Abstract 4680: KRAS activation in gastric adenocarcinoma stimulates epithelial-to-mesenchymal transition to cancer stem-like cells and promotes metastasis

Abstract

BACKGROUND: Our previous work showed that in a mouse model of gastric adenocarcinoma (GA) with loss of p53 and Cdh1 that adding oncogenic Kras (a.k.a triple conditional or Tcon mice) accelerates tumorigenesis and metastasis. The Receptor Tyrosine Kinase (RTK)-RAS signaling pathway is altered in 60% of GAs, and KRAS is amplified or mutated in 17% of GAs. There is some evidence that RTK-RAS signaling and oncogenic KRAS are important in the epithelial-to-mesenchymal transition (EMT) and maintenance of cancer stem-like cells (CSCs). We hypothesized that RTK-RAS activation in GA CSCs increases the metastatic potential of these cells. METHODS: The RTK-RAS pathway and KRAS were examined in nontransformed HFE-145 gastric epithelial cells, tumor-derived organoids derived from Tcon mice, human GA cell lines (AGS and KATOIII), AGS xenografts, and a tissue microarray of human GAs from 115 patients undergoing surgical resection. KRAS was inhibited using shRNA, and the RTK-RAS pathway was blocked using a MEK inhibitor PD0325901. RESULTS: Kras activity was much higher in GA cell lines grown as spheroids compared to GA cell lines grown monolayers. Metastasis following KRAS activation in GA cells results from stimulation of epithelial-to-mesenchymal transition (EMT) to cancer stem-like cells (CSCs). In organoids derived from our mouse model, Kras knockdown decreased spheroid formation, expression of EMT-related proteins, migration, and invasion; similar effects, as well as reversal of chemoresistance, were observed following KRAS knockdown in patient tumor-derived GA cell lines. KRAS inhibition in GA spheroid cells led to reduced flank xenograft growth, loss of the infiltrative tumor border, fewer lung metastases, and increased survival. Supporting clinical relevance, high tumor levels of CD44 (a marker of CSCs) and KRAS activation were independent predictors of worse overall survival in 115 GA patients. CONCLUSION: In this study, we show that the addition of oncogenic KRAS into gastric epithelial cells leads to EMT and acquisition of CSC phenotypes. Inhibition of KRAS in GA cell lines and in tumor derived organoids reverses EMT and inhibit CSC phenotypes. We conclude that metastasis following KRAS activation in GA cells likely results from stimulation of EMT and transition to CSCs. Citation Format: Changhwan Yoon, Jacob Till, Soo-Jeong Cho, Kevin Chang, Jian-Xian Lin, Sandra Ryeom, Sam Yoon. KRAS activation in gastric adenocarcinoma stimulates epithelial-to-mesenchymal transition to cancer stem-like cells and promotes metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4680.