KRAS allelic imbalance drives tumour initiation yet suppresses metastasis in colorectal cancer in vivo

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.


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Uncropped versions of blots in Figure 2c, f are provided in the Source Data File.
NA NA NA NA NA For all in vivo experiments, power analyses were carried out to determine cohort sizes based upon effect size and SD derived from unpublished experiments in similar GA models previously carried out within the lab, and from early pilot studies which were carried out within experimental and control cohorts.Power analyses were carried out using the G* power software package 3.1.9.4 (HHU Dusseldorf), typically defining alpha=0.05 and beta=0.2.Animal studies were also carried out respecting the limited use of animals in line with the 3R system: Replacement, Reduction, Refinement.
No data were excluded.
For all in vivo and ex vivo experiments carried out, individual animals of control and experimental cohorts are biologically unique -here replicate data represents analysis of data/samples from independent replicate animals and is denoted by "n".
To minimise genetic variability, all experimental and control animals were either generated on a pure, inbred genetic background, or where that was not possible, were generated from individual breeding colonies.Control and experimental animals were co-housed independent of genotype and cohorts were comprised of a balance of both male and female animals.in order to reduce the impact of covariates such as gender or housing, animals were recruited to treatment groups in a partially randomised manner while taking these factors into account.
For animal welfare reasons, researchers were not blinded to genotype during study and data collection.The investigator(s) were blinded to genotype or treatment during data analysis.