CD274 and head and neck squamous cell carcinoma: Moreover, the PI3K-AKT signaling pathway upregulated IFN-γ-stimulated PD-L1 expression in NSCLC, CRC, glioma, breast cancer, and melanoma [62–66], while PI3K inhibition downregulated PD-L1 expression in HNSCC cells, CRC cells, melanoma cells, and Her2-amplified cancer cells [58, 67–69].