Stem cells, cancer, adult stem cells, embryonic stem cells, teratoma

Stem Cells: Promise & Peril

Stem Cells: Promise & Peril

Dale H. Peterson, M.D.

As I write this Apple has just released the latest version of their Internet capable cellular telephone – the I-Phone 3G. Lines formed at stores offering the upgraded offering and many disappointed customers found themselves on waiting lists for the latest advance in communications technology.

Technology sells in today’s society. Most people are interested in learning about, and if possible owning new cutting edge products as they become available. This is true in all areas. Take transportation for example. Over 30,000 potential customers have made a $99 deposit for a opportunity to buy a Smart For Two car and over 20,000 have expressed an interest in purchasing GM’s Volt when it becomes available in 2010.

The fascination with new technology is just as strong when it comes to the health care arena as it is in electronics, communications, or transportation. Tens of thousands of people have purchased Lasik procedures to achieve 20/20 vision. Over 5 million have taken advantage of ultrasound scanning of arteries through Life Line Screening alone.

In the medical world today nothing is more high tech than stem cell research. As would be expected, the general public is enthralled with the idea of curing diseases with stem cells. While few people know what stem cells are and what their role is in the body, most are convinced that stem cells are the answer to challenges for which there are no traditional answers. It is generally believed that stem cells will allow the lame to walk, the blind to see, the deaf to hear, and those with degenerative conditions such as Parkinson’s disease and Alzheimer’s disease to regain the vitality of their youth.

Stem cell solutions are the highest of high tech interventions. Stem cell research is beginning to bear fruit, but if you are a regular reader of this letter you know that the answer to long-term health for the vast majority of people is not high-tech, but low-tech. Drinking pure water, eating real food, remaining physically active, providing needed nutrients, and minimizing exposure to toxins remain the key ingredients in maintaining health over the course of one’s lifetime. Interestingly, stem cell research is providing clues as to how and why low tech practices pay such high dividends.

Three characteristics define a stem cell. First, a stem cell is unspecialized. Second, it is capable of renewing itself over long periods of time using cell division. Third, a stem cell has the potential to turn into a specialized cell through various influences. These attributes account for the promise of stem cells, but they also account for the peril that is now believed to exist in stem cell lines.

There are two types of stem cells: embryonic stem cells and adult, or somatic, stem cells. Embryonic stem cells are the cells that are present in the developing embryo three to five days following conception. Embryonic stem cells are capable of becoming any of the over 200 specialized cell types that make up the tissues of a fully developed human being.

Adult cells differ in that they are more tissue specific. Bone marrow, for example, contains two types of stem cells. Hematopoietic stem cells form all of the blood cell types in the body, red blood cells, B lymphocytes, T lymphocytes, natural killer cells, neutrophils, basophils, eosinophils, monocytes, macrophages, and platelets. Stomal cells give rise to cells that form bone, cartilage, fat, and fibrous tissue. In recent years it has been learned that hematopoietic stem cells can also turn into brain cells, skeletal and cardiac (heart) muscle cells, and liver cells. Stromal cells have been shown to produce skeletal and heart muscle cells.

The presence of bone marrow stem cells has been known since the 1960s. Bone marrow stem cells are what make bone marrow transplants possible. The transplanted stem cells are able to renew themselves in the transplant recipient to provide a never-ending supply of unspecialized cells that can be converted to specialized blood cells as needed.

Other types of adult stem cells have been discovered. Brain stem cells were first identified in the 1990s. This was surprising since it had previously been thought that brain cells could not be replaced if they were lost. Brain stem cells are able to specialize as astrocytes, oligodenrocytes, and neurons, which are the three major cell types found in the brain. Stem cells have also been identified in skin, muscle, the digestive tract, blood vessels, and the liver.

No one knows the source of adult stem cells. They may be embryonic stem cells that have lain dormant for years, or they may arise by some as yet unknown mechanism. Adult stem cells can be activated by disease or tissue injury. Once they start dividing they are capable of providing specialized cells to rebuild injured tissue.

Major challenges exist in the arena of stem cell research. The first is establishing a stem cell line that can be maintained over an extended period of time. This is important because few stem cells exist, either in an embryo or in an adult. One embryo contains approximately 30 stem cells. Adult tissues contain at most 1 stem cell per 10,000 specialized cells.

Embryo stem cells are obtained from embryos that have been created in the process of in vitro fertilization. When an infertile couple seeks to achieve a pregnancy through this technology it is a common practice to fertilize multiple eggs and allow them to develop to the embryonic stage. Embryos that are not implanted in the woman’s uterus are stored in a frozen state for later implantation. After a period of time the remaining embryos are discarded, donated to research, or given to another couple desiring a child.

Embryonic stem cell research presents an ethical dilemma. Many believe that human life begins at the moment of conception. If an embryo has a soul, discarding it or using it for research purposes is immoral. Those favoring embryonic stem cell research argue that while the embryo contains the potential to become a human life, it does not yet possess a soul. They believe that use of the cells for purposes other than implantation in a womb is reasonable.

Using mouse embryos, scientists have learned the techniques required to successfully grow embryonic stem cells in the laboratory. The process was slow and laborious, taking over twenty years. Because of what has been learned, however, it is now possible to produce millions of stem cells from one embryo in as little as six months.

Adult stem cells are more difficult to identify and isolate, and no method is yet available for creating adult stem cell lines capable of producing an unlimited number of cells. Developing a protocol for establishing adult stem cell lines is a fertile area of research. Until this is accomplished the ability to effectively use adult stem cells will be severely compromised.

Another challenge facing stem cell researchers is identifying the triggers that cause stem cells to differentiate, that is to turn into specialized cells. As those factors are discovered, new insights into how to prevent and treat disease states will emerge. Without a clear understanding of the mechanisms involved in causing a stem cell to specialize it will not be possible to achieve desired results in tissue and organ repair and regeneration.

If researchers can develop a way to consistently multiply the number of adult stem cells in the laboratory and effectively direct those cells to specialize in the specific cell types desired the promise of stem cell therapy will be within grasp. That is the dream that drives stem cell research forward.

If a brain stem cell could be isolated from an individual who was beginning to show signs of a degenerative disease such as Parkinson’s, multiplied in the laboratory, and enough stem cells reintroduced to the brain perhaps the disease could be reversed. If an individual had developed liver failure from cirrhosis the process could be used to regenerate the liver without the need for a transplant procedure. If cells that produce insulin can be produced and transplanted into diabetics it is possible that the disease could be cured.

Researchers are studying stem cells for other reasons. It is hoped that if the factors that trigger cell specialization can be discovered, drugs that will have the ability to turn cell production on and off can be developed. By understanding the drug’s effects upon stem cells in the laboratory it may be possible to create similar results in the body.

The barriers to practical stem cell use are significant. Beyond the need to develop ways to consistently cause stem cells to multiply and differentiate into the desired cell types, scientists must also cope with the challenge of ensuring that cells survive after they are transplanted into an individual. They must find ways to integrate the transplanted cells into the surrounding tissue and see that they continue to function properly for the remainder of the recipient’s life. Most importantly, they must be able to guarantee that the recipient will not be harmed in any way.

The last challenge may prove to be the most difficult. While research has shown that stem cells play a significant role in the repair of injured tissues, it has also revealed that cancer is, in great measure, a stem cell disease.

The theory that cancer is a stem cell disease is not new. French pathologists noted similarities between cancer and embryonic tissue in the mid-nineteenth century. They suggested that tumors arise from embryo-like cells. The idea that dormant embryonic cells could be activated and become cancer cells became known as the “embryonal rest” theory of cancer. The theory was largely ignored throughout the twentieth century, but recent stem cell research has brought it back to the forefront.

It is clear that some tumors arise from dormant embryonic stem cells. Teratomas and embryonic carcinomas are prime examples.

Teratoma is a Greek word that means “monster tumor”. It is so named because it generally contains examples of tissues that arise from the three primary differentiated cell types. This can make the tumor appear quite grotesque. A teratoma may simply contain various tissues such as brain, liver, and lung, but it can also contain hair, teeth, bone, or even complex organs such as an eye or a hand.

Ironically, one of the characteristics that is used to confirm that a particular cell is indeed an embryonic stem cell is its ability to form a teratoma when injected into an adult. Since this currently occurs 100% of the time, embryonic stem cells cannot currently be used for tissue regeneration. Such use will only become possible if scientists are able to precisely identify and control the influences that cause an embryonic stem cell to differentiate into a specific type of specialized cell. If, and this is very likely the case, those influences are largely electromagnetic in nature and determined by the position of a specific stem cell within an embryo it will be impossible to control the differentiation process outside of the context of a complete and intact embryo. That context is destroyed whenever an embryo is destroyed and the stem cells of its inner lining harvested, and it cannot be recreated in a Petrie dish or a test tube.

An embryonic carcinoma is a type of testicular cancer that often shows several different tissue types including cartilage. Embryonic carcinomas can also occur in ovaries, but this is rare.

It is now believed that many, if not most, cancers arise from adult tissue stem cells. Analysis of the cells found in various cancers indicates that, in every instance, the tumor originated as a specific tissue stem cell. The stem cell may have been damaged in some way or the differentiation process may have been disrupted. In either case, a line of abnormal cells has appeared and is growing out of control.

The stem cell theory of cancer explains how many different carcinogens can trigger tumor growth. It is believed that genes play a significant role in controlling the activity of stem cells. When DNA is damaged, control of stem cell activity may be lost, resulting in uncontrolled reproduction of a specific cell type. DNA damage can be caused by free radicals (which are present in high numbers in cigarette smoke), ultraviolet light, and even microwaves and radio waves.

Chemical damage to stem cells may cause them to start producing cancer cells. Infections may do the same. It was recently reported that infection of stomach stem cells by the Epstein-Barr virus initiates a change of events that culminates in stomach cancer. (The Epstein-Barr virus is the same virus that causes mononucleosis and triggers Burkitt’s lymphoma – a type of cancer.)

While cancer appears to originate from tissue-specific stem cells it is aided by hematopoietic stem cells that escape from the bone marrow and enter the blood stream. These bone marrow stem cells stimulate the growth of new blood vessels within tumors. This facilitates growth. The process of new blood vessel formation, called angiogenesis, is key to cancer growth and spread. If angiogenesis can be stopped, tumors will outstrip their blood supply and die. A great deal of effort is being expended attempting to find agents that will block tumor angiogenesis.

Since stem cells are particularly resistant to chemotherapy and radiation cancer stem cells often survive cancer treatment. This is believed to be the reason that cancer so often reappears after it was thought to have been successfully treated.

Cancer researchers are currently pursuing means to directly attack and destroy cancer stem cells. Some are attempting to identify the triggers that are causing the stem cells to produce differentiated cancer cells. Others are seeking measures that will block the migration of bone marrow stem cells to tumor sites.

One of the unanswered questions in stem cell research is whether adult stem cells can consistently be extracted, manipulated in a laboratory, and placed back into the body without disrupting their normal control mechanisms. Japanese researchers published an article in ScienceExpress on February 14, 2008 in which they reported that adult stem cells they had reprogrammed produced teratomas when injected into adult mice.

The report stated, “Four weeks after transplantation, all mice developed tumors containing various tissues of the three germ lines, including neural tissues, muscle, cartilage, and gut-like epithelial tissues.” It had been the team’s goal to reprogram adult stem cells into embryonic stem cells, and the tumor formation confirmed that they had succeeded.

In most cases, researchers will not be attempting to convert adult stem cells to embryonic stem cells. The question remains, however. How much manipulation can adult stem cells withstand without becoming cancer stem cells?

Clearly much work remains to be done before stem cell therapy becomes a safe, effective, and reliable form of medical treatment. You and I need not wait to take advantage of what has been learned, however. High-tech stem cell research has already confirmed the importance of low-tech measures in the health of individuals.

By drinking pure water, eating whole foods, minimizing exposure to toxins, taking appropriate nutritional supplements, and using electromagnetic protective devices we can guard against stem cell damage. Doing so will go far to ensure that tissue stem cells continue to effectively address injuries appropriately. It will minimize the likelihood that a cancer stem cell line will emerge or that the process of differentiation will be altered to produce cancer cells rather than normal cells.

Applying low-tech measures will support the activity of bone marrow stem cells in producing red blood cells, white blood cells, and platelets. It will decrease the chance that hematopoietic cells will participate in promoting tumor growth and metastasis. Following the basics of wellness, low-tech though they may be, will give the greatest number of people the opportunity to live a long and productive life.

© 2008 Wellness Clubs of


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