Taken together, our analyses of serum sCD26/DPP4 titer variation during a course of YS110 treatment demonstrate that serum sCD26/DPP4 titer variation, particularly at the time point immediately prior to/following the third YS110 infusion on Day29 in the Q2W administration schedule, was a potential prognostic biomarker for YS110 anti-tumor therapy. This evidence concerns the gene DPP4 and neoplasm.