LTO1 Complex as a Therapeutic Target for Enhancing Immunotherapy via Nonsense Mediated RNA Decay-Related MHC-I Upregulation in Tumor Cell
Immune checkpoint inhibitors benefit only a subset of patients, necessitating the development of new sensitizing agents strategies to improve tumor response and efficacy. Major histocompatibility complex class I (MHC-I), vital for tumor antigen presentation and cytotoxic T cell activation, has been an important target of immunotherapy. Nonsense-mediated RNA decay (NMD) is a highly conserved surveillance system that targets mRNAs with premature termination codons (PTCs) and monitors the quantity of about 10% of unmutated mammalian mRNAs. Tumor cells with aneuploidy heavily rely on NMD to compensate the imbalanced DNA levels and lower their antigenicity for immune evasion, making them sensitive to NMD inhibitors. Using an unbiased genome-wide analysis, we unexpectedly identified LTO1/YAE1 complex as novel NMD factors. LTO1/YAE1 complex and its downstream target for iron-sulfur cluster transfer, ABCE1, are widely overexpressed and negatively associated with immune cells infiltration in multiple cancer types. The RNA-sequencing results from these three genes led to the discovery that In tumor cells,compromised NMD is associated with MHC-I upregulation via increased expression of NLRC5, IRF1 and NF-?B in tumor cells. Importantly, we found that low doses of iron chelators, NMD inhibitors in clinical use in treatment of iron overload mimic , enhance MHC-I expression and improvingthese effects and improves immune checkpoint blockade (ICB) efficacy. Our findings suggest that LTO1/YAE1/ABCE1 could be a therapeutic target to enhance cancer immunotherapy by upregulating MHC-I and promoting immune infiltration.  Our workfindings links NMD toand iron homeostasis andto the tumor immune microenvironment. Our findings suggest that , highlighting that targeting the NMD could be a therapeutic strategy promote immune infiltration, potentially enhancing cancer immunotherapy. Overall design: To explore the function of YAE1 and ABCE1,  A375 cells were transduced with lentivirus expressing CRISPR/Cas9 and indicated sgRNA, with irrelevant gRNAs targeting LacZ or Luciferase as negative controls. Seven days after selection with 10 µg/mL puromycin, RNA was isolated and its integrity is evaluated using Agilent 4200 TapeStation. 1 µg RNA per sample was used as input for the library preparation following standard protocols. Library preparations were sequenced on a NovaSeq 6000 platform (Chi-Biotech, Guangzhou, China) and 150 bp stand-specific paired-end reads were generated.