STAT3 is expressed and active in GBM cell lines. The indicated cell lines were lysed in RIPA buffer after serum starvation for 24 hrs. Cell lysates were subjected to electrophoresis on an SDS PAGE gel and processed for Western blotting with anti-phospho-Tyr-STAT3, anti-STAT3, or anti-β-actin antibodies. NHA are primary human astrocytes. All other cell lines are grade IV astrocytoma (GBM).