The nature of inherited susceptibility to cancer
Abstract
The Paterson Laboratories, Christie Hospital and Holt Radium Institute, Wilmslow Road, Manchester 20, UK Introduction Much of the evidence we have about the aetiology of neoplastic diseases points to the strong influence of environmental factors. Ultraviolet and ionizing radiation, chemical carcinogens and viruses are now all implicated in human as well as in animal cancers. Even where no specific agent is recognized the environmental influence can be inferred, as in the change of cancer incidence in immigrant populations to match that of the indigenous population. The temptation, then, is to attribute a certain high percentage of cancers to 'the environment'. This has always seemed to me to be wrong in principle. The phenotype which is the resultant of the interaction between environment and genotype includes disease susceptibility and it is axiomatic that all cancers will have a genetic component. The importance of this component will be dependent, of course, on the strength of the environmental influence. It is not difficult to imagine an influence so potent that individual variation is of trivial significance, but such situations are uncommon. In most cases only a tiny minority of the exposed population develop a cancer. It can be argued that significant