Abstract 3372: Semaphorin 3A normalizes the tumor vasculature and impairs tumor progression in a Nrp-1-independent manner

It is widely described that tumor vessel normalization, occurring in response to certain anti-angiogenic therapies, represents a remarkably advantageous anti-cancer strategy (1). We have demonstrated that Semaphorin 3A (Sema3A), an axon guidance cue part of class 3 semaphorins family, is an endogenous angiogenic inhibitor able to efficiently impair tumor progression, prolong the survival and normalize the tumor vasculature in different mouse models of spontaneous tumorigenesis (2). Moreover, we recently showed that Sema3A, by extending the normalization window and abrogating tumor hypoxia, overcame the resistance to the anti-angiogenic therapy inhibiting metastasis dissemination (3).

Stemming from these findings we sought to investigate the molecular mechanisms of vessel normalization and metastasis inhibition induced by Sema3A. Interestingly, by confocal microscope and western blot analysis, in a co-culture systems of human endothelial cells (ECs) and pericytes grown in contact, we observed that Sema3A dramatically down-modulated its receptor Nrp-1 in both cell types, with the consequent over-expression of PDGF-B and Ang-1, known to promote vessel maturation. Moreover, a wide screening of different genes and pathways modulated in the ECs/pericyte co-cultures revealed that the most modulated was the HGF/Met pathway. In fact, we observed that c-Met phosphorylation was impaired in FACS-sorted ECs co-cultured with human pericytes, compared to ECs grown as single layer. To better investigate the specific role of Sema3A in modulating HGF/Met activation in vessels, we detected a strong inhibition of HGF-induced Met phosphorylation in Nrp-1 silenced ECs induced by Sema3A, suggesting that this semaphorin could directly interfere with Met signaling. Notably, Sema3A impaired HGF-induced Met phosphorylation, not only in ECs, but also in several Nrp-1-silenced gastric, lung and pancreatic tumor cell lines, inducing apoptosis and blocking the invasiveness. Finally, treating an orthotopic mouse model of pancreatic ductal adenocarcinoma (PDAC) with adeno-associate virus (AAV)-8 expressing Sema3A, we observed a strong inhibition of tumor growth, a dramatic reduction of liver metastasis and a normalized and perfused tumor vessels phenotype. Remarkably, we found that Sema3A strongly and specifically inhibited Met activation in both tumor cells and vessels, in parallel to a down-modulation of Nrp-1.

We conclude that Sema3A normalizes the tumor vasculature and blocks cancer progression in a Nrp-1-independent manner, in part by inhibiting HGF/Met pathway.

References

1. Jain RK, et al. Cancer Cell. 2014; 26:605-22.

2. Maione F., et al. J. Clin. Invest. 2009; 119:3356-72.

3. Maione F., et al. J. Clin Invest. 2012; 122:1832-48.

Citation Format: Federica Maione, Cristina Basilico, Elisa Vigna, Mauro Giacca, Guido Serini, Enrico Giraudo. Semaphorin 3A normalizes the tumor vasculature and impairs tumor progression in a Nrp-1-independent manner. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3372.

Abstract 3366: NCL targeting impairs the progression of pancreatic ductal adenocarcinoma and promotes tumor vessel normalization through Ang-2 inhibition

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive tumor, mostly resistant to the standard treatments. NCL is overexpressed in cancers and its inhibition impairs tumor growth. Herein we described, that NCL was overexpressed in human specimens of PDAC, and low NCL staining patients had increased overall survival. Previously, we described a family of multivalent pseudopeptides binding to NCL and inhibiting tumour growth. Here, NCL antagonist N6L, strongly impaired tumor growth, liver metastasis formation and angiogenesis in an orthothopic mouse model of PDAC. N6L inhibited both human and mouse tumor cell proliferation and invasion. Proteome analysis of endothelial cell secreted proteins showed that NCL inhibition decreased Ang-2 levels and switched a pro-angiogenic signature. Importantly, Ang-2 levels were decreased in plasma of N6L-treated PDAC mice. The analysis of tumor vasculature revealed a strong increase of pericyte coverage and vessel perfusion in parallel to an inhibition of tumor hypoxia. As consequence of N6L-induced tumor vessel normalization, pre-treatment with N6L efficiently improved chemotherapeutic drug delivery and increased the anti-tumor properties of gemcitabine in PDAC mice.

In conclusion, NCL inhibition is a new anti-tumor therapeutic strategy that dually blocks tumor progression and normalizes tumor vessels improving the delivery and efficacy of chemotherapeutic drugs in PDAC cancers. Moreover, we identified Ang-2 as a potential target and suitable response biomarker for N6L treatment in PDAC.

Citation Format: Maud-Emmanuelle Gilles, Federica Maione, Mélissande Cossutta, Gilles Carpentier, Laure Caruana, Silvia Di Maria, Damien Destouches, Ksenya Shchors, Christopher Prochasson, Anne Couvelard, José Courty, Enrico Giraudo, Ilaria Cascone. NCL targeting impairs the progression of pancreatic ductal adenocarcinoma and promotes tumor vessel normalization through Ang-2 inhibition. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3366.

Lenalidomide normalizes tumor vessels in colorectal cancer improving chemotherapy activity

Background

Angiogenesis inhibition is a promising approach for treating metastatic colorectal cancer (mCRC). Recent evidences support the seemingly counterintuitive ability of certain antiangiogenic drugs to promote normalization of residual tumor vessels with important clinical implications. Lenalidomide is an oral drug with immune-modulatory and anti-angiogenic activity against selected hematologic malignancies but as yet little is known regarding its effectiveness for solid tumors. The aim of this study was to determine whether lenalidomide can normalize colorectal cancer neo-vessels in vivo, thus reducing tumor hypoxia and improving the benefit of chemotherapy.

Methods

We set up a tumorgraft model with NOD/SCID mice implanted with a patient-derived colorectal cancer liver metastasis. The mice were treated with oral lenalidomide (50 mg/Kg/day for 28 days), intraperitoneal 5-fluorouracil (5FU) (20 mg/Kg twice weekly for 3 weeks), combination (combo) of lenalidomide and 5FU or irrelevant vehicle. We assessed tumor vessel density (CD146), pericyte coverage (NG2; alphaSMA), in vivo perfusion capability of residual vessels (lectin distribution essay), hypoxic areas (HP2-100 Hypoxyprobe) and antitumor activity in vivo and in vitro.

Results

Treatment with lenalidomide reduced tumor vessel density (p = 0.0001) and enhanced mature pericyte coverage of residual vessels (p = 0.002). Perfusion capability of tumor vessels was enhanced in mice treated with lenalidomide compared to controls (p = 0.004). Accordingly, lenalidomide reduced hypoxic tumor areas (p = 0.002) and enhanced the antitumor activity of 5FU in vivo. The combo treatment delayed tumor growth (p = 0.01) and significantly reduced the Ki67 index (p = 0.0002). Lenalidomide alone did not demonstrate antitumor activity compared to untreated controls in vivo or against 4 different mCRC cell lines in vitro.

Conclusions

We provide the first evidence of tumor vessel normalization and hypoxia reduction induced by lenalidomide in mCRC in vivo. This effect, seemingly counterintuitive for an antiangiogenic compound, translates into indirect antitumor activity thus enhancing the therapeutic index of chemotherapy. Our findings suggest that further research should be carried out on synergism between lenalidomide and conventional therapies for treating solid tumors that might benefit from tumor vasculature normalization.

Abstract A16: Semaphorin 3A normalizes the tumor vasculature and impairs cancer progression in a Nrp-1-independent manner

It is widely described that tumor vessel normalization, occurring in response to certain anti-angiogenic therapies, represents a remarkably advantageous anti-cancer strategy (1). We have demonstrated that Semaphorin 3A (Sema3A), an axon guidance cue part of class 3 semaphorins family, is an endogenous angiogenic inhibitor able to efficiently impair tumor progression, prolong the survival and normalize the tumor vasculature in different mouse models of spontaneous tumorigenesis (2). Moreover, we recently showed that Sema3A, by extending the normalization window and abrogating tumor hypoxia, overcame the resistance to the anti-angiogenic therapy inhibiting metastasis dissemination (3).

Stemming from these findings we sought to investigate the molecular mechanisms of vessel normalization and metastasis inhibition induced by Sema3A. Interestingly, by confocal microscope and western blot analysis, in a co-culture systems of human endothelial cells (ECs) and pericytes grown in contact, we observed that Sema3A dramatically down-modulated its receptor Nrp-1 in both cell types, with the consequent over-expression of PDGF-B and Ang-1, known to promote vessel maturation. Moreover, a wide screening of different genes and pathways modulated in the ECs/pericyte co-cultures, revealed that the most modulated was the HGF/Met pathway. In fact, we observed that c-Met phosphorylation was impaired in FACS-sorted ECs co-cultured with human pericytes, compared to ECs grown as single layer. To better investigate the specific role of Sema3A in modulating HGF/Met activation in vessels, we detected a strong inhibition of HGF-induced Met phosphorylation in Nrp-1 silenced ECs induced by Sema3A, suggesting that this semaphorin could directly interfere with Met signaling. Finally, treating an orthotopic mouse model of pancreatic ductal adenocarcinoma (PDAC) with adeno-associate virus (AAV)-8 expressing Sema3A, we observed a strong inhibition of tumor growth, a dramatic reduction of liver metastasis and a normalized and perfused tumor vessels phenotype. Remarkably, we found that Sema3A strongly and specifically inhibited Met activation in both tumor cells and vessels, in parallel to a down-modulation of Nrp-1 in normalized vasculature.

We conclude that Sema3A normalizes the tumor vasculature and blocks cancer progression by acting on Nrp-1 and HGF/Met pathway.

References:

1. Goel S, et al. Physiol Rev. 2011; 91(3):1071–1121.

2. Maione F., et al. J. Clin. Invest. 2009; 119(11):3356-72.

3. Maione F., et al. J. Clin Invest. 2012; 122(5):1832-48.

Citation Format: Federica Maione, Cristina Basilico, Mauro Giacca, Guido Serini, Enrico Giraudo. Semaphorin 3A normalizes the tumor vasculature and impairs cancer progression in a Nrp-1-independent manner. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr A16.

Abstract A02: Nucleolin antagonist peptide N6L, normalizes tumor vasculature by decreasing Ang-2 secretion and inhibits pancreatic ductal adenocarcinoma growth and metastasis

Nucleolin (NCL) is a nucleolar protein regulating ribogenesis and cell cycle progression, and is overexpressed in tumor cells. Shuttling to the cell surface of tumor cells and tumor vessels NCL is a marker of tumor tissues and a target for cancer therapy. Recently, we developed a family of nucleolin antagonist pseudopeptides (NucANT). The N6L peptide, strongly inhibits human tumor growth by inducing apoptosis of tumor cells (1), and is currently in clinical trial for cancer. Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human malignancies, and an explanation of the failure of treatments is that chemotherapies are poorly delivered to the tumor because of a deficient and pathologic vasculature. We investigated the possibility that N6L could dually target tumor cells and tumor vasculature and be a promising new option for the treatment of PDAC.

NCL targeting by N6L inhibited pancreatic tumor cell proliferation and pancreatic tumor cell motility similarly to other tumor cell types (1). Concerning endothelial cells (EC), N6L inhibited EC proliferation, motility, adhesion and tubulogenesis. We screened proteins involved in vascular stability and showed that N6L treatment or NCL depletion regulated the secretion of Ang-2. This N6L effect was specific of NCL targeting because NCL depletion rescued the inhibition of Ang-2 secretion induced by N6L.

We investigated the effect of N6L on the growth and metastasis of a PDAC orthotopic mouse model that was deficient in vasculature such as the human tumors and NCL was highly expressed in tumor ductal epithelial cells. We showed that N6L strongly inhibited the tumor growth by inhibiting NCL expression, tumor cell proliferation, and increasing tumor cell apoptosis. Coherently with the in vitro data, N6L decreased Ang-2 plasma concentration of PDAC mice. By characterizing the PDAC tumor vasculature after treatment, we demonstrated that N6L induced both vessel pruning and normalization of tumor vasculature by improving pericyte coverage and tumor blood vessel perfusion. Moreover, N6L-induced tumor vessel normalization was accompanied by an improved efficiency of chemotherapeutic drugs delivery to cancer tissues and an inhibition of liver metastasis incidence.

We conclude that NCL inhibition by N6L normalizes pancreatic tumor vasculature and suggest Ang-2 as a target and a biomarker of N6L response. N6L-induced PDAC vessel normalization promotes drug delivery and contributes to decrease metastasis formation.

1. Destouches D, et al. (2011) A simple approach to cancer therapy afforded by multivalent pseudopeptides that target cell-surface nucleoproteins. Cancer Res 71(9):3296-3305.

Citation Format: Maud-Emmanuelle Gilles, Federica Maione, Gilles Carpentier, damien Destouches, José Courty, Enrico Giraudo, Ilaria Cascone. Nucleolin antagonist peptide N6L, normalizes tumor vasculature by decreasing Ang-2 secretion and inhibits pancreatic ductal adenocarcinoma growth and metastasis. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr A02.

Abstract B17: In-depth proteomics unveils fatty acid oxidation role in controlling vascular permeability

Endothelial cells (ECs) play a key role in maintaining vascular functionality. Alterations in vessel stability and permeability are hallmarks of tumor angiogenesis and may affect the efficacy of anti-cancer therapy. Modulating EC metabolism has emerged as a promising strategy to target angiogenesis in pathological conditions, but so far, little is known about the role of EC metabolism in the regulation of vessel stability and permeability.

In this work we took advantage of a simplified in-vitro model of angiogenesis, where HUVECs (human umbilical vein endothelial cells) form a vascular-like network on a tridimensional matrix, to elucidate the role of EC metabolism during this process.

By integrating high resolution proteomic data with a human genome scale metabolic model we built up the first predictive model of metabolic fluxes occurring in ECs forming a complex network and identified increased fluxes for reactions involving fatty acid oxidation (FAO) enzymes when ECs are assembled into a fully formed network. Upon inhibition of CPT1, the FAO rate-limiting enzyme, we disrupted the network and reduced cellular ATP levels and oxygen consumption, which were restored by replenishing the tricarboxylic acid cycle (TCAc). Remarkably, phosphoproteomic changes measured upon CPT1A inhibition evoked those triggered by thrombin, a potent inducer of EC permeability through calcium signaling. Indeed, acute CPT1A inhibition increased EC permeability in-vitro and leakage of fully formed blood vessel in-vivo, which were restored by replenishing the TCAc or inhibiting calcium influx.

FAO emerges as central regulator of blood vessel stability, revealing the possibility of targeting FAO to interfere with tumor vessel permeability.

Citation Format: Francesca Patella, Zachary T. Schug, Erez Persi, Lisa J. Neilson, Zahra Erami, Daniele Avanzato, Federica Maione, Juan R. Hernandez-Fernaud, Gillian Mackay, Liang Zheng, Steven Reid, Christian Frezza, Enrico Giraudo, Alessandra Fiorio Pla, Kurt Anderson, Eytan Ruppin, Eyal Gottlieb, Sara Zanivan. In-depth proteomics unveils fatty acid oxidation role in controlling vascular permeability. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Angiogenesis and Vascular Normalization: Bench to Bedside to Biomarkers; Mar 5-8, 2015; Orlando, FL. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl):Abstract nr B17.

Proteomics-based metabolic modeling reveals that fatty acid oxidation (FAO) controls endothelial cell (EC) permeability

Endothelial cells (ECs) play a key role to maintain the functionality of blood vessels. Altered EC permeability causes severe impairment in vessel stability and is a hallmark of pathologies such as cancer and thrombosis. Integrating label-free quantitative proteomics data into genome-wide metabolic modeling, we built up a model that predicts the metabolic fluxes in ECs when cultured on a tridimensional matrix and organize into a vascular-like network. We discovered how fatty acid oxidation increases when ECs are assembled into a fully formed network that can be disrupted by inhibiting CPT1A, the fatty acid oxidation rate-limiting enzyme. Acute CPT1A inhibition reduces cellular ATP levels and oxygen consumption, which are restored by replenishing the tricarboxylic acid cycle. Remarkably, global phosphoproteomic changes measured upon acute CPT1A inhibition pinpointed altered calcium signaling. Indeed, CPT1A inhibition increases intracellular calcium oscillations. Finally, inhibiting CPT1A induces hyperpermeability in vitro and leakage of blood vessel in vivo, which were restored blocking calcium influx or replenishing the tricarboxylic acid cycle. Fatty acid oxidation emerges as central regulator of endothelial functions and blood vessel stability and druggable pathway to control pathological vascular permeability.

Abstract 4807: Zoledronic acid overcomes the resistance to the anti-angiogenic therapy and normalizes tumor vessels by switching from a M2- to a M1-like macrophages phenotype in a mouse model of spontaneous cervical cancer

Recent studies described a resistance to the anti-angiogenic therapy both in pre-clinical and clinical settings. Several mechanisms that contribute to this resistance has been so far proposed and, among these, the recruitment of bone marrow-derived cells to the tumors, seems to be critical.

We have previously showed that an amino-bisphosphonate, Zoledronic acid (ZA), in a mouse model of spontaneous cervical carcinogenesis (HPV16/E2) by targeting MMP-9+ tumor-associated macrophages (TAM), strongly inhibited cancer progression and angiogenesis. Stemming from these data we sought to investigate whether ZA by acting on TAM, was able to overcome the resistance to anti-angiogenic treatments.

We treated tumor-bearing HPV16/E2 mice with ZA alone or combined with the small molecule tyrosine kinase inhibitor Sunitinib or with an anti-VEGFR-2 antibody, DC101, to assess the ability of ZA to block metastasis dissemination. Notably ZA synergized with Sunitinib and DC101 to inhibit primary tumor growth. Interestingly, while these compounds increased the incidence and the number of liver and lung metastasis, ZA alone inhibited basal tumor metastasis in parallel to angiogenesis inhibition. ZA combined with Sunitinib or DC101 showed a greater effect in impairing liver and lung metastasis formation. Confocal analysis of the vasculature revealed that while Sunitinib- or DC101-treated cancers displayed poorly functional vessels, both ZA alone or combined with Sunitinib or DC101 efficiently induced a normalized vasculature highly covered by pericytes and better perfused. Remarkably, gene and protein expression analysis of FACS-sorted macrophages derived from tumors of the different treatment groups, showed that ZA alone or combined with Sunitinib or DC101 inhibited the expression of M2-markers such as MRC-1, Il-10, CCL22 and MMP-9 and simultaneously enhanced the levels of M1-markers such as Il12 and CXCL9 in these cells.

We conclude that ZA, by promoting a M1-like macrophages phenotype in HPV16/E2 cervical cancers and consequently inducing a normalized vasculature, efficiently overcomes the resistance to angiogenesis inhibition by blocking metastasis dissemination.

Citation Format: Stefania Capano, Federica Maione, Oriol Casanovas, Federico Bussolino, Enrico Giraudo. Zoledronic acid overcomes the resistance to the anti-angiogenic therapy and normalizes tumor vessels by switching from a M2- to a M1-like macrophages phenotype in a mouse model of spontaneous cervical cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4807. doi:10.1158/1538-7445.AM2014-4807

Semaphorins in cardiovascular medicine

During organogenesis, patterning is primarily achieved by the combined actions of morphogens. Among these, semaphorins represent a general system for establishing the appropriate wiring architecture of biological nets. Originally discovered as evolutionarily conserved steering molecules for developing axons, subsequent studies on semaphorins expanded their functions to the cardiovascular and immune systems. Semaphorins participate in cardiac organogenesis and control physiological vasculogenesis and angiogenesis, which result from a balance between pro- and anti-angiogenic signals. These signals are altered in several diseases. In this review, we discuss the role of semaphorins in vascular biology, emphasizing the mechanisms by which these molecules control vascular patterning and lymphangiogenesis, as well as in genetically inherited and degenerative vascular diseases.

Peptide-functionalized nanoparticles for selective targeting of pancreatic tumor

Chemotherapy for pancreatic cancer is hampered by the tumor's physio-pathological complexity. Here we show a targeted nanomedicine using a new ligand, the CKAAKN peptide, which had been identified by phage display, as an efficient homing device within the pancreatic pathological microenvironment. Taking advantage of the squalenoylation platform, the CKAAKN peptide was conjugated to squalene (SQCKAAKN) and then co-nanoprecipitated with the squalenoyl prodrug of gemcitabine (SQdFdC) giving near monodisperse nanoparticles (NPs) for safe intravenous injection. By interacting with a novel target pathway, the Wnt-2, the CKAAKN functionalization enabled nanoparticles: (i) to specifically interact with both tumor cells and angiogenic vessels and (ii) to simultaneously promote pericyte coverage, thus leading to the normalization of the vasculature likely improving the tumor accessibility for therapy. All together, this approach represents a unique targeted nanoparticle design with remarkable selectivity towards pancreatic cancer and multiple mechanisms of action.

SILAC-based proteomics of human primary endothelial cell morphogenesis unveils tumor angiogenic markers

Proteomics has been successfully used for cell culture on dishes, but more complex cellular systems have proven to be challenging and so far poorly approached with proteomics. Because of the complexity of the angiogenic program, we still do not have a complete understanding of the molecular mechanisms involved in this process, and there have been no in depth quantitative proteomic studies. Plating endothelial cells on matrigel recapitulates aspects of vessel growth, and here we investigate this mechanism by using a spike-in SILAC quantitative proteomic approach. By comparing proteomic changes in primary human endothelial cells morphogenesis on matrigel to general adhesion mechanisms in cells spreading on culture dish, we pinpoint pathways and proteins modulated by endothelial cells. The cell-extracellular matrix adhesion proteome depends on the adhesion substrate, and a detailed proteomic profile of the extracellular matrix secreted by endothelial cells identified CLEC14A as a matrix component, which binds to MMRN2. We verify deregulated levels of these proteins during tumor angiogenesis in models of multistage carcinogenesis. This is the most in depth quantitative proteomic study of endothelial cell morphogenesis, which shows the potential of applying high accuracy quantitative proteomics to in vitro models of vessel growth to shed new light on mechanisms that accompany pathological angiogenesis. The mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the data set identifier PXD000359.

Preclinical activity of lenalidomide in metastatic colorectal cancer

e14654

Background: Metastatic colorectal cancer (mCRC) is currently considered incurable. Recent evidences support the importance of micro-environment and angiogenesis on survival and propagation of mCRC. Lenalidomide is a derivative of thalidomide, effective in several hematologic disorders, whose activity includes modulation on tumor microenvironment and inhibition of angiogenesis. We investigated the preclinical activity of lenalidomide against mCRC in vitro and in vivo. Methods: CRC cell lines and primary mCRC cells were treated with scalar concentrations of lenalidomide (10 to 150 µM). Two cohorts of NOD/SCID mice (n=8) implanted with mCRC xenografts derived from two different patients were treated orally for 21 consecutive days with Lenalidomide (50 mg/Kg/die). Results: In vivo a significant reduction of tumor growth was observed in one cohort compared to untreated controls (n=8), 247±118 mm3 vs. 567±216 mm3 (P=0.02), while no significant differences occurred in the second cohort. Pathology review on tumor samples removed from the mice revealed a trend toward the restoration of normal colon tissue morphology and architecture in lenalidomide treated samples compared to untreated controls. Quantitative evaluation of tumor angiogenesis on the responsive cohort, by immunohistochemistry for factor VIII, revealed a tumor-vessel reduction of 49% with lenalidomide compared to controls. Moreover, necrotic-hypoxic areas were reduced by 6 fold in lenalidomide treated xenografts compared to untreated controls (P<0.001). Treatment in vitro did not result in any direct antitumor effect. The average rate of cell death in treated samples was 15.5±2.1%, 15.3±6.7%, and 11.5±3.4% at lenalidomide doses of 10, 40 and 150 µM respectively, compared to 14.6±2.6% of untreated controls. Conclusions: Our data indicate a potential activity of lenalidomide against mCRC. The beneficial effect was limited in-vivo, supporting the hypothesis that the main activity of lenalidomide is exerted through modulation of tumor microenvironment and angiogenesis rather than a direct antitumor effect. Our findings may be of clinical relevance and support further investigations to explore the benefit of lenalidomide in the challenging setting of mCRC.

The role of semaphorins and their receptors in vascular development and cancer

Semaphorins (Semas) are a large family of traditional axon guidance molecules. Through interactions with their receptors, Plexins and Neuropilins, Semas play critical roles in a continuously growing list of diverse biological systems. In this review, we focus on their function in regulating vascular development. In addition, over the past few years a number of findings have shown the crucial role that Semas and their receptors play in the regulation of cancer progression and tumor angiogenesis. In particular, Semas control tumor progression by directly influencing the behavior of cancer cells or, indirectly, by modulating angiogenesis and the function of other cell types in the tumor microenvironment (i.e., inflammatory cells and fibroblasts). Some Semas can activate or inhibit tumor progression and angiogenesis, while others may have the opposite effect depending on specific post-translational modifications. Here we will also discuss the diverse biological effects of Semas and their receptor complexes on cancer progression as well as their impact on the tumor microenvironment.

Class 3 semaphorins: physiological vascular normalizing agents for anti-cancer therapy

Findings from preclinical and clinical studies show that vascular normalization represents a novel strategy to enhance the efficacy of and overcome the acquired resistance to anti-angiogenic therapies in cancer. Several mechanisms of tumour vessel normalization have been revealed. Amongst them, secreted class 3 semaphorins (Sema3), which regulate axon guidance and angiogenesis, have been recently identified as novel vascular normalizing agents that inhibit metastatic dissemination by restoring vascular function. Here, we discuss the different biological functions and mechanisms of action of Sema3 in the context of tumour vascular normalization, and their impact on the different cellular components of the tumour microenvironment.

Neuropilin-1 identifies a subset of bone marrow Gr1- monocytes that can induce tumor vessel normalization and inhibit tumor growth

Improving tumor perfusion, thus tempering tumor-associated hypoxia, is known to impair cancer progression. Previous work from our laboratory has shown that VEGF-A165 and semaphorin 3A (Sema3A) promote vessel maturation through the recruitment of a population of circulating monocytes expressing the neuropilin-1 (Nrp1) receptor (Nrp1-expressing monocytes; NEM). Here, we define the characteristics of bone marrow NEMs and assess whether these cells might represent an exploitable tool to induce tumor vessel maturation. Gene expression signature and surface marker analysis have indicated that NEMs represent a specific subset of CD11b+ Nrp1+ Gr1- resident monocytes, distinctively recruited by Sema3A. NEMs were found to produce several factors involved in vessel maturation, including PDGFb, TGF-β, thrombospondin-1, and CXCL10; consistently, they were chemoattractive for vascular smooth muscle cells in vitro. When directly injected into growing tumors, NEMs, isolated either from the bone marrow or from Sema3A-expressing muscles, exerted antitumor activity despite having no direct effects on the proliferation of tumor cells. NEM inoculation specifically promoted mural cell coverage of tumor vessels and decreased vascular leakiness. Tumors treated with NEMs were smaller, better perfused and less hypoxic, and had a reduced level of activation of HIF-1α. We conclude that NEMs represent a novel, unique population of myeloid cells that, once inoculated into a tumor, induce tumor vessel normalization and inhibit tumor growth.

IL-12-dependent innate immunity arrests endothelial cells in G0-G1 phase by a p21(Cip1/Waf1)-mediated mechanism

Innate immunity may activate paracrine circuits able to entail vascular system in the onset and progression of several chronic degenerative diseases. In particular, interleukin (IL)-12 triggers a genetic program in lymphomononuclear cells characterized by the production of interferon-γ and specific chemokines resulting in an angiostatic activity. The aim of this study is to identify molecules involved in the regulation of cell cycle in endothelial cells co-cultured with IL-12-stimulated lymphomonuclear cells. By using a transwell mediated co-culture system we demonstrated that IL-12-stimulated lymphomonuclear cells induce an arrest of endothelial cells cycle in G1, which is mainly mediated by the up-regulation of p21(Cip1/Waf1), an inhibitor of cyclin kinases. This effect requires the activation of STAT1, PKCδ and p38 MAPK, while p53 is ineffective. In accordance, siRNA-dependent silencing of these molecules in endothelial cells inhibited the increase of p21(Cip1/Waf1) and the modification in cell cycle promoted by IL-12-stimulated lymphomonuclear cells. These results indicate that the angiostatic action of IL-12-stimulated lymphomononuclear cells may lie in the capability to arrest endothelial cells in G1 phase through a mechanisms mainly based on the specific up-regulation of p21(Cip1/Waf1) induced by the combined activity of STAT1, PKCδ and p38 MAPK.

Abstract SY41-04: Targeting Semaphorin 3A: A new tool to normalize tumor vasculature and to overcome the evasive resistance to the anti-angiogenic therapy

The critical role of angiogenesis in tumor development, progression and metastatization has long been appreciated and several anti-angiogenic inhibitors are approved for use in cancer therapy. Recently it has been reported in pre-clinical mouse models that angiogenesis inhibitors, induced transient primary tumor shrinkage followed by an evasive resistance to the therapy eliciting tumor invasiveness and increased distal metastasis formation (1). Therefore it is crucial to identify new angiogenic modulators and uncover the underlying mechanisms in order to design more effective anti-angiogenic combinatory regimens. A growing body of evidences demonstrated an important role of class3 Semaphorins (Sema3s), that act via receptor complexes binding neuropilins 1 and 2 (Nrp1/2) and transducing the signal by plexins, in regulating angiogenesis and tumor growth (2).

We have recently demonstrated that Sema3A is an endogenous inhibitor that is lost during tumor progression and its reintroduction into a mouse model of pancreatic neuroendocrine tumors (RIP-Tag2), resulted in reduced vascular density, blood vessel normalization, restoration of cancer normoxia, and inhibition of tumor growth (3).

Herein, we show that the treatment of RIP-Tag2 mice and of a mouse model of cervical cancer (HPV16/E2) with Sema3A by somatic gene transfer employing adeno-associated virus (AAV)-8, induced a dramatic reduction of tumor invasiveness, of metastases formation and a modulation of several epithelial-mesenchymal transition (EMT) genes. Then, we sought to investigate whether the administration of Sema3A in tumors was able to overcome the evasive resistance observed upon treatment with Sunitinib, an anti-angiogenic tyrosine kinase receptors inhibitor (1). Notably, we observed a dramatic reduction of cancer invasiveness and distal metastases formation in both RIP-Tag2 and HPV16/E2 mice simultaneously treated with Sema3A and Sunitinib for 4 weeks, compared to Sunitinib-treated controls. Moreover, while Sunitinib-treated tumors were highly hypoxic and displayed few pericyte-covered vessels, the combinatorial regimen of Sema3A with Sunitinib normalized the vasculature and restored tumor normoxia. Remarkably, Real-Time RT-PCR and confocal microscopy, revealed a strong modulation of EMT genes and a dramatic inhibition of several hypoxia-induced molecules in tumors treated with Sema3A and Sunitinib compared to Sunitinib-treated cancers.

Thus, treatment of tumors with Sema3A may safely improve the therapeutic potential of anti-angiogenic drugs, by normalizing the vasculature, inhibiting tumor hypoxia, and modulating the expression of hypoxic-induced genes activated by anti-angiogenic treatments.

References

1) Paez-Ribes M. et al. Cancer Cell, 2009. 15:220-31

2) Neufeld G. et al. Nat Rev Cancer 2008. 8:632-45

3) Maione F. et al. J.Clin.Invest, 2009. 119:3356-72

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr SY41-04. doi:1538-7445.AM2012-SY41-04

Semaphorin 3A overcomes cancer hypoxia and metastatic dissemination induced by antiangiogenic treatment in mice

Cancer development, progression, and metastasis are highly dependent on angiogenesis. The use of antiangiogenic drugs has been proposed as a novel strategy to interfere with tumor growth, but cancer cells respond by developing strategies to escape these treatments. In particular, animal models show that antiangiogenic drugs currently used in clinical settings reduce tumor tissue oxygenation and trigger molecular events that foster cancer resistance to therapy. Here, we show that semaphorin 3A (Sema3A) expression overcomes the proinvasive and prometastatic resistance observed upon angiogenesis reduction by the small-molecule tyrosine inhibitor sunitinib in both pancreatic neuroendocrine tumors (PNETs) in RIP-Tag2 mice and cervical carcinomas in HPV16/E2 mice. By improving cancer tissue oxygenation and extending the normalization window, Sema3A counteracted sunitinib-induced activation of HIF-1α, Met tyrosine kinase receptor, epithelial-mesenchymal transition (EMT), and other hypoxia-dependent signaling pathways. Sema3A also reduced tumor hypoxia and halted cancer dissemination induced by DC101, a specific inhibitor of the VEGF pathway. As a result, reexpressing Sema3A in cancer cells converts metastatic PNETs and cervical carcinomas into benign lesions. We therefore suggest that this strategy could be developed to safely harnesses the therapeutic potential of the antiangiogenic treatment.

Semaphorin 4A exerts a proangiogenic effect by enhancing vascular endothelial growth factor-A expression in macrophages

The axon guidance cues semaphorins (Semas) and their receptors plexins have been shown to regulate both physiological and pathological angiogenesis. Sema4A plays an important role in the immune system by inducing T cell activation, but to date, the role of Sema4A in regulating the function of macrophages during the angiogenic and inflammatory processes remains unclear. In this study, we show that macrophage activation by TLR ligands LPS and polyinosinic-polycytidylic acid induced a time-dependent increase of Sema4A and its receptors PlexinB2 and PlexinD1. Moreover, in a thioglycollate-induced peritonitis mouse model, Sema4A was detected in circulating Ly6C(high) inflammatory monocytes and peritoneal macrophages. Acting via PlexinD1, exogenous Sema4A strongly increased macrophage migration. Of note, Sema4A-activated PlexinD1 enhanced the expression of vascular endothelial growth factor-A, but not of inflammatory chemokines. Sema4A-stimulated macrophages were able to activate vascular endothelial growth factor receptor-2 and the PI3K/serine/threonine kinase Akt pathway in endothelial cells and to sustain their migration and in vivo angiogenesis. Remarkably, in an in vivo cardiac ischemia/reperfusion mouse model, Sema4A was highly expressed in macrophages recruited at the injured area. We conclude that Sema4A activates a specialized and restricted genetic program in macrophages able to sustain angiogenesis and participates in their recruitment and activation in inflammatory injuries.

Tumour growth inhibition and anti-metastatic activity of a mutated furin-resistant Semaphorin 3E isoform

Secreted Semaphorin 3E (Sema3E) promotes cancer cell invasiveness and metastatic spreading. The pro-metastatic activity of Sema3E is due to its proteolytic fragment p61, capable of transactivating the oncogenic tyrosine kinase ErbB2 that associates with the Sema3E receptor PlexinD1 in cancer cells. Here, we show that a mutated, uncleavable variant of Sema3E (Uncl-Sema3E) binds to PlexinD1 like p61-Sema3E, but does not promote the association of PlexinD1 with ErbB2 nor activates the ensuing signalling cascade leading to metastatic spreading. Furthermore, Uncl-Sema3E competes with endogenous p61-Sema3E produced by tumour cells, thereby hampering their metastatic ability. Uncl-Sema3E also acts independently as a potent anti-angiogenic factor. It activates a PlexinD1-mediated signalling cascade in endothelial cells that leads to the inhibition of adhesion to extracellular matrix, directional migration and cell survival. The putative therapeutic potential of Uncl-Sema3E was validated in multiple orthotopic or spontaneous tumour models in vivo, where either local or systemic delivery of Uncl-Sema3E-reduced angiogenesis, growth and metastasis, even in the case of tumours refractory to treatment with a soluble vascular endothelial growth factor trap. In summary, we conclude that Uncl-Sema3E is a novel inhibitor of tumour angiogenesis and growth that concomitantly hampers metastatic spreading.

A model of vascular tumour growth in mice combining longitudinal tumour size data with histological biomarkers

Optimising the delivery of antiangiogenic drugs requires the development of drug-disease models of vascular tumour growth that incorporate histological data indicative of cytostatic action. In this study, we formulated a model to analyse the dynamics of tumour progression in nude mice xenografted with HT29 or HCT116 colorectal cancer cells. In 30 mice, tumour size was periodically measured, and percentages of hypoxic and necrotic tissue were assessed using immunohistochemistry techniques on tumour samples after euthanasia. The simultaneous analysis of histological data together with longitudinal tumour size data prompted the development of a semi-mechanistic model integrating random effects of parameters. In this model, the peripheral non-hypoxic tissue proliferates according to a generalised-logistic equation where the maximal tumour size is represented by a variable called 'carrying capacity'. The ratio of the whole tumour size to the carrying capacity was used to define the hypoxic stress. As this stress increases, non-hypoxic tissue turns hypoxic. Hypoxic tissue does not stop proliferating, but hypoxia constitutes a transient stage before the tissue becomes necrotic. As the tumour grows, the carrying capacity increases owing to the process of angiogenesis. The model is shown to correctly predict tumour growth dynamics as well as percentages of necrotic and hypoxic tissues within the tumour. We show how the model can be used as a theoretical tool to investigate the effects of antiangiogenic treatments on tumour growth. This model provides a tool to analyse tumour size data in combination with histological biomarkers such as the percentages of hypoxic and necrotic tissue and is shown to be useful for gaining insight into the effects of antiangiogenic drugs on tumour growth and composition.

Increased expression of alpha6 integrin in endothelial cells unveils a proangiogenic role for basement membrane

The integrin alpha6 subunit is part of the alpha6beta1 and alpha6beta4 integrin complexes, which are known to be receptors for laminins and to mediate several biological activities such as embryogenesis, organogenesis, and invasion of carcinoma cells. However, the precise role of alpha6 integrin in angiogenesis has not yet been addressed. We observed that both vascular endothelial growth factor-A and fibroblast growth factor-2 strongly upregulate alpha6 integrin in human endothelial cells. Moreover, alpha6 integrin was positively modulated in angiogenic vessels in pancreatic neuroendocrine carcinoma. In this transgenic mouse model of spontaneous tumorigenesis, alpha6 integrin expression increased in the angiogenic stage, while being expressed at low levels in normal and hyperplastic tissue. We studied the functional role of alpha6 integrin during angiogenesis by lentivirus-mediated gene silencing and blocking antibody. Cell migration and morphogenesis on basement membrane extracts, a laminin-rich matrix, was reduced in endothelial cells expressing low levels of alpha6 integrin. However, we did not observe any differences in collagen matrices. Similar results were obtained in the aortic ring angiogenesis assay. alpha6 integrin was required for vessel sprouting on basement membrane gels but not on collagen gels, as shown by stably silencing this integrin in the murine aorta. Finally, a neutralizing anti-alpha6 integrin antibody inhibited in vivo angiogenesis in chicken chorioallantoic membrane and transgenic tumor mouse model. In summary, we showed that the alpha6 integrin participated in vascular endothelial growth factor-A and fibroblast growth factor-2-driven angiogenesis in vitro and in vivo, suggesting that it might be an attractive target for therapeutic approaches in angiogenesis-dependent diseases such as tumor growth.

Semaphorin 3A is an endogenous angiogenesis inhibitor that blocks tumor growth and normalizes tumor vasculature in transgenic mouse models

Tumor growth and progression rely upon angiogenesis, which is regulated by pro- and antiangiogenic factors, including members of the semaphorin family. By analyzing 3 different mouse models of multistep carcinogenesis, we show here that during angiogenesis, semaphorin 3A (Sema3A) is expressed in ECs, where it serves as an endogenous inhibitor of angiogenesis that is present in premalignant lesions and lost during tumor progression. Pharmacologic inhibition of endogenous Sema3A during the angiogenic switch, the point when pretumoral lesions initiate an angiogenic phase that persists throughout tumor growth, enhanced angiogenesis and accelerated tumor progression. By contrast, when, during the later stages of carcinogenesis following endogenous Sema3A downmodulation, Sema3A was ectopically reintroduced into islet cell tumors by somatic gene transfer, successive waves of apoptosis ensued, first in ECs and then in tumor cells, resulting in reduced vascular density and branching and inhibition of tumor growth and substantially extended survival. Further, long-term reexpression of Sema3A markedly improved pericyte coverage of tumor blood vessels, something that is thought to be a key property of tumor vessel normalization, and restored tissue normoxia. We conclude, therefore, that Sema3A is an endogenous and effective antiangiogenic agent that stably normalizes the tumor vasculature.