FAB M2 Subtype Research Articles

Prognostic Significance of LPCAT1 in Adult Acute Myeloid Leukemia Patients with FAB Subtype M2

To study the prognostic value of LPCAT1 in acute myeloid leukemia (AML). TaqMan-based reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect relative expression of LPCAT1 in 214 newly diagnosed adult AML patients and 24 normal controls. Survival functions were estimated using the Kaplan-Meier method and were compared by the Log-rank test. A Cox proportional hazard regression model was used to identify prognostic factors. The expression level of LPCAT1 in adult AML was 34.37%(1.83%-392.63%), which was significantly lower than 92.81%(2.60%-325.84%) of normal controls (P<0.001). The prognostic significance of LPCAT1 was evaluated in 171 non-acute promyelocytic leukemia patients with complete clinical information and prognostic data. Survival analysis showed that the expression level of LPCAT1 had no significant effect on the prognosis of the whole cohort. However, in AML patients with FAB subtype M2 (AML-M2), the 2-year relapse-free survival (RFS) rate of patients with low LPCAT1 expression was 35.4%(95%CI: 0.107-0.601), which was significantly lower than 79.2%(95%CI: 0.627-0.957) of patients with high LPCAT1 expression (P=0.012). Multivariate analysis showed that low expression of LPCAT1 was an independent risk factor for RFS of AML-M2 patients (HR=0.355, 95%CI: 0.126-0.966, P=0.049). In adult AML patients LPCAT1 shows low expression. Low LPCAT1 expression is an independent risk factor for RFS in M2-AML patients.

Analysis of Coexisting Gene with NRAS in Acute Myeloid Leukemia

To investigate the coexisting mutations and clinical significance of Homo sapiens neuroblastoma RAS viral oncogene homolog (NRAS) gene in acute myeloid leukemia (AML) patients. High-throughput DNA sequencing and Sanger sequencing were used to detect 51 gene mutations. The occurrence, clinical characteristics and treatment efficacy of coexisting genes with NRAS were investigated. A total of 57 NRAS mutations (17.5%) were detected in 326 patients with AML. Compared with the patients in NRAS non-mutation group, patients in the mutant group were younger (P=0.018) and showed lower platelet count (P=0.033), but there was no significant difference in peripheral leukocyte count, hemoglobin, and sex. For FAB classification, NRAS mutation and M2 subtype showed mutually exclusive (P=0.038). Among 57 patients carried with NRAS mutation, 51 (89.5%) patients carried with other gene mutations, 25 (43.9%) carried with double gene mutations, 10 (17.5%) carried with 3 gene mutations, and 16 (28.1%) corried with ≥ 4 gene mutations. The most common coexisting gene mutation was KRAS (24.6%, 14/57), followed by FLT3-ITD (14.0%, 8/57), RUNX1 (12.3%, 7/57), NPM1 (10.5%, 6/57), PTPN11 (10.5%, 6/57), DNMT3A (10.5%, 6/57) and so on. The age (P=0.013, P=0.005) and peripheral platelet count (P=0.007, P=0.021) of patients with NPM1 or DNMT3A mutations were higher than those of the patients with wild type, but there was no significant difference in peripheral leukocyte count and hemoglobin. Also, there was no significant difference in age, peripheral leukocyte count, hemoglobin, and peripheral platelet count between the patients in KRAS, FLT3-ITD, RUNX1 or PTPN11 mutant group and the wild group. Patients with FLT3-ITD mutations showed a lower complete remission (CR) rate (P=0.044). However, there was no significant difference in CR rate between the patients with KRAS, NPM1, RUNX1, PTPN11 or DNMT3A mutations and the wild group. The CR rate of the patents with single gene mutation, double gene mutations, 3 gene mutations, and≥ 4 gene mutations were decreased gradually, and there was no significant difference in CR rate between pairwise comparisons. The mutation rate of NRAS mutation is 17.5%, 89.5% of AML patients with NRAS mutation coexist with additional gene mutations. The type of coexisting mutations has a certain impact on clinical characteristics and CR rate of patients with AML.

Integrated analysis reveals distinct molecular, clinical, and immunological features of B7-H3 in acute myeloid leukemia.

The role of B7‐H3 in acute myeloid leukemia (AML) is not fully understood. Two previous studies investigating its expression and significances in AML are partially different. In this study, we aimed to systematically characterize the genomic and immune landscape in AML patients with altered B7‐H3 expression using multi‐omics data in the public domain. We found significantly increased B7‐H3 expression in AML compared to either other hematological malignancies or healthy controls. Clinically, high B7‐H3 expression was associated with old age, TP53 mutations, wild‐type WT1 and CEBPA, and the M3 and M5 FAB subtypes. Moreover, we observed that increased B7‐H3 expression correlated significantly with a poor outcome of AML patients in four independent datasets. Gene set enrichment analysis (GSEA) revealed the enrichment of the “EMT” oncogenic gene signatures in high B7‐H3 expressers. Further investigation suggested that B7‐H3 was more likely to be associated with immune‐suppressive cells (macrophages, neutrophils, dendritic cells, and Th17 cells). B7‐H3 was also positively associated with a number of checkpoint genes, such as VISTA (B7‐H5), CD80 (B7‐1), CD86 (B7‐2), and CD70. In summary, we uncovered distinct genomic and immunologic features associated with B7‐H3 expression in AML. This may lead to a better understanding of the molecular mechanisms underlying B7‐H3 dysregulation in AML and to the development of novel therapeutic strategies.

Characteristics and Survival of 927 Moroccan Adults with Acute Myeloid Leukemia: Monocentric Experience

Acute myeloïd leukemia (AML) is the most frequent form of acute leukemia among adults and the most aggressive type of leukemia, which is associated with the lowest survival rate. Patients with AML are treated with intensive chemotherapy and many factors could influence the survival of these patients, such as age, cytogenetic abnormalities; white blood cell (WBC) counts. The aim of this work was to study the epidemiological and response profiles of AML adults patients in Morocco.Patients and Methods: A prospective, descriptive study conducted in the Hematology and Pediatric Oncology department, 20 August Hospital Casablanca, and concerned adult patients diagnosed with AML through a period of seven years (January 2011 to December 2017). Statistical analysis was performed using SPSS version 20. The overall survival and disease-free survival were evaluated by using the Kaplan–Meier method. Results: A total of 927 patients diagnosed with AML during the 7 year period. 466 (50.3%) were males and 461 (49.7%) were females. The median age of patients was 46years.The most represented age group was between 18 and 60 years old with a percentage of 83.2%.The FAB subtype M2 occurred most frequently (27%) followed by M1 (24.8%). The cytogenetic study showed that the majority of patients had a normal karyotype. The t (8; 21) was the most detected balanced translocation in our series and the intermediate cytogenetic group was the most represented group (65.4%). A total of 461 patients (53.54%) were treated according to the protocol AML11. The Disease-free survival (DFS) was significantly better for favorable cytogenetic group as compared to other cytogenetic groups (median survival of 41.58 months for the favorable group versus 29.07 months for the adverse group; p-value = 0.02).Conclusion: The age of AML patients was younger compared to other populations. The majority of patients had a normal karyotype and the commonest balanced translocation was the t (8; 21). Survival was higher in patients with good prognosis.

Apatinib exhibits cytotoxicity toward leukemia cells by targeting VEGFR2-mediated prosurvival signaling and angiogenesis

ObjectiveVascular permeability contributes to disease progression and drug resistance in hematological malignancies, including AML. Thus, targeting angiogenic signaling is a promising treatment strategy, especially for relapsed and resistant AML. The aim of this study was to evaluate the efficacy of apatinib, a novel receptor tyrosine kinase inhibitor that selectively targets VEGFR2. MethodsSeveral AML cell lines were exposed to various concentrations of apatinib, and then CCK8 and Annexin V/PI assays were performed to determine IC50 values and apoptosis, respectively. The effect of apatinib against primary AML cells from 57 adult patients and 11 normal controls was also analyzed utilizing an apoptosis assay. Next, we tested the underlying mechanism of apatinib in AML using western blotting and mass cytometry (CyTOF). Finally, the activity of apatinib against tumor growth and angiogenesis was further evaluated in vivo in xenograft models. ResultsWe found apatinib significantly inhibited growth and promoted apoptosis in AML cell lines in vitro. Similarly, apatinib showed cytotoxicity against primary AML cells but didn't affect normal BMMCs. Its effect was highly correlated with several clinical features, such as NPM1 mutation, extramedullary infiltration, relapsed/refractory disease, and M2 and M5 FAB subtypes. In addition, apatinib suppressed AML growth and attenuated angiogenesis in xenograft models. Mechanistically, apatinib-induced cytotoxicity was closely associated with inhibition of the VEGFR2-mediated Src/STAT3 and AKT/mTOR pathways and induction of mitochondria-mediated apoptosis. ConclusionApatinib exerts antileukemia effects by targeting VEGFR2-induced prosurvival signaling and angiogenesis, thus providing a rationale for the application of apatinib in AML.

Overexpressed WT1 exhibits a specific immunophenotype in intermediate and poor cytogenetic risk acute myeloid leukemia.

Many studies have confirmed that overexpressed WT1 exists in leukemic cells, especially in AML. However, the immunophenotypic features of this sort of leukemic cells remain to be unclarified. We retrospectively analyzed the immunophenotype of 283 newly diagnosed AML patients with intermediated and poor cytogenetic risk to evaluate the correlation between phenotype and WT1 overexpression. EVI1 transcripts, KMT2A-PTD, FLT3-ITD, and NPM1 mutations were simultaneously assessed. Our results revealed that overexpressed WT1 was significantly associated with the expression of CD117, CD13, and CD123. Besides, leukemic cells with WT1 overexpression also lacked lymphoid and myeloid differentiation-related markers. FAB subtype M2 patients had higher WT1 levels, compared with other FAB subtype. Multivariate analysis was proved that NPM1 mutation, M2 subtype, and the expression of CD123 were independently associated with WT1 overexpression. These indicated that AML with overexpressed WT1 was proliferated and blocked in the early stage of AML development. It presumably provided some clues to detect overexpressed WT1 cells via multiparameter flow cytometry. CD123-targeted drugs might become one of the alternative treatments for patients with WT1 overexpression.

Prognostic significance of tetraspanin (CD81) expression in patients with acute myeloid leukemia

Objective The aim was to determine the prognostic significance of CD81 expression in patients with acute myeloid leukemia (AML) and its effect on patients’ survival. Patients and methods This study was carried out on 50 patients with newly diagnosed AML. Expression of CD81 was detected by flow cytometry, and then all the patients received chemotherapy and were observed for a period of 12 months regarding clinical and laboratory findings of remission and relapse. Results Our results showed that positive expression of CD81 was detected in 30/50 (60%) patients. Clinical remission was achieved in six (12%) patients with positive expression of CD81, whereas it was achieved in 12 (24%) patients with negative CD81 expression. Relapse occurred in 19 (38%) patients with positive expression of CD81, whereas it occurred in six (12%) patients with negative CD81 expression. Death occurred in five (10%) patients with positive expression of CD81 and in two (4%) patients with negative expression of CD81. Conclusion CD81 expression has a potential role as a prognostic marker as its expression was associated with patients with high-risk AML, with higher white blood cells, higher lactate dehydrogenase, and higher blast percentage in bone marrow, and M1 and M5 FAB subtypes. Decreased overall survival and disease-free survival in patients with CD81-positive expression than in patients with CD81-negative expression was also observed.

RUNX1-ETO-Dependent Transcriptional Repression of RASSF2 Contributes to t(8;21) Leukemia through Evasion of MST1-Driven Apoptosis Signaling

The t(8;21) chromosomal translocation is among the most frequent recurring cytogenetic abnormalities associated with acute myeloid leukemia (AML), found in 8-12% of de novo AML patients. The t(8;21) results in the stable fusion of the RUNX1 and RUNX1T1 genes, and formation of the oncofusion protein RUNX1-ETO (AML1-ETO). RUNX1-ETO is composed of the N-terminal DNA-binding domain of RUNX1 and nearly the entire ETO protein. RUNX1-ETO promotes leukemia development via the recruitment of transcription factor/transcriptional repression complexes (including NCOR, HDACs, p300, etc.) to regulatory regions of RUNX1 target genes known to be critical for myeloid differentiation and function, such as CEBPA, SPI1 (PU.1), NFE2, and CSF1R. Despite this knowledge, additional RUNX1-ETO target genes remain poorly characterized, and the complete molecular mechanism through which RUNX1-ETO leads to leukemic transformation remains to be elucidated. We propose that a better understanding of additional RUNX1-ETO target genes will lead to the potential for development of novel therapeutics to treat these patients.One such gene that we initially identified as markedly downregulated in RUNX1-ETO leukemia cells using a mouse model of t(8;21) AML is RASSF2 (Lo et al, Blood, 2012). Assessment of publicly available gene expression data revealed that RASSF2 is specifically downregulated in the bone marrow of t(8;21) AML patients compared to patients of different cytogenetic subtypes or to non-t(8;21) FAB subtype M2 AML patients. Additionally, RT-qPCR analysis confirmed that RASSF2 transcript is downregulated 10-100-fold in the t(8;21) AML cell lines, Kasumi-1 and SKNO-1, compared to non-t(8;21) AML cell lines and normal CD34+ hematopoietic cells. Expression of RUNX1-ETO in a non-t(8;21) AML cell line led to a reduction in RASSF2 mRNA expression, while knockdown of RUNX1-ETO in Kasumi-1 cells resulted in a ~5-fold increase in RASSF2 expression. Assessment of published ChIP-seq data showed that RUNX1-ETO directly binds at two regulatory regions within the RASSF2 genomic locus in t(8;21) AML cell lines and patient samples.Re-expression of RASSF2 at physiological levels in t(8;21) AML cell lines resulted in a modest negative growth phenotype, and greatly sensitized these cells to apoptosis following stimulation with various pro-apoptotic agents. Re-expression of RASSF2 in RUNX1-ETO-transduced primary mouse bone marrow caused these cells to lose their long-term self-renewal ability after 3 weeks in a serial replating/colony formation assay. This loss of self-renewal ability in co-transduced cells was accompanied by a marked increase in apoptosis during each of the first three weeks of replating. Mechanistically, re-expression of full-length RASSF2, but not of a deletion mutant lacking the SARAH heterodimerization domain (RASSF2ΔSARAH), in t(8;21) AML cell lines resulted in increased protein amount of the pro-apoptotic kinase, MST1. This suggests that RASSF2 may be a critical regulator of MST1 protein stability in AML cells. Importantly, modest (2-3-fold) overexpression of MST1 in t(8;21) AML cell lines resulted in a significant increase in apoptosis and caused growth arrest. The effects of RASSF2 or MST1 expression in non-t(8;21) AML cell lines were greatly reduced, suggesting that the cellular context of RUNX-ETO-driven leukemias makes them highly susceptible to MST1-dependent apoptosis.Overall, we have identified the importance of a MST1-driven pro-apoptotic signaling axis in t(8;21) leukemia. RUNX1-ETO-dependent transcriptional repression of RASSF2 may be essential for evasion of this apoptosis signaling during leukemic transformation via reduction of MST1 protein stability. MST1, perhaps better known as the mammalian orthologue of the drosophila Hippo kinase, is a critical tumor suppressor in many solid tumor types; and we believe our studies warrant the continued investigation of this pathway in hematological malignancy. DisclosuresNo relevant conflicts of interest to declare.

Supraphysiologic levels of the AML1-ETO isoform AE9a are essential for transformation

Chromosomal translocation 8;21 is found in 40% of the FAB M2 subtype of acute myeloid leukemia (AML). The resultant in-frame fusion protein AML1-ETO (AE) acts as an initiating oncogene for leukemia development. AE immortalizes human CD34(+) cord blood cells in long-term culture. We assessed the transforming properties of the alternatively spliced AE isoform AE9a (or alternative splicing at exon 9), which is fully transforming in a murine retroviral model, in human cord blood cells. Full activity was realized only upon increased fusion protein expression. This effect was recapitulated in the AE9a murine AML model. Cotransduction of AE and AE9a resulted in a strong selective pressure for AE-expressing cells. In the context of AE, AE9a did not show selection for increased expression, affirming observations of human t(8;21) patient samples where full-length AE is the dominant protein detected. Mechanistically, AE9a showed defective transcriptional regulation of AE target genes that was partially corrected at high expression. Together, these results bring an additional perspective to our understanding of AE function and highlight the contribution of oncogene expression level in t(8;21) experimental models.

Clinical and Hematological Profile of Acute Myeloid Leukemia (AML) Patients of Sindh

In Acute Myeloid Leukemia (AML) patients, a diversity of clinical and hematological parameters has been examined for possible value in calculating treatment response and survival. The study was conducted at National Institute of Bone Diseases, Karachi (NIBD), Sind, Pakistan, a tertiary care and teaching hospital, affiliated with Liaquat University of Medical and Health Sciences, Jamshoro. This study included 107 cases of de novo AML, both male and female patients of ages between 10-60 years were selected randomly. The clinical features included fever, weakness, loss of weight, vomiting, bleeding gums, liver and spleen enlargement, lymph node enlargement. The Laboratory investigations included CBC (Complete Blood Count) specifically heamoglobin percentage, total leucocyte count, platelet count and blast count: peripheral blood smears, bone marrow aspiration biopsy, trephine biopsy, cytochemistry (Myeloperoxidase Staining, Immunohistochemistry (CD markers)) and DNA extraction for genetic sequencing. Percentage, validity and cumulative index were calculated of all parameters. It was found that about 70% of AML patients were adults and FAB subtype M2 of acute myeloid leukemia was more prevalent than other subtypes, followed by AML, M1.

RASSF2 Functions As a Tumor Suppressor in t(8;21) AML Via Promotion of Apoptosis

The t(8;21) chromosomal translocation is one of the most common chromosomal translocations associated with acute myeloid leukemia (AML), found in approximately 12% of de novo AML cases. The majority of these cases are classified as FAB-subtype M2 AML. The t(8;21) results in the stable fusion of the AML1 (RUNX1) and ETO (RUNX1T1) genes. The AML1-ETO fusion protein is composed of the N-terminal portion of AML1, which includes the DNA-binding Runt-homology domain, and nearly the full-length ETO protein. The primary accepted mechanism by which AML1-ETO promotes leukemia development is through the aberrant recruitment of transcriptional repression/activation complexes to normal AML1 target genes. Therefore, the identification of individual genes or biological pathways that are specifically disrupted in the presence of AML1-ETO will provide further molecular insight into the pathogenesis of t(8;21) AML and lead to the possibility for improved treatment for these patients.We identified RASSF2 as a gene that is specifically downregulated in (2-4 fold) in total bone marrow of t(8;21) patients compared to non-t(8;21) FAB-subtype M2 AML patients by analyzing publicly available gene expression datasets. Similarly, using a mouse model of t(8;21) AML we found Rassf2 mRNA levels to be nearly 30-fold lower in t(8;21) leukemia cells compared to wild-type Lin-Sca-cKit+ (LK) myeloid progenitors. Gene expression analysis by RT-qPCR in leukemia cell lines confirmed that RASSF2 mRNA levels are significantly downregulated (8-10-fold) in both Kasumi-1 and SKNO-1 t(8;21) cell lines as compared to a similar non-t(8;21) HL-60 cell line and to primary human CD34+ control cells. In addition, expression of AML1-ETO in HL-60 or CD34+ cells results in a decrease in RASSF2 mRNA expression, which further suggests that RASSF2 is a target for regulation by AML1-ETO. Assessment of published ChIP-seq data shows that AML1-ETO binds the RASSF2 gene locus at two distinct regions in both primary t(8;21) AML patient samples and in the Kasumi-1 and SKNO-1 cell lines. These regions are similarly bound by several important hematopoietic transcription factors in primary human CD34+ cells, including AML1, ERG, FLI1, and TCF7L2, implicating these two regions as important for the regulation of RASSF2 expression during blood cell differentiation. Overexpression of RASSF2 in human leukemia cell lines using an MSCV-IRES-GFP (MIG) construct revealed that RASSF2 has a strong negative effect on leukemia cell proliferation and viability. The overall percentage of GFP-positive cells in MIG-RASSF2 transduced cells markedly decreased compared to MIG-control transduced cells over a period of 14 days. This effect was primarily due to significantly increased apoptosis in the RASSF2 expressing cell populations. Similarly, we found that expression of RASSF2 significantly inhibits the long-term self-renewal capability of hematopoietic cells transduced with AML1-ETO in a serial replating/colony formation assay. AML1-ETO transduced hematopoietic cells were normally capable of serial replating for more than 6 weeks. However, AML1-ETO transduced cells co-expressing RASSF2 consistently had reduced colony number and lost their ability to replate after 3-4 weeks. This was due to a dramatically increased rate of apoptosis in RASSF2 expressing cells.RASSF2 is reported to be a tumor suppressor that is frequently downregulated at the transcriptional level by hypermethylation in primary tumor samples, but not healthy controls. Here we have identified RASSF2 as a target for repression, and demonstrated its tumor suppressive function in t(8;21) leukemia cells. Further insights into the molecular mechanisms of RASSF2 function in AML will continue to be explored. DisclosuresNo relevant conflicts of interest to declare.

CD25 Expression Is Associated with Inferior Clinical Outcomes in Elderly Patients with Acute Myeloid Leukemia

Background: Elderly patients with acute myeloid leukemia (AML) show unfavorable biologic characteristics and inferior clinical outcomes compared to younger patients. Because some elderly patients can benefit from intensive chemotherapy, the identification of prognostic markers is important for therapeutic decision-making. CD25 (interleukin 2 receptor alpha) has been reported to be highly expressed in leukemia stem cells and correlate with adverse outcomes in younger (less than 60 years) patients with AML. However, the significance of CD25 expression in elderly patients with AML has not yet been investigated.Methods: We retrospectively reviewed 154 newly diagnosed AML (de novo, secondary) patients aged 60 years or over (median: 69, range: 60-85 years), admitted between 2005 and 2013 to Jichi Medical University Hospital. Blast cells from bone marrow at diagnosis were identified by flow cytometry (FCM) using CD45/side scatter properties. CD25 expression in the blast region was analyzed by FCM combined with single- and two-color staining.Results: The two-color FCM analysis showed that CD25 was expressed in CD34, CD117, and CD13-positive blast cells. The median CD25 expression of the blast cells was 0.7% (range: 0-75.3%). On the basis of CD25 expression in bone marrow blasts from healthy volunteers (n=5; median, 3.2%; range, 1.5-5.6%), we defined CD25 expression >10% as positivity. In this setting, we identified CD25-positive blasts in 21 patients (14%). CD25+AML was characterized by the MDS/MPN history (30%) and, a low or zero frequency of favorable cytogenetics (0%), FAB M2 subtype (5%), and FAB M3 subtype (0%) compared with CD25-AML (n=133). Among the 118 patients who underwent induction chemotherapy, including 75 patients who received a combination of anthracyclin and cytarabine (Ara-C), 69 (58%) achieved complete remission (CR). CD25+AML was associated with an inferior CR rate (20 vs. 64%, respectively, P=0.003), inferior event-free survival (EFS) (1-year EFS, 0 vs. 33%, respectively, P< 0.001), and inferior overall survival (OS) (2-year OS, 13 vs. 38%, respectively, P=0.003) compared with CD25-AML. On multivariate analysis using the following factors: cytogenetics, age (over 75 years), MDS/MPN history, and intensity of induction chemotherapy, CD25-positivity was a significant risk factor for the CR rate (HR: 8.0, 95% CI: 1.7-36.6; P=0.008) and EFS (HR: 2.3, 95% CI: 1.1-4.7; P=0.021). For CD25+AML, the CR rate was higher with induction chemotherapy using a regimen of low-dose Ara-C combined with granulocyte colony-stimulating factor (50%) than that using a regimen of daunorubicine and Ara-C (0%). However, there was no significant difference in OS between patients with CD25+AML treated with induction chemotherapy and those who treated with best supportive care (2-year OS, 13 vs. 11%, respectively, P=0.29). There were no patients with CD25+AML received stem cell transplantation due to disease progression.Conclusion: This study demonstrated that CD25 is an independent prognostic factor for elderly AML patients. The prognosis of CD25+AML patients is extremely poor; therefore, it is necessary to develop alternative approaches, such as a regime including anti-CD25 antibody, therapy targeting leukemia stem cells, and nonmyeloablative stem cell transplantation. DisclosuresNo relevant conflicts of interest to declare.

Specific Patterns of Molecular Mutations Determine the Morphologic Differentiation Stages in Acute Myeloid Leukemia (AML)

Background: The FAB classification of AML was based on the differentiation state and the involved cell lineages and recognized some close associations between genetic abnormalities and cytomorphology: CBFB-MYH11 and AML with abnormal eosinophils, PML-RARA and acute promyelocytic leukemia; RUNX1-RUNX1T1 and AML with maturation (FAB subtype M2). Associations with molecular mutations have not been examined in detail yet.Aim: Evaluate the impact of molecular mutations on the AML differentiation state.Material and Methods: The cohort comprized 3,703 patients with de novo AML (median age 67 yrs; range: 18.1-100.5 yrs). All cases were analyzed by cytomorphology and molecular mutation screening for 12 genes by next generation or Sanger sequencing in our laboratory. Based on cytomorphology and immunophenotyping we categorized the cohort into 11 subgroups: 1. AML with minimal differentiation (according to the FAB classification: M0; n=192), 2. AML without maturation (M1; n=1,015), 3. AML with maturation (M2; n=1,324), 4. acute promyelocytic leukemia (APL) with PML-RARA (M3; n=124), 5. the microgranular variant of APL (M3v, n=110), 6. acute myelomonocytic leukemia (M4; n=604), 7. acute myelomonocytic leukemia with abnormal eosinophils and CBFB-MYH11 (M4eo; n=81), 8. acute monoblastic leukemia (M5a; n=86), 9. acute monocytic leukemia (M5b; n=63), and 10. acute erythroid leukemia (M6; n=101). Cases with acute megakaryoblastic leukemia (M7; n=3) were not considered for statistical evaluation. All 3,703 cases were analyzed for FLT3-ITD and FLT3-TKD. All cases except M3/M3v and M4eo (n=3,487) were screened for NPM1 und MLL-PTD. Data on the mutation status of the following genes was available: FLT3-ITD (n=3,703), FLT3-TKD (n=3,703), CEBPA (n=2,684), RUNX1 (n=2,320), WT1 (n=2,224), ASXL1 (n=1,591), DNMT3A (n=1,294), NRAS (n=1,232), TP53 (n=1,046) and TET2 (n=974). Statistical significance of associations between the mutation frequencies and AML subtypes were assessed by Fisher’s exact test and corrected according to Benjamini-Hochberg (1995) to compensate for multiple testing.Results: The mutation rates of the analyzed genes are in line with published data.Total cohort: Significant associations were observed between the mutation frequencies of distinct genes and the differentiation stage of the AML. Figure 1 depicts genes showing significantly different mutation rates within distinct AML subtypes compared to the rate of the total cohort. In detail, mutations in RUNX1 were most frequently observed in M0 (43.6%) and M2 (24.0%) and were nearly absent in M5a (3.5%) and M5b (0%). The highest TP53 mutation rates were observed in M6 (35.3%) and M2 (15.0%), the lowest in M4 (3.0%) and M1 (5.7%). NPM1 mutations were significantly more frequent in M5b (69.8%), M4 (56.3%), M5a (47.7%) and M1 (42.1%) than in M2 (24.2%), M6 (20.8%), M0 (3.1%), and absent in M3, M3v, and M4eo, respectively.NPM1 mutated subcohort (n=1,200): The overall DNMT3A mutation rate in this subcohort was 49.1%. It was significantly higher in M5b (75.0%) and M4 (61.6%) and significantly lower in M1 (40.6%), M5a (22.2%), and M6 (13.3%). Contrary, RUNX1 (overall frequency in NPM1mut cases 1.2%) and ASXL1 (overall 2.5%) mutations were more frequent in M5a (8.3% and 34.8%, respectively), while FLT3-ITD was more frequent in M1 (52.5%), and WT1 mutations more frequent in M6 (26.7%).CEBPA double mutated subcohort (n=108): ASXL1 and RUNX1 mutations were 5- and 7-fold more frequent in M2 than in M1, but did not reach significance.Conclusions:Specific patterns of molecular mutations are linked to distinct AML differentiation stages: 1) RUNX1 and ASXL1 with M0 2) NPM1, ASXL1 and TET2 with M5a, and 3) NPM1 and DNMT3A with M5b. 4) The differentiation stage of NPM1 mutated AML is driven by the presence of additional mutations: DNMT3A mutations lead to a (myelo-)monocytic differentiation, while mutations in RUNX1 or ASXL1 lead to a monoblastic phenotype. 5) FLT3-ITD is most frequent in NPM1 mutated AML without maturation and WT1 mutations are most frequent in acute erythroid leukemia bearing NPM1mut. [Display omitted] DisclosuresRose:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Perglerová:MLL2 s.r.o.: Employment. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Tumor Suppressor RASSF2 Is Downregulated By The RUNX1-ETO Fusion Protein In t(8;21)+ Acute Myeloid Leukemia

IntroductionThe t(8;21) chromosomal translocation is one of the most common chromosomal translocations associated with acute myeloid leukemia (AML), present in greater than 10% of de novo AML cases. Most of these t(8;21) AML cases are classified as FAB subtype M2. This translocation results in the formation of a stable fusion protein made up of portions of the RUNX1 (aka AML1) and ETO (aka MTG8 and RUNX1T1) proteins. RUNX1 is a transcription factor that is essential for regulating the differentiation of hematopoietic cells, and the fusion protein retains its DNA-binding domain. Additionally, ETO contains four Nervy homology (NH) domains which facilitate a number of protein-protein interactions, notably with the NCOR2/SMRT co-repressor complex. The identification of individual genes or biological pathways which are specifically disrupted in the presence of RUNX1-ETO will provide further molecular insight into the pathogenesis of t(8;21)+ AML and lead to the possibility for improved treatment for these patients. Methods/ResultsWe analyzed publicly available gene expression microarray datasets (Oncomine, TCGA) to search for genes whose expression was significantly altered in the blood of t(8;21)+ AML patients as compared to non-t(8;21) FAB subtype M2 AML and to CD34+ cells in healthy controls. One such gene that was consistently significantly downregulated in t(8;21)+ patients was Ras-association domain family member 2 (RASSF2). RASSF2 is a putative tumor suppressor that is capable of mediating apoptosis (in a Ras dependent manner) through its interactions with the MST1/2 kinases and the cancer-specific apoptotic protein Par-4. RASSF2 has previously been shown to be frequently downregulated via hypermethylation in a wide variety of solid tumors, however little is known about its function in leukemia. Here we demonstrate that RASSF2 is a potentially interesting target for downregulation by the RUNX1-ETO fusion protein. Gene expression analysis by RT-qPCR in leukemia cell lines confirmed that RASSF2 is significantly downregulated in both Kasumi-1 and SKNO t(8;21)+ cell lines as compared to a similar non-t(8;21) HL-60 line. We found that exogenous expression of AML1-ETO in HL-60 leukemia cells induces a rapid downregulation of RASSF2, further supporting that it is a target of this leukemogenic fusion protein. Over-expression of RASSF2 in leukemia cells significantly inhibits their proliferative capability, indicating an important biological effect of RASSF2 in blood cells. Finally, over-expression of RASSF2 significantly inhibits the long-term self-renewal capability of RUNX1-ETO expressing hematopoietic cells as measured by their serial replating ability in a colony formation assay. DiscussionBased on the analysis of patient data and our own experiments it appears that RASSF2 is a direct target for downregulation by the AML1-ETO fusion protein. Due to its potential involvement as a mediator of apoptosis in important oncogenic signaling pathways RASSF2 is a strong candidate for further investigation in the context of t(8;21)+ AML pathogenesis. In particular, it will be interesting to continue to investigate the relationship between RASSF2 and apoptotic protein Par-4, as several lines of evidence suggest Par-4 to be therapeutically relevant due to its ability to selectively induce apoptosis in cancer cells. Disclosures:No relevant conflicts of interest to declare.

L-Asparaginase Sensitivity and Asparagine Synthetase Expression In Primary Tumor Cells From AML Patients

Abstract Introduction The rational of use of L-asparaginase (L-Aspa) is based on asparagine synthetase (ASNS) deficiency in leukemic cells. Its efficacy is due to its capacity to deplete plasmatic asparagine, starving the leukemic cells and subsequently inhibiting protein synthesis. It is a mainstay in the treatment of acute lymphoid leukemia (ALL), where it is established that resistance to treatment is in part related to detectable expression of ASNS (Aslanian et al., 2001; Su et al., 2008). In acute myeloid leukemia (AML), promising results have been obtained in clinical trials (Capizzi et al., 1988), with an improvement of complete remission rates from 18% to 54% in refractory patients &lt;60 year old and from 0% to 31% in refractory patients &gt;60 year old. More recently, it has been reported that leukemic cells from AML patients with M1, M4 and M5 FAB subtypes were more sensitive to L-Aspa (Okada et al., 2003).The aim of this study was to investigate the sensitivity to L-Aspa and the ASNS expression in an AML cell line (HL-60) and in primary leukemic cells from newly diagnosed AML patients. Materials and methods AML (HL-60) and ALL (MOLT-4) cell lines were grown according to ATCC recommendations. Primary leukemic cells from the bone marrow of 24 AML patients (median age: 69 years; range: 2-83) were harvested on EDTA and isolated by Ficoll density gradient within 72h. ASNS expression was determined by western-blot on isolated leukemic cells and expressed as a ratio ASNS/cyclophilin A. When a sufficient amount of leukemic cells was available, sensitivity to L-Aspa (expressed as an IC50 - concentration inhibiting 50% of cell viability) was evaluated in vitro by incubating various concentrations of L-Aspa (0.001 to 10 IU/mL) with the cells and by measuring the cell viability with a counting kit (CCK-8 viability assay) at day 4. Results Determination of IC50 for the HL-60 cell line demonstrated that these cells were equally sensitive to L-Aspa than the ALL cell line MOLT-4 in vitro (0.23 IU/mL versus 0.19 IU/mL, respectively). The expression of ASNS in the HL-60 cell line was low but higher than in MOLT-4 which is a well known ASNS deficient cell line. IC50 determination was possible on 17/24 patients. Seven displayed a high sensitivity to L-Aspa (IC50 &lt; 0.01 IU/mL) whereas 5 displayed a moderate sensitivity (IC50 &lt; 0.5 IU/mL). Remaining 5 patients were resistant to L-Aspa. The cells from the healthy subject were resistant (IC50 &gt; 10 IU/mL). To date, ASNS expression has been evaluated on 16 patients with ratio ranges from 0 to 2.27: six were negative, 4 low positive (&lt; 0.2), and 6 positive (&gt; 0.5, amongst them 4 were &gt; 1). No correlation was observed between ASNS expression and FAB grade. However, patients with blasts sensitive to L-Aspa had mainly M1 or M5 AML. Conclusion AML cell line HL-60 and 71% of primary cells from AML patients were found sensitive to L-Aspa. The sensitivity of cells from M1 and M5 AML patients is consistent with the findings of Okada et al. (2003). Globally, these results suggest that L-Aspa is effective for killing AML cells. Based on the epidemiology of AML subtypes (Selter et al., 2011) and our results, L-Aspa therapy may be beneficial for 50-70% of patients with AML. However, L-Aspa has only been used scarcely in the treatment of AML, mainly because of the commonly observed adverse effects that impair its use. A new formulation of L-Aspa encapsulated in homologous red blood cells was reported with a better safety profile, allowing its use even in elderly patients (Hunault et al., ASH 2012). A clinical study is currently recruiting patients unfit for intensive chemotherapy in order to evaluate its efficacy in combination with low-dose cytarabine (NCT01810705) in AML. In this study, L-Aspa sensitivity and ASNS expression in primary tumor cells at diagnosis will be explored to investigate the relationship with clinical response. Disclosures: Berlier: ERYTECH Pharma: Employment. Aguera:ERYTECH Pharma: Employment. Gallix:ERYTECH Pharma: Employment. Bertrand:ERYTECH Pharma: Principal Investigator Other. Thomas:ERYTECH Pharma: Principal Investigator Other; Orphan Europe: Consultancy. Godfrin:ERYTECH Pharma: Employment, Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.

The B7-H3 Protein In Acute Myeloid Leukemia

IntroductionThe B7 family of costimulatory molecules comprises several members, such as PD-L1 (B7-H1), that may participate in the immunoescape of tumor cells. For instance, the expression of PD-L1 in cancer cells can induce immunotolerance by deactivating T cells in several hematological malignancies, including acute myeloid leukemia (AML) and MDS. The B7-H3 (B7-homolog 3 or CD276) is a type I transmembrane protein and a member of the B7 family. B7-H3 is expressed in many tissues and in antigen-presenting cells. Its functions and counter receptor(s) remain unclear. The expression of the B7-H3 protein by the tumor microenvironment and tumor cells modifies the antitumor immune reaction, tumor growth, metastatic ability and drug resistance. B7-H3 is widely expressed in solid cancers and seems to be a prognostic marker in several tumor types. Clinical grade anti-B7-H3 antibodies are under development. The role of B7-H3 and its expression in AML has not yet been well investigated. We examined the expression of B7-H3 in the blast cells of a cohort of patients with AML to determine whether its expression affected the patients' prognoses. MethodsOur retrospective study included 111 patients (18 children and 93 adults) treated for AML between 2009 and 2011. We measured B7-H3 expression in bone marrow mononuclear cells using multiparameter flow cytometry (CD56, B7-H3, CD34, CD123, CD14, CD38 and CD45). We investigated the correlation of B7-H3 expression with biological, molecular and cytogenetic markers as well as the patient's clinical characteristics. FLT3-ITD, NPM1 and CEBPA mutations were screened by the conventional Sanger methodology according to the ELN recommendations. ResultsB7-H3 expression was low and invariable in lymphocytes and high in monocytes. According to the MFI (Mean Fluorescence Intensity) ratio of blasts/lymphocytes, the B7-H3 expression level in blasts was widely variable (0.80 to 10.38). The threshold retained in our study was 3. Twenty seven percent (30/111) of AML samples were positive, and positive samples primarily included the M5 and M3 FAB subtypes (50% of B7-H3 positive patients). The expression of B7-H3 did not correlate with age (p=0.86), sex (p=0.79), leucocytosis (p=0.38) or NPM1 mutation status (p=0.08). The expression of B7-H3 was significantly higher in adverse karyotypes (p<0.05). The expression of B7-H3 was significantly lower in CEBPA mutations (p<0.05) and tended to be lower in Core Binding Factors AML (p = 0.054). In the 54 adults who were treated with intensive chemotherapy, B7-H3 did not affect the complete remission (CR) rate (81% in B7-H3 negative group, 89% in B7-H3, positive group, p=0.62) or the overall survival (p=0.73). ConclusionB7-H3 is highly expressed in a substantial fraction of AML cases, which suggests that it could serve as a possible therapeutic target. The significant differences in the B7-H3 expression between the different subgroups of AML according to FAB, cytogenetic or CEBPA mutational status should encourage further screening of B7-H3 in a larger prospective cohort of AML patients to obtain definitive conclusions about its prognostic value. Disclosures:Berthon:CELGENE: Research Funding. Preudhomme:CELGENE: Research Funding.

Overexpression of miR-378 is frequent and may affect treatment outcomes in patients with acute myeloid leukemia

MicroRNA miR-378 plays important roles in tumorigenesis by enhancing cell survival, reducing apoptosis, promoting tumor growth, angiogenesis and promoting cell migration and invasion. Abnormal expression of miR-378 has been observed in various types of cancers. The aim of this study was to investigate the expression status of miR-378 and its clinical significance in patients with acute myeloid leukemia (AML) using real-time quantitative PCR. miR-378 overexpression was identified in 26 of 84 (31%) AML patients. The patients with miR-378 overexpression had lower hemoglobin level than those without miR-378 overexpression (66 versus 78g/L, respectively, P=0.010). The frequency of miR-378 overexpression in FAB-M2 subtype was higher than other subtypes (44% versus 20%, P=0.032). Moreover, the frequency of miR-378 overexpression was higher in patients with t(8;21) than in others (64% versus 24%, P=0.012). The status of miR-378 expression was not correlated with the mutations of eight genes (FLT3-ITD, NPM1, C-KIT, IDH1/IDH2, DNMT3A, C/EBPA and U2AF1). The difference in relapse-free survival was observed between patients with and without miR-378 overexpression (P=0.049). These findings suggest that miR-378 up-regulation is a common event and might have an adverse impact on prognosis in AML.

Clinical relevance of thrombospondin receptor (CD36) expression in Egyptian de novo adult acute myeloid leukemia

Background Acute myeloid leukemias (AMLs) are a heterogeneous group of disorders that often present with different morphological, immunophenotypic, and cytogenetic patterns. Identification of these characteristics may be useful for a better prognostic evaluation and for a more appropriate therapeutic approach. CD36 is a transmembrane, highly glycosylated, glycoprotein commonly expressed on blasts in acute monocytic leukemia, megakaryoblastic leukemia, and erythroleukemia. Patients and methods We evaluated CD36 surface expression in 97 newly diagnosed AML patients, and the results were correlated with the morphology, immunophenotype, cytogenetic pattern, and clinical outcome. Results CD36 antigen was recorded in 48 of 97 patients (49.5%) and particularly in those with M5 and M6 FAB subtypes. Moreover, CD36 expression was significantly associated with the expression of CD11b ( P =0.001) and CD14 ( P =0.0001), unfavorable cytogenetic abnormalities ( P =0.001), shorter overall survival ( P >0.0001), and leukemia-free survival ( P =0.03). Conclusion On the basis of the results of the study, it can be concluded that CD36 expression in AML patients may identify a subgroup with a poor prognosis, and may thus be a valuable adjunct to be added to the current prognostic factors.

RNAi Screening Identifies BCL-XL As An Erythroid Lineage-Specific 5-Azacytidine Sensitizer While the BCL-2/BCL-XL/BCL-W Inhibitor ABT-737 Results in More Universal Sensitization in Leukemia Cells,

Abstract 3513To identify targets for rational combination therapies with 5-Azacytidine (5-Aza) in myeloid malignancies, we utilized high-throughput RNA-interference (RNAi) viability screening. A siRNA library targeting 572 kinases and a custom collection of 289 putative cancer targets, including cell cycle and apoptosis regulatory genes, were screened alone and in combination with 5-Aza in TF-1 and ML-2 myeloid leukemia cell lines to identify synergistic interactions in reducing cell viability. Of the 572 kinases that were individually silenced, less than 1% significantly increased sensitivity to 5-Aza. The kinase library was also screened in combination with 5-Aza in a third myeloid cell line, THP-1, confirming that few kinases sensitize to 5-Aza when inhibited. While few kinases sensitized to 5-Aza, the anti-apoptotic Bcl-2 family of genes emerged as potent sensitizers to 5-Aza from RNAi screens. Therefore, silencing by siRNA of BCL-XL, BCL-2, BCL-W, MCL-1 and BFL-1 was evaluated in combination with 5-Aza treatment in an expanded panel of myeloid cell lines including TF-1, HEL, THP-1, ML-2 and MDS-L. BCL-XL validated as a vulnerability and potent sensitizer to 5-Aza in erythroid leukemia cell lines TF-1 and HEL, whereas MCL-1 was a strong vulnerability in the monocytic leukemia cell line THP-1 and also a moderate sensitizer to 5-Aza in ML-2, THP-1, TF-1 and HEL. Published proteomics data from our group indicate that M6 and M7 leukemias exhibit higher levels of BCL-XL, while additional unpublished data suggest elevated levels of MCL-1 in M4 and M5 leukemias, supporting our functional observations. Additionally, data from the public database Oncomine suggest that BCL-XL expression is elevated in M6 and M7 leukemias while MCL-1 shows a trend towards elevation in M4 and M5 leukemias. Based on RNAi screening results, siRNA validation experiments and proteomic/mRNA expression data, we evaluated the BCL-2/BCL-XL/BCL-W inhibitor ABT-737 in combination with 5-Aza. ABT-737 resulted in dose-dependent sensitization to 5-Aza in all AML-derived cell lines examined (including M7, M6, M5, M4 and M2 FAB subtypes) and in the MDS cell line MDS-L; however, no sensitization was observed in the CML cell line K562. In extensive ex vivo experiments with 17 primary specimens, potent synergy between 5-Aza and ABT-737 was observed in AML, MDS and MPN samples, but not in most CML samples examined. Calculations with CalcuSyn software demonstrate synergy, with combination index values as low as 0.2, between 5-Aza and ABT-737 both ex vivo and in vitro. The combination of 5-Aza with ABT-737 resulted in substantial induction of apoptosis, measured by the induction of cleaved caspase 3 in TF-1 and HL-60 cells, as compared to either compound alone. Interestingly, although siRNA silencing of MCL-1 in combination with 5-Aza was potent across several cell lines, and silencing of BCL-XL preferentially in an erythroid differentiation background, ABT-737 with 5-Aza sensitized across a variety of cell lines and all myeloid primary specimens ex vivo. We suggest that inhibition of anti-apoptotic Bcl-2 family members is a most promising rational combination strategy with 5-Aza for the treatment of leukemias. Our results also highlight the potential utility of more specific anti-apoptotic Bcl-2 family inhibitors in the lineage-specific treatment of myeloid malignancies. Disclosures:Off Label Use: AraC in AML. Experimental Agent MK1775. Mesa:Incyte: Research Funding; Lilly: Research Funding; SBio: Research Funding; Astra Zeneca: Research Funding; NS Pharma: Research Funding; Celgene: Research Funding.

The Acetylation of AML1-ETO Is Required for Leukemogenesis.

AbstractAbstract 1588Transcription factors and histones are similarly modified through acetylation, phosphorylation, ubiquitination and methylation, which impact on the transcriptional regulation of gene expression and various biological processes in normal and malignant hematopoiesis. The t(8;21) associated AML1-ETO fusion protein is found in 40% of the FAB M2 subtype of acute myeloid leukemia, but how the post-translational modification of AML1-ETO affects its leukemogenicity is largely unknown. Here we show that AML1-ETO directly interacts with the lysine acetyltransferase, p300, via the region containing NHR1 domain and that p300 can acetylate two lysine residues in AML1-ETO and AML1-ETO (exon 9a) in human and mouse leukemia cells. To understand the biological effects of AML1-ETO acetylation, we used human CD34+ cord blood cells as a preleukemia model. The maintenance of CD34+ cells by the acetylation defective form of AML1-ETO was 5 fold less than with AML1-ETO (p<0.01) in the liquid culture assay, and unlike the effect of AML1-ETO, the number of the cobble stone area forming cells (CAFC) was not increased by the mutant AML1-ETO in CAFC assay. However, the block in erythroid and myeloid differentiation conferred by AML1-ETO was still seen in the AML1-ETO acetylation mutant transduced human CD34+ cells. We then approved the impact of acetylation on leukemogenicity using the AML1-ETO9a (AE9a) mouse leukemia model. Mice receiving AE9a acetylation mutant transduced fetal liver cells have not developed leukemia by Day 250, whereas all the mice receiving AE9a transduced cells died due to leukemia before Day 160, with a mean survival time of 109 days (p<0.001). These results suggest that the acetylation of AML1-ETO is required not only for its self-renewal promoting effects and but also for the development of acute leukemia. To gain insight into the mechanisms of AML1-ETO acetylation, we performed luciferase assays and found that the AML1-ETO acetylation mutant lost the ability to activate an M-CSFR promoter driven reporter construct. Furthermore, the expression levels of AML1-ETO activated target genes related to self-renewal were not upregulated in AML1-ETO acetylation mutant transduced human CD34+ cells. These results indicated that the acetylation is crucial to AML1-ETO induced transcription activation. We have also been studying the role of the region containing NHR1 domain (245 to 430 aa) in AML1-ETO: deletion of this region abrogated the binding of p300 to AML1-ETO and led to loss of AML1-ETO lysine acetylation. Furthermore, loss of the region containing NHR1 domain abrogated the self-renewal properties of AML1-ETO and the activation of AML1-ETO target genes in human CD34+ cord blood cells, without affecting its differentiation-blocking activity or its ability to repress gene expression. Given the importance of the acetylation of AML1-ETO in its biological effects, we inhibited p300 function, chemically and using RNA interference; this blocked the transcriptional activation of AML1-ETO target genes, and inhibited the growth of AML1-ETO expressing AML cells in both pre-leukemic and leukemia models. All together, we have found that the acetylation of AML1-ETO via p300 is indispensable for its leukemia-promoting activity and for its ability to activate gene expression. Our work suggests that inhibition of p300 function may represent an important new anti-leukemia strategy that targets self-renewing, leukemia-initiating cells. Disclosures:No relevant conflicts of interest to declare.