SPDL1 and melanoma: sPD-L1 has been previously analyzed as a treatment predictive and prognostic biomarker in several cancers.36–38 Increased PD-L1 expression after anti-PD-1 treatment has been reported in matched post-treatment and pretreatment melanoma tissue samples,39 which suggests that the elevated sPD-L1 most likely derives from the tumor.