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Do Lifestyles and Stressful Experiences Influence Cancer Occurrence or Progression: Biological and Psychosocial Processes
More than any other illness, cancer is probably the most feared, not only because therapies are frequently ineffective, but because the treatments can take a psychological and physical toll on individuals. More than 100 different forms of cancer are attributable to genetic factors in more than 50% of cases, whereas the remainder are provoked or exacerbated by environmental and lifestyle factors.
Cancer cells are ruthless in evading the immune defenses that are aligned against them, even co-opting immune cells to avoid destruction. They develop effective ways of obtaining energy supplies to sustain their proliferation at the expense of healthy cells. Aside from the multiple methods of facilitating their own growth, cancer cells are remarkably adept at escaping therapies that ought to destroy them. Among other things, the tumor microenvironment might serve in a protective capacity for cancer cells and might not be conducive for therapies and immune cells that could potentially attack them. As well, frequent mutations of cancer cells that develop make them more difficult to target. Even when therapies initially appear to produce positive effects, resistance to therapies may develop owing to these mutations or suppression of processes that ordinarily promote cell death, and through epigenetic changes that develop, as well as by altering drug metabolism, and enhanced ability to rid themselves of toxins. Furthermore, cancer cells can leave the primary tumor mass, travel to distant sites where a new cancer colony can be established. These metastasized cells may carry further mutations so that therapies that might initially have been effective in limiting tumor growth no longer are effective in doing so.
To be sure, the effectiveness of cancer therapies has become progressively better so that some cancers that had been untreatable are now eliminated in most affected individuals. For other types of cancers, especially those that are not readily detected until late in their progression, the efficacy of most therapies is limited. Moreover, while new immunotherapies have been developed to treat solid and haematological cancers, they are still only effective in 20-30% of patients, although efficacy can be somewhat enhanced by judicious use of combination treatments.
Cancer: How Lifestyles May Impact Disease Development, Progression, and Treatment
The goal of this book is to delineate the ways in which lifestyles can influence the occurrence and progression of diverse forms of cancer, as well as to offer clues concerning how to limit them – particularly ways of altering well entrenched behaviors that are believed to promote cancer development and the wicked side effects of treatment. Many factors that promote cancer occurrence are not readily modifiable, including exposure to diverse toxicants, with those secondary to climate change. Other risk factors are modifiable by avoiding or diminishing exposure to agents that promote cancer occurrence or by adopting healthy behaviors that foster biological processes that can limit disease occurrence. The development of many forms of cancer can be facilitated by various carcinogenic agents (e.g., tobacco, ultraviolet sun rays) and by intake of commonly used substances, such as alcohol. Having obesity can similarly be aligned with the development of some forms of cancer. Furthermore, whereas certain diets are believed to enhance tumor occurrence and proliferation, other diets (e.g., Mediterranean diets) can limit cancer development. These outcomes may develop owing to their actions on various hormones (e.g., glucocorticoids, estrogen) and growth factors. As well, foods that favor the development of microbiota imbalances (e.g., within the gut) or that allow for the increased abundance of specific harmful microbes can favor cancer growth, whereas those foods (e.g., whole grains, lentils, peas, and vegetables) that enhance short chain fatty acids produced by specific microbiota may affect immune functioning, thereby diminishing cancer occurrence. Thus, diets that contain prebiotic and probiotic factors that affect gut microbes could potentially have beneficial effects. It has been argued that probiotic supplements may have similar positive effects, although this would only occur if a deficiency existed with respect to specific microbes. Aside from bacteria, the gut is teeming with fungi and archaea as well as diverse viruses that can affect bacteria or operate independently in affecting diseases.
Predictably, excessive sedentary behaviors can promote multiple negative outcomes, whereas the adoption of exercise can affect diverse biological systems that influence inflammatory processes that enhance heart health, limit the development of type 2 diabetes, and may act against the development of cancer. Even limited amounts of moderate exercise (30 min a day) can have positive actions by affecting immune functioning, endocrine or growth factors, as well as microbiota abundance and diversity. Likewise, sleep disturbances (or obtaining too much or far too little sleep) have been associated with cancer occurrence, and altered circadian rhythms, such as through shift work or frequent changes in shifts, have been implicated in cancer occurrence or progression. This could possibly be through actions on circulating levels of inflammatory factors (i.e., cytokines).
Chronic stressful experiences are known to undermine many components of innate and adaptive (acquired) immune functioning. Such experiences appear to favor the progression of existent cancers, whereas the involvement of stressful events in the provocation of cancer have less often been observed. Still, most studies that assessed this relationship did so during relatively short periods prior to cancer appearance, rather than many years earlier when cancer cells first appeared and were in stalemate in the battle with the immune system defenses. It is pertinent that adverse childhood experiences, as well as those encountered prenatally (i.e., if mom had been stressed during or prior to pregnancy) may have downstream effects that persist throughout life, and hence may have significant ramifications concerning the development of diverse illnesses. It has likewise been documented that diets adopted during early life can have similar long-term consequences on adult health and disease.
Being a profound stressor, a cancer diagnosis and its treatments may promote clinically significant levels of anxiety and depression and may instigate the development of posttraumatic stress disorder (PTSD), which can undermine treatment adherence and may limit the efficacy of therapies. Accordingly, ways of diminishing distress can be instrumental in enhancing general well-being and might be a tool that could potentially enhance the effectiveness of diverse treatments. This is also the case for diets and the presence of microbiota given that relevant manipulations may enhance the effectiveness of therapies, including immunotherapies.
About the Book Authors
Hymie Anisman received his PhD at the University of Waterloo in 1972 where he examined the time dependent effects of stressful experiences. Since then, his research conducted at Carleton University (Ottawa, Canada) focused on the impact of acute and chronic stressor experiences on diverse hormonal, brain neurochemical, immune, and cytokine processes that have been linked to psychological and physical illnesses. Fundamental to this work has been the analyses of the moderating effects of psychosocial factors in determining the impact of stressors on biological and health outcomes. These have included analyses of the influence of previous stressful experiences, including those encountered during early life, the influence of appraisal and coping processes, cultural influences on stress responses, as well as intergenerational and transgenerational effects associated with collective, historical trauma. In addition to books with Alex Kusnecov that dealt with immune and inflammatory processes in relation to mental health, he has published two textbooks for undergraduate students – one dealing with Stress and Health and the second on Health Psychology. Professor Anisman was a senior fellow of the Ontario Mental Health foundation, held a Canada Research Chair in Behavioral Neuroscience, and is a member of the Royal Society of Canada. His research was primarily funded by the Canadian Institutes of Health Research and the Natural Sciences and Engineering Research Council of Canada.
Alex Kusnecov received his doctorate from the University of Newcastle, New South Wales, Australia in 1990, after which he conducted postdoctoral work in psychoneuroimmunology at the University of Rochester and then in the Department of Pathology, University of Pittsburgh Medical Center. He is currently a Professor within the Department of Psychology at Rutgers University, where his research involves the analyses of functional relationships between the brain and behavior, endocrine systems, and immune processes. His research on psychoneuroimmunology has appeared in prestigious journals, and together with Anisman, he has published two books: an edited volume, Handbook of Psychoneuroimmunology, and The Immune System and Mental Health, published by Elsevier. He has served on several journal editorial boards, grant panels, and acted as undergraduate chair of the Department of Psychology. His research is funded by the National Institutes of Mental Health (NIMH).
Cancer, How Lifestyles May Impact Disease Development, Progression, and Treatment is available in the Elsevier Store.
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