Genome expression profiling of heavy ion irradiation for head and neck cancer using in-house DNA chips.

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Cultured cells of Ca9-22 (originating from squamous cell carcinoma of the gum), G361 (malignant melanoma of the skin), HSG (adenocarcinoma of the salivary gland) and HaCaT (keratinocyte of the skin) were irradiated with x-ray, carbon ions and neon ions. The post-irradiation cell survival rate for each cell lines was determined by the colony assay and a dead cell count taken by the dye exclusion method. The D_<10> and SF_4 show in the order from Ca9-22<G361<HSG<HaCaT in x-ray and G361<HSG<Ca9-22<HaCaT in carbon and neon ions. These findings confirmed that x-ray resistant G361 cells and HSG cells are well controlled by carbon and neon ions.Corresponding genes of x-ray and carbon ions irradiation were identified by gene expression analysis (gene chip U133A). The Ca9-22 cells were irradiated with x-ray and carbon ions, and gene expression analysis was performed four hours after irradiation. The number of up regulated genes was 144 after x-ray and 286 after carbon ions. The number of down regulated genes was 402 in x-ray and 331 in carbon ions.Similarly, G361 cells were irradiated with carbon ions. The number of up regulated genes was 85 and the number of down regulated genes was 111. Comparison of gene expression between Ca9-22 cells and G361 cells shows that 6 genes exhibited an up regulation commonly while six genes revealed a down regulation commonly after both irradiation. From the results of clinical research, malignant melanoma have a higher local control rate by carbon ion radiotherapy than squamous cell carcinoma. From investigations of the genes that are expressed in a specific or consistent manner in either of these cell lines, it was possible to estimate the group of carbon ion sensitive genes and the group of carbon ion resistant genes, respectively. This evidence suggests that certain already known gene groups such as CyclinD1, in particular, determine the differences in the effectiveness of heavy particle radiation.