Activated leukemic oncogenes AML1-ETO and c-kit: role in development of acute myeloid leukemia and current approaches for their inhibition

Roles of Histone Deacetylases in Acute Myeloid Leukemia With Fusion Proteins

Accurate orchestration of gene expression is critical for the process of normal hematopoiesis, and dysregulation is closely associated with leukemogenesis. Epigenetic aberration is one of the major causes contributing to acute myeloid leukemia (AML), where chromosomal rearrangements are frequently found. Increasing evidences have shown the pivotal roles of histone deacetylases (HDACs) in chromatin remodeling, which are involved in stemness maintenance, cell fate determination, proliferation and differentiation, via mastering the transcriptional switch of key genes. In abnormal, these functions can be bloomed to elicit carcinogenesis. Presently, HDAC family members are appealing targets for drug exploration, many of which have been deployed to the AML treatment. As the majority of AML events are associated with chromosomal translocation resulting in oncogenic fusion proteins, it is valuable to comprehensively understand the mutual interactions between HDACs and oncogenic proteins. Therefore, we reviewed the process of leukemogenesis and roles of HDAC members acting in this progress, providing an insight for the target anchoring, investigation of hyperacetylated-agents, and how the current knowledge could be applied in AML treatment.

Targeting Actomyosin Contractility Suppresses Malignant Phenotypes of Acute Myeloid Leukemia Cells

Actomyosin-mediated contractility is required for the majority of force-driven cellular events such as cell division, adhesion, and migration. Under pathological conditions, the role of actomyosin contractility in malignant phenotypes of various solid tumors has been extensively discussed, but the pathophysiological relevance in hematopoietic malignancies has yet to be elucidated. In this study, we found enhanced actomyosin contractility in diverse acute myeloid leukemia (AML) cell lines represented by highly expressed non-muscle myosin heavy chain A (NMIIA) and increased phosphorylation of the myosin regulatory light chain. Genetic and pharmacological inhibition of actomyosin contractility induced multivalent malignancy- suppressive effects in AML cells. In this context, perturbed actomyosin contractility enhances AML cell apoptosis through cytokinesis failure and aryl hydrocarbon receptor activation. Moreover, leukemic oncogenes were downregulated by the YAP/TAZ-mediated mechanotransduction pathway. Our results provide a theoretical background for targeting actomyosin contractility to suppress the malignancy of AML cells.

[Study of clinical outcome and prognosis in pediatric core binding factor-acute myeloid leukemia]

Objective: To analyze the clinical outcome and the prognostic factor in pediatric patients with core binding factor-acute myeloid leukemia (CBF-AML). Methods: A total of 121 newly diagnosed pediatric CBF-AML patients enrolled from Aug. 2005 to Sep. 2017 were retrospectively reviewed. Cumulative incidence of relapse (CIR), event-free survival (EFS) and overall survival (OS) rates were estimated by Kaplan-Meier method and prognostic factors were evaluated by Cox regression with SPSS. Results: Of the 121 patients, 120 patients were assessed for bone marrow remission after induction chemotherapy. 100 cases (83.3%) achieved complete remission (CR) after the first course of chemotherapy. 119 cases (99.2%) achieved CR after the second course of chemotherapy. Of the 121 patients, 13 patients (10.7%) had recurrence with the median interval of recurrence as 13.8 months (3.7 to 58.8 months). 17 patients (14.0%) died. The CIR, EFS and OS at 3 years were 12.7%, 77.5% and 82.8%, respectively. The factors including age at diagnosis, sex, initial WBC count, presence of extramedullary leukemia, C-KIT expression, additional chromosomal abnormalities, and CR after the first course of chemotherapy were analyzed by multivariate regression analysis of Cox. Multivariate analysis identified that additional chromosomal abnormalities was the only independent risk factor affecting OS (HR=4.289, 95%CI 1.070-17.183, P=0.040). Conclusions: Pediatric CBF-AML was a unique setting of prognostic subtypes. Chemotherapy produced good responses. Additional chromosomal abnormalities was the only independent risk factor for OS in pediatric CBF-AML.

Allogeneic hematopoietic stem cell transplantation for relapsed acute myeloid leukemia in ETO positive with reduced-intensity conditioning

Objective

This research is conducted under the intention of exploring the efficacy and safety of reduced-intensity conditioning for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in the treatment of relapsed ETO positive acute myeloid leukemia (AML).

Materials and Methods

Treatment of 15 cases referring to recurrent ETO positive acute myeloid leukemia in an army hospital from January 2010 to January 2013 through allo-HSCT with reduced-intensity conditioning. All participants belonged to the recurrent or refractory type, including 10 males and 5 females, aging from 16 to 48 years old, with the average age of 32.5 years old. Before transplantation, 6 cases were remission while 9 were not, 10 cases were HLA-identical matching and 5 cases were HLA-haploidentical. Donors received G-CSF to mobilize and used peripheral blood stem cell transplantation. Patients received a combination of Fludarabine, Busulfex and cytarabine as conditioning regimen. Preventive donor peripheral blood stem cell infusion was used 3 months after transplantation in order to observe toxicity, graft versus host disease(GVHD) and disease-free survival.

Results

All patients reached hematopoietic reconstitution, the average time were 15.5d and 16.8d respectively with neutrophils > 0.5 × 10⁹/L and platelets > 20 × 10⁹/L. Engraftment was confirmed by the evidence of 100% donor hematopoiesis and T lymphocyte subsets counts increased significantly before and after transplantation. Univariate analysis showed that the levels of CD3+, CD4+, CD8+, CD19+ significantly increased after transplantation (P < 0.05) . Until June 2016 after the duration of 27.5 months, 8 cases presented the presence of GVHD, one died of complication, another 4 died of relapse and the other three remained disease-free survival, the DFS rate of 2-year was 66.7%, with the longest DFS up to 54 months. Considering of the transplantation cases with remission into relief groups (6 cases), and not ease group (9 cases), 2 years of disease-free survival rates were 66.7% and 66.7%. The survival curves of the two groups are demonstrated with no significant statistical significance (P > 0.05).

Conclusions

Reduced-intensity allogeneic hematopoietic stem cell transplantation remains effective for relapsed AML with ETO positive, with safe and effective features and can be used as the method for relapsed AML with ETO positive.

Epigenetic Silencing of Eyes Absent 4 Gene by Acute Myeloid Leukemia 1-Eight-twenty-one Oncoprotein Contributes to Leukemogenesis in t(8;21) Acute Myeloid Leukemia

Background:

The acute myeloid leukemia 1 (AML1)-eight-twenty-one (ETO) fusion protein generated by the t(8;21)(q22;q22) translocation is considered to display a crucial role in leukemogenesis in AML. By focusing on the anti-leukemia effects of eyes absent 4 (EYA4) gene on AML cells, we investigated the biologic and molecular mechanism associated with AML1-ETO expressed in t(8;21) AML.

Methods:

Qualitative polymerase chain reaction (PCR), quantitative reverse transcription PCR (RT-PCR), and Western blotting analysis were used to observe the mRNA and protein expression levels of EYA4 in cell lines. Different plasmids (including mutant plasmids) of dual luciferase reporter vector were built to study the binding status of AML1-ETO to the promoter region of EYA4. Chromatin immunoprecipitation assay was used to study the epigenetic silencing mechanism of EYA4. Bisulfite sequencing was applied to detect the methylation status in EYA4 promoter region. The influence of EYA4 gene in the cell proliferation, apoptosis, and cell clone-forming ability was detected by the technique of Cell Counting Kit-8, flow cytometry, and clonogenic assay.

Results:

EYA4 gene was hypermethylated in AML1-ETO⁺ patients and its expression was down-regulated by 6-fold in Kasumi-1 and SKNO-1 cells, compared to HL-60 and SKNO-1-siA/E cells, respectively. We demonstrated that AML1-ETO triggered the epigenetic silencing of EYA4 gene by binding at AML1-binding sites and recruiting histone deacetylase 1 and DNA methyltransferases. Enhanced EYA4 expression levels inhibited cellular proliferation and suppressed cell colony formation in AML1-ETO⁺ cell lines. We also found EYA4 transfection increased apoptosis of Kasumi-1 and SKNO-1 cells by 1.6-fold and 1.4-fold compared to negative control, respectively.

Conclusions:

Our study identified EYA4 gene as targets for AML1-ETO and indicated it as a novel tumor suppressor gene. In addition, we provided evidence that EYA4 gene might be a novel therapeutic target and a potential candidate for treating AML1-ETO⁺ t (8;21) AML.

CEBPA mutations in patients with de novo acute myeloid leukemia: data analysis in a Chinese population

Background

This study was aimed to explore the clinical characteristics and prognoses of acute myeloid leukemia (AML) patients with CEBPA mutations.

Patients and methods

Three hundred and forty-five patients with de novo AML were retrospectively analyzed with regard to CEBPA mutations, clinical characteristics, therapeutic responses, and long-term outcomes.

Results

CEBPA mutations were detected in 59 patients (17.10%), with 47 cases harboring double mutations and 12 cases harboring single mutations. In those with a normal karyotype (NK), 44 cases (25.29%) were detected with CEBPA mutations. The following characteristics were observed in CEBPA-mutated patients: most (66.10%) of them were M₁ or M₂; they presented with higher peripheral white blood cell counts (23.71 [12.6, 60.02] ×10⁹/L versus 7.34 [2.38, 26.63] ×10⁹/L; u=4.944, P<0.001) and higher hemoglobin levels (89.64±23.05 g/L versus 75.65±23.65 g/L; t=4.156, P<0.001) than those observed in patients without the mutation; and the expression of CD7 and HLA-DR was higher, whereas that of CD34 and CD56 was lower in patients with the mutation than in those without the mutation. Compared with those without the mutation, patients with CEBPA mutations had a superior complete remission rate (75.0% versus 56.54%; χ²=6.185, P=0.013) and superior overall survival (P=0.034).

Conclusion

The frequency of CEBPA mutations may be higher in Chinese patients with AML than has been reported in populations of western countries, and the presence of CEBPA mutations is an indication of favorable prognoses for these patients.

Natural compounds and pharmaceuticals reprogram leukemia cell differentiation pathways

In addition to apoptosis resistance and cell proliferation capacities, the undifferentiated state also characterizes most cancer cells, especially leukemia cells. Cell differentiation is a multifaceted process that depends on complex regulatory networks that involve transcriptional, post-transcriptional and epigenetic regulation of gene expression. The time- and spatially-dependent expression of lineage-specific genes and genes that control cell growth and cell death is implicated in the process of maturation. The induction of cancer cell differentiation is considered an alternative approach to elicit cell death and proliferation arrest. Differentiation therapy has mainly been developed to treat acute myeloid leukemia, notably with all-trans retinoic acid (ATRA). Numerous molecules from diverse natural or synthetic origins are effective alone or in association with ATRA in both in vitro and in vivo experiments. During the last two decades, pharmaceuticals and natural compounds with various chemical structures, including alkaloids, flavonoids and polyphenols, were identified as potential differentiating agents of hematopoietic pathways and osteogenesis.

Esculetin Downregulates the Expression of AML1-ETO and C-Kit in Kasumi-1 Cell Line by Decreasing Half-Life of mRNA

One of the most frequent genetic aberrations in acute myeloid leukemia (AML) is chromosomal translocation between AML1/RUNX1 on chromosome 21 and ETO gene on chromosome 8 resulting in the expression of chimeric oncogene AML1-ETO. Although patients with t(8;21) translocation have good prognosis, 5-year survival is observed only in 50% of the cases. AML1-ETO translocation is usually accompanied by overexpression of mutant C-Kit, a tyrosine kinase, which contributes to uncontrolled proliferation of premature blood cells leading to relapse and poor prognosis. We illustrate the potential use of esculetin on leukemic cell line, Kasumi-1, bearing t(8;21) translocation and mutated C-Kit gene. Esculetin decreases the expression of AML1-ETO at both protein and transcript level within 24 hours of treatment. Half-life of AML1-ETO mRNA was reduced from 7 hours to 1.5 hours. Similarly half-life of C-Kit mRNA was reduced to 2 hours from 5 hours in esculetin treated cells. Esculetin also perturbed the expression of ectopically expressed AML1-ETO in U937 cells. The decreased expression of AML1-ETO chimeric gene was associated with increased expression of LAT1 and RUNX3 genes, targets of AML1. We envisage that discovery of a drug candidate which could target both these mutated genes would be a considerable breakthrough for future application.

Dasatinib

Dasatinib (Sprycel®), a second-generation TKI, has been shown to be effective as an anticancer drug in the treatment of patients with chronic myeloid leukemia or Philadelphia chromosome-positive acute lymphoblastic leukemia who are resistant or intolerant to imatinib. Several methods of gefitinib synthesis are included in this review. UV spectroscopy of dasatinib showed a λmax of approximately 320-330nm, and IR spectroscopy principal peaks were observed at 3418 (NH), 3200 (OH), 1620 (CO), 1582 (CC and CN), 1513 (CHCH) cm(-1). Characteristic NH peaks were observed in nuclear magnetic resonance (NMR) spectroscopy at 11.47 and 9.88ppm. The molecular mass was observed at m/z=487.3((35)Cl) and 488.9((37)Cl) (molecular weight=487.15) and the fragmentation pattern was studied using ion trap mass spectrometry. In addition, different analytical methods for determination of dasatinib are also described in this review. Pharmacokinetically, dasatinib is rapidly absorbed after oral administration where the solubility is dependent on pH. Dasatinib extensively binds to human plasma proteins by approximately 96%. In leukemic patient, the calculated apparent volume of distribution for dasatinib was 2502L and the estimated elimination half-life was approximately 3-5h. Dasatinib is metabolized in humans markedly by CYP3A4 to active metabolites and by phase II drug-metabolizing enzymes, such as UDP glucuronosyltransferase. Dasatinib is mainly eliminated via the feces (85%), of which relatively small amount of dasatinib is excreted unchanged as intact drug (19%). Most of the adverse effects associated with dasatinib therapy are mild to moderate in severity and are usually reversible and manageable with appropriate intervention, such as cardiac failure, hypertension, and coronary artery disease.

NPM1, FLT3-ITD, CEBPA, and c-kit mutations in 312 Chinese patients with de novo acute myeloid leukemia

OBJECTIVES

To explore NPM1, FLT3-ITD, CEBPA, and c-kit mutations in patients with acute myeloid leukemia (AML) from Chinese population.

METHODS

In this study, we retrospectively analyzed the prevalence and clinical profile of NPM1, FLT3-ITD, CEBPA, and c-kit mutations in 312 patients with de novo AML.

RESULTS

The frequencies of NPM1, FLT3-ITD, c-kit, and CEBPA mutations were 15.4, 14.0, 7.64, and 25.6%, respectively. The occurrence rate of NPM1 mutations increased with age in patients younger than 60 years. NPM1, c-kit, and CEBPA mutations were all associated with French-American-British subtypes. Patients with NPM1 mutations and FLT3-ITD presented with higher peripheral white blood cell counts and marrow blast percentages.

CONCLUSION

Both this and previous studies may suggest low frequencies of NPM1 and FLT3-ITD mutations in AML patients from the Chinese population, and they may have a synergistic function in stimulating proliferation of leukemia cells.

The surface molecular signature of leukemic cells is associated with NPM1 mutations and FLT3 -ITD in patients with de novo acute myeloid leukemia

Certain molecular mutations are associated with signs of cell morphology and differentiation in acute myeloid leukemia (AML). However, only limited data are available for the detailed analysis of such correlations. In this study, AML patients were classified into 4 subsets according to CD34, HLA-DR and CD11c expression levels. Significantly low CD34 antigen expression was observed in nucleophosmin (NPM1)-mutated patients and in those with FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD). No correlations were observed among NPM1 mutations, FLT3-ITD and monocytic morphology in patients without CD34 expression. Both NPM1 mutations and FLT3-ITD were absent in cluster IIb patients (CD34(+)CD11c(-)). The associations among NPM1 mutations, FLT3-ITD and the surface molecular signature of leukemic cells may offer beneficial information about the pathogenesis of AML.

Reduced serum retinol-binding protein levels in patients with de novo acute myeloid leukaemia

Retinol-binding protein (RBP) has been used as a nutritional index for children with acute myeloid leukaemia (AML) in previous studies. However, no studies have yet examined RBP levels in AML patients from all age groups. In this study, AML patients presented with lower RBP concentrations than healthy control subjects and patients with benign haematopathies. A negative association was observed between serum RBP level and peripheral white blood cell count in M4 and M5 AML patients. Moreover, patients carrying the FLT3-ITD mutation and young patients had lower RBP levels than those lacking this mutation and elderly patients. In conclusion, these observations suggest that aberrant retinol levels may be associated with AML.

Age-specific distributions of cytogenetic subgroups of acute myeloid leukemia: data analysis in a Chinese population

Although some studies have reported relationships between cytogenetic subgroups, molecular markers and age in acute myeloid leukemia (AML), conclusions based on data from a Chinese population are lacking. In the present study, we evaluated 640 patients with de novo AML. The patients were divided into 8 age groups, i.e. 0-9, 10-19, 20-29, 30-39, 40-49, 50-59, 60-69 and ≥70 years, and were then classified into cytogenetic groups based on normal, balanced and unbalanced karyotypes.

Cellular expression profile for interstitial cells of cajal in bladder - a cell often misidentified as myocyte or myofibroblast

BACKGROUND

Interstitial cells of Cajal (ICC) have been identified in urinary bladder of several species, but their presence in mice remains uncertain. Meanwhile, dozens of reports indicate that dysregulation of connexin 43 plays an important role in bladder overactivity, but its localization has not been clearly defined, with reports of expression in either the smooth muscle or in myofibroblasts. We recently identified a population of ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2) positive cells that resemble ICC and are distinct from smooth muscle, fibroblasts, myofibroblasts and neurons. Thus we sought to define more clearly the molecular signature of ICC and in doing so resolve some of these uncertainties.

PRINCIPLE FINDINGS

Immunofluorescent localization revealed that NTPDase2-positive cells lie closely adjacent to smooth muscle but are separate from them. NTPDase2 positive cells exhibited co-localization with the widely accepted ICC marker - c-kit. They were further shown to co-localize with other ICC markers CD34 and Ano1, but not with mast cell marker tryptase. Significantly, they show convincing co-localization with connexin 43, which was not present in smooth muscle. The identity of these cells as ICC was further confirmed by the presence of three mesenchymal markers - vimentin, desmin, and PDGFβ receptor, which indicates their mesenchymal origin. Finally, we observed for the first time, the presence of merlin/neurofibromin 2 in ICC. Normally considered a neuronal protein, the presence of merlin suggests ICC in bladder may have a role in neurotransmission.

CONCLUSIONS

NTPDase2 positive cells in mice bladder are ICC, which can be defined by the presence of c-Kit, CD34, Ano1, NTPDase2, connexin 43, vimentin, desmin, PDGFβ receptor and merlin/NF2. These data establish a definitive molecular expression profile, which can be used to assist in explorations of their functional roles, and the presence of NTPDase2 suggests that purinergic signaling plays a role in regulation of ICC function.

Deregulation of RAD21 and RUNX1 expression in endometrial cancer

Cohesins and cohesin-regulated genes are deregulated in numerous types of human cancer. However, data concerning their status and role in endometrial cancer are scarce. This study aimed to determine the clinical significance of double-strand-break repair protein rad21 homolog (RAD21) and runt-related transcription factor 1 (RUNX1) gene dosage and mRNA expression in endometrial cancer. RAD21 is a component of the cohesin complex, crucial for chromosome segregation and DNA repair. RUNX1 is the transcription factor implicated in RAD21 regulation. The study group included 144 endometrial cancer patients. RAD21 and RUNX1 expression profiles were measured by reverse-transcription quantitative PCR. RAD21 gene dosage was determined by quantitative PCR. RAD21 gene dosage was associated with RAD21 mRNA expression (ϱ=0.22; p=0.009). Furthermore, RAD21 expression strongly correlated with RUNX1 expression (ϱ=0.43; p<0.0000001). Increased RAD21 gene dosage correlated with more advanced tumor stage (p=0.021), higher grade (p=0.021), cervical involvement (p=0.01) and the absence of obesity (p=0.025), while RAD21 mRNA expression correlatd with cervical involvement (p=0.027). The mRNA expression of RAD21 and RUNX1 was found to be deregulated and co-dependent in endometrial cancer. RAD21 gene dosage is associated with unfavorable tumor characteristics. However, elucidating the role of these molecular markers in endometrial oncogenesis requires further investigation, including functional studies and survival analysis.