Old stem cells are precursors of breast cancer
"Old" stem cells found in mammary glands
Kirill Stasevich, CompulentaStem cells, which can give rise to several types of specialized cells, persist in the mammary glands long after birth.
A characteristic feature of a stem cell is asymmetric division, when one of the daughter cells goes along the path of differentiation, and the other becomes a copy of the maternal stem cell, that is, it does not differentiate and serves to maintain-update the stem line. At the same time, as is known, stem cells have different levels of "strength": there are embryonic cells whose descendants can give rise to any differentiated cell, there are stem cells capable of producing only a limited set of specialized types (like blood stem cells). And there are also known progenitor cells, which, no matter how many they divide, have only one pathway, only one type of differentiated cells.
At the same time, the precursors very often lose the ability to self-renew, that is, when dividing, they do not get a daughter cell that would remain at the same stage as the mother, that is, the precursors inevitably slide into specialization. Usually, with age, the proportion of various progenitor cells in the body increases, and the number of stem cells capable of different ways of differentiation decreases. And, for example, it was believed that all postnatal changes in the mammary glands are carried out at the expense of "monopotent" stem cells and their descendants. That is, the formation of a network of glandular ducts and the formation of myoepithelial zones occurs due to two separate cell lines.
However, as Jane Visvader and her colleagues from the Walter and Eliza Hall Institute for Medical Research discovered to their surprise, even many years after birth, stem cells capable of different development paths remain in the mammary glands. That is, there are not only progenitor cells in the mammary gland, due to which the glands mature during sexual development, but also the ancestors of these precursors - stem cells that control the formation of glandular ducts and in general structural changes in the mammary gland.
The fact that self-renewing stem cells remain in the mammary glands was already known, but no one assumed that they belong to the type that can give different lines of specialized cells: no one thought that such stem cells would "live and work" for so long.
The importance of these results is easy to understand if you remember that actively dividing cells are considered one of the main causes of breast cancer. For example, in 2009, it was possible to link one of the most aggressive types of this tumor with progenitor cells responsible for the glandular ducts. But after all, the detected polypotent stem cells can also provoke a tumor – they live, as it turned out, for a long time, and, consequently, mutations can accumulate.
For successful cancer treatment, it is important to know how it originated and how it developed, and for this you need to imagine which cells started it all, and "new old" stem cells then become one of the main suspects. Although they were found in mice, most likely, these cells are also present in human mammary glands.
Article by Rios et al. In situ identification of bipotent stem cells in the mammary gland is published in the journal Nature – VM.
Prepared based on the materials of the Walter and Eliza Hall Institute of Medical Research:
Long-lived breast stem cells could retain cancer legacy.
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