Hyaluronan hydrogel: an appropriate three-dimensional model for evaluation of anticancer drug sensitivity

Microsphere-Enabled Modular Formation of Miniaturized In Vitro Breast Cancer Models

In search of effective therapeutics for breast cancers, establishing physiologically relevant in vitro models is of great benefit to facilitate the clinical translation. Despite extensive progresses, it remains to develop the tumor models maximally recapturing the key pathophysiological attributes of their native counterparts. Therefore, the current study aimed to develop a microsphere-enabled modular approach toward the formation of in vitro breast tumor models with the capability of incorporating various selected cells while retaining spatial organization. Poly (lactic-co-glycolic acid) microspheres (150-200 mm) with tailorable pore size and surface topography are fabricated and used as carriers to respectively lade with breast tumor-associated cells. Culture of cell-laden microspheres assembled within a customized microfluidic chamber allowed to form 3D tumor models with spatially controlled cell distribution. The introduction of endothelial cell-laden microspheres into cancer-cell laden microspheres at different ratios would induce angiogenesis within the culture to yield vascularized tumor. Evaluation of anticancer drugs such as doxorubicin and Cediranib on the tumor models do demonstrate corresponding physiological responses. Clearly, with the ability to modulate microsphere morphology, cell composition and spatial distribution, microsphere-enabled 3D tumor tissue formation offers a high flexibility to satisfy the needs for pathophysiological study, anticancer drug screening or design of personalized treatment.

5-Fluorouracil-Immobilized Hyaluronic Acid Hydrogel Arrays on an Electrospun Bilayer Membrane as a Drug Patch

The hyaluronic acid (HA) hydrogel array was employed for immobilization of 5-fluorouracil (5-FU), and the electrospun bilayer (hydrophilic: polyurethane/pluronic F-127 and hydrophobic: polyurethane) membrane was used to support the HA hydrogel array as a patch. To visualize the drug propagating phenomenon into tissues, we experimentally investigated how FITC-BSA diffused into the tissue by applying hydrogel patches to porcine tissue samples. The diffusive phenomenon basically depends on the FITC-BSA diffusion coefficient in the hydrogel, and the degree of diffusion of FITC-BSA may be affected by the concentration of HA hydrogel, which demonstrates that the high density of HA hydrogel inhibits the diffusive FITC-BSA migration toward the low concentration region. YD-10B cells were employed to investigate the release of 5-FU from the HA array on the bilayer membrane. In the control group, YD-10B cell viability was over 98% after 3 days. However, in the 5-FU-immobilized HA hydrogel array, most of the YD-10B cells were not attached to the bilayer membrane used as a scaffold. These results suggest that 5-FU was locally released and initiated the death of the YD-10B cells. Our results show that 5-FU immobilized on HA arrays significantly reduces YD-10B cell adhesion and proliferation, affecting cells even early in the cell culture. Our results suggest that when 5-FU is immobilized in the HA hydrogel array on the bilayer membrane as a drug patch, it is possible to control the drug concentration, to release it continuously, and that the patch can be applied locally to the targeted tumor site and administer the drug in a time-stable manner. Therefore, the developed bilayer membrane-based HA hydrogel array patch can be considered for sustained release of the drug in biomedical applications.

Advances in Concentration Gradient Generation Approaches in a Microfluidic Device for Toxicity Analysis

This systematic review aimed to analyze the development and functionality of microfluidic concentration gradient generators (CGGs) for toxicological evaluation of different biological organisms. We searched articles using the keywords: concentration gradient generator, toxicity, and microfluidic device. Only 33 of the 352 articles found were included and examined regarding the fabrication of the microdevices, the characteristics of the CGG, the biological model, and the desired results. The main fabrication method was soft lithography, using polydimethylsiloxane (PDMS) material (91%) and SU-8 as the mold (58.3%). New technologies were applied to minimize shear and bubble problems, reduce costs, and accelerate prototyping. The Christmas tree CGG design and its variations were the most reported in the studies, as well as the convective method of generation (61%). Biological models included bacteria and nematodes for antibiotic screening, microalgae for pollutant toxicity, tumor and normal cells for, primarily, chemotherapy screening, and Zebrafish embryos for drug and metal developmental toxicity. The toxic effects of each concentration generated were evaluated mostly with imaging and microscopy techniques. This study showed an advantage of CGGs over other techniques and their applicability for several biological models. Even with soft lithography, PDMS, and Christmas tree being more popular in their respective categories, current studies aim to apply new technologies and intricate architectures to improve testing effectiveness and reduce common microfluidics problems, allowing for high applicability of toxicity tests in different medical and environmental models.

Nanocelluloses - Nanotoxicology, Safety Aspects and 3D Bioprinting

Nanocelluloses have good rheological properties that facilitate the extrusion of nanocellulose gels in micro-extrusion systems. It is considered a highly relevant characteristic that makes it possible to use nanocellulose as an ink component for 3D bioprinting purposes. The nanocelluloses assessed in this book chapter include wood nanocellulose (WNC), bacterial nanocellulose (BNC), and tunicate nanocellulose (TNC), which are often assumed to be non-toxic. Depending on various chemical and mechanical processes, both cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC) can be obtained from the three mentioned nanocelluloses (WNC, BNC, and TNC). Pre/post-treatment processes (chemical and mechanical) cause modifications regarding surface chemistry and nano-morphology. Hence, it is essential to understand whether physicochemical properties may affect the toxicological profile of nanocelluloses. In this book chapter, we provide an overview of nanotoxicology and safety aspects associated with nanocelluloses. Relevant regulatory requirements are considered. We also discuss hazard assessment strategies based on tiered approaches for safety testing, which can be applied in the early stages of the innovation process. Ensuring the safe development of nanocellulose-based 3D bioprinting products will enable full market use of these sustainable resources throughout their life cycle.

Use of xanthan gum for whole cell immobilization and its impact in bioremediation - a review

Xanthan gum is one of the exo-polysaccharides produced by bacteria and is characterized by unique non-Newtonian properties. Its structure and conformation strongly depend on the fermentation conditions and such factors as temperature and ions concentration. The properties of the xanthan gum were appreciated in the controlled drug delivery but in the crosslinked form. Due to its ability to enhance the survival rate of immobilized bacteria, the potential of a crosslinked form is promising. Unfortunately, xanthan gum crosslinking procedures often require toxic substances or harsh environmental conditions, which cannot be used in the entrapment of living cells. In this study, we summarised a crosslinking method that could potentially be modified to reduce its toxicity to living cells. Moreover, this review also includes using xanthan gum in bioremediation studies and possible utilization methods to avoid carrier accumulation in the environment.

Environmental interplay: Stromal cells and biomaterial composition influence in the glioblastoma microenvironment

Glioblastoma multiforme (GBM) is the most deadly form of brain cancer. Recurrence is common, and established therapies have not been able to significantly extend overall patient survival. One platform through which GBM research can progress is to design biomimetic systems for discovery and investigation into the mechanisms of invasion, cellular properties, as well as the efficacy of therapies. In this review, 2D and 3D GBM in vitro cultures will be discussed. We focus on the effects of biomaterial properties, interactions between stromal cells, and vascular influence on cancer cell survival and progression. This review will summarize critical findings in each of these areas and how they have led to a more comprehensive scientific understanding of GBM. STATEMENT OF SIGNIFICANCE: Glioblastoma multiforme (GBM) is the most deadly form of brain cancer. Recurrence is common, and established therapies have not been able to significantly extend overall patient survival. One platform through which GBM research can progress is to design biomimetic systems for discovery and investigation into the mechanisms of invasion, cellular properties, as well as the efficacy of therapies. In this review, 2D and 3D GBM in vitro cultures will be discussed. We focus on the effects of biomaterial properties, interactions between stromal cells and vascular influence on cancer cell survival and progression. This review will summarize critical findings in each of these areas and how they have lead to a more comprehensive scientific understanding of GBM.

Influences of the 3D microenvironment on cancer cell behaviour and treatment responsiveness: A recent update on lung, breast and prostate cancer models

The majority of in vitro studies assessing cancer treatments are performed in two-dimensional (2D) monolayers and are subsequently validated in in vivo animal models. However, 2D models fail to accurately model the tumour microenvironment. Furthermore, animal models are not directly applicable to mimic the human scenario. Three-dimensional (3D) culture models may help to address the discrepancies of 2D and animal models. When cancer cells escape the primary tumour, they can invade at distant organs building secondary tumours, called metastasis. The development of metastasis leads to a dramatic decrease in the life expectancy of patients. Therefore, 3D systems to model the microenvironment of metastasis have also been developed. Several studies have demonstrated changes in cell behaviour and gene expression when cells are cultured in 3D compared to 2D and concluded a better comparability to cells in vivo. Of special importance is the effect seen in response to anti-cancer treatments as models are built primarily to serve as drug-testing platforms. This review highlights these changes between cancer cells grown in 2D and 3D models for some of the most common cancers including lung, breast and prostate tumours. In addition to models aiming to mimic the primary tumour site, the effects of 3D cell culturing in bone metastasis models are also described. STATEMENT OF SIGNIFICANCE: Most in vitro studies in cancer research are performed in 2D and are subsequently validated in in vivo animal models. However, both models possess numerous limitations: 2D models fail to accurately model the tumour microenvironment while animal models are expensive, time-consuming and can differ considerably from humans. It is accepted that the cancer microenvironment plays a critical role in the disease, thus, 3D models have been proposed as a potential solution to address the discrepancies of 2D and animal models. This review highlights changes in cell behaviour, including proliferation, gene expression and chemosensitivity, between cancer cells grown in 2D and 3D models for some of the most common cancers including lung, breast and prostate cancer as well as bone metastasis.

Hyaluronic acid-based hydrogels to study cancer cell behaviors

Hyaluronic acid (HA) is a natural polysaccharide and a key component of the extracellular matrix (ECM) in many tissues. Therefore, HA-based biomaterials are extensively utilized to create three dimensional ECM mimics to study cell behaviors in vitro. Specifically, derivatives of HA have been commonly used to fabricate hydrogels with controllable properties. In this review, we discuss the various chemistries employed to fabricate HA-based hydrogels as a tunable matrix to mimic the cancer microenvironment and subsequently study cancer cell behaviors in vitro. These include Michael-addition reactions, photo-crosslinking, carbodiimide chemistry, and Diels-Alder chemistry. The utility of these HA-based hydrogels to examine cancer cell behaviors such as proliferation, migration, and invasion in vitro in various types of cancer are highlighted. Overall, such hydrogels provide a biomimetic material-based platform to probe cell-matrix interactions in cancer cells in vitro and study the mechanisms associated with cancer progression.

A novel platform for drug testing: Biomimetic three-dimensional hyaluronic acid-based scaffold seeded with human hepatocarcinoma cells

Hepatic cancer is one of the most widespread maladies worldwide that requires urgent therapies and thus reliable means for testing anti-cancer drugs. The switch from two-dimensional (2D) to three-dimensional (3D) cell cultures produced an improvement in the in vitro outcomes for testing anti-cancer drugs. We aimed to develop a novel hyaluronic acid (HA)-based 3D cell model of human hepatocellular carcinoma (HepG2 cells) for drug testing and to assess comparatively in 3D vs. 2D, the cytotoxicity and the apoptotic response to the anti-tumor agent, cisplatin. The 3D model was developed by seeding HepG2 cells in a HA/poly(methylvinylether-alt-maleic acid) (HA³P50)-based scaffold. Compared to 2D, the cells grown in the HA³P50 scaffold proliferate into larger-cellular aggregates that exhibit liver-like functions by controlling the release of hepatocyte-specific biomarkers (albumin, urea, bile acids, transaminases) and the synthesis of cytochrome-P450 (CYP)7A1 enzyme. Also, growing the cells in the scaffold sensitize the hepatocytes to the anti-tumor effect of cisplatin, by a mechanism involving the activation of ERK/p38α-MAPK and dysregulation of NF-kB/STAT3/Bcl-2 pathways. In conclusion, the newly developed HA-based 3D model is suitable for chemotherapeutic drug testing on hepatocellular carcinoma. Moreover, the system can be adapted and employed as experimental platform functioning as a proper tissue/tumor surrogate.

Pulmonary tissue-mimetic hydrogel niches for small cell lung cancer cell culture

Although small cell lung cancer (SCLC) is characterized by early metastasis and high resistance to most anti-cancer therapeutics, resulting in poor prognosis, surgical treatment is unavailable for most patients. Instead, clinical treatment for SCLC patients relies largely on chemotherapy. Therefore, an analysis platform supporting research into the physiology of SCLC cells and novel anti-cancer drugs is strongly needed. Decellularized extracellular matrix (dECM) hydrogel is a promising candidate cell-culture system that could provide a tissue-specific environment. However, dECM-based hydrogels have limited property control, poor mechanical properties, and loss of components during decellularization. In this study, porcine decellularized lung tissue and hyaluronic acid (HA) were hybridized via photopolymerization to form a pulmonary tissue-mimetic hydrogel. dECM solution was obtained by decellularization and pepsin digestion. The dECM and HA were then modified with methacrylic moieties, which produced dECM-methacrylate (dECM-MA) and HA methacrylate (HA-MA). dECM-MA/HA-MA hydrogels were fabricated by photopolymerization using a photoinitiator under UV light irradiation. The mechanical properties of the dECM-based hydrogel were compared with those of native tissue. SCLC cells (NCI-H69) were encapsulated in multiple types of dECM-based hydrogels, and they exhibited higher cell proliferation, drug resistance, and CD44 expression in the presence of dECM-MA and HA-MA than in the control condition.

The Combination of Cell Cultured Technology and In Silico Model to Inform the Drug Development

Human-derived in vitro models can provide high-throughput efficacy and toxicity data without a species gap in drug development. Challenges are still encountered regarding the full utilisation of massive data in clinical settings. The lack of translated methods hinders the reliable prediction of clinical outcomes. Therefore, in this study, in silico models were proposed to tackle these obstacles from in vitro to in vivo translation, and the current major cell culture methods were introduced, such as human-induced pluripotent stem cells (hiPSCs), 3D cells, organoids, and microphysiological systems (MPS). Furthermore, the role and applications of several in silico models were summarised, including the physiologically based pharmacokinetic model (PBPK), pharmacokinetic/pharmacodynamic model (PK/PD), quantitative systems pharmacology model (QSP), and virtual clinical trials. These credible translation cases will provide templates for subsequent in vitro to in vivo translation. We believe that synergising high-quality in vitro data with existing models can better guide drug development and clinical use.

Engineering Vascularized Organoid-on-a-Chip Models

Recreating human organ-level function in vitro is a rapidly evolving field that integrates tissue engineering, stem cell biology, and microfluidic technology to produce 3D organoids. A critical component of all organs is the vasculature. Herein, we discuss general strategies to create vascularized organoids, including common source materials, and survey previous work using vascularized organoids to recreate specific organ functions and simulate tumor progression. Vascularization is not only an essential component of individual organ function but also responsible for coupling the fate of all organs and their functions. While some success in coupling two or more organs together on a single platform has been demonstrated, we argue that the future of vascularized organoid technology lies in creating organoid systems complete with tissue-specific microvasculature and in coupling multiple organs through a dynamic vascular network to create systems that can respond to changing physiological conditions.

Hydrogels to engineer tumor microenvironments in vitro

Illustration of engineered hydrogel to recapitulate aspects of the tumor microenvironment.

Three-Dimensional Culture System of Cancer Cells Combined with Biomaterials for Drug Screening

Simple Summary

For the research and development of drug discovery, it is of prime importance to construct the three-dimensional (3D) tissue models in vitro. To this end, the enhancement design of cell function and activity by making use of biomaterials is essential. In this review, 3D culture systems of cancer cells combined with several biomaterials for anticancer drug screening are introduced.

Abstract

Anticancer drug screening is one of the most important research and development processes to develop new drugs for cancer treatment. However, there is a problem resulting in gaps between the in vitro drug screening and preclinical or clinical study. This is mainly because the condition of cancer cell culture is quite different from that in vivo. As a trial to mimic the in vivo cancer environment, there has been some research on a three-dimensional (3D) culture system by making use of biomaterials. The 3D culture technologies enable us to give cancer cells an in vitro environment close to the in vivo condition. Cancer cells modified to replicate the in vivo cancer environment will promote the biological research or drug discovery of cancers. This review introduces the in vitro research of 3D cell culture systems with biomaterials in addition to a brief summary of the cancer environment.

Breast cancer cells grown on hyaluronic acid-based scaffolds as 3D in vitro model for electroporation

Nowadays, electroporation (EP) represents a promising method for the intracellular delivery of anticancer drugs. To setting up the process, the EP efficiency is usually evaluated by using cell suspension and adherent cell cultures that are not representative of the in vivo conditions. Indeed, cells are surrounded by extracellular matrix (ECM) whose composition and physical characteristics are different for each tissue. So, various three-dimensional (3D) in vitro models, such as spheroids and hydrogel-based cultures, have been proposed to mimic the tumour microenvironment. Herein, a 3D breast cancer in vitro model has been proposed. HCC1954 cells were seeded on crosslinked and lyophilized matrices composed of hyaluronic acid (HA) and ionic complementary self-assembling peptides (SAPs) already known to provide a fibrous structure mimicking collagen network. Herein, SAPs were functionalized with laminin derived IKVAV adhesion motif. Cultures were characterized by spheroids surrounded by ECM produced by cancer cells as demonstrated by collagen1a1 and laminin B1 transcripts. EP was carried out on both 2D and 3D cultures: a sequence of 8 voltage pulses at 5 kHz with different amplitude was applied using a plate electrode. Cell sensitivity to EP seemed to be modulated by the presence of ECM and the different cell organization. Indeed, cells cultured on HA-IKVAV were more sensitive than those treated in 2D and HA cultures, in terms of both cell membrane permeabilization and viability. Collectively, our results suggest that HA-IKVAV cultures may represent an interesting model for EP studies. Further studies will be needed to elucidate the influence of ECM composition on EP efficiency.

Tumor Cell Behavior in Porous Hydrogels: Effect of Application Technique and Doxorubicin Treatment

The effect of porosity on diffusion characteristics of scaffolds and invasive capacity of MCF-7 and PC-3 tumor cells was studied for gelatin hydrogels. According to MTS test results, the efficiency of population of a macroporous cryogel by cells applied by different techniques increased in the following order: migration from the monolayer<surface adhesion<<injection. Tumor cells in the cryogel differed by the migration and aggregation activity; injection route ensured a more uniform and dense population. In the cryogel-based culture, the cytotoxic effect of doxorubicin was 3-lower than in monolayer culture, which can be explained by supporting effect of the scaffold on cell growth and clustering. The results are of interest for the creation of tumor models and grafts with controlled properties.

Cell-derived extracellular vesicles can be used as a biomarker reservoir for glioblastoma tumor subtyping

Glioblastoma (GBM) is one of the most aggressive solid tumors for which treatment options and biomarkers are limited. Small extracellular vesicles (sEVs) produced by both GBM and stromal cells are central in the inter-cellular communication that is taking place in the tumor bulk. As tumor sEVs are accessible in biofluids, recent reports have suggested that sEVs contain valuable biomarkers for GBM patient diagnosis and follow-up. The aim of the current study was to describe the protein content of sEVs produced by different GBM cell lines and patient-derived stem cells. Our results reveal that the content of the sEVs mirrors the phenotypic signature of the respective GBM cells, leading to the description of potential informative sEV-associated biomarkers for GBM subtyping, such as CD44. Overall, these data could assist future GBM in vitro studies and provide insights for the development of new diagnostic and therapeutic methods as well as personalized treatment strategies.

3D bioprinted glioma cell-laden scaffolds enriching glioma stem cells via epithelial-mesenchymal transition

Glioma stem cells (GSCs) are thought to be the root cause of tumor recurrence and drug resistance in glioma patients. In-depth study of GSCs is of great significance for developing the treatment strategies of glioma. Unfortunately, it is difficult and takes complicated process to obtain GSCs. Therefore, establishing an ideal in vitro model for enriching GSCs will greatly promote the study of GSCs. In this study, the stemness properties of glioma cells were enhanced in three-dimensional (3D) bioprinted tumor model. Furthermore, the possible molecular mechanism of GSCs enrichment: epithelial-mesenchymal transition (EMT) was explored. Compared with two-dimensional cultured cells, the proportion of GSCs and EMT-related genes in 3D cultured cells were significantly increased. Moreover, the 3D cultured glioma cells with improved stemness properties resulted in higher drug resistance in vitro and tumorigenicity in vivo. Taken together, 3D bioprinted glioma cell-laden scaffold provides a proper platform for the enrichment of GSCs and it is expected to further promote the research on glioma drug resistance. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 383-391, 2019.

Integration of Ca2+ signaling regulates the breast tumor cell response to simvastatin and doxorubicin

Recent studies have suggested that the lipid-lowering agent simvastatin holds great promise as a cancer therapeutic; it inhibits the growth of multiple tumors, including triple-negative breast cancer. Doxorubicin- and simvastatin-induced cytotoxicity has been associated with the modulation of Ca2+ signaling, but the underlying mechanisms remain incompletely understood. Here we identify how Ca2+ signaling regulates the breast tumor cell response to doxorubicin and simvastatin. These two drugs inhibit cell survival while increasing apoptosis in two human breast cancer cell lines and five primary breast tumor specimens through the modulation of Ca2+ signaling. Signal transduction and functional studies revealed that both simvastatin and doxorubicin trigger persistent cytosolic Ca2+ release, thereby stimulating the proapoptotic BIM pathway and mitochondrial Ca2+ overload, which are responsible for metabolic dysfunction and apoptosis induction. Simvastatin and doxorubicin suppress the prosurvival ERK1/2 pathway in a Ca2+-independent and Ca2+-dependent manner, respectively. In addition, reduction of the Ca2+ signal by chelation or pharmacological inhibition significantly prevents drug-mediated anticancer signaling. Unexpectedly, a scratch-wound assay indicated that these two drugs induce rapid cell migration, while inhibiting cell invasion and colony formation in a Ca2+-dependent manner. Further, the in vivo data for MDA-MB-231 xenografts demonstrate that upon chelation of Ca2+, the ability of both drugs to reduce the tumor burden was significantly reduced via caspase-3 deactivation. Our results establish a calcium-based mechanism as crucial for executing the cell death process triggered by simvastatin and doxorubicin, and suggest that combining simvastatin with doxorubicin may be an effective regimen for the treatment of breast cancer.

3D cell printing of in vitro stabilized skin model and in vivo pre-vascularized skin patch using tissue-specific extracellular matrix bioink: A step towards advanced skin tissue engineering

3D cell-printing technique has been under spotlight as an appealing biofabrication platform due to its ability to precisely pattern living cells in pre-defined spatial locations. In skin tissue engineering, a major remaining challenge is to seek for a suitable source of bioink capable of supporting and stimulating printed cells for tissue development. However, current bioinks for skin printing rely on homogeneous biomaterials, which has several shortcomings such as insufficient mechanical properties and recapitulation of microenvironment. In this study, we investigated the capability of skin-derived extracellular matrix (S-dECM) bioink for 3D cell printing-based skin tissue engineering. S-dECM was for the first time formulated as a printable material and retained the major ECM compositions of skin as well as favorable growth factors and cytokines. This bioink was used to print a full thickness 3D human skin model. The matured 3D cell-printed skin tissue using S-dECM bioink was stabilized with minimal shrinkage, whereas the collagen-based skin tissue was significantly contracted during in vitro tissue culture. This physical stabilization and the tissue-specific microenvironment from our bioink improved epidermal organization, dermal ECM secretion, and barrier function. We further used this bioink to print 3D pre-vascularized skin patch able to promote in vivo wound healing. In vivo results revealed that endothelial progenitor cells (EPCs)-laden 3D-printed skin patch together with adipose-derived stem cells (ASCs) accelerates wound closure, re-epithelization, and neovascularization as well as blood flow. We envision that the results of this paper can provide an insightful step towards the next generation source for bioink manufacturing.

Peptide and peptide-carbon nanotube hydrogels as scaffolds for tissue & 3D tumor engineering

The use of hybrid self-assembling peptide (EFK8)-carbon nanotube (SWNT) hydrogels for tissue engineering and in vitro 3D cancer spheroid formation is reported. These hybrid hydrogels are shown to enhance the attachment, spreading, proliferation and movement of NIH-3T3 cells relative to that observed using EFK8-only hydrogels. After five days, ∼30% more cells are counted when the hydrogel contains SWNTs. Also, 3D encapsulation of these cells when injected in hydrogels does not adversely affect their behavior. Compressive modulus measurements and microscopic examination suggest that SWNTs have this beneficial effect by providing sites for cell anchorage, spreading and movement rather than by increasing hydrogel stiffness. This shows that the cells have a particular interaction with SWNTs not shared with EFK8 nanofibers despite a similar morphology. The effect of EFK8 and EFK8-SWNT hydrogels on A549 lung cancer cell behavior is also investigated. Increasing stiffness of EFK8-only hydrogels from about 44 Pa to 104 Pa promotes a change in A549 morphology from spheroidal to a stretched one similar to migratory phenotype. EFK8-SWNT hydrogels also promote a stretched morphology, but at lower stiffness. These results are discussed in terms of the roles of both microenvironment stiffness and cell-scaffold adhesion in cancer cell invasion. Overall, this study demonstrates that applications of peptide hydrogels in vitro can be expanded by incorporating SWNTs into their structure which further provides insight into cell-biomaterial interactions.

STATEMENT OF SIGNIFICANCE

For the first time we used hybrid self-assembling peptide-carbon nanotube hybrid hydrogels (that we have recently introduced briefly in the "Carbon" journal in 2014) for tissue engineering and 3D tumor engineering. We showed the potential of these hybrid hydrogels to enhance the efficiency of the peptide hydrogels for tissue engineering application in terms of cell behavior (cell attachment, spreading and migration). This opens up new rooms for the peptide hydrogels and can expand their applications. Also our system (peptide and peptide-CNT hydrogels) was used for cancer cell spheroid formation showing the effect of both tumor microenvironment stiffness and cell-scaffold adhesion on cancer cell invasion. This was only possible based on the presence of CNTs in the hydrogel while the stiffness kept constant. Finally it should be noted that these hybrid hydrogels expand applications of peptide hydrogels through enhancing their capabilities and/or adding new properties to them.

Application of Synthetic Polymeric Scaffolds in Breast Cancer 3D Tissue Cultures and Animal Tumor Models

Preparation of three-dimensional (3D) porous scaffolds from synthetic polymers is a challenge to most laboratories conducting biomedical research. Here, we present a handy and cost-effective method to fabricate polymeric hydrogel and porous scaffolds using poly(lactic-co-glycolic) acid (PLGA) or polycaprolactone (PCL). Breast cancer cells grown on 3D polymeric scaffolds exhibited distinct survival, morphology, and proliferation compared to those on 2D polymeric surfaces. Mammary epithelial cells cultured on PLGA- or PCL-coated slides expressed extracellular matrix (ECM) proteins and their receptors. Estrogen receptor- (ER-) positive T47D breast cancer cells are less sensitive to 4-hydroxytamoxifen (4-HT) treatment when cultured on the 3D porous scaffolds than in 2D cultures. Finally, cancer cell-laden polymeric scaffolds support consistent tumor formation in animals and biomarker expression as seen in human native tumors. Our data suggest that the porous synthetic polymer scaffolds satisfy the basic requirements for 3D tissue cultures both in vitro and in vivo. The scaffolding technology has appealing potentials to be applied in anticancer drug screening for a better control of the progression of human cancers.

Evaluation by quantitative image analysis of anticancer drug activity on multicellular spheroids grown in 3D matrices

Pharmacological evaluation of anticancer drugs using 3D in vitro models provides invaluable information for predicting in vivo activity. Artificial matrices are currently available that scale up and increase the power of such 3D models. The aim of the present study was to propose an efficient and robust imaging and analysis pipeline to assess with quantitative parameters the efficacy of a particular cytotoxic drug. HCT116 colorectal adenocarcinoma tumor cell multispheres were grown in a 3D physiological hyaluronic acid matrix. 3D microscopy was performed with structured illumination, whereas image processing and feature extraction were performed with custom analysis tools. This procedure makes it possible to automatically detect spheres in a large volume of matrix in 96-well plates. It was used to evaluate drug efficacy in HCT116 spheres treated with different concentrations of topotecan, a DNA topoisomerase inhibitor. Following automatic detection and quantification, changes in cluster size distribution with a topotecan concentration-dependent increase of small clusters according to drug cytotoxicity were observed. Quantitative image analysis is thus an effective means to evaluate and quantify the cytotoxic and cytostatic activities of anticancer drugs on 3D multicellular models grown in a physiological matrix.

Polymeric Biomaterials for In Vitro Cancer Tissue Engineering and Drug Testing Applications

Biomimetic polymers and materials have been widely used in tissue engineering for regeneration and replication of diverse types of both normal and diseased tissues. Cancer, being a prevalent disease throughout the world, has initiated substantial interest in the creation of tissue-engineered models for anticancer drug testing. The development of these in vitro three-dimensional (3D) culture models using novel biomaterials has facilitated the investigation of tumorigenic and associated biological phenomena with a higher degree of complexity and physiological context than that provided by established two-dimensional culture models. In this review, an overview of a wide range of natural, synthetic, and hybrid biomaterials used for 3D cancer cell culture and investigation of cancer cell behavior is presented. The role of these materials in modulating cell-matrix interactions and replicating specific tumorigenic characteristics is evaluated. In addition, recent advances in biomaterial design, synthesis, and fabrication are also assessed. Finally, the advantages of incorporating polymeric biomaterials in 3D cancer models for obtaining efficacy data in anticancer drug testing applications are highlighted.

Differential toxicity of an organic PM2.5 extract to human lung cells cultured in three dimensions (3D) and monolayers

Several epidemiological studies have associated PM2.5 (particulate matter, aerodynamic diameter 2.5 µm) exposure with an increase in morbidity and mortality attributed to cardiopulmonary diseases. Based upon these observations and the growing effort to replace the use of animals in research, in vitro A549 cells cultured in three dimensions (3D), an alternative method to the use of animals, as well as monolayers were investigated to examine whether organic PM2.5 extract induced equivalent cytotoxic changes in vitro as compared to in vivo. PM2.5 was collected on Brazil Avenue, Rio de Janeiro, Brazil, from November 2010 to May 2011, except March, and analyzed for the ability to induce cytotoxicity in A549 cells using various established assays. Samples collected in all months significantly decreased viability of A549 cells using both types of cell death assays, and those collected in November showed lower cytotoxicity. It is worthwhile noting that for samples collected in all months except for April, PM2.5 induced greater toxicity in cells grown in monolayers than in 3D. Data demonstrated that cell behavior varied based upon type of culture system employed. Since the 3D cell culture mimics the architecture of in vivo tissue to a greater extent than monolayers, it is suggested that data from 3D studies resemble more closely human exposure conditions and thus may provide more reliable findings to be utilized in risk assessment following PM exposure than results obtained in traditional culture system.

Intracellular Doppler Signatures of Platinum Sensitivity Captured by Biodynamic Profiling in Ovarian Xenografts

Three-dimensional (3D) tissue cultures are replacing conventional two-dimensional (2D) cultures for applications in cancer drug development. However, direct comparisons of in vitro 3D models relative to in vivo models derived from the same cell lines have not been reported because of the lack of sensitive optical probes that can extract high-content information from deep inside living tissue. Here we report the use of biodynamic imaging (BDI) to measure response to platinum in 3D living tissue. BDI combines low-coherence digital holography with intracellular Doppler spectroscopy to study tumor drug response. Human ovarian cancer cell lines were grown either in vitro as 3D multicellular monoculture spheroids or as xenografts in nude mice. Fragments of xenografts grown in vivo in nude mice from a platinum-sensitive human ovarian cell line showed rapid and dramatic signatures of induced cell death when exposed to platinum ex vivo, while the corresponding 3D multicellular spheroids grown in vitro showed negligible response. The differences in drug response between in vivo and in vitro growth have important implications for predicting chemotherapeutic response using tumor biopsies from patients or patient-derived xenografts.

Application of a microfluidic-based perivascular tumor model for testing drug sensitivity in head and neck cancers and toxicity in endothelium

A drug sensitivity test prior to clinical treatment is necessary for individualized cancer therapy.

Bioengineering three-dimensional culture model of human lung cancer cells: an improved tool for screening EGFR targeted inhibitors

Bioengineering a three-dimensional culture model of human lung cancer cells for screening EGFR targeted inhibitors.

Silibinin affects tumor cell growth because of reduction of stemness properties and induction of apoptosis in 2D and 3D models of MDA-MB-468

Silibinin, with a strong antioxidant activity and a weak cytotoxic property, is considered a candidate for cancer prevention. As there is no information on its effect on breast cancer tumor-initiating cells [cancer stem cells (CSCs)] in a 3D culture model, which more closely mimic natural tissues, we carried out this study to determine whether silibinin can target breast CSCs in MDA-MB-468 cells cultured under 3D and 2D conditions. Silibinin was added to culture medium of MDA-MB-468 at a half maximal inhibitory concentration (IC50) dose in 2D and 3D models. Then, stemness properties were assessed using colony and sphere-formation tests. Flow cytometry and real-time PCR were used to determine the different expression levels of stem cell-related marker at protein and mRNA levels under both culture conditions. Our results showed that silibinin inhibits cell growth in a dose-dependent manner by induction of apoptosis, alteration of the cell cycle, reduction of stemness properties and function, and induction of tumoral differentiation. The mechanism of silibinin action and also the response of tumor cells differed when cells were cultured in a 3D model compared with a 2D model. Silibinin may potentially target breast CSCs. Moreover, tumor-initiating cells are more sensitive to silibinin in a 3D culture than in a 2D culture.

Life in 3D is never flat: 3D models to optimise drug delivery

The development of safe, effective and patient-acceptable drug products is an expensive and lengthy process and the risk of failure at different stages of the development life-cycle is high. Improved biopharmaceutical tools which are robust, easy to use and accurately predict the in vivo response are urgently required to help address these issues. In this review the advantages and challenges of in vitro 3D versus 2D cell culture models will be discussed in terms of evaluating new drug products at the pre-clinical development stage. Examples of models with a 3D architecture including scaffolds, cell-derived matrices, multicellular spheroids and biochips will be described. The ability to simulate the microenvironment of tumours and vital organs including the liver, kidney, heart and intestine which have major impact on drug absorption, distribution, metabolism and toxicity will be evaluated. Examples of the application of 3D models including a role in formulation development, pharmacokinetic profiling and toxicity testing will be critically assessed. Although utilisation of 3D cell culture models in the field of drug delivery is still in its infancy, the area is attracting high levels of interest and is likely to become a significant in vitro tool to assist in drug product development thus reducing the requirement for unnecessary animal studies.

The use of collagen-based scaffolds to simulate prostate cancer bone metastases with potential for evaluating delivery of nanoparticulate gene therapeutics

Prostate cancer bone metastases are a leading cause of cancer-related death in men with current treatments offering only marginally improved rates of survival. Advances in the understanding of the genetic basis of prostate cancer provide the opportunity to develop gene-based medicines capable of treating metastatic disease. The aim of this work was to establish a 3D cell culture model of prostate cancer bone metastasis using collagen-based scaffolds, to characterise this model, and to assess the potential of the model to evaluate delivery of gene therapeutics designed to target bone metastases. Two prostate cancer cell lines (PC3 and LNCaP) were cultured in 2D standard culture and compared to 3D cell growth on three different collagen-based scaffolds (collagen and composites of collagen containing either glycosaminoglycan or nanohydroxyapatite). The 3D model was characterised for cell proliferation, viability and for matrix metalloproteinase (MMP) enzyme and Prostate Specific Antigen (PSA) secretion. Chemosensitivity to docetaxel treatment was assessed in 2D in comparison to 3D. Nanoparticles (NPs) containing siRNA formulated using a modified cyclodextrin were delivered to the cells on the scaffolds and gene silencing was quantified. Both prostate cancer cell lines actively infiltrated and proliferated on the scaffolds. Cell culture in 3D resulted in reduced levels of MMP1 and MMP9 secretion in PC3 cells. In contrast, LNCaP cells grown in 3D secreted elevated levels of PSA, particularly on the scaffold composed of collagen and glycosaminoglycans. Both cell lines grown in 3D displayed increased resistance to docetaxel treatment. The cyclodextrin.siRNA nanoparticles achieved cellular uptake and knocked down the endogenous GAPDH gene in the 3D model. In conclusion, development of a novel 3D cell culture model of prostate cancer bone metastasis has been initiated resulting, for the first time, in the successful delivery of gene therapeutics in a 3D in vitro model. Further enhancement of this model will help elucidate the pathogenesis of prostate cancer and also accelerate the design of effective therapies which can penetrate into the bone microenvironment for prostate cancer therapy.

Life is three dimensional-as in vitro cancer cultures should be

For many decades, fundamental cancer research has relied on two-dimensional in vitro cell culture models. However, these provide a poor representation of the complex three-dimensional (3D) architecture of living tissues. The more recent 3D culture systems, which range from ridged scaffolds to semiliquid gels, resemble their natural counterparts more closely. The arrangement of the cells in 3D systems allows better cell-cell interaction and facilitates extracellular matrix secretion, with concomitant effects on gene and protein expression and cellular behavior. Many studies have reported differences between 3D and 2D systems as regards responses to therapeutic agents and pivotal cellular processes such as cell differentiation, morphology, and signaling pathways, demonstrating the importance of 3D culturing for various cancer cell lines.

Prediction of individual response to anticancer therapy: historical and future perspectives

Since the introduction of chemotherapy for cancer treatment in the early 20th century considerable efforts have been made to maximize drug efficiency and at the same time minimize side effects. As there is a great interpatient variability in response to chemotherapy, the development of predictive biomarkers is an ambitious aim for the rapidly growing research area of personalized molecular medicine. The individual prediction of response will improve treatment and thus increase survival and life quality of patients. In the past, cell cultures were used as in vitro models to predict in vivo response to chemotherapy. Several in vitro chemosensitivity assays served as tools to measure miscellaneous endpoints such as DNA damage, apoptosis and cytotoxicity or growth inhibition. Twenty years ago, the development of high-throughput technologies, e.g. cDNA microarrays enabled a more detailed analysis of drug responses. Thousands of genes were screened and expression levels were correlated to drug responses. In addition, mutation analysis became more and more important for the prediction of therapeutic success. Today, as research enters the area of -omics technologies, identification of signaling pathways is a tool to understand molecular mechanism underlying drug resistance. Combining new tissue models, e.g. 3D organoid cultures with modern technologies for biomarker discovery will offer new opportunities to identify new drug targets and in parallel predict individual responses to anticancer therapy. In this review, we present different currently used chemosensitivity assays including 2D and 3D cell culture models and several -omics approaches for the discovery of predictive biomarkers. Furthermore, we discuss the potential of these assays and biomarkers to predict the clinical outcome of individual patients and future perspectives.

Microscale screening systems for 3D cellular microenvironments: platforms, advances, and challenges

The increasing interest in studying cells using more in vivo-like three-dimensional (3D) microenvironments has created a need for advanced 3D screening platforms with enhanced functionalities and increased throughput. 3D screening platforms that better mimic in vivo microenvironments with enhanced throughput would provide more in-depth understanding of the complexity and heterogeneity of microenvironments. The platforms would also better predict the toxicity and efficacy of potential drugs in physiologically relevant conditions. Traditional 3D culture models (e.g., spinner flasks, gyratory rotation devices, non-adhesive surfaces, polymers) were developed to create 3D multicellular structures. However, these traditional systems require large volumes of reagents and cells, and are not compatible with high-throughput screening (HTS) systems. Microscale technology offers the miniaturization of 3D cultures and allows efficient screening of various conditions. This review will discuss the development, most influential works, and current advantages and challenges of microscale culture systems for screening cells in 3D microenvironments.

Direct effect of bevacizumab on glioblastoma cell lines in vitro

Bevacizumab is a humanized monoclonal antibody directed against the pro-angiogenic factor vascular and endothelial growth factor-A (VEGF-A) used in the treatment of glioblastomas. Although most patients respond initially to this treatment, studies have shown that glioblastomas eventually recur. Several non-mutually exclusive theories based on the anti-angiogenic effect of bevacizumab have been proposed to explain these mechanisms of resistance. In this report, we studied whether bevacizumab can act directly on malignant glioblastoma cells. We observe changes in the expression profiles of components of the VEGF/VEGF-R pathway and in the response to a VEGF-A stimulus following bevacizumab treatment. In addition, we show that bevacizumab itself acts on glioblastoma cells by activating the Akt and Erks survival signaling pathways. Bevacizumab also enhances proliferation and invasiveness of glioblastoma cells in hyaluronic acid hydrogel. We propose that the paradoxical effect of bevacizumab on glioblastoma cells could be due to changes in the VEGF-A-dependent autocrine loop as well as in the intracellular survival pathways, leading to the enhancement of tumor aggressiveness. Investigation of how bevacizumab interacts with glioblastoma cells and the resulting downstream signaling pathways will help targeting populations of resistant glioblastoma cells.

β-Catenin-regulated ALDH1A1 is a target in ovarian cancer spheroids

Cancer cells form three dimensional (3D) multicellular aggregates (or spheroids) under non-adherent culture conditions. In ovarian cancer (OC), spheroids serve as a vehicle for cancer cell dissemination in the peritoneal cavity, protecting cells from environmental stress-induced anoikis. To identify new targetable molecules in OC spheroids, we investigated gene expression profiles and networks upregulated in three dimensional (3D) versus traditional monolayer culture conditions. We identified ALDH1A1, a cancer stem cell marker as being overexpressed in OC spheroids and directly connected to key elements of the β-catenin pathway. B-catenin function and ALDH1A1 expression were increased in OC spheroids vs. monolayers and in successive spheroid generations, suggesting that 3D aggregates are enriched in cells with stem cell characteristics. B-catenin knockdown decreased ALDH1A1 expression levels and β-catenin coimmunoprecipitated with the ALDH1A1 promoter, suggesting that ALDH1A1 is a direct β-catenin target. Both siRNA mediated β-catenin knockdown and A37, a novel ALDH1A1 small molecule enzymatic inhibitor described here for the first time, disrupted OC spheroid formation and cell viability (p<0.001). B-catenin knockdown blocked tumor growth and peritoneal metastasis in an OC xenograft model. These data strongly support the role of β-catenin regulated ALDH1A1 in the maintenance of OC spheroids and propose new ALDH1A1 inhibitors targeting this cell population.

A strategy for integrating essential three-dimensional microphysiological systems of human organs for realistic anticancer drug screening

Cancer is one of the leading causes of morbidity and mortality around the world. Despite some success, traditional anticancer drugs developed to reduce tumor growth face important limitations primarily due to undesirable bone marrow and cardiovascular toxicity. Many drugs fail in clinical development after showing promise in preclinical trials, suggesting that the available in vitro and animal models are poor predictors of drug efficacy and toxicity in humans. Thus, novel models that more accurately mimic the biology of human organs are necessary for high-throughput drug screening. Three-dimensional (3D) microphysiological systems can utilize induced pluripotent stem cell technology, tissue engineering, and microfabrication techniques to develop tissue models of human tumors, cardiac muscle, and bone marrow on the order of 1 mm(3) in size. A functional network of human capillaries and microvessels to overcome diffusion limitations in nutrient delivery and waste removal can also nourish the 3D microphysiological tissues. Importantly, the 3D microphysiological tissues are grown on optically clear platforms that offer non-invasive and non-destructive image acquisition with subcellular resolution in real time. Such systems offer a new paradigm for high-throughput drug screening and will significantly improve the efficiency of identifying new drugs for cancer treatment that minimize cardiac and bone marrow toxicity.

Human decellularized adipose tissue scaffold as a model for breast cancer cell growth and drug treatments

Human adipose tissue extracellular matrix, derived through decellularization processing, has been shown to provide a biomimetic microenvironment for adipose tissue regeneration. This study reports the use of human adipose tissue-derived extracellular matrix (hDAM) scaffolds as a three-dimensional cell culturing system for the investigation of breast cancer growth and drug treatments. The hDAM scaffolds have similar extracellular matrix composition to the microenvironment of breast tissues. Breast cancer cells were cultured in hDAM scaffolds, and cell proliferation, migration, morphology, and drug responses were investigated. The growth profiles of multiple breast cancer cell lines cultured in hDAM scaffolds differed from the growth of those cultured on two-dimensional surfaces and more closely resembled the growth of xenografts. hDAM-cultured breast cancer cells also differed from those cultured on two-dimensional surfaces in terms of cell morphology, migration, expression of adhesion molecules, and sensitivity to drug treatment. Our results demonstrated that the hDAM system provides breast cancer cells with a biomimetic microenvironment in vitro that more closely mimics the in vivo microenvironment than existing two-dimensional and Matrigel three-dimensional cultures do, and thus can provide vital information for the characterization of cancer cells and screening of cancer therapeutics.

Three-dimensional lung tumor microenvironment modulates therapeutic compound responsiveness in vitro--implication for drug development

Three-dimensional (3D) cell culture is gaining acceptance in response to the need for cellular models that better mimic physiologic tissues. Spheroids are one such 3D model where clusters of cells will undergo self-assembly to form viable, 3D tumor-like structures. However, to date little is known about how spheroid biology compares to that of the more traditional and widely utilized 2D monolayer cultures. Therefore, the goal of this study was to characterize the phenotypic and functional differences between lung tumor cells grown as 2D monolayer cultures, versus cells grown as 3D spheroids. Eight lung tumor cell lines, displaying varying levels of epidermal growth factor receptor (EGFR) and cMET protein expression, were used to develop a 3D spheroid cell culture model using low attachment U-bottom plates. The 3D spheroids were compared with cells grown in monolayer for 1) EGFR and cMET receptor expression, as determined by flow cytometry, 2) EGFR and cMET phosphorylation by MSD assay, and 3) cell proliferation in response to epidermal growth factor (EGF) and hepatocyte growth factor (HGF). In addition, drug responsiveness to EGFR and cMET inhibitors (Erlotinib, Crizotinib, Cetuximab [Erbitux] and Onartuzumab [MetMab]) was evaluated by measuring the extent of cell proliferation and migration. Data showed that EGFR and cMET expression is reduced at day four of untreated spheroid culture compared to monolayer. Basal phosphorylation of EGFR and cMET was higher in spheroids compared to monolayer cultures. Spheroids showed reduced EGFR and cMET phosphorylation when stimulated with ligand compared to 2D cultures. Spheroids showed an altered cell proliferation response to HGF, as well as to EGFR and cMET inhibitors, compared to monolayer cultures. Finally, spheroid cultures showed exceptional utility in a cell migration assay. Overall, the 3D spheroid culture changed the cellular response to drugs and growth factors and may more accurately mimic the natural tumor microenvironment.

Enrichment of cancer stem cell-like cells by culture in alginate gel beads

Cancer stem cells (CSCs) are most likely the reason of cancer reoccurrence and metastasis. For further elucidation of the mechanism underlying the characteristics of CSCs, it is necessary to develop efficient culture systems to culture and expand CSCs. In this study, a three-dimensional (3D) culture system based on alginate gel (ALG) beads was reported to enrich CSCs. Two cell lines derived from different histologic origins were encapsulated in ALG beads respectively and the expansion of CSCs was investigated. Compared with two-dimensional (2D) culture, the proportion of cells with CSC-like phenotypes was significantly increased in ALG beads. Expression levels of CSC-related genes were greater in ALG beads than in 2D culture. The increase of CSC proportion after being cultured within ALG beads was further confirmed by enhanced tumorigenicity in vivo. Moreover, increased metastasis ability and higher anti-cancer drug resistance were also observed in 3D-cultured cells. Furthermore, we found that it was hypoxia, through the upregulation of hypoxia-inducible factors (HIFs) that occurred in ALG beads to induce the increasing of CSC proportion. Therefore, ALG bead was an efficient culture system for CSC enrichment, which might provide a useful platform for CSC research and promote the development of new anti-cancer therapies targeting CSCs.

Increased Resistance of Breast, Prostate, and Embryonic Carcinoma Cells against Herpes Simplex Virus in Three-Dimensional Cultures

In previous studies we found that uveal melanoma cells grown in extracellular matrix (ECM)-containing three-dimensional (3D) cultures have increased resistance against herpes simplex virus type 1 (HSV-1)-mediated destruction relative to cells cultured without ECM. Using additional tumor cell types including MB-231 human breast cancer cells, PC-3 human prostate cancer cells, and P19 mouse embryonal carcinoma cells, we show here that tumor cell lines other than melanoma are also more resistant to HSV-1-mediated destruction in 3D cultures than cells grown in 2D. We also demonstrate here that one mechanism responsible for the increased resistance of tumor cells to HSV-1 infection in 3D cultures is an ECM-mediated inhibition of virus replication following virus entry into cells. These findings confirm and extend previous observations related to the role of the ECM in tumor resistance against HSV-1 and may lead to improved strategies of oncolytic virotherapy.