Targeted demethylation and activation of NLRC5 augment cancer immunogenicity through MHC class I

Impaired expression of MHC (major histocompatibility complex) class I in cancers constitutes a major mechanism of immune evasion. It has been well documented that the low level of MHC class I is associated with poor prognosis and resistance to checkpoint blockade therapies. However, there is lmited approaches to specifically induce MHC class I to date. Here, we show an approach for robust and specific induction of MHC class I by targeting an MHC class I transactivator (CITA)/NLRC5, using a CRISPR/Cas9-based gene- specific system, designated TRED-I (Targeted reactivation and demethylation for MHC-I). The TRED-I system specifically recruits a demethylating enzyme and transcriptional activators on the NLRC5 promoter, driving increased MHC class I antigen presentation and accelerated CD8+ T cell activation. Introduction of the TRED-I system in an animal cancer model exhibited tumor- suppressive effects accompanied with increased infiltration and activation of CD8+ T cells. Moreover, this approach boosted the efficacy of checkpoint blockade therapy using anti-PD1 (programmed cell death protein) antibody. Therefore, targeting NLRC5 by this strategy provides an attractive therapeutic approach for cancer. Significance MHC class I molecules are a key player in the human immune system and critical for detection and elimination of cancer cells. Although it has been known that augmented MHC class I expression is beneficial for cancer therapy, there has been limited approaches to specifically induce MHC class I. Here, we report specific and robust induction of MHC class I expression in cancer by applying a modified CRISPR/Cas9 technology for enhancement of the expression of MHC class I transactivator, also known as NLRC5. NLRC5 induction activated anticancer immunity, reduced tumor volume, and enhanced the efficacy of checkpoint blockade therapy. Therefore, targeting NLRC5 using this technology is a promising cancer therapeutic approach.