Autophagy inhibition as a potential future targeted therapy for ETV6-RUNX1-driven B-cell precursor acute lymphoblastic leukemia

The potential role of RNA sequencing in diagnosing unexplained insensitivity to conventional chemotherapy in pediatric patients with B-cell acute lymphoblastic leukemia

Pediatric B-cell acute lymphoblastic leukemia (B-ALL) is a highly heterogeneous disease. According to large-scale RNA sequencing (RNA-seq) data, B-ALL patients can be divided into more than 10 subgroups. However, many genomic defects associated with resistance mechanisms have not yet been identified. As an individual clinical tool for molecular diagnostic risk classification, RNA-seq and gene expression pattern-based therapy could be potential upcoming strategies. In this study, we retrospectively analyzed the RNA-seq gene expression profiles of 45 children whose molecular diagnostic classifications were inconsistent with the response to chemotherapy. The relationship between the transcriptome and chemotherapy response was analyzed. Fusion gene identification was conducted for the included patients who did not have known high-risk associated fusion genes or gene mutations. The most frequently detected fusion gene pair in the high-risk group was the DHRSX duplication, which is a novel finding. Fusions involving ABL1, LMNB2, NFATC1, PAX5, and TTYH3 at onset were more frequently detected in the high-risk group, while fusions involving LFNG, TTYH3, and NFATC1 were frequently detected in the relapse group. According to the pathways involved, the underlying drug resistance mechanism is related to DNA methylation, autophagy, and protein metabolism. Overall, the implementation of an RNA-seq diagnostic system will identify activated markers associated with chemotherapy response, and guide future treatment adjustments.

Targeting autophagy as a therapeutic strategy in pediatric acute lymphoblastic leukemia

Autophagy is activated in response to a variety of stress conditions including anti-cancer therapies, and tumors cells often depend on autophagy for survival. In this study, we have evaluated inhibition of autophagy as therapeutic strategy in acute lymphoblastic leukemia (ALL) in children, both as a single treatment and in combination with glucocorticoid (GC) Dexamethasone (Dexa). Analysis of proteomics and RNA-seq of ALL cell lines and primary samples identified an upregulation of Vps34 and ATG14 proteins and autophagy and lysosomal pathway enrichment in a genetic subgroup with a recurrent t(12;21) translocation. Cells from this sugbroup were also significantly more sensitive to the selective autophagy or lysosomal inhibitors than cells with other genetic rearrangements. Further, combination of Dexa with either lysosomal or autophagy inhibitors was either synergistic or additive in killing leukemic cells across various genetic and lineage backgrounds, for both cell lines and primary samples, as assessed using viability assays and SynergyFinder as well as apoptotic caspase 3/7-based live-cell assays. Our data demonstrate that targeting autophagy represents a promising strategy for the treatment of pediatric ALL, both as a selective modality for the t(12;21) pre-B-ALL subgroup, and in combination treatments to sensitize to GC-induced cytotoxicity.

Novel Biomarkers and Molecular Targets in ALL

PURPOSE OF REVIEW

Acute lymphoblastic leukemia (ALL) is a widely heterogeneous disease in terms of genomic alterations, treatment options, and prognosis. While ALL is considered largely curable in children, adults tend to have higher risk disease subtypes and do not respond as favorably to conventional chemotherapy. Identifying genomic drivers of leukemogenesis and applying targeted therapies in an effort to improve disease outcomes is an exciting focus of current ALL research. Here, we review recent updates in ALL targeted therapy and present promising opportunities for future research.

RECENT FINDINGS

With the utilization of next-generation sequencing techniques, the genomic landscape of ALL has greatly expanded to encompass novel subtypes characterized by recurrent chromosomal rearrangements, gene fusions, sequence mutations, and distinct gene expression profiles. The evolution of small molecule inhibitors and immunotherapies, and the exploration of unique therapy combinations are some examples of recent advancements in the field. Targeted therapies are becoming increasingly important in the treatment landscape of ALL to improve outcomes and minimize toxicity. Significant recent advancements have been made in the detection of susceptible genomic drivers and the use of novel therapies to target them.

The Diverse Roles of ETV6 Alterations in B-Lymphoblastic Leukemia and Other Hematopoietic Cancers

Genetic alterations of the repressive ETS family transcription factor gene ETV6 are recurrent in several categories of hematopoietic malignancy, including subsets of B-cell and T-cell acute lymphoblastic leukemias (B-ALL and T-ALL), myeloid neoplasms, and mature B-cell lymphomas. ETV6 is essential for adult hematopoietic stem cells (HSCs), contributes to specific functions of some mature immune cells, and plays a key role in thrombopoiesis as demonstrated by familial ETV6 mutations associated with thrombocytopenia and predisposition to hematopoietic cancers, particularly B-ALL. ETV6 appears to have a tumor suppressor role in several hematopoietic lineages, as demonstrated by recurrent somatic loss-of-function (LoF) and putative dominant-negative alterations in leukemias and lymphomas. ETV6 rearrangements contribute to recurrent fusion oncogenes such as the B-ALL-associated transcription factor (TF) fusions ETV6::RUNX1 and PAX5::ETV6, rare drivers such as ETV6::NCOA6, and a spectrum of tyrosine kinase gene fusions encoding hyperactive signaling proteins that self-associate via the ETV6 N-terminal pointed domain. Another subset of recurrent rearrangements involving the ETV6 gene locus appear to function primarily to drive overexpression of the partner gene. This review surveys what is known about the biochemical and genome regulatory properties of ETV6 as well as our current understanding of how alterations in these functions contribute to hematopoietic and nonhematopoietic cancers.

Dissecting the Role of Autophagy-Related Proteins in Cancer Metabolism and Plasticity

Modulation of autophagy as an anticancer strategy has been widely studied and evaluated in several cell models. However, little attention has been paid to the metabolic changes that occur in a cancer cell when autophagy is inhibited or induced. In this review, we describe how the expression and regulation of various autophagy-related (ATGs) genes and proteins are associated with cancer progression and cancer plasticity. We present a comprehensive review of how deregulation of ATGs affects cancer cell metabolism, where inhibition of autophagy is mainly reflected in the enhancement of the Warburg effect. The importance of metabolic changes, which largely depend on the cancer type and form part of a cancer cell's escape strategy after autophagy modulation, is emphasized. Consequently, pharmacological strategies based on a dual inhibition of metabolic and autophagy pathways emerged and are reviewed critically here.

Possible mechanism of metabolic and drug resistance with L-asparaginase therapy in childhood leukaemia

L-asparaginase, which hydrolyzes asparagine into aspartic acid and ammonia, is frequently used to treat acute lymphoblastic leukaemia in children. When combined with other chemotherapy drugs, the event-free survival rate is 90%. Due to immunogenicity and drug resistance, however, not all patients benefit from it, restricting the use of L-asparaginase therapy in other haematological cancers. To solve the problem of immunogenicity, several L-ASNase variants have emerged, such as Erwinia-ASNase and PEG-ASNase. However, even when Erwinia-ASNase is used as a substitute for E. coli-ASNase or PEG-ASNase, allergic reactions occur in 3%-33% of patients. All of these factors contributed to the development of novel L-ASNases. Additionally, L-ASNase resistance mechanisms, such as the methylation status of ASNS promoters and activation of autophagy, have further emphasized the importance of personalized treatment for paediatric haematological neoplasms. In this review, we discussed the metabolic effects of L-ASNase, mechanisms of drug resistance, applications in non-ALL leukaemia, and the development of novel L-ASNase.

The Landscape of Secondary Genetic Rearrangements in Pediatric Patients with B-Cell Acute Lymphoblastic Leukemia with t(12;21)

The most frequent chromosomal rearrangement in childhood B-cell acute lymphoblastic leukemia (B-ALL) is translocation t(12;21)(p13;q22). It results in the fusion of the ETV6::RUNX1 gene, which is active in the regulation of multiple crucial cellular pathways. Recent studies hypothesize that many translocations are influenced by RAG-initiated deletions, as well as defects in the RAS and NRAS pathways. According to a "two-hit" model for the molecular pathogenesis of pediatric ETV6::RUNX1-positive B-ALL, the t(12;21) translocation requires leukemia-causing secondary mutations. Patients with ETV6::RUNX1 express up to 60 different aberrations, which highlights the heterogeneity of this B-ALL subtype and is reflected in differences in patient response to treatment and chances of relapse. Most studies of secondary genetic changes have concentrated on deletions of the normal, non-rearranged ETV6 allele. Other predominant structural changes included deletions of chromosomes 6q and 9p, loss of entire chromosomes X, 8, and 13, duplications of chromosome 4q, or trisomy of chromosomes 21 and 16, but the impact of these changes on overall survival remains unclarified. An equally genetically diverse group is the recently identified new B-ALL subtype ETV6::RUNX1-like ALL. In our review, we provide a comprehensive description of recurrent secondary mutations in pediatric B-ALL with t(12;21) to emphasize the value of investigating detailed molecular mechanisms in ETV6::RUNX1-positive B-ALL, both for our understanding of the etiology of the disease and for future clinical advances in patient treatment and management.

ETV6 Deficiency Unlocks ERG-Dependent Microsatellite Enhancers to Drive Aberrant Gene Activation in B-Lymphoblastic Leukemia

Distal enhancers play critical roles in sustaining oncogenic gene-expression programs. We identify aberrant enhancer-like activation of GGAA tandem repeats as a characteristic feature of B-cell acute lymphoblastic leukemia (B-ALL) with genetic defects of the ETV6 transcriptional repressor, including ETV6-RUNX1+ and ETV6-null B-ALL. We show that GGAA repeat enhancers are direct activators of previously identified ETV6-RUNX1+/- like B-ALL "signature" genes, including the likely leukemogenic driver EPOR. When restored to ETV6-deficient B-ALL cells, ETV6 directly binds to GGAA repeat enhancers, represses their acetylation, downregulates adjacent genes, and inhibits B-ALL growth. In ETV6-deficient B-ALL cells, we find that the ETS transcription factor ERG directly binds to GGAA microsatellite enhancers and is required for sustained activation of repeat enhancer-activated genes. Together, our findings reveal an epigenetic gatekeeper function of the ETV6 tumor suppressor gene and establish microsatellite enhancers as a key mechanism underlying the unique gene-expression program of ETV6-RUNX1+/- like B-ALL.

SIGNIFICANCE

We find a unifying mechanism underlying a leukemia subtype-defining gene-expression signature that relies on repetitive elements with poor conservation between humans and rodents. The ability of ETV6 to antagonize promiscuous, nonphysiologic ERG activity may shed light on other roles of these key regulators in hematolymphoid development and human disease. See related commentary by Mercher, p. 2. This article is highlighted in the In This Issue feature, p. 1.

Integrating copy number data of 64 iAMP21 BCP-ALL patients narrows the common region of amplification to 1.57 Mb

Background and purpose

Intrachromosomal amplification of chromosome 21 (iAMP21) is a rare subtype of B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). It is unknown how iAMP21 contributes to leukaemia. The currently known commonly amplified region is 5.1 Mb.

Methods

We aimed to narrow down the common region of amplification by using high resolution techniques. Array comparative genomic hybridization (aCGH) was used to determine copy number aberrations, Affymetrix U133 Plus2 expression arrays were used to determine gene expression. Genome-wide expression correlations were evaluated using Globaltest.

Results

We narrowed down the common region of amplification by combining copy number data from 12 iAMP21 cases with 52 cases from literature. The combined common region of amplification was 1.57 Mb, located from 36.07 to 37.64 Mb (GRCh38). This region is located telomeric from, but not including, RUNX1, which is the locus commonly used to diagnose iAMP21. This narrow region, which falls inside the Down Syndrome critical region, includes 13 genes of which the expression of eight genes was significantly upregulated compared with 143 non-iAMP21 B-other cases. Among these, transcriptional repressor RIPPLY3 (also known as DSCR6) was the highest overexpressed gene (fold change = 4.2, FDR < 0.001) and most strongly correlated (R = 0.58) with iAMP21-related genome-wide expression changes.

Discussion

The more precise definition of the common region of amplification could be beneficial in the diagnosis of iAMP21 based on copy number analysis from DNA sequencing or arrays as well as stimulate functional research into the role of the included genes in iAMP21 biology.

Integrative multi-omics and drug response profiling of childhood acute lymphoblastic leukemia cell lines

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer. Although standard-of-care chemotherapeutics are sufficient for most ALL cases, there are subsets of patients with poor response who relapse in disease. The biology underlying differences between subtypes and their response to therapy has only partially been explained by genetic and transcriptomic profiling. Here, we perform comprehensive multi-omic analyses of 49 readily available childhood ALL cell lines, using proteomics, transcriptomics, and pharmacoproteomic characterization. We connect the molecular phenotypes with drug responses to 528 oncology drugs, identifying drug correlations as well as lineage-dependent correlations. We also identify the diacylglycerol-analog bryostatin-1 as a therapeutic candidate in the MEF2D-HNRNPUL1 fusion high-risk subtype, for which this drug activates pro-apoptotic ERK signaling associated with molecular mediators of pre-B cell negative selection. Our data is the foundation for the interactive online Functional Omics Resource of ALL (FORALL) with navigable proteomics, transcriptomics, and drug sensitivity profiles at https://proteomics.se/forall.

Childhood acute lymphoblastic leukemia is characterised by a range of genetic aberrations. Here, the authors use multi-omics profiling of ALL cell lines to connect molecular phenotypes and drug responses to provide an interactive resource of drug sensitivity.

L-asparaginase mediated therapy in L-asparagine auxotrophic cancers: A review

Microbial L-asparaginase is the most effective first-line therapeutic used in the treatment protocols of paediatric and adult leukemia. Leukemic cell's auxotrophy for L-asparagine is exploited as a therapeutic strategy to mediate cell death through metabolic blockade of L-asparagine using L-asparaginase. Escherichia coli and Erwinia chrysanthemi serve as the major enzyme deriving sources accepted in clinical practise and the enzyme has bestowed improvements in patient outcomes over the last 40 years. However, an array of side effects generated by the native enzymes due to glutamine co-catalysis and short serum stays augmenting frequent dosages, intended a therapeutic switch towards the development of biobetter alternatives for the enzyme including the formulations resulting in sustained local depletion of L-asparagine. In addition, the treatment with L-asparaginase in few cancer types has proven to elicit drug-induced cytoprotective autophagy mechanisms and therefore warrants concern. Although the off-target glutamine hydrolysis has been viewed in contributing the drug-induced secondary responses in cells deficient with asparagine synthetase machinery, the beneficial role of glutaminase-asparaginase in proliferative regulation of asparagine prototrophic cells has been looked forward. The current review provides an overview on the enzyme's clinical applications in leukemia and possible therapeutic implications in other solid tumours, recent advancements in drug formulations, and discusses the aspects of two-sided roles of glutaminase-asparaginases and drug-induced cytoprotective autophagy mechanisms.

ChIP-AP: an integrated analysis pipeline for unbiased ChIP-seq analysis

Chromatin immunoprecipitation coupled with sequencing (ChIP-seq) is a technique used to identify protein–DNA interaction sites through antibody pull-down, sequencing and analysis; with enrichment ‘peak’ calling being the most critical analytical step. Benchmarking studies have consistently shown that peak callers have distinct selectivity and specificity characteristics that are not additive and seldom completely overlap in many scenarios, even after parameter optimization. We therefore developed ChIP-AP, an integrated ChIP-seq analysis pipeline utilizing four independent peak callers, which seamlessly processes raw sequencing files to final result. This approach enables (1) better gauging of peak confidence through detection by multiple algorithms, and (2) more thoroughly surveys the binding landscape by capturing peaks not detected by individual callers. Final analysis results are then integrated into a single output table, enabling users to explore their data by applying selectivity and sensitivity thresholds that best address their biological questions, without needing any additional reprocessing. ChIP-AP therefore presents investigators with a more comprehensive coverage of the binding landscape without requiring additional wet-lab observations.

The Role of Phosphatidylinositol 3-Kinase Catalytic Subunit Type 3 in the Pathogenesis of Human Cancer

Phosphatidylinositol 3-kinase catalytic subunit type 3 (PIK3C3), the mammalian ortholog of yeast vesicular protein sorting 34 (Vps34), belongs to the phosphoinositide 3-kinase (PI3K) family. PIK3C3 can phosphorylate phosphatidylinositol (PtdIns) to generate phosphatidylinositol 3-phosphate (PI3P), a phospholipid central to autophagy. Inhibition of PIK3C3 successfully inhibits autophagy. Autophagy maintains cell survival when modifications occur in the cellular environment and helps tumor cells resist metabolic stress and cancer treatment. In addition, PIK3C3 could induce oncogenic transformation and enhance tumor cell proliferation, growth, and invasion through mechanisms independent of autophagy. This review addresses the structural and functional features, tissue distribution, and expression pattern of PIK3C3 in a variety of human tumors and highlights the underlying mechanisms involved in carcinogenesis. The implications in cancer biology, patient prognosis prediction, and cancer therapy are discussed. Altogether, the discovery of pharmacological inhibitors of PIK3C3 could reveal novel strategies for improving treatment outcomes for PIK3C3-mediated human diseases.

The role of macrophages and osteoclasts in the progression of leukemia

ABSTRACTBone marrow microenvironment provides critical regulatory signals for lineage differentiation and maintenance of HSC quiescence, and these signals also contribute to hematological myeloid malignancies. Macrophages exhibit high phenotypic heterogeneity under both physiological and pathological conditions and are mainly divided into proinflammatory M1 and anti-inflammatory M2 macrophages. Furthermore, osteoclasts are multinucleated giant cells that arise by fusion of monocyte/macrophage-like cells, which are commonly known as bone macrophages. Emerging evidence suggests that macrophages and osteoclasts originating from myeloid progenitors lead to two competing differentiation outcomes, and they appear to play an important role in the onset, progression, and bone metastasis of solid cancers. However, little is known about their role in the development of hematological malignancies. In this review, we focus on macrophages and osteoclasts, their role in leukemia, and the potential for targeting these cells in this disease.

Autophagy and Metabolism in Normal and Malignant Hematopoiesis

The hematopoietic system relies on regulation of both metabolism and autophagy to maintain its homeostasis, ensuring the self-renewal and multipotent differentiation potential of hematopoietic stem cells (HSCs). HSCs display a distinct metabolic profile from that of their differentiated progeny, while metabolic rewiring from glycolysis to oxidative phosphorylation (OXPHOS) has been shown to be crucial for effective hematopoietic differentiation. Autophagy-mediated regulation of metabolism modulates the distinct characteristics of quiescent and differentiating hematopoietic cells. In particular, mitophagy determines the cellular mitochondrial content, thus modifying the level of OXPHOS at the different differentiation stages of hematopoietic cells, while, at the same time, it ensures the building blocks and energy for differentiation. Aberrations in both the metabolic status and regulation of the autophagic machinery are implicated in the development of hematologic malignancies, especially in leukemogenesis. In this review, we aim to investigate the role of metabolism and autophagy, as well as their interconnections, in normal and malignant hematopoiesis.

Identification of functional cooperative mutations of GNAO1 in human acute lymphoblastic leukemia

Leukemogenesis is characterized by chromosomal rearrangements with additional molecular disruptions, yet the cooperative mechanisms are still unclear. Using whole-exome sequencing of a pair of monozygotic twins who were discordant for childhood acute lymphoblastic leukemia (ALL) with ETV6-RUNX1 (E/R) gene fusion successively after birth, we identified the R209C mutation of G protein subunit α o1 (GNAO1) as a new ALL risk loci. Moreover, GNAO1 missense mutations are recurrent in ALL patients and are associated with E/R fusion. Ectopic expression of the GNAO1 R209C mutant increased its GTPase activity and promoted cell proliferation and cell neoplastic transformation. Combined with the E/R fusion, the GNAO1 R209C mutation promoted leukemogenesis through activating PI3K/Akt/mTOR signaling. Reciprocally, activated mTORC1 phosphorylated p300 acetyltransferase, which acetylated E/R and thereby enhanced the E/R transcriptional activity of GNAO1 R209C. Thus, our study provides clinical evidence of the functional cooperation of GNAO1 mutations and E/R fusion, suggesting GNAO1 as a therapeutic target in human leukemia.

Amino Acid Metabolic Vulnerabilities in Acute and Chronic Myeloid Leukemias

Amino acid (AA) metabolism plays an important role in many cellular processes including energy production, immune function, and purine and pyrimidine synthesis. Cancer cells therefore require increased AA uptake and undergo metabolic reprogramming to satisfy the energy demand associated with their rapid proliferation. Like many other cancers, myeloid leukemias are vulnerable to specific therapeutic strategies targeting metabolic dependencies. Herein, our review provides a comprehensive overview and TCGA data analysis of biosynthetic enzymes required for non-essential AA synthesis and their dysregulation in myeloid leukemias. Furthermore, we discuss the role of the general control nonderepressible 2 (GCN2) and-mammalian target of rapamycin (mTOR) pathways of AA sensing on metabolic vulnerability and drug resistance.

Role of Autophagy and Apoptosis in Acute Lymphoblastic Leukemia

Background:

Acute lymphoblastic leukemia (ALL) is a malignant disease characterized by an excessive number of immature lymphocytes, including immature precursors of both B- and T cells. ALL affects children more often than adults. Immature lymphocytes lead to arrested differentiation and proliferation of cells. Its conventional treatments involve medication with dexamethasone, vincristine, and other anticancer drugs. Although the current first-line drugs can achieve effective treatment, they still cannot prevent the recurrence of some patients with ALL. Treatments have high risk of recurrence especially after the first remission. Currently, novel therapies to treat ALL are in need. Autophagy and apoptosis play important roles in regulating cancer development. Autophagy involves degradation of proteins and organelles, and apoptosis leads to cell death. These phenomena are crucial in cancer progression. Past studies reported that many potential anticancer agents regulate intracellular signaling pathways.

Methods:

The authors discuss the recent research findings on the role of autophagy and apoptosis in ALL.

Results:

The autophagy and apoptosis are widely used in the treatment of ALL. Most studies showed that many agents regulate autophagy and apoptosis in ALL cell models, clinical trials, and ALL animal models.

Conclusions:

In summary, activating autophagy and apoptosis pathways are the main strategies for ALL treatments. For ALL, combining new drugs with traditional chemotherapy and glucocorticoids treatments can achieve the greatest therapeutic effect by activating autophagy and apoptosis.

Amino Acid Degrading Enzymes and Autophagy in Cancer Therapy

Recently, there has been renewed interest in metabolic therapy for cancer, particularly in amino acid deprivation by enzymes. L-asparaginase was approved for the treatment of acute lymphoblastic leukemia by the U.S. Food and Drug Administration. Arginine deiminase and recombinant human arginase have been developed into clinical trials as potential cancer therapeutic agents for the treatment of arginine-auxotrophic tumors. Moreover, other novel amino acid degrading enzymes, such as glutaminase, methionase, lysine oxidase, phenylalanine ammonia lyase, have been developed for the treatment of malignant cancers. One of the greatest obstacles faced by anticancer drugs is the development of drug resistance, which is reported to be associated with autophagy. Autophagy is an evolutionarily conserved catabolic process that is responsible for the degradation of dysfunctional proteins and organelles. There is a growing body of literature revealing that, in response to metabolism stress, autophagy could be induced by amino acid deprivation. The manipulation of autophagy in combination with amino acid degrading enzymes is actively being investigated as a potential therapeutic approach in preclinical studies. Importantly, shedding light on how autophagy fuels tumor metabolism during amino acid deprivation will enable more potential combinational therapeutic strategies. This study summarizes recent advances, discussing several potential anticancer enzymes, and highlighting the promising combined therapeutic strategy of amino acid degrading enzymes and autophagy modulators in tumors

[Clinical significance of minimal residual disease in B-lineage acute lymphoblastic leukemia pediatric patients with different fusion gene backgrounds]

OBJECTIVE

To study the clinical significance of minimal residual disease (MRD) in B-lineage acute lymphoblastic leukemia (B-ALL) pediatric patients with different fusion gene backgrounds.

METHODS

A retrospective analysis was performed on the medical data of 441 B-ALL children who were treated from January 2008 to April 2015. Among the 441 children, 336 had negative fusion gene, 79 had positive ETV6-RUNX1 fusion gene, and 26 had positive E2A-PBX1 fusion gene. Flow cytometry was used to detect MRD, and the influence of MRD on day 15 (TP1), day 33 (TP2), and week 12 (TP3) of induction therapy on prognosis was analyzed.

RESULTS

In patients with negative fusion gene, the positive MRD group had significantly lower overall survival (OS) rate and event-free survival (EFS) rate (P < 0.05) and significantly higher recurrence rate and mortality rate at TP1, TP2, and TP3, compared with the negative MRD group (P < 0.05). In patients with positive ETV6-RUNX1, the positive MRD group had significantly lower OS and EFS rates (P < 0.05) and significantly higher recurrence rate and mortality rate (P < 0.05) than the negative MRD group only at TP1. In patients with positive E2A-PBX1, there were no significant differences in the OS rate, recurrence rate, and mortality rate between the positive and negative MRD groups at TP1, TP2, and TP3 (P > 0.05).

CONCLUSIONS

MRD has the most definite prognostic significance in pediatric B-ALL patients with negative fusion gene, while it has unsatisfactory prognostic significance in those with positive ETV6-RUNX1 or positive E2A-PBX1.

Single cell characterization of B-lymphoid differentiation and leukemic cell states during chemotherapy in ETV6-RUNX1-positive pediatric leukemia identifies drug-targetable transcription factor activities

BACKGROUND

Tight regulatory loops orchestrate commitment to B cell fate within bone marrow. Genetic lesions in this gene regulatory network underlie the emergence of the most common childhood cancer, acute lymphoblastic leukemia (ALL). The initial genetic hits, including the common translocation that fuses ETV6 and RUNX1 genes, lead to arrested cell differentiation. Here, we aimed to characterize transcription factor activities along the B-lineage differentiation trajectory as a reference to characterize the aberrant cell states present in leukemic bone marrow, and to identify those transcription factors that maintain cancer-specific cell states for more precise therapeutic intervention.

METHODS

We compared normal B-lineage differentiation and in vivo leukemic cell states using single cell RNA-sequencing (scRNA-seq) and several complementary genomics profiles. Based on statistical tools for scRNA-seq, we benchmarked a workflow to resolve transcription factor activities and gene expression distribution changes in healthy bone marrow lymphoid cell states. We compared these to ALL bone marrow at diagnosis and in vivo during chemotherapy, focusing on leukemias carrying the ETV6-RUNX1 fusion.

RESULTS

We show that lymphoid cell transcription factor activities uncovered from bone marrow scRNA-seq have high correspondence with independent ATAC- and ChIP-seq data. Using this comprehensive reference for regulatory factors coordinating B-lineage differentiation, our analysis of ETV6-RUNX1-positive ALL cases revealed elevated activity of multiple ETS-transcription factors in leukemic cells states, including the leukemia genome-wide association study hit ELK3. The accompanying gene expression changes associated with natural killer cell inactivation and depletion in the leukemic immune microenvironment. Moreover, our results suggest that the abundance of G1 cell cycle state at diagnosis and lack of differentiation-associated regulatory network changes during induction chemotherapy represent features of chemoresistance. To target the leukemic regulatory program and thereby overcome treatment resistance, we show that inhibition of ETS-transcription factors reduced cell viability and resolved pathways contributing to this using scRNA-seq.

CONCLUSIONS

Our data provide a detailed picture of the transcription factor activities characterizing both normal B-lineage differentiation and those acquired in leukemic bone marrow and provide a rational basis for new treatment strategies targeting the immune microenvironment and the active regulatory network in leukemia.

ETV6 gene aberrations in non-haematological malignancies: A review highlighting ETV6 associated fusion genes in solid tumors

ETV6 (translocation-Ets-leukemia virus) gene is a transcriptional repressor mainly involved in haematopoiesis and maintenance of vascular networks and has developed to be a major oncogene with the potential ability of forming fusion partners with many other genes with carcinogenic consequences. ETV6 fusions function primarily by constitutive activation of kinase activity of the fusion partners, modifications in the normal functions of ETV6 transcription factor, loss of function of ETV6 or the partner gene and activation of a proto-oncogene near the site of translocation. The role of ETV6 fusion gene in tumorigenesis has been well-documented and more variedly found in haematological malignancies. However, the role of the ETV6 oncogene in solid tumors has also risen to prominence due to an increasing number of cases being reported with this malignancy. Since, solid tumors can be well-targeted, the diagnosis of this genre of tumors based on ETV6 malignancy is of crucial importance for treatment. This review highlights the important ETV6 associated fusions in solid tumors along with critical insights as to existing and novel means of targeting it. A consolidation of novel therapies such as immune, gene, RNAi, stem cell therapy and protein degradation hitherto unused in the case of ETV6 solid tumor malignancies may open further therapeutic avenues.

Observation of the molecular genetics among children with acute lymphoblastic leukemia: A retrospective study based on the SEER database

Acute lymphoblastic leukemia (ALL) is one of the most common malignancies of the hematologic system in children. Typically, ALL children with various genetic changes show different incidences, development, and prognoses. This study aimed to analyze the incidence of molecular genetic subtype among ALL children based on their clinical information, and to further investigate the relationship of genetic varieties with the prognostic factors.From 2010 to 2016, a total of 888 ALL children with TEL-AML1 fusion gene, hyperdiploidy, hypodiloidy, IL3-IGH rearranged, E2A PBX1 fusion gene, BCR-ABL1 fusion gene, or mixed lineage leukemia (MML) rearranged were selected and analyzed through the Surveillance, Epidemiology, and End Results database.Our results suggested that, ALL children who lived in the Northern Plains were more likely to experience genetic varieties. In addition, the TEL-AML1 fusion gene, hyperdiploidy, and hypodiloidy were more likely to be detected in ALL children aged 1 to 9 years, while MLL rearrangement was probably detected among ALL children aged <1 year. On the other hand, the 5-year overall survival varied depending on different regions (East: 42.21%; Alaska: 0.001%; Northern Plains: 1.8%; Pacific Coast: 16.3%; and Southwest: 8%), races (African American: 44.5%; white: 18.2%; and Other: 16.3%), and genetic features (TEL-AML1: 10.1%; hyperdiploidy: 19.4%; hypodiloidy: 64.7%; IL3-IGH: 0.01%; E2A PBX1: 14.2%; BCR-ABL1: 15.2%; MLL rearranged: 12.3%).In conclusion, our study found that genetic varieties among ALL children were closely related to their prognoses, and the detection rate of genetic molecules was associated with the age, race, and living area of children.

Regulation of Small GTPase Rab20 by Ikaros in B-Cell Acute Lymphoblastic Leukemia

Ikaros is a DNA-binding protein that regulates gene expression and functions as a tumor suppressor in B-cell acute lymphoblastic leukemia (B-ALL). The full cohort of Ikaros target genes have yet to be identified. Here, we demonstrate that Ikaros directly regulates expression of the small GTPase, Rab20. Using ChIP-seq and qChIP we assessed Ikaros binding and the epigenetic signature at the RAB20 promoter. Expression of Ikaros, CK2, and RAB20 was determined by qRT-PCR. Overexpression of Ikaros was achieved by retroviral transduction, whereas shRNA was used to knockdown Ikaros and CK2. Regulation of transcription from the RAB20 promoter was analyzed by luciferase reporter assay. The results showed that Ikaros binds the RAB20 promoter in B-ALL. Gain-of-function and loss-of-function experiments demonstrated that Ikaros represses RAB20 transcription via chromatin remodeling. Phosphorylation by CK2 kinase reduces Ikaros’ affinity toward the RAB20 promoter and abolishes its ability to repress RAB20 transcription. Dephosphorylation by PP1 phosphatase enhances both Ikaros’ DNA-binding affinity toward the RAB20 promoter and RAB20 repression. In conclusion, the results demonstrated opposing effects of CK2 and PP1 on expression of Rab20 via control of Ikaros’ activity as a transcriptional regulator. A novel regulatory signaling network in B-cell leukemia that involves CK2, PP1, Ikaros, and Rab20 is identified.

ETV6/RUNX1 Fusion Gene Abrogation Decreases the Oncogenicity of Tumour Cells in a Preclinical Model of Acute Lymphoblastic Leukaemia

BACKGROUND

The t(12;21)(p13;q22), which fuses ETV6 and RUNX1 genes, is the most common genetic abnormality in children with B-cell precursor acute lymphoblastic leukaemia. The implication of the fusion protein in leukemogenesis seems to be clear. However, its role in the maintenance of the disease continues to be controversial.

METHODS

Generation of an in vitroETV6/RUNX1 knock out model using the CRISPR/Cas9 gene editing system. Functional characterization by RNA sequencing, proliferation assays, apoptosis and pharmacologic studies, and generation of edited-cell xenograft model.

RESULTS

The expression of ETV6/RUNX1 fusion gene was completely eliminated, thus generating a powerful model on which to study the role of the fusion gene in leukemic cells. The loss of fusion gene expression led to the deregulation of biological processes affecting survival such as apoptosis resistance and cell proliferation capacity. Tumour cells showed higher levels of apoptosis, lower proliferation rate and a greater sensitivity to PI3K inhibitors in vitro along as a decrease in tumour growth in xenografts models after ETV6/RUNX1 fusion gene abrogation.

CONCLUSIONS

ETV6/RUNX1 fusion protein seems to play an important role in the maintenance of the leukemic phenotype and could thus become a potential therapeutic target.

ZBTB46, SPDEF, and ETV6: Novel Potential Biomarkers and Therapeutic Targets in Castration-Resistant Prostate Cancer

Prostate cancer (PCa) is the second most common killer among men in Western countries. Targeting androgen receptor (AR) signaling by androgen deprivation therapy (ADT) is the current therapeutic regime for patients newly diagnosed with metastatic PCa. However, most patients relapse and become resistant to ADT, leading to metastatic castration-resistant PCa (CRPC) and eventually death. Several proposed mechanisms have been proposed for CRPC; however, the exact mechanism through which CRPC develops is still unclear. One possible pathway is that the AR remains active in CRPC cases. Therefore, understanding AR signaling networks as primary PCa changes into metastatic CRPC is key to developing future biomarkers and therapeutic strategies for PCa and CRPC. In the current review, we focused on three novel biomarkers (ZBTB46, SPDEF, and ETV6) that were demonstrated to play critical roles in CRPC progression, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) drug resistance, and the epithelial-to-mesenchymal transition (EMT) for patients treated with ADT or AR inhibition. In addition, we summarize how these potential biomarkers can be used in the clinic for diagnosis and as therapeutic targets of PCa.

Current Outlook on Autophagy in Human Leukemia: Foe in Cancer Stem Cells and Drug Resistance, Friend in New Therapeutic Interventions

Autophagy is an evolutionarily conserved cellular recycling process in cell homeostasis and stress adaptation. It confers protection and promotes survival in response to metabolic/environmental stress, and is upregulated in response to nutrient deprivation, hypoxia, and chemotherapies. Autophagy is also known to sustain malignant cell growth and contributes to cancer stem cell survival when challenged by cytotoxic and/or targeted therapies, a potential mechanism of disease persistence and drug resistance that has gathered momentum. However, different types of human leukemia utilize autophagy in complex, context-specific manners, and the molecular and cellular mechanisms underlying this process involve multiple protein networks that will be discussed in this review. There is mounting preclinical evidence that targeting autophagy can enhance the efficacy of cancer therapies. Chloroquine and other lysosomal inhibitors have spurred initiation of clinical trials and demonstrated that inhibition of autophagy restores chemosensitivity of anticancer drugs, but with limited autophagy-dependent effects. Intriguingly, several autophagy-specific inhibitors, with better therapeutic indexes and lower toxicity, have been developed. Promising preclinical studies with novel combination approaches as well as potential challenges to effectively eradicate drug-resistant cells, particularly cancer stem cells, in human leukemia are also detailed in this review.