The purine nucleotide content in human leukemia cell lines

The HPLC method was used to determine the purine nucleotide (ATP, ADP, AMP, GTP, GDP, GMP, NAD(+)) contents and the values of the adenylate energy charge (AEC) and guanylate energy charge (GEC) for three human acute myelogenous leukemia (AML) cell lines: HL60 (M3 subtype of AML), THP1 (M5 subtype of AML), and HEL (M6 subtype of AML) in French-American-British classification (FAB) and for one chronic myelogenous leukemia (CML) cell line: K562. The results showed that the examined leukemic cells had some significant changes in their purine nucleotide concentrations relative to healthy cells. On the basis of the obtained results, it seems that two of the tested acute myelogenous leukemia cell lines, HL60 and HEL, have similar purine nucleotide metabolisms, while the third AML cell line, THP1, has a purine nucleotide metabolism like that of the chronic myelogenous leukemia cell line, K562.     

Acadesine Kills Chronic Myelogenous Leukemia (CML) Cells through PKC-Dependent Induction of Autophagic Cell Death

CML is an hematopoietic stem cell disease characterized by the t(9;22) (q34;q11) translocation encoding the oncoprotein p210BCR-ABL. The effect of acadesine (AICAR, 5-Aminoimidazole-4-carboxamide-1-β-D-ribofuranoside) a compound with known antileukemic effect on B cell chronic lymphoblastic leukemia (B-CLL) was investigated in different CML cell lines. Acadesine triggered loss of cell metabolism in K562, LAMA-84 and JURL-MK1 and was also effective in killing imatinib-resistant K562 cells and Ba/F3 cells carrying the T315I-BCR-ABL mutation. The anti-leukemic effect of acadesine did not involve apoptosis but required rather induction of autophagic cell death. AMPK knock-down by Sh-RNA failed to prevent the effect of acadesine, indicating an AMPK-independent mechanism. The effect of acadesine was abrogated by GF109203X and Ro-32-0432, both inhibitor of classical and new PKCs and accordingly, acadesine triggered relocation and activation of several PKC isoforms in K562 cells. In addition, this compound exhibited a potent anti-leukemic effect in clonogenic assays of CML cells in methyl cellulose and in a xenograft model of K562 cells in nude mice. In conclusion, our work identifies an original and unexpected mechanism by which acadesine triggers autophagic cell death through PKC activation. Therefore, in addition to its promising effects in B-CLL, acadesine might also be beneficial for Imatinib-resistant CML patients.     

A Critical Role of CDKN3 in Bcr-Abl-Mediated Tumorigenesis

CDKN3 (cyclin-dependent kinase inhibitor 3), a dual specificity protein phosphatase, dephosphorylates cyclin-dependent kinases (CDKs) and thus functions as a key negative regulator of cell cycle progression. Deregulation or mutations of CDNK3 have been implicated in various cancers. However, the role of CDKN3 in Bcr-Abl-mediated chronic myelogenous leukemia (CML) remains unknown. Here we found that CDKN3 acts as a tumor suppressor in Bcr-Abl-mediated leukemogenesis. Overexpression of CDKN3 sensitized the K562 leukemic cells to imanitib-induced apoptosis and dramatically inhibited K562 xenografted tumor growth in nude mouse model. Ectopic expression of CDKN3 significantly reduced the efficiency of Bcr-Abl-mediated transformation of FDCP1 cells to growth factor independence. In contrast, depletion of CDKN3 expression conferred resistance to imatinib-induced apoptosis in the leukemic cells and accelerated the growth of xenograph leukemia in mice. In addition, we found that CDKN3 mutant (CDKN3-C140S) devoid of the phosphatase activity failed to affect the K562 leukemic cell survival and xenografted tumor growth, suggesting that the phosphatase of CDKN3 was required for its tumor suppressor function. Furthermore, we observed that overexpression of CDKN3 reduced the leukemic cell survival by dephosphorylating CDK2, thereby inhibiting CDK2-dependent XIAP expression. Moreover, overexpression of CDKN3 delayed G1/S transition in K562 leukemic cells. Our results highlight the importance of CDKN3 in Bcr-Abl-mediated leukemogenesis, and provide new insights into diagnostics and therapeutics of the leukemia.     

Characterization of miRNomes in Acute and Chronic Myeloid Leukemia Cell Lines

Myeloid leukemias are highly diverse diseases and have been shown to be associated with microRNA（miRNA） expression aberrations. The present study involved an in-depth miRNome analysis of two human acute myeloid leukemia（AML） cell lines, HL-60 and THP-1, and one human chronic myeloid leukemia（CML） cell line, K562, via massively parallel signature sequencing. mRNA expression profiles of these cell lines that were established previously in our lab facilitated an integrative analysis of miRNA and mRNA expression patterns. miRNA expression profiling followed by differential expression analysis and target prediction suggested numerous miRNA signatures in AML and CML cell lines. Some miRNAs may act as either tumor suppressors or oncomiRs in AML and CML by targeting key genes in AML and CML pathways. Expression patterns of cell type-specific miRNAs could partially reflect the characteristics of K562, HL-60 and THP-1 cell lines, such as actin filament-based processes, responsiveness to stimulus and phagocytic activity. miRNAs may also regulate myeloid differentiation, since they usually suppress differentiation regulators. Our study provides a resource to further investigate the employment of miRNAs in human leukemia subtyping, leukemogenesis and myeloid development. In addition, the distinctive miRNA signatures may be potential candidates for the clinical diagnosis, prognosis and treatment of myeloid leukemias.     

The growth of K562 human leukemia cells was inhibited by therapeutic neural stem cells in cellular and xenograft mouse models

To confirm the anti-tumor effect of engineered neural stem cells (NSCs) expressing cytosine deaminase (CD) and interferon-β (IFN-β) with prodrug 5-fluorocytosine (FC), K562 chronic myeloid leukemia (CML) cells were co-cultured with the neural stem cell lines HB1.F3.CD and HB1.F3.CD.IFN-β in 5-FC containing media. A significant decrease in the viability of K562 cells was observed by the treatment of the NSC lines, HB1.F3.CD and HB1.F3.CD.IFN-β, compared with the control. A modified trans-well assay showed that engineered human NSCs significantly migrated toward K562 CML cells more than human normal lung cells. In addition, the important chemoattractant factors involved in the specific migration ability of stem cells were found to be expressed in K562 CML cells. In a xenograft mouse model, NSC treatments via subcutaneous and intravenous injections resulted in significant inhibitions of tumor mass growth and extended survival dates of the mice. Taken together, these results suggest that gene therapy using genetically engineered stem cells expressing CD and IFN-β may be effective for treating CML in these mouse models.     

Aberrant expressions of leptin and adiponectin receptor isoforms in chronic myeloid leukemia patients

Background

Leptin and adiponectin receptors mediate the role of leptin in stimulating the growth of leukemic cells and the protective function of adiponectin undertaken in several malignancies such as leukemia. In this study, we investigated the involvement of the expression of leptin and adiponectin receptors in chronic myeloid leukemia (CML) pathogenesis.

Methods

The expression of leptin receptor isoforms, OB-Rt, OB-Ra, and OB-Rb, and the expression of adiponectin receptors, AdipoR1 and AdipoR2, were measured as mRNA levels in two CML cell lines (K562 and Meg-01) and 20 CML patients and 24 healthy controls by using RT-PCR.

Results

OB-Rt and OB-Ra isoforms expression of the leptin receptors were found to be significantly lower in Meg-01 cell lines than K562 cells. All leptin receptors were downregulated in CML patients and more particularly OB-Rb level was found to be undetectably low in normal PBMC as well as in CML patients. AdipoR1 expression level was higher in Meg-01 than in K562, whereas AdipoR2 level was found to be unchanged in both cell lines. Interestingly, while AdipoR1 expression increased in CML patients, AdipoR2 decreased. Moreover, imatinib therapy did not affect both leptin and adiponectin isoform expressions.

Conclusion

While the decrease in leptin receptor levels in CML patients was confirmed, the increase in AdipoR1 levels and relevant decrease in AdipoR2 levels depicted their possible involvement in CML pathogenesis. This suggests different functions of adiponectin receptors in CML development.     

Induction of Heme Oxygenase-1 by Na+-H+ Exchanger 1 Protein Plays a Crucial Role in Imatinib-resistant Chronic Myeloid Leukemia Cells

Resistance toward imatinib (IM) and other BCR/ABL tyrosine kinase inhibitors remains troublesome in the treatment of advanced stage chronic myeloid leukemia (CML). The aim of this study was to estimate the reversal effects of down-regulation of Na⁺/H⁺ exchanger 1 (NHE1) on the chemoresistance of BCR-ABL-positive leukemia patients'' cells and cell lines. After treatment with the specific NHE1 inhibitor cariporide to decrease intracellular pH (pH_i), the heme oxygenase-1 (HO-1) levels of the K562R cell line and cells from IM-insensitive CML patients decreased. HO-1, as a Bcr/Abl-dependent survival molecule in CML cells, is important for the resistance to tyrosine kinase inhibitors in patients with newly diagnosed CML or IM-resistant CML. Silencing PKC-β and Nrf-2 or treatment with inhibitors of p38 pathways obviously blocked NHE1-induced HO-1 expression. Furthermore, treatment with HO-1 or p38 inhibitor plus IM increased the apoptosis of the K562R cell line and IM-insensitive CML patients'' cells. Inhibiting HO-1 enhanced the activation of caspase-3 and poly(ADP-ribose) polymerase-1. Hence, the results support the anti-apoptotic role of HO-1 induced by NHE1 in the K562R cell line and IM-insensitive CML patients and provide a mechanism by which inducing HO-1 expression via the PKC-β/p38-MAPK pathway may promote tumor resistance to oxidative stress.     

K562 chronic myeloid leukemia cells modify osteogenic differentiation and gene expression of bone marrow stromal cells

Bone marrow (BM) microenvironment plays an important role in normal and malignant hematopoiesis. As a consequence of interaction with the leukemic cells, the stromal cells of the bone marrow become deregulated in their normal function and gene expression. In our study, we found that mesenchymal stem cells (MSC) from BM of chronic myeloid leukemia (CML) patients have defective osteogenic differentiation and on interaction with K562 CML cells, the normal MSC showed reduced osteogenic differentiation. On interaction with K562 cells or its secreted factors, MSC acquired phenotypic abnormalities and secreted high levels of IL6 through NFκB activation. The MSC derived secreted factors provided a survival advantage to CML cells from imatinib induced apoptosis. Thus, a therapy targeting stromal cells in addition to leukemia cells might be more effective in eliminating CML cells.     

Sphingomyelin synthase 1 activity is regulated by the BCR-ABL oncogene

Sphingomyelin synthase (SMS) produces sphingomyelin while consuming ceramide (a negative regulator of cell proliferation) and forming diacylglycerol (DAG) (a mitogenic factor). Therefore, enhanced SMS activity could favor cell proliferation. To examine if dysregulated SMS contributes to leukemogenesis, we measured SMS activity in several leukemic cell lines and found that it is highly elevated in K562 chronic myelogenous leukemia (CML) cells. The increased SMS in K562 cells was caused by the presence of Bcr-abl, a hallmark of CML; stable expression of Bcr-abl elevated SMS activity in HL-60 cells while inhibition of the tyrosine kinase activity of Bcr-abl with Imatinib mesylate decreased SMS activity in K562 cells. The increased SMS activity was the result of up-regulation of the Sms1 isoform. Inhibition of SMS activity with D609 (a pharmacological SMS inhibitor) or down-regulation of SMS1 expression by siRNA selectively inhibited the proliferation of Bcr-abl-positive cells. The inhibition was associated with an increased production of ceramide and a decreased production of DAG, conditions that antagonize cell proliferation. A similar change in lipid profile was also observed upon pharmacological inhibition of Bcr-abl (K526 cells) and siRNA-mediated down-regulation of BCR-ABL (HL-60/Bcr-abl cells). These findings indicate that Sms1 is a downstream target of Bcr-abl, involved in sustaining cell proliferation of Bcr-abl-positive cells.     

Nilotinib and imatinib are comparably effective in reducing growth of human eosinophil leukemia cells in a newly established xenograft model

We developed a xenograft model of human Chronic Eosinophilic Leukemia (CEL) to study disease progression and remission-induction under therapy with tyrosine kinase inhibitors using imatinib and nilotinib as examples. The FIP1L1/PDGFRA+ human CEL cell lineEOL-1 was injected intravenously into scid mice, and MR imaging and FACS analysis of mouse blood samples were performed to monitor disease development and the effects of imatinib and nilotinib. Organ infiltration was analyzed in detail by immunohistochemistry after sacrifice. All animals developed CEL and within one week of therapy, complete remissions were seen with both imatinib and nilotinib, resulting in reduced total tumor volumes by MR-imaging and almost complete disappearance of EOL-1 cells in the peripheral blood and in tissues. The new model system is feasible for the evaluation of new tyrosine kinase inhibitors and our data suggest that nilotinib may be a valuable additional targeted drug active in patients with FIP1L1/PDGFRA+ CEL.     

Lysis of fresh leukemic blasts by interferon-activated human natural killer cells

In a comprehensive study of 30 leukemia patients, it was found that a measurable fraction of fresh leukemic blasts from 8 of 8 adult patients with chronic myelogenous leukemia (CML) in blast crisis and 10 of 11 pediatric patients with childhood acute lymphocytic leukemia (ALL) were efficiently lysed by human peripheral blood natural killer (NK) cells as measured in 4-hour chromium release assays. The observed lysis of these fresh, noncultured, neoplastic blasts was mediated by a population of interferon-augmentable, FcR-positive, non-adherent large granular lymphoid cells from normal donors, which were also able to kill the 'standard' NK target K562. It was of further interest that all 8 of the patients with blast crisis CML exhibited myeloid type morphology. Furthermore, neoplastic lymphoblasts from 9 of 10 patients with NK-susceptible childhood ALL lacked easily detectable B or T cell markers and were of 'null' cell type. In marked contrast to the lytic susceptibility of fresh leukemic blasts from patients with ALL and CML in blast crisis, fresh neoplastic granulocytes from 5 patients with chronic phase CML (2 of which eventually progressed to myeloid type blast crisis), as well as leukemic blasts from 8 patients with acute myeloid leukemias (AML, AMMoL, and AMoL) were resistant to lysis as mediated by human NK cells from normal donors. The clinical implications of these findings are discussed.     

下调RALA表达抑制人白血病K562细胞迁移和侵袭

目的 研究小干扰RNA（siRNA）抑制v-ral 白血病致病因子RALA基因表达对人白血病K562细胞迁移和侵袭的影响.方法 利用LipofectamineTM 2000将化学合成的RALA siRNA转染体外培养的K562细胞,Real-time PCR检测细胞内RALA mRNA的表达水平;Western印迹检测细胞内RALA蛋白的表达水平;Boyden趋化小室实验检测细胞体外迁移和侵袭能力.结果与随机对照组相比,转染48 h后,RALA siRNA显著下调K562细胞内RALA mRNA和蛋白的表达（P＜0.05）.与随机对照组相比,转染RALA siRNA的K562细胞迁移和侵袭能力显著降低（P＜0.05）.结论 癌基因RALA在人白血病K562细胞迁移和侵袭过程中发挥重要作用,通过siRNA下调RALA的表达可抑制K562细胞迁移和侵袭能力.     

RPS27a promotes proliferation,regulates cell cycle progression and inhibits apoptosis of leukemia cells

Ribosomal protein S27a (RPS27a) could perform extra-ribosomal functions besides imparting a role in ribosome biogenesis and post-translational modifications of proteins. The high expression level of RPS27a was reported in solid tumors, and we found that the expression level of RPS27a was up-regulated in advanced-phase chronic myeloid leukemia (CML) and acute leukemia (AL) patients. In this study, we explored the function of RPS27a in leukemia cells by using CML cell line K562 cells and its imatinib resistant cell line K562/G01 cells. It was observed that the expression level of RPS27a was high in K562 cells and even higher in K562/G01 cells. Further analysis revealed that RPS27a knockdown by shRNA in both K562 and K562G01 cells inhibited the cell viability, induced cell cycle arrest at S and G2/M phases and increased cell apoptosis induced by imatinib. Combination of shRNA with imatinib treatment could lead to more cleaved PARP and cleaved caspase-3 expression in RPS27a knockdown cells. Further, it was found that phospho-ERK(p-ERK) and BCL-2 were down-regulated and P21 up-regulated in RPS27a knockdown cells. In conclusion, RPS27a promotes proliferation, regulates cell cycle progression and inhibits apoptosis of leukemia cells. It appears that drugs targeting RPS27a combining with tyrosine kinase inhibitor (TKI) might represent a novel therapy strategy in TKI resistant CML patients.     

Reactive oxygen species-mediated activation of JNK and down-regulation of DAXX are critically involved in penta-O-galloyl-beta-d-glucose-induced apoptosis in chronic myeloid leukemia K562 cells

Although 1,2,3,4,6-penta-O-galloyl-beta-d-glucose (PGG) was well known to have antitumor activities in breast, prostate, kidney, liver cancers and HL-60 leukemia via regulation of caspase 3, p53, S-phase kinase-associated protein 2 (Skp2) and insulin receptor signaling, the underlying mechanism of PGG-induced apoptosis linked with reactive oxygen species (ROS) mediated c-Jun N-terminal kinase (JNK) and DAXX was never elucidated in chronic myeloid leukemia (CML) K562 cells until now. Herein PGG significantly decreased the viability of CML cell lines such as K562 and KBM-5 without hurting normal peripheral blood lymphocytes (PBLs). PGG increased the number of TUNEL-positive cells and the sub-G1 cell population as well as activated caspase cascades including caspase-8, -9 and -3 in K562 cells. Interestingly, a significant activation of JNK by PGG was observed by MULTIPLEX assay and Western blotting. Conversely, JNK inhibitor D-JNKi suppressed the cleavages of caspase 3 and PARP induced by PGG in K562 cells. Also, PGG dramatically enhanced generation of ROS and reduced the expression of death-domain-associated protein (DAXX). Of note, ROS inhibitor acetyl-l-cysteine (NAC) reversed JNK-dependent apoptosis and DAXX inhibition induced by PGG. Overall, these findings suggest that ROS-dependent JNK activation and DAXX downregulation are critically involved in PGG-induced apoptosis in K562 cells.     

In vitro generation of effector cells cytotoxic to autologous targets from chronic myeloid leukemia patients in remission

Summary Peripheral blood lymphocytes (PBL) from chronic myeloid leukemia (CML) patients in remission were stimulated in vitro, in a 3-cell assay with autologous leukemic cells or autologous bone marrow (BM) cells alone, or each in combination with allogeneic PBL. The responder cells were used as effectors in a 4-h ⁵¹Cr release cytotoxicity assay using autologous targets such as leukemic cells, BM cells, phytohemagglutinin-induced lymphoblasts, and allogeneic K562 (erythroblastoid leukemic cell line) target cells. Sensitization of lymphocytes from CML patients with either autologous leukemic cells or BM cells generated cytotoxic cells (CTCs) capable of killing both the targets. These results suggested that in CML, the PBL may have been sensitized to myeloid maturation-related antigens in vivo, which, on secondary stimulation in vitro, may result in differentiation of CTCs cytotoxic to immature myeloid cells, either from autologous leukemic cells or autologous BM. The inability of PBL from patients with oral cancers to lyse autologous BM cells upon in vitro stimulation, supported this possibility. Clonogenic assays conducted to assess the colony forming potential of BM cells which had interacted with CTCs indicated that there was about 37% reduction in committed granulocyte stem cell colony formation without an appreciable change in committed granulocyte/monocyte stem cell units and clusters. Therefore, since the BM toxicity of the CTCs is not very high, these cells may have a potential clinical use in CML.     

Functional ramifications for the loss of P-selectin expression on hematopoietic and leukemic stem cells

Hematopoiesis is a tightly regulated biological process that relies upon complicated interactions between blood cells and their microenvironment to preserve the homeostatic balance of long-term hematopoietic stem cells (LT-HSCs), short-term HSCs (ST-HSCs), multipotent progenitors (MPPs), and differentiated cells. Adhesion molecules like P-selectin (encoded by the Selp gene) are essential to hematopoiesis, and their dysregulation has been linked to leukemogenesis. Like HSCs, leukemic stem cells (LSCs) depend upon their microenvironments for survival and propagation. P-selectin plays a crucial role in Philadelphia chromosome-positive (Ph(+)) chronic myeloid leukemia (CML). In this paper, we show that cells deficient in P-selectin expression can repopulate the marrow more efficiently than wild type controls. This results from an increase in HSC self-renewal rather than alternative possibilities like increased homing velocity or cell cycle defects. We also show that P-selectin expression on LT-HSCs, but not ST-HSCs and MPPs, increases with aging. In the absence of P-selectin expression, mice at 6 months of age possess increased levels of short-term HSCs and multipotent progenitors. By 11 months of age, there is a shift towards increased levels of long-term HSCs. Recipients of BCR-ABL-transduced bone marrow cells from P-selectin-deficient donors develop a more aggressive CML, with increased percentages of LSCs and progenitors. Taken together, our data reveal that P-selectin expression on HSCs and LSCs has important functional ramifications for both hematopoiesis and leukemogenesis, which is most likely attributable to an intrinsic effect on stem cell self-renewal.     

Comparative proteome profiling and functional analysis of chronic myelogenous leukemia cell lines

The aim of the present study was the molecular profiling of different Ph+ chronic myelogenous leukemia (CML) cell lines (LAMA84, K562, and KCL22) by a proteomic approach. By employing two-dimensional gel electrophoresis combined with mass spectrometry analysis, we have identified 191 protein spots corresponding to 142 different proteins. Among these, 63% were cancer-related proteins and 74% were described for the first time in leukemia cells. Multivariate analysis highlighted significant differences in the global proteomic profile of the three CML cell lines. In particular, the detailed analysis of 35 differentially expressed proteins revealed that LAMA84 cells preferentially expressed proteins associated with an invasive behavior, while K562 and KCL22 cells preferentially expressed proteins involved in drug resistance. These data demonstrate that these CML cell lines, although representing the same pathological phenotype, show characteristics in their protein expression profile that suggest different phenotypic leukemia subclasses. These data contribute a new potential characterization of the CML phenotype and may help to understand interpatient variability in the progression of disease and in the efficacy of a treatment.     

miR-181a post-transcriptionally downregulates oncogenic RalA and contributes to growth inhibition and apoptosis in chronic myelogenous leukemia (CML)

MicroRNAs (miRNAs) are a class of short RNAs that regulate gene expression through either translational repression or mRNA cleavage. miRNA-181a (miR-181a), one of the many miRNAs conserved among vertebrates, is differentially expressed in a variety of leukemia. However, its function in leukemia, particularly chronic myelogenous leukemia (CML), is poorly understood. Here we have reported the identification of miR-181a targets by combining TargetScan software prediction and expression profiling through overexpression of miR-181a mimic in leukemic K562 cells. Four overlapping genes were found to be the likely targets of miR-181a. Among the four genes, RalA is a downstream molecule of bcr-abl fusion protein in ras signaling pathway. However, its role in CML remains elusive. Luciferase reporter and Western blot assays confirmed that RalA is a direct target of miR-181a. overexpression of miR-181a effectively suppresses cell growth and induces G2-phase arrest and apoptosis partially by targeting RalA in leukemic K562 cells. Using the KEGG database combined with recent publications, downstream signaling pathway of RalA was graphed by cytoscape software. Therefore, our study is the first to report that RalA is directly regulated by miR-181a and plays an important role in CML. The approach of computational prediction combined with expression profiling might be valuable for the identification of miRNA targets in animal.     

Comparative analysis of cell surface proteins in chronic and acute leukemia cell lines

This study was designed to identify the cell surface protein markers that can differentiate between chronic myeloid leukemia (CML) and acute promyelocytic leukemia cells (APL). The differentially expressed plasma membrane proteins were analyzed between CML cell line (K562) and APL cell line (NB4) using the comparative proteomic approach. The cell membrane proteins were enriched by labeling with a membrane-impermeable biotinylation reagent, sulfo-NHS-SS-Biotin, and subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS). By comparative proteomic analysis of K562 and NB4 cells, we identified 25 membrane and 14 membrane-associated proteins. The result of LC-MS/MS combined with chemical tagging method was validated by confirming the expression and localization of one of the differentially expressed plasma membrane proteins, CD43, by FACS and confocal microscopy. Our results indicate that CD43 could be a potential candidate for differentiating CML from APL.     

Lapatinib induces autophagy, apoptosis and megakaryocytic differentiation in chronic myelogenous leukemia K562 cells

Lapatinib is an oral, small-molecule, dual tyrosine kinase inhibitor of epidermal growth factor receptors (EGFR, or ErbB/Her) in solid tumors. Little is known about the effect of lapatinib on leukemia. Using human chronic myelogenous leukemia (CML) K562 cells as an experimental model, we found that lapatinib simultaneously induced morphological changes resembling apoptosis, autophagy, and megakaryocytic differentiation. Lapatinib-induced apoptosis was accompanied by a decrease in mitochondrial transmembrane potential and was attenuated by the pancaspase inhibitor z-VAD-fmk, indicating a mitochondria-mediated and caspase-dependent pathway. Lapatinib-induced autophagic cell death was verified by LC3-II conversion, and upregulation of Beclin-1. Further, autophagy inhibitor 3-methyladenine as well as autophagy-related proteins Beclin-1 (ATG6), ATG7, and ATG5 shRNA knockdown rescued the cells from lapatinib-induced growth inhibition. A moderate number of lapatinib-treated K562 cells exhibited features of megakaryocytic differentiation. In summary, lapatinib inhibited viability and induced multiple cellular events including apoptosis, autophagic cell death, and megakaryocytic differentiation in human CML K562 cells. This distinct activity of lapatinib against CML cells suggests potential for lapatinib as a therapeutic agent for treatment of CML. Further validation of lapatinib activity in vivo is warranted.