Evolution of osmotic pressure in solid tumors

The mechanopathology of the tumor microenvironment: detection techniques, molecular mechanisms and therapeutic opportunities

The mechanical properties of the tumor microenvironment (TME) undergo significant changes during tumor growth, primarily driven by alterations in extracellular (ECM) stiffness and tumor viscoelasticity. These mechanical changes not only promote tumor progression but also hinder therapeutic efficacy by impairing drug delivery and activating mechanotransduction pathways that regulate crucial cellular processes such as migration, proliferation, and resistance to therapy. In this review, we examine the mechanisms through which tumor cells sense and transmit mechanical signals to maintain homeostasis in the biomechanically altered TME. We explore current computational modelling strategies for mechanotransduction pathways, highlighting the need for developing models that incorporate additional components of the mechanosignaling machinery. Furthermore, we review available methods for measuring the mechanical properties of tumors in clinical settings and strategies aiming at restoring the TME and blocking deregulated mechanotransduction pathways. Finally, we propose that proper characterization and a deeper understanding of the mechanical landscape of the TME, both at the tissue and cellular levels, are essential for developing therapeutic strategies that account for the influence of mechanical forces on treatment efficacy.

Mechanical Forces in Tumor Growth and Treatment: Perspectives From Biology, Physics, Engineering, and Mathematical Modeling

The progression of tumors is influenced by mechanical forces and biological elements, such as hypoxia and angiogenesis. Mechanical factors, including stress, pressure, interstitial fluid pressure, and cellular traction forces, compromise normal tissue architecture, augmenting stiffness and thus promoting tumor growth and invasion. The selective elimination of specific tumor components can reduce growth-induced mechanical stress, thereby improving therapeutic efficacy. Furthermore, stress-relief drugs have the potential in enhancing chemotherapy outcomes. In this setting, computational modeling functions as an essential tool for quantitatively elucidating the mechanical principles underlying tumor formation. These models can precisely replicate the impact of mechanical pressures on solid tumors, offering insight into the regulation of tumor behavior by these forces. Tumor growth produces mechanical forces, including compression, displacement, and deformation, leading to irregular stress patterns, expedited tumor advancement, and reduced treatment efficacy. This review analyzes the impact of mechanical forces on carcinogenesis and solid tumor proliferation, emphasizing the significance of stress alleviation in regulating tumor growth. Furthermore, we investigate the influence of mechanical forces on tumor dissemination and emphasize the promise of integrating computational modeling with force-targeted cancer therapies to improve treatment efficacy by tackling the fundamental mechanics of tumor proliferation.

Physical principles and mechanisms of cell migration

Cell migration is critical in processes such as developmental biology, wound healing, immune response, and cancer invasion/metastasis. Understanding its regulation is essential for developing targeted therapies in regenerative medicine, cancer treatment and immune modulation. This review examines cell migration mechanisms, highlighting fundamental physical principles, key molecular components, and cellular behaviors, identifying existing gaps in current knowledge, and suggesting potential directions for future research.

Tissue stresses caused by invasive tumour: a biomechanical model

Malignant tumorigenesis is a complex process involving growth, invasion and mechanical deformation of a cancerous tissue. In this paper, a biomechanical model is proposed to couple the mechanical and biological mechanisms governing invasive tumour development. As an example, this model is applied to investigate the spatio-temporal evolution of tissue stresses in an invasive tumour spheroid and its host tissue. I show that cancer invasiveness lowers the compressive tissue stresses and blurs the stress distribution across the cancerous-normal tissue boundary, both consistent with experimental observations. Importantly, with the steady propagation of the cancerous region driven by persistent cancer invasion, tumour stresses are predicted to saturate rather than keep increasing as in benign tumour growth. The model is further used to analyse the deformation and stress state of a cancerous tissue being cut into two pieces, and reproduces the bulge of the cut surface observed in experiments. I hope this study can pave the way for the quantitative evaluation of mechanical states in cancer.

Compressive stresses in cancer: characterization and implications for tumour progression and treatment

Beyond their many well-established biological aberrations, solid tumours create an abnormal physical microenvironment that fuels cancer progression and confers treatment resistance. Mechanical forces impact tumours across a range of biological sizes and timescales, from rapid events at the molecular level involved in their sensing and transmission, to slower and larger-scale events, including clonal selection, epigenetic changes, cell invasion, metastasis and immune response. Owing to challenges with studying these dynamic stimuli in biological systems, the mechanistic understanding of the effects and pathways triggered by abnormally elevated mechanical forces remains elusive, despite clear correlations with cancer pathophysiology, aggressiveness and therapeutic resistance. In this Review, we examine the emerging and diverse roles of physical forces in solid tumours and provide a comprehensive framework for understanding solid stress mechanobiology. We first review the physiological importance of mechanical forces, especially compressive stresses, and discuss their defining characteristics, biological context and relative magnitudes. We then explain how abnormal compressive stresses emerge in tumours and describe the experimental challenges in investigating these mechanically induced processes. Finally, we discuss the clinical translation of mechanotherapeutics that alleviate solid stresses and their potential to synergize with chemotherapy, radiotherapy and immunotherapies.

Mimicking and analyzing the tumor microenvironment

The tumor microenvironment (TME) is increasingly appreciated to play a decisive role in cancer development and response to therapy in all solid tumors. Hypoxia, acidosis, high interstitial pressure, nutrient-poor conditions, and high cellular heterogeneity of the TME arise from interactions between cancer cells and their environment. These properties, in turn, play key roles in the aggressiveness and therapy resistance of the disease, through complex reciprocal interactions between the cancer cell genotype and phenotype, and the physicochemical and cellular environment. Understanding this complexity requires the combination of sophisticated cancer models and high-resolution analysis tools. Models must allow both control and analysis of cellular and acellular TME properties, and analyses must be able to capture the complexity at high depth and spatial resolution. Here, we review the advantages and limitations of key models and methods in order to guide further TME research and outline future challenges.

Sustained Physiological Stretch Induces Abdominal Skin Growth in Pregnancy

Supraphysiological stretches are exploited in skin expanders to induce tissue growth for autologous implants. As pregnancy is associated with large levels of sustained stretch, we investigated whether skin growth occurs in pregnancy. Therefore, we combined a mechanical model of skin and the observations from suction experiments on several body locations of five pregnant women at different gestational ages. The measurements show a continuous increase in stiffness, with the largest change observed during the last trimester. A comparison with numerical simulations indicates that the measured increase in skin stiffness is far below the level expected for the corresponding deformation of abdominal skin. A new set of simulations accounting for growth could rationalize all observations. The predicted amount of tissue growth corresponds to approximately 40% area increase before delivery. The results of the simulations also offered the opportunity to investigate the biophysical cues present in abdominal skin along gestation and to compare them with those arising in skin expanders. Alterations of the skin mechanome were quantified, including tissue stiffness, hydrostatic and osmotic pressure of the interstitial fluid, its flow velocity and electrical potential. The comparison between pregnancy and skin expansion highlights similarities as well as differences possibly influencing growth and remodeling.

A war on many fronts: cross disciplinary approaches for novel cancer treatment strategies

Cancer is a disease characterized by uncontrolled cellular growth where cancer cells take advantage of surrounding cellular populations to obtain resources and promote invasion. Carcinomas are the most common type of cancer accounting for almost 90% of cancer cases. One of the major subtypes of carcinomas are adenocarcinomas, which originate from glandular cells that line certain internal organs. Cancers such as breast, prostate, lung, pancreas, colon, esophageal, kidney are often adenocarcinomas. Current treatment strategies include surgery, chemotherapy, radiation, targeted therapy, and more recently immunotherapy. However, patients with adenocarcinomas often develop resistance or recur after the first line of treatment. Understanding how networks of tumor cells interact with each other and the tumor microenvironment is crucial to avoid recurrence, resistance, and high-dose therapy toxicities. In this review, we explore how mathematical modeling tools from different disciplines can aid in the development of effective and personalized cancer treatment strategies. Here, we describe how concepts from the disciplines of ecology and evolution, economics, and control engineering have been applied to mathematically model cancer dynamics and enhance treatment strategies.

Investigating the synergistic effects of immunotherapy and normalization treatment in modulating tumor microenvironment and enhancing treatment efficacy

We developed a comprehensive mathematical model of cancer immunotherapy that takes into account: i) Immune checkpoint blockers (ICBs) and the interactions between cancer cells and the immune system, ii) characteristics of the tumor microenvironment, such as the tumor hydraulic conductivity, interstitial fluid pressure, and vascular permeability, iii) spatial and temporal variations of the modeled components within the tumor and the surrounding host tissue, iv) the transport of modeled components through the vasculature and between the tumor-host tissue with convection and diffusion, and v) modeling of the tumor draining lymph nodes were the antigen presentation and the development of cytotoxic immune cells take place. Our model successfully reproduced experimental data from various murine tumor types and predicted immune system profiling, which is challenging to achieve experimentally. It showed that combination of ICB therapy and normalization treatments, that aim to improve tumor perfusion, decreases interstitial fluid pressure and increases the concentration of both innate and adaptive immune cells at the tumor center rather than the periphery. Furthermore, using the model, we investigated the impact of modeled components on treatment outcomes. The analysis found that the number of functional vessels inside the tumor region and the ICB dose administered have the largest impact on treatment outcomes.

Mathematical modeling of intratumoral immunotherapy yields strategies to improve the treatment outcomes

Intratumoral injection of immunotherapy aims to maximize its activity within the tumor. However, cytokines are cleared via tumor vessels and escape from the tumor periphery into the host-tissue, reducing efficacy and causing toxicity. Thus, understanding the determinants of the tumor and immune response to intratumoral immunotherapy should lead to better treatment outcomes. In this study, we developed a mechanistic mathematical model to determine the efficacy of intratumorally-injected conjugated-cytokines, accounting for properties of the tumor microenvironment and the conjugated-cytokines. The model explicitly incorporates i) the tumor vascular density and permeability and the tumor hydraulic conductivity, ii) conjugated-cytokines size and binding affinity as well as their clearance via the blood vessels and the surrounding tissue, and iii) immune cells-cancer cells interactions. Model simulations show how the properties of the tumor and of the conjugated-cytokines determine treatment outcomes and how selection of proper parameters can optimize therapy. A high tumor tissue hydraulic permeability allows for the uniform distribution of the cytokines into the tumor, whereas uniform tumor perfusion is required for sufficient access and activation of immune cells. The permeability of the tumor vessels affects the blood clearance of the cytokines and optimal values depend on the size of the conjugates. A size >5 nm in radius was found to be optimal, whereas the binding of conjugates should be high enough to prevent clearance from the tumor into the surrounding tissue. In conclusion, development of strategies to improve vessel perfusion and tissue hydraulic conductivity by reprogramming the microenvironment along with optimal design of conjugated-cytokines can enhance intratumoral immunotherapy.

Cancer reduction in mice with Prakasine nanomedicine immunotherapy

In this study, non-toxic mercury nanoparticle Prakasine (PRK-NP) was synthesized as per 'Prakash theory of metal drugs' and nanoparticle's non toxicity has been demonstrated by employing in vitro MTT (dose = 320ug/ml), SBR (dose = 80ug/ml) and apoptosis assays (dose = 320ug/ml), and in vivo acute and chronic toxicity studies in mice (n = 12, dose = 900 mg/kg body weight oral), rat (n = 14, dose = 500 mg/kg body weight oral for 18 months), rabbit (n = 14, dose = 500 mg/kg body weight oral for 18 months) and dogs (n = 14, dose = 500 mg/kg body weight oral for 18 months). The MTT, SBR and apoptosis assays established no cytotoxicity, no genotoxicity and no cytolytic anticancer effects. The mice, rat, rabbit and dog studies also indicated nontoxicity. The PRK-NPs significantly reduced the breast cancer tumour in murine mammary tumour - C3H/HeJ model 35% and 43.7% in mice at doses of 200 mg/kg and 500 mg/kg respectively. Also, in xenograft mammary tumour mice model the tumour regressions are 25.7% and 83% in the doses of 500 mg/kg and 1000 mg/kg respectively, compared to standard positive control drugs without any adverse effects and toxicity. Thus, the current study beholds anticipation PRK-NPs may play a vital role in therapeutic.

Predicting stress and interstitial fluid pressure in tumors based on biphasic theory

The uncontrolled proliferation of cancer cells causes the growth of the tumor mass. Consequently, the normal surrounding tissue exerts a compressive force on the tumor mass to oppose its expansion. These stresses directly promote tumor metastasis and invasion and affect drug delivery. In the past, the mechanical behavior of solid tumors has been extensively studied using linear elastic and nonlinear hyperelastic constitutive models. In this study, we develop a two-dimensional biomechanical model based on the biphasic assumption of the solid matrix and fluid phase of the tissues. Heterogeneous vasculature and nonuniform blood perfusion are also investigated by incorporating in the model a necrotic core and a well-vascularized zone. The findings of our study demonstrate a significant difference between the linear and nonlinear tissue responses to stress, while the interstitial fluid pressure (IFP) distribution is found to be independent of the constitutive model. The proposed biphasic model may be useful for elasticity imaging techniques aiming at predicting stress and IFP in tumors.

KCl Nanoparticles as Potential Inducer of Immunogenic Cell Death for Cancer Immunotherapy

Immunogenic cell death (ICD) is a promising cancer immunotherapy by inducing antigen-presenting cell maturation. Many inorganic nanomodulators have been developed for cancer therapy via ion overload, and their ICD-inducing properties have also been explored for immunotherapy. Here, we report a potassium chloride nanoparticle (PCNP)-loaded poly(lactic-co-glycolic acid) nanoparticle coated with cancer cell membrane (PC@P-CCM) for cancer therapy. Through cancer cell membrane (CCM)-achieved surface functionalization, the homotypic targeting behaviors of PC@P-CCM are dramatically enhanced. Once internalized by cancer cells, the PC@P-CCM could be degraded in acidic lysosomes, thus releasing K⁺ and Cl^- ions. These ions can change the osmotic pressure of cancer cells, causing a hypertonic state in the cancer cells in a short time and leading to the rupture and death of cancer cells. Furthermore, these ions can stimulate cancer cells to secrete adenosine triphosphate (ATP) and high mobility group box 1 (HMGB-1); meanwhile, calreticulin (CRT) showed increased presentation on the surface of cancer cells, which can further induce dendritic cell maturation and promote the immunotherapy. This work provides a new perspective on KCl nanoparticle-based cancer immunotherapy.

Mechanotransduction in tumor dynamics modeling

Mechanotherapy is a groundbreaking approach to impact carcinogenesis. Cells sense and respond to mechanical stimuli, translating them into biochemical signals in a process known as mechanotransduction. The impact of stress on tumor growth has been studied in the last three decades, and many papers highlight the role of mechanics as a critical self-inducer of tumor fate at the in vitro and in vivo biological levels. Meanwhile, mathematical models attempt to determine laws to reproduce tumor dynamics. This review discusses biological mechanotransduction mechanisms and mathematical-biomechanical models together. The aim is to provide a common framework for the different approaches that have emerged in the literature from the perspective of tumor avascularity and to provide insight into emerging mechanotherapies that have attracted interest in recent years.

Polymeric micelles effectively reprogram the tumor microenvironment to potentiate nano-immunotherapy in mouse breast cancer models

Nano-immunotherapy improves breast cancer outcomes but not all patients respond and none are cured. To improve efficacy, research focuses on drugs that reprogram cancer-associated fibroblasts (CAFs) to improve therapeutic delivery and immunostimulation. These drugs, however, have a narrow therapeutic window and cause adverse effects. Developing strategies that increase CAF-reprogramming while limiting adverse effects is urgent. Here, taking advantage of the CAF-reprogramming capabilities of tranilast, we developed tranilast-loaded micelles. Strikingly, a 100-fold reduced dose of tranilast-micelles induces superior reprogramming compared to free drug owing to enhanced intratumoral accumulation and cancer-associated fibroblast uptake. Combination of tranilast-micelles and epirubicin-micelles or Doxil with immunotherapy increases T-cell infiltration, resulting in cures and immunological memory in mice bearing immunotherapy-resistant breast cancer. Furthermore, shear wave elastography (SWE) is able to monitor reduced tumor stiffness caused by tranilast-micelles and predict response to nano-immunotherapy. Micellar encapsulation is a promising strategy for TME-reprogramming and SWE is a potential biomarker of response.

Regulation of AR mRNA translation in response to acute AR pathway inhibition

We report a new mechanism of androgen receptor (AR) mRNA regulation and cytoprotection in response to AR pathway inhibition (ARPI) stress in prostate cancer (PCA). AR mRNA translation is coordinately regulated by RNA binding proteins, YTHDF3 and G3BP1. Under ambient conditions m6A-modified AR mRNA is bound by YTHDF3 and translationally stimulated, while m6A-unmodified AR mRNA is bound by G3BP1 and translationally repressed. When AR-regulated PCA cell lines are subjected to ARPI stress, m6A-modified AR mRNA is recruited from actively translating polysomes (PSs) to RNA-protein stress granules (SGs), leading to reduced AR mRNA translation. After ARPI stress, m6A-modified AR mRNA liquid–liquid phase separated with YTHDF3, while m6A-unmodified AR mRNA phase separated with G3BP1. Accordingly, these AR mRNA messages form two distinct YTHDF3-enriched or G3BP1-enriched clusters in SGs. ARPI-induced SG formation is cell-protective, which when blocked by YTHDF3 or G3BP1 silencing increases PCA cell death in response to ARPI stress. Interestingly, AR mRNA silencing also delays ARPI stress-induced SG formation, highlighting its supportive role in triggering this stress response. Our results define a new mechanism for stress adaptive cell survival after ARPI stress involving SG-regulated translation of AR mRNA, mediated by m6A RNA modification and their respective regulatory proteins.

3D models of the dynamics of cancer cells under external pressure

Skin cancer is one of the most frequent cancers worldwide. Recently, it has been shown that the tumor proliferation rate in skin and its dynamics can be changed by an osmotic pressure. However, these findings are rather unstructured. A weak pressure can slow down the tumor growth, while a very high pressure can, on the contrary, lead to accelerated growth and metastases. The magnitude and spatial distribution of osmotic pressures in tumors at present cannot be measured experimentally. Therefore, it is of particular interest to find appropriate models that would simulate the effects of additional osmotic pressures in skin and assess the features of its implementation. In this paper, we suggest an improved model based on the principles of the conventional hydrodynamic model for macrophase separations, which allows one to include not only the properties of healthy and cancer cells but also the microenvironment. We study and analyze the proliferation of cancer cells in 3D models of the epidermal layer of skin under an osmotic pressure. There are two suggested 3D models that are based on the same principles: (1) cellular cubic lattice and (2) cell spheroid. This allows expanding the application of the model depending on a given task. Here, we are focused on the study of melanoma at an early stage when there are not many cancer cells. Additional compressive and expansive pressures are added to the central part of the system. Both systems demonstrate similar results in slowing down the rate of tumor growth with a small pressure.

Cancer Acidity and Hypertonicity Contribute to Dysfunction of Tumor-Associated Dendritic Cells: Potential Impact on Antigen Cross-Presentation Machinery

Macrophages (MΦ) and dendritic cells (DC), major players of the mononuclear phagocyte system (MoPh), are potent antigen presenting cells that steadily sense and respond to signals from the surrounding microenvironment, leading to either immunogenic or tolerogenic outcomes. Next to classical MHC-I/MHC-II antigen-presentation pathways described in the vast majority of cell types, a subset of MoPh (CD8⁺, XCR1⁺, CLEC9A⁺, BDCA3⁺ conventional DCs in human) is endowed with a high competence to cross-present external (engulfed) antigens on MHC-I molecules to CD8⁺ T-cells. This exceptional DC function is thought to be a crucial crossroad in cytotoxic antitumor immunity and has been extensively studied in the past decades. Biophysical and biochemical fingerprints of tumor micromilieus show significant spatiotemporal differences in comparison to non-neoplastic tissue. In tumors, low pH (mainly due to extracellular lactate accumulation via the Warburg effect and via glutaminolysis) and high oncotic and osmotic pressure (resulting from tumor debris, increased extracellular matrix components but in part also triggered by nutritive aspects) are—despite fluctuations and difficulties in measurement—likely the most constant general hallmarks of tumor microenvironment. Here, we focus on the influence of acidic and hypertonic micromilieu on the capacity of DCs to cross-present tumor-specific antigens. We discuss complex and in part controversial scientific data on the interference of these factors with to date reported mechanisms of antigen uptake, processing and cross-presentation, and we highlight their potential role in cancer immune escape and poor clinical response to DC vaccines.

Matrix protease production, epithelial-to-mesenchymal transition marker expression and invasion of glioblastoma cells in response to osmotic or hydrostatic pressure

Both hydrostatic and osmotic pressures are altered in the tumour microenvironment. Glioblastoma (GBM) is a brain tumour with high invasiveness and poor prognosis. We hypothesized that physical and osmotic forces regulate glioblastoma (GBM) invasiveness. The osmotic pressure of GBM cell culture medium was adjusted using sodium chloride or water. Alternatively, cells were subjected to increased hydrostatic force. The proteolytic profile and epithelial–mesenchymal transition (EMT) were investigated using zymography and real-time qPCR. The EMT markers assessed were Snail-1, Snail-2, N-cadherin, Twist and vimentin. Invasion was investigated in vitro using extracellular matrix-coated Transwell inserts. In response to osmotic and mechanical pressure, GBM cell lines U87 and U251 and patient-derived neural oncospheres upregulated the expression of urokinase-type plasminogen activator (uPA) and/or matrix metalloproteinases (MMPs) as well as some of the EMT markers tested. The adherent cell lines invaded more when placed in media of increased osmolality. Therefore, GBM respond to osmotic or mechanical pressure by increasing matrix degrading enzyme production, and adopting a phenotype reminiscent of EMT. Better understanding the molecular and cellular mechanisms by which increased pressure promotes GBM invasiveness may help to develop innovative therapeutic approaches.

How Reciprocal Interactions Between the Tumor Microenvironment and Ion Transport Proteins Drive Cancer Progression

Solid tumors comprise two major components: the cancer cells and the tumor stroma. The stroma is a mixture of cellular and acellular components including fibroblasts, mesenchymal and cancer stem cells, endothelial cells, immune cells, extracellular matrix, and tumor interstitial fluid. The insufficient tumor perfusion and the highly proliferative state and dysregulated metabolism of the cancer cells collectively create a physicochemical microenvironment characterized by altered nutrient concentrations and varying degrees of hypoxia and acidosis. Furthermore, both cancer and stromal cells secrete numerous growth factors, cytokines, and extracellular matrix proteins which further shape the tumor microenvironment (TME), favoring cancer progression.Transport proteins expressed by cancer and stromal cells localize at the interface between the cells and the TME and are in a reciprocal relationship with it, as both sensors and modulators of TME properties. It has been amply demonstrated how acid-base and nutrient transporters of cancer cells enable their growth, presumably by contributing both to the extracellular acidosis and the exchange of metabolic substrates and waste products between cells and TME. However, the TME also impacts other transport proteins important for cancer progression, such as multidrug resistance proteins. In this review, we summarize current knowledge of the cellular and acellular components of solid tumors and their interrelationship with key ion transport proteins. We focus in particular on acid-base transport proteins with known or proposed roles in cancer development, and we discuss their relevance for novel therapeutic strategies.

Magnetic nanocarriers: Evolution of spinel ferrites for medical applications

A valuable site-directed application in the field of nanomedicine is targeted drug delivery using magnetic metal oxide nanoparticles by applying an external magnetic field at the target tissue. The magnetic property of these structures allows controlling the orientation and location of particles by changing the direction of the applied external magnetic field. Pharmaceutical design and research in the field of nanotechnology offer novel solutions for diagnosis and therapies. This review summarizes magnetic nanoparticles and magnetic spinel ferrit's properties, remarkable approaches in magnetic liposomes, magnetic polymeric nanoparticles, MRI, hyperthermia and especially magnetic drug delivery systems, which have recently developed in the field of magnetic nanoparticles and their medicinal applications. Here, we discuss spinel ferrite (SF) as magnetic materials that are a significant class of composite metal oxides. They contain ferric ions and have the general structural formula M²⁺Fe₂³⁺O₄ (where M = Co,Ni,Zn,etc.). This structure indicates unique multifunctional properties, such as excellent magnetic characteristics, high specific surface area, surface active sites, high chemical stability, tuneable shape and size, and options for functionalization. The review assesses the current efforts on synthesis, properties and medical application of magnetic spinel ferrites nanoparticles based on cobalt, nickel and zinc. Based on this review, it can be concluded that MNPs and SFNPs have unlimited ability in biomedical applications. However, the practical application of SFNPs on a huge scale still needs to be considered and evaluated.

Towards patient-specific modeling of brain tumor growth and formation of secondary nodes guided by DTI-MRI

Previous studies to simulate brain tumor progression, often investigate either temporal changes in cancer cell density or the overall tissue-level growth of the tumor mass. Here, we developed a computational model to bridge these two approaches. The model incorporates the tumor biomechanical response at the tissue level and accounts for cellular events by modeling cancer cell proliferation, infiltration to surrounding tissues, and invasion to distant locations. Moreover, acquisition of high resolution human data from anatomical magnetic resonance imaging, diffusion tensor imaging and perfusion imaging was employed within the simulations towards a realistic and patient specific model. The model predicted the intratumoral mechanical stresses to range from 20 to 34 kPa, which caused an up to 4.5 mm displacement to the adjacent healthy tissue. Furthermore, the model predicted plausible cancer cell invasion patterns within the brain along the white matter fiber tracts. Finally, by varying the tumor vascular density and its invasive outer ring thickness, our model showed the potential of these parameters for guiding the timing (83–90 days) of cancer cell distant invasion as well as the number (0–2 sites) and location (temportal and/or parietal lobe) of the invasion sites.

Accumulation of mechanical forces in tumors is related to hyaluronan content and tissue stiffness

Hyaluronan is abundant in the extracellular matrix of many desmoplastic tumors and determines in large part the tumor biochemical and mechanical microenvironment. Additionally, it has been identified as one of the major physiological barriers to the effective delivery of drugs to solid tumors and its targeting with the use of pharmaceutical agents has shown to decompress tumor blood vessels, and thus improve tumor perfusion and efficacy of cytotoxic drugs. In this study, we investigated the contribution of hyaluronan to the accumulation of mechanical forces in tumors. Using experimental data from two orthotopic breast tumor models and treating tumors with two clinically approved anti-fibrotic drugs (tranilast and pirfenidone), we found that accumulation of growth-induced, residual forces in tumors are associated with hyaluronan content. Furthermore, mechanical characterization of the tumors revealed a good correlation of the accumulated forces with the elastic modulus of the tissue. Our results provide important insights on the mechano-pathology of solid tumors and can be used for the design of therapeutic strategies that target hyaluronan.

Proteoglycan-targeting applied to hypoxia-activated prodrug therapy in chondrosarcoma: first proof-of-concept

Due to its abundant chondrogenic matrix and hypoxic tissue, chondrosarcoma is chemo- and radio-resistant. Our group has developed a proteoglycan targeting strategy by using a quaternary ammonium (QA) function as a carrier of DNA alkylating agents to chondrosarcoma environment. Here, we assessed the relevance of this strategy applied to hypoxia-activated prodrugs, by conjugating a QA to 2-nitroimidazole phosphoramidate. This derivative, named as 8-QA, was evaluated respectively to its non-QA equivalent and to a QA-conjugated but non-hypoxia activated. Firstly binding to aggrecan was confirmed from dissociation constant determined by Surface Plasmon Resonance. In vitro, in HEMC-SS chondrosarcoma cells cultured in monolayer and in spheroids, 8-QA showed higher cytotoxic activity in hypoxia versus normoxia, and led to a strong accumulation of cells in S phase and apoptosis. In vivo, a HEMC-SS xenograft model was implanted on SCID mice and characterized for hypoxia by photoacoustic imaging as well as proteoglycan content. When HEMC-SS bearing mice were given 8-QA at 47 μmol/kg according to a q4d x 6 schedule, a significant 62.1% inhibition of tumor growth was observed, without associated hematological side effects. Mechanistic studies of treated tumors highlighted decrease in mitotic index associated to increase in both p21 and p53S15 markers. Interestingly, 8-QA treatment induced an increase of DNA damages as measured by γH2AX predominantly found in pimonidazole-positive hypoxic areas. These preclinical results are the first to demonstrate the interest of addressing hypoxia-activated prodrugs selectively to proteoglycan of chondrogenic tumor tissue, as a promising therapeutic strategy.

Experimental measurements and mathematical modeling towards quantification of brain swelling stress

Traumatic brain injury results in brain tissue swelling which can be a life threatening condition due to skull confinement. While previous efforts successfully measured the exhibited volume change in brain tissue swelling, no data exist to provide information about the exhibited stresses. In this study, confined compression mechanical testing was employed to measure swelling stress in murine brain tissue samples by varying the ionic concentration of the bathing solutions. Subsequently, computer simulations of the experimental protocol were employed to confirm a triphasic mathematical model describing the effect and provide insights into the experimental data. We measured the swelling stress to be in the range of 1.2-6.7kPa (9.0-50.2mmHg) depending on the ionic strength of the bathing solution, while a good correspondence was demonstrated among the experimentally measured and simulated responses. Furthermore, the mathematical model featured the osmotic pressure as the primary contributor to the swelling stress, while a parametric analysis showed that the densities of the intracellular fixed charges and of the non-permeable solutes significantly affect the swelling stress.

The Solid Mechanics of Cancer and Strategies for Improved Therapy

Tumor progression and response to treatment is determined in large part by the generation of mechanical stresses that stem from both the solid and the fluid phase of the tumor. Furthermore, elevated solid stress levels can regulate fluid stresses by compressing intratumoral blood and lymphatic vessels. Blood vessel compression reduces tumor perfusion, while compression of lymphatic vessels hinders the ability of the tumor to drain excessive fluid from its interstitial space contributing to the uniform elevation of the interstitial fluid pressure. Hypoperfusion and interstitial hypertension pose major barriers to the systemic administration of chemotherapeutic agents and nanomedicines to tumors, reducing treatment efficacies. Hypoperfusion can also create a hypoxic and acidic tumor microenvironment that promotes tumor progression and metastasis. Hence, alleviation of intratumoral solid stress levels can decompress tumor vessels and restore perfusion and interstitial fluid pressure. In this review, three major types of tissue level solid stresses involved in tumor growth, namely stress exerted externally on the tumor by the host tissue, swelling stress, and residual stress, are discussed separately and details are provided regarding their causes, magnitudes, and remedies. Subsequently, evidence of how stress-alleviating drugs could be used in combination with chemotherapy to improve treatment efficacy is presented, highlighting the potential of stress-alleviation strategies to enhance cancer therapy. Finally, a continuum-level, mathematical framework to incorporate these types of solid stress is outlined.

Hyaluronan-Derived Swelling of Solid Tumors, the Contribution of Collagen and Cancer Cells, and Implications for Cancer Therapy

Despite the important role that mechanical forces play in tumor growth and therapy, the contribution of swelling to tumor mechanopathology remains unexplored. Tumors rich in hyaluronan exhibit a highly negative fixed charge density. Repulsive forces among these negative charges as well as swelling of cancer cells due to regulation of intracellular tonicity can cause tumor swelling and development of stress that might compress blood vessels, compromising tumor perfusion and drug delivery. Here, we designed an experimental strategy, using four orthotopic tumor models, to measure swelling stress and related swelling to extracellular matrix components, hyaluronan and collagen, as well as to tumor perfusion. Subsequently, interventions were performed to measure tumor swelling using matrix-modifying enzymes (hyaluronidase and collagenase) and by repurposing pirfenidone, an approved antifibrotic drug. Finally, in vitro experiments on cancer cell spheroids were performed to identify their contribution to tissue swelling. Swelling stress was measured in the range of 16 to 75 mm Hg, high enough to cause vessel collapse. Interestingly, while depletion of hyaluronan decreased swelling, collagen depletion had the opposite effect, whereas the contribution of cancer cells was negligible. Furthermore, histological analysis revealed the same linear correlation between tumor swelling and the ratio of hyaluronan to collagen content when data from all tumor models were combined. Our data further revealed an inverse relation between tumor perfusion and swelling, suggesting that reduction of swelling decompresses tumor vessels. These results provide guidelines for emerging therapeutic strategies that target the tumor microenvironment to alleviate intratumoral stresses and improve vessel functionality and drug delivery.

Biphasic modeling of brain tumor biomechanics and response to radiation treatment

Biomechanical forces are central in tumor progression and response to treatment. This becomes more important in brain cancers where tumors are surrounded by tissues with different mechanical properties. Existing mathematical models ignore direct mechanical interactions of the tumor with the normal brain. Here, we developed a clinically relevant model, which predicts tumor growth accounting directly for mechanical interactions. A three-dimensional model of the gray and white matter and the cerebrospinal fluid was constructed from magnetic resonance images of a normal brain. Subsequently, a biphasic tissue growth theory for an initial tumor seed was employed, incorporating the effects of radiotherapy. Additionally, three different sets of brain tissue properties taken from the literature were used to investigate their effect on tumor growth. Results show the evolution of solid stress and interstitial fluid pressure within the tumor and the normal brain. Heterogeneous distribution of the solid stress exerted on the tumor resulted in a 35% spatial variation in cancer cell proliferation. Interestingly, the model predicted that distant from the tumor, normal tissues still undergo significant deformations while it was found that intratumoral fluid pressure is elevated. Our predictions relate to clinical symptoms of brain cancers and present useful tools for therapy planning.

Remodeling of extracellular matrix due to solid stress accumulation during tumor growth

Solid stresses emerge as the expanding tumor displaces and deforms the surrounding normal tissue, and also as a result of intratumoral component interplay. Among other things, solid stresses are known to induce extensive extracellular matrix synthesis and reorganization. In this study, we developed a mathematical model of tumor growth that distinguishes the contribution to stress generation by collagenous and non-collagenous tumor structural components, and also investigates collagen fiber remodeling exclusively due to solid stress. To this end, we initially conducted in vivo experiments using an orthotopic mouse model for breast cancer to monitor primary tumor growth and derive the mechanical properties of the tumor. Subsequently, we fitted the mathematical model to experimental data to determine values of the model parameters. According to the model, intratumoral solid stress is compressive, whereas extratumoral stress in the tumor vicinity is compressive in the radial direction and tensile in the periphery. Furthermore, collagen fibers engaged in stress generation only in the peritumoral region, and not in the interior where they were slackened due to the compressive stress state. Peritumoral fibers were driven away from the radial direction, tended to realign tangent to the tumor-host interface, and were also significantly stretched by tensile circumferential stresses. By means of this remodeling, the model predicts that the tumor is enveloped by a progressively thickening capsule of collagen fibers. This prediction is consistent with long-standing observations of tumor encapsulation and histologic sections that we performed, and it further corroborates the expansive growth hypothesis for the capsule formation.

Lymph node biophysical remodeling is associated with melanoma lymphatic drainage

Tissue remodeling is a characteristic of many solid tumor malignancies including melanoma. By virtue of tumor lymphatic transport, remodeling pathways active within the local tumor microenvironment have the potential to be operational within lymph nodes (LNs) draining the tumor interstitium. Here, we show that lymphatic drainage from murine B16 melanomas in syngeneic, immune-competent C57Bl/6 mice is associated with LN enlargement as well as nonuniform increases in bulk tissue elasticity and viscoelasticity, as measured by the response of whole LNs to compression. These remodeling responses, which quickly manifest in tumor-draining lymph nodes (TDLNs) after tumor inoculation and before apparent metastasis, were accompanied by changes in matrix composition, including up to 3-fold increases in the abundance of soluble collagen and hyaluronic acid. Intranodal pressures were also significantly increased in TDLNs (+1 cmH2O) relative to both non-tumor-draining LNs (-1 cmH2O) and LNs from naive animals (-1 to 2 cmH2O). These data suggest that the reorganization of matrix structure, composition, and fluid microenvironment within LNs associated with tumor lymphatic drainage parallels remodeling seen in primary malignancies and has the potential to regulate the adhesion, proliferation, and signaling function of LN-resident cells involved in directing melanoma disease progression.

Stress-mediated progression of solid tumors: effect of mechanical stress on tissue oxygenation, cancer cell proliferation, and drug delivery

Oxygen supply plays a central role in cancer cell proliferation. While vascular density increases at the early stages of carcinogenesis, mechanical solid stresses developed during growth compress tumor blood vessels and, thus, drastically reduce not only the supply of oxygen, but also the delivery of drugs at inner tumor regions. Among other effects, hypoxia and reduced drug delivery compromise the efficacy of radiation and chemo/nanotherapy, respectively. In the present study, we developed a mathematical model of tumor growth to investigate the interconnections among tumor oxygenation that supports cancer cell proliferation, the heterogeneous accumulation of mechanical stresses owing to tumor growth, the non-uniform compression of intratumoral blood vessels due to the mechanical stresses, and the insufficient delivery of oxygen and therapeutic agents because of vessel compression. We found that the high vascular density and increased cancer cell proliferation often observed in the periphery compared to the interior of a tumor can be attributed to heterogeneous solid stress accumulation. Highly vascularized peripheral regions are also associated with greater oxygenation compared with the compressed, less vascularized inner regions. We also modeled the delivery of drugs of two distinct sizes, namely chemotherapy and nanomedicine. Model predictions suggest that drug delivery is affected negatively by vessel compression independently of the size of the therapeutic agent. Finally, we demonstrated the applicability of our model to actual geometries, employing a breast tumor model derived from MR images.