A Cdh3-β-catenin-laminin signaling axis in a subset of breast tumor leader cells control leader cell polarization and directional collective migration

Carcinoma dissemination can occur when heterogeneous tumor and tumor-stromal cell clusters migrate together via collective migration. Cells at the front lead and direct collective migration, yet how these leader cells form and direct migration are not fully appreciated. From live videos of primary mouse and human breast tumor organoids in a 3D microfluidic system mimicking native breast tumor microenvironment, we developed 3D computational models, which hypothesize that leader cells need to generate high protrusive forces and overcome extracellular matrix (ECM) resistance at the leading edge. From single-cell sequencing analyses, we find that leader cells are heterogeneous and identify and isolate a keratin 14- and cadherin-3-positive subpopulation sufficient to lead collective migration. Cdh3 controls leader cell protrusion dynamics through local production of laminin, which is required for integrin/focal adhesion function. Our findings highlight how a subset of leader cells interact with the microenvironment to direct collective migration

Modeling Multiscale Mechanobiological Modulation of Collective Cell Migration

Cells constantly interact with and interpret their environment as they migrate, a process integral to an array of vital physiological events within the body. One such form of cellular migration that is of particular significance is collective migration, a coordinated and group-based movement that is central to various biological processes such as embryogenesis, tissue repair, and cancer metastasis. As these cells navigate through the body, they receive and process a wide array of inputs and cues from their surroundings that guide their direction and velocity. These cues are not simply instantaneous or immediate, they span across time and length, presenting a dynamic and intricate web of interaction that cells must decode. These inputs can be cellular in the form of individual cell polarization or \u27mechanical memory,\u27 whereby cells integrate the information they receive over time. In addition, cells also sense and respond to cues along the length scale of their migration, a key example being the influence of extracellular matrix (ECM) properties. The ECM serves as a physical scaffold for cells and imparts information about the tissue\u27s structural composition, rigidity, and biochemistry, thereby playing a significant role in modulating cellular migration. The exploration of. Here, I present the influence of these multi-dimensional interactions and how cells utilize them during collective migration. Chapter 2 explores the influence of individual cells\u27 repolarization dynamics in regulating the collective migration of heterogeneous cell populations. Using a vertex-based model that encapsulates individual cell behavior and experimental observations, we identify long repolarization intervals as a characteristic of leader cells, contributing to more effective collective migration. Our findings reveal how variations in repolarization dynamics can significantly alter the migration modes of cell populations, providing essential insights into collective cell migration in disease and development. Chapter 3 delves into modeling collective migration in heterogenous breast cancer organoids, focusing on the formation and localization of leader cells in breast tumors. Through computational models developed from live videos of primary mouse and human breast tumor organoids, we identify the need for leader cells to generate high protrusive forces and to overcome extracellular matrix (ECM) resistance at the leading edge. This work highlights the role of a CDH3+ subpopulation in controlling cell protrusion dynamics, underpinning the importance of their interaction with the microenvironment in directing collective migration. The potential therapeutic implications of understanding leader cell heterogeneity in tumor progression and metastatic disease are also addressed. Chapter 4 to 6 are dedicated to examining the implications of the ECM, a pivotal component of the cellular microenvironment. Chapter 4 explores role of ECM stiffness from a timescale perspective, and how cells are able to remember these stiffness cues, aka mechanical memory, even after moving away from the previous cues. We model mechanical memory in cells by integrating transcriptional activity and epigenetic plasticity with conventional models of mechanotransduction, the process by which cells sense their environment. We explore the role of varying priming and memory factor kinetics on kinetics of memory. These insights are validated using experimental findings of memory storage and decay in epithelial cell migration and stem cell differentiation, offering a deeper understanding of cellular memory. Chapter 5 delves into role of ECM dimensionality, causing mechanically primed cells to transfer memory to fibrous matrices, enabling invasion across environments of varying stiffness and dimensionality. Using a lattice-based computational model, we demonstrate that stiff-primed cells generate higher forces to remodel collagen fibers and enhance invasion, thus overcoming the challenges of fibrous environments. Notably, this cell-to-matrix transfer of memory was found to play a crucial role in invasive processes across mechanically distinct environments, offering potential implications for understanding cellular behavior in cancer, fibrosis, and aging. Chapter 6 explores the intriguing process of \u27depth mechanosensing\u27 in layered matrices, which allows cancer cells to sense and migrate in response to deeper, stiffer substrates, unlike healthy epithelial cells. By utilizing layered collagen-polyacrylamide gel systems and energy minimization modeling, we demonstrate how cell-matrix polarity, formed by polarized cellular protrusions and contractility leading to polarized ECM, enable this cell-type-dependent migration. Disruptions to this polarity, through various means, eliminate this depth-mechanosensitive migration, highlighting the crucial crosstalk between cellular and extracellular polarity in facilitating this cell migration mechanism. Overall, this dissertation significantly enhances our understanding of collective migration, particularly the role of cellular and ECM cues. By utilizing a combination of computational models and experimental observations, we have been able to elucidate the mechanisms behind these multi-dimensional interactions. Our findings offer new insights into cellular behavior in development, disease progression, and tissue repair

Reciprocal intra- and extra-cellular polarity enables deep mechanosensing through layered matrices

Summary: Adherent cells migrate on layered tissue interfaces to drive morphogenesis, wound healing, and tumor invasion. Although stiffer surfaces are known to enhance cell migration, it remains unclear whether cells sense basal stiff environments buried under softer, fibrous matrix. Using layered collagen-polyacrylamide gel systems, we unveil a migration phenotype driven by cell-matrix polarity. Here, cancer (but not normal) cells with stiff base matrix generate stable protrusions, faster migration, and greater collagen deformation because of “depth mechanosensing” through the top collagen layer. Cancer cell protrusions with front-rear polarity produce polarized collagen stiffening and deformations. Disruption of either extracellular or intracellular polarity via collagen crosslinking, laser ablation, or Arp2/3 inhibition independently abrogates depth-mechanosensitive migration of cancer cells. Our experimental findings, validated by lattice-based energy minimization modeling, present a cell migration mechanism whereby polarized cellular protrusions and contractility are reciprocated by mechanical extracellular polarity, culminating in a cell-type-dependent ability to mechanosense through matrix layers