Abstract P5-04-26: Expression of cytotoxic T lymphocyte antigen-4 (CTLA-4) is associated with tumor-infiltrating lymphocytes (TILs) levelin HER2-positive breast cancers
Authors: Kim Ahrong , Kim Jee Yeon , Lee So Jeong 
Published: March 2020

Abstract
Though CTLA4 expression was reported in various tumor types, expression of CTLA4 is not well known in breast cancers, especially HER2-positive breast cancers. TILs level has significant role in treatment response and prognosis in HER2-positive breast cancers. Total 167 patients with HER2-positive breast cancers were included. All patients were pre-operatively chemotherapy and radiotherapy naïve. All received adjuvant standard treatment. Histologic TILs evaluation was performed with full face hematoxylin and eosin sections. Immunohistochemistry for CTLA4 was performed with tissue microarray sections. CTLA4 expression was evaluated separately for tumor cells and TILs. Cytoplasmic and/or membranous stains were assessed and human appendix was used as positive control. The intensity and percentage of positivity were evaluated collectively. Immunostaining score was calculated by multiplying percentage of positive cells by staining intensity. Total immunostaining score was obtained by adding tumor cells score and TILs score. Expression level was divided into two categories (low and high) according to mean value. Only 11 patients (6.6%), 47 patients (28.1), and 10 patients (6.0) showed total negative staining for CTLA4 on tumor cells, TILs and both on tumor cells and TILs, respectively. According to mean score on tumor cells, 97 (58.1%) patients showed low level of CTLA4 expression and 70 (41.9%) showed high level of CTLA4 expression. One hundred and two (61.1%) patients had low expression and 65 (38.9%) patients had high expression of CTLA4 on TILs based on the mean value of score of TILs. According to mean value of total score both on tumor cells and TILs, 70 patients (41.9%) were categorized as high expression and 97 patients (58.1%) were categorized as low CTLA4 expression. TILs level, CTLA4 immunostaining score on tumor cells, CTLA4 immunostaining score on TILs, and total CTLA4 immunostaining score on tumor cells and TILs were significantly correlated each other. High expression level of CTLA4 on tumor cells was significantly associated with negative expression of hormone receptor and high TILs level. Also, high CTLA4 expression on TILs significantly correlated with high histologic grade, negative expression of hormone receptor and high TILs level. High level of total CTLA4 expression both on tumor cells and TILs was significantly correlated with negative expression of hormone receptor and high TILs level. However, expression level of CTLA4 was not associated with overall survival and disease-free survival. In conclusions, CTLA4 expression was common in HER2-positive breast cancers and the level of CTLA4 expression was associated with hormone receptor negativity and TILs level in HER2-positive breast cancers.
Table 1. Correlation of TILs level, CTLA4 immunostaining score on tumor cells, TILs, and total immunostaining scoreimmunostaining score on tumor cellsimmunostaining score on TILsTotal immunostaining score on tumor cells and TILsTILs level0.254 (&lt;0.001)0.394 (&lt;0.001)0.312 (&lt;0.001)Immunostaining score of CTLA-4 in tumor cells0.565 (&lt;0.001)0.815 (&lt;0.001)Immunostaining score of CTLA-4 in TILs0.783 (&lt;0.001)
Table 2. Correlation between CTLA-4 expression and clinicopathologic factorsLowHighLowHighLowHighHistologic grade1.0000.0390.754Low (grade 1, 2)51 (52.6)36 (51.4)60 (58.8)27 (41.5)52 (53.6)35 (50.0)High (grade 3)46 (47.4)34 (48.6)42 (41.2)38 (58.5)45 (46.4)35 (50.0)Necrosis0.3251.0000.325Absent30 (30.9)27 (38.6)35 (34.3)22 (33.8)30 (30.9)27 (38.6)Present67 (69.1)43 (61.4)67 (65.7)43 (66.2)67 (69.1)43 (61.4)Lymphovascular invasion0.7540.2650.754Absent51 (52.6)39 (55.7)51 (50.0)39 (60.0)51 (52.6)39 (55.7)Present46 (47.4)31 (44.3)51 (50.0)26 (40.0)46 (47.4)31 (44.3)Hormone receptor expression0.0120.0400.005Negative37 (38.1)41 (58.6)41 (40.2)37 (56.9)36 (37.1)42 (60.0)Positive60 (61.9)29 (41.4)61 (59.8)28 (43.1)61 (62.9)28 (40.0)TILs level0.001&lt;0.001&lt;0.001≤10%42 (43.3)19 (27.1)50 (49.0)11 (16.9)44 (45.4)17 (24.3)20-60%45 (46.4)29 (41.4)43 (42.2)31 (47.7)43 (44.3)31 (44.3)&gt;60%10 (10.3)22 (31.4)9 (8.8)23 (35.4)10 (10.3)22 (31.4)
Citation Format: Ahrong Kim, Jee Yeon Kim, So Jeong Lee. Expression of cytotoxic T lymphocyte antigen-4 (CTLA-4) is associated with tumor-infiltrating lymphocytes (TILs) levelin HER2-positive breast cancers [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-04-26.