title: MELK-T1, a small-molecule inhibitor of protein kinase MELK, decreases DNA-damage tolerance in proliferating cancer cells.
abstract: Maternal embryonic leucine zipper kinase (MELK), a serine/threonine protein kinase, has oncogenic properties and is overexpressed in many cancer cells. The oncogenic function of MELK is attributed to its capacity to disable critical cell-cycle checkpoints and reduce replication stress. Most functional studies have relied on the use of siRNA/shRNA-mediated gene silencing. In the present study, we have explored the biological function of MELK using MELK-T1, a novel and selective small-molecule inhibitor. Strikingly, MELK-T1 triggered a rapid and proteasome-dependent degradation of the MELK protein. Treatment of MCF-7 (Michigan Cancer Foundation-7) breast adenocarcinoma cells with MELK-T1 induced the accumulation of stalled replication forks and double-strand breaks that culminated in a replicative senescence phenotype. This phenotype correlated with a rapid and long-lasting ataxia telangiectasia-mutated (ATM) activation and phosphorylation of checkpoint kinase 2 (CHK2). Furthermore, MELK-T1 induced a strong phosphorylation of p53 (cellular tumour antigen p53), a prolonged up-regulation of p21 (cyclin-dependent kinase inhibitor 1) and a down-regulation of FOXM1 (Forkhead Box M1) target genes. Our data indicate that MELK is a key stimulator of proliferation by its ability to increase the threshold for DNA-damage tolerance (DDT). Thus, targeting MELK by the inhibition of both its catalytic activity and its protein stability might sensitize tumours to DNA-damaging agents or radiation therapy by lowering the DNA-damage threshold.
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Lijs
authors.initials: L
authors.lastname: Beke
authors.affiliation: Laboratory of Biosignaling & Therapeutics, KULeuven Department of Cellular and Molecular Medicine, University of Leuven, Campus Gasthuisberg, O&N1/ Box 901, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Cenk
authors.initials: C
authors.lastname: Kig
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Joannes T M
authors.initials: JT
authors.lastname: Linders
authors.affiliation: Laboratory of Biosignaling & Therapeutics, KULeuven Department of Cellular and Molecular Medicine, University of Leuven, Campus Gasthuisberg, O&N1/ Box 901, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Shannah
authors.initials: S
authors.lastname: Boens
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: Boeckx
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Erika
authors.initials: E
authors.lastname: van Heerde
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Marc
authors.initials: M
authors.lastname: Parade
authors.affiliation: Computational Sciences, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: An
authors.initials: A
authors.lastname: De Bondt
authors.affiliation: Computational Sciences, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Ilse
authors.initials: I
authors.lastname: Van den Wyngaert
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Tarig
authors.initials: T
authors.lastname: Bashir
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Souichi
authors.initials: S
authors.lastname: Ogata
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium.
authors.forename: Lieven
authors.initials: L
authors.lastname: Meerpoel
authors.affiliation: Laboratory of Biosignaling & Therapeutics, KULeuven Department of Cellular and Molecular Medicine, University of Leuven, Campus Gasthuisberg, O&N1/ Box 901, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Aleyde
authors.initials: A
authors.lastname: Van Eynde
authors.affiliation: Astex Pharmaceuticals, 436 Cambridge Science Park, Milton Road, Cambridge CB4 0QA, U.K.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Johnson
authors.affiliation: Laboratory of Biosignaling & Therapeutics, KULeuven Department of Cellular and Molecular Medicine, University of Leuven, Campus Gasthuisberg, O&N1/ Box 901, Herestraat 49, 3000 Leuven, Belgium Monique.Beullems@med.kuleuven.be Mathieu.Bollen@med.kuleuven.be dbrehmer@its.jnj.com.
authors.forename: Monique
authors.initials: M
authors.lastname: Beullens
authors.affiliation: Oncology Discovery, Janssen Research & Development, a division of Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340 Beerse, Belgium Monique.Beullems@med.kuleuven.be Mathieu.Bollen@med.kuleuven.be dbrehmer@its.jnj.com.
authors.forename: Dirk
authors.initials: D
authors.lastname: Brehmer
authors.affiliation: Laboratory of Biosignaling & Therapeutics, KULeuven Department of Cellular and Molecular Medicine, University of Leuven, Campus Gasthuisberg, O&N1/ Box 901, Herestraat 49, 3000 Leuven, Belgium Monique.Beullems@med.kuleuven.be Mathieu.Bollen@med.kuleuven.be dbrehmer@its.jnj.com.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bollen
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins / Q000096:biosynthesis; D001381:Azepines / Q000008:administration & dosage*; D001549:Benzamides / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology / Q000532:radiotherapy; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000008:administration & dosage*; D005260:Female; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors / Q000096:biosynthesis; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D061986:MCF-7 Cells; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D001381:Azepines; D001549:Benzamides; D004791:Enzyme Inhibitors; C107585:FOXM1 protein, human; D000072278:Forkhead Box Protein M1; D051858:Forkhead Transcription Factors; C000610363:MELK-T1; C484610:MELK protein, human; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases
keywords: chemical biology; deoxyribonucleic acid (DNA) damage response; maternal embryonic leucine zipper kinase (MELK) kinase; senescence; small molecule inhibitors