PTEN and central nervous system cancer: Moreover, PD-L1 overexpression induced by PTEN loss in tumour cells was associated with low T cell proliferation rates.53 Similarly, the absence of PTEN expression in melanoma cell lines was associated with the upregulation of PD-L1 expression.112 In gliomas, PTEN loss was significantly associated with PD-L1 overexpression.54PTEN mutations have been linked to anti-PD1 therapy resistance in glioblastomas.22 Indeed, PTEN-intact glioblastomas showed a high density of CD3+CD8+ cells after treatment with PD1 inhibitors, but PTEN-deficient tumours did not exhibit this effect.