Small molecule obatoclax (GX15-070) antagonizes MCL-1 and overcomes MCL-1-mediated resistance to apoptosis

Elevated expression of members of the BCL-2 pro-survival family of proteins can confer resistance to apoptosis in cancer cells. Small molecule obatoclax (GX15-070), which is predicted to occupy a hydrophobic pocket within the BH3 binding groove of BCL-2, antagonizes these members and induces apoptosis, dependent on BAX and BAK. Reconstitution in yeast confirmed that obatoclax acts on the pathway and overcomes BCL-2-, BCL-XL-, BCL-w-, and MCL-1-mediated resistance to BAX or BAK. The compound potently interfered with the direct interaction between MCL-1 and BAK in intact mitochondrial outer membrane and inhibited the association between MCL-1 and BAK in intact cells. MCL-1 has been shown to confer resistance to the BCL-2/BCL-XL/BCL-w-selective antagonist ABT-737 and to the proteasome inhibitor bortezomib. In both cases, this resistance was overcome by obatoclax. These findings support a rational clinical development opportunity for the compound in cancer indications or treatments where MCL-1 contributes to resistance to cell killing.

[1]  Mark J. Smyth,et al.  Analysis of the apoptotic and therapeutic activities of histone deacetylase inhibitors by using a mouse model of B cell lymphoma , 2007, Proceedings of the National Academy of Sciences.

[2]  E. Campo,et al.  The proteasome inhibitor bortezomib induces apoptosis in mantle-cell lymphoma through generation of ROS and Noxa activation independent of p53 status. , 2006, Blood.

[3]  M. Blanchette,et al.  BH3‐ligand regulates access of MCL‐1 to its E3 ligase , 2005, FEBS letters.

[4]  L. Hartwell,et al.  Differential toxicities of anticancer agents among DNA repair and checkpoint mutants of Saccharomyces cerevisiae. , 2000, Cancer research.

[5]  John Calvin Reed,et al.  Mechanisms of apoptosis sensitivity and resistance to the BH3 mimetic ABT-737 in acute myeloid leukemia. , 2006, Cancer cell.

[6]  David L. Vaux,et al.  Bcl-2 gene promotes haemopoietic cell survival and cooperates with c-myc to immortalize pre-B cells , 1988, Nature.

[7]  E. Campo,et al.  The BH3-mimetic GX15-070 synergizes with bortezomib in mantle cell lymphoma by enhancing Noxa-mediated activation of Bak. , 2007, Blood.

[8]  S. Korsmeyer,et al.  Activation of Apoptosis in Vivo by a Hydrocarbon-Stapled BH3 Helix , 2004, Science.

[9]  R. Bataille,et al.  Noxa up-regulation and Mcl-1 cleavage are associated to apoptosis induction by bortezomib in multiple myeloma. , 2007, Cancer research.

[10]  M. Boccadoro,et al.  Bortezomib: efficacy comparisons in solid tumors and hematologic malignancies , 2006, Nature Clinical Practice Oncology.

[11]  D. Andrews,et al.  Bax forms multispanning monomers that oligomerize to permeabilize membranes during apoptosis , 2005, The EMBO journal.

[12]  Brian J. Smith,et al.  Differential targeting of prosurvival Bcl-2 proteins by their BH3-only ligands allows complementary apoptotic function. , 2005, Molecular cell.

[13]  R. Youle.  Cellular Demolition and the Rules of Engagement , 2007, Science.

[14]  S. Korsmeyer,et al.  Development and maintenance of B and T lymphocytes requires antiapoptotic MCL-1 , 2003, Nature.

[15]  John Calvin Reed.  Proapoptotic multidomain Bcl-2/Bax-family proteins: mechanisms, physiological roles, and therapeutic opportunities , 2006, Cell Death and Differentiation.

[16]  G. Shore,et al.  BCL-2 Selectively Interacts with the BID-induced Open Conformer of BAK, Inhibiting BAK Auto-oligomerization* , 2003, Journal of Biological Chemistry.

[17]  John Calvin Reed,et al.  Structure-function comparisons of the proapoptotic protein Bax in yeast and mammalian cells , 1996, Molecular and cellular biology.

[18]  Lin Chen,et al.  Proapoptotic Bak is sequestered by Mcl-1 and Bcl-xL, but not Bcl-2, until displaced by BH3-only proteins. , 2005, Genes & development.

[19]  Wenhua Gao,et al.  Elimination of Mcl-1 is required for the initiation of apoptosis following ultraviolet irradiation. , 2003, Genes & development.

[20]  G. Evan,et al.  Suppression of Myc-Induced Apoptosis in β Cells Exposes Multiple Oncogenic Properties of Myc and Triggers Carcinogenic Progression , 2002, Cell.

[21]  J C Reed,et al.  Comparison of chemical inhibitors of antiapoptotic Bcl-2-family proteins , 2006, Cell Death and Differentiation.

[22]  Z. Oltvai,et al.  Bcl-2 gene family and the regulation of programmed cell death. , 1994, Cold Spring Harbor symposia on quantitative biology.

[23]  S. Korsmeyer.  BCL-2 gene family and the regulation of programmed cell death. , 1995, Cancer research.

[24]  M. Hendrix,et al.  Proteasome inhibitors trigger NOXA-mediated apoptosis in melanoma and myeloma cells. , 2005, Cancer research.

[25]  S. Korsmeyer,et al.  An inhibitor of Bcl-2 family proteins induces regression of solid tumours , 2005, Nature.

[26]  S. Cory,et al.  The Bcl-2 apoptotic switch in cancer development and therapy , 2007, Oncogene.

[27]  S. Trudel,et al.  Preclinical studies of the pan-Bcl inhibitor obatoclax (GX015-070) in multiple myeloma. , 2007, Blood.

[28]  Imran Siddiqi,et al.  Solvated Interaction Energy (SIE) for Scoring Protein-Ligand Binding Affinities, 1. Exploring the Parameter Space , 2007, J. Chem. Inf. Model..

[29]  C. Scott,et al.  The BH3 mimetic ABT-737 targets selective Bcl-2 proteins and efficiently induces apoptosis via Bak/Bax if Mcl-1 is neutralized. , 2006, Cancer cell.

[30]  D. Vaux,et al.  Insights from Bcl-2 and Myc: malignancy involves abrogation of apoptosis as well as sustained proliferation. , 1999, Cancer research.

[31]  P. Nowell,et al.  Oncogenic potential of bcl-2 demonstrated by gene transfer , 1988, Nature.

[32]  E. White,et al.  DNA damage response and MCL-1 destruction initiate apoptosis in adenovirus-infected cells. , 2003, Genes & development.

[33]  E. White,et al.  Key roles of BIM-driven apoptosis in epithelial tumors and rational chemotherapy. , 2005, Cancer cell.

[34]  S. Korsmeyer,et al.  Cell Death Critical Control Points , 2004, Cell.

[35]  K. Roth,et al.  Mcl-1 deficiency results in peri-implantation embryonic lethality. , 2000, Genes & development.

[36]  D. Andrews,et al.  Bcl‐2 changes conformation to inhibit Bax oligomerization , 2006, The EMBO journal.

[37]  Mary K Joseph,et al.  Studies leading to potent, dual inhibitors of Bcl-2 and Bcl-xL. , 2007, Journal of medicinal chemistry.

[38]  E. White,et al.  BAX and BAK mediate p53-independent suppression of tumorigenesis. , 2002, Cancer cell.

[39]  S. Lowe,et al.  Dissecting p53 tumor suppressor functions in vivo. , 2002, Cancer cell.

[40]  R. Johnstone,et al.  P-Glycoprotein Protects Leukemia Cells Against Caspase-Dependent, but not Caspase-Independent, Cell Death , 1999 .

[41]  S. Korsmeyer,et al.  Distinct BH3 domains either sensitize or activate mitochondrial apoptosis, serving as prototype cancer therapeutics. , 2002, Cancer cell.

[42]  Xiaodong Wang,et al.  Mule/ARF-BP1, a BH3-Only E3 Ubiquitin Ligase, Catalyzes the Polyubiquitination of Mcl-1 and Regulates Apoptosis , 2005, Cell.

[43]  A. Petros,et al.  Structural biology of the Bcl-2 family of proteins. , 2004, Biochimica et biophysica acta.

[44]  S. Richardson,et al.  Solution Structure of Prosurvival Mcl-1 and Characterization of Its Binding by Proapoptotic BH3-only Ligands* , 2005, Journal of Biological Chemistry.

[45]  S. Korsmeyer,et al.  bcl-2-Immunoglobulin transgenic mice demonstrate extended B cell survival and follicular lymphoproliferation , 1989, Cell.

[46]  Xiaodong Wang,et al.  Cytochrome C-mediated apoptosis. , 2003, Annual review of biochemistry.