Deletion in Retinoblastoma Protein Pathway-Disrupted Cells Results in DNA Damage and Cancer Progression.

Proliferative control in cancer cells is frequently disrupted by mutations in the retinoblastoma protein (RB) pathway. Intriguingly, mutations can arise late in tumorigenesis in cancer cells whose RB pathway is already compromised by another mutation. In this study, we present evidence for increased DNA damage and instability in cancer cells with RB pathway defects when mutations are induced. We generated isogenic mutant genotypes with CRISPR/Cas9 in a number of cell lines. Cells with even one mutant copy of have increased basal levels of DNA damage and increased mitotic errors. Elevated levels of reactive oxygen species as well as impaired homologous recombination repair underlie this DNA damage. When xenografted into immunocompromised mice, mutant cells exhibit an elevated propensity to seed new tumors in recipient lungs. This study offers evidence that late-arising mutations can facilitate genome instability and cancer progression that are beyond the preexisting proliferative control deficit.