Establishment of a Monoclonal Antibody-Based Enzyme-Linked Immunosorbent Assay to Measure Soluble B7-H5 in Patients with Cancer

B7-H5, an immune checkpoint molecule, is markedly upregulated in multiple cancers and plays an important role in tumor progression and immune escape. However, the expression and significance of soluble B7-H5 (sB7-H5) in cancer remain unclear. Herein, we generated two novel mouse anti-human B7-H5 monoclonal antibodies (mAbs) 2E5 and 7B10, which had different epitopes. Based on the two mAbs, a sandwich enzyme-linked immunosorbent assay (ELISA) system was developed. Using this ELISA, we found that compared with healthy controls (HCs), sB7-H5 levels were significantly increased in the serum of patients with gastric cancer (GC), colorectal cancer (CRC), and lung cancer (LC) and were associated with TNM stage and metastasis. Receiver operating characteristic (ROC) curve analysis showed that sB7-H5 has diagnostic value for GC, CRC, and LC. Collectively, our findings delineate that sB7-H5 may be used as a predictor for diagnosis of cancer and a potential therapeutic target for cancer treatment.