Epigenetic and Epitranscriptomic Modulation by STAT1: Unraveling T Helper Cell Differentiation in NSCLC

The lack of targetable mutations in 50% of NSCLC cases and resistance to therapies underscore the need for alternative treatments, with epigenetic strategies potentially regulating tumor suppressor genes to inhibit growth. Our focus is to understand the STAT1-mediated epigenetic and epitranscriptomic modulations, such as R-loop formation, histone methylation/demethylation, histone acetylation and deacetylation, DNA methylation, and m6A RNA methylation, in T helper cell (TH) differentiation to evoke tumor-protective immune responses in non-small cell lung cancer (NSCLC) by knocking out (KO) and overexpressing (OE) STAT1. Peripheral blood mononuclear cells (PBMCs) were isolated from NSCLC patients and healthy controls using Ficoll-Hypaque density-gradient centrifugation. CD4+ T cells were purified with magnetic activated cell sorting (MACS). Subsequently, CRISPR/Cas9 knock-out and overexpression techniques were applied, followed by qRT-PCR to evaluate 5-mC, m6A RNA methylation, gene expression, and transcription factor enrichment. Mutations in STAT1 can cause severe immunodeficiency and malignancy, linked to genomic instability from R-loops-DNA-RNA hybrids that lead to DNA breaks through transcription-coupled nucleotide excision repair. Our study examines epigenetic regulators in CD4+ T helper cells from NSCLC patients, focusing on the effects of STAT1 depletion and overexpression on R-loop formation at key gene loci specific to T helper cells. Depletion of STAT1 increased R-loop frequencies, DNA methylation, histone deacetylation, and histone methylation, whereas its overexpression decreased them. Abnormal epitranscriptomic alterations, including m6A RNA methylation, were observed, indicating that STAT1 is crucial for T helper cell differentiation and immune responses in NSCLC, presenting promising avenues for targeted therapeutic interventions.