Louisa Windus

Lamellipodia mediate the heterogeneity of central olfactory ensheathing cell interactions

The growth and guidance of primary olfactory axons are partly attributed to the presence of olfactory ensheathing cells (OECs). However, little is understood about the differences between the subpopulations of OECs and what regulates their interactions. We used OEC-axon assays and determined that axons respond differently to peripheral and central OECs. We then further purified OECs from anatomically distinct regions of the olfactory bulb. Cell behaviour assays revealed that OECs from the olfactory bulb were a functionally heterogeneous population with distinct differences which is consistent with their proposed roles in vivo. We found that the heterogeneity was regulated by motile lamellipodial waves along the shaft of the OECs and that inhibition of lamellipodial wave activity via Mek1 abolished the ability of the cells to distinguish between each other. These results demonstrate that OECs from the olfactory bulb are a heterogeneous population that use lamellipodial waves to regulate cell–cell recognition.

Motile membrane protrusions regulate cell–cell adhesion and migration of olfactory ensheathing glia

Olfactory ensheathing cells (OECs) are candidates for therapeutic approaches for neural regeneration due to their ability to assist axon regrowth in central nervous system lesion models. However, little is understood about the processes and mechanisms underlying migration of these cells. We report here that novel lamellipodial protrusions, termed lamellipodial waves, are integral to OEC migration. Time‐lapse imaging of migrating OECs revealed that these highly dynamic waves progress along the shaft of the cells and are crucial for mediating cell–cell adhesion. Without these waves, cell–cell adhesion does not occur and migrational rates decline. The activity of waves is modulated by both glial cell line‐derived neurotrophic factor and inhibitors of the JNK and SRC kinases. Furthermore, the activity of lamellipodial waves can be modulated by Mek1, independently of leading edge activity. The ability to selectively regulate cell migration via lamellipodial waves has implications for manipulating the migratory behavior of OECs during neural repair.

Olfactory glia enhance neonatal axon regeneration

Olfactory ensheathing cells (OECs) migrate with olfactory axons that extend from the nasal epithelium into the olfactory bulb. Unlike other glia, OECs are thought to migrate ahead of growing axons instead of following defined axonal paths. However it remains unknown how the presence of axons and OECs influences the growth and migration of each other during regeneration. We have developed a regeneration model in neonatal mice to examine whether (i) the presence of OECs ahead of olfactory axons affects axonal growth and (ii) the presence of olfactory axons alters the distribution of OECs. We performed unilateral bulbectomy to ablate olfactory axons followed by methimazole administration to further delay neuronal growth. In this model OECs filled the cavity left by the bulbectomy before new axons extended into the cavity. We found that delaying axon growth increased the rate at which OECs filled the cavity. The axons subsequently grew over a significantly larger region and formed more distinct fascicles and glomeruli in comparison with growth in animals that had undergone only bulbectomy. In vitro, we confirmed (i) that olfactory axon growth was more rapid when OECs were more widely distributed than the axons and (ii) that OECs migrated faster in the absence of axons. These results demonstrate that the distribution of OECs can be increased by repressing by growth of olfactory axons and that olfactory axon growth is significantly enhanced if a permissive OEC environment is present prior to axon growth.

Stimulation of olfactory ensheathing cell motility enhances olfactory axon growth

Axons of primary olfactory neurons are intimately associated with olfactory ensheathing cells (OECs) from the olfactory epithelium until the final targeting of axons within the olfactory bulb. However, little is understood about the nature and role of interactions between OECs and axons during development of the olfactory nerve pathway. We have used high resolution time-lapse microscopy to examine the growth and interactions of olfactory axons and OECs in vitro. Transgenic mice expressing fluorescent reporters in primary olfactory axons (OMP-ZsGreen) and ensheathing cells (S100ß-DsRed) enabled us to selectively analyse these cell types in explants of olfactory epithelium. We reveal here that rather than providing only a permissive substrate for axon growth, OECs play an active role in modulating the growth of pioneer olfactory axons. We show that the interactions between OECs and axons were dependent on lamellipodial waves on the shaft of OEC processes. The motility of OECs was mediated by GDNF, which stimulated cell migration and increased the apparent motility of the axons, whereas loss of OECs via laser ablation of the cells inhibited olfactory axon outgrowth. These results demonstrate that the migration of OECs strongly regulates the motility of axons and that stimulation of OEC motility enhances axon extension and growth cone activity.

Copper, nickel, and zinc cyclam-amino acid and cyclam-peptide complexes may be synthesized with "click" chemistry and are noncytotoxic

We describe the synthesis of cyclam metal complexes derivatized with amino acids or a tripeptide using a copper(I)-catalyzed Huisgen click reaction. The linker triazole formed during the synthesis plays an active coordinating role in the complexes. The reaction conditions do not racemize the amino acid stereocenters. However, a methylene group adjacent to the triazole is susceptible to H/D exchange under ambient conditions, an observation which has potentially important implications for structures involving stereocenters adjacent to triazoles in click-derived structures. The successful incorporation of several amino acids is described, including reactive tryptophan and cysteine side chains. All complexes are formed rapidly upon introduction of the relevant metal salt, including synthetically convenient cases where trifluoroacetate salts of cyclam derivatives are used directly in the metalation. None of the metal complexes displayed any cytotoxicity to mammalian cells, suggesting that the attachment of such complexes to amino acids and peptides does not induce toxicity, further supporting their potential suitability for labeling/imaging studies. One Cu(II)-cyclam-triazole-cysteine disulfide complex displayed moderate activity against MCF-10A breast nontumorigenic epithelial cells.

In vivo biomarker expression patterns are preserved in 3D cultures of Prostate Cancer

Here we report that Prostate Cancer (PCa) cell-lines DU145, PC3, LNCaP and RWPE-1 grown in 3D matrices in contrast to conventional 2D monolayers, display distinct differences in cell morphology, proliferation and expression of important biomarker proteins associated with cancer progression. Consistent with in vivo growth rates, in 3D cultures, all PCa cell-lines were found to proliferate at significantly lower rates in comparison to their 2D counterparts. Moreover, when grown in a 3D matrix, metastatic PC3 cell-lines were found to mimic more precisely protein expression patterns of metastatic tumour formation as found in vivo. In comparison to the prostate epithelial cell-line RWPE-1, metastatic PC3 cell-lines exhibited a down-regulation of E-cadherin and α6 integrin expression and an up-regulation of N-cadherin, Vimentin and β1 integrin expression and re-expressed non-transcriptionally active AR. In comparison to the non-invasive LNCaP cell-lines, PC3 cells were found to have an up-regulation of chemokine receptor CXCR4, consistent with a metastatic phenotype. In 2D cultures, there was little distinction in protein expression between metastatic, non-invasive and epithelial cells. These results suggest that 3D cultures are more representative of in vivo morphology and may serve as a more biologically relevant model in the drug discovery pipeline.

Bone-stromal cells up-regulate tumourigenic markers in a tumour-stromal 3D model of prostate cancer

BackgroundThe cellular and molecular mechanisms that mediate interactions between tumour cells and the surrounding bone stroma are to date largely undetermined in prostate cancer (PCa) progression. The purpose of this study was to evaluate the role of alpha 6 and beta 1 integrin subunits in mediating tumour-stromal interactions.MethodsUtilising 3D in vitro assays we evaluated and compared 1. Monocultures of prostate metastatic PC3, bone stromal derived HS5 and prostate epithelial RWPE-1 cells and 2. Tumour-stromal co-cultures (PC3u2009+u2009HS5) to ascertain changes in cellular phenotype, function and expression of metastatic markers.ResultsIn comparison to 3D monocultures of PC3 or HS5 cells, when cultured together, these cells displayed up-regulated invasive and proliferative qualities, along with altered expression of epithelial-to-mesenchymal and chemokine protein constituents implicated in metastatic dissemination. When co-cultured, HS5 cells were found to re-express N-Cadherin and chemokine receptor CXCR7. Alterations in N-Cadherin expression were found to be mediated by soluble factors secreted by PC3 tumour cells, while chemokine receptor re-expression was dependent on direct cell-cell interactions. We have also shown that integrins beta 1 and alpha 6 play an integral role in maintaining cell homeostasis and mediating expression of E-Cadherin, N-Cadherin and vimentin, in addition to chemokine receptor CXCR7.ConclusionsCollectively our results suggest that both PC3 and HS5 cells provide a “protective” and reciprocal milieu that promotes tumour growth. As such 3D co-cultures may serve as a more complex and valid biological model in the drug discovery pipeline.

Chemokine receptor expression on integrin-mediated stellate projections of prostate cancer cells in 3D culture

The chemokine receptor CXCR7 has emerged as a regulator of prostate tumor growth and invasion, along with the well-established role of its closely related receptor, CXCR4, and their shared ligand, SDF-1α. Consequently, inhibition of the CXCR7/CXCR4/SDF-1α axis may assist in controlling prostate tumor growth and progression. To facilitate the development of potential therapeutics, further clarification of CXCR7 function is required, specifically in relation to CXCR4. In this study, we report that CXCR7 and CXCR4 were co-expressed in LNCaP, DU145 and PC3 cell lines in 2D culture. When cultured in 3D using Matrigel, a marked up-regulation of both receptors was observed in PC3 cells. Interestingly, both CXCR7 and CXCR4 co-localized within radiating cellular structures, termed stellate projections, which protruded outward into the matrix. The stellate projections were rich in the expression of pro-invasive integrin β1, β-laminin and MMP-11 proteins. The development of the stellate projections was mediated by integrin β1-mediated interactions with the ECM, which also regulated the expression of CXCR7 and CXCR4. Taken together, these results demonstrate that integrin-mediated cell-ECM interactions can modulate tumor cell morphology, and regulate the expression of chemokine receptors which are associated with the invasive phenotype and progression of PCa.

PCaAnalyser: A 2D-Image Analysis Based Module for Effective Determination of Prostate Cancer Progression in 3D Culture

Three-dimensional (3D) in vitro cell based assays for Prostate Cancer (PCa) research are rapidly becoming the preferred alternative to that of conventional 2D monolayer cultures. 3D assays more precisely mimic the microenvironment found in vivo, and thus are ideally suited to evaluate compounds and their suitability for progression in the drug discovery pipeline. To achieve the desired high throughput needed for most screening programs, automated quantification of 3D cultures is required. Towards this end, this paper reports on the development of a prototype analysis module for an automated high-content-analysis (HCA) system, which allows for accurate and fast investigation of in vitro 3D cell culture models for PCa. The Java based program, which we have named PCaAnalyser, uses novel algorithms that allow accurate and rapid quantitation of protein expression in 3D cell culture. As currently configured, the PCaAnalyser can quantify a range of biological parameters including: nuclei-count, nuclei-spheroid membership prediction, various function based classification of peripheral and non-peripheral areas to measure expression of biomarkers and protein constituents known to be associated with PCa progression, as well as defining segregate cellular-objects effectively for a range of signal-to-noise ratios. In addition, PCaAnalyser architecture is highly flexible, operating as a single independent analysis, as well as in batch mode; essential for High-Throughput-Screening (HTS). Utilising the PCaAnalyser, accurate and rapid analysis in an automated high throughput manner is provided, and reproducible analysis of the distribution and intensity of well-established markers associated with PCa progression in a range of metastatic PCa cell-lines (DU145 and PC3) in a 3D model demonstrated.

Abstract C50: Regulation of the chemokine receptors CXCR7 and CXCR4 in 3-D culture models of prostate cancer

Abstract CXCR7 was recently identified as the second member of the chemokine receptor family to bind stromal derived factor-1α (SDF-1α), a chemokine which is known to influence the establishment of cancer metastasis. Whilst expression of CXCR7 is highly restricted in non-malignant cells, it is widely expressed in many different tumor cell lines. In prostate cancer, a disease known to be highly regulated by the other SDF-1α -binding receptor CXCR4, CXCR7 has been found to regulate cell growth and invasion. In vivo prostate tumor biopsies show a pattern where CXCR7 expression increases with invasive grade, as previously reported for CXCR4. However, there is limited knowledge on the role of CXCR7 and its function in prostate cancer. In this study, we aim to more thoroughly characterize CXCR7 function across prostate cancer cell lines, in particular its regulation of cell growth and behavior. We will also assess its expression and function in response to its ligands and inhibitors, alongside CXCR4, in order to assess how these receptors are regulated in relation to each other. For this we employ western blotting expression studies, immunocytochemical visualization, and metabolic-based proliferation assays. Further, we will study the regulation of both CXCR7 and CXCR4 in 3D culture models of prostate cancer cell lines. Our preliminary data from 2D culture suggests that less invasive prostate cancer cell lines express higher levels of CXCR7 than more invasive cell lines, contrary to reports in vivo where CXCR7 expression was seen to increase with invasive grade. We have chosen to assess these aspects in 3D cultures of prostate cancer cell lines to determine whether culturing in 3D permits a phenotype more reflective of what has been reported for CXCR7 expression in prostate cancer in vivo. Further elucidation of CXCR7 function with respect to CXCR4 will shed light on how these receptors contribute to regulation of the metastatic process in prostate cancer – a process known to be heavily regulated by CXCR4. As CXCR4 has been established as a therapeutic target in prostate cancer, a more detailed knowledge of the CXCR7 receptor with which it shares a partial redundancy may indicate whether combinatorial therapies may be more effective in combating prostate cancer progression. Citation Format: Debra L. Kiss, Louisa CE Windus, Vicky M. Avery. Regulation of the chemokine receptors CXCR7 and CXCR4 in 3-D culture models of prostate cancer [abstract]. In: Proceedings of the AACR Special Conference on Advances in Prostate Cancer Research; 2012 Feb 6-9; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2012;72(4 Suppl):Abstract nr C50.