Abnormal Vasculature Research Articles

Systemic Delivery of a STING Agonist-Loaded Positively Charged Liposome Selectively Targets Tumor Immune Microenvironment and Suppresses Tumor Angiogenesis.

Although stimulator of interferon genes (STING) agonists has shown great promise in preclinical studies, the clinical development of STING agonist therapy is challenged by its limited systemic delivery. Here, positively charged fusogenic liposomes loaded with a STING agonist (PoSTING) are designed for systemic delivery and to preferentially target the tumor microenvironment. When PoSTING is administered intravenously, it selectively targets not only tumor cells but also immune and tumor endothelial cells (ECs). In particular, delivery of STING agonists to tumor ECs normalizes abnormal tumor vasculatures, induces intratumoral STING activation, and elicits robust anti-tumor T cell immunity within the tumor microenvironment. Therefore, PoSTING can be used as a systemic delivery platform to overcome the limitations of using STING agonists in clinical trials.

Biodegradable NIR-II Pseudo Conjugate Polymeric Nanoparticles Amplify Photodynamic Immunotherapy via Alleviation of Tumor Hypoxia and Tumor-Associated Macrophage Reprogramming.

Photodynamic therapy (PDT) has achieved great success in cancer treatment. Despite its great promise, the efficacy of photodynamic immunotherapy can be limited by the hypoxia in solid tumors which is closely related to the abnormal tumor vasculature. These abnormal vasculatures are a hallmark of most solid tumors and facilitate immune evasion. Therefore, tumor vascular normalization is developed as a promising strategy to overcome tumor hypoxia, resulting in improved cancer therapy. Here, a NIR-II bio-degradable pseudo-conjugate polymer (PSP)-based photodynamic polymer is designed to deliver a vascular normalization agent, i.e., regorafenib (Reg) in nanoparticles (NP-PDT@Reg). NP-PDT@Reg under 808nm laser irradiation (NP-PDT@Reg + L) can efficiently release Reg to improve the tumor hypoxia via vascular normalization, making more NP-PDT@Reg and oxygen enter the tumors. Moreover, NP-PDT@Reg + L can further result in generation of more reactive oxygen species (ROS) to eradicate tumor cells while inducing immunogenic cell death (ICD) to activate anti-tumor immune responses. In addition, Reg can reprogram TAM from a pro-tumor M2 phenotype to a tumor-killing M1 phenotype as well, thereby reversing the immunosuppressive tumor microenvironment. Taken together, the current study provides an innovative perspective on the development of novel nanomaterials to overcome the limitations in photodynamic immunotherapy.

Genicular Artery Embolisation in Patients with Osteoarthritis of the Knee (GENESIS 2): Protocol for a Double-Blind Randomised Sham-Controlled Trial

Knee osteoarthritis is a leading cause of chronic disability and economic burden. In many patients who are not surgical candidates, existing treatment options are insufficient. Clinical evidence for a new treatment approach, genicular artery embolisation (GAE), is currently limited to single arm cohort, or small population randomised studies. This trial will investigate the use of a permanent embolic agent for embolisation of abnormal genicular arterial vasculature to reduce pain in patients with mild to moderate knee osteoarthritis. Up to 110 participants, 45 years or older, with knee pain for ≥ 3 months resistant to conservative treatment will be randomised (1:1) to GAE or a sham procedure. The treatment group will receive embolisation using 100-micron Embozene™ microspheres (Varian, a Siemens Healthineers Company) (investigational use for this indication in the UK), and the sham group will receive 0.9% saline in an otherwise identical procedure. Patients will be followed for 24 months. At 6 months, sham participants will be offered crossover to GAE. The primary endpoint is change of 4 Knee Injury and OA Outcome Score subscales (KOOS4) at 6 months post-randomisation. The study will also evaluate quality of life, health economics, imaging findings, and psychosocial pain outcomes. The primary manuscript will be submitted for publication after all participants complete 6 months of follow-up. The trial is expected to run for 3.5 years. Trial Registration: ClinicalTrials.gov, Identifier: NCT05423587.

Microbubbles-assisted ultrasonication to promote tumor accumulation of therapeutics and modulation of tumor microenvironment for enhanced cancer treatments

Abnormal tumor vasculature is reported to severely hinder the therapeutic potency of diverse cancer therapeutics by restricting their intratumoral accumulation and/or causing therapeutic resistance. Herein, a microbubble-assisted ultrasonication technology (MAUT) of systemic administration of octafluoropropane-filled microbubbles together with tumor localized ultrasound (US) exposure is developed to generally promote intratumoral accumulation efficacy of three kinds of anti-tumor drugs with varying sizes through the cavitation effect-induced disruption of tumor blood vessels. MAUT was further shown to enable selective tumor hypoxia attenuation by filling microbubbles with high-purity oxygen and thus reducing the production of immunosuppressive lactic acids by suppressing glycolysis in cancer cells. Resultantly, MAUT markedly enhanced the therapeutic outcome of systemically administered anti-programmed death-1 (anti-PD-1) and chemotherapeutic doxorubicin (DOX) with and without using nanoscale liposomes as delivery vehicles. This work highlights that MAUT is a biocompatible yet versatile strategy to effectively reinforce the therapeutic potency of a broad range of cancer therapeutics, promising for future clinical usage.

Everolimus combined with PD-1 blockade inhibits progression of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer. Due to rapid progression and a lack of targetable receptors, TNBC is exceptionally difficult to treat. Available treatment options are nonspecific cytotoxic agents, which have had modest success; thus, there is a need for novel therapies for TNBC. The mammalian/mechanistic target of rapamycin (mTOR) signaling pathway is aberrantly activated in TNBC, and this pathway has been shown to promote cancer cell survival and chemoresistance. As such, mTOR inhibition has been considered a potential therapeutic strategy for TNBC. The mTOR inhibitor everolimus (EVE) has been approved for the treatment of estrogen positive breast cancer; however, its efficacy in TNBC is still undetermined. In this study, we evaluated the effects of EVE monotherapy and the mechanism of EVE resistance in the 4T1 model of TNBC. Whereas EVE monotherapy inhibited mTOR signaling activity, it did not attenuate tumor progression. Additionally, tumors from EVE-treated mice had abnormal vasculature characterized by disorganized architecture and hyperpermeability. We also found that treatment with EVE increased PD-L1 expression in intratumoral vascular endothelial cells, and this increase in endothelial cell-associated PD-L1 corresponded to reduced CD8 + T cell tumor infiltration. Importantly, combination treatment with anti-PD-1 antibody and EVE normalized the tumor vasculature, rescued CD8 + T cell tumor infiltration, and reduced tumor growth. Taken together, our findings improve our current understanding of mechanisms underlying mTOR inhibition resistance in TNBC and identify a novel combination treatment strategy in the treatment of mTOR resistant tumors.

Delayed fatal intracranial hemorrhage in a pediatric patient following resection and adjuvant cranial radiotherapy for ependymoma: illustrative case.

Cranial radiotherapy (CRT) is an important treatment modality for malignancies of the central nervous system. CRT has deleterious effects that are commonly classified into acute, early delayed, and late delayed. Late-delayed effects include weakening of the cerebral vasculature and the development of structurally abnormal vasculature, potentially leading to ischemic or hemorrhagic events within the brain parenchyma. Such events are not well reported in the pediatric population. The authors present the case of a 14-year-old patient 8.2 years after CRT who experienced intracerebral hemorrhage. Autopsy demonstrated minimal pathological change without evidence of vascular malformation or aneurysm. These findings were unexpected given the degree of hemorrhage in this case. However, in the absence of other etiologies, it was believed that late-delayed radiation effect was the cause of this patient's fatal hemorrhage. Although not all cases of pediatric spontaneous intracerebral hemorrhage will have a determined etiology, the authors' patient's previous CRT may represent a poorly defined risk for late-delayed hemorrhage. This correlation has not been previously reported and should be considered in pediatric patients presenting with spontaneous hemorrhage in a delayed fashion after CRT. Neurosurgeons must not be dismissive of unexpected events in the remote postoperative period.

Optical Coherence Tomography Angiography in Retinal Vascular Disorders.

Traditionally, abnormalities of the retinal vasculature and perfusion in retinal vascular disorders, such as diabetic retinopathy and retinal vascular occlusions, have been visualized with dye-based fluorescein angiography (FA). Optical coherence tomography angiography (OCTA) is a newer, alternative modality for imaging the retinal vasculature, which has some advantages over FA, such as its dye-free, non-invasive nature, and depth resolution. The depth resolution of OCTA allows for characterization of the retinal microvasculature in distinct anatomic layers, and commercial OCTA platforms also provide automated quantitative vascular and perfusion metrics. Quantitative and qualitative OCTA analysis in various retinal vascular disorders has facilitated the detection of pre-clinical vascular changes, greater understanding of known clinical signs, and the development of imaging biomarkers to prognosticate and guide treatment. With further technological improvements, such as a greater field of view and better image quality processing algorithms, it is likely that OCTA will play an integral role in the study and management of retinal vascular disorders. Artificial intelligence methods-in particular, deep learning-show promise in refining the insights to be gained from the use of OCTA in retinal vascular disorders. This review aims to summarize the current literature on this imaging modality in relation to common retinal vascular disorders.

Programmed cell death 10 increased blood-brain barrier permeability through HMGB1/TLR4 mediated downregulation of endothelial ZO-1 in glioblastoma

Dysfunction of blood brain barrier (BBB) contributes to the development of peritumoral edema (PTE) and GBM progression. Programmed cell death 10 (PDCD10) exerts various influence on cancers, especially in glioblastoma (GBM). We previously found that PDCD10 expression was positively correlated with PTE extent in GBM. Thus, the present study aims to investigate the emerging role of PDCD10 in regulating BBB permeability in GBM. Here we found that in vitro indirect co-culture of endothelial cells (ECs) with Pdcd10-overexpressed GL261 cells resulted in a significant increase of FITC-Dextran (MW, 4000) leakage by reducing endothelial zonula occluden-1 (ZO-1) and Claudin-5 expression in ECs respectively. Overexpression of Pdcd10 in GBM cells (GL261) triggered an increase of soluble high mobility group box 1 (HMGB1) release, which in turn activated endothelial toll like receptor 4 (TLR4) and downstream NF-κB, Erk1/2 and Akt signaling in ECs through a paracrine manner. Moreover, Pdcd10-overexpressed GL261 cells facilitated a formation of abnormal vasculature and increased the BBB permeability in vivo. Our present study demonstrates that upregulation of PDCD10 in GBM triggered HMGB1/TLR4 signaling in ECs and significantly decreased endothelial ZO-1 expression, which in turn dominantly increased BBB permeability and contributed to tumor progression in GBM.

Nanomaterial-Based Antivascular Therapy in the Multimodal Treatment of Cancer.

Abnormal tumor vasculature and a hypoxic tumor microenvironment (TME) limit the effectiveness of conventional cancer treatment. Recent studies have shown that antivascular strategies that focus on antagonizing the hypoxic TME and promoting vessel normalization effectively synergize to increase the antitumor efficacy of conventional therapeutic regimens. By integrating multiple therapeutic agents, well-designed nanomaterials exhibit great advantages in achieving higher drug delivery efficiency and can be used as multimodal therapy with reduced systemic toxicity. In this review, strategies for the nanomaterial-based administration of antivascular therapy combined with other common tumor treatments, including immunotherapy, chemotherapy, phototherapy, radiotherapy, and interventional therapy, are summarized. In particular, the administration of intravascular therapy and other therapies with the use of versatile nanodrugs is also described. This review provides a reference for the development of multifunctional nanotheranostic platforms for effective antivascular therapy in combined anticancer treatments.

Abstract 4802: Identification of critical hypoxia induced factors in castrate resistant prostate cancer

Abstract Background: Prostate cancer (PCa) is the second most diagnosed cancer in men and the second cause of cancer-related death amongst men worldwide. PCa is a heterogeneous disease, and the outcome is worse for patients when the disease progresses from localized PCa to a castrate-resistant disease. Androgen receptor (AR) signaling is crucial for PCa development and has been a major therapeutic target for decades. Despite the success made with hormone therapy to block AR signaling, castration resistant disease can arise through mutations and amplifications of the androgen receptor (AR) and AR splice variants (AR-Vs). Amongst them, AR-V7 and AR-V12 can promote AR signaling independent of androgen. Furthermore, prostate tumors are highly hypoxic due to abnormal tumor vasculature. Hypoxia influences the efficacy of local and systemic treatment strategies, such as radiotherapy, hormone therapy, and chemotherapy, resulting in poorer clinical outcomes for PCa patients. Therefore, a complete understanding of AR and AR variant function, as well as how they are modulated by hypoxia and therapy is warranted for developing new strategies to treat PCa. Methods: To identify the transcriptional apparatus associated with the AR and its variants under normal and hypoxic conditions, we carried out Bio-ID proximity labeling mass spectrometry (BioID-MS). We generated stable androgen-independent human prostate cancer cell lines, PC-3 and DU145, expressing AR and the AR-V7 and AR-V12 variants fused to a MiniTurboID (MTID) enzyme. To delineate the AR proximal interaction network, we treated cells with androgen or vehicle for 3 hours and affinity-purified biotinylated proteins after the addition of biotin for the final 2 hours. Cells were grown in normoxia (20% O2) or treated with hypoxia (95% N2,5% CO2 and 0.5% O2) for 24 h. Nonspecific interactions were filtered using controls and statistical methods to identify high-confidence interactomes. Results: BioID proximity labeling in PC3 cells identified several AR-associated proteins, including many knowninteractors, validating the approach. Hypoxic conditions led to a striking alteration in proximal interactions and many metabolic proteins were highly enriched with AR upon exposure of cells to hypoxia for 24h. Among these, phosphoglycerate kinase 1 (PGK1) was a top hit. PGK1 has been reported to interact with AR to mediate the expression of genes that regulates cell proliferation and apoptosis. Additionally, PGK1 has an essential role in metabolic reprogramming induced by c-MYC and HIF-1α, leading to enhanced tumorigenesis. Conclusion: Bio-ID mass spectrometry was used to map the proximal interactome of AR and its variants, identifying novel interactions partners for further analysis. We found that hypoxia strongly alters interactors with the AR, and we identified PGK1 as a hypoxia induced AR interaction in PCA. Current work to functionally validate this interaction will be presented. Citation Format: Oloruntoba I. Osagie, Jordann Smakk, Deborah E. Citrin, Travis H. Stracker. Identification of critical hypoxia induced factors in castrate resistant prostate cancer. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4802.

Abstract 2002: Intravenously administered STING agonist-loaded positively charged liposomes selectively target tumor microenvironments and reprogram tumor vasculature

Abstract Introduction: The stimulator of interferon genes (STING) signaling pathway activates type I interferon (IFN) in antigen-presenting cells to promote T cell priming and activation. STING agonists have shown great potential in preclinical studies, but they are not applicable for most patients due to limited systemic delivery. Therefore, we designed a positively charged liposome loaded with STING agonist (PoSTING) for systemic delivery of STING agonists and to selectively target tumor immunity and tumor vasculature. Method: We designed PoSTING using 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 18:0 PEG2000 PE (PEG-PE), and 1,2-Dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). The properties and stability of PoSTING were evaluated by dynamic light scattering, transmission electron microscopy, and high-performance liquid chromatography. PoSTING (1 mg/kg) was administered intravenously to Lewis lung carcinoma (LLC)-bearing mouse models every three days. Tumor tissues were comprehensively analyzed by histologic, flow cytometric, and Nanostring immune profiling assays. Results: PoSTING efficiently loaded 88.5% of STING agonists. The average particle size was 198.4 nm, which avoided clearance by the mononuclear phagocyte system. PoSTING could fuse with cell membrane of target cells due to a positive surface charge (+44.53 mV). Stability tests found that PoSTING could be stored at 4°C for 12 weeks and remained stable in serum for a week. Intravenously administered PoSTING selectively accumulated in LLC tumor tissues and suppressed tumor growth. In particular, PoSTING was preferentially accumulated in tumor endothelial cells and perivascular cells, and suppressed tumor angiogenesis and normalized abnormal tumor vasculatures. PoSTING also increased expression levels of P-selectin, which is involved in endothelial-lymphocyte interactions and prepares tumor vessels for lymphocyte trafficking. PoSTING induces type I IFN responses in antigen-presenting cells, tumor ECs, and cancer cells, and promotes intratumoral infiltration of CD8+ T cells by remodeling tumor microenvironment. In addition, PoSTING significantly upregulated genes related to type I/II IFNs, Th1/Th2 responses, innate/adaptive immunity, and chemokines. Conclusion: PoSTING is a novel and stable systemic delivery platform that effectively and selectively delivers STING agonists to tumor tissue, triggering vascular normalization and immune reprogramming. Citation Format: Eun-Jin Go, Hannah Yang, Wooram Park, Won suk Lee, So Jung Kong, Seung Joon Lee, Dong Keun Han, Hong Jae Chon, Chan Kim. Intravenously administered STING agonist-loaded positively charged liposomes selectively target tumor microenvironments and reprogram tumor vasculature [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2002.

Nanoparticle-Mediated Radiotherapy Remodels the Tumor Microenvironment to Enhance Antitumor Efficacy.

Radiotherapy (RT) uses ionizing radiation to eradicate localized tumors and, in rare cases, control tumors outside of the irradiated fields via stimulating an antitumor immune response (abscopal effect). However, the therapeutic effect of RT is often limited by inherent physiological barriers of the tumor microenvironment (TME), such as hypoxia, abnormal vasculature, dense extracellular matrix (ECM), and an immunosuppressive TME. Thus, it is critical to develop new RT strategies that can remodel the TME to overcome radio-resistance and immune suppression. In the past decade, high-Z-element nanoparticles have been developed to increase radiotherapeutic indices of localized tumors by reducing X-ray doses and side effects to normal tissues and enhance abscopal effects by activating the TME to elicit systemic antitumor immunity. In this review, the principles of RT and radiosensitization, the mechanisms of radio-resistance and immune suppression, and the use of various nanoparticles to sensitize RT and remodel TMEs for enhanced antitumor efficacy are discussed. The challenges in clinical translation of multifunctional TME-remodeling nanoradiosensitizers are also highlighted.

Therapeutic targeting of vascular malformation in a zebrafish model of hereditary haemorrhagic telangiectasia.

Hereditary haemorrhagic telangiectasia (HHT) causes arteriovenous malformations (AVMs) in multiple organs to cause bleeding, neurological and other complications. HHT is caused by mutations in the BMP co-receptor endoglin. We characterised a range of vascular phenotypes in embryonic and adult endoglin mutant zebrafish and the effect of inhibiting different pathways downstream of Vegf signalling. Adult endoglin mutant zebrafish developed skin AVMs, retinal vascular abnormalities and cardiac enlargement. Embryonic endoglin mutants developed an enlarged basilar artery (similar to the previously described enlarged aorta and cardinal vein) and larger numbers of endothelial membrane cysts (kugeln) on cerebral vessels. Vegf inhibition prevented these embryonic phenotypes, leading us to investigate specific Vegf signalling pathways. Inhibiting mTOR or MEK pathways prevented abnormal trunk and cerebral vasculature phenotypes, whereas inhibiting Nos or Mapk pathways had no effect. Combined subtherapeutic mTOR and MEK inhibition prevented vascular abnormalities, confirming synergy between these pathways in HHT. These results indicate that the HHT-like phenotype in zebrafish endoglin mutants can be mitigated through modulation of Vegf signalling. Combined low-dose MEK and mTOR pathway inhibition could represent a novel therapeutic strategy in HHT.

Conservative Surgery -Bilateral Uterine Artery Ligation for Uterine Av Fistula

An important but rare differential diagnosis for abnormal uterine bleeding is Uterine Arteriovenous fistula. The bleeding in these patients is due to abnormal vasculature in uterus, where is congenital or acquired connection between the arterial and venous circulation of the uterus. Acquired AVM is seen following Endometrial damage. Symptoms can vary from menorrhagia, metrorahgia to acute severe bleeding episode. Treatment options usually offered is uterine artery embolization and in failed cases of embolization, hysterectomy. This case report describes a conservative surgical management by Laparoscopic uterine artery ligation as a treatment option for Uterine AV fistula in young women who desire to retain fertility

The process of methylglyoxal-induced retinal capillary endothelial cell degeneration in rats.

Methylglyoxal, a highly reactive dicarbonyl compound, is increased and accumulated in patients with diabetic mellitus. Methylglyoxal forms advanced glycation end products (AGE), contributing to the pathogenesis of diabetic complications, including diabetic retinopathy. Recent studies have shown that methylglyoxal induces diabetic retinopathy-like abnormalities in retinal vasculature. In this study, we investigated the processes and mechanisms of methylglyoxal-induced retinal capillary endothelial cell degeneration in rats. Morphological changes in vascular components (endothelial cells, pericytes, and basement membranes) were assessed in the retinas 2, 7, and 14days after intravitreal injection of methylglyoxal. Intravitreal methylglyoxal injection induced retinal capillary endothelial cell degeneration in a dose- and time-dependent manner. Changes in the shape and distribution of pericytes occurred before the initiation of capillary regression in the retinas of methylglyoxal-injected eyes. The receptor for AGEs (RAGEs) antagonist FPS-ZM1, and the matrix metalloproteinase (MMP) inhibitor GM6001 significantly attenuated methylglyoxal-induced capillary endothelial cell degeneration. FPS-ZM1 failed to prevent pathological changes in pericytes in methylglyoxal-injected eyes. In situ zymography revealed that MMP activity was enhanced at sites of blood vessels with reduced pericyte coverage in methylglyoxal-injected eyes. These results suggest that intravitreal methylglyoxal injection induces pathological changes in pericytes before the initiation of capillary endothelial cell degeneration via an AGE-RAGE-independent pathway. The capillary endothelial cell degeneration is mediated by activating the AGE-RAGE pathway and increasing MMP activity in endothelial cells by impairing pericyte function in the retina.

Structural abnormalities of choroid vasculature in first-episode psychosis

IntroductionThe eye is considered as a part of the central nervous system and a window of the brain. The eye and the brain, also their microvascular system, share many common features in terms of anatomy and pathophysiology. Choroid and retina related abnormalities have been reported in psychotic disorders, especially in schizophrenia. Choroidal vascularity index (CVI) is a useful tool to assess choroidal structural alterations and CVI is defined as the proportion of luminal area (LA) to the total choroidal area (TCA).ObjectivesThis is the first study to investigate choroidal vascularity index in first-episode psychosis (FEP) using optical coherence tomography (OCT).Methods31 patients with FEP and 30 age and gender-matched healthy controls (HC) included in this study. All participants underwent psychiatric and ophthalmological clinical assessments. Imaging of the choroid was performed using enhanced deep imaging (EDI) protocol - spectral domain OCT. Central choroidal thickness (CCT) with EDI-OCT was measured manually from the inner border of the sclera to the outer border of the RPE vertically using the calipers of the Heidelberg reader subfoveally. The choroidal vascularity index was assessed using the EDI-OCT images.ResultsThere were no statistically significant differences between FEP and HC in terms of CCT (p=0.33), TCA (p=0.809) and LCA (p=0.710). The CVIs were 66.66±2.98% and 62.32±3.32% in FEP and HC, respectively and it was significantly different between groups (p<0.001, effect size d=1.38).ConclusionsThese results suggest that first episode psychosis is characterized by choroidal vascular abnormalities. in vivo ophthalmological imaging with OCT, a non-invasive, fast, and safe technological tool, can be a promising biomarker to quantitatively evaluate microvasculature abnormalities in patients with psychosis.Disclosure of InterestNone Declared

Targeting tumor vasculature to improve antitumor activity of T cells armed ex vivo with T cell engaging bispecific antibody

BackgroundSuccess of T cell immunotherapy hinges on the tumor microenvironment (TME), and abnormal tumor vasculature is a hallmark of most solid tumors and associated with immune evasion. The efficacy of...

Tumor Vasculature as an Emerging Pharmacological Target to Promote Anti-Tumor Immunity

Tumor vasculature abnormality creates a microenvironment that is not suitable for anti-tumor immune response and thereby induces resistance to immunotherapy. Remodeling of dysfunctional tumor blood vessels by anti-angiogenic approaches, known as vascular normalization, reshapes the tumor microenvironment toward an immune-favorable one and improves the effectiveness of immunotherapy. The tumor vasculature serves as a potential pharmacological target with the capacity of promoting an anti-tumor immune response. In this review, the molecular mechanisms involved in tumor vascular microenvironment-modulated immune reactions are summarized. In addition, the evidence of pre-clinical and clinical studies for the combined targeting of pro-angiogenic signaling and immune checkpoint molecules with therapeutic potential are highlighted. The heterogeneity of endothelial cells in tumors that regulate tissue-specific immune responses is also discussed. The crosstalk between tumor endothelial cells and immune cells in individual tissues is postulated to have a unique molecular signature and may be considered as a potential target for the development of new immunotherapeutic approaches.

A phase Ib/II study (IMMCO-1) of atezolizumab plus tivozanib in castrate-resistant prostate cancer and certain other immunologically cold tumors.

TPS293 Background: Castrate resistant prostate cancer (CRPC) is an immunologically cold tumor, with a 5% response rate reported to the PD-L1 inhibitor pembrolizumab. VEGF secreted by tumors may play a key role in hindering the anti-tumor immune response, leading to the development of an abnormal vasculature that may limit immune surveillance. VEGF also inhibits dendritic cell differentiation, limiting the presentation of tumor antigens. The inhibition of VEGF may therefore potentiate the effect of PD-1/L1 directed therapy by enabling immune surveillance and antigen presentation. VEGF-TKI and checkpoint inhibitor combinations are currently approved in the treatment of advanced kidney, cervical, and endometrial cancers. This signal-seeking study aims to determine whether the combination of the VEGF-TKI tivozanib and the PD-L1 inhibitor atezolizumab may be effective in CRPC and certain other immunologically cold tumors. Methods: The trial is a single center phase Ib/II basket study in multiple immunologically cold tumors. Co-primary endpoints are safety and the overall response rate as measured via RECIST v1.1. The phase Ib 3+3 dose de-escalation portion of the study has been completed. The study is designed to test for a 25%+ response rate as compared to a null hypothesis of <7% (one-sided alpha = 0.05; 80% power). A Simon’s two-stage design will be utilized and if ≥2 responses among the first 16 evaluable patients, a further 10 evaluable patients will be accrued for a total of 26. Up to 33 subjects will be enrolled to account for a 20% dropout rate. The null hypothesis will be rejected if at least 5 responses are observed. The University of Florida's Data Integrity and Safety Committee will review significant adverse events. Atezolizumab is given at a dose of 1,680 mg every 28 days. A subsequent protocol amendment decreased the starting dose of tivozanib from 1.34 mg/day for 21 days of each 28-day cycle to 0.89 mg/day for 21 days of each 28-day cycle. Treatment is until disease progression or intolerance. Key inclusion criteria include a diagnosis of certain advanced and unresectable or metastatic immunologically cold tumors (CRPC previously treated with an androgen inhibitor or cytotoxic chemotherapy in the advanced or metastatic setting, bile duct or gallbladder cancer, certain HR-negative HER2-positive breast cancers, ovarian cancer, pancreatic adenocarcinoma, soft tissue sarcoma, or vulvar cancer), at least one prior systemic therapy in this setting, ECOG 0-1 (phase Ib) or ECOG 0-2 (phase II), age ≥ 18, adequate hematologic and end-organ function, life expectancy of at least 12 weeks, and measurable disease by RECIST v1.1. Key exclusion criteria include known mismatch repair deficiency, microsatellite instability, or high tumor mutational burden. Active enrollment continues. Clinical trial information: NCT05000294 .

Metformin enhances T lymphocyte anti-tumor immunity by increasing the infiltration via vessel normalization

Abnormal tumor vasculature blocks the extravasation of T lymphocytes into the tumor, thereby suppressing anti-tumor immunity. Recently, metformin has been shown to affect tumor vasculature and enhance T lymphocyte anti-tumor immunity. However, whether or how metformin affects T lymphocyte anti-tumor immunity via a vascular mechanism remains poorly understood. Herein, we show that a large number of CD8+ lymphocytes gathered in the peri-tumoral region, while very few infiltrated the tumor. Metformin administration increased the expression of anti-tumor immunity-associated genes and the number of tumor-infiltrating CD8+ lymphocytes. Injection of CD8 but not CD4 neutralization antibody into tumor-bearing mice significantly abrogated the anti-tumor effect of metformin. Critically, CD8+ lymphocytes were found to pass through the wall of perfused vessel. Further results of immunofluorescent staining showed that metformin greatly elevated tumor perfusion, which was accompanied by increased vascular maturity in the intratumoral region (ITR) but not peritumoral region (PTR). These findings provide evidence for the vascular mechanism involved in metformin-induced enhancement of T lymphocyte anti-tumor immunity. By remodeling the abnormal tumor vasculature, also called vessel normalization metformin increases vascular maturity and tumor perfusion, thus allowing more CD8+ lymphocytes to infiltrate the tumor.