title: JNK is constitutively active in mantle cell lymphoma: cell cycle deregulation and polyploidy by JNK inhibitor SP600125.
abstract: Mantle cell lymphoma (MCL) is characterized by genetic instability and a poor prognosis. Many blastoid variants are (hypo)tetraploid and have an even worse prognosis. We investigated the role of signalling by mitogen-activated protein kinases (MAPKs) in MCL. As compared to normal tonsil B cells, MCL cells showed higher activation of the JNK MAPK in both an MAPK array and a sandwich ELISA assay. Immunohistochemistry showed overexpression of phospho (p)-JNK (Thr183/Tyr185) in 30 of 37 MCL cases. Inhibition of p-JNK with SP600125 resulted in growth arrest in all four MCL cell lines (Jeko-1, HBL-2, UPN-1, Granta-519), which could be partly reversed by the addition of CD40L and IL-4. Furthermore, SP600125 led to G2/M phase arrest on day 1 and a striking increase in endoreduplication on day 2 and day 3, which was confirmed by karyotype analysis. G2/M arrest was associated with down-regulation of EGR1 and p21 protein expression. SP600125-induced polyploidy could be blocked by the BCL-2 inhibitor YC137. These data suggest that constitutive JNK activity is necessary to promote proliferation and maintain diploidy in MCL. JNK inhibition leads to cell cycle deregulation and endoreduplication, mimicking the tetraploid state seen in a subset of MCL cases. Thus, our data also provide an experimental model to study polyploid MCL cells.
authors.affiliation: Department of Pathology and Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
authors.forename: Miao
authors.initials: M
authors.lastname: Wang
authors.forename: Cigdem
authors.initials: C
authors.lastname: Atayar
authors.forename: Stefano
authors.initials: S
authors.lastname: Rosati
authors.forename: Anneke
authors.initials: A
authors.lastname: Bosga-Bouwer
authors.forename: Philip
authors.initials: P
authors.lastname: Kluin
authors.forename: Lydia
authors.initials: L
authors.lastname: Visser
mesh_terms: D000873:Anthracenes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D016022:Case-Control Studies; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D015870:Gene Expression; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000032:analysis / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020522:Lymphoma, Mantle-Cell / Q000201:enzymology* / Q000235:genetics; D014066:Palatine Tonsil / Q000201:enzymology; D011123:Polyploidy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D000873:Anthracenes; D019253:Proto-Oncogene Proteins c-bcl-2; D013844:Thiazoles; C493272:YC137; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases