Preclinical efficacy of daratumumab in T-cell acute lymphoblastic leukemia

As a consequence of acquired or intrinsic disease resistance, the prognosis for patients with relapsed or refractory T-cell acute lymphoblastic leukemia (T-ALL) is dismal. Novel, less toxic drugs are clearly needed. One of the most promising emerging therapeutic strategies for cancer treatment is targeted immunotherapy. Immune therapies have improved outcomes for patients with other hematologic malignancies including B-cell ALL; however no immune therapy has been successfully developed for T-ALL. We hypothesize targeting CD38 will be effective against T-ALL. We demonstrate that blasts from patients with T-ALL have robust surface CD38 surface expression and that this expression remains stable after exposure to multiagent chemotherapy. CD38 is expressed at very low levels on normal lymphoid and myeloid cells and on a few tissues of nonhematopoietic origin, suggesting that CD38 may be an ideal target. Daratumumab is a human immunoglobulin G1κ monoclonal antibody that binds CD38, and has been demonstrated to be safe and effective in patients with refractory multiple myeloma. We tested daratumumab in a large panel of T-ALL patient-derived xenografts (PDX) and found striking efficacy in 14 of 15 different PDX. These data suggest that daratumumab is a promising novel therapy for pediatric T-ALL patients.

Disulfiram/copper causes ROS levels alteration, cell cycle inhibition, and apoptosis in acute myeloid leukaemia cell lines with modulation in the expression of related genes

The majority of acute myeloid leukaemia (AML) patients will die from their disease or therapy-related complications. There is an inevitable need to improve the survival of AML patients. Previous studies show that disulfiram (DSF), an anti-alcoholism drug with a low toxicity profile, demonstrates anticancer behaviors. Here, we evaluated the cytotoxicity and mechanistic action of DSF on the AML cell lines KG-1, NB4, and U937. The microculture tetrazolium test revealed that DSF alone or in combination with copper (Cu) is highly toxic to the AML cells at concentrations lower than those achievable in the clinical setting, with Cu increasing the DSF-induced inhibition of metabolic activity. Flow cytometric analysis and QRT-PCR indicated that in the two cell lines, NB4 and U-937, DSF/Cu increased reactive oxygen species (ROS) levels in association with the induction of superoxide dismutase 2 (SOD2) expression and suppression of catalase (CAT). In the KG-1 cell line, DSF/Cu reduced the ROS levels in agreement with the induction of CAT expression. The cell cycle and apoptosis assessment by flow cytometry demonstrated that DSF/Cu induced G0/G1 cell cycle arrest and apoptosis. These were associated with the increased expression of FOXO tumor suppressors, decreased expression of the MYC oncogene and the modulation of their known target genes related to the cell cycle and apoptosis. Therefore, DSF/Cu caused the disturbance of the ROS balance, cell cycle arrest and apoptosis in AML cells in coordination with the modulation in expression of their related genes. These results propose the possible use of DSF in AML therapies.

Mechanisms of rapid cancer cell reprogramming initiated by targeted receptor tyrosine kinase inhibitors and inherent therapeutic vulnerabilities

Receptor tyrosine kinase (RTK) pathways serve as frequent oncogene drivers in solid cancers and small molecule and antibody-based inhibitors have been developed as targeted therapeutics for many of these oncogenic RTKs. In general, these drugs, when delivered as single agents in a manner consistent with the principles of precision medicine, induce tumor shrinkage but rarely complete tumor elimination. Moreover, acquired resistance of treated tumors is nearly invariant such that monotherapy strategies with targeted RTK drugs fail to provide long-term control or cures. The mechanisms mediating acquired resistance in tumors at progression treated with RTK inhibitors are relatively well defined compared to the molecular and cellular understanding of the cancer cells that persist early on therapy. We and others propose that these persisting cancer cells, termed "residual disease", provide the reservoir from which acquired resistance eventually emerges. Herein, we will review the literature that describes rapid reprogramming induced upon inhibition of oncogenic RTKs in cancer cells as a mechanism by which cancer cells persist to yield residual disease and consider strategies for disrupting these intrinsic responses for future therapeutic gain.

Modulation of Multidrug Resistance Gene Expression by Coumarin Derivatives in Human Leukemic Cells

The presence of multidrug resistance (MDR) in tumor cells is considered as the major cause of failure of cancer chemotherapy. The mechanism responsible for the phenomenon of multidrug resistance is explained, among others, as overexpression of membrane transporters primarily from the ABC family which actively remove cytostatics from the tumor cell. The effect of 20 coumarin derivatives on the cytotoxicity and expression of MDR1, MRP1, BCRP, and LRP genes (encoding proteins responsible for multidrug resistance) in cancer cells was analyzed in the study. The aim of this research included determination of IC10 and IC50 values of selected coumarin derivatives in the presence and absence of mitoxantrone in leukemia cells and analysis of changes in the expression of genes involved in multidrug resistance: MDR1, MRP, LRP, and BCRP after 24-hour exposure of the investigated cell lines to selected coumarins in the presence and absence of mitoxantrone in IC10 and IC50 concentrations. The designed research was conducted on 5 cell lines derived from the human hematopoietic system: CCRF/CEM, CEM/C1, HL-60, HL-60/MX1, and HL-60/MX2. Cell lines CEM/C1, HL-60/MX1, and HL-60/MX2 exhibit a multidrug resistance phenotype.

Lck is a relevant target in chronic lymphocytic leukaemia cells whose expression variance is unrelated to disease outcome

Pathogenesis of chronic lymphocytic leukaemia (CLL) is contingent upon antigen receptor (BCR) expressed by malignant cells of this disease. Studies on somatic hypermutation of the antigen binding region, receptor expression levels and signal capacity have all linked BCR on CLL cells to disease prognosis. Our previous work showed that the src-family kinase Lck is a targetable mediator of BCR signalling in CLL cells, and that variance in Lck expression associated with ability of BCR to induce signal upon engagement. This latter finding makes Lck similar to ZAP70, another T-cell kinase whose aberrant expression in CLL cells also associates with BCR signalling capacity, but also different because ZAP70 is not easily pharmacologically targetable. Here we describe a robust method of measuring Lck expression in CLL cells using flow cytometry. However, unlike ZAP70 whose expression in CLL cells predicts prognosis, we find Lck expression and disease outcome in CLL are unrelated despite observations that its inhibition produces effects that biologically resemble the egress phenotype taken on by CLL cells treated with idelalisib. Taken together, our findings provide insight into the pathobiology of CLL to suggest a more complex relationship between expression of molecules within the BCR signalling pathway and disease outcome.

Increased Vascular Permeability in the Bone Marrow Microenvironment Contributes to Disease Progression and Drug Response in Acute Myeloid Leukemia

The biological and clinical behaviors of hematological malignancies can be influenced by the active crosstalk with an altered bone marrow (BM) microenvironment. In the present study, we provide a detailed picture of the BM vasculature in acute myeloid leukemia using intravital two-photon microscopy. We found several abnormalities in the vascular architecture and function in patient-derived xenografts (PDX), such as vascular leakiness and increased hypoxia. Transcriptomic analysis in endothelial cells identified nitric oxide (NO) as major mediator of this phenotype in PDX and in patient-derived biopsies. Moreover, induction chemotherapy failing to restore normal vasculature was associated with a poor prognosis. Inhibition of NO production reduced vascular permeability, preserved normal hematopoietic stem cell function, and improved treatment response in PDX.

Dysfunctional diversity of p53 proteins in adult acute myeloid leukemia: projections on diagnostic workup and therapy

The heterogeneous nature of acute myeloid leukemia (AML) and its poor prognosis necessitate therapeutic improvement. Current advances in AML research yield important insights regarding AML genetic, epigenetic, evolutional, and clinical diversity, all in which dysfunctional p53 plays a key role. As p53 is central to hematopoietic stem cell functions, its aberrations affect AML evolution, biology, and therapy response and usually predict poor prognosis. While in human solid tumors TP53 is mutated in more than half of cases, TP53 mutations occur in less than one tenth of de novo AML cases. Nevertheless, wild-type (wt) p53 dysfunction due to nonmutational p53 abnormalities appears to be rather frequent in various AML entities, bearing, presumably, a greater impact than is currently appreciated. Hereby, we advocate assessment of adult AML with respect to coexisting p53 alterations. Accordingly, we focus not only on the effects of mutant p53 oncogenic gain of function but also on the mechanisms underlying nonmutational wtp53 inactivation, which might be of therapeutic relevance. Patient-specific TP53 genotyping with functional evaluation of p53 protein may contribute significantly to the precise assessment of p53 status in AML, thus leading to the tailoring of a rationalized and precision p53-based therapy. The resolution of the mechanisms underlying p53 dysfunction will better address the p53-targeted therapies that are currently considered for AML. Additionally, a suggested novel algorithm for p53-based diagnostic workup in AML is presented, aiming at facilitating the p53-based therapeutic choices.

Time-series analysis in imatinib-resistant chronic myeloid leukemia K562-cells under different drug treatments

Chronic myeloid leukemia (CML) is characterized by the accumulation of active BCR-ABL protein. Imatinib is the first-line treatment of CML; however, many patients are resistant to this drug. In this study, we aimed to compare the differences in expression patterns and functions of time-series genes in imatinib-resistant CML cells under different drug treatments. GSE24946 was downloaded from the GEO database, which included 17 samples of K562-r cells with (n=12) or without drug administration (n=5). Three drug treatment groups were considered for this study: arsenic trioxide (ATO), AMN107, and ATO+AMN107. Each group had one sample at each time point (3, 12, 24, and 48 h). Time-series genes with a ratio of standard deviation/average (coefficient of variation) >0.15 were screened, and their expression patterns were revealed based on Short Time-series Expression Miner (STEM). Then, the functional enrichment analysis of time-series genes in each group was performed using DAVID, and the genes enriched in the top ten functional categories were extracted to detect their expression patterns. Different time-series genes were identified in the three groups, and most of them were enriched in the ribosome and oxidative phosphorylation pathways. Time-series genes in the three treatment groups had different expression patterns and functions. Time-series genes in the ATO group (e.g. CCNA2 and DAB2) were significantly associated with cell adhesion, those in the AMN107 group were related to cellular carbohydrate metabolic process, while those in the ATO+AMN107 group (e.g. AP2M1) were significantly related to cell proliferation and antigen processing. In imatinib-resistant CML cells, ATO could influence genes related to cell adhesion, AMN107 might affect genes involved in cellular carbohydrate metabolism, and the combination therapy might regulate genes involved in cell proliferation.

Outcomes of Chronic Myeloid Leukemia Patients With Early Molecular Response at 3 and 6 Months: A Comparative Analysis of Generic Imatinib and Glivec

BACKGROUND

The molecular response at 3 months of the original imatinib (OI) in patients with chronic myeloid leukemia has prognostic significance; however, this has never been tested for generic imatinib (GI).

PATIENTS AND METHODS

We evaluated the BCR-ABL1 [international reporting scale (IS)] transcript levels at 3 and 6 months to determine whether an early molecular response (EMR) had a prognostic effect on the outcome among chronic myeloid leukemia patients receiving GI. Ninety patients were divided into 2 groups, according to the imatinib they received, as OI (group A) and GI (group B).

RESULTS

Two groups were equally balanced for age, gender, Sokal risk score, and optimal response. The 2 groups did not differ in achieving an EMR at 3 months, and patients with EMR at 3 months had significantly superior complete cytogenetic response and major molecular response rates compared with patients who did not achieve an EMR in both groups. The percentage of an optimal response [BCR-ABL1 (IS), < 1%] and a warning response [BCR-ABL1 (IS), 1%-10%] at 6 months was 93% and 95% for groups A and B, respectively (P = .553). Patients with an optimal response (OR) at both 3 and 6 months had significantly superior event-free survival rates compared with patients without an OR in groups A and B.

CONCLUSION

The results of the present study have demonstrated most probably for the first time that an OR at 3 and 6 months in patients receiving either first-line GI and OI is clearly associated with greater response and event-free survival rates. Prospective randomized trials with larger numbers of patients and longer follow-up periods are needed to address the effect of EMR in patients receiving GI.

Mechanisms of Resistance to ABL Kinase Inhibition in Chronic Myeloid Leukemia and the Development of Next Generation ABL Kinase Inhibitors

Chronic myeloid leukemia is increasingly viewed as a chronic illness; most patients have a life expectancy close to that of the general population. Despite progress made using BCR-ABL1 tyrosine kinase inhibitors (TKIs), drug resistance via BCR-ABL1-dependent and BCR-ABL1-independent mechanisms continues to be an issue. BCR-ABL1-dependent resistance is primarily mediated through oncoprotein kinase domain mutations and usually results in overt resistance to TKIs. However, BCR-ABL1-independent resistance in the setting of effective BCR-ABL1 inhibition is recognized as a major contributor to minimal residual disease. Efforts to eradicate persistent leukemic stem cells have focused on combination therapy.

PTCH1 is a reliable marker for predicting imatinib response in chronic myeloid leukemia patients in chronic phase

Patched homolog 1 gene (PTCH1) expression and the ratio of PTCH1 to Smoothened (SMO) expression have been proposed as prognostic markers of the response of chronic myeloid leukemia (CML) patients to imatinib. We compared these measurements in a realistic cohort of 101 patients with CML in chronic phase (CP) using a simplified qPCR method, and confirmed the prognostic power of each in a competing risk analysis. Gene expression levels were measured in peripheral blood samples at diagnosis. The PTCH1/SMO ratio did not improve PTCH1 prognostic power (area under the receiver operating characteristic curve 0.71 vs. 0.72). In order to reduce the number of genes to be analyzed, PTCH1 was the selected measurement. High and low PTCH1 expression groups had significantly different cumulative incidences of imatinib failure (IF), which was defined as discontinuation of imatinib due to lack of efficacy (5% vs. 25% at 4 years, P = 0.013), probabilities of achieving a major molecular response (81% vs. 53% at first year, P = 0.02), and proportions of early molecular failure (14% vs. 43%, P = 0.015). Every progression to an advanced phase (n = 3) and CML-related death (n = 2) occurred in the low PTCH1 group (P<0.001 for both comparisons). PTCH1 was an independent prognostic factor for the prediction of IF. We also validated previously published thresholds for PTCH1 expression. Therefore, we confirmed that PTCH1 expression can predict the imatinib response in CML patients in CP by applying a more rigorous statistical analysis. Thus, PTCH1 expression is a promising molecular marker for predicting the imatinib response in CML patients in CP.

Investigating critical genes and gene interaction networks that mediate cyclophosphamide sensitivity in chronic myelogenous leukemia

Drug resistance is an obstacle in the treatment of chronic myelogenous leukemia (CML), and is a common reason for treatment failure or disease progression. However, the underlying mechanisms of cyclophosphamide resistance remain poorly defined. In the present study, microarray data concerning cyclophosphamide‑sensitive and ‑resistant chronic myelogenous leukemia cell lines were analyzed. A total of 258 differentially‑expressed genes (DEGs) were identified between these two groups, from which 139 DEGs were upregulated and 119 were downregulated. Several candidate genes that were associated with cyclophosphamide resistance were also identified. These DEGs were subsequently classified using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analysis. A total of 487 biological processes and 17 KEGG pathways were revealed to be enriched. Furthermore, an interaction network was established to identify the core genes that regulated cyclophosphamide resistance. Signal transducer and activator of transcription 5A (STAT5A), FYN proto‑oncogene, Src family tyrosine kinase and spleen associated tyrosine kinase were revealed to be the hub genes in multiple enriched biological processes and signaling pathways, indicating that these were involved in mediating cyclophosphamide sensitivity in CML cells. The expression levels of 5 DEGs were also confirmed in two human CML cell lines (K‑562 and KU812) by reverse transcription‑quantitative polymerase chain reaction. Furthermore, selective knockdown of STAT5A and S100 calcium binding protein A4 (S100A4) recovered cyclophosphamide sensitivity in K‑562 cells, suggesting their involvement in drug resistance. The present study identified several potential genes and pathways contributing to cyclophosphamide resistance, and confirmed the involvement of STAT5A and S100A4 in drug resistance. These results enable improved understanding of the mechanisms underlying drug resistance in CML cells.

Bioinformatic analysis of the effects and mechanisms of decitabine and cytarabine on acute myeloid leukemia

Acute myeloid leukemia (AML) is a frequently occurring malignant disease of the blood and may result from a variety of genetic disorders. The present study aimed to identify the underlying mechanisms associated with the therapeutic effects of decitabine and cytarabine on AML, using microarray analysis. The microarray datasets GSE40442 and GSE40870 were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and differentially methylated sites were identified in AML cells treated with decitabine compared with those treated with cytarabine via the Linear Models for Microarray Data package, following data pre‑processing. Gene Ontology (GO) analysis of DEGs was performed using the Database for Annotation, Visualization and Integrated Analysis Discovery. Genes corresponding to the differentially methylated sites were obtained using the annotation package of the methylation microarray platform. The overlapping genes were identified, which exhibited the opposite variation trend between gene expression and DNA methylation. Important transcription factor (TF)‑gene pairs were screened out, and a regulated network subsequently constructed. A total of 190 DEGs and 540 differentially methylated sites were identified in AML cells treated with decitabine compared with those treated with cytarabine. A total of 36 GO terms of DEGs were enriched, including nucleosomes, protein‑DNA complexes and the nucleosome assembly. The 540 differentially methylated sites were located on 240 genes, including the acid‑repeat containing protein (ACRC) gene that was additionally differentially expressed. In addition, 60 TF pairs and overlapped methylated sites, and 140 TF‑pairs and DEGs were screened out. The regulated network included 68 nodes and 140 TF‑gene pairs. The present study identified various genes including ACRC and proliferating cell nuclear antigen, in addition to various TFs, including TATA‑box binding protein associated factor 1 and CCCTC‑binding factor, which may be potential therapeutic targets of AML.

c-Myc Modulation and Acetylation Is a Key HDAC Inhibitor Target in Cancer

Purpose: Histone deacetylase inhibitors (HDACi) are promising anticancer drugs. Although some HDACi have entered the clinic, the mechanism(s) underlying their tumor selectivity are poorly understood.Experimental Design and Results: Using gene expression analysis, we define a core set of six genes commonly regulated in acute myeloid leukemia (AML) blasts and cell lines. MYC, the most prominently modulated, is preferentially altered in leukemia. Upon HDACi treatment, c-Myc is acetylated at lysine 323 and its expression decreases, leading to TRAIL activation and apoptosis. c-Myc binds to the TRAIL promoter on the proximal GC box through SP1 or MIZ1, impairing TRAIL activation. HDACi exposure triggers TRAIL expression, altering c-Myc-TRAIL binding. These events do not occur in normal cells. Excitingly, this inverse correlation between TRAIL and c-Myc is supported by HDACi treatment ex vivo of AML blasts and primary human breast cancer cells. The predictive value of c-Myc to HDACi responsiveness is confirmed in vivo in AML patients undergoing HDACi-based clinical trials.Conclusions: Collectively, our findings identify a key role for c-Myc in TRAIL deregulation and as a biomarker of the anticancer action of HDACi in AML. The potential improved patient stratification could pave the way toward personalized therapies. Clin Cancer Res; 23(10); 2542-55. ©2016 AACR.

Reprogramming acute myeloid leukemia into sensitivity for retinoic-acid-driven differentiation

The success of all-trans retinoic acid (ATRA) therapy for acute promyelocytic leukemia (APL) provides a rationale for using retinoic acid (RA)-based therapy for other subtypes of acute myeloid leukemia (AML). Recently, several studies showed that ATRA may drive leukemic cells efficiently into differentiation and/or apoptosis in a subset of AML patients with an NPM1 mutation, a FLT3-ITD, an IDH1 mutation, and patients overexpressing EVI-1. Because not all patients within these molecular subgroups respond to ATRA and clinical trials that tested ATRA response in non-APL AML patients have had disappointing results, the identification of additional biomarkers may help to identify patients who strongly respond to ATRA-based therapy. Searching for response biomarkers might also reveal novel RA-based combination therapies with an efficient differentiation/apoptosis-inducing effect in non-APL AML patients. Preliminary studies suggest that the epigenetic or transcriptional state of leukemia cells determines their susceptibility to ATRA. We hypothesize that reprogramming by inhibitors of epigenetic-modifying enzymes or by modulation of microRNA expression might sensitize non-APL AML cells for RA-based therapy. AML relapse is caused by a subpopulation of leukemia cells, named leukemic stem cells (LSCs), which are in a different epigenetic state than the total bulk of the AML. The survival of LSCs after therapy is the main cause of the poor prognosis of AML patients, and novel differentiation therapies should drive these LSCs into maturity. In this review, we summarize the current knowledge on the epigenetic aspects of susceptibility to RA-induced differentiation in APL and non-APL AML.

MicroRNA-9 plays a role in interleukin-10-mediated expression of E-cadherin in acute myelogenous leukemia cells

We previously showed that the CD82/signal transducer and activator of transcription/interleukin-10 (IL-10) axis is activated in CD34⁺ /CD38^- AML cells that favor the bone marrow microenvironment. The present study explored the novel biological function of IL-10 in regulation of expression of adhesion molecules in AML cells and found that exposing AML cells to IL-10 induced expression of E-cadherin, but not other adhesion molecules, including VLA4, CD29, and LFA1. Downregulation of E-cadherin with an siRNA suppressed the adhesion of leukemia cells to bone marrow-derived mesenchymal stem cells and enhanced the anti-leukemia effect of cytarabine. A microRNA (miRNA) database search identified an miR-9 as a candidate miRNA binding onto the 3'-UTR of E-cadherin and regulating its expression. Notably, treatment of leukemia cells with IL-10 decreased miR-9 expression through hypermethylation of the miR-9 CpG islands. In addition, downregulation of DNA methyltransferase 3A by siRNAs decreased E-cadherin expression in parallel with an increase in levels of miR-9 in leukemia cells. Notably, short hairpin RNA-mediated IL-10 downregulation impaired engraftment of human AML cells and enhanced the anti-leukemia effect of cytarabine in conjunction with miR-9 upregulation and E-cadherin downregulation in a human AML xenograft model. Taken together, the IL-10/E-cadherin axis may be a promising therapeutic target for treating AML.

Effects of bufalin on up-regulating methylation of Wilm's tumor 1 gene in human erythroid leukemic cells

OBJECTIVE

To explore the effects of bufalin on inhibiting proliferation, up-regulating methylation of Wilm' tumor 1 gene (WT1) as well as its possible mechanisms in human erythroid leukemic (HEL) cells.

METHODS

The HEL cells were treated with bufalin at various concentrations to observe cellular morphology, proliferation assay and cell cycle. The mRNA and protein expression levels of WT1 were detected by reverse transcription polymerase chain reaction (RT-PCR), Western blot and immunocytochemistry, DNA methylation of WT1 and protein expression levels of DNA methyltransferase 3a (DNMT3a) and DNMT3b were analyzed by methylation-specific PCR, and Western blot respectively.

RESULTS

The bufalin was effective to inhibit proliferation of HEL cells in a dose-dependent manner, their suppression rates were from 23.4%±2.1% to 87.2%±5.4% with an half maximal inhibit concentration (IC50) of 0.046 μmol/L. Typical apoptosis morphology was observed in bufalin-treated HEL cells. The proliferation index of cell cycle decreased from 76.4%±1.9% to 49.7%±1.3%. The expression levels of WT1 mRNA and its protein reduced gradually with increasing doses of bufalin, meanwhile, the methylation status of WT1 gene changed from unmethylated into partially or totally methylated. While, the expression levels of DNMT3a and DNMT3b protein gradually increased by bufalin treatment in a dose-dependent manner.

CONCLUSIONS

Bufalin can not only significantly inhibit the proliferation of HEL cells and arrest cell cycle at G0/G1 phase, but also induce cellular apoptosis and down-regulate the expression level of WT1. Our results provide the evidence of bufalin for anti-leukemia, its mechanism may involve in increasing WT1 methylation status which is related to the up-regulation of DNMT3a and DNMT3b proteins in erythroid leukemic HEL cells.

Determination of differentially regulated proteins upon proteasome inhibition in AML cell lines by the combination of large-scale and targeted quantitative proteomics

The ubiquitin-proteasome pathway (UPP) plays a critical role in the degradation of proteins implicated in cell cycle control, signal transduction, DNA damage response, apoptosis and immune response. Proteasome inhibitors can inhibit the growth of a broad spectrum of human cancer cells by altering the balance of intracellular proteins. However, the targets of these compounds in acute myeloid leukemia (AML) cells have not been fully characterized. Herein, we combined large-scale quantitative analysis by SILAC-MS and targeted quantitative proteomic analysis in order to identify proteins regulated upon proteasome inhibition in two AML cell lines displaying different stages of maturation: immature KG1a cells and mature U937 cells. In-depth data analysis enabled accurate quantification of more than 7000 proteins in these two cell lines. Several candidates were validated by selected reaction monitoring (SRM) measurements in a large number of samples. Despite the broad range of proteins known to be affected by proteasome inhibition, such as heat shock (HSP) and cell cycle proteins, our analysis identified new differentially regulated proteins, including IL-32, MORF family mortality factors and apoptosis inducing factor SIVA, a target of p53. It could explain why proteasome inhibitors induce stronger apoptotic responses in immature AML cells.

UNC2025, a MERTK Small-Molecule Inhibitor, Is Therapeutically Effective Alone and in Combination with Methotrexate in Leukemia Models

Purpose: MERTK tyrosine kinase is ectopically expressed in 30% to 50% of acute lymphoblastic leukemias (ALL) and more than 80% of acute myeloid leukemias (AML) and is a potential therapeutic target. Here, we evaluated the utility of UNC2025, a MERTK tyrosine kinase inhibitor, for treatment of acute leukemia.Experimental Design: Preclinical in vitro and in vivo assays using cell lines and primary leukemia patient samples were used to evaluate antileukemic effects of UNC2025.Results: UNC2025 potently inhibited prosurvival signaling, induced apoptosis, and reduced proliferation and colony formation in MERTK-expressing ALL and AML cell lines and patient samples. Approximately 30% of primary leukemia patient samples (78 of 261 total) were sensitive to UNC2025. Sensitive samples were most prevalent in the AML, T-ALL, and minimally differentiated (M0) AML subsets. UNC2025 inhibited MERTK in bone marrow leukemia cells and had significant therapeutic effects in xenograft models, with dose-dependent decreases in tumor burden and consistent two-fold increases in median survival, irrespective of starting disease burden. In a patient-derived AML xenograft model, treatment with UNC2025 induced disease regression. In addition, UNC2025 increased sensitivity to methotrexate in vivo, suggesting that addition of MERTK-targeted therapy to current cytotoxic regimens may be particularly effective and/or allow for chemotherapy dose reduction.Conclusions: The broad-spectrum activity mediated by UNC2025 in leukemia patient samples and xenograft models, alone or in combination with cytotoxic chemotherapy, supports continued development of MERTK inhibitors for treatment of leukemia. Clin Cancer Res; 23(6); 1481-92. ©2016 AACR.

Stage-Specific Human Induced Pluripotent Stem Cells Map the Progression of Myeloid Transformation to Transplantable Leukemia

Myeloid malignancy is increasingly viewed as a disease spectrum, comprising hematopoietic disorders that extend across a phenotypic continuum ranging from clonal hematopoiesis to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). In this study, we derived a collection of induced pluripotent stem cell (iPSC) lines capturing a range of disease stages encompassing preleukemia, low-risk MDS, high-risk MDS, and secondary AML. Upon their differentiation, we found hematopoietic phenotypes of graded severity and/or stage specificity that together delineate a phenotypic roadmap of disease progression culminating in serially transplantable leukemia. We also show that disease stage transitions, both reversal and progression, can be modeled in this system using genetic correction or introduction of mutations via CRISPR/Cas9 and that this iPSC-based approach can be used to uncover disease-stage-specific responses to drugs. Our study therefore provides insight into the cellular events demarcating the initiation and progression of myeloid transformation and a new platform for testing genetic and pharmacological interventions.

MiRNA182 regulates percentage of myeloid and erythroid cells in chronic myeloid leukemia

The deregulation of lineage control programs is often associated with the progression of haematological malignancies. The molecular regulators of lineage choices in the context of tyrosine kinase inhibitor (TKI) resistance remain poorly understood in chronic myeloid leukemia (CML). To find a potential molecular regulator contributing to lineage distribution and TKI resistance, we undertook an RNA-sequencing approach for identifying microRNAs (miRNAs). Following an unbiased screen, elevated miRNA182-5p levels were detected in Bcr-Abl-inhibited K562 cells (CML blast crisis cell line) and in a panel of CML patients. Earlier, miRNA182-5p upregulation was reported in several solid tumours and haematological malignancies. We undertook a strategy involving transient modulation and CRISPR/Cas9 (clustered regularly interspersed short palindromic repeats)-mediated knockout of the MIR182 locus in CML cells. The lineage contribution was assessed by methylcellulose colony formation assay. The transient modulation of miRNA182-5p revealed a biased phenotype. Strikingly, Δ182 cells (homozygous deletion of MIR182 locus) produced a marked shift in lineage distribution. The phenotype was rescued by ectopic expression of miRNA182-5p in Δ182 cells. A bioinformatic analysis and Hes1 modulation data suggested that Hes1 could be a putative target of miRNA182-5p. A reciprocal relationship between miRNA182-5p and Hes1 was seen in the context of TK inhibition. In conclusion, we reveal a key role for miRNA182-5p in restricting the myeloid development of leukemic cells. We propose that the Δ182 cell line will be valuable in designing experiments for next-generation pharmacological interventions.

Glycodendrimer PPI as a Potential Drug in Chronic Lymphocytic Leukaemia. The Influence of Glycodendrimer on Apoptosis in In Vitro B-CLL Cells Defined by Microarrays

BACKGROUND

Chronic lymphocytic leukaemia (CLL) cells are characterized by failures in the apoptosis pathway and increased proliferation, resulting in the progressive accumulation of B-lymphocytes in blood. Despite the wide range of antileukaemic drugs, CLL remains an incurable disease. However, a breakthrough is expected which will allow more effective treatment.

OBJECTIVE

The study investigates the influence of poly(propyleneimine) (PPI) dendrimer with peripheral amino groups, 30% of which were coated with maltotriose (PPI-G4-OS-Mal-III), on CLL cells, and demonstrates that it acts through the induction of the apoptotic mechanism. It is important to note that the dendrimer was used as a drug itself and not as a drug carrier.

METHOD

CLL and normal lymphocytes were treated in vitro with the dendrimer, either alone or in combination with fludarabine (FA). The percentages of apoptotic and necrotic cells, and the protein expression, were checked using a flow cytometer. Gene expression was screened using a two-colour microarray with 60-mer probes.

RESULTS

The results confirm that PPI-G4-OS-Mal-III influences the viability of CLL cells in vitro and does not exert any significant harmful effect on normal lymphocytes. The dendrimer appears to significantly influence gene and protein expression in CLL cells.

CONCLUSION

Since dendrimers can be specifically targeted, they may be very effective in CLL therapy, especially since in vitro PPI-G4-OS-Mal-III has been found to have stronger effect than fludarabine.

Targeting the transcription factor Myb by small-molecule inhibitors

The transcription factor Myb is a key regulator of hematopoietic cell proliferation, differentiation, and survival and has been implicated in the development of leukemia and several other human cancers. Pharmacological inhibition of Myb is therefore emerging as a potential therapeutic strategy. Recently, the first low-molecular-weight compounds that show Myb inhibitory activity have been identified. Characterization of these compounds suggests disruption of the protein-protein-interaction of Myb and the coactivator p300 as a suitable strategy to inhibit Myb.

Loss of mutL homolog-1 (MLH1) expression promotes acquisition of oncogenic and inhibitor-resistant point mutations in tyrosine kinases

Genomic instability drives cancer progression by promoting genetic abnormalities that allow for the multi-step clonal selection of cells with growth advantages. We previously reported that the IL-9-dependent TS1 cell line sequentially acquired activating substitutions in JAK1 and JAK3 upon successive selections for growth factor independent and JAK inhibitor-resistant cells, suggestive of a defect in mutation avoidance mechanisms. In the first part of this paper, we discovered that the gene encoding mutL homolog-1 (MLH1), a key component of the DNA mismatch repair system, is silenced by promoter methylation in TS1 cells. By means of stable ectopic expression and RNA interference methods, we showed that the high frequencies of growth factor-independent and inhibitor-resistant cells with activating JAK mutations can be attributed to the absence of MLH1 expression. In the second part of this paper, we confirm the clinical relevance of our findings by showing that chronic myeloid leukemia relapses upon ABL-targeted therapy correlated with a lower expression of MLH1 messenger RNA. Interestingly, the mutational profile observed in our TS1 model, characterized by a strong predominance of T:A>C:G transitions, was identical to the one described in the literature for primitive cells derived from chronic myeloid leukemia patients. Taken together, our observations demonstrate for the first time a causal relationship between MLH1-deficiency and incidence of oncogenic point mutations in tyrosine kinases driving cell transformation and acquired resistance to kinase-targeted cancer therapies.

PEITC-mediated inhibition of mRNA translation is associated with both inhibition of mTORC1 and increased eIF2α phosphorylation in established cell lines and primary human leukemia cells

Increased mRNA translation drives carcinogenesis and is an attractive target for the development of new anti-cancer drugs. In this work, we investigated effects of phenethylisothiocyanate (PEITC), a phytochemical with chemopreventive and anti-cancer activity, on mRNA translation. PEITC rapidly inhibited global mRNA translation in human breast cancer-derived MCF7 cells and mouse embryonic fibroblasts (MEFs). In addition to the known inhibitory effects of PEITC on mTORC1 activity, we demonstrate that PEITC increased eIF2α phosphorylation. PEITC also increased formation of stress granules which are typically associated with eIF2α phosphorylation and accumulation of translationally stalled mRNAs. Analysis of genetically modified MEFs demonstrated that optimal inhibition of global mRNA translation by PEITC was dependent on eIF2α phosphorylation, but not mTORC1 inhibition. We extended this study into primary leukemic B cells derived from patients with chronic lymphocytic leukaemia (CLL). CLL cells were stimulated in vitro with anti-IgM to mimic binding of antigen, a major driver of this leukemia. In CLL cells, PEITC increased eIF2α phosphorylation, inhibited anti-IgM-induced mTORC1 activation and decreased both basal and anti-IgM-induced global mRNA translation. PEITC also inhibited transcription and translation of MYC mRNA and accumulation of the MYC oncoprotein, in anti-IgM-stimulated cells. Moreover, treatment of CLL cells with PEITC and the BTK kinase inhibitor ibrutinib decreased anti-IgM-induced translation and induced cell death to a greater extent than either agent alone. Therefore, PEITC can inhibit both global and mRNA specific translation (including MYC) via effects on multiple regulatory pathways. Inhibition of mRNA translation may contribute to the chemopreventive and anti-cancer effects of PEITC.