RESUMO
LB100 sensitizes resistant chronic phase CML stem and progenitor cells to TKIs and spares healthy bone marrow cells.
Assuntos
Leucemia Mielogênica Crônica BCR-ABL Positiva , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Proteínas de Fusão bcr-abl , Humanos , Células-Tronco Neoplásicas/efeitos dos fármacos , Inibidores de Proteínas QuinasesRESUMO
Overcoming drug resistance and targeting leukemic stem cells (LSCs) remain major challenges in curing BCR-ABL+ human leukemia. Using an advanced drug/proliferation screen, we have uncovered a prosurvival role for protein phosphatase 2A (PP2A) in tyrosine kinase inhibitor (TKI)-insensitive leukemic cells, regulated by an Abelson helper integration site-1-mediated PP2A-ß-catenin-BCR-ABL-JAK2 protein complex. Genetic and pharmacological inhibition of PP2A impairs survival of TKI nonresponder cells and sensitizes them to TKIs in vitro, inducing a dramatic loss of several key proteins, including ß-catenin. We also demonstrate that the clinically validated PP2A inhibitors LB100 and LB102, in combination with TKIs, selectively eliminate treatment-naïve TKI-insensitive stem and progenitor cells, while sparing healthy counterparts. In addition, PP2A inhibitors and TKIs act synergistically to inhibit the growth of TKI-insensitive cells, as assessed by combination index analysis. The combination eliminates infiltrated BCR-ABL+ blast cells and drug-insensitive LSCs and confers a survival advantage in preclinical xenotransplant models. Thus, dual PP2A and BCR-ABL inhibition may be a valuable therapeutic strategy to synergistically target drug-insensitive LSCs that maintain minimal residual disease in patients.
Assuntos
Inibidores Enzimáticos/farmacologia , Leucemia Mielogênica Crônica BCR-ABL Positiva/metabolismo , Células-Tronco Neoplásicas/efeitos dos fármacos , Células-Tronco Neoplásicas/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteína Fosfatase 2/antagonistas & inibidores , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/genética , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Resistencia a Medicamentos Antineoplásicos , Sinergismo Farmacológico , Humanos , Camundongos , Proteína Fosfatase 2/genética , Proteína Fosfatase 2/metabolismo , Células Tumorais CultivadasRESUMO
BACKGROUND: Imatinib mesylate (IM) induces clinical remission of chronic myeloid leukemia (CML). The Abelson helper integration site 1 (AHI-1) oncoprotein interacts with BCR-ABL and Janus kinase 2 (JAK2) to mediate IM response of primitive CML cells, but the effect of the interaction complex on the response to ABL and JAK2 inhibitors is unknown. METHODS: The AHI-1-BCR-ABL-JAK2 interaction complex was analyzed by mutational analysis and coimmunoprecipitation. Roles of the complex in regulation of response or resistance to ABL and JAK2 inhibitors were investigated in BCR-ABL (+) cells and primary CML stem/progenitor cells and in immunodeficient NSG mice. All statistical tests were two-sided. RESULTS: The WD40-repeat domain of AHI-1 interacts with BCR-ABL, whereas the N-terminal region interacts with JAK2; loss of these interactions statistically significantly increased the IM sensitivity of CML cells. Disrupting this complex with a combination of IM and an orally bioavailable selective JAK2 inhibitor (TG101209 [TG]) statistically significantly induced death of AHI-1-overexpressing and IM-resistant cells in vitro and enhanced survival of leukemic mice, compared with single agents (combination vs TG alone: 63 vs 53 days, ratio = 0.84, 95% confidence interval [CI] = 0.6 to 1.1, P = .004; vs IM: 57 days, ratio = 0.9, 95% CI = 0.61 to 1.2, P = .003). Combination treatment also statistically significantly enhanced apoptosis of CD34(+) leukemic stem/progenitor cells and eliminated their long-term leukemia-initiating activity in NSG mice. Importantly, this approach was effective against treatment-naive CML stem cells from patients who subsequently proved to be resistant to IM therapy. CONCLUSIONS: Simultaneously targeting BCR-ABL and JAK2 activities in CML stem/progenitor cells may improve outcomes in patients destined to develop IM resistance.