STAT3 and glioblastoma: As proof-of-concept, we treated STAT3-low (NNI-20, -23) and STAT3-high (NNI-21, -24) GBM cells with NT157, a selective inhibitor of insulin receptor substrate (IRS-1/2) that has the potential to inhibit both IGF-1R and STAT3 signaling pathways in cancer and stromal cells of the tumor microenvironment50.