PTPN21 and lung cancer: According to various database analyses, PTPN3, PTPN7, PTPN12, and PTPN14 were expressed at higher levels, while expressions of PTPN1, PTPN5, PTPN6, PTPN9, PTPN12, PTPN13, PTPN18, PTPN21, and PTPN22 were downregulated in lung cancer.