TGFB1 and neoplasm: While it initially limits cancer growth by inhibiting cell cycle progression and inducing apoptosis at later stages of tumorigenesis TGFβ signaling promotes proliferation, invasion and drug resistance.[14] Uncoupling of the proapoptotic signaling arm of TGFβ cascade in pretumorigenic cells is thought to convert TGFβ from a tumor suppressor into an oncogene.