1. <scp>ASCL1</scp> regulates super‐enhancer‐associated <scp>miRNAs</scp> to define molecular subtypes of small cell lung cancer
- Author
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Kazuko Miyakawa, Naoya Miyashita, Masafumi Horie, Yasuhiro Terasaki, Hidenori Tanaka, Hirokazu Urushiyama, Kensuke Fukuda, Yugo Okabe, Takashi Ishii, Naomi Kuwahara, Hiroshi I. Suzuki, Takahide Nagase, and Akira Saito
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Gene Expression Regulation, Neoplastic ,MicroRNAs ,Cancer Research ,Lung Neoplasms ,Oncology ,Cell Line, Tumor ,Basic Helix-Loop-Helix Transcription Factors ,Humans ,General Medicine ,Small Cell Lung Carcinoma - Abstract
Small cell lung cancer (SCLC) is a highly aggressive neuroendocrine tumor with dismal prognosis. Recently, molecular subtypes of SCLC have been defined by the expression status of ASCL1, NEUROD1, YAP1, and POU2F3 transcription regulators. ASCL1 is essential for neuroendocrine differentiation and is expressed in the majority of SCLC. Although previous studies investigated ASCL1 target genes in SCLC cells, ASCL1-mediated regulation of miRNAs and its relationship to molecular subtypes remain poorly explored. Here, we performed genome-wide profiling of chromatin modifications (H3K27me3, H3K4me3, and H3K27ac) by CUTTag assay and ASCL1 knockdown followed by RNA sequencing and miRNA array analyses in SCLC cells. ASCL1 could preferentially regulate genes associated with super-enhancers (SEs) defined by enrichment of H3K27ac marking. Moreover, ASCL1 positively regulated several SE-associated miRNAs, such as miR-7, miR-375, miR-200b-3p, and miR-429, leading to repression of their targets, whereas ASCL1 suppressed miR-455-3p, an abundant miRNA in other molecular subtypes. We further elucidated unique patterns of SE-associated miRNAs in different SCLC molecular subtypes, highlighting subtype-specific miRNA networks with functional relevance. Notably, we found apparent de-repression of common target genes of different miRNAs following ASCL1 knockdown, suggesting combinatorial action of multiple miRNAs underlying molecular heterogeneity of SCLC (e.g., co-targeting of YAP1 by miR-9 and miR-375). Our comprehensive analyses provide novel insights into SCLC pathogenesis and a clue to understanding subtype-dependent phenotypic differences.
- Published
- 2022
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