Loss of PTEN (a tumor suppressor that negatively regulates PI3K-AKT-mTOR signaling) or mutations in PIK3CA (a catalytic subunit of PI3K) leads to elevated PD-L1 expression via constitutive PI3K-ATK-mTOR pathway activation in squamous cell lung carcinoma (132, 133), NSCLC (130), gliomas (134), colorectal cancer (135), prostate cancer (136), and breast cancer (137). Here, PIK3CA is linked to central nervous system cancer.