ABSTRACT
Bcl-2 inhibits apoptosis by two distinct mechanisms but only one is targeted to treat Bcl-2-positive malignancies. In this mechanism, the BH1-3 domains of Bcl-2 form a hydrophobic pocket, binding and inhibiting pro-apoptotic proteins, including Bim. In the other mechanism, the BH4 domain mediates interaction of Bcl-2 with inositol 1,4, 5-trisphosphate receptors (IP3Rs), inhibiting pro-apoptotic Ca2+ signals. The current anti-Bcl-2 agents, ABT-263 (Navitoclax) and ABT-199 (Venetoclax), induce apoptosis by displacing pro-apoptotic proteins from the hydrophobic pocket, but do not inhibit Bcl-2-IP3R interaction. Therefore, to target this interaction we developed BIRD-2 (Bcl-2 IP3 Receptor Disruptor-2), a decoy peptide that binds to the BH4 domain, blocking Bcl-2-IP3R interaction and thus inducing Ca2+-mediated apoptosis in chronic lymphocytic leukemia, multiple myeloma, and follicular lymphoma cells, including cells resistant to ABT-263, ABT-199, or the Bruton's tyrosine kinase inhibitor Ibrutinib. Moreover, combining BIRD-2 with ABT-263 or ABT-199 enhances apoptosis induction compared to single agent treatment. Overall, these findings provide strong rationale for developing novel therapeutic agents that mimic the action of BIRD-2 in targeting the BH4 domain of Bcl-2 and disrupting Bcl-2-IP3R interaction.
Subject(s)
Lymphoma, Follicular/pathology , Multiple Myeloma/pathology , Peptides/chemistry , Proto-Oncogene Proteins c-bcl-2/metabolism , Aniline Compounds/therapeutic use , Animals , Apoptosis , Bridged Bicyclo Compounds, Heterocyclic/therapeutic use , Calcium Signaling , Cell Line, Tumor , Cell Survival , Drug Resistance, Neoplasm , HEK293 Cells , Humans , Hydrophobic and Hydrophilic Interactions , Immunohistochemistry , Inositol 1,4,5-Trisphosphate Receptors/chemistry , Leukemia, Lymphocytic, Chronic, B-Cell/drug therapy , Lymphoma, Follicular/drug therapy , Mice , Mice, Nude , Multiple Myeloma/drug therapy , NIH 3T3 Cells , Neoplasm Transplantation , Protein Structure, Tertiary , Sulfonamides/therapeutic use , bcl-2-Associated X Protein/metabolismABSTRACT
We studied the accuracy of various susceptibility testing methods, including the 2009, 2010, and updated 2010 CLSI recommendations, to identify Klebsiella pneumoniae isolates with reduced susceptibility to carbapenems associated with different mechanisms of resistance. Forty-three wild-type (WT) strains, 42 extended-spectrum ß-lactamase (ESBL) producers, 18 ESBL producers with outer membrane porin protein loss (ESBL/Omp strains), and 42 blaKPC-possessing K. pneumoniae (KPC-Kp) isolates were evaluated. Imipenem (IPM), meropenem (MEM), ertapenem (ERT), and doripenem (DOR) were tested by broth microdilution (BMD), Etest, and disk diffusion (DD), and the modified Hodge test (MHT) was performed using IPM and MEM disks. Results were interpreted according to original as well as recently updated interpretative criteria. MHT was positive for all 42 KPC-Kp isolates and 10 of 18 ESBL/Omp strains and therefore had poor specificity in differentiating between KPC-Kp and ESBL/Omp isolates. Based on the updated CLSI standards, phenotypic susceptibility testing by BMD and DD differentiated most carbapenem-susceptible from carbapenem-nonsusceptible K. pneumoniae isolates without the need for MHT, while the Etest method characterized many KPC-Kp isolates as susceptible, and breakpoints may need to be lowered for this method. However, both the original and updated CLSI criteria do not adequately differentiate between isolates in the KPC-Kp group, which are unlikely to respond to carbapenem therapy, and those in the ESBL/Omp group, which are likely to respond to carbapenem therapy if MICs are within pharmacokinetic/pharmacodynamic targets. Further studies are required to determine if there is a clinical need to differentiate between KPC-Kp and ESBL/Omp groups.
Subject(s)
Anti-Bacterial Agents/pharmacology , Carbapenems/pharmacology , Klebsiella pneumoniae/classification , Klebsiella pneumoniae/drug effects , beta-Lactam Resistance , Bacterial Outer Membrane Proteins/genetics , Humans , Microbial Sensitivity Tests/methods , beta-Lactamases/biosynthesisSubject(s)
Anti-Bacterial Agents/administration & dosage , Enzyme Inhibitors/administration & dosage , Klebsiella pneumoniae/drug effects , beta-Lactamase Inhibitors , beta-Lactams/administration & dosage , Bacterial Proteins/antagonists & inhibitors , Bacterial Proteins/genetics , Humans , In Vitro Techniques , Klebsiella Infections/drug therapy , Klebsiella Infections/microbiology , Klebsiella pneumoniae/enzymology , Klebsiella pneumoniae/genetics , Klebsiella pneumoniae/isolation & purification , Microbial Sensitivity Tests , beta-Lactamases/geneticsABSTRACT
The in vitro activity of ACHN-490, a novel aminoglycoside ("neoglycoside"), was evaluated against 102 multidrug-resistant (MDR) Klebsiella pneumoniae strains, including a subset of 25 strains producing the KPC carbapenemase. MIC50 values for gentamicin, tobramycin, and amikacin were 8 microg/ml, 32 microg/ml, and 2 microg/ml, respectively; MIC90 values for the same antimicrobials were > or = 64 microg/ml, > or = 64 microg/ml, and 32 microg/ml, respectively. ACHN-490 showed an MIC50 of 0.5 microg/ml and an MIC90 of 1 microg/ml, which are significantly lower than those of comparator aminoglycosides. ACHN-490 represents a promising aminoglycoside for the treatment of MDR K. pneumoniae isolates, including those producing KPC beta-lactamase.
