Evaluation of gamma radiation-induced cytotoxicity of breast cancer cells: Is there a time-dependent dose with high efficiency?

Abstract

Radiotherapy is one of the important treatment modalities in the management of breast cancer. The aim of this study is to study the efficient treatment of breast cancer as related to the dose delivery. The human breast cancer cell lines (MCF-7) cells were cultured and exposed by 1, 2, 4, 6, 8, 10, and 20 Gy of γ-rays. Radiation-induced cell death was detected and evaluated, using three assay methods: Cell viability, clonogenic cell survival assay and induction of apoptosis. The cell viability was determined using trypan blue staining, 24 and 72 h post-irradiation. The survival fraction (SF) was determined by colony counting, 14 days after exposure and the apoptotic cell death was determined using the TUNEL assay. One- or two-way analysis of variance was deemed as appropriate, followed by relevant post t-test to determine P values. The difference of MCF-7 cell death through increasing post-radiation time from 24 to 72 h following the dose of 1, 6 and 10 Gy was found to be 2%, 9.6% and 7.14%, respectively. D0of MCF-7 was 220 cGy and the SF in the cells irradiated by 1 Gy and 10 Gy doses were 0.8 and 0.0001, respectively. The estimated variances were 2%, 11.1% and 8.4%, between 24 h and 72 h post-radiation apoptosis death for 1, 6, and 10 Gy, respectively. The dose and time dependence inducing apoptotic death was significant (P = 0.001). The delayed mortality and apoptosis was observed in MCF-7 cell, but the variance of total cell death and apoptosis in 24 and 72 h post-radiation with 6 Gy was obviously more than that with other doses.