Résumé
Objective:To established a method for the detection of soluble programmed death ligand 1 (PD-L1) protein in serum based on the poly nanoantibody of lumazine synthase(LS).Methods:A dual nanobody-based sandwich ELISA was established with a competitive ELISA to screen nanobodies recognizing different epitopes of PD-L1 as paired antibodies. To improve sensitivity, PD-L1 nanobody P3C8 and lumazine synthase(LS) were fused, and nanobodies were obtained in polymeric forms as sPD-L1 protein captures, so as to develop an LS-displayed polymeric nanobody-based sandwich ELISA (LSNbs-ELISA) method to detect sPD-L1.Results:Compared with the Nbs-ELISA method, the LSNbs-ELISA method is approximately 11-fold more sensitive for sPD-L1 detection. The limit of detections (LODs) of Nbs-ELISA and LSNbs-ELISA for sPD-L1 in serum were 2.87 ng/ml and 0.255 ng/ml, respectively. Both assays were highly specific for the detection of sPD-L1 and did not react with structure-related proteins PD-1, CD27, CD70, CD137, and CD147 when spiked into the human serum.Conclusions:The Nbs-ELISA and LSNbs-ELISA assays both have high sensitivity and specificity for detecting sPD-L1 in serum and could have potential clinical applications.
Résumé
@#[Abstract] Objective: Elevated levels of soluble PD-L1 (sPD-L1) are associated with worse prognosis of renal cell carcinoma and multiple myeloma. However, the regulatory roles and functions of sPD-L1 in advanced melanoma are not fully understood. This study was designed to evaluate the association between circulating sPD-L1 concentrations and prognosis of patients with advanced acral or mucosal melanoma. Methods: A total of 102 untreated patients with advanced acral and mucosal melanoma admitted to Peking University Cancer Hospital between January 2012 and December 2015 were enrolled in this study. In the meanwhile, peripheral blood samples were obtained from 40 healthy donors. Circulating sPD-L1 concentrations were determined using an enzyme-linked immunosorbent assay. Results: The advanced melanoma cohort included 58 acral melanoma patients and 44 mucosal melanoma patients. The pre-treatment concentration of sPD-L1 (2.91±2.23 ng/ml) in plasma of patients group was elevated as compared with that in healthy donors (0.59 ng/ml). The concentration of sPD-L1 in serum was significantly upregulated in 39/102 (38.2%) patients and significantly associated with increased LDH level (P=0.021) and number of Tregs (P=0.017). The overall survival rates of patients with high or low concentrations of sPD-L1 were statistically different (8.5 months [high level] vs 11.6 months [low level], P=0.022). Conclusion: sPD-L1 concentration is elevated in patients with advanced acral or mucosal melanoma, which may play an important role in predicting prognosis.