Cantharidin induces apoptosis and suppresses cell migration and invasion of MDA-MB-231 human breast cancer cells through inhibition of EGFR-STAT3 signaling

Abstract

Breast cancer is the most frequently diagnosed life-threatening cancer in women. Common chemotherapeutic agents target three receptors: estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2). Breast cancer cells that lack ER, PR and HER2 are referred to as triple negative breast cancer (TNBC). TNBC occurs in about 15~20 % of diagnosed breast cancer. TNBC is known to increase recurrence and mortality rate within 5 years of cancer detection and is thus considered to have poorer prognosis. Recently, the signal transducer and activator of transcription 3 (STAT3) is reported as a key factor in TNBC treatment, due to high levels of STAT3 expression in TNBC. Bioassay-guided fractionation and purification were performed to isolate the cytotoxic compound from cantharides. The dried cantharides were crushed and extracted with acetonitrile and then separated into methylene chloride, acetonitrile, n-hexane and water layers. Methylene chloride and acetonitrile layerwhich had strong activity were further separated and purificated using various chromatographic techniques. The extract was fractionated into 4 fractions by Prep-LC, and the third fraction showing cytotoxic activity was separated using CCC (Counter-Current Chromatography). Separated fraction was structurally determined and identified as cantharidin by comparing NMR and HRMSdata with literature value. Cantharidin is an active constituent of the blister beetles, belonging to Meloidae family, which is traditionally used to treat wart and relieve blood stasis. Moreover, numerous studies have revealed that cantharidin has a cytotoxic effect on cancer cells. However, there have been no reports on cantharidins effect on inhibiting cell growth of TNBC. Herein, we demonstrated that cantharidin induced cell death in one of TNBC cells, MDA-MB-231, by suppressing STAT3 activation. The result showed that cantharidin reduced STAT3 tyrosine-705 in MDA-MB-231 cells.Cantharidinsignificantly inhibited activation of EGFR, Src, and STAT3, not affecting JAK-STAT3 signaling.Moreover, cantharidin inhibits cell proliferation and induces apoptosis by regulating a transcription of STAT3 target genes such as cox-2, cyclin D1, bcl-2, caspase-3 and parp1. Taken together, this study provides that cantharidin may be used as a potential therapeutic agent against TNBC, especially MDA-MB-231 cells, by reducing EGFR-STAT3 signaling.