Snail expression is associated with a poor prognosis in malignant pleural mesotheliomas

Malignant pleural mesotheliomas (MPMs) are aggressive tumors with a poor prognosis. We aimed to clarify the mechanisms of epithelial-to-mesenchymal transition (EMT) in MPMs by analyzing the expressions of EMT-associated transcription factors and E-cadherin in relation to tumor proliferation rates and patient survival.

One hundred nine patients with MPMs were investigated. Among these patients, there were 61 epithelioid tumors, 21 sarcomatoid tumors, 20 biphasic tumors, and 7 desmoplastic tumors. Immunohistochemical analyses were performed to evaluate the expressions of Snail, ZEB1, Twist, E-cadherin, and the Ki-67 proliferation index.

The expressions of Snail and ZEB1 were significantly higher in the nonepithelioid tumors than in the epithelioid tumors (p<0.0001 and p=0.0051, respectively). Furthermore, the E-cadherin expression was significantly lower in the Snail-high tumors than in the Snail-low tumors (p=0.0423). The E-cadherin expression was significantly lower in the nonepithelioid tumors than in the epithelioid tumors (p=0.0126). The Ki-67 proliferation index was significantly higher in the nonepithelioid tumors than in the epithelioid tumors (p=0.025). Patient survival was significantly lower in patients with Snail-high MPMs than in those with Snail-low MPMs (p=0.0016), especially in patients with nonepithelioid tumors (p=0.0089). The multivariate analysis also demonstrated that nuclear Snail expression was a significant predictor of poor prognosis in patients with MPMs (p=0.0142).

The Snail expression is associated with EMT and a poor prognosis in MPMs. Snail could be a potential molecular target for the treatment of patients with MPMs.