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Breast Cancer Res Treat. 2017 Jun;163(3):461-474. doi: 10.1007/s10549-017-4202-z. Epub 2017 Mar 24.

Tumour suppressor EP300, a modulator of paclitaxel resistance and stemness, is downregulated in metaplastic breast cancer.

Author information

1
Division of Cancer, Imperial College Faculty of Medicine, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
2
Department of Clinical Pharmacy and Pharmacology, University of Dhaka, Dhaka, 1000, Bangladesh.
3
MRC Cancer Unit, Hutchison/MRC Research Centre, Cambridge, CB2 0XZ, UK.
4
Centre for Pathology, Department of Medicine, Imperial College Faculty of Medicine, Charing Cross Hospital, Fulham Palace Rd, London, W6 8RF, UK.
5
Division of Clinical Sciences, Imperial College Faculty of Medicine, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
6
The 3rd Department of Breast Cancer, China Tianjin Breast Cancer Prevention, Treatment and Research Center, National Clinical Research Center of Cancer, Tianjin Medical University Cancer Institute and Hospital, Huan Hu Xi Road, Ti Yuan Bei, He xi District, Tianjin, 300060, People's Republic of China. 417501784@qq.com.
7
Division of Cancer, Imperial College Faculty of Medicine, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK. ernesto.yague@imperial.ac.uk.

Abstract

PURPOSE:

We have previously described a novel pathway controlling drug resistance, epithelial-to-mesenchymal transition (EMT) and stemness in breast cancer cells. Upstream in the pathway, three miRs (miR-106b, miR-93 and miR-25) target EP300, a transcriptional activator of E-cadherin. Upregulation of these miRs leads to the downregulation of EP300 and E-cadherin with initiation of an EMT. However, miRs regulate the expression of many genes, and the contribution to EMT by miR targets other than EP300 cannot be ruled out.

METHODS:

We used lentiviruses expressing EP300-targeting shRNA to downregulate its expression in MCF-7 cells as well as an EP300-knocked-out colon carcinoma cell line. An EP300-expression plasmid was used to upregulate its expression in basal-like CAL51 and MDA-MB-231 breast cancer cells. Drug resistance was determined by short-term proliferation and long-term colony formation assays. Stemness was determined by tumour sphere formation in both soft agar and liquid cultures as well as by the expression of CD44/CD24/ALDH markers. Gene expression microarray analysis was performed in MCF-7 cells lacking EP300. EP300 expression was analysed by immunohistochemistry in 17 samples of metaplastic breast cancer.

RESULTS:

Cells lacking EP300 became more resistant to paclitaxel whereas EP300 overexpression increased their sensitivity to the drug. Expression of cancer stem cell markers, as well as tumour sphere formation, was also increased in EP300-depleted cells, and was diminished in EP300-overexpressing cells. The EP300-regulated gene signature highlighted genes associated with adhesion (CEACAM5), cytoskeletal remodelling (CAPN9), stemness (ABCG2), apoptosis (BCL2) and metastasis (TGFB2). Some genes in this signature were also validated in a previously generated EP300-depleted model of breast cancer using minimally transformed mammary epithelial cells. Importantly, two key genes in apoptosis and stemness, BCL2 and ABCG2, were also upregulated in EP300-knockout colon carcinoma cells and their paclitaxel-resistant derivatives. Immunohistochemical analysis demonstrated that EP300 expression was low in metaplastic breast cancer, a rare, but aggressive form of the disease with poor prognosis that is characterized by morphological and physiological features of EMT.

CONCLUSIONS:

EP300 plays a major role in the reprogramming events, leading to a more malignant phenotype with the acquisition of drug resistance and cell plasticity, a characteristic of metaplastic breast cancer.

KEYWORDS:

ABCG2; BCL2; Cancer stem cells; Drug resistance; EP300 signature; Metastasis

PMID:
28341962
PMCID:
PMC5427146
DOI:
10.1007/s10549-017-4202-z
[Indexed for MEDLINE]
Free PMC Article

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