We first examined the levels of p16, cyclin D1, phospho-RB-Ser780 (an indicator of the functional status) and other relevant proteins in lysates of NPC cell lines and immortalized NPE cell line grown in both 2D monolayer and 3D spheroid cultures for 3 days (Fig. 1a). Here, CDKN2A is linked to nasopharyngeal carcinoma.