Three-Dimensional Cell Cultures as an In Vitro Tool for Prostate Cancer Modeling and Drug Discovery

A Tween-80 modified hypoxia/esterase dual stimulus-activated nanomicelle as a delivery platform for carmustine - Design, synthesis, and biological evaluation

As a clinical anti-glioma agent, the therapeutic effect of carmustine (BCNU) was largely decreased because of the drug resistance mediated by O6-alkylguanine-DNA alkyltransferase (AGT) and the blood-brain barrier (BBB). To overcome these obstacles, we synthesized a BCNU-loaded hypoxia/esterase dual stimulus-activated nanomicelle, abbreviated as T80-HACB/BCNU NPs. In this nano-system, Tween 80 acts as the functional coating on the surface of the micelle to facilitate transport across the BBB. Hyaluronic acid (HA) with active tumor-targeting capability was linked with the hypoxia-sensitive AGT inhibitors (O6-azobenzyloxycarbonyl group) via an esterase-activated ester bond. The obtained T80-HACB/BCNU NPs had an average particle size of 232.10 ± 10.66 nm, the zeta potential of -18.13 ± 0.91 mV, and it showed high drug loading capacity, eximious biocompatibility and dual activation of hypoxia/esterase drug release behavior. The obtained T80-HACB/BCNU NPs showed enhanced cytotoxicity against hypoxic T98G and SF763 cells with IC50 at 132.2 μM and 133.1 μM, respectively. T80 modification improved the transportation of the micelle across an in vitro BBB model. The transport rate of the T80-HACB/Cou6 NPs group was 12.37 %, which was 7.6-fold (p<0.001) higher than the micelle without T80 modification. T80-HACB/BCNU NPs will contribute to the development of novel CENUs chemotherapies with high efficacy.

Growing Role of 3D In Vitro Cell Cultures in the Study of Cellular and Molecular Mechanisms: Short Focus on Breast Cancer, Endometriosis, Liver and Infectious Diseases

Over the past decade, the development of three-dimensional (3D) models has increased exponentially, facilitating the unravelling of fundamental and essential cellular mechanisms by which cells communicate with each other, assemble into tissues and organs and respond to biochemical and biophysical stimuli under both physiological and pathological conditions. This section presents a concise overview of the most recent updates on the significant contribution of different types of 3D cell cultures including spheroids, organoids and organ-on-chip and bio-printed tissues in advancing our understanding of cellular and molecular mechanisms. The case studies presented include the 3D cultures of breast cancer (BC), endometriosis, the liver microenvironment and infections. In BC, the establishment of 3D culture models has permitted the visualization of the role of cancer-associated fibroblasts in the delivery of exosomes, as well as the significance of the physical properties of the extracellular matrix in promoting cell proliferation and invasion. This approach has also become a valuable tool in gaining insight into general and specific mechanisms of drug resistance. Given the considerable heterogeneity of endometriosis, 3D models offer a more accurate representation of the in vivo microenvironment, thereby facilitating the identification and translation of novel targeted therapeutic strategies. The advantages provided by 3D models of the hepatic environment, in conjunction with the high throughput characterizing various platforms, have enabled the elucidation of complex molecular mechanisms underlying various threatening hepatic diseases. A limited number of 3D models for gut and skin infections have been developed. However, a more profound comprehension of the spatial and temporal interactions between microbes, the host and their environment may facilitate the advancement of in vitro, ex vivo and in vivo disease models. Additionally, it may pave the way for the development of novel therapeutic approaches in diverse research fields. The interested reader will also find concluding remarks on the challenges and prospects of using 3D cell cultures for discovering cellular and molecular mechanisms in the research areas covered in this review.

TempEasy 3D Hydrogel Coculture System Provides Mechanistic Insights into Prostate Cancer Bone Metastasis

Patients diagnosed with advanced prostate cancer (PCa) often experience incurable bone metastases; however, a lack of relevant experimental models has hampered the study of disease mechanisms and the development of therapeutic strategies. In this study, we employed the recently established Temperature-based Easy-separable (TempEasy) 3D cell coculture system to investigate PCa bone metastasis. Through coculturing PCa and bone cells for 7 days, our results showed a reduction in PCa cell proliferation, an increase in neovascularization, and an enhanced metastasis potential when cocultured with bone cells. Additionally, we observed increased cell proliferation, higher stemness, and decreased bone matrix protein expression in bone cells when cocultured with PCa cells. Furthermore, we demonstrated that the stiffness of the extracellular matrix had a negligible impact on molecular responses in both primary (PCa cells) and distant malignant (bone cells) sites. The TempEasy 3D hydrogel coculture system is an easy-to-use and versatile coculture system that provides valuable insights into the mechanisms of cell-cell communication and interaction in cancer metastasis.

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.

Effects of docetaxel on metastatic prostate (DU-145) carcinoma cells cultured as 2D monolayers and 3D multicellular tumor spheroids

Docetaxel (DTX) is one of the chemotherapeutic drugs indicated as a first-line treatment against metastatic prostate cancer (mPCa). This study aimed to compare the impact of DTX on mPCa (DU-145) tumor cells cultured as 2D monolayers and 3D multicellular tumor spheroids (MCTS) in vitro. The cells were treated with DTX (1-96 µM) at 24, 48, or 72 hr in cell viability assays (resazurin, phosphatase acid, and lactate dehydrogenase). Cell death was assessed with fluorescent markers and proliferation by clonogenic assay (2D) and morphology, volume, and integrity assay (3D). The cell invasion was determined using transwell (2D) and extracellular matrix (ECM) (3D). Results showed that DTX decreased cell viability in both culture models. In 2D, the IC50 (72 hr) values were 11.06 μM and 14.23 μM for resazurin and phosphatase assays, respectively. In MCTS, the IC50 values for the same assays were 114.9 μM and 163.7 μM, approximately 10-fold higher than in the 2D model. The % of viable cells decreased, while the apoptotic cell number was elevated compared to the control in 2D. In 3D spheroids, only DTX 24 μM induced apoptosis. DTX (≥24 μM at 216 hr) lowered the volume, and DTX 96 μM completely disintegrated the MCTS. DTX reduced the invasion of mPCa cells to matrigel (2D) and migration from MCTS to the ECM. Data demonstrated significant differences in drug response between 2D and 3D cell culture models using mPCa DU-145 tumor cells. MCTS resembles the early stages of solid tumors in vivo and needs to be considered in conjunction with 2D cultures when searching for new therapeutic targets.

Differentiation States of Phenotypic Transition of Melanoma Cells Are Revealed by 3D Cell Cultures

Melanoma is characterized by high metastatic potential favored by the epithelial-to-mesenchymal transition (EMT), leading melanoma cells to exhibit a spectrum of typical EMT markers. This study aimed to analyze the expression of EMT markers in A375 and BLM melanoma cell lines cultured in 2D monolayers and 3D spheroids using morphological and molecular methods. The expression of EMT markers was strongly affected by 3D arrangement and revealed a hybrid phenotype for the two cell lines. Indeed, although E-cadherin was almost undetectable in both A375 and BLM cells, cortical actin was detected in A375 2D monolayers and 3D spheroids and was strongly expressed in BLM 3D spheroids. The mesenchymal marker N-cadherin was significantly up-regulated in A375 3D spheroids while undetectable in BLM cells, but vimentin was similarly expressed in both cell lines at the gene and protein levels. This pattern suggests that A375 cells exhibit a more undifferentiated/mesenchymal phenotype, while BLM cells have more melanocytic/differentiated characteristics. Accordingly, the Zeb1 and 2, Slug, Snail and Twist gene expression analyses showed that they were differentially expressed in 2D monolayers compared to 3D spheroids, supporting this view. Furthermore, A375 cells are characterized by a greater invasive potential, strongly influenced by 3D arrangement, compared to the BLM cell line, as evaluated by SDS-zymography and TIMPs gene expression analysis. Finally, TGF-β1, a master controller of EMT, and lysyl oxidase (LOX), involved in melanoma progression, were strongly up-regulated by 3D arrangement in the metastatic BLM cells alone, likely playing a role in the metastatic phases of melanoma progression. Overall, these findings suggest that A375 and BLM cells possess a hybrid/intermediate phenotype in relation to the expression of EMT markers. The former is characterized by a more mesenchymal/undifferentiated phenotype, while the latter shows a more melanocytic/differentiated phenotype. Our results contribute to the characterization of the role of EMT in melanoma cells and confirm that a 3D cell culture model could provide deeper insight into our understanding of the biology of melanoma.

Phenotypic Characterization of 2D and 3D Prostate Cancer Cell Systems Using Electrical Impedance Spectroscopy

Prostate cancer is the second leading cause of death in men. A challenge in treating prostate cancer is overcoming cell plasticity, which links cell phenotype changes and chemoresistance. In this work, a microfluidic device coupled with electrical impedance spectroscopy (EIS), an electrode-based cell characterization technique, was used to study the electrical characteristics of phenotype changes for (1) prostate cancer cell lines (PC3, DU145, and LNCaP cells), (2) cells grown in 2D monolayer and 3D suspension cell culture conditions, and (3) cells in the presence (or absence) of the anti-cancer drug nigericin. To validate observations of phenotypic change, we measured the gene expression of two epithelial markers, E-cadherin (CDH1) and Tight Junction Protein 1 (ZO-1). Our results showed that PC3, DU145, and LNCaP cells were discernible with EIS. Secondly, moderate phenotype changes based on differences in cell culture conditions were detected with EIS and supported by the gene expression of CDH1. Lastly, we showed that EIS can detect chemoresistant-related cell phenotypes with nigericin drug treatment. EIS is a promising label-free tool for detecting cell phenotype changes associated with chemoresistance. Further development will enable the detection and characterization of many other types of cancer cells.

A cell-impermeable luminogenic probe for near-infrared imaging of prostate-specific membrane antigen in prostate cancer microenvironments

Prostate-specific membrane antigen (PSMA) imaging probes are a promising tool for the diagnosis and image-guided surgery of prostate cancer (PCa). However, PSMA-specific luminescence probes for PCa detection and heterogeneity studies with high imaging contrast are lacking. Here, we report the first near-infrared (NIR) iridium(III) complex for the wash-free and specific imaging of PSMA in PCa cells and spheroids. The conjugation of a PSMA inhibitor, Lys-urea-Glu, to an iridium(III) complex synergizes the PSMA-specific affinity and biocompatibility of the inhibitor with the desirable photophysical properties of the iridium(III) complex, including NIR emission (670 nm), high photostability and a large Stokes shift. The cellular impermeability of the probe along with its strong binding affinity to PSMA enhances its specificity for PSMA, enabling the washing-free luminescent imaging of membrane PSMA with lower cytotoxicity. The probe was successfully applied for selectively visualizing PSMA-expressing cells and for the imaging of PSMA in a multicellular PCa model with good imaging penetration, indicating its potential use in complicated and heterogeneous tumor microenvironments. Furthermore, the probe showed good imaging performance in the PCa-bearing tumor mice via targeting PSMA in vivo. This work provides a novel strategy for the development of highly sensitive and specific NIR probes for PSMA in biological systems in vitro, which is of great significance for the precise diagnosis of PCa and for elucidating PCa heterogeneity.

Assessing Radiosensitivity: Effects of Acute Ionizing Radiation on Inflammation and Apoptosis in Macrophage Cell Line (RAW 264.7)

Introduction: The responses of biological systems to various types of radiation have multifaceted dimensions. In the field of ionizing radiation, in vitro external gamma radiation therapy has primarily been studied as a model to elucidate the challenges that biological systems face from radiation effects. Exposure of cells/organisms to gamma radiation results in a cascade of ionization events that can cause severe and irreversible biological damage. However, the biological responses and oxidative stress-related mechanisms under acute radiation conditions remain poorly understood in inflammatory systems. The present study aimed to provide a model of the effect of ionizing radiation on macrophages, which play a pivotal role in the mechanisms of inflammation, to assess the impact of radiotherapy as an approach to treating inflammatory diseases. Methods: A macrophage cell line (RAW 264.7) was cultured and exposed to different doses of gamma radiation (4, 6, 8, 10 Gy). Cell viability, apoptosis, cell cycle, migration, nitric oxide (NO) and prostaglandin E2 (PGE2) production, expression of pro-inflammatory and apoptotic genes, and cytokine secretion of macrophages were also evaluated. Results: The results showed that gamma radiation at 4 Gy had a low effect on macrophage characteristics and cytokine secretion patterns. In contrast, higher doses (8 and 10 Gy) increased DNA damage, expression of apoptotic genes, and secretion of NO and PGE2 cytokines. 6 Gy radiation, the maximum radiation dose, showed moderate non-destructive effects and inflammation process modulation. In this study, doses higher than 6 Gy of Gamma radiation caused cell mortality. Conclusion: It appears that 6 Gy of gamma radiation modulates the inflammatory cascade caused by macrophage cells.

A Novel NCI-H69AR Drug-Resistant Small-Cell Lung Cancer Mini-Tumor Model for Anti-Cancer Treatment Screening

Small-cell lung cancer is a fast-growing carcinoma with a poor prognosis and a high level of relapse due to multi-drug resistance (MDR). Genetic mutations that lead to the overexpression of efflux transporter proteins can contribute to MDR. In vitro cancer models play a tremendous role in chemotherapy development and the screening of possible anti-cancer molecules. Low-cost and simple in vitro models are normally used. Traditional two-dimensional (2D) models have numerous shortcomings when considering the physiological resemblance of an in vivo setting. Three-dimensional (3D) models aim to bridge the gap between conventional 2D models and the in vivo setting. Some of the advantages of functional 3D spheroids include better representation of the in vivo physiology and tumor characteristics when compared to traditional 2D cultures. During this study, an NCI-H69AR drug-resistant mini-tumor model (MRP1 hyperexpressive) was developed by making use of a rotating clinostat bioreactor system (ClinoStar®; CelVivo ApS, Odense, Denmark). Spheroid growth and viability were assessed over a 25-day period to determine the ideal experimental period with mature and metabolically stable constructs. The applicability of this model for anti-cancer research was evaluated through treatment with irinotecan, paclitaxel and cisplatin for 96 h, followed by a 96 h recovery period. Parameters measured included planar surface area measurements, estimated glucose consumption, soluble protein content, intracellular adenosine triphosphate levels, extracellular adenylate kinase levels, histology and efflux transporter gene expression. The established functional spheroid model proved viable and stable during the treatment period, with retained relative hyperexpression of the MRP1 efflux transporter gene but increased expression of the P-gp transporter gene compared to the cells cultured in 2D. As expected, treatment with the abovementioned anti-cancer drugs at clinical doses (100 mg/m2 irinotecan, 80 mg/m2 paclitaxel and 75 mg/m2 cisplatin) had minimal impact on the drug-resistant mini-tumors, and the functional spheroid models were able to recover following the removal of treatment.

Microfluidic-based prostate cancer model for investigating the secretion of prostate-specific antigen and microRNAs in vitro

The study of prostate cancer in vitro relies on established cell lines that lack important physiological characteristics, such as proper polarization and expression of relevant biomarkers. Microphysiological systems (MPS) can replicate cancer microenvironments and lead to cellular phenotypic changes that better represent organ physiology in vitro. In this study, we developed an MPS model comprising conventional prostate cancer cells to evaluate their activity under dynamic culture conditions. Androgen-sensitive (LNCaP) and androgen-insensitive (PC3) cells were grown in conventional and 3D cultures, both static and dynamic. Cell morphology, the secretion of prostate-specific antigen, and the expression of key prostate markers and microRNAs were analyzed. LNCaP formed spheroids in 3D and MPS cultures, with morphological changes supported by the upregulation of cytokeratins and adhesion proteins. LNCaP also maintained a constant prostate-specific antigen secretion in MPS. PC3 cells did not develop complex structures in 3D and MPS cultures. PSA expression at the gene level was downregulated in LNCaP-MPS and considerably upregulated in PC3-MPS. MicroRNA expression was altered by the 3D static and dynamic culture, both intra- and extracellularly. MicroRNAs associated with prostate cancer progression were mostly upregulated in LNCaP-MPS. Overall dynamic cell culture substantially altered the morphology and expression of LNCaP cells, arguably augmenting their prostate cancer phenotype. This novel approach demonstrates that microRNA expression in prostate cancer cells is sensitive to external stimuli and that MPS can effectively promote important physiological changes in conventional prostate cancer models.

Let’s Go 3D! New Generation of Models for Evaluating Drug Response and Resistance in Prostate Cancer

Prostate cancer (PC) is the third most frequently diagnosed cancer worldwide and the second most frequent in men. Several risk factors can contribute to the development of PC, and those include age, family history, and specific genetic mutations. So far, drug testing in PC, as well as in cancer research in general, has been performed on 2D cell cultures. This is mainly because of the vast benefits these models provide, including simplicity and cost effectiveness. However, it is now known that these models are exposed to much higher stiffness; lose physiological extracellular matrix on artificial plastic surfaces; and show changes in differentiation, polarization, and cell–cell communication. This leads to the loss of crucial cellular signaling pathways and changes in cell responses to stimuli when compared to in vivo conditions. Here, we emphasize the importance of a diverse collection of 3D PC models and their benefits over 2D models in drug discovery and screening from the studies done so far, outlining their benefits and limitations. We highlight the differences between the diverse types of 3D models, with the focus on tumor–stroma interactions, cell populations, and extracellular matrix composition, and we summarize various standard and novel therapies tested on 3D models of PC for the purpose of raising awareness of the possibilities for a personalized approach in PC therapy.

Experimental in vitro, ex vivo and in vivo models in prostate cancer research

Androgen deprivation therapy has a central role in the treatment of advanced prostate cancer, often causing initial tumour remission before increasing independence from signal transduction mechanisms of the androgen receptor and then eventual disease progression. Novel treatment approaches are urgently needed, but only a fraction of promising drug candidates from the laboratory will eventually reach clinical approval, highlighting the demand for critical assessment of current preclinical models. Such models include standard, genetically modified and patient-derived cell lines, spheroid and organoid culture models, scaffold and hydrogel cultures, tissue slices, tumour xenograft models, patient-derived xenograft and circulating tumour cell eXplant models as well as transgenic and knockout mouse models. These models need to account for inter-patient and intra-patient heterogeneity, the acquisition of primary or secondary resistance, the interaction of tumour cells with their microenvironment, which make crucial contributions to tumour progression and resistance, as well as the effects of the 3D tissue network on drug penetration, bioavailability and efficacy.

Three-Dimensional (3D) in vitro cell culture protocols to enhance glioblastoma research

Three-dimensional (3D) cell culture models can help bridge the gap between in vitro cell cultures and in vivo responses by more accurately simulating the natural in vivo environment, shape, tissue stiffness, stressors, gradients and cellular response while avoiding the costs and ethical concerns associated with animal models. The inclusion of the third dimension in 3D cell culture influences the spatial organization of cell surface receptors that interact with other cells and imposes physical restrictions on cells in compared to Two-dimensional (2D) cell cultures. Spheroids' distinctive cyto-architecture mimics in vivo cellular structure, gene expression, metabolism, proliferation, oxygenation, nutrition absorption, waste excretion, and drug uptake while preserving cell-extracellular matrix (ECM) connections and communication, hence influencing molecular processes and cellular phenotypes. This protocol describes the in vitro generation of tumourspheroids using the low attachment plate, hanging drop plate, and cellusponge natural scaffold based methods. The expected results from these protocols confirmed the ability of all these methods to create uniform tumourspheres.

Advances in 3D culture systems for therapeutic discovery and development in brain cancer

This review focuses on recent advances in 3D culture systems that promise more accurate therapeutic models of the glioblastoma multiforme (GBM) tumor microenvironment (TME), such as the unique anatomical, cellular, and molecular features evident in human GBM. The key components of a GBM TME are outlined, including microbiomes, vasculature, extracellular matrix (ECM), infiltrating parenchymal and peripheral immune cells and molecules, and chemical gradients. 3D culture systems are evaluated against 2D culture systems and in vivo animal models. The main 3D culture techniques available are compared, with an emphasis on identifying key gaps in knowledge for the development of suitable platforms to accurately model the intricate components of the GBM TME.

Comparison of Radiation Response between 2D and 3D Cell Culture Models of Different Human Cancer Cell Lines

Radiation therapy is one of the most effective tools in cancer therapy. However, success varies individually, necessitating improved understanding of radiobiology. Three-dimensional (3D) tumor spheroids are increasingly gaining attention, being a superior in vitro cancer model compared to 2D cell cultures. This in vitro study aimed at comparing radiation responses in 2D and 3D cell culture models of different human cancer cell lines (PC-3, LNCaP and T-47D) irradiated with varying doses (1, 2, 4, 6, 8 or 20 Gy) of X-ray beams. Radiation response was analyzed by growth analysis, various cell viability assays (e.g., clonogenic assay, resazurin assay) and amount of DNA damage (γH2AX Western Blot). Results showed decreasing cell proliferation with the increase of radiation doses for all cell lines in monolayers and spheroids of LNCaP and T-47D. However, significantly lower radiosensitivity was detected in spheroids, most pronounced in PC-3, evincing radiation resistance of PC-3 spheroids up to 8 Gy and significant growth inhibition only by a dose escalation of 20 Gy. Cell line comparison showed highest radiosensitivity in LNCaP, followed by T-47D and PC-3 in 2D, whereas, in 3D, T-47D showed highest sensitivity. The results substantiate the significant differences in radiobiological response to X-rays between 2D and 3D cell culture models.

Nano-Hydroxyapatite/PLGA Mixed Scaffolds as a Tool for Drug Development and to Study Metastatic Prostate Cancer in the Bone

(1) Background: Three-dimensional (3D) in vitro, biorelevant culture models that recapitulate cancer progression can help elucidate physio-pathological disease cues and enhance the screening of more effective therapies. Insufficient research has been conducted to generate in vitro 3D models to replicate the spread of prostate cancer to the bone, a key metastatic site of the disease, and to understand the interplay between the key cell players. In this study, we aim to investigate PLGA and nano-hydroxyapatite (nHA)/PLGA mixed scaffolds as a predictive preclinical tool to study metastatic prostate cancer (mPC) in the bone and reduce the gap that exists with traditional 2D cultures. (2) Methods: nHA/PLGA mixed scaffolds were produced by electrospraying, compacting, and foaming PLGA polymer microparticles, +/- nano-hydroxyapatite (nHA), and a salt porogen to produce 3D, porous scaffolds. Physicochemical scaffold characterisation together with an evaluation of osteoblastic (hFOB 1.19) and mPC (PC-3) cell behaviour (RT-qPCR, viability, and differentiation) in mono- and co-culture, was undertaken. (3) Results: The results show that the addition of nHA, particularly at the higher-level impacted scaffolds in terms of mechanical and degradation behaviour. The nHA 4 mg resulted in weaker scaffolds, but cell viability increased. Qualitatively, fluorescent imaging of cultures showed an increase in PC-3 cells compared to osteoblasts despite lower initial PC-3 seeding densities. Osteoblast monocultures, in general, caused an upregulation (or at least equivalent to controls) in gene production, which was highest in plain scaffolds and decreased with increases in nHA. Additionally, the genes were downregulated in PC3 and co-cultures. Further, drug toxicity tests demonstrated a significant effect in 2D and 3D co-cultures. (4) Conclusions: The results demonstrate that culture conditions and environment (2D versus 3D, monoculture versus co-culture) and scaffold composition all impact cell behaviour and model development.

Recent Advances of Organ-on-a-Chip in Cancer Modeling Research

Although many studies have focused on oncology and therapeutics in cancer, cancer remains one of the leading causes of death worldwide. Due to the unclear molecular mechanism and complex in vivo microenvironment of tumors, it is challenging to reveal the nature of cancer and develop effective therapeutics. Therefore, the development of new methods to explore the role of heterogeneous TME in individual patients' cancer drug response is urgently needed and critical for the effective therapeutic management of cancer. The organ-on-chip (OoC) platform, which integrates the technology of 3D cell culture, tissue engineering, and microfluidics, is emerging as a new method to simulate the critical structures of the in vivo tumor microenvironment and functional characteristics. It overcomes the failure of traditional 2D/3D cell culture models and preclinical animal models to completely replicate the complex TME of human tumors. As a brand-new technology, OoC is of great significance for the realization of personalized treatment and the development of new drugs. This review discusses the recent advances of OoC in cancer biology studies. It focuses on the design principles of OoC devices and associated applications in cancer modeling. The challenges for the future development of this field are also summarized in this review. This review displays the broad applications of OoC technique and has reference value for oncology development.

Evaluation of Anticancer and Cytotoxic Effects of Genistein on PC3 Prostate Cell Line under Three-Dimensional Culture Medium

Background

Prostate cancer is a major cause of disease and mortality among men. Genistein (GNT) is an isoflavone found naturally in legumes. Isoflavones, a subset of phytoestrogens, are structurally similar to mammalian estrogens. This study aimed to evaluate the anticancer and cytotoxic effects of GNT on PC3 cell line under three dimensional (3D) culture medium.

Methods

The 3D culture was created by encapsulating the PC3 cells in alginate hydrogel. MTT assay, neutral red uptake, comet assay, and cytochrome C assay were used to study the anticancer and cytotoxic effects of GNT at 120, 240, and 480 μM concentrations. Also, nitric oxide (NO), catalase, and glutathione assay levels were determined to evaluate the effect of GNT on the cellular stress. The culture medium was used as the negative control.

Results

GNT reduced the production of cellular NO and increased the production of catalase and glutathione, confirming the results of the NO test. Evaluation of the toxicity effect of GNT at the concentrations of 120, 240, and 480 μM using comet assay showed that this chemical agent induces apoptosis in PC3 cells in a dose-dependent manner. As the level of cytochrome C in PC3 cells treated with different concentrations of GNT was not significantly different from that of the control, GNT could induce apoptosis in PC3 cells through the non-mitochondrial pathway.

Conclusion

The findings of this study disclose that the anticancer effect of GNT on PC3 cells under 3D culture conditions could increase the effectiveness of treatment. Also, the cell survival rate is dependent on GNT concentration.

The Antitumoral/Antimetastatic Action of the Flavonoid Brachydin A in Metastatic Prostate Tumor Spheroids In Vitro Is Mediated by (Parthanatos) PARP-Related Cell Death

Metastatic prostate cancer (mPCa) is resistant to several chemotherapeutic agents. Brachydin A (BrA), a glycosylated flavonoid extracted from Fridericia platyphylla, displays a remarkable antitumoral effect against in vitro mPCa cells cultured as bidimensional (2D) monolayers. Considering that three-dimensional (3D) cell cultures provide a more accurate response to chemotherapeutic agents, this study investigated the antiproliferative/antimetastatic effects of BrA and the molecular mechanisms underlying its action in mPCa spheroids (DU145) in vitro. BrA at 60–100 μM was cytotoxic, altered spheroid morphology/volume, and suppressed cell migration and tumor invasiveness. High-content analysis revealed that BrA (60–100 µM) reduced mitochondrial membrane potential and increased apoptosis and necrosis markers, indicating that it triggered cell death mechanisms. Molecular analysis showed that (i) 24-h treatment with BrA (80–100 µM) increased the protein levels of DNA disruption markers (cleaved-PARP and p-γ-H2AX) as well as decreased the protein levels of anti/pro-apoptotic (BCL-2, BAD, and RIP3K) and cell survival markers (p-AKT1 and p-44/42 MAPK); (ii) 72-h treatment with BrA increased the protein levels of effector caspases (CASP3, CASP7, and CASP8) and inflammation markers (NF-kB and TNF-α). Altogether, our results suggest that PARP-mediated cell death (parthanatos) is a potential mechanism of action. In conclusion, BrA confirms its potential as a candidate drug for preclinical studies against mPCa.

Stromal Fibroblasts Counteract the Caveolin-1-Dependent Radiation Response of LNCaP Prostate Carcinoma Cells

In prostate cancer (PCa), a characteristic stromal–epithelial redistribution of the membrane protein caveolin 1 (CAV1) occurs upon tumor progression, where a gain of CAV1 in the malignant epithelial cells is accompanied by a loss of CAV1 in the tumor stroma, both facts that were correlated with higher Gleason scores, poor prognosis, and pronounced resistance to therapy particularly to radiotherapy (RT). However, it needs to be clarified whether inhibiting the CAV1 gain in the malignant prostate epithelium or limiting the loss of stromal CAV1 would be the better choice for improving PCa therapy, particularly for improving the response to RT; or whether ideally both processes need to be targeted. Concerning the first assumption, we investigated the RT response of LNCaP PCa cells following overexpression of different CAV1 mutants. While CAV1 overexpression generally caused an increased epithelial-to-mesenchymal phenotype in respective LNCaP cells, effects that were accompanied by increasing levels of the 5′-AMP-activated protein kinase (AMPK), a master regulator of cellular homeostasis, only wildtype CAV1 was able to increase the three-dimensional growth of LNCaP spheroids, particularly following RT. Both effects could be limited by an additional treatment with the SRC inhibitor dasatinib, finally resulting in radiosensitization. Using co-cultured (CAV1-expressing) fibroblasts as an approximation to the in vivo situation of early PCa it could be revealed that RT itself caused an activated, more tumor-promoting phenotype of stromal fibroblats with an increased an increased metabolic potential, that could not be limited by combined dasatinib treatment. Thus, targeting fibroblasts and/or limiting fibroblast activation, potentially by limiting the loss of stromal CAV1 seems to be absolute for inhibiting the resistance-promoting CAV1-dependent signals of the tumor stroma.

Three-dimensional cell culture for the study of nasal polyps

OBJECTIVES

Three-dimensional (3D) cell cultures have many applications such as stem cell biology research, new drug discovery, cancer, and Chronic Rhinosinusitis with Nasal Polyps (CRSwNP). This disease is characterized by a significant impact on quality of life and productivity. The diversity of factors that act in the progression of CRSwNP point to the creation of a cell culture model that allows the integration of different cell types with extracellular matrix. This work aimed to create a cell culture model in 3 dimensions (spheroids) for the study of Nasal Polyposis.

METHODS

Nasal polyp tissue from patients diagnosed with CRSwNP was mechanically dissociated using tweezers and a scalpel and the solution containing cells and small aggregates of nasal polyps was transferred to a Petri dish containing 5 mL of culture medium at the concentration of 10⁶ cells/mL.

RESULTS

The spheroids were cultivated for 20 days, fixed and analyzed using confocal microscopy. In a 3D culture environment, the spheroids were formed both by clustering cells and from small tissue fragments. In the cultures analyzed, the ciliary beat was present from the dissociation of the cells up to 20 days in culture.

CONCLUSION

Our findings also point to these characteristics showing the environment generated in our study, the cells remained differentiated for a longer time and with ciliary beating. Thus, this work shows that nasal polyp-derived cells can be maintained in a 3D environment, enabling better strategies for understanding CRSwNP in situations similar to those found in vivo.

LEVEL OF EVIDENCE

Laboratory studies.

Altered expression of genes identified in rats with prostatic chronic inflammation in a prostate spheroid model treated by estradiol/testosterone

Rats are the standard model for male reproductive toxicity testing. Rat prostates are physiologically and anatomically different from those of humans. Drug and chemical toxicity testing would benefit from an in vitro model of human prostate cells. Recently, spheroids derived by three-dimensional culture of human cell lines have been used for assessing drug and chemical toxicity in vitro as they mimic in vivo environments more closely than two-dimensional culture. However, forming consistently sized, uniform spheroids is technically challenging for toxicity testing. The purpose of this study was to identify potential genetic markers for assessing prostatic toxicity in spheroids. We formed prostate spheroids using agarose-coated plates seeded with human primary prostate epithelial cells. Prostate spheroids were treated with either 17β-estradiol (E2) or testosterone (T) on days 2-7 of culture. Samples were harvested on culture day 7. qPCR was used to examine gene expression levels previously identified in rats with chronic inflammation exposed to estradiol benzoate, E2 and/or T. Changes in some gene expression levels were observed in the spheroids treated with E2 or T. We found that treatment with 1 nM E2 and/or 10 μM T significantly altered spheroid proliferation and viability, as well as the expression levels of genes including Nanog homeobox (NANOG), C-C motif chemokine ligand 2 (CCL2) and bone morphogenetic protein receptor type 2 (BMPR2). Further studies using biologically active molecules with prostatic toxicity are needed to verify the results and to determine whether gene expression changes in the spheroid are specific to E2 or T treatment.

Development and biological evaluation of AzoBGNU: A novel hypoxia-activated DNA crosslinking prodrug with AGT-inhibitory activity

Chloroethylnitrosoureas (CENUs) are an important family of chemotherapies in clinical treatment of cancers, which exert antitumor activity by inducing the formation of DNA interstrand crosslinks (dG-dC ICLs). However, the drug resistance mediated by O⁶-alkylguanine-DNA alkyltransferase (AGT) and absence of tumor-targeting ability largely decrease the antitumor efficacy of CENUs. In this study, we synthesized an azobenzene-based hypoxia-activated combi-nitrosourea prodrug, AzoBGNU, and evaluated its hypoxic selectivity and antitumor activity. The prodrug was composed of a CENU pharmacophore and an O⁶-benzylguanine (O⁶-BG) analog moiety masked by a N,N-dimethyl-4-(phenyldiazenyl)aniline segment as a hypoxia-activated trigger, which was designed to be selectively reduced via azo bond break in hypoxic tumor microenvironment, accompanied with releasing of an O⁶-BG analog to inhibit AGT and a chloroethylating agent to induce dG-dC ICLs. AzoBGNU exhibited significantly increased cytotoxicity and apoptosis-inducing ability toward DU145 cells under hypoxia compared with normoxia, indicating the hypoxia-responsiveness as expected. Predominant higher cytotoxicity was observed in the cells treated by AzoBGNU than those by traditional CENU chemotherapy ACNU and its combination with O⁶-BG. The levels of dG-dC ICLs in DU145 cells induced by AzoBGNU was remarkably enhanced under hypoxia, which was approximately 6-fold higher than those in the AzoBGNU-treated groups under normoxia and those in the ACNU-treated groups. The results demonstrated that azobenzene-based combi-nitrosourea prodrug possessed desirable tumor-hypoxia targeting ability and eliminated chemoresistance compared with the conventional CENUs.

Tumor spheroids and organoids as preclinical model systems

The generation of three-dimensional (3D) cancer models is a novel and fascinating development in the study of personalized medicine and tumor-specific drug delivery. In addition to the classical two-dimensional (2D) adherent cell culture models, 3D spheroid and organoid cancer models that mimic the microenvironment of cancer tissue are emerging as an important preclinical model system. 3D cancer models form, similar to cancer, multiple cell-cell and cell-extracellular matrix interactions and activate different cellular cascades/pathways, like proliferation, quiescence, senescence, and necrotic or apoptotic cell death. Further, it is possible to analyze genetic variations and mutations, the microenvironment of cell-cell interactions, and the uptake of therapeutics and nanoparticles in nanomedicine. Important is also the analysis of cancer stem cells (CSCs), which could play key roles in resistance to therapy and cancer recurrence. Tumor spheroids can be generated from one tumor-derived cell line or from co-culture of two or more cell lines. Tumor organoids can be derived from tumors or may be generated from CSCs that differentiate into multiple facets of cancerous tissue. Similarly, tumorspheres can be generated from a single CSC. By transplanting spheroids and organoids into immune-deficient mice, patient-derived xenografts can serve as a preclinical model to test therapeutics in vivo. Although the handling and analysis of 3D tumor spheroids and organoids is more complex, it will provide insights into various cancer processes that cannot be provided by 2D culture. Here a short overview of 3D tumor systems as preclinical models is provided.

Rational Design of Thermoresponsive Microgel Templates with Polydopamine Surface Coating for Microtissue Applications

Functional microgels provide a versatile basis for synthetic in vitro platforms as alternatives to animal experiments. The tuning of the physical, chemical, and biological properties of synthetic microgels can be achieved by blending suitable polymers and formulating them such to reflect the heterogenous and complex nature of biological tissues. Based on this premise, this paper introduces the development of volume-switchable core-shell microgels as 3D templates to enable cell growth for microtissue applications, using a systematic approach to tune the microgel properties based on a deep conceptual and practical understanding. Microscopic microgel design, such as the tailoring of the microgel size and spherical shape, is achieved by droplet-based microfluidics, while on a nanoscopic scale, a thermoresponsive polymer basis, poly(N-isopropylacrylamide) (PNIPAAm), is used to provide the microgel volume switchability. Since PNIPAAm has only limited cell-growth promoting properties, the cell adhesion on the microgel is further improved by surface modification with polydopamine, which only slightly affects the microgel properties, thereby simplifying the system. To further tune the microgel thermoresponsiveness, different amounts of N-hydroxyethylacrylamide are incorporated into the PNIPAAm network. In a final step, cell growth on the microgel surface is investigated, both at a single microgel platform and in spheroidal cell structures.

In Vitro 3D Cultures to Model the Tumor Microenvironment

Simple Summary

Tumor stroma is known to significantly influence cancer initiation and progression. In the last decade, 3D cell cultures have shown potential in modeling the tumor microenvironment. This review summarizes the main features of current 3D models, shedding light on their importance in the study of cancer biology and treatment.

Abstract

It is now well established that the tumor microenvironment plays a key role in determining cancer growth, metastasis and drug resistance. Thus, it is fundamental to understand how cancer cells interact and communicate with their stroma and how this crosstalk regulates disease initiation and progression. In this setting, 3D cell cultures have gained a lot of interest in the last two decades, due to their ability to better recapitulate the complexity of tumor microenvironment and therefore to bridge the gap between 2D monolayers and animal models. Herein, we present an overview of the 3D systems commonly used for studying tumor–stroma interactions, with a focus on recent advances in cancer modeling and drug discovery and testing.

A Novel SimpleDrop Chip for 3D Spheroid Formation and Anti-Cancer Drug Assay

Cell culture is important for the rapid screening of anti-cancer drug candidates, attracting intense interest. Traditional 2D cell culture has been widely utilized in cancer biological research. However, 3D cellular spheroids are able to recapitulate the in vivo microenvironment of tissues or tumors. Thus far, several 3D cell culture methods have been developed, for instance, the hanging drop method, spinner flasks and micropatterned plates. Nevertheless, these methods have been reported to have some disadvantages, for example, medium replacement is inconvenient or causes cellular damage. Here, we report on an easy-to-operate and useful micro-hole culture chip (SimpleDrop) for 3D cellular spheroid formation and culture and drug analysis, which has advantages over the traditional method in terms of its ease of operation, lack of shear force and environmentally friendliness. On this chip, we observed the formation of a 3D spheroid clearly. Three drugs (paclitaxel, cisplatin and methotrexate) were tested by both cell viability assay and drug-induced apoptotic assay. The results show that the three drugs present a similar conclusion: cell viability decreased over time and concentration. Moreover, the apoptotic experiment showed a similar trend to the live/dead cell assay, in that the fraction of the apoptotic and necrotic cells correlated with the concentration and time. All these results prove that our SimpleDrop method is a useful and easy method for the formation of 3D cellular spheroids, which shows its potential for both cell-cell interaction research, tissue engineering and anticancer drug screening.

Inhibition of the Histone Methyltransferase EZH2 Enhances Protumor Monocyte Recruitment in Human Mesothelioma Spheroids

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a long latency period and dismal prognosis. Recently, tazemetostat (EPZ-6438), an inhibitor of the histone methyltransferase EZH2, has entered clinical trials due to the antiproliferative effects reported on MPM cells. However, the direct and indirect effects of epigenetic reprogramming on the tumor microenvironment are hitherto unexplored. To investigate the impact of tumor-associated macrophages (TAMs) on MPM cell responsiveness to tazemetostat, we developed a three-dimensional MPM spheroid model that recapitulates in vitro, both monocytes’ recruitment in tumors and their functional differentiation toward a TAM-like phenotype (Mo-TAMs). Along with an increased expression of genes for monocyte chemoattractants, inhibitory immune checkpoints, immunosuppressive and M2-like molecules, Mo-TAMs promote tumor cell proliferation and spreading. Prolonged treatment of MPM spheroids with tazemetostat enhances both the recruitment of Mo-TAMs and the expression of their protumor phenotype. Therefore, Mo-TAMs profoundly suppress the antiproliferative effects due to EZH2 inhibition in MPM cells. Overall, our findings indicate that TAMs are a driving force for MPM growth, progression, and resistance to tazemetostat; therefore, strategies of TAM depletion might be evaluated to improve the therapeutic efficacy of pharmacological inhibition of EZH2.

Devices and techniques used to obtain and analyze three-dimensional cell cultures

Cell cultures are indispensable for both basic and applied research. Advancements in cell culture and analysis increase their utility for basic research and translational applications. A marked development in this direction is advent of three-dimensional (3D) cultures. The extent of advancement in 3D cell culture methods over the past decade has warranted referring to a single cell type being cultured as an aggregate or spheroid using simple scaffolds as "traditional." In recent years, the development of "next-generation" devices has enabled cultured cells to mimic their natural environments much better than the traditional 3D culture systems. Automated platforms like chip-based devices, magnetic- and acoustics-based assembly devices, di-electrophoresis (DEP), micro pocket cultures (MPoC), and 3D bio-printing provide a dynamic environment compared to the rather static conditions of the traditional simple scaffold-based 3D cultures. Chip-based technologies, which are centered on principles of microfluidics, are revolutionizing the ways in which cell culture and analysis can be compacted into table-top instruments. A parallel evolution in analytical devices enabled efficient assessment of various complex physiological and pathological endpoints. This is augmented by concurrent development of software enabling rapid large-scale automated data acquisition and analysis like image cytometry, elastography, optical coherence tomography, surface-enhanced Raman scattering (SERS), and biosensors. The techniques and devices utilized for the purpose of 3D cell culture and subsequent analysis depend primarily on the requirement of the study. We present here an in-depth account of the devices for obtaining and analyzing 3D cell cultures.

Three-Dimensional (3D) Culture Models in Cancer Investigation, Drug Testing and Immune Response Evaluation

Preclinical models for the definition of anti-cancer drug safety and efficacy are constantly evolving [...].

Metastatic behavior analyses of tetraspanin TM4SF5-expressing spheres in three-dimensional (3D) cell culture environment

Cancer metastasis involves diverse cellular functions via bidirectional communications between intracellular and extracellular spaces. To achieve development of the anti-metastatic drugs, one needs to consider the efficacy and mode of action (MOA) of the drug candidates to block the metastatic potentials of cancerous cells. Rather than under two-dimensional environment, investigation of the metastatic potentials under three-dimensional environment would be much pharmaceutically beneficent, since it can mimic the in vivo tumor lesions in cancer patients, leading to allowance of drug candidates analyzed in the 3D culture systems to lower failure rates during the anti-metastatic drug development. Here we have reviewed on the analyses of metastatic potentials of certain cancer models in 3D culture systems surrounded with extracellular matrix proteins, which could be supported by TM4SF5- and/or EMT-mediated actions. We particularly focused the initial events of the cancer metastasis, such as invasive outgrowth and dissemination from the cancer cell masses, spheroids, embedded in the 3D gel culture systems. This review summarizes the significance of tetraspanin TM4SF5 and Snail1 that are related to EMT in the metastatic potentials explored in the 3D gel systems.