James DeGregori is a Professor in the Department of Biochemistry and Molecular Genetics at the University of Colorado School of Medicine and the Deputy Director of the University of Colorado Cancer Center. His lab studies the evolution of cancer, in the context of their Adaptive Oncogenesis model, with a focus on how aging and other insults influence cancer initiation. His lab has developed this cancer model based on classic evolutionary principles and substantiated this model by theoretical, experimental, and computational studies. This model is described in his recent book, Adaptive Oncogenesis: A New Understanding of How Cancer Evolves inside Us (Harvard University Press). The following is the introduction to that book. Matt Young will serve as moderator of this thread.
Why do we get diseases like cancer, and why do we get them mostly when we are old? Why do children get cancer? Why do we age? These may seem like existential questions, but there are answers, even if we do not know all of them. If you go to your doctor, you will get proximate explanations, which consider the causes of processes and diseases like aging and cancer within us. You may be told that aging is the result of a lifelong accumulation of damage to your tissues, both from errors that occur as your body maintains itself and from the damaging exposures that we experience during life. Analogously, you will be told that cancer is the result of a lifetime’s accumulation of genetic alterations (mutations) and that the accumulation by chance of a certain set of cancer-promoting mutations explains the increased risk of cancer late in life. Similarly, exposures to carcinogens, such as through smoking, are said to cause cancer by inducing mutations that change normal cells into cancer cells. But the more informative and more useful answers lie in an evolutionary understanding of life history and disease. As the great evolutionary biologist Ernst Mayr said, “No biological problem is solved until both the proximate and the evolutionary causation has been elucidated.”
Cancer is the second leading cause of death in industrialized countries: about 40 percent of people in those countries will develop cancer, and close to half of these individuals will die from their disease. Cancer is largely a disease of old age, with over 90 percent of cancers occurring in individuals over fifty. Other causes of cancer include cigarette smoking, alcohol consumption, sun exposure, pollution exposure, infections, and obesity. The medical and research communities have primarily ascribed associations between aging or exposures and cancer to enhanced mutation accumulation, despite strong evidence challenging such simple relationships.