title: Concurrent up-regulation of BCL-XL and BCL2A1 induces approximately 1000-fold resistance to ABT-737 in chronic lymphocytic leukemia.
abstract: ABT-737 and its orally active analog, ABT-263, are rationally designed inhibitors of BCL2 and BCL-X(L). ABT-263 shows promising activity in early phase 1 clinical trials in B-cell malignancies, particularly chronic lymphocytic leukemia (CLL). In vitro, peripheral blood CLL cells are extremely sensitive to ABT-737 (EC(50) approximately 7 nM), with rapid induction of apoptosis in all 60 patients tested, independent of parameters associated with disease progression and chemotherapy resistance. In contrast to data from cell lines, ABT-737-induced apoptosis in CLL cells was largely MCL1-independent. Because CLL cells within lymph nodes are more resistant to apoptosis than those in peripheral blood, CLL cells were cultured on CD154-expressing fibroblasts in the presence of interleukin-4 (IL-4) to mimic the lymph node microenvironment. CLL cells thus cultured developed an approximately 1000-fold resistance to ABT-737 within 24 hours. Investigations of the underlying mechanism revealed that this resistance occurred upstream of mitochondrial perturbation and involved de novo synthesis of the antiapoptotic proteins BCL-X(L) and BCL2A1, which were responsible for resistance to low and high ABT-737 concentrations, respectively. Our data indicate that after therapy with ABT-737-related inhibitors, resistant CLL cells might develop in lymph nodes in vivo and that treatment strategies targeting multiple BCL2 antiapoptotic members simultaneously may have synergistic activity.
authors.affiliation: Medical Research Council Toxicology Unit, University of Leicester, Leicester, United Kingdom.
authors.forename: Meike
authors.initials: M
authors.lastname: Vogler
authors.forename: Michael
authors.initials: M
authors.lastname: Butterworth
authors.forename: Aneela
authors.initials: A
authors.lastname: Majid
authors.forename: Renata J
authors.initials: RJ
authors.lastname: Walewska
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Sun
authors.forename: Martin J S
authors.initials: MJ
authors.lastname: Dyer
authors.forename: Gerald M
authors.initials: GM
authors.lastname: Cohen
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001713:Biphenyl Compounds / Q000494:pharmacology*; D015153:Blotting, Western; D023201:CD40 Ligand / Q000235:genetics / Q000378:metabolism; D019008:Drug Resistance, Neoplasm; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D015847:Interleukin-4 / Q000235:genetics / Q000378:metabolism; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D008198:Lymph Nodes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008214:Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D015778:Minor Histocompatibility Antigens; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology; D014176:Protein Biosynthesis / Q000187:drug effects; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology*; D015854:Up-Regulation; D051020:bcl-X Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: C501332:ABT-737; C096816:BCL2-related protein A1; C494811:BCL2L1 protein, human; D001713:Biphenyl Compounds; D015778:Minor Histocompatibility Antigens; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009596:Nitrophenols; D010879:Piperazines; D019253:Proto-Oncogene Proteins c-bcl-2; D034741:RNA, Small Interfering; D013449:Sulfonamides; D051020:bcl-X Protein; D023201:CD40 Ligand; D015847:Interleukin-4