title: Inhibition of NF-κB-mediated signaling by the cyclin-dependent kinase inhibitor CR8 overcomes prosurvival stimuli to induce apoptosis in chronic lymphocytic leukemia cells.
abstract: OBJECTIVE
  Chronic lymphocytic leukemia (CLL) is currently incurable with standard chemotherapeutic agents, highlighting the need for novel therapies. Overcoming proliferative and cytoprotective signals generated within the microenvironment of lymphoid organs is essential for limiting CLL progression and ultimately developing a cure.
  
  
  METHODS
  We assessed the potency of cyclin-dependent kinase (CDK) inhibitor CR8, a roscovitine analog, to induce apoptosis in primary CLL from distinct prognostic subsets using flow cytometry-based assays. CLL cells were cultured in in vitro prosurvival and proproliferative conditions to mimic microenvironmental signals in the lymphoid organs, to elucidate the mechanism of action of CR8 in quiescent and proliferating CLL cells using flow cytometry, Western blotting, and quantitative real-time PCR.
  
  
  RESULTS
  CR8 was 100-fold more potent at inducing apoptosis in primary CLL cells than roscovitine, both in isolated culture and stromal-coculture conditions. Importantly, CR8 induced apoptosis in CD40-ligated CLL cells and preferentially targeted actively proliferating cells within these cultures. CR8 treatment induced downregulation of the antiapoptotic proteins Mcl-1 and XIAP, through inhibition of RNA polymerase II, and inhibition of NF-κB signaling at the transcriptional level and through inhibition of the inhibitor of IκB kinase (IKK) complex, resulting in stabilization of IκBα expression.
  
  
  CONCLUSIONS
  CR8 is a potent CDK inhibitor that subverts pivotal prosurvival and proproliferative signals present in the tumor microenvironment of CLL patient lymphoid organs. Our data support the clinical development of selective CDK inhibitors as novel therapies for CLL.
authors.affiliation: Institute of Cancer Sciences, College of Medicine, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Emilio
authors.initials: E
authors.lastname: Cosimo
authors.forename: Alison M
authors.initials: AM
authors.lastname: McCaig
authors.forename: Luke J M
authors.initials: LJ
authors.lastname: Carter-Brzezinski
authors.forename: Helen
authors.initials: H
authors.lastname: Wheadon
authors.forename: Michael T
authors.initials: MT
authors.lastname: Leach
authors.forename: Karine
authors.initials: K
authors.lastname: Le Ster
authors.forename: Christian
authors.initials: C
authors.lastname: Berthou
authors.forename: Emilie
authors.initials: E
authors.lastname: Durieu
authors.forename: Nassima
authors.initials: N
authors.lastname: Oumata
authors.forename: Hervé
authors.initials: H
authors.lastname: Galons
authors.forename: Laurent
authors.initials: L
authors.lastname: Meijer
authors.forename: Alison M
authors.initials: AM
authors.lastname: Michie
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D023201:CD40 Ligand / Q000502:physiology; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D049109:Cell Proliferation; D002470:Cell Survival / Q000187:drug effects*; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D005260:Female; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D020128:Inhibitory Concentration 50; D015847:Interleukin-4 / Q000502:physiology; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D011687:Purines / Q000494:pharmacology*; D011725:Pyridines / Q000494:pharmacology*; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors; D000077546:Roscovitine; D015398:Signal Transduction / Q000187:drug effects; D014407:Tumor Cells, Cultured / Q000187:drug effects; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C532131:CR8 compound; C508598:IL4 protein, human; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D016328:NF-kappa B; D019253:Proto-Oncogene Proteins c-bcl-2; D011687:Purines; D011725:Pyridines; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D000077546:Roscovitine; D023201:CD40 Ligand; D015847:Interleukin-4; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II