Precise and efficient silencing of mutant KrasG12D by CRISPR-CasRx controls pancreatic cancer progression

Rationale: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease with few therapeutic targets and rare effective treatments. Over 90% of PDAC tumors bear a Kras mutation, and the single-site mutation G12D (Kras(G12D)) is most prevalent. Methods: Here, we applied the CRISPR-CasRx system to silence the mutant Kras(G12D) transcript in PDAC cells. We also used a capsid-optimized adenovirus-associated virus 8 vector (AAV8) to deliver the CRISPR-CasRx system into PDAC orthotopic tumors and patient-derived tumor xenografts (PDX). Results: Our data showed that guided by a Kras(G12D)-specific gRNA, CasRx is able to precisely and efficiently silence the mutant Kras(G12D) expression in PDAC cells. The knockdown of mutant Kras(G12D) by CasRx abolishes the aberrant activation of downstream signaling induced by mutant Kras(G12D) and subsequently suppresses the tumor growth and improves the sensitivity of gemcitabine in PDAC. Additionally, delivering CasRx-gRNA via AAV8 into the orthotopic Kras(G12D) PDAC tumors substantially improves the survival of mice without obvious toxicity. Furthermore, targeting Kras(G12D) through CasRx suppresses the growth of PDAC PDXs. In conclusion, our study provides a proof-of-concept that CRISPR-CasRx can be utilized to target and silence mutant Kras(G12D) transcripts and therefore inhibit PDAC malignancy.