Abstract 5985: Marrow immune landscape participates dormancy and activation of disseminated tumor cells in a breast cancer bone metastasis model
Authors: Gong Yingxuan , Wang Yinghao , Jiang Xinyu , Li Xiuzhi , Li Yueming , Chang Ming , Lu Yi , Zhang Jian 
Published: June 2022

Abstract
Breast cancer has the highest incidence rate among women and the second-highest mortality rate in cancer-related death in the world. Although the research on breast cancer treatment has made some progress, metastatic breast cancer is still incurable. Bone is the most common site for breast cancer metastasis. This work is dedicated to the use of mass cytometry and single cell analysis to explore the molecular alterations in the marrow immune microenvironment which participates the dormancy and activation of disseminated tumor cells (DTCs). Firstly, four Balb/c mouse breast cancer bone metastasis groups were established. Animals were divided into intracardiac injection group (n=10), subcutaneous injection group (n=10), tumor resection and suture group (n=10), and control group (n=10). In the intracardiac injection group, a breast cancer bone metastatic model was constructed by directly injecting mCherry-labeled 4T1 cells into the left ventricle. After detecting obvious bone metastasis by bioluminescence imaging (BLI), femur and tibia bone marrow were excised for flow cytometry cell sorting, mass cytometry and single cell analysis. Both the subcutaneous and the resection and suture groups were injected with mCherry-labeled 4T1 cells into the right-back of Balb/c mice. In the tumor resection and suture group, the tumor was removed at the time when the subcutaneous tumor was just palpable. In the subcutaneous injection group, the animals were sacrificed when tumor volume reached 1 cubic centimeter. The classification of bone marrow cells was determined by using fluorescent dye labeled CD45, CD4, CD8, CD19, NK1.1, CD11b, CD11c, IA/IE, Ly6C, Ly6G and other antibodies. Constructed as a local immune landscape in the marrow, certain numbers of B cells and T cells, in the bone marrow of mice with breast cancer bone metastasis were significantly less than those in control mice, indicating that the acquired immunity of the mice with bone metastasis is diminished. In addition, the proportions of CD11b+ myeloid cells and neutrophils in the marrow of mice with bone metastasis were significantly higher than that in the control group, whereas the proportion of macrophages and eosinophils were all significantly decreased indicating that the bone marrow immune environment has changed in the process of tumor occurrence and metastasis. Research is ongoing, including ex-marrow spleen cell analysis in those animals, to explore the mechanism of the interaction between the immune microenvironment and tumor cells that determines tumor heterogeneity and sensitivity to therapy. This work was supported by NSFC projects 81773146, 81972766, 81972420; Shenzhen Science and Technology Commission Project JCYJ20180302174235893; and College students' innovative entrepreneurial training program (S202114325028)
Citation Format: Yingxuan Gong, Yinghao Wang, Xinyu Jiang, Xiuzhi Li, Yueming Li, Ming Chang, Yi Lu, Jian Zhang. Marrow immune landscape participates dormancy and activation of disseminated tumor cells in a breast cancer bone metastasis model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5985.