Genome-wide profiling induced by ionizing radiation (IR) in non-small cell lung cancer (NSCLC) grown as three-dimensional spheroid

Abstract

Lung cancer is one of the most common human malignancies. Approximately over 75% of lung cancer is non-small cell lung cancer (NSCLC). The p53 tumor suppressor gene is mutated in approximately 50% of NSCLC. Radiotherapy using γ-ray was conventionally used for NSCLC treatment. In tumors, radiation induced apoptosis is modulated by their microenvironmental conditions. The definite mechanism of ionizing radiation is required for effective remedial value to NSCLC. However, most studies were performed in monolayer cell culture system which is unable to reflect in vivo microenvironment. Therefore, there is a need for in vitro model which is able to mimic in vivo solid tumor. In this study, we investigated cellular responses, by analysis of gene expression profile against IR to NSCLC forming in vivo mimic spheroids. The results showed that apoptosis inducible radiation dose was determined by acridine orange (AO) staining on three-dimensional (3D) spheroid. Our microarray data exhibited the altered gene expression levels between monolayer cells and 3D cells against IR in p53 null cancer cells. Surprisingly, we found that several genes related with microenvironment such as focal adhesion, adhesion junction and hypoxia had higher expression level in 3D culture system than two-dimensional (2D) culture system. In conclusion, 3D culture system was able to describe and mimic the microenvironment on in vivo solid tumor. Therefore, we suggested that the in vivo mimic 3D culture system approach might provide important clues for the clarification of mechanism of radiation effect for p53 mutated or deleted cancer cells.