Deciphering the molecular mechanism of Wnt trafficking in gastric cancer

Lead Research Organisation: University of Exeter
Department Name: Biosciences

Abstract

Keeping the gastrointestinal lining in a stable state is fundamental because deregulation can lead to devastating diseases such as gastric cancer (GC). Indeed, world-wide 700,000 cases are diagnosed per year and GC is the third most cancer. However, there is a fundamental gap in our knowledge about the biology of the gastrointestinal tract in its healthy and diseased states. This is reflected by the relatively low number of targeted therapies available to treat GC. There is an urgent need to understand the molecular and cellular events regulating gastric homeostasis, and how these are altered during gastric carcinogenesis.

An important family of signalling proteins keeping balance in the gastrointestinal tract is the Wnt signalling family. Wnts regulate many vital cellular processes: Wnts can, for instance, determine how fast cells divide (cellular proliferation); Wnts can dictate the fate of cells (cellular differentiation); and Wnts can control movement of cells (cellular migration). Wnt signalling is therefore fundamental to tissue growth, wound healing, and regeneration in the digestive tract. Aberrant Wnt signalling has been linked to many cancers. The recent cancer atlas has placed the Wnt signalling network at centre stage in GC initiation and progression. Therefore, it is important to understand the Wnt signalling pathway to develop novel strategies to fight GC.

The activation of the Wnt signalling cascade depends on the availability of extracellular Wnt signalling proteins. Wnt proteins are produced and distributed from small, defined cell groups. Adjacent, larger groups of cells then respond to the signal by, for example, increased proliferation. Proper activation of the network is therefore largely dependent on the precise delivery of Wnt proteins from producing cells to a population of responding cells. Currently, we do not understand how Wnt proteins are transported between cells and this proposal aims to address this significant gap in understanding. Recent work by the Principal Investigator has revealed the existence of an unexpected transport mechanism for Wnt proteins. Specific finger-like cell membrane protrusions transport Wnt proteins to neighbouring cells and control Wnt signal activation therein. Impairments in the formation of these signalling protrusions has severe consequences during tissue development - target cells do not follow their correct cellular fate according to their position in a tissue, leading to malformation and uncontrolled growth of tissues.

The central hypothesis of this project is that deregulation of Wnt trafficking promotes initiation and growth of GC tumours.
We hypothesize that the number of these "signalling cell fingers" is crucial for the amplitude of Wnt signal activation. The greater the number of cellular protrusions, the greater is the number of Wnt proteins in a particular tissue, and the faster is tissue growth. Decrease of Wnt transport by blockage of signalling protrusion would reduce tissue growth. To address these hypotheses, we will use state-of-the-art genetic strategies combined with advanced imaging techniques of cancer cells in 2D and in 3D tissue culture approaches.
We have an international lead in this area because we have developed the required techniques to test this new hypothesis. We will (1) study extracellular Wnt trafficking, (2) analyse the molecular mechanisms regulating Wnt transport, and (3) screen for chemicals to manipulate Wnt trafficking in GC.

This fundamental new knowledge will provide the basis to control the activity of Wnt signalling cascades in GC tumour biology in a radically different way, by manipulating Wnt protein transport.

Technical Summary

There is an urgent need to understand the cellular signalling network because it is fundamental to the maintenance of a stable state of mature tissue. Deregulation of this network leads to devastating diseases such as the initiation and growth of tumours. The Wnt signalling pathway contributes to this important signalling network and aberrant activation of Wnt signalling is a major driver of gastric cancer growth and metastasis.

Despite three decades of Wnt research, we are still not able to explain how Wnt ligands are disseminated in a tissue, which is a prerequisite to control the Wnt network effectively during disease. Recently, our work has revealed the existence of an unexpected transport mechanism for Wnt proteins, which changes the way we understand how ligands spread in tissues: Wnt is rapidly loaded on thin cellular extensions to be transferred to target cells for signal activation. However, the mechanism controlling Wnt signalling protrusions is currently unknown. By closing this gap in our understanding of Wnt transport, we will enable the development of novel approaches to control Wnt signalling in malignancies like gastric cancer.

This project will provide new understandings of extracellular Wnt protein trafficking at the molecular, cellular and tissue level. Our hypothesis, supported by preliminary data, is that activating the Wnt pathway in the Wnt producing cells reinforces formation of signal protrusions and thus Wnt signal activation in the neighbouring tissue. This will enable us to understand how Wnt signalling spreads through the tissue to induce proliferation in GC. To test our hypothesis, we will analyse the mechanism of Wnt trafficking and analyse the effect of drugs that limit Wnt signalling protrusions to control tumour growth.

The results of this multiscale, multidisciplinary project will provide a step change in understanding how the Wnt signalling pathway operates in gastric cancer.

Planned Impact

This is a discovery science project with a clear focus on applied science. We aim to generate new knowledge regarding cell-cell communication in gastric tumours. This project is timely because it will answer a major unresolved question in signalling biology in gastric cancer. Currently, we have an international lead because the hypothesis to be tested is novel and the team has developed the techniques to test it thoroughly. The project will have an immediate impact on the following beneficiaries and users with specific targeting and tailored activities.

(1) Academic community: The results generated will be of immediate interest to scientists working in cell and cancer biology. The project will generate a set of cell biological data, receptor-ligand measurements, and imaging data in gastric cancer as well as several mutant and transgenic zebrafish lines. All of the information will be made freely available and lines will be archived both locally and at the European Zebrafish Resource Centre.

(2) Industrial partners: We envisage significant impact on the pharmaceutical industry where there is a current focus on manipulating extracellular signalling to prevent gastric cancer and other chronic diseases. This will provides a completely new strategy for cancer treatment. Furthermore, the results will be of interest to the microscopy industry in the field of super-resolution. The impact of research from this project will be realised through effective partnership with the relevant commercial sectors. The PI has a strong track record of industrial research, i.e. collaborative training programmes such as the EMBO microscopy workshop in 2013 supported by Leica and Bitplane. At the start of the project, the PI will meet the University of Exeter IP & Commercialisation manager within the Innovation, Impact and Business Team to agree a strategy to protect and manage intellectual property and potential commercialisation opportunities that may emerge from the project. A plan will be agreed within the first 6 months of the project, so that potential patent filing can be carried out ahead of publication, as detailed in the plan.

(3) Training for highly skilled researchers: Full training will be provided to the PDRA, the MRC DTP funded PhD student and the research technician in this project in specific skill development in cancer biology, live cell imaging, and cell signalling, in addition to knowledge exchange and intellectual property management. Both co-workers will receive training in Wnt biology, genome editing, high-resolution microscopy & spectroscopy, data processing and bioinformatics. Training will also be provided in data presentation, analysis, the writing of scientific papers and career development. The PDRA and the MRC DTP funded PhD student will have the opportunity to present the work at national and international meetings.

(4) Wider public: Cell-cell communication and cancer biology are topics with a long history of captivating public interest and attention, and have great potential to inspire the wider public about science and learning. The concepts are readily understandable, easy to demonstrate, and benefit from being highly visual. The PI has a wide range of experience dealing with media i.e. contributions to radio, newspaper, and through generation of YouTube videos. Furthermore, results of PI's projects and interesting materials (i.e. pictures, videos) are regularly disseminated via Facebook and Twitter to a wide audience. The PI is fully committed to develop the public understanding of science and will undertake communications through the popular press, as well as social media. Engagement activities with the University of the 3rd Age (U3A) will continue to take place twice per year as described. U3A engagement activities include lectures and hands-on investigative activities for retired people.

Publications

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Rosenbauer J (2020) Modeling of Wnt-mediated tissue patterning in vertebrate embryogenesis. in PLoS computational biology

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Routledge D (2019) Mechanisms of intercellular Wnt transport in Development

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Zhang C (2019) Cytonemes in development. in Current opinion in genetics & development