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^δ716 mutation caused intestinal adenomas and combination with Trp53^R270 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^δ716 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^δ716 plus Trp53^R270H or Tgfbr2 deletion, with the highest incidence of metastasis displayed by tumors with a Apc^δ716 Kras^G12D Tgfbr2^-/- genotype. RNA sequencing analysis of tumor organoids defined distinct gene expression profiles characteristic for the respective combinations of driver mutations, with upre-gulated genes in Apc^δ716 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 TGFβ signaling in intestinal epithelial cells is sufficient for colorectal cancer metastasis, with possible implications for the development of metastasis prevention strategies.