Epithelial-to-mesenchymal transition: possible role in meningiomas.

Epithelial-to-mesenchimal transition (EMT) is a process involved in invasion and metastasis of tumors. The occurrence of EMT during tumor progression resembles the developmental scenario and sheds light on important mechanisms for the initial step of metastasis - invasion where noninvasive tumor cells acquire motility and ultimately disseminate to distant organs. The hallmark of EMT is the loss of expression of the cell-cell adhesion molecule E-cadherin. The numerous reports by many authors as well as our own results indicate that E-cadherin plays a role in CNS tumors - meningiomas. Our studies showed that 73 % of meningiomas had downregulation of E-cadherin. Moreover, loss of heterozygosity of E-cadherin was observed in 32 % of meningiomas. Bound to E-cadherin in adherens junctions is beta-catenin, whose translocation to the nucleus is yet another molecular event involved in EMT. In our study beta-catenin was progressively upregulated from meningothelial to atypical, while 60 % of anaplastic meningiomas showed upregulation and nuclear localization of the protein. The elucidation of molecular mechanisms that govern EMT will offer new approaches and targets to restrain metastasis.