Mesenchymal contribution to early oesophageal tumour formation

Cancer is a deadly disease that forms and evolves as genetic alterations accumulate in our bodies. Constant exposure to our increasingly polluted environment leads to the accumulation of mutations in our DNA. These mutations alter the way our cells behave favouring cancer formation and disease progression.

Recent findings have suggested that mutations are not the sole cause of cancer and that other surrounding mutant-free cells, such as mesenchymal cells normally acting as supporting cells, also contribute to tumour formation from the earliest stages of the disease. Given that mesenchymal cells are thought to be more stable when compared to the ever-changing tumour cells, understanding the mechanisms by which they contribute to cancer formation and progression may represent an ideal opportunity to identify ways to intervene cancer in the clinic.

Despite this, very little is known as to how these supporting mesenchymal cells regulate tumour cell behaviour in the earliest stages of the disease, and the relevance of this cellular cross-talk for cancer progression. This project will use a recently characterised model of early tumour formation (Alcolea, Nat Cell Biol 2014; Frede, Nat Cell Biol, 2016). This model uses a cancer inducing agent found in cigarette smoke to induce discrete tumour lesions in the mouse oesophagus that can be detected from as early as 10 cells in size. Those are nascent tumours that can be visualized and analysed at a stage significantly earlier than those detected in the clinic, opening the possibility to understand the earliest stages of this devastating disease.

In the current proposal I set up to exploit this unique model system to understand how mesenchymal cells contribute to changes in tumour cells and their relevance for disease progression. To do that, I will use genetic tools to mark and visualize cells during the earliest stages of tumour formation. In addition, mechanisms regulating this process will be investigated by studying the molecular signatures of the different cell types, and validated by using a novel 3D ex vivo model designed to recapitulate in vivo tumour formation.

Cancer has traditionally been thought to form and evolve as genetic mutations accumulate, altering cell behaviour and ultimately leading to invasion and death. Recent findings have shown that the contribution of non-cell autonomous components, such as the tumour microenvironment, also play an essential role in the etiopathology of the disease. Mesenchymal fibroblasts, the main cellular component of the stroma in most cancers, have not only been involved in tumour initiation and progression, but have also shown potential prospects for cancer therapeutics. Despite this, very little is known as to how mesenchymal cells regulate epithelial cell behaviour in the earliest stages leading to tumour formation, and the relevance of this cross-talk for cancer progression. Using diethylnitrosamine, a nitrosamine found in cigarette smoke, I have recently developed a model of early tumorigenesis in the mouse oesophagus (Alcolea, Nat Cell Biol 2014). This model recapitulates the appearance of sporadic mutations that accumulate in human carcinogenesis, and creates discrete tumoral lesions identifiable as early as 10 cells in size. In the current proposal I set up to exploit this unique system to dissect epithelial and mesenchymal cross-talk in early neoplasia. To answer this question, I will combine my expertise in in vivo single cell lineage tracing together with transcriptional network analysis to investigate spatio-temporal changes in mesenchymal cell behaviour, and how these changes correlate with alterations in epithelial cell fate during tumour formation. Further mechanistic insights and potential therapeutic relevance will be gained by using an organotypic culture system specifically designed to recapitulate oesophageal cell behaviour ex vivo. Outputs from these studies will provide druggable targets to test their translational potential in preclinical models.

Therapeutic approaches targeting cancer cells have often shown limited efficacy, with development of drug resistance and relapse. The aim of this proposal is to understand how tumour cells interact with their supporting neighbouring cells to determine their relevance for tumour formation and to identify alternative therapeutic strategies that may synergise and potentiate existing ones.

Who might benefit from this research?

The primary aim of this proposal is to benefit the patients and public health system. Pharmacological companies will also benefit from the potential identification of novel drug targets.

This work will advance our understanding in early tumour formation in squamous epithelial tissues such as the oesophagus. Of note, oesophageal models reveal lesions as early as 10 cells in size. Critically, by focussing on these early events we have the unique opportunity to better understand the complex cellular heterogeneity found in tumours, and the molecular networks driving disease progression. Identifying critical networks controlling cellular communication in these heterogeneous populations will ultimately provide a list of actionable targets of potential diagnostic or therapeutic value for the clinic.

How might they benefit from this research?

The proposed research will be focussed at understanding molecular networks involved in communication between tumour cells and mesenchymal cells, the major cellular component of the tumour supporting tissue. Validation of the relevance of targets for which drug inhibitors are available will be performed to produce a list of actionable targets, contributing towards drug target discovery. Most commercial companies use in vitro long passaged cell lines in their studies. This reveals little about the attributes of the cells in vivo, losing their dependence on environmental signals that are of critical relevance in an in vivo setting. One strength of this proposal is the use of an in vivo approach allowing the cellular communication networks to be explored in situ, i.e in the native environment.

Furthermore, we combine our in vivo approaches with a newly developed factor free 3D organotypic culture system that recapitulates the behaviour of epithelial cells in vitro. The peculiarity of this 3D system is that epithelial cells easily reconstruct the epithelial architecture without the need of exogenous matrixes, known to influence cell behaviour. It, therefore, constitutes a simple and cost effective protocol that lends itself to develop scalable and translatable assays to study human disease requiring minimal tissue input. This newly developed system ultimately offers a more physiological platform to test new drug targets, something that would reduce drug costs benefiting patients and the public health system.