The use of BCR-ABL1 tyrosine kinase inhibitors (TKI) has led to excellent clinical responses in patients with chronic phase chronic myeloid leukemia (CML). However these inhibitors have been less effective as single agents in the terminal blast phase (BP). We show that pyrvinium, a FDA-approved anthelminthic drug, selectively targets BP-CML CD34+ progenitor cells. Pyrvinium is effective in inducing apoptosis, inhibiting colony formation and self-renewal capacity of CD34+ cells from TKI-resistant BP-CML patients, while cord blood CD34+ are largely unaffected. The effects of pyrvinium are further enhanced upon combination with dasatinib, a second generation BCR-ABL1 TKI. In a CML xenograft model pyrvinium significantly inhibits tumor growth as a single agent, with complete inhibition in combination with dasatinib. While pyrvinium has been shown to inhibit the Wnt/β-catenin signalling pathway via activation of casein kinase 1α, we find its activity in CML is not dependent on this pathway. Instead, we show that pyrvinium localizes to mitochondria and induces apoptosis by inhibiting mitochondrial respiration. Our study suggests that pyrvinium is a useful addition to the treatment armamentarium for BP-CML and that targeting mitochondrial respiration may be a potential therapeutic strategy in aggressive leukemia.
The resistance of chronic myeloid leukaemia (CML) to tyrosine kinase inhibitors (TKIs) remains a significant clinical problem. Targeting alternative pathways, such as protein prenylation, is known to be effective in overcoming resistance. Simvastatin inhibits 3-hydroxy-3-methylglutaryl-CoA reductase (a key enzyme in isoprenoid-regulation), thereby inhibiting prenylation. We demonstrate that simvastatin alone effectively inhibits proliferation in a panel of TKI-resistant CML cell lines, regardless of mechanism of resistance. We further show that the combination of nilotinib and simvastatin synergistically kills CML cells via an increase in apoptosis and decrease in prosurvival proteins and cellular proliferation. Mechanistically, simvastatin inhibits protein prenylation as shown by increased levels of unprenylated Ras and rescue experiments with mevalonate resulted in abrogation of synergism. The combination also leads to an increase in the intracellular uptake and retention of radiolabelled nilotinib, which further enhances the inhibition of Bcr-Abl kinase activity. In primary CML samples, this combination inhibits clonogenicity in both imatinib-naive and resistant cells. Such combinatorial effects provide the basis for utilising these Food and Drug Administrationapproved drugs as a potential clinical approach in overcoming resistance and improving CML treatment.
2181 Poster Board II-158 The use of Abl tyrosine kinase inhibitors (TKI), such as imatinib mesylate (IM), has seen a major advance in the control of chronic myelogenous leukemia (CML). However, since TKIs do not seem to eliminate CML stem cells, the use of TKIs may not represent a curative approach. Recent reports have shown that the bone marrow (BM) microenvironment, which facilitates the proliferation and renewal of resident hematopoietic stem cells (HSC), is hypoxic. The average BM O2 tension has been measured at 6-7% O2 in humans (physiologic hypoxia), including in patients with leukemia (Fiegl et al. Blood, 2009), while levels in the HSC niche are estimated to be even lower (<1% O2). In light of the above, it is likely that CML stem cells also reside in the HSC niche, and are similarly adapted for survival and self-renewal in this environment. Furthermore, although hypoxia is known to be associated with both radio- and chemo-resistance in solid tumors, its role in leukemia has has not been thoroughly investigated, particularly in the context of resistance to targeted therapies. Accordingly, we hypothesized that hypoxia protects CML progenitor cells from elimination by IM, a phenomenon which may contribute to disease persistence. To test the above, we examined if hypoxia modified the response of CML progenitor cells toward IM. Primary chronic phase (CP) CML samples “from either BM or peripheral blood (PB)” were obtained at the time of diagnosis from seven individuals with clinically-defined IM-sensitive (IM-S) or IM-resistant (IM-R) disease. Cells were then incubated with IM (0, 0.25, 1 or 5μM) under hypoxic (0.5% O2) or normoxic (21% O2) conditions for 96 hours. The treated cells were then harvested and plated in methylcellulose for 14 days (under 21% O2), after which the number of colony-forming cells (CFCs) were counted by two independent observers. In the absence of IM, four of the seven samples had a significant increase in CFCs (1.5-2.4 fold) when cultured in 0.5% O2 vs 21% O2, suggesting that primary CML CFCs may be better maintained in hypoxia. Furthermore, when treated with IM, six out of seven samples cultured under 0.5% O2 demonstrated dramatic increases in CFCs compared to those treated under 21% O2: a 2.3 to 9.0-fold increase at 1μM, and a 4.4 to 35.0-fold increase at 5μM IM. We also found that the protective effect of hypoxia was independent of the original source of the CFCs (BM or PB). In addition, we found that progenitors from both IM-S and IM-R patients were protected from IM under 0.5% O2, suggesting that hypoxia-induced protection is a general feature of CML progenitors. In order to establish a model for further study, we also tested if hypoxia elicits similar responses in four human CML cell lines (K562, AR230, LAMA84, and BV173). In contrast to primary CML cells, we found that hypoxia actually impaired the ability of all four cell lines to form colonies, and also did not confer protection from IM. These results show that CML cell lines have adapted to conditions of normoxia, and are thus inappropriate models to study the hypoxic response in CML. Additional data will be presented describing the mechanisms that may underlie the protective effect of hypoxia, as well as compounds that can counteract such effects. Ongoing experiments using the LT-CIC assay will also determine the response of primitive CML progenitors to growth under conditions of physiologic hypoxia vs normoxia. In conclusion, our results show that physiologic hypoxia protects CML progenitors from IM, and suggest that blocking of hypoxia-induced survival pathway(s) in CML progenitor cells may facilitate the elimination of residual CML progenitors. Disclosures: No relevant conflicts of interest to declare.
To reveal the biology of AML, we compared gene-expression profiles between normal hematopoietic cells from 38 healthy donors and leukemic blasts (LBs) from 26 AML patients. We defined the comparison of LB and unselected BM as experiment 1, LB and CD34+ isolated from BM as experiment 2, LB and unselected PB as experiment 3, and LB and CD34+ isolated from PB as experiment 4. Then, protein–protein interaction network of DEGs was constructed to identify critical genes. Regulatory impact factors were used to identify critical transcription factors from the differential co-expression network constructed via reanalyzing the microarray profile from the perspective of differential co-expression. Gene ontology enrichment was performed to extract biological meaning. The comparison among the number of DEGs obtained in four experiments showed that cells did not tend to differentiation and CD34+ was more similar to cancer stem cells. Based on the results of protein–protein interaction network,CREBBP,F2RL1,MCM2, andTP53were respectively the key genes in experiments 1, 2, 3, and 4. From gene ontology analysis, we found that immune response was the most common one in four stages. Our results might provide a platform for determining the pathology and therapy of AML.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.