Isn't this a bit of an oversimplification? It's not like if you knock out p53 and something else you instantly get a metastatic tumor. Granted if you remove key

Isn't this a bit of an oversimplification? It's not like if you knock out p53 and something else you instantly get a metastatic tumor. Granted if you remove key tumor suppressor genes your probability of mutations persisting skyrockets, but that in itself doesn't create a dangerous tumor. You need many more mutations than 2 to be able to acquire the functionality to grow, persist, escape the local environment, and establish a foot hold in a new environment. Here is the classic review paper on tumor formation: http://www.cell.com/abstract/S0092-8674(11)00127-9 http://www.cell.com/abstract/S0092-8674(11)00127-9