Search for Radiation–Sensitivity Prediction Markers Based on Gene Expression Analysis in Choroidal Malignant Melanoma

Abstract

Abstract: : Purpose: To search for marker genes that predict the sensitivity of cell lines to radiotherapy by comprehensive gene expression analysis. Candidate genes were determined from microarray analyses of cell lines from choroidal malignant melanomas that had different sensitivity to radiation. Methods: Cell lines (92–1, OCM–1, OMM–1) were established from patients with choroidal malignant melanoma. Radiation sensitivity was determined using colony formation assay, and the cell lines were categorized as resistant (SF2>0.6) or sensitive (SF2<0.4). RNA was extracted from non–irradiated cell lines, and gene expression analysis was performed using oligonucleotide microarray containing 10,800 genes. The selected genes were verified by the real–time PCR using other cancer cell lines in which radiation sensitivity has been documented. Results: Analysis of radiation survival curves of the three choroidal malignant melanoma cell lines showed that 92–1 was radiation–sensitivite and OCM–1 and OMM–1 were radiation–resistant. The results of microarray analyses showed that 21 genes had elevated expression levels in OCM–1 and OMM–1 (resistant) cell lines compared to the 92–1 (sensitive) cell line, and 13 genes in the 92–1 cell line compared to the OCM–1 and OMM–1 cell lines. The validity of the expression level of 13 of the 34 genes that was selected by microarray was confirmed by PCR. The candidate genes were selected from the analysis of other cancer cell lines. Conclusions: Gene expression analysis using cell lines of choroidal malignant melanoma can be used to search for radiation sensitivity prediction markers. Comprehensive gene analysis of radiation–sensitive and/or resistant cell lines may provide new insight into mechanisms of radiation–resistance and effectiveness of radiation therapy.

Keywords: candidate gene analysis • gene microarray • melanoma