Angiogenesis inhibitors in early development for ...

Expert Opinion on Investigational Drugs

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Angiogenesis inhibitors in early development for gastric cancer Mauricio P. Pinto, Gareth I. Owen, Ignacio Retamal & Marcelo Garrido To cite this article: Mauricio P. Pinto, Gareth I. Owen, Ignacio Retamal & Marcelo Garrido (2017) Angiogenesis inhibitors in early development for gastric cancer, Expert Opinion on Investigational Drugs, 26:9, 1007-1017, DOI: 10.1080/13543784.2017.1361926 To link to this article: http://dx.doi.org/10.1080/13543784.2017.1361926

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EXPERT OPINION ON INVESTIGATIONAL DRUGS, 2017 VOL. 26, NO. 9, 1007–1017 https://doi.org/10.1080/13543784.2017.1361926

REVIEW

Angiogenesis inhibitors in early development for gastric cancer Mauricio P. Pintoa,b,c, Gareth I. Owena,b,d, Ignacio Retamalb,d and Marcelo Garridob,d School of Biological Sciences, Department of Physiology, Pontificia Universidad Católica de Chile, Santiago, Chile; bCenter UC for Investigation in Oncology (CITO), Pontificia Universidad Católica de Chile, Santiago, Chile; cSchool of Chemistry and Biology, Laboratory on the Immunology of Reproduction, Universidad de Santiago de Chile, Pontificia Universidad Católica de Chile, Santiago, Chile; dSchool of Medicine, Department of Hematology and Oncology, Pontificia Universidad Católica de Chile, Santiago, Chile

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a

ABSTRACT

ARTICLE HISTORY

Introduction: Angiogenesis, or the generation of new blood vessels from pre-existent ones is a critical process for tumor growth and progression. Hence, the development of angiogenesis inhibitors with therapeutic potential has been a central focus for researchers. Most angiogenesis inhibitors target the Vascular Endothelial Growth Factor (VEGF) pathway, however a number of tyrosine kinase inhibitors (TKIs), immunomodulatory drugs (IMiDs) and inhibitors of the mammalian Target-Of-Rapamycin (mTOR) pathway also display antiangiogenic activity. Areas covered: Here we review the effectiveness of a variety of compounds with antiangiogenic properties in preclinical and clinical settings in gastric cancer (GC). Expert opinion: In coming years angiogenesis will remain as a therapeutic target in GC. To date, ramucirumab a monoclonal antibody that targets VEGFR2 is the most successful antiangiogenic tested in clinical studies, and it is now well established as a second-line therapy in GC. The arrival of precision medicine and the success of immune checkpoint inhibitors will increase the number of clinical trials using targeted agents like ramucirumab in combination with immune checkpoint inhibitors. A hypothetical working model that combines ramucirumab with immunotherapy is presented. Also, the impact of nanotechnology and a molecular subtype classification of GC are discussed

Received 11 April 2017 Accepted 27 July 2017

1. Introduction 1.1. Angiogenesis and antiangiogenesis All organs in the human body require blood containing oxygen and nutrients in order to thrive. Certain cells within organs have the ability to synthesize and secrete vascular endothelial growth factor (VEGF) [1], a growth factor responsible for endothelial cell (EC) proliferation and migration [2]. Secreted VEGF binds to specific cell surface receptors (called VEGFRs) expressed on preexistent ECs, triggering the formation blood vessels in a process known as angiogenesis. In bodily homeostasis, angiogenesis is critical for numerous physiological processes such as tissue repair and fetal development; consequently, the VEGF pathway is highly conserved among mammals [3]. In humans, there are five members of the VEGF family of ligands: VEGF-A (hereafter simply VEGF), VEGF-B, VEGF-C, VEGF-D, and the placental growth factor [4]. VEGF mRNA can be spliced to produce several isoforms [3,5,6], and the most relevant being the soluble VEGF121 [7] and VEGF165 [5] isoforms (Figure 1). The main signaling receptor that is abundantly expressed by ECs is VEGFR2, also known as kinase insert domain receptor (KDR) [4]. This tyrosine kinase receptor can regulate EC proliferation and migration [8]. Other VEGF family members are VEGFR1 (or FMS-like tyrosine kinase 1 (FLT1)) involved in the recruitment of endothelial progenitor

KEYWORDS

Angiogenesis; antiangiogenesis; checkpoint inhibitors; gastric cancer; ramucirumab; pembrolizumab; nivolumab

cells and VEGFR3 (or FLT3) that shows specific expression in the lymphatic endothelium [9]. The hijacking of a physiological process in order to potentiate survival and propagation is a recognized strategy in cancer cells, and angiogenesis is no exception. Indeed, tumor angiogenesis was discovered almost 80 years ago [10]. Initial studies observed that tumor growth was accompanied by the formation of new blood vessels; an observation that was extensively confirmed by a variety of experimental models in the following decades [11–13]. In 1971, Folkman postulated that tumor growth was angiogenesis dependent and hypothesized that its inhibition could be therapeutic [14]. Hence the term ‘antiangiogenesis’ was coined, meaning a blockade in the formation of new blood vessels in a growing tumor. Today, angiogenesis is widely recognized as one of the ‘hallmarks of cancer’ [15] and the development of compounds with antiangiogenic (or angiostatic) activity is a central focus for both cancer researchers and the pharmaceutical industry. The VEGF pathway is one of the most studied players in the process of angiogenesis, and accordingly the first antiangiogenic drug commercially developed and approved by the US FDA for clinical use was a VEGF-sequestering agent known as bevacizumab (known commercially as Avastin®) [16]. Bevacizumab is a humanized monoclonal antibody directed against VEGF165, which is the most predominant soluble VEGF isoform [5].

CONTACT Marcelo Garrido [email protected] Facultad de Medicina, Departamento de Hematología y Oncología, Pontificia Universidad Católica de Chile, Diagonal Paraguay #319, Postal Code: 8330032, Santiago, Chile © 2017 Informa UK Limited, trading as Taylor & Francis Group

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Article highlights ● ● ● ● ●

●

Angiogenesis is a key physiological process and cancer cells have the ability to stimulate angiogenesis to enhance tumor growth Angiogenesis is a therapeutic target in many types of cancer, including gastric Currently, the majority of antiangiogenic drugs target the VEGF pathway To date the most successful antiangiogenic in gastric cancer is ramucirumab, a humanized monoclonal VEGFR antibody In addition to VEGF-targeted treatments, Tyrosine Kinase Inhibitors, Inhibitors of the mTOR pathway and immunomodulator drugs also display antiangiogenic activity Given its key role, angiogenesis will remain a therapeutic target in gastric cancer and future studies will determine efficacy of combinatorial treatment regimes with antiangiogenics


This box summarizes key points contained in the article

such as multitargeted tyrosine kinase inhibitors (TKIs) that target the aforementioned pathways. In recent years, the discovery of the immune checkpoint in cancer has confirmed a key role of the immune system in tumor progression [20]. Indeed, immunomodulatory drugs (IMiDs) such as thalidomide and its derivative lenalidomide have been demonstrated effective as angiostatic agents [21]. Finally, a number of selective inhibitors for the mammalian target-of-rapamycin (mTOR) signaling pathway have also shown effective as antiangiogenic agents [22]. For a full list of FDA-approved antiangiogenic drugs for the treatment of various cancer types, please see reference [17]

1.2. Gastric cancer (GC) and antiangiogenesis

Although the VEGF pathway is critical for tumor blood supply and growth, tumor angiogenesis is a complex process that may involve the use of alternative pathways besides VEGF [17], it is well documented that other tyrosine kinase receptors such as the epidermal growth factor (EGF), fibroblast growth factor (FGF), and platelet-derived growth factor (PDGF) can also promote angiogenesis (please refer to Figure 1 [18,19]). Consequently, the list of FDA-approved antiangiogenic drugs have expanded from bevacizumab into other compounds

Over the last 40 years, the 5-year survival rates for GC patients have almost tripled. Despite this, actual overall survival (OS) rates remain low; in fact, less than one in five patients are alive after 5 years from the time of diagnosis. Further, the median OS with advanced disease is about 3 months with best supportive care (BSC), and 10–12 months with combination chemotherapy regimens as first-line [23,24]. GCs like most malignancies are highly heterogeneous and despite recent efforts [25–27], there is still no consensus on a molecular subtype classification of patients with predictive value or reliable biomarkers that would allow patient

Angiogenesis (VEGF pathway) blockade Ramucirumab Trastuzumab Bevacizumab Aflibercept VEGF synthesis and secretion

CANCER RAS mutation and/or PTEN mutation and/or EGFR overexpression

Trebananib

Angiogenic alternative pathways VEGF 165

EGF

FGF

VEGFR2

EGFR

FGFR

Gefitinib Erlotinib

AZD4547

Ang2 PDGF

PDGFR

AKT

HIF1α

c-MET

TIE2

Tivantinib Pazopanib Regorafenib Sunitinib Lapatinib Sorafenib Axitinib Vandetanib Lenvatinib Cabozantinib

Apatinib

mTOR

VEGF mRNA

CANCER CELL

Ang1

Imatinib

PI3K

Genomic DNA

HGF

Rapamycin Everolimus Temsirolimus

ENDOTHELIAL CELL ANGIOGENESIS

?

Thalidomide Lenalidomide IMiDs

Figure 1. Angiogenesis and antiangiogenic drugs reviewed in this article. Cancer cells (left) synthesize and secrete VEGF that activate the endothelial cell (right) to initiate angiogenesis. The use of angiogenesis inhibitors triggers the use of alternative pathways such as EGF, FGF, PDGF and HGF. The mechanism of action of tyrosine kinase inhibitors (TKIs) and targeted therapies are depicted. Additionally, angiopoietins (Ang1, Ang2) can stimulate angiogenesis. The question mark (?) indicates that the mechanism for immunomodulatory drugs (IMiDs) is currently unknown. See text for further details.

EXPERT OPINION ON INVESTIGATIONAL DRUGS


stratification in order to choose more effective targeted therapies. Current standard of care first-line therapies for metastatic or unresectable advanced GC consists of regimens that combine platinum- plus fluoropyrimidine-based compounds [28], sometimes with the addition of epirubicin or a taxane. Although second-line chemotherapy significantly improves OS rates, patient median survival is still 2 years after gastric surgery. As mentioned, GC is a highly heterogeneous disease; a subset of patients are characterized by an aberrant


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Table 1. A summary of the antiangiogenic compounds tested in clinical studies and their main clinical outcomes in GC patients. First author or clinical trial #

Year

Study type

Arms

mPFS (months)

mOS (months)

Mayr M.

2012

Imatinib

Phase I

Hidalgo M. Oh DY. Meulendijks D. Kim ST. Martin-Richard M. Yoon HH.

2006 2015 2016 2016 2013 2016

Temsirolimus Axitinib Bevacizumab + trastuzumab Pazopanib Sorafenib Ramucirumab

Phase Phase Phase Phase Phase Phase

Enzinger PC.

2016

Aflibercept

Phase II

Moehler M.

2016

Sunitinib

Phase II

Pavlakis N.

2016

Regorafenib

Phase II

Ferry D. Dragovich T. NCT00683787

2007 2006 N/A

Gefitinib Erlotinib Vandetanib

Phase II Phase II Phase II

N/A N/A N/A N/A 10.8 6.5 3.0 6.7 6.4 7.3 9.9 3.3 3.5 0.9 2.5* 1.9 N/R

N/A N/A N/A N/A 17.9 10.5 6.5 11.5 11.7 N/R N/R 8.9 10.4 4.5 5.8 4.5 2.0

Ohtsu A.

2011

Bevacizumab

Phase III

Fuchs CS.

2014

Ramucirumab

Phase III

Wilke H.

2014

Ramucirumab

Phase III

Li J.

2016

Apatinib

Phase III

Hecht JR.

2016

Lapatinib

Phase III

Ohtsu A.

2013

Everolimus

Phase III

Imatinib + cisplatin, 5-FU Imatinib + cisplatin, capecitabine Single arm Single arm: + cisplatin + capecitabine Single arm: + docetaxel + oxaliplatin + capecitabine Single arm: + capecitabine + oxaliplatin Single arm: + oxaliplatin Placebo + mFOLFOX6 Ramucirumab + mFOLFOX6 Placebo + mFOLFOX6 Aflibercept + mFOLFOX6 Placebo + FOLFIRI Sunitinib + FOLFIRI Placebo + BSC Regorafenib + BSC Single arm: monotherapy Single arm: monotherapy Placebo + docetaxel Vandetanib (100 mg) + Docetaxel Vandetanib (300 mg) + docetaxel Placebo + capecitabine/FU Bevacizumab + capecitabine/FU Placebo Ramucirumab monotherapy Placebo + paclitaxel Ramucirumab + paclitaxel Placebo Apatinib monotherapy Placebo + capecitabine + oxaliplatin Lapatinib + capecitabine + oxaliplatin Placebo + BSC Everolimus + BSC

Antiangiogenic drug

I I II II II II

N/A, N/R 5.3 6.7* 1.3 2.1 2.9 4.4 1.8 2.6* 5.4 6.0 1.4 1.7

10.1 12.1 3.8 5.2* 7.4 9.6* 4.7 6.5* 10.5 12.2 4.3 5.4

Table shows a summary of the studies using antiangiogenics by author, year, antiangiogenic used, study type, arms considered on the study, median progressionfree survival (PFS) and overall survival (OS) both in months. * indicates statistically significant differences compared to placebo. GC: gastric cancer; FOLFIRI: folinic acid, fluorouracil, and irinotecan; mPFS: median progression-free survival; mOS: median overall survival; BSC: best supportive care; 5-FU: 5-fluoruracil, N/A: not applicable, N/R: not reported.

FGFR signaling [78]. As mentioned previously, GC cell lines that overexpress FGFR2 are particularly sensitive to pazopanib, suggesting FGFR inhibition could also be therapeutic. A recently developed TKI called AZD4547 specifically targets FGFRs (see Figure 1) and has been proven effective in GC patients with FGFR2 gene amplifications [78], and a phase II study is currently under way [79]. Interestingly, in animal models VEGFR2 inhibition blocks tumor growth for approximately 2 weeks; following this period, tumors regrow with a concomitant increase in FGF-1 and -2 [80]. Similarly, bevacizumab-treated colon cancer patients increase their plasma FGF-2 levels following treatment [81]. In fact, studies suggest VEGF and FGF can act synergistically to increase angiogenesis [82]. As explained, angiogenesis is a critical process for both normal and malignant cells and therefore when subjected to a selective pressure (an antiangiogenic drug, for example) they can activate alternative pathways or cellular mechanisms of resistance. In addition to FGF, cancer cells subjected to VEGF inhibition can increase their levels of hepatocyte growth factor (HGF) and angiopoietin-1 (Ang1). Aberrant or dysregulated c-mesenchymal–epithelial transition (MET) factor signaling (the HGF receptor) is commonly seen in many malignancies; a number of specific c-MET inhibitors have demonstrated potential antineoplastic activity in vitro or in vivo. Tivantinib is a TKI that specifically targets c-MET (Figure 1); unpublished

results from a recently completed phase I/II study evaluated tivantinib in combination with FOLFOX6 in advanced GC patients as a first-line therapy, and reports 3 out of 34 patients had extended time on the study. Angiopoietins (Angs) are a family of ligands that bind [83] and activate the EC membrane receptor tyrosine kinase (TIE2), Ang1 and 2 can induce angiogenesis via TIE2 and Ang-inhibition has been postulated as an antiangiogenic strategy (see Figure 1); trebananib (or AMG386) is a recombinant fusion between a peptide and an Fc fragment (a ‘peptibody’) that binds Ang1 and 2 preventing TIE2 activation [84]. Although trebananib has not been tested in GC, a phase III study in recurrent epithelial ovarian cancer patients demonstrates a significant increase in PFS when used in combination with paclitaxel [85]. On the other hand, Ang2 has been postulated as a biomarker for OS associated to liver metastasis in GC [86] and therefore could be evaluated as a future therapeutic target. In recent years, the development of immune checkpoint inhibitors that activate a sustained antitumoral T cell response has revolutionized oncology treatments for patients. Immunotherapies are based on humanized monoclonal antibodies directed against T-cell surface antigens: the cytotoxic-T lymphocyte-associated antigen 4 (CTLA-4) or the programmed death-1 (PD-1). CTLA-4 is a dominant inhibitory receptor that plays a role in immune tolerance and homeostasis [87]; CTLA-4


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blockade by ipilimumab significantly increases median OS in grade III/IV unresectable metastatic melanoma [88]. The other immune checkpoint is known as PD-1, and the PD-1 ligand-1 (PD-L1) is a negative regulator of T cell activation, preventing autoimmune diseases. PD-1/PD-L1 blockade has demonstrated effective against many malignancies in preclinical models [89,90]. Given their effectiveness, several PD-1 targeted immunotherapeutics are currently available. Notably, preliminary results in advanced GC patients using pembrolizumab [91] and nivolumab (#NCT02267343) suggest these treatments are well tolerated and effective. Further, a recent phase III study using nivolumab as a salvage treatment reports significant increases in PFS, ORR, and OS against placebo [92]. Additionally, preliminary results of clinical studies using nivolumab and pembrolizumab were presented at the ASCO meeting this year: first, results using nivolumab in 493 metastatic GC patients as a third-line therapy (phase III) show a 11.2% of response rate, disease control rate was 40.3%, progression of disease was 43.6%, and 26.6% of patients were alive after 12 months versus a 0% of response rate, 25% of disease control rate, 60.3% of progression of disease and 10.9% of patients were alive after 12 months in the placebo group. Second, a phase II clinical trial of pembrolizumab that includes 259 metastatic GC patients also as a third-line therapy shows a 11.6% of response rate, disease control rate was 27%, progression of disease was 56%, and 27% of patients were alive after 12 months. Also, in this study PD-L1 and microsatellital instability were good predictors of response [93]. Experimental in vivo models demonstrate that a simultaneous inhibition of PD-1 and VEGFR2 act synergistically to inhibit tumor growth, promoting T cell infiltration and decreasing neovascularization [94]. Following the success of ramucirumab in the REGARD and the RAINBOW studies, the combination of immune checkpoint inhibitors (pembrolizumab, nivolumab) and ramucirumab may deliver substantial benefits in advanced metastatic GC patients. Indeed, two phase I studies are evaluating the use of a combination of ramucirumab with either pembrolizumab (#NCT02443324) or nivolumab (#NCT02999295); both these studies are currently recruiting advanced GC patients. In addition, given the effectiveness observed with

trastuzumab, a phase II study that uses ramucirumab plus trastuzumab and capecitabine/cisplatin in HER2+ metastatic GC is also recruiting patients (#NCT02726399)

3. Conclusion Angiogenesis is one of the ‘hallmarks of cancer’ and a key process in GC. However, the clinical use of antiangiogenic compounds shows disparate results. Bevacizumab and aflibercept have been shown rather ineffective. On the other hand, ramucirumab has proven effective as a second-line therapy (Table 1). Other VEGF pathway inhibitors including TKIs, IMiDs, and mTOR inhibitors have been tested in experimental in vitro, in vivo models, or in clinical studies (summarized in Figure 1 and Table 1) with disparate results. The discovery of the immune checkpoint inhibitors that target the CTLA4 or the PD-1/PD-L1 pathway has provided promise and enough clinical evidence to suggest a sustained clinical use in the future. In coming years, studies will assess the effect of therapeutic regimens that combine targeted therapies like ramucirumab or trastuzumab along with checkpoint inhibitors. Finally, the arrival of precision medicine and the elucidation of a molecular subtype classification with clinical significance will allow stratification of patients and the selection of more effective therapy regimens, further personalizing GC treatments.

4. Expert opinion 4.1. Antiangiogenesis in GC and future perspectives Angiogenesis is a critical process for tumor growth and progression across many malignancies and will likely remain a therapeutic target in GCs. As we enter the era of precision medicine in oncology, molecular targeted therapies will progressively become the standard for GC patients. To date, the most successful targeted therapies are based on trastuzumab and ramucirumab; in fact, this latter is now established as the second-line therapy in refractory GC patients. There is an ongoing phase III study with ramucirumab plus cisplatin and fluoropirimidines (#NCT02314117) [95], and other combinations of chemotherapy will be tested

Figure 2. Patient response to ramucirumab plus FOLFIRI. Image of Computed Tomography (CT) scan of a GC patient. Highlighted area in the left panel shows an adrenal metastasis of approximately 7.8 cm. Right panel shows the same patient after two months with ramucirumab plus FOLFIRI, showing a reduction to 5.2 cm.


Table 2. Ongoing clinical studies using antiangiogenic compounds or combinatorial regimes in GC. Clinical trial # identifier NCT01457846 NCT02443324 NCT02999295 NCT02726399

Antiangiogenic

NCT02314117

AZD4547 Ramucirumab Ramucirumab Ramucirumab + trastuzumab Ramucirumab

NCT02401971 NCT01248403

Thalidomide Everolimus

Combinatorial drug (s) None Pembrolizumab Nivolumab Capecitabine, cisplatin Cisplatin + fuoropyrimidines Irinotecan Paclitaxel

Study type Phase Phase Phase Phase

II I I/II II

Phase III Phase IV Phase III


Table summarizes ongoing clinical trials using antiangiogenics alone or in combination and indicates study type. GC: gastric cancer.

with ramucirumab. Figure 2 demonstrates a GC patient’s response to the ramucirumab plus FOLFIRI combination. This patient was originally diagnosed with a stage IV GC and received 12 cycles of ramucirumab plus FOLFIRI as a second-line therapy without significant toxicity. Patient’s response was determined by RECIST 1.1 criteria. The highlighted area on the left panel shows an adrenal metastasis that measured 7.8 cm in its major axis, the right panel of the same area shows a reduction to 5.2 cm in its major axis after 2–6 months with the ramucirumab plus FOLFIRI regimen. The successful clinical experience with immune checkpoint inhibitors is expected to rapidly expand into combinatorial treatments for advanced metastatic GC patients. Hence, future studies should explore the combination of checkpoint inhibitors plus targeted therapies such as ramucirumab and/or trastuzumab. Interestingly, an ongoing study is evaluating the addition of ramucirumab and trastuzumab to capecitabine and cisplatin in HER2+ metastatic GC patients (#NCT02726399). A summary of ongoing clinical studies using combinatorial treatments with antiangiogenic compounds is presented in Table 2. As new checkpoint inhibitors become available, new combinations with targeted antibody therapies could be entered into clinical trials. Although the effectiveness of such combinatorial therapy is uncertain, we propose a hypothetical working model in Figure 3. First, gastric tumors express cell surface VEGFR2 and PD-L1 that serve as antigens. Then, ramucirumab binds to VEGFR2 at the surface of cancer cells triggering immune cell infiltration. Previous studies have demonstrated bevacizumab (another monoclonal antibody) treatment increases T-cell infiltration into tumors [96]. At this stage, the Fc fragment of VEGFR2-bound ramucirumab is recognized by Fc receptors (FcR) expressed by infiltrating NK cells. Studies using anti-HER2 antibodies demonstrate that the innate immune system plays a key role in the therapeutic response to antibodies through FcRmediated cytotoxicity; this can be subdivided in three mechanisms: complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, and antibody-

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dependent cellular phagocytosis [97]. Also at this point, PD-1-expressing tumor-infiltrating T-cells bind PD-L1 expressed by tumor cells and therefore remain inactive. Then, the sequential treatment with a checkpoint inhibitor like pembrolizumab binds to PD-1 in T-cells stimulates the adaptive immune system attack on the tumor obtaining a full response and tumor reduction. Indeed, studies demonstrate NK cell infiltration is a good prognosis factor in GC [98]; on the other hand, T-cell infiltration has also been speculated to play a key role in patient prognosis [99], with studies suggesting a full response to monoclonal antibody-based therapies is dependent on both the innate (NK cells) and adaptive (T-cells) immune responses [100,101]. The development of more efficient drug delivery systems is also expected to have an enormous impact in oncology. In particular, the development of nanomaterials and nanocarriers along with the synthesis of nano-conjugated and/or nanoencapsulated antiangiogenic drugs may allow the use of lower doses with lower toxicity levels [102]. Furthermore, this could also imply a reassessment of drugs previously dropped down by clinicians due to their toxicity in patients. Also within this context, the advances in nanoparticle (NP) design and elaboration of multifunctional actively targeted NPs might also improve the therapeutic repertoire. The concept of precision medicine means tailored treatments for patients based on their molecular profiles. Cancer heterogeneity is one of the principal obstacles in developing effective, long-lasting, therapies in patients. Current ‘one-sizefits-all’ therapies should gradually be replaced by personalized treatments based on reliable biomarkers or companion diagnostics. In recent years, The Cancer Genome Atlas project and the Asian Cancer Research Group study had made significant advances toward a molecular classification of GC subtypes. Undoubtedly, an effective stratification of patients along with reliable validated biomarkers (systemic and/or local) are urgently needed; these could significantly improve clinical outcomes by helping oncologists further tailor treatment regimes. Finally, cancer cells are defined by their genetic instability. In evolutionary biology, a selective pressure produces a resilient system through natural selection; as such antiangiogenic drugs can eventually trigger the recurrence of resistant tumors by selecting resistant tumor cells. As occurs with all anticancer therapies, the development of tumor resistance following antiangiogenic therapies is unavoidable. Therefore, future drugs should focus on alternative pathways (i.e. FGF or PDGF) and may consider dual inhibition when toxicity issues are resolved. Additionally, studies on the biology of other mechanisms of resistance to antiangiogenic therapy such as vasculogenic mimicry and vascular co-option (reviewed in references [17,103]) may reveal new molecular targets and open potentially new therapeutic avenues. These drugs could help against antiangiogenic-resistant disease and may offer more alternatives for patients in second- or third-line settings.

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Figure 3. The rationale for a combined sequential therapy using ramucirumab plus a checkpoint inhibitor. Gastric tumors express surface antigens PD-L1 and VEGFR2. We hypothesize that a sequential treatment with ramucirumab and pembrolizumab causes a synergistic antitumoral effect. First, ramucirumab increases infiltration of immune cells into tumors; initially NK cells (innate immune system) recognize the Fc portion of bound ramucirumab and target tumor cells causing a partial response. Concomitantly, infiltrating T-cells expressing PD-1 receptor enter the tumor microenvironment but remain inactive due to the presence of tumor cell expressed PD-L1. The subsequent sequential use of pembrolizumab releases T-cell inhibition by PD-L1 and stimulates antitumoral activity resulting in a synergistic response and tumor shrinkage.


Funding CONICYT-FONDAP 15130011, Millenium Institute on Immunology & Immunotherapy IMII P09/016-F, BMRC 13CTI-21526-P6, CORFO 13IDL218608, and FONDECYT grant #1140970.

Declaration of interest M Garrido is a consultant for, or a board member with Abbot-Recalcine, Merck Sharp & Dohme LLC, Bayer, Bristol-Myers Squibb, Lilly. MG has received a research grant from Novartis. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.


References Papers of special note have been highlighted as either of interest (•) or of considerable interest (••) to readers. 1. Tammela T, Enholm B, Alitalo K, et al. The biology of vascular endothelial growth factors. Cardiovasc Res. 2005;65:550–563. 2. Bernatchez PN, Soker S, Sirois MG. Vascular endothelial growth factor effect on endothelial cell proliferation, migration, and platelet-activating factor synthesis is Flk-1-dependent. J Biol Chem. 1999;274:31047–31054. 3. Holmes DIR, Zachary I. The vascular endothelial growth factor (VEGF) family: angiogenic factors in health and disease. Genome Biol. 2005;6:209. 4. Otrock ZK, Makarem JA, Shamseddine AI. Vascular endothelial growth factor family of ligands and receptors: review. Blood Cells Mol Dis. 2007;38:258–268. 5. Finley SD, Popel AS. Predicting the effects of anti-angiogenic agents targeting specific VEGF isoforms. Aaps J 38. 2012;14:500– 509. 6. McFee RM, Rozell TG, Cupp AS. The balance of proangiogenic and antiangiogenic VEGFA isoforms regulate follicle development. Cell Tissue Res. 2012;349:635–647. 7. Mohamedali KA, Li ZG, Starbuck MW, et al. Inhibition of prostate cancer osteoblastic progression with VEGF121/rGel, a single agent targeting osteoblasts, osteoclasts, and tumor neovasculature. Clin Cancer Res. 2011;17:2328–2338. 8. Flamme I, Breier G, Risau W. Vascular endothelial growth factor (VEGF) and VEGF receptor 2 (flk-1) are expressed during vasculogenesis and vascular differentiation in the quail embryo. Dev Biol. 1995;169:699–712. 9. Shibuya M, Claesson-Welsh L. Signal transduction by VEGF receptors in regulation of angiogenesis and lymphangiogenesis. Exp Cell Res. 2006;312:549–560. 10. Ferrara N. VEGF and intraocular neovascularization: from discovery to therapy. Transl Vis Sci Technol. 2016;5:10. 11. Greenblatt M, Philippe SK. Tumor angiogenesis: transfilter diffusion studies in the hamster by the transparent chamber technique. J Natl Cancer Inst. 1968;41:111–124. 12. Ehrmann RL, Knoth M. Choriocarcinoma. Transfilter stimulation of vasoproliferation in the hamster cheek pouch. Studied by light and electron microscopy. J Natl Cancer Inst. 1968;41:1329–1341. 13. Ribatti D, Vacca A, Dammacco F. The role of the vascular phase in solid tumor growth: a historical review. Neoplasia. 1999;1:293–302. 14. Sherwood LM, Parris EE, Folkman J. Tumor angiogenesis: therapeutic implications. N Engl J Med. 1971;285:1182–1186. 15. Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011;144:646–674. • An update of the original ‘Hallmarks of Cancer’ that confirms angiogenesis as a key process in cancer. 16. Rosen LS. Clinical experience with angiogenesis signaling inhibitors: focus on vascular endothelial growth factor (VEGF) blockers. Cancer Control. 2002;9:36–44.

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17. Pinto MP, Sotomayor P, Carrasco-Avino G, et al. Escaping antiangiogenic therapy: strategies employed by cancer cells. Int J Mol Sci. 2016;17:1489. 18. Van Cruijsen H, Giaccone G, Hoekman K. Epidermal growth factor receptor and angiogenesis: opportunities for combined anticancer strategies. Int J Cancer. 2005;117:883–888. 19. Sato N, Beitz JG, Kato J, et al. Platelet-derived growth factor indirectly stimulates angiogenesis in vitro. Am J Pathol. 1993;142:1119– 1130. 20. Pardoll DM. The blockade of immune checkpoints in cancer immunotherapy. Nat Rev Cancer. 2012;12:252–264. • Summarizes the rationale for immune checkpoint inhibitor therapy in cancer. 21. Anderson KC. Lenalidomide and thalidomide: mechanisms of action - Similarities and differences. Semin Hematol. 2005;42:S3– S8. Elsevier. 22. Karar J, Maity A. PI3K/AKT/mTOR pathway in angiogenesis. Front Mol Neurosci. 2011;4:51. 23. Garrido M, Fonseca PJ, Marı J. Challenges in first line chemotherapy and targeted therapy in advanced gastric cancer. Expert Rev Anticancer Ther. 2014;14:887–900. 24. Wagner AD, Unverzagt S, Grothe W, et al. Chemotherapy for advanced gastric cancer. In: Wagner AD, editor. Cochrane database syst. rev. Chichester, UK: John Wiley & Sons, Ltd; 2010. p. CD004064. 25. Cancer T, Atlas G, Bass AJ, et al. Comprehensive molecular characterization of gastric adenocarcinoma. Nature. 2014;513:202–209. 26. Cristescu R, Lee J, Nebozhyn M, et al. Molecular analysis of gastric cancer identifies subtypes associated with distinct clinical outcomes. Nature. 2015;21:449–456. 27. Lei Z, Tan IB, Das K, et al. Identification of molecular subtypes of gastric cancer with different responses to pi3-kinase inhibitors and 5-fluorouracil. Gastroenterology. 2013;145:554–565. 28. Wagner AD, Grothe W, Haerting J, et al. Chemotherapy in advanced gastric cancer: a systematic review and meta-analysis based on aggregate data. J Clin Oncol. 2006;24:2903–2909. 29. Kang JH, Lee SI, Lim DH, et al. Salvage chemotherapy for pretreated gastric cancer: a randomized phase iii trial comparing chemotherapy plus best supportive care with best supportive care alone. J Clin Oncol. 2012;30:1513–1518. 30. Ford HER, Marshall A, Bridgewater JA, et al. Docetaxel versus active symptom control for refractory oesophagogastric adenocarcinoma (COUGAR-02): an open-label, phase 3 randomised controlled trial. Lancet Oncol. 2014;15:78–86. 31. Thuss-Patience PC, Kretzschmar A, Bichev D, et al. Survival advantage for irinotecan versus best supportive care as second-line chemotherapy in gastric cancer - A randomised phase III study of the Arbeitsgemeinschaft Internistische Onkologie (AIO). Eur J Cancer. 2011;47:2306–2314. 32. Okines AFC, Reynolds AR, Cunningham D. Targeting angiogenesis in esophagogastric adenocarcinoma. Oncologist. 2011;16:844–858. 33. Lieto E, Ferraraccio F, Orditura M, et al. Expression of vascular endothelial growth factor (VEGF) and epidermal growth factor receptor (EGFR) is an independent prognostic indicator of worse outcome in gastric cancer patients. Ann Surg Oncol. 2008;15:69– 79. 34. Kim S-E, Shim K-N, Jung S-A, et al. The clinicopathological significance of tissue levels of hypoxia-inducible factor-1alpha and vascular endothelial growth factor in gastric cancer. Gut Liver. 2009;3:88–94. 35. Liu L, Ma X-L, Xiao Z-L, et al. Prognostic value of vascular endothelial growth factor expression in resected gastric cancer. Asian Pac J Cancer Prev. 2012;13:3089–3097. 36. Peng L, Zhan P, Zhou Y, et al. Prognostic significance of vascular endothelial growth factor immunohistochemical expression in gastric cancer: a meta-analysis. Mol Biol Rep. 2012;39:9473–9484. 37. Jung YD, Mansfield PF, Akagi M, et al. Effects of combination antivascular endothelial growth factor receptor and anti-epidermal growth factor receptor therapies on the growth of gastric cancer in a nude mouse model. Eur J Cancer. 2002;38:1133–1140.


1016

M. P. PINTO ET AL.

38. Ohtsu A, Shah MA, Van Cutsem E, et al. Bevacizumab in combination with chemotherapy as first-line therapy in advanced gastric cancer: a randomized, double-blind, placebo-controlled phase III study. J Clin Oncol. 2011;29:3968–3976. •• The AVAGAST study was the first phase III trial using bevacizumab in combination with chemotherapy in gastric cancer patients. 39. Ohtsu A, Yoshida S, Saijo N. Disparities in gastric cancer chemotherapy between the east and west. J Clin Oncol. 2006;24:2188–2196. 40. Kim R, Tan A, Choi M, et al. Geographic differences in approach to advanced gastric cancer: is there a standard approach? Crit. Rev Oncol Hematol. 2013;88:416–426. 41. Spratlin JL, Cohen RB, Eadens M, et al. Phase I pharmacologic and biologic study of ramucirumab (IMC-1121B), a fully human immunoglobulin G 1 monoclonal antibody targeting the vascular endothelial growth factor receptor-2. J Clin Oncol. 2010;28:780– 787. 42. Chiorean EG, Hurwitz HI, Cohen RB, et al. Phase I study of every 2or 3-week dosing of ramucirumab, a human immunoglobulin G1 monoclonal antibody targeting the vascular endothelial growth factor receptor-2 in patients with advanced solid tumors. Ann Oncol. 2015;26:1230–1237. 43. Fuchs CS, Tomasek J, Yong CJ, et al. Ramucirumab monotherapy for previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (REGARD): an international, randomised, multicentre, placebo-controlled, phase 3 trial. Lancet. 2014;383:31– 39. •• The REGARD study was the first phase III trial demonstrating the efficacy of ramucirumab monotherapy in gastric cancer. 44. Wilke H, Muro K, Van Cutsem E, et al. Ramucirumab plus paclitaxel versus placebo plus paclitaxel in patients with previously treated advanced gastric or gastro-oesophageal junction adenocarcinoma (RAINBOW): A double-blind, randomised phase 3 trial. Lancet Oncol. 2014;15:1224–1235. •• The RAINBOW study demonstrated the efficacy of the combination of ramucirumab plus chemotherapy (paclitaxel) in advance gastric cancer. 45. Yoon HH, Bendell JC, Braiteh FS, et al. Ramucirumab combined with FOLFOX as front-line therapy for advanced esophageal, gastroesophageal junction, or gastric adenocarcinoma: a randomized, double-blind, multicenter Phase II trial. Ann Oncol. 2016;27:21962203. 46. Holash J, Davis S, Papadopoulos N, et al. VEGF-Trap: a VEGF blocker with potent antitumor effects. Proc Natl Acad Sci U S A. 2002;99:11393–11398. 47. Van Cutsem E, Tabernero J, Lakomy R, et al. Addition of aflibercept to fluorouracil, leucovorin, and irinotecan improves survival in a phase III randomized trial in patients with metastatic colorectal cancer previously treated with an oxaliplatin-based regimen. J Clin Oncol. 2012;30:3499–3506. 48. Enzinger PC, McCleary NJ, Zheng H, et al. Multicenter double-blind randomized phase II: FOLFOX + ziv-aflibercept/placebo for patients (pts) with chemo-naive metastatic esophagogastric adenocarcinoma (MEGA). J Clin Oncol. 2016;34:4. 49. Li J, Qin S, Xu J, et al. Randomized, double-blind, placebo-controlled phase III trial of apatinib in patients with chemotherapyrefractory advanced or metastatic adenocarcinoma of the stomach or gastroesophageal junction. J Clin Oncol. 2016;34:1448–1454. 50. Porta C, Gore ME, Rini BI, et al. Long-term safety of sunitinib in metastatic renal cell carcinoma. Eur Urol. 2016;69:345–351. 51. Moehler M, Gepfner-Tuma I, Maderer A, et al. Sunitinib added to FOLFIRI versus FOLFIRI in patients with chemorefractory advanced adenocarcinoma of the stomach or lower esophagus: a randomized, placebo-controlled phase II AIO trial with serum biomarker program. BMC Cancer. 2016;16:699. 52. Kim ST, Lee J, Lee SJ, et al. Prospective phase II trial of pazopanib plus CapeOX (capecitabine and oxaliplatin) in previously untreated patients with advanced gastric cancer. Oncotarget. 2016;7:24088– 24096.

53. Kim ST, Jang H-L, Lee SJ, et al. Pazopanib, a novel multitargeted kinase inhibitor, shows potent in vitro antitumor activity in gastric cancer cell lines with FGFR2 amplification. Mol Cancer Ther. 2014;13:2527–2536. 54. Pavlakis N, Sjoquist KM, Martin AJ, et al. Regorafenib for the treatment of advanced gastric cancer (INTEGRATE): A multinational placebo-controlled phase II Trial. J Clin Oncol. 2016;34:2728–2735. 55. Hecht JR, Bang YJ, Qin SK, et al. Lapatinib in combination with capecitabine plus oxaliplatin in human epidermal growth factor receptor 2-positive advanced or metastatic gastric, esophageal, or gastroesophageal adenocarcinoma: TRIO-013/LOGiC - A randomized phase III trial. J Clin Oncol. 2016;34:443–451. 56. Martin-Richard M, Gallego R, Pericay C, et al. Multicenter phase II study of oxaliplatin and sorafenib in advanced gastric adenocarcinoma after failure of cisplatin and fluoropyrimidine treatment. A gemcad study. Invest New Drugs. 2013;31:1573–1579. 57. Morishita A, Gong J, Masaki T. Targeting receptor tyrosine kinases in gastric cancer. World J Gastroenterol. 2014;20:4536–4545. 58. Ferry DR, Anderson M, Beddard K, et al. A phase II study of gefitinib monotherapy in advanced esophageal adenocarcinoma: evidence of gene expression, cellular, and clinical response. Clin Cancer Res. 2007;13:5869–5875. 59. Dragovich T, McCoy S, Fenoglio-Preiser CM, et al. Phase II trial of erlotinib in gastroesophageal junction and gastric adenocarcinomas: SWOG 0127. J Clin Oncol. 2006;24:4922–4927. 60. Bang YJ, Van Cutsem E, Feyereislova A, et al. Trastuzumab in combination with chemotherapy versus chemotherapy alone for treatment of HER2-positive advanced gastric or gastro-oesophageal junction cancer (ToGA): A phase 3, open-label, randomised controlled trial. Lancet. 2010;376:687–697. 61. Oh D-Y, Doi T, Shirao K, et al. Phase I study of axitinib in combination with cisplatin and capecitabine in patients with previously untreated advanced gastric cancer. Cancer Res Treat. 2015;47:687–696. 62. Yamamoto Y, Matsui J, Matsushima T, et al. Lenvatinib, an angiogenesis inhibitor targeting VEGFR/FGFR, shows broad antitumor activity in human tumor xenograft models associated with microvessel density and pericyte coverage. Vasc Cell. 2014;6:18. 63. Turcotte M, Lu J, Lee S, et al. Abstract 780: multi-targeted tyrosine kinase inhibitor cabozantinib as a therapeutic agent in MET-overexpressing gastric cancer. Cancer Res. 2015;75:4494–4503. 64. Piccaluga PP, Rondoni M, Paolini S, et al. Imatinib mesylate in the treatment of hematologic malignancies. Expert Opin Biol Ther. 2007;7:1597–1611. 65. Mayr M, Becker K, Schulte N, et al. Phase I study of imatinib, cisplatin and 5-fluoruracil or capecitabine in advanced esophageal and gastric adenocarcinoma. BMC Cancer. 2012;12:587. 66. Therapontos C, Erskine L, Gardner ER, et al. Thalidomide induces limb defects by preventing angiogenic outgrowth during early limb formation. Proc Natl Acad Sci U S A. 2009;106:8573–8578. 67. Eleutherakis-Papaiakovou V, Bamias A, Dimopoulos MA. Thalidomide in cancer medicine. Ann Oncol. 2004;15:1151–1160. Oxford University Press. 68. Lambert K, Ward J. The use of thalidomide in the management of bleeding from a gastric cancer. Palliat Med. 2009;23:473–475. 69. Al-Batran S-E, Ducreux M, Ohtsu A. mTOR as a therapeutic target in patients with gastric cancer. Int J Cancer. 2012;130:491–496. 70. Lang SA, Gaumann A, Koehl GE, et al. Mammalian target of rapamycin is activated in human gastric cancer and serves as a target for therapy in an experimental model. Int J Cancer. 2007;120:1803– 1810. 71. Yao C, Liu J, Shao L. Rapamycin inhibits the proliferation and apoptosis of gastric cancer cells by down regulating the expression of survivin. Hepatogastroenterology. 2011;58:1075–1080. 72. Yoon DH, Ryu M-H, Park YS, et al. Phase II study of everolimus with biomarker exploration in patients with advanced gastric cancer refractory to chemotherapy including fluoropyrimidine and platinum. Br J Cancer. 2012;106:1039–1044.



73. Ohtsu A, Ajani JA, Bai Y-X, et al. Everolimus for previously treated advanced gastric cancer: results of the randomized, double-blind, phase III GRANITE-1 study. J Clin Oncol. 2013;31:3935– 3943. 74. Al-Batran S-E, Riera-Knorrenschild J, Pauligk C, et al. A randomized, double-blind, multicenter phase III study evaluating paclitaxel with and without RAD001 in patients with gastric cancer who have progressed after therapy with a fluoropyrimidine/platinum-containing regimen (RADPAC). J Clin Oncol. 2017;35:4-4. 75. Hidalgo M, Buckner JC, Erlichman C, et al. A phase I and pharmacokinetic study of temsirolimus (CCI-779) administered intravenously daily for 5 days every 2 weeks to patients with advanced cancer. Clin Cancer Res. 2006;12:5755–5763. 76. Moehler M, Schwarz S, Wagner AD. Esophagogastric cancer: integration of targeted therapies into systemic chemotherapy. Curr Cancer Drug Targets. 2011;11:681–687. 77. Meulendijks D, Beerepoot LV, Boot H, et al. Trastuzumab and bevacizumab combined with docetaxel, oxaliplatin and capecitabine as first-line treatment of advanced HER2-positive gastric cancer: a multicenter phase II study. Invest New Drugs. 2016;34:119–128. 78. Xie L, Su X, Zhang L, et al. FGFR2 gene amplification in gastric cancer predicts sensitivity to the selective FGFR inhibitor AZD4547. Clin Cancer Res. 2013;19:2572–2583. 79. Bang YJ, Van Cutsem E, Mansoor W, et al. A randomized, openlabel phase II study of AZD4547 (AZD) versus Paclitaxel (P) in previously treated patients with advanced gastric cancer (AGC) with Fibroblast Growth Factor Receptor 2 (FGFR2) polysomy or gene amplification (amp): SHINE study. J Clin Oncol. 2015;33:4014–4014. 80. Casanovas O, Hicklin DJ, Bergers G, et al. Drug resistance by evasion of antiangiogenic targeting of VEGF signaling in late-stage pancreatic islet tumors. Cancer Cell. 2005;8:299–309. 81. Lieu C, Heymach J, Overman M, et al. Beyond VEGF: inhibition of the fibroblast growth factor pathway and antiangiogenesis. Clin Cancer Res. 2011;17:6130–6139. 82. Pepper MS, Ferrara N, Orci L, et al. Potent synergism between vascular endothelial growth factor and basic fibroblast growth factor in the induction of angiogenesis in vitro. Biochem Biophys Res Commun. 1992;189:824–831. 83. Pant S, Patel MR, Kurkjian C, et al. A phase II study of the c-Met inhibitor tivantinib (tiv) in combination with FOLFOX for the treatment of patients (pts) with previously untreated metastatic adenocarcinoma of the distal esophagus, gastroesophageal (GE) junction, or stomach. Cancer Invest. 2017;1-10. 84. Atkins MB, Gravis G, Drosik K, et al. Trebananib (AMG 386) in combination with sunitinib in patients with metastatic renal cell cancer: an open-label, multicenter, phase II study. J Clin Oncol. 2015;33:3431–3438. 85. Monk BJ, Poveda A, Vergote I, et al. Anti-angiopoietin therapy with trebananib for recurrent ovarian cancer (TRINOVA-1): A randomised, multicentre, double-blind, placebo-controlled phase 3 trial. Lancet Oncol. 2014;15:799–808.

1017

86. Hacker UT, Escalona-Espinosa L, Consalvo N, et al. Evaluation of Angiopoietin-2 as a biomarker in gastric cancer: results from the randomised phase III AVAGAST trial. Br J Cancer. 2016;114:855–862. 87. Lenschow DJ, Walunas TL, Jeffrey A. CD28 /B7 system of T cell costimulation. Annu Rev Immunol. 1996;14:233–258. 88. Hodi FS, O’Day SJ, McDermott DF, et al. Improved survival with ipilimumab in patients with metastatic melanoma. N Engl J Med. 2010;363:711–723. 89. Ohigashi Y, Sho M, Yamada Y, et al. Clinical significance of programmed death-1 ligand-1 and programmed death-1 ligand-2 expression in human esophageal cancer. Clin Cancer Res. 2005;11:2947–2953. 90. Nomi T, Sho M, Akahori T, et al. Clinical significance and therapeutic potential of the programmed death-1 ligand/programmed death-1 pathway in human pancreatic cancer. Clin Cancer Res. 2007;13:2151–2157. 91. Smyth EC, Cunningham D. Encouraging results for PD-1 inhibition in gastric cancer. Lancet Oncol. 2016;17:682–683. Elsevier. 92. Kang YK, Satoh T, Ryu MH, et al. Nivolumab (ONO-4538/BMS936558) as salvage treatment after second or later-line chemotherapy for advanced gastric or gastro-esophageal junction cancer (AGC): a double-blinded, randomized, phase III trial. J Clin Oncol. 2017;35:2-2. 93. Fuchs CS, Doi T, Woo-Jun Jang R, et al. KEYNOTE-059 cohort 1: efficacy and safety of pembrolizumab (pembro) monotherapy in patients with previously treated advanced gastric cancer. J Clin Oncol. 2017;35:suppl abstract 4003. 94. Yasuda S, Sho M, Yamato I, et al. Simultaneous blockade of programmed death 1 and vascular endothelial growth factor receptor 2 (VEGFR2) induces synergistic anti-tumour effect in vivo. Clin Exp Immunol. 2013;172:500–506. 95. Alsina M, Hierro C, Tabernero J. Antiangiogenic therapies in gastric cancer: trusting the pathway. Ann Oncol Off J Eur Soc Med Oncol. 2016;27:2141–2143. 96. Oelkrug C, Ramage JM. Enhancement of T cell recruitment and infiltration into tumours. Clin Exp Immunol. 2014;178:1–8. 97. Chester C, Marabelle A, Houot R, et al. Dual antibody therapy to harness the innate anti-tumor immune response to enhance antibody targeting of tumors. Curr Opin Immunol. 2015;33:1–8. 98. Ishigami S, Natsugoe S, Tokuda K, et al. Prognostic value of intratumoral natural killer cells in gastric carcinoma. Cancer. 2000;88:577–583. 99. Melero I, Rouzaut A, Motz GT, et al. T-cell and NK-cell infiltration into solid tumors: A key limiting factor for efficacious cancer immunotherapy. Cancer Discov. 2014;4:522–526. 100. Park S, Jiang Z, Mortenson ED, et al. Cancer Cell. 2010;18;2:160–70. 101. Weiner LM, Surana R, Wang S. Monoclonal antibodies: versatile platforms for cancer immunotherapy. Nat Rev Immunol. 2010;10:317–327. 102. Banerjee D, Harfouche R, Sengupta S. Nanotechnology-mediated targeting of tumor angiogenesis. Vasc Cell. 2011;3:3. 103. Sanhueza C, Wehinger S, Castillo Bennett J, et al. The twisted survivin connection to angiogenesis. Mol Cancer. 2015;14:198.