Understanding the Interaction Mechanism between the Epinephrine Neurotransmitter and Small Gold Nanoclusters (Aun; n = 6, 8, and 10): A Computational Insight.

In this study, the interaction between the neurotransmitter epinephrine and small gold nanoclusters (AunNCs) with n = 6, 8, and 10 is described by density functional theory calculations. The interaction of Au6, Au8, and Au10 nanoclusters with epinephrine is governed by Au-X (X = N and O) anchoring bonding and Au···H-X conventional hydrogen bonding. The interaction mechanism of epinephrine with gold nanoclusters is investigated in terms of electronic energy and geometrical properties. The adsorption energy values for the most favorable configurations of Au6NC@epinephrine, Au8NC@epinephrine, and Au10NC@epinephrine were calculated to be -17.45, -17.86, and -16.07 kcal/mol, respectively, in the gas phase. The results indicate a significant interaction of epinephrine with AunNCs and point to the application of the biomolecular complex AunNC@epinephrine in the fields of biosensing, drug delivery, bioimaging, and other applications. In addition, some important electronic properties, namely, the energy gap between HOMO and LUMO, the Fermi level, and the work function, were computed. The effect of aqueous media on adsorption energy and electronic parameters for the most favorable configurations was also studied to explore the influence of physical biological conditions.

Multi-scale measurement of stiffness in the developing ferret brain.

Cortical folding is an important process during brain development, and aberrant folding is linked to disorders such as autism and schizophrenia. Changes in cell numbers, size, and morphology have been proposed to exert forces that control the folding process, but these changes may also influence the mechanical properties of developing brain tissue. Currently, the changes in tissue stiffness during brain folding are unknown. Here, we report stiffness in the developing ferret brain across multiple length scales, emphasizing changes in folding cortical tissue. Using rheometry to measure the bulk properties of brain tissue, we found that overall brain stiffness increases with age over the period of cortical folding. Using atomic force microscopy to target the cortical plate, we found that the occipital cortex increases in stiffness as well as stiffness heterogeneity over the course of development and folding. These findings can help to elucidate the mechanics of the cortical folding process by clarifying the concurrent evolution of tissue properties.

Theoretical microwave spectra of interstellar nitrogen-containing PAHs.

The recent discovery of naphthalene (C10H8) in cyano-substituted polycyclic aromatic hydrocarbon (CN-PAH) form in the Taurus molecular cloud (TMC-1) has sparked curiosity regarding the search for other nitrogen-containing naphthalenes in similar interstellar environments. In this light, naphthalenes having N atoms in the structure are promising candidates to be searched for in cold, dark molecular clouds such as TMC-1. Since obtaining data on such samples in the laboratory is complicated, the present work reports theoretical microwave spectra of naphthalene in all N-substituted forms. Density functional theory (DFT) calculations are employed to calculate the spectroscopic constants and simulate the rotational spectra with hyperfine splitting. For cold temperature regions such as TMC-1 (about 5 K), the considered N-naphthalene species show the strongest transition around centimetre wavelengths, a typical range for PAH-related species in dark molecular clouds. Accurate rotational data provided here may act as a guide for laboratory experiments and astronomical searches.

A comparative study on surgical outcomes of trabeculectomy with and without anti-metabolites in juvenile open-angle glaucoma.

Purpose: To compare the surgical outcomes of trabeculectomy with and without anti-metabolites in patients with juvenile open-angle glaucoma (JOAG). Methods: This retrospective comparative case series included 98 eyes of 66 patients with JOAG who underwent either trabeculectomy without anti-metabolites (group A, n = 53 eyes) or with anti-metabolites (group B, n = 45 eyes) with a minimum of 2 years follow-up. The main outcome measures were intra-ocular pressure (IOP), number of glaucoma medications, visual acuity, additional surgical interventions, surgical complications, and risk factors for failure. Surgical failure was defined as IOP >18 mmHg or failure to reduce IOP by <30% from the baseline value or IOP ≤5 mmHg or re-operation for refractory glaucoma or a complication or loss of light perception vision. Results: The mean post-operative IOP reduced significantly from baseline at all post-operative visits until 6 months and thereafter. The cumulative probability of failure at 2 years was 28.7% in group A [95% confidence interval (CI) = 17.6-44.8%] and 29.1% in group B (95% CI = 17.1-46.7%) (P = 0.78). Surgical complications occurred in 18 eyes (34%) in group A and 19 eyes (42%) in group B. Re-operations for glaucoma or complications were performed in two eyes (3.8%) in group A and two eyes (4.4%) in group B. Cox-hazard regression model revealed male gender (HR = 0.29; P = 0.008), baseline high IOP (HR = 0.95; P = 0.002), and an increased number of pre-operative glaucoma medications (HR = 2.08; P = 0.010) as significant factors associated with failure. Conclusion: : Our study results on trabeculectomy in JOAG revealed a success of 71% in both groups at 2 years follow-up. There was no significant difference in success or failure rates between the two groups. The risk factors for poor surgical outcome in JOAG were male gender, baseline high IOP, and an increased number of glaucoma medications.

Epithelial multicellular clustering enabled by polarized macrophages on soft matrices.

Formation of epithelial structures of variegated geometries and sizes is essential for organogenesis, tumor growth, and wound repair. Although epithelial cells are predisposed with potential for multicellular clustering, it remains unclear whether immune cells and mechanical cues from their microenvironment influence this process. To explore this possibility, we cocultured human mammary epithelial cells with prepolarized macrophages on soft or stiff hydrogels. In the presence of M1 (proinflammatory) macrophages on soft matrices, epithelial cells migrated faster and subsequently formed larger multicellular clusters compared to cocultures with M0 (unpolarized) or M2 (anti-inflammatory) macrophages. By contrast, stiff matrices disabled active clustering of epithelial cells due to their enhanced migration and cell-ECM adhesion, regardless of macrophage polarization. We found that the copresence of soft matrices and M1 macrophages reduced focal adhesions, but enhanced fibronectin deposition and nonmuscle myosin-IIA expression, which altogether optimize conditions for epithelial clustering. Upon ROCK inhibition, epithelial clustering was abrogated, indicating a requirement for optimized cellular forces. In these cocultures, TNF-α secretion was the highest with M1 macrophages and TGF-ß secretion was exclusively detectable in case of M2 macrophages on soft gels, which indicated potential role of macrophage secreted factors in the observed epithelial clustering. Indeed, exogenous addition of TGF-ß promoted epithelial clustering with M1 coculture on soft gels. According to our findings, optimization of both mechanical and immune factors can tune epithelial clustering responses, which could have implications in tumor growth, fibrosis, and would healing.

Matrix obstructions cause multiscale disruption in collective epithelial migration by suppressing leader cell function.

During disease and development, physical changes in extracellular matrix cause jamming, unjamming, and scattering in epithelial migration. However, whether disruptions in matrix topology alter collective cell migration speed and cell-cell coordination remains unclear. We microfabricated substrates with stumps of defined geometry, density, and orientation, which create obstructions for migrating epithelial cells. Here, we show that cells lose their speed and directionality when moving through densely spaced obstructions. Although leader cells are stiffer than follower cells on flat substrates, dense obstructions cause overall cell softening. Through a lattice-based model, we identify cellular protrusions, cell-cell adhesions, and leader-follower communication as key mechanisms for obstruction-sensitive collective cell migration. Our modeling predictions and experimental validations show that cells' obstruction sensitivity requires an optimal balance of cell-cell adhesions and protrusions. Both MDCK (more cohesive) and α-catenin-depleted MCF10A cells were less obstruction sensitive than wild-type MCF10A cells. Together, microscale softening, mesoscale disorder, and macroscale multicellular communication enable epithelial cell populations to sense topological obstructions encountered in challenging environments. Thus, obstruction-sensitivity could define "mechanotype" of cells that collectively migrate yet maintain intercellular communication.

Transitions in density, pressure, and effective temperature drive collective cell migration into confining environments.

Epithelial cell collectives migrate through tissue interfaces and crevices to orchestrate processes of development, tumor invasion, and wound healing. Naturally, traversal of cell collective through confining environments involves crowding due to the narrowing space, which seems tenuous given the conventional inverse relationship between cell density and migration. However, physical transitions required to overcome such epithelial densification for migration across confinements remain unclear. Here, in contiguous microchannels, we show that epithelial (MCF10A) monolayers accumulate higher cell density before entering narrower channels; however, overexpression of breast cancer oncogene +ErbB2 reduced this need for density accumulation across confinement. While wildtype MCF10A cells migrated faster in narrow channels, this confinement sensitivity reduced after +ErbB2 mutation or with constitutively-active RhoA. The migrating collective developed pressure differentials upon encountering microchannels, like fluid flow into narrowing spaces, and this pressure dropped with their continued migration. These transitions of pressure and density altered cell shapes and increased effective temperature, estimated by treating cells as granular thermodynamic system. While +RhoA cells and those in confined regions were effectively warmer, cancer-like +ErbB2 cells remained cooler. Epithelial reinforcement by metformin treatment increased density and temperature differentials across confinement, indicating that higher cell cohesion could reduce unjamming. Our results provide experimental evidence for previously proposed theories of inverse relationship between density and motility-related effective temperature. Indeed, we show across cell lines that confinement increases pressure and effective temperature, which enable migration by reducing density. This physical interpretation of collective cell migration as granular matter could advance our understanding of complex living systems.

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

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.

Epithelial multicellular clustering enabled by polarized macrophages on soft matrices.

Formation of epithelial structures of variegated geometries and sizes is essential for organogenesis, tumor growth, and wound repair. Although epithelial cells are predisposed with potential for multicellular clustering, it remains unclear whether immune cells and mechanical cues from their microenvironment influence this process. To explore this possibility, we co-cultured human mammary epithelial cells with pre-polarized macrophages on soft or stiff hydrogels. In the presence of M1 (proinflammatory) macrophages on soft matrices, epithelial cells migrated faster and subsequently formed larger multicellular clusters, compared to co-cultures with M0 (unpolarized) or M2 (anti-inflammatory) macrophages. By contrast, stiff extracellular matrix (ECM) disabled active clustering of epithelial cells due to their enhanced migration and cell-ECM adhesion, regardless of macrophage polarization. We found that the co-presence of soft matrices and M1 macrophages reduced focal adhesions, but enhanced fibronectin deposition and non-muscle myosin-IIA expression, which altogether optimize conditions for epithelial clustering. Upon Rho-associated kinase (ROCK) inhibition, epithelial clustering was abrogated, indicating a requirement for optimized cellular forces. In these co-cultures, Tumor Necrosis Factor (TNF)-α secretion was the highest with M1 macrophages and Transforming growth factor (TGF)-ß secretion was exclusively detectable in case of M2 macrophages on soft gels, which indicated potential role of macrophage secreted factors in the observed epithelial clustering. Indeed, exogenous addition of TGB-ß promoted epithelial clustering with M1 co-culture on soft gels. According to our findings, optimization of both mechanical and immune factors can tune epithelial clustering responses, which could have implications in tumor growth, fibrosis, and would healing. Summary: Authors show proinflammatory macrophages on soft matrices enable epithelial cells to form multicellular clusters. This phenomenon is disabled on stiff matrices due to increased stability of focal adhesions. Inflammatory cytokine secretion is macrophage-dependent, and external addition of cytokines accentuates epithelial clustering on soft matrices. Impact Statement: Formation of multicellular epithelial structures is critical to tissue homeostasis. However, it has not been shown how the immune system and mechanical environment affect these structures. The present work illustrates how macrophage type affects epithelial clustering in soft and stiff matrix environments.

Nuclear export inhibition jumbles epithelial-mesenchymal states and gives rise to migratory disorder in healthy epithelia.

Dynamic nucleocytoplasmic transport of E-M factors regulates cellular E-M states; yet, it remains unknown how simultaneously trapping these factors affects epithelia at the macroscale. To explore this question, we performed nuclear export inhibition (NEI) via leptomycin B and Selinexor treatment, which biases nuclear localization of CRM1-associated E-M factors. We examined changes in collective cellular phenotypes across a range of substrate stiffnesses. Following NEI, soft substrates elevate collective migration of MCF10A cells for up to 24 hr, while stiffer substrates reduce migration at all time points. Our results suggest that NEI disrupts migration through competition between intercellular adhesions and mechanoactivation, generally causing loss of cell-cell coordination. Specifically, across substrate stiffnesses, NEI fosters an atypical E-M state wherein MCF10A cells become both more epithelial and more mesenchymal. We observe that NEI fosters a range of these concurrent phenotypes, from more epithelial shYAP MCF10A cells to more mesenchymal MDCK II cells. α-Catenin emerges as a potential link between E-M states, where it maintains normal levels of intercellular adhesion and transmits mechanoactive characteristics to collective behavior. Ultimately, to accommodate the concurrent states observed here, we propose an expanded E-M model, which may help further understand fundamental biological phenomena and inform pathological treatments.

A Cdh3-ß-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.

A comprehensive rotational study of astronomical iso-pentane within 84 to 111 GHz.

The rotational line survey by ALMA (Atacama Large Millimeter/submillimeter Array) recently revealed the presence of i-C3H7CN (i-PrCN) and n-C3H7CN (n-PrCN) in 3-mm atmospheric window between 84 to 111 GHz towards the hot core region Sagittarius B2(N) (Sgr B2(N)). This was the first interstellar detection of a linear straight chain molecule. In this light, we report the rotational spectra of C5H12 isomeric group in the same frequency range. We performed quantum chemical calculations for spectroscopic parameters. The pure rotational spectrum of the species has been simulated using the PGOPHER program. The rotational spectrum of this molecule makes it a good candidate for future astronomical detections since the radio lines can be calculated to very high accuracy in mm/sub-mm wave region.

Mechanically primed cells transfer memory to fibrous matrices for invasion across environments of distinct stiffness and dimensionality.

Cells sense and migrate across mechanically dissimilar environments throughout development and disease progression. However, it remains unclear whether mechanical memory of past environments empowers cells to navigate new, three-dimensional extracellular matrices. Here, we show that cells previously primed on stiff, compared with soft, matrices generate a higher level of forces to remodel collagen fibers and promote invasion. This priming advantage persists in dense or stiffened collagen. We explain this memory-dependent, cross-environment cell invasion through a lattice-based model wherein stiff-primed cellular forces remodel collagen and minimize energy required for future cell invasion. According to our model, cells transfer their mechanical memory to the matrix via collagen alignment and tension, and this remodeled matrix informs future cell invasion. Thus, memory-laden cells overcome mechanosensing of softer or challenging future environments via a cell-matrix transfer of memory. Consistent with model predictions, depletion of yes-associated protein destabilizes the cellular memory required for collagen remodeling before invasion. We release tension in collagen fibers via laser ablation and disable fiber remodeling by lysyl-oxidase inhibition, both of which disrupt cell-to-matrix transfer of memory and hamper cross-environment invasion. These results have implications for cancer, fibrosis, and aging, where a potential cell-to-matrix transfer of mechanical memory of cells may generate a prolonged cellular response.

Nucleoli in epithelial cell collectives respond to tumorigenic, spatial, and mechanical cues.

Cancer cells are known to have larger nucleoli, consistent with their higher transcriptional and translational demands. Meanwhile, on stiff extracellular matrix, normal epithelial cells can exhibit genomic and proteomic mechanoactivation toward tumorigenic transformations, such as epithelial-mesenchymal transition and enhanced migration. However, while nucleolar bodies regulate the protein synthesis required for mechanosensation, it remains unknown whether mechanical and spatial extracellular cues can in turn alter nucleoli. Here, we culture mammary epithelial cell sheets on matrices of varying stiffness and show that cancer cells have more nucleoli, with nucleoli occupying larger areas compared with normal cells. By contrast, within normal epithelial sheets, stiffer matrices and leader positioning of cells induce larger nucleolar areas and more nucleolar bodies over time. The observed leader-follower nucleolar differences stem from distinct rates of cell cycle progression. In the nucleoplasm, leader cells on stiffer matrices exhibit higher heterochromatin marker expression and DNA compaction around nucleolar bodies. Overall, our findings advance the emerging framework of cellular mechanobiology in which mechanical cues from the extracellular matrix transmit into the nucleoplasm to alter nucleolar composition, potentially resulting in mechanosensitive ribosomal biogenesis. Ultimately, this proposed mechanosensitivity of nucleoli and associated protein synthesis could have wide implications in disease, development, and regeneration.

Dynamic self-reinforcement of gene expression determines acquisition of cellular mechanical memory.

Mechanotransduction describes activation of gene expression by changes in the cell's physical microenvironment. Recent experiments show that mechanotransduction can lead to long-term "mechanical memory," in which cells cultured on stiff substrates for sufficient time (priming phase) maintain altered phenotype after switching to soft substrates (dissipation phase) as compared to unprimed controls. The timescale of memory acquisition and retention is orders of magnitude larger than the timescale of mechanosensitive cellular signaling, and memory retention time changes continuously with priming time. We develop a model that captures these features by accounting for positive reinforcement in mechanical signaling. The sensitivity of reinforcement represents the dynamic transcriptional state of the cell composed of protein lifetimes and three-dimensional chromatin organization. Our model provides a single framework connecting microenvironment mechanical history to cellular outcomes ranging from no memory to terminal differentiation. Predicting cellular memory of environmental changes can help engineer cellular dynamics through changes in culture environments.

Control of adhesive ligand density for modulation of nucleus pulposus cell phenotype.

Cells of the nucleus pulposus have been observed to undergo a shift from their notochordal-like juvenile phenotype to a more fibroblast-like state with age and maturation. It has been demonstrated that culture of degenerative adult human nucleus pulposus cells upon soft (<1 kPa) full length laminin-containing hydrogel substrates promotes increased levels of a panel of markers associated with the juvenile nucleus pulposus cell phenotype. In the current work, we observed an ability to use soft polymeric substrates functionalized with short laminin-mimetic peptide sequences to recapitulate the behaviors elicited by soft, full-length laminin containing materials. Furthermore, our work suggests an ability to mimic features of soft systems through control of peptide density upon stiffer substrates. Specifically, results suggest that stiffer polymer-peptide hydrogel substrates can be used to promote the expression of a more juvenile-like phenotype for cells of the nucleus pulposus by reducing adhesive ligand presentation. Here we show how polymer stiffness combined with adhesive ligand presentation can be controlled to be supportive of nucleus pulposus cell phenotype and biosynthesis.

Mechanosensitive transcriptional coactivators MRTF-A and YAP/TAZ regulate nucleus pulposus cell phenotype through cell shape.

Cells of the adult nucleus pulposus (NP) are critically important in maintaining overall disc health and function. NP cells reside in a soft, gelatinous matrix that dehydrates and becomes increasingly fibrotic with age. Such changes result in physical cues of matrix stiffness that may be potent regulators of NP cell phenotype and may contribute to a transition toward a senescent and fibroblastic NP cell with a limited capacity for repair. Here, we investigate the mechanosignaling cues generated from changes in matrix stiffness in directing NP cell phenotype and identify mechanisms that can potentially preserve a biosynthetically active, juvenile NP cell phenotype. Using a laminin-functionalized polyethylene glycol hydrogel, we show that when NP cells form rounded, multicell clusters, they are able to maintain cytosolic localization of myocardin-related transcription factor (MRTF)-A, a coactivator of serum-response factor (SRF), known to promote fibroblast-like behaviors in many cells. Upon preservation of a rounded shape, human NP cells similarly showed cytosolic retention of transcriptional coactivator Yes-associated protein (YAP) and its paralogue PDZ-binding motif (TAZ) with associated decline in activation of its transcription factor TEA domain family member-binding domain (TEAD). When changes in cell shape occur, leading to a more spread, fibrotic morphology associated with stronger F-actin alignment, SRF and TEAD are up-regulated. However, targeted deletion of either cofactor was not sufficient to overcome shape-mediated changes observed in transcriptional activation of SRF or TEAD. Findings show that substrate stiffness-induced promotion of F-actin alignment occurs concomitantly with a flattened, spread morphology, decreased NP marker expression, and reduced biosynthetic activity. This work indicates cell shape is a stronger indicator of SRF and TEAD mechanosignaling pathways than coactivators MRTF-A and YAP/TAZ, respectively, and may play a role in the degeneration-associated loss of NP cellularity and phenotype.-Fearing, B. V., Jing, L., Barcellona, M. N., Witte, S. E., Buchowski, J. M., Zebala, L. P., Kelly, M. P., Luhmann, S., Gupta, M. C., Pathak, A., Setton, L. A. Mechanosensitive transcriptional coactivators MRTF-A and YAP/TAZ regulate nucleus pulposus cell phenotype through cell shape.

Longer collagen fibers trigger multicellular streaming on soft substrates via enhanced forces and cell-cell cooperation.

Grouped cells often leave large cell colonies in the form of narrow multicellular streams. However, it remains unknown how collective cell streaming exploits specific matrix properties, like stiffness and fiber length. It is also unclear how cellular forces, cell-cell adhesion and velocities are coordinated within streams. To independently tune stiffness and collagen fiber length, we developed new hydrogels and discovered invasion-like streaming of normal epithelial cells on soft substrates coated with long collagen fibers. Here, streams arise owing to a surge in cell velocities, forces, YAP activity and expression of mesenchymal marker proteins in regions of high-stress anisotropy. Coordinated velocities and symmetric distribution of tensile and compressive stresses support persistent stream growth. Stiff matrices diminish cell-cell adhesions, disrupt front-rear velocity coordination and do not promote sustained fiber-dependent streaming. Rac inhibition reduces cell elongation and cell-cell cooperation, resulting in a complete loss of streaming in all matrix conditions. Our results reveal a stiffness-modulated effect of collagen fiber length on collective cell streaming and unveil a biophysical mechanism of streaming governed by a delicate balance of enhanced forces, monolayer cohesion and cell-cell cooperation.This article has an associated First Person interview with the first authors of the paper.

EUS of the neck: A comprehensive anatomical reference for the staging of head and neck cancer (with videos).

The use of EUS has application in the nodal staging of head and neck cancer. The technique and the anatomy of head and neck region using EUS have not been described. EUS from three stations in thoracic esophagus, cervical esophagus, and hypopharynx can allow imaging of head and neck. In this article we describe the normal structures from the three stations. The EUS imaging of head and neck can give relevant and additional information in malignancies of head and neck.

DDR2 controls breast tumor stiffness and metastasis by regulating integrin mediated mechanotransduction in CAFs.

Biomechanical changes in the tumor microenvironment influence tumor progression and metastases. Collagen content and fiber organization within the tumor stroma are major contributors to biomechanical changes (e., tumor stiffness) and correlated with tumor aggressiveness and outcome. What signals and in what cells control collagen organization within the tumors, and how, is not fully understood. We show in mouse breast tumors that the action of the collagen receptor DDR2 in CAFs controls tumor stiffness by reorganizing collagen fibers specifically at the tumor-stromal boundary. These changes were associated with lung metastases. The action of DDR2 in mouse and human CAFs, and tumors in vivo, was found to influence mechanotransduction by controlling full collagen-binding integrin activation via Rap1-mediated Talin1 and Kindlin2 recruitment. The action of DDR2 in tumor CAFs is thus critical for remodeling collagen fibers at the tumor-stromal boundary to generate a physically permissive tumor microenvironment for tumor cell invasion and metastases.