American Association for Cancer Research

Responsible Exploration of the Full Spectrum of Stem Cell Biology is Essential to the Advancement of Cancer Research

Approved by the AACR Board of Directors, April 15, 2005

A Position Statement from the American Association for Cancer Research (2005)

The American Association for Cancer Research (AACR) recognizes the potential for stem cell research to improve the prevention, diagnosis and treatment of cancer. Peer-reviewed scientific evidence indicates that stem cells provide powerful models of the cellular and molecular origins of many cancer types. Continued experimentation with human stem cells will elucidate critical aspects of cell growth and differentiation altered during tumorigenesis. This work may improve pre-clinical evaluations of drug toxicity and efficacy, identify markers for early cancer detection and elucidate novel treatment targets.

AACR further recognizes that stem cell research encompasses stem cells of many types, and stresses that each facet of stem cell research is in fact complementary - not duplicative. Research on adult stem cells (tissue-specific stem cells found within adults) may uncover the body’s innate maintenance and repair mechanisms. This area of research includes important classes of blood-forming stem cells, such as the hematopoietic stem cells resident within bone marrow or the umbilical cord blood stem cells harvested at childbirth, as well as emerging studies of cancer stem cells. Embryonic stem cells (unspecialized stem cells found within very early stage embryos called blastocysts) have the ability to transform into the cells of every major organ system. If this characteristic, called pluripotency, can be controlled, then medical researchers could determine the signals directing the development of human tissues, including cancers.

For years, bone marrow stem cells have been used to replenish blood and immune systems damaged by cancer or cancer treatment. The Association welcomes the possibility of more effective applications of this technique through continued research with bone marrow stem cells or umbilical cord blood stem cells. Research on human embryonic stem cells may extend this promise by providing a transplantable cell source that avoids the problems of immune rejection. And by learning to direct stem cell differentiation into various adult cell types, medical researchers may one day use embryonic stem cells to target illnesses in addition to cancer, including heart disease, Parkinson’s, diabetes, Alzheimer’s, HIV/AIDS and spinal paralysis. Finally, recent descriptions of cancer stem cells as the progenitors of breast, prostate, brain and other malignant tumors raise the exciting prospect that tumor recurrence following initial treatment may be avoided, perhaps opening the door to a day when therapies for malignant cancer are truly curative.

AACR supports the ethical use of somatic cell nuclear transfer (also called SCNT or “therapeutic cloning”). This technique promises to reveal the role of specific genetic alterations in tumorigenesis and further refine evaluations of drug activity, as well as generate immune-compatible material for transplant therapies.

AACR vehemently rejects the use of stem cell technology, or any technology, for the purposes of human reproductive cloning - that is, cloning to create a baby. Such attempts have no beneficial goal and can be reasonably assumed to cause harm.

The Association acknowledges the ability of undifferentiated embryonic stem cells to spontaneously form tumors (called teratomas) in animals. Often utilized by researchers as a demonstration of these cells’ powerful differentiative potential, this characteristic has been viewed by some as an insurmountable barrier to the safe use of embryonic stem cells in transplants. However, the goal of transplant therapy is not to transfer undifferentiated stem cells, but instead to use these cells as the precursors of differentiated cells needed to replenish damaged tissue. Data from animal studies indicate that purified preparations of differentiated cells do not inappropriately form tumors, though additional confirmatory studies with human cells are necessary. Thus, recognition of this barrier to a clinical use of embryonic stem cells should not be construed as grounds to abandon the science.

American stem cell biology suffers from a limited pipeline of graduate students, post-doctoral fellows and young faculty. These innovative individuals are essential to the growth of any discipline. The Association urges scientific granting institutions to work toward stable and sufficient funding for meritorious stem cell research projects, free of political uncertainty, so that young investigators are encouraged to devote their careers to this important field.

As with any scientific investigation, explorations of stem cell biology must be pursued in strict accordance with long-standing ethical principles, and with adequate oversight, to safeguard the welfare of research donors and recipients. Individuals donating biological materials for research - including somatic cells, gametes and embryos - need to give their fully informed and voluntary consent through a mechanism uncompromised by financial incentive. The privacy and safety of clinical trial participants must be protected in line with the principles promulgated in the Belmont Report, which underlies human subjects protection in the United States.

In considering its support for research utilizing human embryonic stem cells, AACR recognizes and shares the universal sentiment that the human embryo deserves respect. Research involving human embryonic stem cells must serve important research aims that cannot be reached by other means. Moreover, the Association agrees with the internationally-accepted 14-day limit on the developmental age of blastocysts from which embryonic stem cells are derived.

AACR believes that stem cell research can be conducted in a manner consistent with established ethical principles, and so strongly supports responsible explorations of the full spectrum of stem cell biology, including the use of human embryonic stem cells, for meritorious scientific research and therapy development.