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

Abstract

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 G₂/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 G₂/M cell cycle arrest.

Keywords:

• HDR brachytherapy
• A431 cells
• radiobiology
• tumor progression
• mitotic death

Acknowledgements

We would like to thank Eduardo A. Barcelos for acrylic platform machining and Professor Flávio G. da Fonseca, Emerson Alberto Fonseca and Dr Miguel Torres T. Leite for their contributions. We thank the Radiotherapy staff from Instituto de Radioterapia São Francisco and Hospital Luxemburgo as well as the Flow Cytometry platform from Instituto de Ciências Biológicas-UFMG for the use of their facilities.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

All authors have been working at Federal University of Minas Gerais, Brazil. We are strongly interested in the study of ionizing radiation effects in cancer cell lines especially in models that can help us to improve radiotherapy treatment and understand in deep the radiobiology of head and neck tumors.

Jony Marques Geraldo is a medical physicist and assistant professor of the Department of Image Anatomy at School of Medicine at Federal University of Minas Gerais and the head of Radiation Protection in the Radiotherapy Center from Hospital Luxemburgo. He works with local dosimetry.

Sérgio Scalzo is a Ph.D student at Department of Physiology and Biophysics at Federal University of Minas Gerais, working with cardiac pulses alterations through ionizing radiation.

Daniela S. Reis is an M.Sc student at Department of Physiology and Biophysics at Federal University of Minas Gerais and the main biotechnician of the Flow Cytometry Facility Division.

Thiago L. Leão is a Ph.D student at Department of Microbiology at Federal University of Minas Gerais working with DNA alterations and Reactive Oxygens Species effects via endoplasmic reticulum stress.

Silvia Guatimosim is associated professor at Department of Physiology and Biophysics at Federal University of Minas Gerais working with cardiomyocytes signalling pathways.

Luiz Orlando Ladeira is full professor at the Department of Physics of the Federal University of Minas Gerais, head of Nanomaterials Laboratory, focusing his research on carbon nanotubes and their application in engineering and life sciences, and gold nanoparticles and their application in health sciences, radiobiology and local dosimetry.

Lídia M. Andrade is a researcher at Department of Physics at Federal University of Minas Gerais working with radiobiology of head and neck tumors and gold nanoparticles and their application in cancer treatment by using brachytherapy.

Additional information

Funding

This work was supported by the Brazilian agencies Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) under Grant number BPD-00022-14; Conselho Nacional de Pesquisa e Desenvolvimento Tecnologico (CNPq) under Grant number 402610/2013-0 and CAPES-PNPD fellowship.