RUNX1::ETO and CBFß::MYH11 converge on aberrant activation of BCAT1 to confer a therapeutic vulnerability in core-binding factor-acute myeloid leukaemia.

Effectively targeting transcription factors in therapeutic interventions remains challenging, especially in core-binding factor-acute myeloid leukaemia (CBF-AML) characterized by RUNX1::ETO and CBFß::MYH11 fusions. However, recent studies have drawn attention towards aberrant amino acid metabolisms as actionable therapeutic targets. Here, by integrating the expression profile and genetic makeup in AML cohort, we found higher BCAT1 expression in CBF-AML patients compared with other subtypes. Metabolic profiling revealed that high BCAT1 expression led to reprogrammed branch amino acid metabolism in CBF-AML and was associated with sphingolipid pathway relating to the fitness of leukaemia cells, supported by transcriptomic profiling. Mechanistically, we demonstrated in cell lines and primary patient samples that BCAT1 was directly activated by RUNX1::ETO and CBFß::MYH11 fusion proteins similarly in a RUNX1-dependent manner through rewiring chromatin conformation at the BCAT1 gene locus. Furthermore, BCAT1 inhibition resulted in blunted cell cycle, enhanced apoptosis and myeloid differentiation of CBF-AML cells in vitro, and alleviated leukaemia burden and prolonged survival in vivo. Importantly, pharmacological inhibition of BCAT1 using the specific inhibitor Gabapentin demonstrated therapeutic effects, as evidenced by delayed leukaemia progression and improved survival in vivo. In conclusion, our study uncovers BCAT1 as a genetic vulnerability and a promising targeted therapeutic opportunity for CBF-AML.

Hypoxia inhibits HUNK kinase activity to induce epithelial-mesenchymal transition.

Hypoxia is a common hallmark of cancer and plays a crucial role in promoting epithelial-mesenchymal transition (EMT). Hormonally Upregulated Neu-associated Kinase (HUNK) regulates EMT through its kinase activity. However, whether hypoxia is involved in HUNK-mediated EMT is incompletely understood. This study unveils an association between HUNK kinase activity and hypoxia in colorectal cancer (CRC). Importantly, hypoxia does not alter the expression levels of HUNK, but directly affects the phosphorylation levels of downstream proteins with indication of HUNK activity. Functionally, the upregulation of migration, invasion, and expression of EMT markers in CRC cells under hypoxic conditions can be attributed, in part, to the downregulation of HUNK-mediated phosphorylation of downstream proteins. These findings highlight the intricate relationship between HUNK, hypoxia and the molecular mechanisms of cancer EMT. Understanding these mechanisms may provide valuable insights into therapeutic targets for inhibiting cancer metastasis.

Molecular basis of ETV6-mediated predisposition to childhood acute lymphoblastic leukemia.

There is growing evidence supporting an inherited basis for susceptibility to acute lymphoblastic leukemia (ALL) in children. In particular, we and others reported recurrent germline ETV6 variants linked to ALL risk, which collectively represent a novel leukemia predisposition syndrome. To understand the influence of ETV6 variation on ALL pathogenesis, we comprehensively characterized a cohort of 32 childhood leukemia cases arising from this rare syndrome. Of 34 nonsynonymous germline ETV6 variants in ALL, we identified 22 variants with impaired transcription repressor activity, loss of DNA binding, and altered nuclear localization. Missense variants retained dimerization with wild-type ETV6 with potentially dominant-negative effects. Whole-transcriptome and whole-genome sequencing of this cohort of leukemia cases revealed a profound influence of germline ETV6 variants on leukemia transcriptional landscape, with distinct ALL subsets invoking unique patterns of somatic cooperating mutations. 70% of ALL cases with damaging germline ETV6 variants exhibited hyperdiploid karyotype with characteristic recurrent mutations in NRAS, KRAS, and PTPN11. In contrast, the remaining 30% cases had a diploid leukemia genome and an exceedingly high frequency of somatic copy-number loss of PAX5 and ETV6, with a gene expression pattern that strikingly mirrored that of ALL with somatic ETV6-RUNX1 fusion. Two ETV6 germline variants gave rise to both acute myeloid leukemia and ALL, with lineage-specific genetic lesions in the leukemia genomes. ETV6 variants compromise its tumor suppressor activity in vitro with specific molecular targets identified by assay for transposase-accessible chromatin sequencing profiling. ETV6-mediated ALL predisposition exemplifies the intricate interactions between inherited and acquired genomic variations in leukemia pathogenesis.

ARID5B influences B-cell development and function in mouse.

There is growing evidence for an inherited basis of susceptibility to childhood acute lymphoblastic leukemia. Genomewide association studies by us and others have identified non-coding acute lymphoblastic leukemia risk variants at the ARID5B gene locus, but the molecular mechanisms linking ARID5B to normal and malignant hematopoiesis remain largely unknown. Using a Vav1-driven transgenic mouse model, we characterized the role of Arid5b in hematopoiesis in vivo. Arid5b overexpression resulted in a dramatic reduction in the proportion of circulating B cells, immature, and mature Bcell fractions in the peripheral blood and the bone marrow, and also a decrease of follicular B cells in the spleen. There were significant defects in B-cell activation upon Arid5b overexpression in vitro with hyperactivation of B-cell receptor signaling at baseline. In addition, increased mitochondrial oxygen consumption rate of naïve or stimulated B cells of Arid5b-overexpressing mice was observed, compared to the rate of wild-type counterparts. Taken together, our results indicate that ARID5B may play an important role in B-cell development and function.

A cis-element within the ARF locus mediates repression of p16INK4A expression via long-range chromatin interactions.

Loss of function of CDKN2A/B, also known as INK4/ARF [encoding p16INK4A, p15INK4B, and p14ARF (mouse p19Arf)], confers susceptibility to cancers, whereas its up-regulation during organismal aging provokes cellular senescence and tissue degenerative disorders. To better understand the transcriptional regulation of p16INK4A, a CRISPR screen targeting open, noncoding chromatin regions adjacent to p16INK4A was performed in a human p16INK4A-P2A-mCherry reporter cell line. We identified a repressive element located in the 3' region adjacent to the ARF promoter that controls p16INK4A expression via long-distance chromatin interactions. Coinfection of lentiviral dCas9-KRAB with selected single-guide RNAs against the repressive element abrogated the ARF/p16INK4A chromatin contacts, thus reactivating p16INK4A expression. Genetic CRISPR screening identified candidate transcription factors inhibiting p16INK4A regulation, including ZNF217, which was confirmed to bind the ARF/p16INK4A interaction loop. In summary, direct physical interactions between p16INK4A and ARF genes provide mechanistic insights into their cross-regulation.

Phase 1 study of bendamustine in combination with clofarabine, etoposide, and dexamethasone in pediatric patients with relapsed or refractory hematologic malignancies.

BACKGROUND: A phase 1 study was conducted to determine the maximum tolerated dose of bendamustine when given in combination with clofarabine, etoposide, and dexamethasone daily for 5 days in children and adolescents with relapsed or refractory hematologic malignancies. METHODS: Patients younger than 22 years with second or greater relapsed or refractory acute leukemia or lymphoma after 2 or more prior regimens were eligible. With the rolling 6 design, participants received escalating doses of bendamustine (30, 40, or 60 mg/m2 /d) in combination with clofarabine (40 mg/m2 ), etoposide (100 mg/m2 ), and dexamethasone (8 mg/m2 ) daily for 5 days. Optional pharmacokinetic studies were performed in cycle 1 on day 1 and day 5. RESULTS: Sixteen patients were enrolled. Six patients were treated at the dose level of 30 mg/m2 /d, 6 were treated at the dose level of 40 mg/m2 /d, and 4 were treated at the dose level of 60 mg/m2 /d. The dose-limiting toxicity was prolonged myelosuppression. The combination was otherwise well tolerated. The recommended dose of bendamustine in this combination was 30 mg/m2 /d for 5 days. Ten responses were observed after 1 cycle: 6 complete remissions, 1 durable minimal residual disease-negative complete remission without platelet recovery in a patient with early T-cell precursor leukemia, and 3 partial remissions. Six patients proceeded to transplantation. The event-free survival rate was 40.6% (95% confidence interval [CI], 17.5%-63.7%) at 1 year and 33.9% (95% CI, 11.9%-55.9%) at 3 years. CONCLUSIONS: Bendamustine is well tolerated in combination with clofarabine, etoposide, and dexamethasone. The combination administered over 5 days is effective for multiple relapsed and refractory hematologic malignancies. This trial is registered with ClinicalTrials.gov (NCT01900509). LAY SUMMARY: Improvements to the existing chemotherapy regimen are still needed for patients who relapse after targeted therapies and immunotherapies and for those who are not eligible for or have no access to such therapies. A regimen combining cyclophosphamide, clofarabine, and etoposide has been used in relapsed and refractory pediatric patients with hematologic malignancies. This study shows that substituting bendamustine for cyclophosphamide in combination with clofarabine and etoposide is safe and effective.

Novel susceptibility variants at the ERG locus for childhood acute lymphoblastic leukemia in Hispanics.

Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Characterized by high levels of Native American ancestry, Hispanics are disproportionally affected by this cancer with high incidence and inferior survival. However, the genetic basis for this disparity remains poorly understood because of a paucity of genome-wide investigation of ALL in Hispanics. Performing a genome-wide association study (GWAS) in 940 Hispanic children with ALL and 681 ancestry-matched non-ALL controls, we identified a novel susceptibility locus in the ERG gene (rs2836365; P = 3.76 × 10-8; odds ratio [OR] = 1.56), with independent validation (P = .01; OR = 1.43). Imputation analyses pointed to a single causal variant driving the association signal at this locus overlapping with putative regulatory DNA elements. The effect size of the ERG risk variant rose with increasing Native American genetic ancestry. The ERG risk genotype was underrepresented in ALL with the ETV6-RUNX1 fusion (P < .0005) but enriched in the TCF3-PBX1 subtype (P < .05). Interestingly, ALL cases with germline ERG risk alleles were significantly less likely to have somatic ERG deletion (P < .05). Our results provide novel insights into genetic predisposition to ALL and its contribution to racial disparity in this cancer.

Efficacy of Sodium Tanshinone IIA Sulfonate in Patients with Non-ST Elevation Acute Coronary Syndrome Undergoing Percutaneous Coronary Intervention: Results from a Multicentre, Controlled, Randomized Trial.

BACKGROUND: Sodium tanshinone IIA sulfonate (STS) has been widely used by Chinese medicine practitioners for chronic cardiovascular diseases. However, its direct clinical efficacy in patients with acute coronary syndrome following percutaneous coronary intervention (PCI) has not been reported yet. The present trial aimed to investigate potential cardioprotection of STS in patients undergoing PCI for non-ST elevation acute coronary syndrome (NSTE-ACS). METHODS: In a randomized, double-blind, placebo-controlled trial, 372 patients with NSTE-ACS were randomly assigned to receive STS (n = 192) or saline (n = 180) for 2 days before and 3 days after PCI along with standard therapy. The primary endpoint was the composite incidence of major adverse cardiac events (MACEs), including death, non-fatal myocardial infarction, repeated revascularization of the target vessel, and stent thrombosis, within 30 days after PCI. RESULTS: The 30-day MACEs occurred in 18.8% of the patients in the STS group and in 27.2% of the patients in the control group (P = 0.038); this difference was mostly driven by reduction of myocardial infarction incidence (17.2% vs. 26.7%, P = 0.027). Post-procedural elevation of troponin-I was also significantly lower in the STS group (26.56% vs. 47.78%, P < 0.001). Multivariable analysis identified STS as a predictor of decreased risk of MACE occurrence (odds ratio: 0.60, 95% confidence interval: 0.36 to 0.99; P = 0.045). CONCLUSION: Addition of STS to the standard treatments recommended by the current practice guidelines in patients with NSTE-ACS undergoing PCI could reduce myocardial injury and the occurrence of short-term cardiovascular events, primarily driven by non-fatal myocardial infarction. TRIAL REGISTRATION: ChiCTR-TRC-14005182.

Whole-transcriptome sequencing identifies a distinct subtype of acute lymphoblastic leukemia with predominant genomic abnormalities of EP300 and CREBBP.

Chromosomal translocations are a genomic hallmark of many hematologic malignancies. Often as initiating events, these structural abnormalities result in fusion proteins involving transcription factors important for hematopoietic differentiation and/or signaling molecules regulating cell proliferation and cell cycle. In contrast, epigenetic regulator genes are more frequently targeted by somatic sequence mutations, possibly as secondary events to further potentiate leukemogenesis. Through comprehensive whole-transcriptome sequencing of 231 children with acute lymphoblastic leukemia (ALL), we identified 58 putative functional and predominant fusion genes in 54.1% of patients (n = 125), 31 of which have not been reported previously. In particular, we described a distinct ALL subtype with a characteristic gene expression signature predominantly driven by chromosomal rearrangements of the ZNF384 gene with histone acetyltransferases EP300 and CREBBP ZNF384-rearranged ALL showed significant up-regulation of CLCF1 and BTLA expression, and ZNF384 fusion proteins consistently showed higher activity to promote transcription of these target genes relative to wild-type ZNF384 in vitro. Ectopic expression of EP300-ZNF384 and CREBBP-ZNF384 fusion altered differentiation of mouse hematopoietic stem and progenitor cells and also potentiated oncogenic transformation in vitro. EP300- and CREBBP-ZNF384 fusions resulted in loss of histone lysine acetyltransferase activity in a dominant-negative fashion, with concomitant global reduction of histone acetylation and increased sensitivity of leukemia cells to histone deacetylase inhibitors. In conclusion, our results indicate that gene fusion is a common class of genomic abnormalities in childhood ALL and that recurrent translocations involving EP300 and CREBBP may cause epigenetic deregulation with potential for therapeutic targeting.

Trimethylamine-N-oxide has prognostic value in coronary heart disease: a meta-analysis and dose-response analysis.

BACKGROUND: Previous clinical studies have suggested that trimethylamine-N-oxide (TMAO) could contribute to the development of atherosclerosis cardiovascular disease. However, the synthetic analysis in coronary heart disease (CHD) was not yet performed. We aimed to clarify the relationship between elevated plasma concentrations of TMAO and the incidence of major adverse cardiovascular events (MACE) in CHD patients. METHODS: Meta-analysis and dose-response analysis of hazard ratio data from prospective observational studies reporting on the association between TMAO plasma concentrations and the incidence of MACE in patients with CHD were conducted. RESULTS: Of the 2369 published articles identified in the search, seven papers, with data from nine cohort studies (10,301 patients), were included in the meta-analysis. Combined data showed that elevated plasma TMAO concentrations could increase 58% higher risk of MACE in patients with CHD (hazard ratios [HR]: 1.58; 95% confidence interval [CI] = 1.35-1.84, P = 0.000). For follow-up ≥ 1 year, it was associated with 62% higher risk of MACE in patients with longer-term than shorter-term (HR for follow-up ≥ 4 years: 1.96; 95% CI = 1.52-2.52 vs one to 3 years: 1.34; 95% CI = 1.26-1.43, P = 0.004). The dose-response analysis revealed a 'J' shaped association between TMAO concentration and the incidence of MACE (P = 0.033), with the concentration above 5.1 µmol/L being associated with HR of > 1. CONCLUSIONS: Elevated levels of TMAO are associated with an increased incidence of MACE in patients with CHD. TMAO concentration of 5.1 µmol/L may be a cut-off value for prognosis.

Danqi soft capsule prevents infarct border zone remodelling and reduces susceptibility to ventricular arrhythmias in post-myocardial infarction rats.

Danqi soft capsule (DQ) is a traditional Chinese medicine containing Salvia miltiorrhiza and Panax notoginseng; it is safe and efficient in treating ischaemic heart diseases. The purpose of the present study was to assess whether DQ could prevent infarct border zone (IBZ) remodelling and decrease ventricular arrhythmias occurrence in post-myocardial infarction (MI) stage. MI was induced by a ligation of the left anterior descending coronary artery. DQ was administered to the post-MI rats started from 1 week after MI surgery for 4 weeks. The results showed that DQ treatment significantly attenuated tachyarrhythmia induction rates and arrhythmia score in post-MI rats. In echocardiography, DQ improved left ventricular (LV) systolic and diastolic function. Histological assessment revealed that DQ significantly reduced fibrotic areas and myocyte areas, and increased connexin (Cx) 43 positive areas in IBZ. Western blot revealed that DQ treatment significantly reduced the protein expression levels of type I and III collagens, α-smooth muscle actin (α-SMA), transforming growth factor-ß1 (TGF-ß1) and Smad3 phosphorylation, while increasing Cx43 amounts. Overall, these findings mainly indicated that DQ intervention regulates interstitial fibrosis, Cx43 expression and myocyte hypertrophy by TGF-ß1/Smad3 pathway in IBZ, inhibits LV remodelling and reduces vulnerability to tachyarrhythmias after MI. This study presents a proof of concept for novel antiarrhythmic strategies in preventing IBZ remodelling, modifying the healed arrhythmogenic substrate and thus reducing susceptibility to ventricular arrhythmias in the late post-MI period.

Green-Light-Triggered Phase Transition of Azobenzene Derivatives toward Reversible Adhesives.

Studies on the azobenzene derivative based phase transitions mostly rely on photoisomerization, which require a long time to spontaneously revert back. Here we show a photothermal-driven solid-to-liquid transition and fast reversion of azobenzene derivatives. Owing to the aggregation of suitably substituted azobenzenes, solid-to-liquid transitions can be induced by photothermal effects under irradiation with green light. The liquid-state azobenzene derivatives spontaneously solidify again within 2 min due to heat release in a purely physical fashion. One thus obtains a perfectly reversible adhesion with a strength as high as that of commercial materials. Our work affords a novel concept to construct reversible adhesives via phase transitions of organic compounds induced by light.

PML-RARα interferes with erythropoiesis by repressing LMO2 in acute promyelocytic leukaemia.

The PML-RARα fusion gene, generated by the t(15;17) chromosome translocation, is regarded as the initiating factor of acute promyelocytic leukaemia (APL). In addition to the well-known effects on blocking myeloid differentiation at the promyelocytic stage, promyelocytic leukaemia-retinoic acid receptor α (PML-RARα) has also been reported to interfere with multiple differentiation processes, including erythroid differentiation. However, the detailed molecular mechanism by which PML-RARα impairs erythropoiesis has not yet been fully addressed. By chromatin immunoprecipitation-PCR assay, we found that PML-RARα bound to the distal promoter region of LMO2 (LIM-only protein 2), a critical erythroid-specific transcription factor. Luciferase reporter assays and qRT-PCR results demonstrated that PML-RARα down-regulated the expression of the LMO2 distal transcript through transrepressing its promoter activity. Analysis of gene expression profiling data from large cohorts of acute myeloid leukaemia (AML) patients confirmed that LMO2 expressed at a markedly lower level in APL patients in comparison to non-APL AML patients. Further flow cytometry analysis demonstrated that PML-RARα inhibited erythropoietin-induced erythroid differentiation by down-regulating LMO2 expression. Our findings reveal a previously unidentified mechanism, by which PML-RARα interferes with erythropoiesis through directly targeting and transrepressing LMO2 expression in the development of APL.

[Plasma concentration and pharmacokinetics of ursolic acid carried in self-microemulsifying drug delivery system in rats studied by UPLC-MS/MS].

This study is to report the establishment of an UPLC-MS/MS method for the determination of plasma concentration of UA carried in self-microemulsifying drug delivery system (SMEDDS) and its pharmacokinetics in rats. It was used for determination and analysis when serum with internal standard was extracted from C18 solid-phase column. Acquity UPLC BEH C18 column (100 mm x 2.1 mm, 1.7 microm) was used for separation. The mobile phase was acetonitrile -0.1% ammonia with gradient elution at the flow rate of 0.2 mL x min(-1). The column temperature was 40 degrees C and the detection wave length was 210 nm. It was detected by negative ion using electrospray ionization source (ESI) and scanned by multiple reaction ion monitoring (MRM) mode. The liner relationship of UA was very good in the range of 1.19-3 815.00 ng x mL(-1) (r = 0.999 0). Recovery rate of different concentrations were 87.42%-89.95%. The precision of inter-day and intra-day were less than 11%. The method developed in our study was proved to be sensitive, rapid and simple. It is suitable for the pharmacokinetic study of UA-SMEDDS in rats.

Systematic characterization of the HOXA9 downstream targets in MLL-r leukemia by noncoding CRISPR screens.

Accumulating evidence indicates that HOXA9 dysregulation is necessary and sufficient for leukemic transformation and maintenance. However, it remains largely unknown how HOXA9, as a homeobox transcriptional factor, binds to noncoding regulatory sequences and controls the downstream genes. Here, we conduct dropout CRISPR screens against 229 HOXA9-bound peaks identified by ChIP-seq. Integrative data analysis identifies reproducible noncoding hits, including those located in the distal enhancer of FLT3 and intron of CDK6. The Cas9-editing and dCas9-KRAB silencing of the HOXA9-bound sites significantly reduce corresponding gene transcription and impair cell proliferation in vitro, and in vivo by transplantation into NSG female mice. In addition, RNA-seq, Q-PCR analysis, chromatin accessibility change, and chromatin conformation evaluation uncover the noncoding regulation mechanism of HOXA9 and its functional downstream genes. In summary, our work improves our understanding of how HOXA9-associated transcription programs reconstruct the regulatory network specifying MLL-r dependency.

ETV6 represses inflammatory response genes and regulates HSPC function during stress hematopoiesis in mice.

ETS variant 6 (ETV6) encodes a transcriptional repressor expressed in hematopoietic stem and progenitor cells (HSPCs), where it is required for adult hematopoiesis. Heterozygous pathogenic germline ETV6 variants are associated with thrombocytopenia 5 (T5), a poorly understood genetic condition resulting in thrombocytopenia and predisposition to hematologic malignancies. To elucidate how germline ETV6 variants affect HSPCs and contribute to disease, we generated a mouse model harboring an Etv6R355X loss-of-function variant, equivalent to the T5-associated variant ETV6R359X. Under homeostatic conditions, all HSPC subpopulations are present in the bone marrow (BM) of Etv6R355X/+ mice; however, these animals display shifts in the proportions and/or numbers of progenitor subtypes. To examine whether the Etv6R355X/+ mutation affects HSPC function, we performed serial competitive transplantation and observed that Etv6R355X/+ lineage-sca1+cKit+ (LSK) cells exhibit impaired reconstitution, with near complete failure to repopulate irradiated recipients by the tertiary transplant. Mechanistic studies incorporating cleavage under target and release under nuclease assay, assay for transposase accessible chromatin sequencing, and high-throughput chromosome conformation capture identify ETV6 binding at inflammatory gene loci, including multiple genes within the tumor necrosis factor (TNF) signaling pathway in ETV6-sufficient mouse and human HSPCs. Furthermore, single-cell RNA sequencing of BM cells isolated after transplantation reveals upregulation of inflammatory genes in Etv6R355X/+ progenitors when compared to Etv6+/+ counterparts. Corroborating these findings, Etv6R355X/+ HSPCs produce significantly more TNF than Etv6+/+ cells post-transplantation. We conclude that ETV6 is required to repress inflammatory gene expression in HSPCs under conditions of hematopoietic stress, and this mechanism may be critical to sustain HSPC function.

PAX5 epigenetically orchestrates CD58 transcription and modulates blinatumomab response in acute lymphoblastic leukemia.

Blinatumomab is an efficacious immunotherapeutic agent in B cell acute lymphoblastic leukemia (B-ALL). However, the pharmacogenomic basis of leukemia response to blinatumomab is unclear. Using genome-wide CRISPR, we comprehensively identified leukemia intrinsic factors of blinatumomab sensitivity, i.e., the loss of CD58 as a top driver for resistance, in addition to CD19. Screening 1639 transcription factor genes, we then identified PAX5 as the key activator of CD58. ALL with the PAX5 P80R mutation also expressed the lowest level of CD58 among 20 ALL molecular subtypes in 1988 patients. Genome editing confirmed the effects of this mutation on CD58 expression and blinatumomab sensitivity in B-ALL, with validation in patient leukemic blasts. We described a PAX5-driven enhancer at the CD58 locus, which was disrupted by PAX5 P80R, and the loss of CD58 abolished blinatumomab-induced T cell activation with global changes in transcriptomic/epigenomic program. In conclusion, we identified previously unidentified genetic mechanisms of blinatumomab resistance in B-ALL, suggesting strategies for genomics-guided treatment individualization.

Molecular Mechanisms of ARID5B-Mediated Genetic Susceptibility to Acute Lymphoblastic Leukemia.

BACKGROUND: There is growing evidence for the inherited basis of susceptibility to childhood acute lymphoblastic leukemia (ALL). Genome-wide association studies have identified non-coding ALL risk variants at the ARID5B gene locus, but their exact functional effects and the molecular mechanism linking ARID5B to B-cell ALL leukemogenesis remain largely unknown. METHODS: We performed targeted sequencing of ARID5B in germline DNA of 5008 children with ALL. Variants were evaluated for association with ALL susceptibility using 3644 patients from the UK10K cohort as non-ALL controls, under an additive model. Cis-regulatory elements in ARID5B were systematically identified using dCas9-KRAB-mediated enhancer interference system enhancer screen in ALL cells. Disruption of transcription factor binding by ARID5B variant was predicted informatically and then confirmed using chromatin immunoprecipitation and coimmunoprecipitation. ARID5B variant association with hematological traits was examined using UK Biobank dataset. All statistical tests were 2-sided. RESULTS: We identified 54 common variants in ARID5B statistically significantly associated with leukemia risk, all of which were noncoding. Six cis-regulatory elements at the ARID5B locus were discovered using CRISPR-based high-throughput enhancer screening. Strikingly, the top ALL risk variant (rs7090445, P = 5.57 × 10-45) is located precisely within the strongest enhancer element, which is also distally tethered to the ARID5B promoter. The variant allele disrupts the MEF2C binding motif sequence, resulting in reduced MEF2C affinity and decreased local chromosome accessibility. MEF2C influences ARID5B expression in ALL, likely via a transcription factor complex with RUNX1. Using the UK Biobank dataset (n = 349 861), we showed that rs7090445 was also associated with lymphocyte percentage and count in the general population (P = 8.6 × 10-22 and 2.1 × 10-18, respectively). CONCLUSIONS: Our results indicate that ALL risk variants in ARID5B function by modulating cis-regulatory elements at this locus.