Radiotherapy is increasingly used in adjuvant approaches for colorectal cancer (CRC) to reduce local recurrence and improve survival. However, the principal limitation is the large variability in response among different individuals due to tumor heterogeneity. In the present study, we compared gene expression profiles between radiosensitive and radioresistant colorectal cancer cell lines to identify radiation-related molecules that can be used to evaluate the effects of radiation. The CRC cell line SW620 was irradiated with a high-energy photo beam. Following radiation treatment, RNA was extracted from non-irradiated and irradiated cells, respectively, and gene expression analysis was performed by oligonucleotide microarray and the DAVID bioinformatics method. To further confirm the results, an additional 4 CRC cell lines, COLO205, T84, HCT116, SW480 and SW403 were purchased from ATCC. The radiosensitivities of each were determined by the survival fraction at 2 Gray (SF2) of the surviving cells using the ATPLite assay, and the gene expression profiles after irradiation among the radiosensitive and radioresistant cell lines were analyzed by membrane arrays. The relationships between gene expression and patient clinicopathological features were also analyzed using membrane arrays and RT-PCR. The results from oligonucleotide microarray analysis show that 1601 genes were up-regulated (gene expression ratio of post- to pre-radiation treatment >2). By bioinformatic database analysis, 30 up-regulated genes were identified as involved in DNA damage response pathways, immune response pathways and the complement and coagulation cascades pathway. Fifteen genes showed differential gene expression profiles between radiosensitive (HCT116 and SW620) and radioresistant CRC cell lines (SW403 and SW480). In 110 CRC tissues, we detected five genes CDC25A, VAV1, TP73, BRCA1 and ZAP70 from 15 overexpressed genes that significantly related to prognostic factors (tumor size, advanced stage, invasive depth, lymph node metastasis and differentiation). These findings suggest that CDC25A, VAV1, TP73, BRCA1 and ZAP70 may be novel markers for predicting the effectiveness of radiotherapy in CRC patients.

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