Abstract PS16-28: Runx3 regulates emt during development lapatinib resistance

Abstract

Abstract RUNX3 regulates EMT during development lapatinib resistanceBackground: Lapatinib is a small molecular inhibitor of HER2 and EGFR tyrosine kinase, which is used for HER2 positive metastatic breast cancer patients. However, significant proportion of patients relapse due to acquired resistance. The epithelial to mesenchymal transition (EMT), which induces cell migration, invasion and cancer stem cell progression, was one of the mechanism that confers to drug resistance. We determined the correlation of lapatinib resistance and EMT, and identified a regulatory factor of EMT which associated with the development process of acquired lapatinib resistance.Methods: Acquired lapatinib resistant SK-BR-3 (SK-BR-3 LR) cells were established by continuously exposing to lapatinib for 7 months. The sensitivity of lapatinib was confirmed by MTT assay. Cell cycle progression was verified using flow cytometry analysis. Expression of signal transduction molecules were determined using quantitative PCR, western blotting and transcriptome data analysis. Cell migration and invasion ability were verified using wound healing assay and Boyden chamber assay. siRNA knock-down system were used for further analysis. Results: Lapatinib resistant (SK-BR-3 LR) cells showed aggressive morphology compared with parental cells. The growth rate and cell cycle progression were increased in SK-BR-3 LR cells. Expression of Snail, Vimentin, SOX2, Nanog, TGF-b1 and Smad proteins increased in SK-BR-3 LR cells. In SK-BR-3 LR cells, cell migration and invasion were significantly increased. Correlated with a promoter methylation of RUNX3, expression of RUNX3 was down-regulated in SK-BR-3 LR cells. In Runx3 knock-down cells TGF-b1, SOX2, smad molecules were up-regulated. Conclusion: SK-BR-3 LR cells showed aggressive phenotype. Expression of EMT markers, cancer stem cell markers, TGF-β pathway associated molecules and Smad proteins were increased in SK-BR-3 LR cells. Also, the increase of cell migration and invasion was observed in LR cells. RUNX3 affected to cell migration and invasion through regulation of EMT associated molecules. Therefore, RUNX3 might be a specified molecule, which partially contributes resistance to lapatinib through regulates EMT. Citation Format: So Hyeon Kim, Ahrum Min, Seongyeong Kim, Yoonjung Park, Yu Jin Kim, Seock-Ah Im. Runx3 regulates emt during development lapatinib resistance [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS16-28.