In laboratory studies, scientists at the Paterson Institute at the Christie Hospital in Manchester, England found that eating a diet rich with omega-3 polyunsaturated fatty acid could stop the spread of prostate cancer, but omega-6 fatty acids appear to promote the spread, says new research. Over half a million new cases of prostate cancer are diagnosed every year world wide, and the cancer is the direct cause of over 200,000 deaths.
Omega-6 fats, the kind found in vegetable oils such as margarine, salad dressing, corn and safflower oil, increased the spread of tumor cells into bone marrow. However, the spread was blocked by omega-3 fats, suggesting that a diet rich in omega-3 fatty acids could potentially inhibit the disease in men with early stage prostate cancer.
Prostate cancer, which is the third most common cancer in men, is more treatable if it is diagnosed before it has a chance to spread.
The researchers believe omega-3 fatty acids interfere with functions of omega-6, which cancer cells may use as a source of energy, and prevent them from spreading beyond the prostate gland. The researchers found that a metabolite of Omega-6 Arachidonic Acid, prostaglandin E2, helped the spread of the prostate cancer cells to bone marrow cells. However, when EPA and DHA were present at just half the concentration of the omega-6 fatty acid, this spread of cancer cells was stopped.
Prostatic cancer cells and normal human rib bone marrow cells were used in this study. Bone marrow is the most common site of prostate cancer metastasis. In a real person, in order for the prostatic cancer cells to get beyond the prostate and invade the marrow, the cancer cells must first get past membrane barriers. The researchers achieved a simulation of these membrane barriers by growing the two sets of cells in what they termed an “invasion chamber”. In these chambers, the growing bone marrow inserts were separated from the growing prostatic cancers cells by artificial membrane barriers. After time within the chambers under various conditions (described below), the patterns of the cell growth, including metastatic migration, were viewed under microscopic examination. The quantities of fats within cells were microscopically tracked using special stains.
The researchers were interested in determining the effects of fatty acids within their invasion chambers. Worldwide the incidence of prostate cancer varies regionally. It is three times more common in the United States than in developing countries. These researchers hypothesize that the differences in prostate cancer rates may be attributable to the differences in the quantities and types of fats consumed in the diets. Past research suggests that both the amount and kind of fats may influence the risk of prostate cancer. Omega-6 poly-unsaturated fatty acids may promote prostate cancer, while Omega -3 poly-unsaturated fatty acids may inhibit them.
Prostatic cancer cells were observed to migrate toward the fat cells of the bone marrow and form colonies around fatty areas. If the bone marrow’s ability to grow fat cells was deprived by the addition of hydrocortisone, the prostatic cancer cells were only weakly attracted to the fat-depleted bone marrow. Prostatic cancer cells could again invade the bone marrow if the omega-6 PUFA, arachadonic acid, was added to the fat cell-free bone marrow. However, if either of the omega-3 PUFAs, eicosapentanenoic acid or docasahexaenoic acid, were added to the mix, the prostatic cancer cells did not invade. A range of concentrations was tested. Omega-3 PUFAs, in a ratio of one omega-3 to two omega-6, resulted in inhibition of metastatic migration.
The researchers suggest that an increase in omega-3 PUFA’s in the diet might be of benefit in reducing the risk of aggressive prostate cancer. Both omega-6 and omega-3 PUFA’s are essential fatty acids that are required by the human body, but cannot be synthesized by the body. They come from food sources. Omega-6 PUFAs are relatively plentiful and are found in dairy, meats, fish, and plant sources. They are highly concentrated in vegetable oils - corn, safflower, margarine, etc. Omega-3’s are far scarcer, particularly in the American diet, but are found in cold water marine animals such as wild salmon, and some plant oils such as flax oil.
Epidemiological studies have shown not only a relationship between the intake of dietary lipids and an increased risk of developing metastatic prostate cancer, but also the type of lipid intake that influences the risk of metastatic prostate cancer. The Omega-6 poly-unsaturated fatty acid, Arachidonic acid, has been shown to enhance the proliferation of malignant prostate epithelial cells and increase the risk of advanced prostate cancer. However, its role in potentiating the migration of cancer cells is unknown. Here we show that arachidonic acid at concentrations <5 uM is a potent stimulator of malignant epithelial cellular invasion, which is able to restore invasion toward hydrocortisone-deprived adipocyte-free human bone marrow stroma completely. This observed invasion is mediated by the arachidonic acid metabolite prostaglandin E2 and is inhibited by the Omega-3 poly-unsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid at a ratio of 1:2 Omega-3:Omega-6, and by the COX-2 inhibitor NS-398. These results identify a mechanism by which arachidonic acid may potentiate the risk of metastatic migration and secondary implantation in vivo, a risk which can be reduced with the uptake of Omega-3 poly-unsaturated fatty acids.
M D Brown, C A Hart, E Gazi, S Bagley and N W Clarke. Promotion of prostatic metastatic migration towards human bone marrow stoma by Omega 6 and its inhibition by Omega 3 PUFAs; British Journal of Cancer (2006) 94, 842-853.