Combined Mutation of <i>Apc, Kras</i> , and <i>Tgfbr2</i> 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 (<i>Apc, Kras, Tgfbr2, Trp53, Fbxw7</i>) in intestinal epithelial cells to comprehensively investigate their roles in the development of primary tumors and metastases. <i>Apc^Δ716</i> mutation caused intestinal adenomas and combination with <i>Trp53^R270H</i> mutation or <i>Tgfbr2</i> deletion induced submucosal invasion. The addition of <i>Kras^G12D</i> mutation yielded epithelial-mesenchymal transition (EMT)-like morphology and lymph vessel intravasation of the invasive tumors. In contrast, combinations of <i>Apc^Δ716</i> with <i>Kras^G12D</i> and <i>Fbxw7</i> mutation were insufficient for submucosal invasion, but still induced EMT-like histology. Studies using tumor-derived organoids showed that <i>Kras^G12D</i> was critical for liver metastasis following splenic transplantation, when this mutation was combined with either <i>Apc^Δ716</i> plus <i>Trp53^R270H</i> or <i>Tgfbr2</i> deletion, with the highest incidence of metastasis displayed by tumors with a <i>Apc^Δ716 Kras^G12D Tgfbr2^-/-</i> genotype. RNA sequencing analysis of tumor organoids defined distinct gene expression profiles characteristic for the respective combinations of driver mutations, with upregulated genes in <i>Apc^Δ716 Kras^G12D Tgfbr2^-/-</i> 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.<b>Significance:</b> These findings illuminate how key driver mutations in colon cancer cooperate to drive the development of metastatic disease, with potential implications for the development of suitable prevention strategies. <i>Cancer Res; 78(5); 1334-46. ©2017 AACR</i>.