Exploring the Endeavors of CRISPR/Cas9 Gene-Editing Technology in the Therapy of Cancer and Other Human Diseases

Abstract

Clustered regularly interspaced short palindromic repeats (CRISPR) and the associated Cas9 nuclease have become the dominant platform for genome editing, offering greater efficiency, simplicity and programmability than the zinc finger nucleases and transcription activator-like effector nucleases that preceded them. This review examines the application of CRISPR/Cas9 to cancer and to other human diseases, together with the obstacles that continue to limit its clinical translation. We outline the architecture and DNA-recognition mechanisms of the three programmable nuclease platforms, describe the classification of CRISPR/Cas systems into two classes and their constituent types, and summarise the pooled genome-wide screening formats knock-out, interference and activation libraries through which the technology has been used to identify essential genes, synthetic-lethal interactions and mechanisms of drug resistance. In cancer research, CRISPR/Cas9 has enabled the inactivation of tumour suppressor genes in animal models, the restoration of tumour suppressor function, and the dissection of resistance to targeted agents and cytotoxic chemotherapy. Its most advanced clinical application is in cell therapy, where multiplexed editing has been used to disrupt the endogenous T cell receptor, silence checkpoint genes such as PDCD1 and reduce the risk of graft-versus-host disease; early-phase trials in refractory malignancy have established feasibility and an acceptable safety profile, although objective responses have so far been limited. Beyond oncology, progress is reviewed in Duchenne muscular dystrophy, HIV-1 infection, sickle cell disease, haemophilia B and neurodevelopmental disorders. Off-target cleavage, delivery and vector immunogenicity remain the principal constraints on therapeutic use, and the strategies developed to address them are discussed.