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

Effect of calcium concentration on metastasis of hepatocellular carcinoma cells cultured in alginate gel beads

Changes in sodium alginate and calcium ion concentrations have a considerable impact on the structural properties of calcium alginate gel (ALG) beads, consequently influencing the biological characteristics of the cells encapsulated within them. This study aimed to examine the effects of calcium on the metastatic potential of hepatocellular carcinoma (HCC) cells encapsulated in ALG beads. The results showed that the invasion ability of HCC cells significantly increased when they were encapsulated in beads prepared with a calcium concentration of 200 mM compared to those prepared with a calcium concentration of 50 mM. Furthermore, the expression levels of genes related to metastasis were significantly elevated in ALG beads prepared with a calcium concentration of 200 mM. Specifically, the expression of activated matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), and urokinase-type plasminogen activator system proteins was found to be high. Conversely, the expression of phosphatase and tensin homolog deleted on chromosome 10 was observed to be significantly reduced. These findings indicate that manipulating the calcium ion concentration during the fabrication of ALG beads enables the generation of three-dimensional HCC cells with varying metastatic capacities. This model offers a valuable tool for investigating the mechanisms underlying liver cancer metastasis and screening potential therapeutic drugs.

Redox modulator iron complexes trigger intrinsic apoptosis pathway in cancer cells

The emergence of multidrug resistance in cancer cells necessitates the development of new therapeutic modalities. One way cancer cells orchestrate energy metabolism and redox homeostasis is through overloaded iron pools directed by iron regulatory proteins, including transferrin. Here, we demonstrate that targeting redox homeostasis using nitrogen-based heterocyclic iron chelators and their iron complexes efficiently prevents the proliferation of liver cancer cells (EC50: 340 nM for IITK4003) and liver cancer 3D spheroids. These iron complexes generate highly reactive Fe(IV)=O species and accumulate lipid peroxides to promote oxidative stress in cells that impair mitochondrial function. Subsequent leakage of mitochondrial cytochrome c activates the caspase cascade to trigger the intrinsic apoptosis pathway in cancer cells. This strategy could be applied to leverage the inherent iron overload in cancer cells to selectively promote intrinsic cellular apoptosis for the development of unique iron-complex-based anticancer therapeutics.

A Novel 3D Culture Scaffold to Shorten Development Time for Multicellular Tumor Spheroids

Multicellular tumor spheroids and tumoroids are considered ideal in vitro models that reflect the features of the tumor microenvironment. Biomimetic components resembling the extracellular matrix form scaffolds to provide structure to 3-dimensional (3D) culture systems, supporting the growth of both spheroids and tumoroids. Although Matrigel has long been used to support 3D culture systems, batch variations, component complexity, and the use of components derived from tumors are complicating factors. To address these issues, we developed the ACD 3D culture system to provide better control and consistency. We evaluated spheroid and tumoroid formation using the ACD 3D culture system, including the assessment of cell viability and cancer marker expression. Under ACD 3D culture conditions, spheroids derived from cancer cell lines exhibited cancer stem cell characteristics, including a sphere-forming size and the expression of stem cell marker genes. The ACD 3D culture system was also able to support patient-derived primary cells and organoid cell cultures, displaying adequate cell growth, appropriate morphology, and resistance to oxaliplatin treatment. These spheroids could also be used for drug screening purposes. In conclusion, the ACD 3D culture system represents an efficient tool for basic cancer research and therapeutic development.

Current Advances in 3D Bioprinting for Cancer Modeling and Personalized Medicine

Tumor cells evolve in a complex and heterogeneous environment composed of different cell types and an extracellular matrix. Current 2D culture methods are very limited in their ability to mimic the cancer cell environment. In recent years, various 3D models of cancer cells have been developed, notably in the form of spheroids/organoids, using scaffold or cancer-on-chip devices. However, these models have the disadvantage of not being able to precisely control the organization of multiple cell types in complex architecture and are sometimes not very reproducible in their production, and this is especially true for spheroids. Three-dimensional bioprinting can produce complex, multi-cellular, and reproducible constructs in which the matrix composition and rigidity can be adapted locally or globally to the tumor model studied. For these reasons, 3D bioprinting seems to be the technique of choice to mimic the tumor microenvironment in vivo as closely as possible. In this review, we discuss different 3D-bioprinting technologies, including bioinks and crosslinkers that can be used for in vitro cancer models and the techniques used to study cells grown in hydrogels; finally, we provide some applications of bioprinted cancer models.

Pancreatic Tumor Microenvironment Factor Promotes Cancer Stemness via SPP1-CD44 Axis

BACKGROUND & AIMS

Tumor-microenvironment factors and cancer stem cells (CSCs) play a critical role in the aggressiveness of pancreatic cancer (PC). However, the degree to which tumor-microenvironment factors promote stemness remains unexplored. Here, we examined whether cancer-associated fibroblasts (CAFs) promote CSC features in PC.

METHODS

PC cells were treated long-term (30, 60, and 90 days) with conditioned media (CM)-derived from normal human fibroblasts (NFs) and CAFs. The stemness features of tumorsphere formation and stemness populations, along with CSCs markers, were analyzed using 2-dimensional and 3-dimensional sodium alginate bead-based co-culture models. Immunohistochemistry and immunofluorescence staining were performed for CSCs and fibroblast markers in autochthonous KrasG12D/+; Trp53R172H/+; Pdx1-Cre mice and human pancreatic tumors. Polymerase chain reaction array and gene knockdown were performed to identify the mechanism of stemness enrichment.

RESULTS

Long-term treatment of PC cells with CAF-CM enriched stemness, as indicated by significantly higher CD44+, ALDH+, and AF+ populations in PC cells. Increased tumorsphere formation and elevated CSC, self-renewal, and drug-resistance markers in CAF-CM-treated PC cells were observed. In addition, CAFs co-cultured with PC cells in the 3-dimensional model showed a substantial increase in stemness features. CD44 and α-smooth muscle actin were positively correlated and their expressions progressively increased from the early to late stages of KrasG12D/+; Trp53R172H/+; Pdx1-Cre mouse and human pancreatic tumors. Osteopontin/secreted phosphoprotein 1 was identified as the top differentially overexpressed gene in CAF-CM-treated PC cells and knockdown of osteopontin/secreted phosphoprotein 1 significantly reduced stemness characteristics in CAF-CM-treated PC cells.

CONCLUSIONS

Our data uncovered novel insight into the interplay between CAF and enrichment of stemness population through the osteopontin/secreted phosphoprotein 1-CD44 axis in PC.

A three dimensional in vivo model of breast cancer using a thermosensitive chitosan-based hydrogel and 4 T1 cell line in Balb/c

The two-dimensional (2D) models of breast cancer still exhibit a limited success. Whereas, three-dimensional (3D) models provide more similar conditions to the tumor for growth of cancer cells. In this regard, a 3D in vivo model of breast cancer using 4 T1 cells and chitosan-based thermosensitive hydrogel were designed. Chitosan/β-glycerol phosphate hydrogel (Ch/β-GP) was prepared with a final ratio of 2% and 10%. The hydrogel properties were examined by Fourier transformed infrared spectroscopy, MTT assay, pH, scanning electron microscopy, and biodegradability assay. 3D model of breast cancer was induced by injection of 1 × 106 4 T1 cells in 100 μl hydrogel and 2D model by injection of 1 × 106 4 T1 cells in 100 μl phosphate-buffered saline (PBS) subcutaneously. After 3 weeks, induced tumors were evaluated by size and weight determination, ultrasound, hematoxylin- and eosin and Masson's trichrome staining and evaluating of cancer stem cells with CD44 and CD24 markers. The results showed that hydrogel with physiological pH had no cytotoxicity. In 3D model, tumor size and weight increased significantly (p ≤ .001) in comparison with 2D model. Histological and ultrasound analysis showed that 3D tumor model was more similar to breast cancer. Expression of CD44 and CD24 markers in the 3D model was more than 2D model (p ≤ .001). This 3D in vivo model of breast cancer mimicked native tumor and showed malignant tissue properties. Therefore, the use of such models can be effective in various cancer studies, especially in the field of cancer stem cells.

3D Modeling of Epithelial Tumors-The Synergy between Materials Engineering, 3D Bioprinting, High-Content Imaging, and Nanotechnology

The current statistics on cancer show that 90% of all human cancers originate from epithelial cells. Breast and prostate cancer are examples of common tumors of epithelial origin that would benefit from improved drug treatment strategies. About 90% of preclinically approved drugs fail in clinical trials, partially due to the use of too simplified in vitro models and a lack of mimicking the tumor microenvironment in drug efficacy testing. This review focuses on the origin and mechanism of epithelial cancers, followed by experimental models designed to recapitulate the epithelial cancer structure and microenvironment, such as 2D and 3D cell culture models and animal models. A specific focus is put on novel technologies for cell culture of spheroids, organoids, and 3D-printed tissue-like models utilizing biomaterials of natural or synthetic origins. Further emphasis is laid on high-content imaging technologies that are used in the field to visualize in vitro models and their morphology. The associated technological advancements and challenges are also discussed. Finally, the review gives an insight into the potential of exploiting nanotechnological approaches in epithelial cancer research both as tools in tumor modeling and how they can be utilized for the development of nanotherapeutics.

Liver extracellular matrix hydrogel-based three-dimensional culture system of HepG2 cells to enhance cancer stem cell properties

Both extracellular matrix (ECM) components and three-dimensional (3D) structure play important roles in the expression and maintenance of cancer stem cell (CSC) properties. Considering the excellent biophysical and biochemical properties of hydrogels, the objective of this study was to develop a 3D cell culture system based on liver ECM hydrogel (LEMH) to enhance CSC properties. Results showed that LEMH was devoid of cellular materials but contained the main components of the liver ECM. HepG2 hepatocellular carcinoma cells cultured in LEMH displayed cluster growth and formed multilayer 3D cell structures with increased expression of hepatocyte-specific genes compared to two-dimensional (2D) cells. In addition, enhanced CSC characteristics, including migration, self-renewal and drug-resistance, were observed in 3D cells. More importantly, inhibitory effects of epigallocatechin gallate on CSC self-renewal and metastatic characteristics were observed, confirming the applicability of the LEMH-based 3D model for the research and development of CSC-specific drugs. These findings suggest that LEMH-based 3D culture offers a simple and efficient platform to enhance CSC properties in vitro, thereby providing a novel approach for exploring CSC-specific agents and chemotherapeutic drugs.

Biomaterial-based platforms for cancer stem cell enrichment and study

Cancer stem cells (CSCs) are a relatively rare subpopulation of tumor cell with self-renewal and tumorigenesis capabilities. CSCs are associated with cancer recurrence, progression, and chemoradiotherapy resistance. Establishing a reliable platform for CSC enrichment and study is a prerequisite for understanding the characteristics of CSCs and discovering CSC-related therapeutic strategies. Certain strategies for CSC enrichment have been used in laboratory, particularly fluorescence-activated cell sorting (FACS) and mammosphere culture. However, these methods fail to recapitulate the in vivo chemical and physical conditions in tumors, thus potentially decreasing the malignancy of CSCs in culture and yielding unreliable research results. Accumulating research suggests the promise of a biomaterial-based three-dimensional (3D) strategy for CSC enrichment and study. This strategy has an advantage over conventional methods in simulating the tumor microenvironment, thus providing a more effective and predictive model for CSC laboratory research. In this review, we first briefly discuss the conventional methods for CSC enrichment and study. We then summarize the latest advances and challenges in biomaterial-based 3D CSC platforms. Design strategies for materials, morphology, and chemical and physical cues are highlighted to provide direction for the future construction of platforms for CSC enrichment and study.

The Role of Biomimetic Hypoxia on Cancer Cell Behaviour in 3D Models: A Systematic Review

Simple Summary

Cancer remains one of the leading causes of death worldwide. The advancements in 3D tumour models provide in vitro test-beds to study cancer growth, metastasis and response to therapy. We conducted this systematic review on existing experimental studies in order to identify and summarize key biomimetic tumour microenvironmental features which affect aspects of cancer biology. The review noted the significance of in vitro hypoxia and 3D tumour models on epithelial to mesenchymal transition, drug resistance, invasion and migration of cancer cells. We highlight the importance of various experimental parameters used in these studies and their subsequent effects on cancer cell behaviour.

Abstract

The development of biomimetic, human tissue models is recognized as being an important step for transitioning in vitro research findings to the native in vivo response. Oftentimes, 2D models lack the necessary complexity to truly recapitulate cellular responses. The introduction of physiological features into 3D models informs us of how each component feature alters specific cellular response. We conducted a systematic review of research papers where the focus was the introduction of key biomimetic features into in vitro models of cancer, including 3D culture and hypoxia. We analysed outcomes from these and compiled our findings into distinct groupings to ascertain which biomimetic parameters correlated with specific responses. We found a number of biomimetic features which primed cancer cells to respond in a manner which matched in vivo response.

Cancer Stem Cell Microenvironment Models with Biomaterial Scaffolds In Vitro

Defined by its potential for self-renewal, differentiation and tumorigenicity, cancer stem cells (CSCs) are considered responsible for drug resistance and relapse. To understand the behavior of CSC, the effects of the microenvironment in each tissue are a matter of great concerns for scientists in cancer biology. However, there are many complicated obstacles in the mimicking the microenvironment of CSCs even with current advanced technology. In this context, novel biomaterials have widely been assessed as in vitro platforms for their ability to mimic cancer microenvironment. These efforts should be successful to identify and characterize various CSCs specific in each type of cancer. Therefore, extracellular matrix scaffolds made of biomaterial will modulate the interactions and facilitate the investigation of CSC associated with biological phenomena simplifying the complexity of the microenvironment. In this review, we summarize latest advances in biomaterial scaffolds, which are exploited to mimic CSC microenvironment, and their chemical and biological requirements with discussion. The discussion includes the possible effects on both cells in tumors and microenvironment to propose what the critical factors are in controlling the CSC microenvironment focusing the future investigation. Our insights on their availability in drug screening will also follow the discussion.

3D bioprinted glioma microenvironment for glioma vascularization

Glioblastoma is the most frequently diagnosed primary malignant brain tumor with unfavourable prognosis and high mortality. One of its key features is the extensive abnormal vascular network. Up to now, the mechanism of angiogenesis and the origin of tumor vascularization remain controversial. It is essential to establish an ideal preclinical tumor model to elucidate the mechanism of tumor vascularization, and the role of tumor cells in this process. In this study, both U118 cell and GSC23 cell exhibited good printability and cell proliferation. Compared with 3D-U118, 3D-GSC23 had a greater ability to form cell spheroids, to secrete vascular endothelial growth factor (VEGFA), and to form tubule-like structures in vitro. More importantly, 3D-glioma stem cells (GSC)23 cells had a greater power to transdifferentiate into functional endothelial cells, and blood vessels composed of tumor cells with an abnormal endothelial phenotype was observed in vivo. In summary, 3D bioprinted hydrogel scaffold provided a suitable tumor microenvironment (TME) for glioma cells and GSCs. This bioprinted model supported a novel TME for the research of glioma cells, especially GSCs in glioma vascularization and therapeutic targeting of tumor angiogenesis.

Application of Three-dimensional (3D) Tumor Cell Culture Systems and Mechanism of Drug Resistance

The in-vitro experimental model for the development of cancer therapeutics has always been challenging. Recently, the scientific revolution has improved cell culturing techniques by applying three dimensional (3D) culture system, which provides a similar physiologically relevant in-vivo model for studying various diseases including cancer. In particular, cancer cells exhibiting in-vivo behavior in a model of 3D cell culture is a more accurate cell culture model to test the effectiveness of anticancer drugs or characterization of cancer cells in comparison with two dimensional (2D) monolayer. This study underpins various factors that cause resistance to anticancer drugs in forms of spheroids in 3D in-vitro cell culture and also outlines key challenges and possible solutions for the future development of these systems.

Isolation and characterization of breast cancer stem cell-like phenotype by Oct4 promoter-mediated activity

Cancer stem cells (CSCs) are a small subset of cancer cells responsible for self-renewal activity, drug resistance, and tumor recurrence. CSCs have been derived from diverse tumors and cell lines. The expression of stemness markers has been identified in CSCs. Oct4 is a well-established transcription factor expressed in stem cells and CSCs. In this study, we isolated and characterized breast CSC-like cells from murine MC4-L2 cells by Oct4 promoter-mediated activity. The MC4-L2 cells were electroporated by a plasmid expressing puromycin resistance (Puro^R ) gene from the Oct4 promoter and then selected by puromycin. The isolated cells were named as the MC4-L2^puro cells and characterized for CSCs properties. Immunostaining indicated CD44^high and CD24^high phenotype for the MC4-L2 and MC4-L2^puro cells. The enhanced expression of stem cell markers was detected in the puromycin-selected cells compared with the parental cells. Moreover, the isolated cells only grew up in sphere-formed shape in low attachment plates. Serial dilution transplantation in syngeneic mouse models showed increased tumorigenicity of the MC4-L2^puro cells, as they induced new tumors when injected into the mammary fat pad as few as 10⁴ cells. In conclusion, we designed a novel genetic construct, which allows the isolation of Oct4-positive cells in a cancer population by a simple selection step in a puromycin-containing medium. Transfection of this construct into the MC4-L2 cells resulted in growing a subpopulation of cells having tumor-initiating cell characteristics. To the best of our knowledge, this is the first report on the isolation of CSC-like cells from the mouse breast cancer MC4-L2 cells.

Effects of concentration variation on the physical properties of alginate-based substrates and cell behavior in culture

Nowadays alginate capsules exhibit good biocompatibility and high permeability for nutrients and metabolic wastes making them appealing biomaterial for therapeutic cell encapsulation. Further study of the characteristics of alginate beads which are highly dependent on various environmental conditions to create an optimum microenvironment for cells is also critical. Thus, in this study, the effect of concentration variation on the physical properties of alginate-based beads and entrapped-cells behavior was analyzed. Results showed that the increase of Ca ions concentration brought about the decrease of the average diameter, prolongation of dissolution time, reduction of permeability and swelling, and a rise of crosslinking extent and shrinkage of capsules; while raising sodium alginate concentration had an opposite effect on the diameter and shrinkage. Moreover, the addition of gelatin enhanced the penetration and swelling and slowed down the shrinkage of capsules. And MC3T3-E1 cells enclosed in the particles in which the concentration of calcium chloride, sodium alginate and gelatin was 2.5%, 2.0% and 0.5% (w/v %) had preferable abilities of proliferation and higher expression of alkaline phosphatase. Overall, the ability to tailor this system to support in vitro growth of MC3T3-E1 cells might have significance for the future use of other cell types in regenerative medicine.

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.

Enrichment of cancer stem cells by agarose multi-well dishes and 3D spheroid culture

As the theory of cancer stem cells (CSCs) is maturing, CSC-targeted therapy is emerging as an important therapeutic strategy and seeking the ideal method for rapid enrichment and purification of CSCs has become crucial. So far, based on the known CSC phenotypes and biological characteristics, the methods for enrichment CSCs mainly include low adhesion culture, low oxygen culture, chemotherapy drug stimulation and side population (SP) sorting but these methods cannot realize quick enrichment of the desired CSCs. Herein, we adopt a novel method that efficiently enriches a certain amount of CSCs through agarose multi-well dishes using rubber micro-molds to make cancer cells into cell spheroids (3D). These 3D cancer cell spheroids in the proportions of expression of CSC biomarkers (single stain of CD44, CD44v6 and CD133 or double stain of both CD44 and CD133) were significantly higher than those of the conventional adherent culture (2D) using flow cytometry analysis. In addition, the expression levels of stemness transcription factors such as OCT4, NANOG and SOX2 in 3D were also significantly higher than that in 2D through Western blot (WB) and quantitative polymerase chain reaction (qPCR) assays. In addition, the CSCs in 3D could form colonies with different sizes in soft agar. In conclusion, we developed a new method to enrich some kinds of CSCs, which might be a benefit for future CSC-targeted therapy studies and anti-CSC drug screening applications.

Three-dimensional tissue culture model of human breast cancer for the evaluation of multidrug resistance

Multidrug resistance (MDR) is one of the major obstacles to improving outcomes of chemotherapy in tumour patients. However, progress has been slow to overcome this phenomenon due to the limitations of current cell/tissue models in recapitulating MDR behaviour of tumour cells in vitro. To address this issue, a more pathologically relevant, three-dimensional (3D) culture of human breast cancer cells was developed by seeding the adriamycin-resistant cells MCF-7R in silk-collagen scaffolds. The cultures of the parental cell line MCF-7 served as controls. Distinct growth profiles of MCF-7R and MCF-7 cells were observed when they were cultured in the scaffolds in comparison with those in the monolayer culture, including cell proliferation, cellular aggregate formation, and expression of drug resistance-related genes/proteins. Moreover, the 3D cultures of these cell lines especially the cultures of MCF-7R exhibited a significantly enhanced drug resistance evidenced by their increased IC₅₀ values to the anticancer drugs and improved drug efflux capability. An altered cell cycle distribution and improved percentage of breast cancer stem cell (BCSC)-like cells was also found in the present study. This might play an important role in promoting the drug-resistance production in those 3D cultures. Thus, we established improved 3D cultures of MDR human breast cancer. It would provide a robust tissue model for use to evaluate the efficacy of anticancer drugs, explore mechanisms of MDR, and enrich BCSCs in vitro.

Micropassage-embedding composite hydrogel fibers enable quantitative evaluation of cancer cell invasion under 3D coculture conditions

Cell migration and invasion are of significant importance in physiological phenomena, including wound healing and cancer metastasis. Here we propose a new system for quantitatively evaluating cancer cell invasion in a three-dimensional (3D), in vivo tissue-like environment. This system uses composite hydrogel microfibers whose cross section has a relatively soft micropassage region and that were prepared using a multilayered microfluidic device; cancer cells are encapsulated in the core and fibroblasts are seeded in the shell regions surrounding the core. Cancer cell proliferation is guided through the micropassage because of the physical restriction imposed by the surrounding solid shell regions. Quantitative analysis of cancer cell invasion is possible simply by counting the cancer cell colonies that form outside the fiber. This platform enables the evaluation of anticancer drug efficacy (cisplatin, paclitaxel, and 5-fluorouracil) based on the degree of invasion and the gene expression of cancer cells (A549 cells) with or without the presence of fibroblasts (NIH-3T3 cells). The presented hydrogel fiber-based migration assays could be useful for studying cell behaviors under 3D coculture conditions and for drug screening and evaluation.

Three-dimensional cell culture: A powerful tool in tumor research and drug discovery

In previous years, three-dimensional (3D) cell culture technology has become a focus of research in tumor cell biology, using a variety of methods and materials to mimic the in vivo microenvironment of cultured tumor cells ex vivo. These 3D tumor cells have demonstrated numerous different characteristics compared with traditional two-dimensional (2D) culture. 3D cell culture provides a useful platform for further identifying the biological characteristics of tumor cells, particularly in the drug sensitivity area of the key points of translational medicine. It promises to be a bridge between traditional 2D culture and animal experiments, and is of great importance for further research in the field of tumor biology. In the present review, previous 3D cell culture applications, focusing on anti-tumor drug susceptibility testing, are summarized.

SAHA-induced TRAIL-sensitisation of Multiple Myeloma cells is enhanced in 3D cell culture

BACKGROUND

Multiple Myeloma (MM) is currently incurable despite many novel therapies. Tumour Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) is a potential anti-tumour agent although effects as a single agent are limited. In this study, we investigated whether the Histone Deacetylase (HDAC) inhibitor SAHA can enhance TRAIL-induced apoptosis and target TRAIL resistance in both suspension culture, and 3D cell culture as a model of disseminated MM lesions that form in bone.

METHODS

The effects of SAHA and/or TRAIL in 6 Multiple Myeloma cell lines were assessed in both suspension cultures and in an Alginate-based 3D cell culture model. The effect of SAHA and/or TRAIL was assessed on apoptosis by assessment of nuclear morphology using Hoechst 33342/Propidium Iodide staining. Viable cell number was assessed by CellTiter-Glo luminescence assay, Caspase-8 and -9 activities were measured by Caspase-Glo™ assay kit. TRAIL-resistant cells were generated by culture of RPMI 8226 and NCI-H929 by acute exposure to TRAIL followed by selection of TRAIL-resistant cells.

RESULTS

TRAIL significantly induced apoptosis in a dose-dependent manner in OPM-2, RPMI 8226, NCI-H929, U266, JJN-3 MM cell lines and ADC-1 plasma cell leukaemia cells. SAHA amplified TRAIL responses in all lines except OPM-2, and enhanced TRAIL responses were both via Caspase-8 and -9. SAHA treatment induced growth inhibition that further increased in the combination treatment with TRAIL in MM cells. The co-treatment of TRAIL and SAHA reduced viable cell numbers all cell lines. TRAIL responses were further potentiated by SAHA in 3D cell culture in NCI-H929, RPMI 8226 and U266 at lower TRAIL + SAHA doses than in suspension culture. However TRAIL responses in cells that had been selected for TRAIL resistance were not further enhanced by SAHA treatment.

CONCLUSIONS

SAHA is a potent sensitizer of TRAIL responses in both TRAIL sensitive and resistant cell lines, in both suspension and 3D culture, however SAHA did not sensitise TRAIL-sensitive cell populations that had been selected for TRAIL-resistance from initially TRAIL-sensitive populations. SAHA may increase TRAIL sensitivity in insensitive cells, but not in cells that have specifically been selected for acquired TRAIL-resistance.

Effects of gelling bath on the physical properties of alginate gel beads and the biological characteristics of entrapped HepG2 cells

Optimizing alginate gel beads is necessary to support the survival, proliferation, and function of entrapped hepatocytes. In this study, gelling bath was modified by decreasing calcium ion concentration and increasing sodium ion concentration. Alginate gel beads (using 36% G sodium alginate) prepared in the modified gelling bath had more homogeneous structure and better mass transfer properties compared with the traditional gelling bath that contains only calcium ions. Moreover, alginate gel beads generated in the modified gelling bath could significantly promote the HepG2 cell proliferation and the growth of cell spheroids, and maintain the albumin secretion ability similar to alginate gel beads prepared in the traditional gelling bath with only calcium ions. The mass transfer properties and cell proliferation were similar in ALG beads with different M/G ratio (36% G and 55% G) generated in the modified gelling bath, whereas they were significantly increased compared with alginate gel beads (55% G) in traditional gelling bath. These results indicated that adjusting the gelling bath was a simple and convenient method to enhance the mass transfer properties of alginate gel beads for 3D hepatocyte culture, which might provide more hepatocytes for the bioartificial liver support system.

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.

Development of a Biomimetic Chondroitin Sulfate-modified Hydrogel to Enhance the Metastasis of Tumor Cells

Tumor metastasis with resistance to anticancer therapies is the main cause of death in cancer patients. It is necessary to develop reliable tumor metastasis models that can closely recapitulate the pathophysiological features of the native tumor tissue. In this study, chondroitin sulfate (CS)-modified alginate hydrogel beads (ALG-CS) are developed to mimic the in vivo tumor microenvironment with an abnormally increased expression of CS for the promotion of tumor cell metastasis. The modification mechanism of CS on alginate hydrogel is due to the cross-linking between CS and alginate molecules via coordination of calcium ions, which enables ALG-CS to possess significantly different physical characteristics than the traditional alginate beads (ALG). And quantum chemistry calculations show that in addition to the traditional egg-box structure, novel asymmetric egg-box-like structures based on the interaction between these two kinds of polymers are also formed within ALG-CS. Moreover, tumor cell metastasis is significantly enhanced in ALG-CS compared with that in ALG, as confirmed by the increased expression of MMP genes and proteins and greater in vitro invasion ability. Therefore, ALG-CS could be a convenient and effective 3D biomimetic scaffold that would be used to construct standardized tumor metastasis models for tumor research and anticancer drug screening.

The knee joint loose body as a source of viable autologous human chondrocytes

Loose bodies are fragments of cartilage or bone present in the synovial fluid. In the present study we assessed if loose bodies could be used as a source of autologous human chondrocytes for experimental purposes. Histochemical examination of loose bodies and differential enzymatic digestions were undertaken, the isolated cells were cultured in alginate bead microspheres and immunolocalisations were undertaken for chondrogenic markers such as aggrecan, and type II collagen. Isolated loose body cells had high viability (≥90% viable), expressed chondrogenic markers (aggrecan, type II collagen) but no type I collagen. Loose bodies may be a useful source of autologous chondrocytes of high viability.

Potential effect of matrix stiffness on the enrichment of tumor initiating cells under three-dimensional culture conditions

Cancer stem cell (CSC) or tumor initiating cell (TIC) plays an important role in tumor progression and metastasis. Biophysical forces in tumor microenvironment have an important effect on tumor formation and development. In this study, the potential effect of matrix stiffness on the biological characteristics of human head and neck squamous cell carcinoma (HNSCC) TICs, especially the enrichment of HNSCC TICs, was investigated under three-dimensional (3D) culture conditions by means of alginate gel (ALG) beads with different matrix stiffnesses. ALG beads with soft (21 kPa), moderate (70 kPa) and hard (105 kPa) stiffness were generated by changing alginate concentration. It was found that significant HNSCC TIC enrichment was achieved in the ALG beads with moderate matrix stiffness (70 kPa). The gene expression of stemness markers Oct3/4 and Nanog, TIC markers CD44 and ABCG2 was enhanced in cells under this moderate (70 kPa) stiffness. HNSCC TIC proportion was also highly enriched under moderate matrix stiffness, accompanying with higher tumorigenicity, metastatic ability and drug resistance. And it was also found that the possible molecular mechanism underlying the regulated TIC properties by matrix stiffness under 3D culture conditions was significantly different from 2D culture condition. Therefore, the results achieved in this study indicated that 3D biophysical microenvironment had an important effect on TIC characteristics and alginate-based biomimetic scaffolds could be utilized as a proper platform to investigate the interaction between tumor cells and 3D microenvironment.