AP BIOLOGY

Detailed explanation-1: -TGF functions as a tumor suppressor by mediating its antiproliferative effects in a large variety of cell types. During early stages of tumorigenesis, TGF inhibits cell cycle promotion and evasion of TGF-mediated antiproliferative effects is a prerequisite for advancement of tumor progression (15, 16, 105).

Detailed explanation-2: -TGF- family signals play critical roles both in the maintenance of the pluripotent state of ES cells by inducing the expression of Nanog, Oct4, and Sox2, and in their differentiation into various cell types by regulating the expression of master regulatory genes.

Detailed explanation-3: -TGF- can broadly impede T cell activation by inhibiting TCR signaling (34), but also inhibits specific T helper subsets by suppressing lineage-defining transcription factors, such as T-bet and GATA-3, which are critical for T helper 1 (TH1) and TH2 CD4+ T cell differentiation respectively (41, 42).

Detailed explanation-4: -TGF- functions as a mitogen to activate epithelial cell proliferation, growth, and differentiation. In the gastric mucosa, TGF- production inhibits gastric acid secretion and therefore plays a central role in the pathogenesis of the stomach syndrome Ménétrier’s disease.