Expression of Immune Checkpoint Regulator Cytotoxic T Lymphocyte Antigen 4 (CTLA-4) and Programmed Cell Death Protein Ligand 1 (PD-L1) in Invasive Ductal Carcinoma Breast

Despite significant advancement in the diagnostic and therapeutic aspects of breast carcinoma, the prognosis remains dismal. Recently, with advances in its understanding, various immune system-based management strategies have been developed. CTLA-4 suppresses lymphocyte reactivity, IL-2 secretion, and IL-2 receptor expression and triggers cell cycle arrest. PD-L1 inhibits the proliferation and cytotoxicity of T cells and inhibits release of cytokines. Hence, we planned to evaluate the immunoexpression of CTLA-4 and PD-L1 in invasive ductal carcinoma breast and seek correlation between their immunopositivity and the clinicopathological parameters. This was a retrospective study conducted on archival material of 50 cases of breast carcinoma tissue microarrays. Clinicopathological details were recorded. All cases were evaluated for immunohistochemical expression of CTLA-4 and PD-L1. Cytoplasmic expression of CTLA-4 and membranous expression of PD-L1 were considered positive and staining intensity was recorded as mild, moderate, and intense. Data was recorded and analyzed. Immunopositivity for CTLA-4 was seen in 92% of cases of breast carcinoma. CTLA-4 staining intensity showed significant association with TNM staging of breast carcinomas (p = 0.036). Age group of the breast carcinoma cases showed a statistically significant correlation with PD-L1 immunoexpression (p = 0.002). No significant correlation was found between all other clinicopathological characteristics and CTLA-4 or PD-L1 immunostaining. Our study shows that CTLA-4 is a more important immune checkpoint regulator in breast carcinomas in comparison to PD-L1. Thus, anti-CTLA-4 immunotherapy might prove to be of immense help in the treatment of invasive ductal carcinoma breast showing overexpression of CTLA-4.