title: Proteasome inhibitor MG-132 lowers gastric adenocarcinoma TMK1 cell proliferation via bone morphogenetic protein signaling.
abstract: Proteasome inhibitor is a novel class of cancer therapeutics, of which the mechanism of action is not fully understood. It is reported that proteasome inhibitor enhances bone morphogenetic protein (BMP) signaling in osteoblasts to stimulate bone formation. BMP signaling is also an important tumor-suppressing pathway in gastric carcinogenesis. We therefore sought to determine the anti-mitogenic effect of proteasome inhibition in relation to BMP signaling in gastric cancer cells. Results showed that proteasome inhibitor MG-132 significantly suppressed the proliferation and the colony-forming ability of gastric cancer TMK1 cells. In this connection, MG-132 activated BMP signaling, manifested as an increase in Smad1/5/8 phosphorylation and up-regulation of p21(Waf1/Cip1) mRNA and protein expression. Knockdown of BMP receptor II by RNA interference abolished Smad1/5/8 phosphorylation, p21(Waf1/Cip1) induction, and the inhibition of cell proliferation induced by MG-132. Further analysis revealed that MG-132 up-regulated the expression of BMP1 and BMP4 and suppressed the expression of Smad6. Knockdown of Smad6 also mimicked the effect of MG-132 on BMP signaling. Collectively, these findings suggest that inhibition of proteasome suppresses gastric cancer cell proliferation via activation of BMP signaling. This discovery may open up a novel therapeutic avenue to proteasome inhibitors for the management of gastric cancer.
authors.affiliation: Department of Medicine & Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: William Ka Kei
authors.initials: WK
authors.lastname: Wu
authors.forename: Joseph Jao Yiu
authors.initials: JJ
authors.lastname: Sung
authors.forename: Le
authors.initials: L
authors.lastname: Yu
authors.forename: Chi Hin
authors.initials: CH
authors.lastname: Cho
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D055395:Bone Morphogenetic Protein 1; D055415:Bone Morphogenetic Protein 4; D052006:Bone Morphogenetic Protein Receptors, Type II / Q000235:genetics / Q000378:metabolism; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology*; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000187:drug effects; D061988:Proteasome Inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051905:Smad6 Protein / Q000037:antagonists & inhibitors / Q000378:metabolism; D013274:Stomach Neoplasms / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; C525809:BMP4 protein, human; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D061988:Proteasome Inhibitors; D012333:RNA, Messenger; C497802:SMAD6 protein, human; D051905:Smad6 Protein; D052006:Bone Morphogenetic Protein Receptors, Type II; D008666:Metalloendopeptidases; C525705:BMP1 protein, human; D055395:Bone Morphogenetic Protein 1; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde