To understand the protective role of PTPRO in CRCI, we selected administration of doxorubicin (DOX), which is one of the most active agents for treatment of breast cancer, once a week for 4 weeks to induce a CRCI model in 3-month-old Ptpro+/+ and Ptpro–/– female mice (Figure 3A). This evidence concerns the gene PTPRO and breast cancer.