Cancer is an adaptation mechanism of the aged stem cell against stress.

Although many theories have been proposed for carcinogenesis, no one hypothesis seems adequate to explain all the phenomena associated with cancer. Cancers have been shown to be clonally derived from a single cell, and so it does seem that stem cells are target cells for carcinogenesis. Several examples might support the stem cell theory, but the underlying mechanism is unclear. The hypothesis presented here, which is a radical departure from all previous theories of cancer, explicitly states that cancer is the adaptation of the aged stem cell against sustained stress.