1443P - Characterization of lung tumourspheres reveals cancer stem-like cells potential targets and prognostic markers in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is the first cause of death cancer-related worldwide mainly due to high therapeutic resistance. This resistance is related to cancer stem-like cells (CSCs), for which the identification of targets and markers is still ongoing. Primary cultures from 8 NSCLC patients were established as tumorspheres and as monolayers. CSCs properties were tested for both conditions in vitro and in vivo. The expression of 50 CSCs-related genes was assessed by RTqPCR and proteins of significantly overexpressed genes were examined by immunoblot and immunofluorescence. The prognostic role of these genes was analyzed in a cohort of 661 NSCLC patients from TCGA and validated in an independent cohort of 114 lung adenocarcinoma (ADC) patients. Tumorspheres exhibited self-renewal, unlimited exponential growth, drug resistance, great invasion and differentiation capacities in vitro and higher tumorigenic potential than monolayers in vivo. 17 genes were significantly overexpressed in tumorspheres, being NANOG, NOTCH3, CD44, CDKN1A, SNAI1, and ITGA6 the major contributors to distinguish them from adherent cells. Proteins encoded by these genes showed differential localization and expression patterns in ADC tumorspheres. The expression of CDKN1A, SNAI1 and ITGA6 was associated to prognosis, so a score was built based on their regression coefficients from a multivariate model. TCGA patients with high CSCs score show shorter OS in the entire cohort [37.7 vs. 60.4mo., p=0.001] and the ADC subcohort [36.6 vs. 53.5mo., p=0.003]. Multivariate analysis indicated that this score is an independent biomarker of prognosis for OS in the entire cohort from TCGA [HR: 1.498; 95% CI, 1.167-1.922; p=0.001] and the ADC subcohort [HR: 1.869; 95% CI, 1.275-2.738; p=0.001]. The prognostic value is confirmed in an independent cohort of 114 lung adenocarcinoma patients OS (42.90 vs. NR mo, p=0.020). Lung tumorspheres are a useful method for CSCs enrichment. Elevated expression of CDKN1A, SNAI1 and ITGA6 genes is associated with worse prognosis in NSCLC. Funded by CB16/12/00350 from CIBEROnc, PI12-02838, and PI15-00753 from ISCIII, Fundacion Arnal Planelles and Domingo Martínez. Fundación de Investigación Hospital General de Valencia. CIBEROnc, Instituto de Salud Carlos III; Fundacion Arnal Planelles and Domingo Martínez. All authors have declared no conflicts of interest.