14-3-3ζ-depletion impairs mammary gland development in the mouse

The 14-3-3 family of proteins have roles in regulating several key cellular processes. While their significant structural and functional homology had informed the idea that these proteins acted redundantly, it is now becoming clear that individual family members may have tissue and context specific functions, highlighting the need for a more nuanced understanding of these important proteins. Here, we demonstrate that mice deficient in 14-3-3ζ exhibit developmental defects of the mammary epithelium, associated with dysregulation of key transcription factors involved in the maintenance of mammary stem cell populations. We believe that this model will be prove useful for investigating the role of 14-3-3ζ in the maintenance of mammary stem cell populations and elucidating the transcriptional networks driving specification of the mammary epithelium.

Early Dietary Exposures Epigenetically Program Mammary Cancer Susceptibility through IGF1-mediated Expansion of Mammary Stem Cells

Dietary exposures at early developmental stages have been shown to program lifetime breast cancer susceptibility. We previously reported that manipulation of gestational and postweaning diets leads to different mammary tumor outcomes in carcinogen-treated mice. The high tumor incidence (HT) groups (average 61.5% tumor incidence) received a low-fat, low-sugar, mildly restricted (12%v/v) (DR) diet during gestation, followed by a high-fat, high-sugar (HF) diet postweaning. Conversely, the low tumor incidence (LT) groups (average 20% tumor incidence) received the HF diet during gestation, followed by the DR diet postweaning. Herein, we extended these findings by demonstrating that HT animals had an expanded mammary stem cell (MaSC) population compared to LT animals before puberty, and this expansion persisted into adulthood. IGF1 expression was increased in mammary stromal cells from HT animals, which promoted the self-renewal capacity of MaSCs in a paracrine fashion. This increased IGF1 expression was programmed prepubertally through DNA hypomethylation of the IGF1 promoter 1, mediated by decreased DNMT3b levels. IGFBP5 mRNA and protein levels were also reduced in mammary tissues from HT animals, indicating an increased bioavailability of tissue IGF1. In association with these changes, mammary tissues from carcinogen-treated HT animals developed an increased proportion of mammary adenosquamous carcinomas compared to carcinogen-treated LT animals. This study provides novel mechanistic insights into how early dietary exposures program mammary cancer risk and tumor phenotypes by increasing IGF1 expression through epigenetic alterations, thereby expanding the MaSC population, resulting in a higher number of carcinogen targets susceptible to transformation in adulthood.SignificanceEarly high-fat dietary exposure programs lifetime mammary cancer susceptibility before puberty through epigenetic alterations of IGF1 promoters and IGF1-mediated paracrine regulation of mammary stem cell homeostasis.

Author Correction: MiR-31 promotes mammary stem cell expansion and breast tumorigenesis by suppressing Wnt signaling antagonists

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

3D Differentiation Of Mammosphere Derived Macaca fascicularis’s Mammary Stem Cells

The mammary gland contains adult stem cells that are capable of self-renewal. This population plays an important role in the development of mammary gland and breast cancer pathogenesis. The studies of mammary stem cells are limited due to the difficulty to acquire and expand adult stem cell population in an undifferentiated state. In this study, we developed mammosphere cultures of nulliparous cynomolgus monkeys (Macaca fascicularis; Mf) as a culture system to enrich mammary stem cells. This species has similarity of mammary gland structure as humans including anatomy, developmental stages, and lobule profile of mammary gland. The use of stem cells from primate animals is essential to bridge the knowledge gaps resulting from stem cell research using rodents for clinical trials in human. Small samples of mammary tissues were collected by surgical biopsy; cells were cultured as monolayer and cryopreserved. Cryopreserved cells were cultured into mammospheres, and the expression of markers for mammary stem cells was evaluated using qPCR. Cells were further differentiated with 3D approaches to evaluate morphology and organoid budding. The study showed that mammosphere culture resulted in an increase in the expression of mammary stem cell markers with each passage. The 3D differentiation in matrigel allowed for organoid formation. Mammary gland stem cells have been successfully differentiated which characterized by CSN2 marker expression and differentiation regulators marker STAT5 and GATA3. The results indicate that mammospheres can be successfully developed derived from breast tissue of nulliparous Mf collected via surgical biopsy. As the mammosphere allows for enrichment of mammary stem cell population, the findings also suggest that a 3-dimensional system is efficient as in-vitro model to study mammary stem cells and a useful system to study mammary differentiation in regards to cancer prevention.