The BET inhibitor GNE-987 effectively induces anti-cancer effects in T-cell acute lymphoblastic leukemia by targeting enhancer regulated genes.

T-cell acute lymphoblastic leukemia (T-ALL) is a highly aggressive hematologic malignancy originating from T progenitor cells. It accounts for 15% of childhood and 25% of adult ALL cases. GNE-987 is a novel chimeric molecule developed using proteolysis-targeting chimeras (PROTAC) technology for targeted therapy. It consists of a potent inhibitor of the bromodomain and extraterminal (BET) protein, as well as the E3 ubiquitin ligase Von Hippel-Lindau (VHL), which enables the effective induction of proteasomal degradation of BRD4. Although GNE-987 has shown persistent inhibition of cell proliferation and apoptosis, its specific antitumor activity in T-ALL remains unclear. In this study, we aimed to investigate the molecular mechanisms underlying the antitumor effect of GNE-987 in T-ALL. To achieve this, we employed technologies including RNA sequencing (RNA-seq), chromatin immunoprecipitation sequencing (ChIP-seq) and CUT&Tag. The degradation of BET proteins, specifically BRD4, by GNE-987 has a profound impact on T-ALL cell. In in vivo experiments, sh-BRD4 lentivirus reduced T-ALL cell proliferation and invasion, extending the survival time of mice. The RNA-seq and CUT&Tag analyses provided further insights into the mechanism of action of GNE-987 in T-ALL. These analyses revealed that GNE-987 possesses the ability to suppress the expression of various genes associated with super-enhancers (SEs), including lymphoblastic leukemia 1 (LCK). By targeting these SE-associated genes, GNE-987 effectively inhibits the progression of T-ALL. Importantly, SE-related oncogenes like LCK were identified as critical targets of GNE-987. Based on these findings, GNE-987 holds promise as a potential novel candidate drug for the treatment of T-ALL.

Super enhancer related gene ANP32B promotes the proliferation of acute myeloid leukemia by enhancing MYC through histone acetylation.

BACKGROUND: Acute myeloid leukemia (AML) is a malignancy of the hematopoietic system, and childhood AML accounts for about 20% of pediatric leukemia. ANP32B, an important nuclear protein associated with proliferation, has been found to regulate hematopoiesis and CML leukemogenesis by inhibiting p53 activity. However, recent study suggests that ANP32B exerts a suppressive effect on B-cell acute lymphoblastic leukemia (ALL) in mice by activating PU.1. Nevertheless, the precise underlying mechanism of ANP32B in AML remains elusive. RESULTS: Super enhancer related gene ANP32B was significantly upregulated in AML patients. The expression of ANP32B exhibited a negative correlation with overall survival. Knocking down ANP32B suppressed the proliferation of AML cell lines MV4-11 and Kasumi-1, along with downregulation of C-MYC expression. Additionally, it led to a significant decrease in H3K27ac levels in AML cell lines. In vivo experiments further demonstrated that ANP32B knockdown effectively inhibited tumor growth. CONCLUSIONS: ANP32B plays a significant role in promoting tumor proliferation in AML. The downregulation of ANP32B induces cell cycle arrest and promotes apoptosis in AML cell lines. Mechanistic analysis suggests that ANP32B may epigenetically regulate the expression of MYC through histone H3K27 acetylation. ANP32B could serve as a prognostic biomarker and potential therapeutic target for AML patients.

The RNA polymerase II subunit B (RPB2) functions as a growth regulator in human glioblastoma.

Glioblastoma multiforme (GBM) is the most common and aggressive brain tumor with a poor prognosis. The growth of GBM cells depends on the core transcriptional apparatus, thus rendering RNA polymerase (RNA pol) complex as a candidate therapeutic target. The RNA pol II subunit B (POLR2B) gene encodes the second largest subunit of the RNA pol II (RPB2); however, its genomic status and function in GBM remain unclear. Certain GBM data sets in cBioPortal were used for investigating the genomic status and expression of POLR2B in GBM. The function of RPB2 was analyzed following knockdown of POLR2B expression by shRNA in GBM cells. The cell counting kit-8 assay and PI staining were used for cell proliferation and cell cycle analysis. A xenograft mouse model was established to analyze the function of RPB2 in vivo. RNA sequencing was performed to analyze the RPB2-regulated genes. GO and GSEA analyses were applied to investigate the RPB2-regulated gene function and associated pathways. In the present study, the genomic alteration and overexpression of the POLR2B gene was described in glioblastoma. The data indicated that knockdown of POLR2B expression suppressed tumor cell growth of glioblastoma in vitro and in vivo. The analysis further demonstrated the identification of the RPB2-regulated gene sets and highlighted the DNA damage-inducible transcript 4 gene as the downstream target of the POLR2B gene. The present study provides evidence indicating that RPB2 functions as a growth regulator in glioblastoma and could be used as a potential therapeutic target for the treatment of this disease.

BRD4 inhibitor MZ1 exerts anti-cancer effects by targeting MYCN and MAPK signaling in neuroblastoma.

Neuroblastoma(NB) is a common childhood solid tumor, and most patients in the high-risk group with MYCN gene amplification have a poor prognosis. Inhibition of bromodomain and extra terminal (BET) proteins has shown considerable promise in the investigation of MYCN-driven malignancies in recent years. MZ1 is a novel BET inhibitor that employs proteolytic-targeting chimera (PROTAC) technology for proteasomal degradation of target proteins and has shown excellent effects in some tumors, but its role in neuroblastoma remains poorly understood. Herein, we observed that MZ1 suppressed MYC-amplified NB cell proliferation and normal cell cycle, while simultaneously boosting cell apoptosis. MZ1 also provides a significant therapeutic impact in vivo. Mechanistically, MZ1 exhibits anti-tumor effect in NB cells by suppressing the expression of N-Myc or C-Myc as well as the MAPK signaling pathway. Overall, our data imply that MZ1 might be exploited as a possible therapeutic method for NB therapy.

BRD4 PROTAC degrader ARV-825 inhibits T-cell acute lymphoblastic leukemia by targeting 'Undruggable' Myc-pathway genes.

BACKGROUND: T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disease with a high risk of induction failure and poor outcomes, with relapse due to drug resistance. Recent studies show that bromodomains and extra-terminal (BET) protein inhibitors are promising anti-cancer agents. ARV-825, comprising a BET inhibitor conjugated with cereblon ligand, was recently developed to attenuate the growth of multiple tumors in vitro and in vivo. However, the functional and molecular mechanisms of ARV-825 in T-ALL remain unclear. This study aimed to investigate the therapeutic efficacy and potential mechanism of ARV-825 in T-ALL. METHODS: Expression of the BRD4 were determined in pediatric T-ALL samples and differential gene expression after ARV-825 treatment was explored by RNA-seq and quantitative reverse transcription-polymerase chain reaction. T-ALL cell viability was measured by CCK8 assay after ARV-825 administration. Cell cycle was analyzed by propidium iodide (PI) staining and apoptosis was assessed by Annexin V/PI staining. BRD4, BRD3 and BRD2 proteins were detected by western blot in cells treated with ARV-825. The effect of ARV-825 on T-ALL cells was analyzed in vivo. The functional and molecular pathways involved in ARV-825 treatment of T-ALL were verified by western blot and chromatin immunoprecipitation (ChIP). RESULTS: BRD4 expression was higher in pediatric T-ALL samples compared with T-cells from healthy donors. High BRD4 expression indicated a poor outcome. ARV-825 suppressed cell proliferation in vitro by arresting the cell cycle and inducing apoptosis, with elevated poly-ADP ribose polymerase and cleaved caspase 3. BRD4, BRD3, and BRD2 were degraded in line with reduced cereblon expression in T-ALL cells. ARV-825 had a lower IC50 in T-ALL cells compared with JQ1, dBET1 and OTX015. ARV-825 perturbed the H3K27Ac-Myc pathway and reduced c-Myc protein levels in T-ALL cells according to RNA-seq and ChIP. In the T-ALL xenograft model, ARV-825 significantly reduced tumor growth and led to the dysregulation of Ki67 and cleaved caspase 3. Moreover, ARV-825 inhibited cell proliferation by depleting BET and c-Myc proteins in vitro and in vivo. CONCLUSIONS: BRD4 indicates a poor prognosis in T-ALL. The BRD4 degrader ARV-825 can effectively suppress the proliferation and promote apoptosis of T-ALL cells via BET protein depletion and c-Myc inhibition, thus providing a new strategy for the treatment of T-ALL.

CEBPG promotes acute myeloid leukemia progression by enhancing EIF4EBP1.

BACKGROUND: Acute myeloid leukemia (AML) is a myeloid neoplasm accounts for 7.6% of hematopoietic malignancies. AML is a complex disease, and understanding its pathophysiology is contributing to the improvement in the treatment and prognosis of AML. In this study, we assessed the expression profile and molecular functions of CCAAT enhancer binding protein gamma (CEBPG), a gene implicated in myeloid differentiation and AML progression. METHODS: shRNA mediated gene interference was used to down-regulate the expression of CEBPG in AML cell lines, and knockdown efficiency was detected by RT-qPCR and western blotting. The effect of knockdown on the growth of AML cell lines was evaluated by CCK-8. Western blotting was used to detect PARP cleavage, and flow cytometry were used to determine the effect of knockdown on apoptosis of AML cells. Genes and pathways affected by knockdown of CEBPG were identified by gene expression analysis using RNA-seq. One of the genes affected by knockdown of CEBPG was Eukaryotic translation initiation factor 4E binding protein 1 (EIF4EBP1), a known repressor of translation. Knockdown of EIF4EBP1 was used to assess its potential role in AML progression downstream of CEBPG. RESULTS: We explored the ChIP-Seq data of AML cell lines and non-AML hematopoietic cells, and found CEBPG was activated through its distal enhancer in AML cell lines. Using the public transcriptomic dataset, the Cancer Cell Line Encyclopedia (CCLE) and western blotting, we also found CEBPG was overexpressed in AML. Moreover, we observed that CEBPG promotes AML cell proliferation by activating EIF4EBP1, thus contributing to the progression of AML. These findings indicate that CEBPG could act as a potential therapeutic target for AML patients. CONCLUSION: In summary, we systematically explored the molecular characteristics of CEBPG in AML and identified CEBPG as a potential therapeutic target for AML patients. Our findings provide novel insights into the pathophysiology of AML and indicate a key role for CEBPG in promoting AML progression.

Molecular mechanism of G1 arrest and cellular senescence induced by LEE011, a novel CDK4/CDK6 inhibitor, in leukemia cells.

BACKGROUND: Overexpression of cyclin D1 dependent kinases 4 and 6 (CDK4/6) is a common feature of many human cancers including leukemia. LEE011 is a novel inhibitor of both CDK4 and 6. To date, the molecular function of LEE011 in leukemia remains unclear. METHODS: Leukemia cell growth and apoptosis following LEE011 treatment was assessed through CCK-8 and annexin V/propidium iodide staining assays. Cell senescence was assessed by ß-galactosidase staining and p16INK4a expression analysis. Gene expression profiles of LEE011 treated HL-60 cells were investigated using an Arraystar Human LncRNA array. Gene ontology and KEGG pathway analysis were then used to analyze the differentially expressed genes from the cluster analysis. RESULTS: Our studies demonstrated that LEE011 inhibited proliferation of leukemia cells and could induce apoptosis. Hoechst 33,342 staining analysis showed DNA fragmentation and distortion of nuclear structures following LEE011 treatment. Cell cycle analysis showed LEE011 significantly induced cell cycle G1 arrest in seven of eight acute leukemia cells lines, the exception being THP-1 cells. ß-Galactosidase staining analysis and p16INK4a expression analysis showed that LEE011 treatment can induce cell senescence of leukemia cells. LncRNA microarray analysis showed 2083 differentially expressed mRNAs and 3224 differentially expressed lncRNAs in LEE011-treated HL-60 cells compared with controls. Molecular function analysis showed that LEE011 induced senescence in leukemia cells partially through downregulation of the transcriptional expression of MYBL2. CONCLUSIONS: We demonstrate for the first time that LEE011 treatment results in inhibition of cell proliferation and induction of G1 arrest and cellular senescence in leukemia cells. LncRNA microarray analysis showed differentially expressed mRNAs and lncRNAs in LEE011-treated HL-60 cells and we demonstrated that LEE011 induces cellular senescence partially through downregulation of the expression of MYBL2. These results may open new lines of investigation regarding the molecular mechanism of LEE011 induced cellular senescence.

mRNA expression profiling of histone modifying enzymes in pediatric acute monoblastic leukemia.

Histone modification is dysregulated in various types of cancers, including hematological malignancies. However, the expression profile of histone-modifying enzymes in pediatric acute monoblastic leukemia (AML FAB M5) has not been investigated. In this study, we evaluated the mRNA expression profile of 85 genes that encode enzymes involved in histone-modification in 27 pediatric AML FAB M5 samples by using a novel real-time PCR array. We obtained a gene cluster consisting of a total of 28 genes (15 up-regulated genes and 13 down-regulated genes). This gene signature revealed up-regulated expression of putative oncogenes GCN5L2, SETD8, KDM5C, AURKA and AURKB, and downregulated putative tumor suppressor genes (TSGs) EP300, PRMT3, PRMT8 and NOTCH2. We investigated possible biological interactions between differentially expressed genes using ingenuity pathway analysis (IPA) and found 12 significant networks. Among these, gene expression, cancer, and embryonic development showed the highest number of networks with 39 focus molecules and had an associated significance score of 68. Further, Rb, CDKN2C, and E2F1 were found to be upstream regulators of histone-modifying enzymes. This study provides additional insights into the molecular pathogenesis of pediatric AML FAB M5. These genes represent interesting targets with potential for diagnostic, prognostic and therapeutic application in pediatric AML patients.

Analyzing the gene expression profile of anaplastic histology Wilms' tumor with real-time polymerase chain reaction arrays.

BACKGROUND: Wilms' tumor (WT) is one of the most common malignant neoplasms of the urinary tract in children. Anaplastic histology (unfavorable histology) accounts for about 10% of whole WTs, and it is the single most important histologic predictor of treatment response and survival in patients with WT; however, until now the molecular basis of this phenotype is not very clearly. METHODS: A real-time polymerase chain reaction (PCR) array was designed and tested. Next, the gene expression profile of pediatric anaplastic histology WT and normal adjacent tissues were analyzed. These expression data were anlyzed with Multi Experiment View (MEV) cluster software further. Datasets representing genes with altered expression profiles derived from cluster analyses were imported into the Ingenuity Pathway Analysis Tool (IPA). RESULTS: 88 real-time PCR primer pairs for quantitative gene expression analysis of key genes involved in pediatric anaplastic histology WT were designed and tested. The gene expression profile of pediatric anaplastic histology WT is significantly different from adjacent normal controls; we identified 15 genes that are up-regulated and 16 genes that are down-regulated in the former. To investigate biological interactions of these differently regulated genes, datasets representing genes with altered expression profiles were imported into the IPA for further analysis, which revealed three significant networks: Cancer, Hematological Disease, and Gene Expression, which included 27 focus molecules and a significance score of 43. The IPA analysis also grouped the differentially expressed genes into biological mechanisms related to Cell Death and Survival 1.15E(-12), Cellular Development 2.84E(-11), Cellular Growth and Proliferation 2.84E(-11), Gene Expression 4.43E(-10), and DNA Replication, Recombination, and Repair 1.39E(-07). The important upstream regulators of pediatric anaplastic histology WT were TP53 and TGFß1 signaling (P = 1.15E(-14) and 3.79E(-13), respectively). CONCLUSIONS: Our study demonstrates that the gene expression profile of pediatric anaplastic histology WT is significantly different from adjacent normal tissues with real-time PCR array. We identified some genes that are dysregulated in pediatric anaplastic histology WT for the first time, such as HDAC7, and IPA analysis showed the most important pathways for pediatric anaplastic histology WT are TP53 and TGFß1 signaling. This work may provide new clues into the molecular mechanisms behind pediatric anaplastic histology WT.

Hypermethylation of the GATA binding protein 4 (GATA4) promoter in Chinese pediatric acute myeloid leukemia.

BACKGROUND: Acute myeloid leukemia (AML) is the second-most common form of leukemia in children. Aberrant DNA methylation patterns are a characteristic feature of AML. GATA4 has been suggested to be a tumor suppressor gene regulated by promoter hypermethylation in various types of human cancers although the expression and promoter methylation of GATA4 in pediatric AML is still unclear. METHODS: Transcriptional expression levels of GATA4 were evaluated by semi-quantitative and real-time PCR. Methylation status was investigated by methylation-specific PCR (MSP) and bisulfate genomic sequencing (BGS). The prognostic significance of GATA4 expression and promoter methylation was assessed in 105 cases of Chinese pediatric acute myeloid leukemia patients with clinical follow-up records. RESULTS: MSP and BGS analysis showed that the GATA4 gene promoter is hypermethylated in AML cells, such as the HL-60 and MV4-11 human myeloid leukemia cell lines. 5-Aza treatment significantly upregulated GATA4 expression in HL-60 and MV4-11 cells. Aberrant methylation of GATA4 was observed in 15.0 % (3/20) of the normal bone marrow control samples compared to 56.2 % (59/105) of the pediatric AML samples. GATA4 transcript levels were significantly decreased in AML patients (33.06 ± 70.94; P = 0.011) compared to normal bone marrow/idiopathic thrombocytopenic purpura controls (116.76 ± 105.39). GATA4 promoter methylation was correlated with patient leukocyte counts (WBC, white blood cells) (P = 0.035) and minimal residual disease MRD (P = 0.031). Kaplan-Meier survival analysis revealed significantly shorter overall survival time in patients with GATA4 promoter methylation (P = 0.014). CONCLUSIONS: Epigenetic inactivation of GATA4 by promoter hypermethylation was observed in both AML cell lines and pediatric AML samples; our study implicates GATA4 as a putative tumor suppressor gene in pediatric AML. In addition, our findings imply that GATA4 promoter methylation is correlated with WBC and MRD. Kaplan-Meier survival analysis revealed significantly shorter overall survival in pediatric AML with GATA4 promoter methylation but multivariate analysis shows that it is not an independent factor. However, further research focusing on the mechanism of GATA4 in pediatric leukemia is required.

Molecular targeting of the oncoprotein PLK1 in pediatric acute myeloid leukemia: RO3280, a novel PLK1 inhibitor, induces apoptosis in leukemia cells.

Polo-like kinase 1 (PLK1) is highly expressed in many cancers and therefore a biomarker of transformation and potential target for the development of cancer-specific small molecule drugs. RO3280 was recently identified as a novel PLK1 inhibitor; however its therapeutic effects in leukemia treatment are still unknown. We found that the PLK1 protein was highly expressed in leukemia cell lines as well as 73.3% (11/15) of pediatric acute myeloid leukemia (AML) samples. PLK1 mRNA expression was significantly higher in AML samples compared with control samples (82.95 ± 110.28 vs. 6.36 ± 6.35; p < 0.001). Kaplan-Meier survival analysis revealed that shorter survival time correlated with high tumor PLK1 expression (p = 0.002). The 50% inhibitory concentration (IC50) of RO3280 for acute leukemia cells was between 74 and 797 nM. The IC50 of RO3280 in primary acute lymphocytic leukemia (ALL) and AML cells was between 35.49 and 110.76 nM and 52.80 and 147.50 nM, respectively. RO3280 induced apoptosis and cell cycle disorder in leukemia cells. RO3280 treatment regulated several apoptosis-associated genes. The regulation of DCC, CDKN1A, BTK, and SOCS2 was verified by western blot. These results provide insights into the potential use of RO3280 for AML therapy; however, the underlying mechanisms remain to be determined.

Metallothionein III (MT3) is a putative tumor suppressor gene that is frequently inactivated in pediatric acute myeloid leukemia by promoter hypermethylation.

BACKGROUND: Acute myeloid leukemia (AML) is the second most common form of leukemia in children. Aberrant DNA methylation patterns are a characteristic feature in various tumors, including AML. Metallothionein III (MT3) is a tumor suppresser reported to show promoter hypermethylated in various cancers. However, the expression and molecular function of MT3 in pediatric AML is unclear. METHODS: Eleven human leukemia cell lines and 41 pediatric AML samples and 20 NBM/ITP (Norma bone marrow/Idiopathic thrombocytopenic purpura) control samples were analyzed. Transcription levels of MT3 were evaluated by semi-quantitative and real-time PCR. MT3 methylation status was determined by methylation specific PCR (MSP) and bisulfite genomic sequencing (BSG). The molecular mechanism of MT3 was investigated by apoptosis assays and PCR array analysis. RESULTS: The MT3 promoter was hypermethylated in leukemia cell lines. More CpG's methylated of MT3 was observed 39.0% pediatric AML samples compared to 10.0% NBM controls. Transcription of MT3 was also significantly decreased in AML samples compared to NBM/ITP controls (P < 0.001); patients with methylated MT3 exhibited lower levels of MT3 expression compared to those with unmethylated MT3 (P = 0.049). After transfection with MT3 lentivirus, proliferation was significantly inhibited in AML cells in a dose-dependent manner (P < 0.05). Annexin V assay showed that apoptosis was significantly upregulated MT3-overexpressing AML cells compared to controls. Real-time PCR array analysis revealed 34 dysregulated genes that may be implicated in MT3 overexpression and apoptosis in AML, including FOXO1. CONCLUSION: MT3 may be a putative tumor suppressor gene in pediatric AML. Epigenetic inactivation of MT3 via promoter hypermethylation was observed in both AML cell lines and pediatric AML samples. Overexpression of MT3 may inhibit proliferation and induce apoptosis in AML cells. FOXO1 was dysregulated in MT3-overexpressing cells, offering an insight into the mechanism of MT3-induced apoptosis. However, further research is required to determine the underlying molecular details.

Super-enhancer-driven IRF2BP2 enhances ALK activity and promotes neuroblastoma cell proliferation.

BACKGROUND: Super-enhancers (SEs) typically govern the expression of critical oncogenes and play a fundamental role in the initiation and progression of cancer. Focusing on genes that are abnormally regulated by SE in cancer may be a new strategy for understanding pathogenesis. In the context of this investigation, we have identified a previously unreported SE-driven gene IRF2BP2 in neuroblastoma (NB). METHODS: The expression and prognostic value of IRF2BP2 were detected in public databases and clinical samples. The effect of IRF2BP2 on NB cell growth and apoptosis was evaluated through in vivo and in vitro functional loss experiments. The molecular mechanism of IRF2BP2 was investigated by the study of chromatin regulatory regions and transcriptome sequencing. RESULTS: The sustained high expression of IRF2BP2 results from the activation of a novel SE established by NB master transcription factors MYCN, MEIS2, and HAND2, and they form a new complex that regulates the gene network associated with the proliferation of NB cell populations. We also observed a significant enrichment of the AP-1 family at the binding sites of IRF2BP2. Remarkably, within NB cells, AP-1 plays a pivotal role in shaping the chromatin accessibility landscape, thereby exposing the binding site for IRF2BP2. This orchestrated action enables AP-1 and IRF2BP2 to collaboratively stimulate the expression of the NB susceptibility gene ALK, thereby upholding the highly proliferative phenotype characteristic of NB. CONCLUSIONS: Our findings indicate that SE-driven IRF2BP2 can bind to AP-1 to maintain the survival of tumor cells via regulating chromatin accessibility of the NB susceptibility gene ALK.

METTL14 promotes neuroblastoma formation by inhibiting YWHAH via an m6A-YTHDF1-dependent mechanism.

Neuroblastoma (NB) is a common childhood tumor with a high incidence worldwide. The regulatory role of RNA N6-methyladenosine (m6A) in gene expression has attracted significant attention, and the impact of methyltransferase-like 14 (METTL14) on tumor progression has been extensively studied in various types of cancer. However, the specific influence of METTL14 on NB remains unexplored. Using data from the Target database, our study revealed significant upregulation of METTL14 expression in high-risk NB patients, with strong correlation with poor prognosis. Furthermore, we identified ETS1 and YY1 as upstream regulators that control the expression of METTL14. In vitro experiments involving the knockdown of METTL14 in NB cells demonstrated significant inhibition of cell proliferation, migration, and invasion. In addition, suppressing METTL14 inhibited NB tumorigenesis in nude mouse models. Through MeRIP-seq and RNA-seq analyses, we further discovered that YWHAH is a downstream target gene of METTL14. Mechanistically, we observed that methylated YWHAH transcripts, particularly those in the 5' UTR, were specifically recognized by the m6A "reader" protein YTHDF1, leading to the degradation of YWHAH mRNA. Moreover, the downregulation of YWHAH expression activated the PI3K/AKT signaling pathway, promoting NB cell activity. Overall, our study provides valuable insights into the oncogenic effects of METTL14 in NB cells, highlighting its role in inhibiting YWHAH expression through an m6A-YTHDF1-dependent mechanism. These findings also suggest the potential utility of a biomarker panel for prognostic prediction in NB patients.

Enhancer looping protein LDB1 modulates MYB expression in T-ALL cell lines in vitro by cooperating with master transcription factors.

BACKGROUND: Despite significant progress in the prognosis of pediatric T-cell acute lymphoblastic leukemia (T-ALL) in recent decades, a notable portion of children still confronts challenges such as treatment resistance and recurrence, leading to limited options and a poor prognosis. LIM domain-binding protein 1 (LDB1) has been confirmed to exert a crucial role in various physiological and pathological processes. In our research, we aim to elucidate the underlying function and mechanisms of LDB1 within the background of T-ALL. METHODS: Employing short hairpin RNA (shRNA) techniques, we delineated the functional impact of LDB1 in T-ALL cell lines. Through the application of RNA-Seq, CUT&Tag, and immunoprecipitation assays, we scrutinized master transcription factors cooperating with LDB1 and identified downstream targets under LDB1 regulation. RESULTS: LDB1 emerges as a critical transcription factor co-activator in cell lines derived from T-ALL. It primarily collaborates with master transcription factors (ERG, ETV6, IRF1) to cooperatively regulate the transcription of downstream target genes. Both in vitro and in vivo experiments affirm the essential fuction of LDB1 in the proliferation and survival of cell lines derived from T-ALL, with MYB identified as a significant downstream target of LDB1. CONCLUSIONS: To sum up, our research establishes the pivotal fuction of LDB1 in the tumorigenesis and progression of T-ALL cell lines. Mechanistic insights reveal that LDB1 cooperates with ERG, ETV6, and IRF1 to modulate the expression of downstream effector genes. Furthermore, LDB1 controls MYB through remote enhancer modulation, providing valuable mechanistic insights into its involvement in the progression of T-ALL.

Targeting RBM39 through indisulam induced mis-splicing of mRNA to exert anti-cancer effects in T-cell acute lymphoblastic leukemia.

BACKGROUND: Despite the use of targeted therapeutic approaches, T-cell acute lymphoblastic leukemia (T-ALL) is still associated with a high incidence of complications and a poor prognosis. Indisulam (also known as E7070), a newly identified molecular glue compound, has demonstrated increased therapeutic efficacy in several types of cancer through the rapid degradation of RBM39. This study aimed to evaluate the therapeutic potential of indisulam in T-ALL, elucidate its underlying mechanisms and explore the role of the RBM39 gene. METHODS: We verified the anticancer effects of indisulam in both in vivo and in vitro models. Additionally, the construction of RBM39-knockdown cell lines using shRNA confirmed that the malignant phenotype of T-ALL cells was dependent on RBM39. Through RNA sequencing, we identified indisulam-induced splicing anomalies, and proteomic analysis helped pinpoint protein changes caused by the drug. Comprehensive cross-analysis of these findings facilitated the identification of downstream effectors and subsequent validation of their functional roles. RESULTS: Indisulam has significant antineoplastic effects on T-ALL. It attenuates cell proliferation, promotes apoptosis and interferes with cell cycle progression in vitro while facilitating tumor remission in T-ALL in vivo models. This investigation provides evidence that the downregulation of RBM39 results in the restricted proliferation of T-ALL cells both in vitro and in vivo, suggesting that RBM39 is a potential target for T-ALL treatment. Indisulam's efficacy is attributed to its ability to induce RBM39 degradation, causing widespread aberrant splicing and abnormal translation of the critical downstream effector protein, THOC1, ultimately leading to protein depletion. Moreover, the presence of DCAF15 is regarded as critical for the effectiveness of indisulam, and its absence negates the ability of indisulam to induce the desired functional alterations. CONCLUSION: Our study revealed that indisulam, which targets RBM39 to induce tumor cell apoptosis, is an effective drug for treating T-ALL. Targeting RBM39 through indisulam leads to mis-splicing of pre-mRNAs, resulting in the loss of key effectors such as THOC1.

Super-Enhancer-Driven IRF2BP2 is Activated by Master Transcription Factors and Sustains T-ALL Cell Growth and Survival.

Super enhancers (SEs) are large clusters of transcriptional enhancers driving the expression of genes crucial for defining cell identity. In cancer, tumor-specific SEs activate key oncogenes, leading to tumorigenesis. Identifying SE-driven oncogenes in tumors and understanding their functional mechanisms is of significant importance. In this study, a previously unreported SE region is identified in T-cell acute lymphoblastic leukemia (T-ALL) patient samples and cell lines. This SE activates the expression of interferon regulatory factor 2 binding protein 2 (IRF2BP2) and is regulated by T-ALL master transcription factors (TFs) such as ETS transcription factor ERG (ERG), E74 like ETS transcription factor 1 (ELF1), and ETS proto-oncogene 1, transcription factor (ETS1). Hematopoietic system-specific IRF2BP2 conditional knockout mice is generated and showed that IRF2BP2 has minimal impact on normal T cell development. However, in vitro and in vivo experiments demonstrated that IRF2BP2 is crucial for T-ALL cell growth and survival. Loss of IRF2BP2 affects the MYC and E2F pathways in T-ALL cells. Cleavage under targets and tagmentation (CUT&Tag) assays and immunoprecipitation revealed that IRF2BP2 cooperates with the master TFs of T-ALL cells, targeting the enhancer of the T-ALL susceptibility gene recombination activating 1 (RAG1) and modulating its expression. These findings provide new insights into the regulatory network within T-ALL cells, identifying potential new targets for therapeutic intervention.

CDK5RAP3 is a novel super-enhancer-driven gene activated by master TFs and regulates ER-Phagy in neuroblastoma.

Super enhancers (SEs) are genomic regions comprising multiple closely spaced enhancers, typically occupied by a high density of cell-type-specific master transcription factors (TFs) and frequently enriched in key oncogenes in various tumors, including neuroblastoma (NB), one of the most prevalent malignant solid tumors in children originating from the neural crest. Cyclin-dependent kinase 5 regulatory subunit-associated protein 3 (CDK5RAP3) is a newly identified super-enhancer-driven gene regulated by master TFs in NB; however, its function in NB remains unclear. Through an integrated study of publicly available datasets and microarrays, we observed a significantly elevated CDK5RAP3 expression level in NB, associated with poor patient prognosis. Further research demonstrated that CDK5RAP3 promotes the growth of NB cells, both in vitro and in vivo. Mechanistically, defective CDK5RAP3 interfered with the UFMylation system, thereby triggering endoplasmic reticulum (ER) phagy. Additionally, we provide evidence that CDK5RAP3 maintains the stability of MEIS2, a master TF in NB, and in turn, contributes to the high expression of CDK5RAP3. Overall, our findings shed light on the molecular mechanisms by which CDK5RAP3 promotes tumor progression and suggest that its inhibition may represent a novel therapeutic strategy for NB.

Differential mRNA expression levels of human histone-modifying enzymes in normal karyotype B cell pediatric acute lymphoblastic leukemia.

Histone modification enzymes regulate gene expression by altering the accessibility of promoters to transcription factors. We sought to determine whether the genes encoding histone modification enzymes are dysregulated in pediatric acute lymphoblastic leukemia (ALL). A real-time PCR array was designed, tested and used to profile the expression of 85 genes encoding histone modification enzymes in bone marrow mononuclear cells from 30 pediatric ALL patients and 20 normal controls. The expression profile of histone-modifying genes was significantly different between normal karyotype B cell pediatric ALL and normal controls. Eleven genes were upregulated in pediatric ALL, including the histone deacetylases HDAC2 and PAK1, and seven genes were downregulated, including PRMT2 and the putative tumor suppressor EP300. Future studies will seek to determine whether these genes serve as biomarkers of pediatric ALL. Ingenuity Pathway Analysis revealed that Gene Expression and Organ Morphology was the highest rated network, with 13 focus molecules (significance score = 35). Ingenuity Pathway Analysis also indicated that curcumin and miR-34 are upstream regulators of histone-modifying enzymes; future studies will seek to validate these results and examine the role of curcumin and miR-34 in leukemia. This study provides new clues into the molecular mechanisms of pediatric ALL.

BRD4 PROTAC degrader MZ1 exhibits anti-B-cell acute lymphoblastic leukemia effects via targeting CCND3.

INTRODUCTION: B-cell acute lymphoblastic leukemia (B-ALL) is the most prevalent malignant tumor affecting children. While the majority of B-ALL patients (90%) experience successful recovery, early relapse cases of B-ALL continue to exhibit high mortality rates. MZ1, a novel inhibitor of Bromodomains and extra-terminal (BET) proteins, has demonstrated potent antitumor activity against hematological malignancies. The objective of this study was to examine the role and therapeutic potential of MZ1 in the treatment of B-ALL. METHODS: In order to ascertain the fundamental mechanism of MZ1, a sequence of in vitro assays was conducted on B-ALL cell lines, encompassing Cell Counting Kit 8 (CCK8) assay, Propidium iodide (PI) staining, and Annexin V/PI staining. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were employed to examine protein and mRNA expression levels. Transcriptomic RNA sequencing (RNA-seq) was utilized to screen the target genes of MZ1, and lentiviral transfection was employed to establish stably-expressing/knockdown cell lines. RESULTS: MZ1 has been observed to induce the degradation of Bromodomain Containing 4 (BRD4), Bromodomain Containing 3 (BRD3), and Bromodomain Containing 2 (BRD2) in B-ALL cell strains, leading to inhibited cell growth and induction of cell apoptosis and cycle arrest in vitro. These findings suggest that MZ1 exhibits cytotoxic effects on two distinct molecular subtypes of B-ALL, namely 697 (TCF3/PBX1) and RS4;11 (MLL-AF4) B-ALL cell lines. Additionally, RNA-sequencing analysis revealed that MZ1 significantly downregulated the expression of Cyclin D3 (CCND3) gene in B-ALL cell lines, which in turn promoted cell apoptosis, blocked cell cycle, and caused cell proliferation inhibition. CONCLUSION: Our results suggest that MZ1 has potential anti-B-ALL effects and might be a novel therapeutic target.