The physics of cancer: the role of physical interactions and mechanical forces in metastasis

Monoterpenoids: An upcoming class of therapeutic agents for modulating cancer metastasis

Monoterpenoids, a sub-class of terpenoids, are secondary metabolites frequently extracted from the essential oils of aromatic plants. Their antitumor properties including antiproliferative, apoptotic, antiangiogenic, and antimetastatic effects along with other biological activities have been the subject of extensive study due to their diverse characteristics. In recent years, numerous investigations have been conducted to understand its potential anticancer impacts, specifically focusing on antiproliferative and apoptotic mechanisms. Metastasis, a malignancy hallmark, can exert either protective or destructive influences on tumor cells. Despite this, the potential antimetastatic and antiangiogenic attributes of monoterpenoids need further exploration. This review focuses on specific monoterpenoids, examining their effects on metastasis and relevant signaling pathways. The monoterpenoids exhibit a high level of complexity as natural products that regulate metastatic proteins through various signaling pathways, including phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin, mitogen-activated protein kinase/extracellular signal-regulated kinase/jun N-terminal kinase, nuclear factor kappa B, vascular endothelial growth factor, and epithelial mesenchymal transition process. Additionally, this review delves into the biosynthesis and classification of monoterpenoids, their potential antitumor impacts on cell lines, the plant sources of monoterpenoids, and the current status of limited clinical trials investigating their efficacy against cancer. Moreover, monoterpenoids depict promising potential in preventing cancer metastasis, however, inadequate clinical trials limit their drug usage. State-of-the-art techniques and technologies are being employed to overcome the challenges of utilizing monoterpenoids as an anticancer agent.

Analyzing force measurements of multi-cellular clusters comprising indeterminate geometries

Multi-cellular biomimetic models often comprise heterogenic geometries. Therefore, quantification of their mechanical properties-which is crucial for various biomedical applications-is a challenge. Due to its simplicity, linear fitting is traditionally used in analyzing force-displacement data of parallel compression measurements of multi-cellular clusters, such as tumor spheroids. However, the linear assumption would be artificial when the contact geometry is not planar. We propose here the integrated elasticity (IE) regression, which is based on extrapolation of established elastic theories for well-defined geometries, and is free, extremely simple to apply, and optimal for analyzing coarsely concave multi-cellular clusters. We studied here the quality of the data analysis in force measurements of tumor spheroids comprising different types of melanoma cells, using either the IE or the traditional linear regressions. The IE regression maintained excellent precision also when the contact geometry deviated from planarity (as shown by our image analysis). While the quality of the linear fittings was relatively satisfying, these predicted smaller elastic moduli as compared to the IE regression. This was in accordance with previous studies, in which the elastic moduli predicted by linear fits were smaller compared to those obtained by well-established methods. This suggests that linear regressions underestimate the elastic constants of bio-samples even in cases where the fitting precision seems satisfying, and highlights the need in alternative methods as the IE scheme. For comparison between different types of spheroids we further recommend to increase the soundness by regarding relative moduli, using universal reference samples.

Probing T-cell activation in nanoliter tumor co-cultures using membrane displacement trap arrays

Immune responses against cancer are inherently stochastic, with small numbers of individual T cells within a larger ensemble of lymphocytes initiating the molecular cascades that lead to tumor cytotoxicity. A potential source of this intra-tumor variability is the differential ability of immune cells to respond to tumor cells. Classical microwell co-cultures of T cells and tumor cells are inadequate for reliably culturing and analyzing low cell numbers needed to probe this variability, and have failed in recapitulating the heterogeneous small domains observed in tumors. Here we leverage a membrane displacement trap array technology that overcomes limitations of conventional microwell plates for immunodynamic studies. The microfluidic platform supports on-demand formation of dense nanowell cultures under continuous perfusion reflecting the tumor microenvironment, with real-time monitoring of T cell proliferation and activation within each nanowell. The system enables selective ejection of cells for profiling by fluorescence activated cell sorting, allowing observed on-chip variability in immune response to be correlated with off-chip quantification of T cell activation. The technology offers new potential for probing the molecular origins of T cell heterogeneity and identifying specific cell phenotypes responsible for initiating and propagating immune cascades within tumors. Insight Box Variability in T cell activation plays a critical role in the immune response against cancer. New tools are needed to unravel the mechanisms that drive successful anti-tumor immune response, and to support the development of novel immunotherapies utilizing rare T cell phenotypes that promote effective immune surveillance. To this end, we present a microfluidic cell culture platform capable of probing differential T cell activation in an array of nanoliter-scale wells coupled with off-chip cell analysis, enabling a high resolution view of variable immune response within tumor / T cell co-cultures containing cell ensembles orders of magnitude smaller than conventional well plate studies.

Experimental measurement and numerical modeling of deformation behavior of breast cancer cells passing through constricted microfluidic channels

During the multistep process of metastasis, cancer cells encounter various mechanical forces which make them deform drastically. Developing accurate in-silico models, capable of simulating the interactions between the mechanical forces and highly deformable cancer cells, can pave the way for the development of novel diagnostic and predictive methods for metastatic progression. Spring-network models of cancer cell, empowered by our recently proposed identification approach, promises a versatile numerical tool for developing experimentally validated models that can simulate complex interactions at cellular scale. Using this numerical tool, we presented spring-network models of breast cancer cells that can accurately replicate the experimental data of deformation behavior of the cells flowing in a fluidic domain and passing narrow constrictions comparable to microcapillary. First, using high-speed imaging, we experimentally studied the deformability of breast cancer cell lines with varying metastatic potential (MCF-7 (less invasive), SKBR-3 (medium-high invasive), and MDA-MB-231 (highly invasive)) in terms of their entry time to a constricted microfluidic channel. We observed that MDA-MB-231, that has the highest metastatic potential, is the most deformable cell among the three. Then, by focusing on this cell line, experimental measurements were expanded to two more constricted microchannel dimensions. The experimental deformability data in three constricted microchannel sizes for various cell sizes, enabled accurate identification of the unknown parameters of the spring-network model of the breast cancer cell line (MDA-MB-231). Our results show that the identified parameters depend on the cell size, suggesting the need for a systematic procedure for identifying the size-dependent parameters of spring-network models of cells. As the numerical results show, the presented cell models can simulate the entry process of the cell into constricted channels with very good agreements with the measured experimental data.

A Novel Primary Cilium-Mediated Mechanism Through which Osteocytes Regulate Metastatic Behavior of Both Breast and Prostate Cancer Cells

Bone metastases are a common cause of suffering in breast and prostate cancer patients, however, the interaction between bone cells and cancer cells is poorly understood. Using a series of co-culture, conditioned media, human cancer spheroid, and organ-on-a-chip experiments, this study reveals that osteocytes suppress cancer cell proliferation and increase migration via tumor necrosis factor alpha (TNF-α) secretion. This action is regulated by osteocyte primary cilia and associated intraflagellar transport protein 88 (IFT88). Furthermore, it shows that cancer cells block this mechanism by secreting transforming growth factor beta (TGF-β), which disrupts osteocyte cilia and IFT88 gene expression. This bi-directional crosstalk signaling between osteocytes and cancer cells is common to both breast and prostate cancer. This study also proposes that osteocyte inhibition of cancer cell proliferation decreases as cancer cells increase, producing more TGF-β. Hence, a positive feedback loop develops accelerating metastatic tumor growth. These findings demonstrate the importance of cancer cell-osteocyte signaling in regulating breast and prostate bone metastases and support the development of therapies targeting this pathway.

Kinetics of cancer metastasis

The formation of metastases during cancer is now considered to be induced by migrating metastatic stem cells (MetSCs) in preexisting niches or niches induced by MetSCs or tumor-derived exosomes (TDEs). I propose and compare two simplest generic models describing these two scenarios. The number of tumors is predicted (i) to increase exponentially in the case of preexisting niches and (ii) to diverge during a finite time interval in the case of induced niches. The latter prediction is novel and of interest because rapid collapse in the end of a finite time interval is a well-known feature of the cancer metastasis. Two advanced models describing the two scenarios of cancer metastasis have been scrutinized as well. These models clarify the likely role of various specific factors in the metastasis. In particular, the equations derived in the framework of the advanced model with preexisting niches have been solved analytically allowing (i) to clarify the factors determining the duration of the period from the initiation of the primary tumor to the phase when the metastases start to dominate, (ii) to estimate the number of metastases in the end of this period, and (iii) to explains why the use of chemotherapy typically results in the improvement of the patient state only for a relatively short period. The equations derived in the framework of the advanced model with induced niches have no analytical solution, and their analysis merits additional attention.

Inhibition of the membrane repair protein annexin-A2 prevents tumor invasion and metastasis

Cancer cells are exposed to major compressive and shearing forces during invasion and metastasis, leading to extensive plasma membrane damage. To survive this mechanical stress, they need to repair membrane injury efficiently. Targeting the membrane repair machinery is thus potentially a new way to prevent invasion and metastasis. We show here that annexin-A2 (ANXA2) is required for membrane repair in invasive breast and pancreatic cancer cells. Mechanistically, we show by fluorescence and electron microscopy that cells fail to reseal shear-stress damaged membrane when ANXA2 is silenced or the protein is inhibited with neutralizing antibody. Silencing of ANXA2 has no effect on proliferation in vitro, and may even accelerate migration in wound healing assays, but reduces tumor cell dissemination in both mice and zebrafish. We expect that inhibiting membrane repair will be particularly effective in aggressive, poor prognosis tumors because they rely on the membrane repair machinery to survive membrane damage during tumor invasion and metastasis. This could be achieved either with anti-ANXA2 antibodies, which have been shown to inhibit metastasis of breast and pancreatic cancer cells, or with small molecule drugs.

Single-Cell Plasmonic Immunosandwich Assay Reveals the Modulation of Nucleocytoplasmic Localization Fluctuation of ABL1 on Cell Migration

Cell migration is an essential process of cancer metastasis. The spatiotemporal dynamics of signaling molecules influences cellular phenotypic outcomes. It has been increasingly documented that the Abelson (ABL) family kinases play critical roles in solid tumors. However, ABL1's shuttling dynamics in cell migration still remains unexplored. This is mainly because tools permitting the investigation of translocation dynamics of proteins in single living cells are lacking. Herein, to bridge this gap, we developed a unique multifunctional integrated single-cell analysis method that enables long-term observation of cell migration behavior and monitoring of signaling proteins and complexes at the subcellular level. We found that the shuttling of ABL1's to the cytoplasm results in a higher migration speed, while its trafficking back to the nucleus leads to a lower one. Furthermore, our results indicated that fluctuant protein-protein interactions between 14-3-3 and ABL1 modulate ABL1's nucleocytoplasmic fluctuation and eventually affect the cell speed. Importantly, based on these new insights, we demonstrated that disturbing ABL1's nuclear export traffic and 14-3-3-ABL1 complexes formation can effectively suppress cell migration. Thus, our method opens up a new possibility for simultaneous tracking of internal molecular mechanisms and cell behavior, providing a promising tool for the in-depth study of cancer.

Calcium influx rapidly establishes distinct spatial recruitments of Annexins to cell wounds

To survive daily damage, the formation of actomyosin ring at the wound periphery is required to rapidly close cell wounds. Calcium influx is one of the start signals for these cell wound repair events. Here, we find that rapid recruitment of all three Drosophila calcium responding and phospholipid binding Annexin proteins (AnxB9, AnxB10, AnxB11) to distinct regions around the wound are regulated by the quantity of calcium influx rather than their binding to specific phospholipids. The distinct recruitment patterns of these Annexins regulate the subsequent recruitment of RhoGEF2 and RhoGEF3 through actin stabilization to form a robust actomyosin ring. Surprisingly, we find that reduced extracellular calcium and depletion of intracellular calcium affect cell wound repair differently, despite these two conditions exhibiting similar GCaMP signals. Thus, our results suggest that, in addition to initiating repair events, both the quantity and sources of calcium influx are important for precise Annexin spatiotemporal protein recruitment to cell wounds and efficient wound repair.

Investigating the Influence of Heterogeneity Within Cell Types on Microvessel Network Transport

Background

Current research on the biophysics of circulating tumor cells often overlooks the heterogeneity of cell populations, focusing instead on average cellular properties. This study aims to address the gap by considering the diversity of cell biophysical characteristics and their implications on cancer spread.

Methods

We utilized computer simulations to assess the influence of variations in cell size and membrane elasticity on the behavior of cells within fluid environments. The study controlled cell and fluid properties to systematically investigate the transport of tumor cells through a simulated network of branching channels.

Results

The simulations revealed that even minor differences in cellular properties, such as slight changes in cell radius or shear elastic modulus, lead to significant changes in the fluid conditions that cells experience, including velocity and wall shear stress (p < 0.001).

Conclusion

The findings underscore the importance of considering cell heterogeneity in biophysical studies and suggest that small variations in cellular characteristics can profoundly impact the dynamics of tumor cell circulation. This has potential implications for understanding the mechanisms of cancer metastasis and the development of therapeutic strategies.

Modeling critical interaction for metastasis between circulating tumor cells (CTCs) and platelets adhered to the capillary wall

BACKGROUND AND OBJECTIVE

We used a 2D fluid-solid interaction (FSI) model to investigate the critical conditions for the arrest of the CTCs traveling through the narrowed capillary with a platelet attached to the capillary wall. This computational model allows us to determine the deformations and the progression of the passage of the CTC through different types of microvessels with platelet included.

METHODS

The modeling process is obtained using the strong coupling approach following the remeshing procedure. Also, the 1D FE rope element for simulating active ligand-receptor bonds is implemented in our computational tool (described below).

RESULTS

A relationship between the CTCs properties (size and stiffness), the platelet size and stiffness, and the ligand-receptor interaction intensity, on one side, and the time in contact between the CTCs and platelet and conditions for the cell arrest, on the other side, are determined. The model is further validated in vitro by using a microfluidic device with metastatic breast tumor cells.

CONCLUSIONS

The computational framework that is presented, with accompanying results, can be used as a powerful tool to study biomechanical conditions for CTCs arrest in interaction with platelets, giving a prognosis of disease progression.

Global lipid remodelling by hypoxia aggravates migratory potential in pancreatic cancer while maintaining plasma membrane homeostasis

Hypoxia plays an important role in pancreatic cancer progression. It drives various metabolic reprogramming in cells including that of lipids, which in turn, can modify the structure and function of cell membranes. Homeostatic adaptation of membranes is well-recognized, but how and if it is regulated in hypoxic pancreatic cancer and its relation to aggressive phenotype and metastasis remains elusive. Here we show hypoxia-induced extensive global lipid remodelling spanning changes in lipid classes, unsaturation levels, glyceryl backbone and acyl chain lengths. No major modulation of plasma membrane biophysical properties revealed a decoupling of lipidome modulation from membrane properties under hypoxia. This was supported by observing minor changes in the lipidome of plasma membranes under hypoxia. Further, hypoxia increased migration and invasion underpinned by reduced actin volume, cell cortical stiffness and facile tether dynamics. In conclusion, we demonstrate buffering of the lipidome alterations leading to a homeostatic membrane response. These findings will help to understand the hypoxic regulation of pancreatic membrane homeostasis and identify tangible theranostic avenues.

Prognostic potential of preoperative circulating tumor cells to predict the early progression recurrence in hepatocellular carcinoma patients after hepatectomy

BACKGROUND

The role of circulating tumor cells (CTCs) in prognosis prediction has been actively studied in hepatocellular carcinoma (HCC) patients. However, their efficiency in accurately predicting early progression recurrence (EPR) is unclear. This study aimed to investigate the clinical potential of preoperative CTCs to predict EPR in HCC patients after hepatectomy.

METHODS

One hundred forty-five HCC patients, whose preoperative CTCs were detected, were enrolled. Based on the recurrence times and types, the patients were divided into four groups, including early oligo-recurrence (EOR), EPR, late oligo-recurrence (LOR), and late progression recurrence (LPR).

RESULTS

Among the 145 patients, 133 (91.7%) patients had a postoperative recurrence, including 51 EOR, 42 EPR, 39 LOR, and 1 LPR patient. Kaplan-Meier survival curve analysis indicated that the HCC patients with EPR had the worst OS. There were significant differences in the total-CTCs (T-CTCs) and CTCs subtypes count between the EPR group with EOR and LOR groups. Cox regression analysis indicated that the T-CTC count of > 5/5 mL, the presence of microvascular invasion (MVI) and satellite nodules were the independent risk factors for EPR. The efficiency of T-CTCs was superior as compared to those of the other indicators in predicting EPR. Moreover, the combined model demonstrated a markedly superior area under the curve (AUC).

CONCLUSIONS

The HCC patients with EPR had the worst OS. The preoperative CTCs was served as a prognostic indicator of EPR for HCC patients. The combined models, including T-CTCs, MVI, and satellite nodules, had the best performance to predict EPR after hepatectomy.

Magnetically controlled cyclic microscale deformation of in vitro cancer invasion models

Mechanical cues play an important role in the metastatic cascade of cancer. Three-dimensional (3D) tissue matrices with tunable stiffness have been extensively used as model systems of the tumor microenvironment for physiologically relevant studies. Tumor-associated cells actively deform these matrices, providing mechanical cues to other cancer cells residing in the tissue. Mimicking such dynamic deformation in the surrounding tumor matrix may help clarify the effect of local strain on cancer cell invasion. Remotely controlled microscale magnetic actuation of such 3D in vitro systems is a promising approach, offering a non-invasive means for in situ interrogation. Here, we investigate the influence of cyclic deformation on tumor spheroids embedded in matrices, continuously exerted for days by cell-sized anisotropic magnetic probes, referred to as μRods. Particle velocimetry analysis revealed the spatial extent of matrix deformation produced in response to a magnetic field, which was found to be on the order of 200 μm, resembling strain fields reported to originate from contracting cells. Intracellular calcium influx was observed in response to cyclic actuation, as well as an influence on cancer cell invasion from 3D spheroids, as compared to unactuated controls. Furthermore, RNA sequencing revealed subtle upregulation of certain genes associated with migration and stress, such as induced through mechanical deformation, for spheroids exposed to actuation vs. controls. Localized actuation at one side of a tumor spheroid tended to result in anisotropic invasion toward the μRods causing the deformation. In summary, our approach offers a strategy to test and control the influence of non-invasive micromechanical cues on cancer cell invasion and metastasis.

Enhancing Adaptive Physics Refinement Simulations Through the Addition of Realistic Red Blood Cell Counts

Simulations of cancer cell transport require accurately modeling mm-scale and longer trajectories through a circulatory system containing trillions of deformable red blood cells, whose intercellular interactions require submicron fidelity. Using a hybrid CPU-GPU approach, we extend the advanced physics refinement (APR) method to couple a finely-resolved region of explicitly-modeled red blood cells to a coarsely-resolved bulk fluid domain. We further develop algorithms that: capture the dynamics at the interface of differing viscosities, maintain hematocrit within the cell-filled volume, and move the finely-resolved region and encapsulated cells while tracking an individual cancer cell. Comparison to a fully-resolved fluid-structure interaction model is presented for verification. Finally, we use the advanced APR method to simulate cancer cell transport over a mm-scale distance while maintaining a local region of RBCs, using a fraction of the computational power required to run a fully-resolved model.

Intravital measurements of solid stresses in tumours reveal length-scale and microenvironmentally dependent force transmission

In cancer, solid stresses impede the delivery of therapeutics to tumours and the trafficking and tumour infiltration of immune cells. Understanding such consequences and the origin of solid stresses requires their probing in vivo at the cellular scale. Here we report a method for performing volumetric and longitudinal measurements of solid stresses in vivo, and findings from its applicability to tumours. We used multimodal intravital microscopy of fluorescently labelled polyacrylamide beads injected in breast tumours in mice as well as mathematical modelling to compare solid stresses at the single-cell and tissue scales, in primary and metastatic tumours, in vitro and in mice, and in live mice and post-mortem tissue. We found that solid-stress transmission is scale dependent, with tumour cells experiencing lower stresses than their embedding tissue, and that tumour cells in lung metastases experience substantially higher solid stresses than those in the primary tumours. The dependence of solid stresses on length scale and the microenvironment may inform the development of therapeutics that sensitize cancer cells to such mechanical forces.

Mechanobiology in oncology: basic concepts and clinical prospects

The interplay between genetic transformations, biochemical communications, and physical interactions is crucial in cancer progression. Metastasis, a leading cause of cancer-related deaths, involves a series of steps, including invasion, intravasation, circulation survival, and extravasation. Mechanical alterations, such as changes in stiffness and morphology, play a significant role in all stages of cancer initiation and dissemination. Accordingly, a better understanding of cancer mechanobiology can help in the development of novel therapeutic strategies. Targeting the physical properties of tumours and their microenvironment presents opportunities for intervention. Advancements in imaging techniques and lab-on-a-chip systems enable personalized investigations of tumor biomechanics and drug screening. Investigation of the interplay between genetic, biochemical, and mechanical factors, which is of crucial importance in cancer progression, offers insights for personalized medicine and innovative treatment strategies.

Interfacial morphodynamics of proliferating microbial communities

In microbial communities, various cell types often coexist by occupying distinct spatial domains. What determines the shape of the interface between such domains-which in turn influences the interactions between cells and overall community function? Here, we address this question by developing a continuum model of a 2D spatially-structured microbial community with two distinct cell types. We find that, depending on the balance of the different cell proliferation rates and substrate friction coefficients, the interface between domains is either stable and smooth, or unstable and develops finger-like protrusions. We establish quantitative principles describing when these different interfacial behaviors arise, and find good agreement both with the results of previous experimental reports as well as new experiments performed here. Our work thus helps to provide a biophysical basis for understanding the interfacial morphodynamics of proliferating microbial communities, as well as a broader range of proliferating active systems.

The relationship between cancer and biomechanics

The onset, development, diagnosis, and treatment of cancer involve intricate interactions among various factors, spanning the realms of mechanics, physics, chemistry, and biology. Within our bodies, cells are subject to a variety of forces such as gravity, magnetism, tension, compression, shear stress, and biological static force/hydrostatic pressure. These forces are perceived by mechanoreceptors as mechanical signals, which are then transmitted to cells through a process known as mechanical transduction. During tumor development, invasion and metastasis, there are significant biomechanical influences on various aspects such as tumor angiogenesis, interactions between tumor cells and the extracellular matrix (ECM), interactions between tumor cells and other cells, and interactions between tumor cells and the circulatory system and vasculature. The tumor microenvironment comprises a complex interplay of cells, ECM and vasculature, with the ECM, comprising collagen, fibronectins, integrins, laminins and matrix metalloproteinases, acting as a critical mediator of mechanical properties and a key component within the mechanical signaling pathway. The vasculature exerts appropriate shear forces on tumor cells, enabling their escape from immune surveillance, facilitating their dissemination in the bloodstream, dictating the trajectory of circulating tumor cells (CTCs) and playing a pivotal role in regulating adhesion to the vessel wall. Tumor biomechanics plays a critical role in tumor progression and metastasis, as alterations in biomechanical properties throughout the malignant transformation process trigger a cascade of changes in cellular behavior and the tumor microenvironment, ultimately culminating in the malignant biological behavior of the tumor.

Surface nanotopography and cell shape modulate tumor cell susceptibility to NK cell cytotoxicity

Natural killer (NK) cells are innate cytotoxic lymphocytes exerting cytotoxicity against virally infected cells and tumor cells. NK cell cytotoxicity is primarily determined by biochemical signals received from ligands expressed on target cell surfaces, but it is also possible that biophysical environments of tumor cells, such as nanoscale surface topography typically existing on extracellular matrixes (ECMs) or cell morphology determined by ECM spaces or cell density, regulate NK cell cytotoxicity. In this study, micro/nanofabrication technology was applied to examine this possibility. Tumor cells were plated on flat or nanogrooved surfaces, or micropatterned into circular or elliptical geometries, and the effects of surface topography and tumor cell morphology on NK cell cytotoxicity were investigated. NK cells exhibited significantly higher cytotoxicity against tumor cells on nanogrooved surfaces or tumor cells in elliptical patterns than tumor cells on flat surfaces or tumor cells in circular patterns, respectively. The amounts of stress fiber formation in tumor cells positively correlated with NK cell cytotoxicity, indicating that increased cellular tension of tumor cells, either mediated by nanogrooved surfaces or elongated morphologies, was a key factor regulating NK cell cytotoxicity. These results may provide insight into the design of NK cell-based cancer immunotherapy.

Reuniting philosophy and science to advance cancer research

Cancers rely on multiple, heterogeneous processes at different scales, pertaining to many biomedical fields. Therefore, understanding cancer is necessarily an interdisciplinary task that requires placing specialised experimental and clinical research into a broader conceptual, theoretical, and methodological framework. Without such a framework, oncology will collect piecemeal results, with scant dialogue between the different scientific communities studying cancer. We argue that one important way forward in service of a more successful dialogue is through greater integration of applied sciences (experimental and clinical) with conceptual and theoretical approaches, informed by philosophical methods. By way of illustration, we explore six central themes: (i) the role of mutations in cancer; (ii) the clonal evolution of cancer cells; (iii) the relationship between cancer and multicellularity; (iv) the tumour microenvironment; (v) the immune system; and (vi) stem cells. In each case, we examine open questions in the scientific literature through a philosophical methodology and show the benefit of such a synergy for the scientific and medical understanding of cancer.

A deformability-based biochip for precise label-free stratification of metastatic subtypes using deep learning

Cellular deformability is a promising biomarker for evaluating the physiological state of cells in medical applications. Microfluidics has emerged as a powerful technique for measuring cellular deformability. However, existing microfluidic-based assays for measuring cellular deformability rely heavily on image analysis, which can limit their scalability for high-throughput applications. Here, we develop a parallel constriction-based microfluidic flow cytometry device and an integrated computational framework (ATMQcD). The ATMQcD framework includes automatic training set generation, multiple object tracking, segmentation, and cellular deformability quantification. The system was validated using cancer cell lines of varying metastatic potential, achieving a classification accuracy of 92.4% for invasiveness assessment and stratifying cancer cells before and after hypoxia treatment. The ATMQcD system also demonstrated excellent performance in distinguishing cancer cells from leukocytes (accuracy = 89.5%). We developed a mechanical model based on power-law rheology to quantify stiffness, which was fitted with measured data directly. The model evaluated metastatic potentials for multiple cancer types and mixed cell populations, even under real-world clinical conditions. Our study presents a highly robust and transferable computational framework for multiobject tracking and deformation measurement tasks in microfluidics. We believe that this platform has the potential to pave the way for high-throughput analysis in clinical applications, providing a powerful tool for evaluating cellular deformability and assessing the physiological state of cells.

Predicting cancer stages from tissue energy dissipation

Understanding cancer staging in order to predict its progression is vital to determine its severity and to plan the most appropriate therapies. This task has attracted interest from different fields of science and engineering. We propose a computational model that predicts the evolution of cancer in terms of the intimate structure of the tissue, considering that this is a self-organised structure that undergoes transformations governed by non-equilibrium thermodynamics laws. Based on experimental data on the dependence of tissue configurations on their elasticity and porosity, we relate the cancerous tissue stages with the energy dissipated, showing quantitatively that tissues in more advanced stages dissipate more energy. The knowledge of this energy allows us to know the probability of observing the tissue in its different stages and the probability of transition from one stage to another. We validate our results with experimental data and statistics from the World Health Organisation. Our quantitative approach provides insights into the evolution of cancer through its different stages, important as a starting point for new and integrative research to defeat cancer.

Mechano-induced homotypic patterned domain formation by monocytes

Matrix stiffness and corresponding mechano-signaling play indispensable roles in cellular phenotypes and functions. How tissue stiffness influences the behavior of monocytes, a major circulating leukocyte of the innate system, and how it may promote the emergence of collective cell behavior is less understood. Here, using tunable collagen-coated hydrogels of physiological stiffness, we show that human primary monocytes undergo a dynamic local phase separation to form highly regular, reversible, multicellular, multi-layered domains on soft matrix. Local activation of the β2 integrin initiates inter-cellular adhesion, while global soluble inhibitory factors maintain the steady state domain pattern over days. Patterned domain formation generated by monocytes is unique among other key immune cells, including macrophages, B cells, T cells, and NK cells. While inhibiting their phagocytic capability, domain formation promotes monocytes' survival. We develop a computational model based on the Cahn-Hilliard equation of phase separation, combined with a Turing mechanism of local activation and global inhibition suggested by our experiments, and provides experimentally validated predictions of the role of seeding density and both chemotactic and random cell migration on domain pattern formation. This work reveals that, unlike active matters, cells can generate complex cell phases by exploiting their mechanosensing abilities and combined short-range interactions and long-range signals to enhance their survival.

The Mechanics of Tumor Cells Dictate Malignancy via Cytoskeleton-Mediated APC/Wnt/β-Catenin Signaling

Tumor cells progressively remodel cytoskeletal structures and reduce cellular stiffness during tumor progression, implicating the correlation between cell mechanics and malignancy. However, the roles of tumor cell cytoskeleton and the mechanics in tumor progression remain incompletely understood. We report that softening/stiffening tumor cells by targeting actomyosin promotes/suppresses self-renewal in vitro and tumorigenic potential in vivo. Weakening/strengthening actin cytoskeleton impairs/reinforces the interaction between adenomatous polyposis coli (APC) and β-catenin, which facilitates β-catenin nuclear/cytoplasmic localization. Nuclear β-catenin binds to the promoter of Oct4, which enhances its transcription that is crucial in sustaining self-renewal and malignancy. These results demonstrate that the mechanics of tumor cells dictate self-renewal through cytoskeleton-APC-Wnt/β-catenin-Oct4 signaling, which are correlated with tumor differentiation and patient survival. This study unveils an uncovered regulatory role of cell mechanics in self-renewal and malignancy, and identifies tumor cell mechanics as a hallmark not only for cancer diagnosis but also for mechanotargeting.

Lysyl Oxidases as Targets for Cancer Therapy and Diagnostic Imaging

The understanding of the contribution of the tumour microenvironment to cancer progression and metastasis, in particular the interplay between tumour cells, fibroblasts and the extracellular matrix has grown tremendously over the last years. Lysyl oxidases are increasingly recognised as key players in this context, in addition to their function as drivers of fibrotic diseases. These insights have considerably stimulated drug discovery efforts towards lysyl oxidases as targets over the last decade. This review article summarises the biochemical and structural properties of theses enzymes. Their involvement in tumour progression and metastasis is highlighted from a biochemical point of view, taking into consideration both the extracellular and intracellular action of lysyl oxidases. More recently reported inhibitor compounds are discussed with an emphasis on their discovery, structure-activity relationships and the results of their biological characterisation. Molecular probes developed for imaging of lysyl oxidase activity are reviewed from the perspective of their detection principles, performance and biomedical applications.

Fabrication of a self-assembled and vascularized tumor array via bioprinting on a microfluidic chip

A tumor microenvironment (TME) is a complex system that comprises various components, including blood vessels that play a crucial role in supplying nutrients, oxygen, and growth factors, as well as delivering chemotherapy drugs to the tumor mass through the vascular endothelial barrier. To replicate the TME in vitro, several bioprinting and microfluidic organ-on-a-chip technologies have been developed. However, these technologies have not been fully exploited in terms of potential benefits of bioprinting and microfluidics, such as precise spatial control for biological samples, construction of multiple TMEs per microfluidic device, and the ability to adjust culture environments for better biological similarity. In addition, the complex transport phenomena within the vascular endothelial barrier and the aggregated tumor mass in the TME model should be considered before applying the model to drug treatment and screening. In this study, we describe a novel integrative technology that addresses these issues by introducing a self-organized TME array bioprinted on a microfluidic chip consisting of a vascular endothelial barrier surrounding breast cancer spheroids. To integrate the TME array onto the microfluidic platform, a microfluidic substrate for extrusion bioprinting was developed for a cell culture platform, which enables diffusivity control by microstructures and establishes a perfusion culture environment inside the culture channel. We also analyzed the cellular behaviors within the TME array to investigate the influence of the diffusivity on the self-organization process required to form the vascular endothelial barrier surrounding breast cancer spheroids.

Micro-engineering and nano-engineering approaches to investigate tumour ecosystems

The interactions among tumour cells, the tumour microenvironment (TME) and non-tumour tissues are of interest to many cancer researchers. Micro-engineering approaches and nanotechnologies are under extensive exploration for modelling these interactions and measuring them in situ and in vivo to investigate therapeutic vulnerabilities in cancer and extend a systemic view of tumour ecosystems. Here we highlight the greatest opportunities for improving the understanding of tumour ecosystems using microfluidic devices, bioprinting or organ-on-a-chip approaches. We also discuss the potential of nanosensors that can transmit information from within the TME or elsewhere in the body to address scientific and clinical questions about changes in chemical gradients, enzymatic activities, metabolic and immune profiles of the TME and circulating analytes. This Review aims to connect the cancer biology and engineering communities, presenting biomedical technologies that may expand the methodologies of the former, while inspiring the latter to develop approaches for interrogating cancer ecosystems.

Fluid shear stress enhances natural killer cell's cytotoxicity toward circulating tumor cells through NKG2D-mediated mechanosensing

Tumor cells metastasize to distant organs mainly via hematogenous dissemination, in which circulating tumor cells (CTCs) are relatively vulnerable, and eliminating these cells has great potential to prevent metastasis. In vasculature, natural killer (NK) cells are the major effector lymphocytes for efficient killing of CTCs under fluid shear stress (FSS), which is an important mechanical cue in tumor metastasis. However, the influence of FSS on the cytotoxicity of NK cells against CTCs remains elusive. We report that the death rate of CTCs under both NK cells and FSS is much higher than the combined death induced by either NK cells or FSS, suggesting that FSS may enhance NK cell's cytotoxicity. This death increment is elicited by shear-induced NK activation and granzyme B entry into target cells rather than the death ligand TRAIL or secreted cytokines TNF-α and IFN-γ. When NK cells form conjugates with CTCs or adhere to MICA-coated substrates, NK cell activating receptor NKG2D can directly sense FSS to induce NK activation and degranulation. These findings reveal the promotive effect of FSS on NK cell's cytotoxicity toward CTCs, thus providing new insight into immune surveillance of CTCs within circulation.

Microfluidic Microcirculation Mimetic for Exploring Biophysical Mechanisms of Chemotherapy-Induced Metastasis

There is rapidly emerging evidence from pre-clinical studies, patient samples and patient subpopulations that certain chemotherapeutics inadvertently produce prometastatic effects. Prior to this, we showed that doxorubicin and daunorubicin stiffen cells before causing cell death, predisposing the cells to clogging and extravasation, the latter being a step in metastasis. Here, we investigate which other anti-cancer drugs might have similar prometastatic effects by altering the biophysical properties of cells. We treated myelogenous (K562) leukemic cancer cells with the drugs nocodazole and hydroxyurea and then measured their mechanical properties using a microfluidic microcirculation mimetic (MMM) device, which mimics aspects of blood circulation and enables the measurement of cell mechanical properties via transit times through the device. We also quantified the morphological properties of cells to explore biophysical mechanisms underlying the MMM results. Results from MMM measurements show that nocodazole- and hydroxyurea-treated K562 cells exhibit significantly altered transit times. Nocodazole caused a significant (p < 0.01) increase in transit times, implying a stiffening of cells. This work shows the feasibility of using an MMM to explore possible biophysical mechanisms that might contribute to chemotherapy-induced metastasis. Our work also suggests cell mechanics as a therapeutic target for much needed antimetastatic strategies in general.

The weakness of senescent dermal fibroblasts

Skin is the largest human organ with easily noticeable biophysical manifestations of aging. As human tissues age, there is chronological accumulation of biophysical changes due to internal and environmental factors. Skin aging leads to decreased elasticity and the loss of dermal matrix integrity via degradation. The mechanical properties of the dermal matrix are maintained by fibroblasts, which undergo replicative aging and may reach senescence. While the secretory phenotype of senescent fibroblasts is well studied, little is known about changes in the fibroblasts biophysical phenotype. Therefore, we compare biophysical properties of young versus proliferatively aged primary fibroblasts via fluorescence and traction force microscopy, single-cell atomic force spectroscopy, microfluidics, and microrheology of the cytoskeleton. Results show senescent fibroblasts have decreased cytoskeletal tension and myosin II regulatory light chain phosphorylation, in addition to significant loss of traction force. The alteration of cellular forces is harmful to extracellular matrix homeostasis, while decreased cytoskeletal tension can amplify epigenetic changes involved in senescence. Further exploration and detection of these mechanical phenomena provide possibilities for previously unexplored pharmaceutical targets against aging.

Micropipette-assisted atomic force microscopy for single-cell 3D manipulations and nanomechanical measurements

Mechanical cues play a crucial role in regulating physiological and pathological processes, and atomic force microscopy (AFM) has become an important and standard tool for measuring the mechanical properties of single cells. In particular, providing a capability to manipulate cells in a three-dimensional (3D) space benefits enhancing the applications of AFM measurements in cell biology. Here, we present the complementary integration of AFM and micropipette micromanipulation, which allows precise 3D manipulations and nanomechanical measurements of single living cells. A micropipette micromanipulation system under the guidance of optical microscopy was established to isolate single living cells, and polydimethylsiloxane (PDMS) micropillar substrates were used to physically immobilize the isolated living cells for downstream AFM detection. The viscoelastic properties (Young's modulus, relaxation time, viscosity) of cells were quantitatively measured by AFM-based indentation assay. The effectiveness of micropipette-assisted AFM in single-cell analysis was confirmed on both living animal suspended cells and living animal adherent cells, showing dramatic changes in cell mechanics in different states and revealing the dynamics of single cells grown on micropillar arrays. The study demonstrates the great potential of a micropipette to aid AFM in single-cell manipulations for better accessing the mechanical cues involved in cellular processes, which will allow additional studies of single-cell mechanics and will benefit the field of mechanobiology.

MR Elastography in Cancer

ABSTRACT

The mechanical traits of cancer include abnormally high solid stress as well as drastic and spatially heterogeneous changes in intrinsic mechanical tissue properties. Whereas solid stress elicits mechanosensory signals promoting tumor progression, mechanical heterogeneity is conducive to cell unjamming and metastatic spread. This reductionist view of tumorigenesis and malignant transformation provides a generalized framework for understanding the physical principles of tumor aggressiveness and harnessing them as novel in vivo imaging markers. Magnetic resonance elastography is an emerging imaging technology for depicting the viscoelastic properties of biological soft tissues and clinically characterizing tumors in terms of their biomechanical properties. This review article presents recent technical developments, basic results, and clinical applications of magnetic resonance elastography in patients with malignant tumors.

Mechano-induced homotypic patterned domain formation by monocytes

Matrix stiffness and corresponding mechano-signaling play indispensable roles in cellular phenotypes and functions. How tissue stiffness influences the behavior of monocytes, a major circulating leukocyte of the innate system, and how it may promote the emergence of collective cell behavior is less understood. Here, using tunable collagen-coated hydrogels of physiological stiffness, we show that human primary monocytes undergo a dynamic local phase separation to form highly patterned multicellular multi-layered domains on soft matrix. Local activation of the β2 integrin initiates inter-cellular adhesion, while global soluble inhibitory factors maintain the steady-state domain pattern over days. Patterned domain formation generated by monocytes is unique among other key immune cells, including macrophages, B cells, T cells, and NK cells. While inhibiting their phagocytic capability, domain formation promotes monocytes' survival. We develop a computational model based on the Cahn-Hilliard equation, which includes combined local activation and global inhibition mechanisms of intercellular adhesion suggested by our experiments, and provides experimentally validated predictions of the role of seeding density and both chemotactic and random cell migration on pattern formation.

The promoting effect and mechanism of Nrf2 on cell metastasis in cervical cancer

BACKGROUND

Cervical cancer (CC) has poor prognosis and high mortality rate for its metastasis during the disease progression. Epithelial-mesenchymal transition (EMT) and anoikis are initial and pivotal steps during the metastatic process. Although higher levels of Nrf2 are associated with aggressive tumor behaviors in cervical cancer, the detailed mechanism of Nrf2 in cervical cancer metastasis, especially EMT and anoikis, remains unclear.

METHODS

Immunohistochemistry (IHC) was used to examine Nrf2 expression in CC. Wound healing assay and transwell analysis were used to evaluate the migration ability of CC cells. Western blot, qTR-PCR and immunofluorescent staining were used to verify the expression level of Nrf2, the EMT associated markers and anoikis associated proteins. Flow cytometry assays and cell counting were used to detect the apoptosis of cervical cancer cells. The lung and lymph node metastatic mouse model were established for studies in vivo. The interaction between Nrf2 and Snail1 was confirmed by rescue-of-function assay.

RESULTS

When compared with cervical cancer patients without lymph node metastasis, Nrf2 was highly expressed in patients with lymph node metastasis. And Nrf2 was proved to enhance the migration ability of HeLa and SiHa cells. In addition, Nrf2 was positively correlated with EMT processes and negatively associated with anoikis in cervical cancer. In vivo, a xenograft assay also showed that Nrf2 facilitated both pulmonary and lymphatic distant metastasis of cervical cancer. Rescue-of-function assay further revealed the mechanism that Nrf2 impacted the metastasis of CC through Snail1.

CONCLUSION

Our fundings established Nrf2 plays a crucial role in the metastasis of cervical cancer by enhancing EMT and resistance to anoikis by promoting the expression of Snail1, with potential value as a therapeutic candidate.

Spatial Heterogeneity in Cytoskeletal Mechanics Response to TGF-β1 and Hypoxia Mediates Partial Epithelial-to-Meshenchymal Transition in Epithelial Ovarian Cancer Cells

Metastatic progression of epithelial ovarian cancer (EOC) involves the partial epithelial-to-mesenchymal transition (EMT) of cancer cells in the primary tumor and dissemination into peritoneal fluid. In part to the high degree of heterogeneity in EOC cells, the identification of EMT in highly epithelial cells in response to differences in matrix mechanics, growth factor signaling, and tissue hypoxia is very difficult. We analyzed different degrees of EMT by tracking changes in cell and nuclear morphology, along with the organization of cytoskeletal proteins. In our analysis, we see a small percentage of individual cells that show dramatic response to TGF-β1 and hypoxia treatment. We demonstrate that EOC cells are spatially aware of their surroundings, with a subpopulation of EOC cells at the periphery of a cell cluster in 2D environments exhibited a greater degree of EMT. These peripheral cancer cells underwent partial EMT, displaying a hybrid of mesenchymal and epithelial characteristics, which often included less cortical actin and more perinuclear cytokeratin expression. Collectively, these data show that tumor-promoting microenvironment conditions can mediate invasive cell behavior in a spatially regulated context in a small subpopulation of highly epithelial clustered cancer cells that maintain epithelial characteristics while also acquiring some mesenchymal traits through partial EMT.

Mechanical Properties of Glioblastoma: Perspectives for YAP/TAZ Signaling Pathway and Beyond

Glioblastoma is a highly aggressive brain tumor with a poor prognosis. Recent studies have suggested that mechanobiology, the study of how physical forces influence cellular behavior, plays an important role in glioblastoma progression. Several signaling pathways, molecules, and effectors, such as focal adhesions, stretch-activated ion channels, or membrane tension variations, have been studied in this regard. Also investigated are YAP/TAZ, downstream effectors of the Hippo pathway, which is a key regulator of cell proliferation and differentiation. In glioblastoma, YAP/TAZ have been shown to promote tumor growth and invasion by regulating genes involved in cell adhesion, migration, and extracellular matrix remodeling. YAP/TAZ can be activated by mechanical cues such as cell stiffness, matrix rigidity, and cell shape changes, which are all altered in the tumor microenvironment. Furthermore, YAP/TAZ have been shown to crosstalk with other signaling pathways, such as AKT, mTOR, and WNT, which are dysregulated in glioblastoma. Thus, understanding the role of mechanobiology and YAP/TAZ in glioblastoma progression could provide new insights into the development of novel therapeutic strategies. Targeting YAP/TAZ and mechanotransduction pathways in glioblastoma may offer a promising approach to treating this deadly disease.

The emerging promise of tumour mechanobiology in cancer treatment

Tumour cell biomechanics has lately came to the fore as a disparate feature that fosters cancer development and progression. Tumour mechanosensing entails a mechanical interplay amongst tumour cells, extracellular matrix (ECM) and cells of the tumour microenvironment (TME). Sensory receptors (mechanoceptors) detect changes of extracellular mechanical inputs such as various types of mechanical forces/stress and trigger oncogenic signalling pathways advocating for cancer initiation, growth, survival, angiogenesis, invasion, metastasis, and immune evasion. Moreover, alterations in ECM stiffness and potentiation of mechanostimulated transcriptional regulatory molecules (transcription factors/cofactors) have been shown to strongly correlate with resistance to anticancer drugs. On this basis, new mechanosensitive proteins emerge as potential therapeutic targets and/or biomarkers in cancer. Accordingly, tumour mechanobiology arises as a promising field that can potentially provide novel combinatorial regimens to reverse drug resistance, as well as offer unprecedented targeting approaches that may help to more effectively treat a large proportion of solid tumours and their complications. Here, we highlight recent findings regarding various aspects of tumour mechanobiology in the clinical setting and discuss evidence-based perspectives of developing diagnostic/prognostic tools and therapeutic approaches that exploit tumour-TME physical associations.

Speckle rheological spectroscopy reveals wideband viscoelastic spectra of biological tissues

Mechanical transformation of tissue is not merely a symptom but a decisive driver in pathological processes. Comprising intricate network of cells, fibrillar proteins, and interstitial fluid, tissues exhibit distinct solid-(elastic) and liquid-like (viscous) behaviours that span a wide band of frequencies. Yet, characterization of wideband viscoelastic behaviour in whole tissue has not been investigated, leaving a vast knowledge gap in the higher frequency range that is linked to fundamental intracellular processes and microstructural dynamics. Here, we present wideband Speckle rHEologicAl spectRoScopy (SHEARS) to address this need. We demonstrate, for the first time, analysis of frequency-dependent elastic and viscous moduli up to the sub-MHz regime in biomimetic scaffolds and tissue specimens of blood clots, breast tumours, and bone. By capturing previously inaccessible viscoelastic behaviour across the wide frequency spectrum, our approach provides distinct and comprehensive mechanical signatures of tissues that may provide new mechanobiological insights and inform novel disease prognostication.

Endothelium and Subendothelial Matrix Mechanics Modulate Cancer Cell Transendothelial Migration

Cancer cell extravasation, a key step in the metastatic cascade, involves cancer cell arrest on the endothelium, transendothelial migration (TEM), followed by the invasion into the subendothelial extracellular matrix (ECM) of distant tissues. While cancer research has mostly focused on the biomechanical interactions between tumor cells (TCs) and ECM, particularly at the primary tumor site, very little is known about the mechanical properties of endothelial cells and the subendothelial ECM and how they contribute to the extravasation process. Here, an integrated experimental and theoretical framework is developed to investigate the mechanical crosstalk between TCs, endothelium and subendothelial ECM during in vitro cancer cell extravasation. It is found that cancer cell actin-rich protrusions generate complex push-pull forces to initiate and drive TEM, while transmigration success also relies on the forces generated by the endothelium. Consequently, mechanical properties of the subendothelial ECM and endothelial actomyosin contractility that mediate the endothelial forces also impact the endothelium's resistance to cancer cell transmigration. These results indicate that mechanical features of distant tissues, including force interactions between the endothelium and the subendothelial ECM, are key determinants of metastatic organotropism.

Oxygen-Glucose Deprivation in Organotypic Hippocampal Cultures Leads to Cytoskeleton Rearrangement and Immune Activation: Link to the Potential Pathomechanism of Ischaemic Stroke

Ischaemic stroke is characterized by a sudden loss of blood circulation to an area of the brain, resulting in a corresponding loss of neurologic function. As a result of this process, neurons in the ischaemic core are deprived of oxygen and trophic substances and are consequently destroyed. Tissue damage in brain ischaemia results from a complex pathophysiological cascade comprising various distinct pathological events. Ischaemia leads to brain damage by stimulating many processes, such as excitotoxicity, oxidative stress, inflammation, acidotoxicity, and apoptosis. Nevertheless, less attention has been given to biophysical factors, including the organization of the cytoskeleton and the mechanical properties of cells. Therefore, in the present study, we sought to evaluate whether the oxygen-glucose deprivation (OGD) procedure, which is a commonly accepted experimental model of ischaemia, could affect cytoskeleton organization and the paracrine immune response. The abovementioned aspects were examined ex vivo in organotypic hippocampal cultures (OHCs) subjected to the OGD procedure. We measured cell death/viability, nitric oxide (NO) release, and hypoxia-inducible factor 1α (HIF-1α) levels. Next, the impact of the OGD procedure on cytoskeletal organization was evaluated using combined confocal fluorescence microscopy (CFM) and atomic force microscopy (AFM). Concurrently, to find whether there is a correlation between biophysical properties and the immune response, we examined the impact of OGD on the levels of crucial ischaemia cytokines (IL-1β, IL-6, IL-18, TNF-α, IL-10, IL-4) and chemokines (CCL3, CCL5, CXCL10) in OHCs and calculated Pearsons' and Spearman's rank correlation coefficients. The results of the current study demonstrated that the OGD procedure intensified cell death and nitric oxide release and led to the potentiation of HIF-1α release in OHCs. Moreover, we presented significant disturbances in the organization of the cytoskeleton (actin fibers, microtubular network) and cytoskeleton-associated protein 2 (MAP-2), which is a neuronal marker. Simultaneously, our study provided new evidence that the OGD procedure leads to the stiffening of OHCs and a malfunction in immune homeostasis. A negative linear correlation between tissue stiffness and branched IBA1 positive cells after the OGD procedure suggests the pro-inflammatory polarization of microglia. Moreover, the negative correlation of pro- and positive anti-inflammatory factors with actin fibers density indicates an opposing effect of the immune mediators on the rearrangement of cytoskeleton induced by OGD procedure in OHCs. Our study constitutes a basis for further research and provides a rationale for integrating biomechanical and biochemical methods in studying the pathomechanism of stroke-related brain damage. Furthermore, presented data pointed out the interesting direction of proof-of-concept studies, in which follow-up may establish new targets for brain ischemia therapy.

TrpA1 is a shear stress mechanosensing channel regulating intestinal stem cell proliferation in Drosophila

Adult stem cells are essential for tissue maintenance and repair. Although genetic pathways for controlling adult stem cells are extensively investigated in various tissues, much less is known about how mechanosensing could regulate adult stem cells and tissue growth. Here, we demonstrate that shear stress sensing regulates intestine stem cell proliferation and epithelial cell number in adult Drosophila. Ca2+ imaging in ex vivo midguts shows that shear stress, but not other mechanical forces, specifically activates enteroendocrine cells among all epithelial cell types. This activation is mediated by transient receptor potential A1 (TrpA1), a Ca2+-permeable channel expressed in enteroendocrine cells. Furthermore, specific disruption of shear stress, but not chemical, sensitivity of TrpA1 markedly reduces proliferation of intestinal stem cells and midgut cell number. Therefore, we propose that shear stress may act as a natural mechanical stimulation to activate TrpA1 in enteroendocrine cells, which, in turn, regulates intestine stem cell behavior.

ScRNA-seq revealed an immunosuppression state and tumor microenvironment heterogeneity related to lymph node metastasis in prostate cancer

BACKGROUND

Metastasis is a crucial aspect of disease progression leading to death in patients with prostate cancer (PCa). However, its mechanism remains unclear. We aimed to explore the mechanism of lymph node metastasis (LNM) by analyzing the heterogeneity of tumor microenvironment (TME) in PCa using scRNA-seq.

METHODS

A total of 32,766 cells were obtained from four PCa tissue samples for scRNA-seq, annotated, and grouped. InferCNV, GSVA, DEG functional enrichment analysis, trajectory analysis, intercellular network evaluation, and transcription factor analysis were carried out for each cell subgroup. Furthermore, validation experiments targeting luminal cell subgroups and CXCR4 + fibroblast subgroup were performed.

RESULTS

The results showed that only EEF2 + and FOLH1 + luminal subgroups were present in LNM, and they appeared at the initial stage of luminal cell differentiation, which were comfirmed by verification experiments. The MYC pathway was enriched in the EEF2 + and FOLH1 + luminal subgroups, and MYC was associated with PCa LNM. Moreover, MYC did not only promote the progression of PCa, but also led to immunosuppression in TME by regulating PDL1 and CD47. The proportion of CD8 + T cells in TME and among NK cells and monocytes was lower in LNM than in the primary lesion, while the opposite was true for Th and Treg cells. Furthermore, these immune cells in TME underwent transcriptional reprogramming, including CD8 + T subgroups of CCR7 + and IL7R+, as well as M2-like monocyte subgroups expressing tumor-associated signature genes, like CCR7, SGKI, and RPL31. Furthermore, STEAP4+, ADGRF5 + and CXCR4+, and SRGNC + fibroblast subgroups were closely related to tumor progression, tumor metabolism, and immunosuppression, indicating their contributions in PCa metastasis. Meanwhile, The presence of CXCR4 + Fibroblasts in PCa was confirmed by polychromatic immunofluorescence.

CONCLUSIONS

The significant heterogeneity of luminal, immune, and interstitial cells in PCa LNM may not only directly contribute to tumor progression, but also indirectly result in TME immunosuppression, which may be the cause of metastasis in PCa and in which MYC played an role.

A Novel Approach to Reducing Lung Metastasis in Osteosarcoma: Increasing Cell Stiffness with Carbenoxolone

AIM

Primary malignant bone tumor osteosarcoma can metastasize to the lung. Diminishing lung metastasis would positively affect the prognosis of patients. Our previous studies demonstrated that highly metastatic osteosarcoma cell lines are significantly softer than low-metastasis cell lines. We therefore hypothesized that increasing cell stiffness would suppress metastasis by reducing cell motility. In this study, we tested whether carbenoxolone (CBX) increases the stiffness of LM8 osteosarcoma cells and prevents lung metastasis in vivo.

METHODS

We evaluated the actin cytoskeletal structure and polymerization of CBX-treated LM8 cells using actin staining. Cell stiffness was measured using atomic force microscopy. Metastasis-related cell functions were analyzed using cell proliferation, wound healing, invasion, and cell adhesion assays. Furthermore, lung metastasis was examined in LM8-bearing mice administered with CBX.

RESULTS

Treatment with CBX significantly increased actin staining intensity and stiffness of LM8 cells compared with vehicle-treated LM8 cells (p < 0.01). In Young's modulus images, compared with the control group, rigid fibrillate structures were observed in the CBX treatment group. CBX suppressed cell migration, invasion, and adhesion but not cell proliferation. The number of LM8 lung metastases were significantly reduced in the CBX administration group compared with the control group (p < 0.01).

CONCLUSION

In this study, we demonstrated that CBX increases tumor cell stiffness and significantly reduces lung metastasis. Our study is the first to provide evidence that reducing cell motility by increasing cell stiffness might be effective as a novel anti-metastasis approach in vivo.

Mechanobiology and survival strategies of circulating tumor cells: a process towards the invasive and metastatic phenotype

Metastatic progression is the deadliest feature of cancer. Cancer cell growth, invasion, intravasation, circulation, arrest/adhesion and extravasation require specific mechanical properties to allow cell survival and the completion of the metastatic cascade. Circulating tumor cells (CTCs) come into contact with the capillary bed during extravasation/intravasation at the beginning of the metastatic cascade. However, CTC mechanobiology and survival strategies in the bloodstream, and specifically in the microcirculation, are not well known. A fraction of CTCs can extravasate and colonize distant areas despite the biomechanical constriction forces that are exerted by the microcirculation and that strongly decrease tumor cell survival. Furthermore, accumulating evidence shows that several CTC adaptations, via molecular factors and interactions with blood components (e.g., immune cells and platelets inside capillaries), may promote metastasis formation. To better understand CTC journey in the microcirculation as part of the metastatic cascade, we reviewed how CTC mechanobiology and interaction with other cell types in the bloodstream help them to survive the harsh conditions in the circulatory system and to metastasize in distant organs.

Comparison of thermal and athermal dynamics of the cell membrane slope fluctuations in the presence and absence of Latrunculin-B

Conventionally, only the normal cell membrane fluctuations have been studied and used to ascertain membrane properties like the bending rigidity. A new concept, the membrane local slope fluctuations was introduced recently (Vaippullyet al2020Soft Matter167606), which can be modelled as a gradient of the normal fluctuations. It has been found that the power spectral density (PSD) of slope fluctuations behave as (frequency)-1while the normal fluctuations yields (frequency)-5/3even on the apical cell membrane in the high frequency region. In this manuscript, we explore a different situation where the cell is applied with the drug Latrunculin-B which inhibits actin polymerization and find the effect on membrane fluctuations. We find that even as the normal fluctuations show a power law (frequency)-5/3as is the case for a free membrane, the slope fluctuations PSD remains (frequency)-1, with exactly the same coefficient as the case when the drug was not applied. Moreover, while sometimes, when the normal fluctuations at high frequency yield a power law of (frequency)-4/3, the pitch PSD still yields (frequency)-1. Thus, this presents a convenient opportunity to study membrane parameters like bending rigidity as a function of time after application of the drug, while the membrane softens. We also investigate the active athermal fluctuations of the membrane appearing in the PSD at low frequencies and find active timescales of slower than 1 s.

Recent advances in lab-on-a-chip systems for breast cancer metastasis research

Breast cancer is the leading cause of cancer-related deaths in women. Multiple molecular subtypes, heterogeneity, and their ability to metastasize from the primary site to distant organs make breast cancer challenging to diagnose, treat, and obtain the desired therapeutic outcome. As the clinical importance of metastasis is dramatically increasing, there is a need to develop sustainable in vitro preclinical platforms to investigate complex cellular processes. Traditional in vitro and in vivo models cannot mimic the highly complex and multistep process of metastasis. Rapid progress in micro- and nanofabrication has contributed to soft lithography or three-dimensional printing-based lab-on-a-chip (LOC) systems. LOC platforms, which mimic in vivo conditions, offer a more profound understanding of cellular events and allow novel preclinical models for personalized treatments. Their low cost, scalability, and efficiency have resulted in on-demand design platforms for cell, tissue, and organ-on-a-chip platforms. Such models can overcome the limitations of two- and three-dimensional cell culture models and the ethical challenges involved in animal models. This review provides an overview of breast cancer subtypes, various steps and factors involved in metastases, existing preclinical models, and representative examples of LOC systems used to study and understand breast cancer metastasis and diagnosis and as a platform to evaluate advanced nanomedicine for breast cancer metastasis.

Retinoic acid receptor β modulates mechanosensing and invasion in pancreatic cancer cells via myosin light chain 2

Pancreatic ductal adenocarcinoma (PDAC) is the most common and lethal form of pancreatic cancer, characterised by stromal remodelling, elevated matrix stiffness and high metastatic rate. Retinoids, compounds derived from vitamin A, have a history of clinical use in cancer for their anti-proliferative and differentiation effects, and more recently have been explored as anti-stromal therapies in PDAC for their ability to induce mechanical quiescence in cancer associated fibroblasts. Here, we demonstrate that retinoic acid receptor β (RAR-β) transcriptionally represses myosin light chain 2 (MLC-2) expression in pancreatic cancer cells. As a key regulatory component of the contractile actomyosin machinery, MLC-2 downregulation results in decreased cytoskeletal stiffness and traction force generation, impaired response to mechanical stimuli via mechanosensing and reduced ability to invade through the basement membrane. This work highlights the potential of retinoids to target the mechanical drivers of pancreatic cancer.

Mechanobiology of cancer cell responsiveness to chemotherapy and immunotherapy: Mechanistic insights and biomaterial platforms

Mechanical forces are central to how cancer treatments such as chemotherapeutics and immunotherapies interact with cells and tissues. At the simplest level, electrostatic forces underlie the binding events that are critical to therapeutic function. However, a growing body of literature points to mechanical factors that also affect whether a drug or an immune cell can reach a target, and to interactions between a cell and its environment affecting therapeutic efficacy. These factors affect cell processes ranging from cytoskeletal and extracellular matrix remodeling to transduction of signals by the nucleus to metastasis of cells. This review presents and critiques the state of the art of our understanding of how mechanobiology impacts drug and immunotherapy resistance and responsiveness, and of the in vitro systems that have been of value in the discovery of these effects.