ABSTRACT
The synthetic triterpenoid CDDO-Im-induced apoptosis of patient-derived AML blasts: 11/25 AMLs were highly sensitive, while the remaining were moderately sensitive to CDDO-Im. The addition of TRAIL significantly potentiated the cytotoxic effect of CDDO-Im, through mechanisms involving the induction of TRAIL-R1/TRAIL-R2 and downmodulation of TRAIL-R3/TRAIL-R4. Biochemical studies showed that CDDO-Im: induced a rapid and marked GSH depletion and antioxidants (GSH or NAC) completely inhibited its pro-apoptotic effect; sequentially activated caspase-8, -9 and -3; caspase inhibitors partially protected AML blasts from CDDO-Im-induced apoptosis; resistance of AML blasts to CDDO-Im-induced apoptosis correlated with low caspase-8/FADD and high Bcl-X(L) expression in leukemic blasts.
Subject(s)
Caspase 8/metabolism , Fas-Associated Death Domain Protein/metabolism , Imidazoles/pharmacology , Leukemia, Myeloid, Acute/drug therapy , Oleanolic Acid/analogs & derivatives , Apoptosis/drug effects , Dose-Response Relationship, Drug , Drug Resistance, Neoplasm , Enzyme Activation , Humans , Oleanolic Acid/pharmacology , TNF-Related Apoptosis-Inducing Ligand/analysis , TNF-Related Apoptosis-Inducing Ligand/pharmacology , Tumor Cells, CulturedABSTRACT
The present study explored the sensitivity of leukaemic blasts derived from 30 acute myeloid leukaemia (AML) patients to Bortezomib. Bortezomib induced apoptosis of primary AML blasts: 18/30 AMLs were clearly sensitive to the proapoptotic effects of Bortezomib, while the remaining cases were moderately sensitive to this molecule. The addition of tumour necrosis factor-related-apoptosis-inducing ligand, when used alone, did not induce apoptosis of AML blasts and further potentiated the cytotoxic effects of Bortezomib. The majority of AMLs sensitive to Bortezomib showed immunophenotypic features of the M4 and M5 French-American-British classification subtypes and displayed myelomonocytic features. All AMLs with mutated FLT3 were in the Bortezomib-sensitive group. Biochemical studies showed that: (i) Bortezomib activated caspase-8 and caspase-3 and decreased cellular FLICE [Fas-associated death domain (FADD)-like interleukin-1beta-converting enzyme]-inhibitory protein (c-FLIP) levels in AML blasts; (ii) high c-FLIP levels in AML blasts were associated with low Bortezomib sensitivity. Finally, analysis of the effects of Bortezomib on leukaemic cells displaying high aldehyde dehydrogenase activity suggested that this drug induced in vitro killing of leukaemic stem cells. The findings of the present study, further support the development of Bortezomib as an anti-leukaemic drug and provide simple tools to predict the sensitivity of AML cells to this drug.
Subject(s)
Boronic Acids/therapeutic use , Leukemia, Monocytic, Acute/drug therapy , Leukemia, Myelomonocytic, Acute/drug therapy , Protease Inhibitors/therapeutic use , Pyrazines/therapeutic use , Aldehyde Dehydrogenase/metabolism , Apoptosis , Bortezomib , CASP8 and FADD-Like Apoptosis Regulating Protein/analysis , CASP8 and FADD-Like Apoptosis Regulating Protein/metabolism , Caspase 3/metabolism , Caspase 8/metabolism , Cells, Cultured , Fas-Associated Death Domain Protein/analysis , Fas-Associated Death Domain Protein/metabolism , Flow Cytometry , Humans , Immunophenotyping , Leukemia, Monocytic, Acute/pathology , Leukemia, Myelomonocytic, Acute/pathology , Receptors, TNF-Related Apoptosis-Inducing Ligand/analysis , Stem Cells/drug effects , TNF-Related Apoptosis-Inducing Ligand/analysis , X-Linked Inhibitor of Apoptosis Protein/analysis , X-Linked Inhibitor of Apoptosis Protein/metabolismABSTRACT
We have investigated the expression of podocalyxin in primary cultures of leukemic blast cells from 73 patients with acute myeloid leukemia. Podocalyxin was expressed at moderate levels in 15 patients and at high levels in 13 patients. The analysis of membrane markers showed that Podocalyxin expression in leukemic blasts was associated with a monocytic immunophenotype. Cases of podocalyxin-positive acute myelogenous leukemia had high blast cell counts at diagnosis and elevated CD123, CD135, VLA-4 and CXCR4 expression, features associated with poor prognosis. Podocalyxin expression in leukemic blasts was coupled with the concomitant expression of VEGF-R1, -R2, -R3 and Tie-2, the capacity to release VEGF-A and angiopoietin1 and the ability to differentiate into endothelial cells under appropriate culture conditions. These findings show that podocalyxin is a marker of acute myeloid leukemia with a monocytic phenotype and suggest that podocalyxin-positive cases of acute myeloid leukemia originate from the malignant transformation of progenitors common to the myeloid and endothelial lineages. These observations suggest a possible relationship between the monocytic lineage and podocytes.