Abstract No. 23 Lipiodol-Mediated Potentiation of Cell DNA Damage by External-Beam Radiotherapy: In Vitro Study

To investigate whether Lipiodol amplifies DNA damage induced by external-beam radiotherapy using an in vitro model. HepG2, a human hepatocellular carcinoma cell line, was cultured with Eagle's minimum essential medium and irradiated with 0-6Gy using an experimental irradiator. One group had no Lipiodol, while another had an 18-mm cylindrical Lipiodol placed 1 mm below the HepG2 layer during irradiation procedure. Post-irradiation, a DNA double strand break staining kit (OxiSelect, Cell Biolabs) was used to count the γH2AX signals in the nucleus. γH2AX, a phosphorylated H2A.X variant, is a biomarker for DNA breaks and aids in repair protein recruitment. 200 cells were analyzed per condition using a fluorescence microscopy (Celldiscoverer 7, ZEISS).The number of γH2AX foci/nucleus were compared between the Lipiodol-present and Lipiodol-absent groups using the Mann-Whitney U test. Comparing the results of irradiation in the presence and absence of Lipiodol, DNA double-strand damage was assessed using nuclear γH2AX signals. Mean numbers of γH2AX foci per nucleus in each sub-group are as follows (0, 2, 4 and 6 Gy, respectively): control group (no Lipiodol), 60.9, 92.4, 130.9 and 141.6; Lipiodol group, 66.9, 95.2, 155.7 and 168.0. Statistical analysis showed significant differences at 4Gy (p=0.001) and 6Gy (p=0.001), whereas no significant difference was observed at 0Gy (p=0.747) and 2Gy (p=0.782). The presence of Lipiodol in close proximity to target during radiation therapy suggested a potential increase in local therapeutic effects.