A microarray study of radiation-induced transcriptional responses and the role of Jagged 1 in two closely-related lung cancer cell lines

Abstract

Background: Lung cancer is the most lethal and common cancer in the world. Non-small cell lung cancer accounts for 80% lung cancer cases and its five-year survival rate after radiotherapy is approximately 5%. Patients with lung cancer in the advanced stages are suitable for radiotherapy rather than surgical resection. Unfortunately, radiotherapy alone or in combination with chemotherapy does not significantly improve 5-year survival rates of lung cancer patients. The mechanism by which lung cancer responds to radiation is unclear and needed to be investigated. Methods: Two lung adenocarcinoma cell lines, CL1-0 and CL1-5, that have exhibited different metastasis capacities in previous research, were utilized herein to investigate cellular radio-sensitivity. Clonogenic assay was used to evaluate the radio-sensitivity of CL1-0 and CL1-5. Flow cytometry experiments were performed on both cell lines to understand the change in the cell cycle profile that followed radiation. Gene expression data with the untreated and radiation treated lung cancer cell samples was obtained using Illumina microarrays. Tight hierarchical clustering was conducted to group genes with similar expression profiles. Clonogenic assay and cell cycle distribution were performed with Jagged 1-overexpressed CL1-0 to investigate the role of Jagged 1 in the radio-sensitivity of the lung cancer cells. Results: Clonogenic assay results showed that CL1-5 was more radio-sensitive than CL1-0 after exposure to 10 Gy radiation. The proportion of the CL1-5 cell population in the G2/M phase was found to be markedly higher than that with the CL1-0 cell population following exposure to radiation. Based on the microarray experimental data, 1,595 genes were identified as differentially expressed and sub-grouped into six clusters by hierarchical clustering. The functions of the identified genes in the tight clusters were associated with cell death, cell cycle, cell growth and proliferation, cellular function and maintenance. Moreover, our microarray data suggested that the gene expression levels of Jagged 1, a Notch ligand, differed significantly between CL1-0 and CL1-5. This finding was further verified by real-time PCR and western blot. Clonogenic assay results further revealed a lower survival rate of Jagged 1-overexpressed CL1-0 than that of CL1-0 following exposure to radiation. Conclusions: CL1-5 was shown to be more radio-sensitive than CL1-0 from our clonogenic assay data. The radiation-induced transcriptional responses in lung cancer cells were evaluated with gene expression microarrays in this work. Jagged 1, the Notch receptor ligand, may have an important role in increasing the radio-sensitivity of lung adenocarcinomas. ? 2011 - 2016 Translational Cancer Research. All rights reserved.