Superfund Research Program | News and Events

Obesity ups cancer risk, and here’s how

Joong Park, Eek , Jun Hee Lee, Guann-Yi Yu, Guobin He, Syed Raza Ali, Ryan G. Holzer, Christoph H. Österreicher, Hiroyuki Takahashi, and Michael Karin. 2010 “Dietary and Genetic Obesity Promote Liver Inflammation and Tumorigenesis by Enhancing IL-6 and TNF Expression.” Cell 140:197-208. http://www.cell.com/fulltext/S0092-8674(09)01638-9

UC San Diego Health Sciences, Press Release
Date: January 21, 2010
Contact: Debra Kain, Director, Marketing & Communications, UC San Diego Health Sciences
619-543-6202 (direct), 619-543-6163 (main)

Link Between Obesity and Enhanced Cancer Risk Elucidated

Epidemiological studies indicate that being overweight or obese is associated with increased cancer risk. The most dramatic effect of obesity on cancer risk has been noted for a common form of liver cancer called hepatocellular carcinoma or HCC. Modeling the effect of obesity in mice, researchers at the University of California, San Diego School of Medicine have conclusively demonstrated that obesity is tumor-promoting and have obtained evidence that this effect depends on induction of low-grade, chronic inflammation. (click here to read the entire press release)

Eureka Public release date: 21-Jan-2010
Contact: Cathleen Genova, , 617-397-2802
Cell Press

Obesity ups cancer risk, and here’s how

Obesity comes with plenty of health risks, but there’s one that’s perhaps not so well known: an increased risk of developing cancer, and especially certain types of cancer like liver cancer. Now, a group of researchers reporting in the January 22nd issue of the journal Cell, a Cell Press publication, have confirmed in mice that obesity does indeed act as a “bona fide tumor promoter.” They also have good evidence to explain how that happens.

“Doctors always worry about our weight, but the focus is often on cardiovascular disease and type 2 diabetes, both of which can be managed pretty well with existing drugs,” said Michael Karin of the University of California, San Diego. “However, we should also worry about elevated cancer risk. If we can reduce cancer deaths by as many as 90,000 per year, that’s a lot of people – a lot of lives.” (click here to read the entire press release)

Significance of this Research (posted by the UCSD NIEHS Superfund Research Program)

Research sponsored by the NIEHS Superfund Research Program in the Michael Karin Lab at the University of California, San Diego – School of Medicine has elucidated a molecular mechanism that leads to an increase risk of liver cancer from obesity and exposure to environmental chemicals. Up until now, epidemiological evidence had pointed to a significant increase of type II diabetes, heart disease and liver cancer associated with being overweight or obese but the exact molecular mechanism was not known. In this study, published in the January 22 issue of the journal Cell, obesity in laboratory mice was shown to enhance liver damage caused by exposure to environmental chemicals through increase accumulation of free radicals and other reactive oxygen species in the liver. Obesity promotes the growth of cancerous tumors in the liver by enhancing the production of two signaling molecules that increase liver inflammation (IL6 and TNF) and the activation of an oncogene (STAT3) that promotes tumor growth. When exposed to a known liver carcinogen, mice kept of a high fat diet were observed to have greater liver damage and develop more and bigger tumors than lean mice. The tumor promoting effect of obesity is at least as strong as the most potent liver carcinogens. Further research is needed to determine if obesity increases the risk of developing other cancers.

These findings have important public health implications for Americans since the rate of obesity in the United States has reached epidemic proportions in recent years. Obesity is defined as having a Body Mass Index (BMI) equal to or greater than 30 (calculated as weight (Kg) divided by height (m) squared). According to the Centers for Disease Control (CDC), the range of the obese population in most U.S. states has changed from 0-19% (1991) to 15->30% (2006). Recent studies estimate that as much as two thirds of the U.S. population may be overweight or obese. Research shows that the likelihood of obesity in both children and adults is related to both genetic and environmental factors. A child born to an obese parent has a higher likelihood of growing up to become an obese adult. Obesity is especially problematic among indigenous communities and communities that are economically disadvantaged in the USA. Low income communities tend to have higher risk both due to higher rates of exposure (to environmental contamination) and more prevalent obesity.

Environmental and public health studies suggest that we can reduce rates of obesity in two fundamental ways: (1) Make cities more walkable through better planning and urban design. Right now cars dominate most cities making it difficult and often dangerous to get around on foot or by bicycle; and (2) Make healthy food choices more readily available to consumers, especially in low income areas where good quality food outlets are far and few between. Studies show that low income areas (when compared to more affluent areas) have more fast food establishments, mini marts and liquor stores and less higher quality outlets including supermarkets and farmers markets. The Karin lab’s research suggests that reducing obesity can reduce health risks. This underscores the importance of designing “healthy cities” that enable more walking and bicycling (among other non-motorized means of of getting around), and that make healthy food choices more common and accessible, especially in low income areas.

The Karin lab’s research offers evidence that is useful to those who are beginning to connect urban planning, the built environment and environmental health through concepts like “walkability”, “food systems planning” and equity in the spatial distribution of quality food outlets. A recent book by Jason Corburn is a good example of emergent literature that weaves these topics together:

Corburn, Jason. 2009. Toward the healthy city : people, places, and the politics of urban planning. Cambridge, MA: MIT Press.

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You can read a profile of Michael Karin in PNAS at: http://www.pnas.org/content/103/34/12665.full
The UCSD Superfund Research Program web site is at: http://superfund.ucsd.edu/
The NIEHS Superfund Research Program is at: http://www.niehs.nih.gov/research/supported/srp/

01/22 at 05:18 PM in Research Projects • (0) Comments