In the early 1990s, NCI Laboratory of Human Carcinogenesis chief Curtis Harris, Mehmet Ozturk of Harvard Medical School, and their colleagues discovered a specific aflatoxin-related mutation in the p53 tumor suppressor gene in Chinese and African populations occurring in liver cancer from people exposed to aflatoxin and infected with hepatitis B. This p53 mutation can be measured in DNA from blood plasma and has recently been shown to be a biomarker of aflatoxin exposure and effect by Ruggero Montesano and colleagues at the International Agency for Research on Cancer. The gene discussed is TP53; the disease is hepatitis B virus infection.