Isoenzymes of ascites tumor cells in vivo and in vitro
Cancer cells are different from normal cells in that their growth is not limited by the host. In general, normal cells in adult individuals are continuously dying off and are continuously replaced by new cells. A fairly constant equilibrium is maintained between the death rate of old cells and the rate of multiplication for new cells. During repair of a wound the cells multiply more rapidly and once the repair is completed the equilibrium between death and multiplication of the cells will be reinstated. Such an equilibrium serves as a control exerted by the body to prevent the overgrowth of one type of cells so that harmony is maintained in the body. Somehow, cancer cells multiply continuously faster than they die off, and such growth is not limited by the body. What makes this growth unlimited has not been demonstrated. Since cancer and normal cells are different in their mode of growth a difference somewhere in the cell is also suspected to exist between them. The difference may be minute, but sufficient to effect the unlimited growth of cancer cells. The search for a difference is then logical with the hope of throwing some light on the nature and the origin of cancer.