STAT-1 expression in human glioblastoma and peritumoral tissue

Glioblastoma is a very aggressive brain tumour with poor prognosis despite radical surgery or radiotherapy. Signal transducers and activators of transcription (STAT) proteins are important elements in intracellular signalling and part of the JAK-STAT pathway. They are activated by growth factors and cytokines and translocate into the nucleus upon activation to exert their function as transcription factors. STAT-1 can be induced by interferons and has also been found to be important in sensitizing tumours to chemotherapeutic drugs.

Forty-six glioblastoma samples have been analysed for the expression of STAT-1 by immunohistochemistry.

In our study performed by immunohistochemistry, 22 out of 46 glioblastomas (48%) were strongly positive for staining with a STAT-1 antibody, 9 (20%) showed an intermediate reactivity, 8 (17%) low immunoreactivity, and 7 (15%) were completely negative. In the tumour tissue, STAT-1 expression was mostly localized in the cytoplasm. This location of STAT-1 suggests the predominant presence of an inactive form of STAT-1. Tumour giant cells were frequently strongly stained. Part of the peritumoral brain tissue showed strongly positively reactive glial cells. Interestingly, within the infiltration area strong STAT-1 expression was found in reactive astrocytes, glia, and particularly in microglial components.

The expression of STAT-1 in the majority of glioblastomas, together with its documented role in apoptosis and in the action of chemotherapeutic drugs on tumour cell lines point to a possible function of this protein in the response of glioblastomas to chemotherapy.