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The 8p11-p12 amplicon oncogene ASH2L regulates expression of genes involved in tumorigenic processes via promoter H3K4me3 in luminal breast cancer. (SUM-44 ASH2L knockdown H3K4me3 ChIP-seq)

ABSTRACT: Amplification of the 8p11-p12 genomic region occurs in 30% of luminal B breast cancers and results in coordinate overexpression of several oncogenes, including ASH2L, which upregulates gene expression via promoter tri-methylation of lysine 4 on histone 3 (H3K4me3). Since 8p11-p12 amplification is associated with endocrine resistance, the major cause of breast cancer mortality, understanding the underlying biology is essential to improving treatment options for patients. To explore the role of amplified and overexpressed ASH2L on epigenetic regulation of gene expression, we performed H3K4me3 ChIP-seq and RNA-seq in breast cancer cells with ASH2L amplification and overexpression following ASH2L knockdown and assessed the biological effects of the suite of genes identified in this manner. We discovered that ASH2L-regulated genes are implicated in cell cycle processes and response to the CDK4/6 inhibitor palbociclib and confirmed these effects in additional breast cancer cell lines. We also discovered that ASH2L regulates expression of another 8p11-p12 amplicon oncogene NSD3, also an epigenome modifier, which has previously been shown to result in overexpression and estrogen-independent activation of ERα. Together, these data establish ASH2L as a breast cancer oncogene and an important component of the 8p11-p12 amplicon that acts as an oncogenic unit in breast cancer.

ORGANISM(S): Homo sapiens

PROVIDER: GSE99669 | GEO | 2024/05/24

REPOSITORIES: GEO

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Project description:Estrogen receptor positive breast cancer is the most prevalent form of breast cancer. Although a number of available drugs are highly effective at blocking estrogen mediated receptor activity, thousands of patients die every year from ER positive breast cancers because the disease progresses to a stage at which these drugs are no longer effective. Thus, it is crucial to establish a comprehensive understanding of the biology of the estrogen receptor (ER) in ER:positive breast cancers that progress despite hormone therapy, a gap in knowledge that remains a serious impediment to successful treatment of patients with ER positive breast cancer. A key question that must be answered is how the estrogen receptor retains the capacity to activate transcription in the absence or near absence of estrogen. We have found a partial answer to this question upon investigating the effect of amplification and overexpression of Wolf Hirschhorn Syndrome Candidate 1:Like 1 (WHSC1L1), a gene that is amplified in 15% of breast cancers that codes for a histone:lysine methyltransferase. WHSC1L1 lies in the 8p11:p12 amplicon, a region of gene amplification that is strongly associated with breast cancer. In this study, we performed shRNA knockdown of the catalytically inactive short isoform of WHSC1L1 in SUM44PE breast cancer cells and found that expression of the short isoform of WHSC1L1 is necessary for expression of the estrogen receptor in this highly ER:positive cell line. In addition, we found that the estrogen receptor binds chromatin extensively in the absence of exogenous estrogen, including several actively transcribed canonical ER target genes, indicating that estrogen receptor signaling is active in SUM44 cells in estrogen free conditions. These findings represent a novel model for ER biology in luminal B breast cancers harboring amplification of WHSC1L1 and provide insight into the mechanisms by which ER: positive breast cancers become unresponsive to SERMs or aromatase inhibitors.

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The 8p11-p12 amplicon oncogene ASH2L regulates expression of genes involved in tumorigenic processes via promoter H3K4me3 in luminal breast cancer. (SUM-44 ASH2L knockdown H3K4me3 ChIP-seq)

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