Proliferation Behavior Research Articles

Mathematical Modeling of the Thyroid Regulatory Mechanisms

Mathematical and computational modeling is a promising field in practical study on functioning of regulatory mechanisms (RMs) in live systems at the level of cell communities and tissues. In this article we attempted to describe a computer model to control number of thyroid follicles in both normal conditions and malignancy. The software above was conceived as a computer model to simulate functioning of regulatory mechanisms of a thyroid structural unit, follicular cell community. Prognostic data about cell proliferative behavior, particularly upon alterations taking place as a result of therapeutic effects of external signals, such as, changes in concentrations of thyroxine and triiodothyronine or cytotoxic effects of drugs is of high significance in study on the thyroid pathologies, especially, on malignantly transformed cells of the organ. Both experimental evidence and theoretical data about the thyroid structural – functional organization at the cellular level allow creating mathematical models to quantitavely assess number of a follicular cell community in both normal and abnormal conditions of the basis of the method of live system RM’s modeling and cell community RMs equations.

Unsupervised lineage-based characterization of primate precursors reveals high proliferative and morphological diversity in the OSVZ.

ABSTRACTGeneration of the primate cortex is characterized by the diversity of cortical precursors and the complexity of their lineage relationships. Recent studies have reported miscellaneous precursor types based on observer classification of cell biology features including morphology, stemness, and proliferative behavior. Here we use an unsupervised machine learning method for Hidden Markov Trees (HMTs), which can be applied to large datasets to classify precursors on the basis of morphology, cell‐cycle length, and behavior during mitosis. The unbiased lineage analysis automatically identifies cell types by applying a lineage‐based clustering and model‐learning algorithm to a macaque corticogenesis dataset. The algorithmic results validate previously reported observer classification of precursor types and show numerous advantages: It predicts a higher diversity of progenitors and numerous potential transitions between precursor types. The HMT model can be initialized to learn a user‐defined number of distinct classes of precursors. This makes it possible to 1) reveal as yet undetected precursor types in view of exploring the significant features of precursors with respect to specific cellular processes; and 2) explore specific lineage features. For example, most precursors in the experimental dataset exhibit bidirectional transitions. Constraining the directionality in the HMT model leads to a reduction in precursor diversity following multiple divisions, thereby suggesting that one impact of bidirectionality in corticogenesis is to maintain precursor diversity. In this way we show that unsupervised lineage analysis provides a valuable methodology for investigating fundamental features of corticogenesis. J. Comp. Neurol. 524:535–563, 2016. © 2015 The Authors The Journal of Comparative Neurology Published by Wiley Periodicals, Inc.

Inhibitory effect of vitamin K1 on growth and polyamine biosynthesis of human gastric and colon carcinoma cell lines.

Gastric and colon cancers remain the leading cause of cancer mortality throughout the world. Since the gastrointestinal tract works in a constant link with the external environment, chemoprevention by dietary constituents could represent a possible approach to reduce cancer risk. Dietary vitamin K1 (VK1) has been shown to prevent the growth of many types of cancer cells. However, no data are available on possible different susceptibility to VK1 by gastric or colon neoplastic cell lines. Moreover, the exact mechanism of action of VK1 is still object of investigation, even if it has been reported that VK1 may induce cell cycle arrest and apoptosis. Therefore, molecules affecting cell growth such as the natural polyamines could be of interest in VK1 action. The aim of the present study was to investigate the effects of increasing concentrations of VK1 (from 10 to 200µM) administered up to 72h, on the cell proliferation and apoptosis of a gastric (HGC-27) and a colon (SW480) cancer cell line. Additionally, the polyamine biosynthesis and the MAPK pathway were also examined. VK1 treatments caused an inhibition of cell proliferation and an induction of apoptosis in both cell lines, with a concomitant significant decrease of the polyamine biosynthesis, increased phospho-ERK 1/2 expression was also observed. A different proliferative behavior and a different response to VK1 by gastric and colon cancer cells was evident, with colon cells showing a more pronounced susceptibility to VK1 action. VK1 is safe and without known toxicities in adult humans, consequently it could be effective in prevention and treatment of selected gastrointestinal neoplasms. Protocols based on the use of VK1, along with polyamine inhibitors and/or analogues, could represent a suitable alternative option for improving the efficacy of chemoprevention and treatment in future strategies for gastrointestinal cancer management.

Differences in CART expression and cell cycle behavior discriminate sympathetic neuroblast from chromaffin cell lineages in mouse sympathoadrenal cells.

Adrenal medullary chromaffin cells and peripheral sympathetic neurons originate from a common sympathoadrenal (SA) progenitor cell. The timing and phenotypic changes that mark this lineage diversification are not fully understood. The present study investigated the expression patterns of phenotypic markers, and cell cycle dynamics, in the adrenal medulla and the neighboring suprarenal ganglion of embryonic mice. The noradrenergic marker, tyrosine hydroxylase (TH), was detected in both presumptive adrenal medulla and sympathetic ganglion cells, but with significantly stronger immunostaining in the former. There was intense cocaine and amphetamine-regulated transcript (CART) peptide immunostaining in most neuroblasts, whereas very few adrenal chromaffin cells showed detectable CART immunostaining. This phenotypic segregation appeared as early as E12.5, before anatomical segregation of the two cell types. Cell cycle dynamics were also examined. Initially, 88% of Sox10 positive (+) neural crest progenitors were proliferating at E10.5. Many SA progenitor cells withdrew from the cell cycle at E11.5 as they started to express TH. Whereas 70% of neuroblasts (TH+/CART+ cells) were back in the cell cycle at E12.5, only around 20% of chromaffin (CART negative) cells were in the cell cycle at E12.5 and subsequent days. Thus, chromaffin cell and neuroblast lineages showed differences in proliferative behavior from their earliest appearance. We conclude that the intensity of TH immunostaining and the expression of CART permit early discrimination of chromaffin cells and sympathetic neuroblasts, and that developing chromaffin cells exhibit significantly lower proliferative activity relative to sympathetic neuroblasts.

U0126 inhibits pancreatic cancer progression via the KRAS signaling pathway in a zebrafish xenotransplantation model.

Pancreatic cancer is one of the most aggressive human cancers, and the pharmaceutical outcomes for its treatment remain disappointing. Proper animal models will provide an efficient platform for investigating novel drugs, and the zebrafish has become one of the most promising and comprehensive model animal in cancer research. In the present study, we used a novel xenograft model in zebrafish by transplanting human pancreatic cancer cells to study the progression and metastasis of pancreatic cancer cells and to assay the pharmacological effects of new drug U0126 in vivo. We first established a primary xenograft model of pancreatic cancer by injecting human pancreatic cancer cells into both live larval and adult zebrafish, and then investigated the behaviors of CM-DiI‑labeled human pancreatic cancer cells. Subsequently, we tested the potential of this model for drug screening by evaluating a known small-molecule inhibitor, U0126, which targets the KRAS signaling pathway. Cells with KRAS mutations exhibited significant proliferative and migratory behaviors and invaded the zebrafish vasculature system. In contrast, the proliferation and migration of Mia PaCa-2 cells in zebrafish larvae were substantially repressed following U0126 treatment. These results suggest that zebrafish xenotransplantation can be used as a simple and efficient tool to screen and identify new anti-pancreatic cancer compounds.

CD15 Expression Does Not Identify a Phenotypically or Genetically Distinct Glioblastoma Population.

: Recent research has focused on the hypothesis that the growth and regeneration of glioblastoma (GB) is sustained by a subpopulation of self-renewing stem-like cells. This has led to the prediction that molecular markers for cancer stem cells in GB may provide a treatment target. One candidate marker is CD15: we wanted to determine if CD15 represented a credible stem cell marker in GB. We first demonstrated that CD15-positive (CD15+) cells were less proliferative than their CD15-negative (CD15-) counterparts in 10 patient GB tumors. Next we compared the proliferative activity of CD15+ and CD15- cells in vitro using tumor-initiating primary GB cell lines (TICs) and found no difference in proliferative behavior. Furthermore, TICs sorted for CD15+ and CD15- were not significantly different cytogenetically or in terms of gene expression profile. Sorted single CD15+ and CD15- cells were equally capable of reconstituting a heterogeneous population containing both CD15+ and CD15- cells over time, and both CD15+ and CD15- cells were able to generate tumors in vivo. No difference was found in the phenotypic or genomic behavior of CD15+ cells compared with CD15- cells from the same patient. Moreover, we found that in vitro, cells were able to interconvert between the CD15+ and CD15- states. Our data challenge the utility of CD15 as a cancer stem cell marker. The data from this study contribute to the ongoing debate about the role of cancer stem cells in gliomagenesis. Results showed that CD15, a marker previously thought to be a cancer stem-like marker in glioblastoma, could not isolate a phenotypically or genetically distinct population. Moreover, isolated CD15-positive and -negative cells were able to generate mixed populations of glioblastoma cells in vitro.

Salivary gland homeostasis is maintained through acinar cell self-duplication.

Current dogma suggests that salivary gland homeostasis is stem cell dependent. However, the extent of stem cell contribution to salivary gland maintenance has not been determined. We investigated acinar cell replacement during homeostasis, growth, and regeneration, using an inducible CreER(T2) expressed under the control of the Mist1 gene locus. Genetic labeling, followed by a chase period, showed that acinar cell replacement is not driven by the differentiation of unlabeled stem cells. Analysis using R26(Brainbow2.1) reporter revealed continued proliferation and clonal expansion of terminally differentiated acinar cells in all major salivary glands. Induced injury also demonstrated the regenerative potential of pre-labeled acinar cells. Our results support a revised model for salivary gland homeostasis based predominantly on self-duplication of acinar cells, rather than on differentiation of stem cells. The proliferative capacity of differentiated acinar cells may prove critical in the implementation of cell-based strategies to restore the salivary glands.

Intrapericardial administration of mesenchymal stem cells in a large animal model: a bio-distribution analysis.

The appropriate administration route for cardiovascular cell therapy is essential to ensure the viability, proliferative potential, homing capacity and implantation of transferred cells. At the present, the intrapericardial administration of pharmacological agents is considered an efficient method for the treatment of cardiovascular diseases. However, only a few reports have addressed the question whether the intrapericardial delivery of Mesenchymal Stem Cells (MSCs) could be an optimal administration route. This work firstly aimed to analyze the pericardial fluid as a cell-delivery vehicle. Moreover, the in vivo biodistribution pattern of intrapericardially administered MSCs was evaluated in a clinically relevant large animal model. Our in vitro results firstly showed that, MSCs viability, proliferative behavior and phenotypic profile were unaffected by exposure to pericardial fluid. Secondly, in vivo cell tracking by magnetic resonance imaging, histological examination and Y-chromosome amplification clearly demonstrated the presence of MSCs in pericardium, ventricles (left and right) and atrium (left and right) when MSCs were administered into the pericardial space. In conclusion, here we demonstrate that pericardial fluid is a suitable vehicle for MSCs and intrapericardial route provides an optimal retention and implantation of MSCs.

Sphingosine kinase 2 deficiency increases proliferation and migration of renal mouse mesangial cells and fibroblasts.

Both of the sphingosine kinase (SK) subtypes SK-1 and SK-2 catalyze the production of the bioactive lipid molecule sphingosine 1-phosphate (S1P). However, the subtype-specific cellular functions are largely unknown. In this study, we investigated the cellular function of SK-2 in primary mouse renal mesangial cells (mMC) and embryonic fibroblasts (MEF) from wild-type C57BL/6 or SK-2 knockout (SK2ko) mice. We found that SK2ko cells displayed a significantly higher proliferative and migratory activity when compared to wild-type cells, with concomitant increased cellular activities of the classical extracellular signal regulated kinase (ERK) and PI3K/Akt cascades, and of the small G protein RhoA. Furthermore, we detected an upregulation of SK-1 protein and S1P3 receptor mRNA expression in SK-2ko cells. The MEK inhibitor U0126 and the S1P1/3 receptor antagonist VPC23019 blocked the increased migration of SK-2ko cells. Additionally, S1P3ko mesangial cells showed a reduced proliferative behavior and reduced migration rate upon S1P stimulation, suggesting a crucial involvement of the S1P3 receptor. In summary, our data demonstrate that SK-2 exerts suppressive effects on cell growth and migration in renal mesangial cells and fibroblasts, and that therapeutic targeting of SKs for treating proliferative diseases requires subtype-selective inhibitors.

Control of stem cell self-renewal and differentiation by the heterochronic genes and the cellular asymmetry machinery in Caenorhabditis elegans

Transitions between asymmetric (self-renewing) and symmetric (proliferative) cell divisions are robustly regulated in the context of normal development and tissue homeostasis. To genetically assess the regulation of these transitions, we used the postembryonic epithelial stem (seam) cell lineages of Caenorhabditis elegans. In these lineages, the timing of these transitions is regulated by the evolutionarily conserved heterochronic pathway, whereas cell division asymmetry is conferred by a pathway consisting of Wnt (Wingless) pathway components, including posterior pharynx defect (POP-1)/TCF, APC related/adenomatosis polyposis coli (APR-1)/APC, and LIT-1/NLK (loss of intestine/Nemo-like kinase). Here we explore the genetic regulatory mechanisms underlying stage-specific transitions between self-renewing and proliferative behavior in the seam cell lineages. We show that mutations of genes in the heterochronic developmental timing pathway, including lin-14 (lineage defect), lin-28, lin-46, and the lin-4 and let-7 (lethal defects)-family microRNAs, affect the activity of LIT-1/POP-1 cellular asymmetry machinery and APR-1 polarity during larval development. Surprisingly, heterochronic mutations that enhance LIT-1 activity in seam cells can simultaneously also enhance the opposing, POP-1 activity, suggesting a role in modulating the potency of the cellular polarizing activity of the LIT-1/POP-1 system as development proceeds. These findings illuminate how the evolutionarily conserved cellular asymmetry machinery can be coupled to microRNA-regulated developmental pathways for robust regulation of stem cell maintenance and proliferation during the course of development. Such genetic interactions between developmental timing regulators and cell polarity regulators could underlie transitions between asymmetric and symmetric stem cell fates in other systems and could be deregulated in the context of developmental disorders and cancer.

The Warburg effect: a balance of flux analysis.

Cancer metabolism is characterized by increased macromolecular syntheses through coordinated increases in energy and substrate metabolism. The observation that cancer cells produce lactate in an environment of oxygen sufficiency (aerobic glycolysis) is a central theme of cancer metabolism known as the Warburg effect. Aerobic glycolysis in cancer metabolism is accompanied by increased pentose cycle and anaplerotic activities producing energy and substrates for macromolecular synthesis. How these processes are coordinated is poorly understood. Recent advances have focused on molecular regulation of cancer metabolism by oncogenes and tumor suppressor genes which regulate numerous enzymatic steps of central glucose metabolism. In the past decade, new insights in cancer metabolism have emerged through the application of stable isotopes particularly from 13C carbon tracing. Such studies have provided new evidence for system-wide changes in cancer metabolism in response to chemotherapy. Interestingly, experiments using metabolic inhibitors on individual biochemical pathways all demonstrate similar system-wide effects on cancer metabolism as in targeted therapies. Since biochemical reactions in the Warburg effect place competing demands on available precursors, high energy phosphates and reducing equivalents, the cancer metabolic system must fulfill the condition of balance of flux (homeostasis). In this review, the functions of the pentose cycle and of the tricarboxylic acid (TCA) cycle in cancer metabolism are analyzed from the balance of flux point of view. Anticancer treatments that target molecular signaling pathways or inhibit metabolism alter the invasive or proliferative behavior of the cancer cells by their effects on the balance of flux (homeostasis) of the cancer metabolic phenotype.

Bioengineered Scaffolds for 3D Analysis of Glioblastoma Proliferation and Invasion.

The invasion of malignant glioblastoma (GBM) cells into healthy brain is a primary cause of tumor recurrence and associated morbidity. Here, we describe a high-throughput method for quantitative measurement of GBM proliferation and invasion in three-dimensional (3D) culture. Optically clear hydrogels composed of thiolated hyaluronic acid and gelatin were chemically crosslinked with thiol-reactive poly(ethylene glycol) polymers to form an artificial 3D tumor microenvironment. Characterization of the viscoelasticity and aqueous stability indicated the hydrogels were mechanically tunable with stiffness ranging from 18 Pa to 18.2 kPa and were resistant to hydrolysis for at least 30 days. The proliferation, dissemination and subsequent invasion of U118 and U87R GBM spheroids cultured on the hydrogels were tracked in situ with repeated fluorescence confocal microscopy. Using custom automated image processing, cells were identified and quantified through 500 µm of gel over 14 days. Proliferative and invasive behaviors were observed to be contingent on cell type, gel stiffness, and hepatocyte growth factor availability. These measurements highlight the utility of this platform for performing quantitative, fluorescence imaging analysis of the behavior of malignant cells within an artificial, 3D tumor microenvironment.

The penny pusher: a cellular model of lens growth.

The mechanisms that regulate the number of cells in the lens and, therefore, its size and shape are unknown. We examined the dynamic relationship between proliferative behavior in the epithelial layer and macroscopic lens growth. The distribution of S-phase cells across the epithelium was visualized by confocal microscopy and cell populations were determined from orthographic projections of the lens surface. The number of S-phase cells in the mouse lens epithelium fell exponentially, to an asymptotic value of approximately 200 cells by 6 months. Mitosis became increasingly restricted to a 300-μm-wide swath of equatorial epithelium, the germinative zone (GZ), within which two peaks in labeling index were detected. Postnatally, the cell population increased to approximately 50,000 cells at 4 weeks of age. Thereafter, the number of cells declined, despite continued growth in lens dimensions. This apparently paradoxical observation was explained by a time-dependent increase in the surface area of cells at all locations. The cell biological measurements were incorporated into a physical model, the Penny Pusher. In this simple model, cells were considered to be of a single type, the proliferative behavior of which depended solely on latitude. Simulations using the Penny Pusher predicted the emergence of cell clones and were in good agreement with data obtained from earlier lineage-tracing studies. The Penny Pusher, a simple stochastic model, offers a useful conceptual framework for the investigation of lens growth mechanisms and provides a plausible alternative to growth models that postulate the existence of lens stem cells.

Differential microRNA expression profile comparison between epidermal stem cells and differentiated keratinocytes.

The aim of the current study was to analyze the differential microRNA (miRNA) expression profiles of human epidermal stem cells (ESCs) and differentiated keratinocytes. Enzyme digestion was used in combination with rapid adhesion to collagen IV to isolate primary human ESCs and differentiated keratinocytes, from which total RNA was extracted. Fluorescence labeling, microarray hybridization and differential expression analyses were performed. Reverse transcription quantitative polymerase chain reaction (RT‑qPCR) was performed to validate the reliability of the microarray results and predict the target genes of the differentially expressed miRNAs. A total of 25 miRNAs, including hsa‑miR‑197‑5p, hsa‑miR‑125b‑5p and hsa‑miR‑376a‑3p, were upregulated, whereas 166 miRNAs, including hsa‑miR‑29b‑3p, hsa‑miR‑203 and hsa‑miR‑34a‑3p, were downregulated in the human ESCs compared with the expression in differentiated keratinocytes. RT‑qPCR results confirmed the upregulation of hsa‑miR‑197‑5p and the downregulation of hsa‑miR‑29b‑3p, which were consistent with the microarray results. miRNA target prediction indicated that the miRNA expression levels correlated with cell proliferation, differentiation, apoptosis and senescence. Expression levels of miRNAs significantly differed between human ESCs and differentiated keratinocytes. This finding may be attributed to their biological characteristics, such as proliferative behavior and differentiation abilities.

Transcriptional network analysis reveals that AT1 and AT2 angiotensin II receptors are both involved in the regulation of genes essential for glioma progression.

Gliomas are aggressive primary brain tumors with high infiltrative potential. The expression of Angiotensin II (Ang II) receptors has been associated with poor prognosis in human astrocytomas, the most common type of glioma. In this study, we investigated the role of Angiotensin II in glioma malignancy through transcriptional profiling and network analysis of cultured C6 rat glioma cells exposed to Ang II and to inhibitors of its membrane receptor subtypes. C6 cells were treated with Ang II and specific antagonists of AT1 and AT2 receptors. Total RNA was isolated after three and six hours of Ang II treatment and analyzed by oligonucleotide microarray technology. Gene expression data was evaluated through transcriptional network modeling to identify how differentially expressed (DE) genes are connected to each other. Moreover, other genes co-expressing with the DE genes were considered in these analyses in order to support the identification of enriched functions and pathways. A hub-based network analysis showed that the most connected nodes in Ang II-related networks exert functions associated with cell proliferation, migration and invasion, key aspects for glioma progression. The subsequent functional enrichment analysis of these central genes highlighted their participation in signaling pathways that are frequently deregulated in gliomas such as ErbB, MAPK and p53. Noteworthy, either AT1 or AT2 inhibitions were able to down-regulate different sets of hub genes involved in protumoral functions, suggesting that both Ang II receptors could be therapeutic targets for intervention in glioma. Taken together, our results point out multiple actions of Ang II in glioma pathogenesis and reveal the participation of both Ang II receptors in the regulation of genes relevant for glioma progression. This study is the first one to provide systems-level molecular data for better understanding the protumoral effects of Ang II in the proliferative and infiltrative behavior of gliomas.

On a multiscale model involving cell contractivity and its effects on tumor invasion

Cancer cell migration is an essential feature in the process of tumor spread and establishing of metastasis. It characterizes the invasion observed on the level of the cell population, but it is also tightly connected to the events taking place on the subcellular level. These are conditioning the motile and proliferative behavior of the cells, but are also influenced by it. In this work we propose a multiscale model linking these two levels and aiming to assess their interdependence. On the subcellular, microscopic scale it accounts for integrin binding to soluble and insoluble components present in the peritumoral environment, which is seen as the onset of biochemical events leading to changes in the cell's ability to contract and modify its shape. On the macroscale of the cell population this leads to modifications in the diffusion and haptotaxis performed by the tumor cells and implicitly to changes in the tumor environment. We prove the (local) well posedness of our model and perform numerical simulations in order to illustrate the model predictions.

Proliferative behavior of vaginal fibroblasts from women with pelvic organ prolapse

ObjectivePelvic organ prolapse (POP) significantly impacts quality of life of women, especially with advancing age. Cell proliferation is a critical parameter in both normal and pathophysiological processes. We sought to examine fibroblast proliferation in premenopausal women with and without POP and menopausal women with POP, and examine whether TGF-β1, a fibroblast mitogen, could stimulate proliferation in vaginal fibroblasts from these populations. Study designVaginal wall biopsies were obtained from asymptomatic women (controls) and women with POP (cases). Fibroblasts were cultured from these tissues. Vaginal fibroblasts were treated with or without TGF-β1. Cell proliferation rate (mitotic index) was measured with time-lapse dark-field microscopy. Cell mitosis was counted with ImageJ software after analysis of time-lapse images as Quick time movies. ResultsThere was no significant difference in mitotic index throughout different time points of observation between premenopausal controls and cases of similar ages. However, a significant difference in mitotic index was seen between premenopausal and menopausal cases (p=0.01), with the menopausal group exhibiting significantly lower mitotic indices. When treated with different doses of TGF-β1, premenopausal control fibroblast proliferation increased with 5ng/ml of TGF-β1 compared to non-treated fibroblasts (p=0.04). TGF-β1 stimulation did not affect fibroblasts from either premenopausal or menopausal cases. ConclusionsVaginal fibroblast proliferation decreases with age and this association does not appear to be affected by the presence of pelvic organ prolapse. TGF-β1 stimulation increased cell proliferation of premenopausal control fibroblasts. In contrast, there was no response seen in fibroblasts from premenopausal and menopausal cases.

Abstract 3328: Novel regulation of HER2 degradation and breast cancer cell proliferation by junctional adhesion molecule-a (JAM-A)

Abstract Background: We have previously shown that the adhesion protein Junctional Adhesion Molecule-A (JAM-A) is over-expressed in a population of aggressive and metastatic breast tumours, and that it regulates the migration of breast cells. JAM-dependent regulation of migration could contribute to the likelihood of metastatic disease, since migration is an early event in metastasis. Our objective was to further interrogate the links between JAM-A signalling and markers of disease progression in breast cancer. Approach and Results: Immunohistochemical analysis of JAM-A in two breast cancer tissue microarrays (TMA) revealed that high JAM-A expression correlated significantly with HER2 protein expression, ERnegativity, high grade breast cancers and aggressive luminal B, HER2 and basal subtypes of breast cancer. Using LCC1 and MCF7-HER2 cells which co-express high levels of JAM-A and HER2, we silenced the gene expression of each one in order to examine potential consequences for protein expression of the other. Knockdown of HER2 had no effect on JAM-A protein levels, but knockdown of JAM-A significantly reduced the protein expression of HER2 and its downstream pro-survival effector pAkt. Accordingly, JAM-A knockdown increased apoptosis via a pathway involving Akt activation, as evidenced by apoptosis normalisation upon pharmacological inhibition of Akt. The expressional regulation of HER2 and pAkt by JAM-A was sensitive to inhibition by the proteasomal inhibitor MG132, suggesting that JAM-A regulates the proteasomal degradation of HER2. Finally, over-expression of wild-type JAM-A was sufficient to significantly enhance proliferative and migratory behaviour in breast cell lines. Conclusions: Our results are consistent with a model whereby JAM-A expression inhibits the proteasomal degradation of HER2, facilitating a pro-survival phenotype through increased Akt activity. Therefore JAM-A antagonists may have future therapeutic value in the treatment of breast tumours overexpressing HER2. Citation Format: Kieran Brennan, Elaine A. McSherry, Lance Hudson, Elaine W. Kay, Leonie S. Young, Arnold DK Hill, Ann M. Hopkins. Novel regulation of HER2 degradation and breast cancer cell proliferation by junctional adhesion molecule-a (JAM-A). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3328. doi:10.1158/1538-7445.AM2014-3328

Different neural crest populations exhibit diverse proliferative behaviors.

The rate of proliferation of cells depends on the proportion of cycling cells and the frequency of cell division. Here, we describe in detail methods for quantifying the proliferative behavior of specific cell types in situ, and use the method to examine cell cycle dynamics in two neural crest derivatives--dorsal root ganglia (DRG) using frozen sections, and the enteric nervous system (ENS) using wholemount preparations. In DRG, our data reveal a significant increase in cell cycle length and a decrease in the number of cycling Sox10+ progenitor cells at E12.5-E13.5, which coincides with the commencement of glial cell generation. In the ENS, the vast majority of Sox10+ cells remain proliferative during embryonic development, with only relatively minor changes in cell cycle parameters. Previous studies have identified proliferating cells expressing neuronal markers in the developing ENS; our data suggest that most cells undergoing neuronal differentiation in the developing gut commence expression of neuronal markers during G2 phase of their last division. Combined with previous studies, our findings show that different populations of neural crest-derived cells show tissue-specific patterns of proliferation.

P17.87 * ENDOGENOUS NEURAL PRECURSOR CELLS ACCUMULATE AT METASTATIC BRAIN TUMORS AND TROPISM OF PRECURSOR CELLS IS INDUCED BY TUMOR-RELEASED VEGF-A

OBJECTIVE: Data from transgenic mouse models show that neuronal progenitor cells (NPCs) can migrate towards experimental brain tumors and modulate the course of pathology. However, the pathways attracting NPCs to CNS neoplasms were unknown and it was unexplored if NPCs migrate towards metastatic brain tumors in humans. METHODS: We analyzed the tumor-parenchyma interface of neurosurgical resections for the presence of (NPCs) and distinguished these physiological cells from the tumor mass ( by fluorescence in situ hybridization, FISH). Also, we performed experiments with transgenic mouse models, cell-culture (primary NPC- and glioma cultures of human and murine origin), cell migration assays and immunohistochemistry. RESULTS: We observed that PSA-NCAM-positive NPCs accumulate at CNS metastases. These metastatic tumors are distinguished from neural cells by defined sets of markers. Transplanting murine glioma cells embedded in a cell impermeable hollow fiber capsule into the brains of nestin-gfp reporter mice shows that diffusible factors are sufficient to induce a neurogenic reaction. In vitro, vascular endothelial growth factor (VEGF) secreted from glioma cells increases the migratory and proliferative behavior of adult human brain derived neural stem and progenitor cells via stimulation of VEGF receptor-2 (VEGFR-2). In vivo, inhibiting VEGFR-2 signaling with a function-blocking antibody leads to a reduction in NPC migration in response to tumors. CONCLUSION: Overall, our data reveal a mechanism for NPC attraction to CNS tumors and suggest that NPCs accumulate in human high-grade astrocytomas.