Stochastic fluctuations during mammary development and breast cancer morphogenesis

We all know from everyday experience that parts of our body can have slightly different shapes. Some of this variance is due to differences in genes, but some is also due to natural variability. This variability, where the same genetic program within cells can lead to slightly different results, arises from random (stochastic) physical processes in cells. Although determined by the same genetic program, healthy and diseased organs show a variety of shapes and forms. At present the variability exhibited by tissues is not well understood. In this proposal we will quantify and analyse the stochasticity underlying the adoption of three-dimensional shapes by multicellular structures. We anticipate that our work will identify fundamental principles governing organ and cancer development.

Part of the variability that we intend to explore arises from how cells exert forces and interact mechanically with each other, and part of it arises from the dynamics of stem cells. Cells use their cytoskeleton, an internal architecture capable of exerting forces, to move relative to each other. In addition, stem cells ensure that tissues function properly by dividing and giving rise to different cell types. For example, stem cells replace damaged cells during the repair of injured organs. Also in cancer there are stem cells, so call cancer stem cells, and these cancer stem cells (CSC) are believed to be required for cancer to spread to other sites in the body (metastasis) and are also linked to the re-emergence of cancer (relapse) after therapy.

It is not currently possible to investigate the position and the behaviour of all cells in a living animal organ. In the last few years it has become possible to culture small organ-like structures and cancers in 3 dimensions, in so-called organoids. The cellular functions and interplay in organoids is very similar to what is observed in a living animal, thus organoids represent a unique system to study the collective behaviour of cells.

Here we will explore how tissue variability in mammary gland organoids arises from mechanical forces exerted by cells on each other, and how stem cells divide and give rise to other cell types. We will look at mammary gland organoids because breast cancer is a very common disease and affects 1 in 7 woman. To do this, we will develop a system to image organoids over a prolonged period of time and use it to investigate where the stem cells are, how they divide, what type of progeny cells they generate, and how stem and progeny cells exert forces inside the organoid, to produce different organ and cancer shapes. This imaging will be performed using a custom-built microscope, and the analysis be performed using sophisticated computational and physical modelling approaches.

We will then use methods from physical sciences and numerical simulations to understand how the uncertainty in cellular behaviour results in variability of tissue shapes. Mathematical tools from theoretical physics allow to connect the behaviour of a physical system at different scales. By using a multidisciplinary approach, we will apply these tools to address the question of organ-scale variability.

The proposed research program would benefit:

- Industry - The proposed work of research will produce a highly-skilled workforce (Postdocs) trained in cutting-edge organoid tissue generation and culture, advanced quantitative microscopy approaches, 3D image segmentation and biophysical modelling of tissues, which will be useful to industry. It is expected that our approach to track the development of an organ and cancer over time may be adopted by other researcher and biotech companies to study their organ or cancer of interest. Facilitating this, the Francis Crick Institute is a discovery research institute oriented towards developing discoveries into future therapies, prevention strategies and diagnostic approaches, exemplified in the Crick strategic aim 'Accelerating Translation for Health and Wealth'. The culture of translation at the Crick is supported by a dedicated Translation Team, complemented by experts from industry, entrepreneurs and investors, who work closely with researchers to ensure early identification and accelerated development of discoveries to achieve impact. The team provides expertise in a range of areas from exploitation of internal technology capability, innovative intellectual property development, to partnering with pharma and biotech.

- Medicine - This research will shed light on the function of stem cells in generating a tissue and a tumour. It is postulated that successful cancer treatment needs to eradicate cancer stem cells (CSCs), and the thorough functional characterisation of CSCs has become a crucial endeavour of cancer biology. Thus we are hopeful that long-term by improving the understanding of CSC biology our research could create new opportunities for cancer treatment.

- General public - through events such as: "Einstein Day" laboratory tours (CD); exhibits at public science festivals such as the Imperial Festival (CD); Crick Lates (AB, GS) as well as the Crick's Science Exhibition space; and giving presentations about our work to lay public, such as Pint of Science talks (https://pintofscience.com/) (CD, GS, AB). These events will engage the public and inform them about stem and cancer cell biology, cutting-edge microscopy and biophysical modelling of tissue. Ultimately, the general public may benefit from new therapies to cancer and other diseases derived from the improved understanding of cancer tissue evolution gained during the project.

- Training and professional development: GS is actively involved in interdisciplinary activities, participating in the teaching of an MSc program at the physics/biology interface through the UCL-based Institute for the Physics of Living Systems (IPLS). CD teaches Physics undergraduates and postgraduates on MSc courses in Optics and Photonics and on Diamond Science and Technology. CD and GS will use these opportunities to communicate to and enthuse students about current research and its impact.

Our work aims to deliver an unprecedented advance in the understanding of tissue growth variability using a multidisciplinary approach. Our objective is that it will contribute substantially to the UK's global leadership in stem cell biology and cancer. This is closely aligned with current policy and priorities across UKRI for supporting multidisciplinary research. It is expected that this proposed multidisciplinary research will be of great interest for the cancer, stem cell, microscopy development, bio-computational, and bio-physical communities nationally and internationally. The fundamental importance of the scientific question, together with our innovative methodology and our proven track record to deliver highest quality multidisciplinary research, will lead to high impact publications in reputable journals and open new avenues of investigation for other researchers. Such exposure will help to ensure significant publicity for EPSRC and the UK in general.