Heavy ion irradiation increases apoptosis and STAT-3 expression, led to the cells arrested at G2/M phase in human hepatoma SMMC-7721 cells

Background The impact of STAT-3 expression on the apoptosis of human hepatomas cell SMMC-7721 line induced by X-ray and carbon ion irradiations was investigated. Methods Human hepatoma SMMC-7721 cells were irradiated with a carbon ion beam and X-ray. Cell survival was determined by a standard colony-forming assay. STAT-3 protein expression was analysed by Western Immunoblots. Cell cycle and apoptosis were performed by flow cytometry. Results The viability of SMMC-7721 cells decreased with increasing dose of the carbon ion beam, and the high-LET carbon ion beam led to the cells getting arrested at G₂/M phase. Western Blot analyses show that STAT-3 expression increased with increasing radiation dose. The carbon ion irradiation induced cell apoptosis and significantly promoted the expression of STAT-3 gene compared with the X-ray irradiation. The apoptosis rate is correlated with the expression of STAT-3 in human hepatoma SMMC-7721 cells after exposure to different doses of X-ray and heavy ion beam. Conclusions Heavy ion irradiation increases the expression of STAT-3 gene, makes SMMC-7721 cells arrested at G₂/M phase and increases cell apoptosis in comparison with that induced by low-LET X-ray. The STAT-3 expression may be regarded as a protected reaction when the cancerous cells suffer a strong stimulus such as high-LET irradiation. The interaction of STAT-3 expression and other cytokines in human hepatoma and the relationship between STAT-3 and radiation-induced apoptosis remain to be clarified in the future.