KRAS drives immune evasion in a genetic model of pancreatic cancer

We used CRISPR/Cas9 genome editing to inactivate KRAS in pancreatic cancer cells and isolated cell populations that still produce tumors in mice. We show that the malignant phenotype of KRAS knockout cells is stable. However, KRAS deficient cancer cells fail to avoid detection and elimination by the host immune system, indicating that a key aspect of tumor maintenance by oncogenic KRAS is to promote immune evasion. Our study uncovers changes both in cancer cells and stromal immunoreactive cells attributable to KRAS expression. Complementation studies indicate that BRAF, AKT and MYC are causative drivers of KRAS-mediated immune suppression. These results show that combination treatments that both target KRAS signaling and boost antitumor immunity will be an effective strategy to treat PDAC. scRNAseq was performed on a total of three samples. Tumors were harvested from the pancreas of three sets of syngeneic mice. These mice were injected orthotopically with a) malignant KRASG12D p53R172H/+ b) KRASKO and c) KRAS KO BRAF/MYC cells.