PTEN and central nervous system cancer: However, given the recent appreciation that IFN-γ plays a role in upregulating PD-L1 and in treatment outcomes relating to ICI, we re-examined the relationship between PTEN status and PD-L1 expression in four glioma cell lines (U87, U251, LN229, and T98G) which have been characterized in their PTEN expression (43, 48).