CD274 and breast cancer: To determine whether PI3Kδ inhibition through PI4K IIIα inhibition affects PD-L1 expression, the effect of simeprevir on PD-L1 expression was evaluated in various cancer cell lines including T98G, U87, and U251 glioma cell lines and BT474, MDA-MB-231, and MDA-MB-468 breast cancer cell lines (Figure 7).