Tumor-associated Vasculature Research Articles

Engineering the Extracellular Matrix to Model the Evolving Tumor Microenvironment.

SummaryClinical evidence supports a role for the extracellular matrix (ECM) in cancer risk and prognosis across multiple tumor types, and numerous studies have demonstrated that individual ECM components impact key hallmarks of tumor progression (e.g., proliferation, migration, angiogenesis). However, the ECM is a complex network of fibrillar proteins, glycoproteins, and proteoglycans that undergoes dramatic changes in composition and organization during tumor development. In this review, we will highlight how engineering approaches can be used to examine the impact of changes in tissue architecture, ECM composition (i.e., identity and levels of individual ECM components), and cellular- and tissue-level mechanics on tumor progression. In addition, we will discuss recently developed methods to model the ECM that have not yet been applied to the study of cancer.

Endothelin-1-Mediated Drug Resistance in EGFR-Mutant Non-Small Cell Lung Carcinoma.

Progression on therapy in non-small cell lung carcinoma (NSCLC) is often evaluated radiographically, however, image-based evaluation of said therapies may not distinguish disease progression due to intrinsic tumor drug resistance or inefficient tumor penetration of the drugs. Here we report that the inhibition of mutated EGFR promotes the secretion of a potent vasoconstrictor, endothelin-1 (EDN1), which continues to increase as the cells become resistant with a mesenchymal phenotype. As EDN1 and its receptor (EDNR) is linked to cancer progression, EDNR-antagonists have been evaluated in several clinical trials with disappointing results. These trials were based on a hypothesis that the EDN1-EDNR axis activates the MAPK-ERK signaling pathway that is vital to the cancer cell survival; the trials were not designed to evaluate the impact of tumor-derived EDN1 in modifying tumor microenvironment or contributing to drug resistance. Ectopic overexpression of EDN1 in cells with mutated EGFR resulted in poor drug delivery and retarded growth in vivo but not in vitro. Intratumoral injection of recombinant EDN significantly reduced blood flow and subsequent gefitinib accumulation in xenografted EGFR-mutant tumors. Furthermore, depletion of EDN1 or the use of endothelin receptor inhibitors bosentan and ambrisentan improved drug penetration into tumors and restored blood flow in tumor-associated vasculature. Correlatively, these results describe a simplistic endogenous yet previously unrealized resistance mechanism inherent to a subset of EGFR-mutant NSCLC to attenuate tyrosine kinase inhibitor delivery to the tumors by limiting drug-carrying blood flow and the drug concentration in tumors. SIGNIFICANCE: EDNR antagonists can be repurposed to improve drug delivery in VEGFA-secreting tumors, which normally respond to TKI treatment by secreting EDN1, promoting vasoconstriction, and limiting blood and drug delivery.

Abstract 5203: MGC018, a duocarmycin-based antibody-drug conjugate targeting B7-H3, exhibits immunomodulatory activity and enhanced antitumor activity in combination with checkpoint inhibitors

Abstract Introduction: B7-H3, a member of the B7 family of immunomodulatory molecules, is overexpressed in a wide range of solid tumors. B7-H3 tumor overexpression has been correlated with disease severity and poor outcome. MGC018 is a duocarmycin-based antibody-drug conjugate (ADC) targeting B7-H3. MGC018 exhibits a favorable preclinical profile, with strong reactivity toward tumor cells and tumor-associated vasculature, limited normal tissue reactivity, and potent antitumor activity toward B7-H3-expressing tumor xenografts. With the emergence of immune-checkpoint blockade as a promising treatment for cancer, interest has grown in understanding the potential of cytotoxic agents to promote immune surveillance or stimulate immune responses to dying cancer cells, leading to immunological memory. ADCs bearing tubulin and DNA modifying cytotoxic payloads have been reported to induce immunological cell death (ICD), mediate antitumor immunity in immunocompetent mouse models, and synergistically combine with checkpoint inhibitors to deliver enhanced antitumor responses. Based on those results, we investigated the immunomodulatory potential of MGC018 and the prospect to combine with checkpoint blockade to enhance antitumor responses. Methods: Syngeneic mouse models expressing human B7-H3 were employed to investigate the antitumor activity of MGC018 in an immune competent setting. Studies were conducted to assess the role of the immune system in the MGC018-mediated antitumor responses, whether MGC018 could impart antitumor memory responses in vivo, and the potential to enhance antitumor responses by combining MGC018 with PD-1 blockade. Results: MGC018 demonstrated specific, dose-dependent in vivo antitumor activity toward human B7-H3-bearing tumors in immunocompetent syngeneic mouse models. Depletion of CD8+ T cells led to reduced antitumor responses, indicating that CD8+ T cells contributed to MGC018-mediated antitumor activity. Antitumor activity in these models was enhanced when MGC018 was combined with anti-PD-1. Treatment with MGC018 alone, or in combination with anti-PD-1, led to complete antitumor responses, and the majority of mice rejected subsequent tumor rechallenge. Conclusion: MGC018, a clinical-stage therapeutic comprised of a humanized antibody targeting B7-H3, conjugated to a duocarmycin-based DNA alkylating payload, exhibits a favorable preclinical profile. Results from these syngeneic model studies support the hypothesis that the antitumor activity of the duocarmycin-based MGC018 ADC (1) mediates immunomodulatory activity, (2) is enhanced by combination with checkpoint blockade, and (3) induces immunological memory. Our findings support a clinical strategy that combines MGC018 with checkpoint blockade for the treatment of B7-H3-expressing solid cancers. Citation Format: Juniper A. Scribner, Michael Chiechi, Pam Li, Thomas Son, Jeff Hooley, Ying Li, Anushka De Costa, Peter Lung, Nicholas Yee-Toy, Francine Chen, Bhaswati Barat, Christina Wolff, Valentina Ciccarone, James Tamura, Scott Koenig, Chet Bohac, Jon Wigginton, Paul A. Moore, Ezio Bonvini, Deryk Loo. MGC018, a duocarmycin-based antibody-drug conjugate targeting B7-H3, exhibits immunomodulatory activity and enhanced antitumor activity in combination with checkpoint inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5203.

Endothelial p130cas Confers Resistance to Anti-Angiogenesis Therapy

Adaptive resistance to vascular endothelial growth factor (VEGF)–targeted therapies occurs frequently among cancer patients. To investigate the underlying mechanisms, we established an array of orthotopic mouse models of ovarian cancer with adaptive resistance to anti-VEGF antibodies (AVAs). Genomic profiling showed an important role of endothelial p130cas in AVA resistant tumors. AVA treatment induced internalization of a p130cas/VEGFR2/TNKS1BP1 (a tankyrase-1–binding protein) complex in endothelial cells and initiated cell death and autophagy; knockdown of LC3B or caspase-10 reversed cells’ resistance to AVA treatment. Targeting host p130cas reduced the growth of AVA-resistant orthotopic ovarian tumors. Genomic ablation of vascular p130cas in p130casflox/floxTie2Cre mice significantly prolonged survival of mice carrying syngeneic ovarian tumors with adaptive resistance to AVA therapy. In ovarian cancer patients, higher p130cas expression in tumor-associated vasculature was associated with higher mortality. Collectively, these findings have important implications to guide future therapeutic strategies to overcome resistance to anti-angiogenic therapy.

Fucoidan-based, tumor-activated nanoplatform for overcoming hypoxia and enhancing photodynamic therapy and antitumor immunity

Multifunctional nanoplatforms combined with photodynamic therapy (PDT) and anticancer drugs have shown great promising in cancer therapy. However, their efficacy is limited by the low specificity, low oxygen levels, and a tolerant tumor immune microenvironment. Herein, we developed a biocompatible theranostic nanoplatform (FM@VP) based on co-assembly of a nanocomplex formed by a functional polysaccharide fucoidan and a bioreducible polyamidoamine (PAMAM) dendrimer, a photosensitizer verteporfin (VP), and MnO2 nanoparticles (a tumor microenvironment responsive oxygen evolving nanomaterial) into a multifunctional nanoparticle cluster. The dendrimer-fucoidan polyionic nanocomplex (DFPN) specifically targeted P-selectin-overexpressed triple-negative breast cancer (TNBC) and the tumor-associated vasculature, and was sensitive to glutathione (GSH) in tumor. More importantly, this FM@VP nanocomplex simultaneously overcame tumor hypoxia, suppressed oncogenic signaling, and attenuated tumor-mediated immunosuppression, resulting in improving therapeutic efficacy of PDT while enhancing antitumor immunity and anti-metastasis. This discovery provides a powerful strategy for synergetic cancer targeting/photodynamic/immunotherapy and could serve as a safe clinical translational approach.

Multidimensional hydrogel models reveal endothelial network angiocrine signals increase glioblastoma cell number, invasion, and temozolomide resistance.

Glioblastoma (GBM) is the most common primary malignant brain tumor. The tissue microenvironment adjacent to vasculature, termed the perivascular niche, has been implicated in promoting biological processes involved in glioblastoma progression such as invasion, proliferation, and therapeutic resistance. However, the exact nature of the cues that support tumor cell aggression in this niche is largely unknown. Soluble angiocrine factors secreted by tumor-associated vasculature have been shown to support such behaviors in other cancer types. Here, we exploit macroscopic and microfluidic gelatin hydrogel platforms to profile angiocrine factors secreted by self-assembled endothelial networks and evaluate their relevance to glioblastoma biology. Aggregate angiocrine factors support increases in U87-MG cell number, migration, and therapeutic resistance to temozolomide. We also identify a novel role for TIMP1 in facilitating glioblastoma tumor cell migration. Overall, this work highlights the use of multidimensional hydrogel models to evaluate the role of angiocrine signals in glioblastoma progression.

4071 Dynamic Control of Tumor Vessels Augments Antitumor Responses

OBJECTIVES/GOALS: Our overall objective is to develop a directly observable and reproducible method of enhanced blood flow through tumor vessels (i.e. dynamic control) at the time of systemic treatment delivery. Our central hypothesis is that the dynamic control of tumor vessels will improve (1) systemic drug delivery and (2) effector cell trafficking to target tumor. METHODS/STUDY POPULATION: B16 melanoma cells were inoculated into C57BL/6 (B6) mice (male and female) in both regional (hind leg) and systemic (flank) models. Dynamic control consisted of an IV saline bolus (500 ul) and phenylephrine (10 ug). Tumor vessel response was observed in real-time through window chambers using intravital microscopy (IVM). Dynamic control was combined with melphalan (20 mg/ml) either regionally (isolated limb perfusion) or systemically. Outcomes included tumor growth, survival, IHC, and toxicity. Dynamic control will be combined with adoptive transfer of effector T cells. B6 mice will be inoculated with B16/OVA (flank with window chamber) and treated with fluorescently labeled (calcein), OVA-specific CD8+ T cells from OT-1 transgenic mice. IVM, IHC, and flow cytometry will be used to measure T cell trafficking. RESULTS/ANTICIPATED RESULTS: Dynamic control (1) restored blood flow in non-functional tumor vessels and (2) increased and then transiently reversed blood flow in functional vessels. Vessel diameters did not change, suggesting that shunting of systemic blood to the tumor vasculature accounted for the observed changes. Dynamic control augmented tumor responses in our regional therapy model of melanoma. Increases in DNA adduct formation (melphalan mechanism of action) detected by IHC, decreased tumor growth, and increased survival were observed with dynamic control. There was no increased limb toxicity. Similarly, dynamic control augmented responses in our systemic therapy model (decreased tumor growth and improved survival). We anticipate that dynamic control will improve trafficking of effector T cells in the next set of experiments. DISCUSSION/SIGNIFICANCE OF IMPACT: Heterogeneous responses to systemic therapies represent a major gap in current cancer treatment. An essential requirement for any effective therapy is its ability to reach tumor via the tumor-associated vasculature. We have therefore developed an approach to enhance drug delivery (dynamic control), which we also plan to test in clinical trials.

LCRF-0006, a small molecule mimetic of the N-cadherin antagonist peptide ADH-1, synergistically increases multiple myeloma response to bortezomib.

N‐cadherin is a homophilic cell‐cell adhesion molecule that plays a critical role in maintaining vascular stability and modulating endothelial barrier permeability. Pre‐clinical studies have shown that the N‐cadherin antagonist peptide, ADH‐1, increases the permeability of tumor‐associated vasculature thereby increasing anti‐cancer drug delivery to tumors and enhancing tumor response. Small molecule library screens have identified a novel compound, LCRF‐0006, that is a mimetic of the classical cadherin His‐Ala‐Val sequence‐containing region of ADH‐1. Here, we evaluated the vascular permeability‐enhancing and anti‐cancer properties of LCRF‐0006 using in vitro vascular disruption and cell apoptosis assays, and a well‐established pre‐clinical model (C57BL/KaLwRij/5TGM1) of the hematological cancer multiple myeloma (MM). We found that LCRF‐0006 disrupted endothelial cell junctions in a rapid, transient and reversible manner, and increased vascular permeability in vitro and at sites of MM tumor in vivo. Notably, LCRF‐0006 synergistically increased the in vivo anti‐MM tumor response to low‐dose bortezomib, a frontline anti‐MM agent, leading to regression of disease in 100% of mice. Moreover, LCRF‐0006 and bortezomib synergistically induced 5TGM1 MM tumor cell apoptosis in vitro. Our findings demonstrate the potential clinical utility of LCRF‐0006 to significantly increase bortezomib effectiveness and enhance the depth of tumor response in patients with MM.

The aegis: platelets as biomarkers of tumor progression.

There is increasing awareness that platelets play a significant role in creating a hypercoagulable environment that mediates tumor progression, beyond their classical hemostatic function. Platelets have heterogenic responses to agonists, and differential release and uptake of bioactive molecules may be manipulated via reciprocal cross-talk with cells of the tumor microenvironment. Platelets thus promote tumor progression by enhancing tumor growth, promoting the development of tumor-associated vasculature and encouraging invasion. In the metastatic process, platelets form the shield that protects tumor cells from high-velocity forces and immunosurveillance, while ensuring the establishment of the pre-metastatic niche. This review presents the complexity of these concepts, considering platelets as biomarkers for diagnosis, prognosis and potentially as therapeutic targets in cancer.

Low immunogenicity of intracranial tumors limits immune response to brain malignancies

Abstract The presence of CD8 T cells in tumors, including melanomas, is correlated with longer survival. Cutaneous melanoma is a highly immunogenic malignancy with high rate of dissemination into central nervous system but the brain is considered immunologically privileged due to the blood-brain barrier, which limits T cell entry. To determine if brain tumors are also poorly infiltrated by T cells we evaluated intracranial (IC) and subcutaneous (SC) B16 melanomas expressing different model antigens. CD8 T cells were present in IC tumors 7 days post tumor implantation in B16 melanomas expressing chicken ovalbumin (B16OVA) or influenza M1 protein (B16M1), but infiltrates were only 10% of those observed in SC tumors. We also observed that expression of homing receptor ligands (HRLs) known to mediate T cell infiltration was lower on IC than SC tumor-associated vasculature. Despite the fact that HRL expression decreased over time in tumors grown in both locations, T cell infiltrates increased, suggesting that HRL are not the only factor limiting T cells entry into IC tumors. To determine whether the IC tumor infiltrate size was limited by inefficient stimulation of effectors cells, we vaccinated mice to generate fully activated effector T cells able to recognize tumor associated antigen. Vaccination normalized the infiltrate sizes in IC and SC tumors. Interestingly, this was also dependent on expression of Ag by the tumor cells. This suggests that IC tumors are not able to efficiently elicit a robust immune response, possibly due to limitations on drainage to lymph nodes, while IC tumor vasculature does not impose inherently greater limitations on the ability of T cells to enter.

Abstract P1-10-06: Radiomic measurements of tumor-associated vasculature morphology and function on pretreatment dynamic MRI identifies responders to neoadjuvant chemotherapy

Abstract Background: Angiogenesis is crucial to a tumor's growth and an important factor in therapeutic outcome. Although quantitative analysis of tumors on dynamic contrast enhanced (DCE) MRI can provide indirect characterization of a tumor's vascularization, direct computational analysis of the tumor-associated vessel network remains a promising, but under-explored potential marker of therapeutic response. For instance, surrounding vasculature with a convoluted 3-dimensional shape and poor blood flow may indicate a more aggressive tumor and poorly facilitate delivery of therapeutic agents. In this work, we present a computational approach for the prediction of neoadjuvant chemotherapy response using quantitative imaging features describing the morphology and function of tumor associated vasculature on pretreatment MRI. Methods: 243 patients who received DCE-MRI scans prior to neo-adjuvant chemotherapy (NAC) at institution A [n=83], B [n=76], or one of nine other institutions as part of the ISPY1 Trial [n=84] were divided randomly into training (n=123) and testing (n=120) sets. 148 patients were HER2- and received neoadjuvant AC-T, while the 95 HER2+ patients were treated with TCHP (ISPY predates anti-HER2 therapy and HER2+ ISPY patients were excluded). 79 patients achieved pathological complete response [pCR, ypT0/is] following NAC. MRI exams were collected with a 1.5 or 3 Tesla scanner in the axial or sagittal plane. A baseline scan and 2-5 scans after injection of a gadolinium-based contrast agent with a median temporal resolution of 2.5 minutes were acquired. A portion of the tumor was manually delineated, then semi-automatically expanded to 3D. Vasculature was isolated from subtraction images with a specialized filtering approach to detect vessel-shaped objects. Features describing the 3D shape and architecture of the tumor-associated vessel network (e.g. curvature, torsion, and local orientation) and functional semi-quantitative pharmacokinetic (PK) measurements of temporal contrast enhancement changes (e.g. signal enhancement ratio, time to peak enhancement, and rates of uptake and washout) were calculated. Performance was assessed by area under the receiver operating characteristic curve (AUC), as well as the accuracy, sensitivity, and specificity at the operating point corresponding to the Youden Index. The most discriminating features were determined based on frequency of selection by the random forest classifier. Results: Within the training set, PK parameters of the vessels (AUC=.66) outperformed relative to the PK of tumor (AUC=.63) and the PK of peritumoral regions (AUC=.64); however, a combination of the three yielded best performance (AUC=.75). Vessel shape features alone achieved AUC=.67 in the training set. When multi-region PK features and tumor shape features were combined and applied to the 120-patient independent testing set, the random forest classifier achieved an AUC of 0.70 and identified 81% of patients who would achieve pCR. Non-pCR was best characterized by increased vessel curvature and PK parameters indicating poor perfusion, such as greater time to peak enhancement, slower uptake rate, and quicker washout. Conclusions: Our findings suggest that properties of the tumor-associated vessel network, such as its shape and enhancement profile, might provide value in identifying patients who will respond to NAC before administration of treatment. Accuracy (%)Sensitivity (%)Specificity (%)Full testing set (n=120)678160HER2+ (n=44)709548HER2- (n=76)646365HER2-, HR+ (n=51)678364Triple Negative (n=25)605067 Citation Format: Nathaniel Braman, Prateek Prasanna, Kaustav Bera, Mehdi Alilou, Manasa Vulchi, Maryam Etesami, Paulette Turk, Jame Abraham, Donna Plecha, Anant Madabhushi. Radiomic measurements of tumor-associated vasculature morphology and function on pretreatment dynamic MRI identifies responders to neoadjuvant chemotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-10-06.

Preclinical and Clinical Evidence of Immune Responses Triggered in Oncologic Photodynamic Therapy: Clinical Recommendations.

Photodynamic therapy (PDT) is an anticancer strategy utilizing light-mediated activation of a photosensitizer (PS) which has accumulated in tumor and/or surrounding vasculature. Upon activation, the PS mediates tumor destruction through the generation of reactive oxygen species and tumor-associated vasculature damage, generally resulting in high tumor cure rates. In addition, a PDT-induced immune response against the tumor has been documented in several studies. However, some contradictory results have been reported as well. With the aim of improving the understanding and awareness of the immunological events triggered by PDT, this review focuses on the immunological effects post-PDT, described in preclinical and clinical studies. The reviewed preclinical evidence indicates that PDT is able to elicit a local inflammatory response in the treated site, which can develop into systemic antitumor immunity, providing long-term tumor growth control. Nevertheless, this aspect of PDT has barely been explored in clinical studies. It is clear that further understanding of these events can impact the design of more potent PDT treatments. Based on the available preclinical knowledge, recommendations are given to guide future clinical research to gain valuable information on the immune response induced by PDT. Such insights directly obtained from cancer patients can only improve the success of PDT treatment, either alone or in combination with immunomodulatory approaches.

Anti-DLL4 VNAR targeted nanoparticles for targeting of both tumour and tumour associated vasculature.

Whilst there is an extensive body of preclinical nanomedicine research, translation to clinical settings has been slow. Here we present a novel approach to the targeted nanoparticle (NP) concept: utilizing both a novel targeting ligand, VNAR (Variable New Antigen Receptor), a shark-derived single chain binding domain, and an under-investigated target in delta-like ligand 4 (DLL4). We describe the development of an anti-DLL4 VNAR and the site-specific conjugation of this to poly(lactic-co-glycolic) acid PEGylated NPs using surface maleimide functional groups. These nanoconjugates were shown to specifically bind DLL4 with high affinity and were preferentially internalized by DLL4-expressing pancreatic cancer cell lines and endothelial cells. Furthermore, a distinct anti-angiogenic effect endowed by the anti-DLL4 VNAR was evident in in vitro tubulogenic assays. Taken together these findings highlight the potential of anti-DLL4 targeted polymeric NPs as a novel therapeutic approach in pancreatic cancer.

A minimal modeling framework of radiation and immune system synergy to assist radiotherapy planning

Recent evidence indicates the ability of radiotherapy to induce local and systemic tumor-specific immune responses as a result of immunogenic cell death. However, fractionation regimes routinely used in clinical practice typically ignore the synergy between radiation and the immune system, and instead attempt to completely eradicate tumors by the direct lethal effect of radiation on cancer cells. This paradigm is expected to change in the near future due to the potential benefits of considering radiation-induced antitumor immunity during treatment planning. Towards this goal, we propose a minimal modeling framework based on key aspects of the tumor-immune system interplay to simulate the effects of radiation on tumors and the immunological consequences of radiotherapy. The impacts of tumor-associated vasculature and intratumoral oxygen-mediated heterogeneity on treatment outcomes are ininvestigated. The model provides estimates of the minimum radiation doses required for tumor eradication given a certain number of treatment fractions. Moreover, estimates of treatment duration for disease control given predetermined fractional radiation doses can be also obtained. Although theoretical in nature, this study motivates the development and establishment of immune-based decision-support tools in radiotherapy planning.

18F]Fluciclatide PET as a biomarker of response to combination therapy of pazopanib and paclitaxel in platinum-resistant/refractory ovarian cancer

BackgroundAngiogenesis is a driver of platinum resistance in ovarian cancer. We assessed the effect of combination pazopanib and paclitaxel followed by maintenance pazopanib in patients with platinum-resistant/refractory ovarian cancer. Integrins αvβ3 and αvβ5 are both upregulated in tumor-associated vasculature. [18F]Fluciclatide is a novel PET tracer that has high affinity for integrins αvβ3/5, and was used to assess the anti-angiogenic effect of pazopanib.Patients and methodsWe conducted an open-label, phase Ib study in patients with platinum-resistant/refractory ovarian cancer. Patients received 1 week of single-agent pazopanib (800 mg daily) followed by combination therapy with weekly paclitaxel (80 mg/m2). Following completion of 18 weeks of combination therapy, patients continued with single-agent pazopanib until disease progression. Dynamic [18F]fluciclatide-PET imaging was conducted at baseline and after 1 week of pazopanib. Response (RECIST 1.1), toxicities, and survival outcomes were recorded. Circulating markers of angiogenesis were assessed with therapy.ResultsFourteen patients were included in the intention-to-treat analysis. Complete and partial responses were seen in seven patients (54%). Median progression-free survival (PFS) was 10.63 months, and overall survival (OS) was 18.5 months. Baseline [18F]fluciclatide uptake was predictive of long PFS. Elevated baseline circulating angiopoietin and fibroblast growth factor (FGF) were predictive of greater reduction in SUV60,mean following pazopanib. Kinetic modeling of PET data indicated a reduction in K1 and Ki following pazopanib indicating reduced radioligand delivery and retention.ConclusionsCombination therapy followed by maintenance pazopanib is effective and tolerable in platinum-resistant/refractory ovarian cancer. [18F]Fluciclatide-PET uptake parameters predict clinical outcome with pazopanib therapy indicating an anti-angiogenic response.

Abstract AP21: A NOVEL TARGET FOR OVERCOMING ADAPTIVE RESISTANCE TO ANTI-ANGIOGENIC THERAPY IN OVARIAN CANCER

Abstract Anti-angiogenic therapy such as anti-VEGF antibody (AVA) has been being increasingly applied in patients with ovarian cancer, while vast majority developed adaptive resistance, highlighting the need for new therapies. We have screened a cohort of patients with high-grade serous cancer (HGSC) using cDNA-genomic array and immunohistochemistry. Our results indicated that p130cas [Crk-associated substrate], a central node in FAK/Src-mediated angiogenesis, was significantly upregulated in tumor-associated vascular endothelium, and the clinical analysis showed that HGSC patients with increased vascular p130cas have significantly shorter disease-progression survival than those with lower vascular p130cas levels. Our cell-based studies showed that AVA treatment in endothelial cells led to internalization of a 100-kD fragment of VEGFR2, which was released by caspase-10 cleavage from membrane-tethered VGFR2. This 100-kD form of VEGFR2 bound with TNKS1BP1 (a tankyrase-1-binding protein involved in p53-mediated cell cycle arrest) and internalized into LC3-tagged autophagosomes or translocated into nucleus to initiate cell death. Furthermore, the gene ablation of p130cas with CRISPR/CAS9 in endothelial cells that were originally resistant to AVA therapy re-sensitized them to AVA treatment. Our in vivo studies on targeting vascular p130cas with host-specific siRNA showed a robust inhibition of tumor growth and progression in orthotopic HGSC tumors through initiating autophagy-associated cell death in tumor-associated endothelial cells. To functionally characterize role of vascular p130cas in angiogenesis, we established the p130casflox/flox-Tie2Cre genomic-engineered mice (GEM) model. Using the ID8 syngeneic model, we found that depletion of vascular p130cas diminished resistance to AVA therapy and compromised angiogenesis by inducing elevated VEGFR2/TNKS1BP1 in autophagosomes and nucleus of tumor-associated endothelial cells, which were followed by cell death. To further explore the therapeutic potential of blocking tumor-associated vascular p130cas as a novel anti-angiogenic strategy, we have constituted a cell-permeable, peptide-nanoparticle complex using a p130cas antagonist encapsulated with biodegradable, long-circulating, core-crosslinked polymeric micelles (CCPM). This CCPM-p130cas antagonist contains a mutated Src-binding domain and is linked with Arg-Gly-Asp (RGD) peptide, which specifically targets angiogenic endothelial cells. We also performed the cell-based studies to show that this CCPM-p130cas antagonist is able to bind to the FAK and Src complex with high affinity and effectively block FAK/Src mediated angiogenic property in endothelial cells. Ongoing studies are focused on investigating the therapeutic efficacy and mechanism of actions for RGD-CCPM-p130cas antagonist as a novel anti-angiogenic therapy to overcome adaptive resistance occurred in patients with HGSC. In summary, our studies provided new knowledge regarding the pivotal role of vascular p130cas in tumor-associated endothelial vasculature, and the critical pre-clinical evidences for applying the RGD-CCPM-p130cas antagonist as a novel therapeutic for treatment of ovarian cancer. Citation Format: Yunfei Wen, Alpa M Nick, G Lopez-Berestein, Gary E Gallick, Robert L Coleman Robert , Mien-Chie Hung, and Anil K Sood. A NOVEL TARGET FOR OVERCOMING ADAPTIVE RESISTANCE TO ANTI-ANGIOGENIC THERAPY IN OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr AP21.

Zinc(II) phthalocyanines as photosensitizers for antitumor photodynamic therapy.

Photodynamic therapy (PDT) is a highly specific and clinically approved method for cancer treatment in which a nontoxic drug known as photosensitizer (PS) is administered to a patient. After selective tumor irradiation, an almost complete eradication of the tumor can be reached as a consequence of reactive oxygen species (ROS) generation, which not only damage tumor cells, but also lead to tumor-associated vasculature occlusion and the induction of an immune response. Despite exhaustive investigation and encouraging results, zinc(II) phthalocyanines (ZnPcs) have not been approved as PSs for clinical use yet. This review presents an overview on the physicochemical properties of ZnPcs and biological results obtained both in vitro and in more complex models, such as 3D cell cultures, chicken chorioallantoic membranes and tumor-bearing mice. Cell death pathways induced after PDT treatment with ZnPcs are discussed in each case. Finally, combined therapeutic strategies including ZnPcs and the currently available clinical trials are mentioned.

Abstract 4084: Radiation enhances efficacy of TEM1-specific cancer vaccination

Abstract Tumor endothelial marker 1 (TEM1 or CD248) is a protein found in both tumor vasculature and stroma. In prior experiments, we showed that immunizing with Tem1-TT plasmid-DNA (Tem1 cDNA fused to the minimal domain of the C fragment of tetanus toxoid) was effective in controlling tumor progression in three mouse tumor models in a T cell-dependent manner. Moreover, effective Tem1-TT vaccination reduced tumor vascularity without impacting normal angiogenesis. Radiation therapy (RT) is an established curative and palliative cancer treatment regimen which uses high-energy radiation to kill cancer cells. RT modulates the tumor microenvironment - by increasing MHC-I expression, inducing immunological cell death, and damaging the tumor-associated vasculature - potentially synergizing with anti-cancer immunotherapies. Here, we combined RT and Tem1-TT heterologous vaccination and showed that combination of the two therapies was more effective in controlling CT26 and TC1 tumor progression than either single therapy alone. Interestingly adding RT to Tem1-TT vaccine resulted in a stronger vaccine-specific immune response and increased epitope spreading toward gp70, a TAA expressed by CT26 tumor cell line. Further analysis of the tumor microenvironment revealed a significant increment of PD-L1 expression in both tumor cells and tumor vasculature after single or either combination therapy. This led us to test whether blocking the PD1/PD-L1 axe would further improve the efficacy of RT plus Tem1-TT therapy. Our results demonstrate that administration of anti-PD-L1 antibody further synergized with RT plus Tem1-TT and improved mice survival. In conclusion, triple combination of Tem1-TT vaccine, RT and anti-PD-L1 can offer a therapeutic advantage for TEM1-positive tumors which also express PD-L1. Citation Format: Stefano Pierini, Mireia Uribe-Herranz, Renzo Perales-Linares, Silvia Beghi, Francesca Costabile, Sergei Pustylnikov, Andrea Facciabene. Radiation enhances efficacy of TEM1-specific cancer vaccination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4084.

Expression of Prostate-Specific Membrane Antigen in Tumor-Associated Vasculature Predicts Poor Prognosis in Hepatocellular Carcinoma.

INTRODUCTION:Prostate-specific membrane antigen (PSMA) was originally found to be specifically expressed in normal prostate, and its expression was upregulated in almost all stages of prostate cancer. In recent years, PSMA was also found to be expressed in tumor-associated vasculature in many nonprostatic solid tumors. However, the expression pattern of PSMA in hepatocellular carcinoma (HCC) is not well studied.METHODS:In this study, we examined PSMA expression in 103 HCC tissues using immunohistochemical staining and analyzed the association between PSMA expression and other clinicopathological features and prognosis.RESULTS:Among the 103 cases, 27 cases (26%) showed PSMA expression in more than 50% of tumor-associated vasculature, 49 cases (48%) showed PSMA expression in less than 50% of vasculature, and 27 cases (26%) did not have detectable PSMA expression. Vascular PSMA expression was associated with several clinicopathological features, such as tumor stage, tumor differentiation, lymph node metastasis, and Ki-67 index. Furthermore, high vascular PSMA expression was also associated with poor prognosis in patients with HCC. Univariate and multivariate analyses showed that high vascular PSMA expression can be used as an independent prognostic marker for HCC.DISCUSSION:Our study provides the evidence that PSMA is specifically expressed in tumor-associated vasculature of HCC, and vascular PSMA expression may be used as a novel prognostic marker and a vascular therapeutic target for HCC.

18F] Fluciclatide PET as a biomarker of clinical response to combination therapy of pazopanib and paclitaxel in patients with platinum-resistant or platinum-refractory advanced ovarian cancer: Results of a phase Ib study.

3070 Background: Angiogenesis has been shown to be a driver of platinum resistance in ovarian cancer. We assessed the effect of combination pazopanib and paclitaxel followed by maintenance pazopanib in patients with platinum resistant/refractory ovarian cancer. Integrins αvβ3 and αvβ5 are both up-regulated in tumour-associated vasculature. [18F]Fluciclatide is a novel PET tracer that has high affinity for integrins αvβ3/5, and was used to assess the anti-angiogenic effect of pazopanib. Methods: We conducted an open-label, phase Ib study in patients with platinum resistant/refractory ovarian cancer. Patients received 1 week of single agent pazopanib (800mg daily) followed by combination therapy with weekly paclitaxel 80mg/m2. Following completion of 18 weeks of therapy, patients continued with single agent pazopanib until disease progression. Dynamic [18F]Fluciclatide-PET imaging was conducted at baseline and after 1 week of pazopanib. Response (RECIST 1.1), toxicities and survival outcomes were recorded. Circulating markers of angiogenesis were assessed with therapy. Results: Fourteen patients were included in the intention-to-treat analysis. Complete and partial response was seen in 7 patients (54%). Median progression free survival (PFS) was 7.97 months, and overall survival (OS) was 18.5 months. A reduction in [18F]fluciclatide uptake was observed following 1 week of pazopanib, and the reduction in uptake was predictive of long PFS. Elevated baseline circulating angiopoietin and FGF were predictive of greater reduction in SUV60,mean following pazopanib. Kinetic modelling indicated a reduction in K1 and Ki following pazopanib indicating reduced radiotracer delivery and retention. Conclusions: Combination therapy followed by maintenance pazopanib is effective and tolerable in patients with platinum resistant/refractory ovarian cancer. We have shown that [18F]fluciclatide-PET uptake parameters alter with pazopanib therapy indicating an anti-angiogenic response. Clinical trial information: NCT01608009.