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Arsenic trioxide preferentially induces nonapoptotic cell deaths as well as actin cytoskeleton rearrangement in the CHO AA8 cell line.

INTRODUCTION
The therapeutic effect of arsenic trioxide (ATO, As2O3) has been investigated for many years. However, the precise molecular mechanisms underlying the antitumor activity of ATO are still not fully understood, but seem to depend on cell types, dosage, and duration of exposure. The purpose of this study was to assess the actin cytoskeleton rearrangement during the cell death process induced by arsenic trioxide in the CHO AA8 cells. A better understanding the mechanisms of ATO-action is likely to lead to more rational use of this drug either as monotherapies or in combination with other anticancer agents.


MATERIAL AND METHODS
The effect of ATO on actin cytoskeleton was studied in Chinese Hamster Ovary AA8 cell line. Actin was visualized by fluorescence microscopy and phalloidin conjugated to Alexa Fluor® 488. Morphological and ultrastructural alterations in the CHO AA8 cells were evaluated by using light and electron microscope, respectively. For quantitative measurement of cell death, Annexin V-Alexa Fluor® 488 and Propidium Iodide assay was performed. The vital staining of CHO AA8 cells with acridine orange was applied to detect the development of acidic vesicular organelles (AVOs).


RESULTS
The performed experiments revealed a dose-dependent decrease in the cell survival. The morphological and ultrastructural features acquired by the cells after ATO-treatment were considered as typical for autophagy and mitotic cell death. As was shown by acridine orange staining, arsenic trioxide treatment increased red fluorescence signals in dose-dependent manner, indicating the development of AVOs, a hallmark of autophagy. Low level of apoptosis was induced in the ATO-treated CHO AA8 cells. Furthermore, the rearrangement of actin filaments associated with cell death process was also detected.


CONCLUSIONS
The obtained results suggest that arsenic trioxide preferentially induces nonapoptotic cell deaths, autophagy and mitotic cell death, in p53-deficient CHO AA8 cells. Furthermore, the distinctive patterns of F-actin remodeling after As2O3 treatment were associated with different modes of cell death, confirming that cytoskeleton is a dynamic structure actively involved in the cell death process.