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

Sonopermeation combined with stroma normalization enables complete cure using nano-immunotherapy in murine breast tumors

Nano-immunotherapy shows great promise in improving patient outcomes, as seen in advanced triple-negative breast cancer, but it does not cure the disease, with median survival under two years. Therefore, understanding resistance mechanisms and developing strategies to enhance its effectiveness in breast cancer is crucial. A key resistance mechanism is the pronounced desmoplasia in the tumor microenvironment, which leads to dysfunction of tumor blood vessels and thus, to hypoperfusion, limited drug delivery and hypoxia. Ultrasound sonopermeation and agents that normalize the tumor stroma have been employed separately to restore vascular abnormalities in tumors with some success. Here, we performed in vivo studies in two murine, orthotopic breast tumor models to explore if combination of ultrasound sonopermeation with a stroma normalization drug can synergistically improve tumor perfusion and enhance the efficacy of nano-immunotherapy. We found that the proposed combinatorial treatment can drastically reduce primary tumor growth and in many cases tumors were no longer measurable. Overall survival studies showed that all mice that received the combination treatment survived and rechallenge experiments revealed that the survivors obtained immunological memory. Employing ultrasound elastography and contrast enhanced ultrasound along with proteomics analysis, flow cytometry and immunofluorescene staining, we found the combinatorial treatment reduced tumor stiffness to normal levels, restoring tumor perfusion and oxygenation. Furthermore, it increased infiltration and activity of immune cells and altered the levels of immunosupportive chemokines. Finally, using machine learning analysis, we identified that tumor stiffness, CD8+ T cells and M2-type macrophages were strong predictors of treatment response.

Using mathematical modelling and AI to improve delivery and efficacy of therapies in cancer

Mathematical modelling has proven to be a valuable tool in predicting the delivery and efficacy of molecular, antibody-based, nano and cellular therapy in solid tumours. Mathematical models based on our understanding of the biological processes at subcellular, cellular and tissue level are known as mechanistic models that, in turn, are divided into continuous and discrete models. Continuous models are further divided into lumped parameter models - for describing the temporal distribution of medicine in tumours and normal organs - and distributed parameter models - for studying the spatiotemporal distribution of therapy in tumours. Discrete models capture interactions at the cellular and subcellular levels. Collectively, these models are useful for optimizing the delivery and efficacy of molecular, nanoscale and cellular therapy in tumours by incorporating the biological characteristics of tumours, the physicochemical properties of drugs, the interactions among drugs, cancer cells and various components of the tumour microenvironment, and for enabling patient-specific predictions when combined with medical imaging. Artificial intelligence-based methods, such as machine learning, have ushered in a new era in oncology. These data-driven approaches complement mechanistic models and have immense potential for improving cancer detection, treatment and drug discovery. Here we review these diverse approaches and suggest ways to combine mechanistic and artificial intelligence-based models to further improve patient treatment outcomes.

Design Strategies for Hyaluronic Acid-based Drug Delivery Systems in Cancer Immunotherapy

Despite its robust therapeutic potential, cancer immunotherapy has provided little progress towards improved survival rates for patients bearing immunologically refractory tumors. The implementation of advanced drug delivery systems represents a powerful means of improving cancer immunotherapy by relieving immunosuppression and promoting immune response; however, the overall impact of these systems on immunotherapy currently remains modest. Hyaluronic acid represents a widely used polymer in drug delivery; meanwhile, recent studies linking hyaluronic acid to the immune system make this polymer an attractive component in the design of next-generation cancer immunotherapies. Herein, we review our current understanding of the immunological properties of hyaluronic acid and discuss them in the context of bioactive functions and immune-related interactions with receptors, immune, and cancer cells. We analyze the potential of hyaluronic acid as a component in advanced drug delivery systems, highlighting strategies for the design of more effective vaccines and cancer chemo-immunotherapies. Finally, we discuss critical considerations to facilitate design and clinical translation to overcome existing challenges and maximize therapeutic potential.

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.

Combined use of super-resolution ultrasound imaging and shear-wave elastography for differential diagnosis of breast masses

Objectives

Shear-wave elastography (SWE) provides valuable stiffness within breast masses, making it a useful supplement to conventional ultrasound imaging. Super-resolution ultrasound (SRUS) imaging enhances microvascular visualization, aiding in the differential diagnosis of breast masses. Current clinical ultrasound diagnosis of breast cancer primarily relies on gray-scale ultrasound. The combined diagnostic potential of tissue stiffness and microvascular characteristics, two critical tumor biomarkers, remains insufficiently explored. This study aims to evaluate the correlation between the elastic modulus, assessed using SWE, and microvascular characteristics captured through SRUS, in order to evaluate the effectiveness of combining these techniques in distinguishing between benign and malignant breast masses.

Materials and methods

In this single-center prospective study, 97 patients underwent SWE to obtain parameters including maximum elasticity (Emax), minimum elasticity (Emin), mean elasticity (Emean), standard deviation of elasticity (Esd), and elasticity ratio. SRUS was used to calculate the microvascular flow rate and microvessel density (MVD) within the breast masses. Spearman correlation analysis was used to explore correlations between Emax and MVD. Receiver operating characteristic curves and nomogram were employed to assess the diagnostic efficacy of combining SRUS with SWE, using pathological results as the gold standard.

Results

Emax, Emean, Esd, and MVD were significantly higher in malignant breast masses compared to benign ones (p < 0.001), while Emin was significantly lower in malignant masses (p < 0.05). In Spearman correlation analysis, Emax was significantly positively correlated with MVD (p < 0.01). The area under the curve for SRUS combined with SWE (0.924) was significantly higher than that for SWE (0.883) or SRUS (0.830) alone (p < 0.001), thus indicating improved diagnostic accuracy. The decision curve analysis of the nomogram indicated that SWE combined with SRUS model had a higher net benefit in predicting breast cancer.

Conclusions

The MVD of the breast mass shows a significant positive correlation with Emax. By integrating SRUS with SWE, this study proposes a novel diagnostic approach designed to improve specificity and accuracy in breast cancer detection, surpassing the limitations of current ultrasound-based methods. This approach shows promise for early breast cancer detection, with the potential to reduce the need for unnecessary biopsies and improve patient outcomes.

Hybrid model of tumor growth, angiogenesis and immune response yields strategies to improve antiangiogenic therapy

Solid tumors harbor a complex and dynamic microenvironment that hinders the delivery and efficacy of therapeutic interventions. In this study, we developed and utilized a hybrid, discrete-continuous mathematical model to explore the interplay between solid tumor growth, immune response, tumor-induced angiogenesis, and antiangiogenic drugs. By integrating published data with anti-angiogenic drugs, we elucidate three primary mechanisms by which anti-angiogenesis influences tumor progression and treatment outcomes: reduction in tumor growth rate by mitigating and temporally delaying angiogenesis, normalization of blood vessel structure and function, and improving immune cell extravasation and activation. Our results indicate a significant increase in functional blood vessels and perfusion following anti-angiogenic treatment, which in turn improves the intratumoral distribution of immune cells. The normalization window, or optimal time frame for anti-angiogenic drug administration, and the dose of the drug arise naturally in the model and are highlighted as crucial factors in maximizing treatment benefits. Prolonged anti-angiogenic treatment triggers cancer cell migration into healthy tissue and induces immunosuppression due to hypoxia, potentially leading to negative effects because these cancer cells will rapidly proliferate upon treatment termination. In conclusion, the positive contribution of anti-angiogenic treatment must balance the possible negative effects by choosing a proper treatment protocol as well as combining it with proper anti-cancer treatment. Our findings provide valuable insights and a framework for the design of protocols with anti-angiogenic treatment, targeted immunotherapy, and non-targeted anti-cancer therapies.

Mechanical forces inducing oxaliplatin resistance in pancreatic cancer can be targeted by autophagy inhibition

Pancreatic cancer remains one of the most lethal malignancies, with limited treatment options and poor prognosis. A common characteristic among pancreatic cancer patients is the biomechanically altered tumor microenvironment (TME), which among others is responsible for the elevated mechanical stresses in the tumor interior. Although significant research has elucidated the effect of mechanical stress on cancer cell proliferation and migration, it has not yet been investigated how it could affect cancer cell drug sensitivity. Here, we demonstrated that mechanical stress triggers autophagy activation, correlated with increased resistance to oxaliplatin treatment in pancreatic cancer cells. Our results demonstrate that inhibition of autophagy using hydroxychloroquine (HCQ) enhanced the oxaliplatin-induced apoptotic cell death in pancreatic cancer cells exposed to mechanical stress. The combined treatment of HCQ with losartan, a known modulator of mechanical abnormalities in tumors, synergistically enhanced the therapeutic efficacy of oxaliplatin in murine pancreatic tumor models. Furthermore, our study revealed that the use of HCQ enhanced the efficacy of losartan to alleviate mechanical stress levels and restore blood vessel integrity beyond its role in autophagy modulation. These findings underscore the potential of co-targeting mechanical stresses and autophagy as a promising therapeutic strategy to overcome drug resistance and increase chemotherapy efficacy.

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.

A convolutional attention model for predicting response to chemo-immunotherapy from ultrasound elastography in mouse tumor models

BACKGROUND

In the era of personalized cancer treatment, understanding the intrinsic heterogeneity of tumors is crucial. Despite some patients responding favorably to a particular treatment, others may not benefit, leading to the varied efficacy observed in standard therapies. This study focuses on the prediction of tumor response to chemo-immunotherapy, exploring the potential of tumor mechanics and medical imaging as predictive biomarkers. We have extensively studied "desmoplastic" tumors, characterized by a dense and very stiff stroma, which presents a substantial challenge for treatment. The increased stiffness of such tumors can be restored through pharmacological intervention with mechanotherapeutics.

METHODS

We developed a deep learning methodology based on shear wave elastography (SWE) images, which involved a convolutional neural network (CNN) model enhanced with attention modules. The model was developed and evaluated as a predictive biomarker in the setting of detecting responsive, stable, and non-responsive tumors to chemotherapy, immunotherapy, or the combination, following mechanotherapeutics administration. A dataset of 1365 SWE images was obtained from 630 tumors from our previous experiments and used to train and successfully evaluate our methodology. SWE in combination with deep learning models, has demonstrated promising results in disease diagnosis and tumor classification but their potential for predicting tumor response prior to therapy is not yet fully realized.

RESULTS

We present strong evidence that integrating SWE-derived biomarkers with automatic tumor segmentation algorithms enables accurate tumor detection and prediction of therapeutic outcomes.

CONCLUSIONS

This approach can enhance personalized cancer treatment by providing non-invasive, reliable predictions of therapeutic outcomes.

Extracellular Matrix Components and Mechanosensing Pathways in Health and Disease

Glycosaminoglycans (GAGs) and proteoglycans (PGs) are essential components of the extracellular matrix (ECM) with pivotal roles in cellular mechanosensing pathways. GAGs, such as heparan sulfate (HS) and chondroitin sulfate (CS), interact with various cell surface receptors, including integrins and receptor tyrosine kinases, to modulate cellular responses to mechanical stimuli. PGs, comprising a core protein with covalently attached GAG chains, serve as dynamic regulators of tissue mechanics and cell behavior, thereby playing a crucial role in maintaining tissue homeostasis. Dysregulation of GAG/PG-mediated mechanosensing pathways is implicated in numerous pathological conditions, including cancer and inflammation. Understanding the intricate mechanisms by which GAGs and PGs modulate cellular responses to mechanical forces holds promise for developing novel therapeutic strategies targeting mechanotransduction pathways in disease. This comprehensive overview underscores the importance of GAGs and PGs as key mediators of mechanosensing in maintaining tissue homeostasis and their potential as therapeutic targets for mitigating mechano-driven pathologies, focusing on cancer and inflammation.

Stabilizing Tumor-Resident Mast Cells Restores T-Cell Infiltration and Sensitizes Sarcomas to PD-L1 Inhibition

PURPOSE

To explore the cellular cross-talk of tumor-resident mast cells (MC) in controlling the activity of cancer-associated fibroblasts (CAF) to overcome tumor microenvironment (TME) abnormalities, enhancing the efficacy of immune-checkpoint inhibitors in sarcoma.

EXPERIMENTAL DESIGN

We used a coculture system followed by further validation in mouse models of fibrosarcoma and osteosarcoma with or without administration of the MC stabilizer and antihistamine ketotifen. To evaluate the contribution of ketotifen in sensitizing tumors to therapy, we performed combination studies with doxorubicin chemotherapy and anti-PD-L1 (B7-H1, clone 10F.9G2) treatment. We investigated the ability of ketotifen to modulate the TME in human sarcomas in the context of a repurposed phase II clinical trial.

RESULTS

Inhibition of MC activation with ketotifen successfully suppressed CAF proliferation and stiffness of the extracellular matrix accompanied by an increase in vessel perfusion in fibrosarcoma and osteosarcoma as indicated by ultrasound shear wave elastography imaging. The improved tissue oxygenation increased the efficacy of chemoimmunotherapy, supported by enhanced T-cell infiltration and acquisition of tumor antigen-specific memory. Importantly, the effect of ketotifen in reducing tumor stiffness was further validated in sarcoma patients, highlighting its translational potential.

CONCLUSIONS

Our study suggests the targeting of MCs with clinically administered drugs, such as antihistamines, as a promising approach to overcome resistance to immunotherapy in sarcomas.

The impact of tumor microenvironment: unraveling the role of physical cues in breast cancer progression

Metastasis accounts for the vast majority of breast cancer-related fatalities. Although the contribution of genetic and epigenetic modifications to breast cancer progression has been widely acknowledged, emerging evidence underscores the pivotal role of physical stimuli in driving breast cancer metastasis. In this review, we summarize the changes in the mechanics of the breast cancer microenvironment and describe the various forces that impact migrating and circulating tumor cells throughout the metastatic process. We also discuss the mechanosensing and mechanotransducing molecules responsible for promoting the malignant phenotype in breast cancer cells. Gaining a comprehensive understanding of the mechanobiology of breast cancer carries substantial potential to propel progress in prognosis, diagnosis, and patient treatment.

Machine learning analysis reveals tumor stiffness and hypoperfusion as biomarkers predictive of cancer treatment efficacy

In the pursuit of advancing cancer therapy, this study explores the predictive power of machine learning in analyzing tumor characteristics, specifically focusing on the effects of tumor stiffness and perfusion (i.e., blood flow) on treatment efficacy. Recent advancements in oncology have highlighted the significance of these physiological properties of the tumor microenvironment in determining treatment outcomes. We delve into the relationship between these tumor attributes and the effectiveness of cancer therapies in preclinical tumor models. Utilizing robust statistical methods and machine learning algorithms, our research analyzes data from 1365 cases of various cancer types, assessing how tumor stiffness and perfusion influence the efficacy of treatment protocols. We also investigate the synergistic potential of combining drugs that modulate tumor stiffness and perfusion with standard cytotoxic treatments. By incorporating these predictors into treatment planning, our study aims to enhance the precision of cancer therapy, tailoring treatment to individual tumor profiles. Our findings demonstrate a significant correlation between stiffness/perfusion and treatment efficacy, highlighting a new way for personalized cancer treatment strategies.

Insights into the mechanobiology of cancer metastasis via microfluidic technologies

During cancer metastasis, cancer cells will encounter various microenvironments with diverse physical characteristics. Changes in these physical characteristics such as tension, stiffness, viscosity, compression, and fluid shear can generate biomechanical cues that affect cancer cells, dynamically influencing numerous pathophysiological mechanisms. For example, a dense extracellular matrix drives cancer cells to reorganize their cytoskeleton structures, facilitating confined migration, while this dense and restricted space also acts as a physical barrier that potentially results in nuclear rupture. Identifying these pathophysiological processes and understanding their underlying mechanobiological mechanisms can aid in the development of more effective therapeutics targeted to cancer metastasis. In this review, we outline the advances of engineering microfluidic devices in vitro and their role in replicating tumor microenvironment to mimic in vivo settings. We highlight the potential cellular mechanisms that mediate their ability to adapt to different microenvironments. Meanwhile, we also discuss some important mechanical cues that still remain challenging to replicate in current microfluidic devices in future direction. While much remains to be explored about cancer mechanobiology, we believe the developments of microfluidic devices will reveal how these physical cues impact the behaviors of cancer cells. It will be crucial in the understanding of cancer metastasis, and potentially contributing to better drug development and cancer therapy.

A synergistic approach for modulating the tumor microenvironment to enhance nano-immunotherapy in sarcomas

The lack of properly perfused blood vessels within tumors can significantly hinder the distribution of drugs, leading to reduced treatment effectiveness and having a negative impact on the quality of life of patients with cancer. This problem is particularly pronounced in desmoplastic cancers, where interactions between cancer cells, stromal cells, and the fibrotic matrix lead to tumor stiffness and the compression of most blood vessels within the tumor. To address this issue, two mechanotherapy approaches-mechanotherapeutics and ultrasound sonopermeation-have been employed separately to treat vascular abnormalities in tumors and have reached clinical trials. Here, we performed in vivo studies in sarcomas, to explore the conditions under which these two mechanotherapy strategies could be optimally combined to enhance perfusion and the efficacy of nano-immunotherapy. Our findings demonstrate that combination of the anti-histamine drug ketotifen, as a mechanotherapeutic, and sonopermeation effectively alleviates mechanical forces by decreasing 50 % collagen and hyaluronan levels and thus, reshaping the tumor microenvironment. Furthermore, the combined therapy normalizes the tumor vasculature by increasing two-fold the pericytes coverage. This combination not only improves six times tumor perfusion but also enhances drug delivery. As a result, blood vessel functionality is enhanced, leading to increased infiltration by 40 % of immune cells (CD4+ and CD8+ T-cells) and improving the antitumor efficacy of Doxil nanomedicine and anti-PD-1 immunotherapy. In conclusion, our research underscores the unique and synergistic potential of combining mechanotherapeutics and sonopermeation. Both approaches are undergoing clinical trials to enhance cancer therapy and have the potential to significantly improve nano-immunotherapy in sarcomas.

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.

Tumor proliferation and invasion are intrinsically coupled and unraveled through tunable spheroid and physics-based models

Proliferation and invasion are two key drivers of tumor growth that are traditionally considered independent multicellular processes. However, these processes are intrinsically coupled through a maximum carrying capacity, i.e., the maximum spatial cell concentration supported by the tumor volume, total cell count, nutrient access, and mechanical properties of the tissue stroma. We explored this coupling of proliferation and invasion through in vitro and in silico methods where we modulated the mechanical properties of the tumor and the surrounding extracellular matrix. E-cadherin expression and stromal collagen concentration were manipulated in a tunable breast cancer spheroid to determine the overall impacts of these tumor variables on net tumor proliferation and continuum invasion. We integrated these results into a mixed-constitutive formulation to computationally delineate the influences of cellular and extracellular adhesion, stiffness, and mechanical properties of the extracellular matrix on net proliferation and continuum invasion. This framework integrates biological in vitro data into concise computational models of invasion and proliferation to provide more detailed physical insights into the coupling of these key tumor processes and tumor growth. STATEMENT OF SIGNIFICANCE: Tumor growth involves expansion into the collagen-rich stroma through intrinsic coupling of proliferation and invasion within the tumor continuum. These processes are regulated by a maximum carrying capacity that is determined by the total cell count, tumor volume, nutrient access, and mechanical properties of the surrounding stroma. The influences of biomechanical parameters (i.e., stiffness, cell elongation, net proliferation rate and cell-ECM friction) on tumor proliferation or invasion cannot be unraveled using experimental methods alone. By pairing a tunable spheroid system with computational modeling, we delineated the interdependencies of each system parameter on tumor proliferation and continuum invasion, and established a concise computational framework for studying tumor mechanobiology.

Extracellular matrix biomechanical roles and adaptation in health and disease

Extracellular matrices (ECMs) are dynamic 3D macromolecular networks that exhibit structural characteristics and composition specific to different tissues, serving various biomechanical and regulatory functions. The interactions between ECM macromolecules such as collagen, elastin, glycosaminoglycans (GAGs), proteoglycans (PGs), fibronectin, and laminin, along with matrix effectors and water, contribute to the unique cellular and tissue functional properties during organ development, tissue homoeostasis, remodeling, disease development, and progression. Cells adapt to environmental changes by adjusting the composition and array of ECM components. ECMs, forming the 3D bioscaffolds of our body, provide mechanical support for tissues and organs and respond to the environmental variables influencing growth and final adult body shape in mammals. Different cell types display distinct adaptations to the respective ECM environments. ECMs regulate biological processes by controlling the diffusion of infections and inflammations, sensing and adapting to external stimuli and gravity from the surrounding habitat, and, in the context of cancer, interplaying with and regulating cancer cell invasion and drug resistance. Alterations in the ECM composition in pathological conditions drive adaptive responses of cells and could therefore result in abnormal cell behavior and tissue dysfunction. Understanding the biomechanical functionality, adaptation, and roles of distinct ECMs is essential for research on various pathologies, including cancer progression and multidrug resistance, which is of crucial importance for developing targeted therapies. In this Viewpoint article, we critically present and discuss specific biomechanical functions of ECMs and regulatory adaptation mechanisms in both health and disease, with a particular focus on cancer progression.

Ultrasound Localization Microscopy for Breast Cancer Imaging in Patients: Protocol Optimization and Comparison with Shear Wave Elastography

OBJECTIVE

Ultrasound localization microscopy (ULM) has gained increasing attention in recent years because of its ability to visualize blood vessels at super-resolution. The field of oncology, in particular, could benefit from detailed vascular characterization, for example, for diagnosis and therapy monitoring. This study was aimed at refining ULM for breast cancer patients by optimizing the measurement protocol, identifying translational challenges and combining ULM and shear wave elastography.

METHODS

We computed ULM images of 11 patients with breast cancer by recording contrast-enhanced ultrasound (CEUS) sequences and post-processing them in an offline pipeline. For CEUS, two different doses and injection speeds of SonoVue were applied. The best injection protocol was determined based on quantitative parameters derived from so-called occurrence maps. In addition, a suitable measurement time window was determined, also considering the occurrence of motion. ULM results were compared with shear wave elastography and histological vessel density.

RESULTS

At the higher dose and injection speed, the highest number of microbubbles, number of tracks and vessel coverage were achieved, leading to the most detailed representation of tumor vasculature. Even at the highest concentration, no significant overlay of microbubble signals occurred. Motion significantly reduced the number of usable frames, thus limiting the measurement window to 3.5 min. ULM vessel coverage was comparable to the histological vessel fraction and correlated significantly with mean tumor elasticity.

CONCLUSION

The settings for microbubble injection strongly influence ULM images, thus requiring optimized protocols for different indications. Patient and examiner motion was identified as the main translational challenge for ULM.

Pirfenidone-Loaded Polymeric Micelles as an Effective Mechanotherapeutic to Potentiate Immunotherapy in Mouse Tumor Models

Ongoing research is actively exploring the use of immune checkpoint inhibitors to treat solid tumors by inhibiting the PD-1/PD-L1 axis and reactivating the function of cytotoxic T effector cells. Many types of solid tumors, however, are characterized by a dense and stiff stroma and are difficult to treat. Mechanotherapeutics have formed a recent class of drugs that aim to restore biomechanical abnormalities of the tumor microenvironment, related to increased stiffness and hypo-perfusion. Here, we have developed a polymeric formulation containing pirfenidone, which has been successful in restoring the tumor microenvironment in breast tumors and sarcomas. We found that the micellar formulation can induce similar mechanotherapeutic effects to mouse models of 4T1 and E0771 triple negative breast tumors and MCA205 fibrosarcoma tumors but with a dose 100-fold lower than that of the free pirfenidone. Importantly, a combination of pirfenidone-loaded micelles with immune checkpoint inhibition significantly delayed primary tumor growth, leading to a significant improvement in overall survival and in a complete cure for the E0771 tumor model. Furthermore, the combination treatment increased CD4+ and CD8+ T cell infiltration and suppressed myeloid-derived suppressor cells, creating favorable immunostimulatory conditions, which led to immunological memory. Ultrasound shear wave elastography (SWE) was able to monitor changes in tumor stiffness during treatment, suggesting optimal treatment conditions. Micellar encapsulation is a promising strategy for mechanotherapeutics, and imaging methods, such as SWE, can assist their clinical translation.

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.

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.

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

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

Hyaluronic acid: More than a carrier, having an overpowering extracellular and intracellular impact on cancer

Hyaluronic acid (HA), also named hyaluronan, is an omnipresent component of the tissue microenvironment. It is extensively used to formulate targeted drug delivery systems for cancer. Although HA itself has pivotal influences in various cancers, its calibers are somewhat neglected when using it as delivering platform to treat cancer. In the last decade, multiple studies revealed roles of HA in cancer cell proliferation, invasion, apoptosis, and dormancy through pathways like mitogen-activated protein kinase-extracellular signal-regulated kinase (MAPK/ERK), P³⁸, and nuclear factor kappa-light chain-enhancer of activated B cells (NFκB). A more fascinating fact is that the distinct molecular weight (MW) of HA exerts disparate effects on the same type of cancer. Its overwhelming use in cancer therapy and other therapeutic products make collective research on the sundry impact of it on various types of cancer, an essential aspect to be considered in all of these domains. Even the development of new therapies against cancer needed meticulous studies on HA because of its divergence of activity based on MW. This review will provide painstaking insight into the extracellular and intracellular bioactivity of HA, its modified forms, and its MW in cancers, which may improve the management of cancer.

Evaluation of growth-induced, mechanical stress in solid tumors and spatial association with extracellular matrix content

Mechanical stresses in solid tumors play an important role in tumor progression and treatment efficacy but their quantification is under-investigated. Here, we developed an experimental and computational approach to calculate growth-induced, residual stresses and applied it to the breast (4T1), pancreatic (PAN02), and fibrosarcoma (MCA205) tumor models. Following resection, tumors are embedded in agarose gels and cuts are made in two perpendicular directions to release residual stress. With the use of image processing, the detailed bulging displacement profile is measured and finite elements models of the bulging geometry are developed for the quantification of the stress levels. The mechanical properties of the tumors are measured in vivo prior to resection with shear wave elastography. We find that the average magnitude of residual stresses ranges from 3.31 to 10.88 kPa, and they are non-uniformly distributed within the tissue due to the heterogeneity of the tumor microenvironment. Interestingly, we demonstrate that a second cut can still release a significant amount of stresses. We further find a strong association of spatial hyaluronan and collagen content with the spatial profile of stress for the MCA205 and PAN02 tumors and a partial association for the 4T1. Interestingly the colocalization of hyaluronan and collagen content had a stronger association with the spatial profile of stress for MCA205, PAN02, and 4T1. Finally, measurements of the elastic modulus with shear wave elastography show a nonlinear correlation with tumor volume for the more fibrotic MCA205 and 4T1 tumors. Overall, our results provide insights for a better understanding of the mechanical behavior of tumors.

Exploring the role of intratendinous pressure in the pathogenesis of tendon pathology: a narrative review and conceptual framework

Despite the high prevalence of tendon pathology in athletes, the underlying pathogenesis is still poorly understood. Various aetiological theories have been presented and rejected in the past, but the tendon cell response model still holds true. This model describes how the tendon cell is the key regulator of the extracellular matrix and how pathology is induced by a failed adaptation to a disturbance of tissue homeostasis. Such failure has been attributed to various kinds of stressors (eg, mechanical, thermal and ischaemic), but crucial elements seem to be missing to fully understand the pathogenesis. Importantly, a disturbance of tissue pressure homeostasis has not yet been considered a possible factor, despite it being associated with numerous pathologies. Therefore, we conducted an extensive narrative literature review on the possible role of intratendinous pressure in the pathogenesis of tendon pathology. This review explores the current understanding of pressure dynamics and the role of tissue pressure in the pathogenesis of other disorders with structural similarities to tendons. By bridging these insights with known structural changes that occur in tendon pathology, a conceptual model was constituted. This model provides an overview of the possible mechanism of how an increase in intratendinous pressure might be involved in the development and progression of tendon pathology and contribute to tendon pain. In addition, some therapies that could reduce intratendinous pressure and accelerate tendon healing are proposed. Further experimental research is encouraged to investigate our hypotheses and to initiate debate on the relevance of intratendinous pressure in tendon pathology.

Modulating tumor mechanics with nanomedicine for cancer therapy

Over the past several decades, the importance of the tumor mechanical microenvironment (TMME) in cancer progression or cancer therapy has been recognized by researchers worldwide. The abnormal mechanical properties of tumor tissues include high mechanical stiffness, high solid stress, and high interstitial fluid pressure (IFP), which form physical barriers resulting in suboptimal treatment efficacy and resistance to different types of therapy by preventing drugs infiltrating the tumor parenchyma. Therefore, preventing or reversing the establishment of the abnormal TMME is critical for cancer therapy. Nanomedicines can enhance drug delivery by exploiting the enhanced permeability and retention (EPR) effect, so nanomedicines that target and modulate the TMME can further boost antitumor efficacy. Herein, we mainly discuss the nanomedicines that can regulate mechanical stiffness, solid stress, and IFP, with a focus on how nanomedicines change abnormal mechanical properties and facilitate drug delivery. We first introduce the formation, characterizing methods and biological effects of tumor mechanical properties. Conventional TMME modulation strategies will be briefly summarized. Then, we highlight representative nanomedicines capable of modulating the TMME for augmented cancer therapy. Finally, current challenges and future opportunities for regulating the TMME with nanomedicines will be provided.

Ultrasound stiffness and perfusion markers correlate with tumor volume responses to immunotherapy

Immunotherapy has revolutionized the treatment of dozens of cancers and became a standard of care for some tumor types. However, the majority of patients do not benefit from current immunotherapeutics and many develop severe toxicities. Therefore, the identification of biomarkers to classify patients as likely responders or non-responders to immunotherapy is a timely task. Here, we test ultrasound imaging markers of tumor stiffness and perfusion. Ultrasound imaging is non-invasive and clinically available and can be used both for stiffness and perfusion evaluation. In this study, we employed syngeneic orthotopic models of two breast cancers, a fibrosarcoma and melanoma, to demonstrate that ultrasound-derived measures of tumor stiffness and perfusion (i.e., blood volume) correlate with the efficacy of immune checkpoint inhibition (ICI) in terms of changes in primary tumor volume. To modulate tumor stiffness and perfusion and thus, get a range of therapeutic outcomes, we employed the mechanotherapeutic tranilast. Mechanotherapeutics combined with ICI are advancing through clinical trials, but biomarkers of response have not been tested until now. We found the existence of linear correlations between tumor stiffness and perfusion imaging biomarkers as well as strong linear correlations between the stiffness and perfusion markers with ICI efficacy on primary tumor growth rates. Our findings set the basis for ultrasound imaging biomarkers predictive of ICI therapy in combination with mechanotherapeutics. STATEMENT OF SIGNIFICANCE: Hypothesis: Monitoring Tumor Microenvironment (TME) mechanical abnormalities can predict the efficacy of immune checkpoint inhibition (ICI) and provide biomarkers predictive of response. Tumor stiffening and solid stress elevation are hallmarks of tumor patho-physiology in desmoplastic tumors. They induce hypo-perfusion and hypoxia by compressing tumor vessels, posing major barriers to immunotherapy. Mechanotherapeutics is a new class of drugs that target the TME to reduce stiffness and improve perfusion and oxygenation. In this study, we show that measures of stiffness and perfusion derived from ultrasound shear wave elastography and contrast enhanced ultrasound can provide biomarkers of tumor response.

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.

The role of glycans in the mechanobiology of cancer

Although cancer is a genetic disease, physical changes such as stiffening of the extracellular matrix also commonly occur in cancer. Cancer cells sense and respond to extracellular matrix stiffening through the process of mechanotransduction. Cancer cell mechanotransduction can enhance cancer-promoting cell behaviors such as survival signaling, proliferation, and migration. Glycans, carbohydrate-based polymers, have recently emerged as important mediators and/or modulators of cancer cell mechanotransduction. Stiffer tumors are characterized by increased glycan content on cancer cells and their associated extracellular matrix. Here we review the role of cancer-associated glycans in coupled mechanical and biochemical alterations during cancer progression. We discuss the recent evidence on how increased expression of different glycans, in the form of glycoproteins and proteoglycans, contributes to both mechanical changes in tumors and corresponding cancer cell responses. We conclude with a summary of emerging tools that can be used to modify glycans for future studies in cancer mechanobiology.

Pancreatic Cancer Presents Distinct Nanomechanical Properties During Progression

Cancer progression is closely related to changes in the structure and mechanical properties of the tumor microenvironment (TME). In many solid tumors, including pancreatic cancer, the interplay among the different components of the TME leads to a desmoplastic reaction mainly due to collagen overproduction. Desmoplasia is responsible for the stiffening of the tumor, poses a major barrier to effective drug delivery and has been associated with poor prognosis. The understanding of the involved mechanisms in desmoplasia and the identification of nanomechanical and collagen-based properties that characterize the state of a particular tumor can lead to the development of novel diagnostic and prognostic biomarkers. In this study, in vitro experiments were conducted using two human pancreatic cell lines. Morphological and cytoskeleton characteristics, cells' stiffness and invasive properties were assessed using optical and atomic force microscopy techniques and cell spheroid invasion assay. Subsequently, the two cell lines were used to develop orthotopic pancreatic tumor models. Tissue biopsies were collected at different times of tumor growth for the study of the nanomechanical and collagen-based optical properties of the tissue using Atomic Force Microscopy (AFM) and picrosirius red polarization microscopy, respectively. The results from the in vitro experiments demonstrated that the more invasive cells are softer and present a more elongated shape with more oriented F-actin stress fibers. Furthermore, ex vivo studies of orthotopic tumor biopsies on MIAPaCa-2 and BxPC-3 murine tumor models highlighted that pancreatic cancer presents distinct nanomechanical and collagen-based optical properties relevant to cancer progression. The stiffness spectrums (in terms of Young's modulus values) showed that the higher elasticity distributions were increasing during cancer progression mainly due desmoplasia (collagen overproduction), while a lower elasticity peak was evident - due to cancer cells softening - on both tumor models. Optical microscopy studies highlighted that collagen content increases while collagen fibers tend to form align patterns. Consequently, during cancer progression nanomechanical and collagen-based optical properties alter in relation to changes in collagen content. Therefore, they have the potential to be used as novel biomarkers for assessing and monitoring tumor progression and treatment outcomes.

The interface stiffness and topographic feature dictate interfacial invasiveness of cancer spheroids

During cancer metastasis, tumor cells likely navigate, in a collective manner, discrete tissue spaces comprising inherently heterogeneous extracellular matrix microstructures where interfaces may be frequently encountered. Studies have shown that cell migration modes can be determined by adaptation to mechanical/topographic cues from interfacial microenvironments. However, less attention has been paid to exploring the impact of interfacial mechnochemical attributes on invasive and metastatic behaviors of tumor aggregates. Here, we excogitated a collagen matrix-solid substrate interface platform to investigate the afore-stated interesting issue. Our data revealed that stiffer interfaces stimulated spheroid outgrowth by motivating detachment of single cells and boosting their motility and velocity. However, stronger interfacial adhesive strength between matrix and substrate led to the opposite outcomes. Besides, this interfacial parameter also affected the morphological switch between migration modes of the detached cells and their directionality. Mechanistically, myosin II-mediated cell contraction, compared to matrix metalloproteinases-driven collagen degradation, was shown to play a more crucial role in the invasive outgrowth of tumor spheroids in interfacial microenvironments. Thus, our findings highlight the importance of heterogeneous interfaces in addressing and combating cancer metastasis.

The versatile roles of ADAM8 in cancer cell migration, mechanics, and extracellular matrix remodeling

The posttranslational proteolytic cleavage is a unique and irreversible process that governs the function and half-life of numerous proteins. Thereby the role of the family of A disintegrin and metalloproteases (ADAMs) plays a leading part. A member of this family, ADAM8, has gained attention in regulating disorders, such as neurogenerative diseases, immune function and cancer, by attenuating the function of proteins nearby the extracellular membrane leaflet. This process of "ectodomain shedding" can alter the turnover rate of a number of transmembrane proteins that function in cell adhesion and receptor signal transduction. In the past, the major focus of research about ADAMs have been on neurogenerative diseases, such as Alzheimer, however, there seems to be evidence for a connection between ADAM8 and cancer. The role of ADAMs in the field of cancer research has gained recent attention, but it has been not yet been extensively addressed. Thus, this review article highlights the various roles of ADAM8 with particular emphasis on pathological conditions, such as cancer and malignant cancer progression. Here, the shedding function, direct and indirect matrix degradation, effects on cancer cell mobility and transmigration, and the interplay of ADAM8 with matrix-embedded neighboring cells are presented and discussed. Moreover, the most probable mechanical impact of ADAM8 on cancer cells and their matrix environment is addressed and debated. In summary, this review presents recent advances in substrates/ligands and functions of ADAM8 in its new role in cancer and its potential link to cell mechanical properties and discusses matrix mechanics modifying properties. A deeper comprehension of the regulatory mechanisms governing the expression, subcellular localization, and activity of ADAM8 is expected to reveal appropriate drug targets that will permit a more tailored and fine-tuned modification of its proteolytic activity in cancer development and metastasis.

Squeezing the eggs to grow: The mechanobiology of mammalian folliculogenesis

The formation of functional eggs (oocyte) in ovarian follicles is arguably one of the most important events in early mammalian development since the oocytes provide the bulk genetic and cytoplasmic materials for successful reproduction. While past studies have identified many genes that are critical to normal ovarian development and function, recent studies have highlighted the role of mechanical force in shaping folliculogenesis. In this review, we discuss the underlying mechanobiological principles and the force-generating cellular structures and extracellular matrix that control the various stages of follicle development. We also highlight emerging techniques that allow for the quantification of mechanical interactions and follicular dynamics during development, and propose new directions for future studies in the field. We hope this review will provide a timely and useful framework for future understanding of mechano-signalling pathways in reproductive biology and diseases.

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.

Targeting the tumor biophysical microenvironment to reduce resistance to immunotherapy

Immunotherapy based on immune checkpoint inhibitors has evolved into a new pillar of cancer treatment in clinics, but dealing with treatment resistance (either primary or acquired) is a major challenge. The tumor microenvironment (TME) has a substantial impact on the pathological behaviors and treatment response of many cancers. The biophysical clues in TME have recently been considered as important characteristics of cancer. Furthermore, there is mounting evidence that biophysical cues in TME play important roles in each step of the cascade of cancer immunotherapy that synergistically contribute to immunotherapy resistance. In this review, we summarize five main biophysical cues in TME that affect resistance to immunotherapy: extracellular matrix (ECM) structure, ECM stiffness, tumor interstitial fluid pressure (IFP), solid stress, and vascular shear stress. First, the biophysical factors involved in anti-tumor immunity and therapeutic antibody delivery processes are reviewed. Then, the causes of these five biophysical cues and how they contribute to immunotherapy resistance are discussed. Finally, the latest treatment strategies that aim to improve immunotherapy efficacy by targeting these biophysical cues are shared. This review highlights the biophysical cues that lead to immunotherapy resistance, also supplements their importance in related technologies for studying TME biophysical cues in vitro and therapeutic strategies targeting biophysical cues to improve the effects of immunotherapy.

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.

Fracture Risk Evaluation of Bone Metastases: A Burning Issue

Major progress has been achieved to treat cancer patients and survival has improved considerably, even for stage-IV bone metastatic patients. Locomotive health has become a crucial issue for patient autonomy and quality of life. The centerpiece of the reflection lies in the fracture risk evaluation of bone metastasis to guide physician decision regarding physical activity, antiresorptive agent prescription, and local intervention by radiotherapy, surgery, and interventional radiology. A key mandatory step, since bone metastases may be asymptomatic and disseminated throughout the skeleton, is to identify the bone metastasis location by cartography, especially within weight-bearing bones. For every location, the fracture risk evaluation relies on qualitative approaches using imagery and scores such as Mirels and spinal instability neoplastic score (SINS). This approach, however, has important limitations and there is a need to develop new tools for bone metastatic and myeloma fracture risk evaluation. Personalized numerical simulation qCT-based imaging constitutes one of these emerging tools to assess bone tumoral strength and estimate the femoral and vertebral fracture risk. The next generation of numerical simulation and artificial intelligence will take into account multiple loadings to integrate movement and obtain conditions even closer to real-life, in order to guide patient rehabilitation and activity within a personalized-medicine approach.

Ultrasound and microbubbles to beat barriers in tumors: Improving delivery of nanomedicine

Successful delivery of drugs and nanomedicine to tumors requires a functional vascular network, extravasation across the capillary wall, penetration through the extracellular matrix, and cellular uptake. Nanomedicine has many merits, but penetration deep into the tumor interstitium remains a challenge. Failure of cancer treatment can be caused by insufficient delivery of the therapeutic agents. After intravenous administration, nanomedicines are often found in off-target organs and the tumor extracellular matrix close to the capillary wall. With circulating microbubbles, ultrasound exposure focused toward the tumor shows great promise in improving the delivery of therapeutic agents. In this review, we address the impact of focused ultrasound and microbubbles to overcome barriers for drug delivery such as perfusion, extravasation, and transport through the extracellular matrix. Furthermore, we discuss the induction of an immune response with ultrasound and delivery of immunotherapeutics. The review discusses mainly preclinical results and ends with a summary of ongoing clinical trials.

Collagenase-Expressing Salmonella Targets Major Collagens in Pancreatic Cancer Leading to Reductions in Immunosuppressive Subsets and Tumor Growth

Therapeutic resistance in pancreatic ductal adenocarcinoma (PDAC) can be attributed, in part, to a dense extracellular matrix containing excessive collagen deposition. Here, we describe a novel Salmonella typhimurium (ST) vector expressing the bacterial collagenase Streptomyces omiyaensis trypsin (SOT), a serine protease known to hydrolyze collagens I and IV, which are predominantly found in PDAC. Utilizing aggressive models of PDAC, we show that ST-SOT selectively degrades intratumoral collagen leading to decreases in immunosuppressive subsets, tumor proliferation and viability. Ultimately, we found that ST-SOT treatment significantly modifies the intratumoral immune landscape to generate a microenvironment that may be more conducive to immunotherapy.

Hyaluronan and the Fascial Frontier

The buzz about hyaluronan (HA) is real. Whether found in face cream to increase water volume loss and viscoelasticity or injected into the knee to restore the properties of synovial fluid, the impact of HA can be recognized in many disciplines from dermatology to orthopedics. HA is the most abundant polysaccharide of the extracellular matrix of connective tissues. HA can impact cell behavior in specific ways by binding cellular HA receptors, which can influence signals that facilitate cell survival, proliferation, adhesion, as well as migration. Characteristics of HA, such as its abundance in a variety of tissues and its responsiveness to chemical, mechanical and hormonal modifications, has made HA an attractive molecule for a wide range of applications. Despite being discovered over 80 years ago, its properties within the world of fascia have only recently received attention. Our fascial system penetrates and envelopes all organs, muscles, bones and nerve fibers, providing the body with a functional structure and an environment that enables all bodily systems to operate in an integrated manner. Recognized interactions between cells and their HA-rich extracellular microenvironment support the importance of studying the relationship between HA and the body’s fascial system. From fasciacytes to chronic pain, this review aims to highlight the connections between HA and fascial health.

Transforming growth factor-β blockade modulates tumor mechanical microenvironments for enhanced antitumor efficacy of photodynamic therapy

Photodynamic therapy (PDT) is frequently used in cancer treatment in clinical settings. However, its applications in stroma-rich solid tumors, e.g., triple negative breast cancer, are limited by abnormal mechanical microenvironments. Solid stress accumulated in stroma-rich solid tumors compresses tumor blood vessels, hampers the delivery of photosensitizers (PSs) in tumor tissues, and poses a major challenge for potent PDT. Here, we report a novel combination strategy to augment PDT based cancer therapy by combining hydroxyethyl starch-chlorin e6 conjugate self-assembled nanoparticles (HES-Ce6 NPs) with the transforming growth factor-β (TGFβ) inhibitor LY2157299 (LY). HES-Ce6 conjugates, as synthesized by one step esterification reaction, could self-assemble into uniform HES-Ce6 NPs, which exhibited enhanced photostability and generated more reactive oxygen species (ROS) under 660 nm laser irradiation than free Ce6. Prior to PDT, intragastric administration of LY decreased collagen deposition, alleviated solid stress, and decompressed tumor blood vessels. As a result, the reconstructed tumor mechanical microenvironment promoted accumulation and penetration of HES-Ce6 NPs into tumor tissues, contributing to augmented antitumor efficacy of HES-Ce6 NP mediated PDT. Modulating tumor mechanical microenvironments using TGFβ blockade to enhance the delivery of PSs in tumors with excessive extracellular matrix represents an efficient strategy for treating stroma-rich solid tumors.

The cell surface hyaluronidase TMEM2 regulates cell adhesion and migration via degradation of hyaluronan at focal adhesion sites

The extracellular matrix (ECM) plays an important role in maintaining tissue homeostasis and poses a significant physical barrier to in vivo cell migration. Accordingly, as a means of enhancing tissue invasion, tumor cells use matrix metalloproteinases to degrade ECM proteins. However, the in vivo ECM is comprised not only of proteins but also of a variety of nonprotein components. Hyaluronan (HA), one of the most abundant nonprotein components of the interstitial ECM, forms a gel-like antiadhesive barrier that is impenetrable to particulate matter and cells. Mechanisms by which tumor cells penetrate the HA barrier have not been addressed. Here, we demonstrate that transmembrane protein 2 (TMEM2), the only known transmembrane hyaluronidase, is the predominant mediator of contact-dependent HA degradation and subsequent integrin-mediated cell–substrate adhesion. We show that a variety of tumor cells are able to eliminate substrate-bound HA in a tightly localized pattern corresponding to the distribution of focal adhesions (FAs) and stress fibers. This FA-targeted HA degradation is mediated by TMEM2, which itself is localized at site of FAs. TMEM2 depletion inhibits the ability of tumor cells to attach and migrate in an HA-rich environment. Importantly, TMEM2 directly binds at least two integrins via interaction between extracellular domains. Our findings demonstrate a critical role for TMEM2-mediated HA degradation in the adhesion and migration of cells on HA-rich ECM substrates and provide novel insight into the early phase of FA formation.

Normalizing the Microenvironment Overcomes Vessel Compression and Resistance to Nano-immunotherapy in Breast Cancer Lung Metastasis

Nano-immunotherapy regimens have high potential to improve patient outcomes, as already demonstrated in advanced triple negative breast cancer with nanoparticle albumin-bound paclitaxel and the immune checkpoint blocker (ICB) atezolizumab. This regimen, however, does not lead to cures with median survival lasting less than two years. Thus, understanding the mechanisms of resistance to and development of strategies to enhance nano-immunotherapy in breast cancer are urgently needed. Here, in human tissue it is shown that blood vessels in breast cancer lung metastases are compressed leading to hypoxia. This pathophysiology exists in murine spontaneous models of triple negative breast cancer lung metastases, along with low levels of perfusion. Because this pathophysiology is consistent with elevated levels of solid stress, the mechanotherapeutic tranilast, which decompressed lung metastasis vessels, is administered to mice bearing metastases, thereby restoring perfusion and alleviating hypoxia. As a result, the nanomedicine Doxil causes cytotoxic effects into metastases more efficiently, stimulating anti-tumor immunity. Indeed, when combining tranilast with Doxil and ICBs, synergistic effects on efficacy, with all mice cured in one of the two ICB-insensitive tumor models investigated is resulted. These results suggest that strategies to treat breast cancer with nano-immunotherapy should also include a mechanotherapeutic to decompress vessels.

Recapitulating pancreatic tumor microenvironment through synergistic use of patient organoids and organ-on-a-chip vasculature

Tumor progression relies heavily on the interaction between the neoplastic epithelial cells and their surrounding stromal partners. This cell cross-talk affects stromal development, and ultimately the heterogeneity impacts drug efflux and efficacy. To mimic this evolving paradigm, we have micro-engineered a three-dimensional (3D) vascularized pancreatic adenocarcinoma tissue in a tri-culture system composed of patient derived pancreatic organoids, primary human fibroblasts and endothelial cells on a perfusable InVADE platform situated in a 96-well plate. Uniquely, through synergistic engineering we combined the benefits of cellular fidelity of patient tumor derived organoids with the addressability of a plastic organ-on-a-chip platform. Validation of this platform included demonstrating the growth of pancreatic tumor organoids by monitoring the change in metabolic activity of the tissue. Investigation of tumor microenvironmental behavior highlighted the role of fibroblasts in symbiosis with patient organoid cells, resulting in a six-fold increase of collagen deposition and a corresponding increase in tissue stiffness in comparison to fibroblast free controls. The value of a perfusable vascular network was evident in drug screening, as perfusion of gemcitabine into a stiffened matrix did not show the dose-dependent effects on tumor viability as those under static conditions. These findings demonstrate the importance of studying the dynamic synergistic relationship between patient cells with stromal fibroblasts, in a 3D perfused vascular network, to accurately understand and recapitulate the tumor microenvironment.

Mapping cellular-scale internal mechanics in 3D tissues with thermally responsive hydrogel probes

Local tissue mechanics play a critical role in cell function, but measuring these properties at cellular length scales in living 3D tissues can present considerable challenges. Here we present thermoresponsive, smart material microgels that can be dispersed or injected into tissues and optically assayed to measure residual tissue elasticity after creep over several weeks. We first develop and characterize the sensors, and demonstrate that internal mechanical profiles of live multicellular spheroids can be mapped at high resolutions to reveal broad ranges of rigidity within the tissues, which vary with subtle differences in spheroid aggregation method. We then show that small sites of unexpectedly high rigidity develop in invasive breast cancer spheroids, and in an in vivo mouse model of breast cancer progression. These focal sites of increased intratumoral rigidity suggest new possibilities for how early mechanical cues that drive cancer cells towards invasion might arise within the evolving tumor microenvironment.

Biomechanical modelling of spinal tumour anisotropic growth

Biomechanical abnormalities of solid tumours involve stiffening of the tissue and accumulation of mechanical stresses. Both abnormalities affect cancer cell proliferation and invasiveness and thus, play a crucial role in tumour morphology and metastasis. Even though, it has been known for more than two decades that high mechanical stresses reduce cancer cell proliferation rates driving growth towards low-stress regions, most biomechanical models of tumour growth account for isotropic growth. This cannot be valid, however, in tumours that grow within multiple host tissues of different mechanical properties, such as the spine. In these cases, structural heterogeneity would result in anisotropic growth of tumours. To this end, we present a biomechanical, biphasic model for anisotropic growth of spinal tumours. The model that accounts for both the fluid and the solid phase of the tumour was used to predict the evolution of solid stress and interstitial fluid pressure in intramedullary spinal tumours and highlight the differences between isotropic and anisotropic growth. Varying the degree of anisotropy, we found considerable differences in the shape of the tumours, leading to tumours of more realistic ellipsoidal shapes.

Distinguishing Specific CXCL12 Isoforms on Their Angiogenesis and Vascular Permeability Promoting Properties

Angiogenesis is associated with increased vessel sprouting and permeability. Important mediators of these angiogenic responses include local environment of signaling molecules and supporting extracellular matrix (ECM). However, dissecting the interplay of these instructive signals in vivo with multiple cells and extracellular molecules remains a central challenge. Here, microfluidic biomimicry is integrated with 3D ECM hydrogels that are well-characterized for molecular-binding and mechanical properties to reconstitute vessel-like analogues in vitro. This study focuses on three distinct isoforms of the pro-metastatic chemokine CXCL12. In collagen-only hydrogel, CXCL12-α is the most potent isoform in promoting sprouting and permeability, followed by CXCL12-β and CXCL12-γ. Strikingly, addition of hyaluronan (HA), a large and negatively charged glycosaminoglycan, with collagen matrices selectively increases vessel sprouting and permeability conferred by CXCL12-γ. This outcome is supported by the measured binding affinities to collagen/HA ECM, suggesting that negatively charged HA increases the binding of CXCL12-γ to augment its angiogenic potency. Moreover, it is shown that addition of HA to collagen matrices on its own decreases vessel sprouting and permeability, and these responses are nullified by blocking the HA receptor CD44. Collectively, these results demonstrate that differences in binding to extracellular HA help underlie CXCL12 isoform-specific responses toward directing angiogenesis.