A robust protocol for the systematic collection and expansion of cells from ER+ breast cancertumors and their matching tumor-adjacent tissues

Therapy resistance and tumor recurrence are major challenges in the clinical management of breast cancer. Current data indicates that the breast tumor microenvironment (TME) and the tumor immune microenvironment (TIME) are important modulators of breast cancer cell response to chemotherapies and the development of therapy resistance. To this end, the ability to recreate the tumor microenvironment in the laboratory using autologous primary cells that make up the breast TME has become an indispensable tool for cancer researchers as it allows the study of tumor immunobiology in the context of therapy resistance. Moreover, the clinical relevance of data obtained from single cell transcriptomics and proteomics platforms would be greatly improved if primary autologous tumor cells were used. In this article, we report a robust and efficient workflow to obtain autologous cancer cells, cancer-associated fibroblasts, and tumor-infiltrating immune cells from primary human breast cancer tumors obtained from mastectomy procedures. As well, we show that this protocol can be used to obtain normal-like epithelial cells, fibroblasts, and immune cells from the matching tumor-adjacent breast tissue samples. Also, a robust methodology to expand each of these primary cell types in vitro is presented that allows the maintenance of the primary tumor cell phenotype. The availability of a large number of autologous primary human breast tumor cells and their matching tumor-adjacent tissues will facilitate the study of differential and cancer cell-specific gene expression patterns that will further our understanding of how the TME and TIME influence therapy resistance in the breast tumor context.