Functional CD3+ CD8+ PD-1- T cells accumulation and PD-L1 expression increases during tumor invasion in DCIS of the breast

Abstract Background The changes in T cell subsets and programmed death ligand 1 (PD-L1) expression during the transition from ductal carcinoma in situ (DCIS) to early invasive breast cancer had not been well studied. Patients and Methods A total of 85 DCIS patients were classified into 49 DCIS (clinical stage: Tis, noninvasive) and 36 with a minimally infiltrating lesion (MIL;  Results We observed increased infiltration of CD3-positive (CD3 + )CD8 + programmed death 1 (PD1)-negative T cells and higher PD-L1 expression in DCIS with MIL. Elevated PD1 expression correlated with PD-L1 expression in MIL and DCIS. Conclusion We conclude that during the transition from DCIS to an invasive lesion, the host cytolytic T cells begin interacting with the tumor and destroy the tumor tissue, leading to an adaptive upregulation of PD-L1 and tumor protection against immune destruction.