Epithelial-to-Mesenchymal Transition in Paclitaxel-Resistant Ovarian Cancer Cells Is Downregulated by Luteolin

Ovarian cancer (OVCA) is the deadliest of all gynecological cancers which is attributed to late presentation, persistence, and development of chemoresistance. The objectives were to evaluate the association between OVCA paclitaxel-resistance and epithelial-to-mesenchymal transition (EMT) and to determine the capability of luteolin to chemosensitize OVCA cells. X10 and X22 cells were 11.8-25.3-fold and 7.8-8.6-fold resistant to paclitaxel than 1AP cells. X10 and X22 cells exhibited a mesenchymal phenotype, while 1AP has an epithelial characteristics. Furthermore, the expression of the epithelial marker E-cadherin was downregulated, while mesenchymal markers Vimentin and N-cadherin were upregulated in X10 and X22 cells when compared to 1AP cells. Transcription factors Snail, Slug, and Twist1 were upregulated in X10 cells, while Twist1 was highly expressed in X22 cells. Luteolin treatment caused cytotoxicity being most potent to X10 OVCA cells. Treatment of non-cytotoxic dose of luteolin at 15.625 μM chemosensitized X10 and X22 OVCA cells to paclitaxel as evidenced by reduced ED₅₀ values from 11.8 to 0.2 μM and 8.6 to 3.6 μM for X10 and X22 cells, respectively. Moreover, luteolin treatment led to a more epithelial phenotype of X10 and X22 cells and modification of EMT markers indicating reversal of EMT. The mechanism involved is through reduction of phosphorylation of FAK and ERK leading to reduced nuclear translocation of p65. Our results highlight the significance of EMT in OVCA resistance to paclitaxel and warrant the investigation of luteolin as a potential therapeutic agent in chemoresistant OVCA. J. Cell. Physiol. 232: 391-401, 2017. © 2016 Wiley Periodicals, Inc.