|| Checking for direct PDF access through Ovid
Many tumours are characterised by increased levels of apoptosis. This observation establishes significance for this process in tumour development, but it does little to elucidate the nature of this role, nor does it yield information relevant to the early stages of carcinogenesis. To gain a better understanding of the importance of apoptosis, it has been necessary to create a number of transgenic model systems wherein the apoptotic response has been modified. Using this strategy, a number of genetic lesions have been identified which affect both the apoptotic pathway and predisposition to malignancy. These lesions can operate either directly, by blocking the induction of apoptosis; or indirectly, by increasing the selective pressure for further genetic change. The consequent deregulation of growth control and increase in mutation burden represent two key steps in carcinogenesis, underlining the pivotal role played in tumour suppression by the normal induction of apoptosis.