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Effect of heterogeneity of cancer cells on collective invasion

Periodic Reporting for period 1 - HeteroCancerInvasion (Effect of heterogeneity of cancer cells on collective invasion)

Reporting period: 2016-05-01 to 2018-04-30

Cancer tissue is known to be composed of heterogeneous cancer cells and various stromal cells, and these cells are dynamically interacting each other. Although interaction between cancer cells and associated stromal cells in terms of tumour growth and resistance to anticancer drugs had been well studied, our understanding of association between heterogeneous cells in the context of invasion was very limited.
Invasion of cancer cells into neighbouring tissue is a critical first step of metastasis, which is the leading cause of mortality among cancer patients. In the past decade, advanced imaging studies of both cultured cells and cells in living animals had revealed that cancer cells invade either as individually single cell or as well-organised adherent collectives. Extensive studies had provided substantial amount of insight into the molecular mechanism of how single cell moves; how to change their shape, activate the signalling pathway inside of the cells, and regulate cytoskeletal dynamics during migration/invasion. However, our understanding of collective invasion was less advanced. This partly reflected the likelihood that it is not a single invasive behaviour, but a combination of different behaviours. An additional complication was the well-documented heterogeneity of cancer cells even within a single tumour. This diversity may be genetic, epigenetic, related to ‘cancer stem cell’ hierarchies, or caused variation in local environmental cues. Therefore, to understand the process of collective cancer invasion one must consider possible heterogeneity between cancer cells in the cluster. This requires considering concepts such as relative migratory fitness, cell sorting, and cell competition. The objective of this project was to study collective cell migration involving heterogeneous populations of cells by using complementary experimental and computational models of collective cancer cell invasion.
During the contract period, a comprehensive analysis of collective cancer cell invasion was performed with complementary experimental and computational approaches to investigate how interactions between cancer cells, cancer associated fibroblasts (CAFs) and the extracellular matrix (ECM) affect the invasion patterns of squamous cell carcinoma (SCC).

Following is an outline of the main project results:
An up-to-date computational modelling of two settings of collective SCC invasion assay has been developed, which enables us to investigate cellular behaviour with physical parameters that are experimentally unreproducible. The modelling results predicted unexpected contribution of cancer cell-cancer cell adhesion and ECM degradation ability of cancer cells to invasion extent and patterns of collective invasion. To test these results, we generated phenotypically different SCC cell lines (low cell-cell adhesion and/or low or high ECM degradation) by genome editing utilising CRISPR-Cas9 technology. The experimental results well agreed with computational model and further investigation was done with mutual feed backs between experimental and computational approach.
Additionally, we found that unanticipated role of cell-cell adhesion in widening of invasive region which could be linked to the growth of cancer cells at invasion site, where cancer cells are surrounded by stromal ECM. In vitro and in vivo tumour growth assay in confined environment also showed efficient SCC cell growth in ECM requires cell-cell adhesion, which is also predicted by our computational modelling. We found spatially restricted activation of actomyosin contractility as a mechanism underlies cell-cell adhesion dependent cell growth in confined environment.

Alongside the study about cancer cell-cancer cell interaction, we found heterotypic interaction between cancer cells and CAFs through heterophilic binding of E-cadherin/N-cadherin enables cooperative tumour invasion (Labernadie, Kato, et al Nature Cell Biology 2017).

Further investigation about the effect of heterogeneity of cancer cells on collective invasion revealed that invasion of highly invasive cells could be non-cell autonomously suppressed by less invasive cells lacking protease activity through being ejected from cell-matrix boundary. This surprising result indicates that uniform cancer cell phenotype favours invasion.
This project shed light to the previously unanticipated role of cell’s physical properties such as cell-cell adhesion and ECM remodelling in invasive behaviour of cancer cells that will enhance our understanding of important biomedical questions of tumour progression. Our results provide new opportunities to design alternative strategy of cancer therapeutics. Also, our finding of the importance of cell-cell adhesion in cancer growth in 3D confined Environment could be a novel target for cancer treatment.
Invasion of heterogenous cancer cells