A 2006 study (Cancer Research) was the first human investigation to show that green tea catechins (GTC) are highly effective in reversing premalignant prostate lesions (high-grade prostate intra-epithelial neoplasia), an established precursor to prostate cancer.
Men in the GTC-treated group also had consistently lower PSA levels than the placebo-treated group throughout the study period. Supplementation with GTC also improved symptoms of prostate enlargement (benign prostatic hyperplasia) and reduced lower urinary tract symptoms. No significant side effects / adverse effects were reported by the men supplementing with GTC.
GTC for Localized Prostate Cancer
Based on the success of the 2006 study described above, a second study using GTC was published in 2009 (Cancer Prevention Research). In this case, GTC were provided to men with established localized prostate cancer who were awaiting surgical treatment in the form of radical prostatectomy.2
In this study, 26 men with positive prostate biopsies ingested a supplement containing 800 mg GTC daily until the time of radical prostatectomy (median dosing period was 34.5 days). Serum was collected before initiation of the study and on the day of prostatectomy. The study showed that GTC supplementation in these men produced a decrease in many prostate cancer biomarkers, including:
- Prostate Specific Antigen (PSA) – Prostate cancer cells secrete PSA. The higher the blood PSA level, the greater the number of active prostate cancer cells. High PSA signifies more advanced prostate cancer disease.
- Hepatocyte Growth Factor (HGF) – The stromal tissue around cancer cells is known to secrete this growth factor, which promotes cancer cell division and increased tumor vascularization to promote metastasis. High HGF signifies higher risk for metastasis.
- Vascular Endothelial Growth Factor (VEGF) – This growth factor promotes the growth of new blood vessels to feed the tumor and promote metastasis. High VEGF levels signified higher risk for metastasis.
- Insulin-like Growth Factor and its Binding Proteins (IGF-I, IGFBP-3, and the IGF-I/IGFBP-3) – Higher IGF-1 and lower IGF-1 binding protein levels encourage more rapid cell division of cancer cells. IGF-I/IGFBP-3 ratio decreased significantly during the study.
- Liver Function Tests – In this study, all of the liver function tests also decreased, five of them significantly: total protein, albumin, aspartate aminotransferase, alkaline phosphatase and amylase.
The researchers commented that their results indicate a significant reduction in serum levels of PSA, HGF and VEGF in men with prostate cancer after brief treatment with a GTC supplement, and with no elevation of liver enzymes. They further suggest GTC supplementation may play a potential role in the treatment or prevention of prostate cancer.
Proposed Mechanism of Action
Various experimental studies have shown that certain green tea catechins (EGCG and ECG) can inhibit the HGF/c-Met signaling pathway in both breast and prostate carcinoma cells. Hepatocyte Growth Factor (HGF) is normally secreted by mesenchymal cells and acts primarily upon epithelial cells and endothelial cells, but also acts on haemopoietic progenitor cells. It has been shown to have a major role in embryonic organ development, specifically in myogenesis, adult organ regeneration and wound healing.
The c-Met receptor is normally expressed by cells of epithelial origin. HGF normally stimulates the c-Met receptor on target tissues, which prompts them to replicate via up-regulation of the tyrosine kinase pathway. Thus, it plays an important role in embryonic growth and wound healing.
In prostate cancer, the transmembrane receptor c-Met is often over-expressed (a greater number of c-Met receptors than is considered normal) in primary tumors and metastases. High levels of c-Met are directly correlated with a higher Gleason score and associated with poorly differentiated tumors. Additionally, high serum levels of the c-Met ligand, HGF, have been found to be associated with metastatic disease and decreased overall survival.
Often the overproduction of HGF occurs in cancer-associated fibroblasts located in the stromal tissue surrounding the tumor. Many studies have now shown that the tumor stroma plays a very important role in cancer progression. A number of cells associated with the stroma, including macrophages, endothelial cells and fibroblasts, provide factors that facilitate proliferation, survival and invasion of tumor cells. As such, studies show that dysregulation of the HGF/c-Met pathway leads to increased proliferation, motility and invasion of cancer cells.
Other in vitro experiments show that GTC also block the production of VEGF and HGF in at least two different prostate cancer–associated fibroblast cell lines.2
Clinical Takeaway and Lifestyle Recommendations for Patients
Overall, the data suggests that supplementation with green tea catechins could be useful as an adjuvant therapy in men with prostate cancer by lowering the levels of cytokines (HGF, VEGF) that contribute to prostate cancer progression.2 In a previous article in this publication (May 20, 2010 DC), I reviewed the studies in which supplement and dietary practices have shown a positive result in the adjunctive management of prostate cancer cases.3 In light of this new evidence, I would add to this approach the inclusion of GTC (from decaffeinated green tea) at a daily dosage of 600-800 mg per day.
Prostate cancer is the second leading cause of cancer mortality in men in the United States, accounting for 27,000 deaths each year. Rates of recurrence for early-stage disease are relatively high, and mortality rates for late-stage disease have not improved significantly over the past 10 years.2
In regard to prostate cancer prevention, as much as 75 percent of prostate cancer is attributable to dietary and lifestyle factors, according to data published in the Journal of the National Cancer Institute. In my opinion, health practitioners should advise men on the lifestyle approach to prostate cancer prevention as part of their case management. Studies suggest the best advice to provide to them includes the following:
Dietary Recommendations
- Avoid high-fat animal foods such as red meat, pork products and high-fat dairy products, as well as foods high in trans fats, and deep-fried and pan-fried foods.
- Ingest no more than 2-3 alcoholic drinks per week on average.
- Eat one serving of a cruciferous vegetable at least three times per week (broccoli, Brussels sprouts, cabbage, cauliflower).
- Consume tomatoes and tomato products (e.g., tomato sauce, tomato juice) at least 4-5 times per week to acquire the protective properties of lycopene.
- Include soy products in your diet regularly. Studies show that soy foods and/or soy extract supplements block key steps in prostate cancer development and help manage many existing prostate cancer cases.
- Drink 4-8 ounces of pomegranate juice daily.
- Consume 2 tablespoons of ground flaxseed daily.
- Drink 3 cups of green tea daily.
Supplement Recommendations
- Take a daily high-potency multivitamin/mineral supplement that contains the following levels of antioxidants and vitamin D, shown to help inhibit prostate cancer development in various studies: vitamin C – 1,000 mg, vitamin E (succinate) – 400 IU, vitamin D – 1,000 IU, selenium – 200 mcg, and lycopene (5 percent) – 6 mg.
- Take an essential fatty acid supplement daily that contains 400 mg each of borage seed oil, flaxseed oil and fish oil (30 percent EPA / 20 percent DHA).
- Take some additional vitamin D (1,000-3,000 IU) during the winter months if you live above or below 40 degrees latitude, ensuring a blood level of at least 85 nmol/L.
- Green tea catechins – Take a supplement containing 300-600 mg of GTC derived from decaffeinated green tea.
- After age 40, take a prostate support supplement that contains specific ingredients that block the build-up of the dangerous form of testosterone (DHT); and blocks the overstimulation of testosterone and estrogen on the prostate gland. This is vital for men over age 40, as this is when these hormones enlarge the prostate and promote cancer development. A supplement of this type should contain saw palmetto – 640 mg (standardized to 45 percent fatty acids and sterols), Pygeum Africanum – 100 mg (standardized to 25 percent triterpenes), beta-sitosterol – 144 mg, soy extract – 100 mg (20 percent isoflavones), stinging nettle – 60 mg (5:1), lycopene (5 percent) – 25 mg, and pumpkin seed extract (4:1) – 50 mg.
- Melatonin – Take 1-3 mg of melatonin 60-90 minutes before bedtime daily after age 40.
References
- Bettuzzi S, Brausi M, Rizzi F, et al. Chemoprevention of human prostate cancer by oral administration of green tea catechins in volunteers with high-grade prostate intraepithelial neoplasia: a preliminary report from a one-year proof-of-principle study. Cancer Res, Jan. 15, 2006;66;1234.
- McLarty J, Bigelow R, Smith M, et al. 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, July 2009;2:673.
- Meschino J. "Nutrition for Prostate Cancer: Research Review." Dynamic Chiropractic, May 20, 2010.
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