Mechanical Compression Regulates Brain Cancer Cell Migration Through MEK1/Erk1 Pathway Activation and GDF15 Expression

Mechanical models and measurement methods of solid stress in tumors

In addition to genetic mutations, biomechanical factors also affect the structures and functions of the tumors during tumor growth, including solid stress, interstitial fluid pressure, stiffness, and microarchitecture. Solid stress affects tumors by compressing cancer and stromal cells and deforming blood and lymphatic vessels which reduce supply of oxygen, nutrients and drug delivery, making resistant to treatment. Researchers simulate the stress by creating mechanical models both in vitro and in vivo. Cell models in vitro are divided into two dimensions (2D) and three dimensions (3D). 2D models are simple to operate but exert pressure on apical surface of the cells. 3D models, the multicellular tumor spheres, are more consistent with the actual pathological state in human body. However, the models are more difficult to establish compared with the 2D models. Besides, the procedure of the animal models in vivo is even more complex and tougher to operate. Then, researchers challenged to quantify the solid stress through some measurement methods. We compared the advantages and limitations of these models and methods, which may help to explore new therapeutic targets for normalizing the tumor's physical microenvironment. KEY POINTS: •This is the first review to conclude the mechanical models and measurement methods in tumors. •The merit and demerit of these models and methods are compared. •Insights into further models are discussed.

Mechanical compression regulates tumor spheroid invasion into a 3D collagen matrix

Uncontrolled growth of tumor cells in confined spaces leads to the accumulation of compressive stress within the tumor. Although the effects of tension within 3D extracellular matrices (ECMs) on tumor growth and invasion are well established, the role of compression in tumor mechanics and invasion is largely unexplored. In this study, we modified a Transwell assay such that it provides constant compressive loads to spheroids embedded within a collagen matrix. We used microscopic imaging to follow the single cell dynamics of the cells within the spheroids, as well as invasion into the 3D ECMs. Our experimental results showed that malignant breast tumor (MDA-MB-231) and non-tumorigenic epithelial (MCF10A) spheroids responded differently to a constant compression. Cells within the malignant spheroids became more motile within the spheroids and invaded more into the ECM under compression; whereas cells within non-tumorigenic MCF10A spheroids became less motile within the spheroids and did not display apparent detachment from the spheroids under compression. These findings suggest that compression may play differential roles in healthy and pathogenic epithelial tissues and highlight the importance of tumor mechanics and invasion.

Toward innovative approaches for exploring the mechanically regulated tumor-immune microenvironment

Within the complex tumor microenvironment, cells experience mechanical cues-such as extracellular matrix stiffening and elevation of solid stress, interstitial fluid pressure, and fluid shear stress-that significantly impact cancer cell behavior and immune responses. Recognizing the significance of these mechanical cues not only sheds light on cancer progression but also holds promise for identifying potential biomarkers that would predict therapeutic outcomes. However, standardizing methods for studying how mechanical cues affect tumor progression is challenging. This challenge stems from the limitations of traditional in vitro cell culture systems, which fail to encompass the critical contextual cues present in vivo. To address this, 3D tumor spheroids have been established as a preferred model, more closely mimicking cancer progression, but they usually lack reproduction of the mechanical microenvironment encountered in actual solid tumors. Here, we review the role of mechanical forces in modulating tumor- and immune-cell responses and discuss how grasping the importance of these mechanical cues could revolutionize in vitro tumor tissue engineering. The creation of more physiologically relevant environments that better replicate in vivo conditions will eventually increase the efficacy of currently available treatments, including immunotherapies.

Uncovering potential diagnostic and pathophysiological roles of α-synuclein and DJ-1 in melanoma

BACKGROUND

Melanoma, the most lethal skin cancer type, occurs more frequently in Parkinson's disease (PD), and PD is more frequent in melanoma patients, suggesting disease mechanisms overlap. α-synuclein, a protein that accumulates in PD brain, and the oncogene DJ-1, which is associated with PD autosomal recessive forms, are both elevated in melanoma cells. Whether this indicates melanoma progression or constitutes a protective response remains unclear. We hereby investigated the molecular mechanisms through which α-synuclein and DJ-1 interact, suggesting novel biomarkers and targets in melanoma.

METHODS

The Cancer Genome Atlas (TCGA) expression profiles derived from UCSC Xena were used to obtain α-synuclein and DJ-1 expression and correlated with survival in skin cutaneous melanoma (SKCM). Immunohistochemistry determined the expression in metastatic melanoma lymph nodes. Protein-protein interactions (PPIs) and molecular docking assessed protein binding and affinity with chemotherapeutic drugs. Further validation was performed using in vitro cellular models and ELISA immunoassays.

RESULTS

α-synuclein and DJ-1 were upregulated in primary and metastatic SKCM. Aggregated α-synuclein was selectively detected in metastatic melanoma lymph nodes. α-synuclein overexpression in SK-MEL-28 cells induced the expression of DJ-1, supporting PPI and a positive correlation in melanoma patients. Molecular docking revealed a stable protein complex, with differential binding to chemotherapy drugs such as temozolomide, dacarbazine, and doxorubicin. Parallel reduction of both proteins in temozolomide-treated SK-MEL-28 spheroids suggests drug binding may affect protein interaction and/or stability.

CONCLUSION

α-synuclein, together with DJ-1, may play a role in melanoma progression and chemosensitivity, constituting novel targets for therapeutic intervention, and possible biomarkers for melanoma.

Transducing compressive forces into cellular outputs in cancer and beyond

In living organisms, cells sense mechanical forces (shearing, tensile, and compressive) and respond to those physical cues through a process called mechanotransduction. This process includes the simultaneous activation of biochemical signaling pathways. Recent studies mostly on human cells revealed that compressive forces selectively modulate a wide range of cell behavior, both in compressed and in neighboring less compressed cells. Besides participating in tissue homeostasis such as bone healing, compression is also involved in pathologies, including intervertebral disc degeneration or solid cancers. In this review, we will summarize the current scattered knowledge of compression-induced cell signaling pathways and their subsequent cellular outputs, both in physiological and pathological conditions, such as solid cancers.

Mechanical compression regulates tumor spheroid invasion into a 3D collagen matrix

Uncontrolled growth of tumor cells in confined spaces leads to the accumulation of compressive stress within the tumor. Although the effects of tension within 3D extracellular matrices on tumor growth and invasion are well established, the role of compression in tumor mechanics and invasion is largely unexplored. In this study, we modified a Transwell assay such that it provides constant compressive loads to spheroids embedded within a collagen matrix. We used microscopic imaging to follow the single cell dynamics of the cells within the spheroids, as well as invasion into the 3D extracellular matrices (EMCs). Our experimental results showed that malignant breast tumor (MDA-MB-231) and non-tumorigenic epithelial (MCF10A) spheroids responded differently to a constant compression. Cells within the malignant spheroids became more motile within the spheroids and invaded more into the ECM under compression; whereas cells within non-tumorigenic MCF10A spheroids became less motile within the spheroids and did not display apparent detachment from the spheroids under compression. These findings suggest that compression may play differential roles in healthy and pathogenic epithelial tissues and highlights the importance of tumor mechanics and invasion.

Intracellular and microenvironmental regulation of mitochondrial membrane potential in cancer cells

Cancer cells have an abnormally high mitochondrial membrane potential (ΔΨm ), which is associated with enhanced invasive properties in vitro and increased metastases in vivo. The mechanisms underlying the abnormal ΔΨm in cancer cells remain unclear. Research on different cell types has shown that ΔΨm is regulated by various intracellular mechanisms such as by mitochondrial inner and outer membrane ion transporters, cytoskeletal elements, and biochemical signaling pathways. On the other hand, the role of extrinsic, tumor microenvironment (TME) derived cues in regulating ΔΨm is not well defined. In this review, we first summarize the existing literature on intercellular mechanisms of ΔΨm regulation, with a focus on cancer cells. We then offer our perspective on the different ways through which the microenvironmental cues such as hypoxia and mechanical stresses may regulate cancer cell ΔΨm . This article is categorized under: Cancer > Environmental Factors Cancer > Biomedical Engineering Cancer > Molecular and Cellular Physiology.

Glycosylation spectral signatures for glioma grade discrimination using Raman spectroscopy

BACKGROUND

Gliomas are the most common brain tumours with the high-grade glioblastoma representing the most aggressive and lethal form. Currently, there is a lack of specific glioma biomarkers that would aid tumour subtyping and minimally invasive early diagnosis. Aberrant glycosylation is an important post-translational modification in cancer and is implicated in glioma progression. Raman spectroscopy (RS), a vibrational spectroscopic label-free technique, has already shown promise in cancer diagnostics.

METHODS

RS was combined with machine learning to discriminate glioma grades. Raman spectral signatures of glycosylation patterns were used in serum samples and fixed tissue biopsy samples, as well as in single cells and spheroids.

RESULTS

Glioma grades in fixed tissue patient samples and serum were discriminated with high accuracy. Discrimination between higher malignant glioma grades (III and IV) was achieved with high accuracy in tissue, serum, and cellular models using single cells and spheroids. Biomolecular changes were assigned to alterations in glycosylation corroborated by analysing glycan standards and other changes such as carotenoid antioxidant content.

CONCLUSION

RS combined with machine learning could pave the way for more objective and less invasive grading of glioma patients, serving as a useful tool to facilitate glioma diagnosis and delineate biomolecular glioma progression changes.

Compressed Prostate Cancer Cells Decrease Osteoclast Activity While Enhancing Osteoblast Activity In Vitro

Once prostate cancer cells metastasize to bone, they perceive approximately 2 kPa compression. We hypothesize that 2 kPa compression stimulates the epithelial-to-mesenchymal transition (EMT) of prostate cancer cells and alters their production of paracrine signals to affect osteoclast and osteoblast behavior. Human DU145 prostate cancer cells were subjected to 2 kPa compression for 2 days. Compression decreased expression of 2 epithelial genes, 5 out of 13 mesenchymal genes, and increased 2 mesenchymal genes by DU145 cells, as quantified by qPCR. Conditioned medium (CM) of DU145 cells was added to human monocytes that were stimulated to differentiate into osteoclasts for 21 days. CM from compressed DU145 cells decreased osteoclast resorptive activity by 38% but did not affect osteoclast size and number compared to CM from non-compressed cells. CM was also added to human adipose stromal cells, grown in osteogenic medium. CM of compressed DU145 cells increased bone nodule production (Alizarin Red) by osteoblasts from four out of six donors. Compression did not affect IL6 or TNF-α production by PC DU145 cells. Our data suggest that compression affects EMT-related gene expression in DU145 cells, and alters their production of paracrine signals to decrease osteoclast resorptive activity while increasing mineralization by osteoblasts is donor dependent. This observation gives further insight in the altered behavior of PC cells upon mechanical stimuli, which could provide novel leads for therapies, preventing bone metastases.

Extracellular matrix mechanobiology in cancer cell migration

The extracellular matrix (ECM) is pivotal in modulating tumor progression. Besides chemically stimulating tumor cells, it also offers physical support that orchestrates the sequence of events in the metastatic cascade upon dynamically modulating cell mechanosensation. Understanding this translation between matrix biophysical cues and intracellular signaling has led to rapid growth in the interdisciplinary field of cancer mechanobiology in the last decade. Substantial efforts have been made to develop novel in vitro tumor mimicking platforms to visualize and quantify the mechanical forces within the tissue that dictate tumor cell invasion and metastatic growth. This review highlights recent findings on tumor matrix biophysical cues such as fibrillar arrangement, crosslinking density, confinement, rigidity, topography, and non-linear mechanics and their implications on tumor cell behavior. We also emphasize how perturbations in these cues alter cellular mechanisms of mechanotransduction, consequently enhancing malignancy. Finally, we elucidate engineering techniques to individually emulate the mechanical properties of tumors that could help serve as toolkits for developing and testing ECM-targeted therapeutics on novel bioengineered tumor platforms. STATEMENT OF SIGNIFICANCE: Disrupted ECM mechanics is a driving force for transitioning incipient cells to life-threatening malignant variants. Understanding these ECM changes can be crucial as they may aid in developing several efficacious drugs that not only focus on inducing cytotoxic effects but also target specific matrix mechanical cues that support and enhance tumor invasiveness. Designing and implementing an optimal tumor mimic can allow us to predictively map biophysical cue-modulated cell behaviors and facilitate the design of improved lab-grown tumor models with accurately controlled structural features. This review focuses on the abnormal changes within the ECM during tumorigenesis and its implications on tumor cell-matrix mechanoreciprocity. Additionally, it accentuates engineering approaches to produce ECM features of varying levels of complexity which is critical for improving the efficiency of current engineered tumor tissue models.

Mechanical and metabolic interplay in the brain metastatic microenvironment

In this Perspective, we provide our insights and opinions about the contribution—and potential co-regulation—of mechanics and metabolism in incurable breast cancer brain metastasis. Altered metabolic activity can affect cancer metastasis as high glucose supply and demand in the brain microenvironment favors aerobic glycolysis. Similarly, the altered mechanical properties of disseminating cancer cells facilitate migration to and metastatic seeding of the brain, where local metabolites support their progression. Cancer cells in the brain and the brain tumor microenvironment often possess opposing mechanical and metabolic properties compared to extracranial cancer cells and their microenvironment, which inhibit the ease of extravasation and metastasis of these cells outside the central nervous system. We posit that the brain provides a metabolic microenvironment that mechanically reinforces the cellular structure of cancer cells and supports their metastatic growth while restricting their spread from the brain to external organs.

Coupling solid and fluid stresses with brain tumour growth and white matter tract deformations in a neuroimaging-informed model

Brain tumours are among the deadliest types of cancer, since they display a strong ability to invade the surrounding tissues and an extensive resistance to common therapeutic treatments. It is therefore important to reproduce the heterogeneity of brain microstructure through mathematical and computational models, that can provide powerful instruments to investigate cancer progression. However, only a few models include a proper mechanical and constitutive description of brain tissue, which instead may be relevant to predict the progression of the pathology and to analyse the reorganization of healthy tissues occurring during tumour growth and, possibly, after surgical resection. Motivated by the need to enrich the description of brain cancer growth through mechanics, in this paper we present a mathematical multiphase model that explicitly includes brain hyperelasticity. We find that our mechanical description allows to evaluate the impact of the growing tumour mass on the surrounding healthy tissue, quantifying the displacements, deformations, and stresses induced by its proliferation. At the same time, the knowledge of the mechanical variables may be used to model the stress-induced inhibition of growth, as well as to properly modify the preferential directions of white matter tracts as a consequence of deformations caused by the tumour. Finally, the simulations of our model are implemented in a personalized framework, which allows to incorporate the realistic brain geometry, the patient-specific diffusion and permeability tensors reconstructed from imaging data and to modify them as a consequence of the mechanical deformation due to cancer growth.

Quantification of Tissue Compression Identifies High-Grade Glioma Patients with Reduced Survival

The compression of peritumoral healthy tissue in brain tumor patients is considered a major cause of the life-threatening neurologic symptoms. Although significant deformations caused by the tumor growth can be observed radiologically, the quantification of minor tissue deformations have not been widely investigated. In this study, we propose a method to quantify subtle peritumoral deformations. A total of 127 MRI longitudinal studies from 23 patients with high-grade glioma were included. We estimate longitudinal displacement fields based on a symmetric normalization algorithm and we propose four biomarkers. We assess the interpatient and intrapatient association between proposed biomarkers and the survival based on Cox analyses, and the potential of the biomarkers to stratify patients according to their survival based on Kaplan−Meier analysis. Biomarkers show a significant intrapatient association with survival (p < 0.05); however, only compression biomarkers show the ability to stratify patients between those with higher and lower overall survival (AUC = 0.83, HR = 6.30, p < 0.05 for CompCH). The compression biomarkers present three times higher Hazard Ratios than those representing only displacement. Our study provides a robust and automated method for quantifying and delineating compression in the peritumoral area. Based on the proposed methodology, we found an association between lower compression in the peritumoral area and good prognosis in high-grade glial tumors.

Mechanical Stress Signaling in Pancreatic Cancer Cells Triggers p38 MAPK- and JNK-Dependent Cytoskeleton Remodeling and Promotes Cell Migration via Rac1/cdc42/Myosin II

Advanced or metastatic pancreatic cancer is highly resistant to existing therapies, and new treatments are urgently needed to improve patient outcomes. Current studies focus on alternative treatment approaches that target the abnormal microenvironment of pancreatic tumors and the resulting elevated mechanical stress in the tumor interior. Nevertheless, the underlying mechanisms by which mechanical stress regulates pancreatic cancer metastatic potential remain elusive. Herein, we used a proteomic assay to profile mechanical stress-induced signaling cascades that drive the motility of pancreatic cancer cells. Proteomic analysis, together with selective protein inhibition and siRNA treatments, revealed that mechanical stress enhances cell migration through activation of the p38 MAPK/HSP27 and JNK/c-Jun signaling axes, and activation of the actin cytoskeleton remodelers: Rac1, cdc42, and myosin II. In addition, mechanical stress upregulated transcription factors associated with epithelial-to-mesenchymal transition and stimulated the formation of stress fibers and filopodia. p38 MAPK and JNK inhibition resulted in lower cell proliferation and more effectively blocked cell migration under mechanical stress compared with control conditions. The enhanced tumor cell motility under mechanical stress was potently reduced by cdc42 and Rac1 silencing with no effects on proliferation. Our results highlight the importance of targeting aberrant signaling in cancer cells that have adapted to mechanical stress in the tumor microenvironment, as a novel approach to effectively limit pancreatic cancer cell migration.

IMPLICATIONS

Our findings highlight that mechanical stress activated the p38 MAPK and JNK signaling axis and stimulated pancreatic cancer cell migration via upregulation of the actin cytoskeleton remodelers cdc42 and Rac1.

A Portable Controllable Compressive Stress Device to Monitor Human Breast Cancer Cell Protrusions at Single-Cell Resolution

In vitro devices offer more numerous methods than in vivo models to investigate how cells respond to pressure stress and quantify those responses. Several in vitro devices have been developed to study the cell response to compression force. However, they are unable to observe morphological changes of cells in real-time. There is also a concern about cell damage during the process of harvesting cells from 3D gels. Here we report a device employing transparent, thin gel layers to clamp cells between the interfaces and applied a controllable compression force by stacking multiple layers on the top. In this approach, cells can be monitored for alteration of cellular protrusions, whose diversity has been proven to promote cancer cell dissemination, with single-cell resolution under compression force. Furthermore, p-Rac-1 and rhodamine staining on the device directly to confirm the actin filaments of lamellipodia. The method was able to fulfill real-time live-cell observation at single-cell resolution and can be readily used for versatile cell analysis. MDA-MB-231 and MCF7 breast cancer cells were utilized to demonstrate the utility of the device, and the results showed that the stimuli of compression force induce MDA-MB-231 and MCF7 to form lamellipodia and bleb protrusions, respectively. We envision the device may be used as a tool to explore mechanisms of membrane protrusion transitions and to screen drug candidates for inhibiting cancer cell protrusion plasticity for cancer therapy.

Inducing Biomechanical Heterogeneity in Brain Tumor Modeling by MR Elastography: Effects on Tumor Growth, Vascular Density and Delivery of Therapeutics

Simple Summary

Biomechanical forces aggravate brain tumor progression. In this study, magnetic resonance elastography (MRE) is employed to extract tissue biomechanical properties from five glioblastoma patients and a healthy subject, and data are incorporated in a mathematical model that simulates tumor growth. Mathematical modeling enables further understanding of glioblastoma development and allows patient-specific predictions for tumor vascularity and delivery of drugs. Incorporating MRE data results in a more realistic intratumoral distribution of mechanical stress and anisotropic tumor growth and a better description of subsequent events that are closely related to the development of stresses, including heterogeneity of the tumor vasculature and intrapatient variations in tumor perfusion and delivery of drugs.

Abstract

The purpose of this study is to develop a methodology that incorporates a more accurate assessment of tissue mechanical properties compared to current mathematical modeling by use of biomechanical data from magnetic resonance elastography. The elastography data were derived from five glioblastoma patients and a healthy subject and used in a model that simulates tumor growth, vascular changes due to mechanical stresses and delivery of therapeutic agents. The model investigates the effect of tumor-specific biomechanical properties on tumor anisotropic growth, vascular density heterogeneity and chemotherapy delivery. The results showed that including elastography data provides a more realistic distribution of the mechanical stresses in the tumor and induces anisotropic tumor growth. Solid stress distribution differs among patients, which, in turn, induces a distinct functional vascular density distribution—owing to the compression of tumor vessels—and intratumoral drug distribution for each patient. In conclusion, incorporating elastography data results in a more accurate calculation of intratumoral mechanical stresses and enables a better mathematical description of subsequent events, such as the heterogeneous development of the tumor vasculature and intrapatient variations in tumor perfusion and delivery of drugs.

GDF15 Supports the Inflammatory Response of PdL Fibroblasts Stimulated by P. gingivalis LPS and Concurrent Compression

Periodontitis is characterized by bacterially induced inflammatory destruction of periodontal tissue. This also affects fibroblasts of the human periodontal ligaments (HPdLF), which play a coordinating role in force-induced tissue and alveolar bone remodeling. Excessive inflammation in the oral tissues has been observed with simultaneous stimulation by pathogens and mechanical forces. Recently, elevated levels of growth differentiation factor 15 (GDF15), an immuno-modulatory member of the transforming growth factor (TGFB) superfamily, were detected under periodontitis-like conditions and in force-stressed PdL cells. In view of the pleiotropic effects of GDF15 in various tissues, this study aims to investigate the role of GDF15 in P. gingivalis-related inflammation of HPdLF and its effect on the excessive inflammatory response to concurrent compressive stress. To this end, the expression and secretion of cytokines (IL6, IL8, COX2/PGE2, TNFα) and the activation of THP1 monocytic cells were analyzed in GDF15 siRNA-treated HPdLF stimulated with P. gingivalis lipopolysaccharides alone and in combination with compressive force. GDF15 knockdown significantly reduced cytokine levels and THP1 activation in LPS-stimulated HPdLF, which was less pronounced with additional compressive stress. Overall, our data suggest a pro-inflammatory role for GDF15 in periodontal disease and demonstrate that GDF15 partially modulates the force-induced excessive inflammatory response of PdLF under these conditions.

A computational model of glioma reveals opposing, stiffness-sensitive effects of leaky vasculature and tumor growth on tissue mechanical stress and porosity

A biphasic computational model of a growing, vascularized glioma within brain tissue was developed to account for unique features of gliomas, including soft surrounding brain tissue, their low stiffness relative to brain tissue, and a lack of draining lymphatics. This model is the first to couple nonlinear tissue deformation with porosity and tissue hydraulic conductivity to study the mechanical interaction of leaky vasculature and solid growth in an embedded glioma. The present model showed that leaky vasculature and elevated interstitial fluid pressure produce tensile stress within the tumor in opposition to the compressive stress produced by tumor growth. This tensile effect was more pronounced in softer tissue and resulted in a compressive stress concentration at the tumor rim that increased when tumor was softer than host. Aside from generating solid stress, fluid pressure-driven tissue deformation decreased the effective stiffness of the tumor while growth increased it, potentially leading to elevated stiffness in the tumor rim. A novel prediction of reduced porosity at the tumor rim was corroborated by direct comparison with estimates from our in vivo imaging studies. Antiangiogenic and radiation therapy were simulated by varying vascular leakiness and tissue hydraulic conductivity. These led to greater solid compression and interstitial pressure in the tumor, respectively, the former of which may promote tumor infiltration of the host. Our findings suggest that vascular leakiness has an important influence on in vivo solid stress, stiffness, and porosity fields in gliomas given their unique mechanical microenvironment.

Compressive force regulates cementoblast migration via downregulation of autophagy

BACKGROUND

Migration of cementoblasts to resorption lacunae is the foundation for repairing root resorption during orthodontic tooth movement. Previous studies reported that autophagy was activated by compression in periodontal ligament cells. The aim of this study was to investigate the migration of cementoblasts and determine whether autophagy is involved in the regulation of cementoblast migration under compressive force.

METHODS

Flow cytometry was employed to examine the apoptosis of murine cementoblasts (OCCM-30) at different compression times (0, 6, 12, and 24 hours) and magnitudes (0, 1.0, 1.5, and 2.0 g/cm² ). Cell proliferation was examined using the CCK-8 method. Wound healing migration assays and transwell migration assays were performed to compare the migration of cementoblasts. Chloroquine (CQ) and rapamycin were used to inhibit and activate autophagy, respectively. The level of autophagy was determined using western blotting and immunofluorescence staining. The expression of matrix metalloproteinases (MMPs) was assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot analysis, and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Cell apoptosis and proliferation did not significantly change in OCCM-30 cells under mechanical compression at magnitude of 1.5 g/cm² for 12 hours. However, the migration of cementoblasts was significantly inhibited after the application of compressive force. MMP2, MMP9, and MMP13 mRNA expression was decreased, and MMP9 and MMP13 protein expression and secretion level were also decreased. Further, autophagic activity was inhibited in cementoblasts under compressive force. Treatment with chloroquine reduced the cellular migration, and rapamycin partially relieved the inhibition of cementoblast migration induced by the compressive force. MMP9 and MMP13 mRNA expression, protein expression, and secretion levels showed a similar trend.

CONCLUSION

Migration of OCCM-30 cells was inhibited under compressive force partially dependent on the inhibition of MMPs, which was mediated by downregulation of autophagy. The findings provide new insights into the role of autophagy in biological behaviors of cementoblasts under compressive force and a potential therapeutic strategy for reducing external root resorption.

The Role of Tumor Microenvironment in Cancer Metastasis: Molecular Mechanisms and Therapeutic Opportunities

Simple Summary

Metastasis, the process by which cancer cells escape primary tumor site and colonize distant organs, is responsible for most cancer-related deaths. The tumor microenvironment (TME), comprises different cell types, including immune cells and cancer-associated fibroblasts, as well as structural elements, such as collagen and hyaluronan that constitute the extracellular matrix (ECM). Intratumoral interactions between the cellular and structural components of the TME regulate the aggressiveness, and dissemination of malignant cells and promote immune evasion. At the secondary site, the TME also facilitates escape from dormancy to enhance metastatic tumor outgrowth. Moreover, the ECM applies mechanical forces on tumors that contribute to hypoxia and cancer cell invasiveness whereas also hinders drug delivery and efficacy in both primary and metastatic sites. In this review, we summarize the latest developments regarding the role of the TME in cancer progression and discuss ongoing efforts to remodel the TME to stop metastasis in its tracks.

Abstract

The tumor microenvironment (TME) regulates essential tumor survival and promotion functions. Interactions between the cellular and structural components of the TME allow cancer cells to become invasive and disseminate from the primary site to distant locations, through a complex and multistep metastatic cascade. Tumor-associated M2-type macrophages have growth-promoting and immunosuppressive functions; mesenchymal cells mass produce exosomes that increase the migratory ability of cancer cells; cancer associated fibroblasts (CAFs) reorganize the surrounding matrix creating migration-guiding tracks for cancer cells. In addition, the tumor extracellular matrix (ECM) exerts determinant roles in disease progression and cancer cell migration and regulates therapeutic responses. The hypoxic conditions generated at the primary tumor force cancer cells to genetically and/or epigenetically adapt in order to survive and metastasize. In the circulation, cancer cells encounter platelets, immune cells, and cytokines in the blood microenvironment that facilitate their survival and transit. This review discusses the roles of different cellular and structural tumor components in regulating the metastatic process, targeting approaches using small molecule inhibitors, nanoparticles, manipulated exosomes, and miRNAs to inhibit tumor invasion as well as current and future strategies to remodel the TME and enhance treatment efficacy to block the detrimental process of metastasis.

GDF-15: Diagnostic, prognostic, and therapeutic significance in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the commonest primary malignant brain tumor and has a remarkably weak prognosis. According to the aggressive form of GBM, understanding the accurate molecular mechanism associated with GBM pathogenesis is essential. Growth differentiation factor 15 (GDF-15) belongs to transforming growth factor-β superfamily with important roles to control biological processes. It affects cancer growth and progression, drug resistance, and metastasis. It also can promote stemness in many cancers, and also can stress reactions control, bone generation, hematopoietic growth, adipose tissue performance, and body growth, and contributes to cardiovascular disorders. The role GDF-15 to develop and progress cancer is complicated and remains unclear. GDF-15 possesses tumor suppressor properties, as well as an oncogenic effect. GDF-15 antitumorigenic and protumorigenic impacts on tumor development are linked to the cancer type and stage. However, the GDF-15 signaling and mechanism have not yet been completely identified because of no recognized cognate receptor.

Mechanical Control of Cell Proliferation Increases Resistance to Chemotherapeutic Agents

While many cellular mechanisms leading to chemotherapeutic resistance have been identified, there is an increasing realization that tumor-stroma interactions also play an important role. In particular, mechanical alterations are inherent to solid cancer progression and profoundly impact cell physiology. Here, we explore the influence of compressive stress on the efficacy of chemotherapeutics in pancreatic cancer spheroids. We find that increased compressive stress leads to decreased drug efficacy. Theoretical modeling and experiments suggest that mechanical stress decreases cell proliferation which in turn reduces the efficacy of chemotherapeutics that target proliferating cells. Our work highlights a mechanical form of drug resistance and suggests new strategies for therapy.

Compressive Stimulation Enhances Ovarian Cancer Proliferation, Invasion, Chemoresistance, and Mechanotransduction via CDC42 in a 3D Bioreactor

This report investigates the role of compressive stress on ovarian cancer in a 3D custom built bioreactor. Cells within the ovarian tumor microenvironment experience a range of compressive stimuli that contribute to mechanotransduction. As the ovarian tumor expands, cells are exposed to chronic load from hydrostatic pressure, displacement of surrounding cells, and growth induced stress. External dynamic stimuli have been correlated with an increase in metastasis, cancer stem cell marker expression, chemoresistance, and proliferation in a variety of cancers. However, how these compressive stimuli contribute to ovarian cancer progression is not fully understood. In this report, high grade serous ovarian cancer cell lines were encapsulated within an ECM mimicking hydrogel comprising of agarose and collagen type I, and stimulated with confined cyclic or static compressive stresses for 24 and 72 h. Compression stimulation resulted in a significant increase in proliferation, invasive morphology, and chemoresistance. Additionally, CDC42 was upregulated in compression stimulated conditions, and was necessary to drive increased proliferation and chemoresistance. Inhibition of CDC42 lead to significant decrease in proliferation, survival, and increased chemosensitivity. In summary, the dynamic in vitro 3D platform developed in this report, is ideal for understanding the influence of compressive stimuli, and can be widely applicable to any epithelial cancers. This work reinforces the critical need to consider compressive stimulation in basic cancer biology and therapeutic developments.

Hydroethanolic Extract of Lampaya Medicinalis Phil. (Verbenaceae) Decreases Proinflammatory Marker Expression in Palmitic Acid-exposed Macrophages

BACKGROUND

Obesity is a major health problem associated with increased comorbidities, which are partially triggered by inflammation. Proinflammatory macrophage infiltration in adipose tissue of individuals with obesity increases chronic inflammation. Obesity is associated with elevated plasma levels of saturated fatty acids, such as palmitic acid (PA), which promotes inflammation in vivo and in vitro. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in the folk medicine of Northern Chile to counteract inflammation of rheumatic diseases. Hydroethanolic extract of lampaya (HEL) contains spectrophotometrically defined compounds that may contribute to the observed effect on inflammation.

METHODS

We evaluated the phytochemical composition of HEL by high-performance liquid chromatography coupled to diode array detection (HPLC-DAD) and liquid chromatography-electrospray ionization- tandem mass spectrometry (LC-ESI-MS/MS). We assessed whether the exposure to HEL affects PA-induced expression of proinflammatory factors in THP-1 macrophages.

RESULTS

HPLC-DAD and LC-ESI-MS/MS analyses showed the presence of considerable amounts of flavonoids in HEL. The PA-induced phosphorylation of the inflammatory pathway mediators IKK and NF-κB, as well as the elevated expression and secretion of proinflammatory cytokines (IL-6, TNF-α), were reduced in cells pre-exposed to HEL.

CONCLUSION

These findings give new insights about the effect of HEL reducing IKK/NF-κB proinflammatory pathway, likely explained by the number of flavonoids contained in the extract. More studies would be needed to define the possible role of Lampaya as a preventive approach in subjects with obesity whose circulating PA might contribute to chronic inflammation.