title: The proteasome inhibitor bortezomib acts independently of p53 and induces cell death via apoptosis and mitotic catastrophe in B-cell lymphoma cell lines.
abstract: Bortezomib is a proteasome inhibitor with proven efficacy in multiple myeloma and non-Hodgkin's lymphoma. This study reports the effects of bortezomib in B-cell lymphoma cell lines with differing sensitivity to bortezomib to investigate factors that influence sensitivity. Bortezomib induced a time- and concentration-dependent reduction in cell viability in five lymphoma cell lines, with EC(50) values ranging from 6 nmol/L (DHL-7 cells) to 25 nmol/L (DHL-4 cells) after 72 h. Bortezomib cytotoxicity was independent of p53 function, as all cell lines exhibited mutations by sequence analysis. The difference in sensitivity was not explained by proteasome or nuclear factor-kappaB (NF-kappaB) inhibition as these were similar in the most and least sensitive cells. NF-kappaB inhibition was less marked than that of a specific NF-kappaB inhibitor, Bay 11-7082. Cell cycle analysis showed a marked G(2)-arrested population in the least sensitive DHL-4 line only, an effect that was not present with Bay 11-7082 treatment. Conversely, in DHL-7 cells, bortezomib treatment resulted in cells moving into an aberrant mitosis, indicative of mitotic catastrophe that may contribute to increased sensitivity to bortezomib. These studies show that although bortezomib treatment had similar effects on apoptotic and NF-kappaB signaling pathways in these cell lines, different cell cycle effects were observed and induction of a further mechanism of cell death, mitotic catastrophe, was observed in the more sensitive cell line, which may provide some pointers to the difference in sensitivity between cell lines. An improved understanding of how DHL-7 cells abrogate the G(2)-M cell cycle checkpoint may help identify targets to increase the efficacy of bortezomib.
authors.affiliation: Cancer Research UK Medical Oncology Unit, St. Bartholomew's Hospital, London, UK.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Strauss
authors.forename: Karen
authors.initials: K
authors.lastname: Higginbottom
authors.forename: Simone
authors.initials: S
authors.lastname: Jüliger
authors.forename: Lenushka
authors.initials: L
authors.lastname: Maharaj
authors.forename: Paul
authors.initials: P
authors.lastname: Allen
authors.forename: David
authors.initials: D
authors.lastname: Schenkein
authors.forename: T Andrew
authors.initials: TA
authors.lastname: Lister
authors.forename: Simon P
authors.initials: SP
authors.lastname: Joel
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D020169:Caspases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D006801:Humans; D016393:Lymphoma, B-Cell / Q000188:drug therapy* / Q000473:pathology; D008938:Mitosis / Q000187:drug effects*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011719:Pyrazines / Q000494:pharmacology*; D013450:Sulfones / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000502:physiology*
chemical_list: C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D000970:Antineoplastic Agents; D001897:Boronic Acids; D018797:Cell Cycle Proteins; D016328:NF-kappa B; D009570:Nitriles; D011480:Protease Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; D011719:Pyrazines; D013450:Sulfones; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D000069286:Bortezomib; D020169:Caspases