Elevation of Histone deacetylase-3 and -7 mediates lapatinib-induced cell migration and invasion of triple-negative breast cancer cells through COX-2 overexpression Yu-Hao He1, Min-Hsiang Hsu1, Ya-Lin Wei3, Meng-Chieh Yu1, Wei-Chien Huang1,2,3,4. From Graduate Institute of Cancer Biology1 and the Ph.D. program for Cancer Biology and Drug Discovery2, China Medical University and Hospital, Taichung 404, Taiwan Center for Molecular Medicine, China Medical University Hospital, Taichung 404, Taiwan3 Department of Biotechnology, Asia University, Taichung 413, Taiwan4 Running Title: Elevation of HDAC by lapatinib confers metastasis of triple-negative cells
Keywords: Breast cancer, HDAC, lapatinib, COX-2, metastasis
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Abstract
Lapatinib, a dual EGFR/HER2 tyrosine kinase inhibitor, has been shown to improve the survival rate of patients with advanced HER2-positive breast cancers. In attempt to broaden its clinical use, lapatinib was tested in combination with chemotherapy in HER2-negative diseases according to its activity against EGFR, but unfortunately has been shown to worsen overall survival of breast cancer patients with triple-negative (TN) or HER2-negative/PgR-negative tumors. Our previous study also explored that treatment with lapatinib renders TN cells more metastatic via increasing COX-2 and EGFR expressions, providing a possible explanation for the clinical observation. However, the molecular mechanism underlying the induction of COX-2 and EGFR expressions by lapatinib remains unclear. Here, we showed that up-regulation of histone deacetylases (HDAC) 3 and 7, accompanying with the deacetylation of histone H3K9 and H2BK5, were found in the lapatinib-treated TN cells. Treatment with HDAC inhibitors (SAHA and TSA) or HDAC3 and HDAC7 siRNA dramatically reduced lapatinib-mediated cell migration and invasion through down-regulation of COX-2 expression transcriptionally. Both activations of AP-1 and NF-kB were
observed and mediated the COX-2 gene expression in the lapatinib-treated TN cells, HDAC3/7 inhibition inhibited AP-1 but not NF-kB activation. Interestingly, treatment
with TSA, but not SAHA and HDAC3/7 siRNA, attenuated the expression of EGFR via up-regulating miR-7 expression which can target the 3’-UTR of EGFR mRNA,
suggesting that inhibitions of HDAC3 and HDAC7 by TSA and SAHA more specifically reduced COX-2 transcription in a AP-1-dependent but NF-kB-independent manner and that inhibitions of other HDACs by TSA may contribute to miR-7 expression and the subsequent EGFR down-regulation. Unexpectedly, our data further showed that lapatinib-treated TN cells are more sensitive to TSA or SAHA than their parental cells. Moreover, silence of HDAC7, but not HDAC3, expression dramatically reduced the viability of lapatinib-treated TN cells through induction of apoptosis, suggesting that targeting HDAC7 may be crucial for the antitumor activity of HDAC inhibitor. Together, our results revealed that alterations of HDAC3/7 expression are involved in
lapatinib-induced COX-2 expression and migration of triple-negative cells, and that co-treatment with HDAC inhibitors may show benefits for patients who received lapatinib therapy.
