Interferon-Induced Bone Marrow Stromal Antigen 2 (BST2) Is A Functional Tumor-Initiating Cell Marker In Triple-Negative Breast Cancer.

Tumor-initiating cells (TIC) are a tumor cell subpopulation thought to be responsible for therapeutic resistance and metastasis. Using a S ignal T ransducer and A ctivator of T ranscription (STAT) reporter, and a STAT-responsive lineage tracing system, we enriched for cells with enhanced mammosphere-forming potential in some, but not all, triple-negative breast cancer xenograft models (TNBC) indicating TIC-related and TIC-independent functions for STAT signaling. Single-cell RNA sequencing (scRNA-seq) of reporter-tagged xenografts identified a common interferon-associated transcriptional state, previously linked to inflammation and macrophage differentiation, in TIC. Similar transcriptional states exist in human breast cancer patient scRNA-seq datasets. Flow cytometric sorting using bone marrow stromal cell antigen 2 (BST2), a marker of this state, enriched for TIC, and BST2 knockdown reduced mammosphere-forming potential. These results suggest TIC may exploit the interferon response pathway to promote their activity in TNBC. Our results lay the groundwork to target interferon-associated pathways in TIC in a subset of TNBC.

Hoxd10 Is Required Systemically for Secretory Activation in Lactation and Interacts Genetically with Hoxd9.

Targeted disruption of the murine Hoxd10 gene (ΔHoxd10) leads to a high frequency of localized (gland-to-gland or regionally within a gland) lactation impairment in homozygous mutant mice as a single gene mutation. The effect of Hoxd10 disruption was enhanced by simultaneous disruption of Hoxd9 (ΔHoxd9/d10), a mutation shown previously to have no effect on mammary function as a single gene alteration. Mammary glands of homozygous ΔHoxd10 and ΔHoxd9/d10 females were indistinguishable from those of wild type littermate and age-matched control mice in late pregnancy. However, in lactation, 47% of homozygous ΔHoxd10 females, and 100% of homozygous ΔHoxd9/d10 females, showed localized or complete failure of two or more glands to undergo lactation-associated morphological changes and to secrete milk. Affected regions of ΔHoxd10 and ΔHoxd9/d10 mutants showed reduced prolactin receptor expression, reduced signal transducer and activator transcription protein 5 (STAT5) phosphorylation, reduced expression of downstream milk proteins, mislocalized glucose transporter 1 (GLUT1), increased STAT3 expression and phosphorylation, recruitment of leukocytes, altered cell cycle status, and increased apoptosis relative to unaffected regions and wild type control glands. Despite these local effects on alveolar function, transplantation results and hormone analysis indicate that Hoxd10 primarily has systemic functions that confer attenuated STAT5 phosphorylation on both wild type and ΔHoxd10 transplants when placed in ΔHoxd10 hosts, thereby exacerbating an underlying propensity for lactation failure in C57Bl/6 mice.

S100a4-Cre-mediated deletion of Patched1 causes hypogonadotropic hypogonadism: role of pituitary hematopoietic cells in endocrine regulation.

Hormones produced by the anterior pituitary gland regulate an array of important physiological functions, but pituitary hormone disorders are not fully understood. Herein we report that genetically-engineered mice with deletion of the hedgehog signaling receptor Patched1 by S100a4 promoter-driven Cre recombinase (S100a4-Cre;Ptch1fl/fl mutants) exhibit adult-onset hypogonadotropic hypogonadism and multiple pituitary hormone disorders. During the transition from puberty to adult, S100a4-Cre;Ptch1fl/fl mice of both sexes develop hypogonadism coupled with reduced gonadotropin levels. Their pituitary glands also display severe structural and functional abnormalities, as revealed by transmission electron microscopy and expression of key genes regulating pituitary endocrine functions. S100a4-Cre activity in the anterior pituitary gland is restricted to CD45+ cells of hematopoietic origin, including folliculo-stellate cells and other immune cell types, causing sex-specific changes in the expression of genes regulating the local microenvironment of the anterior pituitary. These findings provide in vivo evidence for the importance of pituitary hematopoietic cells in regulating fertility and endocrine function, in particular during sexual maturation and likely through sexually dimorphic mechanisms. These findings support a previously unrecognized role of hematopoietic cells in causing hypogonadotropic hypogonadism and provide inroads into the molecular and cellular basis for pituitary hormone disorders in humans.

Carbon nanotube capsules enhance the in vivo efficacy of cisplatin.

Over the past few years, numerous nanotechnology-based drug delivery systems have been developed in an effort to maximize therapeutic effectiveness of conventional drug delivery, while limiting undesirable side effects. Among these, carbon nanotubes (CNTs) are of special interest as potential drug delivery agents due to their numerous unique and advantageous physical and chemical properties. Here, we show in vivo favorable biodistribution and enhanced therapeutic efficacy of cisplatin (CDDP) encapsulated within ultra-short single-walled carbon nanotube capsules (CDDP@US-tubes) using three different human breast cancer xenograft models. In general, the CDDP@US-tubes demonstrated greater efficacy in suppressing tumor growth than free CDDP in both MCF-7 cell line xenograft and BCM-4272 patient-derived xenograft (PDX) models. The CDDP@US-tubes also demonstrated a prolonged circulation time compared to free CDDP which enhanced permeability and retention (EPR) effects resulting in significantly more CDDP accumulation in tumors, as determined by platinum (Pt) analysis via inductively-coupled plasma mass spectrometry (ICP-MS). STATEMENT OF SIGNIFICANCE: Over the past decade, drug-loaded nanocarriers have been widely fabricated and studied to enhance tumor specific delivery. Among the diverse classes of nanomaterials, carbon nanotubes (CNTs), or more specifically ultra-short single-walled carbon nanocapsules (US-tubes), have been shown to be a popular, new platform for the delivery of various medical agents for both imaging and therapeutic purposes. Here, for the first time, we have shown that US-tubes can be utilized as a drug delivery platform in vivo to deliver the chemotherapeutic drug, cisplatin (CDDP) as CDDP@US-tubes. The studies have demonstrated the ability of the US-tube platform to promote the delivery of encapsulated CDDP by increasing the accumulation of drug in breast cancer resistance cells, which reveals how CDDP@US-tubes help overcome CDDP resistance.

Epithelial and non-epithelial Ptch1 play opposing roles to regulate proliferation and morphogenesis of the mouse mammary gland.

Patched 1 (Ptch1) has epithelial, stromal and systemic roles in murine mammary gland organogenesis, yet specific functions remain undefined. Cre-recombinase-mediated Ptch1 ablation in mammary epithelium increased proliferation and branching, but did not phenocopy transgenic expression of activated smoothened (SmoM2). The epithelium showed no evidence of canonical hedgehog signaling, and hyperproliferation was not blocked by smoothened (SMO) inhibition, suggesting a non-canonical function of PTCH1. Consistent with this possibility, nuclear localization of cyclin B1 was increased. In non-epithelial cells, heterozygous Fsp-Cre-mediated Ptch1 ablation increased proliferation and branching, with dysplastic terminal end buds (TEB) and ducts. By contrast, homozygous Ptch1 ablation decreased proliferation and branching, producing stunted ducts filled with luminal cells showing altered ovarian hormone receptor expression. Whole-gland transplantation into wild-type hosts or estrogen/progesterone treatment rescued outgrowth and hormone receptor expression, but not the histological changes. Bone marrow transplantation failed to rescue outgrowth. Ducts of Fsp-Cre;Ptch1fl/fl mice were similar to Fsp-Cre;SmoM2 ducts, but Fsp-Cre;SmoM2 outgrowths were not stunted, suggesting that the histology might be mediated by Smo in the local stroma, with systemic Ptch1 required for ductal outgrowth and proper hormone receptor expression in the mammary epithelium.

Wnt-responsive cancer stem cells are located close to distorted blood vessels and not in hypoxic regions in a p53-null mouse model of human breast cancer.

Cancer stem cells (CSCs, or tumor-initiating cells) may be responsible for tumor formation in many types of cancer, including breast cancer. Using high-resolution imaging techniques, we analyzed the relationship between a Wnt-responsive, CSC-enriched population and the tumor vasculature using p53-null mouse mammary tumors transduced with a lentiviral Wnt signaling reporter. Consistent with their localization in the normal mammary gland, Wnt-responsive cells in tumors were enriched in the basal/myoepithelial population and generally located in close proximity to blood vessels. The Wnt-responsive CSCs did not colocalize with the hypoxia-inducible factor 1α-positive cells in these p53-null basal-like tumors. Average vessel diameter and vessel tortuosity were increased in p53-null mouse tumors, as well as in a human tumor xenograft as compared with the normal mammary gland. The combined strategy of monitoring the fluorescently labeled CSCs and vasculature using high-resolution imaging techniques provides a unique opportunity to study the CSC and its surrounding vasculature.

A mystery wrapped in an enigma: Matrigel enhancement of mammary cell growth and morphogenesis.

The analysis of normal mammary morphogenesis is facilitated by the use of mammary fat pad transplantation. The recent experiments on analysis of normal mammary epithelial stem cell activity rely heavily on this technique. In this review, we discuss the known and unknown attributes of using Matrigel in the injection of the mammary epithelial cell suspension. Matrigel greatly increases the "take" frequency of the injected cell suspension; however, there is some uncertainty regarding the interpretation of some of the results. After consideration of these issues, our conclusion is that Matrigel is important in order to obtain rigorous and reproducible results.

Methods for preparing fluorescent and neutral red-stained whole mounts of mouse mammary glands.

Whole mount preparations of mouse mammary glands are useful for evaluating overall changes in growth and morphology, and are essential for detecting and evaluating focal or regionally-localized phenotypes that would be difficult to detect or analyze using other techniques. We present three newly developed methods for preparing whole mounts of mammary glands from genetically-engineered mice expressing fluorescent proteins, as well as using either neutral red or a variety of fluorescent dyes. Unlike traditional hematoxylin- or carmine-stained preparations, neutral red-stained and some fluorescent preparations can be used for several common downstream analyses.

Ptch1 is required locally for mammary gland morphogenesis and systemically for ductal elongation.

Systemic hormones and local growth factor-mediated tissue interactions are essential for mammary gland development. Using phenotypic and transplantation analyses of mice carrying the mesenchymal dysplasia (mes) allele of patched 1 (Ptch1(mes)), we found that Ptch1(mes) homozygosity led to either complete failure of gland development, failure of post-pubertal ductal elongation, or delayed growth with ductal dysplasia. All ductal phenotypes could be present in the same animal. Whole gland and epithelial fragment transplantation each yielded unique morphological defects indicating both epithelial and stromal functions for Ptch1. However, ductal elongation was rescued in all cases, suggesting an additional systemic function. Epithelial function was confirmed using a conditional null Ptch1 allele via MMTV-Cre-mediated disruption. In Ptch1(mes) homozygotes, failure of ductal elongation correlated with diminished estrogen and progesterone receptor expression, but could not be rescued by exogenous ovarian hormone treatment. By contrast, pituitary isografts were able to rescue the ductal elongation phenotype. Thus, Ptch1 functions in the mammary epithelium and stroma to regulate ductal morphogenesis, and in the pituitary to regulate ductal elongation and ovarian hormone responsiveness.