KrasG12D inhibition partially reverts the metastatic transcriptional cell state to a non-metastatic cell state

Colorectal cancer, a leading cause of cancer-related mortality due to distant metastases, is driven by activating mutations in the Wnt and MAPK pathways. Understanding the interplay between these crucial pathways during metastatic progression is essential for developing effective treatments. Here we developed an immunocompetent mouse model of metastatic colorectal cancer using in vivo orthotopic passaging. We demonstrate that highly metastatic tumor cells exhibit chromosomal amplifications in MAPK pathway genes, leading to increased MAPK activity, which in turn suppresses Wnt-associated transcriptional programs, including stem cell-associated genes. Inhibiting mutant KrasG12D effectively reversed this metastatic transcriptional state, reducing MAPK-driven gene expression and restoring Wnt activity. Overall design: We have developed an immuno-competent mouse model of metastatic colorectal cancer by sequentially passaging small intestinal organoids with mutations in Apc, Kras, Tp53 and Smad4 in vivo. Passage 5 (m484) organoids harboring mutations in Apc (ko), KrasG12D, P53 (ko), Smad4 (ko) (AKPS) were orthotopically injected into the colon of C57BL/6N mice. 4.5 weeks post orthotopic injection into the colon, mice were treated with vehicle for 3d (n=4), MRTX1133 for 3d (n=4) and MRTX1133 for 16d (n=4). MRTX1133 treatment: 30mg/kg intraperitoneal injections B.I.D.