We have shown that: (1) BTK protein expression predicts good prognosis in GBM; (2) BTK is not expressed in state-of-the art GBM stem-like cell lines, but can be expressed in mixed cancer and immune cell populations within matched GBM tissue; and (3) because BTK inhibitors is already being planned for clinical trials, developing better ex vivo cell cultures that recapitulate BTK protein heterogeneity in tissue (Fig 8) will better inform the use of BTK inhibitors either as a type of immunotherapy and/or cancer cell therapy. The gene discussed is BTK; the disease is cancer.