Aminopeptidase inhibition as a targeted treatment strategy in myeloma.
Myeloma cells are highly dependent on the unfolded protein response to assemble folded immunoglobulins correctly. Therefore, targeting protein handling within a myeloma cell by inhibiting the aminopeptidase enzyme system, which catalyses the hydrolysis of amino acids from the proteins NH2 terminus, represents a therapeutic approach. CHR-2797, a novel aminopeptidase inhibitor, is able to inhibit proliferation and induce growth arrest and apoptosis in myeloma cells, including cells resistant to conventional chemotherapeutics. It causes minimal inhibition of bone marrow stromal cell (BMSC) proliferation but is able to overcome the microenvironmental protective effects, inhibiting the proliferation of myeloma cells bound to BMSCs and the increase in vascular endothelial growth factor levels seen when myeloma cells and BMSCs are bound together. Additive and synergistic effects are seen with bortezomib, melphalan, and dexamethasone. Apoptosis occurs via both caspase-dependent and non-caspase-dependent pathways with an increase in Noxa, cleavage of Mcl-1, and activation of the unfolded protein response. Autophagy is also seen. CHR-2797 causes an up-regulation of genes involved in the proteasome/ubiquitin pathway, as well as aminopeptidases, and amino acid deprivation response genes. In conclusion, inhibiting protein turnover using the aminopeptidase inhibitor CHR-2797 results in myeloma cell apoptosis and represents a novel therapeutic approach that warrants further investigation in the clinical setting.
Section of Haemato-Oncology, Institute of Cancer Research, 15 Cotswold Road, Sutton, Surrey SM2 5NG, United Kingdom.
Hannah E
HE
Moore
Emma L
EL
Davenport
Emma M
EM
Smith
Srikanth
S
Muralikrishnan
Alan S
AS
Dunlop
Brian A
BA
Walker
David
D
Krige
Alan H
AH
Drummond
Leon
L
Hooftman
Gareth J
GJ
Morgan
Faith E
FE
Davies
D000626:Aminopeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D014408:Biomarkers, Tumor / Q000378:metabolism; D001854:Bone Marrow Cells / Q000201:enzymology / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology*; D015151:Immunoblotting; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000201:enzymology*; D017154:Stromal Cells / Q000201:enzymology / Q000473:pathology; D014407:Tumor Cells, Cultured; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D014408:Biomarkers, Tumor; D006877:Hydroxamic Acids; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D000626:Aminopeptidases; D020169:Caspases; C531970:tosedostat; D005998:Glycine