Differences in tumor microenvironment between HER2-positive and HER2-negative breast cancer.

Abstract

e12562 Background: The tumor microenvironment of breast cancer is extremely complex, which containing different types of lymphocytes, macrophages, NK cells and other immune cell subtypes. At present, the relationship between immune cell subtypes and molecular subtypes of breast cancer is still unclear. Methods: Tumor tissue samples of 20 breast cancer patients were collected from January 2020. Then the density (number of positive cells/mm2) and ratio of immune cells in intratumoral area and stromal area were detected by multiple fluorescence immunohistochemistry (mIHC), the detection range was included CD3+T cells, CD4+T cells,CD8+T cells,PD-1+CD8+T cells,Tregs,M1/M2 tumor associated macrophages (TAM), PD-L1+CD68+TAM,B cells,CD56bright NK cells and CD56dim NK cells and so on. The immune cell subtypes of all area were included both intratumoral area and stromal area. Graphpad prism (version 7.01) was used for t test and the statistical significance was set at p=0.05. Results: These 20 patients were divided into two groups, HER2 positive (n=8) and HER2 negative group (n=12). The density of CD3+T cells in all area (including intratumoral area and stromal area) of tumor tissue in HER2 positive breast cancer patients were significantly higher than that of HER2 negative breast cancer patients (median density, HER2 positive group vs. HER2 negative group=2998 vs. 1520/mm², p=0.031) as well as the CD8+T cells (median density, HER2 positive group vs. HER2 negative group=536 vs. 175/mm², p=0.015). Meanwhile, the density of Tregs in all area of tumor tissue in HER2 positive breast cancer patients was also significantly higher (median density, HER2 positive group vs. HER2 negative group=119 vs. 27/mm², p=0.022).However, there was no significant difference in the other subtypes of immune cells infiltrated in tumor tissue between HER2 positive and HER2 negative samples, such as CD4+T cells, M1/M2 macrophages, B cells and so on (p＞0.05). Conclusions: Our research indicates that the patterns of immune cell subtypes in different types of early breast cancer are different. Further exploration of the immune microenvironment in different molecular types of breast cancer may provide additional targets for immunotherapy.