Ductal Tree Research Articles

Subclinical focal cholangitis mimicking liver metastasis in asymptomatic patients with history of pancreatic ductal adenocarcinoma and biliary tree intervention

BackgroundCholangitis is an inflammatory process of the biliary tract with a wide range of clinical manifestations and it is not always considered in the differential diagnosis in asymptomatic patients. To the best of our knowledge there is no previous report in the English literature of focal cholangitis manifesting exclusively as liver parenchymal changes mimicking liver metastasis in asymptomatic patients with pancreatic ductal adenocarcinoma (PDAC) and history of manipulation of the biliary tree. The purpose of this article is to present six cases of subclinical focal cholangitis mimicking liver metastasis in asymptomatic patients with history of PDAC and biliary tree intervention.Case presentationThere are six cases with new hepatic lesions detected on follow-up scans in asymptomatic patients with history of PDAC and manipulation of biliary tree. Overall seven lesions were detected, all of them were on the liver periphery, five were hypovascular and two were hypervascular. None of those patients had elevation of CA 19.9 compared with the previous exams. The three patients that had magnetic resonance imaging presented restriction on diffusion weighted imaging and high signal intensity on T2-weighted image. Two patients underwent liver biopsy, which showed only inflammatory changes. All patients were treated with antibiotics and underwent imaging follow-up, which demonstrated resolution of the lesions. None of the patients showed imaging or clinical signs of disease progression during this interval.ConclusionRadiologists and oncologists need to be aware of the possibility of focal cholangitis causing hepatic lesions mimicking neoplasia in patients with history of biliary tree intervention, even in the absence of clinical symptoms.

Islet inflammation and ductal proliferation may be linked to increased pancreatitis risk in type 2 diabetes

Pancreatitis is more frequent in type 2 diabetes mellitus (T2DM), although the underlying cause is unknown. We tested the hypothesis that ongoing β cell stress and apoptosis in T2DM induces ductal tree proliferation, particularly the pancreatic duct gland (PDG) compartment, and thus potentially obstructs exocrine outflow, a well-established cause of pancreatitis. PDG replication was increased 2-fold in human pancreas from individuals with T2DM, and was associated with increased pancreatic intraepithelial neoplasia (PanIN), lesions associated with pancreatic inflammation and with the potential to obstruct pancreatic outflow. Increased PDG replication in the prediabetic human-IAPP-transgenic (HIP) rat model of T2DM was concordant with increased β cell stress but preceded metabolic derangement. Moreover, the most abundantly expressed chemokines released by the islets in response to β cell stress in T2DM, CXCL1, -4, and -10, induced proliferation in human pancreatic ductal epithelium. Also, the diabetes medications reported as potential modifiers for the risk of pancreatitis in T2DM modulated PDG proliferation accordingly. We conclude that chronic stimulation and proliferation of the PDG compartment in response to islet inflammation in T2DM is a potentially novel mechanism that serves as a link to the increased risk for pancreatitis in T2DM and may potentially be modified by currently available diabetes therapy.

In vivo reprogramming of non-mammary cells to an epithelial cell fate is independent of amphiregulin signaling

AREG-/- mice demonstrate impaired mammary development and form only rudimentary ductal epithelial trees, however, AREG-/- glands are still capable of undergoing alveologenesis and lactogenesis during pregnancy. Transplantation of AREG-/- mammary epithelial cells into cleared mouse mammary fat pads results in a diminished capacity for epithelial growth (∼15%) as compared to wild type mammary epithelial cells. To determine whether ERα and/or AREG signaling were necessary for non-mammary cell redirection, we inoculated either ERα-/- or AREG-/- mammary cells with non-mammary progenitor cells (WapCre/Rosa26LacZ+ male testicular cells or GFP+ embryonic neuronal stem cells). ERα-/- cells possessed a limited ability to grow or reprogram non-mammary cells in transplanted mammary fat pads. AREG-/- mammary cells were capable of redirecting both types of non-mammary cell populations to mammary phenotypes in regenerating mammary outgrowths. Transplantation of fragments from AREG-reprogrammed chimeric outgrowths resulted in secondary outgrowths in 6 out of 10 fat pads, demonstrating the self-renewing capacity of the redirected non-mammary cells to contribute new progeny to chimeric outgrowths. Nestin was detected at the leading edges of developing alveoli suggesting its expression may be essential for lobular expansion.

Abstract 1046: Conditional knockout of N-Myc and STAT Interactor disrupts normal mammary development and enhances metastatic ability of mammary tumors

Abstract The process of development requires a delicate balance between plasticity and differentiation. This balance is disrupted in cancer initiation and progression, ultimately ending in metastasis and plummeting rates of patient survival. Recent findings from our lab have revealed that protein expression of evolutionarily conserved, N-Myc and STAT Interactor (NMI) is decreased in 70% of primary patient specimens with metastatic breast cancer. To study how Nmi loss facilitates metastatic behavior and gain insight into its role in normal mammary biology, we created a novel mammary specific Nmi knock out mouse model, which we then challenged with carcinogen and oncogene induced tumorigenesis. Our studies show that Nmi is induced at the onset of pregnancy and its expression remains throughout lactation. Furthermore, prolactin stimulation and differentiation of HC11 murine mammary epithelial cells is accompanied by up-regulation of Nmi. STAT5 is the downstream effector of prolactin and is essential for differentiation of secretory alveolar epithelium. NMI interacts with STAT5 and this interaction appears to be critical to normal differentiation of mammary epithelium. Indeed, loss of Nmi in vivo caused a decrease in STAT5 activity and a subsequent transcriptomic shift in mammary epithelial and breast cancer cells. Moreover, knockdown of Nmi in HC11 cells impedes the expression of beta-casein upon differentiation with prolactin. Concurrently, Nmi knock out alveoli exhibit an extensive presence of nuclear beta-catenin, a mediator of stem cell maintenance in the mammary gland. As a result, mice exhibit an increased number of alveoli and more proliferating mammary epithelial cells (MECs). The Nmi knock out pubertal ductal tree extends into the mammary fat pad at an accelerated rate and exhibits enhanced terminal end bud numbers, a phenotype that mirrors mice altered for Wnt signaling. Tumors derived from Nmi null mammary epithelium contain significantly more cells with stem and progenitor markers, indicating that these tumors are less differentiated than their littermate counterparts. In addition, Nmi null mammary tumors exhibit invasive morphology as well as enhanced distant metastasis. We observe that conditional Nmi loss disrupts differentiation in the mammary gland and promotes the progression of tumors with aggressive metastatic characteristics. Citation Format: Hawley Christine Pruitt, Brandon J. Metge, Shannon E. Weeks, Dongquan Chen, Shi Wei, Lalita A. Shevde, Rajeev S. Samant. Conditional knockout of N-Myc and STAT Interactor disrupts normal mammary development and enhances metastatic ability of mammary tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1046. doi:10.1158/1538-7445.AM2017-1046

Inhibition of ubiquitin-specific protease 34 (USP34) induces epithelial-mesenchymal transition and promotes stemness in mammary epithelial cells

Ubiquitin-specific protease 34 (USP34) is a deubiquitinating enzyme that regulates Axin stability and plays a critical role in Wnt/β-catenin signaling. We sought to investigate the role of USP34 on epithelial-mesenchymal (EMT) induction and its effects on mammary epithelial stem cells. USP34 expression levels were relatively lower in MDA-MB-231 and 4T1 mesenchymal-like cells when compared to epithelial-like cells. Inhibition of USP34 in NMuMG cells induced EMT, as evidenced by the upregulation of EMT markers including N-cadherin, phospho-Smad3, Snail and active-β-catenin, as well as the downregulation of Axin 1 and E-cadherin. USP34 knockdown (KD) in these cells also resulted in the acquisition of invasive behavior, and promoted stemness as indicated by enhanced mammosphere-forming ability, concomitant with the upregulation of Nanog, Oct4 and Sox2 mRNA expression. Endogenous USP34 expression was observed to be at low levels in virgin mouse mammary glands in vivo. When USP34-KD cells were transplanted into the cleared mammary fat pads (CFP) of mice, these cells reconstituted the mammary gland with ductal tree development within 3months. Our findings suggest a previously unknown role for USP34 in mammary gland development.

Diagnosis of Nipple Discharge: Value of Magnetic Resonance Imaging and Ultrasonography in Comparison with Ductoscopy.

Background:Pathologic nipple discharge, which is a common reason for referral to the breast imaging service, refers to spontaneous or bloody nipple discharge that arises from a single duct. The most common cause of nipple discharge is benign breast lesions, such as solitary intraductal papilloma and papillomatosis. Nevertheless, in rare cases, a malignant cause of nipple discharge can be found.Aims:To study the diagnostic value of ultrasonography, magnetic resonance imaging, and ductoscopy in patients with pathologic nipple discharge, compare their efficacy, and investigate the importance of magnetic resonance imaging in the diagnosis of intraductal pathologies.Study Design:Diagnostic accuracy study.Methods:Fifty patients with pathologic nipple discharge were evaluated by ultrasonography and magnetic resonance imaging. Of these, 44 ductoscopic investigations were made. The patients were classified according to magnetic resonance imaging, ultrasonography, and ductoscopy findings. A total of 25 patients, whose findings were reported as intraductal masses, underwent surgery oincluding endoscopic excision for two endoscopic excision. Findings were compared with the pathology results that were accepted as the gold standard in the description of the aetiology of nipple discharge. In addition, magnetic resonance imaging, ultrasonography and ductoscopy findings were analysed comparatively in patients who had no surgery.Results:Intraductal masses were reported in 26 patients, 20 of whom operated and established accurate diagnosis of 18 patients on magnetic resonance imaging. According to the ultrasonography, intraductal masses were identified in 22 patients, 17 of whom underwent surgery. Ultrasonography established accurate diagnoses in 15 patients. Intraductal mass was identified in 22 patients and ductoscopy established accurate diagnoses based on histopathologic results in 16 patients. The sensitivities of methods were 75% in ultrasonography, 90% in magnetic resonance imaging, and 94.6% in ductoscopy. The specificities were 66.7% in ultrasonography, 66.7% in magnetic resonance imaging, and 40% in ductoscopy. Intraductal papillomas were mostly observed as oval nodules with well-circumscribed smooth margins within dilated ducts and persistant in the dynamic analysis. Lesions that protruded into the lumen of the ducts, either solitary or multiple, were characteristic ductoscopy findings of our patients who were diagnosed as having papilloma/papillomatosis.Conclusion:Magnetic resonance imaging and ductoscopy had no statistical superiority over each other, however they were superior to ultrasonography in the diagnosis of pathologic nipple discharge. Magnetic resonance imaging may be highly sensitive for diagnosing nipple discharge with new techniques and sequences and a non-invasive method that more advantageous for showing ductal tree visualization and is able to detect completely obstructed intraductal lesions.

The mouse mammary gland as a sentinel organ: distinguishing \u2018control\u2019 populations with diverse environmental histories

BackgroundThere are numerous examples of laboratory animals that were inadvertently exposed to endocrine disrupting chemicals (EDCs) during the process of conducting experiments. Controlling contaminations in the laboratory is challenging, especially when their source is unknown. Unfortunately, EDC contaminations can interfere with the interpretation of data during toxicological evaluations. We propose that the male CD-1 mouse mammary gland is a sensitive bioassay to evaluate the inadvertent contamination of animal colonies.MethodsWe evaluated mammary glands collected from two CD-1 mouse populations with distinct environmental histories. Population 1 was born and raised in a commercial laboratory with unknown EDC exposures; Population 2 was the second generation raised in an animal facility with limited exposures to xenoestrogens from caging, feed, etc. Mammary glands were collected from all animals and evaluated using morphometric techniques to quantify morphological characteristics of the mammary gland.ResultsPopulation 1 (with suspected history of environmental chemical exposure) and Population 2 (with known limited history of xenoestrogen exposure) were morphologically distinguishable in adult males, prepubertal females, and pubertal females. Mammary glands from males raised in the commercial animal facility were significantly more developed, with larger ductal trees and more branching points. The appearance of these mammary glands was consistent with prior reports of male mice exposed to low doses of bisphenol A (BPA) during early development. In females, the two populations were morphologically distinct at both prepuberty and puberty, with the most striking differences observed in the number, size, and density of terminal end buds, e.g. highly proliferative structures found in the developing mammary gland.ConclusionsCollectively, these results suggest that the mouse mammary gland has the potential to be used as a sentinel organ to evaluate and distinguish animal colonies raised in different environmental conditions including potential EDC exposures. Our findings could help researchers that wish to perform a posteriori evaluations to determine whether inadvertent contamination with xenoestrogens (and potentially other EDCs) has occurred in their animal colonies, especially after new materials (feed, caging, water bottles) have been introduced. Finally, our results challenge the relatively common practice of using historical controls in toxicological experiments.

Intraductal Delivery to the Rabbit Mammary Gland.

Localized intraductal treatments for breast cancer offer potential advantages, including efficient delivery to the tumor and reduced systemic toxicity and adverse effects1,2,3,4,5,6,7. However, several challenges remain before these treatments can be applied more widely. The development and validation of intraductal therapeutics in an appropriate animal model facilitate the development of intraductal therapeutic strategies for patients. While the mouse mammary gland has been widely used as a model system of mammary development and tumorigenesis, the anatomy is distinct from the human gland. A larger animal model, such as the rabbit, may serve as a better model for mammary gland structure and intraductal therapeutic development. In contrast to mice, in which ten ductal trees are spatially distributed along the body axis, each terminating in a separate teat, the rabbit mammary gland more closely resembles the human gland, with multiple overlapping ductal systems that exit through separate openings in one teat. Here, we present minimally invasive methods for the delivery of reagents directly into the rabbit mammary duct and for visualization of the delivery itself with high-resolution ultrasound imaging.

Abstract P4-05-01: Diet, development and predisposition to breast cancer: The impact of sugar derived metabolites (AGEs) on pubertal mammary gland development

Abstract The mammary gland is one of the few organs that continues to develop postnatally through stages including puberty, pregnancy, lactation, and involution. The gland is composed of epithelial and stromal cells that include fibroblasts, adipocytes, endothelial cells, nerve cells, and macrophages. Terminal end bud (TEB) structures are found exclusively in the pubertal developmental stage. The formation of TEBs and side branching drives mammary gland epithelial cell invasion into the mammary fat pad, continuing until the entire fat pad is filled. Pubertal mammary gland morphogenesis integrates a balance of epithelial cell proliferation, differentiation, and apoptosis. Several studies have shown that the interaction between mammary epithelial and stromal cells is crucial for the proper postnatal development of the mammary ductal tree. Interestingly, studies have shown that processes important in mammary gland development are often deregulated during breast cancer tumorigenesis. Thus, understanding the complex signaling network as well as the interactions between the different cell types during mammary gland development will be vital for elucidating the mechanisms underlying breast cancer progression and metastasis. Glycation is the non-enzymatic glycosylation of sugar moieties to biological macromolecules such as protein and DNA which produces reactive metabolites known as advanced glycation end products (AGE's). AGE content in the Western Diet has consistently increased over the last 50 years due to increased consumption of sugar laden and cheap processed/manufactured foods which are high in reactive AGE metabolites. AGE containing food can lead to the accumulation of AGEs in the body overtime leading to pro-inflammatory and pro-oxidant effects when signaling through receptor for advanced glycation end products (RAGE). Leading too many complications associated with diseases including diabetes, Alzheimer's, heart disease and cancer. Preliminary data in our lab has shown that AGEs also have an effect on phosphorylation and signaling of estrogen receptor α (ERα), a key receptor and signaling pathway in the regulation of mammary gland development during puberty. This observation, together with the links between diet, mammary gland development and immune cell recruitment lead us to examine the biological effects of a diet high in AGEs on pubertal mammary gland development in mice. We observed a significant disruption of normal pubertal mammary gland development in mice fed a high AGE diet when compared to mice fed a control diet. Mice fed the high AGE diet showed increases in TEB number as well as width, length and area. We also observed an increase in ductal branching and a decrease in ductal extension. Future studies will assess the role of macrophage recruitment to the developing gland, specifically around the TEBs based on its reported role in normal TEB function. We also plan to assess ERa signaling in mice fed the high AGE diet based on the reported role of estrogen signaling in ductal elongation. Citation Format: Krisanits BA, Nogueira LM, Findlay VJ, Turner DP. Diet, development and predisposition to breast cancer: The impact of sugar derived metabolites (AGEs) on pubertal mammary gland development [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-05-01.

In vivo reprogramming of non-mammary cells to an epithelial cell fate is independent of amphiregulin signaling.

Amphiregulin (AREG)-/- mice demonstrate impaired mammary development and form only rudimentary ductal epithelial trees; however, AREG-/- glands are still capable of undergoing alveologenesis and lactogenesis during pregnancy. Transplantation of AREG-/- mammary epithelial cells into cleared mouse mammary fat pads results in a diminished capacity for epithelial growth (∼15%) as compared to that of wild-type mammary epithelial cells. To determine whether estrogen receptor α (ERα, also known as ESR1) and/or AREG signaling were necessary for non-mammary cell redirection, we inoculated either ERα-/- or AREG-/- mammary cells with non-mammary progenitor cells (WAP-Cre/Rosa26LacZ+ male testicular cells or GFP-positive embryonic neuronal stem cells). ERα-/- cells possessed a limited ability to grow or reprogram non-mammary cells in transplanted mammary fat pads. AREG-/- mammary cells were capable of redirecting both types of non-mammary cell populations to mammary phenotypes in regenerating mammary outgrowths. Transplantation of fragments from AREG-reprogrammed chimeric outgrowths resulted in secondary outgrowths in six out of ten fat pads, demonstrating the self-renewing capacity of the redirected non-mammary cells to contribute new progeny to chimeric outgrowths. Nestin was detected at the leading edges of developing alveoli, suggesting that its expression may be essential for lobular expansion.

Gallbladder Carcinoma Presenting with Manubrium Metastasis: A Rare Phenomenon

Gallbladder carcinoma is the 5th most common malignancy of the gastrointestinal tract. Symptoms in the early stages are similar to other benign diseases and thus it is rarely diagnosed early. Distant metastasis to bone is uncommon with the most common sites of metastasis being regional lymph nodes, liver parenchyma, peritoneum, and lungs. A 78-year-old female with past medical history of hypertension, gastroesophageal reflux disease, and complete heart block with a dual chamber pacemaker presented with chest pain that developed after PO intake. The pain typically lasted for 30 minutes and was associated with increased belching, bloating, and mild constipation. Patient was a former smoker and had moderate alcohol use. Physical exam showed no jaundice, abdominal tenderness, or palpable masses. Labs showed AST 19 U/L, ALT 16 U/L, total bilirubin 0.7 mg/dL and elevated ALP at 123 U/L. Patient's recent cardiac stress test showed no ischemia. Abdominal ultrasound showed common bile duct dilatation at 1.5 cm and a hypoechoic mass-like area in the neck of the gallbladder suspicious for a gallbladder mass. Hepatobiliary (HIDA) scan revealed an abnormal function response to cholecystokinin (CCK) with an ejection fraction of 8.7%. General surgery was consulted and a diagnostic laparoscopic cholecystectomy was performed. A thickened gallbladder wall was found and pathology was sent, which resulted positive for poorly differentiated adenocarcinoma of the gallbladder. Computed tomography (CT) chest ordered for staging showed a 3 cm mass with bony destruction involving the left manubrium. Interventional radiology performed ultrasound-guided biopsy of the left manubrium, which revealed metastatic moderately differentiated adenocarcinoma with mucinous features. Positron emission tomography (PET) scan showed increased FDG uptake within the cervical and thoracic spine and sternum and hypermetabolic lymph nodes. Magnetic resonance cholangiopancreatography (MRCP) showed mild intra and extrahepatic biliary ductal dilation but no filling defects, strictures, or masses were identified in the biliary ductal tree. The patient ultimately refused further treatment, including chemotherapy, and was discharged with home hospice. Although rare, gallbladder carcinoma can present with chest pain secondary to bone metastasis. Further work-up should be considered in patients presenting with chest pain of unknown etiology and associated gastrointestinal symptoms.Figure 1Figure 2

A hybrid agent-based model of the developing mammary terminal end bud

Mammary gland ductal elongation is spearheaded by terminal end buds (TEBs), where populations of highly proliferative cells are maintained throughout post-pubertal organogenesis in virgin mice until the mammary fat pad is filled by a mature ductal tree. We have developed a hybrid multiscale agent-based model to study how cellular differentiation pathways, cellular proliferation capacity, and endocrine and paracrine signaling play a role during development of the mammary gland. A simplified cellular phenotypic hierarchy that includes stem, progenitor, and fully differentiated cells within the TEB was implemented. Model analysis finds that mammary gland development was highly sensitive to proliferation events within the TEB, with progenitors likely undergoing 2–3 proliferation cycles before transitioning to a non-proliferative phenotype, and this result is in agreement with our previous experimental work. Endocrine and paracrine signaling were found to provide reliable ductal elongation rate regulation, while variations in the probability a new daughter cell will be of a proliferative phenotype were seen to have minimal effects on ductal elongation rates. Moreover, the distribution of cellular phenotypes within the TEB was highly heterogeneous, demonstrating significant allowable plasticity in possible phenotypic distributions while maintaining biologically relevant growth behavior. Finally, simulation results indicate ductal elongation rates due to cellular proliferation within the TEB may have a greater sensitivity to upstream endocrine signaling than endothelial to stromal paracrine signaling within the TEB. This model provides a useful tool to gain quantitative insights into cellular population dynamics and the effects of endocrine and paracrine signaling within the pubertal terminal end bud.

Quantitative Assessment of Mouse Mammary Gland Morphology Using Automated Digital Image Processing and TEB Detection.

The assessment of rodent mammary gland morphology is largely used to study the molecular mechanisms driving breast development and to analyze the impact of various endocrine disruptors with putative pathological implications. In this work, we propose a methodology relying on fully automated digital image analysis methods including image processing and quantification of the whole ductal tree and of the terminal end buds as well. It allows to accurately and objectively measure both growth parameters and fine morphological glandular structures. Mammary gland elongation was characterized by 2 parameters: the length and the epithelial area of the ductal tree. Ductal tree fine structures were characterized by: 1) branch end-point density, 2) branching density, and 3) branch length distribution. The proposed methodology was compared with quantification methods classically used in the literature. This procedure can be transposed to several software and thus largely used by scientists studying rodent mammary gland morphology.

Abstract A27: An in vivo gain-of-function screening identified the Williams-Beuren syndrome gene GTF2IRD1 as a mammary tumor promoter

Abstract Precision medicine has shown great efficacy in oncology, but its broad application requires a full understanding of the cancer genome. We have performed the first gain-of-function screening in mice to functionally identify candidates from a “druggable” gene set for their roles in breast cancer. We transduced mammary gland stem/progenitor cells isolated from MMTV-ErbB2 transgenic mice with a lentiviral cDNA library and implanted them into the cleared fat pads of syngeneic recipients. The transplanted mammary gland cells formed a normal mammary ductal tree within 6 weeks. After another 8 months latency, small lesions were detected along the mammary ducts in mice harboring cells that had been transduced with the lentiviral library. We isolated genomic DNA from these lesions to amplify any lentiviral cDNA sequences within the lesions and identified individual genes by sequencing. Gain-of-function of five genes, including RET, GTF2IRD1, ADORA1, LARS2, and DPP8, was found to promote mammary tumor growth consistently. We further studied one novel tumor promoting gene, transcription factor GTF2IRD1. GTF2IRD1 regulates the expression of multiple genes in the mammary gland system, including OPN, TβR2, and BMPR1b. In tissue culture, high levels of GTF2IRD1 inhibited cell proliferation but increased the colony formation ability of the un-transformed mammary gland cell line MCF10A. In mice, the mis-regulation of GTF2IRD1, OPN, TβR2, and BMPR1b, also individually promoted mammary cancer development. Silencing of TβR2 delayed the incidence of tumor formation by GTF2IRD1. We also found that GTF2IRD1 is highly expressed in human breast tumors, correlating with high tumor grades and poor prognosis. In conclusion, we performed the first gain-of-function screening in vivo for breast cancer promoting genes. All candidate genes from this study are potential drug targets to treat cancer. We showed that GTF2IRD1 promotes breast cancer development in mice through regulation of its downstream targets, and correlates clinically with high tumor grades and poor prognosis. We believe our in vivo screening method is readily expandable to whole genome annotation of cancer genes. Citation Format: Yongliang Huo, Yinghao Su, Qiuyin Cai, Ian Macara. An in vivo gain-of-function screening identified the Williams-Beuren syndrome gene GTF2IRD1 as a mammary tumor promoter. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr A27.

Abstract PR03: GLUT1 is required for induction of mammary tumorigenesis by activated ErbB2/HER2/Neu

Abstract Alterations in tumor cell metabolism have been investigated for decades, and include changes in glucose utilization, as well as changes in mitochondrial and fatty acid metabolism; however, it is unclear at what point during the process of tumorigenesis these metabolic changes occur. We hypothesized that elevated glucose uptake represents the first metabolic adaptation to transformation, and thus may be a target for the prevention of breast cancer. The GLUT1 transporter is expressed in breast cancer cells and is responsible for the majority of their glucose uptake. Not surprisingly, breast cancer patients with high levels of GLUT1 have a poorer clinical outcome than those with lower levels, likely due to the association between glucose uptake and high tumor grade. We previously showed that the reduction of GLUT1 in established tumor cells resulted in a 50% decrease in glucose consumption and lactate generation. There was a corresponding decrease in proliferation in both two and three-dimensional culture, and in tumor growth in immunodeficient mice. Mammary epithelial cells from GLUT1fl/fl mice were transformed using polyoma middle tumor antigen (PyMT), and GLUT1 excised using Cre recombinase. Cells expressing GLUT1 were tumorigenic in immunodeficient mice, while cells lacking GLUT1 were not tumorigenic. This suggests that in mammary epithelial cells transformed in vitro, loss of GLUT1 was sufficient to prevent tumor outgrowths when injected into the mammary fat pad of nude mice. This indicates that GLUT1 and by extension glucose, are critical at an early stage of mammary tumorigenesis. To test the hypothesis that elevated glucose uptake is required very early in the process of tumor formation, we crossed the MMTV-NIC (NIC) mice, which contain activated NeuNT, an internal ribosome entry site (IRES), and Cre recombinase, to mice bearing floxed alleles of GLUT1, and monitored tumor development. All of the control MMTV-NIC mice developed tumors in less than 200 days. In contrast, none of the NIC-GLUT1fl/fl mice developed mammary tumors even after eighteen months. We anticipated that loss of one allele of GLUT1 would significantly delay mammary tumorigenesis; however, we did not observe any tumors in these mice, even at eighteen months of age. Tumors that formed in the NIC mice were typical Neu-dependent tumors observed in similar transgenic mice with a high proliferative index (38% by Ki67 staining), and there was evidence of preneoplastic lesions in the non tumor-bearing mammary glands. Small Cre-positive lesions were also positive for GLUT1 indicating GLUT1 expression increases very early in Neu-mediated tumorigenesis. The mammary ductal tree developed normally in NIC-Glut1fl/fl and NIC-Glut1fl/+ mice. Mammary glands from mice lacking one allele of GLUT1 had increased epithelial content and higher proliferative index, compared to mice lacking both Glut1 alleles; however, no palpable tumors ever formed in either group. These results suggest that loss of a single allele of GLUT1 is sufficient to suppress Neu-induced mammary tumorigenesis and that there is an absolute requirement for GLUT1 at the earliest stages of tumorigenesis. Citation Format: Elizabeth A. Wellberg, Angelo D'Allessandro, Andrew S. Lewis, Kristina Terrell, E. Dale Abel, William A. Muller, Kirk A. Hansen, Steven M. Anderson. GLUT1 is required for induction of mammary tumorigenesis by activated ErbB2/HER2/Neu. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr PR03.

Light and Electron Microscopic Studies on Prenatal Differentiation of Exocrine Pancreas in Buffalo.

The study was conducted on pancreas of 24 buffalo fetuses collected from abattoir and Veterinary clinics, GADVASU, Ludhiana. The buffalo fetuses were divided into three groups after measuring their CVRL, namely, group I (CVRL between 0 and 20 cm), group II (CVRL above 20 cm and up to 40 cm), and group III (CVRL above 40 cm) and their approximate age was calculated. The tissues were processed for light and ultrastructural studies. In group I, at 1.2 cm CVRL (34 days), the pancreas comprised tubules and solid nest of undifferentiated epithelial cells. At 7.5 cm CVRL (63 days) acinar cells with zymogen granules were observed. These acinar cells varied in shape from columnar to pyramidal. At 12.8 cm CVRL (86 days), parenchyma began to organize into lobes and lobules. The centroacinar cells were observed at 12.8 cm CVRL (86 days). In group II, at 28.3 cm CVRL (137 days), there was extensive branching of tubules that resulted in highly branched ductal tree connecting exocrine secretary units to the duct system. The interlobular and intralobular ducts were well observed at this age yet the intercalated ducts were not completely developed. In group III, exocrine pancreas showed a massive growth at 48 cm CVRL (182 days) with distinct pancreatic lobes and lobules. At 54 cm CVRL (195 days), well developed pancreatic architecture was seen with the presence of extensive development of exocrine part organized in lobes and lobules with interlobular and intralobular ducts whereas the intercalated ducts were observed in 80 cm CVRL (254 days).

Reawakening the Duct Cell Progenitor?

The generation of new -cells from progenitors is an area of immense research interest in diabetes, given the potential not only for therapeutic -cell replacement by transplantation but also regeneration of endogenous -cells. Defining the progenitors that serve as sources of new -cells in vivo has been an area of considerable debate and research effort (1, 2). Replication of existing -cells has been shown to be an important source of new -cells in rodents throughout life, in health and in response to injury (3). Evidence for transdifferentiation of non-cells, including -cells (4) and pancreatic acinar cells (5, 6) has also emerged in rodents. Most studies have employed models of -cell regeneration after severe -cell loss or pancreatic injury, potentially inducing “facultative” stem cell differentiation, leaving questions as to the importance of these putative progenitors in a physiological context. Pancreatic ductal cells have perhaps received the most interest and study as a potential -cell progenitor. Lineage tracing studies in mice in which carbonic anhydrase-expressing (and therefore likely ductal) cells were marked, provided persuasive evidence that ductal cells can differentiate into -cells in mice after ductal ligation (7), but limitations to such studies, such as the fidelity of the carbonic anhydrase promoter, raised questions that have lingered for a number of years. Although numerous histological studies have shown islets in close association with ducts, and are suggestive that new islets originate from ducts (8) and in response to -cell loss, there have been near as many reports that do not support the idea that ductal cells can give rise to -cells in adult mice (9, 10). An innovative whole-mount imaging approach with 3-dimensional reconstruction employed by El-Gohary et al in this issue of Endocrinology (11) sheds new light on this debate and provides compelling evidence that, at least under certain conditions, pancreatic duct cells can give rise to -cells postnatally. Using whole-mount immunostaining, small ducts were found to reside within the islets, and moreover these intraislet ducts appear to arise from larger pancreatic ducts outside of the islet. Importantly, wholemount imaging of a limited number of young human pancreas samples demonstrated the presence of intraislet ducts in humans as well. The presence of these intraislet ducts was highly age dependent in both mice and humans, peaking in mice at about 5 weeks of age, and being most prevalent in 1-2 month-old human sample. Notably these are times when -cell genesis is high. Somewhat surprisingly, -cell regeneration induced after partial pancreatectomy did not increase the number of intraislet ducts, at least in older (10-wk-old) mice. Building on their earlier finding that TGF may inhibit -cell neogenesis (12), the authors performed partial pancreatectomy in transgenic mice in which TGF signaling is suppressed by constitutive expression of a dominant negative TGF -type II receptor. This transgenic mouse model phenocopied the young mouse with extensive intraislet ducts and allowed El-Gohary et al to carry out lineage tracing to provide further support for their assertion that -cells can arise from ductal cells. For these studies, the pancreatic ductal tree of a Cre-reporter mouse line was infused with an adeno-associated virus serotype 6 virus expressing Cre recombinase under control of the “ductal” Sox9 promoter. After partial pancreatectomy, insulinpositive cells were observed to be lineage labeled, supporting their conclusion that -cells can be derived by neogenesis from pancreatic ductal cells.

Intraislet Pancreatic Ducts Can Give Rise to Insulin-Positive Cells.

A key question in diabetes research is whether new β-cells can be derived from endogenous, nonendocrine cells. The potential for pancreatic ductal cells to convert into β-cells is a highly debated issue. To date, it remains unclear what anatomical process would result in duct-derived cells coming to exist within preexisting islets. We used a whole-mount technique to directly visualize the pancreatic ductal network in young wild-type mice, young humans, and wild-type and transgenic mice after partial pancreatectomy. Pancreatic ductal networks, originating from the main ductal tree, were found to reside deep within islets in young mice and humans but not in mature mice or humans. These networks were also not present in normal adult mice after partial pancreatectomy, but TGF-β receptor mutant mice demonstrated formation of these intraislet duct structures after partial pancreatectomy. Genetic and viral lineage tracings were used to determine whether endocrine cells were derived from pancreatic ducts. Lineage tracing confirmed that pancreatic ductal cells can typically convert into new β-cells in normal young developing mice as well as in adult TGF-β signaling mutant mice after partial pancreatectomy. Here the direct visual evidence of ducts growing into islets, along with lineage tracing, not only represents strong evidence for duct cells giving rise to β-cells in the postnatal pancreas but also importantly implicates TGF-β signaling in this process.

Progenitor potential of nkx6.1-expressing cells throughout zebrafish life and during beta cell regeneration.

BackgroundIn contrast to mammals, the zebrafish has the remarkable capacity to regenerate its pancreatic beta cells very efficiently. Understanding the mechanisms of regeneration in the zebrafish and the differences with mammals will be fundamental to discovering molecules able to stimulate the regeneration process in mammals. To identify the pancreatic cells able to give rise to new beta cells in the zebrafish, we generated new transgenic lines allowing the tracing of multipotent pancreatic progenitors and endocrine precursors.ResultsUsing novel bacterial artificial chromosome transgenic nkx6.1 and ascl1b reporter lines, we established that nkx6.1-positive cells give rise to all the pancreatic cell types and ascl1b-positive cells give rise to all the endocrine cell types in the zebrafish embryo. These two genes are initially co-expressed in the pancreatic primordium and their domains segregate, not as a result of mutual repression, but through the opposite effects of Notch signaling, maintaining nkx6.1 expression while repressing ascl1b in progenitors. In the adult zebrafish, nkx6.1 expression persists exclusively in the ductal tree at the tip of which its expression coincides with Notch active signaling in centroacinar/terminal end duct cells. Tracing these cells reveals that they are able to differentiate into other ductal cells and into insulin-expressing cells in normal (non-diabetic) animals. This capacity of ductal cells to generate endocrine cells is supported by the detection of ascl1b in the nkx6.1:GFP ductal cell transcriptome. This transcriptome also reveals, besides actors of the Notch and Wnt pathways, several novel markers such as id2a. Finally, we show that beta cell ablation in the adult zebrafish triggers proliferation of ductal cells and their differentiation into insulin-expressing cells.ConclusionsWe have shown that, in the zebrafish embryo, nkx6.1+ cells are bona fide multipotent pancreatic progenitors, while ascl1b+ cells represent committed endocrine precursors. In contrast to the mouse, pancreatic progenitor markers nkx6.1 and pdx1 continue to be expressed in adult ductal cells, a subset of which we show are still able to proliferate and undergo ductal and endocrine differentiation, providing robust evidence of the existence of pancreatic progenitor/stem cells in the adult zebrafish. Our findings support the hypothesis that nkx6.1+ pancreatic progenitors contribute to beta cell regeneration. Further characterization of these cells will open up new perspectives for anti-diabetic therapies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0179-4) contains supplementary material, which is available to authorized users.

Spontaneous Pancreatitis Caused by Tissue-Specific Gene Ablation of Hhex in Mice.

Background & AimsPerturbations in pancreatic ductal bicarbonate secretion cause chronic pancreatitis. The physiologic mechanism of ductal secretion is known, but its transcriptional control is not. We determine the role of the transcription factor hematopoietically expressed homeobox protein (Hhex) in ductal secretion and pancreatitis.MethodsWe derived mice with pancreas-specific, Cre-mediated Hhex gene ablation to determine the requirement of Hhex in the pancreatic duct in early life and in adult stages. Histologic and immunostaining analyses were used to detect the presence of pathology. Pancreatic primary ductal cells were isolated to discover differentially expressed transcripts upon acute Hhex ablation on a cell autonomous level.ResultsHhex protein was detected throughout the embryonic and adult ductal trees. Ablation of Hhex in pancreatic progenitors resulted in postnatal ductal ectasia associated with acinar-to-ductal metaplasia, a progressive phenotype that ultimately resulted in chronic pancreatitis. Hhex ablation in adult mice, however, did not cause any detectable pathology. Ductal ectasia in young mice did not result from perturbation of expression of Hnf6, Hnf1β, or the primary cilia genes. RNA-seq analysis of Hhex-ablated pancreatic primary ductal cells showed mRNA levels of the G-protein coupled receptor natriuretic peptide receptor 3 (Npr3), implicated in paracrine signaling, up-regulated by 4.70-fold.ConclusionsAlthough Hhex is dispensable for ductal cell function in the adult, ablation of Hhex in pancreatic progenitors results in pancreatitis. Our data highlight the critical role of Hhex in maintaining ductal homeostasis in early life and support ductal hypersecretion as a novel etiology of pediatric chronic pancreatitis.