American researchers at the Johns Hopkins University School of Medicine adapted the CRISPR-Cas9 technology to specifically target somatic mutations that generate protospacer adjacent motifs (PAMs) within pancreatic cancer genomes. Whole genome sequencing of tumours and normal tissues from pancreatic cancer patients revealed numerous somatic PAMs, providing specific targets for CRISPR-induced double-strand breaks (DSBs). This selective targeting method resulted in significant cancer cell death with minimal off-target effects.

The CRISPR approach involves the identification and utilisation of single base substitutions that create over 400 novel PAM sequences unique to the cancer cells. Researchers developed a bioinformatics pipeline named PAMfinder to pinpoint these mutations across the cancer genome.

By designing sgRNAs to target these novel PAMs, CRISPR-Cas9 can selectively introduce DSBs in cancer cells, leading to their destruction while sparing normal cells. This method leverages the high mutational burden in cancer cells, particularly in non-coding regions, to create a broad array of specific targets for CRISPR-mediated cell killing.

Functional tests in three pancreatic cancer cell lines demonstrated 69–99% selective cell death using 4-9 sgRNAs designed to target the PAM sequences. Moreover, the absence of any off-target effects confirmed the efficacy of the strategy, demonstrating high specificity and substantial reduction in cancer cell viability. The study underscores the potential of CRISPR-Cas9 as a selective cancer treatment approach, leveraging tumour-specific mutations for precise genetic targeting.

The study was led by James R. Eshleman at the Johns Hopkins University School of Medicine, and it was published in NAR Cancer on 19 June 2024.