Cells undergo many changes in the proteins they make when they transform into cancer cells.
One of the tasks of the cancer biologist is to find out which of these changes genuinely contribute to malignancy and which are simply by-products of the process. This independent growth is one of the crucial stages in the development of a cancer cell, as it enables the cell to elude one of the main controls exerted by the body on unwanted cell multiplication. One of its functions is as a 'protease', a biological catalyst or enzyme that can break down other proteins. If this is the case, it is easy to see why its loss has such catastrophic effects. But cancer cells are never that simple.