The cytotoxic effect of TGF-β1 on mesothelial cells via apoptosis in early peritoneal carcinomatosis.

Peritoneal dissemination is one of the main causes of death in gastric cancer patients. We have previously reported that gastric cancer cells can induce peritoneal apoptosis, lead to damage of peritoneum integrity, and therefore promote peritoneal metastasis. However, the soluble factors secreted by cancer cells to trigger the damaging cascade remain unclear. TGF-β1, a cytokine known for its capacity to induce proliferative and transformative changes of cells is found in significantly higher quantities correlated with peritoneal metastasis and TNM stages of gastric cancer. High levels of TGF-β1 in the subperitoneal milieu may affect the morphology and function of mesothelial cells, so that the resulting environment becomes favorable for peritoneal metastases. We observed apoptosis induced by TGF-β1 in mesothelial cells in peritoneal carcinomatosis. Knockdown of the smad2 gene by siRNA silencing can partially inhibit these effects. TGF-β1 could upregulate the expressions of Bax and suppress Bcl-2 in mesothelial cells. We conclude that TGF-β1 could induce apoptosis of mesothelial cells, which involves the smad2 signaling pathway in peritoneal carcinomatosis. Bcl-2 and Bax may contribute to this phenomenon.