Oncogenes induce a vimentin filament collapse mediated by HDAC6 that is linked to cell stiffness

Cytoskeletal crosstalk: A focus on intermediate filaments

The cytoskeleton, comprising actin microfilaments, microtubules, and intermediate filaments, is crucial for cell motility and tissue integrity. While prior studies largely focused on individual cytoskeletal networks, recent research underscores the interconnected nature of these systems in fundamental cellular functions like adhesion, migration, and division. Understanding the coordination of these distinct networks in both time and space is essential. This review synthesizes current findings on the intricate interplay between these networks, emphasizing the pivotal role of intermediate filaments. Notably, these filaments engage in extensive crosstalk with microfilaments and microtubules through direct molecular interactions, cytoskeletal linkers, and molecular motors that form molecular bridges, as well as via more complex regulation of intracellular signaling.

Determining the degree of chromosomal instability in breast cancer cells by atomic force microscopy

Chromosomal instability (CIN) is a source of genetic variation and is highly linked to the malignance of cancer. Determining the degree of CIN is necessary for understanding the role that it plays in tumor development. There is currently a lack of research on high-resolution characterization of CIN and the relationship between CIN and cell mechanics. Here, a method to determine CIN of breast cancer cells by high resolution imaging with atomic force microscopy (AFM) is explored. The numerical and structural changes of chromosomes in human breast cells (MCF-10A), moderately malignant breast cells (MCF-7) and highly malignant breast cells (MDA-MB-231) were observed and analyzed by AFM. Meanwhile, the nuclei, cytoskeleton and cell mechanics of the three kinds of cells were also investigated. The results showed the differences in CIN between the benign and cancer cells. Also, the degree of structural CIN increased with enhanced malignancy of cancer cells. This was also demonstrated by calculating the probability of micronucleus formation in these three kinds of cells. Meanwhile, we found that the area of the nucleus was related to the number of chromosomes in the nucleus. In addition, reduced or even aggregated actin fibers led to decreased elasticities in MCF-7 and MDA-MB-231 cells. It was found that the rearrangement of actin fibers would affect the nucleus, and then lead to wrong mitosis and CIN. Using AFM to detect chromosomal changes in cells with different malignancy degrees provides a new detection method for the study of cell carcinogenesis with a perspective for targeted therapy of cancer.

Biophysics in tumor growth and progression: from single mechano-sensitive molecules to mechanomedicine

Evidence from physical sciences in oncology increasingly suggests that the interplay between the biophysical tumor microenvironment and genetic regulation has significant impact on tumor progression. Especially, tumor cells and the associated stromal cells not only alter their own cytoskeleton and physical properties but also remodel the microenvironment with anomalous physical properties. Together, these altered mechano-omics of tumor tissues and their constituents fundamentally shift the mechanotransduction paradigms in tumorous and stromal cells and activate oncogenic signaling within the neoplastic niche to facilitate tumor progression. However, current findings on tumor biophysics are limited, scattered, and often contradictory in multiple contexts. Systematic understanding of how biophysical cues influence tumor pathophysiology is still lacking. This review discusses recent different schools of findings in tumor biophysics that have arisen from multi-scale mechanobiology and the cutting-edge technologies. These findings range from the molecular and cellular to the whole tissue level and feature functional crosstalk between mechanotransduction and oncogenic signaling. We highlight the potential of these anomalous physical alterations as new therapeutic targets for cancer mechanomedicine. This framework reconciles opposing opinions in the field, proposes new directions for future cancer research, and conceptualizes novel mechanomedicine landscape to overcome the inherent shortcomings of conventional cancer diagnosis and therapies.

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.

Regulation of cellular contractile force, shape and migration of fibroblasts by oncogenes and Histone deacetylase 6

The capacity of cells to adhere to, exert forces upon and migrate through their surrounding environment governs tissue regeneration and cancer metastasis. The role of the physical contractile forces that cells exert in this process, and the underlying molecular mechanisms are not fully understood. We, therefore, aimed to clarify if the extracellular forces that cells exert on their environment and/or the intracellular forces that deform the cell nucleus, and the link between these forces, are defective in transformed and invasive fibroblasts, and to indicate the underlying molecular mechanism of control. Confocal, Epifluorescence and Traction force microscopy, followed by computational analysis, showed an increased maximum contractile force that cells apply on their environment and a decreased intracellular force on the cell nucleus in the invasive fibroblasts, as compared to normal control cells. Loss of HDAC6 activity by tubacin-treatment and siRNA-mediated HDAC6 knockdown also reversed the reduced size and more circular shape and defective migration of the transformed and invasive cells to normal. However, only tubacin-mediated, and not siRNA knockdown reversed the increased force of the invasive cells on their surrounding environment to normal, with no effects on nuclear forces. We observed that the forces on the environment and the nucleus were weakly positively correlated, with the exception of HDAC6 siRNA-treated cells, in which the correlation was weakly negative. The transformed and invasive fibroblasts showed an increased number and smaller cell-matrix adhesions than control, and neither tubacin-treatment, nor HDAC6 knockdown reversed this phenotype to normal, but instead increased it further. This highlights the possibility that the control of contractile force requires separate functions of HDAC6, than the control of cell adhesions, spreading and shape. These data are consistent with the possibility that defective force-transduction from the extracellular environment to the nucleus contributes to metastasis, via a mechanism that depends upon HDAC6. To our knowledge, our findings present the first correlation between the cellular forces that deforms the surrounding environment and the nucleus in fibroblasts, and it expands our understanding of how cells generate contractile forces that contribute to cell invasion and metastasis.

Mechanical profile of human keratinocytes expressing HPV-18 oncogenes

During tumorigenesis, the mechanical properties of cancer cells change markedly, with decreased stiffness often accompanying a more invasive phenotype. Less is known about the changes in mechanical parameters at intermediate stages in the process of malignant transformation. We have recently developed a pre-tumoral cell model by stably transducing the immortalized but non-tumorigenic human keratinocyte cell line HaCaT with the E5, E6 and E7 oncogenes from HPV-18, one of the leading causes of cervical cancer and other types of cancer worldwide. We have used atomic force microscopy (AFM) to measure cell stiffness and to obtain mechanical maps of parental HaCaT and HaCaT E5/E6/E7-18 cell lines. We observed a significant decrease in Young's modulus in HaCaT E5/E6/E7-18 cells measured by nanoindentation in the central region, as well as decreased cell rigidity in regions of cell-cell contact measured by Peakforce Quantitative Nanomechanical Mapping (PF-QNM). As a morphological correlate, HaCaT E5/E6/E7-18 cells displayed a significantly rounder cell shape than parental HaCaT cells. Our results therefore show that decreased stiffness with concomitant perturbations in cell shape are early mechanical and morphological changes during the process of malignant transformation.

Paradigms of endothelial stiffening in cardiovascular disease and vascular aging

Endothelial cells, the inner lining of the blood vessels, are well-known to play a critical role in vascular function, while endothelial dysfunction due to different cardiovascular risk factors or accumulation of disruptive mechanisms that arise with aging lead to cardiovascular disease. In this review, we focus on endothelial stiffness, a fundamental biomechanical property that reflects cell resistance to deformation. In the first part of the review, we describe the mechanisms that determine endothelial stiffness, including RhoA-dependent contractile response, actin architecture and crosslinking, as well as the contributions of the intermediate filaments, vimentin and lamin. Then, we review the factors that induce endothelial stiffening, with the emphasis on mechanical signals, such as fluid shear stress, stretch and stiffness of the extracellular matrix, which are well-known to control endothelial biomechanics. We also describe in detail the contribution of lipid factors, particularly oxidized lipids, that were also shown to be crucial in regulation of endothelial stiffness. Furthermore, we discuss the relative contributions of these two mechanisms of endothelial stiffening in vasculature in cardiovascular disease and aging. Finally, we present the current state of knowledge about the role of endothelial stiffening in the disruption of endothelial cell-cell junctions that are responsible for the maintenance of the endothelial barrier.

ALD-R491 regulates vimentin filament stability and solubility, cell contractile force, cell migration speed and directionality

Metastasizing cells express the intermediate filament protein vimentin, which is used to diagnose invasive tumors in the clinic. However, the role of vimentin in cell motility, and if the assembly of non-filamentous variants of vimentin into filaments regulates cell migration remains unclear. We observed that the vimentin-targeting drug ALD-R491 increased the stability of vimentin filaments, by reducing filament assembly and/or disassembly. ALD-R491-treatment also resulted in more bundled and disorganized filaments and an increased pool of non-filamentous vimentin. This was accompanied by a reduction in size of cell-matrix adhesions and increased cellular contractile forces. Moreover, during cell migration, cells showed erratic formation of lamellipodia at the cell periphery, loss of coordinated cell movement, reduced cell migration speed, directionality and an elongated cell shape with long thin extensions at the rear that often detached. Taken together, these results indicate that the stability of vimentin filaments and the soluble pool of vimentin regulate the speed and directionality of cell migration and the capacity of cells to migrate in a mechanically cohesive manner. These observations suggest that the stability of vimentin filaments governs the adhesive, physical and migratory properties of cells, and expands our understanding of vimentin functions in health and disease, including cancer metastasis.

Establishment and characterization of an immortalized epithelial cell line from human gallbladder

Background

Although a plethora of studies have employed multiple gallbladder cancer (GBC) cell lines, it is surprisingly noted that there is still lack of a normal gallbladder epithelial cell line as a normal counterpart, thus impeding substantially the progress of mechanistic studies on the transformation of normal epithelial cells to cancer. Here, we created a normal gallbladder epithelial cell line named L-2F7 from human gallbladder tissue.

Methods

Gallbladder tissues from a diagnosed cholecystitis female patient were collected, and epithelial cells were enriched by magnetic cell sorting. Then, the cells were immortalized by co-introduction of human telomerase reverse transcriptase (hTERT) and Simian virus 40 large T antigen (LT-SV40) via a lentivirus infection system. After clonal selection and isolation, L-2F7 cells were tested for epithelial markers CK7, CK19, CK20, and CD326, genomic feature, cell proliferation, and migration using Western blot, immunofluorescence, whole genome sequencing, karyotyping, and RNA sequencing. L-2F7 cells were also transplanted to Nude (nu/nu) mice to determine tumorigenicity.

Results

We successfully identified one single-cell clone named L-2F7 which highly expressed epithelial markers CD326, CK7, CK19, and CK20. This cell line proliferated with a doubling time of 23 h and the epithelial morphology sustained over 30 passages following immortalization. Transient gene transduction of L-2F7 cells led to expression of exogenous GFP and FLAG protein. L-2F7 cells exhibited both distinct non-synonymous mutations from those of gallbladder cancer tissues and differential non-cancerous gene expression patterns similar to normal tissue. Although they displayed unexpected mobility, L-2F7 cells still lacked the ability to develop tumors.

Conclusion

We developed a non-cancerous gallbladder epithelial cell line, offering a valuable system for the study of gallbladder cancer and other gallbladder-related disorders.

How do cells stiffen?

Cell stiffness is an important characteristic of cells and their response to external stimuli. In this review, we survey methods used to measure cell stiffness, summarize stimuli that alter cell stiffness, and discuss signaling pathways and mechanisms that control cell stiffness. Several pathological states are characterized by changes in cell stiffness, suggesting this property can serve as a potential diagnostic marker or therapeutic target. Therefore, we consider the effect of cell stiffness on signaling and growth processes required for homeostasis and dysfunction in healthy and pathological states. Specifically, the composition and structure of the cell membrane and cytoskeleton are major determinants of cell stiffness, and studies have identified signaling pathways that affect cytoskeletal dynamics both directly and by altered gene expression. We present the results of studies interrogating the effects of biophysical and biochemical stimuli on the cytoskeleton and other cellular components and how these factors determine the stiffness of both individual cells and multicellular structures. Overall, these studies represent an intersection of the fields of polymer physics, protein biochemistry, and mechanics, and identify specific mechanisms involved in mediating cell stiffness that can serve as therapeutic targets.

CK2 and the Hallmarks of Cancer

Cancer is a leading cause of death worldwide. Casein kinase 2 (CK2) is commonly dysregulated in cancer, impacting diverse molecular pathways. CK2 is a highly conserved serine/threonine kinase, constitutively active and ubiquitously expressed in eukaryotes. With over 500 known substrates and being estimated to be responsible for up to 10% of the human phosphoproteome, it is of significant importance. A broad spectrum of diverse types of cancer cells has been already shown to rely on disturbed CK2 levels for their survival. The hallmarks of cancer provide a rationale for understanding cancer’s common traits. They constitute the maintenance of proliferative signaling, evasion of growth suppressors, resisting cell death, enabling of replicative immortality, induction of angiogenesis, the activation of invasion and metastasis, as well as avoidance of immune destruction and dysregulation of cellular energetics. In this work, we have compiled evidence from the literature suggesting that CK2 modulates all hallmarks of cancer, thereby promoting oncogenesis and operating as a cancer driver by creating a cellular environment favorable to neoplasia.

Biomechanics of cancer stem cells

Cancer stem cells (CSCs) have been believed to be one driving force for tumor progression and drug resistance. Despite the significance of biochemical signaling in malignancy, highly malignant tumor cells or CSCs exhibit lower cellular stiffness than weakly malignant cells or non-CSCs, which are softer than their healthy counterparts, suggesting the inverse correlation between cell stiffness and malignancy. Recent years have witnessed the rapid accumulation of evidence illustrating the reciprocity between cell cytoskeleton/mechanics and CSC functions and the potential of cellular stiffness for specific targeting of CSCs. However, a systematic understanding of tumor cell mechanics and their role in CSCs and tumor progression is still lacking. The present review summarizes the recent progress in the alterations of tumor cell cytoskeleton and stiffness at different stages of tumor progression and recapitulates the relationship between cellular stiffness and CSC functions. The altered cell mechanics may mediate the mechanoadaptive responses that possibly empower CSCs to survive and thrive during metastasis. Furthermore, we highlight the possible impact of tumor cell mechanics on CSC malignancy, which may potentiate low cell stiffness as a mechanical marker for CSC targeting.

Intermediate filaments: Integration of cell mechanical properties during migration

Cell migration is a vital and dynamic process required for the development of multicellular organisms and for immune system responses, tissue renewal and wound healing in adults. It also contributes to a variety of human diseases such as cancers, autoimmune diseases, chronic inflammation and fibrosis. The cytoskeleton, which includes actin microfilaments, microtubules, and intermediate filaments (IFs), is responsible for the maintenance of animal cell shape and structural integrity. Each cytoskeletal network contributes its unique properties to dynamic cell behaviour, such as cell polarization, membrane protrusion, cell adhesion and contraction. Hence, cell migration requires the dynamic orchestration of all cytoskeleton components. Among these, IFs have emerged as a molecular scaffold with unique mechanical features and a key player in the cell resilience to mechanical stresses during migration through complex 3D environment. Moreover, accumulating evidence illustrates the participation of IFs in signalling cascades and cytoskeletal crosstalk. Teaming up with actin and microtubules, IFs contribute to the active generation of forces required for cell adhesion and mesenchymal migration and invasion. Here we summarize and discuss how IFs integrate mechanical properties and signalling functions to control cell migration in a wide spectrum of physiological and pathological situations.

Roles of vimentin in health and disease

More than 27 yr ago, the vimentin knockout (Vim-/- ) mouse was reported to develop and reproduce without an obvious phenotype, implying that this major cytoskeletal protein was nonessential. Subsequently, comprehensive and careful analyses have revealed numerous phenotypes in Vim-/- mice and their organs, tissues, and cells, frequently reflecting altered responses in the recovery of tissues following various insults or injuries. These findings have been supported by cell-based experiments demonstrating that vimentin intermediate filaments (IFs) play a critical role in regulating cell mechanics and are required to coordinate mechanosensing, transduction, signaling pathways, motility, and inflammatory responses. This review highlights the essential functions of vimentin IFs revealed from studies of Vim-/- mice and cells derived from them.

Re-evaluation of the Fijianolide/Laulimalide Chemotype Suggests an Alternate Mechanism of Action for C-15/C-20 Analogs

Herein, we report on naturally derived microtubule stabilizers with activity against triple negative breast cancer (TNBC) cell lines, including paclitaxel, fijianolide B/laulimalide (3), fijianolide B di-acetate (4), and two new semisynthetic analogs of 3, which include fijianolide J (5) and fijianolide L (6). Similar to paclitaxel, compound 3 demonstrated classic microtubule stabilizing activity with potent (GI₅₀ = 0.7-17 nM) antiproliferative efficacy among the five molecularly distinct TNBC cell lines. Alternatively, compounds 5 or 6, generated from oxidation of C-20 or C-15 and C-20 respectively, resulted in a unique profile with reduced potency (GI₅₀ = 4-9 μM), but improved efficacy in some lines, suggesting a distinct mechanism of action. The C-15, C-20 di-acetate, and dioxo modifications on 4 and 6 resulted in compounds devoid of classic microtubule stabilizing activity in biochemical assays. While 4 also had no detectable effect on cellular microtubules, 6 promoted a reorganization of the cytoskeleton resulting in an accumulation of microtubules at the cell periphery. Compound 5, with a single C-20 oxo substitution, displayed a mixed phenotype, sharing properties of 3 and 6. These results demonstrate the importance of the C-15/C-20 chiral centers, which appear to be required for the potent microtubule stabilizing activity of this chemotype and that oxidation of these sites promotes unanticipated cytoskeletal alterations that are distinct from classic microtubule stabilization, likely through a distinct mechanism of action.

Metastasising Fibroblasts Show an HDAC6-Dependent Increase in Migration Speed and Loss of Directionality Linked to Major Changes in the Vimentin Interactome

Metastasising cells express the intermediate filament protein vimentin, which is used to diagnose invasive tumours in the clinic. We aimed to clarify how vimentin regulates the motility of metastasising fibroblasts. STED super-resolution microscopy, live-cell imaging and quantitative proteomics revealed that oncogene-expressing and metastasising fibroblasts show a less-elongated cell shape, reduced cell spreading, increased cell migration speed, reduced directionality, and stronger coupling between these migration parameters compared to normal control cells. In total, we identified and compared 555 proteins in the vimentin interactome. In metastasising cells, the levels of keratin 18 and Rab5C were increased, while those of actin and collagen were decreased. Inhibition of HDAC6 reversed the shape, spreading and migration phenotypes of metastasising cells back to normal. Inhibition of HDAC6 also decreased the levels of talin 1, tropomyosin, Rab GDI β, collagen and emilin 1 in the vimentin interactome, and partially reversed the nanoscale vimentin organisation in oncogene-expressing cells. These findings describe the changes in the vimentin interactome and nanoscale distribution that accompany the defective cell shape, spreading and migration of metastasising cells. These results support the hypothesis that oncogenes can act through HDAC6 to regulate the vimentin binding of the cytoskeletal and cell–extracellular matrix adhesion components that contribute to the defective motility of metastasising cells.

Propolin G-Suppressed Epithelial-to-Mesenchymal Transition in Triple-Negative Breast Cancer Cells via Glycogen Synthase Kinase 3β-Mediated Snail and HDAC6-Regulated Vimentin Degradation

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer with a poor prognosis. The incidence and mortality rate of TNBC are frequently found in younger women. Due to the absence of a good therapeutic strategy, effective remedies for inhibiting TNBC have been developed for improving the cure rate. Epithelial-to-mesenchymal transition (EMT) is a critical mechanism to regulate cancer cell motility and invasion. Furthermore, ectopic expression of EMT molecules correlates with the metastasis and poor prognosis of TNBC. Targeting EMT might be a strategy for the therapy and prevention of TNBC. Propolin G, an active c-prenylflavanone in Taiwanese propolis, has been shown to possess anti-cancer activity in many cancers. However, the anti-metastasis activity of propolin G on TNBC is still unclear. The present study showed that the migration and invasion activities of TNBC cells was suppressed by propolin G. Down-regulated expression of Snail and vimentin and up-regulated expression of E-cadherin were dose- and time-dependently observed in propolin G-treated MDA-MB-231 cells. Propolin G inhibited Snail and vimentin expressions via the signaling pathways associated with post-translational modification. The activation of glycogen synthase kinase 3β (GSK-3β) by propolin G resulted in increasing GSK-3β interaction with Snail. Consequently, the nuclear localization and stability of Snail was disrupted resulting in promoting the degradation. Propolin G-inhibited Snail expression and the activities of migration and invasion were reversed by GSK-3β inhibitor pretreatment. Meanwhile, the outcomes also revealed that histone deacetylase 6 (HDAC6) activity was dose-dependently suppressed by propolin G. Correspondently, the amounts of acetyl-α-tubulin, a down-stream substrate of HDAC6, were increased. Dissociation of HDAC6/Hsp90 with vimentin leading to increased vimentin acetylation and degradation was perceived in the cells with the addition of propolin G. Moreover, up-regulated expression of acetyl-α-tubulin by propolin G was attenuated by HDAC6 overexpression. On the contrary, down-regulated expression of vimentin, cell migration and invasion by propolin G were overturned by HDAC6 overexpression. Conclusively, restraint cell migration and invasion of TNBC by propolin G were activated by the expression of GSK-3β-suppressed Snail and the interruption of HDAC6-mediated vimentin protein stability. Aiming at EMT, propolin G might be a potential candidate for TNBC therapy.

Biomechanical properties of erythrocytes circulating in artificial hearts measured by dielectrophoretic method

Blood damage is recognized as one of the major problems caused by non-physiological shear force induced by artificial hearts. At present, the generally accepted manifestation of mechanical blood damage is the amount of free hemoglobin released into the blood. However, there is little research on the changes of blood cell state after circulating in artificial hearts at the single-cell level. It is well known that the mechanical properties of cells are of enormous relevance in the regulation of cellular physiological and pathological processes. In this regard, it is highly needed to study the mechanical properties of blood cells affected by non-physiological shear force. In this paper, a dielectrophoresis-based method of measuring the mechanical properties of erythrocytes circulating in artificial hearts was proposed, which was quantified with some crucial parameters such as strain, elongation index (EI), and Young's modulus. Experimental results indicated that with the increase of the working time of artificial hearts, the deformability of erythrocytes decreased, the stiffness substantially increased, and the mechanical stability decreased, particularly at long exposure times. The proposed method provides a deep insight into the mechanism of subhemolytic damage at the single-cell level and has a great potential to serve as a new tool for in vitro evaluation of potential blood damage in artificial hearts.

Vimentin Is at the Heart of Epithelial Mesenchymal Transition (EMT) Mediated Metastasis

Epithelial-mesenchymal transition (EMT) is a reversible plethora of molecular events where epithelial cells gain the phenotype of mesenchymal cells to invade the surrounding tissues. EMT is a physiological event during embryogenesis (type I) but also happens during fibrosis (type II) and cancer metastasis (type III). It is a multifaceted phenomenon governed by the activation of genes associated with cell migration, extracellular matrix degradation, DNA repair, and angiogenesis. The cancer cells employ EMT to acquire the ability to migrate, resist therapeutic agents and escape immunity. One of the key biomarkers of EMT is vimentin, a type III intermediate filament that is normally expressed in mesenchymal cells but is upregulated during cancer metastasis. This review highlights the pivotal role of vimentin in the key events during EMT and explains its role as a downstream as well as an upstream regulator in this highly complex process. This review also highlights the areas that require further research in exploring the role of vimentin in EMT. As a cytoskeletal protein, vimentin filaments support mechanical integrity of the migratory machinery, generation of directional force, focal adhesion modulation and extracellular attachment. As a viscoelastic scaffold, it gives stress-bearing ability and flexible support to the cell and its organelles. However, during EMT it modulates genes for EMT inducers such as Snail, Slug, Twist and ZEB1/2, as well as the key epigenetic factors. In addition, it suppresses cellular differentiation and upregulates their pluripotent potential by inducing genes associated with self-renewability, thus increasing the stemness of cancer stem cells, facilitating the tumour spread and making them more resistant to treatments. Several missense and frameshift mutations reported in vimentin in human cancers may also contribute towards the metastatic spread. Therefore, we propose that vimentin should be a therapeutic target using molecular technologies that will curb cancer growth and spread with reduced mortality and morbidity.

Luteolin inhibits the proliferation, adhesion, migration and invasion of choroidal melanoma cells in vitro

Choroidal melanoma is a devastating disease that causes visual loss and a high mortality rate due to metastasis. Luteolin, a potential anticancer compound, is widely found in natural plants. The aim of this study was to evaluate the antiproliferative, antiadhesive, antimigratory and anti-invasive effects of luteolin on choroidal melanoma cells in vitro and to explore its potential mechanism. Cell counting kit-8 (CCK-8) assays, 5-ethynyl-2'-deoxyuridine (EdU) assays, Cell adhesion, migration, and invasion assays were performed to examine the inhibitory effects of luteolin on cell cell viability, proliferation, adhesion, migration and invasion capacities, respectively. Considering the correlation between Matrix metalloenzymes and tumor metastasis, Enzyme-linked immunosorbent assays (ELISAs) were used to assess matrix metalloproteases MMP-2 and MMP-9 secretion. Western blotting was performed to detect p-PI3K P85, Akt, and p-Akt protein expression. The cytoskeletal proteins vimentin were observed with cell immunofluorescence staining. Luteolin can inhibit OCM-1 cell proliferation, migration, invasion and adhesion and C918 cell proliferation, migration, and invasion through the PI3K/Akt signaling pathway. Therefore, Luteolin may have potential as a therapeutic medication for Choroidal melanoma.

Biomechanical Properties of Cancer Cells

Since the crucial role of the microenvironment has been highlighted, many studies have been focused on the role of biomechanics in cancer cell growth and the invasion of the surrounding environment. Despite the search in recent years for molecular biomarkers to try to classify and stratify cancers, much effort needs to be made to take account of morphological and nanomechanical parameters that could provide supplementary information concerning tissue complexity adaptation during cancer development. The biomechanical properties of cancer cells and their surrounding extracellular matrix have actually been proposed as promising biomarkers for cancer diagnosis and prognosis. The present review first describes the main methods used to study the mechanical properties of cancer cells. Then, we address the nanomechanical description of cultured cancer cells and the crucial role of the cytoskeleton for biomechanics linked with cell morphology. Finally, we depict how studying interaction of tumor cells with their surrounding microenvironment is crucial to integrating biomechanical properties in our understanding of tumor growth and local invasion.

Karyotype Aberrations in Action: The Evolution of Cancer Genomes and the Tumor Microenvironment

Cancer is a disease of cellular evolution. For this cellular evolution to take place, a population of cells must contain functional heterogeneity and an assessment of this heterogeneity in the form of natural selection. Cancer cells from advanced malignancies are genomically and functionally very different compared to the healthy cells from which they evolved. Genomic alterations include aneuploidy (numerical and structural changes in chromosome content) and polyploidy (e.g., whole genome doubling), which can have considerable effects on cell physiology and phenotype. Likewise, conditions in the tumor microenvironment are spatially heterogeneous and vastly different than in healthy tissues, resulting in a number of environmental niches that play important roles in driving the evolution of tumor cells. While a number of studies have documented abnormal conditions of the tumor microenvironment and the cellular consequences of aneuploidy and polyploidy, a thorough overview of the interplay between karyotypically abnormal cells and the tissue and tumor microenvironments is not available. Here, we examine the evidence for how this interaction may unfold during tumor evolution. We describe a bidirectional interplay in which aneuploid and polyploid cells alter and shape the microenvironment in which they and their progeny reside; in turn, this microenvironment modulates the rate of genesis for new karyotype aberrations and selects for cells that are most fit under a given condition. We conclude by discussing the importance of this interaction for tumor evolution and the possibility of leveraging our understanding of this interplay for cancer therapy.

A constriction channel analysis of astrocytoma stiffness and disease progression

Studies have demonstrated that cancer cells tend to have reduced stiffness (Young's modulus) compared to their healthy counterparts. The mechanical properties of primary brain cancer cells, however, have remained largely unstudied. To investigate whether the stiffness of primary brain cancer cells decreases as malignancy increases, we used a microfluidic constriction channel device to deform healthy astrocytes and astrocytoma cells of grade II, III, and IV and measured the entry time, transit time, and elongation. Calculating cell stiffness directly from the experimental measurements is not possible. To overcome this challenge, finite element simulations of the cell entry into the constriction channel were used to train a neural network to calculate the stiffness of the analyzed cells based on their experimentally measured diameter, entry time, and elongation in the channel. Our study provides the first calculation of stiffness for grades II and III astrocytoma and is the first to apply a neural network analysis to determine cell mechanical properties from a constriction channel device. Our results suggest that the stiffness of astrocytoma cells is not well-correlated with the cell grade. Furthermore, while other non-central-nervous-system cell types typically show reduced stiffness of malignant cells, we found that most astrocytoma cell lines had increased stiffness compared to healthy astrocytes, with lower-grade astrocytoma having higher stiffness values than grade IV glioblastoma. Differences in nucleus-to-cytoplasm ratio only partly explain differences in stiffness values. Although our study does have limitations, our results do not show a strong correlation of stiffness with cell grade, suggesting that other factors may play important roles in determining the invasive capability of astrocytoma. Future studies are warranted to further elucidate the mechanical properties of astrocytoma across various pathological grades.

Vimentin protects differentiating stem cells from stress

Vimentin is one of the first cytoplasmic intermediate filaments to be expressed in mammalian cells during embryogenesis, but its role in cellular fitness has long been a mystery. Vimentin is acknowledged to play a role in cell stiffness, cell motility, and cytoplasmic organization, yet it is widely considered to be dispensable for cellular function and organismal development. Here, we show that Vimentin plays a role in cellular stress response in differentiating cells, by recruiting aggregates, stress granules, and RNA-binding proteins, directing their elimination and asymmetric partitioning. In the absence of Vimentin, pluripotent embryonic stem cells fail to differentiate properly, with a pronounced deficiency in neuronal differentiation. Our results uncover a novel function for Vimentin, with important implications for development, tissue homeostasis, and in particular, stress response.

LncRNA LINC00472 regulates cell stiffness and inhibits the migration and invasion of lung adenocarcinoma by binding to YBX1

There is increasing evidence that long non-coding RNAs (lncRNAs) play important roles in human tumorigenesis. By using publicly available expression profiling data from lung adenocarcinoma and integrating bioinformatics analysis, we screened a lncRNA, LINC00472. LINC00472 expression in lung adenocarcinoma tissues was significantly lower and tightly associated with patient prognosis and TNM clinical stages in lung adenocarcinoma. LINC00472 also inhibited lung adenocarcinoma cell migration and invasion and increased cell stiffness and adhesion. RNA pull down and RIP assays identified that LINC00472 interacted with the transcription factor Y-box binding protein 1 (YBX1), which partially reversed the inhibition of cell migration and invasion and increased LINC00472-induced cell stiffness and adhesion. LINC00472 also regulated the density and integrity of F-actin in A549 and PC-9 cells possibly via YBX1. LINC00472 inhibited the cell epithelial-mesenchymal transition (EMT) processes via the modulation of YBX1. These results indicated that LINC00472 inhibited the cell EMT process by binding to YBX1, and affected the mechanical properties of the cell, ultimately inhibited its ability to invade and metastasize. Collectively, the present study provides the first evidence that LINC00472 changes the mechanical properties and inhibits the invasion and metastasis of lung adenocarcinoma cells.

The Major Capsid Protein, VP1, of the Mouse Polyomavirus Stimulates the Activity of Tubulin Acetyltransferase 1 by Microtubule Stabilization

Viruses have evolved mechanisms to manipulate microtubules (MTs) for the efficient realization of their replication programs. Studying the mechanisms of replication of mouse polyomavirus (MPyV), we observed previously that in the late phase of infection, a considerable amount of the main structural protein, VP1, remains in the cytoplasm associated with hyperacetylated microtubules. VP1–microtubule interactions resulted in blocking the cell cycle in the G2/M phase. We are interested in the mechanism leading to microtubule hyperacetylation and stabilization and the roles of tubulin acetyltransferase 1 (αTAT1) and deacetylase histone deacetylase 6 (HDAC6) and VP1 in this mechanism. Therefore, HDAC6 inhibition assays, αTAT1 knock out cell infections, in situ cell fractionation, and confocal and TIRF microscopy were used. The experiments revealed that the direct interaction of isolated microtubules and VP1 results in MT stabilization and a restriction of their dynamics. VP1 leads to an increase in polymerized tubulin in cells, thus favoring αTAT1 activity. The acetylation status of MTs did not affect MPyV infection. However, the stabilization of MTs by VP1 in the late phase of infection may compensate for the previously described cytoskeleton destabilization by MPyV early gene products and is important for the observed inhibition of the G2→M transition of infected cells to prolong the S phase.

Differential Contributions of Actin and Myosin to the Physical Phenotypes and Invasion of Pancreatic Cancer Cells

INTRODUCTION

Metastasis is a fundamentally physical process in which cells deform through narrow gaps and generate forces to invade surrounding tissues. While it is commonly thought that increased cell deformability is an advantage for invading cells, we previously found that more invasive pancreatic ductal adenocarcinoma (PDAC) cells are stiffer than less invasive PDAC cells. Here we investigate potential mechanisms of the simultaneous increase in PDAC cell stiffness and invasion, focusing on the contributions of myosin II, Arp2/3, and formins.

METHOD

We measure cell invasion using a 3D scratch wound invasion assay and cell stiffness using atomic force microscopy (AFM). To determine the effects of actin- and myosin-mediated force generation on cell stiffness and invasion, we treat cells with pharmacologic inhibitors of myosin II (blebbistatin), Arp2/3 (CK-666), and formins (SMIFH2).

RESULTS

We find that the activity of myosin II, Arp2/3, and formins all contribute to the stiffness of PDAC cells. Interestingly, we find that the invasion of PDAC cell lines is differentially affected when the activity of myosin II, Arp2/3, or formins is inhibited, suggesting that despite having similar tissue origins, different PDAC cell lines may rely on different mechanisms for invasion.

CONCLUSIONS

These findings deepen our knowledge of the factors that regulate cancer cell mechanotype and invasion, and incite further studies to develop therapeutics that target multiple mechanisms of invasion for improved clinical benefit.

Microtubules in Polyomavirus Infection

Microtubules, part of the cytoskeleton, are indispensable for intracellular movement, cell division, and maintaining cell shape and polarity. In addition, microtubules play an important role in viral infection. In this review, we summarize the role of the microtubules' network during polyomavirus infection. Polyomaviruses usurp microtubules and their motors to travel via early and late acidic endosomes to the endoplasmic reticulum. As shown for SV40, kinesin-1 and microtubules are engaged in the release of partially disassembled virus from the endoplasmic reticulum to the cytosol, and dynein apparently assists in the further disassembly of virions prior to their translocation to the cell nucleus-the place of their replication. Polyomavirus gene products affect the regulation of microtubule dynamics. Early T antigens destabilize microtubules and cause aberrant mitosis. The role of these activities in tumorigenesis has been documented. However, its importance for productive infection remains elusive. On the other hand, in the late phase of infection, the major capsid protein, VP1, of the mouse polyomavirus, counteracts T-antigen-induced destabilization. It physically binds microtubules and stabilizes them. The interaction results in the G2/M block of the cell cycle and prolonged S phase, which is apparently required for successful completion of the viral replication cycle.

Vimentin Intermediate Filaments as Potential Target for Cancer Treatment

Intermediate filaments constitute the third component of the cellular skeleton. Unlike actin and microtubule cytoskeletons, the intermediate filaments are composed of a wide variety of structurally related proteins showing distinct expression patterns in tissues and cell types. Changes in the expression patterns of intermediate filaments are often associated with cancer progression; in particular with phenotypes leading to increased cellular migration and invasion. In this review we will describe the role of vimentin intermediate filaments in cancer cell migration, cell adhesion structures, and metastasis formation. The potential for targeting vimentin in cancer treatment and the development of drugs targeting vimentin will be reviewed.

Molecular Imaging in Oncology: Advanced Microscopy Techniques

Preclinical studies usually require high levels of morphological, functional, and biochemical information at subcellular resolution. This type of information cannot be obtained from clinical imaging techniques, such as MRI, PET/CT, or US. Luckily, many microscopy techniques exist that can offer this information, also for malignant tissues and therapeutic approaches. In this overview, we discuss the various advanced optical microscopy techniques and their applications in oncological research. After a short introduction in Sect. 16.1, we continue in Sect. 16.2 with a discussion on fluorescent labelling strategies, followed in Sect. 16.3 by an in-depth description of confocal, light-sheet, two-photon, and super-resolution microscopy. We end in Sect. 16.4 with a focus on the applications, specifically in oncology.

Finite Element Modelling of Single Cell Based on Atomic Force Microscope Indentation Method

The stiffness of cells, especially cancer cells, is a key mechanical property that is closely associated with their biomechanical functions, such as the mechanotransduction and the metastasis mechanisms of cancer cells. In light of the low survival rate of single cells and measurement uncertainty, the finite element method (FEM) was used to quantify the deformations and predict the stiffness of single cells. To study the effect of the cell components on overall stiffness, two new FEM models were proposed based on the atomic force microscopy (AFM) indentation method. The geometric sizes of the FEM models were determined by AFM topography images, and the validity of the FEM models was verified by comparison with experimental data. The effect of the intermediate filaments (IFs) and material properties of the cellular continuum components on the overall stiffness were investigated. The experimental results showed that the stiffness of cancer cells has apparent positional differences. The FEM simulation results show that IFs contribute only slightly to the overall stiffness within 10% strain, although they can transfer forces directly from the membrane to the nucleus. The cytoskeleton (CSK) is the major mechanical component of a cell. Furthermore, parameter studies revealed that the material properties (thickness and elasticity) of the continuum have a significant influence on the overall cellular stiffness while Poisson's ratio has less of an influence on the overall cellular stiffness. The proposed FEM models can determine the contribution of the major components of the cells to the overall cellular stiffness and provide insights for understanding the response of cells to the external mechanical stimuli and studying the corresponding mechanical mechanisms and cell biomechanics.

The focal adhesion scaffold protein Hic-5 regulates vimentin organization in fibroblasts

Focal adhesion (FA)-stimulated reorganization of the F-actin cytoskeleton regulates cellular size, shape, and mechanical properties. However, FA cross-talk with the intermediate filament cytoskeleton is poorly understood. Genetic ablation of the FA-associated scaffold protein Hic-5 in mouse cancer-associated fibroblasts (CAFs) promoted a dramatic collapse of the vimentin network, which was rescued following EGFP-Hic-5 expression. Vimentin collapse correlated with a loss of detergent-soluble vimentin filament precursors and decreased vimentin S72/S82 phosphorylation. Additionally, fluorescence recovery after photobleaching analysis indicated impaired vimentin dynamics. Microtubule (MT)-associated EB1 tracking and Western blotting of MT posttranslational modifications indicated no change in MT dynamics that could explain the vimentin collapse. However, pharmacological inhibition of the RhoGTPase Cdc42 in Hic-5 knockout CAFs rescued the vimentin collapse, while pan-formin inhibition with SMIFH2 promoted vimentin collapse in Hic-5 heterozygous CAFs. Our results reveal novel regulation of vimentin organization/dynamics by the FA scaffold protein Hic-5 via modulation of RhoGTPases and downstream formin activity.

Vimentin disruption by lipoxidation and electrophiles: Role of the cysteine residue and filament dynamics

The intermediate filament protein vimentin constitutes a critical sensor for electrophilic and oxidative stress, which induce extensive reorganization of the vimentin cytoskeletal network. Here, we have investigated the mechanisms underlying these effects. In vitro, electrophilic lipids, including 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) and 4-hydroxynonenal (HNE), directly bind to vimentin, whereas the oxidant diamide induces disulfide bond formation. Mutation of the single vimentin cysteine residue (Cys328) blunts disulfide formation and reduces lipoxidation by 15d-PGJ2, but not HNE. Preincubation with these agents differentially hinders NaCl-induced filament formation by wild-type vimentin, with effects ranging from delayed elongation and increased filament diameter to severe impairment of assembly or aggregation. Conversely, the morphology of vimentin Cys328Ser filaments is mildly or not affected. Interestingly, preformed vimentin filaments are more resistant to electrophile-induced disruption, although chemical modification is not diminished, showing that vimentin (lip)oxidation prior to assembly is more deleterious. In cells, electrophiles, particularly diamide, induce a fast and drastic disruption of existing filaments, which requires the presence of Cys328. As the cellular vimentin network is under continuous remodeling, we hypothesized that vimentin exchange on filaments would be necessary for diamide-induced disruption. We confirmed that strategies reducing vimentin dynamics, as monitored by FRAP, including cysteine crosslinking and ATP synthesis inhibition, prevent diamide effect. In turn, phosphorylation may promote vimentin disassembly. Indeed, treatment with the phosphatase inhibitor calyculin A to prevent dephosphorylation intensifies electrophile-induced wild-type vimentin filament disruption. However, whereas a phosphorylation-deficient vimentin mutant is only partially protected from disorganization, Cys328Ser vimentin is virtually resistant, even in the presence of calyculin A. Together, these results indicate that modification of Cys328 and vimentin exchange are critical for electrophile-induced network disruption.

The Cytoskeleton-A Complex Interacting Meshwork

The cytoskeleton of animal cells is one of the most complicated and functionally versatile structures, involved in processes such as endocytosis, cell division, intra-cellular transport, motility, force transmission, reaction to external forces, adhesion and preservation, and adaptation of cell shape. These functions are mediated by three classical cytoskeletal filament types, as follows: Actin, microtubules, and intermediate filaments. The named filaments form a network that is highly structured and dynamic, responding to external and internal cues with a quick reorganization that is orchestrated on the time scale of minutes and has to be tightly regulated. Especially in brain tumors, the cytoskeleton plays an important role in spreading and migration of tumor cells. As the cytoskeletal organization and regulation is complex and many-faceted, this review aims to summarize the findings about cytoskeletal filament types, including substructures formed by them, such as lamellipodia, stress fibers, and interactions between intermediate filaments, microtubules and actin. Additionally, crucial regulatory aspects of the cytoskeletal filaments and the formed substructures are discussed and integrated into the concepts of cell motility. Even though little is known about the impact of cytoskeletal alterations on the progress of glioma, a final point discussed will be the impact of established cytoskeletal alterations in the cellular behavior and invasion of glioma.

Predicting cancer cell invasion by single-cell physical phenotyping

The physical properties of cells are promising biomarkers for cancer diagnosis and prognosis. Here we determine the physical phenotypes that best distinguish human cancer cell lines, and their relationship to cell invasion. We use the high throughput, single-cell microfluidic method, quantitative deformability cytometry (q-DC), to measure six physical phenotypes including elastic modulus, cell fluidity, transit time, entry time, cell size, and maximum strain at rates of 102 cells per second. By training a k-nearest neighbor machine learning algorithm, we demonstrate that multiparameter analysis of physical phenotypes enhances the accuracy of classifying cancer cell lines compared to single parameters alone. We also discover a set of four physical phenotypes that predict invasion; using these four parameters, we generate the physical phenotype model of invasion by training a multiple linear regression model with experimental data from a set of human ovarian cancer cells that overexpress a panel of tumor suppressor microRNAs. We validate the model by predicting invasion based on measured physical phenotypes of breast and ovarian human cancer cell lines that are subject to genetic or pharmacologic perturbations. Taken together, our results highlight how physical phenotypes of single cells provide a biomarker to predict the invasion of cancer cells.

Vimentin Diversity in Health and Disease

Vimentin is a protein that has been linked to a large variety of pathophysiological conditions, including cataracts, Crohn's disease, rheumatoid arthritis, HIV and cancer. Vimentin has also been shown to regulate a wide spectrum of basic cellular functions. In cells, vimentin assembles into a network of filaments that spans the cytoplasm. It can also be found in smaller, non-filamentous forms that can localise both within cells and within the extracellular microenvironment. The vimentin structure can be altered by subunit exchange, cleavage into different sizes, re-annealing, post-translational modifications and interacting proteins. Together with the observation that different domains of vimentin might have evolved under different selection pressures that defined distinct biological functions for different parts of the protein, the many diverse variants of vimentin might be the cause of its functional diversity. A number of review articles have focussed on the biology and medical aspects of intermediate filament proteins without particular commitment to vimentin, and other reviews have focussed on intermediate filaments in an in vitro context. In contrast, the present review focusses almost exclusively on vimentin, and covers both ex vivo and in vivo data from tissue culture and from living organisms, including a summary of the many phenotypes of vimentin knockout animals. Our aim is to provide a comprehensive overview of the current understanding of the many diverse aspects of vimentin, from biochemical, mechanical, cellular, systems biology and medical perspectives.

Acidic pHe regulates cytoskeletal dynamics through conformational integrin β1 activation and promotes membrane protrusion

An acidic extracellular pH (pHe) in the tumor microenvironment has been suggested to facilitate tumor growth and metastasis. However, the molecular mechanisms by which tumor cells sense acidic signal to induce a transition to an aggressive phenotype remain elusive. Here, we showed that an acidic pHe (pH 6.5) stimulation resulted in protrusion and epithelial-mesenchymal transition (EMT) of cancer cells, which promoted migration and matrix degeneration. Using computational molecular dynamics simulations, we reported acidic pHe-induced opening of the Integrin dimers (α5β1) headpiece which indicated the activation of integrin. Moreover, acidic pHe promoted maturation of focal adhesions, temporal activation of Rho GTPases and microfilament reorganization through integrin β1-activated FAK signaling. Furthermore, mechanical balance of cytoskeleton (actin, tubulin and vimentin) contributed to acidic pHe-triggered protrusion and morphology change. Taken together, these findings revealed that integrin β1 could be a novel pH-regulated sensitive molecule which confers protrusion and malignant phenotype of cancer cells.

Compressive Force Spectroscopy: From Living Cells to Single Proteins

One of the most successful applications of atomic force microscopy (AFM) in biology involves monitoring the effect of force on single biological molecules, often referred to as force spectroscopy. Such studies generally entail the application of pulling forces of different magnitudes and velocities upon individual molecules to resolve individualistic unfolding/separation pathways and the quantification of the force-dependent rate constants. However, a less recognized variation of this method, the application of compressive force, actually pre-dates many of these "tensile" force spectroscopic studies. Further, beyond being limited to the study of single molecules, these compressive force spectroscopic investigations have spanned samples as large as living cells to smaller, multi-molecular complexes such as viruses down to single protein molecules. Correspondingly, these studies have enabled the detailed characterization of individual cell states, subtle differences between seemingly identical viral structures, as well as the quantification of rate constants of functionally important, structural transitions in single proteins. Here, we briefly review some of the recent achievements that have been obtained with compressive force spectroscopy using AFM and highlight exciting areas of its future development.

Lab-on-a-Chip Platforms for Biophysical Studies of Cancer with Single-Cell Resolution

Recent cancer research has more strongly emphasized the biophysical aspects of tumor development, progression, and microenvironment. In addition to genetic modifications and mutations in cancer cells, it is now well accepted that the physical properties of cancer cells such as stiffness, electrical impedance, and refractive index vary with tumor progression and can identify a malignant phenotype. Moreover, cancer heterogeneity renders population-based characterization techniques inadequate, as individual cellular features are lost in the average. Hence, platforms for fast and accurate characterization of biophysical properties of cancer cells at the single-cell level are required. Here, we highlight some of the recent advances in the field of cancer biophysics and the development of lab-on-a-chip platforms for single-cell biophysical analyses of cancer cells.

Computational modeling of single-cell mechanics and cytoskeletal mechanobiology

Cellular cytoskeletal mechanics plays a major role in many aspects of human health from organ development to wound healing, tissue homeostasis and cancer metastasis. We summarize the state-of-the-art techniques for mathematically modeling cellular stiffness and mechanics and the cytoskeletal components and factors that regulate them. We highlight key experiments that have assisted model parameterization and compare the advantages of different models that have been used to recapitulate these experiments. An overview of feed-forward mechanisms from signaling to cytoskeleton remodeling is provided, followed by a discussion of the rapidly growing niche of encapsulating feedback mechanisms from cytoskeletal and cell mechanics to signaling. We discuss broad areas of advancement that could accelerate research and understanding of cellular mechanobiology. A precise understanding of the molecular mechanisms that affect cell and tissue mechanics and function will underpin innovations in medical device technologies of the future. WIREs Syst Biol Med 2018, 10:e1407. doi: 10.1002/wsbm.1407 This article is categorized under: Models of Systems Properties and Processes > Mechanistic Models Physiology > Mammalian Physiology in Health and Disease Models of Systems Properties and Processes > Cellular Models.

Busulfan administration produces toxic effects on epididymal morphology and inhibits the expression of ZO-1 and vimentin in the mouse epididymis

Busulfan is an alkane sulphonate currently used as an anticancer drug and to prepare azoospermic animal models, because it selectively destroys differentiated spermatogonia in the testes. However, few studies have focussed on the exact effects of busulfan treatment on the epididymis currently. The present study assessed the effect of busulfan on epididymal morphology and the blood-epididymis barrier in mice. We treated mice with a single injection of busulfan and detected the effect at different time points. We showed that busulfan was toxic to the morphological structure and function of the epididymis. Furthermore, busulfan treatment down-regulated the epididymal expression of vimentin and zonula occludens-1 (ZO-1) at the mRNA and protein levels. In addition, there was an increase in total androgen receptor (AR) levels, whereas the estrogen receptor-α (ER-α) levels were reduced, both in the caput and cauda regions after busulfan treatment, which may be secondary to the testicular damage. In conclusion, our study describes the effects of busulfan administration on the mouse epididymis and also provides a potential understanding of male infertility arising from chemotherapy-related defects in the epididymis.

AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting

Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface-surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), α-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch-particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient-steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen-steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture-due to the fast condensation kinetics-leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive effect under the same ambient conditions. The markedly different behavior detected by force measurements clearly shows the sticky and nonsticky propensity of the materials and allows a mechanistic description.

Xenophagic pathways and their bacterial subversion in cellular self-defense - παντα ρει - everything is in flux

Autophagy is an evolutionarily ancient and highly conserved eukaryotic mechanism that targets cytoplasmic material for degradation. Autophagic flux involves the formation of autophagosomes and their degradation by lysosomes. The process plays a crucial role in maintaining cellular homeostasis and responds to various environmental conditions. While autophagy had previously been thought to be a non-selective process, it is now clear that it can also selectively target cellular organelles, such as mitochondria (referred to as mitophagy) and/or invading pathogens (referred to as xenophagy). Selective autophagy is characterized by specific substrate recognition and requires distinct cellular adaptor proteins. Here we review xenophagic mechanisms involved in the recognition and autolysosomal or autophagolysosomal degradation of different intracellular bacteria. In this context, we also discuss a recently discovered cellular self-defense pathway, termed mito-xenophagy, which occurs during bacterial infection of dendritic cells and depends on a TNF-α-mediated metabolic switch from oxidative phosphorylation to glycolysis.

Cell-instructive high-resolution micropatterned polylactic acid surfaces

Micro and nanoscale topographical structuring of biomaterial surfaces has been a valuable tool for influencing cell behavior, including cell attachment, proliferation and differentiation. However, most fabrication techniques for surface patterning of implantable biomaterials suffer from a limited resolution, not allowing controlled generation of sub-cellular three-dimensional features. Here, a direct laser lithography technique based on two-photon absorption was used to construct several patterns varying in size between 500 nm and 15 μm. Through replication via an intermediate mold, the patterns were transferred into polylactic acid (PLA), a widely used biomedical polymer, while retaining the original geometry. An osteoblast-like cell line, MG-63 was used for characterizing the morphological response to the topographical patterns. The results indicated that semi-continuous (dashed) lines, with a height of 1 μm were able to induce cell elongation in the direction of the lines. However, when dashes with a height of 0.5 μm were combined with perpendicularly crossing continuous lines (rails) with a height of 8 μm, the contact guidance effect of the dashes was lost and elongation of the cells was observed in the direction of the larger features. A second pattern, consisting of different arrays of pillars showed that, depending on the pillar height, the cells were either able to spread over the pattern or were confined between the pattern features. These differences in the ability of cells to spread further resulted in the formation of tension forces through stress fibers and displacement of vimentin. The method for high-resolution micropatterning of PLA as presented here can also be applied to other biomedical polymers, making it useful both for fundamental studies and for designing new biomaterials with improved functionality.

Single and collective cell migration: the mechanics of adhesions

Chemical and physical properties of the environment control cell proliferation, differentiation, or apoptosis in the long term. However, to be able to move and migrate through a complex three-dimensional environment, cells must quickly adapt in the short term to the physical properties of their surroundings. Interactions with the extracellular matrix (ECM) occur through focal adhesions or hemidesmosomes via the engagement of integrins with fibrillar ECM proteins. Cells also interact with their neighbors, and this involves various types of intercellular adhesive structures such as tight junctions, cadherin-based adherens junctions, and desmosomes. Mechanobiology studies have shown that cell-ECM and cell-cell adhesions participate in mechanosensing to transduce mechanical cues into biochemical signals and conversely are responsible for the transmission of intracellular forces to the extracellular environment. As they migrate, cells use these adhesive structures to probe their surroundings, adapt their mechanical properties, and exert the appropriate forces required for their movements. The focus of this review is to give an overview of recent developments showing the bidirectional relationship between the physical properties of the environment and the cell mechanical responses during single and collective cell migration.

Mito-xenophagic killing of bacteria is coordinated by a metabolic switch in dendritic cells

Chlamydiae are bacterial pathogens that grow in vacuolar inclusions. Dendritic cells (DCs) disintegrate these compartments, thereby eliminating the microbes, through auto/xenophagy, which also promotes chlamydial antigen presentation via MHC I. Here, we show that TNF-α controls this pathway by driving cytosolic phospholipase (cPLA)2-mediated arachidonic acid (AA) production. AA then impairs mitochondrial function, which disturbs the development and integrity of these energy-dependent parasitic inclusions, while a simultaneous metabolic switch towards aerobic glycolysis promotes DC survival. Tubulin deacetylase/autophagy regulator HDAC6 associates with disintegrated inclusions, thereby further disrupting their subcellular localisation and stability. Bacterial remnants are decorated with defective mitochondria, mito-aggresomal structures, and components of the ubiquitin/autophagy machinery before they are degraded via mito-xenophagy. The mechanism depends on cytoprotective HSP25/27, the E3 ubiquitin ligase Parkin and HDAC6 and promotes chlamydial antigen generation for presentation on MHC I. We propose that this novel mito-xenophagic pathway linking innate and adaptive immunity is critical for effective DC-mediated anti-bacterial resistance.