EFFECTS OF PLUMBAGIN ON CYTOTOXICITY, TAMOXIFEN SENSITIVITY AND EPITHELIAL-MESENCHYMAL TRANSITION-ASSOCIATED METASTASIS IN ENDOCRINE RESISTANT BREAST CANCER CELLS

Abstract

This present study was aimed at investigating the growth inhibition effect of Plumbagin (PLB) on endocrine resistant breast MCF-7/LCC2 and MCF-7/LCC9 cells using the MTT method, followed by tamoxifen response assay and combination index (CI) analyses to identify the reversal of endocrine therapy by PLB of nuclear receptor coactivator 3 (NCoA3) involved in transcriptional activity of ER target genes. PLB has been shown to inhibit NF-kB which requires in EMT and endocrine resistance mechanism, so reverse transcriptase polymerase chain reaction (RT-PCR) was performed to determine the expression of ER target genes Cyclin D1, MYC and EMT-related genes including E-cadherin, Vimentin, and Snail. Furthermore, cellular migration and invasive capacities were also investigated in endocrine resistant breast cancer cells in the presence or absence of PLB. The results demonstrated that i) PLB has significantly cytotoxic activity with the IC50 values of 1.47, 1.22 μM for MCF-7 and 1.69, 1.58 μM for MCF-7/LCC2 and 1.24, 1.17 μM for MCF-7/LCC9 cells after 24 and 48 h of treatment respectively, ii) PLB synergistically enhanced cytotoxicity and restored tamoxifen sensitivity to resistant MCF-7/LCC2 and MCF-7/LCC9 breast cancer cells with combination index (CI) of 0.56 and 0.94 respectively, iii) EMT-like behaviors were observed in endocrine resistant breast cancer cells, iv) PLB decreased the expression of Cyclin D1, MYC, NCoA3, Vimentin, and Snail, while the expression level of E-cadherin was increased and v) PLB inhibited the motility and invasiveness of these resistant cells at non-toxic concentration. This study is the first report highlighted the pharmacological properties of PLB on endocrine resistant breast cancer cells and recognized the background molecular knowledge, especially PLB inhibited EMT process. Therefore, PLB will be a novel therapeutic target for ER-positive breast cancer patients who are unresponsive to endocrine therapy.