title: Antitumoral activity of lenalidomide in in vitro and in vivo models of mantle cell lymphoma involves the destabilization of cyclin D1/p27KIP1 complexes.
abstract: OBJECTIVE
  Clinical responses to the immmunomodulatory drug lenalidomide have been observed in patients with relapsed/refractory mantle cell lymphoma (MCL), although its mechanism of action remains partially unknown. We investigated whether the expression and subcellular localization of cyclin D1, a major cell-cycle regulator overexpressed in MCL, and the cyclin-dependent kinase inhibitor p27(KIP1), could identify MCL cases sensitive to lenalidomide, and whether the compound could modulate cyclin D1/p27(KIP1) complexes in MCL cells.
  
  
  METHODS
  MCL primary samples and cell lines were analyzed for subcellular levels of cyclin D1/p27(KIP1) complexes by Western blot, immunohistochemistry, immunoprecipitation, and flow cytometry. Activity of lenalidomide in vitro and its effect on cyclin D1/p27(KIP1) complexes were evaluated by real-time PCR, immunoprecipitation, immunofluorescence, and Western blot. In vivo validation was carried out in a mouse xenograft model of human MCL.
  
  
  RESULTS
  We found cyclin D1 and p27(KIP1) to be coordinately expressed in all the MCL samples tested. Immunoprecipitation analyses and siRNA assays suggested a direct role of cyclin D1 in the regulation of p27(KIP1) levels. The nuclear accumulation of both proteins correlated with MCL cell tumorigenicity in vivo, and sensitivity to lenalidomide activity in vitro and in vivo. Lenalidomide mechanism of action relied on cyclin D1 downregulation and disruption of cyclin D1/p27(KIP1) complexes, followed by cytosolic accumulation of p27(KIP1), cell proliferation arrest, apoptosis, and angiogenesis inhibition.
  
  
  CONCLUSIONS
  These results highlight a mechanism of action of lenalidomide in MCL cases with increased tumorigenicity in vivo, which is mediated by the dissociation of cyclin D1/p27(KIP1) complexes, and subsequent proliferation blockade and apoptosis induction.
authors.affiliation: Authors' Affiliations: Hemato-oncology Department, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS); Hematopathology Unit, Hospital Clínic, Barcelona, Spain; and Normandie Univ, UNICAEN, MILPAT, Caen, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Moros
authors.forename: Sophie
authors.initials: S
authors.lastname: Bustany
authors.forename: Julie
authors.initials: J
authors.lastname: Cahu
authors.forename: Ifigènia
authors.initials: I
authors.lastname: Saborit-Villarroya
authors.forename: Antonio
authors.initials: A
authors.lastname: Martínez
authors.forename: Dolors
authors.initials: D
authors.lastname: Colomer
authors.forename: Brigitte
authors.initials: B
authors.lastname: Sola
authors.forename: Gaël
authors.initials: G
authors.lastname: Roué
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D019938:Cyclin D1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D015870:Gene Expression; D064593:Heterografts; D006801:Humans; D000077269:Lenalidomide; D020522:Lymphoma, Mantle-Cell / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability; D013792:Thalidomide / Q000031:analogs & derivatives* / Q000494:pharmacology; D047368:Tumor Burden / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D013792:Thalidomide; D000077269:Lenalidomide