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Injury prevents Ras mutant cell expansion in mosaic skin

ABSTRACT: Healthy skin is a tapestry of wild-type and mutant clones. Although injury can cooperate with Ras mutations to promote tumorigenesis, the consequences in genetically mosaic skin are unknown. Here, we show that wild-type cells suppress oncogenic Ras-induced aberrant growth after injury. While HrasG12V/+ and KrasG12D/+ cells outcompete wild-type cells in uninjured, mosaic tissue, their expansion is prevented after injury due to an increase in the fraction of proliferating wild-type cells. Mechanistically, we show that, unlike HrasG12V/+ cells, wild-type cells respond to autocrine and paracrine secretion of EGFR ligands, and this differential activation of the EGFR pathway explains the competitive switch during injury-repair. Inhibition of EGFR by both drug and genetic approaches diminished the proportion of dividing wild-type cells after injury, leading to the expansion of HrasG12V/+ cells. Increased wild-type cell proliferation through a global loss of the cell cycle inhibitor p21 counteracted the expansion of HrasG12V/+ cells even without injury. Thus, injury plays an unanticipated role in switching the competitive balance between oncogenic and wild-type cells in genetically mosaic skin.

ORGANISM(S): Mus musculus

PROVIDER: GSE195892 | GEO | 2023/03/31

REPOSITORIES: GEO

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Project description:We are studying the natural history, pathogenesis and treatment of patients with WHIM syndrome, an immunodeficiency disorder characterized by warts, hypogammaglobulinemia, recurrent infections and neutropenia usually due to autosomal dominant gain-of-function mutations in chemokine receptor CXCR4. We have identified a patient born with WHIM syndrome and the WHIM mutation CXCR4R334X who has been disease-free for 20 years and who lacks CXCR4R334X in myeloid cells, the cells that drive disease manifestations. She is a genetic and hematopoietic mosaic, since she still has the mutation in lymphoid cells and non-hematopoietic cells. Cytogenetics and microarray analysis revealed that the mechanism of loss of the mutation was deletion of the mutant allele from one copy of chromosome 2. Whole genome sequencing of patient neutrophil and skin fibroblast genomic DNA revealed that the mechanism of deletion was chromothripsis, a process of chromosome shattering resulting in deletions and rearrangements of the non-deleted chromosomal segments. In the patient, this process evidently occurred in a single hematopoietic stem cell (HSC), resulting in deletion of the disease allele CXCR4R334X and one copy of 163 other genes on chromosome 2. This HSC evidently acquired a growth advantage and repopulated the HSC population and the myeloid lineage. Consistent with this, studies using gene targeted mice in competitive bone marrow transplantation experiments revealed that selective Cxcr4 haploinsufficiency (inactivation of one copy of Cxcr4 and not of any other genes) was sufficient to confer a strong engraftment advantage over bone marrow cells from wild type mice as well as bone marrow cells from a mouse model of WHIM syndrome. These results suggest that CXCR4 knockdown may be a useful strategy to enhance bone marrow engraftment in the absence of toxic bone marrow conditioning regimens.

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Injury prevents Ras mutant cell expansion in mosaic skin

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