Comparative analysis of tumor spheroid generation techniques for differential in vitro drug toxicity

Preparation of Highly Functional Spheroid of Endocrine Cells Based on Thermosensitive Glycol Chitosan

BACKGROUND

Pancreatic islet transplantation holds great potential as a therapeutic approach for treating type 1 diabetes mellitus (T1D). However, large islets suffer from hypoxia due to the limited diffusion distance of oxygen, leading to cell loss. Therefore, smaller spheroids are needed for better transplantation outcomes. This study aims to develop a method for forming highly functional islet spheroids using glycol chitosan (GC) derivatives, such as N-acetylated glycol chitosan (AGC) and N-hexanoyl glycol chitosan (HGC).

METHODS

Thermogelling polymers were produced by performing N-acylation of GC using the correspondingly carboxylic anhydrides. Islet spheroids were formed using a dual application with AGC-coated plates and HGC gelation. The AGC solution was applied to the plate for coating and evenly distributed using a 1 mL syringe. Then, the HGC encapsulated with islet single cells was cultured on top of it. Spheroid viability and functionality were evaluated using CCK-8 assay and glucose-stimulated insulin secretion assay.

RESULTS

The aqueous solutions of AGC (4%, w/v) and HGC (36% hexanoylation) (2%, w/v) demonstrated a sol-gel transition temperature around 37 °C, suitable for the physiological environment. These polymers also showed no cytotoxicity to intact islets. Islet single cells were cultured on HGC gels with varying degrees of hexanoylation (DH) values, where higher DH values led to smaller and more uniform spheroids. The resulting spheroids formed on AGC-coated plates and HGC36 gelation were smaller and more uniform than those formed on untreated plates. These spheroids exhibited significantly improved glucose responsiveness, with superior insulin secretion.

CONCLUSION

The optimized method using AGC and HGC offers a more efficient way to produce smaller, uniform, and functional spheroids.

Dynamic Culture of Bioprinted Liver Tumor Spheroids in a Pillar/Perfusion Plate for Predictive Screening of Anticancer Drugs

Recent advancements in three-dimensional (3D) cell culture technologies, such as cell spheroids, organoids, and 3D bioprinted tissue constructs, have significantly improved the physiological relevance of in vitro models. These models better mimic tissue structure and function, closely emulating in vivo characteristics and enhancing phenotypic analysis, critical for basic research and drug screening in personalized cancer therapy. Despite their potential, current 3D cell culture platforms face technical challenges, which include user-unfriendliness in long-term dynamic cell culture, incompatibility with rapid cell encapsulation in biomimetic hydrogels, and low throughput for compound screening. To address these issues, we developed a 144-pillar plate with sidewalls and slits (144PillarPlate) and a complementary 144-perfusion plate with perfusion wells and reservoirs (144PerfusionPlate) for dynamic 3D cell culture and predictive compound screening. To accelerate biomimetic tissue formation, small Hep3B liver tumor spheroids suspended in alginate were printed and encapsulated on the 144PillarPlate rapidly by using microsolenoid valve-driven 3D bioprinting technology. The microarray bioprinting technology enabled precise and rapid loading of small spheroids in alginate on the pillar plate, facilitating reproducible and scalable formation of large tumor spheroids with minimal manual intervention. The bioprinted Hep3B spheroids on the 144PillarPlate were dynamically cultured in the 144PerfusionPlate and tested with anticancer drugs to measure drug effectiveness and determine the concentration required to inhibit 50% of the cell viability (IC50 value). The perfusion plate enabled the convenient dynamic culture of tumor spheroids and facilitated the dynamic testing of anticancer drugs with increased sensitivity. It is envisioned that the integration of microarray bioprinting of tumor spheroids onto the pillar plate, along with dynamic 3D cell culture in the perfusion plate, could more accurately replicate tumor microenvironments. This advancement has the potential to enhance the predictive drug screening process in personalized cancer therapy significantly.

Single-Step Fabrication of V-Shaped Polymeric Microwells to Enhance Cancer Spheroid Formation

Traditional cancer research has long relied on two-dimensional (2D) cell cultures, which inadequately mimic the complex three-dimensional (3D) microenvironments of in vivo tumors. Recent advancements in 3D cell cultures, particularly cancer spheroids, have highlighted their superior physiological relevance. However, existing methods for spheroid generation often require complex, multistep fabrication processes that limit scalability and reproducibility. In this study, we present a novel single-step photolithographic technique to fabricate high-aspect-ratio V-slanted hydrogel microwells. By employing polyethylene glycol (PEG)-based hydrogels, we create biocompatible, extracellular matrix (ECM)-like scaffolds that enhance gas and nutrient exchange while promoting uniform spheroid formation. The hydrogel microwells allow precise control of spheroid size, achieving a physiologically relevant diameter of 425 μm within 12-24 h, and the resulting spheroids exhibiting high viability over 3 weeks. Moreover, the method facilitates the creation of scalable multiwell arrays for high-throughput applications, making it suitable for both small-scale and large-scale experimental needs. This platform addresses the limitations of traditional microwell fabrication, offering a robust, efficient, and reproducible system for generating physiologically relevant 3D models with valuable applications in cancer research, drug testing, and tissue engineering.

Advances in regenerative medicine-based approaches for skin regeneration and rejuvenation

Significant progress has been made in regenerative medicine for skin repair and rejuvenation. This review examines core technologies including stem cell therapy, bioengineered skin substitutes, platelet-rich plasma (PRP), exosome-based therapies, and gene editing techniques like CRISPR. These methods hold promise for treating a range of conditions, from chronic wounds and burns to age-related skin changes and genetic disorders. Challenges remain in optimizing these therapies for broader accessibility and ensuring long-term safety and efficacy.

Maraviroc/cisplatin combination inhibits gastric cancer tumoroid growth and improves mice survival

BACKGROUND

Gastric cancer (GC) is a significant cancer-related cause of death worldwide. GC's most used chemotherapeutic regimen is based on platinum drugs such as cisplatin (CDDP). However, CDDP chemoresistance reduces the survival rate of advanced GC. The immune C-C chemokine receptor type 5 (CCR5) have been proposed as a pivotal factor in cancer progression since its blockade has been linked with antineoplastic effects on tumor cell proliferation; nevertheless, its role in the chemoresistance of GC has not been elucidated. This study aimed to determine the effects induced by the CCR5 using Maraviroc (MVC), a highly selective CCR5 antagonist, on CDDP-resistant AGS cells (AGS R-CDDP), tumoroids (3D tumor spheroids), and animal models.

RESULTS

The combined CDDP and MVC treatment reduced cell viability and inhibited tumoroid formation in AGS R-CDDP cells. The effects of the MVC/CDDP combination on apoptosis and cell cycle progression were correlated with the increase in CDDP (dose-dependent). The mRNA levels of C-C Motif Chemokine Ligand 5 (CCL5), the main ligand for CCR5, decreased significantly in cells treated with the MVC/CDDP combination. MVC in the MVC/CDDP combination improved the survival rate and biochemical parameters of CDDP-treated mice by reducing the side effects of CDDP alone.

CONCLUSIONS

This finding suggests that MVC/CDDP combination could be a potential complementary therapy for GC.

Principles of Hanging Drop Method (Spheroid Formation) in Cell Culture

A type of three-dimensional (3D) cell culture models which is simple and easy is hanging drop method. The hanging drop method emerges as a pivotal technique with diverse applications in cancer research and cell biology. This method facilitates the formation of multicellular spheroids, providing a unique environment for studying cell behavior dynamics. The hanging drop method's theoretical underpinning relies on gravity-enforced self-assembly, allowing for cost-effective, reproducible 3D cell cultures with controlled spheroid sizes. The advantages of this approach include its efficiency in producing cellular heterogeneity, particularly in non-adherent 3D cultures, and its ability to create hypoxic spheroids, making it a suitable model for studying cancer. Moreover, the hanging drop method has proven valuable in investigating various aspects such as tissue structure, signaling pathways, immune activation of cancer cells, and notably, cell proliferation. Researchers have utilized the hanging drop method to explore the dynamics of cell proliferation, studying the effects of mesenchymal stem cells (MSC) secretome on cancer cells. The method's application involves co-culturing different cell lines, assessing spheroid formations, and quantifying their sizes over time. These studies have unveiled intricate cell behavior dynamics, demonstrating how the MSC secretome influences cancer cell growth and viability within a three-dimensional co-culture paradigm.

Macrophage Checkpoint Nanoimmunotherapy Has the Potential to Reduce Malignant Progression in Bioengineered In Vitro Models of Ovarian Cancer

Most ovarian carcinoma (OvCa) patients present with advanced disease at the time of diagnosis. Malignant, metastatic OvCa is invasive and has poor prognosis, exposing the need for improved therapeutic targeting. High CD47 (OvCa) and SIRPα (macrophage) expression has been linked to decreased survival, making this interaction a significant target for therapeutic discovery. Even so, previous attempts have fallen short, limited by CD47 antibody specificity and efficacy. Macrophages are an important component of the OvCa tumor microenvironment and are manipulated to aid in cancer progression via CD47-SIRPα signaling. Thus, we have leveraged lipid-based nanoparticles (LNPs) to design a therapy uniquely situated to home to phagocytic macrophages expressing the SIRPα protein in metastatic OvCa. CD47-SIRPα presence was evaluated in patient histological sections using immunohistochemistry. 3D tumor spheroids generated on a hanging drop array with OVCAR3 high-grade serous OvCa and THP-1-derived macrophages created a representative model of cellular interactions involved in metastatic OvCa. Microfluidic techniques were employed to generate LNPs encapsulating SIRPα siRNA (siSIRPα) to affect the CD47-SIRPα signaling between the OvCa and macrophages. siSIRPα LNPs were characterized for optimal size, charge, and encapsulation efficiency. Uptake of the siSIRPα LNPs by macrophages was assessed by Incucyte. Following 48 h of 25 nM siSIRPα treatment, OvCa/macrophage heterospheroids were evaluated for SIRPα knockdown, platinum chemoresistance, and invasiveness. OvCa patient tumors and in vitro heterospheroids expressed CD47 and SIRPα. Macrophages in OvCa spheroids increased carboplatin resistance and invasion, indicating a more malignant phenotype. We observed successful LNP uptake by macrophages causing significant reduction in SIRPα gene and protein expressions and subsequent reversal of pro-tumoral alternative activation. Disrupting CD47-SIRPα interactions resulted in sensitizing OvCa/macrophage heterospheroids to platinum chemotherapy and reversal of cellular invasion outside of heterospheroids. Ultimately, our results strongly indicate the potential of using LNP-based nanoimmunotherapy to reduce malignant progression of ovarian cancer.

Multicellular tumor spheroids: A convenient in vitro model for translational cancer research

In the attempts to mitigate uncertainties in the results of monolayer culture for the identification of cancer therapeutic targets and compounds, there has been a growing interest in using 3D cancer spheroid models, which include tumorospheres (TSs), tissue-derived tumor spheres (TDTSs), organotypic multicellular tumor spheroids (OMSs), and multicellular tumor spheroids (MCTSs). The MCTSs, either Mono-MCTSs or Hetero-MCTSs, with or without scaffold, in particular, offer numerous advantages over other spheroid models, including easy cultivation, high reproducibility, accessibility, high throughput, controllable size, well-rounded shape, simplicity of genetic manipulation, economical and availability of various biological methods for their development. In this review, we have attempted to discuss the role of MCTSs concerning various aspects of translational cancer research, such as drug response and penetration, cell-cell interaction, and invasion and metastasis. However, the Mono-MCTSs, either scaffold-free or scaffold-based, may not adequately represent the cellular heterogeneity and complexity of clinical tumors, limiting their utility in translational cancer research. Conversely, Hetero-MCTS models, both scaffold-free and scaffold-based, show better suitability due to the presence of a similar in vivo type tumor microenvironment. Nonetheless, scaffold-based Hetero-MCTS models show batch variability and challenges in performing quantitative assays due to difficulties extracting spheroids and cells from scaffolds. Further, incorporating stromal cells with cancer cells in a more precise ratio to develop Hetero-MCTSs can enhance the model's relevance, yielding more clinically reliable outcomes for drug candidates and improving insights into tumor biology.

Polymeric Nanoparticles Potentiate the Anticancer Activity of Novel PI3Kα Inhibitors Against Triple-Negative Breast Cancer Cells

Background: Dysregulation in phosphoinositide-3-kinase alpha (PI3Kα) signaling is implicated in the development of various cancers, including triple-negative breast cancer (TNBC). We have previously synthesized a series of N-phenyl-6-chloro-4-hydroxy-2-quinolone-3-carboxamides as targeted inhibitors against PI3Kα. Herein, two drug candidates, R7 and R11, were selected to be further investigated as a nanoparticle (NP) formulation against TNBC. Methods: R7 and R11 were entrapped in D-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS) polymeric NPs by nanoprecipitation. Following their physicochemical characterization, the anticancer activity of the compounds and their NP formulations was evaluated in the TNBC cell line MDA-MB-231 by conducting viability, uptake, and apoptosis assays, as well as penetration assays in a multicellular tumor spheroid model. Results: The NPs exhibited a particle size of 100-200 nm, excellent drug loading efficiencies, and sustained release under physiologic conditions. Viability assays revealed superior potency for the NP formulations, with IC50 values of 20 µM and 30 µM for R7- and R11-loaded NPs, respectively, compared to the free compounds, which exhibited IC50 values of 280 µM and 290 µM for R7 and R11, respectively. These results were attributed to the inherent antiproliferative activity of TPGS, as evidenced by the cytotoxicity of the drug-free NPs, as well as the enhanced cellular uptake enabled by the NP vehicle, as demonstrated by fluorescence microscopy imaging and flow cytometry measurements. Further investigations showed that the NPs promoted apoptosis via a mitochondrial-dependent pathway that involved the activation of proapoptotic caspases. Moreover, the NP formulations enhanced the penetration ability of the free compounds in multicellular tumor spheroids, causing a time- and concentration-dependent disruption of the spheroids. Conclusions: Our findings highlight the important role nanotechnology can play in improving the biopharmaceutical properties of new drug candidates and facilitating their in vivo translation.

Using microfluidic and conventional platforms to evaluate the effects of lanthanides on spheroid formation

Metastasis contributes to the increased mortality rate of cancer, but the intricate mechanisms remain unclear. Cancer cells from a primary tumor invade nearby tissues and access the lymphatic or circulatory system. If these cells manage to survive and extravasate from the vasculature into distant tissues and ultimately adapt to survive, they will proliferate and facilitate malignant tumor formation. Traditional two-dimensional (2D) cell cultures offer a rapid and convenient method for validating the efficacy of anticancer drugs within a reasonable cost range, but their utility is limited because of tumors' high heterogeneity in vivo and spatial complexities. Three-dimensional (3D) cell cultures that mimic the physiological conditions of cancer cells in vivo have gained considerable interest. In these cultures, cells assemble into spheroids through gravity, magnetic forces, or their low-adhesion to the plates. Although these approaches address some of the limitations of 2D cultures, they often require a considerable amount of time and cost. Therefore, this study aims to enhance the effectiveness of 3D culture techniques by using microfluidic systems to provide a high-throughput and sensitive pipeline for drug screening. Using these systems, we studied the effects of lanthanide elements, which have garnered interest in cancer treatment, on spheroid formation and cell spreading. Our findings suggest that these elements alter the compactness of cell spheroids and decrease cell mobility.

Metabolic adaptation in epithelial ovarian cancer metastasis

Epithelial ovarian cancer (EOC) is highly lethal due to its unique metastatic characteristics. EOC spheroids enter a non-proliferative state, with hypoxic cores and reduced oncogenic signaling, all of which contribute to tumour dormancy during metastasis. We investigated the metabolomic states of EOC cells progressing through the three steps to metastasis. Metabolomes of adherent, spheroid, and re-adherent cells were validated by isotopic metabolic flux analysis and mitochondrial functional assays to identify metabolic pathways that were previously unknown to promote EOC metastasis. Although spheroids were thought to exist in a dormant state, metabolomic analysis revealed an unexpected upregulation of energy production pathways in spheroids, accompanied by increased abundance of tricarboxylic acid (TCA) cycle and electron transport chain proteins. Tracing of 13C-labelled glucose and glutamine showed increased pyruvate carboxylation and decreased glutamine anaplerosis in spheroids. Increased reductive carboxylation suggests spheroids adjust redox homeostasis by shuttling cytosolic NADPH into mitochondria via isocitrate dehydrogenase. Indeed, we observed spheroids have increased respiratory capacity and mitochondrial ATP production. Relative to adherent cells, spheroids reduced serine consumption and metabolism, processes which were reversed upon spheroid re-adherence. The data reveal a distinct metabolism in EOC spheroids that enhances energy production by the mitochondria while maintaining a dormant state with respect to growth and proliferation. The findings advance our understanding of EOC metastasis and identify the TCA cycle and mitochondrional activity as novel targets to disrupt EOC metastasis, providing new approaches to treat advanced disease.

Modelling bone metastasis in spheroids to study cancer progression and screen cisplatin efficacy

Most bone metastases are caused by primary breast or prostate cancer cells settling in the bone microenvironment, affecting normal bone physiology and function and reducing 5-year survival rates to 10% and 6%, respectively. To expedite clinical availability of novel and effective bone metastases treatments, reliable and predictive in vitro models are urgently required to screen for novel therapies as current in vitro 2D planar mono-culture models do not accurately predict the clinical efficacy. We herein engineered a novel human in vitro 3D co-culture model based on spheroids to study dynamic cellular quantities of (breast or prostate) cancer cells and human bone marrow stromal cells and screen chemotherapeutic efficacy and specificity of the common anticancer drug cisplatin. Bone metastatic spheroids (BMSs) were formed rapidly within 24 h, while the morphology of breast versus prostate cancer BMS differed in terms of size and circularity upon prolonged culture periods. Prestaining cell types prior to BMS formation enabled confocal imaging and quantitative image analysis of in-spheroid cellular dynamics for up to 7 days of BMS culture. We found that cancer cells in BMS proliferated faster and were less susceptible to cisplatin treatment compared to 2D control cultures. Based on these findings and the versatility of our methodology, BMS represent a feasible 3D in vitro model for screening of new bone cancer metastases therapies.

CAR T cell infiltration and cytotoxic killing within the core of 3D breast cancer spheroids under the control of antigen sensing in microwell arrays

The success of chimeric antigen receptor (CAR) T cells in blood cancers has intensified efforts to develop CAR T therapies for solid cancers. In the solid tumor microenvironment, CAR T cell trafficking and suppression of cytotoxic killing represent limiting factors for therapeutic efficacy. Here, we present a microwell platform to study CAR T cell interactions with 3D breast tumor spheroids and determine predictors of anti-tumor CAR T cell function. To precisely control antigen sensing, we utilized a switchable adaptor CAR system that covalently attaches to co-administered antibody adaptors and mediates antigen recognition. Following the addition of an anti-HER2 adaptor antibody, primary human CAR T cells exhibited higher infiltration, clustering, and secretion of effector cytokines. By tracking CAR T cell killing in individual spheroids, we showed the suppressive effects of spheroid size and identified the initial CAR T cell to spheroid area ratio as a predictor of cytotoxicity. We demonstrate that larger spheroids exhibit higher hypoxia levels and are infiltrated by CAR T cells with a suppressed activation state, characterized by reduced expression of IFN-γ, TNF-α, and granzyme B. Spatiotemporal analysis revealed lower CAR T cell numbers and cytotoxicity in the spheroid core compared to the periphery. Finally, increasing CAR T cell seeding density resulted in higher CAR T cell infiltration and cancer cell elimination in the spheroid core. Our findings provide new quantitative insight into CAR T cell function within 3D cancer spheroids. Given its miniaturized nature and live imaging capabilities, our microfabricated system holds promise for screening cellular immunotherapies.

Tumoroids, a valid preclinical screening platform for monitoring cancer angiogenesis

In recent years, biologists and clinicians have witnessed prominent advances in in vitro 3D culture techniques related to biomimetic human/animal tissue analogs. Numerous data have confirmed that unicellular and multicellular (tumoroids) tumor spheroids with dense native cells in certain matrices are sensitive and valid analytical tools for drug screening, cancer cell dynamic growth, behavior, etc. in laboratory settings. Angiogenesis/vascularization is a very critical biological phenomenon to support oxygen and nutrients to tumor cells within the deep layer of solid masses. It has been shown that endothelial cell (EC)-incorporated or -free spheroid/tumoroid systems provide a relatively reliable biological platform for monitoring the formation of nascent blood vessels in micron/micrometer scales. Besides, the paracrine angiogenic activity of cells within the spheroid/tumoroid systems can be monitored after being treated with different therapeutic approaches. Here, we aimed to collect recent advances and findings related to the monitoring of cancer angiogenesis using unicellular and multicellular tumor spheroids. Vascularized spheroids/tumoroids can help us in the elucidation of mechanisms related to cancer formation, development, and metastasis by monitoring the main influencing factors.

Patient-derived melanoma models

Melanoma is a very aggressive, rapidly metastasizing tumor that has been studied intensively in the past regarding the underlying genetic and molecular mechanisms. More recently developed treatment modalities have improved response rates and overall survival of patients. However, the majority of patients suffer from secondary treatment resistance, which requires in depth analyses of the underlying mechanisms. Here, melanoma models based on patients-derived material may play an important role. Consequently, a plethora of different experimental techniques have been developed in the past years. Among these are 3D and 4D culture techniques, organotypic skin reconstructs, melanoma-on-chip models and patient-derived xenografts, Every technique has its own strengths but also weaknesses regarding throughput, reproducibility, and reflection of the human situation. Here, we provide a comprehensive overview of currently used techniques and discuss their use in different experimental settings.

Enhancing scaffold-free spheroid models: 3D cell bioprinting method for metastatic HSC3-Oral squamous carcinoma cell line

3D in vitro systems offer advantages over the shortcomings of two-dimensional models by simulating the morphological and functional features of in vivo-like environments, such as cell-cell and cell-extracellular matrix interactions, as well as the co-culture of different cell types. Nevertheless, these systems present technical challenges that limit their potential in cancer research requiring cell line- and culture-dependent standardization. This protocol details the use of a magnetic 3D bioprinting method and other associated techniques (cytotoxicity assay and histological analysis) using oral squamous cell carcinoma cell line, HSC3, which offer advantages compared to existing widely used approaches. This protocol is particularly timely, as it validates magnetic bioprinting as a method for the rapid deployment of 3D cultures as a tool for compound screening and development of heterotypic cultures such as co-culture of oral squamous cell carcinoma cells with cancer-associated fibroblasts (HSC3/CAFs).

Uniform sized cancer spheroids production using hydrogel-based droplet microfluidics: a review

Three-dimensional (3D) cell culture models have been extensively utilized in various mechanistic studies as well as for drug development studies as superior in vitro platforms than conventional two-dimensional (2D) cell culture models. This is especially the case in cancer biology, where 3D cancer models, such as spheroids or organoids, have been utilized extensively to understand the mechanisms of cancer development. Recently, many sophisticated 3D models such as organ-on-a-chip models are emerging as advanced in vitro models that can more accurately mimic the in vivo tissue functions. Despite such advancements, spheroids are still considered as a powerful 3D cancer model due to the relatively simple structure and compatibility with existing laboratory instruments, and also can provide orders of magnitude higher throughput than complex in vitro models, an extremely important aspects for drug development. However, creating well-defined spheroids remain challenging, both in terms of throughputs in generation as well as reproducibility in size and shape that can make it challenging for drug testing applications. In the past decades, droplet microfluidics utilizing hydrogels have been highlighted due to their potentials. Importantly, core-shell structured gel droplets can avoid spheroid-to-spheroid adhesion that can cause large variations in assays while also enabling long-term cultivation of spheroids with higher uniformity by protecting the core organoid area from external environment while the outer porous gel layer still allows nutrient exchange. Hence, core-shell gel droplet-based spheroid formation can improve the predictivity and reproducibility of drug screening assays. This review paper will focus on droplet microfluidics-based technologies for cancer spheroid production using various gel materials and structures. In addition, we will discuss emerging technologies that have the potential to advance the production of spheroids, prospects of such technologies, and remaining challenges.

Live Microscopy of Multicellular Spheroids with the Multimodal Near-Infrared Nanoparticles Reveals Differences in Oxygenation Gradients

Assessment of hypoxia, nutrients, metabolite gradients, and other hallmarks of the tumor microenvironment within 3D multicellular spheroid and organoid models represents a challenging analytical task. Here, we report red/near-infrared (NIR) emitting cell staining with O2-sensitive nanoparticles, which enable measurements of spheroid oxygenation on a conventional fluorescence microscope. Nanosensor probes, termed "MMIR" (multimodal infrared), incorporate an NIR O2-sensitive metalloporphyrin (PtTPTBPF) and deep red aza-BODIPY reference dyes within a biocompatible polymer shell, allowing for oxygen gradient quantification via fluorescence ratio and phosphorescence lifetime readouts. We optimized staining techniques and evaluated the nanosensor probe characteristics and cytotoxicity. Subsequently, we applied nanosensors to the live spheroid models based on HCT116, DPSCs, and SKOV3 cells, at rest, and treated with drugs affecting cell respiration. We found that the growth medium viscosity, spheroid size, and formation method influenced spheroid oxygenation. Some spheroids produced from HCT116 and dental pulp stem cells exhibited "inverted" oxygenation gradients, with higher core oxygen levels than the periphery. This contrasted with the frequently encountered "normal" gradient of hypoxia toward the core caused by diffusion. Further microscopy analysis of spheroids with an "inverted" gradient demonstrated metabolic stratification of cells within spheroids: thus, autofluorescence FLIM of NAD(P)H indicated the formation of a glycolytic core and localization of OxPhos-active cells at the periphery. Collectively, we demonstrate a strong potential of NIR-emitting ratiometric nanosensors for advanced microscopy studies targeting live and quantitative real-time monitoring of cell metabolism and hypoxia in complex 3D tissue models.

Formation Pattern Analysis of Spheroids Formed by a Droplet-Based Microfluidic System for Predicting the Aggressiveness of Tumor Cells

Examining tumor heterogeneity is essential for selecting an appropriate anticancer treatment for an individual. This study aimed to distinguish low- and high-aggressive tumor cells by analyzing the formation patterns of spheroids. The droplet-based microfluidic system was employed for the formation of each spheroid from four different subtypes of breast tumor cells. Additionally, heterotypic spheroids with T lymphocytes and cancer-associated fibroblasts (CAFs) were produced, and distinctions between low- and high-aggressive tumor cells were explored through the analysis of formation patterns using circularity, convexity, and cell distributions. In both homotypic spheroids and heterotypic spheroids with T lymphocytes, spheroids formed from low-aggressive tumor cells exhibited high circularity and convexity. On the other hand, spheroids formed from high-aggressive tumor cells had relatively low circularity and convexity. In the case of heterotypic spheroids with CAFs, circularity and convexity did not exhibit clear differences between low- and high-aggressive tumor cells, but distinct variations were observed in cell distributions. CAFs and low-aggressive tumor cells were evenly distributed, whereas the CAFs were predominantly located in the inner layer, and high-aggressive tumor cells were primarily located in the outer layer. This finding can offer valuable insights into predicting the aggressiveness of unknown tumor cells.

Engineering Tumor Stroma Morphogenesis Using Dynamic Cell-Matrix Spheroid Assembly

The tumor microenvironment consists of resident tumor cells organized within a compositionally diverse, three-dimensional (3D) extracellular matrix (ECM) network that cannot be replicated in vitro using bottom-up synthesis. We report a new self-assembly system to engineer ECM-rich 3D MatriSpheres wherein tumor cells actively organize and concentrate microgram quantities of decellularized ECM dispersions which modulate cell phenotype. 3D colorectal cancer (CRC) MatriSpheres were created using decellularized small intestine submucosa (SIS) as an orthotopic ECM source that had greater proteomic homology to CRC tumor ECM than traditional ECM formulations such as Matrigel. SIS ECM was rapidly concentrated from its environment and assembled into ECM-rich 3D stroma-like regions by mouse and human CRC cell lines within 4-5 days via a mechanism that was rheologically distinct from bulk hydrogel formation. Both ECM organization and transcriptional regulation by 3D ECM cues affected programs of malignancy, lipid metabolism, and immunoregulation that corresponded with an in vivo MC38 tumor cell subpopulation identified via single cell RNA sequencing. This 3D modeling approach stimulates tumor specific tissue morphogenesis that incorporates the complexities of both cancer cell and ECM compartments in a scalable, spontaneous assembly process that may further facilitate precision medicine.

CAR T cell infiltration and cytotoxic killing within the core of 3D breast cancer spheroids under control of antigen sensing in microwell arrays

The success of chimeric antigen receptor (CAR) T cells in blood cancers has intensified efforts to develop CAR T therapies for solid cancers. In the solid tumor microenvironment, CAR T cell trafficking and suppression of cytotoxic killing represent limiting factors for therapeutic efficacy. Here, we present a microwell platform to study CAR T cell interactions with 3D tumor spheroids and determine predictors of anti-tumor CAR T cell function. To precisely control antigen sensing by CAR T cells, we utilized a switchable adaptor CAR system, that instead of directly binding to an antigen of interest, covalently attaches to co-administered antibody adaptors that mediate tumor antigen recognition. Following addition of an anti-HER2 adaptor antibody, primary human CAR T cells exhibited higher infiltration and clustering compared to the no adaptor control. By tracking CAR T cell killing at the individual spheroid level, we showed the suppressive effects of spheroid size and identified the initial CAR T cell : spheroid area ratio as a predictor of cytotoxicity. Spatiotemporal analysis revealed lower CAR T cell numbers and cytotoxicity in the spheroid core compared to the periphery. Finally, increasing CAR T cell seeding density, resulted in higher CAR T cell infiltration and cancer cell elimination in the spheroid core. Our findings provide new quantitative insights into CAR T cell-mediated killing of HER2+ breast tumor cells. Given the miniaturized nature and live imaging capabilities, our microfabricated system holds promise for discovering cell-cell interaction mechanisms that orchestrate antitumor CAR T cell functions and screening cellular immunotherapies in 3D tumor models.

An inexpensive "do-it-yourself" device for rapid generation of uniform tumor spheroids

Three-dimensional (3D) cancer cell culture models such as tumor spheroids better recapitulate in vivo tumors than conventional two-dimensional (2D) models. However, two major challenges limit the routine use of 3D tumor spheroids. Firstly, most existing methods of generating tumor spheroids are not high-throughput. Secondly, tumor spheroids generated using current methods are highly variable in dimension. Here, we describe a simple 'Do-It-Yourself (DIY)' device that can be assembled for less than $7 of parts and generate uniform tumor spheroids in a high-throughput manner. We used a simple phone coin vibrating motor to superimpose the vibration for breaking a laminar jet of cell-loaded alginate solution into equally sized spherical beads. We generated 3,970 tumor spheroids/min, which exhibited a hypoxic core recapitulating in vivo tumors and could be used to test the diffusion efficacy of anticancer drugs. Such low-cost, easy-to-fabricate, simple-to-operate systems with high-throughput outcomes are essential to democratize and standardize cancer research.

Segregation of co-cultured multicellular systems: review and modeling consideration

Cell segregation caused by collective cell migration (CCM) is crucial for morphogenesis, functional development of tissue parts, and is an important aspect in other diseases such as cancer and its metastasis process. Efficiency of the cell segregation depends on the interplay between: (1) biochemical processes such as cell signaling and gene expression and (2) physical interactions between cells. Despite extensive research devoted to study the segregation of various co-cultured systems, we still do not understand the role of physical interactions in cell segregation. Cumulative effects of these physical interactions appear in the form of physical parameters such as: (1) tissue surface tension, (2) viscoelasticity caused by CCM, and (3) solid stress accumulated in multicellular systems. These parameters primarily depend on the interplay between the state of cell-cell adhesion contacts and cell contractility. The role of these physical parameters on the segregation efficiency is discussed on model systems such as co-cultured breast cell spheroids consisting of two subpopulations that are in contact. This review study aims to: (1) summarize biological aspects related to cell segregation, mechanical properties of cell collectives, effects along the biointerface between cell subpopulations and (2) describe from a biophysical/mathematical perspective the same biological aspects summarized before. So that overall it can illustrate the complexity of the biological systems that translate into very complex biophysical/mathematical equations. Moreover, by presenting in parallel these two seemingly different parts (biology vs. equations), this review aims to emphasize the need for experiments to estimate the variety of parameters entering the resulting complex biophysical/mathematical models.

Targeted HBx gene editing by CRISPR/Cas9 system effectively reduces epithelial to mesenchymal transition and HBV replication in hepatoma cells

BACKGROUND AND AIMS

Hepatitis B virus X protein (HBx) play a key role in pathogenesis of HBV-induced hepatocellular carcinoma (HCC) by promoting epithelial to mesenchymal transition (EMT). In this study, we hypothesized that inhibition of HBx is an effective strategy to combat HCC.

METHODOLOGY AND RESULTS

We designed and synthesized novel HBx gene specific single guide RNA (sgRNA) with CRISPR/Cas9 system and studied its in vitro effects on tumour properties of HepG2-2.15. Full length HBx gene was excised using HBx-CRISPR that resulted in significant knockdown of HBx expression in hepatoma cells. HBx-CRISPR also decreased levels of HBsAg and HBV cccDNA expression. A decreased expression of mesenchymal markers, proliferation and tumorigenic properties was observed in HBx-CRISPR treated cells as compared to controls in both two- and three- dimensional (2D and 3D) tumour models. Transcriptomics data showed that out of 1159 differentially expressed genes in HBx-CRISPR transfected cells as compared to controls, 70 genes were upregulated while 1089 genes associated with cell proliferation and EMT pathways were downregulated.

CONCLUSION

Thus, targeting of HBx by CRISPR/Cas9 gene editing system reduces covalently closed circular DNA (cccDNA) levels, HBsAg production and mesenchymal characteristics of HBV-HCC cells. We envision inhibition of HBx by CRISPR as a novel therapeutic approach for HBV-induced HCC.

A comprehensive overview of advanced dynamic in vitro intestinal and hepatic cell culture models

Orally administered drugs pass through the gastrointestinal tract before being absorbed in the small intestine and metabolised in the liver. To test the efficacy and toxicity of drugs, animal models are often employed; however, they are not suitable for investigating drug-tissue interactions and making reliable predictions, since the human organism differs drastically from animals in terms of absorption, distribution, metabolism and excretion of substances. Likewise, simple static in vitro cell culture systems currently used in preclinical drug screening often do not resemble the native characteristics of biological barriers. Dynamic models, on the other hand, provide in vivo-like cell phenotypes and functionalities that offer great potential for safety and efficacy prediction. Herein, current microfluidic in vitro intestinal and hepatic models are reviewed, namely single- and multi-tissue micro-bioreactors, which are associated with different methods of cell cultivation, i.e., scaffold-based versus scaffold-free.

In vitro induction of hair follicle signatures using human dermal papilla cells encapsulated in fibrin microgels

Cellular spheroids have been described as an appropriate culture system to restore human follicle dermal papilla cells (hFDPc) intrinsic properties; however, they show a low and variable efficiency to promote complete hair follicle formation in in vivo experiments. In this work, a conscientious analysis revealed a 25% cell viability in the surface of the dermal papilla spheroid (DPS) for all culture conditions, questioning whether it is an appropriate culture system for hFDPc. To overcome this problem, we propose the use of human blood plasma for the generation of fibrin microgels (FM) with encapsulated hFDPc to restore its inductive signature, either in the presence or in the absence of blood platelets. FM showed a morphology and extracellular matrix composition similar to the native dermal papilla, including Versican and Collagen IV and increasing cell viability up to 85%. While both systems induce epidermal invaginations expressing hair-specific keratins K14, K15, K71, and K75 in in vitro skin cultures, the number of generated structures increases from 17% to 49% when DPS and FM were used, respectively. These data show the potential of our experimental setting for in vitro hair follicle neogenesis with wild adult hFDPc using FM, being a crucial step in the pursuit of human hair follicle regeneration therapies.

3D tumor spheroids: morphological alterations a yardstick to anti-cancer drug response

Tumor spheroids are one of the well-characterized 3D culture systems bearing close resemblance to the physiological tissue organization and complexity of avascular solid tumor stage with hypoxic core. They hold a wide-spread application in the field of pharmaceutical science and anti-cancer drug research. However, the difficulty in determining optimal technique for the generation of spheroids with uniform size and shape, evaluation of experimental outputs, or mass production often limits their usage in anti-cancer research and in high-throughput drug screening. In recent times, several studies have demonstrated various simple techniques for generating uniform-size 3D spheroids, including the hanging drop (HD), liquid overlay technique (LOT), and microfluidic approaches. Morphological alterations apart from biochemical assays, and staining techniques are suitably employed for the evaluation of experimental outcomes within 3D spheroid models. Morphological alterations in response to effective anti-cancer drug treatment in 3D tumor spheroids such as reduced spheroid size, loss of spheroid compactness and integrity or smooth surface, are highly reliable. These alterations can significantly reduce the need for biochemical assays and staining techniques, resulting in both time and cost savings. The present article specifically covers a variety of available procedures in spheroid generation. For practical applicability, we have supplemented our review study with the generation of glioblastoma U87 spheroids using HD and LOT methods. Additionally, we have also incorporated the outcome of U87 spheroid treatment with doxorubicin on spheroid morphology.

In Vitro Models of Head and Neck Cancer: From Primitive to Most Advanced

For several decades now, researchers have been trying to answer the demand of clinical oncologists to create an ideal preclinical model of head and neck squamous cell carcinoma (HNSCC) that is accessible, reproducible, and relevant. Over the past years, the development of cellular technologies has naturally allowed us to move from primitive short-lived primary 2D cell cultures to complex patient-derived 3D models that reproduce the cellular composition, architecture, mutational, or viral load of native tumor tissue. Depending on the tasks and capabilities, a scientific laboratory can choose from several types of models: primary cell cultures, immortalized cell lines, spheroids or heterospheroids, tissue engineering models, bioprinted models, organoids, tumor explants, and histocultures. HNSCC in vitro models make it possible to screen agents with potential antitumor activity, study the contribution of the tumor microenvironment to its progression and metastasis, determine the prognostic significance of individual biomarkers (including using genetic engineering methods), study the effect of viral infection on the pathogenesis of the disease, and adjust treatment tactics for a specific patient or groups of patients. Promising experimental results have created a scientific basis for the registration of several clinical studies using HNSCC in vitro models.

Proteomic and Phosphoproteomic Reprogramming in Epithelial Ovarian Cancer Metastasis

Epithelial ovarian cancer (EOC) is a high-risk cancer presenting with heterogeneous tumors. The high incidence of EOC metastasis from primary tumors to nearby tissues and organs is a major driver of EOC lethality. We used cellular models of spheroid formation and readherence to investigate cellular signaling dynamics in each step toward EOC metastasis. In our system, adherent cells model primary tumors, spheroid formation represents the initiation of metastatic spread, and readherent spheroid cells represent secondary tumors. Proteomic and phosphoproteomic analyses show that spheroid cells are hypoxic and show markers for cell cycle arrest. Aurora kinase B abundance and downstream substrate phosphorylation are significantly reduced in spheroids and readherent cells, explaining their cell cycle arrest phenotype. The proteome of readherent cells is most similar to spheroids, yet greater changes in the phosphoproteome show that spheroid cells stimulate Rho-associated kinase 1 (ROCK1)-mediated signaling, which controls cytoskeletal organization. In spheroids, we found significant phosphorylation of ROCK1 substrates that were reduced in both adherent and readherent cells. Application of the ROCK1-specific inhibitor Y-27632 to spheroids increased the rate of readherence and altered spheroid density. The data suggest ROCK1 inhibition increases EOC metastatic potential. We identified novel pathways controlled by Aurora kinase B and ROCK1 as major drivers of metastatic behavior in EOC cells. Our data show that phosphoproteomic reprogramming precedes proteomic changes that characterize spheroid readherence in EOC metastasis.

Cell Culture Model Evolution and Its Impact on Improving Therapy Efficiency in Lung Cancer

Optimizing cell culture conditions is essential to ensure experimental reproducibility. To improve the accuracy of preclinical predictions about the response of tumor cells to different classes of drugs, researchers have used 2D or 3D cell cultures in vitro to mimic the cellular processes occurring in vivo. While 2D cell culture provides valuable information on how therapeutic agents act on tumor cells, it cannot quantify how the tumor microenvironment influences the response to therapy. This review presents the necessary strategies for transitioning from 2D to 3D cell cultures, which have facilitated the rapid evolution of bioengineering techniques, leading to the development of microfluidic technology, including organ-on-chip and tumor-on-chip devices. Additionally, the study aims to highlight the impact of the advent of 3D bioprinting and microfluidic technology and their implications for improving cancer treatment and approaching personalized therapy, especially for lung cancer. Furthermore, implementing microfluidic technology in cancer studies can generate a series of challenges and future perspectives that lead to the discovery of new predictive markers or targets for antitumor treatment.

Cell spheroid creation by transcytotic intercellular gelation

Cell spheroids bridge the discontinuity between in vitro systems and in vivo animal models. However, inducing cell spheroids by nanomaterials remains an inefficient and poorly understood process. Here we use cryogenic electron microscopy to determine the atomic structure of helical nanofibres self-assembled from enzyme-responsive D-peptides and fluorescent imaging to show that the transcytosis of D-peptides induces intercellular nanofibres/gels that potentially interact with fibronectin to enable cell spheroid formation. Specifically, D-phosphopeptides, being protease resistant, undergo endocytosis and endosomal dephosphorylation to generate helical nanofibres. On secretion to the cell surface, these nanofibres form intercellular gels that act as artificial matrices and facilitate the fibrillogenesis of fibronectins to induce cell spheroids. No spheroid formation occurs without endo- or exocytosis, phosphate triggers or shape switching of the peptide assemblies. This study-coupling transcytosis and morphological transformation of peptide assemblies-demonstrates a potential approach for regenerative medicine and tissue engineering.

Inkjet-printed morphogenesis of tumor-stroma interface using bi-cellular bioinks of collagen-poly(N-isopropyl acrylamide-co-methyl methacrylate) mixture

Recent advances in biomaterials and 3D printing/culture methods enable various tissue-engineered tumor models. However, it is still challenging to achieve native tumor-like characteristics due to lower cell density than native tissues and prolonged culture duration for maturation. Here, we report a new method to create tumoroids with a mechanically active tumor-stroma interface at extremely high cell density. This method, named "inkjet-printed morphogenesis" (iPM) of the tumor-stroma interface, is based on a hypothesis that cellular contractile force can significantly remodel the cell-laden polymer matrix to form densely-packed tissue-like constructs. Thus, differential cell-derived compaction of tumor cells and cancer-associated fibroblasts (CAFs) can be used to build a mechanically active tumor-stroma interface. In this methods, two kinds of bioinks are prepared, in which tumor cells and CAFs are suspended respectively in the mixture of collagen and poly (N-isopropyl acrylamide-co-methyl methacrylate) solution. These two cellular inks are inkjet-printed in multi-line or multi-layer patterns. As a result of cell-derived compaction, the resulting structure forms tumoroids with mechanically active tumor-stroma interface at extremely high cell density. We further test our working hypothesis that the morphogenesis can be controlled by manipulating the force balance between cellular contractile force and matrix stiffness. Furthermore, this new concept of "morphogenetic printing" is demonstrated to create more complex structures beyond current 3D bioprinting techniques.

Advances in tissue engineering of cancer microenvironment-from three-dimensional culture to three-dimensional printing

Cancer treatment development is a complex process, with tumor heterogeneity and inter-patient variations limiting the success of therapeutic intervention. Traditional two-dimensional cell culture has been used to study cancer metabolism, but it fails to capture physiologically relevant cell-cell and cell-environment interactions required to mimic tumor-specific architecture. Over the past three decades, research efforts in the field of 3D cancer model fabrication using tissue engineering have addressed this unmet need. The self-organized and scaffold-based model has shown potential to study the cancer microenvironment and eventually bridge the gap between 2D cell culture and animal models. Recently, three-dimensional (3D) bioprinting has emerged as an exciting and novel biofabrication strategy aimed at developing a 3D compartmentalized hierarchical organization with the precise positioning of biomolecules, including living cells. In this review, we discuss the advancements in 3D culture techniques for the fabrication of cancer models, as well as their benefits and limitations. We also highlight future directions associated with technological advances, detailed applicative research, patient compliance, and regulatory challenges to achieve a successful bed-to-bench transition.

Insights into high-grade serous carcinoma pathobiology using three-dimensional culture model systems

Epithelial ovarian cancer (EOC) research has become more complex as researchers try to fully understand the metastatic process. Especially as we delve into the concept of tumour dormancy, where cells transition between proliferative and dormant states to survive during disease progression. Thus, the in vitro models used to conduct this research need to reflect this vast biological complexity. The innovation behind the many three-dimensional (3D) spheroid models has been refined to easily generate reproducible spheroids so that we may understand the various molecular signaling changes of cells during metastasis and determine therapeutic efficacy of treatments. This ingenuity was then used to develop the 3D ex vivo patient-derived organoid model, as well as multiple co-culture model systems for EOC research. Although, researchers need to continue to push the boundaries of these current models for in vitro and even in vivo work in the future. In this review, we describe the 3D models already in use, where these models can be developed further and how we can use these models to gain the most knowledge on EOC pathogenesis and discover new targeted therapies.

Advancements in melanoma cancer metastasis models

Metastatic melanoma is a complex and deadly disease. Due to its complexity, the development of novel therapeutic strategies to inhibit metastatic melanoma remains an outstanding challenge. Our ability to study metastasis is advanced with the development of in vitro and in vivo models that better mimic the different steps of the metastatic cascade beginning from primary tumor initiation to final metastatic seeding. In this review, we provide a comprehensive summary of in vitro models, in vivo models, and in silico platforms to study the individual steps of melanoma metastasis. Furthermore, we highlight the advantages and limitations of each model and discuss the challenges of how to improve current models to enhance translation for melanoma cancer patients and future therapies.

Rapid generation of homogenous tumor spheroid microtissues in a scaffold-free platform for high-throughput screening of a novel combination nanomedicine

Combination nanomedicine is a potent strategy for cancer treatment. Exploiting different mechanisms of action, a novel triple drug delivery system of 5-fluorouracil, curcumin, and piperine co-loaded human serum albumin nanoparticles (5FU-CUR-PIP-HSA-NPs) was developed via the self-assembly method for suppressing breast tumor. Both hydrophobic and hydrophilic drugs were successfully encapsulated in the HSA NPs with a high drug loading efficiency (DLE) of 10%. Successful clinical translation of nanomedicines, however, is a challenging process requiring considerable preclinical in vitro and in vivo animal tests. The aim of this study was to develop a homemade preclinical 3D culture model in the standard 96-well plates in a cost and time-effective novel approach for the rapid generation of homogenous compact tumor spheroids for disease modeling, and anticancer therapeutic/nanomedicine screening. The knowledge of drug screening can be enhanced by employing such a model in a high-throughput manner. Accordingly, to validate the formulated drug delivery system and investigate the cellular uptake and cytotoxicity effect of the nanoformulation, 3D tumor spheroids were employed. The practicality of the nanomedicine system was substantiated in different tests. The in vitro uptake of the NPs into the tight 3D tumor spheroids was facilitated by the semi-spherical shape of the NPs with a proper size and surface charge. 5FU-CUR-PIP-HSA-NPs demonstrated high potency of migration inhibition as a part of successful anti-metastatic therapy as well. The remarkable differences in 2D and 3D cytotoxicities emphasize the importance of employing 3D tumor models as an intermediate step prior to in vivo animal experiments for drug/nanomedicine screening.

Enhanced motility and interaction of nasopharyngeal carcinoma with epithelial cells in confined microwells

The three-dimensional (3D) structure of the extracellular matrix and cell-cell contacts are two important cues to altering cell migration behavior and the tumor formation process. In this work, we designed and fabricated microwell arrays with a grating-patterned bottom in polydimethylsiloxane platforms to systematically study the effects of confinement, changes in topography, and cell-cell contacts on the migration behavior of nasopharyngeal carcinoma (NPC43) and immortalized nasopharyngeal epithelial (NP460) cells by time-lapse imaging. When two types of cells were co-cultured in microwells, the migration speed and spreading area of NPC43 cells were significantly increased, which might be attributed to the heterotypic cell-cell contacts with NP460 cells. On a flat surface, NPC43 cells could not form clusters due to the frequent interruptions by the active movements of NP460 cells. However, in 3D microwell arrays, clusters of NPC43 cells formed on the bottom surface while the majority of NP460 cells migrated onto the sidewalls. These cell clusters could be further processed to form spheroids for drug screening. These results also revealed that the 3D microenvironments and cell-cell contacts could have significant implications for NPC cell migration and initiation of tumor formation, which will provide insight for NPC progression and dissemination.

Spheroid Engineering in Microfluidic Devices

Two-dimensional (2D) cell culture techniques are commonly employed to investigate biophysical and biochemical cellular responses. However, these culture methods, having monolayer cells, lack cell-cell and cell-extracellular matrix interactions, mimicking the cell microenvironment and multicellular organization. Three-dimensional (3D) cell culture methods enable equal transportation of nutrients, gas, and growth factors among cells and their microenvironment. Therefore, 3D cultures show similar cell proliferation, apoptosis, and differentiation properties to in vivo. A spheroid is defined as self-assembled 3D cell aggregates, and it closely mimics a cell microenvironment in vitro thanks to cell-cell/matrix interactions, which enables its use in several important applications in medical and clinical research. To fabricate a spheroid, conventional methods such as liquid overlay, hanging drop, and so forth are available. However, these labor-intensive methods result in low-throughput fabrication and uncontrollable spheroid sizes. On the other hand, microfluidic methods enable inexpensive and rapid fabrication of spheroids with high precision. Furthermore, fabricated spheroids can also be cultured in microfluidic devices for controllable cell perfusion, simulation of fluid shear effects, and mimicking of the microenvironment-like in vivo conditions. This review focuses on recent microfluidic spheroid fabrication techniques and also organ-on-a-chip applications of spheroids, which are used in different disease modeling and drug development studies.

Polystyrene-Based Slippery Surfaces Enable the Generation and Easy Retrieval of Tumor Spheroids

Multicellular tumor spheroids are the most well-characterized organotypic models for cancer research. Generally, scaffold-based and scaffold-free techniques are widely used for culturing spheroids. In scaffold-free techniques, the hanging drop (HD) method is a more versatile technique, but the retrieval of three-dimensional (3D) cell spheroids in the hanging drop method is usually labor-intensive. We developed oil-coated polystyrene nanofiber-based reusable slippery surfaces for the generation and easy retrieval of 3D spheroids. The developed slippery surfaces facilitated the rolling and gliding of the cell medium drops as well as holding the hydrophilic drops for more than 72 h by the virtue of surface tension as in the hanging drop method. In this study, polystyrene nanofibers were developed by the facile technique of electrospinning and the morphological evaluation was performed by scanning electron microscopy (SEM) and cryo-FESEM. We modeled the retrieval process of 3D spheroids with the ingredients of 3D spheroid generation, such as water, cell culture media, collagen, and hyaluronic acid solution, demonstrating the faster and easy retrieval of 3D spheroids within a few seconds. We created MCF-7 spheroids as a proof of concept with a developed slippery surface. 3D spheroids were characterized for their size, homogeneity, reactive oxygen species, proliferative marker (Ki-67), and hypoxic inducing factor 1ά (HIF-1ά). These 3D tumor spheroids were further tested for evaluating the cellular toxicity of the doxorubicin drug. Hence, the proposed slippery surfaces demonstrated the potential alternative of culturing 3D tumor spheroids with an easy retrieval process with intact 3D spheroids.

Remote Magnetic Microengineering and Alignment of Spheroids into 3D Cellular Fibers

Developing in vitro models that recapitulate the in vivo organization of living cells in a 3D microenvironment is one of the current challenges in the field of tissue engineering. In particular for anisotropic tissues where alignment of precursor cells is required for them to create functional structures. Herein, a new method is proposed that allows aligning in the direction of a uniform magnetic field both individual cells (muscle, stromal, and stem cells) or spheroids in a thermoresponsive collagen hydrogel. In an all‐in‐one approach, spheroids are generated at high throughput by magnetic engineering using microfabricated micromagnets and are used as building blocks to create 3D anisotropic tissue structures of different scales. The magnetic cells and spheroids alignment process is optimized in terms of magnetic cell labeling, concentration, and size. Anisotropic structures are induced to form fibers in the direction of the magnetic alignment, with the respective roles of the magnetic field, the mechanical stretching of hydrogel or co‐culture of the aligned cells with non‐magnetic stromal cells, being investigated. Over days, spheroids fuse into 3D tubular structures, oriented in the direction of the magnetic alignment. Moreover, in the case of the muscle cells model, multinucleated cells can be observed within the fibers.

Comparison of EMT-Related and Multi-Drug Resistant Gene Expression, Extracellular Matrix Production, and Drug Sensitivity in NSCLC Spheroids Generated by Scaffold-Free and Scaffold-Based Methods

Multicellular 3D tumor models are becoming a powerful tool for testing of novel drug products and personalized anticancer therapy. Tumor spheroids, a commonly used 3D multicellular tumor model, more closely reproduce the tumor microenvironment than conventional 2D cell cultures. It should be noted that spheroids can be produced using different techniques, which can be subdivided into scaffold-free (SF) and scaffold-based (SB) methods. However, it remains unclear, to what extent spheroid properties depend on the method of their generation. In this study, we aimed to carry out a head-to-head comparison of drug sensitivity and molecular expression profile in SF and SB spheroids along with a monolayer (2D) cell culture. Here, we produced non-small cell lung cancer (NSCLC) spheroids based on human lung adenocarcinoma cell line A549. Drug sensitivity analysis of the tested cell cultures to five different chemotherapeutics resulted in IC50 (A549-SB) > IC50 (A549-SF) > IC50 (A549-2D) trend. It was found that SF and SB A549 spheroids displayed elevated expression levels of epithelial-to-mesenchymal transition (EMT) markers and proteins associated with drug resistance compared with the monolayer A549 cell culture. Enhanced drug resistance of A549-SB spheroids can be a result of larger diameters and elevated deposition of extracellular matrix (ECM) that impairs drug penetration into spheroids. Thus, the choice of the spheroid production method can influence the properties of the generated 3D cell culture and their drug resistance. This fact should be considered for correct interpretation of drug testing results.

Current strategies with implementation of three-dimensional cell culture: the challenge of quantification

From growing cells in spheroids to arranging them on complex engineered scaffolds, three-dimensional cell culture protocols are rapidly expanding and diversifying. While these systems may often improve the physiological relevance of cell culture models, they come with technical challenges, as many of the analytical methods used to characterize traditional two-dimensional (2D) cells must be modified or replaced to be effective. Here we review the advantages and limitations of quantification methods based either on biochemical measurements or microscopy imaging. We focus on the most basic of parameters that one may want to measure, the number of cells. Precise determination of this number is essential for many analytical techniques where measured quantities are only meaningful when normalized to the number of cells (e.g. cytochrome p450 enzyme activity). Thus, accurate measurement of cell number is often a prerequisite to allowing comparisons across different conditions (culturing conditions or drug and treatment screening) or between cells in different spatial states. We note that this issue is often neglected in the literature with little or no information given regarding how normalization was performed, we highlight the pitfalls and complications of quantification and call for more accurate reporting to improve reproducibility.

Bench to Bedside: New Therapeutic Approaches with Extracellular Vesicles and Engineered Biomaterials for Targeting Therapeutic Resistance of Cancer Stem Cells

Cancer has recently been the second leading cause of death worldwide, trailing only cardiovascular disease. Cancer stem cells (CSCs), represented as tumor-initiating cells (TICs), are mainly liable for chemoresistance and disease relapse due to their self-renewal capability and differentiating capacity into different types of tumor cells. The intricate molecular mechanism is necessary to elucidate CSC's chemoresistance properties and cancer recurrence. Establishing efficient strategies for CSC maintenance and enrichment is essential to elucidate the mechanisms and properties of CSCs and CSC-related therapeutic measures. Current approaches are insufficient to mimic the in vivo chemical and physical conditions for the maintenance and growth of CSC and yield unreliable research results. Biomaterials are now widely used for simulating the bone marrow microenvironment. Biomaterial-based three-dimensional (3D) approaches for the enrichment of CSC provide an excellent promise for future drug discovery and elucidation of molecular mechanisms. In the future, the biomaterial-based model will contribute to a more operative and predictive CSC model for cancer therapy. Design strategies for materials, physicochemical cues, and morphology will offer a new direction for future modification and new methods for studying the CSC microenvironment and its chemoresistance property. This review highlights the critical roles of the microenvironmental cues that regulate CSC function and endow them with drug resistance properties. This review also explores the latest advancement and challenges in biomaterial-based scaffold structure for therapeutic approaches against CSC chemoresistance. Since the recent entry of extracellular vesicles (EVs), cell-derived nanostructures, have opened new avenues of investigation into this field, which, together with other more conventionally studied signaling pathways, play an important role in cell-to-cell communication. Thus, this review further explores the subject of EVs in-depth. This review also discusses possible future biomaterial and biomaterial-EV-based models that could be used to study the tumor microenvironment (TME) and will provide possible therapeutic approaches. Finally, this review concludes with potential perspectives and conclusions in this area.

Assessment of Antitumor and Antiproliferative Efficacy and Detection of Protein-Protein Interactions in Cancer Cells from 3D Tumor Spheroids

When compared to two-dimensional (2D) cell cultures, 3D spheroids have been considered suitable in vitro models for drug discovery research and other studies of drug activity. Based on different 3D cell culture procedures, we describe procedures we have used to obtain 3D tumor spheroids by both the hanging-drop and ultra-low-attachment plate methods and to analyze the antiproliferative and antitumor efficacy of different chemotherapeutic agents, including a peptidomimetic. We have applied this method to breast and lung cancer cell lines such as BT-474, MCF-7, A549, and Calu-3. We also describe a proximity ligation assay of the cells from the spheroid model to detect protein-protein interactions of EGFR and HER2. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Growth of 3D spheroids using the hanging-drop method Basic Protocol 2: Growth of spheroids using ultra-low-attachment plates Support Protocol 1: Cell viability assay of tumor spheroids Support Protocol 2: Antiproliferative and antitumor study in 3D tumor spheroids Support Protocol 3: Proximity ligation assay on cells derived from 3D spheroids.

A fungicide, fenhexamid, is involved in the migration and angiogenesis in breast cancer cells expressing estrogen receptors

Fenhexamid (Fen) is used to eradicate gray mold of fruits and vegetables leading to greater detection of its residual concentration in wine than other fungicides. Here, we further investigated the malign influence of Fen on the migration and angiogenesis via regulation of the estrogen receptor (ER) and phosphoinositide 3-kinase (PI3K) pathways in breast cancer models. ER-positive MCF-7 and ER-negative MDA-MB-231 breast cancer cells were exposed to 17β-estradiol (E2, 10^-9 M), Fen (10^-5 M and 10^-7 M), ICI 182,780 (ICI; an ER antagonist, 10^-8 M) or/and Pictilisib (Pic; a PI3K inhibitor, 10^-7 M), and subsequently subjected to migration assay, live cell motility monitoring, trans-chamber assay, immunofluorescence, angiogenesis assay, tumor spheroid formation, and Western blot analysis. In MCF-7 cells, E2 and Fen induced cell migration by regulating the cell migration-related proteins. Although expressions of N-cadherin and Vimentin remained unchanged E2 and Fen induced the decrease of E-cadherin and Occludin in the immunofluorescence assay and Western blot analysis. In addition, Fen increased vessel formation in HUVEC cells. Furthermore, Fen treatment induced the formation of larger and denser tumor spheroids in MCF-7 cells. Western blot further confirmed the increased expressions of vascular endothelial growth factor (VEGF) and sex-determining region Y-box 2 (SOX2) after exposure to Fen. We conclude that Fen plays an important role as an endocrine-disrupting chemical in breast cancer migration and metastasis through the regulation of ER and PI3K signaling pathways.

Three-dimensional in vitro culture models in oncology research

Cancer is a multifactorial disease that is responsible for 10 million deaths per year. The intra- and inter-heterogeneity of malignant tumors make it difficult to develop single targeted approaches. Similarly, their diversity requires various models to investigate the mechanisms involved in cancer initiation, progression, drug resistance and recurrence. Of the in vitro cell-based models, monolayer adherent (also known as 2D culture) cell cultures have been used for the longest time. However, it appears that they are often less appropriate than the three-dimensional (3D) cell culture approach for mimicking the biological behavior of tumor cells, in particular the mechanisms leading to therapeutic escape and drug resistance. Multicellular tumor spheroids are widely used to study cancers in 3D, and can be generated by a multiplicity of techniques, such as liquid-based and scaffold-based 3D cultures, microfluidics and bioprinting. Organoids are more complex 3D models than multicellular tumor spheroids because they are generated from stem cells isolated from patients and are considered as powerful tools to reproduce the disease development in vitro. The present review provides an overview of the various 3D culture models that have been set up to study cancer development and drug response. The advantages of 3D models compared to 2D cell cultures, the limitations, and the fields of application of these models and their techniques of production are also discussed.

Appropriate tension sensitivity of α-catenin ensures rounding morphogenesis of epithelial spheroids

The adherens junction (AJ) is an actin filament-anchoring junction. It plays a central role in epithelial morphogenesis through cadherin-based recognition and adhesion among cells. The stability and plasticity of AJs are required for the morphogenesis. An actin-binding α-catenin is an essential component of the cadherin-catenin complex and functions as a tension transducer that changes its conformation and induces AJ development in response to tension. Despite much progress in understanding molecular mechanisms of tension sensitivity of α-catenin, its significance on epithelial morphogenesis is still unknown. Here we show that the tension sensitivity of α-catenin is essential for epithelial cells to form round spheroids through proper multicellular rearrangement. Using a novel in vitro suspension culture model, we found that epithelial cells form round spheroids even from rectangular-shaped cell masses with high aspect ratios without using high tension and that increased tension sensitivity of α-catenin affected this morphogenesis. Analyses of AJ formation and cellular tracking during rounding morphogenesis showed cellular rearrangement, probably through AJ remodeling. The rearrangement occurs at the cell mass level, but not single-cell level. Hypersensitive α-catenin mutant-expressing cells did not show cellular rearrangement at the cell mass level, suggesting that the appropriate tension sensitivity of α-catenin is crucial for the coordinated round morphogenesis.Key words: α-catenin, vinculin, adherens junction, morphogenesis, mechanotransduction.

Morphometrical, Morphological, and Immunocytochemical Characterization of a Tool for Cytotoxicity Research: 3D Cultures of Breast Cell Lines Grown in Ultra-Low Attachment Plates

Three-dimensional cell cultures may better mimic avascular tumors. Yet, they still lack characterization and standardization. Therefore, this study aimed to (a) generate multicellular aggregates (MCAs) of four breast cell lines: MCF7, MDA-MB-231, and SKBR3 (tumoral) and MCF12A (non-tumoral) using ultra-low attachment (ULA) plates, (b) detail the methodology used for their formation and analysis, providing technical tips, and (c) characterize the MCAs using morphometry, qualitative cytology (at light and electron microscopy), and quantitative immunocytochemistry (ICC) analysis. Each cell line generated uniform MCAs with structural differences among cell lines: MCF7 and MDA-MB-231 MCAs showed an ellipsoid/discoid shape and compact structure, while MCF12A and SKBR3 MCAs were loose, more flattened, and presented bigger areas. MCF7 MCAs revealed glandular breast differentiation features. ICC showed a random distribution of the proliferating and apoptotic cells throughout the MCAs, not fitting in the traditional spheroid model. ICC for cytokeratin, vimentin, and E-cadherin showed different results according to the cell lines. Estrogen (ER) and progesterone (PR) receptors were positive only in MCF7 and human epidermal growth factor receptor 2 (HER-2) in SKBR3. The presented characterization of the MCAs in non-exposed conditions provided a good baseline to evaluate the cytotoxic effects of potential anticancer compounds.

VEGF‑mediated tumour growth and EMT in 2D and 3D cell culture models of hepatocellular carcinoma

The purpose of the present study was to evaluate the effects of vascular endothelial growth factor (VEGF) on tumorigenic properties in two-dimensional (2D) and three-dimensional (3D) cultures of hepatoma cells. The proliferation and invasion of hepatoma cells was assessed using wound healing, chemotaxis Transwell, invasion, tube-forming and hanging drop assays in both 2D and 3D cultures. The expression levels of epithelial-mesenchymal transition (EMT) and stemness markers were analysed using reverse transcription-quantitative PCR (RT-qPCR) for mRNA expression and immunofluorescence assay for protein expression. To validate the role of VEGF in tumour growth, a VEGF receptor (VEGFR) inhibitor (sorafenib) was used. The results demonstrated that the hepatoma cells formed 3D spheroids that differed in size and density in the absence and presence of the growth factor, VEGF. In all spheroids, invasion and angiogenesis were more aggressive in 3D cultures in comparison to 2D conditions following treatment with VEGF. Mechanistically, the VEGF-mediated increase in the levels of EMT markers, including Vimentin, N-cadherin 2 (Cadherin 2) and Thy-1 Cell Surface Antigen was observed in the 2D and 3D cultures. Sorafenib treatment for 24 h culminated in a marked reduction in cell migration, cell-cell adhesion, spheroid compaction and EMT gene expression in 3D models as compared to the 2D models. On the whole, the findings of the present study suggested that as compared to the 2D cell cultures, 3D cell cultures model may be used as a more realistic model for the study of tumour growth and invasion in the presence of angiogenic factors, as well as for tumour inhibitor screening.