KRAS allelic imbalance drives tumour initiation yet suppresses metastasis in colorectal cancer in vivo
Arafath K. Najumudeen, Sigrid K. Fey, Laura M. Millett, Catriona A. Ford, Kathryn Gilroy, Nuray Gündüz, Rachel A. Ridgway, E. S. Anderson, Douglas Strathdee, William Clark, Colin Nixon, Jennifer P. Morton, Andrew D. Campbell, Owen J. Sansom
Abstract
Oncogenic KRAS mutations are well-described functionally and are known to drive tumorigenesis. Recent reports describe a significant prevalence of KRAS allelic imbalances or gene dosage changes in human cancers, including loss of the wild-type allele in KRAS mutant cancers. However, the role of wild-type KRAS in tumorigenesis and therapeutic response remains elusive. We report an in vivo murine model of colorectal cancer featuring deletion of wild-type Kras in the context of oncogenic Kras. Deletion of wild-type Kras exacerbates oncogenic KRAS signalling through MAPK and thus drives tumour initiation. Absence of wild-type Kras potentiates the oncogenic effect of KRASG12D, while incidentally inducing sensitivity to inhibition of MEK1/2. Importantly, loss of the wild-type allele in aggressive models of KRASG12D-driven CRC significantly alters tumour progression, and suppresses metastasis through modulation of the immune microenvironment. This study highlights the critical role for wild-type Kras upon tumour initiation, progression and therapeutic response in Kras mutant CRC.