engleski

Increased osteopontin expression correlates with proliferation and survival in glioblastoma

Osteopontin (OPN) is a phosphorylated glycoprotein with diverse functions including the role in angiogenesis, bone remodelling, T-cell mediated immunity, ability to act as a cytokine in cell signalling, and as a cell-attachment protein. OPN has also been detected in a number of human tumor tissues and assessed as a potential marker of tumor progression. This study was aimed to analyze the expression of OPN in 50 glioblastomas, and its correlation with tumor cell proliferation and patient outcome. By immunohistochemistry we found cytoplasmic OPN expression in 43 tumors with heterogenous staining pattern ranging from focal and faint to strong and diffuse staining of whole tumor tissue. In 14 cases (28%) high staining intensity of more than 25% of tumor cells was observed and these cases were considered positive, while those with faint OPN positivity or strong positivity in less than 25% of tumor cell were considered negative. In 25 cases (50%) OPN was also present in the interstitium, between tumor cells. This staining pattern was accentuated around necrosis and, in most of the cases, also around blood vessels. In addition to tumor cells, microglial cells and some endothelial cells were also positive for OPN protein. The association of staining for OPN with survival times of the patients has been evaluated using life tables and analysed using log rank test. Patients whose tumors have been classified as OPN positive had lower survival rate compared to those with OPN negative tumors (p=0.02). OPN expression was associated with higher proliferative activity of tumor cells measured as Ki67 labelling index (Student’ s t test, p=0.03). Our results showed that OPN protein is expressed in glioblastoma cells and suggest the role of OPN in glioblastoma progression.

glioblastoma; osteopontin; immunohistochemistry

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