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.