Lowering of tumor interstitial fluid pressure reduces tumor cell proliferation in a xenograft tumor model

Decoding complex transport patterns in flow-induced autologous chemotaxis of multicellular systems

Cell migration via autologous chemotaxis in the presence of interstitial fluid flow is important in cancer metastasis and embryonic development. Despite significant recent progress, our understanding of flow-induced autologous chemotaxis of multicellular systems remains poor. The literature presents inconsistent findings regarding the effectiveness of collective autologous chemotaxis of densely packed cells under interstitial fluid flow. Here, we present a high-fidelity computational model to analyze the migration of multicellular systems performing autologous chemotaxis in the presence of interstitial fluid flow. Our simulations show that the details of the complex transport dynamics of the chemoattractant and fluid flow patterns that occur in the extracellular space, previously overlooked, are essential to understand this cell migration mechanism. We find that, although flow-induced autologous chemotaxis is a robust migration mechanism for individual cells, the cell-cell interactions that occur in multicellular systems render autologous chemotaxis an inefficient mechanism of collective cell migration. Our results offer new perspectives on the potential role of autologous chemotaxis in the tumor microenvironment, where fluid flow is an important modulator of transport.

Linking cell mechanical memory and cancer metastasis

Metastasis causes most cancer-related deaths; however, the efficacy of anti-metastatic drugs is limited by incomplete understanding of the biological mechanisms that drive metastasis. Focusing on the mechanics of metastasis, we propose that the ability of tumour cells to survive the metastatic process is enhanced by mechanical stresses in the primary tumour microenvironment that select for well-adapted cells. In this Perspective, we suggest that biophysical adaptations favourable for metastasis are retained via mechanical memory, such that the extent of memory is influenced by both the magnitude and duration of the mechanical stress. Among the mechanical cues present in the primary tumour microenvironment, we focus on high matrix stiffness to illustrate how it alters tumour cell proliferation, survival, secretion of molecular factors, force generation, deformability, migration and invasion. We particularly centre our discussion on potential mechanisms of mechanical memory formation and retention via mechanotransduction and persistent epigenetic changes. Indeed, we propose that the biophysical adaptations that are induced by this process are retained throughout the metastatic process to improve tumour cell extravasation, survival and colonization in the distant organ. Deciphering mechanical memory mechanisms will be key to discovering a new class of anti-metastatic drugs.

Lyotropic liquid crystalline 2D and 3D mesophases: Advanced materials for multifunctional anticancer nanosystems

Cancer remains a leading cause of mortality. Despite significant breakthroughs in conventional therapies, treatment is still far from ideal due to high toxicity in normal tissues and therapeutic inefficiency caused by short drug lifetime in the body and resistance mechanisms. Current research moves towards the development of multifunctional nanosystems for delivery of chemotherapeutic drugs, bioactives and/or radionuclides that can be combined with other therapeutic modalities, like gene therapy, or imaging to use in therapeutic screening and diagnosis. The preparation and characterization of Lyotropic Liquid Crystalline (LLC) mesophases self-assembled as 2D and 3D structures are addressed, with an emphasis on the unique properties of these nanoassemblies. A comprehensive review of LLC nanoassemblies is also presented, highlighting the most recent advances and their outstanding advantages as drug delivery systems, including tailoring strategies that can be used to overcome cancer challenges. Therapeutic agents loaded in LLC nanoassemblies offer qualitative and quantitative enhancements that are superior to conventional chemotherapy, particularly in terms of preferential accumulation at tumor sites and promoting enhanced cancer cell uptake, lowering tumor volume and weight, improving survival rates, and increasing the cytotoxicity of their loaded therapeutic agents. In terms of quantitative anticancer efficacy, loaded LLC nanoassemblies reduced the IC50 values from 1.4-fold against lung cancer cells to 125-fold against ovarian cancer cells.

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.

Challenges and Opportunities Associated With Drug Delivery for the Treatment of Solid Tumors

In this review, we discuss the effectiveness of drug delivery system based on metal nanoparticles, and also, describe the problems associated with their delivery to tumor cells. Throughout recent years, more reports have appeared in the literature that demonstrate promising results for the treatment of various types of cancer using metal-based nanoparticles. Due to their unique physical and chemical properties, metal nanoparticles are effectively being used for the delivery of drug to the tumor cells, for cancer diagnosis and treatment. They can also be synthesized allowing the control of size and shape. However, the effectiveness of the metal nanoparticles for cancer treatment largely depends on their stability, biocompatibility, and ability to selectively affect tumor cells after their systemic or local administration. Another major problem associated with metal nanoparticles is their ability to overcome tumor tissue barriers such as atypical blood vessel structure, dense and rigid extracellular matrix, and high pressure of tumor interstitial fluid. The review also describes the design of tumor drug delivery systems that are based on metal nanoparticles. The mechanism of action of metal nanoparticles on cancer cells is also discussed. Considering the therapeutic safety and toxicity of metal nanoparticles, the prospects for their use for future clinical applications are being currently reviewed.

Natural Compounds: Co-Delivery Strategies with Chemotherapeutic Agents or Nucleic Acids Using Lipid-Based Nanocarriers

Cancer is one of the leading causes of death, and latest predictions indicate that cancer- related deaths will increase over the next few decades. Despite significant advances in conventional therapies, treatments remain far from ideal due to limitations such as lack of selectivity, non-specific distribution, and multidrug resistance. Current research is focusing on the development of several strategies to improve the efficiency of chemotherapeutic agents and, as a result, overcome the challenges associated with conventional therapies. In this regard, combined therapy with natural compounds and other therapeutic agents, such as chemotherapeutics or nucleic acids, has recently emerged as a new strategy for tackling the drawbacks of conventional therapies. Taking this strategy into consideration, the co-delivery of the above-mentioned agents in lipid-based nanocarriers provides some advantages by improving the potential of the therapeutic agents carried. In this review, we present an analysis of the synergistic anticancer outcomes resulting from the combination of natural compounds and chemotherapeutics or nucleic acids. We also emphasize the importance of these co-delivery strategies when reducing multidrug resistance and adverse toxic effects. Furthermore, the review delves into the challenges and opportunities surrounding the application of these co-delivery strategies towards tangible clinical translation for cancer treatment.

Application of microfluidic chips in the simulation of the urinary system microenvironment

The urinary system, comprising the kidneys, ureters, bladder, and urethra, has a unique mechanical and fluid microenvironment, which is essential to the urinary system growth and development. Microfluidic models, based on micromachining and tissue engineering technology, can integrate pathophysiological characteristics, maintain cell-cell and cell-extracellular matrix interactions, and accurately simulate the vital characteristics of human tissue microenvironments. Additionally, these models facilitate improved visualization and integration and meet the requirements of the laminar flow environment of the urinary system. However, several challenges continue to impede the development of a tissue microenvironment with controllable conditions closely resemble physiological conditions. In this review, we describe the biochemical and physical microenvironment of the urinary system and explore the feasibility of microfluidic technology in simulating the urinary microenvironment and pathophysiological characteristics in vitro. Moreover, we summarize the current research progress on adapting microfluidic chips for constructing the urinary microenvironment. Finally, we discuss the current challenges and suggest directions for future development and application of microfluidic technology in constructing the urinary microenvironment in vitro.

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 underexplored links between cancer and the internal body climate: Implications for cancer prevention and treatment

In order to effectively manage and cure cancer we should move beyond the general view of cancer as a random process of genetic alterations leading to uncontrolled cell proliferation or simply a predictable evolutionary process involving selection for traits that increase cell fitness. In our view, cancer is a systemic disease that involves multiple interactions not only among cells within tumors or between tumors and surrounding tissues but also with the entire organism and its internal "milieu". We define the internal body climate as an emergent property resulting from spatial and temporal interactions among internal components themselves and with the external environment. The body climate itself can either prevent, promote or support cancer initiation and progression (top-down effect; i.e., body climate-induced effects on cancer), as well as be perturbed by cancer (bottom-up effect; i.e., cancer-induced body climate changes) to further favor cancer progression and spread. This positive feedback loop can move the system towards a "cancerized" organism and ultimately results in its demise. In our view, cancer not only affects the entire system; it is a reflection of an imbalance of the entire system. This model provides an integrated framework to study all aspects of cancer as a systemic disease, and also highlights unexplored links that can be altered to both prevent body climate changes that favor cancer initiation, progression and dissemination as well as manipulate or restore the body internal climate to hinder the success of cancer inception, progression and metastasis or improve therapy outcomes. To do so, we need to (i) identify cancer-relevant factors that affect specific climate components, (ii) develop 'body climate biomarkers', (iii) define 'body climate scores', and (iv) develop strategies to prevent climate changes, stop or slow the changes, or even revert the changes (climate restoration).

A brief glimpse of a tangled web in a small world: Tumor microenvironment

A tumor is a result of stepwise accumulation of genetic and epigenetic alterations. This notion has deepened the understanding of cancer biology and has introduced the era of targeted therapies. On the other hand, there have been a series of attempts of using the immune system to treat tumors, dating back to ancient history, to sporadic reports of inflamed tumors undergoing spontaneous regression. This was succeeded by modern immunotherapies and immune checkpoint inhibitors. The recent breakthrough has broadened the sight to other players within tumor tissue. Tumor microenvironment is a niche or a system orchestrating reciprocal and dynamic interaction of various types of cells including tumor cells and non-cellular components. The output of this complex communication dictates the functions of the constituent elements present within it. More complicated factors are biochemical and biophysical settings unique to TME. This mini review provides a brief guide on a range of factors to consider in the TME research.

CAR T Cell Locomotion in Solid Tumor Microenvironment

The promising outcomes of chimeric antigen receptor (CAR) T cell therapy in hematologic malignancies potentiates its capability in the fight against many cancers. Nevertheless, this immunotherapy modality needs significant improvements for the treatment of solid tumors. Researchers have incrementally identified limitations and constantly pursued better CAR designs. However, even if CAR T cells are armed with optimal killer functions, they must overcome and survive suppressive barriers imposed by the tumor microenvironment (TME). In this review, we will discuss in detail the important role of TME in CAR T cell trafficking and how the intrinsic barriers contribute to an immunosuppressive phenotype and cancer progression. It is of critical importance that preclinical models can closely recapitulate the in vivo TME to better predict CAR T activity. Animal models have contributed immensely to our understanding of human diseases, but the intensive care for the animals and unreliable representation of human biology suggest in vivo models cannot be the sole approach to CAR T cell therapy. On the other hand, in vitro models for CAR T cytotoxic assessment offer valuable insights to mechanistic studies at the single cell level, but they often lack in vivo complexities, inter-individual heterogeneity, or physiologically relevant spatial dimension. Understanding the advantages and limitations of preclinical models and their applications would enable more reliable prediction of better clinical outcomes.

Pressure increases PD-L1 expression in A549 lung adenocarcinoma cells and causes resistance to anti-ROR1 CAR T cell-mediated cytotoxicity

Due to the abnormal vasculation and proliferation, the tumor microenvironment is hypoxic, lacking nutrients, and under high interstitial pressure. Compared to oxygen and nutrients, the effect of pressure on cancer biology remains poorly studied. Here we constructed αROR1-CAR T cells and co-cultured with A549 cells with and without elevated pressure. We then measured apoptosis and cell death by flow cytometry and luciferase activity. We also measured cytokine (IL-2, IFN-γ, and TNF-α) release by ELISA. The results show that pressure-preconditioned A549 cells are much resistant to αROR1-CAR T cell-mediated cytotoxicity. Pressure preconditioning does not appear to affect the expression of αROR1-CAR or cytokine production. However, pressure preconditioning upregulates PD-L1 expression in A549 cells and decreases cytokine release from αROR1-CAR T cells. In addition, Pembrolizumab and Cemiplimab that block PD-1::PD-L1 interaction increase the cytokine production in αROR1-CAR T cells, increase the apoptotic cell death in A549 cells, and improve the αROR1-CAR T-mediated cytotoxicity. In xenograft mice, pressure preconditioning increases tumorigenesis of A549 cells, which can be blocked by a combined therapy using Pembrolizumab and αROR1-CAR T cells. Together, our studies suggest that elevated pressure in the tumor microenvironment could blunt the T cell therapy by upregulating PD-L1 expression, which could be overcome by combining CAR T therapy with immune checkpoint inhibitors.

Tumor microenvironment and nanotherapeutics: intruding the tumor fort

Over recent years, advancements in nanomedicine have allowed new approaches to diagnose and treat tumors. Nano drug delivery systems exploit the enhanced permeability and retention (EPR) effect and enter the tumor tissue's interstitial space. However, tumor barriers play a crucial role, and cause inefficient EPR or the homing effect. Mounting evidence supports the hypothesis that the components of the tumor microenvironment, such as the extracellular matrix, and cellular and physiological components collectively or cooperatively hinder entry and distribution of drugs, and therefore, limit the theragnostic applications of cancer nanomedicine. This abnormal tumor microenvironment plays a pivotal role in cancer nanomedicine and was recently recognized as a promising target for improving nano-drug delivery and their therapeutic outcomes. Strategies like passive or active targeting, stimuli-triggered nanocarriers, and the modulation of immune components have shown promising results in achieving anticancer efficacy. The present review focuses on the tumor microenvironment and nanoparticle-based strategies (polymeric, inorganic and organic nanoparticles) for intruding the tumor barrier and improving therapeutic effects.

Enabling peristalsis of human colon tumor organoids on microfluidic chips

Peristalsis in the digestive tract is crucial to maintain physiological functions. It remains challenging to mimic the peristaltic microenvironment in gastrointestinal organoid culture. Here, we present a method to model the peristalsis for human colon tumor organoids on a microfluidic chip. The chip contains hundreds of lateral microwells and a surrounding pressure channel. Human colon tumor organoids growing in the microwell were cyclically contracted by pressure channel, mimicking thein vivomechano-stimulus by intestinal muscles. The chip allows the control of peristalsis amplitude and rhythm and the high throughput culture of organoids simultaneously. By applying 8% amplitude with 8 ∼ 10 times min^-1, we observed the enhanced expression of Lgr5 and Ki67. Moreover, ellipticine-loaded polymeric micelles showed reduced uptake in the organoids under peristalsis and resulted in compromised anti-tumor efficacy. The results indicate the importance of mechanical stimuli mimicking the physiological environment when usingin vitromodels to evaluate nanoparticles. This work provides a method for attaining more reliable and representative organoids models in nanomedicine.

Mechanics of 3D Cell-Hydrogel Interactions: Experiments, Models, and Mechanisms

Hydrogels are highly water-swollen molecular networks that are ideal platforms to create tissue mimetics owing to their vast and tunable properties. As such, hydrogels are promising cell-delivery vehicles for applications in tissue engineering and have also emerged as an important base for ex vivo models to study healthy and pathophysiological events in a carefully controlled three-dimensional environment. Cells are readily encapsulated in hydrogels resulting in a plethora of biochemical and mechanical communication mechanisms, which recapitulates the natural cell and extracellular matrix interaction in tissues. These interactions are complex, with multiple events that are invariably coupled and spanning multiple length and time scales. To study and identify the underlying mechanisms involved, an integrated experimental and computational approach is ideally needed. This review discusses the state of our knowledge on cell-hydrogel interactions, with a focus on mechanics and transport, and in this context, highlights recent advancements in experiments, mathematical and computational modeling. The review begins with a background on the thermodynamics and physics fundamentals that govern hydrogel mechanics and transport. The review focuses on two main classes of hydrogels, described as semiflexible polymer networks that represent physically cross-linked fibrous hydrogels and flexible polymer networks representing the chemically cross-linked synthetic and natural hydrogels. In this review, we highlight five main cell-hydrogel interactions that involve key cellular functions related to communication, mechanosensing, migration, growth, and tissue deposition and elaboration. For each of these cellular functions, recent experiments and the most up to date modeling strategies are discussed and then followed by a summary of how to tune hydrogel properties to achieve a desired functional cellular outcome. We conclude with a summary linking these advancements and make the case for the need to integrate experiments and modeling to advance our fundamental understanding of cell-matrix interactions that will ultimately help identify new therapeutic approaches and enable successful tissue engineering.

Molecular cancer cell responses to solid compressive stress and interstitial fluid pressure

Alterations to the mechanical properties of the microenvironment are a hallmark of cancer. Elevated mechanical stresses exist in many solid tumors and elicit responses from cancer cells. Uncontrolled growth in confined environments gives rise to elevated solid compressive stress on cancer cells. Recruitment of leaky blood vessels and an absence of functioning lymphatic vessels causes a rise in the interstitial fluid pressure. Here we review the role of the cancer cell cytoskeleton and the nucleus in mediating both the initial and adaptive cancer cell response to these two types of mechanical stresses. We review how these mechanical stresses alter cancer cell functions such as proliferation, apoptosis, and migration.

Study on the Expansion Dynamics of MDCK Epithelium by Interstitial Flow Using a Traction Force-Measurable Microfluidic Chip

The movement of collective cells is affected through changes in physical interactions of cells in response to external mechanical stimuli, including fluid flow. Most tissues are affected by fluid flow at the interstitial level, but few studies have investigated the physical effects in collective cells affected by a low flow rate. In this study, collective cell migration of Madin-Darby canine kidney (MDCK) epithelial cells was investigated under static or interstitial flow (0, 0.1, and 1 μL/min) using a traction microfluidic device. The optimization of calculation of cellular traction forces was first achieved by changing interrogation window size from the fluorescent bead images. Migration analysis of cell collectives patterned with a 700 μm circular shape reveals that cells under the slow flow (0.1 and 1 μL/min) showed the inhibitory migration by decreasing cell island size and cellular speed compared to that of static condition. Analysis of cellular forces shows that level of traction forces was lower in the slow flow condition (~20 Pa) compared to that of static condition (~50 Pa). Interestingly, the standard deviation of traction force of cells was dramatically decreased as the flow rate increased from 0 to 1 μL/min, which indicates that flow affects the distribution of cellular traction forces among cell collectives. Cellular tension was increased by 50% in the cells under the fluid flow rate of 1 μL/min. Treatment of calcium blocker increased the migratory speed of cells under the flow condition, whereas there is little change of cellular forces. In conclusion, it has been shown that the interstitial flow inhibited the collective movement of epithelial cells by decreasing and re-distributing cellular forces. These findings provide insights into the study of the effect of interstitial flow on cellular behavior, such as development, regeneration, and morphogenesis.

Endothelial YAP/TAZ Signaling in Angiogenesis and Tumor Vasculature

Solid tumors are dependent on vascularization for their growth. The hypoxic, stiff, and pro-angiogenic tumor microenvironment induces angiogenesis, giving rise to an immature, proliferative, and permeable vasculature. The tumor vessels promote tumor metastasis and complicate delivery of anti-cancer therapies. In many types of tumors, YAP/TAZ activation is correlated with increased levels of angiogenesis. In addition, endothelial YAP/TAZ activation is important for the formation of new blood and lymphatic vessels during development. Oncogenic activation of YAP/TAZ in tumor cell growth and invasion has been studied in great detail, however the role of YAP/TAZ within the tumor endothelium remains insufficiently understood, which complicates therapeutic strategies aimed at targeting YAP/TAZ in cancer. Here, we overview the upstream signals from the tumor microenvironment that control endothelial YAP/TAZ activation and explore the role of their downstream targets in driving tumor angiogenesis. We further discuss the potential for anti-cancer treatments and vascular normalization strategies to improve tumor therapies.

Cell – extracellular matrix interaction in glioma growth. In silico model

The study aims to investigate the role of viscoelastic interactions between cells and extracellular matrix (ECM) in avascular tumor growth. Computer simulations of glioma multicellular tumor spheroid (MTS) growth are being carried out for various conditions. The calculations are based on a continuous model, which simulates oxygen transport into MTS; transitions between three cell phenotypes, cell transport, conditioned by hydrostatic forces in cell–ECM composite system, cell motility and cell adhesion. Visco-elastic cell aggregation and elastic ECM scaffold represent two compressible constituents of the composite. Cell–ECM interactions form a Transition Layer on the spheroid surface, where mechanical characteristics of tumor undergo rapid transition. This layer facilitates tumor progression to a great extent. The study demonstrates strong effects of ECM stiffness, mechanical deformations of the matrix and cell–cell adhesion on tumor progression. The simulations show in particular that at certain, rather high degrees of matrix stiffness a formation of distant multicellular clusters takes place, while at further increase of ECM stiffness subtumors do not form. The model also illustrates to what extent mere mechanical properties of cell–ECM system may contribute into variations of glioma invasion scenarios.

Receptor-based targeting of engineered nanocarrier against solid tumors: Recent progress and challenges ahead

Background In past few decades, the research on engineered nanocarriers (NCs) has gained significant attention in cancer therapy due to selective delivery of drug molecules on the diseased cells thereby preventing unwanted uptake into healthy cells to cause toxicity. Scope of review The applicability of enhanced permeability and retention (EPR) effect for the delivery of nanomedicines in cancer therapy has gained limited success due to poor accessibility of the drugs to the target cells where non-specific payload delivery to the off target region lack substantial reward over the conventional therapeutic systems. Major conclusions In spite of the fact, nanomedicines fabricated from the biocompatible nanocarriers have reduced targeting potential for meaningful clinical benefits. However, over expression of receptors on the tumor cells provides opportunity to design functional nanomedicine to bind substantially and deliver therapeutics to the cells or tissues of interest by alleviating the bio-toxicity and unwanted effects. This critique will give insight into the over expressed receptor in various tumor and targeting potential of functional nanomedicine as new therapeutic avenues for effective treatment. General significance This review shortly shed light on EPR-based drug targeting using nanomedicinal strategies, their limitation, and advances in therapeutic targeting to the tumor cells.

Photodynamic Therapy and the Biophysics of the Tumor Microenvironment

Targeting the tumor microenvironment (TME) provides opportunities to modulate tumor physiology, enhance the delivery of therapeutic agents, impact immune response and overcome resistance. Photodynamic therapy (PDT) is a photochemistry-based, nonthermal modality that produces reactive molecular species at the site of light activation and is in the clinic for nononcologic and oncologic applications. The unique mechanisms and exquisite spatiotemporal control inherent to PDT enable selective modulation or destruction of the TME and cancer cells. Mechanical stress plays an important role in tumor growth and survival, with increasing implications for therapy design and drug delivery, but remains understudied in the context of PDT and PDT-based combinations. This review describes pharmacoengineering and bioengineering approaches in PDT to target cellular and noncellular components of the TME, as well as molecular targets on tumor and tumor-associated cells. Particular emphasis is placed on the role of mechanical stress in the context of targeted PDT regimens, and combinations, for primary and metastatic tumors.

Hyperthermia can alter tumor physiology and improve chemo- and radio-therapy efficacy

Hyperthermia has demonstrated clinical success in improving the efficacy of both chemo- and radio-therapy in solid tumors. Pre-clinical and clinical research studies have demonstrated that targeted hyperthermia can increase tumor blood flow and increase the perfused fraction of the tumor in a temperature and time dependent manner. Changes in tumor blood circulation can produce significant physiological changes including enhanced vascular permeability, increased oxygenation, decreased interstitial fluid pressure, and reestablishment of normal physiological pH conditions. These alterations in tumor physiology can positively impact both small molecule and nanomedicine chemotherapy accumulation and distribution within the tumor, as well as the fraction of the tumor susceptible to radiation therapy. Hyperthermia can trigger drug release from thermosensitive formulations and further improve the accumulation, distribution, and efficacy of chemotherapy.

Cell Nanomechanics Based on Dielectric Elastomer Actuator Device

As a frontier of biology, mechanobiology plays an important role in tissue and biomedical engineering. It is a common sense that mechanical cues under extracellular microenvironment affect a lot in regulating the behaviors of cells such as proliferation and gene expression, etc. In such an interdisciplinary field, engineering methods like the pneumatic and motor-driven devices have been employed for years. Nevertheless, such techniques usually rely on complex structures, which cost much but not so easy to control. Dielectric elastomer actuators (DEAs) are well known as a kind of soft actuation technology, and their research prospect in biomechanical field is gradually concerned due to their properties just like large deformation (> 100%) and fast response (< 1 ms). In addition, DEAs are usually optically transparent and can be fabricated into small volume, which make them easy to cooperate with regular microscope to realize real-time dynamic imaging of cells. This paper first reviews the basic components, principle, and evaluation of DEAs and then overview some corresponding applications of DEAs for cellular mechanobiology research. We also provide a comparison between DEA-based bioreactors and current custom-built devices and share some opinions about their potential applications in the future according to widely reported results via other methods.

A Microfluidic Tumor-on-a-Chip for Assessing Multifunctional Liposomes' Tumor Targeting and Anticancer Efficacy

Two principal methods for cancer drug testing are widely used, namely, in vitro 2D cell monolayers and in vivo animal models. In vitro 2D culture systems are simple and convenient but are unable to capture the complexity of biological processes. Animal models are costly, time-consuming, and often fail to replicate human activity. Here a microfluidic tumor-on-a-chip (TOC) model designed for assessing multifunctional liposome cancer targeting and efficacy is presented. The TOC device contains three sets of hemispheric wells with different sizes for tumor spheroid formation and evaluation of liposomes under a controlled flow condition. There is good agreement between time-elapsed tumor targeting of fluorescent liposomes in the TOC model and in in vivo mouse models. Evaluation of the anticancer efficacy of four PTX-loaded liposome formulations shows that compared to 2D cell monolayers and 3D tumor spheroid models, the TOC model better predicts the in vivo anticancer efficacy of targeted liposomes. Lastly, the TOC model is used to assess the effects of flow rates and tumor size on treatment outcome. This study demonstrates that the TOC model provides a convenient and powerful platform for rapid and reliable cancer drug evaluation.

Stromal integrin α11-deficiency reduces interstitial fluid pressure and perturbs collagen structure in triple-negative breast xenograft tumors

Background

Cancer progression is influenced by a pro-tumorigenic microenvironment. The aberrant tumor stroma with increased collagen deposition, contractile fibroblasts and dysfunctional vessels has a major impact on the interstitial fluid pressure (PIF) in most solid tumors. An increased tumor PIF is a barrier to the transport of interstitial fluid into and within the tumor. Therefore, understanding the mechanisms that regulate pressure homeostasis can lead to new insight into breast tumor progression, invasion and response to therapy. The collagen binding integrin α11β1 is upregulated during myofibroblast differentiation and expressed on fibroblasts in the tumor stroma. As a collagen organizer and a probable link between contractile fibroblasts and the complex collagen network in tumors, integrin α11β1 could be a potential regulator of tumor PIF.

Methods

We investigated the effect of stromal integrin α11-deficiency on pressure homeostasis, collagen organization and tumor growth using orthotopic and ectopic triple-negative breast cancer xenografts (MDA-MB-231 and MDA-MB-468) in wild type and integrin α11-deficient mice. PIF was measured by the wick-in-needle technique, collagen by Picrosirius Red staining and electron microscopy, and uptake of radioactively labeled 5FU by microdialysis. Further, PIF in heterospheroids composed of MDA-MB-231 cells and wild type or integrin α11-deficient fibroblasts was measured by micropuncture.

Results

Stromal integrin α11-deficiency decreased PIF in both the orthotopic breast cancer models. A concomitant perturbed collagen structure was seen, with fewer aligned and thinner fibrils. Integrin α11-deficiency also impeded MDA-MB-231 breast tumor growth, but no effect was observed on drug uptake. No effects were seen in the ectopic model. By investigating the isolated effect of integrin α11-positive fibroblasts on MDA-MB-231 cells in vitro, we provide evidence that PIF regulation was mediated by integrin α11-positive fibroblasts.

Conclusion

We hereby show the importance of integrin α11β1 in pressure homeostasis in triple-negative breast tumors, indicating a new role for integrin α11β1 in the tumor microenvironment. Our data suggest that integrin α11β1 has a pro-tumorigenic effect on triple-negative breast cancer growth in vivo. The significance of the local microenvironment is shown by the different effects of integrin α11β1 in the orthotopic and ectopic models, underlining the importance of choosing an appropriate preclinical model.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5449-z) contains supplementary material, which is available to authorized users.

Regulation of Blood and Lymphatic Vessels by Immune Cells in Tumors and Metastasis

Research over the last decades has provided strong evidence for the pivotal role of the tumor-associated blood and lymphatic vasculature in supporting immunoevasion and in subverting T cell-mediated immunosurveillance. Conversely, tumor blood and lymphatic vessel growth is in part regulated by the immune system, with infiltrating innate as well as adaptive immune cells providing both immunosuppressive and various angiogenic signals. Thus, tumor angiogenesis and escape of immunosurveillance are two cancer hallmarks that are tightly linked and interregulated by cell constituents from compartments secreting both chemokines and cytokines. In this review, we discuss the implication and regulation of innate and adaptive immune cells in regulating blood and lymphatic angiogenesis in tumor progression and metastases. Moreover, we also highlight novel therapeutic approaches that target the tumor vasculature as well as the immune compartment to sustain and improve therapeutic efficacy in cancer.

Microfluidic modelling of the tumor microenvironment for anti-cancer drug development

Cancer is the leading cause of death worldwide. The complex and disorganized tumor microenvironment makes it very difficult to treat this disease. The most common in vitro drug screening method now is based on 2D culture models which poorly represent actual tumors. Therefore, many 3D tumor models which are more physiologically relevant have been developed to conduct in vitro drug screening and alleviate this situation. Among all these models, the microfluidic tumor model has the unique advantage of recapitulating the tumor microenvironment in a comparatively easier and representative fashion. While there are many review papers available on the related topic of microfluidic tumor models, in this review we aim to focus more on the possibility of generating "clinically actionable information" from these microfluidic systems, besides scientific insight. Our topics cover the tumor microenvironment, conventional 2D and 3D cultures, animal models, and microfluidic tumor models, emphasizing their link to anti-cancer drug discovery and personalized medicine.

Chemoresistance and the Self-Maintaining Tumor Microenvironment

The progression of cancer is associated with alterations in the tumor microenvironment, including changes in extracellular matrix (ECM) composition, matrix rigidity, hypervascularization, hypoxia, and paracrine factors. One key malignant phenotype of cancer cells is their ability to resist chemotherapeutics, and elements of the ECM can promote chemoresistance in cancer cells through a variety of signaling pathways, inducing changes in gene expression and protein activity that allow resistance. Furthermore, the ECM is maintained as an environment that facilitates chemoresistance, since its constitution modulates the phenotype of cancer-associated cells, which themselves affect the microenvironment. In this review, we discuss how the properties of the tumor microenvironment promote chemoresistance in cancer cells, and the interplay between these external stimuli. We focus on both the response of cancer cells to the external environment, as well as the maintenance of the external environment, and how a chemoresistant phenotype emerges from the complex signaling network present.

Tumor Microenvironment Targeted Nanotherapy

Recent developments in nanotechnology have brought new approaches to cancer diagnosis and therapy. While enhanced permeability and retention effect promotes nano-chemotherapeutics extravasation, the abnormal tumor vasculature, high interstitial pressure and dense stroma structure limit homogeneous intratumoral distribution of nano-chemotherapeutics and compromise their imaging and therapeutic effect. Moreover, heterogeneous distribution of nano-chemotherapeutics in non-tumor-stroma cells damages the non-tumor cells, and interferes with tumor-stroma crosstalk. This can lead not only to inhibition of tumor progression, but can also paradoxically induce acquired resistance and facilitate tumor cell proliferation and metastasis. Overall, the tumor microenvironment plays a vital role in regulating nano-chemotherapeutics distribution and their biological effects. In this review, the barriers in tumor microenvironment, its consequential effects on nano-chemotherapeutics, considerations to improve nano-chemotherapeutics delivery and combinatory strategies to overcome acquired resistance induced by tumor microenvironment have been summarized. The various strategies viz., nanotechnology based approach as well as ligand-mediated, redox-responsive, and enzyme-mediated based combinatorial nanoapproaches have been discussed in this review.

Distraction-suppression effect on osteosarcoma

Osteosarcoma is the most common primary malignant bone tumor. It occurs mainly in children and adolescents. In patients with open growth plate, epiphyseal distraction is used to separate the uninvolved epiphysis from adjacent tumor. This helps preserve the growth potential and restore joint and limb function to a great extent. Interestingly, epiphyseal distraction also appears to inhibit the proliferation of osteosarcoma tumor cells and to increase sensitivity to chemotherapy. Tumor interstitial pressure (TIP) is often elevated in the microenvironment of most solid tumors, including osteosarcoma. Elevated TIP can promote the proliferation, invasion, and migration ability of osteosarcoma cells and also decrease the uptake and distribution of chemotherapeutic agents. Studies have confirmed that the sustained volumetric strain produced in distracted tissue decreases TIP; it stretches extracellular matrix, decreases interstitial density, and increases vessel diameter. We hypothesize that lowering of TIP during the period of epiphyseal distraction inhibits the proliferation and invasion of osteosarcoma cell and, at the same time, increases blood perfusion in the tumor and thus enhances uptake and distribution of chemotherapy agents. If the hypothesis is proved to be true, distraction of tumor segment could be a novel supplementary treatment for osteosarcoma by manipulation of TIP.

Fluid Shear Stress Induces Cell Cycle Arrest in Human Urinary Bladder Transitional Cell Carcinoma Through Bone Morphogenetic Protein Receptor-Smad1/5 Pathway

Introduction

Mechanical force generated from the interstitial fluid flow inside and surrounding tissue has been known to play a significant role in cancer pathophysiology. In this study, we aimed to investigate the role of laminar shear stress (LSS) in modulating the cell cycle of human bladder transitional carcinoma (BFTC-905) cells which are frequently stimulated by not only the interstitial fluid flow, but also the urine flow transported from kidney to bladder in the urinary tract.

Methods

The BFTC-905 cells were subjected to 0-12 dynes cm^-2 LSS for 1, 4, 8, or 12 h, respectively, followed by cellular and molecular assays for investigations of cell cycle regulation protein expressions, cell growth rates, and the potential mechanism.

Results

The results showed that the LSS with ≥ 8 dynes cm^-2 for ≥ 8 h significantly increased protein expressions of cyclin B1, Wee1, p21, and p-CDK1^(Tyr15) (p < 0.05 for each), but conversely decreased protein expressions of cyclin A2, D1, E1, and CDK-1, -2, -4, and -6 (p < 0.05 for each) in the BFTC-905 cells, indicating that a G₂/M cell cycle arrest was obtained after shearing stimulation. Furthermore, our data demonstrated that the LSS-induced G₂/M arrest and the corresponding changes in cell cycle regulatory protein expressions were modulated by bone morphogenetic protein (BMP) receptor-Smad1/5 signaling pathway.

Conclusions

Our findings provided evidences for the effect of mechanical microenvironment on urothelial cancer pathobiology and generated insights into mechanism of LSS-regulated bladder tumor cell cycle.

Investigating Low-Velocity Fluid Flow in Tumors with Convection-MRI

Several distinct fluid flow phenomena occur in solid tumors, including intravascular blood flow and interstitial convection. Interstitial fluid pressure is often raised in solid tumors, which can limit drug delivery. To probe low-velocity flow in tumors resulting from raised interstitial fluid pressure, we developed a novel MRI technique named convection-MRI, which uses a phase-contrast acquisition with a dual-inversion vascular nulling preparation to separate intra- and extravascular flow. Here, we report the results of experiments in flow phantoms, numerical simulations, and tumor xenograft models to investigate the technical feasibility of convection-MRI. We observed a significant correlation between estimates of effective fluid pressure from convection-MRI with gold-standard, invasive measurements of interstitial fluid pressure in mouse models of human colorectal carcinoma. Our results show how convection-MRI can provide insights into the growth and responsiveness to vascular-targeting therapy in colorectal cancers.Significance: A noninvasive method for measuring low-velocity fluid flow caused by raised fluid pressure can be used to assess changes caused by therapy. Cancer Res; 78(7); 1859-72. ©2018 AACR.

Loss of LSR affects epithelial barrier integrity and tumor xenograft growth of CaCo-2 cells

The lipolysis-stimulated lipoprotein receptor (LSR) is a lipoprotein receptor, serves as host receptor for clostridial iota-like toxins and is involved in the formation of tricellular contacts. Of particular interest is the role of LSR in progression of various cancers. Here we aimed to study the tumor growth of LSR-deficient colon carcinoma-derived cell lines HCT116 and CaCo-2 in a mouse xenograft model. Whereas knockout of LSR had no effect on tumor growth of HCT116 cells, we observed that CaCo-2 LSR knockout tumors grew to a smaller size than their wild-type counterparts. Histological analysis revealed increased apoptotic and necrotic cell death in a tumor originating from LSR-deficient CaCo-2 cells. LSR-deficient CaCo-2 cells exhibited increased cell proliferation in vitro and an altered epithelial morphology with impaired targeting of tricellulin to tricellular contacts. In addition, loss of LSR reduced the transepithelial electrical resistance of CaCo-2 cell monolayers and increased permeability for small molecules. Moreover, LSR-deficient CaCo-2 cells formed larger cysts in 3D culture than their wild-type counterparts. Our study provides evidence that LSR affects epithelial morphology and barrier formation in CaCo-2 cells and examines for the first time the effects of LSR deficiency on the tumor growth properties of colon carcinoma-derived cell lines.

Hydrodynamics in Cell Studies

Hydrodynamic phenomena are ubiquitous in living organisms and can be used to manipulate cells or emulate physiological microenvironments experienced in vivo. Hydrodynamic effects influence multiple cellular properties and processes, including cell morphology, intracellular processes, cell–cell signaling cascades and reaction kinetics, and play an important role at the single-cell, multicellular, and organ level. Selected hydrodynamic effects can also be leveraged to control mechanical stresses, analyte transport, as well as local temperature within cellular microenvironments. With a better understanding of fluid mechanics at the micrometer-length scale and the advent of microfluidic technologies, a new generation of experimental tools that provide control over cellular microenvironments and emulate physiological conditions with exquisite accuracy is now emerging. Accordingly, we believe that it is timely to assess the concepts underlying hydrodynamic control of cellular microenvironments and their applications and provide some perspective on the future of such tools in in vitro cell-culture models. Generally, we describe the interplay between living cells, hydrodynamic stressors, and fluid flow-induced effects imposed on the cells. This interplay results in a broad range of chemical, biological, and physical phenomena in and around cells. More specifically, we describe and formulate the underlying physics of hydrodynamic phenomena affecting both adhered and suspended cells. Moreover, we provide an overview of representative studies that leverage hydrodynamic effects in the context of single-cell studies within microfluidic systems.

Microenvironment Influences Cancer Cell Mechanics from Tumor Growth to Metastasis

The microenvironment in a solid tumor includes a multitude of cell types, matrix proteins, and growth factors that profoundly influence cancer cell mechanics by providing both physical and chemical stimulation. This tumor microenvironment, which is both dynamic and heterogeneous in nature, plays a critical role in cancer progression from the growth of the primary tumor to the development of metastatic and drug-resistant tumors. This chapter provides an overview of the biophysical tools used to study cancer cell mechanics and mechanical changes in the tumor microenvironment at different stages of cancer progression, including growth of the primary tumor, local invasion, and metastasis. Quantitative single cell biophysical analysis of intracellular mechanics, cell traction forces, and cell motility can easily be combined with analysis of critical cell fate processes, including adhesion, proliferation, and drug resistance, to determine how changes in mechanics contribute to cancer progression. This biophysical approach can be used to systematically investigate the parameters in the tumor that control cancer cell interactions with the stroma and to identify specific conditions that induce tumor-promoting behavior, along with strategies for inhibiting these conditions to treat cancer. Increased understanding of the underlying biophysical mechanisms that drive cancer progression may provide insight into novel therapeutic approaches in the fight against cancer.

Activation of PKB/Akt and p44/42 by mechanical stretch utilizes desmosomal structures and the keratin filament

BACKGROUND

Mechanical stress is an ubiquitous challenge of human cells with fundamental impact on cell physiology. Previous studies have shown that stretching promotes signalling cascades involved in proliferation and tissue enlargement.

OBJECTIVE

The present study is dedicated to learn more about cellular structures contributing to perception and signal transmission of cell stretch. In particular, we hypothesized that desmosmal contacts and the adjacent keratin filament build an intercellular matrix providing information about the mechanical load.

METHODS

Epidermal cells with different keratin equipment were seeded on flexible silicon dishes and stretched. As read out parameter the activation of PKB/Akt and p44/42 was monitored by Western blotting. Likewise desomosomal contacts were manipulated by depletion or addition of calcium. Moreover, desmoglein 3 and desmocollin 3 were blocked by either specific antibodies or siRNA.

RESULTS

It was found that the omission of calcium from the medium, a necessary cofactor for desmosomal cadherins, inhibited stretch mediated activation of PKB/Akt and p44/42. The relevance of desmosomes in this context was further substantiated by experiments using a desmoglein 3 blocking antibody (AK23) and siRNA against desmocollin 3. Moreover, disruption of the keratin filament by sodium orthovanadate also abrogates PKB/Akt and p44/42 activation in response to stretch. Likewise, KEB-7 keratinocytes harbouring a mutation in the keratin 14 gene and genetically modified keratinocytes devoid of any keratin show an altered signalling after stretch indicating the relevance of the keratin filament in this context.

CONCLUSION

Besides their important role in cell architecture our results identify desmosomes and keratins as mechanosensing structures.

Dendrimer-doxorubicin conjugates exhibit improved anticancer activity and reduce doxorubicin-induced cardiotoxicity in a murine hepatocellular carcinoma model

Hepatocellular carcinoma (HCC) is the 2^nd leading cause of cancer-related deaths every year globally. The most common form of treatment, hepatic arterial infusion (HAI), involves the direct injection of doxorubicin (DOX) into the hepatic artery. It is plagued with limited therapeutic efficacy and the occurrence of severe toxicities (e.g. cardiotoxicity). We aim to improve the therapeutic index of DOX delivered via HAI by loading the drug onto generation 5 (G5) poly(amidoamine) (PAMAM) dendrimers targeted to hepatic cancer cells via N-acetylgalactosamine (NAcGal) ligands. DOX is attached to the surface of G5 molecules via two different enzyme-sensitive linkages, L3 or L4, to achieve controllable drug release inside hepatic cancer cells. We previously reported on P1 and P2 particles that resulted from the combination of NAcGal-targeting with L3- or L4-DOX linkages, respectively, and showed controllable DOX release and toxicity towards hepatic cancer cells comparable to free DOX. In this study, we demonstrate that while the intratumoral delivery of free DOX (1 mg/kg) into HCC-bearing nod scid gamma (NSG) mice achieves a 2.5-fold inhibition of tumor growth compared to the saline group over 30 days, P1 and P2 particles delivered at the same DOX dosage achieve a 5.1- and 4.4-fold inhibition, respectively. Incubation of the particles with human induced pluripotent stem cell derived cardiomyocytes (hiPSC CMs) showed no effect on monolayer viability, apoptosis induction, or CM electrophysiology, contrary to the effect of free DOX. Moreover, magnetic resonance imaging revealed that P1- and P2-treated mice maintained cardiac function after intraperitoneal administration of DOX at 1 mg/kg for 21 days, unlike the free DOX group at an equivalent dosage, confirming that P1/P2 can avoid DOX-induced cardiotoxicity. Taken together, these results highlight the ability of P1/P2 particles to improve the therapeutic index of DOX and offer a replacement therapy for clinical HCC treatment.

Alk5 inhibition increases delivery of macromolecular and protein-bound contrast agents to tumors

Limited transendothelial permeability across tumor microvessels represents a significant bottleneck in the development of tumor-specific diagnostic agents and theranostic drugs. Here, we show an approach to increase transendothelial permeability of macromolecular and nanoparticle-based contrast agents via inhibition of the type I TGF-β receptor, activin-like kinase 5 (Alk5), in tumors. Alk5 inhibition significantly increased tumor contrast agent delivery and enhancement on imaging studies, while healthy organs remained relatively unaffected. Imaging data correlated with significantly decreased tumor interstitial fluid pressure, while tumor vascular density remained unchanged. This immediately clinically translatable concept involving Alk5 inhibitor pretreatment prior to an imaging study could be leveraged for improved tumor delivery of macromolecular and nanoparticle-based imaging probes and, thereby, facilitate development of more sensitive imaging tests for cancer diagnosis, enhanced tumor characterization, and personalized, image-guided therapies.

Scanning Acoustic Microscopy-A Novel Noninvasive Method to Determine Tumor Interstitial Fluid Pressure in a Xenograft Tumor Model

Elevated tumor interstitial fluid pressure (TIFP) is a prominent feature of solid tumors and hampers the transmigration of therapeutic macromolecules, for example, large monoclonal antibodies, from tumor-supplying vessels into the tumor interstitium. TIFP values of up to 40 mm Hg have been measured in experimental solid tumors using two conventional invasive techniques: the wick-in-needle and the micropuncture technique. We propose a novel noninvasive method of determining TIFP via ultrasonic investigation with scanning acoustic microscopy at 30-MHz frequency. In our experimental setup, we observed for the impedance fluctuations in the outer tumor hull of A431-vulva carcinoma–derived tumor xenograft mice. The gain dependence of signal strength was quantified, and the relaxation of tissue was calibrated with simultaneous hydrostatic pressure measurements. Signal patterns from the acoustical images were translated into TIFP curves, and a putative saturation effect was found for tumor pressures larger than 3 mm Hg. This is the first noninvasive approach to determine TIFP values in tumors. This technique can provide a potentially promising noninvasive assessment of TIFP and, therefore, can be used to determine the TIFP before treatment approach as well to measure therapeutic efficacy highlighted by lowered TFP values.

Increased hydrostatic pressure enhances motility of lung cancer cells

Interstitial fluid pressures within most solid tumors are significantly higher than that in the surrounding normal tissues. Therefore, cancer cells must proliferate and migrate under the influence of elevated hydrostatic pressure while a tumor grows. In this study, we developed a pressurized cell culture device and investigated the influence of hydrostatic pressure on the migration speeds of lung cancer cells (CL1-5 and A549). The migration speeds of lung cancer cells were increased by 50-60% under a 20 mmHg hydrostatic pressure. We also observed that the expressions of aquaporin in CL1-5 and A549 cells were increased under the hydrostatic pressure. Our preliminary results indicate that increased hydrostatic pressure plays an important role in tumor metastasis.

Flow shear stress regulates endothelial barrier function and expression of angiogenic factors in a 3D microfluidic tumor vascular model

Endothelial cells lining blood vessels are exposed to various hemodynamic forces associated with blood flow. These include fluid shear, the tangential force derived from the friction of blood flowing across the luminal cell surface, tensile stress due to deformation of the vessel wall by transvascular flow, and normal stress caused by the hydrodynamic pressure differential across the vessel wall. While it is well known that these fluid forces induce changes in endothelial morphology, cytoskeletal remodeling, and altered gene expression, the effect of flow on endothelial organization within the context of the tumor microenvironment is largely unknown. Using a previously established microfluidic tumor vascular model, the objective of this study was to investigate the effect of normal (4 dyn/cm(2)), low (1 dyn/cm(2)), and high (10 dyn/cm(2)) microvascular wall shear stress (WSS) on tumor-endothelial paracrine signaling associated with angiogenesis. It is hypothesized that high WSS will alter the endothelial phenotype such that vascular permeability and tumor-expressed angiogenic factors are reduced. Results demonstrate that endothelial permeability decreases as a function of increasing WSS, while co-culture with tumor cells increases permeability relative to mono-cultures. This response is likely due to shear stress-mediated endothelial cell alignment and tumor-VEGF-induced permeability. In addition, gene expression analysis revealed that high WSS (10 dyn/cm(2)) significantly down-regulates tumor-expressed MMP9, HIF1, VEGFA, ANG1, and ANG2, all of which are important factors implicated in tumor angiogenesis. This result was not observed in tumor mono-cultures or static conditioned media experiments, suggesting a flow-mediated paracrine signaling mechanism exists with surrounding tumor cells that elicits a change in expression of angiogenic factors. Findings from this work have significant implications regarding low blood velocities commonly seen in the tumor vasculature, suggesting high shear stress-regulation of angiogenic activity is lacking in many vessels, thereby driving tumor angiogenesis.

Development and Characterization of an Engraftable Tissue-Cultured Skin Autograft: Alternative Treatment for Severe Electrical Injuries

BACKGROUND/AIMS

Optimizing the treatment regimens of extensive or nonhealing defects is a constant challenge. Tissue-cultured skin autografts may be an alternative to mesh grafts and keratinocyte suspensions that are applied during surgical defect coverage.

METHODS

Autologous epidermal and dermal cells were isolated, in vitro expanded and seeded on collagen-elastin scaffolds. The developed autograft was immunohistochemically and electron microscopically characterized. Subsequently, it was transplanted onto lesions of a severely burned patient.

RESULTS

Comparability of the skin equivalent to healthy human skin could be shown due to the epidermal strata, differentiation, proliferation markers and development of characteristics of a functional basal lamina. Approximately 2 weeks after skin equivalent transplantation the emerging new skin correlated closely to the adjacent normal skin.

CONCLUSION

The present study demonstrates the comparability of the developed organotypic skin equivalent to healthy human skin and its versatility for clinical applications.

Use of Targeted Liposome-based Chemotherapeutics to Treat Breast Cancer

The use of nanocarriers such as liposomes to deliver anticancer drugs to tumors can significantly enhance the therapeutic index of otherwise unencapsulated cytotoxic agents. This is in part because of the fact that the phospholipid bilayer can protect healthy sensitive tissue from the damaging effects of these types of drugs. Furthermore, the ease with which the phospholipid bilayer surface can be modified to allow for polyethylene glycol incorporation resulting in pegylated liposomes allow for increased circulation times in vivo, and thus an overall increase in the concentration of the drug delivered to the tumor site. This explains the clinical success of the liposomal-based drug Doxil, which has proven to be quite efficacious in the treatment of breast cancer. However, significant challenges remain involving poor drug transfer between the liposome and tumor cells with this type of nontargeted drug delivery system. Thus, future work involves the development of "smart" drugs, or targeted drug delivery intended for improved colocalization between the drug and cancerous cells. While it is not possible to entirely discuss such a rapidly growing field of study involving many different types of chemotherapeutics here, in this review, we discuss some of the recent advancements involving the development of targeted liposome-based chemotherapeutics to treat breast cancer.

Reformulating Tylocrebrine in Epidermal Growth Factor Receptor Targeted Polymeric Nanoparticles Improves Its Therapeutic Index

Several promising anticancer drug candidates have been sidelined owing to their poor physicochemical properties or unfavorable pharmacokinetics, resulting in high overall cost of drug discovery and development. Use of alternative formulation strategies that alleviate these issues can help advance new molecules to the clinic at a significantly lower cost. Tylocrebrine is a natural product with potent anticancer activity. Its clinical trial was discontinued following the discovery of severe central nervous system toxicities. To improve the safety and potency of tylocrebrine, we formulated the drug in polymeric nanoparticles targeted to the epidermal growth factor receptor (EGFR) overexpressed on several types of tumors. Through in vitro studies in different cancer cell lines, we found that EGFR targeted nanoparticles were significantly more effective in killing tumor cells than the free drug. In vivo pharmacokinetic studies revealed that encapsulation in nanoparticles resulted in lower brain penetration and enhanced tumor accumulation of the drug. Further, targeted nanoparticles were characterized by significantly enhanced tumor growth inhibitory activity in a mouse xenograft model of epidermoid cancer. These results suggest that the therapeutic index of drugs that were previously considered unusable could be significantly improved by reformulation. Application of novel formulation strategies to previously abandoned drugs provides an opportunity to advance new molecules to the clinic at a lower cost. This can significantly increase the repertoire of treatment options available to cancer patients.