Unknown,Transcriptomics,Genomics,Proteomics

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Inhibition of the histone methyltrasferares DOT1L deregulates hormone responsive breast cancer cells methylome

ABSTRACT: Estrogen Receptor αlpha (ERα) is the master regulator of estrogen signaling in hormone-responsive breast cancer (BC), however epigenetic mechanisms, including DNA methylation, are emerging as key processes for regulation of critical cell functions including tumorigenesis. We have recently reported the epigenetic writer DOT1L (DOT1 Like Histone Lysine Methyltransferase) to associated to ERα, part of chromatin bound multiprotein complex and that the pharmacological inhibition of this enzyme reduces the transcription rate of several genes involved in ERα-mediated signaling leading to inhibition of BC cell proliferation. Here, we investigated the functional impact of DOT1L inhibition on methylome changes in BC and its possible contribution to deregulation of transcriptional pathways associated to the progression of this disease.

INSTRUMENT(S): NextSeq 500

ORGANISM(S): Homo sapiens

SUBMITTER: Giorgio Giurato

PROVIDER: E-MTAB-12635 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Abstract Several endocrine therapy (ET) resistance mechanisms for ER-positive (ER+) breast cancer (BC) have been proposed, including acquired ESR1 (ERα gene) mutations. The two most common ESR1 mutations are Y537S and D538G, which give rise to a constitutively active receptor with reduced affinity for agonists and antagonists. The discovery of new effective therapies remains a significant challenge in treating mutated ER+ BC. In this context, Poly (ADP-ribose) polymerase-1 (PARP-1) has captured considerable interest as a target for therapeutic inhibitors in specific types of cancers. Here, we report that crosstalk between PARP-1 and ERα may represent a novel therapeutic approach for ER+ BC. We have demonstrated that the up-regulation of PARP-1 expression, stimulated by 17-β estradiol (E2), was blocked by treatment with fulvestrant (Ful), a potent ERα antagonist, or ESR1 siRNA in ER+ MCF7 and T47D BC cell models that express both wild type ERα and the Y537S mutation, indicating that ERα regulates the expression of PARP-1. In addition, ERα-mediated transcriptional activity depended on PARP-1 activity in these models, as confirmed by ERα target gene expression and ERE reporter gene analyses +/- niraparib (Nira). Notably, PARP-1 modulates the estrogen-dependent genomic binding of ERα and FoxA1, which play a crucial role in the proliferation of ER+ BC. We also showed that PARP-1 inhibition prevented proliferation and cell cycle activities of ERα WT and ERα Y537S cells upon ERα activation. In vivo, Nira and lasofoxifene (Laso), an ERα antagonist, significantly reduced primary tumor growth versus vehicle, both as single agents and in combination. Moreover, RNA-seq analyses demonstrated the downregulation of ERα signaling in the mammary glands of mice treated with Nira versus Vehicle. Our results provide novel insights into the molecular events through which PARP-1 may serve as a more comprehensive therapeutic approach to target ET BC resistance in women with advanced ER+ BC.

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Inhibition of the histone methyltrasferares DOT1L deregulates hormone responsive breast cancer cells methylome

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