title: Activin receptor-like kinase5 inhibition suppresses mouse melanoma by ubiquitin degradation of Smad4, thereby derepressing eomesodermin in cytotoxic T lymphocytes.
abstract: Varieties of transforming growth factor-β (TGF-β) antagonists have been developed to intervene with excessive TGF-β signalling activity in cancer. Activin receptor-like kinase5 (ALK5) inhibitors antagonize TGF-β signalling by blocking TGF-β receptor-activated Smad (R-Smad) phosphorylation. Here we report the novel mechanisms how ALK5 inhibitors exert a therapeutic effect on a mouse B16 melanoma model. Oral treatment with a novel ALK5 inhibitor, EW-7197 (2.5 mg/kg daily) or a representative ALK5 inhibitor, LY-2157299 (75 mg/kg bid) suppressed the progression of melanoma with enhanced cytotoxic T-lymphocyte (CTL) responses. Notably, ALK5 inhibitors not only blocked R-Smad phosphorylation, but also induced ubiquitin-mediated degradation of the common Smad, Smad4 mainly in CD8(+) T cells in melanoma-bearing mice. Accordingly, T-cell-specific deletion of Smad4 was sufficient to suppress the progression of melanoma. We further identified eomesodermin (Eomes), the T-box transcription factor regulating CTL functions, as a specific target repressed by TGF-β via Smad4 and Smad3 in CD8(+) T cells. Thus, ALK5 inhibition enhances anti-melanoma CTL responses through ubiquitin-mediated degradation of Smad4 in addition to the direct inhibitory effect on R-Smad phosphorylation.
authors.affiliation: Department of Experimental Pathology, Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Japan; Department of Internal Medicine, Research Institute of Aging and Metabolism, Kyungpook National University School of Medicine, Daegu, Korea; Department of Molecular Pathology, Tokyo Medical University, Tokyo, Japan; Department of Microbiology, CHA University, Seoul, Korea.
authors.forename: Jeong-Hwan
authors.initials: JH
authors.lastname: Yoon
authors.forename: Su Myung
authors.initials: SM
authors.lastname: Jung
authors.forename: Seok Hee
authors.initials: SH
authors.lastname: Park
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Kato
authors.forename: Tadashi
authors.initials: T
authors.lastname: Yamashita
authors.forename: In-Kyu
authors.initials: IK
authors.lastname: Lee
authors.forename: Katsuko
authors.initials: K
authors.lastname: Sudo
authors.forename: Susumu
authors.initials: S
authors.lastname: Nakae
authors.forename: Jin Soo
authors.initials: JS
authors.lastname: Han
authors.forename: Ok-Hee
authors.initials: OH
authors.lastname: Kim
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Oh
authors.forename: Takayuki
authors.initials: T
authors.lastname: Sumida
authors.forename: Masahiko
authors.initials: M
authors.lastname: Kuroda
authors.forename: Ji-Hyeon
authors.initials: JH
authors.lastname: Ju
authors.forename: Kyeong Cheon
authors.initials: KC
authors.lastname: Jung
authors.forename: Seong Hoe
authors.initials: SH
authors.lastname: Park
authors.forename: Dae-Kee
authors.initials: DK
authors.lastname: Kim
authors.forename: Mizuko
authors.initials: M
authors.lastname: Mamura
mesh_terms: D000818:Animals; D005260:Female; D006801:Humans; D008297:Male; D008545:Melanoma / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D059748:Proteolysis; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism*; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D013602:T-Lymphocytes, Cytotoxic / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D054875:Ubiquitination; D015854:Up-Regulation
chemical_list: C491198:Eomes protein, mouse; D018125:Receptors, Transforming Growth Factor beta; D051901:Smad4 Protein; D020825:T-Box Domain Proteins; D025801:Ubiquitin; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse
keywords: ALK5 inhibitor; Eomes; Smad4; TGF-β; melanoma