A new study published in JAMA, the Journal of the American Medical Association reveals the first-ever genetic link between obesity and colon cancer risk. This finding that could lead to greater accuracy in testing for the colon cancer, said a colon cancer and may also improve efforts to ward off colon cancer with obesity-fighting activities like exercise, weight loss and healthy eating. 

"Our hope is that we can significantly improve the screening and early detection for this disease, and open new avenues for better understanding the genetic and lifestyle factors that influence colon cancer risk," said Boris Pasche, M.D., Ph.D., director of the division of hematology and oncology at the University of Alabama at Birmingham Comprehensive Cancer Center and lead author of the JAMA study.

The research focuses on a gene called ADIPOQ that results in the formation of a fat hormone called adiponectin. It shows those who inherit a common genetic variant of ADIPOQ carry up to 30 percent reduced risk of colon cancer compared to others.

In other words, Pasche said, those identified without the gene variant or those who have unhealthy blood levels of adiponectin may benefit from early colorectal testing. Additional studies are needed to confirm whether those without the variant benefit from cancer-prevention lifestyle changes such as diet and exercise.

Colon cancer is the third-leading cancer killer of Americans. This year 149,000 people will be diagnosed with colon cancer and 50,000 will die from the disease, according to estimates from the American Cancer Society.

One-third of people with colon cancer have a clear family history of the disease, and now scientists are homing in on the exact DNA sequences or mutations within the ADIPOQ gene that influence colon cancer risk, Pasche said.

It has already been proven that obesity is influenced by genetics, and colon cancer is influenced by genetics. The JAMA study is the first to make a three-way scientific connection between genetic variation, obesity and colon cancer risk.

Other research has shown adiponectin is associated with diabetes, insulin resistance, cardiovascular disease and with influencing cell growth in colonic tissues. Exactly how adiponectin or its genes directly impact tumor growth is still unknown, but those cell pathways are being widely studied, Pasche said.

A separate gene variant in ADIPOQ is a known modifier for breast-cancer risk, according a recent study in the journal Cancer Research that was co-authored by Pasche.

The new JAMA study was performed with blood samples taken from 1,497 participants, including healthy volunteers and colon cancer patients. It includes both sexes and a mix of age, race and ethnicity.

The study's collaborators include researchers from Northwestern University in Chicago, the University of Chicago, Harvard Medical School in Boston, Memorial Sloan-Kettering Cancer Center in New York and Dartmouth Medical School in Hanover, N.H. Funding was provided by the Walter S. Mander Foundation, the Lynn Sage Foundation, the Niehaus Clinical Cancer Genetics Initiative, the National Institutes of Health, a Jeannik M. Littlefield grant from the American Association for Cancer Research and the American Society of Clinical Oncology.

About Obesity

Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of humans and other mammals, exceeds healthy limits. It is commonly defined as a body mass index (BMI) (weight divided by height squared) of 30 kg/m² or higher.

Mortality is increased in obesity, with a BMI of over 32 being associated with a doubled risk of death.  Central obesity (male-type or waist-predominant obesity, characterized by a high waist-hip ratio), is an important risk factor for the metabolic syndrome, the clustering of a number of diseases and risk factors that heavily predispose for cardiovascular disease. These are diabetes mellitus, Type 2 diabetes mellitus, high blood pressure, high blood cholesterol, and triglyceride levels (combined hyperlipidemia).

Apart from the metabolic syndrome, obesity is also correlated with a variety of other complications. For some of these complaints, it has not been clearly established to what extent they are caused directly by obesity itself, or have some other cause (such as limited exercise) that causes obesity as well. The affected health conditions include but are not limited to:

• Cardiovascular: congestive heart failure, stroke, enlarged heart and its associated arrhythmias and dizziness, varicose veins, and pulmonary embolism
• Endocrine: type 2 diabetes mellitus, insulin resistance, polycystic ovarian syndrome (PCOS), menstrual disorders, and infertility
• Gastrointestinal: gastroesophageal reflux disease (GERD), fatty liver disease, cholelithiasishernia, and colorectal cancer
• Renal and genitourinary: erectile dysfunction, urinary incontinence, chronic renal failure, hypogonadism (male), breast cancer (female), uterine cancer (female), stillbirth
• Integument (skin and appendages): stretch marks, acanthosis nigricans, lymphedema, cellulitis, carbuncles, intertrigo
• Musculoskeletal: hyperuricemia (which predisposes to gout), immobility, joint pain, osteoarthritis, low back pain
• Neurologic: stroke, meralgia paresthetica, headache, carpal tunnel syndrome, dementia, idiopathic intracranial hypertension
• Respiratory: obstructive sleep apnea, obesity hypoventilation syndrome, asthma
• Psychological: depression, low self esteem, body dysmorphic disorder, social stigmatization
• Erectile Dysfunction
  

About Colon Cancer

Colon cancer is cancer that starts in the large intestine (colon) or the rectum (end of the colon). Such cancer is sometimes referred to as "colorectal cancer."

Other types of colon cancer such as lymphoma, carcinoid tumors, melanoma, and sarcomas are rare. In this article, use of the term "colon cancer" refers to colon carcinoma and not these rare types of colon cancer.

According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States.

There is no single cause for colon cancer. Nearly all colon cancers begin as non-cancerous (benign) polyps, which slowly develop into cancer.

• Cancer elsewhere in the body
• Colorectal polyps
• Crohn's disease
• Family history of colon cancer
• Personal history of breast cancer
• Ulcerative colitis

• High-fat, low-fiber diet and red meat.
• Smoking cigarettes.

• Abdominal pain and tenderness in the lower abdomen
• Blood in the stool
• Diarrhea, constipation, or other change in bowel habits
• Intestinal obstruction
• Narrow stools
• Unexplained anemia
• Weight loss with no known reason

• Black, tar-like stools
• Blood during a bowel movement
• Change in bowel habits