Origin Story of IARC's 10 Key Characteristics of Carcinogens

The 10 Key Characteristics of Carcinogens (KCs) were developed by the International Agency for Research on Cancer (IARC) as a framework for organizing mechanistic data for evaluating agents as potential human carcinogens. They emerged from more than half a century of insight into the mechanisms of carcinogenesis. In particular, the Hallmarks of Cancer described by D. Hannahan and R.A. Weinberg in 2000 and 2011 stimulated thinking about how carcinogens resulted in the features of cancer cells. A Workshop at the Environmental Mutagen Society meeting in 2007 produced a list of 15 Key Events Associated with Carcinogenesis (Guyton et al. Mutat Res 681:230, 2009). Also in 2007, IARC organized an Advisory Meeting to update the literature on the approximately 100 IARC Group 1 (known) human carcinogens, resulting in IARC Monograph Vol. 100 in 2012. IARC then recognized the need to identify the mechanistic events associated with human carcinogens, addressing these in a Workshop in April and November 2012, during which the KCs were developed. Along with IARC, other agencies began incorporating the KCs into cancer evaluations, and the KCs were soon modified for evaluating agents for a variety of toxicological endpoints beyond cancer. After experience using the KCs for cancer evaluations, IARC convened a workshop in 2023 to assess the KCs, publishing a summary of the workshop and a technical report in 2025. The concept underlying the KCs has provided a universal framework for organizing the mechanistic literature of agents for their potential as human carcinogens and many other toxicological endpoints.