[Down-regulation of Caspase-3 expression in precancerous lesions and its relation to gastric carcinogenesis]

To study the level of expression of Caspase-3 protein in precancerous lesions of stomach and its relation to gastric carcinogenesis.

Formalin-fixed paraffin embedded tissues from 184 cases of gastric mucosa biopsy and surgically removed specimens, including gastric cancer (GC, N = 20), chronic atrophic gastritis (CAG, N = 6), atrophic gastritis with intestinal metaplasia (IM, N = 31), atrophic gastritis with dysplasia (DYS, N = 114) and normal controls (N = 13) were examined for expression of Caspase-3 protein and Ki-67 index by SABC immunohistochemistry, and for apoptosis by TdT-mediated dUTP biotin nick end labeling (TUNEL) method. Caspase-3, Ki-67 and TUNEL index were compared in different stages of gastric precancerous lesions and their correlation was analyzed.

The positive index of Caspase-3 protein in severe DYS (29.8% +/- 3.9%) showed no significant difference compared with that in GC (26.9% +/- 3.0%, P > 0.05), but was significantly lower than that in low (58.3% +/- 4.2%) and moderate grade DYS (50.4% +/- 4.8%), CAG (68.3% +/- 3.3%) and IM (70.9% +/- 4.3%, P < 0.05). Caspase-3 positive index was significantly correlated with that of apoptosis detected by TUNEL (r = 0.94, P < 0.05). Ki-67 index in Caspase-3 protein positive group (18.3% +/- 2.2%) was significantly lower than that in Caspase-3 negative group (48.9% +/- 3.1%, P < 0.05).

Caspase-3 protein expression was upregulated in CAG with or without IM and low or moderately low in DYS, while down-regulated in severe DYS and gastric carcinoma, and significantly positively correlated with cell apoptosis. It is suggested that down-regulated expression of Caspase-3 protein somehow contributes to gastric carcinogenesis through an imbalance between cell apoptosis and proliferation.