Trichosanthin‐induced apoptosis in gastric cancer is related to the downexpression of bcl‐2

Abstract

OBJECTIVE: To study: (i) the induction of apoptosis in gastric cancer cells by trichosanthin; and (ii) the relationship between apoptosis and the expression of bcl-2. METHODS: During in vitro experiments, morphological studies and the terminal deoxynucleotidyl transferase-mediated dUTP–digoxigenin nick end-labeling (TUNEL) method were used to detect apoptosis in gastric adenocarcinoma cell line SGC-7901 before and after trichosanthin treatment. An immunohistochemical staining method and northern blot hybridization were used to detect the expression of the apoptosis-related gene bcl-2 before and after trichosanthin treatment. RESULTS: When SGC-7901 cells were treated with trichosanthin (0.1 μg/mL, 36 h), they presented some typical apoptotic morphological changes that were observed by fluorescent staining. These morphological changes included nuclear condensation and nucleosomal fragments forming a lunate body under the nuclear membrane. When SGC-7901 cells were treated with trichosanthin (0.1 μg/mL) for 36, 42 or 48 h, TUNEL staining revealed a significant increase in the apoptotic index (AI), from 3.78 ± 1.11%, 3.98 ± 1.12% and 3.85 ± 1.08%, to 11.30 ± 2.33%, 10.22 ± 2.00% and 11.18 ± 1.85% (P < 0.01), respectively. When SGC-7901 cells were treated with trichosanthin (0.1 μg/mL, 32 h), immunohistochemical staining revealed a decreased expression of the bcl-2 protein product: the staining density decreased from ++/+++ to –/+ (P < 0.01). When SGC-7901 cells were treated with trichosanthin (0.1 μg/mL, 24 h), northern blot hybridization showed a decreased expression of bcl-2 RNA: hybridization decreased from 35.19 ± 2.34 to 22.27 ± 3.90 (P < 0.01). CONCLUSIONS: Trichosanthin is able to induce apoptosis in gastric cancer. The apoptosis may be mediated by the downexpression of the apoptosis-related gene bcl-2.