RESUMO
Imatinib, a tyrosine kinase inhibitor (TKI) has significantly improved clinical outcome for chronic myeloid leukemia (CML) patients. However, patients develop resistance when the disease progresses to the blast phase (BP) and the mechanisms are not well understood. Here we show that BCR-ABL activates BLT2 in hematopoietic stem/progenitor cells to promote leukemogenesis and this involves the p53 signaling pathway. Compared to normal bone marrow (NBM), the mRNA and protein levels of BLT2 are significantly increased in BP-CML CD34(+) stem/progenitor cells. This is correlated with increasing BCR-ABL expression. In contrast, knockdown of BCR-ABL or inhibition of its tyrosine kinase activity decreases Blt2 protein level. BLT2 inhibition induces apoptosis, inhibits proliferation, colony formation and self-renewal capacity of CD34(+) cells from TKI-resistant BP-CML patients. Importantly, the inhibitory effects of BCR-ABL TKI on CML stem/progenitor cells are further enhanced upon combination with BLT2 inhibition. We further show that BLT2 activation selectively suppresses p53 but not Wnt or BMP-mediated luciferase activity and transcription. Our results demonstrate that BLT2 is a novel pathway activated by BCR-ABL and critically involved in the resistance of BP-CML CD34(+) stem/progenitors to TKIs treatment. Our findings suggest that BLT2 and p53 can serve as therapeutic targets for CML treatment.
Assuntos
Proteínas de Fusão bcr-abl/metabolismo , Leucemia Mielogênica Crônica BCR-ABL Positiva/patologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/terapia , Células-Tronco Neoplásicas/patologia , Receptores do Leucotrieno B4/antagonistas & inibidores , Receptores do Leucotrieno B4/metabolismo , Apoptose/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos , Proteínas de Fusão bcr-abl/antagonistas & inibidores , Proteínas de Fusão bcr-abl/genética , Humanos , Leucemia Mielogênica Crônica BCR-ABL Positiva/genética , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Células-Tronco Neoplásicas/efeitos dos fármacos , Células-Tronco Neoplásicas/metabolismo , Inibidores de Proteínas Quinases/farmacologia , RNA Interferente Pequeno/genética , Terapêutica com RNAi , Receptores do Leucotrieno B4/genética , Proteína Supressora de Tumor p53/metabolismoRESUMO
Targeting mitochondrial respiration has emerged as an attractive therapeutic strategy in blood cancer due to their unique metabolic dependencies. In this study, we show that pyrvinium, a FDA-approved anthelmintic drug, selectively targets lymphoma T-cells though inhibition of mitochondrial functions and JAK2/STAT5. Pyrvinium induces apoptosis of malignant T-cell line Jurkat and primary T-cells from lymphoma patients while sparing T-cells from healthy donors. Increased level of active caspase-3 and decreased levels of Bcl-2 and Mcl-1 were also observed in Jurkat and lymphoma T-cells but not normal T-cells treated with pyrvinium. In addition, pyrvinium impairs mitochondrial functions by inhibit mitochondrial respiration, suppressing mitochondrial respiratory complex I activity, increasing ROS and decreasing ATP levels. However, the effects of pyrvinium were abolished in mitochondrial respiration-deficient Jurkat ρ(0) cells, confirming that pyrvinium acts on lymphoma T-cells via targeting mitochondrial respiration. We further show that lymphoma T-cells derived from patients depend more on mitochondrial respiration than normal T-cells, and this explains the selective toxicity of pyrvinium in lymphoma versus normal T-cells. Finally, we demonstrate that pyrvinium also suppresses JAK2/STAT5 signaling pathway in Jurkat cells. Our study suggests that pyrvinium is a useful addition to T-cell lymphoma treatment, and emphasizes the potential therapeutic value of the differences in the mitochondrial characteristics between malignant and normal T-cells in blood cancer.
