Blocking Fra-1 sensitizes triple-negative breast cancer to olaparib
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ABSTRACT: Fra-1 (FOSL1) is overexpressed in triple-negative breast cancer (TNBC). Fra-1 is a member of the activator protein 1 (AP-1) transcription factor complex, which plays crucial roles in tumor progression and treatment resistance. We have previously identified 118 proteins that interact with endogenous chromatin-bound Fra-1 in TNBC cells in a large screen, and these included PARP1(Poly (ADP-ribose) polymerase 1). PARP1 inhibitor olaparib is currently in clinical use for treatment of BRCA-mutated TNBC breast cancer. Here, we demonstrate that this interaction impacts the efficacy of olaparib treatment. We corroborate that PARP1 interacts with Fra-1, and we show that PARP1 downregulates Fra-1 and consequently reduces AP-1 transcriptional activity. Inhibition of PARP1, on the other hand, increases Fra-1 levels and enhances its transcriptional activity, which in turn can increase treatment resistance. However, by inhibiting Fra-1, we found that TNBC cells became sensitized to olaparib treatment. We compared Fra-1 chromatin binding sites with the Fra-1 and PARP1 regulated transcriptomes, and found that a large fraction of PARP1-regulated genes was dependent on Fra-1. We further show that PARP1 protein levels significantly correlate with Fra-1 in clinical breast cancer tumors, and we identify that high PARP1 expression is indicative of a poor clinical outcome in breast cancer patients overall, but not in basal-like tumors. In conclusion, by exploring the functionality of the Fra-1 and PARP1 interaction, we propose that targeting Fra-1 could serve as a therapeutic approach to improve olaparib treatment outcome for TNBC patients.
ORGANISM(S): Homo sapiens
PROVIDER: GSE149621 | GEO | 2022/04/21
REPOSITORIES: GEO
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