Molecular biology of bcr-abl1-positive chronic myeloid leukemia

Monitoring Chronic Myeloid Leukemia: How Molecular Tools May Drive Therapeutic Approaches

More than 15 years ago, imatinib entered into the clinical practice as a "magic bullet"; from that point on, the prognosis of patients affected by chronic myeloid leukemia (CML) became comparable to that of aged-matched healthy subjects. The aims of treatment with tyrosine kinase inhibitors (TKIs) are for complete hematological response after 3 months of treatment, complete cytogenetic response after 6 months, and a reduction of the molecular disease of at least 3 logs after 12 months. Patients who do not reach their goal can switch to another TKI. Thus, the molecular monitoring of response is the main consideration of management of CML patients. Moreover, cases in deep and persistent molecular response can tempt the physician to interrupt treatment, and this "dream" is possible due to the quantitative PCR. After great international effort, today the BCR-ABL1 expression obtained in each laboratory is standardized and expressed as "international scale." This aim has been reached after the establishment of the EUTOS program (in Europe) and the LabNet network (in Italy), the platforms where biologists meet clinicians. In the field of quantitative PCR, the digital PCR is now a new and promising, sensitive and accurate tool. Some authors reported that digital PCR is able to better classify patients in precise "molecular classes," which could lead to a better identification of those cases that will benefit from the interruption of therapy. In addition, digital PCR can be used to identify a point mutation in the ABL1 domain, mutations that are often responsible for the TKI resistance. In the field of resistance, a prominent role is played by the NGS that enables identification of any mutation in ABL1 domain, even at sub-clonal levels. This manuscript reviews how the molecular tools can lead the management of CML patients, focusing on the more recent technical advances.

Protective autophagy or autophagic death: effects of BEZ235 on chronic myelogenous leukemia

Purpose

To investigate the effects of BEZ235 on chronic myeloid leukemia (CML) cells.

Methods

MTS assay was used to detect the proliferation of CML cells. The proteins expression were detected by Western blot assay. The effects of BEZ235 on autophagy in CML cells were verified through transmission electron microscopy and evaluated by laser confocal microscopy. Annexin V-FITC/PI double staining flow cytometry was used to detect apoptosis. A xenograft model was established to observe the therapeutic effect of BEZ235 in vivo.

Results

BEZ235 could inhibit the proliferation of CML cells; CQ and 3-MA could increase the proliferation inhibition and Z-VAD-FMK can reduce the proliferation inhibition of BEZ235 on CML cells (P<0.05). Results of TEM showed that the autophagosomes of CML cells treated with BEZ235 increased (P<0.05). The results by confocal microscopy showed that the autophagic activity of K562 cells increased with BEZ235 treatment. When BEZ235 combined with CQ, BEZ235-induced autophagic flow was blocked. FCM results showed that BEZ235 could induces apoptosis in CML cells. Z-VAD-FMK could decrease the apoptosis of CML cells induced by BEZ235. CQ increased the apoptosis of CML cells induced by BEZ235 (P<0.05). Western blot showed that BEZ235 inhibited the phosphorylation of AKT and S6K. BEZ235 alone could upregulate the expression of cleaved caspase-3 and LC3II. When combined with Z-VAD-FMK, the expression of cleaved caspase-3 was lower than that of BEZ235 alone. When combined with CQ, the expression of cleaved caspase-3 and LC3II were higher than those of BEZ235 alone (P<0.05). BEZ235 could inhibit the growth of xenografts of CML cell line.

Conclusion

BEZ235 can inhibit the proliferation of CML cells, induce apoptosis, and enhance autophagy activity. It induces protective autophagy. The combination of CQ can enhance the apoptosis and proliferation inhibition of CML cells induced by BEZ235.

Nilotinib interferes with cell cycle, ABC transporters and JAK-STAT signaling pathway in CD34+/lin- cells of patients with chronic phase chronic myeloid leukemia after 12 months of treatment

Chronic myeloid leukemia (CML) is characterized by the constitutive tyrosine kinase activity of the oncoprotein BCR-ABL1 in myeloid progenitor cells that activates multiple signal transduction pathways leading to the leukemic phenotype. The tyrosine-kinase inhibitor (TKI) nilotinib inhibits the tyrosine kinase activity of BCR-ABL1 in CML patients. Despite the success of nilotinib treatment in patients with chronic-phase (CP) CML, a population of Philadelphia-positive (Ph+) quiescent stem cells escapes the drug activity and can lead to drug resistance. The molecular mechanism by which these quiescent cells remain insensitive is poorly understood. The aim of this study was to compare the gene expression profiling (GEP) of bone marrow (BM) CD34+/lin- cells from CP-CML patients at diagnosis and after 12 months of nilotinib treatment by microarray, in order to identify gene expression changes and the dysregulation of pathways due to nilotinib action. We selected BM CD34+/lin- cells from 78 CP-CML patients at diagnosis and after 12 months of first-line nilotinib therapy and microarray analysis was performed. GEP bioinformatic analyses identified 2,959 differently expressed probes and functional clustering determined some significantly enriched pathways between diagnosis and 12 months of nilotinib treatment. Among these pathways, we observed the under expression of 26 genes encoding proteins belonging to the cell cycle after 12 months of nilotinib treatment which led to the up-regulation of chromosome replication, cell proliferation, DNA replication, and DNA damage checkpoint at diagnosis. We demonstrated the under expression of the ATP-binding cassette (ABC) transporters ABCC4, ABCC5, and ABCD3 encoding proteins which pumped drugs out of the cells after 12 months of nilotinib. Moreover, GEP data demonstrated the deregulation of genes involved in the JAK-STAT signaling pathway. The down-regulation of JAK2, IL7, STAM, PIK3CA, PTPN11, RAF1, and SOS1 key genes after 12 months of nilotinib could demonstrate the up-regulation of cell cycle, proliferation and differentiation via MAPK and PI3K-AKT signaling pathways at diagnosis.

Invasive fungal infections in the immunocompromised host: Mechanistic insights in an era of changing immunotherapeutics

The use of cytotoxic chemotherapy in the treatment of malignant and inflammatory disorders is beset by considerable adverse effects related to nonspecific cytotoxicity. Accordingly, a mechanistic approach to therapeutics has evolved in recent times with small molecular inhibitors of intracellular signaling pathways involved in disease pathogenesis being developed for clinical use, some with unparalleled efficacy and tolerability. Nevertheless, there are emerging concerns regarding an association with certain small molecular inhibitors and opportunistic infections, including invasive fungal diseases. This is perhaps unsurprising, given that the molecular targets of such agents play fundamental and multifaceted roles in orchestrating innate and adaptive immune responses. Nevertheless, some small molecular inhibitors appear to possess intrinsic antifungal activity and may therefore represent novel therapeutic options in future. This is particularly important given that antifungal resistance is a significant, emerging concern. This paper is a comprehensive review of the state-of-the-art in the molecular immunology to fungal pathogens as applied to existing and emerging small molecular inhibitors.

Overcoming Tyrosine Kinase Inhibitor Resistance in Transformed Cell Harboring SEPT9-ABL1 Chimeric Fusion Protein

Hematological malignancies harboring various ABL1 fusions are expected to be sensitive to tyrosine kinase inhibitors (TKIs), similar to those with BCR-ABL1. However, SEPT9-ABL1 exhibits TKI resistance both in vitro and in vivo. SEPT9-ABL1 has the same ABL1 region as seen in BCR-ABL1 but no point mutation in its kinase domain, which is one of the main mechanisms underlying TKI resistance in the leukemic cells harboring BCR-ABL1. The purpose of this study was to reveal the mechanism underlying TKI resistance induced by SEPT9-ABL1. We focused on the TP53 status because TKI-induced apoptosis in BCR-ABL1–positive cells is achieved through TP53. Mouse TP53 homologue TRP53 was downregulated and less phosphorylated in the cells expressing SEPT9-ABL1 than in those with BCR-ABL1, resulting in the prevention of apoptosis induced by TKIs. The CRM1 inhibitor KPT-330 accumulated nuclear TRP53 and NFKB1A (also known as IκBα), which is thought to capture TRP53 in the cytoplasm, and induced apoptosis in the hematopoietic cells expressing SEPT9-ABL1. In addition, the combination treatment of KPT-330 and imatinib, which induced the marked nuclear accumulation of PP2A and SET, reactivated PP2A through its dephosphorylation and inhibited SET expression, resulting in the effective induction of the apoptosis in the cells expressing SEPT9-ABL1. The combination treatment with KPT-330 and imatinib successfully reduced the subcutaneous masses expressing SEPT9-ABL1 and extended the survival of the mice intraperitoneally transplanted with SEPT9-ABL1–expressing cells. These results show that therapy with CRM1 inhibitors may be effective for overcoming TKI resistance induced by SEPT9-ABL1.

Comparison of BCR-ABL Transcript Variants Between Patients With Chronic Myeloid Leukaemia and Leukaemia Cell Lines

BACKGROUND/AIM

Chronic myeloid leukaemia (CML) is a myeloproliferative disorder characterized by the presence of breakpoint cluster region-Abelson murine leukemia (BCR-ABL1) gene fusion as a hallmark that is expressed as two major transcripts b2a2 and b3a2. The aim of this study was to compare the BCR-ABL transcripts in the blood cells of patients with CML, and in chemoresistant and chemosensitive CML cell lines to validate their use as a good method to elucidate CML biology.

MATERIALS AND METHODS

Twelve patients with CML and CML cell lines (K562, K562-LUCENA and FEPS) were analyzed by real-time polymerase chain reaction to evaluate gene expression of BCR-ABL transcripts.

RESULTS

All patients had the same expression levels of b2a2 and b3a3 transcripts, however, CML cell lines presented only b3a2 expression. There were no significant differences in absolute b3a2 expression between patients and CML cell lines.

CONCLUSION

CML cell lines provide a good in vitro alternative in that they have the same BCR-ABL expression as patients.

Identification and characterization of a murine model of BCR‑ABL1+ acute B‑lymphoblastic leukemia with central nervous system metastasis

Breakpoint cluster region (BCR)-Abelson murine leukemia (ABL)1⁺ acute B-lymphoblastic leukemia (B-ALL) is a disease associated with a dismal prognosis and a high incidence of central nervous system (CNS) metastasis. However, BCR-ABL1⁺ B-ALL with CNS infiltration has not been previously characterized, at least to the best of our knowledge. In the present study, a murine model of BCR-ABL1⁺ B-ALL with CNS metastasis was established using retroviral transduction. The vast majority of BCR-ABL1⁺ leukemic cells were found to be immature B cells with a variable proportion of pro-B and pre-B populations. The present results indicated that the BCR-ABL1⁺ B-leukemic cells expressed high levels integrin subunit alpha 6 (Itga6) and L-selectin adhesion molecules, and have an intrinsic ability to disseminate and accumulate in CNS tissues, predominantly in meninges. On the whole, these results provide an approach for addressing the mechanisms of BCR-ABL1⁺ B-ALL with CNS metastasis and may guide the development of novel therapeutic strategies.

Regulatory Molecules and Corresponding Processes of BCR-ABL Protein Degradation

The BCR-ABL fusion protein with strong tyrosine kinase activity is one of the molecular biological bases of leukemia. Imatinib (Gleevec), a specific targeted drug for the treatment of chronic myeloid leukemia (CML), was developed for inhibiting the kinase activity of the BCR-ABL fusion protein. Despite the positive clinical efficacy of imatinib, the proportion of imatinib resistance has gradually increased. The main reason for the resistance is a decrease in sensitivity to imatinib caused by mutation or amplification of the BCR-ABL gene. In response to this phenomenon, the new generation of tyrosine kinase inhibitors (TKIs) targeting the BCR-ABL fusion protein was developed to solve the problem. However this strategy only selectively inhibits the tyrosine kinase activity of the BCR-ABL protein without eliminating the BCR-ABL protein, it does not fundamentally cure the BCR-ABL-positive leukemia patients. With the accumulation of the knowledge of cellular molecular biology, it has become possible to specifically eliminate certain proteins by cellular proteases in a specific way. Therefore, the therapeutic strategy to induce the degradation of the BCR-ABL fusion protein is superior to the strategy of inhibiting its activity. The protein degradation strategy is also a solution to the TKI resistance caused by different BCR-ABL gene point mutations. In order to provide possible exploration directions and clues for eliminating the BCR-ABL fusion protein in tumor cells, we summarize the significant molecules involved in the degradation pathway of the BCR-ABL protein, as well as the reported potent compounds that can target the BCR-ABL protein for degradation.

Traditional and Novel Mechanisms of Heat Shock Protein 90 (HSP90) Inhibition in Cancer Chemotherapy Including HSP90 Cleavage

HSP90 is a molecular chaperone that increases the stability of client proteins. Cancer cells show higher HSP90 expression than normal cells because many client proteins play an important role in the growth and survival of cancer cells. HSP90 inhibitors mainly bind to the ATP binding site of HSP90 and inhibit HSP90 activity, and these inhibitors can be distinguished as ansamycin and non-ansamycin depending on the structure. In addition, the histone deacetylase inhibitors inhibit the activity of HSP90 through acetylation of HSP90. These HSP90 inhibitors have undergone or are undergoing clinical trials for the treatment of cancer. On the other hand, recent studies have reported that various reagents induce cleavage of HSP90, resulting in reduced HSP90 client proteins and growth suppression in cancer cells. Cleavage of HSP90 can be divided into enzymatic cleavage and non-enzymatic cleavage. Therefore, reagents inducing cleavage of HSP90 can be classified as another class of HSP90 inhibitors. We discuss that the cleavage of HSP90 can be another mechanism in the cancer treatment by HSP90 inhibition.

[Pre-therapeutic and evolutive characteristics of patients suffering from chronic myeloid leukemia, in Abidjan, Ivory Coast]

INTRODUCTION

The diagnosis of chronic myeloid leukemia is based on the presence of translocation t(9,22). Additional cytogenetic abnormalities may exist at diagnosis and have prognostic value. The authors evaluated the relationship between these additional chromosomal abnormalities, clinical presentation, and therapeutic response.

METHOD

In a retrospective and comparative study from 2005 to 2015, at Yopougon university hospital, 51 cases of myeloid leukemia were selected, including 22 cases with additional chromosomal abnormalities.

RESULTS

Thirteen types of additional Ph1 abnormalities were detected in one group, with a median age of 39years (13-73); a sex ratio of 1.4 and a low social class (49%). The median consultation time is 13months (2-29). Hepatomegaly (54%, P=0.05); fever (81.8%, P=0.0017); bone pain (63.6%, P=0.0001); lymphadenopathies (27.3% P=0.014); poor general condition [WHO>1 (77.3%, P=0.001)], high Sokal index (63.6%, P=0.0019), eosinophilia>5% (72.7, P=0.02) and circulating blastosis were found more frequent in the group with additional abnormalities treated with imatinib mesylate. We obtained 13.6% hematologic remission and 22.7% cytogenetic remission (P=0.02). The average survival was relatively short (20months vs. 76.4months, Log-rank<0.0001). We deplored a high death rate (59.1%).

CONCLUSION

The presence of an additional anomaly constitutes a pejorative element refractory to imatinib.

Response to Imatinib therapy is inferior for e13a2 BCR-ABL1 transcript type in comparison to e14a2 transcript type in chronic myeloid leukaemia

Background

The BCR-ABL1 fusion gene underlying the pathogenesis of CML can arise from a variety of breakpoints. The e13a2 and e14a2 transcripts formed by breakpoints occurring around exon 13 and exon 14 of the BCR gene respectively are the most common.

Methods

We undertook a retrospective audit using local laboratory database and electronic patient care records of 69 CML patients with an e13a2 or e14a2 transcript type identified in our regional population.

Results

The e13a2 group was on average significantly younger (45.0 years v 54.5 years), had a higher average white cell count (189.8 × 10⁹/l v 92.40 × 10⁹/l) and lower platelet count (308 × 10⁹/l v 644 × 10⁹/l) in comparison to the e14a2 group suggesting that these are distinct biological entities. Over an average follow-up of 33.8 months and 27.2 months for the e13a2 and e14a2 groups we observed an inferior molecular response to imatinib in the e13a2 group. A significantly lower number of patients in the e13a2 arm met European Leukemia Net criteria for optimal response at 12 months therapy (17.64% v 50.0%) and were slower to obtain deep molecular responses MR⁴ or MR^4.5.

Conclusion

Patients with an e13a2 transcript demonstrate an inferior molecular response to imatinib in our regional population.

Analytical Validation of a Highly Sensitive, Multiplexed Chronic Myeloid Leukemia Monitoring System Targeting BCR-ABL1 RNA

This study describes the analytical performance of the QuantideX qPCR BCR-ABL IS Kit, the first Food and Drug Administration–cleared assay designed to monitor breakpoint cluster region–Abelson tyrosine-protein kinase 1 (BCR-ABL1) fusion transcripts isolated from peripheral blood specimens from patients with chronic myeloid leukemia. This multiplex real-time quantitative RT-PCR assay amplifies both e13a2 and e14a2 Major BCR-ABL1 transcripts and the reference target ABL1. The test results are provided in international scale (IS) values by incorporating armored RNA-based calibrators that have defined IS values tied directly to the World Health Organization BCR-ABL1 Primary Reference Materials, without the necessity of determining and maintaining conversion factors. For each batch run, the integrated interpretive software evaluates run and specimen quality control metrics (including a sufficient amount of ABL1 control transcripts to ensure a minimal limit of detection) and calculates both molecular response (MR) and %IS values for each specimen. The test has a limit of detection of MR4.7 (0.002%IS) and a linear range from MR0.3 (50%IS) to MR4.7 (0.002%IS) for both Major transcripts. Single-site and multisite precision studies demonstrated a maximum SD of 0.13 MR (30% CV within the assay range between MR0.7 and MR3.7). The performance of this BCR-ABL1 monitoring test meets all of the clinical guideline recommendations for sensitivity and IS reporting for the management of chronic myeloid leukemia patients.

[The mechanisms of taxodione-induced apoptosis in BCR-ABL-positive leukemia cells]

Chronic myeloid leukemia (CML) and acute lymphoblastic leukemia (ALL) are caused by a fusion protein, BCR-ABL, which induces cellular transformation by activating the signaling molecules, STAT5 and Akt. The specific BCR-ABL inhibitors including imatinib, nilotinib, and dasatinib, are clinically utilized in the treatment with CML and ALL patients. Although these BCR-ABL inhibitors are initially successful in the treatment of leukemia, many patients develop drug resistance due to the appearance of the gatekeeper mutation of BCR-ABL, T315I. Recently, we found that taxodione, a quinone methide diterpene isolated from a conifer, Taxodium distichum, significantly induced apoptosis in human myelogenous leukemia-derived K562 cells, which is positive for the bcr-abl gene. Taxodione reduced the activities of mitochondrial respiratory chain complex III, leading to the production of reactive oxygen species (ROS). An antioxidant agent, N-acetylcysteine (NAC), canceled taxodione-induced ROS production and apoptotic cell death, suggesting that taxodione induced apoptosis through ROS accumulation. Furthermore, in K562 cells treated with taxodione, BCR-ABL, STAT5 and Akt were sequestered in mitochondrial fraction, and their localization changes decrease their abilities to stimulate cell proliferation. Strikingly, NAC canceled these taxodione-caused inhibition of BCR-ABL, STAT5 and Akt. In addition, taxodione significantly induced apoptosis in transformed Ba/F3 cells by not only BCR-ABL but also T315I-mutated BCR-ABL through the generation of ROS, suggesting that taxodione has potential as anti-tumor drug with high efficacy to overcome BCR-ABL T315I mutation-mediated resistance in leukemia cells. It's also expected that these knowledge becomes an important clue in the development of anti-cancer drugs against the broad range of tumors.

Development of a Potent Protein Degrader against Oncogenic BCR-ABL Protein

Chromosomal translocation occurs in some cancer cells, resulting in the expression of aberrant oncogenic fusion proteins that include BCR-ABL in chronic myelogenous leukemia (CML). Inhibitors of ABL tyrosine kinase, such as imatinib and dasatinib, exhibit remarkable therapeutic effects, although emergence of drug resistance hampers the therapy during long-term treatment. An alternative approach to treat CML is to downregulate expression of the BCR-ABL protein. Recently, we have devised a protein knockdown system by hybrid molecules named Specific and Nongenetic inhibitor of apoptosis protein [IAP]-dependent Protein Erasers (SNIPER). This system is designed to induce IAP-mediated ubiquitylation and proteasomal degradation of target proteins. In this review, we describe the development of SNIPER against BCR-ABL, and discuss the features and prospect for treatment of CML.

Impact of Additional Chromosomal Aberrations on the Disease Progression of Chronic Myelogenous Leukemia

The emergence of additional chromosomal abnormalities (ACAs) in Philadelphia chromosome/BCR-ABL1 positive chronic myeloid leukemia (CML), is considered to be a feature of disease evolution. However, their frequency of incidence, impact on prognosis and treatment response effect in CML is not conclusive. In the present study, we performed a chromosome analysis of 489 patients in different clinical stages of CML, using conventional GTG-banding, Fluorescent in situ Hybridization and Spectral Karyotyping. Among the de novo CP cases, ACAs were observed in 30 patients (10.20%) with lowest incidence, followed by IM resistant CP (16.66%) whereas in AP and BC, the occurrence of ACAs were higher, and was about 40.63 and 50.98%, respectively. The frequency of occurrence of ACAs were compared between the study groups and it was found that the incidence of ACAs was higher in BC compared to de novo and IM resistant CP cases. Likewise, it was higher in AP patients when compared between de novo and IM resistant CP cases, mirroring the fact of cytogenetic evolution with disease progression in CML. In addition, we observed 10 novel and 10 rare chromosomal aberrations among the study subjects. This study pinpoints the fact that the genome of advanced phase patients was highly unstable, and this environment of genomic instability is responsible for the high occurrence of ACAs. Treatment response analysis revealed that compared to initial phases, ACAs were associated with an adverse prognostic effect during the progressive stages of CML. This study further portrayed the cytogenetic mechanism of disease evolution in CML.

Does BCR-ABL transcript type influence the prognosis of patients in chronic myelogenous leukemia chronic phase?

Introduction and objective

In this study, we evaluated the influence of the transcript type on hematological and clinical parameters, as well as the event-free survival of 50 patients in the Chronic myeloid leukemia chronic phase.

Methods

We reviewed the medical records of 55 patients with Chronic myeloid leukemia. The eligibility criteria were based on the availability of hematological and clinical baseline data in the medical records. Data on BCR-ABL transcripts were obtained from medical records.

Results

Eighteen patients (36%) had the b2a2 transcript, 24 (48%) had b3a2 and 8 (16%) had b2a2/b3a2. The median platelet count for transcripts b2a2, b3a2 and b2a2/b3a2 was 320.65 × 10³/L, 396 × 10³/L, and 327.05 × 10³/L, respectively (p = 0.896). We could not find any differences in relation to the other hematological parameters, when compared to the transcript type. Comparison between spleen and liver size and type of transcript did not differ inside the groups (p = 0.395 and p = 0.647, respectively) and the association between risk scores and transcript type did not show statistical significance (p > 0.05). The 21-month probability for event-free survival was 21%, 48% and 66% for the transcripts b2a2, b3a2 and b2a2/b3a2 respectively (p = 0.226)

Conclusion

We conclude that the expression BCR-ABL transcripts have no influence on hematological, clinical and event-free survival parameters of patients in the Chronic myeloid leukemia chronic phase.

Identification and Optimization of Novel Small c-Abl Kinase Activators Using Fragment and HTS Methodologies

Abelson kinase (c-Abl) is a ubiquitously expressed, nonreceptor tyrosine kinase which plays a key role in cell differentiation and survival. It was hypothesized that transient activation of c-Abl kinase via displacement of the N-terminal autoinhibitory "myristoyl latch", may lead to an increased hematopoietic stem cell differentiation. This would increase the numbers of circulating neutrophils and so be an effective treatment for chemotherapy-induced neutropenia. This paper describes the discovery and optimization of a thiazole series of novel small molecule c-Abl activators, initially identified by a high throughput screening. Subsequently, a scaffold-hop, which exploited the improved physicochemical properties of a dihydropyrazole analogue, identified through fragment screening, delivered potent, soluble, cell-active c-Abl activators, which demonstrated the intracellular activation of c-Abl in vivo.

BCR-Abl Silencing by siRNA: A Potent Approach to Sensitize Chronic Myeloid Leukemia Cells to Tyrosine Kinase Inhibitor Therapy

Nonviral gene therapy with specific short interfering RNAs (siRNAs) against BCR-Abl can be an alternative and/or supportive therapy of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors (TKIs), given the often observed resistance to TKIs in clinical setting. In this study, we explored the feasibility of BCR-Abl siRNA therapy in CML K562 cells in vitro by employing a cationic polymer derived from cholesterol (Chol) grafted low-molecular weight polyethyleneimine (PEI). The first generation TKI imatinib upregulated the expression of BCR-Abl in K562 cells as expected. Delivery of BCR-Abl siRNA in both drug-sensitive and drug-resistant K562 cells significantly downregulated the mRNA levels in both cell types. Similarly, the BCR-Abl siRNA treatment arrested the growth of both drug-sensitive and drug-resistant K562 cells with no obvious differences despite a large difference in drug responsiveness. The BCR-Abl gene silencing in combination with TKI treatments exhibited significant synergism in drug-resistant K562 cells in generating substantial antileukemic activity, where the TKIs on their own were not effective. The effect of BCR-Abl siRNA and TKIs on non-CML cells (Jurkat and primary fibroblast) was negligible, indicating the specificity of the proposed therapy. This strategy can significantly overcome TKI resistance in CML cells, suggesting a feasible and effective treatment model for CML patients suffering from clinical resistances.

Design, synthesis and broad-spectrum Bcr-Abl inhibitory activity of novel thiazolamide-benzamide derivatives

Bcr-Abl plays an important role in the pathogenesis and development of chronic myeloid leukemia (CML). But Bcr-Abl is prone to mutation, so it increases the difficulty of clinical treatment. Therefore, it is crucial to design a new class of broad-spectrum Bcr-Abl inhibitors. Herein, forty novel thiazolamide-benzamide derivatives were synthesized and evaluated their broad-spectrum Bcr-Abl inhibitory activities. The newly synthesized compounds were characterized by using spectrum data (1H NMR, APCI-MS and IR) and elemental analysis. The protein kinase results indicated that eight compounds (3a, 3e, 3m, 3n, 3p, 4c, 4f, 4g) showed high activities to wild-type and T315I mutation. The most potent compound 3m exhibited an Abl IC50 value as low as 1.273 μM and showed inhibition to the T315I mutant with IC50 value 39.89 μM. 3m could prove to be a new promising lead compound for the further development of broad-spectrum Bcr-Abl inhibitors to overcome clinical acquired resistance.

Leukemia Stem Cells in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder characterized by a chromosome translocation that generates the BCR-ABL oncogene encoding a constitutively activated tyrosine kinase. Although BCR-ABL tyrosine kinase inhibitors (TKIs) are highly effective in treating CML at chronic phase, a number of patients develop drug resistance due to the inability of TKIs to kill leukemia stem cells (LSCs). Similar to other types of hematopoietic malignancies, LSCs in CML are believed to be a rare cell population responsible for leukemia initiation, disease progression, and drug resistance. Therefore, a full understanding of the biology of LSCs will help to develop novel therapeutic strategies for effective treatment of CML to possibly reach a cure. In recent years, a significant progress has been made in studying the biology of LSCs in both animal models and human patients at cellular and molecular levels, providing a basis for designing and testing potential molecular targets for eradicating LSCs in CML.

Dasatinib: A Review in Pediatric Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a rare hematopoietic stem cell disease that is typically characterized by the abnormal BCR-ABL1 fusion gene on the Philadelphia (Ph) chromosome in neoplastic cells. Dasatinib (Sprycel^®) is an orally administered, small molecule tyrosine kinase inhibitor indicated for the treatment of certain hematological malignancies, including Ph-positive CML in the chronic phase (Ph+ CML-CP) in adult and pediatric patients. In open-label phase 1 and phase 2 clinical trials, dasatinib produced early and durable target responses (i.e. molecular, cytogenetic and/or hematologic) in pediatric patients with Ph+ CML-CP that was newly diagnosed or resistant/intolerant to imatinib, with some recipients of the drug also experiencing deep molecular responses. Dasatinib therapy in pediatric patients with Ph+ CML-CP was reported to have a similar safety profile to that observed in adults, except there were no occurrences of pleural effusion, pericardial effusion, pulmonary edema, or pulmonary hypertension adverse events. Although long-term outcomes remain to be determined, dasatinib expands the first- and second-line options available for the treatment of Ph+ CML-CP in pediatric patients.

A new BCR-ABL1 Drosophila model as a powerful tool to elucidate the pathogenesis and progression of chronic myeloid leukemia

The oncoprotein BCR-ABL1 triggers chronic myeloid leukemia. It is clear that the disease relies on constitutive BCR-ABL1 kinase activity, but not all the interactors and regulators of the oncoprotein are known. We describe and validate a Drosophila leukemia model based on inducible human BCR-ABL1 expression controlled by tissue-specific promoters. The model was conceived to be a versatile tool for performing genetic screens. BCR-ABL1 expression in the developing eye interferes with ommatidia differentiation and expression in the hematopoietic precursors increases the number of circulating blood cells. We show that BCR-ABL1 interferes with the pathway of endogenous dAbl with which it shares the target protein Ena. Loss of function of ena or Dab, an upstream regulator of dAbl, respectively suppresses or enhances both the BCR-ABL1-dependent phenotypes. Importantly, in patients with leukemia decreased human Dab1 and Dab2 expression correlates with more severe disease and Dab1 expression reduces the proliferation of leukemia cells. Globally, these observations validate our Drosophila model, which promises to be an excellent system for performing unbiased genetic screens aimed at identifying new BCR-ABL1 interactors and regulators in order to better elucidate the mechanism of leukemia onset and progression.

In silico and in vitro screening of small molecule Inhibitors against SYT-SSX1 fusion protein in synovial sarcoma

Synovial sarcoma (SS) is characterized by a tumour specific chromosomal translocation t(X;18) (p11;q11) which results in the formation of SYT-SSX1 fusion protein. This fusion protein represents a clear therapeutic target and molecules specifically targeting SYT-SSX1 fusion protein are currently not available. In this study, SYT-SSX1 fusion protein sequence was retrieved from Uniprot and 3D structure was generated using I-TASSER modeling program. A structure based computational screening approach has been employed using Glide docking software to identify potential SYT-SSX1 small molecule inhibitors that bind to the junction region of the fusion protein. The obtained inhibitors were further filtered based on the docking score and ADME/T properties. Ten best fit compounds were chosen for in vitro studies. The anti-proliferative activities of these 10 compounds were screened in Yamato, ASKA (carries SYT-SSX1 fusion protein) and other sarcoma cell lines such as A673, 143B to understand the specificity of inhibition of the chosen compounds. The in vitro activity was compared against HEK293 cell lines. The compound 5-fluoro-3-(1-phenyl-1H-tetraazol-5-yl)-1H-indole (FPTI) was found to be selectively cytotoxic in synovial sarcoma cell lines (Yamato and ASKA) and this compound also showed insignificant anti proliferative activity on other cell lines. Further, target gene expression study confirmed that FPTI treatment down-regulated SYT-SSX1 and modulated its downstream target genes. Cell cycle analysis revealed the involvement of an apoptotic mechanism of cell death. Further experimental validations may elucidate the therapeutic potentials of FPTI against SYT-SSX1 fusion protein.

External quality assessment of p210 BCR-ABL1 transcript quantification by RT-qPCR: Findings and recommendations

INTRODUCTION

External quality assessment (EQA) is an essential tool for quality assurance of analytical testing processes of p210 BCR-ABL1 transcripts by RT-qPCR. As an EQA provider, the National Center for Clinical Laboratories organized an EQA scheme of p210 BCR-ABL1 testing in China for the first time to identify existing problems and ensure the reliability of p210 BCR-ABL1 testing.

METHODS

Using armored RNA technology, we first constructed pACYC-MS2-p210 and CG recombinant plasmids and expressed p210 and CG armored RNAs, with packaging segments of p210 BCR-ABL1 fusion gene (FG) and four common control gene (CG) transcripts. Using these armored RNAs, we prepared lyophilized p210 quality control (QC) sample panels and evaluated detection performance of participating laboratories in China.

RESULTS

Of the 66 participating laboratories, great variation was found with coefficient of variation (CV%) of raw p210 BCR-ABL1 results basically ranging from 60.0% to 100.0%. In 24 International Scale (IS) laboratories, the CV% of results decreased from 82.4% to 61.6%, and the percentage of laboratories within 2-, 3-, and 5-fold of the median values increased from 78.2%, 87.0%, and 92.1% to 80.1%, 89.4%, and 97.2%, respectively, after conversion with a laboratory-specific conversion factor (CF); however, poorly converted results were also observed in laboratories resulting from changed components of RT-qPCR procedures. False-negative and false-positive results were also found in the EQA.

CONCLUSIONS

Various problems were found for p210 BCR-ABL1 detection in the EQA. By solving the existing problems, the performance of p210 BCR-ABL1 detection can be improved, ensuring robust laboratory diagnostic capacities in China.

Parthenolide and DMAPT induce cell death in primitive CML cells through reactive oxygen species

Tyrosine kinase inhibitors (TKI) have become a first-line treatment for chronic myeloid leuakemia (CML). TKIs efficiently target bulk CML cells; however, they are unable to eliminate the leukaemic stem cell (LSC) population that causes resistance and relapse in CML patients. In this study, we assessed the effects of parthenolide (PTL) and dimethyl amino parthenolide (DMAPT), two potent inhibitors of LSCs in acute myeloid leukaemia (AML), on CML bulk and CML primitive (CD34⁺ lin^- ) cells. We found that both agents induced cell death in CML, while having little effect on the equivalent normal hematopoietic cells. PTL and DMAPT caused an increase in reactive oxygen species (ROS) levels and inhibited NF-κB activation. PTL and DMAPT inhibited cell proliferation and induced cell cycle arrest in G₀ and G₂ phases. Furthermore, we found cell cycle inhibition to correlate with down-regulation of cyclin D1 and cyclin A. In summary, our study shows that PTL and DMAPT have a strong inhibitory effect on CML cells. Given that cell cycle arrest was not dependent on ROS induction, we speculate that this effect could be a direct consequence of NF-κB inhibition and if this mechanism was to be evaded, PTL and DMAPT induced cell death would be potentiated.

FusionPathway: Prediction of pathways and therapeutic targets associated with gene fusions in cancer

Numerous gene fusions have been uncovered across multiple cancer types. Although the ability to target several of these fusions has led to the development of some successful anti-cancer drugs, most of them are not druggable. Understanding the molecular pathways of a fusion is important in determining its function in oncogenesis and in developing therapeutic strategies for patients harboring the fusion. However, the molecular pathways have been elucidated for only a few fusions, in part because of the labor-intensive nature of the required functional assays. Therefore, we developed a domain-based network approach to infer the pathways of a fusion. Molecular interactions of a fusion are first predicted by using its protein domain composition, and its associated pathways are then inferred from these molecular interactions. We demonstrated the capabilities of this approach by primarily applying it to the well-studied BCR-ABL1 fusion. The approach was also applied to two undruggable fusions in sarcoma, EWS-FL1 and FUS-DDIT3. We successfully identified known genes and pathways associated with these fusions and satisfactorily validated these predictions using several benchmark sets. The predictions of EWS-FL1 and FUS-DDIT3 also correlate with results of high-throughput drug screening. To our best knowledge, this is the first approach for inferring pathways of fusions.

We present a computational framework, FusionPathway, to infer the oncogenesis pathways of a fusion and help develop therapeutic strategies in these pathways for patients harboring the fusion. In this work, we successfully validated the capabilities of this approach through its application to the well-studied BCR-ABL1 fusion and two undruggable fusions in sarcoma, EWS-FL1 and FUS-DDIT3. Especially, the predictions of EWS-FL1 and FUS-DDIT3 correlate well with results of high-throughput drug screening in sarcoma cells. Therefore, FusionPathway can be an effective method to infer pathways and potential therapeutic targets that are associated with those undruggable fusions. Our results of BCR-ABL1 also suggest that FusionPathway may be able to help elucidate pathway-dependent mechanisms of resistances to those kinase fusion-targeting therapies and develop strategies to overcome the resistances. In addition, the developed R package of FusionPathways (https://github.com/perwu/FusionPathway/) can help people easily apply our approach to study other important fusions in cancer.

Chronic Myeloid Leukemia with b3a3 (e14a3) Fusion: A Rare BCR/ABL Rearrangement Presenting with Thrombocytosis - Does MTHFR Polymorphism Matter

Fusion of b2a2 is the most common BCR/ABL rearrangement in CML; however, absent a2 exons are very rare. We describe a case with Philadelphia-positive chronic myeloid leukemia (CML) with a very rare b3a3 (e14a3) BCR/ABL junction. To our knowledge, only 15 such cases of CML have previously been reported. These uncommon transcripts may be under-reported, since RT-PCR-based assays may fail to detect these fusions due to the location of the primers and probes used. We are reporting this case for the first time which presented with MTHFR mutation and significant thrombocytosis. There is very limited information on how this genotype expresses and responds to treatment, especially to tyrosine kinase inhibitors, as compared to classic CML. Also, the relationship between MTHFR mutation and CML is not clear, although studies have been done.

Droplet digital PCR for BCR/ABL(P210) detection of chronic myeloid leukemia: A high sensitive method of the minimal residual disease and disease progression

OBJECTIVE

This study intended to establish a droplet digital PCR (dd-PCR) for monitoring minimal residual disease (MRD) in patients with BCR/ABL (P210)-positive chronic myeloid leukemia (CML), thereby achieving deep-level monitoring of tumor load and determining the efficacy for guided clinically individualized treatment.

METHODS

Using dd-PCR and RT-qPCR, two cell suspensions were obtained from K562 cells and normal peripheral blood mononuclear cells by gradient dilution and were measured at the cellular level. At peripheral blood (PB) level, 61 cases with CML-chronic phase (CML-CP) were obtained after tyrosine kinase inhibitor (TKI) treatment and regular follow-ups. By RT-qPCR, BCR/ABL (P210) fusion gene was undetectable in PB after three successive analyses, which were performed once every 3 months. At the same time, dd-PCR was performed simultaneously with the last equal amount of cDNA. Ten CML patients with MR4.5 were followed up by the two methods.

RESULTS

At the cellular level, consistency of results of dd-PCR and RT-qPCR reached R²  ≥ 0.99, with conversion equation of Y = 33.148X^1.222 (Y: dd-PCR results; X: RT-qPCR results). In the dd-PCR test, 11 of the 61 patients with CML (18.03%) tested positive and showed statistically significant difference (P < .01). In the follow-up of 10 CML patients who were in MR4.5. All patients were loss of MR4.0, and 4 were tested positive by dd-PCR 3 months earlier than by RT-qPCR.

CONCLUSION

In contrast with RT-qPCR, dd-PCR is more sensitive, thus enabling accurate conversion of dd-PCR results into internationally standard RT-qPCR results by conversion equation, to achieve a deeper molecular biology-based stratification of BCR/ABL(P210) MRD. It has some reference value to monitor disease progression in clinic.

Deregulation of calcium homeostasis in Bcr-Abl-dependent chronic myeloid leukemia

Background

Chronic myeloid leukemia (CML) results from hematopoietic stem cell transformation by the bcr-abl chimeric oncogene, encoding a 210 kDa protein with constitutive tyrosine kinase activity. In spite of the efficiency of tyrosine kinase inhibitors (TKI; Imatinib), other strategies are explored to eliminate CML leukemia stem cells, such as calcium pathways.

Results

In this work, we showed that Store-Operated Calcium Entry (SOCE) and thrombin induced calcium influx were decreased in Bcr-Abl expressing 32d cells (32d-p210). The 32d-p210 cells showed modified Orai1/STIM1 ratio and reduced TRPC1 expression that could explain SOCE reduction. Decrease in SOCE and thrombin induced calcium entry was associated to reduced Nuclear Factor of Activated T cells (NFAT) nucleus translocation in 32d-p210 cells. We demonstrated that SOCE blockers enhanced cell mobility of 32d-p210 cells and reduced the proliferation rate in both 32d cell lines. TKI treatment slightly reduced the thrombin-induced response, but imatinib restored SOCE to the wild type level. Bcr-Abl is also known to deregulate Protein Kinase C (PKC), which was described to modulate calcium entries. We showed that PKC enhances SOCE and thrombin induced calcium entries in control cells while this effect is lost in Bcr-Abl-expressing cells.

Conclusion

The tyrosine kinase activity seems to regulate calcium entries probably not directly but through a global cellular reorganization involving a PKC pathway. Altogether, calcium entries are deregulated in Bcr-Abl-expressing cells and could represent an interesting therapeutic target in combination with TKI.

Dasatinib Plus Intensive Chemotherapy in Children, Adolescents, and Young Adults With Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia: Results of Children's Oncology Group Trial AALL0622

Purpose Addition of imatinib to intensive chemotherapy improved survival for children and young adults with Philadelphia chromosome-positive acute lymphoblastic leukemia. Compared with imatinib, dasatinib has increased potency, CNS penetration, and activity against imatinib-resistant clones. Patients and Methods Children's Oncology Group (COG) trial AALL0622 (Bristol Myers Squibb trial CA180-204) tested safety and feasibility of adding dasatinib to intensive chemotherapy starting at induction day 15 in patients with newly diagnosed Philadelphia chromosome-positive acute lymphoblastic leukemia age 1 to 30 years. Allogeneic hematopoietic stem-cell transplantation (HSCT) was recommended for patients at high risk based on slow response and for those with a matched family donor regardless of response after at least 11 weeks of therapy. Patients at standard risk based on rapid response received chemotherapy plus dasatinib for an additional 120 weeks. Patients with overt CNS leukemia received cranial irradiation. Results Sixty eligible patients were enrolled. Five-year overall (OS) and event-free survival rates (± standard deviations [SD]) were 86% ± 5% and 60% ± 7% overall, 87% ± 5% and 61% ± 7% for standard-risk patients (n = 48; 19% underwent HSCT), and 89% ± 13% and 67% ± 19% for high-risk patients (n = 9; 89% underwent HSCT), respectively. Five-year cumulative incidence (± SD) of CNS relapse was 15% ± 6%. Outcomes (± SDs) were similar to those in COG AALL0031, which used the same chemotherapy with continuous imatinib: 5-year OS of 81% ± 6% versus 86% ± 5% ( P = .63) and 5-year disease-free survival of 68% ± 7% versus 60% ± 7% ( P = 0.31) for AALL0031 versus AALL0622, respectively. IKZF1 deletions, present in 56% of tested patients, were associated with significantly inferior OS and event-free survival overall and in standard-risk patients. Conclusion Dasatinib was well tolerated with chemotherapy and provided outcomes similar to those with imatinib in COG AALL0031, where all patients received cranial irradiation. Our results support limiting HSCT to slow responders and suggest a potential role for transplantation in rapid responders with IKZF1 deletions.

Laboratory Monitoring of Chronic Myeloid Leukemia in Patients on Tyrosine Kinase Inhibitors

Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm characterized by translocation of genetic material from chromosome 9 to chromosome 22 to form a fusion gene (BCR-ABL1) that is responsible for abnormal tyrosine kinase activity and alteration of various downstream signaling pathways. In addition to morphological diagnosis of CML phase, it is essential to detect BCR-ABL1 fusion by either metaphase cytogenetics or reverse transcriptase polymerase chain reaction that also determines type of mRNA transcript. Once treatment begins, monitoring the response to Tyrosine Kinase Inhibitor (TKI) using standardized techniques and guidelines is important to check for failure of response and thus, plan timely intervention by increasing the dose of TKI or opting for second line TKIs. The goal is to stop evolution of CML to accelerated phase or blast crisis that has poor response to treatment. Also, it is desirable to achieve good outcomes and even treatment free remission in patients of CML on TKI. Thus, molecular monitoring by reverse transcriptase quantitative PCR (RT-qPCR) is done at regular intervals. There are international recommendations and quality control measures to standardize the reporting of fusion gene transcript levels by quantitative PCR (RT-qPCR) in CML to achieve and maintain sensitivity in molecular detection of CML disease burden. Various state-of-the-art molecular techniques have emerged to accurately determine the number of fusion-gene transcript levels. This review highlights various methodologies and their practical implications in management of CML patients on TKI.

Cryptic BCR-ABL fusion gene as variant rearrangement in chronic myeloid leukemia: molecular cytogenetic characterization and influence on TKIs therapy

At diagnosis, about 5% of Chronic Myeloid Leukemia (CML) patients lacks Philadelphia chromosome (Ph), despite the presence of the BCR/ABL rearrangement. Two mechanisms have been proposed about the occurrence of this rearrangement: the first one is a cryptic insertion between chromosomes 9 and 22; the second one involves two sequential translocations: a classic t(9;22) followed by a reverse translocation, which reconstitutes the normal morphology of the partner chromosomes. Out of 398 newly diagnosed CML patients, we selected 12 Ph-negative cases. Six Ph-negative patients treated with tyrosine kinase inhibitors (TKIs) were characterized, in order to study the mechanisms leading to the rearrangement and the eventual correlation with prognosis in treatment with TKIs. FISH analysis revealed cryptic insertion in 5 patients and classic translocation in the last one. In more detail, we observed 4 different patterns of rearrangement, suggesting high genetic heterogeneity of these patients. In our cases, the BCR/ABL rearrangement mapped more frequently on 9q34 region than on 22q11 region, in contrast to previous reports. Four patients, with low Sokal risk, achieved Complete Cytogenetic Response and/or Major Molecular Response after TKIs therapy. Therapy resistance was observed in one patient with duplication of BCR/ABL rearrangement and in another one with high risk. Even if the number patient is inevitably low, we can confirm that the rare Ph-negative CML patients do not constitute a “warning” category, meanwhile the presence of further cytogenetic abnormalities remains an adverse prognostic factor even in TKI era.

The novel anticancer agent JNJ-26854165 is active in chronic myeloid leukemic cells with unmutated BCR/ABL and T315I mutant BCR/ABL through promoting proteosomal degradation of BCR/ABL proteins

Chronic myeloid leukemia (CML) is a clonal malignant disease caused by the expression of BCR/ABL. MDM2 (human homolog of the murine double minute-2) inhibitors such as Nutlin-3 have been shown to induce apoptosis in a p53-dependent manner in CML cells and sensitize cells to Imatinib. Here, we demonstrate that JNJ-26854165, an inhibitor of MDM2, inhibits proliferation and triggers cell death in a p53-independent manner in various BCR/ABL-expressing cells, which include primary leukemic cells from patients with CML blast crisis and cells expressing the Imatinib-resistant T315I BCR/ABL mutant. The response to JNJ-26854165 is associated with the downregulation of BCR/ABL dependently of proteosome activation. Moreover, in all tested CML cells, with the exception of T315I mutation cells, combining JNJ-26854165 and tyrosine kinase inhibitor (TKI) Imatinib or PD180970 leads to a synergistic effect. In conclusion, our results suggest that JNJ-26854165, used either alone or in combination with TKIs, represents a promising novel targeted approach to overcome TKI resistance and improve patient outcome in CML.

Curcumin targets multiple enzymes involved in the ROS metabolic pathway to suppress tumor cell growth

Curcumin has been reported to exhibit anti-tumorigenic activity; however, since its precise actions remain unclear, its effects are considered to be deceptive. In the present study, we confirmed the anti-tumorigenic effects of curcumin on CML-derived leukemic cells in a xenograft model and in vitro culture system. In vitro pull-down and mass analyses revealed a series of enzymes (carbonyl reductase, glutathione-S-transferase, glyoxalase, etc.) that function in a reactive oxygen species (ROS) metabolic pathway as curcumin-binding targets, the expression of which was up-regulated in human leukemia. Curcumin increased ROS levels over the threshold in leukemic cells, and the antioxidant, glutathione (GSH) and overexpression of curcumin-binding enzymes partially mitigated the up-regulation of ROS and growth inhibition caused by curcumin. These results show that curcumin specifically inhibits tumor growth by increasing ROS levels over the threshold through the miscellaneous inhibition of ROS metabolic enzymes. Curcumin has potential in therapy to regulate ROS levels in tumor cells, thereby controlling tumor growth.

Down regulation of G protein-coupled receptor 137 expression inhibits proliferation and promotes apoptosis in leukemia cells

Background

G protein-coupled receptors (GPR) are involved in a wide range of physiological processes, some of which, however, can be hijacked by tumor cells. Over-expression of G protein-coupled receptors 137 (GPR137) are associated with the growth of tumor cells, but under-expression of GPR137 has shown to inhibit cell proliferation in several different types of cancers. Currently, the role of GPR137 in leukemia is still unclear. In this study, the effect of under-expression of GPR137 on inhibiting the proliferation of leukemia cells is explored, to identify a novel target for leukemia treatment.

Materials and methods

In this study, lentivirus-mediated RNA interference (RNAi) was employed to investigate the role of GPR137 in two leukemia cell lines K562 and HL60. The gene expression of GPR137 was analyzed by RT-PCR and its protein expression was determined by Western blot. Flow cytometry and Annexin V/7-AAD Apoptosis Detection Kit was used respectively in cell cycle and apoptosis analysis. The protein expression of CyclinD1, CDK4, BCL-2 and caspase-3 were also determined.

Results

There was high level of constitutive expression of GPR137 in leukemia cancer cell lines K562 and HL60. Lentivirus-mediated RNAi could significantly down-regulate gene and protein expression of GPR137 in both cell lines. Down regulation of GPR137 was associated with the reduction in proliferation rate and colony forming capacity. In addition, down regulation of GPR137 arrested cells in the G0/G1 phase of cell cycle and induced apoptosis in both leukemia cell lines K562 and HL60.

Conclusions

The expression of GPR137 is associated with the proliferation of leukemia cell lines. Down regulation of GPR137 could inhibit proliferation and promote apoptosis in leukemia cells, which makes it a promising bio-marker and therapeutic target to treat patients with leukemia.

Dual gene activation and knockout screen reveals directional dependencies in genetic networks

Understanding the direction of information flow is essential for characterizing how genetic networks affect phenotypes. However, methods to find genetic interactions largely fail to reveal directional dependencies. We combine two orthogonal Cas9 proteins from Streptococcus pyogenes and Staphylococcus aureus to carry out a dual screen in which one gene is activated while a second gene is deleted in the same cell. We analyse the quantitative effects of activation and knockout to calculate genetic interaction and directionality scores for each gene pair. Based on the results from over 100,000 perturbed gene pairs, we reconstruct a directional dependency network for human K562 leukemia cells and demonstrate how our approach allows the determination of directionality in activating genetic interactions. Our interaction network connects previously uncharacterised genes to well-studied pathways and identifies targets relevant for therapeutic intervention.

A simple fluorescence biosensing strategy for ultrasensitive detection of the BCR–ABL1 fusion gene based on a DNA machine and multiple primer-like rolling circle amplification

A one-step, rapid fluorescence biosensing method has been developed for ultrasensitive detection of BCR–ABL1 fusion gene based on a DNA machine and multiple primer-like rolling circle amplification.

Role of ZNF224 in c-Myc repression and imatinib responsiveness in chronic myeloid leukemia

The transcription factor ZNF224 plays a key proapoptotic role in chronic myelogenous leukemia (CML), by modulating Wilms Tumor protein 1 (WT1) dependent apoptotic genes transcription. Recently, we demonstrated that Bcr-Abl signaling represses ZNF224 expression in Bcr-Abl positive CML cell lines and in CML patients. Interestingly, Imatinib and second-generation tyrosine kinase inhibitors specifically increase ZNF224 expression.

On the other hand, Bcr-Abl positively modulates, via JAK2 activation, the expression of the c-Myc oncogene, which is required for Bcr-Abl oncogenic transformation in CML. Consequently, JAK2 inhibitors represent promising molecular therapeutic tools in CML.

In this work, we demonstrate that ZNF224 is a novel transcriptional repressor of c-Myc in CML. We also show that ZNF224 induction by Imatinib and AG490, a specific JAK2 inhibitor, is responsible for the transcriptional repression of c-MYC, thus highlighting the crucial role of the ZNF224/c-Myc axis in Imatinib responsiveness.

Interestingly, we also report that ZNF224 is induced by AG490 in Imatinib-resistant CML cells, leading to c-Myc repression and apoptosis induction. These findings suggest that the development of molecular tools able to induce ZNF224 expression could provide promising means to bypass Imatinib resistance in CML.

Altered intracellular signaling by imatinib increases the anti-cancer effects of tyrosine kinase inhibitors in chronic myelogenous leukemia cells

Tyrosine kinase inhibitors (TKI), including imatinib (IM), improve the outcome of CML therapy. However, TKI treatment is long‐term and can induce resistance to TKI, which often leads to a poor clinical outcome in CML patients. Here, we examined the effect of continuous IM exposure on intracellular energy metabolism in K562 cells, a human Philadelphia chromosome‐positive CML cell line, and its subsequent sensitivity to anti‐cancer agents. Contrary to our expectations, we found that continuous IM exposure increased sensitivity to TKI. Cancer energy metabolism, characterized by abnormal glycolysis, is linked to cancer cell survival. Interestingly, glycolytic activity was suppressed by continuous exposure to IM, and autophagy increased to maintain cell viability by compensating for glycolytic suppression. Notably, increased sensitivity to TKI was not caused by glycolytic inhibition but by altered intracellular signaling, causing glycolytic suppression and increased autophagy, as evidenced by suppression of p70 S6 kinase 1 (S6K1) and activation of AMP‐activated protein kinase (AMPK). Using another human CML cell line (KCL22 cells) and BCR/ABL+ Ba/F3 cells (mimicking Philadelphia chromosome‐positive CML cells) confirmed that suppressing S6K1 and activating AMPK increased sensitivity to TKI. Furthermore, suppressing S6K1 and activating AMPK had a synergistic anti‐cancer effect by inhibiting autophagy in the presence of TKI. The present study provides new insight into the importance of signaling pathways that affect cellular energy metabolism, and suggests that co‐treatment with agents that disrupt energy metabolic signaling (using S6K1 suppressors and AMPK activators) plus blockade of autophagy may be strategies for TKI‐based CML therapy.

Exosomes derived from imatinib-resistant chronic myeloid leukemia cells mediate a horizontal transfer of drug-resistant trait by delivering miR-365

Chronic myeloid leukemia (CML) is a malignant disorder of hematopoietic stem/progenitor cells. Majority of patients can be effectively treated with tyrosine kinase inhibitors (TKIs) such as imatinib, but a portion of patients will develop drug resistance. Accumulated evidences have identified exosomes in cancer as promoters of tumor progression. Herein, we found that exosomes derived from imatinib resistant CML cells can be internalized into sensitive CML cells and confer drug-resistance traits. We also demonstrated a significant higher level of miR-365 in exosomes derived from drug-resistant CML cells compared with those from sensitive ones using microarray and qRT-PCR. The imatinib sensitive CML cells transfected with pre-miR-365 displayed lower chemosensitivity and apoptosis rate compared with controls. We further confirmed that exosomal transfer of miR-365 induced drug resistance by inhibiting expression of pro-apoptosis protein in sensitive CML cells. In conclusion, our study reveals that exosomes mediate a horizontal transfer of drug-resistant trait in chronic myeloid leukemia cell by delivering miR-365.

Accurate prediction of the age incidence of chronic myeloid leukemia with an improved two-mutation mathematical model

Chronic myeloid leukemia (CML) is a malignant clonal disorder whose hallmark is a reciprocal translocation between chromosomes 9 and 22 occurring in 95% of affected patients. This translocation causes the expression of a deregulated BCR/ABL fusion oncogene and, interestingly, is detectable in healthy individuals. Based on this information we assumed that the sole presence of the BCR/ABL transcript represents a necessary but not sufficient event for the clonal expansion of CML precursors. We developed a mathematical model introducing a probability that any normal cell undergoes a first aberration, and a probability that a cell that experienced a first mutation undergoes a second mutation as well. Two variants are proposed and analyzed: in the first the probability of the first mutation is supposed to be age independent and in the second, it depends on the hemopoietic cell turnover and mass. The model parameters have been estimated by regression from the observed CML incidence curves. Our models offer a significantly improved version of existing one-step and two-steps models, as they integrate key clinical and biological data reported in the literature and accurately fit the observed incidence. Our models also estimate the increased radiation-associated mutation rate at a younger age in atomic bomb survivors. Although this work focuses on CML, the modelling approach can be applied to all types of leukemia and lymphoma.

Neuroendocrine tumor of cecum in patient treated with imatinib mesylate for blastic phase of chronic myeloid leukemia

Imatinib mesylate (IM), a tyrosine kinase inhibitor, is the treatment of choice in patients with chronic myeloid leukemia (CML). It is considered a very safe drug, with mostly mild and reversible side effects. Lately, it has been suggested that adverse events may occur after a long term. We report a case of a 72-year-old woman diagnosed with blastic phase of Philadelphia chromosome positive CML treated with IM for 28 months. The patient presented first with ascites as a side effect of the drug. When the ascites re-occurred, it was caused by neuroendocrine tumor (NET) with peritoneal carcinomatosis. We believe this is the first case of a NET as a secondary malignancy (SM) after IM treatment. SM have been described in patients on IM before. It is unclear whether these tumors are caused by imatinib or found more easily because of close follow-up.

Mast cells and cancer

Mast cells (MCs) are a potent proangiogenic factor in tumors, they product several pro-angiogenic factors such as fibroblast growth factor 2 (FGF-2), vascular epithelial growth factor (VEGF), tryptase and chymase. Tryptase is a serine protease classified as α-tryptase and β-tryptase, both produced by MCs. Tryptase degrades the tissues, playing an important role in angiogenesis and in the development of metastases. Serum tryptase increases with age, with increased damage to cells and risk of developing a malignancy and it could be considered the expression of a fundamental role of MCs in tumor growth or, on the contrary, in the antitumor response. Many biomarkers have been developed in clinical practice for improving diagnosis and prognosis of some neoplasms. Elevated tryptase levels are found in subgroups of patients with haematologic and solid cancers. In the current review, we want to update the perspectives of tryptase as a potential biomarker in daily practice in different neoplasms.

The Natural Antiangiogenic Compound AD0157 Induces Caspase-Dependent Apoptosis in Human Myeloid Leukemia Cells

Evasion of apoptosis is a hallmark of cancer especially relevant in the development and the appearance of leukemia drug resistance mechanisms. The development of new drugs that could trigger apoptosis in aggressive hematological malignancies, such as AML and CML, may be considered a promising antileukemic strategy. AD0157, a natural marine pyrrolidinedione, has already been described as a compound that inhibits angiogenesis by induction of apoptosis in endothelial cells. The crucial role played by defects in the apoptosis pathways in the pathogenesis, progression and response to conventional therapies of several forms of leukemia, moved us to analyze the effect of this compound on the growth and death of leukemia cells. In this work, human myeloid leukemia cells (HL60, U937 and KU812F) were treated with AD0157 ranging from 1 to 10 μM and an experimental battery was applied to evaluate its apoptogenic potential. We report here that AD0157 was highly effective to inhibit cell growth by promotion of apoptosis in human myeloid leukemia cells, and provide evidence of its mechanisms of action. The apoptogenic activity of AD0157 on leukemia cells was verified by an increased chromatin condensation and DNA fragmentation, and confirmed by an augmentation in the apoptotic subG1 population, translocation of the membrane phosphatidylserine from the inner face of the plasma membrane to the cell surface and by cleavage of the apoptosis substrates PARP and lamin-A. In addition, AD0157 in the low micromolar range significantly enhanced the activities of the initiator caspases-8 and -9, and the effector caspases-3/-7 in a dose-dependent manner. Results presented here throw light on the apoptogenic mechanism of action of AD0157, mediated through caspase-dependent cascades, with an especially relevant role played by mitochondria. Altogether, these results suggest the therapeutic potential of this compound for the treatment of human myeloid leukemia.

Global gene expression profiles of hematopoietic stem and progenitor cells from patients with chronic myeloid leukemia: the effect of in vitro culture with or without imatinib

In this study, we determined the gene expression profiles of bone marrow‐derived cell fractions, obtained from normal subjects and Chronic Myeloid Leukemia (CML) patients, that were highly enriched for hematopoietic stem (HSCs) and progenitor (HPCs) cells. Our results indicate that the profiles of CML HSCs and HPCs were closer to that of normal progenitors, whereas normal HSCs showed the most different expression profile of all. We found that the expression profiles of HSCs and HPCs from CML marrow were closer to each other than those of HSCs and HPCs from normal marrow. The major biologic processes dysregulated in CML cells included DNA repair, cell cycle, chromosome condensation, cell adhesion, and the immune response. We also determined the genomic changes in both normal and CML progenitor cells under culture conditions, and found that several genes involved in cell cycle, steroid biosynthesis, and chromosome segregation were upregulated, whereas genes involved in transcription regulation and apoptosis were downregulated. Interestingly, these changes were the same, regardless of the addition of Imatinib (IM) to the culture. Finally, we identified three genes—PIEZO2, RXFP1, and MAMDC2‐ that are preferentially expressed by CML primitive cells and that encode for cell membrane proteins; thus, they could be used as biomarkers for CML stem cells.