Insight into the molecular pathogenesis of myeloid malignancies

ER Stress and Unfolded Protein Response in Leukemia: Friend, Foe, or Both?

The unfolded protein response (UPR) is an evolutionarily conserved adaptive signaling pathway triggered by a stress of the endoplasmic reticulum (ER) lumen compartment, which is initiated by the accumulation of unfolded proteins. This response, mediated by three sensors-Inositol Requiring Enzyme 1 (IRE1), Activating Transcription Factor 6 (ATF6), and Protein Kinase RNA-Like Endoplasmic Reticulum Kinase (PERK)—allows restoring protein homeostasis and maintaining cell survival. UPR represents a major cytoprotective signaling network for cancer cells, which frequently experience disturbed proteostasis owing to their rapid proliferation in an usually unfavorable microenvironment. Increased basal UPR also participates in the resistance of tumor cells against chemotherapy. UPR activation also occurs during hematopoiesis, and growing evidence supports the critical cytoprotective role played by ER stress in the emergence and proliferation of leukemic cells. In case of severe or prolonged stress, pro-survival UPR may however evolve into a cell death program called terminal UPR. Interestingly, a large number of studies have revealed that the induction of proapoptotic UPR can also strongly contribute to the sensitization of leukemic cells to chemotherapy. Here, we review the current knowledge on the consequences of the deregulation of UPR signaling in leukemias and their implications for the treatment of these diseases.

Circulating microRNA as diagnostic biomarkers for haematological cancers: a systematic review and meta-analysis

Purpose: Recent studies have validated microRNAs (miRNAs) as a diagnostic biomarker for haematological cancers. This study aimed to estimate the overall diagnostic accuracy of circulating miRNAs in haematological malignancies.

Materials and Methods: Multiple databases (Google Scholar, PubMed, EMBASE, Cochrane Library,) were searched until 19^th August 2017.

Results: The meta-analysis included 50 studies from 20 publications. The diagnostic accuracy was assessed by pooled specificity, sensitivity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and area under the curve area (AUC) by random effect model. We used QUADAS (Quality Assessment for diagnostic accuracy studies) to evaluate the quality of the included studies. To perform the meta-analysis, we used Meta-Disk 1.4, Revman 5.3 and Stata 12.0 software. High diagnostic accuracy was demonstrated, with a sensitivity of 0.81, a specificity of 0.85, a PLR of 5.28, an NLR of 0.22, a DOR of 30.39, and an AUC of 0.91. Subgroup analyses showed better outcomes for the African population, combined miRNAs and leukaemia patients compared with other subgroups.

Conclusion: Our results indicated that circulating miRNAs especially combined miRNA can be used as a diagnostic marker in haematological cancers.

Expression of RASSF1A and Cyclin A2 in intrahepatic cholangiocarcinoma

AIM: To detect the expression of RASSF1A and CyclinA2 in intrahepatic cholangiocarcinoma (ICC) and to analyze their relationship with the biological behavior of ICC.

METHODS: Thirty ICC specimens and 18 tumor-adjacent tissue specimens were collected from January 2010 to September 2011 in Department of Hepatobiliary Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology. The expression of RASSF1A and CyclinA2 in these specimens was detected by immunohistochemistry. The relationship between the expression of RASSF1A and CyclinA2 and clinicopathologic parameters of ICC was then analyzed.

RESULTS: The positive rate of expression of RASSF1A in ICC was significantly lower than that in tumor-adjacent tissue (36.67% vs 83.33%, P < 0.05), while the positive rate of expression of Cyclin A2 in ICC was significantly higher than that in tumor-adjacent tissue (73.33% vs 11.11%, P < 0.05). There was a negative correlation between the expression of RASSF1A and that of Cyclin A2 in ICC (P < 0.01, r = 0.54).

CONCLUSION: RASSF1A and CyclinA2 may be involved in the occurrence and development of ICC. Inactivation of RASSF1A may contribute to the invasion and metastasis of ICC. CyclinA2 may play a significant role in the tumor inhibition mechanism mediated by RASSF1A.

Diagnosis and management of acute myeloid leukemia in children and adolescents: recommendations from an international expert panel

Despite major improvements in outcome over the past decades, acute myeloid leukemia (AML) remains a life-threatening malignancy in children, with current survival rates of ∼70%. State-of-the-art recommendations in adult AML have recently been published in this journal by Döhner et al. The primary goal of an international expert panel of the International BFM Study Group AML Committee was to set standards for the management, diagnosis, response assessment, and treatment in childhood AML. This paper aims to discuss differences between childhood and adult AML, and to highlight recommendations that are specific to children. The particular relevance of new diagnostic and prognostic molecular markers in pediatric AML is presented. The general management of pediatric AML, the management of specific pediatric AML cohorts (such as infants) or subtypes of the disease occurring in children (such as Down syndrome related AML), as well as new therapeutic approaches, and the role of supportive care are discussed.

Allogeneic stem cell transplantation in first complete remission

PURPOSE OF REVIEW

The optimal postremission therapy of acute myeloid leukemia (AML) in first complete remission (CR1) is uncertain. This review summarizes the recent developments in the clinical research and therapeutic applications defining the role of allogeneic hematopoietic stem cell transplantation (allo-HCT) in CR1.

RECENT FINDINGS

Molecular markers in combinations with cytogenetics have improved the risk stratification and informed decision-making in patients with AML in CR1. In parallel, several important advances in the transplant field, such as better supportive care, improved transplant technology, increased availability of alternative donors, and reduced-intensity conditioning, have improved the safety as well as access of allo-HCT for a larger number of patients.

SUMMARY

The progress in risk stratification and in transplant technology dictate that early donor identification search should be initiated for all eligible AML patients in CR1.

miR-29a and miR-142-3p downregulation and diagnostic implication in human acute myeloid leukemia

Expression profiling of microRNAs (miRNAs) in most diseases might be popular and provide the possibility for diagnostic implication, but few studies have accurately quantified the expression level of dysregulated miRNAs in acute myeloid leukemia (AML). In this study, we analyzed the peripheral blood mononuclear cells (PBMCs) from 10 AML patients (subtypes M1 to M5) and six normal controls by miRNA microarray and identified several differentially expressed miRNAs. Among them miR-29a and miR-142-3p were selectively encountered in Northern blot analysis and their significantly decreased expression in AML was further confirmed. Quantitative real-time PCR in 52 primarily diagnosed AML patients and 100 normal controls not only verified the expression properties of these 2 miRNAs, but also established that the expression level of miR-142-3p and miR-29a in PBMCs could be used as novel diagnostic markers. A better diagnostic outcome was achieved by combining miR-29a and miR-142-3p with about 90% sensitivity, 100% specificity, and an area under the ROC curve (AUC) of 0.97. Our results provide insights into the involvement of miRNAs in leukemogenesis, and offer candidates for AML diagnosis and therapeutic strategy.

Molecular genetics in acute myeloid leukemia

PURPOSE OF REVIEW

Acute myeloid leukemia (AML) is a highly heterogeneous disorder being composed of various genetically defined subtypes. In recent years, molecular research provided the basis for a more differentiated characterization of AML patients, for example, of the large subgroup with normal karyotypes. This review summarizes the current status of molecular diagnostics in AML and refers to the diagnostic techniques being most suitable for the individual markers.

RECENT FINDINGS

A molecular data set based on mutations of the NPM1, FLT3, and CEBPA genes and the MLL-PTD provides a prognostically relevant risk stratification that can support the decision pro or con an allogeneic hematopoietic stem cell transplantation in first remission. The panel of known molecular markers is continuously increasing, for example, considering the recently described TET2 and IDH1 mutations. The introduction of next generation sequencing will certainly catalyze the molecular characterization of AML. Monitoring of the minimal residual disease load with quantitative real-time PCR can be performed for NPM1 and MLL-PTD-mutated cases.

SUMMARY

Targeted therapy studies with FLT3 inhibitors for patients with FLT3-mutated AML as single agents or combined with chemotherapy illustrate the translation of the molecular techniques into clinical practice already being realized in distinct subgroups of AML.

Comparison of cytogenetic clonal evolution patterns following allogeneic hematopoietic transplantation versus conventional treatment in patients at relapse of AML

Relapse of acute myelogenous leukemia has been associated with clonal cytogenetic evolution, but no study focused specifically on relapse after allogeneic hematopoietic stem cell transplantation (HSCT). We compared karyotypes in 160 patients at both diagnosis and relapse either after allo-HSCT (n = 26) or standard chemotherapy (n = 134) using chromosome banding analysis combined with fluorescein in situ hybridization. There were 71 females and 89 males (19.7-80.6 years). At diagnosis, aberrant karyotypes were more frequent in the HSCT than in the chemotherapy cohort (16 of 26; 61.5% versus 63 of 134; 47.0%). This was most obvious in patients with unfavorable cytogenetics (8 of 26; 30.8% versus 19 of 134; 14.2%; P = .032). Differences in the karyotypes between diagnosis and relapse were more frequent in the allo-cohort (14 of 26; 53.8% versus 49 of 134; 36.6%) than in the conventional cohort (n.s.), mainly because of newly emerging cytogenetic alterations. Appearance of ≥ 3 new clonal alterations was more frequent in the allo-cohort (6 of 12; 50.0% with clonal evolution versus 5 of 41; 12.2%, P = .005). The mean number of cytogenetic alterations per patient was increasing from 2.0 at diagnosis to 4.0 at relapse in the allo-cohort, in the conventionally treated patients from 0.9 to 1.3 (both P < .001). Thus, higher frequencies of clonal evolution and increasing cytogenetic complexity were observed in the stem cell recipients probably related to the more unfavorable cytogenetic profiles already depicted at diagnosis.

Differential expression of specific microRNA and their targets in acute myeloid leukemia

Acute myeloid leukemia (AML) the most common acute leukemia in adults is characterized by various cytogenetic and molecular abnormalities. However, the genetic etiology of the disease is not yet fully understood. MicroRNAs (miRNA) are small noncoding RNAs which regulate the expression of target mRNAs both at transcriptional and translational level. In recent years, miRNAs have been identified as a novel mechanism in gene regulation, which show variable expression during myeloid differentiation. We studied miRNA expression of leukemic blasts of 29 cases of newly diagnosed and genetically defined AML using quantitative reverse transcription polymerase chain reaction (RT-PCR) for 365 human miRNA. We showed that miRNA expression profiling reveals distinctive miRNA signatures that correlate with cytogenetic and molecular subtypes of AML. Specific miRNAs with consolidated role on cell proliferation and differentiation such as miR-155, miR-221, let-7, miR-126 and miR-196b appear to be associated with particular subtypes. We observed a significant differentially expressed miRNA profile that characterizes two subgroups of AML with different mechanism of leukemogenesis: core binding factor (CBF) and cytogenetically normal AML with mutations in the genes of NPM1 and FLT3-ITD. We demonstrated, for the first time, the inverse correlation of expression levels between miRNA and their targets in specific AML genetic groups. We suggest that miRNA deregulation may act as complementary hit in the multisteps mechanism of leukemogenesis offering new therapeutic strategies.

Functional differences between myeloid leukemia-initiating and transient leukemia cells in Down's syndrome

Children with constitutional trisomy 21 or Down's syndrome (DS) are predisposed to develop myeloid leukemia (ML) at a young age. DS-ML is frequently preceded by transient leukemia (TL), a spontaneously resolving accumulation of blasts during the newborn period. Somatic mutations of GATA1 in the blasts of TL and DS-ML likely function as an initiating event. We hypothesized that the phenotypic difference between TL and DS-ML is due to a divergent functional repertoire of the leukemia-initiating cells. Using an NOD/SCID model, we found that cells initiating DS-ML engrafted, disseminated to distant bone marrow sites, and propagated the leukemic clone in secondary recipients. In contrast, TL cells lacked the ability to expand and to migrate, but were able to persist in the recipient bone marrow. We found some evidence of genomic progression with 1 of 9 DS-ML samples and none of 11 TL samples harboring a mutation of N-RAS. The findings of this pilot study provide evidence for the functional impact of second events underlying the transformation of TL into DS-ML and a needed experimental tool for the functional testing of these promoting events.

Molecular genetic pathways as therapeutic targets in acute myeloid leukemia

The heterogeneity of acute myeloid leukemia (AML) results from a complex network of cytogenetic aberrations and molecular mutations. These genetic markers are the basis for the categorization of cases within distinct subgroups and are highly relevant for the prediction of prognosis and for therapeutic decisions in AML. Clinical variances within distinct genetically defined subgroups could in part be linked to the interaction of diverse mutation classes, and the subdivision of normal karyotype AML on the basis of recurrent molecular mutations gains increasing relevance for therapeutic decisions. In parallel to these important insights in the complexity of the genetic networks in AML, a variety of diverse new compounds is being investigated in preclinical and clinical studies. These approaches aim to develop targeted treatment concepts that are based on interference with molecular genetic or epigenetic mechanisms. This review provides an overview on the most relevant genetic markers, which serve as basis for targeted therapy approaches now or might represent options for such approaches in the future, and summarizes recent results of targeted therapy studies.

Distinctive expression of myelomonocytic markers and down-regulation of CD34 in acute myelogenous leukaemia with FLT3 tandem duplication and nucleophosmin mutation

OBJECTIVE

Patients with acute myelogenous leukaemia (AML) show co-existing frequently internal tandem duplications of FLT3 (FLT3-ITD) and mutations of nucleophosmin (NPM1-Mt). We investigated the biological and clinical significance of FLT3-ITD and/or NPM1-Mt in this context.

METHODS

We analysed 89 AML patients according to whether NPM1 and FLT3-ITD were single mutants, double mutants, or wild type for both.

RESULTS

FLT3-ITD was detected in 19 of 89 patients (21.3%), while NPM1-Mt was detected in 19 of 89 patients (21.3%); eight of 89 patients (9.0%) carried both FLT3-ITD and NPM1-Mt. By multivariate analysis, white blood cell count and peripheral blood blast cell count at diagnosis were significantly higher in patients with FLT3-ITD but not in those with only NPM1-Mt. NPM1-Mt was significantly related to female gender, normal karyotype, and M4 or M5 disease according to French-American-British criteria. In addition, leukaemic blast cells with NPM1-Mt, FLT3-ITD, or both expressed CD34 less frequently than wild-type blasts (P < 0.0001 and P = 0.005 respectively), while myelomonocytic markers such as CD11b and CD14 were expressed more frequently in patients with NPM1-Mt.

CONCLUSION

FLT3-ITD may increase potential for cell proliferation to produce a leukaemic population; NPM1-Mt may cause cells to develop along the myelomonocytic lineage. Extensive analyses and detailed experiments will be required to clarify how NPM1 and FLT3 mutations interact in leukaemogenesis.