The proneural transcription factor ASCL1 regulates cell proliferation and primes for differentiation in neuroblastoma

A novel APP splice variant-dependent marker system to precisely demarcate maturity in SH-SY5Y cell-derived neurons

SH-SY5Y, a neuroblastoma cell line, can be converted into mature neuronal phenotypes, characterized by the expression of mature neuronal and neurotransmitter markers. However, the mature phenotypes described across multiple studies appear inconsistent. As this cell line expresses common neuronal markers after a simple induction, there is a high chance of misinterpreting its maturity. Therefore, sole reliance on common neuronal markers is presumably inadequate. The Alzheimer's disease (AD) central gene, amyloid precursor protein (APP), has shown contrasting transcript variant dynamics in various cell types. We differentiated SH-SY5Y cells into mature neuron-like cells using a concise protocol and observed the upregulation of total APP throughout differentiation. However, APP transcript variant-1 was upregulated only during the early to middle stages of differentiation and declined in later stages. We identified the maturity state where this post-transcriptional shift occurs, terming it "true maturity." At this stage, we observed a predominant expression of mature neuronal and cholinergic markers, along with a distinct APP variant pattern. Our findings emphasize the necessity of using a differentiation state-sensitive marker system to precisely characterize SH-SY5Y differentiation. Moreover, this study offers an APP-guided, alternative neuronal marker system to enhance the accuracy of the conventional markers.

Identification of molecular subtypes based on chromatin regulator-related genes and experimental verification of the role of ASCL1 in conferring chemotherapy resistance to breast cancer

Objective

The aim of this study was to identify the molecular subtypes of breast cancer based on chromatin regulator-related genes.

Methods

The RNA sequencing data of The Cancer Genome Atlas-Breast Cancer cohort were obtained from the official website, while the single-cell data were downloaded from the Gene Expression Omnibus database (GSE176078). Validation was performed using the Molecular Taxonomy of Breast Cancer International Consortium dataset. Furthermore, the immune characteristics, tumor stemness, heterogeneity, and clinical characteristics of these molecular subtypes were analyzed. The correlation between chromatin regulators and chemotherapy resistance was examined in vitro using the quantitative real-time polymerase chain reaction (qRT-PCR) and Cell Counting Kit-8 (CCK8) assays.

Results

This study identified three stable molecular subtypes with different prognostic and pathological features. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and protein-protein interaction analyses revealed that the differentially expressed genes were associated with disease processes, such as mitotic nuclear division, chromosome segregation, condensed chromosome, and specific chromosome region. The T stage and subtypes were correlated with the clinical features. Tumor heterogeneity (mutant-allele tumor heterogeneity, tumor mutational burden, purity, and homologous recombination deficiency) and tumor stemness (RNA expression-based stemness score, epigenetically regulated RNA expression-based stemness score, DNA methylation-based stemness score, and epigenetically regulated DNA methylation-based stemness score) significantly varied between the three subtypes. Furthermore, Western blotting, qRT-PCR, and CCK8 assays demonstrated that the expression of ASCL1 was positively correlated with chemotherapy resistance in breast cancer.

Conclusion

This study identified the subtypes of breast cancer based on chromatin regulators and analyzed their clinical features, gene mutation status, immunophenotype, and drug sensitivity. The results of this study provide effective strategies for assessing clinical prognosis and developing personalized treatment strategies.

HNRNPA2B1 and HNRNPR stabilize ASCL1 in an m6A-dependent manner to promote neuroblastoma progression

HNRNPA2B1 and HNRNPR stabilize ASCL1 mRNA in neuroblastoma, but whether their regulatory effects depend on m6A modification and whether their function involves ASCL1 remain unknown. This study investigated the m6A-dependent binding of HNRNPA2B1 and HNRNPR to ASCL1 and subsequent regulation, as well as the expression, clinical significance, and function of HNRNPA2B1 and HNRNPR in neuroblastoma. We revealed that METTL14 mediated ASCL1 m6A modification to stabilize ASCL1. HNRNPA2B1 and HNRNPR significantly enriched ASCL1 mRNA by binding to the 5' and 3' untranslated regions, respectively, and METTL14 knockdown reduced this enrichment. Mutations in m6A sites in the untranslated regions of ASCL1 mRNA considerably decreased probe capacity to engage HNRNPA2B1 and HNRNPR. HNRNPR interacts with IGF2BP1, and knocking down either impaired binding to ASCL1 mRNA. HNRNPA2B1 and HNRNPR knockdown suppressed neuroblastoma cell growth and invasion, while ASCL1 overexpression restored these effects. The high HNRNPA2B1 and HNRNPR expression in neuroblastoma correlated with ASCL1 expression. Thus, HNRNPA2B1 and HNRNPR bind and stabilize ASCL1 mRNA in an m6A-dependent manner to promote neuroblastoma progression. This study not only discovered a new mechanism underlying the high ASCL1 expression in neuroblastoma but also identified the HNRNPA2B1/HNRNPR/ASCL1 axis as a promising target for inhibiting neuroblastoma progression.

ASCL1 characterizes adrenergic neuroblastoma via its pioneer function and cooperation with core regulatory circuit factors

Neuroblastoma originates from developing neural crest and can interconvert between the mesenchymal (MES) and adrenergic (ADRN) states, each of which are controlled by different sets of transcription factors forming the core regulatory circuit (CRC). However, the roles of CRC factors in induction and maintenance of specific state are poorly understood. Here, we demonstrate that overexpression of ASCL1, an ADRN CRC factor, in MES neuroblastoma cells opens closed chromatin at the promoters of key ADRN genes, accompanied by epigenetic activation and establishment of enhancer-promoter interactions, initiating the ADRN gene expression program. ASCL1 inhibits the transforming growth factor β-SMAD2/3 pathway but activates the bone morphogenetic protein SMAD1-ID3/4 pathway. ASCL1 and other CRC members potentiate each other's activity, increasing the expression of the original targets and inducing a new set of genes, thereby fully inducing the ADRN program. Our results demonstrate that ASCL1 serves as a pioneer factor and cooperates with CRC factors to characterize the ADRN gene expression program.

ASCL1 Is Involved in the Pathogenesis of Schizophrenia by Regulation of Genes Related to Cell Proliferation, Neuronal Signature Formation, and Neuroplasticity

Schizophrenia (SZ) is a common psychiatric neurodevelopmental disorder with a complex genetic architecture. Genome-wide association studies indicate the involvement of several transcription factors, including ASCL1, in the pathogenesis of SZ. We aimed to identify ASCL1-dependent cellular and molecular mechanisms associated with SZ. We used Capture-C, CRISPR/Cas9 systems and RNA-seq analysis to confirm the involvement of ASCL1 in SZ-associated pathogenesis, establish a mutant SH-SY5Y line with a functional ASCL1 knockout (ASCL1-del) and elucidate differentially expressed genes that may underlie ASCL1-dependent pathogenic mechanisms. Capture-C confirmed the spatial interaction of the ASCL1 promoter with SZ-associated loci. Transcriptome analysis showed that ASCL1 regulation may be through a negative feedback mechanism. ASCL1 dysfunction affects the expression of genes associated with the pathogenesis of SZ, as well as bipolar and depressive disorders. Genes differentially expressed in ASCL1-del are involved in cell mitosis, neuronal projection, neuropeptide signaling, and the formation of intercellular contacts, including the synapse. After retinoic acid (RA)-induced differentiation, ASCL1 activity is restricted to a small subset of genes involved in neuroplasticity. These data suggest that ASCL1 dysfunction promotes SZ development predominantly before the onset of neuronal differentiation by slowing cell proliferation and impeding the formation of neuronal signatures.

[Aumolertinib inhibits proliferation, invasion and migration and promotes apoptosis of neuroblastoma cells by downregulating MMP2 and MMP9 expression]

OBJECTIVE

To investigate the effects of aumolertinib, an epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), on biological behaviors of neuroblastoma SH-SY5Y cells.

METHODS

CCK-8 assay, colony-forming assay, Transwell assay and flow cytometry were used to assess the effects of 2, 4 and 8 μmol/L aumolertinib on proliferation, survival, migration, invasion and apoptosis of SH-SY5Y cells, and the changes in ultrastructure of the cells were observed using transmission electron microscopy. The protein expressions of Bax, Bcl-2, E-cadherin, vimentin, MMP2, and MMP9 in the treated cells were detected using Western blotting. A nude mouse model bearing subcutaneous SH-SY5Y cell xenograft were treated with aumolertinib (15 mg/kg) or cyclophosphamide (20 mg/kg), and the tumor volume and body mass changes was measured. HE staining was used to observe adverse effects of the treatment on the heart, liver, spleen, lungs and kidneys.

RESULTS

Aumolertinib significantly inhibited the proliferation and viability of SH-SY5Y cells (P<0.05) with IC50 of 5.004, 3.728 and 3.228 µmol/L at 24, 48 and 72 h, respectively. Aumolertinib treatment induced obvious apoptosis of the cells, which showed characteristic morphological changes of apoptosis under transmission electron microscope. The treatment also inhibited the invasion and migration abilities of SH-SY5Y cells (P<0.01), up-regulated the expression levels of E-cadherin and Bax and lowered the expression levels of Bcl-2, vimentin, MMP2 and MMP9 (P<0.05). In the nude mouse models, treatment with aumolertinib effectively inhibited the growth of neuroblastoma without causing significant toxicity to the vital organs.

CONCLUSION

Aumolertinib inhibits proliferation, survival, invasion and migration and induces apoptosis in SH-SY5Y cells by downregulating MMP2 and MMP9 expression.