pep005 and Leukemia--Myeloid

Angiogenesis seems important for both leukemogenesis and chemosensitivity in acute myelogenous leukemia (AML). Angiogenesis is regulated by the balance between pro- and antiangiogenic cytokines, which also indicates an important role of matrix metalloproteases (MMPs) and their natural inhibitors, tissue inhibitors of metalloproteases (TIMPs). We investigated the constitutive release of MMPs and TIMPs for a large group of consecutive AML patients.. AML cells were cultured in vitro either alone or together with microvascular endothelial cells, and levels of MMPs and TIMPs were determined in culture supernatants.. AML cells showed constitutive release of several MMPs and TIMPs. For all patients, detectable MMP-10 release was observed, and most patients showed detectable release of at least one additional MMP, usually MMP-9 or MMP-2. A significant correlation was found between MMP-9 and TIMP-1 release and the release of several CCL and CXCL chemokines. MMP-9 release was higher for AML cells with monocytic differentiation corresponding to the FAB-subtype M4/M5 AML; it was mainly released in its inactive form, but endogenously active MMP-9 could be detected even in the presence of the constitutively released TIMP-1/2. Endothelial cells released relatively high levels of MMP-10, and these levels were further increased by coculture with AML cells. Patients achieving complete hematological remission after only one induction cycle showed relatively low constitutive MMP-2 release.. We conclude that primary human AML cells show constitutive release of both MMPs and TIMPs, and this release may be important for leukemogenesis and possibly also for chemosensitivity.

Topics: Acute Disease; Adult; Aged; Aged, 80 and over; Angiopoietin-2; Anthracyclines; Antineoplastic Combined Chemotherapy Protocols; Boronic Acids; Bortezomib; Cells, Cultured; Chemokines; Coculture Techniques; Culture Media, Serum-Free; Cytarabine; Diterpenes; Endothelial Cells; Female; Humans; Imidazoles; Leukemia, Myeloid; Male; Matrix Metalloproteinase Inhibitors; Matrix Metalloproteinases; Middle Aged; Neoplasm Proteins; NF-kappa B; Protease Inhibitors; Pyrazines; Quinoxalines; Receptor, TIE-2; Recombinant Proteins; Tissue Inhibitor of Metalloproteinases; Tumor Cells, Cultured

Ingenol 3-angelate (PEP005) is a selective small molecule activator of protein kinase C (PKC) extracted from the plant Euphorbia peplus, whose sap has been used as a traditional medicine for the treatment of skin conditions including warts and cancer. We report here that PEP005 also has potent antileukemic effects, inducing apoptosis in myeloid leukemia cell lines and primary acute myeloid leukemia (AML) cells at nanomolar concentrations. Of importance, PEP005 did not induce apoptosis in normal CD34+ cord blood myeloblasts at up to 2-log concentrations higher than those required to induce cell death in primary AML cells. The effects of PEP005 were PKC dependent, and PEP005 efficacy correlated with expression of PKC-delta. The delta isoform of PKC plays a key role in apoptosis and is therefore a rational potential target for antileukemic therapies. Transfection of KG1a leukemia cells, which did not express PKC-delta or respond to PEP005, with enhanced green fluorescent protein (EGFP)-PKC-delta restored sensitivity to induction of apoptosis by PEP005. Our data therefore suggest that activation of PKC-delta provides a novel approach for treatment of acute myeloid leukemia and that screening for PKC-delta expression may identify patients for potential responsiveness to PEP005.

Topics: Apoptosis; Diterpenes; Enzyme Inhibitors; Esters; Humans; Leukemia; Leukemia, Myeloid; Prognosis; Protein Kinase C; Protein Kinase C-delta; Transfection; Tumor Cells, Cultured