FAB M4 and high CD14 surface expression is associated with high cellular resistance to Ara-C and daunorubicin: implications for clinical outcome in acute myeloid leukaemia

Monocytic Differentiation in Acute Myeloid Leukemia Cells: Diagnostic Criteria, Biological Heterogeneity, Mitochondrial Metabolism, Resistance to and Induction by Targeted Therapies

We review the importance of monocytic differentiation and differentiation induction in non-APL (acute promyelocytic leukemia) variants of acute myeloid leukemia (AML), a malignancy characterized by proliferation of immature myeloid cells. Even though the cellular differentiation block is a fundamental characteristic, the AML cells can show limited signs of differentiation. According to the French-American-British (FAB-M4/M5 subset) and the World Health Organization (WHO) 2016 classifications, monocytic differentiation is characterized by morphological signs and the expression of specific molecular markers involved in cellular communication and adhesion. Furthermore, monocytic FAB-M4/M5 patients are heterogeneous with regards to cytogenetic and molecular genetic abnormalities, and monocytic differentiation does not have any major prognostic impact for these patients when receiving conventional intensive cytotoxic therapy. In contrast, FAB-M4/M5 patients have decreased susceptibility to the Bcl-2 inhibitor venetoclax, and this seems to be due to common molecular characteristics involving mitochondrial regulation of the cellular metabolism and survival, including decreased dependency on Bcl-2 compared to other AML patients. Thus, the susceptibility to Bcl-2 inhibition does not only depend on general resistance/susceptibility mechanisms known from conventional AML therapy but also specific mechanisms involving the molecular target itself or the molecular context of the target. AML cell differentiation status is also associated with susceptibility to other targeted therapies (e.g., CDK2/4/6 and bromodomain inhibition), and differentiation induction seems to be a part of the antileukemic effect for several targeted anti-AML therapies. Differentiation-associated molecular mechanisms may thus become important in the future implementation of targeted therapies in human AML.

High Mitochondrial Protein Expression as a Potential Predictor of Relapse Risk in Acute Myeloid Leukemia Patients with the Monocytic FAB Subtypes M4 and M5

AML is a highly aggressive and heterogeneous form of hematological cancer. Proteomics-based stratification of patients into more refined subgroups may contribute to a more precise characterization of the patient-derived AML cells. Here, we reanalyzed liquid chromatography-tandem mass spectrometry (LC-MS/MS) generated proteomic and phosphoproteomic data from 26 FAB-M4/M5 patients. The patients achieved complete hematological remission after induction therapy. Twelve of them later developed chemoresistant relapse (RELAPSE), and 14 patients were relapse-free (REL_FREE) long-term survivors. We considered not only the RELAPSE and REL_FREE characteristics but also integrated the French-American-British (FAB) classification, along with considering the presence of nucleophosmin 1 (NPM1) mutation and cytogenetically normal AML. We found a significant number of differentially enriched proteins (911) and phosphoproteins (257) between the various FAB subtypes in RELAPSE patients. Patients with the myeloblastic M1/M2 subtype showed higher levels of RNA processing-related routes and lower levels of signaling related to terms like translation and degranulation when compared with the M4/M5 subtype. Moreover, we found that a high abundance of proteins associated with mitochondrial translation and oxidative phosphorylation, particularly observed in the RELAPSE M4/M5 NPM1 mutated subgroup, distinguishes relapsing from non-relapsing AML patient cells with the FAB subtype M4/M5. Thus, the discovery of subtype-specific biomarkers through proteomic profiling may complement the existing classification system for AML and potentially aid in selecting personalized treatment strategies for individual patients.

(6)-Gingerolinduced myeloid leukemia cell death is initiated by reactive oxygen species and activation of miR-27b expression

The natural polyphenolic alkanone (6)-gingerol (6G) has established anti-inflammatory and antitumoral properties. However, its precise mechanism of action in myeloid leukemia cells is unclear. In this study, we investigated the effects of 6G on myeloid leukemia cells in vitro and in vivo. The results of this study showed that 6G inhibited proliferation of myeloid leukemia cell lines and primary myeloid leukemia cells while sparing the normal peripheral blood mononuclear cells, in a concentration- and time-dependent manner. Mechanistic studies using U937 and K562 cell lines revealed that 6G treatment induced reactive oxygen species (ROS) generation by inhibiting mitochondrial respiratory complex I (MRC I), which in turn increased the expression of the oxidative stress response-associated microRNA miR-27b and DNA damage. Elevated miR-27b expression inhibited PPARγ, with subsequent inhibition of the inflammatory cytokine gene expression associated with the oncogenic NF-κB pathway, whereas the increased DNA damage led to G2/M cell cycle arrest. The 6G induced effects were abolished in the presence of anti-miR-27b or the ROS scavenger N-acetylcysteine. In addition, the results of the in vivo xenograft experiments in mice indicated that 6G treatment inhibited tumor cell proliferation and induced apoptosis, in agreement with the in vitro studies. Our data provide new evidence that 6G-induced myeloid leukemia cell death is initiated by reactive oxygen species and mediated through an increase in miR-27b expression and DNA damage. The dual induction of increased miR-27b expression and DNA damage-associated cell cycle arrest by 6G may have implications for myeloid leukemia treatment.

Reasons for treating secondary AML as de novo AML

In a Danish bi-regional registry-based study, we conducted an analysis of the incidence and clinical importance of secondary acute myeloid leukaemia (AML). In a total of 630 cases of AML, we found 157 (25%) cases of secondary AML. The secondary leukaemia arose from MDS (myelodysplastic syndrome) in 77 cases (49%), CMPD (chronic myeloproliferative disorder) in 43 cases (27%) and was therapy-related AML (t-AML) in 37 cases (24%). Median age at diagnosis of AML was 69 yr in secondary cases when compared to 66 yr in de novo cases (P = 0.006). In univariate analyses, secondary AML was associated with an inferior complete remission (CR) rate (P = 0.008) and poorer overall survival (OS, P = 0.003) whereas in complete remitters, disease-free survival (DFS) of secondary cases was equal to that of de novo cases. Interestingly, in all further analyses of CR-rates, OS and DFS, when correcting for the influence of age, cytogenetic abnormalities, performance status and leucocyte count (WBC), presence of secondary AML completely lost prognostic significance. We conclude that the presence of secondary AML does not per se convey an unfavourable prognosis and that patients with secondary AML should be offered the chance of benefiting from treatment according to current frontline AML protocols.

Induction of gene expression by 5-Aza-2'-deoxycytidine in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) but not epithelial cells by DNA-methylation-dependent and -independent mechanisms

The methylation inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR, decitabine) has therapeutic efficacy in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). Using microarray analysis, we investigated global changes in gene expression after 5-Aza-CdR treatment in AML. In the AML cell line OCI-AML2, Aza-CdR induced the expression of 81 out of 22 000 genes; 96 genes were downregulated (> or =2-fold change in expression). RT-PCR analysis of 10 randomly selected genes confirmed the changes of expression in AML cells. Similar results were obtained with primary AML and MDS cells after treatment with 5-Aza-CdR ex vivo and in vivo, respectively. In contrast, significantly fewer changes in gene expression and cytotoxicity were detected in normal peripheral blood mononuclear and bone marrow cells or transformed epithelial cells treated with 5-Aza-CdR. Interestingly, only 50.6% of the induced genes contain putative CpG islands in the 5' region. To further investigate the significance of promoter methylation in the induced genes, we analyzed the actual methylation status of randomly selected 5-Aza-CdR-inducible genes. We detected hypermethylation exclusively in the 5' region of the myeloperoxidase (MPO) gene. DNA methylation inversely correlated with MPO expression in newly diagnosed untreated AML patients (P< or =0.004). In contrast, all other analyzed 5-Aza-CdR-inducible genes revealed no CpG methylation in the promoter region, suggesting a methylation-independent effect of 5-Aza-CdR.

Evidence for a bimodal relation between serum lysozyme and prognosis in 232 patients with acute myeloid leukaemia

Lysozyme values are sometimes used as an aid for diagnostic subtyping of acute myeloid leukaemia (AML), since monocytic forms often show high levels. We wanted to study if pretreatment serum lysozyme has any relation to prognosis in AML. For this purpose, 232 adult AML patients who had received remission induction therapy at two hospitals were reviewed retrospectively. Their median age was 65.5 yr. Sixty-three patients were FAB classified as "monocytic" AML (M4, M5) and 169 as "non-monocytic" AML (M0, M1, M2, M3, M6). A linear relation was rejected, and a bimodal relation was found between lysozyme and prognosis where values below 20 or above 80 mg L-1 were indicative of better outcome than values in the range 20-80 mg L-1. Analysed in three categories with cut-off levels at 20 and 80 mg L-1, lysozyme showed an independent effect on complete remission (CR) frequency (P = 0.0003), overall survival (P < 0.0001), and CR duration (P = 0.0005) in multivariate analysis. The hazard ratios (HR) for lysozyme <20, 20-80, and >80 mg L-1 regarding overall survival were 1.0, 3.3, and 0.7. Influence of lysozyme on survival was bimodal both in "non-monocytic" AML (HR 1.0, 3.0, and 0.1) and M4-M5 (HR 1.0, 10.1, and 1.2). Our finding of a bimodal relation between serum lysozyme and prognosis in AML should be regarded as a new hypothesis and controlled in other studies.