Broad targeting of angiogenesis for cancer prevention and therapy

Semin Cancer Biol. 2015 Dec;35 Suppl:S224-S243. doi: 10.1016/j.semcancer.2015.01.001. Epub  2015 Jan 16.
Broad targeting of angiogenesis for cancer prevention and therapy.
Wang Z1, Dabrosin C2, Yin X3, Fuster MM3, Arreola A4, Rathmell WK4, Generali D5, Nagaraju GP6, El-Rayes B6, Ribatti D7, Chen YC8, Honoki K9, Fujii H9, Georgakilas AG10, Nowsheen S11, Amedei A12, Niccolai E12, Amin A13, Ashraf SS14, Helferich B15, Yang X15, Guha G16, Bhakta D16, Ciriolo MR17, Aquilano K17, Chen S18, Halicka D19, Mohammed SI20, Azmi AS21, Bilsland A22, Keith WN22, Jensen LD23.

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Deregulation of angiogenesis–the growth of new blood vessels from an existing vasculature–is a main driving force in many severe human diseases including cancer. As such, tumor angiogenesis is important for delivering oxygen and nutrients to growing tumors, and therefore considered an essential pathologic feature of cancer, while also playing a key role in enabling other aspects of tumor pathology such as metabolic deregulation and tumor dissemination/metastasis. Recently, inhibition of tumor angiogenesis has become a clinical anti-cancer strategy in line with chemotherapy, radiotherapy and surgery, which underscore the critical importance of the angiogenic switch during early tumor development. Unfortunately the clinically approved anti-angiogenic drugs in use today are only effective in a subset of the patients, and many who initially respond develop resistance over time. Also, some of the anti-angiogenic drugs are toxic and it would be of great importance to identify alternative compounds, which could overcome these drawbacks and limitations of the currently available therapy. Finding “the most important target” may, however, prove a very challenging approach as the tumor environment is highly diverse, consisting of many different cell types, all of which may contribute to tumor angiogenesis. Furthermore, the tumor cells themselves are genetically unstable, leading to a progressive increase in the number of different angiogenic factors produced as the cancer progresses to advanced stages. As an alternative approach to targeted therapy, options to broadly interfere with angiogenic signals by a mixture of non-toxic natural compound with pleiotropic actions were viewed by this team as an opportunity to develop a complementary anti-angiogenesis treatment option. As a part of the “Halifax Project” within the “Getting to know cancer” framework, we have here, based on a thorough review of the literature, identified 10 important aspects of tumor angiogenesis and the pathological tumor vasculature which would be well suited as targets for anti-angiogenic therapy: (1) endothelial cell migration/tip cell formation, (2) structural abnormalities of tumor vessels, (3) hypoxia, (4) lymphangiogenesis, (5) elevated interstitial fluid pressure, (6) poor perfusion, (7) disrupted circadian rhythms, (8) tumor promoting inflammation, (9) tumor promoting fibroblasts and (10) tumor cell metabolism/acidosis. Following this analysis, we scrutinized the available literature on broadly acting anti-angiogenic natural products, with a focus on finding qualitative information on phytochemicals which could inhibit these targets and came up with 10 prototypical phytochemical compounds: (1) oleanolic acid, (2) tripterine, (3) silibinin, (4) curcumin, (5) epigallocatechin-gallate, (6) kaempferol, (7) melatonin, (8) enterolactone, (9) withaferin A and (10) resveratrol. We suggest that these plant-derived compounds could be combined to constitute a broader acting and more effective inhibitory cocktail at doses that would not be likely to cause excessive toxicity. All the targets and phytochemical approaches were further cross-validated against their effects on other essential tumorigenic pathways (based on the “hallmarks” of cancer) in order to discover possible synergies or potentially harmful interactions, and were found to generally also have positive involvement in/effects on these other aspects of tumor biology. The aim is that this discussion could lead to the selection of combinations of such anti-angiogenic compounds which could be used in potent anti-tumor cocktails, for enhanced therapeutic efficacy, reduced toxicity and circumvention of single-agent anti-angiogenic resistance, as well as for possible use in primary or secondary cancer prevention strategies.
Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Angiogenesis; Anti-angiogenic; Cancer; Phytochemicals; Treatment

PMID:   25600295
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PMCID:   PMC4737670

Designing a broad-spectrum integrative approach for cancer prevention and treatment


Targeted therapies and the consequent adoption of “personalized” oncology have achieved notable successes in some cancers; however, significant problems remain with this approach. Many targeted therapies are highly toxic, costs are extremely high, and most patients experience relapse after a few disease-free months. Relapses arise from genetic heterogeneity in tumors, which harbor therapy-resistant immortalized cells that have adopted alternate and compensatory pathways (i.e., pathways that are not reliant upon the same mechanisms as those which have been targeted). To address these limitations, an international task force of 180 scientists was assembled to explore the concept of a low-toxicity “broad-spectrum” therapeutic approach that could simultaneously target many key pathways and mechanisms. Using cancer hallmark phenotypes and the tumor microenvironment to account for the various aspects of relevant cancer biology, interdisciplinary teams reviewed each hallmark area and nominated a wide range of high-priority targets (74 in total) that could be modified to improve patient outcomes. For these targets, corresponding low-toxicity therapeutic approaches were then suggested, many of which were phytochemicals. Proposed actions on each target and all of the approaches were further reviewed for known effects on other hallmark areas and the tumor microenvironment. Potential contrary or procarcinogenic effects were found for 3.9% of the relationships between targets and hallmarks, and mixed evidence of complementary and contrary relationships was found for 7.1%. Approximately 67% of the relationships revealed potentially complementary effects, and the remainder had no known relationship. Among the approaches, 1.1% had contrary, 2.8% had mixed and 62.1% had complementary relationships. These results suggest that a broad-spectrum approach should be feasible from a safety standpoint. This novel approach has potential to be relatively inexpensive, it should help us address stages and types of cancer that lack conventional treatment, and it may reduce relapse risks. A proposed agenda for future research is offered.

Aspirin could boost immune response to cancer

John Murphy, MDLinx, 09/08/2015
Adding aspirin to immunotherapy could greatly improve cancer treatment, according to a new study published online September 3, 2015 in Cell.

Aspirin could halt cancer cells’ protective barrier and unleash the full power of the immune system.

The study builds on research that tumor cells are often able to evade the immune system, although how tumor cells do this is not fully understood. But prior research has found that cyclooxygenase (COX) in tumors produces prostaglandin E2 (PGE2), which is associated with enhanced cancer cell survival, growth, migration, and immunosuppression.
In this study, researchers determined that melanoma, colorectal, and breast cancers produce excess PGE2, which suppresses tumor immunity and induces inflammation associated with cancer progression.
“We’ve added to the growing evidence that some cancers produce PGE2 as a way of escaping the immune system,” said study author Caetano Reis e Sousa, DPhil, senior group leader at the Francis Crick Institute in London, U.K. “If you can take away cancer cells’ ability to make PGE2, you effectively lift this protective barrier and unleash the full power of the immune system.”
Asprin, a COX inhibitor, could stop the production of PGE2, which would prevent tumors from evading the immune system. When the researchers tested it in mice, they found that aspirin combined with an immune checkpoint blocker (anti-PD-1 monoclonal antibody) substantially slowed melanoma and colorectal cancer growth, compared with immunotherapy alone.
“Giving patients COX inhibitors like aspirin at the same time as immunotherapy could potentially make a huge difference to the benefit they get from treatment,” said Dr. Reis e Sousa. “It’s still early work but this could help make cancer immunotherapy even more effective, delivering life-changing results for patients.”