ADAR1 expression is associated with cervical cancer progression and negatively regulates NK cell activity
ADAR1 edits double-stranded (ds) RNAs by deaminating adenosines into inosines preventing aberrant activation of innate immunity by endogenous dsRNAs, which may resemble viral structures. Several tumors exploit ADAR1 to evade immune surveillance; indeed, its deletion reduces tumor viability and reshapes infiltrating leukocytes. Here, we investigated the role of ADAR1 in immune evasion mechanisms during cervical cancer (CC) progression. Patients' biopsies showed higher ADAR1 expression already in pre-malignant (SIL) lesions, and a substantially reduced percentage of infiltrating CD7+ innate cells in in situ and invasive carcinomas, compared to normal mucosa, with CD56+ NK cells showing phenotypic alterations that might impact their functional responses. In CC-derived cell lines (SiHa, CaSki), ADAR1 silencing reduced cell proliferation, an effect further enhanced by exogenous IFNbeta administration. It also induced pro-inflammatory gene expression, as demonstrated by RNAseq analysis, and conditioned supernatants collected from these cells activated several NK cell effector functions. NK cell infiltration and activation was also confirmed in organotypic 3D tissue models of SiHa cells knocked-out for ADAR1. In conclusion, ADAR1 expression increases with CC progression and is accompanied by alterations of tumor-infiltrating NK cells, but its silencing in CC-derived cell lines potentiated anti-tumor NK cell activities. Thus, ADAR1 inhibition may represent a therapeutic perspective for CC and possibly other malignancies. Overall design: RNA library was prepared using 1,5 micrograms of RNA with Kapa RNA HyperPrep with RiboErase (total RNA) and Kapa Globin Depletion Hybridization Oligos (Roche), from CaSki and SiHa cells. We compared two conditions (siCtr and siADAR). Samples were sequenced by NovaSeq 6000 Sequencing System, RUN 2x101 bp, Illumina Instrument, with an average number of reads from each sample of 140 M.