Analysis of clonal expansions through the normal and premalignant human breast epithelium reveals the presence of luminal stem cells

Abstract

It is widely accepted that the cell of origin of breast cancer is the adult mammary epithelial stem cell; however, demonstrating the presence and location of tissue stem cells in the human breast has proved difficult. Furthermore, we do not know the clonal architecture of the normal and premalignant mammary epithelium or its cellular hierarchy. Here, we use deficiency in the mitochondrial enzyme cytochrome c oxidase (CCO), typically caused by somatic mutations in the mitochondrial genome, as a means to perform lineage tracing in the human mammary epithelium. PCR sequencing of laser‐capture microdissected cells in combination with immunohistochemistry for markers of lineage differentiation was performed to determine the clonal nature of the mammary epithelium. We have shown that in the normal human breast, clonal expansions (defined here by areas of CCO deficiency) are typically uncommon and of limited size, but can occur at any site within the adult mammary epithelium. The presence of a stem cell population was shown by demonstrating multi‐lineage differentiation within CCO‐deficient areas. Interestingly, we observed infrequent CCO deficiency that was restricted to luminal cells, suggesting that niche succession, and by inference stem cell location, is located within the luminal layer. CCO‐deficient areas appeared large within areas of ductal carcinoma in situ, suggesting that the rate of clonal expansion was altered in the premalignant lesion. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

A single‐cell RNA expression atlas of normal, preneoplastic and tumorigenic states in the human breast

“…The diffusion map places the "tail" cells downstream of the other basal cells in pseudo-time and between the basal and luminal lineages, suggesting that they represent transient intermediates prior to luminal lineage commitment (Fig 1I). These data are compatible with studies of X chromosome inactivation as well as clonal tracking of cells deficient in Cytochrome C oxidase, both of which have indicated the presence of bipotent precursor cells (Tsai et al, 1996;Cereser et al, 2018).…”

Reduced Basal Nitric Oxide Production Induces Precancerous Mammary Lesions via ERBB2 and TGFβ

“…Advances in imaging and screening technologies have enabled the detection of precancerous, early-stage breast lesions, the majority of which are ductal carcinoma in situ (DCIS) 2 . Precancerous lesions arise from clonal expansion of a single cell 140 . Precancerous lesions are the precursors to invasive breast cancers, and about 40% of them could progress to invasive forms, if untreated 2 .…”

Integrating single-cell RNA-sequencing and functional assays to decipher mammary cell states and lineage hierarchies

“…Of course, human breast tissue cannot be lineage-traced through transgene activation as one can in the mouse, but use of cytochrome C oxidase (CCO) mutations in the mitochondrial genome has proven feasible as an approach. Cereser et al 70 report the presence of CCO-deficient clonal expansions in both ducts and TDLUs of normal breast 70 . Notably, the expansions were limited to the luminal layers, and they found no evidence of luminal CCO-deficient clones contributing to the basal layer.…”