Abstract P5-01-06: Single cell profile of tumor and immune cells in primary triple-negative breast cancer and different sites in the axillary lymph nodes

Abstract Purpose: Little is known about the host-tumor interaction in the lymph node basin at a single cell level. This study examines single cell sequences in breast cancer nodal metastasis of a patient with triple negative breast cancer. Methods: The primary breast tumor, sentinel lymph node, an adjacent lymph node with metastatic involvement and a clinically normal-appearing lymph node were collected during operation. Single-cell sequencing was performed on all specimens. Results: 14,016 cells were clustered as 6 cell populations. Cancer cells demonstrated the molecular characteristics of TNBC basal B subtype and highly expressed genes in the MAPK signaling cascade. Tumor associated macrophages regulated antigen processing and presentation and other immune-related pathways to promote tumor invasion. CD8+ and CD4+ T lymphocytes concentrated more in sentinel lymph node and mainly stratified as two transcriptional states. The immune cell amount variation among primary tumor, sentinel and normal lymph nodes showed the similar tendency between the scRNA-seq profile of TNBC samples and a previous reported bulk RNA-seq profile of a breast cancer cohort including all four breast cancer subtype samples. Discussion: Single-cell sequencing analysis suggested that the sentinel lymph node was the initial meeting site of tumor infiltration and immune response, where partial T lymphocytes perform anti-tumor activity while other T cells exhibit an exhaustion state. We proposed a molecular explanation to the well-established clinical principle that the 5-year and 10-year survival outcomes were noninferior between SLND and ALND. Citation Format: Ning Liao, Cheukfai Li, Li Cao, Yanhua Chen, Chongyang Ren, Xiaoqing Chen, Hsiaopei Mok, Lingzhu Wen, Kai Li, Yulei Wang, Yuchen Zhang, Yingzi Li, Jiaoyi Lv, Fangrong Cao, Yuting Luo, Hongrui Li, Wendy Wu, Charles M. Balch, Armando E. Giuliano. Single cell profile of tumor and immune cells in primary triple-negative breast cancer and different sites in the axillary lymph nodes [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-01-06.