Radio- or chemo-sensitivity and analysis of gene transduction for induction of apoptosis for human tumor cell

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Apoptotic death is reported to be important factor for radio- or chemo-sensitivity to tumor.Purpose is to investigate the differences between two rat yolk sac tumour cell lines with different radiosensitivities by different induction of apoptotic cells in paclitaxl sensitivity and in the sensitizing effects of paclitaxl in combination with irradiation. NMT-1 is a parent radiosensitive cell line and NMT-1R is a variant radioresistant cell line. Clonogenic assay demonstrated almost the same paclitaxl sensitivity with Do of 5.15 nM in NMT-1 and 5.02 nM in NMT-1R.Many apoptotic cells and DNA ladder formations were observed at 24 h after exposure to paclitaxl in both cell lines. The incidences of DNA fragmentation after 24 h exposure to 20 nM paclitaxl were 12.4 (]SY.+-。[) 3.3 % for NMT-1, and 13.0(]SY.+-。[) 1.9 % for NMT-1R.Paclitaxl showed a supra-additive effect in combination with radiation in both cell lines at 12 h after paclitaxl treatment only when the accumulation of cells in the G2M phase reached its peak.Paclitaxl had the same degree of cytotoxic effect in two cell lines with different radiosensitivity due to the induction of apoptosis. A supra-additive effect to radiation was observed with 12 h pretreatment in both cell lines. Paclitaxl may be effective for tumors with a component of different radiosensitivity in combination with irradiation.