title: The host defense peptide LL-37 activates the tumor-suppressing bone morphogenetic protein signaling via inhibition of proteasome in gastric cancer cells.
abstract: The human cathelicidin LL-37, a pleiotropic host defense peptide, is down-regulated in gastric adenocarcinomas. We therefore investigated whether this peptide suppresses gastric cancer growth. LL-37 lowered gastric cancer cell proliferation and delayed G(1)-S transition in vitro and inhibits the growth of gastric cancer xenograft in vivo. In this connection, LL-37 increased the tumor-suppressing bone morphogenetic protein (BMP) signaling, manifested as an increase in BMP4 expression and the subsequent Smad1/5 phosphorylation and the induction of p21(Waf1/Cip1). The anti-mitogenic effect, Smad1/5 phosphorylation, and p21(Waf1/Cip1) up-regulation induced by LL-37 were reversed by the knockdown of BMP receptor II. The activation of BMP signaling was paralleled by the inhibition of chymotrypsin-like and caspase-like activity of proteasome. In this regard, proteasome inhibitor MG-132 mimicked the effect of LL-37 by up-regulating BMP4 expression and Smad1/5 phosphorylation. Further analysis of clinical samples revealed that LL-37 and p21(Waf1/Cip1) mRNA expressions were both down-regulated in gastric cancer tissues and their expressions were positively correlated. Collectively, we describe for the first time that LL-37 inhibits gastric cancer cell proliferation through activation of BMP signaling via a proteasome-dependent mechanism. This unique biological activity may open up novel therapeutic avenue for the treatment of gastric cancer.
authors.affiliation: Department of Medicine & Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China. wukakei@cuhk.edu.hk
authors.forename: William Ka Kei
authors.initials: WK
authors.lastname: Wu
authors.forename: Joseph Jao Yiu
authors.initials: JJ
authors.lastname: Sung
authors.forename: Ka Fai
authors.initials: KF
authors.lastname: To
authors.forename: Le
authors.initials: L
authors.lastname: Yu
authors.forename: Hai Tao
authors.initials: HT
authors.lastname: Li
authors.forename: Zhi Jie
authors.initials: ZJ
authors.lastname: Li
authors.forename: Kin Man
authors.initials: KM
authors.lastname: Chu
authors.forename: Jun
authors.initials: J
authors.lastname: Yu
authors.forename: Chi Hin
authors.initials: CH
authors.lastname: Cho
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000368:Aged; D000818:Animals; D023181:Antimicrobial Cationic Peptides; D000970:Antineoplastic Agents / Q000494:pharmacology; D055415:Bone Morphogenetic Protein 4 / Q000378:metabolism*; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000378:metabolism; D054804:Cathelicidins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010766:Phosphorylation; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051785:Smad Proteins / Q000378:metabolism; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors; D047368:Tumor Burden; D015854:Up-Regulation; D023041:Xenograft Model Antitumor Assays
chemical_list: D023181:Antimicrobial Cationic Peptides; D000970:Antineoplastic Agents; C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; C493956:CDKN1A protein, human; D054804:Cathelicidins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; D051785:Smad Proteins; D052006:Bone Morphogenetic Protein Receptors, Type II; D046988:Proteasome Endopeptidase Complex