PTPN6 and neoplasm: However, T cell-specific deletion of Ptpn11 does not impact T cell responses to PD-1 [55], whereas the concomitant deletion of both Ptpn6 and Ptpn11 in T cells has been reported to abrogate the anti-tumour efficacy of PD-1 blockade in the MC38 colorectal cancer model [67] but not impede PD-1 function in other settings [68].