HDR brachytherapy decreases proliferation rate and cellular progression of a radioresistant human squamous cell carcinoma in vitro

Purpose: To investigate the effects of high dose rate (HDR) brachytherapy on cellular progression of a radioresistant human squamous cell carcinoma in vitro, based on clinical parameters. Materials and methods: An acrylic platform was designed to attach tissue culture flasks and assure source positioning during irradiation. At exponential phase, A431cells, a human squamous cell carcinoma, were irradiated twice up to 1100 cGy. Cellular proliferation was assessed by Trypan blue exclusion assay and survival fraction was calculated by clonogenic assay. DNA content analysis and cell cycle phases were assessed by flow cytometry and gel electrophoresis, respectively. Cellular death patterns were measured by HOPI double-staining method. Results: Significant decreasing cellular proliferation rate (p < 0.05) as well as reduced survival fraction (p<0.001) in irradiated cells were observed. Moreover, increased percentage of cells arrested in the G(2)/M phase (32.3 +/- 1.5%) in the irradiated group as compared with untreated cells (8.22 +/- 1.2%) was detected. Also, a significant (p < 0.0001) nuclei shrinking in irradiated cells without evidence of necrosis or apoptosis was found. Conclusion: HDR brachytherapy led to a decreased proliferation rate and cell survival and also hampered cellular progression to mitosis suggesting that tumor cell death mainly occurred due to mitotic death and G(2)/M cell cycle arrest.