Phosphorylated ezrin is located in the nucleus of the osteosarcoma cell.

The survival of osteosarcoma patients is connected to metastasis. The ezrin expression is associated with the development of metastasis and poor outcome in osteosarcoma. Ezrin is present in the cytoplasm and after phosphorylation assumes an active form and links F-actin to the cell membrane. This study evaluated ezrin and phosphorylated ezrin at site Tyr354 and Thr567 expression and its subcellular localization in osteosarcoma. We studied 50 osteosarcoma patients (mean follow-up 9.8 years). Ezrin expression was assessed using immunohistochemical and immunofluorescence analysis on tissue microarray and cultured cells of human osteosarcoma 143B. The western blot analysis was carried out on cultured cells. The majority of osteosarcomas, showing cytoplasmic positivity for ezrin, phosphorylated and unphosphorylated, were associated with membranous and nuclear positivity for phosphorylated ezrin Thr567 and phosphorylated ezrin Tyr354, respectively. Ezrin expression was associated with high-grade osteosarcoma (P=0.04), with metastasis (P=0.04) and with tumors that developed metastasis (P=0.04); phosphorylated ezrin Thr567 expression was present mostly in tumors with metastasis (P=0.01) and in osteosarcomas that did not develop metastasis (P=0.002). The osteosarcoma patients with ezrin expression have a short survival. The cytoplasmic ezrin expression in osteosarcoma matches its role of membrane-cytoskeleton linker protein. The subcellular trafficking of ezrin is not blocked and it is linked to ezrin phosphorylation, also in cancer. The phosphorylated ezrin Tyr354 nuclear localization suggests its possible role as a nuclear factor in osteosarcoma. The phosphorylated ezrin Thr567 phosphorylation may not be necessary in osteosarcoma metastatic progression but it was modulated. The ezrin expression is associated with more aggressive osteosarcomas and with metastasis.