Abstract 299: Targeting epithelial-mesenchymal transition in breast cancer cells using Honokiol, a natural phenolic compound.

Abstract

Abstract Introduction: The epithelial-mesenchymal transition (EMT) presents a critical step in the acquisition of metastatic state. Tumor cells undergoing EMT not only exhibit increased migration and invasion potential but also acquire increased resistance to chemotherapy and radiation therapy. Hence, EMT is an attractive target for therapeutic interventions directed against tumor metastasis. Honokiol (HNK) is a natural phenolic compound isolated from an extract of seed cones from Magnolia grandiflora. Recent studies from our lab show that honokiol inhibits breast carcinogenesis. The present study is designed to systematically elucidate if nontoxic lower doses of honokiol can be used to specifically inhibit EMT in breast cancer cells. Results: Our studies show that HNK inhibits EMT in human breast cancer cells. Exposure of estrogen-independent and estrogen-responsive breast cancer cells to nontoxic lower doses of HNK results in significant downregulation of mesenchymal marker proteins (Fibronectin, Vimentin) along with simultaneous upregulation of epithelial markers (E-cadherin, Cytokeratin-18). HNK also inhibits expression and nuclear translocation of transcriptional modulators of EMT-related genes (Snail, ZEB1/2 and Twist). Experimental EMT induced by exposure to TGFβ and TNFα in a spontaneously immortalized nontumorigenic human mammary epithelial cell line (MCF-10A) was also completely reversed by HNK treatment as evidenced by morphological changes (inhibition of fibroblast-like appearance, decreased pseudopodia and actin reorganization to membrane-bound location in TGFβ and TNFα treated MCF10A cells) as well as molecular changes (downregulation of Fibronectin, Vimentin, Snail, Zeb1/2 and upregulation of E-cadherin and Cytokeratin-18). Mechanistically, HNK inhibits MTA1-Wnt1 axis leading to stabilization and nuclear translocation of β-catenin to inhibit EMT. Analysis of breast tumors treated with honokiol show modulation of EMT markers and inhibition of key molecules of MTA1-Wnt1-β-catenin axis corroborating our in vitro findings. Conclusions: Taken together, these data provide the first in vitro and in vivo evidence of the potential of HNK as a novel, non-toxic and non-endocrine therapeutic strategy for breast carcinoma. MTA1, Wnt1 and β-catenin appear to be novel biomarkers associated with HNK treatment. Citation Format: Dimiter B. Avtanski, Arumugam Nagalingam, Panjamurthi Kupusamy, Neeraj K. Saxena, Dipali Sharma. Targeting epithelial-mesenchymal transition in breast cancer cells using Honokiol, a natural phenolic compound. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 299. doi:10.1158/1538-7445.AM2013-299