[Morphological changes of mitochondria in apoptosis of esophageal carcinoma cells induced by As(2)O(3)].

OBJECTIVE: In order to make clear how As(2)O(3) targets the cells of esophageal carcinoma, the morphology of mitochondria and expression of bcl-2/bax were selected to study the SHEEC1 cell line during early apoptosis. METHODS: The esophageal carcinoma cell line SHEEC1 was treated by As(2)O(3) with concentrations of 1, 2 and 3 micromol/L for the periods of 2, 4, 6, 12 and 24 h. Annexin-V-Fluorescein and DNA histogram were used to detect the early apoptotic cells by flow cytometry. The morphologic changes of the apoptotic cells were examined by means of light and electron microscopy. Changes in mitochondria of living cells were detected with Rhodamin 123 fluorescent probe by fluorescent microscopy. The expression of bcl-2 and bax in floating cells were determined by immunohistochemical procedures. RESULTS: Typical apoptotic morphological changes were found in SHEEC1 at 24 h after As(2)O(3) treatment. Cells in the early stage of apoptosis were detected by Annexin-V labeled at 4 h. The ultrastructural alterations of mitochondria were found as following: within 4 h after administrating As(2)O(3), mitochondrial hyperplasia with small electron-dense materials in its matrix was the earliest manifestation of cell injury. At 6 h progressive mitochondrial swelling lead to balloon-like appearance and its outer membrane disrupted at 12 h. In all groups, down regulated expression of bcl-2 and over expression of bax were always found in damaged cells. CONCLUSION: In the SHEEC1 cell line morphological changes of mitochondria are the early events in apoptosis induced by As(2)O(3) and apoptosis is closely related to over expression of bax and down-regulating expression of bcl-2. It is possible that As(2)O(3) is a mitochondriotoxic anticancer agent for esophageal carcinoma.