Download How to Battle Cancer Linked to Obesity

How to Battle Cancer Linked to Obesity
We are in the midst of a worldwide epidemic of obesity. The facts are well-known, but still frightening:
More than one-third of the U.S. population is obese, with another third overweight. This problem is not
restricted to this country or developed nations. More than 2 billion people around the world — more
than one-quarter of the planet’s population — are estimated to be obese or overweight.
Sadly, obesity is an affliction of all ages. In the U.S., the number of obese children has grown from 5
percent in 1980 to 18 percent in 2010. It continues to rise.
The health consequences associated with obesity are staggering. Most of us know that obesity leads
to type 2 diabetes and heart disease. New data also reveal a direct link to other maladies, such as
asthma, liver disease, psoriasis, arthritis and Alzheimer’s disease. But perhaps the most worrisome
complication of obesity is one only recently documented and still not fully appreciated — cancer.
The data linking obesity and cancer are convincing. Compelling evidence suggests the incidence of
esophageal, pancreatic, colon and rectum, breast, endometrial, kidney, thyroid and gallbladder cancers
are markedly increased in obese patients. There are indications that obesity is associated with other
cancer types as well. These connections span virtually every population and all racial and ethnic groups.
They are not restricted to specific regions. The only common denominator is obesity.
Why does being obese predispose for a greater risk of cancer? Frankly, we don’t know. Scientists have
explored possibilities, and hypotheses have emerged that might explain the connection.
One idea is that hormones like insulin that are elevated in obese people might drive the growth of
cancer cells, while fat cells in the mammary gland can produce estrogens, contributing to breast
cancer development well beyond menopause. Another idea is that chronic inflammation caused by
obesity contributes to a microenvironment that promotes cancer cell growth. Perhaps obesity stresses
cells to the point of tipping them into a cancerous state? Or maybe changes in sugar and fat metabolism
associated with obesity provide the fuel cancer cells need to thrive or metastasize.
We and colleagues at UC San Diego have been exploring these and other ideas, closely examining the
metabolism of cancer cells, evaluating the impact of obesity in experimental animals, studying the
intersection of pathways in cells that control both growth and metabolism. We’re testing obesity and
diabetes drugs in cancer studies.
Current open clinical trials at UC San Diego are also exploring some fundamental questions, such as how
much can one reduce the risk of developing cancer by increasing physical activity and how weight loss
programs and routine exercise might shield overweight or obese cancer survivors from tumor relapse.
These efforts are fueled by frequent and deep interactions between scientists and clinicians who study
both diabetes and cancer.
What can we do to have a bigger impact on this problem? First, we can recognize that obesity is a bona
fide disease. No one volunteers to become obese; the forces that drive us to consume and preserve
calories are powerful. We need to understand better how our bodies regulate metabolism so that we
can come up with new approaches to help patients modify their metabolism and eating habits. We also
need to investigate in greater depth how obesity somehow produces a tumor-friendly state so that we
can directly attack this problem.
Devising new approaches to treating and preventing obesity-associated cancer will require considerable
effort. We need to bring together scientists and clinicians from disparate fields. There is already ample
evidence that sharing ideas and approaches benefits everyone involved, especially patients. For
example, one of the major targeted therapies now used for melanoma and other cancers was developed
against a protein originally identified because of its proposed role in controlling blood sugar.
We are confident new and great progress can be made by tackling the health threats of cancer and
diabetes in tandem.
Saltiel, Ph.D., is professor of medicine and director of the Institute for Diabetes and Metabolic Health at
UC San Diego School of Medicine. Gutkind, Ph.D., is professor of pharmacology and associate director,
basic science, at UC San Diego Moores Cancer Center.
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