EP300 and SIRT1/6 co-regulate lapatinib sensitivity via modulating FOXO3-acetylation and activity in breast cancer

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Title: EP300 and SIRT1/6 co-regulate lapatinib sensitivity via modulating FOXO3-acetylation and activity in breast cancer
Authors: Lam, E
Mahmud, Z
Gomes, A
Aimjongjun, S
Jiramongkol, Y
Yao, S
Zona, S
Alasiri, G
Yague, E
Item Type: Journal Article
Abstract: Forkhead Box O3 (FOXO3) is a tumour suppressor whose activity is fine-tuned by post-translational modifications (PTMs). In this study, using the BT474 breast cancer cells and a recently established lapatinib resistant (BT474-LapR) cell line, we observed that higher FOXO3 and acetylated (Ac)-FOXO3 levels correlate with lapatinib sensitivity. Subsequent ectopic expression of EP300 led to an increase in acetylated-FOXO3 in sensitive, but not in resistant cells. Drug sensitivity assays revealed that sensitive BT474 cells show increased lapatinib cytotoxicity upon over-expression of wild-type but not acetylation-deficient EP300. Moreover, FOXO3 recruitment to target gene promoters is associated with target gene expression and drug response in sensitive cells, and the inability of FOXO3 to bind its target genes correlates with lapatinib-resistance in BT474-LapR cells. In addition, using SIRT1/6 specific siRNAs and chemical inhibitor, we also found that sirtuin 1 and -6 (SIRT1 and -6) play a part in fine-tuning FOXO3 acetylation and lapatinib sensitivity. Consistent with this, immunohistochemistry results from different breast cancer subtypes showed that high SIRT6/1 levels are associated with constitutive high FOXO3 expression which is related to FOXO3 deregulation/inactivation and poor prognosis in breast cancer patient samples. Collectively, our results suggest the involvement of FOXO3 acetylation in regulating lapatinib sensitivity of HER2-positive breast cancers.
Issue Date: 28-Jul-2019
Date of Acceptance: 25-Jul-2019
URI: http://hdl.handle.net/10044/1/72222
ISSN: 2072-6694
Publisher: MDPI AG
Journal / Book Title: Cancers
Copyright Statement: This paper is embargoed until publication. Once published it will be available fully open access.
Sponsor/Funder: Cancer Research UK
Breast Cancer Now
Commonwealth Scholarship Commission
Royal Embassy Of Saudi Arabia
Imperial College Trust
Breast Cancer Now
Medical Research Council (MRC)
Funder's Grant Number: C37/A12011
Publication Status: Accepted
Embargo Date: publication subject to indefinite embargo
Appears in Collections:Division of Surgery
Division of Cancer

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