{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,3]],"date-time":"2026-09-03T12:05:54Z","timestamp":1788437154765,"version":"build-2803163510"},"reference-count":42,"publisher":"MDPI AG","issue":"20","license":[{"start":{"date-parts":[[2022,10,14]],"date-time":"2022-10-14T00:00:00Z","timestamp":1665705600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005847","name":"Health and Medical Research Fund","doi-asserted-by":"publisher","award":["07182026"],"award-info":[{"award-number":["07182026"]}],"id":[{"id":"10.13039\/501100005847","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005847","name":"Health and Medical Research Fund","doi-asserted-by":"publisher","award":["07182046"],"award-info":[{"award-number":["07182046"]}],"id":[{"id":"10.13039\/501100005847","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005847","name":"Health and Medical Research Fund","doi-asserted-by":"publisher","award":["17113020"],"award-info":[{"award-number":["17113020"]}],"id":[{"id":"10.13039\/501100005847","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005847","name":"Health and Medical Research Fund","doi-asserted-by":"publisher","award":["202111160035"],"award-info":[{"award-number":["202111160035"]}],"id":[{"id":"10.13039\/501100005847","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Research Grants Council","award":["07182026"],"award-info":[{"award-number":["07182026"]}]},{"name":"Research Grants Council","award":["07182046"],"award-info":[{"award-number":["07182046"]}]},{"name":"Research Grants Council","award":["17113020"],"award-info":[{"award-number":["17113020"]}]},{"name":"Research Grants Council","award":["202111160035"],"award-info":[{"award-number":["202111160035"]}]},{"name":"Committee on Research and Conference Grants from the University of Hong Kong","award":["07182026"],"award-info":[{"award-number":["07182026"]}]},{"name":"Committee on Research and Conference Grants from the University of Hong Kong","award":["07182046"],"award-info":[{"award-number":["07182046"]}]},{"name":"Committee on Research and Conference Grants from the University of Hong Kong","award":["17113020"],"award-info":[{"award-number":["17113020"]}]},{"name":"Committee on Research and Conference Grants from the University of Hong Kong","award":["202111160035"],"award-info":[{"award-number":["202111160035"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Breast cancer is a heterogeneous disease. Tamoxifen is frequently used to treat ER-positive breast cancer. Our team has identified a novel splice variant of NCOR2, BQ323636.1 (BQ), that mediates tamoxifen resistance. However, the upstream factors that modulate BQ expression are not apparent. This study reveals that tamoxifen treatment causes induction of DNA damage which can enhance BQ expression. We show that DNA damage can activate the ATM\/CHK2 and ATR\/CHK1 signalling cascades and confirm that ATM\/CHK2 signalling is responsible for enhancing the protein stability of BQ. siRNA or a small inhibitor targeting CHK2 resulted in the reduction in BQ expression through reduced phosphorylation and enhanced poly-ubiquitination of BQ. Inhibition of CHK2 by CCT241533 could reverse tamoxifen resistance in vitro and in vivo. Using clinical samples in the tissue microarray, we confirmed that high p-CHK2 expression was significantly associated with high nuclear BQ expression, tamoxifen resistance and poorer overall and disease-specific survival. In conclusion, tamoxifen treatment can enhance BQ expression in ER-positive breast cancer by activating the ATM\/CHK2 axis. Targeting CHK2 is a promising approach to overcoming tamoxifen resistance in ER-positive breast cancer.<\/jats:p>","DOI":"10.3390\/ijms232012290","type":"journal-article","created":{"date-parts":[[2022,10,17]],"date-time":"2022-10-17T02:29:46Z","timestamp":1665973786000},"page":"12290","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Checkpoint Kinase 2 Inhibition Can Reverse Tamoxifen Resistance in ER-Positive Breast Cancer"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2037-9575","authenticated-orcid":false,"given":"Ho","family":"Tsoi","sequence":"first","affiliation":[{"name":"Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wai-Chung","family":"Tsang","sequence":"additional","affiliation":[{"name":"Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ellen P. S.","family":"Man","sequence":"additional","affiliation":[{"name":"Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Man-Hong","family":"Leung","sequence":"additional","affiliation":[{"name":"Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chan-Ping","family":"You","sequence":"additional","affiliation":[{"name":"Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sum-Yin","family":"Chan","sequence":"additional","affiliation":[{"name":"Department of Clinical Oncology, Queen Mary Hospital, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9793-9273","authenticated-orcid":false,"given":"Wing-Lok","family":"Chan","sequence":"additional","affiliation":[{"name":"Department of Clinical Oncology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2200-7505","authenticated-orcid":false,"given":"Ui-Soon","family":"Khoo","sequence":"additional","affiliation":[{"name":"Department of Pathology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,10,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"7","DOI":"10.3322\/caac.21590","article-title":"Cancer statistics, 2020","volume":"70","author":"Siegel","year":"2020","journal-title":"Cancer J. Clin"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.pharmthera.2017.12.012","article-title":"Selective estrogen receptor modulators (SERMs) and selective estrogen receptor degraders (SERDs) in cancer treatment","volume":"186","author":"Patel","year":"2018","journal-title":"Pharmacol. Therapeut."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"771","DOI":"10.1016\/S0140-6736(11)60993-8","article-title":"Relevance of breast cancer hormone receptors and other factors to the efficacy of adjuvant tamoxifen: Patient-level meta-analysis of randomised trials","volume":"378","author":"Davies","year":"2011","journal-title":"Lancet"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"643","DOI":"10.1677\/erc.1.00776","article-title":"Mechanisms of tamoxifen resistance","volume":"11","author":"Ring","year":"2004","journal-title":"Endocr Relat Cancer"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"926","DOI":"10.1093\/jnci\/djh166","article-title":"Mechanisms of tamoxifen resistance: Increased estrogen receptor-HER2\/neu cross-talk in ER\/HER2-positive breast cancer","volume":"96","author":"Shou","year":"2004","journal-title":"J. Natl. Cancer Inst."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.canlet.2007.03.016","article-title":"Pathways to tamoxifen resistance","volume":"256","author":"Riggins","year":"2007","journal-title":"Cancer Lett."},{"key":"ref_7","first-page":"421606","article-title":"Alternative splicing: Role in cancer development and progression","volume":"2013","author":"Sette","year":"2013","journal-title":"Int. J. Cell Biol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"246","DOI":"10.1158\/0008-5472.CAN-12-2241","article-title":"SpliceArray Profiling of Breast Cancer Reveals a Novel Variant of NCOR2\/SMRT That Is Associated with Tamoxifen Resistance and Control of ER alpha Transcriptional Activity","volume":"73","author":"Zhang","year":"2013","journal-title":"Cancer Res."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"e554","DOI":"10.1002\/ctm2.554","article-title":"KPNA1 regulates nuclear import of NCOR2 splice variant BQ323636.1 to confer tamoxifen resistance in breast cancer","volume":"11","author":"Tsoi","year":"2021","journal-title":"Clin. Transl. Med."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Tsoi, H., Shi, L., Leung, M.-H., Man, E.P.S., So, Z.-Q., Chan, W.-L., and Khoo, U.-S. (2022). Overexpression of BQ323636.1 Modulated AR\/IL-8\/CXCR1 Axis to Confer Tamoxifen Resistance in ER-Positive Breast Cancer. Life, 12.","DOI":"10.3390\/life12010093"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1007\/s12672-021-00411-y","article-title":"Tamoxifen and oxidative stress: An overlooked connection","volume":"12","author":"Ahmed","year":"2021","journal-title":"Discov. Oncol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"101084","DOI":"10.1016\/j.redox.2018.101084","article-title":"ROS and the DNA damage response in cancer","volume":"25","author":"Srinivas","year":"2019","journal-title":"Redox Biol"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1595","DOI":"10.1038\/s41467-018-03951-0","article-title":"Tamoxifen-resistant breast cancer cells are resistant to DNA-damaging chemotherapy because of upregulated BARD1 and BRCA1","volume":"9","author":"Zhu","year":"2018","journal-title":"Nat. Commun."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"3681","DOI":"10.1158\/1078-0432.CCR-17-2259","article-title":"BQ323636.1, a Novel Splice Variant to NCOR2, as a Predictor for Tamoxifen-Resistant Breast Cancer","volume":"24","author":"Gong","year":"2018","journal-title":"Clin. Cancer Res."},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Leung, M.H., Tsoi, H., Gong, C., Man, E.P.S., Zona, S., Yao, S., Lam, E.W.F., and Khoo, U.S. (2020). A Splice Variant of NCOR2, BQ323636.1, Confers Chemoresistance in Breast Cancer by Altering the Activity of NRF2. Cancers, 12.","DOI":"10.3390\/cancers12030533"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"e1012976","DOI":"10.1080\/23723556.2015.1012976","article-title":"Trial Watch: Targeting ATM-CHK2 and ATR-CHK1 pathways for anticancer therapy","volume":"2","author":"Manic","year":"2015","journal-title":"Mol. Cell. Oncol."},{"key":"ref_17","first-page":"106","article-title":"Estrogen signaling and the DNA damage response in hormone dependent breast cancers","volume":"4","author":"Caldoe","year":"2014","journal-title":"Front. Oncol"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"801","DOI":"10.1016\/j.molcel.2017.05.015","article-title":"ATM, ATR, and DNA-PK: The Trinity at the Heart of the DNA Damage Response","volume":"66","author":"Blackford","year":"2017","journal-title":"Mol. Cell"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"359","DOI":"10.1038\/s41467-020-20520-6","article-title":"Dual RNA 3\u2032-end processing of H2A.X messenger RNA maintains DNA damage repair throughout the cell cycle","volume":"12","author":"Griesbach","year":"2021","journal-title":"Nat. Commun."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"463","DOI":"10.1158\/0008-5472.CAN-10-1252","article-title":"CCT241533 Is a Potent and Selective Inhibitor of CHK2 that Potentiates the Cytotoxicity of PARP Inhibitors","volume":"71","author":"Anderson","year":"2011","journal-title":"Cancer Res."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"816","DOI":"10.1124\/jpet.109.154997","article-title":"Cellular Inhibition of Checkpoint Kinase 2 (Chk2) and Potentiation of Camptothecins and Radiation by the Novel Chk2 Inhibitor PV1019 [7-Nitro-1H-indole-2-carboxylic acid {4-[1-(guanidinohydrazone)-ethyl]-phenyl}-amide]","volume":"331","author":"Jobson","year":"2009","journal-title":"J. Pharmacol. Exp. Ther"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"592912","DOI":"10.3389\/fphar.2020.592912","article-title":"Progress in the Understanding of the Mechanism of Tamoxifen Resistance in Breast Cancer","volume":"11","author":"Yao","year":"2020","journal-title":"Front. Pharmacol."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"111322","DOI":"10.1016\/j.mce.2021.111322","article-title":"Mechanisms of endocrine therapy resistance in breast cancer","volume":"532","author":"Rasha","year":"2021","journal-title":"Mol. Cell. Endocrinol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/j.pharmthera.2017.02.037","article-title":"PI3K-AKT-mTOR inhibitors in breast cancers: From tumor cell signaling to clinical trials","volume":"175","author":"Dey","year":"2017","journal-title":"Pharmacol. Ther."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"628690","DOI":"10.3389\/fphar.2021.628690","article-title":"Activation of PI3K\/AKT\/mTOR Pathway Causes Drug Resistance in Breast Cancer","volume":"12","author":"Dong","year":"2021","journal-title":"Front. Pharmacol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"4587","DOI":"10.1007\/s11033-020-05435-1","article-title":"Role of PI3K\/AKT pathway in cancer: The framework of malignant behavior","volume":"47","author":"Jiang","year":"2020","journal-title":"Mol. Biol Rep."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"105","DOI":"10.1038\/s41392-020-00218-3","article-title":"PI3K activation is enhanced by FOXM1D binding to p110 and p85 subunits","volume":"5","author":"Wang","year":"2020","journal-title":"Signal Transduct. Target. Ther."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"797","DOI":"10.1038\/s41419-020-02998-6","article-title":"PI3K\/AKT pathway as a key link modulates the multidrug resistance of cancers","volume":"11","author":"Liu","year":"2020","journal-title":"Cell Death Dis."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1038\/nrclinonc.2018.28","article-title":"Targeting the PI3K pathway in cancer: Are we making headway?","volume":"15","author":"Janku","year":"2018","journal-title":"Nat. Rev. Clin. Oncol."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"379","DOI":"10.1007\/s12282-017-0772-1","article-title":"Overcoming aromatase inhibitor resistance in breast cancer: Possible mechanisms and clinical applications","volume":"25","author":"Hanamura","year":"2018","journal-title":"Breast Cancer"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2951","DOI":"10.1200\/JCO.2013.53.8272","article-title":"Mutational Analysis of PI3K\/AKT Signaling Pathway in Tamoxifen Exemestane Adjuvant Multinational Pathology Study","volume":"32","author":"Sabine","year":"2014","journal-title":"J. Clin. Oncol."},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Mishra, R., Patel, H., Alanazi, S., Kilroy, M.K., and Garrett, J.T. (2021). PI3K Inhibitors in Cancer: Clinical Implications and Adverse Effects. Int. J. Mol. Sci., 22.","DOI":"10.3390\/ijms22073464"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Tsoi, H., Man, E.P.S., Chau, K.M., and Khoo, U.S. (2021). Targeting the IL-6\/STAT3 Signalling Cascade to Reverse Tamoxifen Resistance in Estrogen Receptor Positive Breast Cancer. Cancers, 13.","DOI":"10.3390\/cancers13071511"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"10502","DOI":"10.1074\/jbc.TM118.000371","article-title":"How cells ensure correct repair of DNA double-strand breaks","volume":"293","author":"Her","year":"2018","journal-title":"J. Biol. Chem."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"15069","DOI":"10.1021\/acs.jmedchem.1c00994","article-title":"Discovery and Development of a Potent, Selective, and Orally Bioavailable CHK1 Inhibitor Candidate: 5-((4-((3-Amino-3-methylbutyl)amino)-5-(trifluoromethyl)pyrimidin-2-yl)amino)picolinonitrile","volume":"64","author":"Jin","year":"2021","journal-title":"J. Med. Chem."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1016\/S1470-2045(18)30009-3","article-title":"Prexasertib, a cell cycle checkpoint kinase 1 and 2 inhibitor, in BRCA wild-type recurrent high-grade serous ovarian cancer: A first-in-class proof-of-concept phase 2 study","volume":"19","author":"Lee","year":"2018","journal-title":"Lancet Oncol."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"270","DOI":"10.3389\/fgene.2014.00270","article-title":"Physicochemical mechanisms of protein regulation by phosphorylation","volume":"5","author":"Nishi","year":"2014","journal-title":"Front. Genet."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"6723","DOI":"10.1038\/s41388-019-0928-x","article-title":"AKT-mediated phosphorylation enhances protein stability and transcription activity of ZNF322A to promote lung cancer progression","volume":"38","author":"Liao","year":"2019","journal-title":"Oncogene"},{"key":"ref_39","doi-asserted-by":"crossref","unstructured":"Liu, H., Wang, K.T., Chen, S., Sun, Q., Zhang, Y.K., Chen, L., and Sun, X.L. (2017). NFATc1 phosphorylation by DYRK1A increases its protein stability. PLoS ONE, 12.","DOI":"10.1371\/journal.pone.0172985"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"13457","DOI":"10.1073\/pnas.1919507117","article-title":"MYC protein stability is negatively regulated by BRD4","volume":"117","author":"Devaiah","year":"2020","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"1900100","DOI":"10.1002\/pmic.201900100","article-title":"Emerging Roles and Research Tools of Atypical Ubiquitination","volume":"20","author":"Huang","year":"2020","journal-title":"Proteomics"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"1170","DOI":"10.1038\/sj.cdd.4401801","article-title":"Regulation of the antioncogenic Chk2 kinase by the oncogenic Wip1 phosphatase","volume":"13","author":"Fujimoto","year":"2006","journal-title":"Cell Death Differ."}],"container-title":["International Journal of Molecular Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1422-0067\/23\/20\/12290\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T00:54:22Z","timestamp":1760144062000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1422-0067\/23\/20\/12290"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2022,10,14]]},"references-count":42,"journal-issue":{"issue":"20","published-online":{"date-parts":[[2022,10]]}},"alternative-id":["ijms232012290"],"URL":"https:\/\/doi.org\/10.3390\/ijms232012290","relation":{},"ISSN":["1422-0067"],"issn-type":[{"value":"1422-0067","type":"electronic"}],"subject":[],"published":{"date-parts":[[2022,10,14]]}}}