Modelling western dietary habits in the mouse: easier said than done
The recent debate on the relative importance of environmental vs. intrinsic factors in the onset of malignancy has raised major concerns that the general public might conclude that cancer prevention programmes are not worthwhile. In their original report (1), Tomasetti and Vogelstein concluded that a majority of cancers can be explained by the high number of stem cell divisions in tissues with a high cell turn-over, due to generation of random mutations and their accumulation each time DNA replicates. In a subsequent report (2), Wu and colleagues employed a different mathematical model and extended the data set to reach the opposing conclusion that spontaneous mutations occurring during stem cell division rarely reach the level necessary to underlie cancer development. In the majority of cases, exposure to environmental risk factors represents a fundamental requirement for the onset of malignant disease. Of note, in the mathematical approach of the former study (1), the intrinsic rate of stem cell division and the environmental risk factors were regarded as entirely independent variables whereas it is plausible to think that extrinsic factors do affect stem cell homeostasis.