Theoretical analysis of two-stage carcinogenesis leads us to indicate that cancer occurs on the basis of two different mechanisms, which are to make distortion and to amplify the distortion. Two-stage carcinogenesis is a famous experimental carcinogenesis that occurs through two steps: initiation and promotion. Theoretically, the initiation and the promotion can be considered different steps as follows. Initiation is a step that a cell distorts its metabolism; promotion is a step that a cell with metabolic distortion amplifies the distortion.
Initiation indicates a step that a tissue is treated with a chemical substance named Initiator. Medical science has pointed out that an initiator has the ability to interfere with nucleic acid metabolism, and to cause genomal instability. In addition, once a cell is treated with an initiator, it semipermanently holds the genomal instability. On the basis of this genomal instability, the cell will change the original cellular metabolism into distorted one. Thus, initiation can be considered a process: A cell treated with an initiator semipermanently causes the genomal instability, on the basis of which it changes the original cellular metabolism into distorted one.
Promotion indicates a step that a tissue already treated with an initiator is also treated with a chemical substance named Promoter. Medical science has explained that a promoter has the ability to cause acute inflammation in a tissue. Acute inflammation, as already explained in section 3, can theoretically be regarded as a phenomenon that a tissue increases the momentum. In addition, two-stage carcinogenesis causes cancer through the process as follows: after a tissue is treated with an initiator, it also needs to be many times treated with a promoter in order to cause cancer. From these points, promotion can be considered a process: An initiated cell treated with a promoter amplifies the distorted cellular metabolism by increasing the momentum.
In summary, theoretical analysis of two-stage carcinogenesis leads us to conclude that initiation and promotion are different steps as follows. Initiation is a step that a cell causes genomal instability, followed by changing the original cellular metabolism into distorted one. On the other hand, promotion is a step that a cell with distorted cellular metabolism amplifies the distortion by increasing the momentum. In short, initiation is to make distortion; promotion is to amplify the distortion. The figures below illustrate theoretical analysis of two-stage carcinogenesis in vitro, and show the difference in mechanism between the initiation and the promotion.