Periodic Reporting for period 1 - SHAPINCELLFATE (Impact of cell shapes on cell behaviour and fate)
Reporting period: 2023-04-01 to 2024-09-30
Cells are often depicted as irregular spherical objects - the shape they adopt in suspension. However, the packed environment of tissues alters this simple shape, causing large cell deformations. This occurs during normal tissue growth and is even more pronounced upon tissue overgrowth, as in the case of solid tumors. Cell shape changes frequently occur in migratory cells, such as immune cells that patrol the organism within interstitial tissues, and cancer metastases that escape from the primary tumor to invade healthy tissues. In all cases, cells adapt and survive even to very large deformations. The mechanisms underlying such response and the long-term consequences that repeated cell shape changes have on physiology and pathology remain largely unknown.
We have observed that changes in the shape of cells and organelle(s) induce reversible and irreversible modifications in their behaviour and function(s). We hypothesize that cells use such mechanisms to integrate the successive deformations of distinct amplitudes and durations that they experience during their lifetime. This implies the existence of “shape-induced memory effects” that not only encode the geometrical and mechanical history of the cell but also dictate its fate. Here, we propose to tackle the molecular mechanisms and physical principles accounting for shape-induced memory effects and to evaluate their impact on immunity and cancer. We will focus on two cell types that undergo large shape changes in vivo, and communicate to establish cancer immunity: (1) dendritic cells (hereafter referred to as DCs), which initiate adaptive immune responses, and (2) cancer cells derived from mammary epithelia that can migrate leading to metastasis. Our project will reveal whether boundary conditions imposed by physical confinement are overarching determinants of cellular behaviours at different spatial and temporal scales, and may further establish novel clinical paths for a holistic understanding of early malignancies and their recognition by the immune system.
We have observed that changes in the shape of cells and organelle(s) induce reversible and irreversible modifications in their behaviour and function(s). We hypothesize that cells use such mechanisms to integrate the successive deformations of distinct amplitudes and durations that they experience during their lifetime. This implies the existence of “shape-induced memory effects” that not only encode the geometrical and mechanical history of the cell but also dictate its fate. Here, we propose to tackle the molecular mechanisms and physical principles accounting for shape-induced memory effects and to evaluate their impact on immunity and cancer. We will focus on two cell types that undergo large shape changes in vivo, and communicate to establish cancer immunity: (1) dendritic cells (hereafter referred to as DCs), which initiate adaptive immune responses, and (2) cancer cells derived from mammary epithelia that can migrate leading to metastasis. Our project will reveal whether boundary conditions imposed by physical confinement are overarching determinants of cellular behaviours at different spatial and temporal scales, and may further establish novel clinical paths for a holistic understanding of early malignancies and their recognition by the immune system.
DCs are immune cells found in a variety of peripheral tissues, where they sample the environment in the lookout for threats such as microbial infections. When they find such threats, they subsequently migrate from the peripheral tissues to the lymph nodes where they transmit this information to T cells. These migration steps are accompanied by changes in DC shape and we set out to quantify such changes, their molecular mechanisms and long-term phenotypic and functional consequences. DC migration from the peripheral tissues to the lymph nodes requires the expression of specific chemokine receptors (CCR7) that recognize chemokine gradients guiding them to the lymphatic vessels. To understand the effects of environmentally-induced shape changes on DCs, we subjected skin DCs to various levels of physical confinement they can find in tissues and we unexpectedly uncovered a precise deformation amplitude at which DCs activate a shape-sensing mechanism that leads to an increased expression of the CCR7 chemokine receptor. This subsequently leads to the steady state migration of DCs from peripheral tissues to the lymph nodes and a global transcriptional reprogramming that is different from the one triggered upon microbial sensing. These results show that DCs have a shape-sensing mechanism that defines their migratory behaviour and immune phenotype in steady state conditions. Rather than sensing molecular biochemical signals, these cells might sense the physical constraints they encounter while patrolling their environment. These unexpected results highlight the importance of physical properties and their subsequent cues to tissue organization and function, and how these can shape immunity (published in 2024 DOI 10.1038/s41590-024-01856-3).
We also uncovered the molecular drivers of migration of cells that do not attach to surfaces, such as the two cell types we focus on in this project. These cells move through the creation of intracellular actomyosin zones of distinct rigidity: a soft front that deforms to squeeze through spaces, a rigid middle to hold its shape, and a rear that acts as the cell’s ‘muscle’ to push forward. This organization allows cells to generate force and move effectively. When physically confined, these cells can also create protrusions that eventually detach as motile cell fragments with capacity to migrate. This finding mirrors recent intravital microscopy studies in live tumors, where scientists observed cancer cells fragmenting in real time, with pieces breaking off and moving independently through tissues (published in 2024 DOI 10.1016/j.devcel.2024.06.023 ).
As stated above, we also set out to analyze the influence of physical constraints in breast cancer cells (BCCs). It has been observed that rounder BCCs are correlated with solid-like and tumor suppressive states. The transition to a malignant state is often accompanied by the acquisition of more fluid-like features required for cell proliferation, migration and dissemination, a process we call unjamming. Here we uncovered that the changes in cell density resulting from the unjamming phenomenon result in mechanical deformations of cells and nuclei that ultimately lead to an alteration of the cell states towards the emergence of malignant features that include epithelial-to-mesenchymal plasticity and chemoresistance (published in 2022 DOI 10.1038/s41563-022-01431-x).
SHAPINCELLFATE teams continue the project, aiming at understanding the mechanisms linked to cell shape and the memory-induced changes.
We also uncovered the molecular drivers of migration of cells that do not attach to surfaces, such as the two cell types we focus on in this project. These cells move through the creation of intracellular actomyosin zones of distinct rigidity: a soft front that deforms to squeeze through spaces, a rigid middle to hold its shape, and a rear that acts as the cell’s ‘muscle’ to push forward. This organization allows cells to generate force and move effectively. When physically confined, these cells can also create protrusions that eventually detach as motile cell fragments with capacity to migrate. This finding mirrors recent intravital microscopy studies in live tumors, where scientists observed cancer cells fragmenting in real time, with pieces breaking off and moving independently through tissues (published in 2024 DOI 10.1016/j.devcel.2024.06.023 ).
As stated above, we also set out to analyze the influence of physical constraints in breast cancer cells (BCCs). It has been observed that rounder BCCs are correlated with solid-like and tumor suppressive states. The transition to a malignant state is often accompanied by the acquisition of more fluid-like features required for cell proliferation, migration and dissemination, a process we call unjamming. Here we uncovered that the changes in cell density resulting from the unjamming phenomenon result in mechanical deformations of cells and nuclei that ultimately lead to an alteration of the cell states towards the emergence of malignant features that include epithelial-to-mesenchymal plasticity and chemoresistance (published in 2022 DOI 10.1038/s41563-022-01431-x).
SHAPINCELLFATE teams continue the project, aiming at understanding the mechanisms linked to cell shape and the memory-induced changes.
Even though the project just arrived to the term of its first 18 months, we consider that some of the obtained results are significant scientific breakthroughs:
Alraies et al. reports an unexpected finding, since it was not our initial hypothesis that the deformation of the nuclei of immune cells, for a specific range of deformation, would be informative for these cells and trigger a very specific state, likely contributing to immune tolerance. It is also a breakthrough, since there was so far no known stimulus to trigger the migration of dendritic cells to lymph nodes in the absence of inflammation or infection.
Frittoli & Palamidessi et al. also represents a major advance in the contribution of tissue and cell mechanical cues on cellular phenotypes and states. Using various tumor modesl, we uncovered that changes in cell density resulting from the unjamming phenomenon result in repeated mechanical deformations of cells and nuclei (increased size and stiffness) that ultimately lead to a transcriptional rewiring altering cell states towards the emergence of malignant features including epithelial-to-mesenchymal plasticity and chemoresistance. These results highlight the importance of tissue mechanical properties triggering the acquisition of intracellular traits leading to changes in cell states.
Garcia et al. reports a very basic finding that clarifies how almost any cell can develop a fast mode of migration, by unleashing a generic property of acto-myosin. It is advancing the field of cell migration beyond the state of the art and represents mostly a conceptual advance, with the notion of advected percolation, which is new not only for biology but even for the physics of materials in general and could serve as a basic principle to produce moving objects.
Alraies et al. reports an unexpected finding, since it was not our initial hypothesis that the deformation of the nuclei of immune cells, for a specific range of deformation, would be informative for these cells and trigger a very specific state, likely contributing to immune tolerance. It is also a breakthrough, since there was so far no known stimulus to trigger the migration of dendritic cells to lymph nodes in the absence of inflammation or infection.
Frittoli & Palamidessi et al. also represents a major advance in the contribution of tissue and cell mechanical cues on cellular phenotypes and states. Using various tumor modesl, we uncovered that changes in cell density resulting from the unjamming phenomenon result in repeated mechanical deformations of cells and nuclei (increased size and stiffness) that ultimately lead to a transcriptional rewiring altering cell states towards the emergence of malignant features including epithelial-to-mesenchymal plasticity and chemoresistance. These results highlight the importance of tissue mechanical properties triggering the acquisition of intracellular traits leading to changes in cell states.
Garcia et al. reports a very basic finding that clarifies how almost any cell can develop a fast mode of migration, by unleashing a generic property of acto-myosin. It is advancing the field of cell migration beyond the state of the art and represents mostly a conceptual advance, with the notion of advected percolation, which is new not only for biology but even for the physics of materials in general and could serve as a basic principle to produce moving objects.