Diverse Macrophage Populations Contribute to the Inflammatory Microenvironment in Premalignant Lesions During Localized Invasion

Abstract

Myeloid cell heterogeneity remains poorly studied in breast cancer, and particularly in premalignancy. Here, we used single cell RNA sequencing to characterize macrophage diversity in mouse pre-invasive lesions as compared to lesions undergoing localized invasion. Several subpopulations of macrophages with transcriptionally distinct profiles were identified, two of which resembled macrophages in the steady state. While all subpopulations expressed tumor-promoting genes, many of the populations expressed pro-inflammatory genes, differing from reports in tumor-associated macrophages. Gene profiles of the myeloid cells were similar between early and late stages of premalignancy, although expansion of some subpopulations occurred. These results unravel macrophage heterogeneity in early progression and may provide insight into early intervention strategies that target macrophages.

Characterization of Gene Expression Signatures for the Identification of Cellular Heterogeneity in the Developing Mammary Gland

“…S10D). Further analysis utilizing classic lineage markers confirmed the B-cell identity of hTM11, in addition to predicting identities of epithelial clusters hTM4, hTM6, hTM8 and hTM10 (EPCAM + , KRT8 + and KRT5 +) and non-epithelial clusters, based on the expression of immune markers (CD3E, Granzyme A (GZMA), Serpin Family E Member 1 (SER-PINE1), A Receptor Tyrosine Kinase (AXL) and HEXB, endothelial markers CLDN5 [13,27,77,[99][100][101][102][103][104], fibroblasts marker Myocilin (MYOC) [105], and adipocytes markers Gap Junction Protein Alpha 4 (GJA4), and Procollagen C-Endopeptidase Enhancer (PCOLCE) [106,107]. We also noted that some lineage specific markers of non-epithelial cells were expressed by epithelial lineages, such as HEXB and AXL (Supplementary Fig.…”

“…Outside of the lymphocytic-biased lineage, we identified myeloid-biased clusters, including a population of dendritic cells (mNEC7), marked by the expression of dendritic master regulator Basic Leucine Zipper ATF-Like Transcription Factor 3 (Batf3) [96], and macrophage-like cells characterized by the expression of classical markers such as Cd14 [97], Lysozyme C-2 (Lyz2) [98] and Hexosaminidase Subunit Beta (Hexb) [99] (Fig. 4C, Supplementary Fig.…”

Transition to invasive breast cancer is associated with progressive changes in the structure and composition of tumor stroma

“…With this in mind, we sought to determine to what extent similar features involving myoepithelial, stromal, and immune cells in the DCIS TME might play a pivotal role in breast cancer progression. Each of these have been implicated previously to promote local invasion (Barsky and Karlin, 2005;Ibrahim et al, 2020), metastasis (Pelon et al, 2020;Shani et al, 2020), and to correlate with clinical progression (Yang et al, 2018;Zhou et al, 2018).…”

Parity-induced changes to mammary epithelial cells control NKT cell expansion and mammary oncogenesis

“…Therefore, we developed an inducible mouse model of Brca1 loss of function, for the purpose of investigating how pregnancy-induced changes influences Brca1 null mammary tumor development. In this model, tamoxifen (TAM) induces homozygous loss of Brca1 function in cells that express the cytokeratin 5 gene (KRT5+ cells), which include MECs (dos Santos et al, 2013), cells from gastrointestinal tract (Sulahian et al, 2015), reproductive organs (Ricciardelli et al, 2017), and additional epithelial tissue (Castillo-Martin et al, 2010;Majumdar et al, 2012), in p53 heterozygous background (Krt5 CRE-ERT2 Brca1 fl/fl p53 -/+ , hereafter referred as Brca1 KO mouse).…”

“…For example, CD4+ T-helper cells guide lineage commitment and differentiation of MECs, while macrophages provide growth factors and assist in removal of cellular debris arising from apoptotic events, during postnatal stages of mammary development (Dawson et al, 2020;Hitchcock et al, 2020;Plaks et al, 2015;Rahat et al, 2016;Stewart et al, 2019;Wang et al, 2020). Accordingly, changes that impact immune cell function and abundance can also influence the development and progression of mammary oncogenesis (Bach et al, 2021;Ibrahim et al, 2020).…”