Matrix Stiffness Differentially Regulates Cellular Uptake Behavior of Nanoparticles in Two Breast Cancer Cell Lines

Impact of mechanical cues on key cell functions and cell-nanoparticle interactions

In recent years, it has been recognized that mechanical forces play an important regulative role in living organisms and possess a direct impact on crucial cell functions, ranging from cell growth to maintenance of tissue homeostasis. Advancements in mechanobiology have revealed the profound impact of mechanical signals on diverse cellular responses that are cell type specific. Notably, numerous studies have elucidated the pivotal role of different mechanical cues as regulatory factors influencing various cellular processes, including cell spreading, locomotion, differentiation, and proliferation. Given these insights, it is unsurprising that the responses of cells regulated by physical forces are intricately linked to the modulation of nanoparticle uptake kinetics and processing. This complex interplay underscores the significance of understanding the mechanical microenvironment in shaping cellular behaviors and, consequently, influencing how cells interact with and process nanoparticles. Nevertheless, our knowledge on how localized physical forces affect the internalization and processing of nanoparticles by cells remains rather limited. A significant gap exists in the literature concerning a systematic analysis of how mechanical cues might bias the interactions between nanoparticles and cells. Hence, our aim in this review is to provide a comprehensive and critical analysis of the existing knowledge regarding the influence of mechanical cues on the complicated dynamics of cell-nanoparticle interactions. By addressing this gap, we would like to contribute to a detailed understanding of the role that mechanical forces play in shaping the complex interplay between cells and nanoparticles.

Effect of biophysical properties of tumor extracellular matrix on intratumoral fate of nanoparticles: Implications on the design of nanomedicine

Nanomedicine has a profound impact on various research domains including drug delivery, diagnostics, theranostics, and regenerative medicine. Nevertheless, the clinical translation of nanomedicines for solid cancer remains limited due to the abundant physiological and pathological barriers in tumor that hinder the intratumoral penetration and distribution of these nanomedicines. In this article, we review the dynamic remodeling of tumor extracellular matrix during the tumor progression, discuss the impact of biophysical obstacles within tumors on the penetration and distribution of nanomedicines within the solid tumor and collect innovative approaches to surmount these obstacles for improving the penetration and accumulation of nanomedicines in tumor. Furthermore, we dissect the challenges and opportunities of the respective approaches, and propose potential avenues for future investigations. The purpose of this review is to provide a perspective guideline on how to effectively enhance the penetration of nanomedicines within tumors using promising methods.

Cancer-associated fibroblasts: protagonists of the tumor microenvironment in gastric cancer

Enhanced knowledge of the interaction of cancer cells with their environment elucidated the critical role of tumor microenvironment in tumor progression and chemoresistance. Cancer-associated fibroblasts act as the protagonists of the tumor microenvironment, fostering the metastasis, stemness, and chemoresistance of cancer cells and attenuating the anti-cancer immune responses. Gastric cancer is one of the most aggressive cancers in the clinic, refractory to anti-cancer therapies. Growing evidence indicates that cancer-associated fibroblasts are the most prominent risk factors for a poor tumor immune microenvironment and dismal prognosis in gastric cancer. Therefore, targeting cancer-associated fibroblasts may be central to surpassing resistance to conventional chemotherapeutics, molecular-targeted agents, and immunotherapies, improving survival in gastric cancer. However, the heterogeneity in cancer-associated fibroblasts may complicate the development of cancer-associated fibroblast targeting approaches. Although single-cell sequencing studies started dissecting the heterogeneity of cancer-associated fibroblasts, the research community should still answer these questions: "What makes a cancer-associated fibroblast protumorigenic?"; "How do the intracellular signaling and the secretome of different cancer-associated fibroblast subpopulations differ from each other?"; and "Which cancer-associated fibroblast subtypes predominate specific cancer types?". Unveiling these questions can pave the way for discovering efficient cancer-associated fibroblast targeting strategies. Here, we review current knowledge and perspectives on these questions, focusing on how CAFs induce aggressiveness and therapy resistance in gastric cancer. We also review potential therapeutic approaches to prevent the development and activation of cancer-associated fibroblasts via inhibition of CAF inducers and CAF markers in cancer.

Force-Mediated Endocytosis of Iron Oxide Nanoparticles for Magnetic Targeting of Stem Cells

Stem cell therapy represents one of the most promising approaches for tissue repair and regeneration. However, the full potential of stem cell therapy remains to be realized. One major challenge is the insufficient homing and retention of stem cells at the desired sites after in vivo delivery. Here, we provide a proof-of-principle demonstration of magnetic targeting and retention of human muscle-derived stem cells (hMDSCs) in vitro through magnetic force-mediated internalization of magnetic iron oxide nanoparticles (MIONs) and the use of a micropatterned magnet. We found that the magnetic force-mediated cellular uptake of MIONs occurs through an endocytic pathway, and the MIONs were exclusively localized in the lysosomes. The intracellular MIONs had no detrimental effect on the proliferation of hMDSCs or their multilineage differentiation, and no MIONs were translocated to other cells in a coculture system. Using hMDSCs and three other cell types including human umbilical vein endothelial cells (HUVECs), human dermal fibroblasts (HDFs), and HeLa cells, we further discovered that the magnetic force-mediated MION uptake increased with MION size and decreased with cell membrane tension. We found that the cellular uptake rate was initially increased with MION concentration in solution and approached saturation. These findings provide important insight and guidance for magnetic targeting of stem cells in therapeutic applications.

Surface physical cues mediate the uptake of foreign particles by cancer cells

Cancer phenotypes are often associated with changes in the mechanical states of cells and their microenvironments. Numerous studies have established correlations between cancer cell malignancy and cell deformability at the single-cell level. The mechanical deformation of cells is required for the internalization of large colloidal particles. Compared to normal epithelial cells, cancer cells show higher capacities to distort their shapes during the engulfment of external particles, thus performing phagocytic-like processes more efficiently. This link between cell deformability and particle uptake suggests that the cell's adherence state may affect this particle uptake, as cells become stiffer when plated on a more rigid substrate and vice versa. Based on this, we hypothesized that cancer cells of the same origin, which are subjected to external mechanical cues through attachment to surfaces with varying rigidities, may express different capacities to uptake foreign particles. The effects of substrate rigidity on cancer cell uptake of inert particles (0.8 and 2.4 μm) were examined using surfaces with physiologically relevant rigidities (from 0.5 to 64 kPa). Our data demonstrate a wave-like ("meandering") dependence of cell uptake on the rigidity of the culture substrate explained by a superposition of opposing physical and biological effects. The uptake patterns were inversely correlated with the expression of phosphorylated paxillin, indicating that the initial passive particle absorbance is the primary limiting step toward complete uptake. Overall, our findings may provide a foundation for mechanical rationalization of particle uptake design.

Severe COVID-19-A Review of Suggested Mechanisms Based on the Role of Extracellular Matrix Stiffness

The severity of COVID-19 commonly depends on age-related tissue stiffness. The aim was to review publications that explain the effect of microenvironmental extracellular matrix stiffness on cellular processes. Platelets and endothelial cells are mechanosensitive. Increased tissue stiffness can trigger cytokine storm with the upregulated expression of pro-inflammatory cytokines, such as tumor necrosis factor alpha and interleukin IL-6, and tissue integrity disruption, leading to enhanced virus entry and disease severity. Increased tissue stiffness in critically ill COVID-19 patients triggers platelet activation and initiates plague formation and thrombosis development. Cholesterol content in cell membrane increases with aging and further enhances tissue stiffness. Membrane cholesterol depletion decreases virus entry to host cells. Membrane cholesterol lowering drugs, such as statins or novel chitosan derivatives, have to be further developed for application in COVID-19 treatment. Statins are also known to decrease arterial stiffness mitigating cardiovascular diseases. Sulfated chitosan derivatives can be further developed for potential use in future as anticoagulants in prevention of severe COVID-19. Anti-TNF-α therapies as well as destiffening therapies have been suggested to combat severe COVID-19. The inhibition of the nuclear factor kappa-light-chain-enhancer of activated B cells pathway must be considered as a therapeutic target in the treatment of severe COVID-19 patients. The activation of mechanosensitive platelets by higher matrix stiffness increases their adhesion and the risk of thrombus formation, thus enhancing the severity of COVID-19.

Substrate stiffness reduces particle uptake by epithelial cells and macrophages in a size-dependent manner through mechanoregulation

Cells continuously exert forces on their environment and respond to changes in mechanical forces by altering their behaviour. Many pathologies such as cancer and fibrosis are hallmarked by dysregulation in the extracellular matrix, driving aberrant behaviour through mechanotransduction pathways. We demonstrate that substrate stiffness can be used to regulate cellular endocytosis of particles in a size-dependent fashion. Culture of A549 epithelial cells and J774A.1 macrophages on polystyrene/glass (stiff) and polydimethylsiloxane (soft) substrates indicated that particle uptake is increased up to six times for A549 and two times for macrophages when cells are grown in softer environments. Furthermore, we altered surface characteristics through the attachment of submicron-sized particles as a method to locally engineer substrate stiffness and topography to investigate the biomechanical changes which occurred within adherent epithelial cells, i.e. characterization of A549 cell spreading and focal adhesion maturation. Consequently, decreasing substrate rigidity and particle-based topography led to a reduction of focal adhesion size. Moreover, expression levels of Yes-associated protein were found to correlate with the degree of particle endocytosis. A thorough appreciation of the mechanical cues may lead to improved solutions to optimize nanomedicine approaches for treatment of cancer and other diseases with abnormal mechanosignalling.

Host-guest interaction-based supramolecular prodrug self-assemblies for GSH-consumption augmented chemotherapy

The over-expressed cellular glutathione (GSH) severely restricts the chemotherapeutic efficacy due to the GSH-induced detoxification of chemical drugs. Herein, how to construct effective drug delivery systems with GSH-consumption property is still a general concern and a major challenge. In this study, the host-guest interactions between water-soluble pillar[6]arene (WP[6]) and chlorambucil-arylboronic acid (Cb-BA) were utilized to construct supramolecular prodrug self-assemblies (SPSAs) with specific stimuli-responsive property. Notably, the BA moiety could not only consume GSH but also rapidly bind curcumin (Cur), which could inhibit the thioredoxin reductase (TrxR) to further reduce the GSH biosynthesis pathway. Benefiting from the functionality of BA-Cur conjugates, the GSH levels could be significantly downregulated, paving a novel way to enhance chemotherapeutic efficacy. In vitro and in vivo investigations demonstrated that this two-pronged GSH-depletion strategy could amplify the cellular oxidative stress and achieve excellent anti-tumor efficacy.

Biomechanical Dependence of SARS-CoV-2 Infections

Older people have been disproportionately vulnerable to the current SARS-CoV-2 pandemic, with an increased risk of severe complications and death compared to other age groups. A mix of underlying factors has been speculated to give rise to this differential infection outcome including changes in lung physiology, weakened immunity, and severe immune response. Our study focuses on the impact of biomechanical changes in lungs that occur as individuals age, that is, the stiffening of the lung parenchyma and increased matrix fiber density. We used hydrogels with an elastic modulus of 0.2 and 50 kPa and conventional tissue culture surfaces to investigate how infection rate changes with parenchymal tissue stiffness in lung epithelial cells challenged with SARS-CoV-2 Spike (S) protein pseudotyped lentiviruses. Further, we employed electrospun fiber matrices to isolate the effect of matrix density. Given the recent data highlighting the importance of alternative virulent strains, we included both the native strain identified in early 2020 and an early S protein variant (D614G) that was shown to increase the viral infectivity markedly. Our results show that cells on softer and sparser scaffolds, closer resembling younger lungs, exhibit higher infection rates by the WT and D614G variant. This suggests that natural changes in lung biomechanics do not increase the propensity for SARS-CoV-2 infection and that other factors, such as a weaker immune system, may contribute to increased disease burden in the elderly.

Resveratrol-Loaded TPGS-Resveratrol-Solid Lipid Nanoparticles for Multidrug-Resistant Therapy of Breast Cancer: In Vivo and In Vitro Study

Multidrug resistance (MDR) is a serious problem during cancer therapy. The purpose of the present study was to formulate D-α-Tocopheryl polyethylene glycol 1000 succinate-resveratrol-solid lipid nanoparticles (TPGS-Res-SLNs) to improve its therapeutic efficacy against breast cancer. In this study, the solvent injection method was used to prepare the TPGS-Res-SLNs. It was found that the TPGS-Res-SLNs exhibited zeta potential and drug-loading of -25.6 ± 1.3 mV and 32.4 ± 2.6%, respectively. Therefore, it was evident that the TPGS-Res-SLNs can increase cellular uptake of chemotherapeutic drugs, induce mitochondrial dysfunction, and augment tumor treatment efficiency by inducing apoptosis. Moreover, it was found that SKBR3/PR cells treated with TPGS-Res-SLNs exhibited significant inhibition of cell migration and invasion, as compared with free resveratrol. In addition, results from in vivo SKBR3/PR xenograft tumor models revealed that TPGS-Res-SLNs has better efficacy in promoting apoptosis of tumor cells owing to high therapeutic outcomes on tumors when compared with the efficacy of free resveratrol. In conclusion, the findings of the present study indicate significant potential for use of TPGS-Res-SLNs as an efficient drug delivery vehicle to overcome drug resistance in breast cancer therapy.

Meet me halfway: Are in vitro 3D cancer models on the way to replace in vivo models for nanomedicine development?

The complexity and diversity of the biochemical processes that occur during tumorigenesis and metastasis are frequently over-simplified in the traditional in vitro cell cultures. Two-dimensional cultures limit researchers' experimental observations and frequently give rise to misleading and contradictory results. Therefore, in order to overcome the limitations of in vitro studies and bridge the translational gap to in vivo applications, 3D models of cancer were developed in the last decades. The three dimensions of the tumor, including its cellular and extracellular microenvironment, are recreated by combining co-cultures of cancer and stromal cells in 3D hydrogel-based growth factors-inclusive scaffolds. More complex 3D cultures, containing functional blood vasculature, can integrate in the system external stimuli (e.g. oxygen and nutrient deprivation, cytokines, growth factors) along with drugs, or other therapeutic compounds. In this scenario, cell signaling pathways, metastatic cascade steps, cell differentiation and self-renewal, tumor-microenvironment interactions, and precision and personalized medicine, are among the wide range of biological applications that can be studied. Here, we discuss a broad variety of strategies exploited by scientists to create in vitro 3D cancer models that resemble as much as possible the biology and patho-physiology of in vivo tumors and predict faithfully the treatment outcome.

Investigation on the Composition of Agarose-Collagen I Blended Hydrogels as Matrices for the Growth of Spheroids from Breast Cancer Cell Lines

Three-dimensional (3D) cell culture systems mimic the structural complexity of the tissue microenvironment and are gaining increasing importance as they resemble the extracellular matrix (ECM)–cell and cell–cell physical interactions occurring in vivo. Several scaffold-based culture systems have been already proposed as valuable tools for large-scale production of spheroids, but they often suffer of poor reproducibility or high costs of production. In this work, we present a reliable 3D culture system based on collagen I-blended agarose hydrogels and show how the variation in the agarose percentage affects the physical and mechanical properties of the resulting hydrogel. The influence of the different physical and mechanical properties of the blended hydrogels on the growth, size, morphology, and cell motility of the spheroids obtained by culturing three different breast cancer cell lines (MCF-7, MDA-MB-361, and MDA-MB-231) was also evaluated. As proof of concept, the cisplatin penetration and its cytotoxic effect on the tumor spheroids as function of the hydrogel stiffness were also investigated. Noteworthily, the possibility to recover the spheroids from the hydrogels for further processing and other biological studies has been considered. This feature, in addition to the ease of preparation, the lack of cross-linking chemistry and the high reproducibility, makes this hydrogel a reliable biomimetic matrix for the growth of 3D cell structures.

Unexpected Role of Nonimmune Cells: Amateur Phagocytes

Effective and efficient efferocytosis of dead cells and associated cellular debris are critical to tissue homeostasis and healing of injured tissues. This important task was previously thought to be restricted to professional phagocytes (PPs). However, accumulating evidence has revealed another type of phagocyte, the amateur phagocyte (AP), which can also participate in efferocytosis. APs are non-myeloid progenitor/nonimmune cells that include differentiated cells (e.g., epithelial cells, fibroblasts, and endothelial cells [ECs]) and stem cells (e.g., neuronal progenitor cells and mesenchymal cells) and can be found throughout the human body. Studies have shown that APs have two prominent roles: identifying and removing dead cells presumably before PPs reach the site of injury and assisting PPs in the removal of cell corpses and the resolution of inflamed tissue. With respect to the engulfment and degradation of dead cells, APs are slower and less efficient than PPs. However, APs are fundamental to preventing the spread of inflammation over a large area. In this review, we present the diversity and characteristics of healthy and non-neoplastic APs in mammals. We also propose a hypothetical mechanism of the efferocytosis of immunoglobulin G (IgG)-opsonized myelin debris by ECs (APs). Furthermore, the ingestion and clearance of dead cells can induce proinflammatory or anti-inflammatory cytokine production, endothelial activation, and cellular fate transition, which contribute to the progression of disease. An understanding of the role of APs is necessary to develop effective intervention strategies, including potential molecular targets for clinical diagnosis and drug development, for inflammation-related diseases.

Integrating Biophysics in Toxicology

Integration of biophysical stimulation in test systems is established in diverse branches of biomedical sciences including toxicology. This is largely motivated by the need to create novel experimental setups capable of reproducing more closely in vivo physiological conditions. Indeed, we face the need to increase predictive power and experimental output, albeit reducing the use of animals in toxicity testing. In vivo, mechanical stimulation is essential for cellular homeostasis. In vitro, diverse strategies can be used to model this crucial component. The compliance of the extracellular matrix can be tuned by modifying the stiffness or through the deformation of substrates hosting the cells via static or dynamic strain. Moreover, cells can be cultivated under shear stress deriving from the movement of the extracellular fluids. In turn, introduction of physical cues in the cell culture environment modulates differentiation, functional properties, and metabolic competence, thus influencing cellular capability to cope with toxic insults. This review summarizes the state of the art of integration of biophysical stimuli in model systems for toxicity testing, discusses future challenges, and provides perspectives for the further advancement of in vitro cytotoxicity studies.

Effect of fluid shear stress on the internalization of kidney-targeted delivery systems in renal tubular epithelial cells

Renal tubular epithelial cells (RTECs) are important target cells for the development of kidney-targeted drug delivery systems. Under physiological conditions, RTECs are under constant fluid shear stress (FSS) from original urine in the renal tubule and respond to changes of FSS by altering their morphology and receptor expression patterns, which may affect reabsorption and cellular uptake. Using a microfluidic system, controlled shear stress was applied to proximal tubule epithelial cell line HK-2. Next, 2-glucosamine, bovine serum albumin, and albumin nanoparticles were selected as representative carriers to perform cell uptake studies in HK-2 cells using the microfluidic platform system with controlled FSS. FSS is proven to impact the morphology of HK-2 cells and upregulate the levels of megalin and clathrin, which then led to enhanced cellular uptake efficiencies of energy-driven carrier systems such as macromolecular and albumin nanoparticles in HK-2 cells. To further investigate the effects of FSS on endocytic behavior mediated by related receptors, a mice model of acute kidney injury with reduced fluid shear stress was established. Consistent with in vitro findings, in vivo studies have also shown reduced fluid shear stress down-regulated the levels of megalin receptors, thereby reducing the renal distribution of albumin nanoparticles.

A Soft Mechanical Phenotype of SH-SY5Y Neuroblastoma and Primary Human Neurons Is Resilient to Oligomeric Aβ(1-42) Injury

Aggregated amyloid beta (Aβ) is widely reported to cause neuronal dystrophy and toxicity through multiple pathways: oxidative stress, disrupting calcium homeostasis, and cytoskeletal dysregulation. The neuro-cytoskeleton is a dynamic structure that reorganizes to maintain cell homeostasis in response to varying soluble and physical cues presented from the extracellular matrix (ECM). Due this relationship between cell health and the ECM, we hypothesize that amyloid toxicity may be directly influenced by physical changes to the ECM (stiffness and dimensionality) through mechanosensitive pathways, and while previous studies demonstrated that Aβ can distort focal adhesion signaling with pathological consequences, these studies do not address the physical contribution from a physiologically relevant matrix. To test our hypothesis that physical cues can adjust Aβ toxicity, SH-SY5Y human neuroblastoma and primary human cortical neurons were plated on soft and stiff, 2D polyacrylamide matrices or suspended in 3D collagen gels. Each cell culture was exposed to escalating concentrations of oligomeric or fibrillated Aβ(1-42) with MTS viability and lactate dehydrogenase toxicity assessed. Actin restructuring was further monitored in live cells by atomic force microscopy nanoindentation, and our results demonstrate that increasing either matrix stiffness or exposure to oligomeric Aβ promotes F-actin polymerization and cell stiffening, while mature Aβ fibrils yielded no apparent cell stiffening and minor toxicity. Moreover, the rounded, softer mechanical phenotype displayed by cells plated onto a compliant matrix also demonstrated a resilience to oligomeric Aβ as noted by a significant recovery of viability when compared to same-dosed cells plated on traditional tissue culture plastic. This recovery was reproduced pharmacologically through inhibiting actin polymerization with cytochalasin D prior to Aβ exposure. These studies indicate that the cell-ECM interface can modify amyloid toxicity in neurons and the matrix-mediated pathways that promote this protection may offer unique targets in amyloid pathologies like Alzheimer's disease.

Matrix stiffness regulates microvesicle-induced fibroblast activation

Extracellular vesicles released by cancer cells have recently been implicated in the differentiation of stromal cells to their activated, cancer-supporting states. Microvesicles, a subset of extracellular vesicles released from the plasma membrane of cancer cells, contain biologically active cargo, including DNA, mRNA, and miRNA, which are transferred to recipient cells and induce a phenotypic change in behavior. While it is known that microvesicles can alter recipient cell phenotype, little is known about how the physical properties of the tumor microenvironment affect fibroblast response to microvesicles. Here, we utilized cancer cell-derived microvesicles and synthetic substrates designed to mimic the stiffness of the tumor and tumor stroma to investigate the effects of microvesicles on fibroblast phenotype as a function of the mechanical properties of the microenvironment. We show that microvesicles released by highly malignant breast cancer cells cause an increase in fibroblast spreading, α-smooth muscle actin expression, proliferation, cell-generated traction force, and collagen gel compaction. Notably, our data indicate that these phenotypic changes occur only on stiff matrices mimicking the stiffness of the tumor periphery and are dependent on the cell type from which the microvesicles are shed. Overall, these results show that the effects of cancer cell-derived microvesicles on fibroblast activation are regulated by the physical properties of the microenvironment, and these data suggest that microvesicles may have a more robust effect on fibroblasts located at the tumor periphery to influence cancer progression.

Reduced Extracellular Matrix Stiffness Prompts SH-SY5Y Cell Softening and Actin Turnover To Selectively Increase Aβ(1-42) Endocytosis

Alzheimer's disease (AD), the most common neurodegenerative disorder, is characterized by the extracellular deposition of dense amyloid beta plaques. Emerging evidence suggests that the production of these plaques is initiated by the intracellular uptake and lysosomal preconcentration of the amyloid-beta (Aβ) peptide. All previous endocytosis studies assess Aβ uptake with cells plated on traditional tissue culture plastic; however, brain tissue is distinctly soft with a low-kPa stiffness. Use of an ultrastiff plastic/glass substrate prompts a mechanosensitive response (increased cell spreading, cell stiffness, and membrane tension) that potentially distorts a cell's endocytic behavior from that observed in vivo or in a more physiologically relevant mechanical environment. Our studies demonstrate substrate stiffness significantly modifies the behavior of undifferentiated SH-SY5Y neuroblastoma, where cells plated on soft (∼1 kPa) substrates display a rounded morphology, decreased actin polymerization, reduced adhesion (decreased β₁ integrin expression), and reduced cell stiffness compared to cells plated on tissue culture plastic. Moreover, these neuroblastoma on softer substrates display a preferential increase in the uptake of the Aβ(1-42) compared to Aβ(1-40), while both isoforms display a clear stiffness-dependent increase of uptake relative to cells plated on plastic. Considering the brain is a soft tissue that continues to soften with age, this mechanosensitive endocytosis of Aβ has significant implications for understanding age-related neurodegeneration and the mechanism behind Aβ uptake and fibril production. Overall, identifying these physical factors that contribute to the pathology of AD may offer novel avenues of therapeutic intervention.

Matrix stiffness regulates epithelial-mesenchymal transition via cytoskeletal remodeling and MRTF-A translocation in osteosarcoma cells

Matrix stiffness is known to alter cellular behaviors in various biological contexts. Previous investigations have shown that epithelial-mesenchymal transition (EMT) promotes the progression and invasion of tumor. Mechanical signaling is identified as a regulator of EMT. However, the molecular mechanisms underlying the influence exerted by matrix stiffness on EMT in osteosarcoma remains largely unknown. Using polyacrylamide hydrogel model, we investigate the effects of matrix stiffness on EMT and migration in osteosarcoma. Our data indicates that high matrix stiffness regulates cell morphology and promotes EMT and migration in osteosarcoma MG63 cell line in vitro. Notably, matrix stiffness promotes polymerization of actin and nuclear accumulation of myocardin-related transcription factor A (MRTF-A). Furthermore, inhibiting MRTF-A by CCG 203971 significantly reduces EMT and migration on rigid gels. These data suggest that matrix stiffness of the tumor microenvironment actively regulate osteosarcoma EMT and migration through cytoskeletal remodeling and translocation of MRTF-A, which may contribute to cancer progression.

Substrate stiffness regulated migration and invasion ability of adenoid cystic carcinoma cells via RhoA/ROCK pathway

OBJECTIVES

Human salivary adenoid cystic carcinoma (SACC) is one of the most common malignant tumours of the salivary gland and has strong migratory and invasive ability, which often lead to poor prognosis and lower survival rate. Tumour tissue tends to stiffen during solid tumour progression. This study aimed to investigate the influence of various substrate stiffness on the migration and invasion of SACC.

METHODS

Salivary adenoid cystic carcinoma cell line ACC2 cells were cultured on polydimethylsiloxane substrates (PDMS) with varying stiffness for investigating the effects of substrate stiffness on the activities of MMPs and TIMPs. The underlying mechanism was also explored.

RESULTS

When ACC2 cells were cultured on various stiffness of PDMS, the expressions of matrix metalloproteinases 2 (MMP2), MMP9, MMP14, RhoA, Rac1, Rho-associated protein kinase 1 (ROCK1) and ROCK2 were up-regulated with increasing substrate stiffness, whereas that of tissue inhibitor of matrix metalloproteinase 1 (TIMP1), TIMP2 and TIMP4 were down-regulated with increasing substrate stiffness.

CONCLUSIONS

Our results showed that substrate stiffness regulated the activities of MMPs and TIMPs and then modulate migratory and invasive ability of ACC2 cells via RhoA/ROCK pathway. This work indicate that matrix stiffness played an important role in progression of SACC, which not only can help understand the strong invasive ability of SACC, but also suggested that therapeutically targeting matrix stiffness may help reduce migration and invasion of SACC and improve effective therapies.