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SUMOylation modulates FOXK2-mediated paclitaxel sensitivity in breast cancer cells

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Title: SUMOylation modulates FOXK2-mediated paclitaxel sensitivity in breast cancer cells
Authors: Nestal de Moraes, G
Ji, Z
Lavender, F
Yao, S
Zona, S
Sharrocks, AD
Lam, EW
Item Type: Journal Article
Abstract: The forkhead transcription factor FOXK2 plays a critical role in suppressing tumorigenesis and mediating cytotoxic drug action in breast cancer. However, the mechanism by which the biological function of FOXK2 is regulated remains poorly understood. Here, we investigated the role of SUMOylation in modulating FOXK2-mediated drug sensitivity. We identified SUMOylation consensus motifs within the FOXK2 sequence and constructed two SUMOylation-defective double mutants by converting lysine 527 and 633 to arginines and glutamic acid 529 and 635 to alanines, respectively. We found that both the FOXK2 SUMOylation-deficient (K527/633 R) and (E529/635 A) mutants were ineffective in mediating the cytotoxic function of paclitaxel when compared to the wild-type (WT) FOXK2. When overexpressed, unlike the wild-type (WT) FOXK2, the K527/633 R mutant had little effect on the sensitivity of MCF-7 and MDA-MB-231 cells to paclitaxel, as examined by cell viability and clonogenic assays. Our results also showed that MCF-7 cells overexpressing the K527/633 R mutant form of FOXK2 or the empty expression vector have lower protein and mRNA levels of its tumour suppressive transcriptional target FOXO3 compared to the wild-type FOXK2. Consistently, ChIP assays revealed that unlike wild-type FOXK2, the SUMOylation-defective (K527/633 R) mutant is unable to bind to the FOXO3 promoter, despite expressing comparable levels of protein and having the same subcellular localization as the wild-type FOXK2 in MCF-7 cells. Interestingly, expression of neither the wild-type nor the K527/633 R mutant FOXK2 had any effect on the proliferation and paclitaxel sensitivity of the MCF-7 TaxR paclitaxel-resistant cells. In agreement, both the wild-type and the (K527/633 R) mutant FOXK2 failed to bind to the endogenous FOXO3 promoter in these cells. Collectively, our results suggest that SUMOylation positively regulates FOXK2 transcriptional activity and has a role in mediating the cytotoxic response to paclitaxel through the tumour suppressor FOXO3.
Issue Date: 13-Mar-2018
Date of Acceptance: 8-Feb-2018
URI: http://hdl.handle.net/10044/1/56877
DOI: https://dx.doi.org/10.1038/s41389-018-0038-6
ISSN: 2157-9024
Publisher: Nature Publishing Group
Journal / Book Title: Oncogenesis
Volume: 7
Copyright Statement: © The Author(s) 2018. This article is licensed under a Creative Commons Attribution 4.0 Internat ional License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the origina l author(s) and the source, provide a li nktotheCreativeC ommons license, and indicate if changes were made. The images or other third party material in this article are included in the article ’ s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article ’ s Creative Commons license and your intended use is not permitted by sta tutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright hol der. To view a copy of this license, visit http://creativecommons .org/licenses/by/4.0
Sponsor/Funder: Cancer Research UK
Breast Cancer Now
Breast Cancer Now
Breast Cancer Now
Imperial College Trust
Medical Research Council (MRC)
Funder's Grant Number: C37/A12011
Keywords: Science & Technology
Life Sciences & Biomedicine
Publication Status: Published
Article Number: 29
Appears in Collections:Department of Surgery and Cancer