Abstract P5-08-07: Study of diphenylamine analogs as inducers of mesenchymal to epithelial transition in breast cancer

The organization of cell cytoskeleton is altered in events of epithelial to mesenchymal transition (EMT), promotion of cell motility, and cancer metastases. EMT is associated with decreased cell-cell adhesion, downregulation of epithelial markers like E-Cadherin, cytokeratins, and occludins, and upregulation of mesenchymal markers such as N-cadherin, vimentin, and various transcription factors such as slug and ZEB. Epithelial to mesenchymal transition is also a consequence of drug resistance and is responsible for cancer metastases. Triple negative breast cancer is highly aggressive cancer and patients show poor prognosis and disease-free survival due to the lack of targeted therapy. Mitogen activated protein kinase pathway, including extracellular activated kinase ERK1/2 and ERK5, and phosphoinositide 3-kinase (PI3K) pathway are known to alter the cytoskeleton through the downstream activation of oncogenes such as FRA-1 and loss of focal adhesions. Of these pathways, the MEK5-ERK5 pathway is understudied in triple negative breast cancer TNBC, and there are few research tools available to selectively inhibit this pathway. The diphenylamine analogs were derived from the parent molecule Mekinist, a FDA approved MEK1/2 inhibitor for melanoma, and modified to gain selectivity towards MEK5. SC-1-151, a type-III allosteric inhibitor of MEK5 is a dual MEK1/2 (98.6%) and MEK5 (59%) inhibitor; the molecule inhibits cell viability and colony formation, and attenuates tumor growth. SC-1-151 was serendipitously identified as a mesenchymal to epithelial transition activator in TNBC cell line MDA-MB-231. E-cadherin protein expression and cell morphology were examined to study MET after the treatment of MDA-MB-231 cells with different structural analogs of SC-1-151 after treatment for 5 days. The compound was further found to induce E-cadherin expression and epithelial phenotype in tamoxifen resistant estrogen positive MCF-7 cell line that underwent EMT. The compound is identified to promote this activity by targeting at least the ERK-FRA1-ZEB1 axis. Alkyl or N-Methyl piperazine substituents on the amide of ring 1 produced similar result as SC-1-151, and substituting the amide group with acid or ester also induced MET. In contrast, ortho-fluoro, para-iodo functional groups of the arene ring 2, when replaced with a meta-bromo substituent did not induce MET. We aim to test the compounds on EGF treated MDA-MB-468 cells to observe the attenuation of EGF induced EMT. Future studies will be performed to determine the specific protein interactions of the promising compounds. Citation Format: Bhatt AB, Wright TD, Anna K, Gupta M, Chakrabarty S, Flaherty PT, Hoang V, Burow M, Cavanaugh JE. Study of diphenylamine analogs as inducers of mesenchymal to epithelial transition in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-08-07.