Abstract A131: Measurement of immune infiltration in ER, PR, and HER2 IHC subtypes reveals populations that may benefit from immunotherapy

Abstract

Abstract Expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), as measured by immunohistochemistry, is routinely used to guide appropriate therapy in breast cancer. HER2 targeted therapy is used to treat HER2 overexpressing patients and endocrine therapy is used to treat ER+ or PR+ patients. However, therapeutic options are limited for patients who are triple negative, relapsed HER2 overexpressed patients, and ER+ or PR+ patients who are refractory to endocrine therapy. For these breast cancer patients, immunotherapy has the potential to improve survival by targeting cancer cells. Although, the role of immune response in breast cancer is not fully understood, studies have observed high number of natural killer (NK) cells, B cells, and cytotoxic T cells suppress tumor growth while high number of macrophages, and regulatory T cells (Treg) promote tumor growth. The purpose of this study is to measure levels of immune cells infiltration (cytotoxic, helper, and regulatory T cells, NK cells, & macrophages) between different ER, PR, and HER2 IHC subtypes. Tissue microarrays were constructed from 106 breast cancer patients consisting of 36 triple negatives, 11 HER2 overexpressed (ER-/PR-), 7 ER+/PR-/HER2-, 24 ER+/PR+/HER2-, 8 ER+/PR-/HER2+, and 20 ER+/PR+/HER2+ assessed by a pathologist based on immunohistochemical stains. Utilizing the constructed TMAs, MultiOmyx hyperplexed immunofluorescence assay was performed on IHC4 (HER2, ER, PR, Ki67), and immune (CD3, CD4, CD8, CD45RO, CD56, CD68, FOXP3) markers. MultiOmyx technology enables visualization and characterization of multiple biomarkers from a single 4 micron formalin-fixed paraffin-embedded tissue section. PanCK marker was used to differentiate between tumor and stromal regions. A representative tumor was assessed for immune infiltration in each of the following subtypes: ER+/PR+/HER2-, ER+/PR+/HER2+, ER+/PR-/HER2-, ER+/PR-/HER2+, HER2 overexpressed ER-/PR-, and triple negative. Level of immune cells infiltration is defined as a percentage of positive immune cells relative to the total number of stromal cells. Percentage of immune cells infiltration in each IHC subtypes is 5.6% (ER+/PR+/HER2-), 14.7% (ER+/PR+/HER2+), 33% (ER+/PR-/HER2-), 9% (ER+/PR-/HER2+), 58% (HER2 overexpressed ER-/PR-), and 16% in triple negative. Comprehensive analysis of all 106 breast cancer patients will be reported. Differences in the levels of immune cells infiltration across different ER, PR, and HER2 IHC subtypes suggests that some subtypes may benefit from immunotherapy targeting immune checkpoints (anti-PD-L1, anti-CTLA-4) while other subtypes may benefit from immune activation (adoptive T cell therapy). Citation Format: Pinky Tripathi, Nam Tran, Raghavkrishna Padmanabhan, Richard Hartsfield, Edward J. Moler, Nicholas Hoe, Kenneth Bloom. Measurement of immune infiltration in ER, PR, and HER2 IHC subtypes reveals populations that may benefit from immunotherapy. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A131.