SPDL1 and neoplasm: In contrast, a statistically significant correlation between serum sPD-L1 concentration and tumour PD-L1 expression (R =  + 0.214, p = 0.001) was observed by Murakami et al. [18] Frigola et al. detected that sPD-L1 retains its receptor-binding domain, which could deliver pro-apoptotic signals to T lymphocytes [20].