When we think about studies that have identified the molecular mechanisms of cancer pathogenesis or therapeutic effects, we usually envision experiments in cultured cells or mouse models. However, studies in human populations have also provided important molecular information about cancer causes and treatment.

On page 930, Scott Lippman and colleagues describe how clinical trials to test the safety of statins and other lipid-lowering agents for patients with cardiovascular disease resulted in the surprising finding that these drugs also prevented colorectal cancer and melanoma. This observation led to many subsequent studies into the importance of inflammation and immunomodulation in tumour development, and also led to the discovery that statins block tumour angiogenesis. Learning more about the complex cellular effects of statins might result in new cancer treatment and prevention strategies.

Deborah Winn discusses on page 986 how epidemiological studies into the increased incidence of breast cancer in certain regions of the United States revealed that, in most cases, breast cancer risk was not associated with increased exposure to pesticides or other chemicals, as originally predicted, but was instead associated with lifestyle factors such as reproductive history, diet and alcohol intake.

Finally, on page 965, John C. Bell discusses clinical studies of oncolytic virus efficacy and safety. These initial trials have revealed important information about how these therapeutic vectors can be better engineered to overcome obstacles such as tumour cell specificity, tumour access, and the host antiviral immune response.

Studies such as these remind us that humans are ultimately the most valuable cancer research model.