Low cytoplasmic NUB1 protein exerts hypoxic cell death with poorer prognosis in oestrogen receptor negative breast cancer patients.

Current prognostic biomarkers fall short in stratifying Oestrogen receptor (ER)-negative breast cancer patients regarding tumour progression risk at diagnosis. The role of AIPL1 in activating its tumour suppressor client protein, NEDD8 Ultimate Buster-1 (NUB1) remains unknown in cancer. Our study demonstrated how downregulated AIPL1 results in the deactivated NUB1 protein under hypoxic conditions. We examined the AIPL1-NUB1 pathwayin vitro using cell lines i.e. MCF-7, MDA-MB-231, RCC4 etc. NUB1 expression was assessed using Oncomine, and cBioPortal was performed to assess NUB1's prognostic significance in human cancers. In the John Radcliffe Hospital cohort (n = 122), immunohistochemistry analysis revealed downregulated AIPL1 (Log2 fold change=-0.28; p < 0.001) and upregulated NUB1 transcripts (Log2 fold change=0.59; p < 0.001) compared to adjacent normal tissues. In severe chronic hypoxia, multimerised AIPL1 localisedin the cytoplasm while NUB1 protein migrated to the nucleus, where the absence of NUB1 nuclear localisation led to cell cycle arrest. Biopsies showed that patients with lower cytoplasmic NUB1 expression (n = 57) had poorer overall survival compared to those with higher cytoplasmic expression (n = 57), HR=1.78; 95 % CI=1.01-3.35, p = 0.048. Low NUB1 protein levels in both normoxic and hypoxic conditions were associated with cell cycle arrest and upregulation ofp21 and p27 in breast cancer cell lines, correlating significantly withpoorer survival outcomes in all breast cancer and ER-negative breast cancer patients.

ADGRL4/ELTD1 Expression in Breast Cancer Cells Induces Vascular Normalization and Immune Suppression.

ELTD1/ADGRL4 expression is increased in the vasculature of a number of tumor types and this correlates with a good prognosis. Expression has also been reported in some tumor cells with high expression correlating with a good prognosis in hepatocellular carcinoma (HCC) and a poor prognosis in glioblastoma. Here we show that 35% of primary human breast tumors stain positively for ELTD1, with 9% having high expression that correlates with improved relapse-free survival. Using immunocompetent, syngeneic mouse breast cancer models we found that tumors expressing recombinant murine Eltd1 grew faster than controls, with an enhanced ability to metastasize and promote systemic immune effects. The Eltd1-expressing tumors had larger and better perfused vessels and tumor-endothelial cell interaction led to the release of proangiogenic and immune-modulating factors. M2-like macrophages increased in the stroma along with expression of programmed death-ligand 1 (PD-L1) on tumor and immune cells, to create an immunosuppressive microenvironment that allowed Eltd1-regulated tumor growth in the presence of an NY-ESO-1-specific immune response. Eltd1-positive tumors also responded better to chemotherapy which could explain the relationship to a good prognosis observed in primary human cases. Thus, ELTD1 expression may enhance delivery of therapeutic antibodies to reverse the immunosuppression and increase response to chemotherapy and radiotherapy in this subset of tumors. ELTD1 may be useful as a selection marker for such therapies. IMPLICATIONS: ELTD1 expression in mouse breast tumors creates an immunosuppressive microenvironment and increases vessel size and perfusion. Its expression may enhance the delivery of therapies targeting the immune system.

Role of Delta-like 4 in Jagged1-induced tumour angiogenesis and tumour growth.

Delta-like 4 (DLL4) and Jagged1 (JAG1) are two key Notch ligands implicated in tumour angiogenesis. They were shown to have opposite effects on mouse retinal and adult regenerative angiogenesis. In tumours, both ligands are upregulated but their relative effects and interactions in tumour biology, particularly in tumour response to therapeutic intervention are unclear. Here we demonstrate that DLL4 and JAG1 displayed equal potency in stimulating Notch target genes in HMEC-1 endothelial cells but had opposing effects on sprouting angiogenesis in vitro. Mouse DLL4 or JAG1 expressed in glioblastoma cells decreased tumour cell proliferation in vitro but promoted tumour growth in vivo. mDLL4-expressing tumours showed fewer but larger vessels whereas mJAG1-tumours produced more vessels. In both tumour types pericyte coverage was decreased but the vessels were more perfused. Both ligands increased tumour resistance towards anti-VEGF therapy but the resistance was higher in mDLL4-tumours versus mJAG1-tumours. However, their sensitivity to the therapy was restored by blocking Notch signalling with dibenzazepine. Importantly, anti-DLL4 antibody blocked the effect of JAG1 on tumour growth and increased vessel branching in vivo. The mechanism behind the differential responsiveness was due to a positive feedback loop for DLL4-Notch signalling, rendering DLL4 more dominant in activating Notch signalling in the tumour microenvironment. We concluded that DLL4 and JAG1 promote tumour growth by modulating tumour angiogenesis via different mechanisms. JAG1 is not antagonistic but utilises DLL4 in tumour angiogenesis. The results suggest that anti-JAG1 therapy should be explored in conjunction with anti-DLL4 treatment in developing anti-Notch therapies in clinics.

Association between hypoxic volume and underlying hypoxia-induced gene expression in oropharyngeal squamous cell carcinoma.

BACKGROUND: Hypoxia imaging is a promising tool for targeted therapy but the links between imaging features and underlying molecular characteristics of the tumour have not been investigated. The aim of this study was to compare hypoxia biomarkers and gene expression in oropharyngeal squamous cell carcinoma (OPSCC) diagnostic biopsies with hypoxia imaged with 64Cu-ATSM PET/CT. METHODS: 64Cu-ATSM imaging, molecular and clinical data were obtained for 15 patients. Primary tumour SUVmax, tumour to muscle ratio (TMR) and hypoxic volume were tested for association with reported hypoxia gene signatures in diagnostic biopsies. A putative gene signature for hypoxia in OPSCCs (hypoxic volume-associated gene signature (HVS)) was derived. RESULTS: Hypoxic volume was significantly associated with a reported hypoxia gene signature (rho=0.57, P=0.045), but SUVmax and TMR were not. Immunohistochemical staining with the hypoxia marker carbonic anhydrase 9 (CA9) was associated with a gene expression hypoxia response (rho=0.63, P=0.01). Sixteen genes were positively and five genes negatively associated with hypoxic volume (adjusted P<0.1; eight genes had adjusted P<0.05; HVS). This signature was associated with inferior 3-year progression-free survival (HR=1.5 (1.0-2.2), P=0.047) in an independent patient cohort. CONCLUSIONS: 64Cu-ATSM-defined hypoxic volume was associated with underlying hypoxia gene expression response. A 21-gene signature derived from hypoxic volume from patients with OPSCCs in our study may be linked to progression-free survival.

Methods: Using Three-Dimensional Culture (Spheroids) as an In Vitro Model of Tumour Hypoxia.

Regions of hypoxia in tumours can be modelled in vitro in 2D cell cultures with a hypoxic chamber or incubator in which oxygen levels can be regulated. Although this system is useful in many respects, it disregards the additional physiological gradients of the hypoxic microenvironment, which result in reduced nutrients and more acidic pH. Another approach to hypoxia modelling is to use three-dimensional spheroid cultures. In spheroids, the physiological gradients of the hypoxic tumour microenvironment can be inexpensively modelled and explored. In addition, spheroids offer the advantage of more representative modelling of tumour therapy responses compared with 2D culture. Here, we review the use of spheroids in hypoxia tumour biology research and highlight the different methodologies for spheroid formation and how to obtain uniformity. We explore the challenge of spheroid analyses and how to determine the effect on the hypoxic versus normoxic components of spheroids. We discuss the use of high-throughput analyses in hypoxia screening of spheroids. Furthermore, we examine the use of mathematical modelling of spheroids to understand more fully the hypoxic tumour microenvironment.

Why some tumours trigger neovascularisation and others don't: the story thus far.

BACKGROUND: Angiogenesis is not essential for tumours to develop and expand, as cancer can also grow in a non-angiogenic fashion, but why this type of growth occurs is unknown. Surprisingly, our data from mRNA transcription profiling did not show any differences in the classical angiogenic pathways, but differences were observed in mitochondrial metabolic pathways, suggesting a key role for metabolic reprogramming. We then validated these results with mRNA profiling by investigating differential protein expression via immunohistochemistry in angiogenic and non-angiogenic non-small cell lung cancers (NSCLCs). METHODS: Immunohistochemical staining for 35 angiogenesis- and hypoxia-related biomarkers were performed on a collection of 194 angiogenic and 73 non-angiogenic NSCLCs arranged on tissue microarrays. Sequencing of P53 was performed with frozen tissue samples of NSCLC. RESULTS: The non-angiogenic tumours were distinguished from the angiogenic ones by having higher levels of proteins associated with ephrin pathways, mitochondria, cell biogenesis, and hypoxia-inducible factor 1 (HIF1) regulation by oxygen and transcription of HIF-controlled genes but lower levels of proteins involved in the stroma, cell-cell signaling and adhesion, integrins, and Delta-Notch and epidermal growth factor (EGF)-related signaling. However, proteins classically associated with angiogenesis were present in both types of tumours at very comparable levels. Cytoplasmic expression of P53 was strongly associated with non-angiogenic tumours. A pilot investigation showed that P53 mutations were observed in 32.0% of angiogenic cases but in 71.4% of non-angiogenic tumours. CONCLUSIONS: Our observations thus far indicate that both angiogenic and non-angiogenic tumours experience hypoxia/HIF and vascular endothelial growth factor (VEGF) pathway protein expression in a comparable fashion. However, angiogenesis does not ensue in the non-angiogenic tumours. Surprisingly, metabolic reprogramming seems to distinguish these two types of neoplastic growth. On the basis of these results, we raise the hypothesis that in some, but not in all cases, initial tissue remodeling and/or inflammation could be one of the secondary steps necessary to trigger angiogenesis. In the non-angiogenic tumours, in which neovascularisation fails to occur, HIF pathway activation could be the driving force toward metabolic reprogramming.

Paracrine effect of GTP cyclohydrolase and angiopoietin-1 interaction in stromal fibroblasts on tumor Tie2 activation and breast cancer growth.

Cancer-associated fibroblasts (CAFs) play a key role in promoting tumor growth, acting through complex paracrine regulation. GTP cyclohydrolase (GTPCH) expression for tetrahydrobiopterin synthesis in tumor stroma is implicated in angiogenesis and tumor development. However, the clinical significance of GTPCH expression in breast cancer is still elusive and how GTPCH regulates stromal fibroblast and tumor cell communication remains unknown. We found that GTPCH was upregulated in breast CAFs and epithelia, and high GTPCH RNA was significantly correlated with larger high grade tumors and worse prognosis. In cocultures, GTPCH expressing fibroblasts stimulated breast cancer cell proliferation and motility, cancer cell Tie2 phosphorylation and consequent downstream pathway activation. GTPCH interacted with Ang-1 in stromal fibroblasts and enhanced Ang-1 expression and function, which in turn phosphorylated tumor Tie2 and induced cell proliferation. In coimplantation xenografts, GTPCH in fibroblasts enhanced tumor growth, upregulating Ang-1 and alpha-smooth muscle actin mainly in fibroblast-like cells. GTPCH inhibition resulted in the attenuation of tumor growth and angiogenesis. GTPCH/Ang-1 interaction in stromal fibroblasts and activation of Tie2 on breast tumor cells could play an important role in supporting breast cancer growth. GTPCH may be an important mechanism of paracrine tumor growth and hence a target for therapy in breast cancer.

A Phase I First-in-Human Study of Enoticumab (REGN421), a Fully Human Delta-like Ligand 4 (Dll4) Monoclonal Antibody in Patients with Advanced Solid Tumors.

PURPOSE: Enoticumab (REGN421) is a fully human IgG1 monoclonal antibody that binds human Dll4 and disrupts Notch-mediated signaling. The main objectives of this trial were to determine the safety, dose-limiting toxicities (DLT), pharmacokinetics (PK), and recommended phase II dose (RP2D) of enoticumab. EXPERIMENTAL DESIGN: Enoticumab was administered intravenously, with dose escalations from 0.25 to 4 mg/kg every 3 weeks (Q3W) and 0.75 to 3 mg/kg every 2 weeks (Q2W). RESULTS: Of 53 enrolled patients, 31 patients were treated Q3W and 22 patients were treated Q2W. Two DLTs occurred: grade 3 nausea (0.5 mg/kg Q3W) and grade 3 abdominal pain (1 mg/kg Q2W). An MTD was not reached on either schedule. The most frequent adverse events (AE) were fatigue, nausea, vomiting, hypertension, headache, and anorexia. Six treatment-related serious AEs were reported in 4 patients: brain natriuretic peptide (BNP) increase (0.25 mg/kg Q3W, Gr1), troponin I increase (4 mg/kg Q3W, Gr3), right ventricular dysfunction and pulmonary hypertension (1.5 mg/kg Q2W, both Gr3), and left ventricular dysfunction and pulmonary hypertension (3 mg/kg Q2W, both Gr3). Enoticumab was characterized by nonlinear, target-mediated PK, and had a terminal half-life of 8 to 9 days. With multiple Q2W or Q3W dosing, accumulation was not observed. Antitumor activity included two partial responses (non-small cell lung cancer bronchoalveolar-type with a ß-catenin mutation, and ovarian cancer) and 16 patients with stable disease (3> 6 months). CONCLUSIONS: Enoticumab was tolerated, with RP2D of 4 mg/kg Q3W and 3 mg/kg Q2W based on PK profile and clinical activity. Responses and SD were noted in ovarian cancer and other solid tumors. Clin Cancer Res; 21(12); 2695-703. ©2015 AACR.

JMY protein, a regulator of P53 and cytoplasmic actin filaments, is expressed in normal and neoplastic tissues.

JMY is a p300-binding protein with dual action: by enhancing P53 transcription in the nucleus, it plays an important role in the cellular response to DNA damage, while by promoting actin filament assembly in the cytoplasm; it induces cell motility in vitro. Therefore, it has been argued that, depending of the cellular setting, it might act either as tumor suppressor or as oncogene. In order to further determine its relevance to human cancer, we produced the monoclonal antibody HMY 117 against a synthetic peptide from the N-terminus region and characterized it on two JMY positive cell lines, MCF7 and HeLa, wild type and after transfection with siRNA to switch off JMY expression. JMY was expressed in normal tissues and heterogeneously in different tumor types, with close correlation between cytoplasmic and nuclear expression. Most noticeable was the loss of expression in some infiltrating carcinomas compared to normal tissue and in in situ carcinomas of the breast, which is consistent with a putative suppressor role. However, as in lymph node metastases, expression of JMY was higher than in primary colorectal and head and neck carcinomas, it might also have oncogenic properties depending on the cellular context by increasing motility and metastatic potential.

ADAM10 mediates trastuzumab resistance and is correlated with survival in HER2 positive breast cancer.

Trastuzumab prolongs survival in HER2 positive breast cancer patients. However, resistance remains a challenge. We have previously shown that ADAM17 plays a key role in maintaining HER2 phosphorylation during trastuzumab treatment. Beside ADAM17, ADAM10 is the other well characterized ADAM protease responsible for HER ligand shedding. Therefore, we studied the role of ADAM10 in relation to trastuzumab treatment and resistance in HER2 positive breast cancer. ADAM10 expression was assessed in HER2 positive breast cancer cell lines and xenograft mice treated with trastuzumab. Trastuzumab treatment increased ADAM10 levels in HER2 positive breast cancer cells (p ≤ 0.001 in BT474; p ≤ 0.01 in SKBR3) and in vivo (p ≤ 0.0001) compared to control, correlating with a decrease in PKB phosphorylation. ADAM10 inhibition or knockdown enhanced trastuzumab response in naïve and trastuzumab resistant breast cancer cells. Trastuzumab monotherapy upregulated ADAM10 (p ≤ 0.05); and higher pre-treatment ADAM10 levels correlated with decreased clinical response (p ≤ 0.05) at day 21 in HER2 positive breast cancer patients undergoing a trastuzumab treatment window study. Higher ADAM10 levels correlated with poorer relapse-free survival (p ≤ 0.01) in a cohort of HER2 positive breast cancer patients. Our studies implicate a role of ADAM10 in acquired resistance to trastuzumab and establish ADAM10 as a therapeutic target and a potential biomarker for HER2 positive breast cancer patients.

Blood vessel invasion and other variables as predictors of long-term survival in Japanese and British patients with primary invasive breast cancer.

This study was undertaken to investigate the associations of blood vessel invasion (BVI), lymphatic vessel invasion (LVI) or other variables and long-term survival in 173 Japanese and 184 British patients with primary invasive breast cancer, and whether they are associated with survival differences between Japanese and British patients. BVI was detected by objective methods, using both factor VIII-related antigen (F-VIII) staining and elastica van Gieson (E v G) staining. BVI was classified into three subtypes. 1) BVI e, BVI detected by E v G staining alone, 2) BVI f, BVI detected by F-VIII staining alone, 3) BVIef, BVI evaluated by combining BVIf and BVIe. LVI was also detected by objective methods, using lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1) staining alone. There was a borderline significance between the frequencies for BVIef of British patients and those of Japanese patients (8.2% vs 3.5%; P = 0.06) but not for LVI (P = 0.36). British patients had a significantly worse relapse-free survival (RFS) and overall survival (OS) than Japanese patients (P < 0.01, P < 0.01, respectively) even though their tumors were smaller and more ER-positive with a similar prevalence of lymph-node involvement. LVI was not significantly associated with RFS and OS, however, BVIef positive tumors had a significantly worse RFS and OS compared with BVIef negative patients, after statistical adjustment for the other variables (P = 0.02, P = 0.01, respectively). The present study shows that BVIef variability might contribute to the Japanese and British disparities in breast cancer outcomes.

The G-protein-coupled receptor CLR is upregulated in an autocrine loop with adrenomedullin in clear cell renal cell carcinoma and associated with poor prognosis.

PURPOSE: The G-protein-coupled receptor (GPCR) calcitonin receptor-like receptor (CLR) and its ligand peptide adrenomedullin (encoded by ADM gene) are implicated in tumor angiogenesis in mouse models but poorly defined in human cancers. We therefore investigated the diagnostic/prognostic use for CLR in human tumor types that may rely on adrenomedullin signaling and in clear cell renal cell carcinoma (RCC), a highly vascular tumor, in particular. EXPERIMENTAL DESIGN: In silico gene expression mRNA profiling microarray study (n = 168 tumors) and cancer profiling cDNA array hybridization (n = 241 pairs of patient-matched tumor/normal tissue samples) were carried out to analyze ADM mRNA expression in 13 tumor types. Immunohistochemistry on tissue microarrays containing patient-matched renal tumor/normal tissues (n = 87 pairs) was conducted to study CLR expression and its association with clinicopathologic parameters and disease outcome. RESULTS: ADM expression was significantly upregulated only in RCC and endometrial adenocarcinoma compared with normal tissue counterparts (P < 0.01). CLR was localized in tumor cells and vessels in RCC and upregulated as compared with patient-matched normal control kidney (P < 0.001). Higher CLR expression was found in advanced stages (P < 0.05), correlated with high tumor grade (P < 0.01) and conferred shorter overall survival (P < 0.01). CONCLUSIONS: In human tissues ADM expression is upregulated in cancer type-specific manner, implicating potential role for adrenomedullin signaling in particular in RCC, where CLR localization suggests autocrine/paracrine mode for adrenomedullin action within the tumor microenvironment. Our findings reveal previously unrecognized CLR upregulation in an autocrine loop with adrenomedullin in RCC with potential application for this GPCR as a target for future functional studies and drug development.

Dichloroacetate reverses the hypoxic adaptation to bevacizumab and enhances its antitumor effects in mouse xenografts.

Inhibition of vascular endothelial growth factor increases response rates to chemotherapy and progression-free survival in glioblastoma. However, resistance invariably occurs, prompting the urgent need for identification of synergizing agents. One possible strategy is to understand tumor adaptation to microenvironmental changes induced by antiangiogenic drugs and test agents that exploit this process. We used an in vivo glioblastoma-derived xenograft model of tumor escape in presence of continuous treatment with bevacizumab. U87-MG or U118-MG cells were subcutaneously implanted into either BALB/c SCID or athymic nude mice. Bevacizumab was given by intraperitoneal injection every 3 days (2.5 mg/kg/dose) and/or dichloroacetate (DCA) was administered by oral gavage twice daily (50 mg/kg/dose) when tumor volumes reached 0.3 cm(3) and continued until tumors reached approximately 1.5-2.0 cm(3). Microarray analysis of resistant U87 tumors revealed coordinated changes at the level of metabolic genes, in particular, a widening gap between glycolysis and mitochondrial respiration. There was a highly significant difference between U87-MG-implanted athymic nude mice 1 week after drug treatment. By 2 weeks of treatment, bevacizumab and DCA together dramatically blocked tumor growth compared to either drug alone. Similar results were seen in athymic nude mice implanted with U118-MG cells. We demonstrate for the first time that reversal of the bevacizumab-induced shift in metabolism using DCA is detrimental to neoplastic growth in vivo. As DCA is viewed as a promising agent targeting tumor metabolism, our data establish the timely proof of concept that combining it with antiangiogenic therapy represents a potent antineoplastic strategy.

CD31 angiogenesis and combined expression of HIF-1α and HIF-2α are prognostic in primary clear-cell renal cell carcinoma (CC-RCC), but HIFα transcriptional products are not: implications for antiangiogenic trials and HIFα biomarker studies in primary CC-RCC.

Hypoxia-inducible factors, HIF-1α and HIF-2α, are expressed in the majority of clear-cell renal cell carcinoma (CC-RCC). In vitro, HIFα isoforms regulate a differential set of genes, and their effects in vivo within CC-RCC tumours may affect outcome. The role of angiogenesis and HIFα transcriptional products, including those involved in cell metabolism and morphological dedifferentiation have not been extensively investigated and might have relevance to the development of antiangiogenic or anti-HIFα trials in primary CC-RCC, either before or after radical nephrectomy. We analysed 168 consecutive clear-cell renal tumours from 1983 to 1999 within tissue microarrays and assessed expression of HIF-1α and HIF-2α together with the protein expression of seven of their target genes (BNIP3, CA9, Cyclin D1, GLUT-1, LDH5, Oct-4 and VEGF). The expression of these factors was compared with patient overall survival and CD31 angiogenesis. We found that HIFα antigenicity deteriorated with the age of the paraffin block (P < 0.0001) and in tumours from 1983 to 1992 was deemed not to be reliable. Similar findings were found in aged archival osteosarcoma samples. This might have important implications for retrospective biomarker studies that rely on archival tissue material. HIF-1α(HIGH)/HIF-2α(LOW) tumours had a worse overall survival compared with HIF-1α(LOW)/HIF-2α(LOW) tumours (P = 0.04). Surprisingly, on multivariate analysis, high levels of CD31(+) angiogenesis was shown to be an independent prognostic marker of increased overall survival (P = 0.003). We propose that better differentiation of vascular endothelium may be a reflection of a greater production of vessel stabilization factors versus pro-angiogenic factors, and therefore a less aggressive phenotype.

Carbonic anhydrase IX promotes tumor growth and necrosis in vivo and inhibition enhances anti-VEGF therapy.

PURPOSE: Bevacizumab, an anti-VEGFA antibody, inhibits the developing vasculature of tumors, but resistance is common. Antiangiogenic therapy induces hypoxia and we observed increased expression of hypoxia-regulated genes, including carbonic anhydrase IX (CAIX), in response to bevacizumab treatment in xenografts. CAIX expression correlates with poor prognosis in most tumor types and with worse outcome in bevacizumab-treated patients with metastatic colorectal cancer, malignant astrocytoma, and recurrent malignant glioma. EXPERIMENTAL DESIGN: We knocked down CAIX expression by short hairpin RNA in a colon cancer (HT29) and a glioblastoma (U87) cell line which have high hypoxic induction of CAIX and overexpressed CAIX in HCT116 cells which has low CAIX. We investigated the effect on growth rate in three-dimensional (3D) culture and in vivo, and examined the effect of CAIX knockdown in combination with bevacizumab. RESULTS: CAIX expression was associated with increased growth rate in spheroids and in vivo. Surprisingly, CAIX expression was associated with increased necrosis and apoptosis in vivo and in vitro. We found that acidity inhibits CAIX activity over the pH range found in tumors (pK = 6.84), and this may be the mechanism whereby excess acid self-limits the build-up of extracellular acid. Expression of another hypoxia inducible CA isoform, CAXII, was upregulated in 3D but not two-dimensional culture in response to CAIX knockdown. CAIX knockdown enhanced the effect of bevacizumab treatment, reducing tumor growth rate in vivo. CONCLUSION: This work provides evidence that inhibition of the hypoxic adaptation to antiangiogenic therapy enhances bevacizumab treatment and highlights the value of developing small molecules or antibodies which inhibit CAIX for combination therapy.

DLL4-Notch signaling mediates tumor resistance to anti-VEGF therapy in vivo.

Resistance to VEGF inhibitors is emerging as a major clinical problem. Notch signaling has been implicated in tumor angiogenesis. Therefore, to investigate mechanisms of resistance to angiogenesis inhibitors, we transduced human glioblastoma cells with retroviruses encoding Notch delta-like ligand 4 (DLL4), grew them as tumor xenografts and then treated the murine hosts with the VEGF-A inhibitor bevacizumab. We found that DLL4-mediated tumor resistance to bevacizumab in vivo. The large vessels induced by DLL4-Notch signaling increased tumor blood supply and were insensitive to bevacizumab. However, blockade of Notch signaling by dibenzazepine, a γ-secretase inhibitor, disrupted the large vessels and abolished the tumor resistance. Multiple molecular mechanisms of resistance were shown, including decreased levels of hypoxia-induced VEGF and increased levels of the VEGF receptor VEGFR1 in the tumor stroma, decreased levels of VEGFR2 in large blood vessels, and reduced levels of VEGFR3 overall. DLL4-expressing tumors were also resistant to a VEGFR targeting multikinase inhibitor. We also observed activation of other pathways of tumor resistance driven by DLL4-Notch signaling, including the FGF2-FGFR and EphB4-EprinB2 pathways, the inhibition of which reversed tumor resistance partially. Taken together, our findings show the importance of classifying mechanisms involved in angiogenesis in tumors, and how combination therapy to block DLL4-Notch signaling may enhance the efficacy of VEGF inhibitors, particularly in DLL4-upregulated tumors, and thus provide a rational base for the development of novel strategies to overcome antiangiogenic resistance in the clinic.

Roles of tetrahydrobiopterin in promoting tumor angiogenesis.

Nitric oxide (NO), which is derived from endothelial NO synthase (eNOS), provides crucial signals for angiogenesis in the tumor microenvironment. Tetrahydrobiopterin (BH4) is an absolute requirement for eNOS activity. In this study, we investigated whether this activation is both maintained by a wild-type Ras/phosphatidylinositol 3-kinase (PI3K)/Akt-positive feedback loop in endothelial cells and affects tumor angiogenesis. We found that supplementation of BH4 (via the pterin salvage pathway with Sep) increased Akt/eNOS phosphorylation in both human eNOS-transfected COS-7 cells and endothelial cells concomitant with increases in NO production, cell proliferation, migration, and tube formation. This augmentation was abrogated by a PI3K inhibitor. Sepiapterin (Sep) also increased GTP-bound wild-type Ras and PI3K/Akt/eNOS activation, which was prevented by the eNOS inhibitor, Nω-Nitro-L-arginine methyl ester (L-NAME). Furthermore, expression of GTP cyclohydrolase I (the rate-limiting enzyme in de novo BH4 synthesis) under doxycycline control potentiated in vivo tumorigenesis, tumor cell proliferation, as well as angiogenesis. Conversely, both switching off GTP cyclohydrolase I expression as well as inhibiting its enzymatic activity significantly decreased eNOS expression and tumor vascularization. This study demonstrates an important role for BH4 synthesis in angiogenesis by the activation of eNOS for NO production, which is maintained by a PI3K/Akt-positive feedback loop through effects on wild-type Ras in endothelial cells. Our findings suggest that BH4 synthesis may be a rational target for antiangiogenesis therapy for tumors.

The histone demethylase JMJD2B is regulated by estrogen receptor alpha and hypoxia, and is a key mediator of estrogen induced growth.

Estrogen receptor alpha (ERalpha) plays an important role in breast cancer. Upregulation of HIF-1alpha in ER(alpha)-positive cancers suggests that HIF-1alpha may cooperate with ERalpha to promote breast cancer progression and consequently affect breast cancer treatment. Here, we show the histone demethylase JMJD2B is regulated by both ERalpha and HIF-1alpha, drives breast cancer cell proliferation in normoxia and hypoxia, and epigenetically regulates the expression of cell cycle genes such as CCND1, CCNA1, and WEE1. We also show that JMJD2B and the hypoxia marker CA9 together stratify a subclass of breast cancer patients and predict a worse outcome of these breast cancers. Our findings provide a biological rationale to support the therapeutic targeting of histone demethylases in breast cancer patients.

Effects of HIF-1alpha and HIF2alpha on Growth and Metabolism of Clear-Cell Renal Cell Carcinoma 786-0 Xenografts.

In cultured clear-cell renal carcinoma (CCRCC) 786-0 cells transfected with HIF1alpha (HIF-1+), HIF-2alpha (HIF-2+), or empty vector (EV), no significant differences were observed in the growth rates in vitro, but when grown in vivo as xenografts HIF-2alpha significantly increased, and HIF-1alpha significantly decreased growth rates, compared to EV tumors. Factors associated with proliferation were increased and factors associated with cell death were decreased in HIF-2+ tumors. Metabolite profiles showed higher glucose and lower lactate and alanine levels in the HIF-2+ tumors whilst immunostaining demonstrated higher pyruvate dehydrogenase and lower pyruvate dehydrogenase kinase 1, compared to control tumors. Taken together, these results suggest that overexpression of HIF-2alpha in CCRCC 786-0 tumors regulated growth both by maintaining a low level of glycolysis and by allowing more mitochondrial metabolism and tolerance to ROS induced DNA damage. The growth profiles observed may be mediated by adaptive changes to a more oxidative phenotype.

New mechanism for Notch signaling to endothelium at a distance by Delta-like 4 incorporation into exosomes.

Notch signaling is an evolutionary conserved pathway that is mediated by cell-cell contact. It is involved in a variety of developmental processes and has an essential role in vascular development and angiogenesis. Delta-like 4 (Dll4) is a Notch ligand that is up-regulated during angiogenesis. It is expressed in endothelial cells and regulates the differentiation between tip cells and stalk cells of neovasculature. Here, we present evidence that Dll4 is incorporated into endothelial exosomes. It can also be incorporated into the exosomes of tumor cells that overexpress Dll4. These exosomes can transfer the Dll4 protein to other endothelial cells and incorporate it into their cell membrane, which results in an inhibition of Notch signaling and a loss of Notch receptor. Transfer of Dll4 was also shown in vivo from tumor cells to host endothelium. Addition of Dll4 exosomes confers a tip cell phenotype on the endothelial cell, which results in a high Dll4/Notch-receptor ratio, low Notch signaling, and filopodia formation. This was further evidenced by increased branching in a tube-formation assay and in vivo. This reversal in phenotype appears to enhance vessel formation and is a new form of signaling for Notch ligands that expands their signaling potential beyond cell-cell contact.