PDCD1 and neoplasm: The absence of tumor neoantigen expression and presentation leads to a lack of recognition by T-cells and results in the inability of tumors to respond to PD-1/PD-L1 inhibitor therapy (Bai J. et al., 2017), moreover, other alterations such as apoptosis suppression or DNA repair promoted are also associated with treatment resistance (Mansoori et al., 2017).