Areas of future study include the correlation of SHP-1 and radiation-induced signaling through pro-survival pathways (e.g., epidermal growth factor receptor; PI3K/Akt), as well as the correlation with the expression of radiation-activated transcription factor (activator protein 1 and nuclear factor κB), and the expression of p21 and p27kip1 in the NPC cell lines studied (45–47). This evidence concerns the gene CDKN1B and nasopharyngeal carcinoma.