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SETDB1 interactions with PELP1 contributes to breast cancer endocrine therapy resistance
Zexuan Liu1,2, Junhao Liu1,2, Behnam Ebrahimi1
1Division of Reproductive Research, Department of Obstetrics and Gynecology, University of Texas Health San Antonio, 7703 Floyd Curl Drive, Mail Code 7836, San Antonio, TX, 78229-3900, USA.
Background:
Methyltransferase SETDB1 is highly expressed in breast cancer (BC), however, the mechanisms by which SETDB1 promotes BC progression to endocrine therapy resistance remains elusive. In this study, we examined the mechanisms by which SETDB1 contribute to BC endocrine therapy resistance.
Methods:
We utilized therapy sensitive (MCF7 and ZR75), therapy resistant (MCF7-TamR, MCF7-FR, MCF7-PELP1cyto, MCF7-SETDB1) estrogen receptor alpha positive (ER+)BC models and conducted in vitro cell viability, colony formation, 3-dimensional cell growth assays to investigate the role of SETDB1 in endocrine resistance. RNA-seq of parental and SETDB1 knock down ER+ BC cells was used to identify unique pathways. SETDB1 interaction with PELP1 was identified by yeast-two hybrid screen and confirmed by immunoprecipitation and GST-pull down assays. Mechanistic studies were conducted using Western blotting, reporter gene assays, RT-qPCR, and in vitro methylation assays. Xenograft assays were used to establish the role of PELP1 in SETDB1 mediated BC progression.
Results:
RNA-seq analyses showed that SETDB1 regulates expression of a subset of estrogen receptor (ER) and Akt target genes that contribute to endocrine therapy resistance. Importantly, using yeast-two hybrid screen, we identified ER coregulator PELP1 as a novel interacting protein of SETDB1. Biochemical analyses confirmed SETDB1 and PELP1 interactions in multiple BC cells. Mechanistic studies confirmed that PELP1 is necessary for SETDB1 mediated Akt methylation and phosphorylation. Further, SETDB1 overexpression promotes tamoxifen resistance in BC cells, and PELP1 knockdown abolished these effects. Using xenograft model, we provided genetic evidence that PELP1 is essential for SETDB1 mediated BC progression in vivo. Analyses of TCGA datasets revealed SETDB1 expression is positively correlated with PELP1 expression in ER+ BC patients.
Conclusions:
This study suggests that the PELP1/SETDB1 axis play an important role in aberrant Akt activation and serves as a novel target for treating endocrine therapy resistance in breast cancer.
Insights
The PELP1/SETDB1 axis drives endocrine therapy resistance in breast cancer by promoting aberrant Akt activation. Targeting this axis offers a novel therapeutic strategy for resistant breast cancer.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Methyltransferase SETDB1 is highly expressed in breast cancer (BC).
- Mechanisms of SETDB1 in promoting BC progression to endocrine therapy resistance are not fully understood.
- This study investigates SETDB1's role in BC endocrine therapy resistance.
Purpose of the Study:
- To elucidate the mechanisms by which SETDB1 contributes to endocrine therapy resistance in breast cancer.
- To identify novel interacting partners of SETDB1 involved in BC progression.
- To explore the therapeutic potential of targeting the SETDB1 pathway.
Main Methods:
- Utilized multiple estrogen receptor-positive (ER+) BC cell models (sensitive and resistant).
- Performed in vitro assays (viability, colony formation, 3D growth) and RNA-sequencing.
- Identified SETDB1-PELP1 interaction via yeast-two hybrid and confirmed with biochemical assays.
- Conducted mechanistic studies (Western blotting, reporter assays, RT-qPCR, methylation assays) and xenograft studies.
Main Results:
- SETDB1 regulates ER and Akt target genes contributing to endocrine resistance.
- Identified PELP1 as a novel interacting partner of SETDB1.
- PELP1 is essential for SETDB1-mediated Akt methylation and phosphorylation.
- SETDB1 overexpression promotes tamoxifen resistance, abolished by PELP1 knockdown.
- SETDB1 expression correlates positively with PELP1 in ER+ BC patients (TCGA data).
Conclusions:
- The PELP1/SETDB1 axis is crucial for aberrant Akt activation in breast cancer.
- This axis represents a novel therapeutic target for overcoming endocrine therapy resistance.
- Targeting the PELP1/SETDB1 interaction may improve treatment outcomes for resistant breast cancer.
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