Multicellular spheroids. A review on cellular aggregates in cancer research

Emerging In Vitro and In Vivo Models: Hope for the Better Understanding of Cancer Progression and Treatment

Various cancer models have been developed to aid the understanding of the underlying mechanisms of tumor development and evaluate the effectiveness of various anticancer drugs in preclinical studies. These models accurately reproduce the critical stages of tumor initiation and development to mimic the tumor microenvironment better. Using these models for target validation, tumor response evaluation, resistance modeling, and toxicity comprehension can significantly enhance the drug development process. Herein, various in vivo or animal models are presented, typically consisting of several mice and in vitro models ranging in complexity from transwell models to spheroids and CRISPR-Cas9 technologies. While in vitro models have been used for decades and dominate the early stages of drug development, they are still limited primary to simplistic tests based on testing on a single cell type cultivated in Petri dishes. Recent advancements in developing new cancer therapies necessitate the generation of complicated animal models that accurately mimic the tumor's complexity and microenvironment. Mice make effective tumor models as they are affordable, have a short reproductive cycle, exhibit rapid tumor growth, and are simple to manipulate genetically. Human cancer mouse models are crucial to understanding the neoplastic process and basic and clinical research improvements. The following review summarizes different in vitro and in vivo metastasis models, their advantages and disadvantages, and their ability to serve as a model for cancer research.

Effect of non-linear strain stiffening in eDAH and unjamming

In cell clusters, the prominent factors at play encompass contractility-based enhanced tissue surface tension and cell unjamming transition. The former effect pertains to the boundary effect, while the latter constitutes a bulk effect. Both effects share outcomes of inducing significant elongation in cells. This elongation is so substantial that it surpasses the limits of linear elasticity, thereby giving rise to additional effects. To investigate these effects, we employ atomic force microscopy (AFM) to analyze how the mechanical properties of individual cells change under such considerable elongation. Our selection of cell lines includes MCF-10A, chosen for its pronounced demonstration of the extended differential adhesion hypothesis (eDAH), and MDA-MB-436, selected due to its manifestation of cell unjamming behavior. In the AFM analyses, we observe a common trend in both cases: as elongation increases, both cell lines exhibit strain stiffening. Notably, this effect is more prominent in MCF-10A compared to MDA-MB-436. Subsequently, we employ AFM on a dynamic range of 1-200 Hz to probe the mechanical characteristics of cell spheroids, focusing on both surface and bulk mechanics. Our findings align with the results from single cell investigations. Specifically, MCF-10A cells, characterized by strong contractile tissue tension, exhibit the greatest stiffness on their surface. Conversely, MDA-MB-436 cells, which experience significant elongation, showcase their highest stiffness within the bulk region. Consequently, the concept of single cell strain stiffening emerges as a crucial element in understanding the mechanics of multicellular spheroids (MCSs), even in the case of MDA-MB-436 cells, which are comparatively softer in nature.

Relatively Rare Populations of Invasive Cells Drive Progression of Heterogeneous Tumors

Introduction

Breast tumors often display an astonishing degree of spatial and temporal heterogeneity, which are associated with cancer progression, drug resistance, and relapse. Triple-negative breast cancer (TNBC) is a particularly aggressive and heterogeneous subtype for which targeted therapies are scarce. Consequently, patients with TNBC have a poorer overall prognosis compared to other breast cancer patients. Within heterogeneous tumors, individual clonal subpopulations may exhibit differences in their rates of growth and degrees of invasiveness. We hypothesized that such phenotypic heterogeneity at the single-cell level may accelerate tumor progression by enhancing the overall growth and invasion of the entire tumor.

Methods

To test this hypothesis, we isolated and characterized clonal subpopulations with distinct morphologies and biomarker expression from the inherently heterogeneous 4T1 mouse mammary carcinoma cell line. We then leveraged a 3D microfluidic tumor model to reverse-engineer intratumoral heterogeneity and thus investigate how interactions between phenotypically distinct subpopulations affect tumor growth and invasion.

Results

We found that the growth and invasion of multiclonal tumors were largely dictated by the presence of cells with epithelial and mesenchymal traits, respectively. The latter accelerated overall tumor invasion, even when these cells comprised less than 1% of the initial population. Consistently, tumor progression was delayed by selectively targeting the mesenchymal subpopulation.

Discussion

This work reveals that highly invasive cells can dominate tumor phenotype and that specifically targeting these cells can slow the progression of heterogeneous tumors, which may help inform therapeutic approaches.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-023-00792-w.

Bioprinting Using Organ Building Blocks: Spheroids, Organoids, and Assembloids

Three-dimensional (3D) bioprinting, a promising advancement in tissue engineering technology, involves the robotic, layer-by-layer additive biofabrication of functional 3D tissue and organ constructs. This process utilizes biomaterials, typically hydrogels and living cells, following digital models. Traditional tissue engineering uses a classic triad of living cells, scaffolds, and physicochemical signals in bioreactors. A scaffold is a temporary, often biodegradable, support structure. Tissue engineering primarily falls into two categories: (i) scaffold based and (ii) scaffold free. The latter, scaffold-free 3D bioprinting, is gaining increasing popularity. Organ building blocks (OBB), capable of self-assembly and self-organization, such as tissue spheroids, organoids, and assembloids, have begun to be utilized in scaffold-free bioprinting. This article discusses the expanding range of OBB, presents the rapidly evolving collection of bioprinting and bioassembly methods using these OBB, and finally, outlines the advantages, challenges, and future perspectives of using OBB in organ printing.

Evaluating the Pharmacokinetics and Pharmacodynamics of Chemotherapeutics within a Spatial SILAC-Labeled Spheroid Model System

Tumors have considerable cellular heterogeneity that is impossible to explore with simple cell cultures. Spheroid cultures contain pathophysiological and chemical gradients similar to in vivo tumors and show complex responses to therapeutics, similar to a tumor. Using pulsed isotopic labels, we demonstrate the pronounced differential response of the proteome to the drug Regorafenib, a multikinase inhibitor, in HCT 116 spheroids. Regorafenib treatment of outer spheroids inhibits proteins involved in critical pathways such as mTOR signaling, extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) signaling, and colorectal cancer metastasis signaling, resulting in decreased proliferation and cellular apoptosis. By contrast, analysis of the treated core cells shows upregulation of MAPK1 and KRAS, possibly implicating drug resistance within these late apoptotic cells. Thus, pulsed isotopic labeling enables evaluation of the distinct proteomic responses for cells residing in the different chemical microenvironments of the spheroid. This platform promises great utility in assisting researchers' predictions of pharmacodynamic therapeutic responses within complex tumors.

The third dimension of tumor microenvironment-The importance of tumor stroma in 3D cancer models

Recent advances in the three-dimensional (3D) cancer models give rise to a plethora of new possibilities in the development of anti-cancer drug therapies and bring us closer to personalized medicine. Three-dimensional models are undoubtedly more authentic than traditional two-dimensional (2D) cell cultures. Nowadays, they are becoming preferentially used in most cancer research fields due to their more accurate biomimetic characteristics. On the contrary, they still lack the cellular and matrix complexity of the native tumor microenvironment (TME). This review focuses on the description of existing 3D models, the incorporation of TME and fluidics into these models, and their perspective in the future research. It is clear that such an improvement would need not only biological but also technical progress. Therefore, the modern approach to anti-cancer drug discovery should involve various fields.

Sophorolipid Candidates Demonstrate Cytotoxic Efficacy against 2D and 3D Breast Cancer Models

Sophorolipids are biosurfactants derived from the nonpathogenic yeasts such as Starmerella bombicola with potential efficacy in anticancer applications. Simple and cost-effective synthesis of these drugs makes them a promising alternative to traditional chemotherapeutics, pending their success in preliminary drug-screening. Drug-screening typically utilizes 2D cell monolayers due to their simplicity and ease of high-throughput assessment. However, 2D assays fail to capture the complexity and 3D context of the tumor microenvironment and have consequently been implicated in the high percentage of drugs investigated in vitro that later fail in clinical trials. Herein, we screened two sophorolipid candidates and a clinically-used chemotherapeutic, doxorubicin, on in vitro breast cancer models ranging from 2D monolayers to 3D spheroids, employing optical coherence tomography to confirm these morphologies. We calculated corresponding IC50 values for these drugs and found one of the sophorolipids to have comparable toxicities to the chemotherapeutic control. Our findings show increased drug resistance associated with model dimensionality, such that all drugs tested showed that 3D spheroids exhibited higher IC50 values than their 2D counterparts. These findings demonstrate promising preliminary data to support the use of sophorolipids as a more affordable alternative to traditional clinical interventions and demonstrate the importance of 3D tumor models in assessing drug response.

Tumor Organoid and Spheroid Models for Cervical Cancer

Cervical cancer is one of the most common malignant diseases in women worldwide. Despite the global introduction of a preventive vaccine against the leading cause of cervical cancer, human papillomavirus (HPV) infection, the incidence of this malignant disease is still very high, especially in economically challenged areas. New advances in cancer therapy, especially the rapid development and application of different immunotherapy strategies, have shown promising pre-clinical and clinical results. However, mortality from advanced stages of cervical cancer remains a significant concern. Precise and thorough evaluation of potential novel anti-cancer therapies in pre-clinical phases is indispensable for efficient development of new, more successful treatment options for cancer patients. Recently, 3D tumor models have become the gold standard in pre-clinical cancer research due to their capacity to better mimic the architecture and microenvironment of tumor tissue as compared to standard two-dimensional (2D) cell cultures. This review will focus on the application of spheroids and patient-derived organoids (PDOs) as tumor models to develop novel therapies against cervical cancer, with an emphasis on the immunotherapies that specifically target cancer cells and modulate the tumor microenvironment (TME).

Molecularly Engineered Surfactin Analogues Induce Nonapoptotic-Like Cell Death and Increased Selectivity in Multiple Breast Cancer Cell Types

Surfactin, a negatively charged amphiphilic lipopeptide biosurfactant, is synthesized by the bacterium Bacillus subtilis. It consists of a cyclic heptapeptide and an 11-15C β-hydroxy fatty acid. To probe how the modification of the molecular skeleton of surfactin influences its selectivity and activity against breast cancer, six synthetic surfactins were generated. Modifications were accomplished by conjugating amine-functionalized molecules to the Glu and Asp carboxyl moieties of the heptapeptide. The resulting synthetic surfactins provided a diverse series of molecules with differences in charge, size, and hydrophilicity. After purification and structural analysis, insights into biological activity and specificity were generated for each compound. Dose-dependent growth inhibition was determined for four tumorigenic breast cancer cell lines in monolayer and spheroid morphologies, as well as nontumorigenic fibroblasts and sheep erythrocytes, which were utilized to determine selectivity indices. Results indicated that two compounds, which have amplified anionic charge, had increased activity on breast cancer, with reduced activity on nontumorigenic fibroblasts and erythrocytes. Cationic derivative surf-ethylenediamine has increased activity on all cell lines tested. Novel correlations between dose-response activities and physicochemical properties of all compounds determined that there is a significant correlation between the critical micelle concentration and activity against multiple cell lines.

State-dependent evolutionary models reveal modes of solid tumour growth

Spatial properties of tumour growth have profound implications for cancer progression, therapeutic resistance and metastasis. Yet, how spatial position governs tumour cell division remains difficult to evaluate in clinical tumours. Here, we demonstrate that faster division on the tumour periphery leaves characteristic genetic patterns, which become evident when a phylogenetic tree is reconstructed from spatially sampled cells. Namely, rapidly dividing peripheral lineages branch more extensively and acquire more mutations than slower-dividing centre lineages. We develop a Bayesian state-dependent evolutionary phylodynamic model (SDevo) that quantifies these patterns to infer the differential division rates between peripheral and central cells. We demonstrate that this approach accurately infers spatially varying birth rates of simulated tumours across a range of growth conditions and sampling strategies. We then show that SDevo outperforms state-of-the-art, non-cancer multi-state phylodynamic methods that ignore differential sequence evolution. Finally, we apply SDevo to single-time-point, multi-region sequencing data from clinical hepatocellular carcinomas and find evidence of a three- to six-times-higher division rate on the tumour edge. With the increasing availability of high-resolution, multi-region sequencing, we anticipate that SDevo will be useful in interrogating spatial growth restrictions and could be extended to model non-spatial factors that influence tumour progression.

A bicellular fluorescent ductal carcinoma in situ (DCIS)-like tumoroid to study the progression of carcinoma: practical approaches and optimization

Recently, many types of 3D culture systems have been developed to preserve the physicochemical environment and biological characteristics of the original tumors better than the conventional 2D monolayer culture system. There are various types of models belonging to this culture, such as the culture based on non-adherent and/or scaffold-free matrices to form the tumors. Agarose mold has been widely used to facilitate tissue spheroid assembly, as it is essentially non-biodegradable, bio-inert, biocompatible, low-cost, and low-attachment material that can promote cell spheroidization. As no studies have been carried out on the development of a fluorescent bicellular tumoroid mimicking ductal carcinoma in situ (DCIS) using human cell lines, our objective was to detail the practical approaches developed to generate this model, consisting of a continuous layer of myoepithelial cells (MECs) around a previously formed in situ breast tumor. The practical approaches developed to generate a bi-cellular tumoroid mimicking ductal carcinoma in situ (DCIS), consisting of a continuous layer of myoepithelial cells (MECs) around a previously formed in situ breast tumoroid. Firstly, the optimal steps and conditions of spheroids generation using a non-adherent agarose gel were described, in particular, the appropriate medium, seeding density of each cell type and incubation period. Next, a lentiviral transduction approach to achieve stable fluorescent protein expression (integrative system) was used to characterize the different cell lines and to track tumoroid generation through immunofluorescence, the organization of the two cell types was validated, specific merits and drawbacks were compared to lentiviral transduction. Two lentiviral vectors expressing either EGFP (Enhanced Green Fluorescent Protein) or m-Cherry (Red Fluorescent Protein) were used. Various rates of a multiplicity of infection (MOI) and multiple types of antibodies (anti-p63, anti-CK8, anti-Maspin, anti-Calponin) for immunofluorescence analysis were tested to determine the optimal conditions for each cell line. At MOI 40 (GFP) and MOI 5 (m-Cherry), the signals were almost homogeneously distributed in the cells which could then be used to generate the DCIS-like tumoroids. Images of the tumoroids in agarose molds were captured with a confocal microscope Micro Zeiss Cell Observer Spinning Disk or with IncuCyte® to follow the progress of the generation. Measurement of protumoral cytokines such as IL-6, IL8 and leptin confirmed their secretion in the supernatants, indicating that the properties of our cells were not altered. Finally the advantages and disadvantages of each fluorescent approach were discussed. This model could also be used for other solid malignancies to study the complex relationship between different cells such as tumor and myoepithelial cells in various microenvironments (inflammatory, adipose and tumor, obesity, etc.). Although, this new model is well established to monitor drug screening applications and perform pharmacokinetic and pharmacodynamic analyses.

Hybrid computational models of multicellular tumour growth considering glucose metabolism

Cancer cells metabolize glucose through metabolic pathways that differ from those used by healthy and differentiated cells. In particular, tumours have been shown to consume more glucose than their healthy counterparts and to use anaerobic metabolic pathways, even under aerobic conditions. Nevertheless, scientists have still not been able to explain why cancer cells evolved to present an altered metabolism and what evolutionary advantage this might provide them. Experimental and computational models have been increasingly used in recent years to understand some of these biological questions. Multicellular tumour spheroids are effective experimental models as they replicate the initial stages of avascular solid tumour growth. Furthermore, these experiments generate data which can be used to calibrate and validate computational studies that aim to simulate tumour growth. Hybrid models are of particular relevance in this field of research because they model cells as individual agents while also incorporating continuum representations of the substances present in the surrounding microenvironment that may participate in intracellular metabolic networks as concentration or density distributions. Henceforth, in this review, we explore the potential of computational modelling to reveal the role of metabolic reprogramming in tumour growth.

Organ Chips and Visualization of Biological Systems

Organ-on-a-chip (OOC) is an emerging frontier cross-cutting science and technology developed in the past 10 years. It was first proposed by the Wyss Institute for Biologically Inspired Engineering of Harvard Medical School. It consists of a transparent flexible polymer the size of a computer memory stick, with hollow microfluidic channels lined with living human cells. Researchers used bionics methods to simulate the microenvironment of human cells on microfluidic chips, so as to realize the basic physiological functions of corresponding tissues and organs in vitro. Transparent chip materials can perform real-time visualization and high-resolution analysis of various human life processes in a way that is impossible in animal models, so as to better reproduce the microenvironment of human tissue and simulate biological systems in vitro to observe drug metabolism and other life processes. It provides innovative research systems and system solutions for in vitro bionics of biological systems. It also has gradually become a new tool for disease mechanism research and new drug development. In this chapter, we will take the current research mature single-organ-on-a-chip and multi-organ human-on-a-chip as examples; give an overview of the research background and underlying technologies in this field, especially the application of in vitro bionic models in visualized medicine; and look forward to the foreseeable future development prospects after the integration of organ-on-chip and organoid technology.

A review of challenges and prospects of 3D cell-based culture models used for studying drug induced liver injury during early phases of drug development

Drug-induced liver injury (DILI) is the leading cause of compound attrition during drug development. Over the years, a battery of in-vitro cell culture toxicity tests is being conducted to evaluate the toxicity of compounds prior to testing in laboratory animals. Two-dimensional (2D) in-vitro cell culture models are commonly used and have provided a great deal of knowledge; however, these models often fall short in mimicking natural structures of tissues in-vivo. Testing in humans is the most logical method, but unfortunately there are ethical limitations associated with human tests. To overcome these limitations better human-relevant, predictive models are required. The past decade has witnessed significant efforts towards the development of three-dimensional (3D) in-vitro cell culture models better mimicking in-vivo physiology. 3D cell culture has advantages in being representative of the interactions of cells in-vivo and when validated can act as an interphase between 2D cell culture models and in-vivo animal models. The current review seeks to provide an overview of the challenges that make biomarkers used for detection of DILI not to be sensitive enough during drug development and explore how 3D cell culture models can be used to address the gap with the current models.

A preclinical model of cutaneous melanoma based on reconstructed human epidermis

Malignant melanoma is among the tumor entities with the highest increase of incidence worldwide. To elucidate melanoma progression and develop new effective therapies, rodent models are commonly used. While these do not adequately reflect human physiology, two-dimensional cell cultures lack crucial elements of the tumor microenvironment. To address this shortcoming, we have developed a melanoma skin equivalent based on an open-source epidermal model. Melanoma cell lines with different driver mutations were incorporated into these models forming distinguishable tumor aggregates within a stratified epidermis. Although barrier properties of the skin equivalents were not affected by incorporation of melanoma cells, their presence resulted in a higher metabolic activity indicated by an increased glucose consumption. Furthermore, we re-isolated single cells from the models to characterize the proliferation state within the respective model. The applicability of our model for tumor therapeutics was demonstrated by treatment with a commonly used v-raf murine sarcoma viral oncogene homolog B (BRAF) inhibitor vemurafenib. This selective BRAF inhibitor successfully reduced tumor growth in the models harboring BRAF-mutated melanoma cells. Hence, our model is a promising tool to investigate melanoma development and as a preclinical model for drug discovery.

PRP-1, a toll-like receptor ligand, upregulates the unfolded protein response in human chondrosarcoma cells

BACKGROUND

Previous studies showed that proline-rich polypeptide (PRP-1) is a ligand for innate immunity toll-like receptors (TLR), and an inhibitor of the mammalian target of rapamycin complex 1 (mTORC1) which induces the death of chondrosarcoma cancer stem cells (CSC). The aim of this study was to investigate the effect of PRP-1 on the regulation of unfolded protein response (UPR) in human chondrosarcoma cells.

MATERIALS AND METHODS

Lysates were prepared from a monolayer (bulk or ALDH^high population), or spheroids chondrosarcoma cell cultures and treated with PRP-1 or control, followed by protein levels quantification by western blotting and mRNA expression by RT-qPCR of protein-RNA-like endoplasmic reticulum kinase (PERK), eukaryotic translation initiation factor 2α (eIF2α), activating transcription factor 4 (ATF4), CCAAT-enhancer-binding protein homologous protein (CHOP), activating transcription factor 6 (ATF6), inositol-requiring enzyme 1 (IRE1α), and X-box binding protein (XBP1).

RESULTS

The PRP-1 has been shown to increase the expression of PERK, eIF2α, ATF4, CHOP, ATF6, IRE1α, and XBP1, on both protein and mRNA levels.

CONCLUSION

PRP-1 activated UPR branches in monolayer, spheroid, and stem cell populations of human chondrosarcoma.

Preclinical assessment of synergistic efficacy of MELK and CDK inhibitors in adrenocortical cancer

BACKGROUND

Adrenocortical cancer (ACC) is a rare and aggressive cancer with dismal 5-year survival due to a lack of effective treatments. We aimed to identify a new effective combination of drugs and investigated their synergistic efficacy in ACC preclinical models.

METHODS

A quantitative high-throughput drug screening of 4,991 compounds was performed on two ACC cell lines, SW13 and NCI-H295R, based on antiproliferative effect and caspase-3/7 activity. The top candidate drugs were pairwise combined to identify the most potent combinations. The synergistic efficacy of the selected inhibitors was tested on tumorigenic phenotypes, such as cell proliferation, migration, invasion, spheroid formation, and clonogenicity, with appropriate mechanistic validation by cell cycle and apoptotic assays and protein expression of the involved molecules. We tested the efficacy of the drug combination in mice with luciferase-tagged human ACC xenografts. To study the mRNA expression of target molecules in ACC and their clinical correlations, we analyzed the Gene Expression Omnibus and The Cancer Genome Atlas.

RESULTS

We chose the maternal embryonic leucine zipper kinase (MELK) inhibitor (OTS167) and cyclin-dependent kinase (CDK) inhibitor (RGB-286638) because of their potent synergy from the pairwise drug combination matrices derived from the top 30 single drugs. Multiple publicly available databases demonstrated overexpression of MELK, CDK1/2, and partnering cyclins mRNA in ACC, which were independently associated with mortality and other adverse clinical features. The drug combination demonstrated a synergistic antiproliferative effect on ACC cells. Compared to the single-agent treatment groups, the combination treatment increased G2/M arrest, caspase-dependent apoptosis, reduced cyclins A2, B1, B2, and E2 expression, and decreased cell migration and invasion with reduced vimentin. Moreover, the combination effectively decreased Foxhead Box M1, Axin2, glycogen synthase kinase 3-beta, and β-catenin. A reduction in p-stathmin from the combination treatment destabilized microtubule assembly by tubulin depolymerization. The drug combination treatment in mice with human ACC xenografts resulted in a significantly lower tumor burden than those treated with single-agents and vehicle control groups.

CONCLUSIONS

Our preclinical study revealed a novel synergistic combination of OTS167 and RGB-286638 in ACC that effectively targets multiple molecules associated with ACC aggressiveness. A phase Ib/II clinical trial in patients with advanced ACC is therefore warranted.

Dynamic Culture of Mesenchymal Stromal/Stem Cell Spheroids and Secretion of Paracrine Factors

In recent years, conditioned medium (CM) obtained from the culture of mesenchymal stromal/stem cells (MSCs) has been shown to effectively promote tissue repair and modulate the immune response in vitro and in different animal models, with potential for application in regenerative medicine. Using CM offers multiple advantages over the implantation of MSCs themselves: 1) simpler storage, transport, and preservation requirements, 2) avoidance of the inherent risks of cell transplantation, and 3) potential application as a ready-to-go biologic product. For these reasons, a large amount of MSCs research has focused on the characterization of the obtained CM, including soluble trophic factors and vesicles, preconditioning strategies for enhancing paracrine secretion, such as hypoxia, a three-dimensional (3D) environment, and biochemical stimuli, and potential clinical applications. In vitro preconditioning strategies can increase the viability, proliferation, and paracrine properties of MSCs and therefore improve the therapeutic potential of the cells and their derived products. Specifically, dynamic cultivation conditions, such as fluid flow and 3D aggregate culture, substantially impact cellular behaviour. Increased levels of growth factors and cytokines were observed in 3D cultures of MSC grown on orbital or rotatory shaking platforms, in stirred systems, such as spinner flasks or stirred tank reactors, and in microgravity bioreactors. However, only a few studies have established dynamic culture conditions and protocols for 3D aggregate cultivation of MSCs as a scalable and reproducible strategy for CM production. This review summarizes significant advances into the upstream processing, mainly the dynamic generation and cultivation of MSC aggregates, for de CM manufacture and focuses on the standardization of the soluble factor production.

Anticancer bioactivity of zerumbone on pediatric rhabdomyosarcoma cells

PURPOSE

Natural products are generally regarded as safe and have been shown to mediate anticancer activities against a variety of cell types. Zerumbone is a natural cyclic sesquiterpene derived from the rhizome of Zingiber zerumbet, which has attracted extensive attention in the recent decade for anticancer activities. The present study investigates the in vitro effect of zerumbone on rhabdomyosarcoma cells.

METHODS

Two rhabdomyosarcoma cell lines (RD and RH30) were used as the model system. The growth inhibition of zerumbone was measured by MTT-assay, apoptosis via flow cytometry, gene expression by real-time PCR, the migration by transwell assay, and intracellular signaling by Western blotting.

RESULTS

Zerumbone shows anticancer effects on RD and RH30 cells in a dose-dependent manner via cell growth inhibition and induction of apoptosis. Exposure of RD and RH30 cells on zerumbone also resulted in a decrease of migration and downregulation of the hedgehog pathway.

CONCLUSIONS

Taken together, our study provided the first evidence that zerumbone imparted strong inhibitory and apoptotic effects on pediatric rhabdomyosarcoma cell lines and merit further investigation as a promising candidate for the anticancer therapy.

Exploring the Bio-Functional Breaking Point of Living Tissue Subjected to External Physical Pressure

Long before reaching its mechanical breaking point, a bio-system begins responding to stress at its own “bio-functional breaking point,” a phase of life activity dysfunction. However, little is known about the correlation between tissue flexibility and the conditions under which cellular response, damage, and death occur. We are now developing a new confocal microscopy-based observation method to analyze cell aggregates (spheroids) that are under physical pressure. The method concomitantly assesses cellular responses, stress levels, and cellular structure changes. Using this method, we found that the artificial suppression of the gene expression of fibronectin, a major component of the extracellular matrix, provides different mechanical characteristics to hepatoma-derived cell line spheroids than does the control wild type. This study may aid in the prediction of the characteristics of a tissue of interest by simply analyzing the tissue gene expression pattern, providing valuable information for the development and operation of wearable devices. It may also help in the preparation of custom devices that suit specific individuals.

Transcriptional Factor Repertoire of Breast Cancer in 3D Cell Culture Models

Simple Summary

Knowledge of the transcriptional regulation of breast cancer tumorigenesis is largely based on studies performed in two-dimensional (2D) monolayer culture models, which lack tissue architecture and therefore fail to represent tumor heterogeneity. However, three-dimensional (3D) cell culture models are better at mimicking in vivo tumor microenvironment, which is critical in regulating cellular behavior. Hence, 3D cell culture models hold great promise for translational breast cancer research.

Abstract

Intratumor heterogeneity of breast cancer is driven by extrinsic factors from the tumor microenvironment (TME) as well as tumor cell–intrinsic parameters including genetic, epigenetic, and transcriptomic traits. The extracellular matrix (ECM), a major structural component of the TME, impacts every stage of tumorigenesis by providing necessary biochemical and biomechanical cues that are major regulators of cell shape/architecture, stiffness, cell proliferation, survival, invasion, and migration. Moreover, ECM and tissue architecture have a profound impact on chromatin structure, thereby altering gene expression. Considering the significant contribution of ECM to cellular behavior, a large body of work underlined that traditional two-dimensional (2D) cultures depriving cell–cell and cell–ECM interactions as well as spatial cellular distribution and organization of solid tumors fail to recapitulate in vivo properties of tumor cells residing in the complex TME. Thus, three-dimensional (3D) culture models are increasingly employed in cancer research, as these culture systems better mimic the physiological microenvironment and shape the cellular responses according to the microenvironmental cues that will regulate critical cell functions such as cell shape/architecture, survival, proliferation, differentiation, and drug response as well as gene expression. Therefore, 3D cell culture models that better resemble the patient transcriptome are critical in defining physiologically relevant transcriptional changes. This review will present the transcriptional factor (TF) repertoire of breast cancer in 3D culture models in the context of mammary tissue architecture, epithelial-to-mesenchymal transition and metastasis, cell death mechanisms, cancer therapy resistance and differential drug response, and stemness and will discuss the impact of culture dimensionality on breast cancer research.

One-step visualization of natural cell activities in non-labeled living spheroids

3D cultured cell aggregates, including spheroids, reflect the gene expression patterns of living tissues/organs. Mass preparation of spheroids enables high-throughput drug screening (HTS). However, conventional optical imaging of spheroids makes it difficult to obtain sufficient resolution of individual living cells in the thick cellular stack. Rapid and accurate assessment of cellular responses in spheroids is required for effective drug screening. Here, we show that negative contrast imaging (NCI) of spheroids overcomes this issue. Hydrophilic fluorescent dye added into the culture medium rapidly diffused into the intercellular space of living spheroids within a few minutes. Confocal microscopy showed the NCI of individual cells as dark and detailed contours clearly separated with fluorescence signals in the intercellular space. NCI enables the visualization of the alteration of cell morphology after anti-tumor drug application to living spheroids and the measurement of the fluorescent dye diffusion rate without any complicated pretreatments. Using this system, we found that the antitumor drug doxorubicin reduced the intercellular space of spheroids consisting of the human hepatocyte carcinoma cell line HepG2, through the activation of TGF-β signaling and upregulation of ECM protein expression, implicating a drug resistance mechanism. Collectively, the combination of NCI of spheroids and HTS may enhance the efficiency of drug discovery.

Genetically Modified Cell Transplantation Through Macroencapsulated Spheroids with Scaffolds to Treat Fabry Disease

Cell transplantation is expected to be another strategy to treat lysosomal diseases, having several advantages compared to enzyme replacement therapy, such as continuous enzyme secretion and one-time treatment to cure diseases. However, cell transplantation for lysosomal diseases holds issues to be resolved for the clinical field. In this study, we developed a new ex vivo gene therapy platform using a transplant pack, which consists of a porous membrane made of ethylene-vinyl alcohol in the pack-type and spheroids with scaffolds. These membranes have countless pores of less than 0.1 µm² capable of secreting proteins, including alpha-galactosidase enzyme, and segregating the contents from the host immune system. When the packs were subcutaneously transplanted into the backs of green fluorescent protein (GFP) mice, no GFP-positive cells migrated to the transplanted pack in either autogenic or allogenic mice. The transplanted cells in the pack survived for 28 days after transplantation. When cells overexpressing alpha-galactosidase were used as donor cells for the packs and implanted into Fabry disease model mice, the accumulation of the alpha-galactosidase enzyme was also observed in the livers. In this study, we reported a new ex vivo therapeutic strategy combining macroencapsulation and cellular spheroids with scaffolds. This pack, macroencapsulated spheroids with scaffolds, can also be applied to other types of lysosomal diseases by modifying genes of interest.

Spatial Stable Isotopic Labeling by Amino Acids in Cell Culture: Pulse-Chase Labeling of Three-Dimensional Multicellular Spheroids for Global Proteome Analysis

Three-dimensional cell cultures, or spheroids, are important model systems for cancer research because they recapitulate chemical and phenotypic aspects of in vivo tumors. Spheroids develop radially symmetric chemical gradients, resulting in distinct cellular populations. Stable isotopic labeling by amino acids in cell culture (SILAC) is a well-established approach to quantify protein expression and has previously been used in a pulse-chase format to evaluate temporal changes. In this article, we demonstrate that distinct isotopic signatures can be introduced into discrete spatial cellular populations, effectively tracking proteins to original locations in the spheroid, using a platform that we refer to as spatial SILAC. Spheroid populations were grown with light, medium, and heavy isotopic media, and the concentric shells of cells were harvested by serial trypsinization. Proteins were quantitatively analyzed by ultraperformance liquid chromatography-tandem mass spectrometry. The isotopic signatures correlated with the spatial location and the isotope position do not significantly impact the proteome of each individual layer. Spatial SILAC can be used to examine the proteomic changes in the different layers of the spheroid and to identify protein biomarkers throughout the structure. We show that SILAC labels can be discretely pulsed to discrete positions, without altering the spheroid's proteome, promising future combined pharmacodynamic and pharmacokinetic studies.

From cell spheroids to vascularized cancer organoids: Microfluidic tumor-on-a-chip models for preclinical drug evaluations

Chemotherapy is one of the most effective cancer treatments. Starting from the discovery of new molecular entities, it usually takes about 10 years and 2 billion U.S. dollars to bring an effective anti-cancer drug from the benchtop to patients. Due to the physiological differences between animal models and humans, more than 90% of drug candidates failed in phase I clinical trials. Thus, a more efficient drug screening system to identify feasible compounds and pre-exclude less promising drug candidates is strongly desired. For their capability to accurately construct in vitro tumor models derived from human cells to reproduce pathological and physiological processes, microfluidic tumor chips are reliable platforms for preclinical drug screening, personalized medicine, and fundamental oncology research. This review summarizes the recent progress of the microfluidic tumor chip and highlights tumor vascularization strategies. In addition, promising imaging modalities for enhancing data acquisition and machine learning-based image analysis methods to accurately quantify the dynamics of tumor spheroids are introduced. It is believed that the microfluidic tumor chip will serve as a high-throughput, biomimetic, and multi-sensor integrated system for efficient preclinical drug evaluation in the future.

Cell Transplantation Combined with Recombinant Collagen Peptides for the Treatment of Fabry Disease

Fabry disease is caused by a decrease in or loss of the activity of alpha-galactosidase, which causes its substrates globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) to accumulate in cells throughout the body. This accumulation results in progressive kidney injury due to glomerulosclerosis and in heart failure due to hypertrophy. Enzyme replacement therapy (ERT) has been used as the standard therapy for Fabry disease, but it causes a significant financial burden, and regular administration is inconvenient for patients. Because of the short half-life of alpha-galactosidase in vivo, therapeutic methods that can supplement or replace ERT are expected to involve continuous release of alpha-galactosidase, even at low doses. Cell transplantation therapy is one of these methods; however, its use has been hindered by the short-term survival of transplanted cells. CellSaic technology, which utilizes cell spheroids that form after cells are seeded simultaneously with a recombinant collagen peptide scaffold called a μ-piece, has been used to improve cell survival upon implantation. In this study, syngeneic murine embryonic fibroblasts were used to generate CellSaic that were transplanted into Fabry mice. These spheroids survived for 28 days in the renal subcapsular space with forming blood vessels. These results indicate CellSaic technology could be a platform to promote cellular graft survival and may facilitate the development of cell transplantation methods for lysosomal diseases.

Comparison of Pluripotency, Differentiation, and Mitochondrial Metabolism Capacity in Three-Dimensional Spheroid Formation of Dental Pulp-Derived Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are valuable candidates in tissue engineering and stem cell-based therapy. Traditionally, MSCs derived from various tissues have been successfully expanded in vitro using adherent culture plates commonly called as monolayer two-dimensional (2D) cultures. Recently, many studies demonstrated that stemness and multilineage differentiation potential could be enhanced to greater extent when MSCs are cultured as suspended aggregates by means of three-dimensional (3D) culturing techniques. However, there are limited reports on changed mitochondrial metabolism on 3D spheroid formation of MSCs. Therefore, the present study was aimed at investigating the stemness, differentiation potential, and mitochondrial metabolism capacity of 3D dental pulp-derived MSC (DPSC) spheroids in comparison to monolayer cultured DPSCs. We isolated dental pulp-derived MSCs (DPSCs) and successfully developed a 3D culture system which facilitated the formation of MSC spheroids. The cell aggregation was observed after 2 hours, and spheroids were formed after 24 hours and remained in shape for 72 hours. After spheroid formation, the levels of pluripotent markers increased along with enhancement in adipogenic and osteogenic potential compared to 2D cultured control cells. However, decreased proliferative capacity, cell cycle arrest, and elevated apoptosis rate were observed with the time course of the 3D culture except for the initial 24-hour aggregation. Furthermore, oxygen consumption rates of living cells decreased with the time course of the aggregation except for the initial 24 hours. Overall, our study indicated that the short-term 3D culture of MSCs could be a suitable alternative to culture the cells.

3D Cell Culture Models in COVID-19 Times: A Review of 3D Technologies to Understand and Accelerate Therapeutic Drug Discovery

In the last decades, emerging viruses have become a worldwide concern. The fast and extensive spread of the disease caused by SARS-CoV-2 (COVID-19) has impacted the economy and human activity worldwide, highlighting the human vulnerability to infectious diseases and the need to develop and optimize technologies to tackle them. The three-dimensional (3D) cell culture models emulate major tissue characteristics such as the in vivo virus-host interactions. These systems may help to generate a quick response to confront new viruses, establish a reliable evaluation of the pathophysiology, and contribute to therapeutic drug evaluation in pandemic situations such as the one that humanity is living through today. This review describes different types of 3D cell culture models, such as spheroids, scaffolds, organoids, and organs-on-a-chip, that are used in virus research, including those used to understand the new severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2).

Controlled orientation and sustained rotation of biological samples in a sono-optical microfluidic device

In cell biology, recently developed technologies for studying suspended cell clusters, such as organoids or cancer spheroids, hold great promise relative to traditional 2D cell cultures. There is, however, growing awareness that sample confinement, such as fixation on a surface or embedding in a gel, has substantial impact on cell clusters. This creates a need for contact-less tools for 3D manipulation and inspection. This work addresses this demand by presenting a reconfigurable, hybrid sono-optical system for contact-free 3D manipulation and imaging, which is suitable for biological samples up to a few hundreds of micrometers in liquid suspension. In our sono-optical device, three independently addressable MHz transducers, an optically transparent top-transducer for levitation and two side-transducers, provide ultrasound excitation from three orthogonal directions. Steerable holographic optical tweezers give us an additional means of manipulation of the acoustically trapped specimen with high spatial resolution. We demonstrate how to control the reorientation or the spinning of complex samples, for instance for 3D visual inspection or for volumetric reconstruction. Whether continuous rotation or transient reorientation takes place depends on the strength of the acoustic radiation torque, arising from pressure gradients, compared to the acoustic viscous torque, arising from the shear forces at the viscous boundary layer around the particle. Based on numerical simulations and experimental insights, we develop a strategy to achieve a desired alignment or continuous rotation around a chosen axis, by tuning the relative strengths of the transducers and thus adjusting the relative contributions of viscous and radiation torques. The approach is widely applicable, as we discuss in several generic examples, with limitations dictated by size and shape asymmetry of the samples.

Vestigial suppresses apoptosis and cell migration in a manner dependent on the level of JNK-Caspase signaling in the Drosophila wing disc

The Decapentaplegic (Dpp) and Wingless (Wg) signal pathways play important roles in numerous biological processes in Drosophila. The Drosophila vestigial (vg) gene is selectively required for wing imaginal disc cell proliferation, which is essential for the formation of the adult wing and halter structures, and is regulated by Dpp and Wg signaling. Using a Drosophila invasion model of wing epithelium, we showed herein that inhibition of Dpp or Wg signaling promoted cells to migrate across the cell lineage restrictive anterior/posterior (A/P) compartment boundary. Being downstream of both Dpp and Wg signaling, vg can block cell migration induced by loss of either pathway. In addition, suppression of vg is sufficient to induce cell migration across the A/P boundary. Transcriptomic analysis revealed potential downstream genes involved in the cell migration after suppressing vg in the wing disc. We further demonstrated that the c-Jun N-terminal kinase (JNK) signaling promoted cell migration induced by vg suppression by upregulating Caspase activity. Taken together, our results revealed the requirement of Vg for suppressing cell migration and clarified how developmental signals collaborate to stabilize cells along the compartment boundary.

Engineering Functional Rat Ovarian Spheroids Using Granulosa and Theca Cells

Although menopausal hormone therapy (MHT) is the most effective approach to managing the loss of ovarian activity, serious side effects have been reported. Cell-based therapy is a promising alternative for MHT. This study constructed engineered ovarian cell spheroids and investigated their endocrine function. Theca and granulosa cells were isolated from ovaries of 10-week-old rats. Two types of engineered ovarian cell spheroids were fabricated through forced aggregation in microwells, multilayered spheroids with centralized granulosa aggregates surrounded by an outer layer of theca cells and mixed ovarian spheroids lacking spatial rearrangement. The ovarian cell spheroids were encapsulated into a collagen gel. Non-aggregated ovarian cells served as controls. The endocrine function of the engineered ovarian spheroids was assessed over 30 days. The structure of the spheroids was well maintained during culture. The secretion of 17β-estradiol from both types of engineered ovarian cell spheroids was higher than in the control group and increased continuously in a time-dependent manner. Secretion of 17β-estradiol in the multi-layered ovarian cell spheroids was higher than in the non-layered constructs. Increased secretion of progesterone was detected in the multi-layered ovarian cell spheroids at day 5 of culture and was sustained during the culture period. The initial secretion level of progesterone in the non-layered ovarian cell spheroids was similar to those from the controls and increased significantly from days 21 to 30. An in vitro rat model of engineered ovarian cell spheroids was developed that was capable of secreting sex steroid hormones, indicating that the hormone secreting function of ovaries can be recapitulated ex vivo and potentially adapted for MHT.

HIF2alpha-Associated Pseudohypoxia Promotes Radioresistance in Pheochromocytoma: Insights from 3D Models

Pheochromocytomas and paragangliomas (PCCs/PGLs) are rare neuroendocrine tumors arising from chromaffin tissue located in the adrenal or ganglia of the sympathetic or parasympathetic nervous system. The treatment of non-resectable or metastatic PCCs/PGLs is still limited to palliative measures, including somatostatin type 2 receptor radionuclide therapy with [¹⁷⁷Lu]Lu-DOTA-TATE as one of the most effective approaches to date. Nevertheless, the metabolic and molecular determinants of radiation response in PCCs/PGLs have not yet been characterized. This study investigates the effects of hypoxia-inducible factor 2 alpha (HIF2α) on the susceptibility of PCCs/PGLs to radiation treatments using spheroids grown from genetically engineered mouse pheochromocytoma (MPC) cells. The expression of Hif2α was associated with the significantly increased resistance of MPC spheroids to external X-ray irradiation and exposure to beta particle-emitting [¹⁷⁷Lu]LuCl₃ compared to Hif2α-deficient controls. Exposure to [¹⁷⁷Lu]LuCl₃ provided an increased long-term control of MPC spheroids compared to single-dose external X-ray irradiation. This study provides the first experimental evidence that HIF2α-associated pseudohypoxia contributes to a radioresistant phenotype of PCCs/PGLs. Furthermore, the external irradiation and [¹⁷⁷Lu]LuCl₃ exposure of MPC spheroids provide surrogate models for radiation treatments to further investigate the metabolic and molecular determinants of radiation responses in PCCs/PGLs and evaluate the effects of neo-adjuvant-in particular, radiosensitizing-treatments in combination with targeted radionuclide therapies.

Continuum Theory of Active Phase Separation in Cellular Aggregates

Dense cellular aggregates are common in biology, ranging from bacterial biofilms to organoids, cell spheroids, and tumors. Their dynamics, driven by intercellular forces, is intrinsically out of equilibrium. Motivated by bacterial colonies as a model system, we present a continuum theory to study dense, active, cellular aggregates. We describe the process of aggregate formation as an active phase separation phenomenon, while the merging of aggregates is rationalized as a coalescence of viscoelastic droplets where the key timescales are linked to the turnover of the active force. Our theory provides a general framework for studying the rheology and nonequilibrium dynamics of dense cellular aggregates.

Biomimetic Mineralization on 3D Printed PLA Scaffolds: On the Response of Human Primary Osteoblasts Spheroids and In Vivo Implantation

This study aimed to assess the response of 3D printed polylactic acid (PLA) scaffolds biomimetically coated with apatite on human primary osteoblast (HOb) spheroids and evaluate the biological response to its association with Bone Morphogenetic Protein 2 (rhBMP-2) in rat calvaria. PLA scaffolds were produced via 3D printing, soaked in simulated body fluid (SBF) solution to promote apatite deposition, and characterized by physical-chemical, morphological, and mechanical properties. PLA-CaP scaffolds with interconnected porous and mechanical properties suitable for bone repairing were produced with reproducibility. The in vitro biological response was assessed with human primary osteoblast spheroids. Increased cell adhesion and the rise of in vitro release of growth factors (Platelet-Derived Growth Factor (PDGF), Basic Fibroblast Growth Factor (bFGF), Vascular Endothelial Growth Factor (VEGF) was observed for PLA-CaP scaffolds, when pre-treated with fetal bovine serum (FBS). This pre-treatment with FBS was done in a way to enhance the adsorption of serum proteins, increasing the number of bioactive sites on the surface of scaffolds, and to partially mimic in vivo interactions. The in vivo analysis was conducted through the implantation of 3D printed PLA scaffolds either alone, coated with apatite (PLA-CaP) or PLA-CaP loaded with rhBMP-2 on critical-sized defects (8 mm) of rat calvaria. PLA-CaP+rhBMP2 presented higher values of newly formed bone (NFB) than other groups at all in vivo experimental periods (p < 0.05), attaining 44.85% of NFB after six months. These findings indicated two new potential candidates as alternatives to autogenous bone grafts for long-term treatment: (i) 3D-printed PLA-CaP scaffold associated with spheroids, since it can reduce the time of repair in situ by expression of biomolecules and growth factors; and (ii) 3D-printed PLA-CaP functionalized rhBMP2 scaffold, a biocompatible, bioactive biomaterial, with osteoconductivity and osteoinductivity.

Non-Destructive Tumor Aggregate Morphology and Viability Quantification at Cellular Resolution, During Development and in Response to Drug

Three-dimensional (3D) tissue-engineered in vitro models, particularly multicellular spheroids and organoids, have become important tools to explore disease progression and guide the development of novel therapeutic strategies. These avascular constructs are particularly powerful in oncological research due to their ability to mimic several key aspects of in vivo tumors, such as 3D structure and pathophysiologic gradients. Advancement of spheroid models requires characterization of critical features (i.e., size, shape, cellular density, and viability) during model development, and in response to treatment. However, evaluation of these characteristics longitudinally, quantitatively and non-invasively remains a challenge. Herein, Optical Coherence Tomography (OCT) is used as a label-free tool to assess 3D morphologies and cellular densities of tumor spheroids generated via the liquid overlay technique. We utilize this quantitative tool to assess Matrigel's influence on spheroid morphologic development, finding that the absence of Matrigel produces flattened, disk-like aggregates rather than 3D spheroids with physiologically-relevant features. Furthermore, this technology is adapted to quantify cell number within tumor spheroids, and to discern between live and dead cells, to non-destructively provide valuable information on tissue/construct viability, as well as a proof-of-concept for longitudinal drug efficacy studies. Together, these findings demonstrate OCT as a promising noninvasive, quantitative, label-free, longitudinal and cell-based method that can assess development and drug response in 3D cellular aggregates at a mesoscopic scale.

Natural and Synthetic Biomaterials for Engineering Multicellular Tumor Spheroids

The lack of in vitro models that represent the native tumor microenvironment is a significant challenge for cancer research. Two-dimensional (2D) monolayer culture has long been the standard for in vitro cell-based studies. However, differences between 2D culture and the in vivo environment have led to poor translation of cancer research from in vitro to in vivo models, slowing the progress of the field. Recent advances in three-dimensional (3D) culture have improved the ability of in vitro culture to replicate in vivo conditions. Although 3D cultures still cannot achieve the complexity of the in vivo environment, they can still better replicate the cell-cell and cell-matrix interactions of solid tumors. Multicellular tumor spheroids (MCTS) are three-dimensional (3D) clusters of cells with tumor-like features such as oxygen gradients and drug resistance, and represent an important translational tool for cancer research. Accordingly, natural and synthetic polymers, including collagen, hyaluronic acid, Matrigel^®, polyethylene glycol (PEG), alginate and chitosan, have been used to form and study MCTS for improved clinical translatability. This review evaluates the current state of biomaterial-based MCTS formation, including advantages and disadvantages of the different biomaterials and their recent applications to the field of cancer research, with a focus on the past five years.

Cell quality evaluation with gene expression analysis of spheroids (3D) and adherent (2D) adipose stem cells

Adipose stem cells (ASCs) represent a reliable source of stem cells with a widely demonstrated potential in regenerative medicine and tissue engineering applications. New recent insights suggest that three-dimensional (3D) models may closely mimic the native tissue properties; spheroids from adipose derived stem cells (SASCs) exhibit enhanced regenerative abilities compared with those of 2D models. Stem cell therapy success is determined by "cell-quality"; for this reason, the involvement of stress signals and cellular aging need to be further investigated. Here, we performed a comparative analysis of genes connected with stemness, aging, telomeric length and oxidative stress, in 3D and 2D primary cultures. The expression levels of stemness-related markers and anti-aging Sirtuin1 were significantly up-regulated (P < 0.001) in SASCs-3D while gene expression of aging-related p16INK4a was increased in ASCs-2D (P < 0.001). The 3D and 2D cultures also had a different gene expression profile for genes related to telomere maintenance (Shelterin complex, RNA Binding proteins and DNA repair genes) (P < 0.01 and P < 0.001) and oxidative stress (aldehyde dehydrogenase class1 and 3) (P < 0.05, P < 0.01 and P < 0.001) and presented a striking large variation in their cellular redox state. Based on our findings, we propose a "cell quality" model of SASCs, highlighting a precise molecular expression of several genes involved with stemness (SOX2, POU5F1 and NANOG), anti-aging (SIRT1), oxidative stress (ALDH3) and telomeres maintenance.

In-situ gelling xyloglucan formulations as 3D artificial niche for adipose stem cell spheroids

Three-dimensional spheroidal cell aggregates of adipose stem cells (SASCs) are a distinct upstream population of stem cells present in adipose tissue, with enhanced regeneration properties in vivo. The preservation of the 3D structure of the cells, from extraction to administration, can be a promising strategy to ensure optimal conditions for cell viability and maintenance of stemness potential. With this aim, an artificial niche was created by incorporating the spheroids into an injectable, in-situ gelling solution of partially degalactosylated xyloglucan (dXG) and an ad hoc formulated culture medium for the preservation of stem cell spheroid features. The evolution of the mechanical properties and the morphological structure of this artificial niche was investigated by small amplitude rheological analysis and scanning electron microscopy, respectively. Comparatively, systems produced with the same polymer and the typical culture medium (DMEM) used for adipose stem cell (ASC) growth in adherent cell culture conditions were also characterised. Cell viability of both SASCs and ASCs incorporated inside the hydrogel or seeded on top of the hydrogel were investigated as well as the preservation of SASC stemness conditions when embedded in the hydrogel.

Bacterial Cellulose (Komagataeibacter rhaeticus) Biocomposites and Their Cytocompatibility

A series of novel polysaccharide-based biocomposites was obtained by impregnation of bacterial cellulose produced by Komagataeibacter rhaeticus (BC) with the solutions of negatively charged polysaccharides-hyaluronan (HA), sodium alginate (ALG), or κ-carrageenan (CAR)-and subsequently with positively charged chitosan (CS). The penetration of the polysaccharide solutions into the BC network and their interaction to form a polyelectrolyte complex changed the architecture of the BC network. The structure, morphology, and properties of the biocomposites depended on the type of impregnated anionic polysaccharides, and those polysaccharides in turn determined the nature of the interaction with CS. The porosity and swelling of the composites increased in the order: BC-ALG-CS > BC-HA-CS > BC-CAR-CS. The composites show higher biocompatibility with mesenchymal stem cells than the original BC sample, with the BC-ALG-CS composite showing the best characteristics.

Transport of nanoprobes in multicellular spheroids

The efficient delivery of drugs to cells depends on their diffusion through the extracellular matrix (ECM) of tissues. Here we present a study on the diffusion of nanoprobes of radius from 1 nm to over 100 nm in the ECM of spheroids of three cell types (HeLa, MCF-7 and fibroblasts). We quantified the nanoparticle transport in the spheroids' proliferating zone. We determined the size-dependent viscosity of the ECM. We revealed that nanoobjects up to 10 nm in radius exhibited unobstructed diffusion in the ECM, regardless of the spheroid type. The presented length-scale dependent viscosity profiles for spheroids pave the way for advanced modelling of drug administration through tissues.

An on-lattice agent-based Monte Carlo model simulating the growth kinetics of multicellular tumor spheroids

PURPOSE

To develop an on-lattice agent-based model describing the growth of multicellular tumor spheroids using simple Monte Carlo tools.

METHODS

Cells are situated on the vertices of a cubic grid. Different cell states (proliferative, hypoxic or dead) and cell evolution rules, driven by 10 parameters, and the effects of the culture medium are included. About twenty spheroids of MCF-7 human breast cancer were cultivated and the experimental data were used for tuning the model parameters.

RESULTS

Simulated spheroids showed adequate sizes of the necrotic nuclei and of the hypoxic and proliferative cell phases as a function of the growth time, mimicking the overall characteristics of the experimental spheroids. The relation between the radii of the necrotic nucleus and the whole spheroid obtained in the simulations was similar to the experimental one and the number of cells, as a function of the spheroid volume, was well reproduced. The statistical variability of the Monte Carlo model described the whole volume range observed for the experimental spheroids. Assuming that the model parameters vary within Gaussian distributions it was obtained a sample of spheroids that reproduced much better the experimental findings.

CONCLUSIONS

The model developed allows describing the growth of in vitro multicellular spheroids and the experimental variability can be well reproduced. Its flexibility permits to vary both the agents involved and the rules that govern the spheroid growth. More general situations, such as, e. g., tumor vascularization, radiotherapy effects on solid tumors, or the validity of the tumor growth mathematical models can be studied.

A three dimensional model of multicellular aggregate compression

Multicellular aggregates are an excellent model system to explore the role of tissue biomechanics, which has been demonstrated to play a crucial role in many physiological and pathological processes. In this paper, we propose a three-dimensional mechanical model and apply it to the uniaxial compression of a multicellular aggregate in a realistic biological setting. In particular, we consider an aggregate of initially spherical shape and describe both its elastic deformations and the reorganisation of the cells forming the spheroid. The latter phenomenon, understood as remodelling, is accounted for by assuming that the aggregate undergoes plastic-like distortions. The study of the compression of the spheroid, achieved by means of two parallel, compressive plates, needs the formulation of a contact problem between the living spheroid itself and the plates, and is solved with the aid of the augmented Lagrangian method. The results of the performed numerical simulations are in qualitative agreement with the biological observations reported in the literature and can also be used to estimate quantitatively some fundamental aggregate mechanical parameters.

Multiscale modeling of solid stress and tumor cell invasion in response to dynamic mechanical microenvironment

Mathematical models can provide a quantitatively sophisticated description of tumor cell (TC) behaviors under mechanical microenvironment and help us better understand the role of specific biophysical factors based on their influences on the TC behaviors. To this end, we propose an off-lattice cell-based multiscale mathematical model to describe the dynamic growth-induced solid stress during tumor progression and investigate the influence of the mechanical microenvironment on TC invasion. At the cellular level, cell-cell and cell-matrix interactive forces depend on the mechanical properties of the cells and the cancer-associated fibroblasts in the stroma, respectively. The constitutive relationship between the interactive forces and cell migrations obeys the Hooke's law and damping effects. At the tissue level, the integrated growth-induced forces caused by proliferating cells within the simulation region are balanced by the external forces applied by the surrounding host tissues. Then, the cell movements are calculated according to the Newton's second law of motion, and the morphology of TC invasion is updated. The simulation results reveal the continuous changes of the macroscopic mechanical forces due to the interactions among the structural components and the microscopic environmental factors. Moreover, the simulation results demonstrate the adverse effect of the stiffness of tumor tissue on tumor growth and invasion. A decrease in the stiffness of tumor and matrix can promote TCs to proliferate at a much faster rate and invade into the surrounding healthy tissue more easily, whereas an increase in the stiffness can lead to an aggressive morphology of tumor invasion. We envision that the proposed model can be served as a quantitative theoretical platform to study the underlying biophysical role of the mechanical microenvironmental factors during tumor invasion and metastasis.

Inhibition of bone morphogenetic protein signaling reduces viability, growth and migratory potential of non-small cell lung carcinoma cells

PURPOSE

BMP signaling has an oncogenic and tumor-suppressing activity in lung cancer that makes the prospective therapeutic utility of BMP signaling in lung cancer treatment complex. A more in-depth analysis of lung cancer subtypes is needed to identify BMP-related therapeutic targets. We sought to examine the influence of BMP signaling on the viability, growth and migration properties of the cell line LCLC-103H, which originates from a large cell lung carcinoma with giant cells and an extended aneuploidy.

METHODS

We used BMP-4 and LDN-214117 as agonist/antagonist system for the BMP receptor type I signaling. Using flow cytometry, wound healing assay, trans-well assay and spheroid culture, we examined the influence of BMP signaling on cell viability, growth and migration. Molecular mechanisms underlying observed changes in cell migration were investigated via gene expression analysis of epithelial-mesenchymal transition (EMT) markers.

RESULTS

BMP signaling inhibition resulted in LCLC-103H cell apoptosis and necrosis 72 h after LDN-214117 treatment. Cell growth and proliferation are markedly affected by BMP signaling inhibition. Chemotactic motility and migratory ability of LCLC-103H cells were clearly hampered by LDN-214117 treatment. Cell migration changes after BMP signaling inhibition were shown to be coupled with considerable down-regulation of transcription factors involved in EMT, especially Snail.

CONCLUSIONS

BMP signaling inhibition in LCLC-103H cells leads to reduced growth and proliferation, hindered migration and accelerated cell death. The findings contribute to the pool of evidence on BMP signaling in lung cancer with a possibility of introducing BMP signaling inhibition as a novel therapeutic approach for the disease.

Quantitative characterization of viscoelastic fracture induced by time-dependent intratumoral pressure in a 3D model tumor

In the tumor environment, interstitial pressure drives interstitial flow drainage from the tumor core to the lymphatic vessels. Recent studies have highlighted the key role of interstitial pressure in tumor development and cell migration. High intratumoral pressures, up to 60 mm Hg , have been reported in cancer patients. In a previous study, we showed that such pressure levels induce fracture in an experimental tumor model consisting of a microfluidic system holding a cellular aggregate. Here, we investigate and quantify the characteristics of tumor model fracture under a range of flow conditions. Our findings suggest a strong dependence of viscoelastic fracture behavior on the loading rate exerted by flow. The aggregate exhibits fragile fracture at high loading rates and ductile fracture at lower rates. The loading rate also modifies the permeability of the cellular aggregate, as well as the persistence time of the load required to induce fracture. The quantification parameters we propose here, evaluated for an in vitro model tumor without the extracellular matrix, could be applied to characterize tumor fracture under more realistic interstitial flow conditions.

3D Microfluidic Bone Tumor Microenvironment Comprised of Hydroxyapatite/Fibrin Composite

Bone is one of the most common sites of cancer metastasis, as its fertile microenvironment attracts tumor cells. The unique mechanical properties of bone extracellular matrix (ECM), mainly composed of hydroxyapatite (HA) affect a number of cellular responses in the tumor microenvironment (TME) such as proliferation, migration, viability, and morphology, as well as angiogenic activity, which is related to bone metastasis. In this study, we engineered a bone-mimetic microenvironment to investigate the interactions between the TME and HA using a microfluidic platform designed for culturing tumor cells in 3D bone-mimetic composite of HA and fibrin. We developed a bone metastasis TME model from colorectal cancer (SW620) and gastric cancer (MKN74) cells, which has very poor prognosis but rarely been investigated. The microfluidic platform enabled straightforward formation of 3D TME composed the hydrogel and multiple cell types. This facilitated monitoring of the effect of HA concentration and culture time on the TME. In 3D bone mimicking culture, we found that HA rich microenvironment affects cell viability, proliferation and cancer cell cytoplasmic volume in a manner dependent on the different metastatic cancer cell types and culture duration indicating the spatial heterogeneity (different origin of metastatic cancer) and temporal heterogeneity (growth time of cancer) of TME. We also found that both SW620 and MKN72 cells exhibited significantly reduced migration at higher HA concentration in our platform indicating inhibitory effect of HA in both cancer cells migration. Next, we quantitatively analyzed angiogenic sprouts induced by paracrine factors that secreted by TME and showed paracrine signals from tumor and stromal cell with a high HA concentration resulted in the formation of fewer sprouts. Finally we reconstituted vascularized TME allowing direct interaction between angiogenic sprouts and tumor-stroma microspheroids in a bone-mimicking microenvironment composing a tunable HA/fibrin composite. Our multifarious approach could be applied to drug screening and mechanistic studies of the metastasis, growth, and progression of bone tumors.

Coherent Timescales and Mechanical Structure of Multicellular Aggregates

Multicellular aggregates are an excellent model system to explore the role of tissue biomechanics in specifying multicellular reorganization during embryonic developments and malignant invasion. Tissue-like spheroids, when subjected to a compressive force, are known to exhibit liquid-like behaviors at long timescales (hours), largely because of cell rearrangements that serve to effectively dissipate the applied stress. At short timescales (seconds to minutes), before cell rearrangement, the mechanical behavior is strikingly different. The current work uses shape relaxation to investigate the structural characteristics of aggregates and discovers two coherent timescales: one on the order of seconds, the other tens of seconds. These timescales are universal, conserved across a variety of tested species, and persist despite great differences in other properties such as tissue surface tension and adhesion. A precise mathematical theory is used to correlate the timescales with mechanical properties and reveals that aggregates have a relatively strong envelope and an unusually "soft" interior (weak bulk elastic modulus). This characteristic is peculiar, considering that both layers consist of identical units (cells), but is consistent with the fact that this structure can engender both structural integrity and the flexibility required for remodeling. In addition, tissue surface tension, elastic modulus, and viscosity are proportional to each other. Considering that these tissue-level properties intrinsically derive from cellular-level properties, the proportionalities imply precise coregulation of the latter and in particular of the tension on the cell-medium and cell-cell interfaces.