Targeting Chromatin Complexes in Myeloid Malignancies and Beyond: From Basic Mechanisms to Clinical Innovation

The aberrant function of chromatin regulatory networks (epigenetics) is a hallmark of cancer promoting oncogenic gene expression. A growing body of evidence suggests that the disruption of specific chromatin-associated protein complexes has therapeutic potential in malignant conditions, particularly those that are driven by aberrant chromatin modifiers. Of note, a number of enzymatic inhibitors that block the catalytic function of histone modifying enzymes have been established and entered clinical trials. Unfortunately, many of these molecules do not have potent single-agent activity. One potential explanation for this phenomenon is the fact that those drugs do not profoundly disrupt the integrity of the aberrant network of multiprotein complexes on chromatin. Recent advances in drug development have led to the establishment of novel inhibitors of protein–protein interactions as well as targeted protein degraders that may provide inroads to longstanding effort to physically disrupt oncogenic multiprotein complexes on chromatin. In this review, we summarize some of the current concepts on the role epigenetic modifiers in malignant chromatin states with a specific focus on myeloid malignancies and recent advances in early-phase clinical trials.

Trio-WES reveals a novel de novo missense mutation of KMT2A in a Chinese patient with Wiedemann-Steiner syndrome: A case report

BACKGROUND

Wiedemann-Steiner Syndrome (WSS) is an autosomal dominant genetic condition caused by mutations in the KMT2A gene. Lysine methyltransferase, encoded by KMT2A, plays critical roles in the regulation of gene expression during early development.

METHODS

Trio-based whole exome sequencing (Trio-WES) was performed on a 15 months old Chinese girl and her two parents by MyGenostics (Beijing, China) using the Illumina HiSeq X ten system. Variants were confirmed with Sanger sequencing. She exhibited mild/moderate intellectual disability (ID), hypotonia, hypertrichosis cubiti, hypertrichosis on the back, dysmorphic facies, psychomotor retardation, growth delay, small and puffy hands, fat pads anterior to calcanei, and palmar/plantar grooves.

RESULTS

Trio-WES revealed a novel de novo mutation of KMT2A gene (NM_001197104.1: c.3566G>T, p.Cys1189Phe). WSS was diagnosed based on WES and clinical features.

CONCLUSION

Our findings expand the phenotypic and mutation spectra of WSS.

Wiedemann-Steiner Syndrome as a Differential Diagnosis of Cornelia de Lange Syndrome Using Targeted Next-Generation Sequencing: A Case Report

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant disorder with a variable clinical phenotype including synophrys, hypertelorism, thick eyebrows, long eyelashes, wide nasal bridge, long philtrum, hypertrichosis, growth retardation, and intellectual disability. Cornelia de Lange syndrome (CdLS) is a rare disease characterized by synophrys, long eyelashes, limb abnormalities, generalized hirsutism, growth retardation, and intellectual disability. In both WDSTS and CdLS, the malformations are due to transcriptome disturbance caused by defects in the genes encoding the components of chromatin regulation and transcription process. The overlapping features in these two syndromes may complicate the original diagnosis of a patient. Here, we report on a Wiedemann-Steiner patient found to have a de novo pathogenic KMT2A variation who had been clinically suspected as CdLS. We suggest that targeted next-generation sequencing is a feasible tool for the precise diagnosis of patients who have phenotypically and clinically overlapping features of CdLS and WDSTS.

Decitabine mildly attenuates MLL-rearranged acute lymphoblastic leukemia in vivo, and represents a poor chemo-sensitizer

MLL-rearranged acute lymphoblastic leukemia (ALL) represents a highly aggressive ALL subtype, characterized by aberrant DNA methylation patterns. DNA methyltransferase inhibitors, such as decitabine have previously been demonstrated to be effective in eradicating MLL-rearranged ALL cells in vitro. Here, we assessed the in vivo anti-leukemic potential of low-dose DNA methyltransferase inhibitor decitabine using a xenograft mouse model of human MLL-rearranged ALL. Furthermore, we explored whether prolonged exposure to low-dose decitabine could chemo-sensitize MLL-rearranged ALL cells toward conventional chemotherapy as well as other known epigenetic-based and anti-neoplastic compounds. Our data reveal that decitabine prolonged survival in xenograft mice of MLL-rearranged ALL by 8.5 days (P = .0181), but eventually was insufficient to prevent leukemia out-growth, based on the examination of the MLLAF4 cell line SEM. Furthermore, we observe that prolonged pretreatment of low-dose decitabine mildly sensitized toward the conventional drugs prednisolone, vincristine, daunorubicin, asparaginase, and cytarabine in a panel of MLL-rearranged cell lines. Additionally, we assessed synergistic effects of decitabine with other epigenetic-based or anticancer drugs using high-throughput drug library screens. Validation of the top hits, including histone deacetylase inhibitor panobinostat, BCL2 inhibitor Venetoclax, MEK inhibitor pimasertib, and receptor tyrosine kinase foretinib, revealed additive and moderate synergistic effects for the combination of each drug together with decitabine in a cell line-dependent manner.

Identification of a novel KMT2A/GIMAP8 gene fusion in a pediatric patient with acute undifferentiated leukemia

Acute undifferentiated leukemia (AUL) is a very rare hematologic neoplasm that expresses no markers specific for either myeloid or lymphoid lineages. While commonly observed in several acute leukemias, KMT2A rearrangements in AUL have been rarely reported in the literature. We report the third case to our knowledge of AUL harboring a KMT2A rearrangement. Furthermore, the KMT2A/GIMAP8 gene fusion identified in this case represents a novel KMT2A rearrangement.

Expanding the phenotype of Wiedemann-Steiner syndrome: Craniovertebral junction anomalies

Wiedemann-Steiner syndrome (WDSTS) is a rare autosomal dominant condition caused by heterozygous loss of function variants in the KMT2A (MLL) gene, encoding a lysine N-methyltransferase that mediates a histone methylation pattern specific for epigenetic transcriptional activation. WDSTS is characterized by a distinctive facial phenotype, hypertrichosis, short stature, developmental delay, intellectual disability, congenital malformations, and skeletal anomalies. Recently, a few patients have been reported having abnormal skeletal development of the cervical spine. Here we describe 11 such individuals, all with KMT2A de novo loss-of-function variants: 10 showed craniovertebral junction anomalies, while an 11th patient had a cervical abnormality in C7. By evaluating clinical and diagnostic imaging data we characterized these anomalies, which consist primarily of fused cervical vertebrae, C1 and C2 abnormalities, small foramen magnum and Chiari malformation type I. Craniovertebral anomalies in WDSTS patients have been largely disregarded so far, but the increasing number of reports suggests that they may be an intrinsic feature of this syndrome. Specific investigation strategies should be considered for early identification and prevention of craniovertebral junction complications in WDSTS patients.

Mutational landscape and clinical outcome of patients with de novo acute myeloid leukemia and rearrangements involving 11q23/KMT2A

Balanced rearrangements involving the KMT2A gene, located at 11q23, are among the most frequent chromosome aberrations in acute myeloid leukemia (AML). Because of numerous fusion partners, the mutational landscape and prognostic impact of specific 11q23/KMT2A rearrangements are not fully understood. We analyzed clinical features of 172 adults with AML and recurrent 11q23/KMT2A rearrangements, 141 of whom had outcome data available. We compared outcomes of these patients with outcomes of 1,097 patients without an 11q23/KMT2A rearrangement categorized according to the 2017 European LeukemiaNet (ELN) classification. Using targeted next-generation sequencing, we investigated the mutational status of 81 leukemia/cancer-associated genes in 96 patients with 11q23/KMT2A rearrangements with material for molecular studies available. Patients with 11q23/KMT2A rearrangements had a low number of additional gene mutations (median, 1; range 0 to 6), which involved the RAS pathway (KRAS, NRAS, and PTPN11) in 32% of patients. KRAS mutations occurred more often in patients with t(6;11)(q27;q23)/KMT2A-AFDN compared with patients with the other 11q23/KMT2A subsets. Specific gene mutations were too infrequent in patients with specific 11q23/KMT2A rearrangements to assess their associations with outcomes. We demonstrate that younger (age <60 y) patients with t(9;11)(p22;q23)/KMT2A-MLLT3 had better outcomes than patients with other 11q23/KMT2A rearrangements and those without 11q23/KMT2A rearrangements classified in the 2017 ELN intermediate-risk group. Conversely, outcomes of older patients (age ≥60 y) with t(9;11)(p22;q23) were poor and comparable to those of the ELN adverse-risk group patients. Our study shows that patients with an 11q23/KMT2A rearrangement have distinct mutational patterns and outcomes depending on the fusion partner.

Acute myeloid leukemia with 11q23 rearrangements: A study of therapy-related disease and therapeutic outcomes

We described the clinical features and outcomes for 63 adult patients with acute myeloid leukemia (AML) with a translocation involving the 11q23 locus (MLL) who were treated at Memorial Sloan Kettering Cancer Center (MSK). The population included 40 female (63 %) and 23 male (37 %) patients, with a median age of 51 years old (range 18-82 years). Of the 31 patients who had had an antecedent malignancy, 14 (45 %) had had breast cancer or DCIS and 22 (71 %) had received anthracycline-based systemic chemotherapy. The translocation partner for the 11q23 rearrangement was identified in 60 of the 63 patients (95 %) studied. The distribution of translocation partners differed for those who had previously received cytotoxic chemotherapy. Most patients with therapy-related disease had a 9p22 or 19p13 partner, as compared to those with de novo disease (95 % vs. 68 %, p = 0.023). Of the 30 patients who received all therapy under observation, 15 (50 %) patients had de novo disease and 15 (50 %) had received antecedent chemotherapy. No significant difference in survival was observed between groups (p = 0.44). Twenty-two patients received induction as up-front therapy, of whom 11 (50 %) achieved CR / CRi. The achievement of CR / CRi with one course of induction was associated with improved OS, with a 6-month OS of 73 % as compared to 23 % for those who did not (p = 0.018). The achievement of CR / CRi with a single course of induction may be a marker of favorable survival in this subtype of high-risk AML. KEY POINT: Response to a single induction was associated with favorable survival in this population.

Detection of leukemia gene fusions by targeted RNA-sequencing in routine diagnostics

BACKGROUND

We have evaluated an NGS-based method to detect recurrent gene fusions of diagnostic and prognostic importance in hematological malignancies. Our goal was to achieve a highly specific assay with a simple workflow, short turnaround time and low cost.

METHOD

The assay uses a commercially available anchored multiplex PCR panel for target enrichment and library preparation, followed by sequencing using a MiSeq instrument. The panel includes all recurrent gene fusions in AML and ALL and is designed to detect gene-specific fusions without prior knowledge of the partner sequence or specific break points. Diagnostic RNA samples from 27 cases with hematological malignancies encompassing 23 different transcript variants were analyzed. In addition, 12 cases from a validation cohort were assessed.

RESULT

All known fusion transcripts were identified with a high degree of confidence, with a large number of reads covering the breakpoints. Importantly, we could identify gene fusions where conventional methods had failed due to cryptic rearrangements or rare fusion partners. The newly-identified fusion partners were verified by RT-PCR and transcript-specific qPCR was designed for patient-specific follow-up. In addition, 12 cases were correctly assessed in a blind test, without prior knowledge of molecular cytogenetics or diagnosis.

CONCLUSION

In summary, our results demonstrate that targeted RNA sequencing using anchored multiplex PCR can be implemented in a clinical laboratory for the detection of recurrent and rare gene fusions in hematological diagnostic samples.

KMT2B and Neuronal Transdifferentiation: Bridging Basic Chromatin Mechanisms to Disease Actionability

The role of bona fide epigenetic regulators in the process of neuronal transdifferentiation was until recently largely uncharacterized, despite their key role in the physiological processes of neural fate acquisition and maintenance. In this commentary, we describe the main findings of our recent paper “KMT2B is selectively required for neuronal transdifferentiation, and its loss exposes dystonia candidate genes,” where we investigated the role of this histone H3K4 methyltransferase during mouse embryonic fibroblasts (MEFs) to induced neuronal cells (iNs) direct conversion. Indeed, Kmt2b^–/– MEFs, transduced with three neuronal-specific transcription factors (TFs), Brn2, Ascl1, and Myt1l, show lower transdifferentiation efficiency, defective iN maturation, and augmented alternative cell fates acquisition, with respect to controls. Here, we went beyond the data, hypothesizing how KMT2B executes its fundamental role. In particular, we supposed that MYT1L, which has been proven to be fundamental for iN maturation and the switch-off of alternative cell fates, directly or indirectly needs KMT2B. Indeed, KMT2B could be important both to make MYT1L-target genes accessible, because MYT1L is not a pioneer TF and preferentially binds to open chromatin, and to activate MYT1L-downstream genes.

Molecular markers in ALL: Clinical implications

Acute lymphoblastic leukemia (ALL) is the most common childhood cancer and remains a main cause of death in children despite recent improvements in cure rates. In the past decade, development of massively parallel sequencing has enabled large scale genome profiling studies of ALL, which not only led to identification of new subtypes in both B-cell precursor ALL (BCP-ALL) and T-cell ALL (T-ALL), but has also identified potential new therapeutic approaches to target vulnerabilities of many subtypes. Several of these approaches have been validated in preclinical models and are now being formally evaluated in prospective clinical trials. In this review, we provide an overview of the recent advances in our knowledge of genomic bases of BCP-ALL, T-ALL, and relapsed ALL, and discuss their clinical implications.

KMT2A regulates cervical cancer cell growth through targeting VDAC1

Cervical cancer is an aggressive cutaneous malignancy, illuminating the molecular mechanisms of tumorigenesis and discovering novel therapeutic targets are urgently needed. KMT2A is a transcriptional co-activator regulating gene expression during early development and hematopoiesis, but the role of KMT2A in cervical cancer remains unknown. Here, we demonstrated that KMT2A regulated cervical cancer growth via targeting VADC1. Knockdown of KMT2A significantly suppressed cell proliferation and migration and induced apoptosis in cervical cancer cells, accompanying with activation of PARP/caspase pathway and inhibition of VADC1. Overexpression of VDAC1 reversed the KMT2A knockdown-mediated regulation of cell proliferation, migration and apoptosis. The in vivo results from a cervical cancer xenograft mouse model also validated that KMT2A knockdown suppressed tumor growth by inhibiting VDAC1, whereas KMT2A overexpression promoted cervical cancer growth. Moreover, analyses of Biewenga cervix database and clinical samples showed that both KMT2A and VDAC1 were upregulated in cervix squamous cell carcinoma compared with cervix uteri tissues, and their expression was negatively correlated with the differentiation grade of cervical cancer. Our results therefore indicated that the KMT2A/VDAC1 signaling axis may be a potential new mechanism of cervical carcinogenesis.

The phenotype-driven computational analysis yields clinical diagnosis for patients with atypical manifestations of known intellectual disability syndromes

BACKGROUND

Due to extensive clinical and genetic heterogeneity of intellectual disability (ID) syndromes, the process of diagnosis is very challenging even for expert clinicians. Despite recent advancements in molecular diagnostics methodologies, a significant fraction of ID patients remains without a clinical diagnosis.

METHODS, RESULTS, AND CONCLUSIONS

Here, in a prospective study on a cohort of 21 families (trios) with a child presenting with ID of unknown etiology, we executed phenotype-driven bioinformatic analysis method, PhenIX, utilizing targeted next-generation sequencing (NGS) data and Human Phenotype Ontology (HPO)-encoded phenotype data. This approach resulted in clinical diagnosis for eight individuals presenting with atypical manifestations of Rubinstein-Taybi syndrome 2 (MIM 613684), Spastic Paraplegia 50 (MIM 612936), Wiedemann-Steiner syndrome (MIM 605130), Cornelia de Lange syndrome 2 (MIM 300590), Cerebral creatine deficiency syndrome 1 (MIM 300352), Glass Syndrome (MIM 612313), Mental retardation, autosomal dominant 31 (MIM 616158), and Bosch-Boonstra-Schaaf optic atrophy syndrome (MIM 615722).

Acute myeloid leukemia with t(11;19)(q23;p13.1) in a patient with a gastrointestinal stromal tumor undergoing imatinib therapy: A case report

BACKGROUND

Acute myeloid leukemia (AML) harboring 11q23 translocations is classified as therapy-related AML in patients who have undergone prior treatment with cytotoxic agents. There have been only a few reports of AML that subsequently developed during imatinib mesylate (IM) treatment for gastrointestinal stromal tumors (GISTs).

CASE SUMMARY

A 63-year-old woman was diagnosed with a hepatic GIST recurrence in April 2012; she was administered IM 400 mg/d. In November 2015, she developed dyspnea with pancytopenia while IM treatment was continued for 42 mo. A chromosome study using a bone marrow sample showed a 46, XX karyotype with t(11;19)(q23;p13.1) in 22 of 26 analyzed metaphase cells. Fluorescence in situ hybridization using the locus-specific indicator (11q23) gene break-apart probe showed positive rearrangement in 82% of interphase cells. Reverse-transcription polymerase chain reactions subsequently confirmed the KMT2A/ELL transcript. She achieved complete response with incomplete neutrophil recovery with two decitabine treatment cycles. After the third cycle of decitabine, the disease relapsed, and she refused further treatment. She died of hemorrhagic stroke 5 mo after diagnosis. To the best of our knowledge, this is the first report of AML with KMT2A gene rearrangements in a patient with a GIST receiving IM treatment.

CONCLUSION

Physicians should consider the potential risks of developing hematologic malignancies, including therapy-related AML, in patients with GISTs receiving IM treatment.

Cryptic and atypical KMT2A-USP2 and KMT2A-USP8 rearrangements identified by mate pair sequencing in infant and childhood leukemia

Infant leukemias are a rare group of neoplasms that are clinically and biologically distinct from their pediatric and adult counterparts. Unlike leukemia in older children where survival rates are generally favorable, infants with leukemia have a 5-year event-free survival rate of <50%. The majority of infant leukemias are characterized by KMT2A (MLL) rearrangements (~70 to 80% in acute lymphoblastic leukemia), which appear to be drivers of early leukemogenesis. In this report, we describe three cases: a 9-month-old female infant with B-acute lymphoblastic leukemia (B-ALL), an 8-month-old female presenting with B/myeloid mixed phenotype acute leukemia (MPAL), and a 16-month-old male with B-ALL. The first case had a normal karyotype and B-ALL FISH results consistent with an atypical KMT2A rearrangement. The second case had trisomy 10 as the sole chromosomal abnormality and a normal KMT2A FISH result. Case 3 had trisomy 8 and a t(11;15)(q23;q21), an atypical KMT2A rearrangement by FISH studies, and a focal deletion of 15q with a breakpoint within the USP8 gene by chromosomal microarray. Mate pair sequencing was performed on all three cases and identified a KMT2A-USP2 rearrangement (cases 1 and 2) or a KMT2A-USP8 rearrangement (case 3). These recently characterized KMT2A fusions have been described exclusively in infant and pediatric leukemia cases where the incidence varies vary according to leukemia subtype, are considered high-risk, with a high incidence of central nervous system involvement, poor response to initial prednisone treatment, and poor event free survival. Additionally, approximately half of cases are unable to be resolved using standard cytogenetic approaches and are likely under recognized. Therefore, targeted molecular approaches are suggested in genetically unresolved infant leukemia cases to characterize these prognostically relevant clones.

MTHFR rs1801133 polymorphism is associated with increased risk of B-cell precursor lymphoblastic leukaemia with recurrent genetic aberrations of fetal origin

BACKGROUND

Childhood acute lymphoblastic leukaemia (ALL) is a heterogeneous disease associated with multiple risk factors including genetic susceptibility. Polymorphisms in folate genes have been associated with a protective effect against ALL, although some studies contradict these findings. We aimed to test whether there is an association between the MTHFR rs1801133 variant and the occurrence of B-cell precursor ALL (BCP-ALL) taking in account molecularly distinct subtypes of fetal origin.

METHODS

We performed a case-control genotyping study with 2067 samples, 1309 ALL and 758 controls, from children aged ≤ 15 years for MTHFR rs1801133 polymorphism. Risk associations were calculated by odds ratios estimated with unconditional logistic regression, adjusted for frequency-matched ethnic groups.

RESULTS

Overall, MTHFR rs1801133 does not impact ALL risk in children with more than 6 years of age. A significant positive association for MTHFR rs1801133 variant was found for ALL with KMT2A-r in the dominant model (adj. OR, 1.48, 95 % CI, 1.01-2.17), while ETV6-RUNX1 and Hyperdiploid subgroups have shown a borderline effect (adj. OR, 1.33, 95 % CI, 0.99-1.78).

CONCLUSIONS

The polymorphism MTHFR rs1801133 increased the risk of infant ALL in Brazilian population.

Acute Leukemias of Ambiguous Lineage: Clarification on Lineage Specificity

Acute leukemias of ambiguous lineage (ALAL) include acute undifferentiated leukemia and mixed-phenotype acute leukemia (MPAL). This article provides an overview of the diagnosis of ALAL and focuses on the data accounting for the current lineage-assignment criteria for blasts harboring more than one lineage-associated marker. In addition, the currently known molecular data are reviewed, which show that MPAL-associated gene mutations, methylation signatures, and expression profiles are a mixture of those seen in both acute myeloid leukemia and acute lymphoblastic leukemia. Finally, the prognosis and current treatments of MPAL are briefly discussed.

Enhancing Hematopoiesis from Murine Embryonic Stem Cells through MLL1-Induced Activation of a Rac/Rho/Integrin Signaling Axis

The Mixed Lineage Leukemia (MLL1, KMT2A) gene is critical for development and maintenance of hematopoietic stem cells (HSCs), however, whether this protein is limiting for HSC development is unknown due to lack of physiologic model systems. Here, we develop an MLL1-inducible embryonic stem cell (ESC) system and show that induction of wild-type MLL1 during ESC differentiation selectively increases hematopoietic potential from a transitional c-Kit⁺/Cd41⁺ population in the embryoid body and also at sites of hematopoiesis in embryos. Single-cell sequencing analysis illustrates inherent heterogeneity of the c-Kit⁺/Cd41⁺ population and demonstrates that MLL1 induction shifts its composition toward multilineage hematopoietic identities. Surprisingly, this does not occur through increasing Hox or other canonical MLL1 targets but through an enhanced Rac/Rho/integrin signaling state, which increases responsiveness to Vla4 ligands and enhances hematopoietic commitment. Together, our data implicate a Rac/Rho/integrin signaling axis in the endothelial to hematopoietic transition and demonstrate that MLL1 actives this axis.

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Increasing MLL1 enhances hematopoietic potential in vitro and in vivo

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scRNA sequencing illustrates the heterogeneity of an EMP-like population from EBs

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MLL1 activates Rac/Rho/integrin signaling during hematopoietic specification

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MLL1-induced HSPCs are primed for hematopoiesis via integrin-mediated adhesion

KMT2A rearranged acute lymphoblastic leukaemia: Unravelling the genomic complexity and heterogeneity of this high-risk disease

KMT2A rearranged (KMT2Ar) acute lymphoblastic leukaemia (ALL) is a high-risk genomic subtype, with long-term survival rates of less than 60% across all age groups. These cases present a complex clinical challenge, with a high incidence in infants, high-risk clinical features and propensity for aggressive relapse. KMT2A rearrangements are highly pathogenic leukaemic drivers, reflected by the high incidence of KMT2Ar ALL in infants, who carry few leukaemia-associated cooperative mutations. However, transgenic murine models of KMT2Ar ALL typically exhibit long latency and mature or mixed phenotype, and fail to recapitulate the aggressive disease observed clinically. Next-generation sequencing has revealed that KMT2Ar ALL also occurs in adolescents and adults, and potentially cooperative genomic lesions such as PI3K-RAS pathway variants are present in KMT2Ar patients of all ages. This review addresses the aetiology of KMT2Ar ALL, with a focus on the cell of origin and mutational landscape, and how genomic profiling of KMT2Ar ALL patients in the era of next-generation sequencing demonstrates that KMT2Ar ALL is a complex heterogenous disease. Ultimately, understanding the underlying biology of KMT2Ar ALL will be important in improving long-term outcomes for these high-risk patients.

MicroRNA-769-5p Promotes The Growth Of Glioma Cells By Targeting Lysine Methyltransferase 2A

Background

Accumulating evidence supports the involvement of microRNAs (miRNAs) in the progression of human cancers including glioma. Recently, miR-769-5p has been reported to play a tumor suppressive role in colorectal cancer and lung cancer, whereas it exerts an oncogenic role in melanoma. However, the role of miR-769-5p and its related mechanism are poorly elucidated.

Methods

The levels of miR-769-5p in glioma tissues and adjacent non-tumor tissues were detected by qRT-PCR. In addition, the effects of miR-769-5p on cell proliferation and apoptosis were evaluated by CCK-8, EdU, colony formation and flow cytometric assays, respectively. Meanwhile, the dual-luciferase reporter assay was used to investigate the interaction of miR-769-5p and lysine methyltransferase 2A (KMT2A) in glioma.

Results

We found that miR-769-5p expression was strongly upregulated in glioma tissues and cell lines. Glioma tissues with high World Health Organization (WHO) grades had obvious higher levels of miR-769-5p compared to samples with low WHO grades. Interestingly, glioma patients highly expressing miR-769-5p showed prominent poorer survivals. Knockdown of miR-769-5p significantly suppressed cell proliferation and resulted in apoptosis in glioma cells. Additionally, miR-769-5p silencing restrained in vivo growth of glioma cells in mice. Interestingly, KMT2A was identified to be a direct target of miR-769-5p in glioma cells. The expression of KMT2A mRNA was downregulated in glioma tissues and inversely correlated with miR-769-5p level. KMT2A overexpression inhibited cell proliferation and induced the apoptosis of A172 cells. Moreover, siRNA-mediated KMT2A silencing could partially abolish miR-769-5p knockdown-induced suppressive effects on A172 cells.

Conclusion

In summary, our findings suggest that targeting miR-769-5p/KMT2A axis may be a promising therapeutic target for glioma treatment.

Cytogenetic and molecular genetic characterization of KMT2A-PTD positive acute myeloid leukemia in comparison to KMT2A-Rearranged acute myeloid leukemia

To define the biological differences in acute myeloid leukaemia (AML) with KMT2A gene involvements and their prognostic impact, we compared 190 de novo AML patients at diagnosis, 95 harbouring KMT2A-rearrangement (KMT2Ar) and 95 KMT2A-PTD by performing cytogenetic and molecular genetic analyses. Both AML subtypes had an unfavourable outcome, particularly in patients > 60 years. Patients with KMT2Ar were younger compared to patients with KMT2A-PTD (mean 52 vs 65 years, p < 0.001) and had a higher rate of additional cytogenetic abnormalities (ACA) (46% vs 25% of cases). In both groups, occurrence of ACA did not influence the overall survival (OS). Regarding molecular genetics, 66% of patients with KMT2Ar and 99% of patients with KMT2A-PTD had additional gene mutations. In multivariate analysis, KRAS mutations and 10p12 rearrangement resulted as adverse prognostic factors in KMT2Ar subgroup. In the KMT2A-PTD group, apart from age, only the occurrence of DNMT3A non-R882 mutations correlated with shorter OS.

MLL-Rearranged Acute Leukemia with t(4;11)(q21;q23)-Current Treatment Options. Is There a Role for CAR-T Cell Therapy?

The MLL (mixed-lineage leukemia) gene, located on chromosome 11q23, is involved in chromosomal translocations in a subtype of acute leukemia, which represents approximately 10% of acute lymphoblastic leukemia and 2.8% of acute myeloid leukemia cases. These translocations form fusions with various genes, of which more than 80 partner genes for MLL have been identified. The most recurrent fusion partner in MLL rearrangements (MLL-r) is AF4, mapping at chromosome 4q21, accounting for approximately 36% of MLL-r leukemia and particularly prevalent in MLL-r acute lymphoblastic leukemia (ALL) cases (57%). MLL-r leukemia is associated with a sudden onset, aggressive progression, and notoriously poor prognosis in comparison to non-MLL-r leukemias. Despite modern chemotherapeutic interventions and the use of hematopoietic stem cell transplantations, infants, children, and adults with MLL-r leukemia generally have poor prognosis and response to these treatments. Based on the frequency of patients who relapse, do not achieve complete remission, or have brief event-free survival, there is a clear clinical need for a new effective therapy. In this review, we outline the current therapy options for MLL-r patients and the potential application of CAR-T therapy.

A molecular study of synovial chondromatosis

Synovial chondromatosis (SC) is a rare benign cartilaginous neoplasm in which recurrent fibronectin 1 (FN1) and activin receptor 2A (ACVR2A) gene rearrangements have been recently reported. Triggered by a case of malignant transformation in SC (synovial chondrosarcoma) showing a novel KMT2A-BCOR gene fusion by targeted RNA sequencing, we sought to evaluate the molecular abnormalities in a cohort of 27 SC cases using a combined methodology of fluorescence in situ hybridization (FISH) and/or targeted RNA sequencing. Results showed that FN1 and /or ACVR2A gene rearrangements were noted in 18 cases (67%), with an FN1-ACVR2A fusion being confirmed in 15 (56%) cases. Two cases showed only FN1 gene rearrangement, without other abnormalities. A novel FN1-NFATc2 gene fusion was noted in one case by RNA sequencing. The remaining nine cases showed no abnormalities in FN1 and ACVR2A genes. No additional cases showed BCOR gene alterations. In conclusion, this study confirms that FN1-ACVR2A fusion is the leading pathogenetic event in SC, at even higher frequency than previously reported. FISH methodology emerges as an appropriate tool in the identification of FN1 and ACVR2A gene abnormalities, which can be used in challenging cases. Further studies are needed to determine the recurrent potential of BCOR abnormalities in this disease.

Crosstalk between 14-3-3θ and AF4 enhances MLL-AF4 activity and promotes leukemia cell proliferation

PURPOSE

The t(4;11)(q21;q23) translocation characterizes a form of acute lymphoblastic leukemia with a poor prognosis. It results in a fusion gene encoding a chimeric transcription factor, MLL-AF4, that deregulates gene expression through a variety of still controversial mechanisms. To provide new insights into these mechanisms, we examined the interaction between AF4, the most common MLL fusion partner, and the scaffold protein 14-3-3θ, in the context of t(4;11)-positive leukemia.

METHODS

Protein-protein interactions were analyzed using immunoprecipitation and in vitro binding assays, and by fluorescence microscopy in t(4;11)-positive RS4;11 and MV4-11 leukemia cells and in HEK293 cells. Protein and mRNA expression levels were determined by Western blotting and RT-qPCR, respectively. A 5-bromo-2'-deoxyuridine assay and an annexin V/propidium iodide assay were used to assess proliferation and apoptosis rates, respectively, in t(4;11)-positive and control cells. Chromatin immunoprecipitation was performed to assess binding of 14-3-3θ and AF4 to a specific promoter element.

RESULTS

We found that AF4 and 14-3-3θ are nuclear interactors, that 14-3-3θ binds Ser⁵⁸⁸ of AF4 and that 14-3-3θ forms a complex with MLL-AF4. In addition, we found that in t(4;11)-positive cells, 14-3-3θ knockdown decreased the expression of MLL-AF4 target genes, induced apoptosis and hampered cell proliferation. Moreover, we found that 14-3-3θ knockdown impaired the recruitment of AF4, but not of MLL-AF4, to target chromatin. Overall, our data indicate that the activity of the chimeric transcription factor MLL-AF4 depends on the cellular availability of 14-3-3θ, which triggers the transactivating function and subsequent degradation of AF4.

CONCLUSIONS

From our data we conclude that the scaffold protein 14-3-3θ enhances the aberrant activity of the chimeric transcription factor MLL-AF4 and, therefore, represents a new player in the molecular pathogenesis of t(4;11)-positive leukemia and a new promising therapeutic target.