Significance of tumor satellite variables in reflecting the epithelial-mesenchymal transition of tongue cancer.

The epithelial-mesenchymal transition (EMT) is important in determining the biological behaviors and clinical prognosis of tongue cancer. However, the heterogeneous nature of the cancer populations renders clinical grading controversial. The main purpose of EMT analysis is to identify the cell population with the greatest metastatic potentials. Therefore, tumor satellites that form at the invasive front of tongue cancer may be the optimal target for EMT evaluation. From 1999 to 2002, surgical samples of 117 consecutive tongue cancer patients diagnosed and treated at the National Taiwan University Hospital were collected. EMT-related biomarkers, including E-cadherin and vimentin, were analyzed in tongue cancer specimens to verify the association with tumor satellite variables. The results showed that the down-regulation of epithelial markers, manifested by E-cadherin loss, was significantly different compared to the pattern of invasion (p=0.011), tumor satellite formation (p=0.019), and tumor satellite size (p=0.019). For mesenchymal phenotype acquisition, vimentin expression significantly differs in groups stratified by tumor satellite distance (TSD) (p=0.018). EMT positive immunoreaction was more frequent in the cases with tumor satellite formation (p=0.042) and in those with greater TSD (p=0.023). In addition, in the EMT positive cases, the average TSD was 0.79±1.20mm compared to 0.36±0.52mm in the EMT-negative cases (p=0.010). The results demonstrated the correlation between tumor satellite variables and EMT. Loss of epithelial features contributes to tumor satellite formation, whereas acquisition of the mesenchymal phenotype is beneficial to tumor satellite spreading. The current results indicate the importance of evaluating tumor satellite variables in assessing the EMT of tongue cancer.