title: Use of a TGFbeta type I receptor inhibitor in mouse skin carcinogenesis reveals a dual role for TGFbeta signaling in tumor promotion and progression.
abstract: Pharmacological inhibitors of the transforming growth factor β (TGFβ) type I receptor (ALK5) have shown promise in blocking growth of xenotransplanted cancer cell lines but the effect on a multistage cancer model is not known. To test this, we treated mouse skin with SB431542 (SB), a well-characterized ALK5 inhibitor, during a two-stage skin carcinogenesis assay. Topical SB significantly reduced the total number, incidence and size of papillomas compared with 12-O-tetradecanoylphorbol 13-acetate (TPA) promotion alone, and this was linked to increased epidermal apoptosis, decreased proliferation and decreased cutaneous inflammation during promotion. In contrast, the frequency of conversion to squamous cell carcinoma (SCC) was 2-fold higher in papillomas treated with SB. Although there was no difference in tumor cell proliferation in early premalignant lesions, those that formed after SB treatment exhibited reduced squamous differentiation and an altered inflammatory microenvironment similar to SCC. In an inducible epidermal RAS transgenic model, treatment with SB enhanced proliferation and cutaneous inflammation in skin but decreased expression of keratin 1 and increased expression of simple epithelial keratin 18, markers of premalignant progression. In agreement with increased frequency of progression in the multistage model, SB treatment resulted in increased tumor formation with a more malignant phenotype following long-term RAS induction. In contrast to the current paradigm for TGFβ in carcinogenesis, these results demonstrate that cutaneous TGFβ signaling enables promotion of benign tumors but suppresses premalignant progression through context-dependent regulation of epidermal homeostasis and inflammation.
authors.affiliation: Department of Veterinary and Biomedical Sciences, The Center for Molecular Toxicology and Carcinogenesis, Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Mordasky Markell
authors.forename: Rolando
authors.initials: R
authors.lastname: Pérez-Lorenzo
authors.forename: Katelyn E
authors.initials: KE
authors.lastname: Masiuk
authors.forename: Mary J
authors.initials: MJ
authors.lastname: Kennett
authors.forename: Adam B
authors.initials: AB
authors.lastname: Glick
mesh_terms: D000818:Animals; D001549:Benzamides / Q000494:pharmacology; D004149:Dioxoles / Q000494:pharmacology; D018450:Disease Progression; D011905:Genes, ras; D051379:Mice; D010212:Papilloma / Q000209:etiology / Q000517:prevention & control; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors*; D015398:Signal Transduction / Q000187:drug effects; D012878:Skin Neoplasms / Q000209:etiology*; D051899:Smad2 Protein / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000502:physiology*
chemical_list: C459179:4-(5-benzo(1,3)dioxol-5-yl-4-pyridin-2-yl-1H-imidazol-2-yl)benzamide; D001549:Benzamides; D004149:Dioxoles; D018125:Receptors, Transforming Growth Factor beta; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D053773:Transforming Growth Factor beta1; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625842:Tgfbr1 protein, mouse; D013755:Tetradecanoylphorbol Acetate