ZAP70 and nasopharyngeal carcinoma: We previously reported that SP (side population) cells with a CSC function play a role in promoting the proliferation and metastasis of NPC by activating zeta chain of T cell receptor associated protein kinase 70 (ZAP70) to regulate the phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt) pathway in NPC cells.