The microvasculature and immune cells are major components of the tumor microenvironment (TME). Hypoxia plays a pivotal role in the TME through hypoxia-inducible factor 1-alpha (HIF-1α) which upregulates vascular endothelial growth factor (VEGF). VEGF, an angiogenesis stimulator, suppresses tumor immunity by inhibiting the maturation of dendritic cells, and induces immunosuppressive cells such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells. HIF-1α directly induces immune checkpoint molecules. VEGF/VEGF receptor (VEGFR)-targeted therapy as a cancer treatment has not only anti-angiogenic effects, but also immune-supportive effects. Anti-angiogenic therapy has the potential to change the immunological "cold tumors" into the "hot tumors". Glioblastoma (GB) is a hypervascular tumor with high VEGF expression which leads to development of an immuno suppressive TME. Therefore, in the last decade, several combination immunotherapies with anti-angiogenic agents have been developed for numerous tumors including GBs. In particular, combination therapy with an immune checkpoint inhibitor and VEGF/VEGFR-targeted therapy has been suggested as a synergic treatment strategy that may show favorable changes in the TME. In this article, we discuss the cross talk among immunosuppressive cells exposed to VEGF in the hypoxic TME of GBs. Current efficient combination strategies using VEGF/VEGFR-targeted therapy are reviewed and proposed as novel cancer treatments.
Neurofibromatosis (NF) is a neurocutaneous syndrome characterized by the development of tumors of the central or peripheral nervous system including the brain, spinal cord, organs, skin, and bones. There are three types of NF: NF1 accounting for 96% of all cases, NF2 in 3%, and schwannomatosis (SWN) in <1%. The NF1 gene is located on chromosome 17q11.2, which encodes for a tumor suppressor protein, neurofibromin, that functions as a negative regulator of Ras/MAPK and PI3K/mTOR signaling pathways. The NF2 gene is identified on chromosome 22q12, which encodes for merlin, a tumor suppressor protein related to ezrin-radixin-moesin that modulates the activity of PI3K/AKT, Raf/MEK/ERK, and mTOR signaling pathways. In contrast, molecular insights on the different forms of SWN remain unclear. Inactivating mutations in the tumor suppressor genes SMARCB1 and LZTR1 are considered responsible for a majority of cases. Recently, treatment strategies to target specific genetic or molecular events involved in their tumorigenesis are developed. This study discusses molecular pathways and related targeted therapies for NF1, NF2, and SWN and reviews recent clinical trials which involve NF patients.
Macrophages are significant in immune responses, assuming a defensive role. In contrast, macrophages often cause undesirable changes. These reactions are processes by which macrophages express different functional programs in response to microenvironmental signals, defined as M1/M2 polarization. Tumor immunity has been acknowledged for contributing to the elucidation of the mechanism and clinical application in cancer therapy. One of the mechanisms for the refractoriness to cancer immunotherapy is the production of inhibitory cytokines by tumor cells or macrophages. Therefore, therapeutic strategy targeting macrophage or macrophage-derived cytokines may be effective and attractive. This review aims to investigate macrophage-associated pathophysiology and biological behavior in cancers, especially related to microenvironment, such as hypoxia, and current topics regarding some therapies involving macrophages.
Vascular endothelial growth factor (VEGF) is an attractive target of antiangiogenic therapy in glioblastomas. Bevacizumab (Bev), a humanized anti-VEGF antibody, is associated with the improvement of progression-free survival and performance status in patients with glioblastoma. However, randomized trials uniformly suggest that these favorable clinical effects of Bev do not translate into an overall survival benefit. The mechanisms of action of Bev appear to include the inhibition of tumor angiogenesis, as well as indirect effects such as the depletion of niches for glioma stem cells and stimulation of antitumor immunity. Although several molecules/pathways have been reported to mediate adaptation and resistance to Bev, including the activation of alternative pro-angiogenic pathways, the resistance mechanisms have not been fully elucidated; for example, the mechanism that reinduces tumor hypoxia remains unclarified. The identification of imaging characteristics or biomarkers predicting the response to Bev, as well as the better understanding of the mechanisms of action and resistance, is crucial to improve the overall clinical outcome and optimize individual therapy. In this article, the authors review the results of important clinical trials/studies, the current understanding of the mechanisms of action and resistance, and the knowledge of imaging characteristics and biomarkers predicting the response to Bev.
To date, no clinical observations have been reported for histopathological changes in human gliomas under antiangiogenic treatment.We collected six glioblastomas resected under bevacizumab treatment. Histopathological investigation was performed by hematoxilyn-eosin staining and immunohistochemistry for CD34, VEGF, VEGFR1/2, HIF-1α, CA9, and nestin as compared to eleven control glioblastomas to assess the differences in histological features, microvessel density, expression of VEGF and its receptors, tumor oxygenation, and status of glioma stem-like cells.In the six tumors resected under bevacizumab, microvascular proliferation was absent, and microvessel density had significantly decreased compared with that of the controls. The expressions of VEGF and its receptors were downregulated in two cases of partial response. HIF-1α or CA9 expression was decreased in five of the six tumors, whereas the decreased expression of these markers was noted in only one of the 11 control glioblastomas. The expression of nestin significantly decreased in the six tumors compared with that of the controls, with the remaining nestin-positive cells being relatively concentrated around vessels.We provide the first clinicopathological evidence that antiangiogenic therapy induces the apparent normalization of vascular structure, decrease of microvessel density, and improvement of tumor oxygenation in glioblastomas. These in situ observations will help to optimize therapy.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.