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MicroRNA-mediated post-transcriptional regulation plays key roles in stem cell self-renewal and tumorigenesis. However, the in vivo functions of specific microRNAs in controlling mammary stem cell (MaSC) activity and breast cancer formation remain poorly understood. Here we show that miR-31 is highly expressed in MaSC-enriched mammary basal cell population and in mammary tumors, and is regulated by NF-κB signaling. We demonstrate that miR-31 promotes mammary epithelial proliferation and MaSC expansion at the expense of differentiation in vivo. Loss of miR-31 compromises mammary tumor growth, reduces the number of cancer stem cells, as well as decreases tumor-initiating ability and metastasis to the lung, supporting its pro-oncogenic function. MiR-31 modulates multiple signaling pathways, including Prlr/Stat5, TGFβ and Wnt/β-catenin. Particularly, it activates Wnt/β-catenin signaling by directly targeting Wnt antagonists, including Dkk1. Importantly, Dkk1 overexpression partially rescues miR31-induced mammary defects. Together, these findings identify miR-31 as the key regulator of MaSC activity and breast tumorigenesis.

SMAD4 is a tumor suppressor mutated or silenced in multiple cancers, including oral cavity squamous cell carcinoma (OSCC). Human clinical samples and cell lines, mouse models and organoid culture were used to investigate the role that SMAD4 plays in progression from benign disease to invasive OSCC. Human OSCC lost detectable SMAD4 protein within tumor epithelium in 24% of cases, and this loss correlated with worse progression‐free survival independent of other major clinical and pathological features. A mouse model engineered for KrasG12D expression in the adult oral epithelium induced benign papillomas, however the combination of KrasG12D with loss of epithelial Smad4 expression resulted in rapid development of invasive carcinoma with features of human OSCC. Examination of regulatory pathways in 3D organoid cultures of SMAD4+ and SMAD4− mouse tumors with Kras mutation found that either loss of SMAD4 or inhibition of TGFβ signaling upregulated the WNT pathway and altered the extracellular matrix. The gene signature of the mouse tumor organoids lacking SMAD4 was highly similar to the gene signature of human head and neck squamous cell carcinoma. In summary, this work has uncovered novel mechanisms by which SMAD4 acts as a tumor suppressor in OSCC. © 2024 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland. [ABSTRACT FROM AUTHOR]

Although regeneration through the reprogramming of one cell lineage to another occurs in fish and amphibians, it has not been observed in mammals. We discovered in the mouse that during wound healing, adipocytes regenerate from myofibroblasts, a cell type thought to be differentiated and nonadipogenic. Myofibroblast reprogramming required neogenic hair follicles, which triggered bone morphogenetic protein (BMP) signaling and then activation of adipocyte transcription factors expressed during development. Overexpression of the BMP antagonist Noggin in hair follicles or deletion of the BMP receptor in myofibroblasts prevented adipocyte formation. Adipocytes formed from human keloid fibroblasts either when treated with BMP or when placed with human hair follicles in vitro. Thus, we identify the myofibroblast as a plastic cell type that may be manipulated to treat scars in humans.

Wnt/β-catenin signaling is a central regulator of adult stem cells. Variable sensitivity of Wnt reporter transgenes, β-catenin's dual roles in adhesion and signaling, and hair follicle degradation and inflammation resulting from broad deletion of epithelial β-catenin have precluded clear understanding of Wnt/β-catenin's functions in adult skin stem cells. By inducibly deleting β-catenin globally in skin epithelia, only in hair follicle stem cells, or only in interfollicular epidermis and comparing the phenotypes with those caused by ectopic expression of the Wnt/β-catenin inhibitor Dkk1, we show that this pathway is necessary for hair follicle stem cell proliferation. However, β-catenin is not required within hair follicle stem cells for their maintenance, and follicles resume proliferating after ectopic Dkk1 has been removed, indicating persistence of functional progenitors. We further unexpectedly discovered a broader role for Wnt/β-catenin signaling in contributing to progenitor cell proliferation in nonhairy epithelia and interfollicular epidermis under homeostatic, but not inflammatory, conditions.

Introduction Lung cancer is the leading cause of cancer-associated deaths worldwide, and adenocarcinoma is the predominant subtype of non-small-cell lung cancer (NSCLC) (1). The processes necessary for the initiation and [...], MicroRNA (miR) are important regulators of gene expression, and aberrant miR expression has been linked to oncogenesis; however, little is understood about their contribution to lung tumorigenesis. Here, we determined that miR-31 is overexpressed in human lung adenocarcinoma and this overexpression independently correlates with decreased patient survival. We developed a transgenic mouse model that allows for lung-specific expression of miR-31 to test the oncogenic potential of miR-31 in the lung. Using this model, we observed that miR-31 induction results in lung hyperplasia, followed by adenoma formation and later adenocarcinoma development. Moreover, induced expression of miR-31 in mice cooperated with mutant KRAS to accelerate lung tumorigenesis. We determined that miR-31 regulates lung epithelial cell growth and identified 6 negative regulators of RAS/MAPK signaling as direct targets of miR-31. Our study distinguishes miR-31 as a driver of lung tumorigenesis that promotes mutant KRAS-mediated oncogenesis and reveals that miR-31 directly targets and reduces expression of negative regulators of RAS/MAPK signaling.

Author(s): Mayumi Ito [1]; Zaixin Yang [1]; Thomas Andl [1]; Chunhua Cui [1]; Noori Kim [1]; Sarah E. Millar [1]; George Cotsarelis (corresponding author) [1] The mammalian hair follicle is [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2006.12.020 Byline: Jaroslav Stark (1), Thomas Andl (2), Sarah E. Millar (2) Abstract: Hair follicles in the skin have a characteristic spacing and orientation. Two recent papers () report the use of contrasting mathematical models and experimental manipulations to gain insight into the mechanisms underlying patterns of hair-follicle distribution and orientation. Author Affiliation: (1) Department of Mathematics and Centre for Integrative Systems Biology, Imperial College London, 180 Queen's Gate, London, SW7 2AZ, UK (2) Departments of Dermatology and Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA

Skin lies at the interface between the complex physiology of the body and the external environment. This essential epidermal barrier, composed of cornified proteins encased in lipids, prevents both water loss and entry of infectious or toxic substances. We uncover that the transcription factor GATA-3 is required to establish the epidermal barrier and survive in the ex utero environment. Analysis of Gata-3 mutant transcriptional profiles at three critical developmental stages identifies a specific defect in lipid biosynthesis and a delay in differentiation. Genomic analysis identifies highly conserved GATA-3 binding sites bound in vivo by GATA-3 in the first intron of the lipid acyltransferase gene AGPAT5. Skin from both Gata-3-/- and previously characterized barrier-deficient Kruppel-like factor 4-/- newborns up-regulate antimicrobial peptides, effectors of innate immunity. Comparison of these animal models illustrates how impairment of the skin barrier by two genetically distinct mechanisms leads to innate immune responses, as observed in the common human skin disorders psoriasis and atopic dermatitis.

Branching morphogenesis in the lung serves as a model for the complex patterning that is reiterated in multiple organs throughout development. [beta]-catenin and Wnt signaling mediate critical functions in cell fate specification and differentiation, but specific functions during branching morphogenesis have remained unclear. Here, we show that Wnt/[beta]-catenin signaling regulates proximal distal differentiation of airway epithelium. Inhibition of Wnt/[beta]-catenin signaling, either by expression of Dkk1 or by tissue-specific deletion of [beta]-catenin, results in disruption of distal airway development and expansion of proximal airways. Wnt/[beta]-catenin functions upstream of BMP4, FGF signaling, and Nmyc. Moreover, we show that [beta]-catenin and LEF/TCF activate the promoters of BMP4 and N-myc. Thus, Wnt/[beta]-catenin signaling is a critical upstream regulator of proximal--distal patterning in the lung, in part, through regulation of N-myc, BMP4, and FGF signaling. Keywords: Wnt; [beta]-catenin; Dickkopf-1; BMP; FGF; Lung development

Prostate cancer (PCa) progression relies on androgen receptor (AR) function, making AR a top candidate for PCa therapy. However, development of drug resistance is common, which eventually leads to development of castration-resistant PCa. This warrants a better understanding of the pathophysiology of PCa that facilitates the aberrant activation of key signaling pathways including AR. MicroRNAs (miRNAs) function as regulators of cancer progression as they modulate various cellular processes. Here, we demonstrate a multidimensional function of miR-30e through the regulation of genes involved in various signaling pathways. We noted loss of miR-30e expression in prostate tumors, which, when restored, led to cell cycle arrest, induction of apoptosis, improved drug sensitivity of PCa cells and reduced tumor progression in xenograft models. We show that experimental upregulation of miR-30e reduces expression of mRNAs including AR, FBXO45, SRSF7 and MYBL2 and a novel long noncoding RNA (lncRNA) HELLPAR, which are involved in cell cycle, apoptosis and ubiquitination, and the effects could be rescued by inhibition of miR-30e expression. RNA immunoprecipitation analysis confirmed direct interactions between miR-30e and its RNA targets. We noted a newly identified reciprocal relationship between miR-30e and HELLPAR, as inhibition of HELLPAR improved stabilization of miR-30e. Transcriptome profiling and quantitative real-time PCR (qRT-PCR) validation of miR-30eexpressing PCa cells showed differential expression of genes involved in cell cycle progression, apoptosis and ubiquitination, which supports our in vitro study. This study demonstrates an integrated function of miR-30e on dysregulation of miRNA/lncRNA/mRNA axes that may have diagnostic and therapeutic significance in aggressive PCa. [ABSTRACT FROM AUTHOR]