Project description:Cancer metabolism adapts the metabolic network of its tissue-of-origin. However, breast cancer is not a disease of a singular origin. Multiple epithelial populations serve as the culprit cell-of-origin for specific breast cancer subtypes, yet our knowledge of the metabolic network of normal mammary epithelial cells is limited. Using a multi-OMIC approach, here we identify the diverse metabolic programs operating in normal mammary populations. The proteomes of basal, luminal progenitor, and mature luminal cell populations revealed enrichment of glycolysis in basal cells and of oxidative phosphorylation in luminal progenitors. Single-cell transcriptomes corroborated lineage-specific metabolic identities and additional intra-lineage heterogeneity. Mitochondrial form-and-function differed across lineages, with clonogenicity correlating to mitochondrial activity. Targeting oxidative phosphorylation and glycolysis with inhibitors exposed lineage-rooted metabolic vulnerabilities of mammary progenitors. Bioinformatics indicated breast cancer subtypes retain metabolic features of their putative cell-of-origin. Thus, lineage-rooted metabolic identities of normal mammary cells may underlie breast cancer metabolic heterogeneity and targeting these vulnerabilities could advance breast cancer therapy.
Project description:Global proteomic profiling of three mammary epithelial cell types in normal human breast tissue. Primary breast specimens were obtained from 10 women undergoing reduction mammoplasties. Clinical co-variates include age (28-67), hormone status (follicular, luteal, post-menopausal) and mammary epithelial cell type (basal, luminal progenitor, mature luminal).
Project description:The mammary epithelium depends on specific lineages and their stem and progenitor function to accommodate hormone-triggered physiological demands in the adult female. Perturbations of these lineages underpin breast cancer risk, yet our understanding of normal mammary cell composition is incomplete. Here, we build a multimodal resource for the adult gland through comprehensive profiling of primary cell epigenomes, transcriptomes, and proteomes. We define systems-level relationships between chromatin–DNA–RNA–protein states, identify lineage-specific DNA methylation of transcription factor binding sites, and pinpoint proteins underlying progesterone responsiveness. Comparative proteomics of estrogen and progesterone receptor–positive and –negative cell populations, extensive target validation, and drug testing lead to discovery of stem and progenitor cell vulnerabilities. Top epigenetic drugs exert cytostatic effects; prevent adult mammary cell expansion, clonogenicity, and mammopoiesis; and deplete stem cell frequency. Select drugs also abrogate human breast progenitor cell activity in normal and high-risk patient samples. This integrative computational and functional study provides fundamental insight into mammary lineage and stem cell biology.
PMID: 29921600 (Table S5 and Table S7)
Project description:Mammary gland homeostasis is maintained by adult tissue stem-progenitor cells residing within the luminal and basal epithelia. Dysregulation of mammary stem cells is a key mechanism for cancer development. However, stem cell characterization is challenging because reporter models using cell-specific promoters do not fully recapitulate the mammary stem cell populations. We previously found that a 270-basepair Runx1 enhancer element, named eR1, marked stem cells in the blood and stomach. Here, we identified eR1 activity in a rare subpopulation of the ERα-negative luminal epithelium in mouse mammary glands. Lineage-tracing using an eR1-CreERT2 mouse model revealed that eR1+ luminal cells generated the entire luminal lineage and milk-secreting alveoli – eR1 therefore specifically marks lineage-restricted luminal stem cells. eR1-targeted-conditional knockout of Runx1 led to the expansion of luminal epithelial cells, accompanied by elevated ERα expression. Our findings demonstrate a definitive role for Runx1 in the regulation of the eR1-positive luminal stem cell proliferation during mammary homeostasis. Our findings identify a mechanistic link for Runx1 in stem cell proliferation and its dysregulation in breast cancer. Runx1 inactivation is therefore likely to be an early hit in the cell-of-origin of ERα+ luminal type breast cancer.
Project description:Luminal to basal transition in mammary gland is accompanied by the changes of epithelial cell lineage plasticity, however, the underlying mechanism remains elusive. Here, we demonstrated that loss of the scaffold protein FRMD3 in breast cancer predicts poor outcomes. Knockout of Frmd3 inhibits mammary gland lineage development and induces mammary epithelium cells (MECs) stemness, and later on emerge of TNBC. Loss of Frmd3 in PyMT mice results in luminal to basal phenotype transition. Single- MEC mRNA sequencing analysis indicated that knockout of Frmd3 corresponds to inhibition of Notch signaling pathway. Mechanistically, FRMD3 assists Dishevelled-2 degradation via enhancing its interaction with the deubiquitinase USP9x. FRMD3 also interrupts the interaction of Dishevelled-2 with CK1, FOXK1, FOXK2 and NICD, causing a decrease in Dishevelled-2 phosphorylation, entry into the nucleus and impairing the Notch-dependent luminal epithelial lineage plasticity in MECs respectively. Taken together, FRMD3 is a tumor suppressor and an endogenous activator of the Notch signaling pathway that regulates mammary epithelial cell lineage plasticity.