AT-101 induces apoptosis in CLL B cells and overcomes stromal cell-mediated Mcl-1 induction and drug resistance.
Resistance to apoptosis in CLL B cells is associated with overexpression of Bcl-2 family antiapoptotic proteins. Their expression is endogenous, but is also induced by signals from the microenvironment resulting in intrinsic and extrinsic drug resistance. Because AT-101 binds to the BH3 motif of all Bcl-2-family antiapoptotic proteins, we hypothesized that this molecule could overcome resistance. AT-101 treatment (20 microM for 24 hours) resulted in a median 72% apoptosis in CLL cells (patients; n = 32, P < .001). Stromal cells protected CLL B cells from spontaneous and fludarabine-induced apoptosis (P = .003) by increasing the Mcl-1 protein levels. However, AT-101 induced similar extent of down-regulation of Mcl-1 and apoptosis in CLL lymphocytes cultured in suspension or on stroma (P = .999). Stromal cells expressed undetectable levels of antiapoptotic but high levels of activated ERK and AKT proteins and had low or no apoptosis with AT-101. Collectively, these data demonstrate that AT-101 induces apoptosis in CLL B cells and overcomes microenvironment-mediated resistance while sparing normal stromal cells.
Department of Experimental Therapeutics, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Kumudha
K
Balakrishnan
Jan A
JA
Burger
William G
WG
Wierda
Varsha
V
Gandhi
D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects; D002450:Cell Communication / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D006072:Gossypol / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000473:pathology; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014740:Vidarabine / Q000031:analogs & derivatives / Q000494:pharmacology
D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D014740:Vidarabine; D006072:Gossypol; C024352:fludarabine; C028178:gossypol acetic acid