Mutations of PHF6 are associated with mutations of NOTCH1, JAK1 and rearrangement of SET-NUP214 in T-cell acute lymphoblastic leukemia

Concurrent Bone Marrow Acute Undifferentiated Leukemia and Mediastinal T-Lymphoblastic Lymphoma With Identical SET::NUP214 Fusion and PHF6 and EZH2 Mutations

Acute undifferentiated leukemia (AUL) is a rare hematologic malignancy lacking lineage-specific markers. Concurrent, clonally related AUL and T-lymphoblastic lymphoma (T-LBL) has not been reported previously. Here we describe a patient who was diagnosed with AUL in the bone marrow and T-LBL in the mediastinum after a thorough immunophenotyping by flow cytometry and immunohistochemistry. Despite their immunophenotypic differences, the AUL and T-LBL showed identical genetic alterations: SET::NUP214 fusion, PHF6, and EZH2 mutations. The patient achieved and remained in complete remission after chemotherapy and stem cell transplantation. This case underscores the value of comprehensive immunophenotyping and genetic analysis in rare hematologic malignancies.

Should we perform baseline NGS testing in precursor T lymphoblastic leukaemias: a single centre experience from Eastern India

Introduction

T-lymphoblastic leukaemia accounts for approximately one-fourth of acute lymphoblastic leukaemia cases. Sequencing approaches have identified >100 genes that can be mutated in T-cell acute lymphoblastic leukaemia (T-ALL). However, the revised WHO 2022 edition of lymphoid neoplasms still does not incorporate molecular signatures into the T-ALL subgrouping unlike B-ALLs and acute myeloid leukemia, which are classified mainly based on molecular landscapes.

Methods

This retrospective observational study included all newly diagnosed patients of T-lymphoblastic leukaemia of all age groups who presented during the period between January 2022 and October 2023 in whom complete baseline diagnostic work-up was available including flow cytometry, fluorescence in situ hybridization and next generation sequencing studies.

Results

There was a lower frequency of karyotypic abnormalities in adult early T progenitor (ETP)-ALLs than in other sub-groups. Non-ETP ALLs showed significant association with NOTCH1 mutations (p ≤ 0.00001), followed by JAK3 (p = 0.01), FBXW7 (p = 0.066) and PHF6 (p = 0.09) mutations. There was no difference between adult and pediatric patients, in terms of genomic profiling except in the PHF6 gene. There was no significant difference between NOTCH1-mutated and NOTCH1-wild T-ALL patients as well as NOTCH1-heterodimerization versus NOTCH1-PEST mutated patients in terms of measurable residual disease (MRD), relapse-free survival (RFS) and/or overall survival (OS). 45.1% of all TALL patients harboured ≥3 mutations. However, the complex molecular profile did not correlate significantly with MRD positivity and poor RFS and/or OS rates.

Conclusion

Molecular profiling of TALLs do not significantly impact long-term survival outcomes. In resource-constrained settings, we can get away by not doing comprehensive molecular profiling of TALLs at baseline and restrict the sequencing assay to only those cases that are persistently MRD positive or have relapsed.

Comprehensive genomic characterization of hematologic malignancies at a pediatric tertiary care center

Despite the increasing availability of comprehensive next generation sequencing (NGS), its role in characterizing pediatric hematologic malignancies remains undefined. We describe findings from comprehensive genomic profiling of hematologic malignancies at a pediatric tertiary care center. Patients enrolled on a translational research protocol to aid in cancer diagnosis, prognostication, treatment, and detection of cancer predisposition. Disease-involved samples underwent exome and RNA sequencing and analysis for single nucleotide variation, insertion/deletions, copy number alteration, structural variation, fusions, and gene expression. Twenty-eight patients with hematologic malignancies were nominated between 2018-2021. Eighteen individuals received both germline and somatic sequencing; two received germline sequencing only. Germline testing identified patients with cancer predisposition syndromes and non-cancer carrier states. Fifteen patients (15/18, 83%) had cancer-relevant somatic findings. Potential therapeutic targets were identified in seven patients (7/18, 38.9%); three (3/7, 42.9%) received targeted therapies and remain in remission an average of 47 months later.

NUP214 Rearrangements in Leukemia Patients: A Case Series From a Single Institution

Background

The three best-known NUP214 rearrangements found in leukemia (SET:: NUP214, NUP214::ABL1, and DEK::NUP214) are associated with treatment resistance and poor prognosis. Mouse experiments have shown that NUP214 rearrangements alone are insufficient for leukemogenesis; therefore, the identification of concurrent mutations is important for accurate assessment and tailored patient management. Here, we characterized the demographic characteristics and concurrent mutations in patients harboring NUP214 rearrangements.

Methods

To identify patients with NUP214 rearrangements, RNA-sequencing results of diagnostic bone marrow aspirates were retrospectively studied. Concurrent targeted next-generation sequencing results, patient demographics, karyotypes, and flow cytometry information were also reviewed.

Results

In total, 11 patients harboring NUP214 rearrangements were identified, among whom four had SET::NUP214, three had DEK::NUP214, and four had NUP214::ABL1. All DEK::NUP214-positive patients were diagnosed as having AML. In patients carrying SET::NUP214 and NUP214::ABL1, T-lymphoblastic leukemia was the most common diagnosis (50%, 4/8). Concurrent gene mutations were found in all cases. PFH6 mutations were the most common (45.5%, 5/11), followed by WT1 (27.3%, 3/11), NOTCH1 (27.3%, 3/11), FLT3-internal tandem duplication (27.3%, 3/11), NRAS (18.2%, 2/11), and EZH2 (18.2%, 2/11) mutations. Two patients represented the second and third reported cases of NUP214::ABL1-positive AML.

Conclusions

We examined the characteristics and concurrent test results, including gene mutations, of 11 leukemia patients with NUP214 rearrangement. We hope that the elucidation of the context in which they occurred will aid future research on tailored monitoring and treatment.

Integrated analysis of transcriptome and genome variations in pediatric T cell acute lymphoblastic leukemia: data from north Indian tertiary care center

INTRODUCTION

T-cell acute lymphoblastic leukemia (T-ALL) is a genetically heterogeneous disease with poor prognosis and inferior outcome. Although multiple studies have been perform on genomics of T-ALL, data from Indian sub-continent is scarce.

METHODS

In the current study we aimed to identify the genetic variability of T-ALL in an Indian cohort of pediatric (age ≤ 12 years) T-ALL patients (n = 25) by whole transcriptome sequencing along with whole exome sequencing and correlated the findings with clinical characteristics and disease outcome.

RESULTS

The median age was 7 years (range 3 -12 years). RNA sequencing revealed a definitive fusion event in 14 cases (56%) (including a novel fusions) with STIL::TAL1 in 4 (16%), followed by NUP21::ABL1, TCF7::SPI1, ETV6::HDAC8, LMO1::RIC3, DIAPH1::JAK2, SETD2::CCDC12 and RCBTB2::LPAR6 in 1 (4%) case each. Significant aberrant expression was noted in RAG1 (64%), RAG2 (80%), MYCN (52%), NKX3-1 (52%), NKX3-2 (32%), TLX3 (28%), LMO1 (20%) and MYB (16%) genes. WES data showed frequent mutations in NOTCH1 (35%) followed by WT1 (23%), FBXW7 (12%), KRAS (12%), PHF6 (12%) and JAK3 (12%). Nearly 88.2% of cases showed a deletion of CDKN2A/CDKN2B/MTAP genes. Clinically significant association of a better EFS and OS (p=0.01) was noted with RAG2 over-expression at a median follow up of 22 months, while a poor EFS (p=0.041) and high relapse rate (p=0.045) was observed with MYB over-expression.

CONCLUSION

Overall, the present study demonstrates the frequencies of transcriptomic and genetic alterations from Indian cohort of pediatric T-ALL and is a salient addition to current genomics data sets available in T-ALL.

PHF6-altered T-ALL Harbor Epigenetic Repressive Switch at Bivalent Promoters and Respond to 5-Azacitidine and Venetoclax

PURPOSE

To assess the impact of PHF6 alterations on clinical outcome and therapeutical actionability in T-cell acute lymphoblastic leukemia (T-ALL).

EXPERIMENTAL DESIGN

We described PHF6 alterations in an adult cohort of T-ALL from the French trial Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL)-2003/2005 and retrospectively analyzed clinical outcomes between PHF6-altered (PHF6ALT) and wild-type patients. We also used EPIC and chromatin immunoprecipitation sequencing data of patient samples to analyze the epigenetic landscape of PHF6ALT T-ALLs. We consecutively evaluated 5-azacitidine efficacy, alone or combined with venetoclax, in PHF6ALT T-ALL.

RESULTS

We show that PHF6 alterations account for 47% of cases in our cohort and demonstrate that PHF6ALT T-ALL presented significantly better clinical outcomes. Integrative analysis of DNA methylation and histone marks shows that PHF6ALT are characterized by DNA hypermethylation and H3K27me3 loss at promoters physiologically bivalent in thymocytes. Using patient-derived xenografts, we show that PHF6ALT T-ALL respond to the 5-azacytidine alone. Finally, synergism with the BCL2-inhibitor venetoclax was demonstrated in refractory/relapsing (R/R) PHF6ALT T-ALL using fresh samples. Importantly, we report three cases of R/R PHF6ALT patients who were successfully treated with this combination.

CONCLUSIONS

Overall, our study supports the use of PHF6 alterations as a biomarker of sensitivity to 5-azacytidine and venetoclax combination in R/R T-ALL.

SET-CAN/NUP214 fusion gene in leukemia: general features and clinical advances

SET-CAN/NUP214 fusion is a recurrent event commonly observed in adult male patients diagnosed with T-cell acute lymphoblastic leukemia (T-ALL) and has occasionally been reported in other diseases such as acute myeloid leukemia (AML), myeloid sarcoma (MS), acute undifferentiated leukemia (AUL), chronic myeloid leukemia (CML) and B-cell acute lymphoblastic leukemia (B-ALL). This fusion gene is derived from chromosome del(9)(q34.11;q34.13) or t(9;9)(q34;q34) and may have an inhibitory effect on primitive progenitor differentiation. The prognosis of the reported patients is varied, with these patients often show resistance to chemotherapy regimens that include high doses of glucocorticoids. The optional treatment has not been determined, more cases need to be accumulated and evaluated. The scope of this review is to summarize the general features and prognostic significance in leukemia associated with the SET-CAN/NUP214 fusion gene and to discuss the methods of detection and treatment, aiming at providing some useful references for relevant researchers in the field of blood tumor.

Genomic signatures and prognosis of advanced stage Chinese pediatric T cell lymphoblastic lymphoma by whole exome sequencing

Objective

To investigate the genomic signatures and prognosis of advanced-stage T cell lymphoblastic lymphoma (T-LBL) and to examine the relationship between T-LBL and T cell acute lymphoblastic leukemia (T-ALL).

Methods

35 Chinese T-LBL children with stage III or IV disease were recruited for this study. They were treated with combination chemotherapy and whole exome sequencing. The relationship of the clinical features, prognosis and specific gene mutations was researched. Gene chips of T-LBL and T-ALL were downloaded from a database, and differential gene expression was analyzed.

Results

Germline causal gene mutations (CARS or MAP2K2) were detected in 2 patients; 3.06 ± 2.21 somatic causal gene mutations were identified in the 35 patients, and somatic mutations were observed in the NOTCH1, FBXW7, PHF6 and JAK3 genes. NOTCH1 mutations were significantly associated with FBXW7 mutations, and the age at diagnosis of patients with NOTCH1-FBXW7 mutations was less than that of patients without such mutations (P < 0.05). 32 patients achieved complete remission (CR), and 14 and 18 patients were classified into the intermediate risk (IR) group and high risk (HR) group. During a median follow-up of 44 months, 3 patients relapsed. Three-year prospective event free survival (pEFS) was 82.286%, and no significant differences of pEFS were found for different sexes, ages, or statuses of NOTCH1-FBXW7 mutations, (P > 0.05); however, the mean survival time of the IR group was longer than that of the HR group (P < 0.05). Differential expression of genes in the T-LBL and/or T-ALL datasets was analyzed using the R package limma, and 1/3 of the differentially expressed genes were found in both the T-ALL and T-LBL datasets. High expression of PI3K-Akt signal pathway genes and the USP34 gene was found in the T-LBL dataset.

Conclusion

Although T-ALL and T-LBL both originate from precursor T-cells and are considered different manifestations of the same disease and the outcome of T-LBL is favorable when using T-ALL-based chemotherapy, there are differences in the gene distribution between T-LBL and T-ALL. It seems that the PI3K-Akt signaling pathway and the USP34 gene play important roles in T-LBL, but medicines targeting the USP34 gene or the PI3K-Akt pathway may be invalid.

Investigating the physiological role of S199A and S199D mutants of PHF6 protein in T-cell acute lymphoblastic leukemia

Background/aim

T-cell acute lymphoblastic leukemia (T-ALL) is a form of leukemia characterized by the proliferation of immature T lymphocytes. NOTCH1 is one of the most frequently mutated genes in T-ALL. NOTCH1 expression in T-cell development depends on plant homeodomain finger protein 6 (PHF6), which plays a tumor suppressor role in T-ALL. Several studies have shown that PHF6 expression is essential for NOTCH1 expression. Therefore, whether posttranslational modification of PHF6 plays a role in the regulation of NOTCH1 expression and T-ALL cell line proliferation was investigated herein.

Materials and methods

The amino acid sequence of PHF6 was analyzed and it was found that a putative protein kinase A (PKA) phosphorylation motif RDRS199 was conserved in several vertebrate species and the S199 site was expected to be phosphorylated according to the PhosphoSite database. Therefore, an eukaryotic expression vector of human PHF6 was constructed, and the codon 199 was changed to the codon encoding the nonphosphorylatable alanine and the phosphorylation-mimicking aspartic acid via site-directed mutagenesis. After confirming the ectopic expressions of the PHF6 vectors by western blot analysis, the effects of these proteins were identified on the NOTCH1 expression using western blot analysis, leukemic cell proliferation using MTT assay, and expressions of the cell surface markers of T-cells using flow cytometry.

Results

The ectopic expression of wild-type PHF6 stimulated the formation of CD4 + T-cells. While the expression of the wild-type PHF6 suppressed the growth of the leukemic cell line, this effect was diminished in both the alanine and aspartic acid mutants of PHF6. In addition, both mutants also seemed to negatively affect the NOTCH1 expression, although the effect of the alanine mutant was more severe.

Conclusion

Taken together, the different biological activities exerted by the conserved S199 phosphorylation-site mutants shown in this study implicate that signaling pathway(s) leading to differential phosphorylation of this residue may have a substantial effect on the activity of PHF6, and thus may constitute a potential therapeutic target in T-ALL.

R274X-mutated Phf6 increased the self-renewal and skewed T cell differentiation of hematopoietic stem cells

The PHD finger protein 6 (PHF6) mutations frequently occurred in hematopoietic malignancies. Although the R274X mutation in PHF6 (PHF6^R274X) is one of the most common mutations identified in T cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML) patients, the specific role of PHF6^R274X in hematopoiesis remains unexplored. Here, we engineered a knock-in mouse line with conditional expression of Phf6^R274X-mutated protein in the hematopoietic system (Phf6^R274X mouse). The Phf6^R274X mice displayed an enlargement of hematopoietic stem cells (HSCs) compartment and increased proportion of T cells in bone marrow. More Phf6^R274X T cells were in activated status than control. Moreover, Phf6^R274X mutation led to enhanced self-renewal and biased T cells differentiation of HSCs as assessed by competitive transplantation assays. RNA-sequencing analysis confirmed that Phf6^R274X mutation altered the expression of key genes involved in HSC self-renewal and T cell activation. Our study demonstrated that Phf6^R274X plays a critical role in fine-tuning T cells and HSC homeostasis.

Integrated clinical genotype-phenotype characteristics of early T-cell precursor acute lymphoblastic leukemia

BACKGROUND

Early T-cell precursor acute lymphoblastic leukemia (ETP-ALL) is a distinct subtype of T-ALL with a unique immunophenotype and high treatment failure rate. The molecular genetic abnormalities and their prognostic impact in ETP-ALL patients are poorly understood.

METHODS

The authors performed systematic analyses of the clinicopathologic features with an emphasis on molecular genetic aspects of 32 patients with ETP-ALL.

RESULTS

The median age was 43 years (range, 16-71). The blasts were positive for cytoplasmic CD3 and CD7 and negative for CD1a and CD8. Other markers expressed included CD34 (88%), CD33 (72%), CD117 (68%), CD13 (58%), CD5 (partial, 56%), CD2 (38%), CD10 (25%), CD56 (partial, 19%), and CD4 (6%). Cytogenetic analyses revealed a diploid karyotype in 10 patients, simple (1-2) abnormalities in 10 patients, and complex karyotype in 10 patients. Next-generation sequencing for 21 patients demonstrated that all had gene mutations (median, four mutations per patient). The most frequently mutated genes were WT1 (38%), NOTCH1 (29%), NRAS (29%), PHF6 (25%), TP53 (24%), ASXL1 (19%), FLT3 (19%), and IKZF1 (19%). All patients except one received multi-agent chemotherapy, and 22 patients underwent allogeneic stem cell transplantation. Thrombocytopenia, an abnormal karyotype, and TP53 mutation were associated with markedly shortened overall survival. Stem cell transplantation significantly improved overall survival.

CONCLUSIONS

Patients with ETP-ALL often have high mutation burden with increased genomic instability. TP53 mutation was the only molecular prognostic marker and was associated with complex karyotype and greater than or equal to five mutations. These patients may benefit from stem cell transplantation, and recurrent gene mutations may be novel therapeutic markers.

Integrative genomic and transcriptomic profiling reveals distinct molecular subsets in adult mixed phenotype acute leukemia

Mixed phenotype acute leukemia (MPAL) is a subtype of leukemia in which lymphoid and myeloid markers are co-expressed. Knowledge regarding the genetic features of MPAL is lacking due to its rarity and heterogeneity. Here, we applied an integrated genomic and transcriptomic approach to explore the molecular characteristics of 176 adult patients with MPAL, including 86 patients with T-lymphoid/myeloid MPAL (T/My MPAL-NOS), 42 with Ph+ MPAL, 36 with B-lymphoid/myeloid MPAL (B/My MPAL-NOS), 4 with t(v;11q23), and 8 with MPAL, NOS, rare types. Genetically, T/My MPAL-NOS was similar to B/T MPAL-NOS but differed from Ph+ MPAL and B/My MPAL-NOS. T/My MPAL-NOS exhibited higher CEBPA, DNMT3A, and NOTCH1 mutations. Ph+ MPAL demonstrated higher RUNX1 mutations. B/T MPAL-NOS showed higher NOTCH1 mutations. By integrating next-generation sequencing and RNA sequencing data of 89 MPAL patients, we defined eight molecular subgroups (G1-G8) with distinct mutational and gene expression characteristics. G1 was associated with CEBPA mutations, G2 and G3 with NOTCH1 mutations, G4 with BCL11B rearrangement and FLT3 mutations, G5 and G8 with BCR::ABL1 fusion, G6 with KMT2A rearrangement/KMT2A rearrangement-like features, and G7 with ZNF384 rearrangement/ZNF384 rearrangement-like characteristics. Subsequently, we analyzed single-cell RNA sequencing data from five patients. Groups G1, G2, G3, and G4 exhibited overexpression of hematopoietic stem cell disease-like and common myeloid progenitor disease-like signatures, G5 and G6 had high expression of granulocyte-monocyte progenitor disease-like and monocyte disease-like signatures, and G7 and G8 had common lymphoid progenitor disease-like signatures. Collectively, our findings indicate that integrative genomic and transcriptomic profiling may facilitate more precise diagnosis and develop better treatment options for MPAL.

The Role of PHF6 in Hematopoiesis and Hematologic Malignancies

Epigenetic regulation of gene expression represents an important mechanism in the maintenance of stem cell function. Alterations in epigenetic regulation contribute to the pathogenesis of hematological malignancies. Plant homeodomain finger protein 6 (PHF6) is a member of the plant homeodomain (PHD)-like zinc finger family of proteins that is involved in transcriptional regulation through the modification of the chromatin state. Germline mutation of PHF6 is the causative genetic alteration of the X-linked mental retardation Borjeson-Forssman-Lehmann syndrome (BFLS). Somatic mutations in PHF6 are identified in human leukemia, such as adult T-cell acute lymphoblastic leukemia (T-ALL, ~ 38%), pediatric T-ALL (~ 16%), acute myeloid leukemia (AML, ~ 3%), chronic myeloid leukemia (CML, ~ 2.5%), mixed phenotype acute leukemia (MPAL, ~ 20%), and high-grade B-cell lymphoma (HGBCL, ~ 3%). More recent studies imply an oncogenic effect of PHF6 in B-cell acute lymphoblastic leukemia (B-ALL) and solid tumors. These data demonstrate that PHF6 could act as a double-edged sword, either a tumor suppressor or an oncogene, in a lineage-dependent manner. However, the underlying mechanisms of PHF6 in normal hematopoiesis and leukemogenesis remain largely unknown. In this review, we summarize current knowledge of PHF6, emphasizing the role of PHF6 in hematological malignancies. Epigenetic regulation of PHF6 in B-ALL. PHF6 maintains a chromatin structure that is permissive to B-cell identity genes, but not T-cell-specific genes (left). Loss of PHF6 leads to aberrant expression of B-cell- and T-cell-specific genes resulting from lineage promiscuity and binding of T-cell transcription factors (right).

PHF6 mutation is associated with poor outcome in acute myeloid leukaemia

INTRODUCTION

Mutation of plant homeodomain finger protein 6 (PHF6) occurs in approximately 3% of acute myeloid leukaemia (AML) cases. Although it was reported to be associated with poor prognosis, it was not confirmed by other groups. Recently, propensity score matching has provided an effective way to minimise bias by creating two groups that are well balanced with respect to baseline characteristics, providing more convincing results, which has an advantage, especially for rare subtype studies. To provide further evidence on the role of PHF6 mutation, we performed a retrospective propensity score-matched cohort study to assess the therapeutic responses and survival outcomes of AML patients with PHF6 mutation compared with those without PHF6 mutation after balancing age, sex and risk categories.

PATIENTS AND METHODS

A total of 22 patients with PHF6 mutation from 801 consecutive newly diagnosed AML cases in our center were identified, and 43 patients with the PHF6 wild-type genotype were successfully matched at a 1:2 ratio.

RESULTS

AML harbouring PHF6 mutation was associated with a lower complete remission (CR) rate (41% vs. 69%; OR = 3.64, 95% CI 1.10, 12.10; p = 0.035) and shorter median overall survival (OS) (6.0 vs. 39.0 months; p < 0.001) and event-free survival (EFS) (2.0 vs. 11.0 months; p = 0.013) compared with PHF6 wild-type patients. Further multivariate analysis supported that PHF6 mutation was an independent risk factor for overall survival in AML (HR = 8.910, 95% CI 3.51, 22.63; p < 0.001). In addition, allogeneic haematopoietic stem cell transplantation (allo-HSCT) seemed to ameliorate the poor prognosis of AML with PHF6 mutation in this study.

CONCLUSION

Our data revealed that PHF6 mutation was associated with a lower chemotherapy response and shorter survival, suggesting that PHF6 mutation is a predictor of poor prognosis in AML.

Prognostic Significance of Comprehensive Gene Mutations and Clinical Characteristics in Adult T-Cell Acute Lymphoblastic Leukemia Based on Next-Generation Sequencing

Background

Adult T-cell acute lymphoblastic leukemia (T-ALL) is a heterogeneous malignant tumor with poor prognosis. However, accurate prognostic stratification factors are still unclear.

Methods

Data from 90 adult T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) patients were collected. The association of gene mutations detected by next-generation sequencing and clinical characteristics with the outcomes of T-ALL/LBL patients were retrospectively analyzed to build three novel risk stratification models through Cox proportional hazards model.

Results

Forty-seven mutated genes were identified. Here, 73.3% of patients had at least one mutation, and 36.7% had ≥3 mutations. The genes with higher mutation frequency were NOTCH1, FBXW7, and DNMT3A. The most frequently altered signaling pathways were NOTCH pathway, transcriptional regulation pathway, and DNA methylation pathway. Age (45 years old), platelet (PLT) (50 G/L), actate dehydrogenase (LDH) (600 U/L), response in D19-BMR detection, TP53 and cell cycle signaling pathway alterations, and hematopoietic stem cell transplantation (HSCT) were integrated into a risk stratification model of event-free survival (EFS). Age (45 years old), white blood cell (WBC) count (30 G/L), response in D19-BMR detection, TP53 and cell cycle signaling pathway alterations, and HSCT were integrated into a risk stratification model of overall survival (OS). According to our risk stratification models, the 1-year EFS and OS rates in the low-risk group were significantly higher than those in the high-risk group.

Conclusions

Our risk stratification models exhibited good prognostic roles in adult T-ALL/LBL patients and might guide individualized treatment and ultimately improve their outcomes.

Oncogenesis induced by combined Phf6 and Idh2 mutations through increased oncometabolites and impaired DNA repair

The pathogenesis of acute leukemia involves interaction among genetic alterations. Mutations of IDH1/2 and PHF6 are common and co-exist in some patients of hematopoietic malignancies, but their cooperative effects remain unexplored. In this study, we addressed the question by characterizing the hematopoietic phenotypes of mice harboring neither, Phf6 knockout, Idh2 R172K, or combined mutations. We found that the combined Phf6^KOIdh2^R172K mice showed biased hematopoietic differentiation toward myeloid lineages and reduced long-term hematopoietic stem cells. They rapidly developed neoplasms of myeloid and lymphoid lineages, with much shorter survival compared with single mutated and wild-type mice. The marrow and spleen cells of the combined mutated mice produced a drastically increased amount of 2-hydroxyglutarate compared with mice harboring Idh2 R172K. Single-cell RNA sequencing revealed distinct patterns of transcriptome of the hematopoietic stem/progenitor cells from the combined mutated mice, including aberrant expression of metabolic enzymes, increased expression of several oncogenes, and impairment of DNA repairs, as confirmed by the enhanced γH2AX expression in the marrow and spleen cells. We conclude that Idh2 and Phf6 mutations are synergistic in leukemogenesis, at least through overproduction of 2-hydroxyglutarate and impairment of DNA repairs.

Genetics and Diagnostic Approach to Lymphoblastic Leukemia/Lymphoma

Our understanding of the genetics and biology of lymphoblastic leukemia/lymphoma (acute lymphoblastic leukemia, ALL) has advanced rapidly in the past decade with advances in sequencing and other molecular techniques. Besides recurrent chromosomal abnormalities detected by karyotyping or fluorescence in situ hybridization, these leukemias/lymphomas are characterized by a variety of mutations, gene rearrangements as well as copy number alterations. This is particularly true in the case of Philadelphia-like (Ph-like) ALL, a major subset which has the same gene expression signature as Philadelphia chromosome-positive ALL but lacks BCR-ABL1 translocation. Ph-like ALL is associated with a worse prognosis and hence its detection is critical. However, techniques to detect this entity are complex and are not widely available. This chapter discusses various subsets of ALL and describes our approach to the accurate classification and prognostication of these cases.

PHF6 Mutations in Hematologic Malignancies

Next generation sequencing has uncovered several genes with associated mutations in hematologic malignancies that can serve as potential biomarkers of disease. Keeping abreast of these genes is therefore of paramount importance in the field of hematology. This review focuses on PHF6, a highly conserved epigenetic transcriptional regulator that is important for neurodevelopment and hematopoiesis. PHF6 serves as a tumor suppressor protein, with PHF6 mutations and deletions often implicated in the development of T-lymphoblastic leukemia and less frequently in acute myeloid leukemia and other myeloid neoplasms. PHF6 inactivation appears to be an early event in T-lymphoblastic leukemogenesis, requiring cooperating events, including NOTCH1 mutations or overexpression of TLX1 and TLX3 for full disease development. In contrast, PHF6 mutations tend to occur later in myeloid malignancies, are frequently accompanied by RUNX1 mutations, and are often associated with disease progression. Moreover, PHF6 appears to play a role in lineage plasticity within hematopoietic malignancies, with PHF6 mutations commonly present in mixed phenotype acute leukemias with a predilection for T-lineage marker expression. Due to conflicting data, the prognostic significance of PHF6 mutations remains unclear, with a subset of studies showing no significant difference in outcomes compared to malignancies with wild-type PHF6, and other studies showing inferior outcomes in certain patients with mutated PHF6. Future studies are necessary to elucidate the role PHF6 plays in development of T-lymphoblastic leukemia, progression of myeloid malignancies, and its overall prognostic significance in hematopoietic neoplasms.

T-cell lymphoblastic lymphoma and leukemia: different diseases from a common premalignant progenitor?

T-cell lymphoblastic lymphoma (T-LBL) and lymphoblastic leukemia (T-ALL) represent malignancies that arise from the transformation of immature precursor T cells. Similarities in T-LBL and T-ALL have raised the question whether these entities represent 1 disease or reflect 2 different diseases. The genetic profiles of T-ALL have been thoroughly investigated over the last 2 decades, whereas fairly little is known about genetic driver mutations in T-LBL. Nevertheless, the comparison of clinical, immunophenotypic, and molecular observations from independent T-LBL and T-ALL studies lent strength to the theory that T-LBL and T-ALL reflect different presentations of the same disease. Alternatively, T-LBL and T-ALL may simultaneously evolve from a common malignant precursor cell, each having their own specific pathogenic requirements or cellular dependencies that differ among stroma-embedded blasts in lymphoid tissues compared with solitary leukemia cells. This review aims to cluster recent findings with regard to clinical presentation, genetic predisposition, and the acquisition of additional mutations that may give rise to differences in gene expression signatures among T-LBL and T-ALL patients. Improved insight in T-LBL in relation to T-ALL may further help to apply confirmed T-ALL therapies to T-LBL patients.

Determining the Appropriate Treatment for T-Cell Acute Lymphoblastic Leukemia With SET-CAN/NUP214 Fusion: Perspectives From a Case Report and Literature Review

SET-CAN/NUP214 fusion is a recurrent event most commonly seen in T-cell acute lymphoblastic leukemia (T-ALL). It is related to resistance to glucocorticoids and chemotherapy; however, the reported prognosis of T-ALL with SET-CAN/NUP214 fusion is diverse, and the optimal treatment option remains undetermined. Here, we present the treatment process of an illuminating case of T-ALL with SET-CAN/NUP214 fusion. The patient showed early resistance to routine VICLP chemotherapy (at 15^th day, 79.2% blasts), but the leukemia burden was significantly reduced after 28-day induction chemotherapy (18.85% blasts), even though she still didn't achieve complete remission (CR) after a second course of high-dose methotrexate (3 g/m2) and pegaspargase. Ex vivo drug sensitivity screening using a panel of 165 kinds of cytotoxic drugs, targeted therapy drugs, combination chemotherapy drugs, etc., was conducted on the refractory leukemia cells, which showed extensive resistance to various regimens. Surprisingly, AML-like scheme DAE scheme (daunorubicin + cytarabine + etoposide) and carfilzomib showed the highest ex vivo inhibition rate. The patient received DAE regimen chemotherapy, and finally achieved complete remission and received allogenic hematopoietic stem cell transplantation (allo-HSCT). According to our own findings and a literature survey, we found that T-ALL patients with SET-CAN/NUP214 fusion usually shows early resistance to chemotherapy, but they have a delayed response, and the CR rate is not compromised; thus, a chemotherapy regimen featuring a 28-day long course, such as that used in GRAALL 2003 or 2005, is recommended for induction therapy. For refractory patients, AML-like therapy such as DAE or CLAG in combination with asparaginase may be beneficial. In addition, carfilzomib may be a useful therapeutic drug and is worthy of further study. Allo-HSCT improves prognosis and we recommend HSCT if possible. Additional chromosomal or molecular events may affect the prognosis, and further investigation is needed. We believe that through proper treatment, the prognosis of patients with SET-CAN/NUP214 fusion can be greatly improved, at least not worse than that of other T-ALL patients.

Mutations that collaborate with IL-7Ra signaling pathways to drive ALL

The IL-7 pathway is required for normal T cell development and survival. In recent years the pathway has been shown to be a major driver of acute lymphoblastic leukemia (ALL), the most common cancer in children. Gain-of-function mutations in the alpha chain of the IL-7 receptor found in ALL patients clearly demonstrated that this pathway was a driver. However mutant IL-7R alone was insufficient to transform primary T cell progenitors, indicating that cooperating mutations were required. Here we review evidence for additional oncogenic mutations in the IL-7 pathway. We discuss several oncogenes, loss of tumor suppressor genes and epigenetic effects that can cooperate with mutant IL-7 receptor. These include NRas, HOXA, TLX3, Notch 1, Arf, PHF6, WT1, PRC, PTPN2 and CK2. As new therapeutics targeting the IL-7 pathway are developed, combination with agents directed to cooperating pathways offer hope for novel therapies for ALL.

Plant homeodomain finger protein 6 in the regulation of normal and malignant hematopoiesis

PURPOSE OF REVIEW

Even though an increasing amount of sequencing data on the leukemia genome has highlighted a tumor-suppressive function for plant homeodomain finger protein 6 (PHF6), its role in the hematopoietic system remained elusive until recently. The purpose of this review is to describe the role of PHF6 in normal hematopoiesis and leukemogenesis based on recent findings from knockout mouse models.

RECENT FINDINGS

In a mouse model, the loss of Phf6 enhanced the bone marrow repopulating capacity of hematopoietic stem cells (HSCs) during serial transplantations without transforming hematopoietic cells, whereas donor mice, which lacked Phf6 expression in the hematopoietic system, did not show any apparent phenotypes in the steady-state. Mechanistically, Phf6 activates effectors in the tumor necrosis factor α (Tnfα) pathway. Therefore, a Phf6 deficiency attenuates the expression of the effectors and confers resistance against Tnfα-mediated growth inhibition to HSCs. Moreover, the loss of Phf6 promoted the development of leukemia induced by aberrant TLX3 expression or an active NOTCH mutation.

SUMMARY

Phf6 restricts the self-renewal of HSCs by governing the Tnfα pathway. Phf6 fulfills a tumor-suppressive function, and its loss synergizes with leukemic lesions to promote the onset of hematological malignancies.

PHF6 Expression Levels Impact Human Hematopoietic Stem Cell Differentiation

Transcriptional control of hematopoiesis involves complex regulatory networks and functional perturbations in one of these components often results in malignancies. Loss-of-function mutations in PHF6, encoding a presumed epigenetic regulator, have been primarily described in T cell acute lymphoblastic leukemia (T-ALL) and the first insights into its function in normal hematopoiesis only recently emerged from mouse modeling experiments. Here, we investigated the role of PHF6 in human blood cell development by performing knockdown studies in cord blood and thymus-derived hematopoietic precursors to evaluate the impact on lineage differentiation in well-established in vitro models. Our findings reveal that PHF6 levels differentially impact the differentiation of human hematopoietic progenitor cells into various blood cell lineages, with prominent effects on lymphoid and erythroid differentiation. We show that loss of PHF6 results in accelerated human T cell development through reduced expression of NOTCH1 and its downstream target genes. This functional interaction in developing thymocytes was confirmed in vivo using a phf6-deficient zebrafish model that also displayed accelerated developmental kinetics upon reduced phf6 or notch1 activation. In summary, our work reveals that appropriate control of PHF6 expression is important for normal human hematopoiesis and provides clues towards the role of PHF6 in T-ALL development.

Single-cell analysis of structural variations and complex rearrangements with tri-channel processing

Structural variation (SV), involving deletions, duplications, inversions and translocations of DNA segments, is a major source of genetic variability in somatic cells and can dysregulate cancer-related pathways. However, discovering somatic SVs in single cells has been challenging, with copy-number-neutral and complex variants typically escaping detection. Here we describe single-cell tri-channel processing (scTRIP), a computational framework that integrates read depth, template strand and haplotype phase to comprehensively discover SVs in individual cells. We surveyed SV landscapes of 565 single cells, including transformed epithelial cells and patient-derived leukemic samples, to discover abundant SV classes, including inversions, translocations and complex DNA rearrangements. Analysis of the leukemic samples revealed four times more somatic SVs than cytogenetic karyotyping, submicroscopic copy-number alterations, oncogenic copy-neutral rearrangements and a subclonal chromothripsis event. Advancing current methods, single-cell tri-channel processing can directly measure SV mutational processes in individual cells, such as breakage-fusion-bridge cycles, facilitating studies of clonal evolution, genetic mosaicism and SV formation mechanisms, which could improve disease classification for precision medicine.

MicroRNA-214 suppresses cell proliferation and migration and cell metabolism by targeting PDK2 and PHF6 in hepatocellular carcinoma

MiR-214 has been reported to act as a tumor suppressor or oncogene involved in various malignancies. However, the biological functions and molecular mechanisms of miR-214 in hepatocellular carcinoma (HCC) still remain unclear. Previous studies suggest that pyruvate dehydrogenase kinase 2 (PDK2) and plant homeodomain finger protein 6 (PHF6) may be involved in some tumor cell proliferation and migration. Therefore, we studied the relationship between PDK2/PHF6 and miR-214. The expression of miR-214, PDK2, and PHF6 was determined by quantitative real-time polymerase chain reaction in HCC tissues and cell lines. The Luciferase reporter assay was used to confirm the interaction between miR-214 and PDK2/PHF6. Cell proliferation, apoptosis, and migration were evaluated by cell counting kit-8 assay, flow cytometry, and transwell assay, respectively. The expressions levels of α-smooth muscle actin (α-SMA) and E-cadherin were detected via immunofluorescence assay. Here, we found that the expression of miR-214 decreased in HCC and was negatively correlated with PDK2 and PHF6. Moreover, PDK2 and PHF6 were the direct targets of miR-214 in HCC cells. Functional analysis showed that knockdown of PDK2 or PHF6 as well as miR-214 overexpression significantly suppressed cell proliferation and migration in HCC cells. Furthermore, we found that the suppression of cell proliferation and migration through PDK2 or PHF6 knockdown could be partially reversed by miR-214 down-regulation. Moreover, we demonstrated a decrease of mesenchymal cell marker α-SMA and increase of the epithelial marker E-cadherin after miR-214 overexpression, PDK2 knockdown or PHF6 knockdown, respectively, which also suggested that cell proliferation and migration were suppressed. Additionally, lactate and pyruvic acid production experiments confirmed miR-214 could suppress the HCC cell lactate and pyruvic acid levels by down-regulating PDK2/PHF6. In conclusion, MiR-214 may act as a tumor suppressor gene, presenting its suppressive role in cell proliferation and migration of HCC cells by targeting PDK2 and PHF6, and might provide a potential therapy target for patients with HCC.

PHF6 and DNMT3A mutations are enriched in distinct subgroups of mixed phenotype acute leukemia with T-lineage differentiation

The genetic aberrations that drive mixed phenotype acute leukemia (MPAL) remain largely unknown, with the exception of a small subset of MPALs harboring BCR -ABL1 and MLL translocations. We performed clinicopathologic and genetic evaluation of 52 presumptive MPAL cases at Memorial Sloan Kettering Cancer Center. Only 29 out of 52 (56%) cases were confirmed to be bona fide MPAL according to the 2016 World Heath Organization classification. We identified PHF6 and DNMT3A mutations as the most common recurrent mutations in MPAL, each occurring in 6 out of 26 (23%) cases. These mutations are mutually exclusive of each other and BCR-ABL1/MLL translocations. PHF6- and DNMT3A-mutated MPAL showed marked predilection for T-lineage differentiation (5/6 PHF6 mutated, 6/6 DNMT3A mutated). PHF6-mutated MPAL occurred in a younger patient cohort compared with DNMT3A-mutated cases (median age, 27 years vs 61 years, P < .01). All 3 MPAL cases with both T- and B-lineage differentiation harbored PHF6 mutations. MPAL with T-lineage differentiation was associated with nodal or extramedullary involvement (9/15 [60%] vs 0, P = .001) and a higher relapse incidence (78% vs 22%, P = .017) compared with those without T-lineage differentiation. Sequencing studies on flow-cytometry-sorted populations demonstrated that PHF6 mutations are present in all blast compartments regardless of lineage differentiation with high variant allele frequency, implicating PHF6 as an early mutation in MPAL pathogenesis. In conclusion, PHF6 and DNMT3A mutations are the most common somatic alterations identified in MPAL and appear to define 2 distinct subgroups of MPAL with T-lineage differentiation with inferior outcomes.

Downregulation of PHF6 Inhibits Cell Proliferation and Migration in Hepatocellular Carcinoma

Background: The plant homeodomain finger 6 (PHF6) was originally identified as single gene mutated in Börjeson-Forssman-Lehmann syndrome, which was reported to be a tumor suppressor in T-cell acute lymphoblastic leukemia. However, the biological function of PHF6 in hepatocellular carcinoma (HCC) has been poorly characterized. Materials and Methods: In this study, we first determined the mRNA levels of PHF6 in HCC tissues and adjacent normal tissues using quantitative real-time PCR. Then the expression of PHF6 was knocked down in HCC cell lines (HepG2, SMMC-7721, and Bel-7402) by siRNA transfection. A series of functional experiments, including EdU proliferation assay, colony formation assay, and Transwell assay, were performed in HCC cells. Western blot analysis was used to detect the expression of PHF6, E-cadherin, and Vimentin. Results: We found that PHF6 was significantly elevated in HCC tissues and positively correlated with TNM stage, differentiation, and lymph node metastasis. Silencing PHF6 significantly inhibited cell proliferation, colony formation, and migration in HCC cells. Furthermore, silencing PHF6 obviously increased E-cadherin and decreased Vimentin expression. Conclusions: These findings suggest that PHF6 plays a positive role in the growth of HCC cells, and targeting PHF6 could serve as a promising therapeutic strategy for human HCC.

PHF6 regulates hematopoietic stem and progenitor cells and its loss synergizes with expression of TLX3 to cause leukemia

Somatically acquired mutations in PHF6 (plant homeodomain finger 6) frequently occur in hematopoietic malignancies and often coincide with ectopic expression of TLX3. However, there is no functional evidence to demonstrate whether these mutations contribute to tumorigenesis. Similarly, the role of PHF6 in hematopoiesis is unknown. We report here that Phf6 deletion in mice resulted in a reduced number of hematopoietic stem cells (HSCs), an increased number of hematopoietic progenitor cells, and an increased proportion of cycling stem and progenitor cells. Loss of PHF6 caused increased and sustained hematopoietic reconstitution in serial transplantation experiments. Interferon-stimulated gene expression was upregulated in the absence of PHF6 in hematopoietic stem and progenitor cells. The numbers of hematopoietic progenitor cells and cycling hematopoietic stem and progenitor cells were restored to normal by combined loss of PHF6 and the interferon α and β receptor subunit 1. Ectopic expression of TLX3 alone caused partially penetrant leukemia. TLX3 expression and loss of PHF6 combined caused fully penetrant early-onset leukemia. Our data suggest that PHF6 is a hematopoietic tumor suppressor and is important for fine-tuning hematopoietic stem and progenitor cell homeostasis.

NUP214 in Leukemia: It's More than Transport

NUP214 is a component of the nuclear pore complex (NPC) with a key role in protein and mRNA nuclear export. Chromosomal translocations involving the NUP214 locus are recurrent in acute leukemia and frequently fuse the C-terminal region of NUP214 with SET and DEK, two chromatin remodeling proteins with roles in transcription regulation. SET-NUP214 and DEK-NUP214 fusion proteins disrupt protein nuclear export by inhibition of the nuclear export receptor CRM1, which results in the aberrant accumulation of CRM1 protein cargoes in the nucleus. SET-NUP214 is primarily associated with acute lymphoblastic leukemia (ALL), whereas DEK-NUP214 exclusively results in acute myeloid leukemia (AML), indicating different leukemogenic driver mechanisms. Secondary mutations in leukemic blasts may contribute to the different leukemia outcomes. Additional layers of complexity arise from the respective functions of SET and DEK in transcription regulation and chromatin remodeling, which may drive malignant hematopoietic transformation more towards ALL or AML. Another, less frequent fusion protein involving the C terminus of NUP214 results in the sequestosome-1 (SQSTM1)-NUP214 chimera, which was detected in ALL. SQSTM1 is a ubiquitin-binding protein required for proper autophagy induction, linking the NUP214 fusion protein to yet another cellular mechanism. The scope of this review is to summarize the general features of NUP214-related leukemia and discuss how distinct chromosomal translocation partners can influence the cellular effects of NUP214 fusion proteins in leukemia.

Clinical and biological relevance of genetic alterations in pediatric T-cell acute lymphoblastic leukemia in Taiwan

BACKGROUND

The leukemogenesis of T-cell acute lymphoblastic leukemia (T-ALL) involves multistep processes of genetic alterations. We aimed to determine the genetic alterations including common fusion transcripts, overexpression of T-cell transcription factor oncogenes, and deletion or mutation of targeted genes in pediatric T-ALL in Taiwan as well as their impact on outcomes in those treated with the Taiwan Pediatric Oncology Group-ALL-2002 protocol.

PROCEDURE

Between 1995 and 2015, bone marrow samples obtained from 102 children aged <18 years consecutively diagnosed with T-ALL were examined. Thirty-two genetic alterations were examined by reverse transcription polymerase chain reaction (PCR) assays-PCR-based assays-followed by direct sequencing, real time quantitative PCR with TaqMan assays, or multiplex ligase probe amplification.

RESULTS

TAL1 overexpression, CDKN2A/2B deletions, and NOTCH1 mutation were the most frequent aberrations while none had NF1, SUZ12 deletion, JAK1 or JAK2 mutations, or NUP214-ABL1 fusion in our cohort. The most frequent cooperating occurrence of genetic alterations included CDKN2A/2B and MTAP, MTAP and CDKN2B, LEF1 and PTPN2, and HOX11L2 and PHF6 mutation/deletion. NOTCH1 mutations conferred a favorable overall survival, whereas SIL-TAL1 fusion, TAL overexpression, LEF1 deletion, and PHF6 deletion/mutation were associated with an inferior outcome. By multivariate analysis, PHF6 mutation/deletion was the only independent predictor for inferior overall survival.

CONCLUSIONS

The present study showed that the frequencies of genetic alterations in Taiwanese children with T-ALL differed considerably from those reported in Western countries. PHF6 mutation/deletion was an independently adverse predictor.

Clinical and molecular characteristics of MEF2D fusion-positive B-cell precursor acute lymphoblastic leukemia in childhood, including a novel translocation resulting in MEF2D-HNRNPH1 gene fusion

Fusion genes involving MEF2D have recently been identified in precursor B-cell acute lymphoblastic leukemia, mutually exclusive of the common risk stratifying genetic abnormalities, although their true incidence and associated clinical characteristics remain unknown. We identified 16 cases of acute lymphoblastic leukemia and 1 of lymphoma harboring MEF2D fusions, including MEF2D-BCL9 (n=10), MEF2D-HNRNPUL1 (n=6), and one novel MEF2D-HNRNPH1 fusion. The incidence of MEF2D fusions overall was 2.4% among consecutive precursor B-cell acute lymphoblastic leukemia patients enrolled onto a single clinical trial. They frequently showed a cytoplasmic μ chain-positive pre-B immunophenotype, and often expressed an aberrant CD5 antigen. Besides up- and down-regulation of HDAC9 and MEF2C, elevated GATA3 expression was also a characteristic feature of MEF2D fusion-positive patients. Mutations of PHF6, recurrent in T-cell acute lymphoblastic leukemia, also showed an unexpectedly high frequency (50%) in these patients. MEF2D fusion-positive patients were older (median age 9 years) with elevated WBC counts (median: 27,300/ml) at presentation and, as a result, were mostly classified as NCI high risk. Although they responded well to steroid treatment, MEF2D fusion-positive patients showed a significantly worse outcome, with 53.3% relapse and subsequent death. Stem cell transplantation was ineffective as salvage therapy. Interestingly, relapse was frequently associated with the presence of CDKN2A/CDKN2B gene deletions. Our observations indicate that MEF2D fusions comprise a distinct subgroup of precursor B-cell acute lymphoblastic leukemia with a characteristic immunophenotype and gene expression signature, associated with distinct clinical features.

Ikaros family zinc-finger 1 mutation is an independent factor for the poor prognosis of adult B-cell acute lymphoblastic leukemia, and allogeneic hematopoietic stem cell transplantation can improve clinical outcomes

To investigate the prognosis of patients with adult B-cell acute lymphoblastic leukemia (B-ALL) with Ikaros family zinc-finger 1 (IKZF1) mutation and determine the role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in improving the clinical outcome, we detected the IKZF1 mutation and BCR-ABL fusion gene at diagnosis in the bone marrow of 164 adult patients with B-ALL, and analyzed the clinical data of these patients retrospectively. Our analysis showed that grade III-IV acute graft-versus-host disease and IKZF1 mutation in the transplantation group and age and IKZF1 mutation in the non-transplantation group were independent factors for poor prognosis by univariate and multivariate analyses.The 3-year overall survival (OS) and leukemia-free survival (LFS) rates were much lower in the IKZF1+/BCR-ABL+ subgroup than in the IKZF1+/BCR-ABL- and IKZF1-/BCR-ABL- subgroups in both the transplantation and non-transplantation groups. The 3-year OS and LFS rates were significantly higher in the transplantation group than in the non-transplantation group with IKZF1 mutation.The study demonstrated that IKZF1 mutation was an independent factor indicating the poor prognosis of adult B-ALL and much worse prognosis in the BCR-ABL+ subgroup in both non-transplantation and transplantation groups. However, allo-HSCT significantly improved the OS and LFS of patients and also their clinical outcomes.

New Challenges in Targeting Signaling Pathways in Acute Lymphoblastic Leukemia by NGS Approaches: An Update

The identification and study of genetic alterations involved in various signaling pathways associated with the pathogenesis of acute lymphoblastic leukemia (ALL) and the application of recent next-generation sequencing (NGS) in the identification of these lesions not only broaden our understanding of the involvement of various genetic alterations in the pathogenesis of the disease but also identify new therapeutic targets for future clinical trials. The present review describes the main deletions, amplifications, sequence mutations, epigenetic lesions, and new structural DNA rearrangements detected by NGS in B-ALL and T-ALL and their clinical importance for therapeutic procedures. We reviewed the molecular basis of pathways including transcriptional regulation, lymphoid differentiation and development, TP53 and the cell cycle, RAS signaling, JAK/STAT, NOTCH, PI3K/AKT/mTOR, Wnt/β-catenin signaling, chromatin structure modifiers, and epigenetic regulators. The implementation of NGS strategies has enabled important mutated genes in each pathway, their associations with the genetic subtypes of ALL, and their outcomes, which will be described further. We also discuss classic and new cryptic DNA rearrangements in ALL identified by mRNA-seq strategies. Novel cooperative abnormalities in ALL could be key prognostic and/or predictive biomarkers for selecting the best frontline treatment and for developing therapies after the first relapse or refractory disease.

Allogeneic Hematopoietic Stem Cell Transplantation with Myeloablative Conditioning Is Associated with Favorable Outcomes in Mixed Phenotype Acute Leukemia

Mixed phenotype acute leukemia (MPAL) represents a poorly characterized group of acute leukemias that lack an accepted therapeutic approach and are typically associated with poor outcomes. We present our experience of genomic profiling, pretransplantation therapy, and transplantation outcomes for 36 well-characterized pediatric and adult patients with MPAL, defined according to the 2016 World Health Organization leukemia update. A predominance of acute lymphoid leukemia (ALL)-associated mutations and cytogenetic abnormalities was noted. Remission rates after induction appeared comparable among adults (20 of 23) and children (11 of 13) and among those who received ALL (10 of 11) or acute myeloid leukemia-type (21 of 25) induction. Adults underwent transplantation in first remission while children underwent transplantation in the setting of relapse or MLL rearrangement. The median follow-up among the 25 patients who underwent transplantation was 39.6 months and median overall survival was not reached. Relapse after transplantation was associated with MLL rearrangement (P = .022), reduced-intensity conditioning (P < .001), and higher WBC at diagnosis (P = .034). These data highlight differing therapeutic approaches between adult and pediatric MPAL and demonstrate favorable survival of adult MPAL patients consolidated with allogeneic hematopoietic cell transplantation.

TP53 in adult acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is characterized by a great biological and clinical heterogeneity. Despite most adult patients enter complete hematologic remission after induction therapy only 40% survive five or more years. Over the last 20 years, the definition of an accurate biologic leukemia profile and the minimal residual disease evaluation in addition to conventional risk criteria led to a significant improvement for the risk stratification. The alterations of the oncosuppressor gene TP53, including deletions, sequence mutations and defect in its expression due to regulatory defects, define a new important predictor of adverse outcome. More recently, new drugs have been developed with the aim of targeting p53 protein itself or its regulatory molecules, such as Mdm2, and restoring the pathway functionality. Therefore, TP53 alterations should be considered in the diagnostic work-up to identify high risk ALL patients in need of intensive treatment strategies or eligible for new innovative targeted therapies.

PHF6 regulates phenotypic plasticity through chromatin organization within lineage-specific genes

In this study, Soto-Feliciano et al. describe the function of the plant homeodomain finger 6 (PHF6) protein in leukemia and define its role in regulating chromatin accessibility to lineage-specific transcription factors. Their findings suggest that active maintenance of a precise chromatin landscape is essential for sustaining proper leukemia cell identity and that loss of a single factor (PHF6) can cause focal changes in chromatin accessibility and nucleosome positioning that render cells susceptible to lineage transition.

Developmental and lineage plasticity have been observed in numerous malignancies and have been correlated with tumor progression and drug resistance. However, little is known about the molecular mechanisms that enable such plasticity to occur. Here, we describe the function of the plant homeodomain finger protein 6 (PHF6) in leukemia and define its role in regulating chromatin accessibility to lineage-specific transcription factors. We show that loss of Phf6 in B-cell leukemia results in systematic changes in gene expression via alteration of the chromatin landscape at the transcriptional start sites of B-cell- and T-cell-specific factors. Additionally, Phf6^KO cells show significant down-regulation of genes involved in the development and function of normal B cells, show up-regulation of genes involved in T-cell signaling, and give rise to mixed-lineage lymphoma in vivo. Engagement of divergent transcriptional programs results in phenotypic plasticity that leads to altered disease presentation in vivo, tolerance of aberrant oncogenic signaling, and differential sensitivity to frontline and targeted therapies. These findings suggest that active maintenance of a precise chromatin landscape is essential for sustaining proper leukemia cell identity and that loss of a single factor (PHF6) can cause focal changes in chromatin accessibility and nucleosome positioning that render cells susceptible to lineage transition.

Biallelic JAK1 mutations in immunodeficient patient with mycobacterial infection

Mutations in genes encoding components of the immune system cause primary immunodeficiencies. Here, we study a patient with recurrent atypical mycobacterial infection and early-onset metastatic bladder carcinoma. Exome sequencing identified two homozygous missense germline mutations, P733L and P832S, in the JAK1 protein that mediates signalling from multiple cytokine receptors. Cells from this patient exhibit reduced JAK1 and STAT phosphorylation following cytokine stimulations, reduced induction of expression of interferon-regulated genes and dysregulated cytokine production; which are indicative of signalling defects in multiple immune response pathways including Interferon-γ production. Reconstitution experiments in the JAK1-deficient cells demonstrate that the impaired JAK1 function is mainly attributable to the effect of the P733L mutation. Further analyses of the mutant protein reveal a phosphorylation-independent role of JAK1 in signal transduction. These findings clarify JAK1 signalling mechanisms and demonstrate a critical function of JAK1 in protection against mycobacterial infection and possibly the immunological surveillance of cancer.

JAK1 mediates intracellular signalling from multiple cytokine receptors. Here, Eletto et al. identify JAK1 mutations that disrupt multiple signalling pathways and are associated with primary immunodeficiency, atypical mycobacterial infection susceptibility and early-onset metastatic bladder carcinoma.

Novel dynamin 2 mutations in adult T-cell acute lymphoblastic leukemia

Genetic mutations on signaling pathways are found in patients with T-cell acute lymphoblastic leukemia (T-ALL) and act as markers of high-risk leukemia. Mutations in dynamin 2 (DNM2) have been reported in T-ALL, particularly in early T-cell precursor-ALL. In the present study, DNM2 mutations were screened by sequencing DNM2 exons obtained by polymerase chain reaction amplification and gel purification in adult T-ALL patients. A total of 4 novel DNM2 mutations were identified in adult T-ALL patients, with a mutation rate of 9.5%, and the DNM2 mutations were found to co-exist with NOTCH1 and PHD finger protein 6, and were also associated with high-risk leukemia. A high rate of silent mutation was also found in the patients, but no significant association was found between the silent mutations and patients' clinical features. The present findings suggested the DNM2 mutations may be involved in the oncogenesis of T-ALL.

Co-existence of PHF6 and NOTCH1 mutations in adult T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) results from the collaboration of multiple genetic abnormalities in the transformation of T-cell progenitors. Plant homeodomain finger protein 6 (PHF6) has recently been established as a key tumor suppressor, which is mutated in T-ALL; however, the clinical significance of PHF6 mutations has not been fully determined in adult T-ALL. In the present study, amplification of the PHF6 exons was performed, followed by DNA sequencing to identify the genomic mutations and examine the expression of PHF6 in adult patients with T-ALL. The correlation between PHF6 mutations and clinical features was also analyzed using a χ² test, and between PHF6 mutations and survival curve using the Kaplan-Meier methods. PHF6 mutations were detected in 27.1% of the Chinese adults with T-ALL (16/59), 10 of which were found to be novel mutations. A significantly lower expression level of PHF6 was observed in T-ALL patients with PHF6 mutations compared with those without mutations. Of the observed mutations in PHF6, 6/16 were frame-shift mutations, indicating a PHF6 dysfunction in those patients. Of note, PHF6 mutations were found to be significantly associated with older age, lower hemoglobin levels, higher frequency of CD13 positivity and higher incidence of splenomegaly or lymphadenopathy. Furthermore, PHF6 mutations were found to be significantly correlated with Notch homolog 1, translocation-associated (Drosophila) (NOTCH1) mutations. The patients with T-ALL with co-existence of the two mutations had a significantly shorter event-free survival and a poor prognosis. The present results indicated that PHF6 is inactivated in adult T-ALL, due to its low expression and mutations. The present data indicated the synergistic effect of PHF6 and NOTCH1 mutations, as well as their co-existence, on the oncogenesis of adult T-ALL, and their potential as a prognostic marker for the disease.

The potential role of PHF6 as an oncogene: a genotranscriptomic/proteomic meta-analysis

Epigenetic complexes control various pathways within the cells. Their abnormalities can be involved in the initiation and the progression of different types of cancer. Nucleosome remodeling and deacetylase (NuRD) is an epigenetic complex that comprises several subunits such as PHF6. Although PHF6 is reported as a tumor suppressor in some of the hematopoietic malignancies, its function is still challenging in other cancers. Our study aimed at investigating the role of PHF6 in different types of cancer. We conducted a meta-analysis of PHF6 in human cancers at genomic, transcriptomic, and proteomic levels. For this purpose, we acquired the data from several databases, and tried to statistically integrate and analyze the data in order to find the potential role of PHF6 in different tumors. The results demonstrated that although PHF6 has been previously known as a tumor suppressor gene, it was remarkably overexpressed in many cancer types such as breast and colorectal cancers. Notably, PHF6 was under-expressed in a few types of cancer, including esophageal tumors. Moreover, the results indicated that although the mutation rate of PHF6 is relatively low, it is mutated in some tumor types.  In addition, our data for 40 epigenetic genes showed that missense and nonsense mutations were associated with overexpression and under-expression, respectively. Our results suggest that PHF6 may function as an oncogenic factor in several types of cancer. We also hypothesize that PHF6 may also play its role in a tissue-specific manner. Our findings suggest further investigations regarding the exact role of PHF6 in tumor types.

B-cell acute lymphoblastic leukemia associated with SET-NUP214 rearrangement: A case report and review of the literature

The SET nuclear proto-oncogene (SET)-nucleoporin (NUP)214 fusion gene, which results from cryptic t(9;9)(q34;q34) or del(9)(q34.11q34.13), is a rare genetic event in hematological malignancies. The majority of patients carrying SET-NUP214 experience T-cell acute lymphoblastic leukemia (T-ALL), but rarely experience acute undifferentiated leukemia or acute myeloid leukemia. The current study presents the case of a 19-year-old male patient with B-cell ALL (B-ALL) carrying the SET-NUP214 fusion gene, in addition to an fms-related tyrosine kinase 3-internal tandem duplication mutation and a complex karyotype abnormality. The patient exhibited chemotherapy resistance. To the best of our knowledge, the present study is the first report of a case of B-ALL carrying the SET-NUP214 fusion gene, and provides a review of the literature.

Genetic mutational profiling analysis of T cell acute lymphoblastic leukemia reveal mutant FBXW7 as a prognostic indicator for inferior survival

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive neoplasm for which there are currently no adequate biomarkers for developing risk-adapted therapeutic regimens to improve the treatment outcome. In this prospective study of 83 Chinese patients (54 children and 29 adults) with de novo T-ALL, we analyzed mutations in 11 T-ALL genes: NOTCH1, FBXW7, PHF6, PTEN, N-RAS, K-RAS, WT1, IL7R, PIK3CA, PIK3RA, and AKT1. NOTCH1 mutations were identified in 51.9 and 37.9 % of pediatric and adult patients, respectively, and these patients showed improved overall survival (OS) and event-free survival (EFS). The FBXW7 mutant was present in 25.9 and 6.9 % of pediatric and adult patients, respectively, and was associated with inferior OS and EFS in pediatric T-ALL. Multivariate analysis revealed that mutant FBXW7 was an independent prognostic indicator for inferior EFS (hazard ratio [HR] 4.38; 95 % confidence interval [CI] 1.15-16.71; p = 0.03) and tended to be associated with reduced OS (HR 2.81; 95 % CI 0.91-8.69; p = 0.074) in pediatric T-ALL. Mutant PHF6 was present in 13 and 20.7 % of our childhood and adult cohorts, respectively, while PTEN mutations were noted in 11.1 % of the pediatric patients. PTEN and NOTCH1 mutations were almost mutually exclusive, while IL7R and WT1 mutations were rare in pediatric T-ALL and PTPN11 and AKT1 mutations were infrequent in adult T-ALL. This study revealed differences in the mutational profiles of pediatric and adult T-ALL and suggests mutant FBXW7 as an independent prognostic indicator for inferior survival in pediatric T-ALL.

Epigenetics in T-cell acute lymphoblastic leukemia

Normal T-cell development is a strictly regulated process in which hematopoietic progenitor cells migrate from the bone marrow to the thymus and differentiate from early T-cell progenitors toward mature and functional T cells. During this maturation process, cooperation between a variety of oncogenes and tumor suppressors can drive immature thymocytes into uncontrolled clonal expansion and cause T-cell acute lymphoblastic leukemia (T-ALL). Despite improved insights in T-ALL disease biology and comprehensive characterization of its genetic landscape, clinical care remained largely similar over the past decades and still consists of high-dose multi-agent chemotherapy potentially followed by hematopoietic stem cell transplantation. Even with such aggressive treatment regimens, which are often associated with considerable side effects, clinical outcome is still extremely poor in a significant subset of T-ALL patients as a result of therapy resistance or hematological relapses. Recent genetic studies have identified recurrent somatic alterations in genes involved in DNA methylation and post-translational histone modifications in T-ALL, suggesting that epigenetic homeostasis is critically required in restraining tumor development in the T-cell lineage. In this review, we provide an overview of the epigenetic regulators that could be implicated in T-ALL disease biology and speculate how the epigenetic landscape of T-ALL could trigger the development of epigenetic-based therapies to further improve the treatment of human T-ALL.

PHF6 Degrees of Separation: The Multifaceted Roles of a Chromatin Adaptor Protein

The importance of chromatin regulation to human disease is highlighted by the growing number of mutations identified in genes encoding chromatin remodeling proteins. While such mutations were first identified in severe developmental disorders, or in specific cancers, several genes have been implicated in both, including the plant homeodomain finger protein 6 (PHF6) gene. Indeed, germline mutations in PHF6 are the cause of the Börjeson–Forssman–Lehmann X-linked intellectual disability syndrome (BFLS), while somatic PHF6 mutations have been identified in T-cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML). Studies from different groups over the last few years have made a significant impact towards a functional understanding of PHF6 protein function. In this review, we summarize the current knowledge of PHF6 with particular emphasis on how it interfaces with a distinct set of interacting partners and its functional roles in the nucleoplasm and nucleolus. Overall, PHF6 is emerging as a key chromatin adaptor protein critical to the regulation of neurogenesis and hematopoiesis.

Diagnosis and subclassification of acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is a disseminated malignancy of B- or T-lymphoblasts which imposes a rapid and accurate diagnostic process to support an optimal risk-oriented therapy and thus increase the curability rate. The need for a precise diagnostic algorithm is underlined by the awareness that both ALL therapy and related success rates may vary greatly between ALL subsets, from standard chemotherapy in patients with standard-risk ALL, to allotransplantation (SCT) and targeted therapy in high-risk patients and cases expressing suitable biological targets, respectively. This review summarizes how best to identify ALL and the most relevant ALL subsets.