DPP4 and breast cancer: To determine the regulator of DPP4 expression in post-chemotherapy breast cancer, we performed the genetic perturbation similarity analysis (GPSA) based on the database (http://guotosky.vip:13838/GPSA/) and calculated the differential expression of DPP4 from gene knock down/out RNAseq datasets of breast cancer cell lines (Fig. 5A).