Expression of Programmed Death Ligand-1 and Correlation with Clinicopathological Features and CD8 Infiltration in Breast Cancer

Background: Breast cancer (BC) is considered one of the most diversified types of tumors, characterized by a high mutational burden in the tumor milieu and a lack of immune cell makeup. The programmed death receptor-1 (PD -1)/programmed death ligand-1 (PD -L1) axis has been identified as a new target in the field of immunotherapy because, when activated, they worsen the future scenarios of the disease by helping tumor cells (TC) to escape immune surveillance. This study aims to investigate the expression of PD-L1 in BC tissues from Sudanese women and correlate the expression with clinicopathological features and the infiltration of CD8+T lymphocytes by immunohistochemistry (IHC). Methods: One hundred and fifty archived BC blocks were collected from the National Public Health Laboratory from January 2019 to August 2020. Data regarding age, TNM staging, grade, and hormonal status were considered. Tissue sections were examined using IHC to determine the expression of PD-L1 and CD8. Results: Among one hundred and fifty BC samples, 73 (48.7%) were TNBCs, and 77 (51.3%) were hormone-positive BCs. PDL-1 was significantly associated with BC subtypes, especially TNBCs (P = 0.001), a similar significant association was shown with CD8 infiltration (P = 0.006). None of the clinicopathological features was associated with PD-L1 expression. Conclusion: PD-L1 expression is strongly associated with TNBC’s and linked to CD8+ cells infiltration to the tumor milieu. Moreover, no correlation has been observed between the expression of PD-L1 and clinicopathological features in this study.