title: Acquired resistance to ABT-737 in lymphoma cells that up-regulate MCL-1 and BFL-1.
abstract: ABT-737 is a small-molecule antagonist of BCL-2 currently under evaluation in clinical trials in the oral form of ABT-263. We anticipate that acquired resistance to this promising drug will inevitably arise. To study potential mechanisms of resistance to ABT-737, we derived resistant lines from initially sensitive OCI-Ly1 and SU-DHL-4 lymphoma cell lines via long-term exposure. Resistance was based in the mitochondria and not due to an inability of the drug to bind BCL-2. Resistant cells had increased levels of BFL-1 and/or MCL-1 proteins, which are not targeted by ABT-737. Proapoptotic BIM was displaced from BCL-2 by ABT-737 in both parental and resistant cells, but in resistant cells, BIM was sequestered by the additional BFL-1 and/or MCL-1. Decreasing MCL-1 levels with flavopiridol, PHA 767491, or shRNA restored sensitivity to ABT-737 resistant cells. MCL-1 was up-regulated not by protein stabilization but rather by increased transcript levels. Surprisingly, in addition to stable increases in MCL-1 transcript and protein in resistant cells, there was a dynamic increase within hours after ABT-737 treatment. BFL-1 protein and transcript levels in resistant cells were similarly dynamically up-regulated. This dynamic increase suggests a novel mechanism whereby modulation of antiapoptotic protein function communicates with nuclear transcriptional machinery.
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA.
authors.forename: Derek
authors.initials: D
authors.lastname: Yecies
authors.forename: Nicole E
authors.initials: NE
authors.lastname: Carlson
authors.forename: Jing
authors.initials: J
authors.lastname: Deng
authors.forename: Anthony
authors.initials: A
authors.lastname: Letai
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D001713:Biphenyl Compounds / Q000494:pharmacology*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D016403:Lymphoma, Large B-Cell, Diffuse / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D015778:Minor Histocompatibility Antigens; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013449:Sulfonamides / Q000494:pharmacology*; D015854:Up-Regulation
chemical_list: C501332:ABT-737; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C096816:BCL2-related protein A1; C000606775:BCL2L11 protein, human; D051023:BH3 Interacting Domain Death Agonist Protein; D000072224:Bcl-2-Like Protein 11; D001713:Biphenyl Compounds; D008565:Membrane Proteins; D015778:Minor Histocompatibility Antigens; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides