Search

Natural Medicine Journal

October 21, 2020

Antiangiogenic Phytochemicals Best Poised for Clinical Trial Testing

A literature review of the most promising natural agents for integrative oncology research

Athanasios Psihogios

ND
Green tea, curcumin, resveratrol, and ginsenosides have some of the most robust evidence for inhibiting malignant angiogenesis in a clinically meaningful way.

This article is part of our October 2020 special issue. Download the full issue here.

Abstract

Angiogenesis is a normal physiological process involving the production and organization of blood vessels, a process required for wound healing and general health maintenance. In the case of cancer, however, the angiogenic process becomes an enabling characteristic that allows tumors to grow and metastasize more effectively. As 1 of the hallmarks of cancer, angiogenesis is also a vulnerable point for malignancy that is susceptible to influence by external modulators. Conventional treatments have the capacity to help hinder cancer growth and spread through antiangiogenic agents; however, they also have associated toxicity that can create side effects that limit their application. A number of natural health products have shown promise in clinical application against cancer through antiangiogenic mechanisms. In this paper we explore a few of these agents that have some of the strongest related research for application. We discuss some of the clinical evidence that currently exists and, importantly, how to enable effective research to further explore this topic.

Introduction & Background

Angiogenesis Process

Similar to normal tissue, malignant tumors require a sustained delivery of nutrients and removal of waste to subsist. Delivery and removal are primarily achieved through tumor neovascularization via a process called angiogenesis, which involves the formation of new blood vessels from existing vasculature. Unlike normal tissue, malignancies circumvent the ordinarily quiescent and well-organized nature of angiogenesis and exploit the process to facilitate unimpeded malignant growth.1,2

The process of cancer-related angiogenesis is heavily influenced by mediators in the tumor environment and is accelerated by localized tissue breakdown. Amongst other angiogenic mediators, vascular endothelial growth factor (VEGF) is the primary signal protein implicated in the process of angiogenesis.1,3 As a ligand, it stimulates VEGF receptor 2 (VEGFR-2), which is highly expressed by endothelial cells engaging in angiogenesis.3 Binding results in up-regulation of genes that mediate proliferation and migration of endothelial cells, while promoting survival and permeability of the vasculature.3

Angiogenesis in Modern Cancer Care

In the early 1970s, Dr Judah Folkman theorized that angiogenesis could serve as a potential therapeutic target,4 with the first approved pharmaceutical agents coming out in the early 2000s.3-6 Bevacizumab, a monoclonal antibody that binds circulating VEGF, was the first FDA-approved angiogenesis inhibitor, which when combined with standard chemotherapy, improved survival for patients with metastatic colorectal cancer.7 Similarly, patients with advanced non-small-cell lung cancer (NSCLC) experienced a survival benefit with bevacizumab in combination with standard chemotherapy.8 Overall, pharmaceutical VEGF inhibitors have shown modest benefit when added to standard care and have proven to be a valuable addition to standard care in certain circumstances.3

Based on 33 randomized controlled clinical trials (RCTs) (N= 17,396 NSCLC participants), the addition of approved angiogenesis inhibitors significantly improved progression-free survival (PFS; HR: 0.81, 95% CI 0.76–0.85, P<0.001), overall survival (OS; HR: 0.95, 95% CI 0.92–0.98, P= 0.004), objective response rate (ORR; RR: 1.54, 95% CI 1.37–1.73 P<0.001), and disease control rate (DCR; RR: 1.18, 95% CI 1.10–1.27, P<0.001) compared to non-angiogenesis inhibitor treatments.9 Approved angiogenesis inhibitors have also demonstrated improved survival outcomes for patients with ovarian10 and gastric11 cancers. In contrast, a meta-analysis of 7 RCTs (N=1,322 participants) exploring use of angiogenesis inhibitors in small-cell lung cancer (SCLC) found angiogenesis inhibitors did not significantly improve prognosis,12 indicating the potential for cancer-type specificity related to clinical impact.

The clinical value of pharmaceutical angiogenesis inhibitors is tempered by notable side effects. Possible serious adverse events include hemorrhage, hypertension, neutropenia, thromboembolic events, and impaired wound healing.13 Balancing positive effects on prognosis against patients’ quality of life and side-effect burden is an essential part of the evidence-based medicine model and needs to be factored into clinical decision making.

Natural Health Products & Angiogenesis

Compounds found in nature exist that possess antiangiogenic properties when ingested.14 An effort to both research and develop agents from phytochemical sources to address a hallmark1 of cancer progression—angiogenesis—could yield additional options to accompany conventional cancer care. Scrutiny of available evidence to select promising phytochemicals for further investigation would foster efficient and collective efforts that could support the identification of new therapeutic options for patients with cancer. This review presents certain phytochemicals with some of the most robust current evidence for clinically meaningful angiogenic-inhibitory effects. We suggest that if natural health products are to be used for this objective (antiangiogenic effects), these agents deserve priority consideration and future investigations through more rigorous clinical research.

Angiogenesis-Inhibiting Compounds Found in Nature

Notable phytochemicals with evidence for antiangiogenic effects through different pathways include resveratrol, green tea catechins, curcumin, silymarin/silibinin, castanospermine, sanguinarine, brucine, tylophorine, colchicine, vinblastine, ginsenosides, taxol, and triphala churna.14 These compounds have been found to act on different angiogenesis targets and are classified into 3 major families: polyphenols, alkaloids, and terpenoids/tannins.14 Of these, certain compounds have more extensive research, making them better poised for immediate clinical investigation and judicious clinical consideration on a case-by-case basis. For each of the compounds below, the curated preclinical evidence, bioavailability, and clinical trial data provide a comprehensive review of each phytochemical, which may also be utilized for future investigation.

Green Tea

Produced from the common tea plant (Camellia sinensis), green tea has been extensively studied for its effects on health and human physiology, which are thought to be largely due to its catechin content, specifically (-)-epigallocatechin-3-gallate (EGCG). Epidemiological studies have found that green tea consumption is associated with a reduced risk of prostate cancer,15 liver cancer,16 breast cancer,17 and cardiovascular disease.18 At the cellular level, EGCG has been observed to inhibit VEGF expression and activity in certain cancer cell lines including gastric cancer,19 head and neck squamous cell carcinoma, and breast20 cancer, among others.

Preclinical Evidence of Antiangiogenic Activity

Green tea catechins have been extensively researched in preclinical models to identify and understand their antiangiogenic properties. A green tea extract product containing 65% EGCG inhibited invasion of MDA-MB231 breast cancer cells by up to 40% compared to controls in a concentration-dependent manner, and inhibited neovascularization in vivo in C57BL/6 mice.21 Intraperitoneal injection of EGCG inhibited gastric cancer growth in nude mice by 60.4%, with reduced tumor micro-vessel density, VEGF-induced endothelial cell proliferation, tube formation, and migration.22 EGCG treatment of human cervical carcinoma and hepatoma cells inhibited hypoxia and serum-induced hypoxia-inducible factor (HIF) 1-alpha accumulation, resulting in significant VEGF-expression reduction.23 Treatment with EGCG dose-dependently inhibited VEGF expression and platelet-derived growth factor in human vascular smooth muscle cells.24

Bioavailability

While in vitro studies show antiangiogenic activity, achievable EGCG serum concentrations in humans are hindered by poor bioavailability, likely explaining inconsistencies in epidemiological research.25 Following oral administration in humans and animals, peak catechin plasma levels are often in the sub- or very low micromolar range, falling short of the effective concentration range of 1 to 100 μmol/L.25 Human oral bioavailability studies have yielded plasma levels that are 5 to 50 times less than those in preclinical models.26 Rat studies have shown that <5% of orally administered tea catechins present in systemic circulation, and in humans about 0.16% present in plasma.25 A small portion of ingested tea catechins undergo extensive phase II enzyme metabolism in the small intestine (primarily absorbed through passive diffusion), with the remainder passing to the colon where microorganism degradation likely occurs.25

Several approaches have been tested to increase the systemic absorption of oral EGCG. One randomized, controlled crossover trial26 assessed the effect of fasting states with differing catechin dosing in healthy volunteers. A 3.5-fold increase was observed for the average maximum plasma concentration (free EGCG) during a fasting state compared to a fed state, but no significant differences for total plasma levels.26 Other areas of active research to improve bioavailability include the formation of nanostructure carriers, molecular modification, and coadministration with bioactive components.25

Clinical Research of Antiangiogenic Effects

An open-label, single-arm phase 1 clinical trial of 26 males with prostate cancer awaiting radical prostatectomy found that 800 mg of EGCG for 6 weeks resulted in a significant reduction in plasma serum levels of VEGF compared to baseline (P<0.03), with 6 out of 25 participants experiencing ≥25% reduction.27 A double-blind, placebo-controlled, multicentered study of 33 participants with bladder cancer, split into 3 arms (800 mg EGCG, 1,200 mg EGCG, or placebo), found no significant differences between groups for VEGF tissue levels.28 A randomized, placebo-controlled, double-blind “split-face” dermatological study of 4 volunteers with significant facial erythema and telangiectasia found that an EGCG cream (2.5% weight for weight) significantly reduced VEGF levels in biopsy samples compared to control (P<0.005).29

Curcumin

Isolated from the common spice turmeric (Curcuma longa), curcumin is estimated to have been used in traditional medicine for thousands of years.30 Contemporary research has shown that curcumin is tolerated in high doses (up to 12 grams), and exerts antioxidant and anti-inflammatory effects.30 Further research has yielded evidence of VEGF-pathway alteration in models of breast cancer,31 human intestinal microvascular endothelial cells,32 and hepatocellular carcinoma.33 While traditionally turmeric as a whole has been implemented therapeutically, recent investigations have focused primarily on curcumin itself at levels beyond what would be typically consumed, in hopes of achieving drug-like actions.

Preclinical Evidence of Antiangiogenic Activity

A gastric cancer cell line study (AGS and SGC-7901 cell lines) showed that curcumin exerts antilymphangiogenic activity via inhibition of HMGB1/VEGF-D signalling.34 In a hepatocellular cancer model, curcumin significantly induced H22 cell apoptosis at the 40 µM and 80 µM concentrations compared to untreated controls (P<0.05 and P<0.01, respectively),35 and in mice treated with 50 mg/kg curcumin, it significantly reduced H22 tumor growth (P<0.05).35 The mechanism of observed effects in both the cell line and mouse model was the significant inhibition of VEGF expression and PI3K/AKT signalling.35 A colorectal cancer model study found that in vitro, curcumin inhibited CT26 cell proliferation and migration and exerted apoptotic activity, while inhibiting tumor growth in vivo through VEGF signalling modulation.36 Nude mice injected with A549 lung cancer cells and given 100 mg/kg curcumin intraperitoneally experienced reduced tumor weight and size, with suppression of VEGF expression.37

Bioavailability

Pure curcumin absorbs poorly in humans, resulting in low achievable serum concentrations.38 Pharmacokinetic studies have shown that curcumin undergoes both extensive phase I and II liver metabolism, and is further metabolized by microbiota.38

In 25 participants with high-risk/premalignant lesions, oral daily doses of 1,000, 2,000, 4,000, 8,000, and 12,000 mg/day curcumin were found to cause serum curcumin peaks at 1 to 2 hours, with the average concentrations ranging from 0.51 +/- 0.11 µM to 1.77 +/- 1.8 µM (dose-dependently).38,39 These concentrations are notably lower than the controlled environments created in experimental preclinical models. A turmeric extract dose of 0.4 to 2.2 g (containing 36-180 mg of curcumin) given to 15 patients with chemotherapy-refractory colorectal cancer yielded metabolites that were undetectable in both blood and urine.38,40 These studies, among others, present a notable bioavailability issue with unaltered oral curcumin, resulting in novel approaches to circumvent this problem.

Unlike normal tissue, malignancies circumvent the ordinarily quiescent and well-organized nature of angiogenesis and exploit the process to facilitate unimpeded malignant growth.

The problem of absorption has been addressed extensively, with patented formulations being produced. The contrast of 2 similar controlled studies describes the progress of altered forms of curcumin influencing bioavailability and achievable serum concentrations.41,42 A 2008 study that used 8 grams (8,000 mg) of curcumin orally (simple plant extract with no composition alteration) in patients with pancreatic cancer reported low peak levels of 22 to 41 ng/mL, which remained relatively constant over 4 weeks.41 A 2013 study assessed a novel curcumin formulation (Theracurmin®) in a similar population in order to investigate bioavailability changes.42 This formulation is composed of microscopic particles contained in a colloidal agent. In 10 participants with either pancreatic or biliary tract cancer resistant to chemotherapy, an escalating dose of 200 to 400 mg of Theracurmin resulted in a median peak plasma level of 342 ng/mL (range 47-1,029 ng/mL) at the 200-mg dose, and 440 ng/mL (range 179-1,380 ng/mL) at the 400-mg dose.42 Authors report that no unexpected adverse events occurred, and it was safely continued in 3 surviving patients for over 9 months.42

In addition to Theracurmin, other patented formulations such as Meriva®43 and BCM-95®,44 along with additive approaches such as piperine45 products combined with curcumin, are an active field of study pertaining to optimizing absorption.

Clinical Research of Antiangiogenic Effects

One randomized, controlled, double-blind, crossover study involving 30 obese participants found that 1 gram of a curcumin-complex product for 4 weeks significantly reduced VEGF (P=0.01) compared to control.46

Resveratrol

A unique type of polyphenol called a stilbene, resveratrol is primarily found in the skins of berries and grapes. At therapeutic doses, it exerts antiangiogenic effects in experimental tumor models.14 In comparison to other natural health products, resveratrol has had extensive human clinical investigation via supplementation trials for a number of non-cancer-related conditions, including dyslipidemia,47 metabolic syndrome,48 and hypertension,49 with overall mixed results. Preclinical angiogenesis resveratrol studies primarily focused on ovarian cancer models.

Preclinical Evidence of Antiangiogenic Activity

A 3D ovarian cancer cell aggregate model (ie, an organoid) treated with increasing doses (10, 20, or 30 μM) of resveratrol or a derivative (acetyl-resveratrol) reduced cell growth and suppressed VEGF secretion.50 An earlier, similar ovarian organoid model study found that resveratrol or acetyl-resveratrol suppressed VEGF secretion in a dose-dependent fashion.51 A lung cancer model (A549 cells) found that treatment with resveratrol reduced both interleukin (IL-6) and VEGF secretion.52 Hepatocarcinoma cells (HepG2) treated with escalating concentrations of resveratrol (ranging from 0-40 μM) experienced inhibition of VEGF gene expression, resulting in inhibited proliferation.53

Bioavailability

While resveratrol has low water solubility and absorbs primarily via passive diffusion, hindering absorption, its capacity to form a wide range of complexes increases intestinal permeability.54 While it is fairly well established that distribution of resveratrol in tissues is very low and overall it has low bioavailability, resveratrol appears to show efficacy in vivo; this is thought to be due to metabolic conversion and recirculation of metabolites that may have biological activity.54 Multiple approaches are being investigated to improve the bioavailability of resveratrol, including lipid nanocarriers, liposomes, nanoemulsions, micelle solutions, polymeric nanoparticles, solid dispersions, and nanocrystals.55 It should be noted that while resveratrol absorption is a concern for clinical efficacy, there is risk of toxicity with higher dosing, indicating a possibly narrow therapeutic window.56 The dosing approach is not linear, in the sense that higher doses don’t necessarily equate to more favorable outcomes, and future investigations should not only focus on increasing absorption but also, more importantly, regulating the dosing to offset toxicity.

Clinical Research of Antiangiogenic Effects

A triple-blind, placebo-controlled, randomized study of 61 polycystic ovary syndrome participants receiving 800 mg/day resveratrol for 40 days reported significant reduction in VEGF expression in recovered granulosa cells (P<0.0001).57 A randomized, double-blind placebo-controlled study of 72 participants undergoing peritoneal dialysis found that those receiving high-dose trans-resveratrol (450 mg/day) had significantly lower rates of VEGF in retrieved effluent compared to the low-dose and placebo groups.58

Ginsenosides

Triterpene saponins concentrated in the roots of red ginseng (Panax ginseng), ginsenosides have been found to exert antiangiogenic effects.14 Ginsenosides are classified using an “Rx” system, with the “R” representing the root and the “x” describing the chromatographic polarity (alphabetical order).59 Over 30 ginsenosides have been identified, with researchers adopting standardized products via specific extraction processes to improve consistency.59 A vast amount of research exists for ginsenosides’ antiangiogenic activity in multiple cancer models and using many different forms, of which Rg3 is the most rigorously studied.

Preclinical Evidence of Antiangiogenic Activity

In a dual in vitro and in vivo study, Rg3 inhibited migration and invasion in 4 thyroid cancer cell models and suppressed pulmonary metastasis in nude mice, with inhibition of VEGF expression observed.60 In a gastric cancer cell model study, where hypoxia was induced to stimulate vascular growth factors, levels of VEGF were significantly lower in the Rg3-treated group (P<0.05).61 Under induced hypoxic conditions, an esophageal cancer cell model study found that Rg3 significantly inhibited proliferation and reduced VEGF messenger RNA (mRNA).62 In an endometriosis model utilizing allotransplantation in rats, Rg3 was found to inhibit growth of ectopic endometrium in a dose-dependent fashion via downregulation of VEGF, p-Akt, and p-mTOR pathways.63

Bioavailability

Ginsenoside absorption across intestinal mucosa has not been clearly described; however, it appears to cross via energy-dependent transport and appears nonsaturable.59 One in vivo study using A/J mouse intestinal models determined that certain bacterial families are involved in the conversion of ginsenosides into active secondary metabolites.64 A comparative mouse study (Walker 256 tumor-bearing mice vs normal mice) using 50 mg/kg of oral Rg3 discovered that Rh2 ginsenosides were found in plasma, likely due to glycosylation hydrolysis.65 One diabetes clinical trial using ginsenoside Re found that oral administration resulted in no detectable plasma amounts at the 30-minute and 6-hour point.66 The absorption, biotransformation, and overall bioavailability of ginsenosides appear complex and variable between different forms, requiring further exploration.

Clinical Research of Antiangiogenic Effects

A randomized, placebo-controlled study of Rg3 supplementation in 20 patients with acute leukemia for 2 months in conjunction with chemotherapy significantly reduced serum VEGF levels.67 A randomized controlled trial of 71 postoperative participants with advanced gastric cancer found that those who received Rg3 + mitomycin C/tegafur, compared to chemotherapy alone, after 14 weeks experienced VEGF levels within normal range, with the median survival being 40 and 25 months, respectively (P=0.047).68 A 3-armed, randomized, controlled study (Rg3 vs Rg3 + chemotherapy vs chemotherapy alone) of postoperative patients with NSCLC found no significant survival differences over 3 years between groups (P>0.05), with VEGF levels not associated with outcomes.69 A study of 60 patients with advanced esophageal cancer receiving either Rg3 + gemcitabine/cisplatin or chemotherapy found that the intervention group had significantly lower posttreatment VEGF levels (P=0.002).70

Clinical Implications & Closing Remarks

Green tea catechins (especially EGCG), curcumin, resveratrol, and ginsenosides are phytochemicals that currently hold extensive foundational antiangiogenesis research. These 4 compounds possess preclinical, bioavailability, and preliminary clinical research, poising them for rigorous clinical investigation, compared to other phytochemicals that still require further preliminary investigation prior to being considered candidates for extensive clinical investigation. The next step would be to select 1 or a combination of phytochemicals and perform a formal systematic search to identify all relevant research, including on safety, clinical data, and pharmacokinetics/dynamics. In addition, an accompanying review of the literature should be performed in order to determine the most accurate and feasible ways to assess the effects of an intervention on angiogenesis in homine.

It is notable that while the identified compounds possess an ample amount of preclinical evidence to indicate antiangiogenic effects, data of this sort cannot be relied on alone to predict effects in patients, especially in highly vulnerable patient populations, such as those with cancer. The shortcomings of preclinical data translating to human effects are twofold, with consistent evidence showing that often: 1) preclinical data are a poor predictor of effect (often no significant benefit/effect is found);71 and 2) human subjects often experience unanticipated harms even when the intervention appears safe in preclinical models, as they are also poor predictors of toxicity.72,73 Collectively, while reviewed information provides a strong rationale for subsequent clinical trial investigation, caution is warranted for extrapolating data further directly to clinical care.

Based on available evidence, a future well-designed clinical trial, with the objective of addressing malignant angiogenesis in cancer patients via phytochemical supplementation, would do best by using an agent with human-level and preclinical data showing VEGF effects, and by choosing a highly bioavailable form of that agent. By fast-tracking a select few phytochemicals that already have essential pieces of evidence into a rigorous clinical trial, rather than investigating a number of agents lacking foundational research, we can execute more efficient trials and hopefully identify meaningful associations.

Categorized Under

Athanasios Psihogios

ND

Athanasios (Thanasi) Psihogios, ND, is an integrative oncology researcher dedicated to advancing this pioneer-type field in order to provide patients with safe and efficacious therapy options. Currently, in order to expand his research abilities and knowledge, Psihogios is completing a Master of Public Health degree. In addition to health research, with his background and passion for philosophy, Psihogios is particularly interested in the reasoning and modes of thinking behind people's decision to use integrative medicine.

Dugald Seely

ND, MSc, FABNO

Dugald Seely, ND, MSc, FABNO, runs a clinical practice with a multidisciplinary team of healthcare practitioners at the Centre for Health Innovation (home of the Ottawa Integrative Cancer Centre). Seely is the executive director for the Patterson Institute for Integrative Oncology Research at the Canadian College of Naturopathic Medicine as well as serving as an affiliate investigator for the Ottawa Hospital Research Institute, and adjunct professor with the School of Epidemiology and Public Health at the University of Ottawa. Seely completed his master of science in cancer research at the University of Toronto and has been awarded over 11 million dollars in grant research funding. Past-president for the Oncology Association of Naturopathic Physicians and recipient of the 2017 Rogers Prize, Seely aims to build on the evidence for naturopathic oncology and the practice of integrative oncology as a whole.

References

  1. Hanahan D, Weinberg RA. Hallmarks of cancer: the next generation. Cell. 2011;144(5):646-674.
  2. Hanahan D, Folkman J. Patterns and emerging mechanisms of the angiogenic switch during tumorigenesis. Cell. 1996;86(3):353-364.
  3. Kerbel RS. Tumor angiogenesis. N Engl J Med. 2008;358(19):2039-2049.
  4. Folkman J. Tumor angiogenesis: therapeutic implications. N Engl J Med. 1971;285(21):1182-1186.
  5. Folkman J. Angiogenesis: an organizing principle for drug discovery? Nat Rev Drug Discov. 2007;6(4):273-286.
  6. Ferrara N, Hillan KJ, Gerber H-P, Novotny W. Discovery and development of bevacizumab, an anti-VEGF antibody for treating cancer. Nat Rev Drug Discov. 2004;3(5):391-400.
  7. Hurwitz H, Fehrenbacher L, Novotny W, et al. Bevacizumab plus irinotecan, fluorouracil, and leucovorin for metastatic colorectal cancer. N Engl J Med. 2004;350(23):2335-2342.
  8. Sandler A, Gray R, Perry MC, et al. Paclitaxel-carboplatin alone or with bevacizumab for non-small-cell lung cancer. N Engl J Med. 2006;355(24):2542-2550.
  9. Hong S, Tan M, Wang S, Luo S, Chen Y, Zhang L. Efficacy and safety of angiogenesis inhibitors in advanced non-small cell lung cancer: a systematic review and meta-analysis. J Cancer Res Clin Oncol. 2015;141(5):909-921.
  10. Wang H, Xu T, Zheng L, Li G. Angiogenesis inhibitors for the treatment of ovarian cancer: an updated systematic review and meta-analysis of randomized controlled trials. Int J Gynecol Cancer. 2018;28(5):903-914.
  11. Yu J, Zhang Y, Leung L-H, Liu L, Yang F, Yao X. Efficacy and safety of angiogenesis inhibitors in advanced gastric cancer: a systematic review and meta-analysis. J Hematol Oncol. 2016;9(1):1
  12. Li Q, Wu T, Jing L, et al. Angiogenesis inhibitors for the treatment of small cell lung cancer (SCLC): a meta-analysis of 7 randomized controlled trials. Medicine. 2017;96(13):e64
  13. Reck M. Examining the safety profile of angiogenesis inhibitors: implications for clinical practice. Target Oncol. 2010;5(4):257-267.
  14. Lu K, Bhat M, Basu S. Plants and their active compounds: natural molecules to target angiogenesis. Angiogenesis. 2016;19(3):287-295.
  15. Guo Y, Zhi F, Chen P, et al. Green tea and the risk of prostate cancer: a systematic review and meta-analysis. Medicine (Baltimore). 2017;96(13):e6426.
  16. Ni CX, Gong H, Liu Y, Qi Y, Jiang CL, Zhang JP. Green tea consumption and the risk of liver cancer: a meta-analysis. Nutr Cancer. 2017;69(2):211-220.
  17. Gianfredi V, Nucci D, Abalsamo A, et al. Green tea consumption and risk of breast cancer and recurrence-a systematic review and meta-analysis of observational studies. Nutrients. 2018;10(12):1886.
  18. Zhang C, Qin YY, Wei X, Yu FF, Zhou YH, He J. Tea consumption and risk of cardiovascular outcomes and total mortality: a systematic review and meta-analysis of prospective observational studies. Eur J Epidemiol. 2015;30(2):103-113.
  19. Zhu BH, Chen HY, Zhan WH, et al. (-)-Epigallocatechin-3-gallate inhibits VEGF expression induced by IL-6 via Stat3 in gastric cancer. World J Gastroenterol. 2011;17(18):2315-2325.
  20. Masuda M, Suzui M, Lim JT, Deguchi A, Soh JW, Weinstein IB. Epigallocatechin-3-gallate decreases VEGF production in head and neck and breast carcinoma cells by inhibiting EGFR-related pathways of signal transduction. J Exp Ther Oncol. 2002;2(6):350-359.
  21. Leong H, Mathur PS, Greene GL. Green tea catechins inhibit angiogenesis through suppression of STAT3 activation. Breast Cancer Res Treat. 2009;117(3):505-515.
  22. Zhu BH, Zhan WH, Li ZR, et al. (-)-Epigallocatechin-3-gallate inhibits growth of gastric cancer by reducing VEGF production and angiogenesis. World J Gastroenterol. 2007;13(8):1162-1169.
  23. Zhang Q, Tang X, Lu Q, Zhang Z, Rao J, Le AD. Green tea extract and (-)-epigallocatechin-3-gallate inhibit hypoxia- and serum-induced HIF-1alpha protein accumulation and VEGF expression in human cervical carcinoma and hepatoma cells. Mol Cancer Ther. 2006;5(5):1227-1238.
  24. Park JS, Kim MH, Chang HJ, et al. Epigallocatechin-3-gallate inhibits the PDGF-induced VEGF expression in human vascular smooth muscle cells via blocking PDGF receptor and Erk-1/2. Int J Oncol. 2006;29(5):1247-1252.
  25. Cai ZY, Li XM, Liang JP, et al. Bioavailability of tea catechins and its improvement. Molecules. 2018;23(9):2346.
  26. Chow HH, Hakim IA, Vining DR, et al. Effects of dosing condition on the oral bioavailability of green tea catechins after single-dose administration of Polyphenon E in healthy individuals. Clin Cancer Res. 2005;11(12):4627-4633.
  27. McLarty J, Bigelow RL, Smith M, Elmajian D, Ankem M, Cardelli JA. Tea polyphenols decrease serum levels of prostate-specific antigen, hepatocyte growth factor, and vascular endothelial growth factor in prostate cancer patients and inhibit production of hepatocyte growth factor and vascular endothelial growth factor in vitro. Cancer Prev Res (Phila). 2009;2(7):673-682.
  28. Gee JR, Saltzstein DR, Kim K, et al. A phase II randomized, double-blind, presurgical trial of Polyphenon E in bladder cancer patients to evaluate pharmacodynamics and bladder tissue biomarkers. Cancer Prev Res (Phila). 2017;10(5):298-307.
  29. Domingo DS, Camouse MM, Hsia AH, et al. Anti-angiogenic effects of epigallocatechin-3-gallate in human skin. Int J Clin Exp Pathol. 2010;3(7):705-709.
  30. Rahmani AH, Alsahli MA, Aly SM, Khan MA, Aldebasi YH. Role of curcumin in disease prevention and treatment. Adv Biomed Res. 2018;7:38.
  31. Ferreira LC, Arbab AS, Jardim-Perassi BV, et al. Effect of curcumin on pro-angiogenic factors in the xenograft model of breast cancer. Anticancer Agents Med Chem. 2015;15(10):1285-1296.
  32. Binion DG, Otterson MF, Rafiee P. Curcumin inhibits VEGF-mediated angiogenesis in human intestinal microvascular endothelial cells through COX-2 and MAPK inhibition. Gut. 2008;57(11):1509-1517.
  33. Yoysungnoen P, Wirachwong P, Bhattarakosol P, Niimi H, Patumraj S. Effects of curcumin on tumor angiogenesis and biomarkers, COX-2 and VEGF, in hepatocellular carcinoma cell-implanted nude mice. Clin Hemorheol Microcirc. 2006;34(1-2):109-115.
  34. Da W, Zhang J, Zhang R, Zhu J. Curcumin inhibits the lymphangiogenesis of gastric cancer cells by inhibiton of HMGB1/VEGF-D signaling. Int J Immunopathol Pharmacol. 2019;33:2058738419861600.
  35. Pan Z, Zhuang J, Ji C, Cai Z, Liao W, Huang Z. Curcumin inhibits hepatocellular carcinoma growth by targeting VEGF expression. Oncol Lett. 2018;15(4):4821-4826.
  36. Moradi-Marjaneh R, Hassanian SM, Rahmani F, Aghaee-Bakhtiari SH, Avan A, Khazaei M. Phytosomal curcumin elicits anti-tumor properties through suppression of angiogenesis, cell proliferation and induction of oxidative stress in colorectal cancer. Curr Pharm Des. 2018;24(39):4626-4638.
  37. Li X, Ma S, Yang P, et al. Anticancer effects of curcumin on nude mice bearing lung cancer A549 cell subsets SP and NSP cells. Oncol Lett. 2018;16(5):6756-6762.
  38. Dei Cas M, Ghidoni R. Dietary curcumin: correlation between bioavailability and health potential. Nutrients. 2019;11(9):2147.
  39. Cheng AL, Hsu CH, Lin JK, et al. Phase I clinical trial of curcumin, a chemopreventive agent, in patients with high-risk or pre-malignant lesions. Anticancer Res. 2001;21(4B):2895-2900.
  40. Sharma RA, McLelland HR, Hill KA, et al. Pharmacodynamic and pharmacokinetic study of oral Curcuma extract in patients with colorectal cancer. Clin Cancer Res. 2001;7(7):1894-1900.
  41. Dhillon N, Aggarwal BB, Newman RA, et al. Phase II trial of curcumin in patients with advanced pancreatic cancer. Clin Cancer Res. 2008;14(14):4491-4499.
  42. Kanai M, Otsuka Y, Otsuka K, et al. A phase I study investigating the safety and pharmacokinetics of highly bioavailable curcumin (Theracurmin) in cancer patients. Cancer Chemother Pharmacol. 2013;71(6):1521-1530.
  43. Cuomo J, Appendino G, Dern AS, et al. Comparative absorption of a standardized curcuminoid mixture and its lecithin formulation. J Nat Prod. 2011;74(4):664-669.
  44. Antony B, Merina B, Iyer VS, Judy N, Lennertz K, Joyal S. A pilot cross-over study to evaluate human oral bioavailability of BCM-95CG (Biocurcumax), a novel bioenhanced preparation of curcumin. Indian J Pharm Sci. 2008;70(4):445-449.
  45. Prasad S, Tyagi AK, Aggarwal BB. Recent developments in delivery, bioavailability, absorption and metabolism of curcumin: the golden pigment from golden spice. Cancer Res Treat. 2014;46(1):2-18.
  46. Ganjali S, Sahebkar A, Mahdipour E, et al. Investigation of the effects of curcumin on serum cytokines in obese individuals: a randomized controlled trial. ScientificWorldJournal. 2014;2014:898361.
  47. Haghighatdoost F, Hariri M. Effect of resveratrol on lipid profile: an updated systematic review and meta-analysis on randomized clinical trials. Pharmacol Res. 2018;129:141-150.
  48. Asgary S, Karimi R, Momtaz S, Naseri R, Farzaei MH. Effect of resveratrol on metabolic syndrome components: a systematic review and meta-analysis. Rev Endocr Metab Disord. 2019;20(2):173-186.
  49. Akbari M, Tamtaji OR, Lankarani KB, et al. The effects of resveratrol supplementation on endothelial function and blood pressures among patients with metabolic syndrome and related disorders: a systematic review and meta-analysis of randomized controlled trials. High Blood Press Cardiovasc Prev. 2019;26(4):305-319.
  50. Tino AB, Chitcholtan K, Sykes PH, Garrill A. Resveratrol and acetyl-resveratrol modulate activity of VEGF and IL-8 in ovarian cancer cell aggregates via attenuation of the NF-kappaB protein. J Ovarian Res. 2016;9(1):84.
  51. Hogg SJ, Chitcholtan K, Hassan W, Sykes PH, Garrill A. Resveratrol, acetyl-resveratrol, and polydatin exhibit antigrowth activity against 3D cell aggregates of the SKOV-3 and OVCAR-8 ovarian cancer cell lines. Obstet Gynecol Int. 2015;2015:279591.
  52. Sahin E, Baycu C, Koparal AT, Burukoglu Donmez D, Bektur E. Resveratrol reduces IL-6 and VEGF secretion from co-cultured A549 lung cancer cells and adipose-derived mesenchymal stem cells. Tumour Biol. 2016;37(6):7573-7582.
  53. Zhang H, Yang R. Resveratrol inhibits VEGF gene expression and proliferation of hepatocarcinoma cells. Hepatogastroenterology. 2014;61(130):410-412.
  54. Gambini J, Ingles M, Olaso G, et al. Properties of resveratrol: in vitro and in vivo studies about metabolism, bioavailability, and biological effects in animal models and humans. Oxid Med Cell Longev. 2015;2015:837042.
  55. Chimento A, De Amicis F, Sirianni R, et al. Progress to improve oral bioavailability and beneficial effects of resveratrol. Int J Mol Sci. 2019;20(6):1381.
  56. Shaito A, Posadino AM, Younes N, et al. Potential adverse effects of resveratrol: a literature review. Int J Mol Sci. 2020;21(6):2084.
  57. Bahramrezaie M, Amidi F, Aleyasin A, et al. Effects of resveratrol on VEGF & HIF1 genes expression in granulosa cells in the angiogenesis pathway and laboratory parameters of polycystic ovary syndrome: a triple-blind randomized clinical trial. J Assist Reprod Genet. 2019;36(8):1701-1712.
  58. Lin CT, Sun XY, Lin AX. Supplementation with high-dose trans-resveratrol improves ultrafiltration in peritoneal dialysis patients: a prospective, randomized, double-blind study. Ren Fail. 2016;38(2):214-221.
  59. Leung KW, Wong AS. Pharmacology of ginsenosides: a literature review. Chin Med. 2010;5:20.
  60. Wu W, Zhou Q, Zhao W, et al. Ginsenoside Rg3 inhibition of thyroid cancer metastasis is associated with alternation of actin skeleton. J Med Food. 2018;21(9):849-857.
  61. Li B, Qu G. Inhibition of the hypoxia-induced factor-1alpha and vascular endothelial growth factor expression through ginsenoside Rg3 in human gastric cancer cells. J Cancer Res Ther. 2019;15(7):1642-1646.
  62. Chen QJ, Zhang MZ, Wang LX. Gensenoside Rg3 inhibits hypoxia-induced VEGF expression in human cancer cells. Cell Physiol Biochem. 2010;26(6):849-858.
  63. Cao Y, Ye Q, Zhuang M, et al. Ginsenoside Rg3 inhibits angiogenesis in a rat model of endometriosis through the VEGFR-2-mediated PI3K/Akt/mTOR signaling pathway. PLoS One. 2017;12(11):e0186520.
  64. Niu T, Smith DL, Yang Z, et al. Bioactivity and bioavailability of ginsenosides are dependent on the glycosidase activities of the A/J mouse intestinal microbiome defined by pyrosequencing. Pharm Res. 2013;30(3):836-846.
  65. Fan H, Xiao-Ling S, Yaliu S, et al. Comparative pharmacokinetics of ginsenoside Rg3 and ginsenoside Rh2 after oral administration of ginsenoside Rg3 in normal and walker 256 tumor-bearing rats. Pharmacogn Mag. 2016;12(45):21-24.
  66. Reeds DN, Patterson BW, Okunade A, Holloszy JO, Polonsky KS, Klein S. Ginseng and ginsenoside Re do not improve beta-cell function or insulin sensitivity in overweight and obese subjects with impaired glucose tolerance or diabetes. Diabetes Care. 2011;34(5):1071-1076.
  67. Zeng D, Wang J, Kong P, Chang C, Li J, Li J. Ginsenoside Rg3 inhibits HIF-1alpha and VEGF expression in patient with acute leukemia via inhibiting the activation of PI3K/Akt and ERK1/2 pathways. Int J Clin Exp Pathol. 2014;7(5):2172-2178.
  68. Chen ZJ, Cheng J, Huang YP, et al. [Effect of adjuvant chemotherapy of ginsenoside Rg3 combined with mitomycin C and tegafur in advanced gastric cancer]. Zhonghua Wei Chang Wai Ke Za Zhi. 2007;10(1):64-66.
  69. Lu P, Su W, Miao ZH, Niu HR, Liu J, Hua QL. Effect and mechanism of ginsenoside Rg3 on postoperative life span of patients with non-small cell lung cancer. Chin J Integr Med. 2008;14(1):33-36.
  70. Huang JY, Sun Y, Fan QX, Zhang YQ. [Efficacy of Shenyi Capsule combined with gemcitabine plus cisplatin in treatment of advanced esophageal cancer: a randomized controlled trial]. Zhong Xi Yi Jie He Xue Bao. 2009;7(11):1047-1051.
  71. Bracken MB. Why animal studies are often poor predictors of human reactions to exposure. J R Soc Med. 2009;102(3):120-122.
  72. Van Norman GA. Limitations of animal studies for predicting toxicity in clinical trials: is it time to rethink our current approach? JACC Basic Transl Sci. 2019;4(7):845-854.
  73. Akhtar A. The flaws and human harms of animal experimentation. Camb Q Healthc Ethics. 2015;24(4):407-419.

Diversified Communications
© 2024 Diversified Communications. All rights reserved.