High expression of ferroptosis-sensitizer ACSL4 as an indicator of good response to immune checkpoint inhibitors and preferable survival with increased TIICs in skin cutaneous melanoma.

Abstract

e21594 Background: Skin cutaneous melanoma (SKCM) has a high incidence and mortality. Immune checkpoint inhibitors (ICIs) are promising but show heterogeneous efficacy in the SKCM treatment. T cell-promoted tumor ferroptosis is a vital anti-tumor mechanism of ICIs. Acyl-CoA synthetase long chain family member 4 (ACSL4) can sensitize ferroptosis by facilitating lipid peroxidation. So we proposed that ACSL4 is a positive predictor for ICIs efficacy and correlated with tumor-infiltrating immune cells (TIICs) in SKCM. Methods: The responses of SKCM patients to ICIs were evaluated from Tumor Immune Dysfunction and Exclusion (TIDE) using the gene expression data of The Cancer Genome Atlas (TCGA)-SKCM downloaded from UCSC Xena browser and datasets within TIDE. The correlation between ACLS4 expression and survival was obtained from the Online consensus Survival webserver for Skin Cutaneous Melanoma (OSskcm) and TIDE databases. The relationships between ACSL4 and TIICs were evaluated using the database of Tumor Immune Estimation Resource 2.0 (TIMER2.0). Results: ACSL4 expression was positively correlated with the predicted responder of ICIs in TCGA dataset (R = 0.12, p = 0.0093) and therapy outcomes of ICIs in Gide2019_PD1+CTLA4 (Progression-free survival(PFS), contimuous z = -2.39, p = 0.0169) and Lauss2017_ACT (PFS, contimuous z = -2.08, p = 0.0371; overall survival(OS), contimuous z = -2.96, p = 0.00309). Favorable OS was observed in the patients with high ACSL4 expression in the TCGA (HR = 0.6567, 95% CI = 0.5015̃0.8599, p = 0.0022) and GSE19234 (HR = 0.4135, 95% CI = 0.1748̃0.9784, p = 0.0445) from OSskcm and the GSE8401 (contimuous z = -2,24, p = 0.025) and GSE54467 (contimuous z = -2.26, p = 0.0239) from TIDE database. TIICs including CD8+ T cells, CD4+ T cells (memory, Th2), B cells, neutrophils, monocytes, M1 macrophages, and cancer-associated fibroblasts (CAFs) were positively associated with the expression level of ACSL4. Conclusions: High ACSL4 expression maybe indicates a good response to ICIs and long survival in SKCM. The increased T cells within the tumor microenvironment correlated with high ACSL4 expression possibly implied the synergism effects of ferroptosis and ICIs, deserving further investigation. Keywords: ACSL4, ICIs, TIICs, SKCM.