Biography
Dr. Freedman received his PhD in Biomedical sciences from the University of California, San Francisco in 2004 and a Masters in Public Health from the Harvard School of Public Health in 2005. He joined the Nutritional Epidemiology Branch of the Division of Cancer Epidemiology and Genetics as a Cancer Prevention Fellow in the fall of 2005. As a fellow, he used large case-control and cohort studies to identify dietary and environmental risk factors for upper gastrointestinal tract cancers of the head and neck, esophagus, and stomach. He became an investigator in the spring of 2009. In this position, he draws on his training in molecular biology and epidemiology to understand the etiology of alimentary tract cancers, with a particular focus on those of the liver, esophagus, and stomach.
Research Interests
Research
Diet, energy balance, and liver cancer
Liver cancer is sixth in cancer incidence and third in cancer mortality worldwide. Strong risk factors have been identified including aflatoxin, alcohol, and chronic hepatitis B and C infection, but data from several case series suggest that a substantial proportion of liver cancer cases in the United States lack these exposures. Diet and energy balance may play important etiologic roles. The liver is a major metabolic organ, important for the regulation of fatty acid, insulin, and glucose signaling. Diabetes and adiposity are consistent risk factors for liver cancer, suggesting an important role for energy balance in the incidence of this cancer. Diet may also be important, with proposed associations for coffee, red meat, fat, and fruits and vegetables.
Sex differences in cancer risk
Incidence rates of alimentary tract cancers, along with many other cancers, are dramatically higher in men than women. Differences in incidence rates by sex likely serve as a clue for understanding the underlying etiologies of these cancers. One possible explanation is that men and women are differentially exposed to strong environmental risk factors, such as cigarette smoking. Alternatively, physiologic differences in men and women may contribute to differences in cancer incidence rates. I am formally comparing the association of risk factors in men and women, with a focus on cohort studies where it is possible to calculate incidence rates. Where known risk factors do not seem to explain differences in incidence rates, I am investigating physiological differences.
Role of the microbiome in dietary and carcinogen metabolism and cancer risk
The human body contains 10-fold more bacteria than human cells, suggesting a critical role for bacteria in human health and disease. Despite some notable successes, such as the identification of Helicobacter pylori as a cause of gastric cancer, the role of bacteria in cancer risk is poorly understood. The advent of high throughput agnostic technologies now allow for the characterization of bacterial communities in healthy and diseased tissue for the first time. My interests lie in understanding the role of bacteria in dietary and carcinogen metabolism, and to examine the association of particular bacterial types or communities with cancer risk.
Selected Publications
- Freedman ND, Lacey JV, Hollenbeck AR, Leitzmann MF, Schatzkin A, Abnet CC. The association of menstrual and reproductive factors with upper gastrointestinal tract cancers in the NIH-AARP cohort. Cancer, in press.
- Freedman ND, Everhart JE, Lindsay KL, Ghany MG, Curto TM, Shiffman ML, Lee WM, Lok AS, Di Bisceglie AM, Bonkovsky HL, Hoefs JC, Dienstag JL, Morishima C Abnet CC, Sinha R, and the HALT-C Trial Group. Coffee intake is associated with lower rates of liver disease progression in chronic hepatitis C: findings from the Hepatitis C Antiviral Long-Term Treatment against Cirrhosis (HALT-C) Trial. Hepatology, in press.
- Freedman ND, Ahn J, Hou L, Lissowska J, Zatonski W, Yeager M, Chanock SJ, Chow WH, Abnet CC.
Polymorphisms in estrogen- and androgen-metabolizing genes and the risk of gastric cancer.
Carcinogenesis 2009 Jan;30(1):71-7.
- Freedman ND, Leitzmann MF, Hollenbeck AR, Schatzkin A, Abnet CC.
Cigarette smoking and subsequent risk of lung cancer in men and women: analysis of a prospective cohort study.
Lancet Oncol 2008 Jul;9(7):649-56.
- Freedman ND, Chow WH, Gao YT, Shu XO, Ji BT, Yang G, Lubin JH, Li HL, Rothman N, Zheng W, Abnet CC.
Menstrual and reproductive factors and gastric cancer risk in a large prospective study of women.
Gut 2007 Dec;56(12):1671-7.