INVESTIGATION OF EFFECT OF THE CELL-CELL CONTACT INHIBITION ON RADIATION SENSITIVITY AND DETERMINATION OF THE RELATING FACTORS

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In many cultured cells, sensitivity to ionizing radiation (IR) is different between in log-phase and plateau phase of cell growth or spatial growing condition such as in monolayer and spheroid. Since these facts occur to us the cell-to-cell connecting factors, particularly gap junctions such as connexins, we started this, project. When plateau phase MDCK cells or UMRC-6 (human renal cell carcinoma) cells were given 2-10Gy of gamma ray with 100uM oleamide (a gap junction inhibitor) in the culture medium, augmentation of the IR sensitivity was observed using alamar blue assay. Although both ethanol and DMSO (dimethylsulfoxide) are known as solvent for oleamide, augmentation of the IR sensitivity could be detected only when using the former. Another gap junction inhibitor, 18-beta-glycyrrhetinic acid had strong cytotoxicity and maintaining cells to plateau phase was difficult, then we abandoned to using it for further experiments. Next we made a dominant negative connexin 43 expression vector (Δaa.130-136). But a control DNA transfection experiment using lacZ-expression vector did not work, we could not perform the experiment using above-mentioned mutant connexin 43 vector and obtain any results for the effect of inhibiting a specific gap junction factor (=connexin 43) upon the radiation sensitivity.