Ionizing Radiation Promotes Epithelial-Mesenchymal Transition Phenotype and Stem Cell Marker in The Lung adenocarcinoma: In Vitro and Bioinformatic Studies
Authors: Mehdi Raei; Mahdi Bagheri; Safieh Aghaabdollahian; Masoud Ghorbani; Afshin Sadeghi
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Objective: Ionizing radiation (IR) is one of the major therapeutic approaches in the non-small cell lung cancer (NSCLC);
however, it can paradoxically result in cancer progression likely through promoting epithelial-mesenchymal transition
(EMT) and the cancer stem cell phenotype. Therefore, we aimed to determine whether IR promote EMT/CSC and to
investigate the clinical relevance of EMT/CSC hallmark genes.
Materials and Methods: In this experimental and bioinformatic study, A549 cell line was irradiated with a high dosage
(6 Gy) or a fractionated regimen (2 Gy/day for 15 fractions). The EMT-related features, including cellular morphology,
migratory and invasive capacities were evaluated using scratch assay and transwell migration/invasion assays. The
mRNA levels of EMT-related genes (CDH1, CDH2, SNAI1 and TWIST1), stemness-related markers (CD44, PROM1,
and ALDH1A1) and the CDH2/CDH1 ratio were evaluated via real-time polymerase chain reaction (PCR). The clinical
significance of these genes was assessed in the lung adenocarcinoma (LUAD) samples using online databases.
Results: Irradiation resulted in a dramatic elongation of cell shape and enhanced invasion and migration capabilities. These
EMT-like alterations were accompanied with enhanced levels of SNAI1, CDH2, TWIST1, CD44, PROM1, and ALDH1A1 as
well as an enhanced CDH2/CDH1 ratio. TCGA analysis revealed that, TWIST1, CDH1, PROM1 and CDH2 were upregulated;
whereas, CD44, SNAI1 and ALDH1A1 were downregulated. Additionally, correlations between SNAI1-TWIST1, CDH2-
TWIST1, CDH2-SNAI1, and ALDH1A1-PROM1 was positive. Kaplan-Meier survival analysis identified lower expression of
CDH1, PROM1 and ALDH1A1 and increased expression of CDH2, SNAI1, and TWIST1 as well as CDH2/CDH1 ratio predict
overall survival. Additionally, downregulation of ALDH1A1 and upregulation of CDH2, SNAI1 and TWIST1 could predict a
shorter first progression.
Conclusion: Altogether, these findings demonstrated that IR promotes EMT phenotype and stem cell markers in A549
cell line and these genes could function as diagnostic or prognostic indicators in LUAD samples.