How Fat Tissue Can Spur Cancer Development
The type of fat and its location in the body appear to play a role in cancer risk.
We’ve all been told that maintaining a healthy body weight is important to our overall health and is one potential way to reduce our risk of cancer.
Of course, it’s not always easy to stay trim. But a new study indicates that adipose tissue, commonly known as fat, may influence the development of cancer in diverse ways, making it clear that maintaining a healthy weight and staying fit carries major health benefits.
In a recent issue of Cancer Prevention Research, a journal of the American Association for Cancer Research, a study by Cornelia M. Ulrich, PhD, senior director of Population Sciences at the Huntsman Cancer Institute at the University of Utah in Salt Lake City, explored how fat affects carcinogenesis, or cancer development.
Dr. Ulrich said carcinogenesis depends upon "crosstalk," or the ways cells react when the same signal is shared by more than one signaling pathway in two different cell types. Identifying ways to interrupt the crosstalk could help researchers identify new cancer prevention strategies, she added.
"Obesity is increasing dramatically worldwide, and is now also recognized as one of the major risk factors for cancer, with more than a dozen types of cancer linked to obesity," Ulrich said. "We urgently need to identify the specific mechanisms that link obesity to cancer."
Ulrich explained that researchers already have some information on how fat affects cancer development. For example, obesity increases the risk of inflammation, which has long been associated with cancer. Also, obesity is believed to affect cancer cell metabolism and the immune system, all of which can contribute to the growth and spread of tumors, she said.
In order to get a deeper look into the mechanisms of carcinogenesis, Ulrich and colleagues, including researchers from the University of North Carolina, conducted a literature review of PubMed/Medline, covering publications from January 1946 to March 2017, seeking studies that explored crosstalk between adipose tissues and carcinomas.
Ulrich said several studies showed that adipose stromal cells have the power to infiltrate cancer lesions and promote the growth of tumors. These cells were found in greater number in obese prostate cancer and obese breast cancer patients, studies showed.
Ulrich said the review also showed how some types of fat are more "metabolically active," secreting more substances that led to the growth of cancer.
Ulrich’s study analyzed the effects of fat on breast, colorectal, esophageal, endometrial, prostate, and ear-nose-throat cancer, taking into consideration the proximity of adipose tissue relative to the organs. For example, Ulrich explained, in colorectal cancer, adipose tissue is typically located adjacent to tumors, whereas in breast cancer, adipose tissue is part of the direct tumor microenvironment. She said that future research would be useful in evaluating the role of tissue distance in the obesity-cancer connection, and whether there are ways to intercept the processes that fuel tumor growth.
"We are just beginning to unravel the ways crosstalk occurs and the substances involved," Ulrich said. "The more we understand this process, the better we can identify targets and strategies for decreasing the burden of obesity-related cancer."
Ulrich added that the study supports the importance of maintaining a healthy body weight. Because fat exists both under the skin and deeper inside the body, even slender people may have excess fat surrounding internal organs. Healthy diets and exercise that includes strength training to build lean muscle mass can help fight the development of excess fat, she said.
Ulrich said the primary limitation of the review is that the link between obesity and cancer is just beginning to be understood; therefore, there was little existing research on the topic.
Meanwhile, obesity remains a public health concern. In October 2017, the Centers for Disease Control and Prevention said that nearly four out of 10 Americans are obese. Among youth ages 2 to 19, the obesity rate is 18.5 percent.