CRISPR/Cas9 Genome Editing in Oncology: Mechanisms, Therapeutic Platforms and Translational Challenges

The CRISPR/Cas9 genome editing technology has had a significant impact on cancer research and therapeutic development, providing unprecedented precision in manipulating cancer-associated genes. Although this review focuses on Cas9, we situate it within the broader CRISPR landscape that includes DNA-targeting effectors (Cas9/Cas12), RNA-targeting systems such as Cas13, and type III systems with dual DNA and RNA activity, modalities that expand both experimental and therapeutic possibilities. This comprehensive review examines the current applications of CRISPR/Cas9 in oncology, including its mechanisms and the challenges associated with its clinical translation. Knockout, interference, and activation CRISPR screening platforms have transformed functional genomics by systematically interrogating gene function, identifying therapeutic vulnerabilities, and clarifying resistance mechanisms across diverse cancer phenotypes. This technology has also reshaped cancer modeling, enabling precise recapitulation of disease-relevant mutations from engineered cell lines to patient-derived xenografts that capture tumor heterogeneity and microenvironmental interactions. Notably, the integration of CRISPR/Cas9 with CAR-T therapy has enabled multiplex editing to eliminate alloreactivity, overcome checkpoint-mediated exhaustion, and engineer universal CAR-T cells. Emerging in vivo strategies that directly generate or reprogram CAR-T cells in patients via targeted viral and nonviral delivery underscore accelerating translational momentum. However, significant challenges, including off-target mutagenesis, delivery barriers, p53-mediated selective pressure favoring potentially oncogenic populations, and Cas9 immunogenicity, continue to hinder clinical translation. These limitations necessitate high-fidelity nucleases, optimized guide designs, and improved delivery systems. The future of CRISPR/Cas9 in cancer therapy will depend on technological innovation, comprehensive safety frameworks, and rigorous clinical evaluation as next-generation editing modalities advance toward transformative precision oncology.