Expression of PD-L1 in Relation to Intrinsic Molecular Subtypes of Breast Cancer in Hainan Free Trade Port, China

Abstract

Background: Intrinsic molecular subtype and histological grade are closely related to clinical prognosis in breast cancer. However, their relationship with Programmed Cell Death-Ligand 1 (PD-L1) expression is not very clear, particularly for Hainan Aboriginal patients. Herein, this research aims to reveal the relationship between PD-L1 expression and intrinsic molecular subtypes of breast cancer. Methods: 225 breast tumor samples from female patients were analyzed for PD-L1 expression using the Immunohistochemistry (IHC) method. The PDL1 expression level was detected by IHC and the relationship between the expression and clinical parameters was analyzed statistically. Results: Positive staining of PD-L1 was mainly found in the plasma membrane. In all cases, the positive rate was 12.0% (27/225). The PD-L1 expression level was significantly reduced in Luminal A subtype (the corrected ratio OR=0.15, p=0.04) whereas increased in HER2-positive subtype (OR=4.2, p=0.01). PD-L1 was significantly related to HER2-positive subtype (p<0.05) and histological grade 3 (p<0.05). There was statistically significant association between PD-L1 expression and metastasis (p=0.046), but not with the patient’s age, the tumor stage and menstruation (p>0.05). Moreover, there was a significant difference in the frequency of intrinsic subtypes between patients with positive and negative PD-L1 expression (p<0.001) among patients with metastasis. Conclusions: PD-L1 expression in breast cancer was positively correlated with HER2-positive subtype, higher pathological grade and metastasis of breast cancer, while negatively correlated with Luminal A in female patients in Hainan, China. PD-L1 may be a new independent marker to predict the prognostic factor in HER2-positive subtype breast cancer.