Evading Growth Suppressors

Processes related to cell proliferation are regulated by factors that promote cell division as well as factors that inhibit cell division. There is a whole spectrum of factors that inhibit cell division, and tumor cells have to circumvent their action. These factors include pathways activated by tumor-suppressor genes. Several tumor-suppressor genes are known to restrict cell growth and division by different mechanisms. These genes are characterized by their inactivation in tumor cells. Examples are the genes encoding retinoblastoma-associated (RB) protein and TP53. Both function as central control nodes in two key complementary cellular regulatory circuits that determine whether a cell will proliferate or whether the aging processes and proapoptotic program will be activated (Hanahan and Weinberg 2011).