Combined Mutation of Apc, Kras, and Tgfbr2 Effectively Drives Metastasis of Intestinal Cancer

Colorectal cancer is driven by the accumulation of driver mutations, but the contributions of specific mutations to different steps in malignant progression are not fully understood. In this study, we generated mouse models harboring different combinations of key colorectal cancer driver mutations (Apc, Kras, Tgfbr2, Trp53, Fbxw7) in intestinal epithelial cells to comprehensively investigate their roles in the development of primary tumors and metastases. Apc(Delta 716) mutation caused intestinal adenomas and combination with Trp53(R270H) mutation or Tgfbr2 deletion induced submucosal invasion. The addition of Kras(G12D) mutation yielded epithelial-mesenchymal transition (EMT)-like morphology and lymph vessel intravasation of the invasive tumors. In contrast, combinations of Apc(Delta 716) with Kras(G12D) and Fbxw7 mutation were insufficient for submucosal invasion, but still induced EMT-like histology. Studies using tumor-derived organoids showed that Kras(G12D) was critical for liver metastasis following splenic transplantation, when this mutation was combined with either Apc(Delta 716) plus Trp53R270H or Tgfbr2 deletion, with the highest incidence of metastasis displayed by tumors with a Apc(Delta 716) Kras(G12D) Tgfbr2(-/-) genotype. RNA sequencing analysis of tumor organoids defined distinct gene expression profiles characteristic for the respective combinations of driver mutations, with upregulated genes in Apc(Delta 716) Kras(G12D) Tgfbr2(-/-) tumors found to be similarly upregulated in specimens of human metastatic colorectal cancer. Our results show how activation of Wnt and Kras with suppression of TGF beta signaling in intestinal epithelial cells is sufficient for colorectal cancer metastasis, with possible implications for the development of metastasis prevention strategies. Significance: These findings illuminate howkey driver mutations in colon cancer cooperate to drive the development of metastatic disease, with potential implications for the development of suitable prevention strategies. (C) 2017 AACR.