We prioritized CA2 for further evaluation based on the following reasons: 1) CA2 had 4 unique peptides identified in the shotgun mode (Fig. 4a, and Supplementary Fig. S2), and the SWATH results could pass the manual spectra inspection; 2) Wu et al. previously reported that CA2 was up-regulated in the serum of NPC xenograft mice29; and 3) the CA2’s diagnostic power had not been reported in the NPC field. Here, CA2 is linked to nasopharyngeal carcinoma.