Abstract 947: Differential expressions of immune check point receptors on tumor infiltrating lymphocytes after neo-adjuvant chemotherapy (NAC) in patients with locally advanced breast cancer (LABC)
Authors: Abbasov Ayxan , Çetin Esin , Cabioglu Neslihan , Mollavelioglu Baran , Onder Semen , Emiroglu Selman , Tukenmez Mustafa , Muslumanoglu Mahmut , Igci Abdullah , Deniz Gunnur , Ozmen Vahit 
Published: September 2020

Abstract
Background: Recent advances in tumor biology and immune system have identified check points modulating the anti-tumoral immune response. This study aimed to determine immune check point expressions patients with locally advanced breast cancer to explore any associations between clinical and prognostic factors to show effectiveness of targeted therapies for these molecules.
Materials and Methods: This prospective study was carried out between September 2018 and November 2019 in the Department of General Surgery of Istanbul University Istanbul Faculty of Medicine Breast Unit. Twenty-four patients with LABC with a partial response to neoadjuvant chemotherapy (NAC) were included in the study. Tumor infiltrating lymphocytes (TILs) were isolated from the residual tumor burden separated from the surgical material with cell dissociation kit by using MACS tumor separation device. Expressions of immune checkpoints receptors including PD-1, LAG-3, TIM-3, TIGIT and CTLA-4 on CD8 T lymphocytes and Natural Killer (NK) cell subsets obtained from TIL were analyzed by using flow cytometry.
Results: TILs of patients &lt;50 years were more likely to express CTLA-4 on CD8−T lymphocytes in compared to patients ≥ 50 years (p= 0.004). In addition, patients with an initially advanced clinical tumor stage pT3-T4 were more likely to have increased LAG 3 expression on CD56+ NK cells and PD-1, CTLA-4 expression on CD8+ T cells in regards to pT1-T2 (p = 0.014, p = 0.018, p = 0.042; respectively). Contrarly, PD-1 expression on cytokine secreting CD56bright NK cells were found to be lower in patients with pN+ than those patients with pN- (p= 0.022). Interestingly, increased TIGIT, LAG-3, PD-1 and CTLA-4 expressions in CD16+ NK cells were demonstrated in patients with extensive intra-ductal component (p=0,024, p=0,003, p=0,032, p=0,013; respectively). However, HER2+ patients were more likely to have increased TIM-3 expressions on cytotoxic CD8- T cells compared to others (p = 0.043). Furthermore, TIGIT expressions in CD8+ T and CD56bright NK cells were significantly higher in patients with higher response to NAC (p = 0.014, p = 0.030; respectively). Finally, there was a significant correlation between pathological regression scores and CTLA-4 expressions of cytotoxic NK cells in Pearson analyses (p = 0.03).
Conclusion: Our results suggest that patients with a younger age and advanced tumor burden are more likely to benefit from immunotherapeutical approaches using immune check point inhibitors. Furthermore, combination of systemic chemotherapy with immunotherapy may increase the pathologic response rate in breast cancer patients.
Citation Format: Ayxan Abbasov, Esin Çetin, Neslihan Cabioglu, Baran Mollavelioglu, Semen Onder, Selman Emiroglu, Mustafa Tukenmez, Mahmut Muslumanoglu, Abdullah Igci, Gunnur Deniz, Vahit Ozmen. Differential expressions of immune check point receptors on tumor infiltrating lymphocytes after neo-adjuvant chemotherapy (NAC) in patients with locally advanced breast cancer (LABC) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 947.