1449PAnalysis of immunosuppressive factors produced by tumorspheres in NSCLC: Prognostic value of galectin-3 in adenocarcinoma

Abstract Background Cancer stem cells (CSCs) are targets poorly recognized by the immune surveillance system given that they induce an immunosuppressive microenvironment. The aim of this work is to study the interactions between CSCs and the immune microenvironment in NSCLC. Methods Tumor cells from 8 resected NSCLC patients and 12 cell lines were established as tumorspheres enriched in CSCs and as monolayers. The gene expression of IL-4, IL-10, IL6, IL8 and LGALS-3 was analyzed by RTqPCR. Results were validated at a protein level by a sensitivity bead-based multiplex immunoassay using the Millipore kit for Luminex 100/200. The prognostic value of these factors in silico was determined in a cohort of 661 patients from The Cancer Genome Atlas (TCGA). Prognostic value was assessed by Cox regression and Kaplan‐Meier curves (long rank‐test). Results Patients’ median age was 67 years [57-74], 62% were male, and 62.5% were adenocarcinomas (ADC). Gene expression analysis revealed that LGALS3 was significantly higher expressed in lung tumorspheres. By contrast, adherent cells had significantly higher expression of IL6. In accordance with gene expression levels, we observed significant differences in the secretion of these two soluble factors (IL-6 and Galectin-3) between adherent cells and tumorspheres. No significant results were observed for IL-8, IL-10 and IL-4 expression and secretion. Survival analysis showed that ADC patients with higher LGALS3 expression decreased overall survival (OS, 40.49 vs. 87.90 months, p = 0.005) and relapse-free survival (RFS, 25.28 vs. 41.25 months, p = 0.003) than the group with LGALS3 expression below the median. The multivariate analysis reported that LGALS3 expression can be established as an independent prognostic biomarker for OS [HR = 1.75; 95% CI, 1.19-2.59; p = 0.004] and for PFS in lung adenocarcinoma [HR = 1.68; 95% CI, 1.22-2.32; p = 0.001]. Conclusions The secretion of Galectin-3 by Lung CSCs may be involved in the modulation of the immune microenvironment. Galectin-3 is an independent prognostic biomarker for overall survival and relapse-free survival in lung adenocarcinomas. Supported by grants CB16/12/00350, PI18/00266 and PI15-00753 from ISCIII and ACIF/2018/275 from GVA and FSE. Legal entity responsible for the study Fundacion Hospital General Universitario de Valencia. Funding CB16/12/00350, PI18/00266 and PI15-00753 from ISCIII and ACIF/2018/275 from GVA and FSE. Disclosure All authors have declared no conflicts of interest.