Gao et al. [88] designed a giant magnetoresistance (GMR) multi-biomarker immunoassay biosensor that could simultaneously detect 12 kinds of tumor marker (AFP, CEA, CYFRA21-1, NSE, SCC, PG I, PG II, CA19-9, total PSA, free PSA, free-beta-hCG, and Tg) to screen patients with lung cancer, liver cancer, digestive tract cancer, prostate cancer, etc. The GMR sensor chip was based on a double-antibody sandwich immunoassay method. This evidence concerns the gene KLK3 and prostate cancer.