transforming-growth-factor-beta and Anus-Neoplasms

TGFbetas are thought to have tumor suppressor activity in many organ systems, but receptor inactivation in mouse models has not previously resulted in increased spontaneous tumorigenesis. A study in this issue of Cancer Cell shows that mice with a targeted knockout of the type II TGFbeta receptor in stratified epithelia specifically develop spontaneous squamous cell carcinomas in the anogenital region, but not in the skin. Loss of TGFbeta signaling appears to destabilize the epithelium such that homeostasis fails in the face of persistent proliferative challenge, a normal feature of the anogenital site, and latent invasive and migratory phenotypes are unmasked.

Topics: Animals; Anus Neoplasms; Apoptosis; Carcinoma, Squamous Cell; Cell Movement; Cell Proliferation; Cell Transformation, Neoplastic; Epithelial Cells; Extracellular Matrix; Focal Adhesion Protein-Tyrosine Kinases; Homeostasis; Humans; Integrins; Keratin-14; Keratinocytes; Mice; Mice, Knockout; Mutation; Neoplasm Invasiveness; Papilloma; Promoter Regions, Genetic; Protein Serine-Threonine Kinases; ras Proteins; Receptor, Transforming Growth Factor-beta Type II; Receptors, Transforming Growth Factor beta; Signal Transduction; Skin; Skin Neoplasms; src-Family Kinases; Time Factors; Transforming Growth Factor beta; Urogenital Neoplasms; Wound Healing

Although TGFbeta is a potent inhibitor of proliferation, epithelia lacking the essential receptor (TbetaRII) for TGFbeta signaling display normal tissue homeostasis. By studying asymptomatic TbetaRII-deficient stratified epithelia, we show that tissue homeostasis is maintained by balancing hyperproliferation with elevated apoptosis. Moreover, rectal and genital epithelia, which are naturally proliferative, develop spontaneous squamous cell carcinomas with age when TbetaRII is absent. This progression is associated with a reduction in apoptosis and can be accelerated in phenotypically normal epidermis by oncogenic mutations in Ras. We show that TbetaRII deficiency leads to enhanced keratinocyte motility and integrin-FAK-Src signaling. Together, these mechanisms provide a molecular framework to account for many of the characteristics of TbetaRII-deficient invasive SQCCs.

Topics: Animals; Anus Neoplasms; Apoptosis; Carcinoma, Squamous Cell; Cell Movement; Cell Proliferation; Cell Transformation, Neoplastic; Cells, Cultured; Epithelial Cells; Extracellular Matrix; Focal Adhesion Protein-Tyrosine Kinases; Homeostasis; Humans; Integrins; Keratin-14; Keratinocytes; Male; Mice; Mice, Knockout; Mutation; Neoplasm Invasiveness; Papilloma; Promoter Regions, Genetic; Protein Serine-Threonine Kinases; ras Proteins; Receptor, Transforming Growth Factor-beta Type II; Receptors, Transforming Growth Factor beta; Signal Transduction; Skin; Skin Neoplasms; src-Family Kinases; Time Factors; Transforming Growth Factor beta; Urogenital Neoplasms; Wound Healing