title: Vorinostat, a histone deacetylase (HDAC) inhibitor, promotes cell cycle arrest and re-sensitizes rituximab- and chemo-resistant lymphoma cells to chemotherapy agents.
abstract: OBJECTIVE
  Preclinical models of chemotherapy resistance and clinical observations derived from the prospective multicenter phase III collaborative trial in relapsed aggressive lymphoma (CORAL) study demonstrated that primary refractory/relapsed B cell diffuse large B cell lymphoma has a poor clinical outcome with current available second-line treatments. Preclinically, we found that rituximab resistance is associated with a deregulation on the mitochondrial potential rendering lymphoma cells resistant to chemotherapy-induced apoptotic stimuli. There is a dire need to develop agents capable to execute alternative pathways of cell death in an attempt to overcome chemotherapy resistance. Posttranscriptional histone modification plays an important role in regulating gene transcription and is altered by histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs regulate several key cellular functions, including cell proliferation, cell cycle, apoptosis, angiogenesis, migration, antigen presentation, and/or immune regulation. Given their influence in multiple regulatory pathways, HDAC inhibition is an attractive strategy to evaluate its anti-proliferation activity in cancer cells. To this end, we studied the anti-proliferation activity and mechanisms of action of suberoylanilide hydroxamic acid (SAHA, vorinostat) in rituximab-chemotherapy-resistant preclinical models.
  
  
  METHODS
  A panel of rituximab-chemotherapy-sensitive (RSCL) and rituximab-chemotherapy-resistant cell lines (RRCL) and primary tumor cells isolated from relapsed/refractory B cell lymphoma patients were exposed to escalating doses of vorinostat. Changes in mitochondrial potential, ATP synthesis, and cell cycle distribution were determined by Alamar blue reduction, Titer-Glo luminescent assays, and flow cytometric, respectively. Protein lysates were isolated from vorinostat-exposed cells, and changes in members of Bcl-2 family, cell cycle regulatory proteins, and the acetylation status of histone H3 were evaluated by Western blotting. Finally, cell lines were pre-exposed to vorinostat for 48 h and subsequently exposed to several chemotherapy agents (cisplatin, etoposide, or gemcitabine); changes in cell viability were determined by CellTiter-Glo(®) luminescence assay (Promega, Fitchburg, WI), and synergistic activity was evaluated using the CalcuSyn software.
  
  
  RESULTS
  Vorinostat induced dose-dependent cell death in RRCL and in primary tumor cells. In addition, in vitro exposure of RRCL to vorinostat resulted in an increase in p21 and acetylation of histone H3 leading to G1 cell cycle arrest. Vorinostat exposure resulted in apoptosis in RSCL cell lines but not in RRCL. This finding suggests that in RRCL, vorinostat induces cell death by alternative pathways (i.e., irreversible cell cycle arrest). Of interest, vorinostat was found to reverse acquired chemotherapy resistance in RRCL.
  
  
  CONCLUSIONS
  Our data suggest that vorinostat is active in RRCL with a known defective apoptotic machinery, it can active alternative cell death pathways. Given the multiple pathways affected by HDAC inhibition, vorinostat can potentially be used to overcome acquired resistant to chemotherapy in aggressive B cell lymphoma.
authors: Department of Medical Oncology, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China.
authors: Kai
authors: K
authors: Xue
authors: Departments of Medicine and Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA.
authors: Juan J
authors: JJ
authors: Gu
authors: Department of Medical Oncology, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China.
authors: Qunling
authors: Q
authors: Zhang
authors: Departments of Medicine and Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA.
authors: Cory
authors: C
authors: Mavis
authors: Departments of Medicine and Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA.
authors: Francisco J
authors: FJ
authors: Hernandez-Ilizaliturri
authors: Departments of Medicine and Immunology, Roswell Park Cancer Institute, Buffalo, NY, USA.
authors: Myron S
authors: MS
authors: Czuczman
authors: Department of Medical Oncology, Fudan University Shanghai Cancer Center, Shanghai, People's Republic of China. pattrickguo@gmail.com.|Department of Oncology, Shanghai Medical College, Fudan University, Shanghai, People's Republic of China. pattrickguo@gmail.com.
authors: Ye
authors: Y
authors: Guo
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002051:Burkitt Lymphoma / Q000188:drug therapy / Q000473:pathology; D048708:Cell Growth Processes / Q000187:drug effects; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D004357:Drug Synergism; D059585:G1 Phase Cell Cycle Checkpoints / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D006689:Hodgkin Disease / Q000188:drug therapy / Q000473:pathology; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000494:pharmacology*; D008223:Lymphoma / Q000188:drug therapy* / Q000473:pathology; D016403:Lymphoma, Large B-Cell, Diffuse / Q000188:drug therapy* / Q000473:pathology; D000069283:Rituximab / Q000008:administration & dosage / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D000077337:Vorinostat
chemical_list: D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D000069283:Rituximab; D000077337:Vorinostat
keywords: Chemotherapy resistance; Histone deacetylase inhibitors; Lymphoma; Vorinostat