Tumor suppressor genes (TSGs) can be grouped into the following categories: caretaker genes, gatekeeper genes, and more recently landscaper genes. Caretaker genes ensure stability of the genome via DNA repair and subsequently when mutated allow mutations to accumulate. Meanwhile gatekeeper genes directly regulate cell growth by either inhibiting cell cycle progression or inducing apoptosis. Lastly landscaper genes regulate growth by contributing to the surrounding environment, when mutated can cause an environment that promotes unregulated proliferation. The classification schemes are evolving as medical advances are being made from fields including molecular biology, genetics, and epigenetics.