By Vaclav Vetvicka, Ph.D Associate Professor at the Department of pathology, Division of Experimental Immunology and Immunopathology of the School of Medicine, University of Louisville, Louisville, Kentucky
Since the first scientific discovery 40 years ago, the anti-tumor activity of beta glucan has been clearly demonstrated in numerous animal and human studies involving a wide range of tumors including breast, lung, and gastrointestinal cancer. In Japan, beta glucan is a licensed immunostimulant for cancer treatment and numerous clinical trials are currently under way, both in the United States and in several European countries.
Cancer cells have mechanisms to evade the body's defenses and make them difficult to destroy. These cells have changed their normal characteristics and constantly attack our body in an effort to either overcome the immune system, which, after some time, becomes exhausted, or escapes recognition and subsequent destruction by our natural defense mechanisms. Cancer overwhelms or overpowers our numerous immune cells (white blood cells including macrophages, dendritic cells and natural killer or NK cells).
In healthy bodies, these defender cells successfully manage to fight the invading pathogens and tumor cells, but the ability of our body to heal is not endless. In addition, stress, allergies, pollutants and age have negative effects on the strength of our natural defensive reactions. Under normal conditions, the immune system is able to overcome the invasion of cancer cells, but at times of extreme conditions, the natural line of defense is often just not strong enough. When the immune system is compromised, there is severe risk of the development of tumors. Clearly, our immune cells need any help they can get, and this is the reason immunomodulators like beta glucan are so important.
There are several positive effects of beta glucan in tumor therapy. One is the direct positive enhancement of macrophages and NK Cells. Macrophages form the first line of defense and protect our body against any type of invaders- including cancer cells. NK cells represent a special subtype of "bloodthirsty" lymphocytes, with a single but extremely important function - to specifically recognize and kill tumor cells. The job of these cells isn't easy, considering the fact that they perform this function 24 hours a day, seven days a week. Again, they can use all the help they can get.
Recent animal studies have shown that beta glucan is extremely active in cooperation with antibodies, which naturally occur in case of cancer. This is one way that tumor cells are recognized by the immune system. Even a healthy immune system cannot adequately deal with fast growing cancer cells alone and the situation can get serious very fast. Antibodies alone cannot make tumor cells disappear, but following the binding of antibodies and a blood protein called complement on the surface of cancer cells, beta glucan- primed immune cells specifically recognize these compliment-antibody complexes and kill the tumor cells. The cooperation of antibodies with beta glucan is more active than either irradiation or chemotherapy. Compared to traditional treatment of cancer, this type of treatment has one big advantage - it acts without any negative side effects.
Despite the fact that most tumors are recognized by the immune system, the antibody response is usually only light and often not strong enough to destroy the cancer growth. Again, beta glucan comes to the rescue. It is able to "cooperate" with antibodies. After tumor cells are recognized as foreign, antibodies specific to that cancer are formed, and subsequently bind to the cancer cells. Without the beta glucan-derived activation of immune cells, the cancer cells remain coated, but no killing occurs.
Beta glucan binds to the surface of both macrophages and NK cells, interacts with the surface molecules, and triggers the activation processes. The result of this interaction is that the highly activated tumor killers circulate in our body and actively seek and destroy their preferred targets - cancer cells. Upon contact with these cancer cells they kill them in a specific way, which means they destroy only the cancer cells and leave the surrounding tissues and organs remains intact and unharmed.
The miraculous effects of beta glucan do not end in activation of immunocytes. Beside the ability to stimulate the cells of the immune system to perform optimally and maximally, beta glucan also "cares" about their numbers. It is well established that all cells involved in immune reactions originate from common precursors - stem cells originating from bone marrow. The influx of new cells from bone marrow is steady throughout our entire life.
Beta glucan stimulates the production of precursor cells in bone marrow, resulting in a more rapid flow of new immunocytes into the bloodstream and into the various lymphoid organs throughout the body. These effects are important not only under normal conditions, as the increased amount of immunocytes in circulation means increased surveillance against potential invaders, but particularly in case of extreme stress such as cancer, where the limited influx is further reduced by exhaustion of the immune system and by treatments such as irradiation and chemotherapy.
These effects alone would be enough to consider beta glucan one of the most significant anti-cancerous immunostimulants we know, but beta glucan has still another ace up its sleeve. In addition to the already mentioned specific stimulation of cell surface receptors, beta glucan is able to nonspecifically activate of the immune system via the release of biologically important molecules.
Upon entering the blood stream, beta glucan activates various cells of the body to release numerous biological factors and signals molecules known to influence our defensive systems. Among these factors are: tumor necrosis factor (TNF), interleukins 1 and 6, hydrogen peroxide, and gamma interferon, all of which are proven effective in our fight against cancers and other invading microorganisms.
These effects are systemic, which means that even after localized application of glucan, these immunoactive molecules can influence the activity of immune system throughout the entire human body. In addition to the direct effects on tumor cells, the synthesis and release of these signals also has a direct impact on macrophages and T lymphocytes capable of producing other cytokines. In this nonspecific way, beta glucan helps to boost defensive reactions by triggering the whole complicated cascade of events leading to a fully armed immune system.
Despite decades of intensive research and great achievements of medicine in the last decade, the incidence of various tumors and cancers is still increasing rapidly. The National Cancer Institute estimates that 1 in 5 humans in the U.S. are likely to get cancer in their lifetimes. This qualifies as a bona-fide epidemic, and the occurrence of cancer is increasing every year. More and more people are living under stressful and relatively toxic conditions, and diseases such as allergy and cancer have become too common.
It is clear that the ability to boost the activity of defense reaction by easily obtained, safe, inexpensive, and commercially available immunostimulants is extremely important to our health. Investigations of various beta-glucans affecting immune reactions are currently the focus of not only intensive preclinical investigation, but also in numerous clinical trials in several parts of the globe.
There are currently well over a thousand scientific papers describing various biological effects of beta glucan, and new exciting data are appearing every week. Its cancerostatic and immunostimulating properties make beta glucan one of the most important substances available to us in the ongoing fight against cancer. At the same time, only a few drugs have similar advantages as beta glucan, most of all it is safe, natural, and highly effective.