Investigation of the structure of the nuclei of the Ehrlich adenocarcinoma cell line with a radioresistant phenotype

Abstract

BACKGROUND: One of the obstacles in successful radiation therapy of malignant tumors is the emergence of cell subpopulation that have lower radiosensitivity than the original tumor. Use of fractionated irradiation in this case leads to a possibility of the radioresistant cells to substitute the initial cell population. We assume that changes in epigenetic profile of a cell affect chromatin packaging in the cell nucleus. This in turn represents changes leading to formation of the radioresistant phenotype.

AIM: The aim is to study the structure of nuclei of a subpopulation of Ehrlich adenocarcinoma cells with a radioresistant phenotype.

METHODS: In the present study the cells of ascitic Erlich adenocarcinoma have been sequentially irradiated in the PX-γ-30 (source is ⁶⁰Co, dose output is 0.87 Gy/min). Then the cells have been inoculated into female outbred mice ICR (CD-1). Irradiation of the original population of Erlich adenocarcinoma showed that cells were losing an ability to transplantation after a dose of 20 Gy. In the series of irradiations with a gradual dose increase (from 10 to 40 Gy) there was obtained a cell subpopulation that retains an ability to transplantation after a dose of 40 Gy. The original and radioresistant cell subpopulations were tested for sensitivity to ionizing radiation. Nuclei were collected from these cells for further structure investigation with the method of small angle X-ray scattering (SAXS).

RESULTS: Analysis of SAXS data of the nuclei showed no significant changes in nucleus structures of Erlich adenocarcinoma initial cells that survived irradiation with doses of 20 and 30 Gy. At the same time, Erlich adenocarcinoma cells that survived irradiation with a dose of 40 Gy demonstrated abnormally low fractal dimension on mass fractal mode (in a size of 40–200 nm).

CONCLUSION: Observations of chromatin packing variations well conform with data obtained by biological characterization of researched samples and appear as a crucial aspect of understanding mechanisms of radioresistance occurrence.

Keywords

Erlich’s adenocarcinoma / in vivo / malignant tumors / small angle X-ray scattering / gamma irradiation / epigenetics / chromatin / cell nucleus / radioresistance

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