its discovery in 1996. In fact, increasing evidence demonstrates that epithelial and hematopoietic tumor cells exploit the interaction between CXCR4 and its natural ligand, stromal cellderived factor (SDF)-1α, which normally regulates leukocyte migration. The CXCR4 and/or SDF-1α expression patterns in tumor cells also determine the sites of metastatic spread. In addition, the activation of CXCR4 by SDF-1α promotes invasion and proliferation of tumor cells, enhances tumor-associated neoangiogenesis, and assists in the degradation of the extracellular matrix and basement membrane. As such, the evaluation of CXCR4 and/or SDF-1α expression levels has a significant prognostic value in various types of malignancies. Several therapeutic challenges remain to be overcome before the use of CXCR4 inhibitors can be translated into clinical practice, but promising preclinical data demonstrate that CXCR4 antagonists can mobilize tumor cells from their protective microenvironments, interfere with their metastatic and tumorigenic potentials, and/or make tumor cells more susceptible to chemotherapy.

RNA interference-mediated silencing of speckle-type POZ protein promotes apoptosis of renal cell cancer cells

This study aimed to investigate the effects of silencing the speckle-type POZ protein (SPOP) gene on renal cell cancer (RCC) cells and to explore its possible mechanism. The A498 and ACHN RCC cells were transfected with small interference RNA (siRNA)-SPOP by lipofection methods. The silencing efficiency was monitored by quantitative real-time polymerase chain reaction and Western blot. The effects of SPOP silencing on cell apoptosis, cell viability, colony formation ability, cell migration ability, and chemosensitivity to Sorafenib were assessed by flow cytometry, an MTT assay, a colony formation assay, a trans-well migration assay, and a CCK-8 assay, respectively. Its effects on the expression of several cytokines were determined by a protein microarray. Relevant signaling pathways were also analyzed. Compared with the control group, the cell apoptosis rate was significantly higher; the cell viability, the colony formation, and migration ability were significantly decreased in the siRNA-SPOP group. The protein microarray screening showed that the expression of vascular endothelial growth factor receptor, matrix metallopeptidase-9, vascular cell adhesion molecule-1, and stromal cell-derived factor-1 in the siRNA group was significantly decreased and that the expression of granulocyte-macrophage colony-stimulating factor and E-cadherin was significantly increased (P<0.05). The relevant signaling pathways were the integrin-mediated cell surface interactions pathway and extracellular matrix organization signal pathway. SPOP gene silencing induced cell apoptosis, decreased cell viability, colony formation, and migration ability, and elevated the drug sensitivity in the RCC cells. A possible mechanism is that silencing SPOP induces the differential expression of E-cadherin, vascular endothelial growth factor receptor, matrix metallopeptidase-9, and vascular cell adhesion molecule, which are related to the integrin-mediated cell surface interactions and extracellular matrix organization signaling pathway.

G Protein Coupled Receptor Kinase 3 Regulates Breast Cancer Migration, Invasion, and Metastasis

Triple negative breast cancer (TNBC) is a heterogeneous disease that has a poor prognosis and limited treatment options. Chemokine receptor interactions are important modulators of breast cancer metastasis; however, it is now recognized that quantitative surface expression of one important chemokine receptor, CXCR4, may not directly correlate with metastasis and that its functional activity in breast cancer may better inform tumor pathogenicity. G protein coupled receptor kinase 3 (GRK3) is a negative regulator of CXCR4 activity, and we show that GRK expression correlates with tumorigenicity, molecular subtype, and metastatic potential in human tumor microarray analysis. Using established human breast cancer cell lines and an immunocompetent in vivo mouse model, we further demonstrate that alterations in GRK3 expression levels in tumor cells directly affect migration and invasion in vitro and the establishment of distant metastasis in vivo. The effects of GRK3 modulation appear to be specific to chemokine-mediated migration behaviors without influencing tumor cell proliferation or survival. These data demonstrate that GRK3 dysregulation may play an important part in TNBC metastasis.