In GBM, CD39+ T cells were very poorly represented in an immune microenvironment background displaying low levels of inflammatory and T cell-recruiting cytokines [40]; indeed, the expression of CD39 on the CD8+ TILs has been correlated to the presence of active, tissue-resident, tumor-specific T cells, frequently correlating to different tumor types, with a better prognosis [45,46]. The gene discussed is ENTPD1; the disease is glioblastoma.