To assess the expression of PTN and PTPRZ1 in breast cancer and their relationship with chemotherapy, we obtained RNA sequencing expression data for 291 normal breast tissue samples and 1085 cancer tissue samples from the GEPIA database (http://gepia.cancer-pku.cn/index.html); none of the patients who donated the samples were treated with chemotherapy; additionally, we downloaded matched before and after chemotherapy gene expression data for breast cancer tissue samples from 69 patients from the GEO database (GSE87455) (https://www.ncbi.nlm.nih.gov/geo/). This evidence concerns the gene PTN and cancer.