Modern medicine has made most infectious diseases of bacterial origin easily managed. However, research has shown that chronic infections caused by a handful of viruses, bacteria, and parasites play a significant role in the development of certain cancers. Andrew Dannenberg, MD, is director of the Cancer Center at New York-Presbyterian Hospital/Weill Cornell Medical Center, and Henry R. Erle, M.D.–Roberts Family Professor of Medicine at Weill Cornell Medical College. He spoke on the subject at the recent AACR Frontiers in Cancer Prevention Research meeting and shared his thoughts with ONI about this important issue.
ONI: What role do infections play in the development of cancers?
DR. DANNENBERG: A widely held figure is that at least 15% to 20% of all cancer worldwide is caused by infections; however, the number could be larger. Estimates of infection-related cancers are, for a number of reasons, potentially conservative. For instance, infections may very well be involved in the etiology of cancers that haven't yet been confirmed as infection-related, such as skin (see page 53), prostate, colon, gallbladder, bladder, and certain types of lymphomas and leukemias. So the true number remains uncertain until more research is done.
ONI: Is infection-related cancer more prevalent in certain parts of the world?
DR. DANNENBERG: Clearly, the problem is much more severe in developing nations where, for example, chronic hepatitis B and H pylori are major causes of liver and gastric cancers, respectively.
ONI: What is the causal relationship between infections and cancer?
DR. DANNENBERG: Infectious organisms cause cancer by a variety of mechanisms including inactivation of tumor suppressor genes. The infection-inflammation connection is also important for understanding the pathogenesis of malignancy. Chronic inflammation predisposes to malignancy via multiple mechanisms. So, in addition to trying to prevent chronic infection with vaccines and anti-infectives, targeted therapies that disrupt chronic inflammatory processes may protect against cancer. Naturally, there's a lot of work and research needed in this area.