Increased survival of glioblastoma patients who respond to antiangiogenic therapy with elevated blood perfusion

Biomaterials with cancer cell-specific cytotoxicity: challenges and perspectives

Significant advances have been made in materials for biomedical applications, including tissue engineering, bioimaging, cancer treatment, etc. In the past few decades, nanostructure-mediated therapeutic strategies have been developed to improve drug delivery, targeted therapy, and diagnosis, maximizing therapeutic effectiveness while reducing systemic toxicity and side effects by exploiting the complicated interactions between the materials and the cell and tissue microenvironments. This review briefly introduces the differences between the cells and tissues of tumour or normal cells. We summarize recent advances in tumour microenvironment-mediated therapeutic strategies using nanostructured materials. We then comprehensively discuss strategies for fabricating nanostructures with cancer cell-specific cytotoxicity by precisely controlling their composition, particle size, shape, structure, surface functionalization, and external energy stimulation. Finally, we present perspectives on the challenges and future opportunities of nanotechnology-based toxicity strategies in tumour therapy.

Modulating cancer mechanopathology to restore vascular function and enhance immunotherapy

Solid tumor pathology, characterized by abnormalities in the tumor microenvironment (TME), challenges therapeutic effectiveness. Mechanical factors, including increased tumor stiffness and accumulation of intratumoral forces, can determine the success of cancer treatments, defining the tumor's "mechanopathology" profile. These abnormalities cause extensive vascular compression, leading to hypoperfusion and hypoxia. Hypoperfusion hinders drug delivery, while hypoxia creates an unfavorable TME, promoting tumor progression through immunosuppression, heightened metastatic potential, drug resistance, and chaotic angiogenesis. Strategies targeting TME mechanopathology, such as vascular and stroma normalization, hold promise in enhancing cancer therapies with some already advancing to the clinic. Normalization can be achieved using anti-angiogenic agents, mechanotherapeutics, immune checkpoint inhibitors, engineered bacterial therapeutics, metronomic nanomedicine, and ultrasound sonopermeation. Here, we review the methods developed to rectify tumor mechanopathology, which have even led to cures in preclinical models, and discuss their bench-to-bedside translation, including the derivation of biomarkers from tumor mechanopathology for personalized therapy.

Antiangiogenic-immune-checkpoint inhibitor combinations: lessons from phase III clinical trials

Antiangiogenic agents, generally antibodies or tyrosine-kinase inhibitors that target the VEGF-VEGFR pathway, are currently among the few combination partners clinically proven to improve the efficacy of immune-checkpoint inhibitors (ICIs). This benefit has been demonstrated in pivotal phase III trials across different cancer types, some with practice-changing results; however, numerous phase III trials have also had negative results. The rationale for using antiangiogenic drugs as partners for ICIs relies primarily on blocking the multiple immunosuppressive effects of VEGF and inducing several different vascular-modulating effects that can stimulate immunity, such as vascular normalization leading to increased intratumoural blood perfusion and flow, and inhibition of pro-apoptotic effects of endothelial cells on T cells, among others. Conversely, VEGF blockade can also cause changes that suppress antitumour immunity, such as increased tumour hypoxia, and reduced intratumoural ingress of co-administered ICIs. As a result, the net clinical benefits from antiangiogenic-ICI combinations will be determined by the balance between the opposing effects of VEGF signalling and its inhibition on the antitumour immune response. In this Perspective, we summarize the results from the currently completed phase III trials evaluating antiangiogenic agent-ICI combinations. We also discuss strategies to improve the efficacy of these combinations, focusing on aspects that include the deleterious functions of VEGF-VEGFR inhibition on antitumour immunity, vessel co-option as a driver of non-angiogenic tumour growth, clinical trial design, or the rationale for drug selection, dosing and scheduling.

Unlocking Hope: Anti-VEGFR inhibitors and their potential in glioblastoma treatment

PURPOSE

This systematic review summarizes evidence of VEGFR gene mutations and VEGF/VEGFR protein expression in glioblastoma multiforme (GBM) patients, alongside the efficacy and safety of anti-VEGFR tyrosine kinase inhibitors (TKIs) for GBM treatment.

METHODS

A comprehensive literature review was conducted using PubMed up to August 2023. Boolean operators and MeSH term "glioma," along with specific VEGFR-related keywords, were utilized following thorough examination of existing literature.

RESULTS

VEGFR correlates with glioma grade and GBM progression, presenting a viable therapeutic target. Regorafenib and axitinib show promise among studied TKIs. Other multi-targeted TKIs (MTKI) and combination therapies exhibit potential, albeit limited by blood-brain barrier penetration and toxicity. Combining treatments like radiotherapy and enhancing BBB penetration may benefit patients. Further research is warranted in patient quality of life and biomarker-guided selection.

CONCLUSION

While certain therapies hold promise for GBM, future research should prioritize personalized medicine and innovative strategies for improved treatment outcomes.

Machine learning analysis reveals tumor stiffness and hypoperfusion as biomarkers predictive of cancer treatment efficacy

In the pursuit of advancing cancer therapy, this study explores the predictive power of machine learning in analyzing tumor characteristics, specifically focusing on the effects of tumor stiffness and perfusion (i.e., blood flow) on treatment efficacy. Recent advancements in oncology have highlighted the significance of these physiological properties of the tumor microenvironment in determining treatment outcomes. We delve into the relationship between these tumor attributes and the effectiveness of cancer therapies in preclinical tumor models. Utilizing robust statistical methods and machine learning algorithms, our research analyzes data from 1365 cases of various cancer types, assessing how tumor stiffness and perfusion influence the efficacy of treatment protocols. We also investigate the synergistic potential of combining drugs that modulate tumor stiffness and perfusion with standard cytotoxic treatments. By incorporating these predictors into treatment planning, our study aims to enhance the precision of cancer therapy, tailoring treatment to individual tumor profiles. Our findings demonstrate a significant correlation between stiffness/perfusion and treatment efficacy, highlighting a new way for personalized cancer treatment strategies.

An Anti-VEGF-B Antibody Reduces Abnormal Tumor Vasculature and Enhances the Effects of Chemotherapy

The vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are key regulators of blood vessel formation, including in tumors, where their deregulated function can promote the production of aberrant, leaky blood vessels, supporting tumor development. Here we investigated the VEGFR1 ligand VEGF-B, which we demonstrate to be expressed in tumor cells and in tumor stroma and vasculature across a range of tumor types. We examined the anti-VEGF-B-specific monoclonal antibody 2H10 in preclinical xenograft models of breast and colorectal cancer, in comparison with the anti-VEGF-A antibody bevacizumab. Similar to bevacizumab, 2H10 therapy was associated with changes in tumor blood vessels and intra-tumoral diffusion consistent with normalization of the tumor vasculature. Accordingly, treatment resulted in partial inhibition of tumor growth, and significantly improved the response to chemotherapy. Our studies indicate the importance of VEGF-B in tumor growth, and the potential of specific anti-VEGF-B treatment to inhibit tumor development, alone or in combination with established chemotherapies.

Abnormal vascular structure and function within brain metastases is linked to pembrolizumab resistance

BACKGROUND

We recently conducted a phase 2 trial (NCT028865685) evaluating intracranial efficacy of pembrolizumab for brain metastases (BM) of diverse histologies. Our study met its primary efficacy endpoint and illustrates that pembrolizumab exerts promising activity in a select group of patients with BM. Given the importance of aberrant vasculature in mediating immunosuppression, we explored the relationship between immune checkpoint inhibitor (ICI) efficacy and vascular architecture in the hopes of identifying potential mechanisms of intracranial ICI response or resistance for BM.

METHODS

Using Vessel Architectural Imaging, a histologically validated quantitative metric for in vivo tumor vascular physiology, we analyzed dual-echo DSC/DCE MRI for 44 patients on trial. Tumor and peri-tumor cerebral blood volume/flow, vessel size, arterial and venous dominance, and vascular permeability were measured before and after treatment with pembrolizumab.

RESULTS

BM that progressed on ICI were characterized by a highly aberrant vasculature dominated by large-caliber vessels. In contrast, ICI-responsive BM possessed a more structurally balanced vasculature consisting of both small and large vessels, and there was a trend toward a decrease in under-perfused tissue, suggesting a reversal of the negative effects of hypoxia. In the peri-tumor region, the development of smaller blood vessels, consistent with neo-angiogenesis, was associated with tumor growth before radiographic evidence of contrast enhancement on anatomical MRI.

CONCLUSIONS

This study, one of the largest functional imaging studies for BM, suggests that vascular architecture is linked with ICI efficacy. Studies identifying modulators of vascular architecture, and effects on immune activity, are warranted and may inform future combination treatments.

Enhancement of Tumor Perfusion and Antiangiogenic Therapy in Murine Models of Clear Cell Renal Cell Carcinoma Using Ultrasound-Stimulated Microbubbles

OBJECTIVE

To explore the effect of ultrasound-stimulated microbubble cavitation (USMC) on enhancing antiangiogenic therapy in clear cell renal cell carcinoma.

MATERIALS AND METHODS

We explored the effects of USMC with different mechanical indices (MIs) on tumor perfusion, 36 786-O tumor-bearing nude mice were randomly assigned into four groups: (i) control group, (ii) USMC0.25 group (MI = 0.25), (iii) USMC1.4 group (MI = 1.4) (iv) US1.4 group (MI = 1.4). Tumor perfusion was assessed by contrast-enhanced ultrasound (CEUS) before the USMC treatment and 30 min, 4h and 6h after the USMC treatment, respectively. Then we evaluated vascular normalization(VN) induced by low-MI (0.25) USMC treatment, 12 tumor-bearing nude mice were randomly divided into two groups: (i) control group (ii) USMC0.25 group. USMC treatment was performed, and tumor microvascular imaging and blood perfusion were analyzed by MicroFlow imaging (MFI) and CEUS 30 min after each treatment. In combination therapy, a total of 144 tumor-bearing nude mice were randomly assigned to six groups (n = 24): (i) control group, (ii) USMC1.4 group, (iii) USMC0.25 group, (iv) bevacizumab(BEV) group, (v) USMC1.4 +BEV group, (vi) USMC0.25 +BEV group. BEV was injected on the 6th, 10th, 14th, and 18th d after the tumors were inoculated, while USMC treatment was performed 24 h before and after every BEV administration. We examined the effects of the combination therapy through a series of experiments.

RESULTS

Tumor blood perfusion enhanced by USMC with low MI (0.25)could last for more than 6h, inducing tumor VN and promoting drug delivery. Compared with other groups, USMC0.25+BEV combination therapy had the strongest inhibition on tumor growth, led to the longest survival time of the mice.

CONCLUSION

The optimized USMC is a promising therapeutic approach that can be combined with antiangiogenic therapy to combat tumor progression.

Endothelial cells in tumor microenvironment: insights and perspectives

The tumor microenvironment is a highly complex and dynamic mixture of cell types, including tumor, immune and endothelial cells (ECs), soluble factors (cytokines, chemokines, and growth factors), blood vessels and extracellular matrix. Within this complex network, ECs are not only relevant for controlling blood fluidity and permeability, and orchestrating tumor angiogenesis but also for regulating the antitumor immune response. Lining the luminal side of vessels, ECs check the passage of molecules into the tumor compartment, regulate cellular transmigration, and interact with both circulating pathogens and innate and adaptive immune cells. Thus, they represent a first-line defense system that participates in immune responses. Tumor-associated ECs are involved in T cell priming, activation, and proliferation by acting as semi-professional antigen presenting cells. Thus, targeting ECs may assist in improving antitumor immune cell functions. Moreover, tumor-associated ECs contribute to the development at the tumor site of tertiary lymphoid structures, which have recently been associated with enhanced response to immune checkpoint inhibitors (ICI). When compared to normal ECs, tumor-associated ECs are abnormal in terms of phenotype, genetic expression profile, and functions. They are characterized by high proliferative potential and the ability to activate immunosuppressive mechanisms that support tumor progression and metastatic dissemination. A complete phenotypic and functional characterization of tumor-associated ECs could be helpful to clarify their complex role within the tumor microenvironment and to identify EC specific drug targets to improve cancer therapy. The emerging therapeutic strategies based on the combination of anti-angiogenic treatments with immunotherapy strategies, including ICI, CAR T cells and bispecific antibodies aim to impact both ECs and immune cells to block angiogenesis and at the same time to increase recruitment and activation of effector cells within the tumor.

Tumor-derived lactate promotes resistance to bevacizumab treatment by facilitating autophagy enhancer protein RUBCNL expression through histone H3 lysine 18 lactylation (H3K18la) in colorectal cancer

Bevacizumab plays an important role in the first and second line treatment for metastatic colorectal cancer (CRC). And induction of hypoxia and the tumors response to it plays an important role in determining the efficacy of antiangiogenic therapy while the connection between them remains unclear. Here, we found that lactate accumulated in the tumor environment of CRC and acted as substrates for histone lactylation, and this process was further induced by cellular enhanced glycolysis in hypoxia. We determined that CRC patients resistant to bevacizumab treatment presented with elevated levels of histone lactylation and inhibition of histone lactylation efficiently suppressed CRC tumorigenesis, progression and survival in hypoxia. Histone lactylation promoted the transcription of RUBCNL/Pacer, facilitating autophagosome maturation through interacting with BECN1 (beclin 1) and mediating the recruitment and function of the class III phosphatidylinositol 3-kinase complex, which had a crucial role in hypoxic cancer cells proliferation and survival. Moreover, combining inhibition of histone lactylation and macroautophagy/autophagy with bevacizumab treatment demonstrated remarkable treatment efficacy in bevacizumab-resistance patients-derived pre-clinical models. These findings delivered a new exploration and important supplement of metabolic reprogramming-epigenetic regulation, and provided a new strategy for improving clinical efficacy of bevacizumab in CRC by inhibition of histone lactylation.Abbreviations: 2-DG: 2-deoxy-D-glucose; BECN1: beclin 1; CQ: chloroquine; CRC: colorectal cancer; DMOG: dimethyloxalylglycine; H3K18la: histone H3 lysine 18 lactylation; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; Nala: sodium lactate; PDO: patient-derived orgnoid; PDX: patient-derived xenograft; RUBCNL/Pacer: rubicon like autophagy enhancer; SQSTM1/p62: sequestosome 1.

MRI Assessment of Changes in Tumor Vascularization during Neoadjuvant Anti-Angiogenic Treatment in Locally Advanced Breast Cancer Patients

Anti-VEGF (vascular endothelial growth factor) treatment improves response rates, but not progression-free or overall survival in advanced breast cancer. It has been suggested that subgroups of patients may benefit from this treatment; however, the effects of adding anti-VEGF treatment to a standard chemotherapy regimen in breast cancer patients are not well studied. Understanding the effects of the anti-vascular treatment on tumor vasculature may provide a selection of patients that can benefit. The aim of this study was to study the vascular effect of bevacizumab using clinical dynamic contrast-enhanced MRI (DCE-MRI). A total of 70 women were randomized to receive either chemotherapy alone or chemotherapy with bevacizumab for 25 weeks. DCE-MRI was performed at baseline and at 12 and 25 weeks, and in addition 25 of 70 patients agreed to participate in an early MRI after one week. Voxel-wise pharmacokinetic analysis was performed using semi-quantitative methods and the extended Tofts model. Vascular architecture was assessed by calculating the fractal dimension of the contrast-enhanced images. Changes during treatment were compared with baseline and between the treatment groups. There was no significant difference in tumor volume at any point; however, DCE-MRI parameters revealed differences in vascular function and vessel architecture. Adding bevacizumab to chemotherapy led to a pronounced reduction in vascular DCE-MRI parameters, indicating decreased vascularity. At 12 and 25 weeks, the difference between the treatment groups is severely reduced.

Structural and functional vascular dysfunction within brain metastases is linked to pembrolizumab inefficacy

Structurally and functionally aberrant vasculature is a hallmark of tumor angiogenesis and treatment resistance. Given the synergistic link between aberrant tumor vasculature and immunosuppression, we analyzed perfusion MRI for 44 patients with brain metastases (BM) undergoing treatment with pembrolizumab. To date, vascular-immune communication, or the relationship between immune checkpoint inhibitor (ICI) efficacy and vascular architecture, has not been well-characterized in human imaging studies. We found that ICI-responsive BM possessed a structurally balanced vascular makeup, which was linked to improved vascular efficiency and an immune-stimulatory microenvironment. In contrast, ICI-resistant BM were characterized by a lack of immune cell infiltration and a highly aberrant vasculature dominated by large-caliber vessels. Peri-tumor region analysis revealed early functional changes predictive of ICI resistance before radiographic evidence on conventional MRI. This study was one of the largest functional imaging studies for BM and establishes a foundation for functional studies that illuminate the mechanisms linking patterns of vascular architecture with immunosuppression, as targeting these aspects of cancer biology may serve as the basis for future combination treatments.

Assessment and prediction of glioblastoma therapy response: challenges and opportunities

Glioblastoma is the most aggressive type of primary adult brain tumour. The median survival of patients with glioblastoma remains approximately 15 months, and the 5-year survival rate is <10%. Current treatment options are limited, and the standard of care has remained relatively constant since 2011. Over the last decade, a range of different treatment regimens have been investigated with very limited success. Tumour recurrence is almost inevitable with the current treatment strategies, as glioblastoma tumours are highly heterogeneous and invasive. Additionally, another challenging issue facing patients with glioblastoma is how to distinguish between tumour progression and treatment effects, especially when relying on routine diagnostic imaging techniques in the clinic. The specificity of routine imaging for identifying tumour progression early or in a timely manner is poor due to the appearance similarity of post-treatment effects. Here, we concisely describe the current status and challenges in the assessment and early prediction of therapy response and the early detection of tumour progression or recurrence. We also summarize and discuss studies of advanced approaches such as quantitative imaging, liquid biomarker discovery and machine intelligence that hold exceptional potential to aid in the therapy monitoring of this malignancy and early prediction of therapy response, which may decisively transform the conventional detection methods in the era of precision medicine.

Signaling pathways in brain tumors and therapeutic interventions

Brain tumors, although rare, contribute to distinct mortality and morbidity at all ages. Although there are few therapeutic options for brain tumors, enhanced biological understanding and unexampled innovations in targeted therapies and immunotherapies have considerably improved patients' prognoses. Nonetheless, the reduced response rates and unavoidable drug resistance of currently available treatment approaches have become a barrier to further improvement in brain tumor (glioma, meningioma, CNS germ cell tumors, and CNS lymphoma) treatment. Previous literature data revealed that several different signaling pathways are dysregulated in brain tumor. Importantly, a better understanding of targeting signaling pathways that influences malignant behavior of brain tumor cells might open the way for the development of novel targeted therapies. Thus, there is an urgent need for a more comprehensive understanding of the pathogenesis of these brain tumors, which might result in greater progress in therapeutic approaches. This paper began with a brief description of the epidemiology, incidence, risk factors, as well as survival of brain tumors. Next, the major signaling pathways underlying these brain tumors' pathogenesis and current progress in therapies, including clinical trials, targeted therapies, immunotherapies, and system therapies, have been systemically reviewed and discussed. Finally, future perspective and challenges of development of novel therapeutic strategies in brain tumor were emphasized.

Molecular Mechanisms and Future Implications of VEGF/VEGFR in Cancer Therapy

Angiogenesis, the sprouting of new blood vessels from existing vessels, is one of six known mechanisms employed by solid tumors to recruit blood vessels necessary for their initiation, growth, and metastatic spread. The vascular network within the tumor facilitates the transport of nutrients, oxygen, and immune cells and is regulated by pro- and anti-angiogenic factors. Nearly four decades ago, VEGF was identified as a critical factor promoting vascular permeability and angiogenesis, followed by identification of VEGF family ligands and their receptors (VEGFR). Since then, over a dozen drugs targeting the VEGF/VEGFR pathway have been approved for approximately 20 solid tumor types, usually in combination with other therapies. Initially designed to starve tumors, these agents transiently "normalize" tumor vessels in preclinical and clinical studies, and in the clinic, increased tumor blood perfusion or oxygenation in response to these agents is associated with improved outcomes. Nevertheless, the survival benefit has been modest in most tumor types, and there are currently no biomarkers in routine clinical use for identifying which patients are most likely to benefit from treatment. However, the ability of these agents to reprogram the immunosuppressive tumor microenvironment into an immunostimulatory milieu has rekindled interest and has led to the FDA approval of seven different combinations of VEGF/VEGFR pathway inhibitors with immune checkpoint blockers for many solid tumors in the past 3 years. In this review, we discuss our understanding of the mechanisms of response and resistance to blocking VEGF/VEGFR, and potential strategies to develop more effective therapeutic approaches.

Endothelial VEGFR Coreceptors Neuropilin-1 and Neuropilin-2 Are Essential for Tumor Angiogenesis

Neuropilin (NRP) expression is highly correlated with poor outcome in multiple cancer subtypes. As known coreceptors for VEGFRs, core drivers of angiogenesis, past investigations have alluded to their functional roles in facilitating tumorigenesis by promoting invasive vessel growth. Despite this, it remains unclear as to whether NRP1 and NRP2 act in a synergistic manner to enhance pathologic angiogenesis. Here we demonstrate, using NRP1 ECKO , NRP2 ECKO , and NRP1/NRP2 ECKO mouse models, that maximum inhibition of primary tumor development and angiogenesis is achieved when both endothelial NRP1 and NRP2 are targeted simultaneously. Metastasis and secondary site angiogenesis were also significantly inhibited in NRP1/NRP2 ECKO animals. Mechanistic studies revealed that codepleting NRP1 and NRP2 in mouse-microvascular endothelial cells stimulates rapid shuttling of VEGFR-2 to Rab7+ endosomes for proteosomal degradation. Our results highlight the importance of targeting both NRP1 and NRP2 to modulate tumor angiogenesis.

Significance

The findings presented in this study demonstrate that tumor angiogenesis and growth can be arrested completely by cotargeting endothelial NRP1 and NRP2. We provide new insight into the mechanisms of action regulating NRP-dependent tumor angiogenesis and signpost a novel approach to halt tumor progression.

Metabolic Reprogramming in Tumor Endothelial Cells

The dynamic crosstalk between the different components of the tumor microenvironment is critical to determine cancer progression, metastatic dissemination, tumor immunity, and therapeutic responses. Angiogenesis is critical for tumor growth, and abnormal blood vessels contribute to hypoxia and acidosis in the tumor microenvironment. In this hostile environment, cancer and stromal cells have the ability to alter their metabolism in order to support the high energetic demands and favor rapid tumor proliferation. Recent advances have shown that tumor endothelial cell metabolism is reprogrammed, and that targeting endothelial metabolic pathways impacts developmental and pathological vessel sprouting. Therefore, the use of metabolic antiangiogenic therapies to normalize the blood vasculature, in combination with immunotherapies, offers a clinical niche to treat cancer.

Tumor Vascular Remodeling Affects Molecular Dissemination to Lymph Node and Systemic Leukocytes

Angiogenic and lymphangiogenic remodeling has long been accepted as a hallmark of cancer development and progression; however, the impacts of this remodeling on immunological responses, which are paramount to the responses to immunotherapeutic treatments, are underexplored. As immunotherapies represent one of the most promising new classes of cancer therapy, in this study, we explore the effects of angiogenic and lymphangiogenic normalization on dissemination of molecules injected into the tumor microenvironment to immune cells in lymph nodes draining the tumor as well as in systemically distributed tissues. A system of fluorescent tracers, size-matched to biomolecules of interest, was implemented to track different mechanisms of tumor transport and access to immune cells. This revealed that the presence of a tumor, and either angiogenic or lymphangiogenic remodeling, altered local retention of model biomolecules, trended toward normalizing dissemination to systemic organs, and modified access to lymph node-resident immune cells in manners dependent on mechanism of transport. More specifically, active cell migration by skin-derived antigen presenting cells was enhanced by both the presence of a tumor and lymphangiogenic normalization, while both angiogenic and lymphangiogenic normalization restored patterns of immune cell access to passively draining species. As a whole, this work uncovers the potential ramifications of tumor-induced angiogenesis and lymphangiogenesis, along with impacts of interrogation into these pathways, on access of tumor-derived species to immune cells. Impact Statement Angiogenic and lymphangiogenic normalization strategies have been utilized clinically to interrogate tumor vasculature with some success. In the age of immunotherapy, the impacts of these therapeutic interventions on immune remodeling are unclear. This work utilizes mouse models of angiogenic and lymphangiogenic normalization, along with a system of fluorescently tagged tracers, to uncover the impacts of angiogenesis and lymphangiogenesis on access of tumor-derived species to immune cell subsets within various organs.

Effective low-dose Anlotinib induces long-term tumor vascular normalization and improves anti-PD-1 therapy

Anlotinib is a new multitarget tyrosine kinase inhibitor for tumor angiogenesis, and its monotherapy exhibits a decent clinical efficacy. However, the process of combining Anlotinib and immune checkpoint therapy to achieve optimal antitumor effects while limiting side effects remains unclear. In this study, we found that effective low-dose Anlotinib was sufficient to inhibit tumor growth while reducing side effects compared with high doses. Effective low-dose Anlotinib treatments induced durable tumor vascular normalization and improved anti-PD-1 therapy in both short- and long-term treatment regimens. Mechanistically, the combination therapy increased the proportions of intratumoral CD4⁺ T, CD8⁺ T, and NK cells. Anlotinib-associated antitumor effects were independent of interferon γ; however, the combination therapy required CD8⁺ T cells to suppress tumor growth. Together, these results suggest that the combination of effective low-dose Anlotinib and PD-1 blockade induces durable antitumor effects with fewer side effects. Our findings indicate that antiangiogenic treatments combined with immune checkpoint therapy at an effective low-dose, rather than a tolerable high dose, would be more efficacious and safer.

Opportunities for improving brain cancer treatment outcomes through imaging-based mathematical modeling of the delivery of radiotherapy and immunotherapy

Immunotherapy has become a fourth pillar in the treatment of brain tumors and, when combined with radiation therapy, may improve patient outcomes and reduce the neurotoxicity. As with other combination therapies, the identification of a treatment schedule that maximizes the synergistic effect of radiation- and immune-therapy is a fundamental challenge. Mechanism-based mathematical modeling is one promising approach to systematically investigate therapeutic combinations to maximize positive outcomes within a rigorous framework. However, successful clinical translation of model-generated combinations of treatment requires patient-specific data to allow the models to be meaningfully initialized and parameterized. Quantitative imaging techniques have emerged as a promising source of high quality, spatially and temporally resolved data for the development and validation of mathematical models. In this review, we will present approaches to personalize mechanism-based modeling frameworks with patient data, and then discuss how these techniques could be leveraged to improve brain cancer outcomes through patient-specific modeling and optimization of treatment strategies.

Multiphoton Phosphorescence Quenching Microscopy Reveals Kinetics of Tumor Oxygenation during Antiangiogenesis and Angiotensin Signaling Inhibition

PURPOSE

The abnormal function of tumor blood vessels causes tissue hypoxia, promoting disease progression and treatment resistance. Although tumor microenvironment normalization strategies can alleviate hypoxia globally, how local oxygen levels change is not known because of the inability to longitudinally assess vascular and interstitial oxygen in tumors with sufficient resolution. Understanding the spatial and temporal heterogeneity should help improve the outcome of various normalization strategies.

EXPERIMENTAL DESIGN

We developed a multiphoton phosphorescence quenching microscopy system using a low-molecular-weight palladium porphyrin probe to measure perfused vessels, oxygen tension, and their spatial correlations in vivo in mouse skin, bone marrow, and four different tumor models. Further, we measured the temporal and spatial changes in oxygen and vessel perfusion in tumors in response to an anti-VEGFR2 antibody (DC101) and an angiotensin-receptor blocker (losartan).

RESULTS

We found that vessel function was highly dependent on tumor type. Although some tumors had vessels with greater oxygen-carrying ability than those of normal skin, most tumors had inefficient vessels. Further, intervessel heterogeneity in tumors is associated with heterogeneous response to DC101 and losartan. Using both vascular and stromal normalizing agents, we show that spatial heterogeneity in oxygen levels persists, even with reductions in mean extravascular hypoxia.

CONCLUSIONS

High-resolution spatial and temporal responses of tumor vessels to two agents known to improve vascular perfusion globally reveal spatially heterogeneous changes in vessel structure and function. These dynamic vascular changes should be considered in optimizing the dose and schedule of vascular and stromal normalizing strategies to improve the therapeutic outcome.

Towards Immunotherapy-Induced Normalization of the Tumor Microenvironment

Immunotherapies modulate the function of immune cells to eradicate cancer cells through various mechanisms. These therapies are successful across a spectrum of cancers, but they are curative only in a subset of patients. Indeed, a major obstacle to the success of immunotherapies is the immunosuppressive nature of the tumor microenvironment (TME), comprising the stromal component and immune infiltrate of tumors. Importantly, the TME in most solid cancers is characterized by sparsely perfused blood vessels resulting from so-called pathological angiogenesis. In brief, dysregulated development of new vessels results in leaky tumor blood vessels that inefficiently deliver oxygen and other nutrients. Moreover, the occurrence of dysregulated fibrosis around the lesion, known as pathological desmoplasia, further compresses tumor blood vessels and impairs blood flow. TME normalization is a clinically tested treatment strategy to reverse these tumor blood vessel abnormalities resulting in stimulated antitumor immunity and enhanced immunotherapy efficacy. TME normalization includes vascular normalization to reduce vessel leakiness and reprogramming of cancer-associated fibroblast to decompress vessels. How immunotherapies themselves normalize the TME is poorly understood. In this review, we summarize current concepts and progress in TME normalization. Then, we review observations of immunotherapy-induced TME normalization and discuss the considerations for combining vascular normalizing and immunotherapies. If TME could be more completely normalized, immunotherapies could be more effective in more patients.

Inducing Biomechanical Heterogeneity in Brain Tumor Modeling by MR Elastography: Effects on Tumor Growth, Vascular Density and Delivery of Therapeutics

Simple Summary

Biomechanical forces aggravate brain tumor progression. In this study, magnetic resonance elastography (MRE) is employed to extract tissue biomechanical properties from five glioblastoma patients and a healthy subject, and data are incorporated in a mathematical model that simulates tumor growth. Mathematical modeling enables further understanding of glioblastoma development and allows patient-specific predictions for tumor vascularity and delivery of drugs. Incorporating MRE data results in a more realistic intratumoral distribution of mechanical stress and anisotropic tumor growth and a better description of subsequent events that are closely related to the development of stresses, including heterogeneity of the tumor vasculature and intrapatient variations in tumor perfusion and delivery of drugs.

Abstract

The purpose of this study is to develop a methodology that incorporates a more accurate assessment of tissue mechanical properties compared to current mathematical modeling by use of biomechanical data from magnetic resonance elastography. The elastography data were derived from five glioblastoma patients and a healthy subject and used in a model that simulates tumor growth, vascular changes due to mechanical stresses and delivery of therapeutic agents. The model investigates the effect of tumor-specific biomechanical properties on tumor anisotropic growth, vascular density heterogeneity and chemotherapy delivery. The results showed that including elastography data provides a more realistic distribution of the mechanical stresses in the tumor and induces anisotropic tumor growth. Solid stress distribution differs among patients, which, in turn, induces a distinct functional vascular density distribution—owing to the compression of tumor vessels—and intratumoral drug distribution for each patient. In conclusion, incorporating elastography data results in a more accurate calculation of intratumoral mechanical stresses and enables a better mathematical description of subsequent events, such as the heterogeneous development of the tumor vasculature and intrapatient variations in tumor perfusion and delivery of drugs.

Glioma targeted therapy: insight into future of molecular approaches

Gliomas are the common type of brain tumors originating from glial cells. Epidemiologically, gliomas occur among all ages, more often seen in adults, which males are more susceptible than females. According to the fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5), standard of care and prognosis of gliomas can be dramatically different. Generally, circumscribed gliomas are usually benign and recommended to early complete resection, with chemotherapy if necessary. Diffuse gliomas and other high-grade gliomas according to their molecule subtype are slightly intractable, with necessity of chemotherapy. However, for glioblastoma, feasible resection followed by radiotherapy plus temozolomide chemotherapy define the current standard of care. Here, we discuss novel feasible or potential targets for treatment of gliomas, especially IDH-wild type glioblastoma. Classic targets such as the p53 and retinoblastoma (RB) pathway and epidermal growth factor receptor (EGFR) gene alteration have met failure due to complex regulatory network. There is ever-increasing interest in immunotherapy (immune checkpoint molecule, tumor associated macrophage, dendritic cell vaccine, CAR-T), tumor microenvironment, and combination of several efficacious methods. With many targeted therapy options emerging, biomarkers guiding the prescription of a particular targeted therapy are also attractive. More pre-clinical and clinical trials are urgently needed to explore and evaluate the feasibility of targeted therapy with the corresponding biomarkers for effective personalized treatment options.

Clinically approved combination immunotherapy: Current status, limitations, and future perspective

Immune-checkpoint inhibitor-based combination immunotherapy has become a first-line treatment for several major types of cancer including hepatocellular carcinoma (HCC), renal cell carcinoma, lung cancer, cervical cancer, and gastric cancer. Combination immunotherapy counters several immunosuppressive elements in the tumor microenvironment and activates multiple steps of the cancer-immunity cycle. The anti-PD-L1 antibody, atezolizumab, plus the anti-vascular endothelial growth factor antibody, bevacizumab, represents a promising class of combination immunotherapy. This combination has produced unprecedented clinical efficacy in unresectable HCC and become a landmark in HCC therapy. Advanced HCC patients treated with atezolizumab plus bevacizumab demonstrated impressive improvements in multiple clinical endpoints including overall survival, progress-free survival, objective response rate, and patient-reported quality of life when compared to current first-line treatment with sorafenib. However, atezolizumab plus bevacizumab first-line therapy has limitations. First, cancer patients falling into the criteria for the combination therapy may need to be further selected to reap benefits while avoiding some potential pitfalls. Second, the treatment regimen of atezolizumab plus bevacizumab at a fixed dose may require adjustment for optimal normalization of the tumor microenvironment to obtain maximum efficacy and reduce adverse events. Third, utilization of predictive biomarkers is urgently needed to guide the entire treatment process. Here we review the current status of clinically approved combination immunotherapies and the underlying immune mechanisms. We further provide a perspective analysis of the limitations for combination immunotherapies and potential approaches to overcome the limitations.

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ICI-based combination immunotherapies become a 1st-line therapy for major cancers.

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Atezolizumab plus bevacizumab has produced unprecedented efficacy in HCC.

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Further optimization of patient selection, doses and biomarkers is needed.

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Potential approaches may overcome these limitations of combination immunotherapies.

Antiangiogenesis: Vessel Regression, Vessel Normalization, or Both?

The concepts of antiangiogenic tumor therapy were pioneered on the assumption that the inhibition of tumor angiogenesis should lead to the complete regression of the tumor-associated vasculature and thereby hold the tumor in an avascular dormant state. Yet, clinical trials revealed limited efficacy of angiogenesis inhibitors when used as monotherapy. Instead, antiangiogenic drugs proved effective to extend overall survival when used in combination with chemotherapy. This counterintuitive observation-inhibition of tumor vascularization should lead to less and not more delivery of chemotherapy to the tumor-led to the concepts of "vessel normalization." This refers to the notion that antiangiogenic drugs prune the most immature tumor vessels and spare mature vessels, thereby resulting in a more normal-appearing vasculature that leads to better access of chemotherapy to the tumor. The concepts of vessel normalization were first laid out in a landmark publication in Cancer Research in 2004. More than 600 studies on different aspects of vessel normalization have been published since then. Nevertheless, it is to this day less clear than ever to what extent vessel regression (leading to tumor starvation) and vessel normalization (facilitating chemotherapy) contribute to the clinical efficacy of antiangiogenic tumor therapy. This "Landmark Commentary" puts the concepts of tumor vessel normalization in historical context and develops thereupon some of the most burning questions in the field of translational angiogenesis research that need to be answered to further advance the application of tumor vascular stroma reprogramming therapies.See related article by Tong and colleagues, Cancer Res 2004;64:3731-6.

A tale of two multi-focal therapies for glioblastoma: An antibody targeting ELTD1 and nitrone-based OKN-007

Glioblastoma (GBM) is the most common primary malignant brain tumour in adults. Despite a multimodal treatment response, survival for GBM patients remains between 12 and 15 months. Anti‐ELTD1 antibody therapy is effective in decreasing tumour volumes and increasing animal survival in an orthotopic GBM xenograft. OKN‐007 is a promising chemotherapeutic agent that is effective in various GBM animal models and is currently in two clinical trials. In this study, we sought to compare anti‐ELTD1 and OKN‐007 therapies, as single agents and combined, against bevacizumab, a commonly used therapeutic agent against GBM, in a human G55 xenograft mouse model. MRI was used to monitor tumour growth, and immunohistochemistry (IHC) was used to assess tumour markers for angiogenesis, cell migration and proliferation in the various treatment groups. OKN and anti‐ELTD1 treatments significantly increased animal survival, reduced tumour volumes and normalized the vasculature. Additionally, anti‐ELTD1 was also shown to significantly affect other pro‐angiogenic factors such as Notch1 and VEGFR2. Unlike bevacizumab, anti‐ELTD1 and OKN treatments did not induce a pro‐migratory phenotype within the tumours. Anti‐ELTD1 treatment was shown to be as effective as OKN therapy. Both OKN and anti‐ELTD1 therapies show promise as potential single‐agent multi‐focal therapies for GBM patients.

Effects of contrast-enhanced ultrasound treatment on neoadjuvant chemotherapy in breast cancer

Purpose: Preclinical and clinical data indicate that contrast-enhanced ultrasound can enhance tumor perfusion and vessel permeability, thus, improving chemotherapy accumulation and therapeutic outcome. Therefore, we investigated the effects of high mechanical index (MI) contrast-enhanced Doppler ultrasound (CDUS) on tumor perfusion in breast cancer. Methods: In this prospective study, breast cancer patients were randomly assigned to receive either 18 minutes of high MI CDUS during chemotherapy infusion (n = 6) or chemotherapy alone (n = 5). Tumor perfusion was measured before and after at least six chemotherapy cycles using motion-model ultrasound localization microscopy. Additionally, acute effects of CDUS on vessel perfusion and chemotherapy distribution were evaluated in mice bearing triple-negative breast cancer (TNBC). Results: Morphological and functional vascular characteristics of breast cancer in patients were not significantly influenced by high MI CDUS. However, complete clinical tumor response after neoadjuvant chemotherapy was lower in high MI CDUS-treated (1/6) compared to untreated patients (4/5) and size reduction of high MI CDUS treated tumors tended to be delayed at early chemotherapy cycles. In mice with TNBC high MI CDUS decreased the perfused tumor vessel fraction (p < 0.01) without affecting carboplatin accumulation or distribution. Higher vascular immaturity and lower stromal stabilization may explain the stronger vascular response in murine than human tumors. Conclusion: High MI CDUS had no detectable effect on breast cancer vascularization in patients. In mice, the same high MI CDUS setting did not affect chemotherapy accumulation although strong effects on the tumor vasculature were detected histologically. Thus, sonopermeabilization in human breast cancers might not be effective using high MI CDUS protocols and future applications may rather focus on low MI approaches triggering microbubble oscillations instead of destruction. Furthermore, our results show that there are profound differences in the response of mouse and human tumor vasculature to high MI CDUS, which need to be further explored and considered in clinical translation.

Anti-angiogenic therapies in the management of glioblastoma

Angiogenesis is a central feature of glioblastoma (GBM), with contribution from several mechanisms and signaling pathways to produce an irregular, poorly constructed, and poorly connected tumor vasculature. Targeting angiogenesis has been efficacious for disease control in other cancers, and given the (I) highly vascularized environment in GBM and (II) correlation between glioma grade and prognosis, angiogenesis became a prime target of therapy in GBM as well. Here, we discuss the therapies developed to target these pathways including vascular endothelial growth factor (VEGF) signaling, mechanisms of tumor resistance to these drugs in the context of disease progression, and the evolving role of anti-angiogenic therapy in GBM.

Targeting tumor vascularization: promising strategies for vascular normalization

Tumor recurrence after the clinical cure of tumor often results from the presence of an abnormal microenvironment, including an aberrant vasculature. The tumor microenvironment is rich in pro-angiogenic factors but lacks pro-maturation factors. Pro-angiogenic conditions in the tumor microenvironment, such as hypoxia, are double-edged swords, promoting both the repair of normal tissues and the development of an abnormal blood vessel network. The coexistence of perfusion and hypoxic zones and uneven blood vessel distribution in tumor tissues profoundly influence tumor deterioration, recurrence, and metastasis. Traditional anti-angiogenic therapies have shown limited efficacy, and promote drug resistance, and even metastasis. In contrast, vascular normalization therapy induces a more physiological-like state, leading to better outcomes and fewer side effects. Vascular normalization entails modifying the tumor vascular system to improve tumor oxygenation and substance transport, thereby contributing to improving the efficacy of radiotherapy, chemotherapy, and immunotherapy. This review mainly focuses on the process of tumor vascularization; potential therapeutic targets, including cells, metabolism, signaling pathways, and angiogenesis-related genes; and possible strategies to normalize blood vessels through regulating tumor vessel generation, the development of tumor vessels, and blood vessel fusion and pruning.

MR spectroscopic imaging predicts early response to anti-angiogenic therapy in recurrent glioblastoma

Background

Determining failure to anti-angiogenic therapy in recurrent glioblastoma (GBM) (rGBM) remains a challenge. The purpose of the study was to assess treatment response to bevacizumab-based therapy in patients with rGBM using MR spectroscopy (MRS).

Methods

We performed longitudinal MRI/MRS in 33 patients with rGBM to investigate whether changes in N-acetylaspartate (NAA)/Choline (Cho) and Lactate (Lac)/NAA from baseline to subsequent time points after treatment can predict early failures to bevacizumab-based therapies.

Results

After stratifying based on 9-month survival, longer-term survivors had increased NAA/Cho and decreased Lac/NAA levels compared to shorter-term survivors. ROC analyses for intratumoral NAA/Cho correlated with survival at 1 day, 2 weeks, 8 weeks, and 16 weeks. Intratumoral Lac/NAA ROC analyses were predictive of survival at all time points tested. At the 8-week time point, 88% of patients with decreased NAA/Cho did not survive 9 months; furthermore, 90% of individuals with an increased Lac/NAA from baseline did not survive at 9 months. No other metabolic ratios tested significantly predicted survival.

Conclusions

Changes in metabolic levels of tumoral NAA/Cho and Lac/NAA can serve as early biomarkers for predicting treatment failure to anti-angiogenic therapy as soon as 1 day after bevacizumab-based therapy. The addition of MRS to conventional MR methods can provide better insight into how anti-angiogenic therapy affects tumor microenvironment and predict patient outcomes.

Remodeling tumor microenvironment with nanomedicines

The tumor microenvironment (TME) has been recognized as a major contributor to cancer malignancy and therapeutic resistance. Thus, strategies directed to re-engineer the TME are emerging as promising approaches for improving the efficacy of antitumor therapies by enhancing tumor perfusion and drug delivery, as well as alleviating the immunosuppressive TME. In this regard, nanomedicine has shown great potential for developing effective treatments capable of re-modeling the TME by controlling drug action in a spatiotemporal manner and allowing long-lasting modulatory effects on the TME. Herein, we review recent progress on TME re-engineering by using nanomedicine, particularly focusing on formulations controlling TME characteristics through targeted interaction with cellular components of the TME. Importantly, the TME should be re-engineering to a quiescent phenotype rather than be destroyed. Finally, immediate challenges and future perspectives of TME-re-engineering nanomedicines are discussed, anticipating further innovation in this growing field. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

DLL1 orchestrates CD8+ T cells to induce long-term vascular normalization and tumor regression

The immunosuppressive and hypoxic tumor microenvironment (TME) remains a major obstacle to impede cancer immunotherapy. Here, we showed that elevated levels of Delta-like 1 (DLL1) in the breast and lung TME induced long-term tumor vascular normalization to alleviate tumor hypoxia and promoted the accumulation of interferon γ (IFN-γ)-expressing CD8⁺ T cells and the polarization of M1-like macrophages. Moreover, increased DLL1 levels in the TME sensitized anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA4) treatment in its resistant tumors, resulting in tumor regression and prolonged survival. Mechanically, in vivo depletion of CD8⁺ T cells or host IFN-γ deficiency reversed tumor growth inhibition and abrogated DLL1-induced tumor vascular normalization without affecting DLL1-mediated macrophage polarization. Together, these results demonstrate that elevated DLL1 levels in the TME promote durable tumor vascular normalization in a CD8⁺ T cell- and IFN-γ-dependent manner and potentiate anti-CTLA4 therapy. Our findings unveil DLL1 as a potential target to persistently normalize the TME to facilitate cancer immunotherapy.

Therapeutic Targeting of the Tumor Microenvironment

Strategies to therapeutically target the tumor microenvironment (TME) have emerged as a promising approach for cancer treatment in recent years due to the critical roles of the TME in regulating tumor progression and modulating response to standard-of-care therapies. Here, we summarize the current knowledge regarding the most advanced TME-directed therapies, which have either been clinically approved or are currently being evaluated in trials, including immunotherapies, antiangiogenic drugs, and treatments directed against cancer-associated fibroblasts and the extracellular matrix. We also discuss some of the challenges associated with TME therapies, and future perspectives in this evolving field. SIGNIFICANCE: This review provides a comprehensive analysis of the current therapies targeting the TME, combining a discussion of the underlying basic biology with clinical evaluation of different therapeutic approaches, and highlighting the challenges and future perspectives.

The role of the renin-angiotensin system inhibitors in malignancy: a review

Hypertension is one of the most prevalent diseases in cardiology. The angiotensin receptor blockers (ARBs)/angiotensin converting enzyme inhibitors (ACEIs) are widely used drugs to stabilize the blood pressure via inhibition of the renin-angiotensin system (RAS). Studies have found that the exposure to RAS inhibitors (RASi) can suppress the development of cancers via multimodal mechanisms and has attracted increased attentions in the recent past. Owing the potential of RASi to inhibit tumor growth, proliferation and metastasis, they are considered as the potential and exciting candidates to enhance the effect of chemo-radiotherapy and targeted therapy efficacy. However, there are conflicting reports as to the use of ARB/ACEI in all facets of tumor growth. In this study, we comprehensively summarize and review the potential mechanisms of RASi in cancer treatment, like inhibition of tumor angiogenesis, reduction of cancer-associated fibroblasts (CAFs) and extracellular matrix (ECM), regulation of immune cells and improvement of hypoxia. Additionally, based on the basic and clinical experiments, we analyze the views and results regarding the role of RASi plays in tumor from genesis to recurrence, and certainly cancer treatment (chemo-radiotherapy and targeted therapy). In the last, not only do we discuss the prospects of using RASi to enhance cancer treatment efficacy but also point out the conflicting situation with the intention to give some directions and inspiration on this topic.

Imaging Glioblastoma Posttreatment: Progression, Pseudoprogression, Pseudoresponse, Radiation Necrosis

Radiographic monitoring of posttreatment glioblastoma is important for clinical trials and determining next steps in management. Evaluation for tumor progression is confounded by the presence of treatment-related radiographic changes, making a definitive determination less straight-forward. The purpose of this article was to describe imaging tools available for assessing treatment response in glioblastoma, as well as to highlight the definitions, pathophysiology, and imaging features typical of true progression, pseudoprogression, pseudoresponse, and radiation necrosis.

Steps in metastasis: an updated review

Metastasis is the most complex and deadly event. Tumor-stromal interface is a place where invasion of tumor cells in the form of single-cell or collective migration occurs, with the latter being less common but more efficient. Initiation of metastasis relies on the tumor cell cross-talking with stromal cells and taking an epithelial-mesenchymal transition (EMT) in single cells, and a hybrid EMT in collective migratory cells. Stromal cross-talking along with an abnormal leaky vasculature facilitate intravasation of tumor cells, here the cells are called circulating tumor cells (CTCs). Tumor cells isolated from the primary tumor exploit several mechanisms to maintain their survival including rewiring metabolic demands to use sources available within the new environments, avoiding anoikis cell death when cells are detached from extracellular matrix (ECM), adopting flow mechanic by acquiring platelet shielding and immunosuppression by negating the activity of suppressor immune cells, such as natural killer (NK) cells. CTCs will adhere to the interstituim of the secondary organ/s, within which the newly arrived disseminative tumor cells (DTCs) undergo either dormancy or proliferation. Metastatic outgrowth is under the influence of several factors, such as the activity of macrophages, impaired autophagy and secondary site inflammatory events. Metastasis can be targeted by multiple ways, such as repressing the promoters of pre-metastatic niche (PMN) formation, suppressing environmental contributors, such as hypoxia, oxidative and metabolic stressors, and targeting signaling and cell types that take major contribution to the whole process. These strategies can be used in adjuvant with other therapeutics, such as immunotherapy.

The Current Landscape of Immune Checkpoint Blockade in Hepatocellular Carcinoma: A Review

Importance

For more than a decade, sorafenib has been the only systemic treatment option for patients with advanced hepatocellular carcinoma (HCC). However, rapid progress over the past few years led to approval of other angiogenesis inhibitors and several immune checkpoint blockers (ICBs) that have been added to the treatment armamentarium for advanced HCC. Moreover, the recent success of a combination of bevacizumab with atezolizumab signals an important change in the front-line treatment of HCC.

Observations

This review summarizes rapidly emerging clinical data on the promise and challenges of implementing ICBs in HCC and discusses the unmet need of biomarkers to predict response or resistance to therapy. Two strategies to target immunosuppression in tumors are also discussed: one proven (vascular endothelial growth factor pathway inhibition) and one currently under investigation (transforming growth factor-β pathway inhibition). The rationale and preliminary evidence on how their inhibition may reprogram the immunosuppressive milieu and enhance the efficacy of ICBs in HCC are reviewed.

Conclusion and Relevance

The recent successes and failures of angiogenesis inhibitors and ICBs, alone and in combination, have provided important insights into how to implement this novel systemic therapy in HCC and led to new avenues to enhance immunotherapy efficacy in this disease.

Full three-dimensional segmentation and quantification of tumor vessels for photoacoustic images

Quantitative analysis of tumor vessels is of great significance for tumor staging and diagnosis. Photoacoustic imaging (PAI) has been proven to be an effective way to visualize comprehensive tumor vascular networks in three-dimensional (3D) volume, while previous studies only quantified the vessels projected in one plane. In this study, tumor vessels were segmented and quantified in a full 3D framework. It had been verified in the phantom experiments that the 3D quantification results have better accuracy than 2D. Furthermore, in vivo vessel images were quantified by 2D and 3D quantification methods respectively. And the difference between these two results is significant. In this study, complete vessel segmentation and quantification method within a 3D framework was implemented, which showed obvious advantage in the analysis accuracy of 3D photoacoustic images, and potentially improve tumor study and diagnosis.

Radiological Recurrence Patterns after Bevacizumab Treatment of Recurrent High-Grade Glioma: A Systematic Review and Meta-Analysis

Objective

To categorize the radiological patterns of recurrence after bevacizumab treatment and to derive the pooled proportions of patients with recurrent malignant glioma showing the different radiological patterns.

Materials and Methods

A systematic literature search in the Ovid-MEDLINE and EMBASE databases was performed to identify studies reporting radiological recurrence patterns in patients with recurrent malignant glioma after bevacizumab treatment failure until April 10, 2019. The pooled proportions according to radiological recurrence patterns (geographically local versus non-local recurrence) and predominant tumor portions (enhancing tumor versus non-enhancing tumor) after bevacizumab treatment were calculated. Subgroup and meta-regression analyses were also performed.

Results

The systematic review and meta-analysis included 17 articles. The pooled proportions were 38.3% (95% confidence interval [CI], 30.6–46.1%) for a geographical radiologic pattern of non-local recurrence and 34.2% (95% CI, 27.3–41.5%) for a non-enhancing tumor-predominant recurrence pattern. In the subgroup analysis, the pooled proportion of non-local recurrence in the patients treated with bevacizumab only was slightly higher than that in patients treated with the combination with cytotoxic chemotherapy (34.9% [95% CI, 22.8–49.4%] versus 22.5% [95% CI, 9.5–44.6%]).

Conclusion

A substantial proportion of high-grade glioma patients show non-local or non-enhancing radiologic patterns of recurrence after bevacizumab treatment, which may provide insight into surrogate endpoints for treatment failure in clinical trials of recurrent high-grade glioma.

PET Imaging of Tumor Perfusion: A Potential Cancer Biomarker?

Perfusion, as measured by imaging, is considered a standard of care biomarker for the evaluation of many tumors. Measurements of tumor perfusion may be used in a number of ways, including improving the visual detection of lesions, differentiating malignant from benign findings, assessing aggressiveness of tumors, identifying ischemia and by extension hypoxia within tumors, and assessing treatment response. While most clinical perfusion imaging is currently performed with CT or MR, a number of methods for PET imaging of tumor perfusion have been described. The inert PET radiotracer 15O-water PET represents the recognized gold standard for absolute quantification of tissue perfusion in both normal tissue and a variety of pathological conditions including cancer. Other cancer PET perfusion imaging strategies include the use of radiotracers with high first-pass uptake, analogous to those used in cardiac perfusion PET. This strategy produces more visually pleasing high-contrast images that provide relative rather than absolute perfusion quantification. Lastly, multiple timepoint imaging of PET tracers such as 18F-FDG, are not specifically optimized for perfusion, but have advantages related to availability, convenience, and reimbursement. Multiple obstacles have thus far blocked the routine use of PET imaging for tumor perfusion, including tracer production and distribution, image processing, patient body coverage, clinical validation, regulatory approval and reimbursement, and finally feasible clinical workflows. Fortunately, these obstacles are being overcome, especially within larger imaging centers, opening the door for PET imaging of tumor perfusion to become standard clinical practice. In the foreseeable future, it is possible that whole-body PET perfusion imaging with 15O-water will be able to be performed in a single imaging session concurrent with standard PET imaging techniques such as 18F-FDG-PET. This approach could establish an efficient clinical workflow. The resultant ability to measure absolute tumor blood flow in combination with glycolysis will provide important complementary information to inform prognosis and clinical decisions.

Photoacoustic visualization of the fluence rate dependence of photodynamic therapy

This study investigates the fluence rate effect, an essential modulating mechanism of photodynamic therapy (PDT), by using photoacoustic imaging method. To the best of our knowledge, this is the first time that the fluence rate dependence is investigated at a microscopic scale, as opposed to previous studies that are based on tumor growth/necrosis or animal surviving rate. This micro-scale examination enables subtle biological responses, including the vascular damage and the self-healing response, to be studied. Our results reveal the correlations between fluence rate and PDT efficacy/self-healing magnitude, indicating that vascular injuries induced by high fluence rates are more likely to recover and by low fluence rates (≤126 mW/cm²) are more likely to be permanent. There exists a turning point of fluence rate (314 mW/cm²), above which PDT practically produces no permanent therapeutic effect and damaged vessels can fully recover. These findings have practical significance in clinical setting. For cancer-related diseases, the 'effective fluence rate' is useful to provoke permanent destruction of tumor vasculature. Likewise, the 'non effective range' can be applied when PDT is used in applications such as opening the blood brain barrier to avoid permanent brain damage.

Normalizing Function of Tumor Vessels: Progress, Opportunities, and Challenges

Abnormal blood and lymphatic vessels create a hostile tumor microenvironment characterized by hypoxia, low pH, and elevated interstitial fluid pressure. These abnormalities fuel tumor progression, immunosuppression, and treatment resistance. In 2001, we proposed a novel hypothesis that the judicious use of antiangiogenesis agents-originally developed to starve tumors-could transiently normalize tumor vessels and improve the outcome of anticancer drugs administered during the window of normalization. In addition to providing preclinical and clinical evidence in support of this hypothesis, we also revealed the underlying molecular mechanisms. In parallel, we demonstrated that desmoplasia could also impair vascular function by compressing vessels, and that normalizing the extracellular matrix could improve vascular function and treatment outcome in both preclinical and clinical settings. Here, we summarize the progress made in understanding and applying the normalization concept to cancer and outline opportunities and challenges ahead to improve patient outcomes using various normalizing strategies.

Dynamic contrast-enhanced magnetic resonance imaging for monitoring the anti-angiogenesis efficacy in a C6 glioma rat model

BACKGROUND

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is useful in predicting responses to angiogenic therapy of malignant tumors.

PURPOSE

To observe the dynamics of DCE-MRI parameters in evaluating early effects of antiangiogenic therapy in a C6 glioma rat model.

MATERIAL AND METHODS

The Bevacizumab or vehicle treatment was started from the 14th day after glioma model was established. The treated and control groups (n = 13 per group) underwent DCE-MRI scans on days 0, 1, 3, 5, and 7 after treatment. Tumor volume was calculated according to T2-weighted images. Hematoxylin and eosin, microvessel density (MVD), and proliferating cell nuclear antigen (PCNA) examination were performed on day 7. The MRI parameters between the two groups were compared and correlations with immunohistochemical scores were analyzed.

RESULTS

The average tumor volume of treated group was significantly lower than that of control group on day 7 (81.764 ± 1.043 vs. 103.634 ± 3.868 mm³, P = 0.002). K^trans and K_ep decreased in the treated group while they increased in the control group. The differences were observed on day 5 (K^trans: 0.045 ± 0.018 vs. 0.093 ± 0.014 min^-1, P < 0.001; K_ep: 0.062 ± 0.018 vs. 0.134 ± 0.047 min^-1, P = 0.005) and day 7 (K^trans: 0.032 ± 0.010 vs. 0.115 ± 0.025 min^-1, P < 0.001; K_ep: 0.045 ± 0.016 vs. 0.144 ± 0.042 min^-1, P < 0.001). The difference of V_e was observed on day 5 (0.847 ± 0.248 vs. 0.397 ± 0.151, P = 0.009) and 7 (0.920 ± 0.154 vs. 0.364 ± 0.105, P = 0.006). K^trans and K_ep showed positive correlations with MVD and V_e showed negative correlation with PCNA.

CONCLUSION

DCE-MRI can assess the changes of early effects of anti-angiogenic therapy in preclinical practice.

Mesoporous Silica-Coated Silver Nanoframes as Drug-Delivery Vehicles for Chemo/Starvation/Metal Ion Multimodality Therapy

Cutting off the energy supply by glucose oxidase (GOx) to starve cancer cells has been a feasible and efficient oncotherapy strategy. The employment of GOx can effectively starve tumor cells by aerobic hydrolysis of glucose hopefully strengthening the abnormality (including the decrease in pH, the increase of hypoxia, and toxic hydrogen peroxide) in the tumor microenvironment (TME). On this basis, we designed and fabricated a GOx-conjugated yolk-shell Ag@mSiO₂ nanoframe with Ag NPs and GOx-conjugated mesoporous silica as the yolk and the shell, respectively, to make full use of changes the GOx induces in TME. Specifically, lower pH and H₂O₂ could accelerate the transformation of Ag nanoparticles to poisonous Ag ions. At the same time, the anabatic hypoxia condition in turn activated chemotherapy drug tirapazamine (TPZ) to exert a chemotherapeutic effect, thereby achieving effective chemo/starvation and metal ion multimodality therapy. The drug release experiment in vitro demonstrated that the GOx is the key to the nanocarriers, which can activate the whole system. The excellent cellular uptake performances of nanocarriers were corroborated by a confocal laser scanning microscope (CLSM). In addition, its superb cancer-killing effect has been confirmed by cytotoxicity and apoptosis experiments. These results indicated that the drug-delivery system achieved the cascade cancer-killing process in situ and synergistic chemo/starvation/metal ion therapy, which has a bright prospect for treating cancer.

Dual inhibition of PFKFB3 and VEGF normalizes tumor vasculature, reduces lactate production, and improves chemotherapy in glioblastoma: insights from protein expression profiling and MRI

Rationale: Tumor vascular normalization (TVN) is emerging to enhance the efficacy of anticancer treatment in many cancers including glioblastoma (GBM). However, a common and severe challenge being currently faced is the transient TVN effect, hampering the sustained administration of anticancer therapy during TVN window. Additionally, the lack of non-contrast agent-based imaging biomarkers to monitor TVN process postpones the clinical translation of TVN strategy. In this study, we investigated whether dual inhibition of VEGF and the glycolytic activator PFKFB3 could reinforce the TVN effect in GBM. Dynamic contrast-enhanced-magnetic resonance imaging (DCE-MRI) and intravoxel incoherent motion (IVIM)-MRI were performed to monitor TVN process and to identify whether IVIM-MRI is a candidate or complementary imaging biomarker for monitoring TVN window without exogenous contrast agent administration. Methods: Patient-derived orthotopic GBM xenografts in mice were established and treated with bevacizumab (BEV), 3PO (PFKFB3 inhibitor), BEV+3PO dual therapy, or saline. The vascular morphology, tumor hypoxia, and lactate level were evaluated before and at different time points after treatments. Doxorubicin was used to evaluate chemotherapeutic efficacy and drug delivery. Microarray of angiogenesis cytokines and western blotting were conducted to characterize post-treatment molecular profiling. TVN process was monitored by DCE- and IVIM-MRI. Correlation analysis of pathological indicators and MRI parameters was further analyzed. Results: Dual therapy extended survival and delayed tumor growth over each therapy alone, concomitant with a decrease of cell proliferation and an increase of cell apoptosis. The dual therapy reinforces TVN effect, thereby alleviating tumor hypoxia, reducing lactate production, and improving the efficacy and delivery of doxorubicin. Mechanistically, several angiogenic cytokines and pathways were downregulated after dual therapy. Notably, dual therapy inhibited Tie1 expression, the key regulator of TVN, in both endothelial cells and tumor cells. DCE- and IVIM-MRI data showed that dual therapy induced a more homogenous and prominent TVN effect characterized by improved vascular function in tumor core and tumor rim. Correlation analysis revealed that IVIM-MRI parameter D* had better correlations with TVN pathological indicators compared with the DCE-MRI parameter Ktrans. Conclusions: Our results propose a rationale to overcome the current limitation of BEV monotherapy by integrating the synergistic effects of VEGF and PFKFB3 blockade to enhance chemotherapy efficacy through a sustained TVN effect. Moreover, we unveil IVIM-MRI parameter D* has much potential as a complementary imaging biomarker to monitor TVN window more precisely without exogenous contrast agent injection.

Hyperthermia and smart drug delivery systems for solid tumor therapy

Chemotherapy is a cornerstone of cancer therapy. Irrespective of the administered drug, it is crucial that adequate drug amounts reach all cancer cells. To achieve this, drugs first need to be absorbed, then enter the blood circulation, diffuse into the tumor interstitial space and finally reach the tumor cells. Next to chemoresistance, one of the most important factors for effective chemotherapy is adequate tumor drug uptake and penetration. Unfortunately, most chemotherapeutic agents do not have favorable properties. These compounds are cleared rapidly, distribute throughout all tissues in the body, with only low tumor drug uptake that is heterogeneously distributed within the tumor. Moreover, the typical microenvironment of solid cancers provides additional hurdles for drug delivery, such as heterogeneous vascular density and perfusion, high interstitial fluid pressure, and abundant stroma. The hope was that nanotechnology will solve most, if not all, of these drug delivery barriers. However, in spite of advances and decades of nanoparticle development, results are unsatisfactory. One promising recent development are nanoparticles which can be steered, and release content triggered by internal or external signals. Here we discuss these so-called smart drug delivery systems in cancer therapy with emphasis on mild hyperthermia as a trigger signal for drug delivery.