P066 | STAT3-mediated circular RNAs dysregulation in neutropenic T-large granular lymphocyte leukemia patients

Introduction. T-Large Granular Lymphocyte Leukemia (T-LGLL) is a rare chronic lymphoproliferative disorder with unclear pathogenesis. Clonal expansion is driven by pro-inflammatory cytokines that induce JAK/STAT stimulation. Activating STAT mutations have been identified, with STAT3 lesions being typical of CD8+ T-LGLL and distinguishing symptomatic cases, mainly for neutropenia, from indolent ones. The discovery of the STAT3-miR-146b-FasL axis in STAT3-mutated CD8+ cases has highlighted the role of non-coding RNAs (ncRNAs). This study aims to clarify the role of circular RNAs (circRNAs), a class of ncRNAs, whose involvement in T-LGLL remains unexplored.Methods. We considered RNA-sequencing (RNA-seq) data (GEO GSE228868) of 20 T-LGLL cases and 5 healthy donors (HD). CircRNA identification and analysis was carried out using the CircCompara2/edgeR pipeline. Candidate circRNAs were validated in an independent cohort (n=26) through Sanger sequencing and RT-qPCR. Patient cells were treated with IL-6 (20 ng/μL) or the STAT3 inhibitor STATTIC (ST) (3.5 μM). After 24 hours cell viability, STAT3 activation, and circRNA expression were assessed via Annexin V staining, western blot, and RT-qPCR, respectively.Results. A total of 5,948 circRNAs (p-adj