Abstract PO3-25-06: Expression of CD28, Fas, PD1, and CTLA4 molecules on cellular immune response in the blood peripheral of patients with locally advanced triple-negative breast cancer

Abstract Background: Locally advanced triple-negative breast cancer (TNBC) represents a public health problem in Brazil; its standard treatment consists of neoadjuvant chemotherapy followed by surgical and radiotherapy, with highly variable success rates are depended on access to appropriate cancer treatment, and the type of pathological response. In the last decade, the immune system's role in breast cancer has gained space by demonstrating the favorable impact of lymphocyte tumor infiltrate (TILs) and gene expression of the immune response, especially in tumors with high proliferation rates and negative estrogen receptors. The cellular immune response is regulated by co-stimulatory and co-inhibitory proteins such as CD28, Fas, PD1, and CTLA4 molecules. Methods: This was a longitudinal study with follow-up performed between 2015 and 2017. The study was conducted at the Hospital de Cancer de Pernambuco and Translational Research Laboratory of the Instituto de Medicina Integral Prof. Fernando Figueira (IMIP). Thirty women (18 to 60 years) diagnosed with locally advanced TNBC submitted to neoadjuvant chemotherapy (NAC), and 30 healthy women as a control group were included. The co-stimulatory and co-inhibitory proteins analyses were performed in the peripheral blood of TNBC women before (Pre-NAC) and after NAC (Post-NAC) Results: High levels of CD28+CD3+ T, CD28+CD4+ T, PD1+CD3+ T, and CTLA4+CD3+ T cells in the pathological complete response (pCR) and non-pCR groups compared to the control group (p 0.05). High levels of Fas+CD4+T cells and PD1+CD8+T cells in the non-pCR compared to the pCR group (p 0.05). In the paired analysis, significant differences were observed in CD3+T and CD4+T levels with CD28, Fas, and PD1 expression between pre- and post-NAC. Conclusion: Fas+CD4+T and PD1+CD8+T levels in peripheral blood in TNBC are associated with pCR, suggesting potential predictive biomarkers of NAC response. Preliminary results allow us to infer that neoadjuvant chemotherapy modulates the cellular immune response in TNBC women. Citation Format: Marcelo Salgado, Fernando Soares, Denise Viana, Amanda Salgado, Carolina Vasconcelos, Carlos Eduardo Anunciação, Eduardo Salgado, Leuridan Torres. Expression of CD28, Fas, PD1, and CTLA4 molecules on cellular immune response in the blood peripheral of patients with locally advanced triple-negative breast cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-25-06.