bms-214662 and Blast-Crisis

The cytotoxic farnesyl transferase inhibitor BMS-214662 has been shown to potently induce mitochondrial apoptosis in primitive CD34+ chronic myeloid leukaemia (CML) stem/progenitor cells. Here, to enhance the BMS-214662 apoptotic effect, we further targeted the extracellular signal-regulated kinase (ERK) pathway, downstream of BCR-ABL, by treating CD34+ CML stem/progenitor cells with a highly selective adenosine triphosphate (ATP) non-competitive MEK inhibitor, PD184352. PD184352 increased the apoptotic effect of BMS-214662 in a CML blast crisis cell line, K562, and in primary chronic phase CD34+ CML cells. Compared with BMS-214662, after combination treatment we observed inhibition of ERK phosphorylation, increased Annexin-V levels, caspase-3, -8 and -9 activation and potentiated mitochondrial damage, associated with decreased levels of anti-apoptotic BCL-2 family protein MCL-1. Inhibition of K-RAS function by a dominant-negative mutant resulted in CML cell death and this process was further enhanced by the addition of BMS-214662 and PD184352. Together, these findings suggest that the addition of a MEK inhibitor improves the ability of BMS-214662 to selectively target CML stem/progenitor cells, notoriously insensitive to tyrosine kinase inhibitor treatment and presumed to be responsible for the persistence and relapse of the disease.

Topics: Antigens, CD34; Apoptosis; Benzamides; Benzodiazepines; Blast Crisis; Drug Screening Assays, Antitumor; Drug Synergism; Enzyme Inhibitors; Farnesyltranstransferase; Genes, Dominant; Genes, ras; Hematopoietic Stem Cells; Humans; Imidazoles; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukemia, Myeloid, Chronic-Phase; MAP Kinase Kinase 1; MAP Kinase Kinase Kinases; Neoplasm Proteins; Neoplastic Stem Cells; Oncogene Protein p21(ras); Recombinant Fusion Proteins; Tumor Cells, Cultured

Chronic myeloid leukemia (CML), a hematopoietic stem-cell disorder, cannot be eradicated by conventional chemotherapy or the tyrosine kinase inhibitor imatinib mesylate (IM). To target CML stem/progenitor cells, we investigated BMS-214662, a cytotoxic farnesyltransferase inhibitor, previously reported to kill nonproliferating tumor cells. IM or dasatinib alone reversibly arrested proliferation of CML stem/progenitor cells without inducing apoptosis. In contrast, BMS-214662, alone or in combination with IM or dasatinib, potently induced apoptosis of both proliferating and quiescent CML stem/progenitor cells with less than 1% recovery of Philadelphia-positive long-term culture-initiating cells. Normal stem/progenitor cells were relatively spared by BMS-214662, suggesting selectivity for leukemic stem/progenitor cells. The ability to induce selective apoptosis of leukemic stem/progenitor cells was unique to BMS-214662 and not seen with a structurally similar agent BMS-225975. BMS-214662 was cytotoxic against CML blast crisis stem/progenitor cells, particularly in combination with a tyrosine kinase inhibitor and equally effective in cell lines harboring wild-type vs mutant BCR-ABL, including the T315I mutation. This is the first report of an agent with activity in resistant and blast crisis CML that selectively kills CML stem/progenitor cells through apoptosis and offers potential for eradication of chronic phase CML.

Topics: Antigens, CD34; Antineoplastic Agents; Apoptosis; Benzamides; Benzodiazepines; Blast Crisis; Caspase 3; Cell Death; Cell Survival; Dasatinib; Drug Screening Assays, Antitumor; Drug Synergism; Farnesyltranstransferase; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; Imidazoles; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Mutation; Neoplastic Stem Cells; Philadelphia Chromosome; Piperazines; Protein Kinase Inhibitors; Protein Structure, Tertiary; Pyrimidines; Thiazoles