Targeting DNA mismatch repair pathway by CRISPR nanosystem for boosting checkpoint blockade cancer immunotherapy

Abstract

Immune checkpoint blockade (ICB) therapy has exhibited great clinical benefits in multiple cancers types. However, most cancer patients such as colorectal cancers (CRC) show poor response to ICB. Here, we develop a magnetic nanoparticle (MNP)-mediated delivery of CRISPR/Cas9 system (LMPM) to target the DNA repair pathway and inactivate endogenous DNA mismatch repair (MMR)-related Mlh1 gene as a new strategy of immunotherapy. The genetically knockout of Mlh1 can be effectively realized by CRISPR/Cas9 edition with external magnetic field control. As a consequence, the inactivation of Mlh1 lead to an increased tumor mutation burden and enhancement of tumor immunogenicity in situ, which can elicit strong antitumor immunity. Both in vitro and in vivo studies demonstrate that deploying such a strategy of targeting inactivation of Mlh1 shows high inhibition efficacy in the established tumors. In this way, tumor infiltration of CD8+ T cells and ICB response are significantly improved compared with α-PD1 monotherapy. In short, it is certified that precision targeting of DNA MMR pathway can boost specific anti-tumor immune response and display the potent potential in versatile tumor immunotherapy therapeutic exploitation.