中文摘要：

The sensitivity of cancer cells to radiation therapy varies based on cell cycle phase. Here we evaluated the differences between X-ray and carbon-ion irradiation with respect to cellular radiosensitivity and cancer cycle arrest in the breast cancer cell line, MCF-7. The cell survival rate, cell cycle distribution and the presence of apoptosis were measured by clonogenic assay and flow cytometry. BRCA1 and p21 protein levels were analyzed by Western blot, and the levels of human telomerase reverse transcriptase(h TERT) m RNA expression and telomere length were detected with real-time polymerase chain reaction. The results show a significant dose-dependent effects on survival rate, apoptosis and protein levels in the carbon-ion group of MCF-7 cells. Decreased proliferation was not observed at 2 Gy X-ray irradiation. There were significant differences in cellular cycle arrest, apoptosis percentages and BRCA1 and p21 protein expression between X-ray and heavy-ion groups. The results indicatedthat increasing in BRCA1 and p21 expression, and attenuation of h TERT gene expression induced by heavy-ion irradiation in MCF-7 cells might relate to mechanism of cellular radiosensitivity in G2/M arrested phase.

英文摘要：

The sensitivity of cancer cells to radiation therapy varies based on cell cycle phase. Here we evalu- ated the differences between X-ray and carbon-ion irradi- ation with respect to cellular radiosensitivity and cancer cycle arrest in the breast cancer cell line, MCF-7. The cell survival rate, cell cycle distribution and the presence of apoptosis were measured by clonogenic assay and flow cytometry. BRCA1 and p21 protein levels were analyzed by Western blot, and the levels of human telomerase reverse transcriptase （hTERT） mRNA expression and telomere length were detected with real-time polymerase chain reaction. The results show a significant dose-depen- dent effects on survival rate, apoptosis and protein levels in the carbon-ion group of MCF-7 cells. Decreased prolifer- ation was not observed at 2 Gy X-ray irradiation. There were significant differences in cellular cycle arrest, apop- tosis percentages and BRCA1 and p21 protein expression between X-ray and heavy-ion groups. The results indicated that increasing in BRCA1 and p21 expression, and atten- uation of hTERT gene expression induced by heavy-ion irradiation in MCF-7 cells might relate to mechanism of cellular radiosensitivity in G2/M arrested phase.