PTPN1 and breast cancer: To further validate the role of PTPN1 in the immune microenvironment of breast cancer in vivo, we knocked down the expression of PTPN1 in 4T1 breast cancer cells using two different short hairpin RNAs (shRNAs; shPTPN1#1 and shPTPN1#2), and a non-target shRNA as a control (shCtrl) (Figure 8A).