Analysis of Gene Expression in 3D Spheroids Highlights a Survival Role for ASS1 in Mesothelioma

Fluorescence-Guided Spatial Drug Screening in 3D Colorectal Cancer Spheroids

The limited recapitulation of critical cancer features in 2D cultures causes poor translatability of preclinical results from in vitro assays to in vivo tumor models. This contributes to slow drug development with a low success rate. 3D cultures better recapitulate the tumor microenvironment, enabling more accurate predictions when screening drug candidates and improving the development of chemotherapeutics. Platinum (Pt) (IV) compounds are promising prodrugs designed to reduce the severe systemic toxicity of widely used Food and Drug Administration (FDA)-approved Pt(II) drugs such as cisplatin. Here, this work presents spatiotemporal evaluations in 3D colorectal cancer (CRC) spheroids of mitochondria-targeting Pt(IV) complexes. CRC spheroids provide a greater pathophysiological recapitulation of in vivo tumors than 2D cultures by a marked upregulation of the ABCG2 chemoresistance marker expression. Furthermore, new 3D-staining protocols are introduced to evaluate the real-time decrease in mitochondria membrane potential (ΔΨ) in CRC spheroids, and a Pt-sensing dye to quantify the Pt mitochondrial accumulation. Finally, this work demonstrates a correlation between in vitro results and the efficacy of the compounds in vivo. Overall, the CRC spheroids represent a fast and cost-effective model to assess the behavior of Pt compounds in vitro and predict their translational potential in CRC treatment.

3D cell subculturing pillar dish for pharmacogenetic analysis and high-throughput screening

A pillar dishe for subculture of 3D cultured cells on hydrogel spots (Matrigel and alginate) have been developed. Cells cultured in 3D in an extracellular matrix (ECM) can retain their intrinsic properties, but cells cultured in 2D lose their intrinsic properties as the cells stick to the bottom of the well. Previously, cells and ECM spots were dispensed on a conventional culture dish for 3D cultivation. However, as the spot shape and location depended on user handling, pillars were added to the dish to realize uniform spot shape and stable subculture, supporting 3D cell culture-based high-throughput screening (HTS). Matrigel and alginate were used as ECMs during 6-passage subculture. The growth rate of lung cancer cell (A549) was higher on Matrigel than on alginate. Cancer cell was subcultured in three dimensions in the proposed pillar dish and used for drug screening and differential gene expression analysis. Interestingly, stemness markers, which are unique characteristics of lung cancer cells inducing drug resistance, were upregulated in 3D-subcultured cells compared with those in 2D-subcultured cells. Additionally, the PI3K/Akt/mTOR, VEGFR1/2, and Wnt pathways, which are promising therapeutic targets for lung cancer, were activated, showing high drug sensitivity under 3D-HTS using the 3D-subcultured cells.

Establishment of an experimental model of canine malignant mesothelioma organoid culture using a three-dimensional culture method

Canine malignant mesothelioma (cMM) is a rare and drug-resistant malignant tumor. Due to few patients and experimental models, there have not been enough studies to demonstrate the pathogenesis of the disease and novel effective treatment for cMM. Since cMM resembles human MM (hMM) in histopathological characteristics, it is also considered a promising research model of hMM. Compared with conventional 2-dimensional (2D) culture methods, 3-dimensional (3D) organoid culture can recapitulate the properties of original tumor tissues. However, cMM organoids have never been developed. In the present study, we for the first time generated cMM organoids using the pleural effusion samples. Organoids from individual MM dogs were successfully generated. They exhibited the characteristics of MM and expressed mesothelial cell markers, such as WT-1 and mesothelin. The sensitivity to anti-cancer drugs was different in each strain of cMM organoids. RNA sequencing analysis showed cell adhesion molecule pathways were specifically upregulated in cMM organoids compared with their corresponding 2D cultured cells. Among these genes, the expression level of E-cadherin was drastically higher in the organoids than that in the 2D cells. In conclusion, our established cMM organoids might become a new experimental tool to provide new insights into canine and human MM therapy.

Three-dimensional culture conditioned bone marrow MSC secretome accelerates wound healing in a burn injury mouse model

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising regenerative therapeutic approach for wound healing. To determine the effects of cultured MSCs as a 2D monolayer (2D-MSCs) and 3D spheroids (3D-MSCs) on their secretomes, and to examine the effect of 3D-MSC secretomes on endothelial cells (ECs) and MSCs in a burn injury mouse model. MSCs were cultured as 2D monolayers (2D-MSCs) and 3D spheroids (3D-MSCs) and their cellular characteristics were evaluated by western blotting. 2D-MSC and 3D-MSC secretomes (condition medium: CM) were analyzed using an angiogenic array. The activation of ECs by 2D-MSC and 3D-MSC CMs was examined in cellular proliferation, migration, and tube formation assays. The wound healing effects of 2D-MSCs and 3D-MSCs were determined in vivo using a burn injury mouse model. 3D culture conditions altered the markers of components that regulate cell survival, cytoskeletal, adhesion, and proliferation. Interleukin-6 (IL-6), vascular endothelial growth factor A (VEGFA), IL-8, and chemokine (CXC motif) ligand 1 (CXCL1) were present at high levels in the CM of 3D-MSCs compared with 2D-MCs. 3D-MSC-CMs promoted the proliferation, migration, and tube formation of ECs. Furthermore, 3D-MSC treatment enhanced wound healing in a burn injury mouse model. 3D culture improves proangiogenic factors in the MSC secretome and 3D-MSCs represent a new cell-based treatment strategy for wound healing.

BAP1 Loss Is Associated with Higher ASS1 Expression in Epithelioid Mesothelioma: Implications for Therapeutic Stratification

The nuclear deubiquitylase BRCA1-associated protein 1 (BAP1) is frequently inactivated in malignant pleural mesothelioma (MPM) and germline BAP1 mutation predisposes to cancers including MPM. To explore the influence on cell physiology and drug sensitivity, we sequentially edited a predisposition mutation (w-) and a promoter trap (KO) into human mesothelial cells. BAP1w-/KO MeT5A cells express less BAP1 protein and phenocopy key aspects of BAP1 loss in MPM. Stable isotope labeling with amino acids in cell culture-mass spectrometry revealed evidence of metabolic adaptation, with concomitant alteration of cellular metabolites. In MeT5A, BAP1 deficiency reduces glycolytic enzyme levels but increases enzymes involved in the tricarboxylic acid cycle and anaplerotic pathways. Notably both argininosuccinate synthase 1 (ASS1), essential for cellular synthesis of arginine, and its substrate aspartate, are elevated in BAP1w-/KO MeT5A cells. Likewise, ASS1 expression is higher in BAP1-altered MPM cell lines, and inversely correlates with BAP1 in The Cancer Genome Atlas MESO dataset. Elevated ASS1 is also evident by IHC staining in epithelioid MPM lacking nuclear BAP1 expression, with improved survival among patients with BAP1-negative/ASS1-expressing tumors. Alterations in arginine metabolism may sensitize cells to metabolic drugs and we find that BAP1-negative/ASS1-expressing MPM cell lines are more sensitive to ASS1 inhibition, although not to inhibition of purine synthesis by mizoribine. Importantly, BAP1w-/KO MeT5A become desensitized to arginine deprivation by pegylated arginine deiminase (ADI-PEG20), phenocopying BAP1-negative/ASS1-expressing MPM cell lines.

IMPLICATIONS

Our data reveal an interrelationship between BAP1 and arginine metabolism, providing a potential means of identifying patients with epithelioid MPM likely to benefit from ADI-PEG20.

EGFR-targeted bacteriophage lambda penetrates model stromal and colorectal carcinoma tissues, is taken up into carcinoma cells, and interferes with 3-dimensional tumor formation

Introduction

Colorectal cancer and other adult solid cancers pose a significant challenge for successful treatment because the tumor microenvironment both hinders the action of conventional therapeutics and suppresses the immune activities of infiltrating leukocytes. The immune suppression is largely the effect of enhanced local mediators such as purine nucleosides and eicosanoids. Genetic approaches have the promise of interfering with these mechanisms of local immunosuppression to allow both intrinsic and therapeutic immunological anticancer processes. Bacterial phages offer a novel means of enabling access into tissues for therapeutic genetic manipulations.

Methods

We generated spheroids of fibroblastic and CRC cancer cells to model the 3-dimensional stromal and parenchymal components of colorectal tumours. We used these to examine the access and effects of both wildtype (WT) and epidermal growth factor (EGF)-presenting bacteriophage λ (WT- λ and EGF-λ) as a means of delivery of targeted genetic interventions in solid cancers. We used both confocal microscopy of spheroids exposed to AF488-tagged phages, and the recovery of viable phages as measured by plaque-forming assays to evaluate access; and measures of mitochondrial enzyme activity and cellular ATP to evaluate the outcome on the constituent cells.

Results

Using flourescence-tagged derivatives of these bacteriophages (AF488-WT-λ and AF488-EGF-λ) we showed that phage entry into these tumour microenvironments was possible and that the EGF ligand enabled efficient and persistent uptake into the cancer cell mass. EGF-λ became localized in the intracellular portion of cancer cells and was subjected to subsequent cellular processing. The targeted λ phage had no independent effect upon mature tumour spheroids, but interfered with the early formation and growth of cancer tissues without the need for addition of a toxic payload, suggesting that it might have beneficial effects by itself in addition to any genetic intervention delivered to the tumour. Interference with spheroid formation persisted over the duration of culture.

Discussion

We conclude that targeted phage technology is a feasible strategy to facilitate delivery into colorectal cancer tumour tissue (and by extension other solid carcinomas) and provides an appropriate delivery vehicle for a gene therapeutic that can reduce local immunosuppression and/or deliver an additional direct anticancer activity.

The Chick Embryo Xenograft Model for Malignant Pleural Mesothelioma: A Cost and Time Efficient 3Rs Model for Drug Target Evaluation

Malignant pleural mesothelioma (MPM) has limited treatment options and poor prognosis. Frequent inactivation of the tumour suppressors BAP1, NF2 and P16 may differentially sensitise tumours to treatments. We have established chick chorioallantoic membrane (CAM) xenograft models of low-passage MPM cell lines and protocols for evaluating drug responses. Ten cell lines, representing the spectrum of histological subtypes and tumour suppressor status, were dual labelled for fluorescence/bioluminescence imaging and implanted on the CAM at E7. Bioluminescence was used to assess viability of primary tumours, which were excised at E14 for immunohistological staining or real-time PCR. All MPM cell lines engrafted efficiently forming vascularised nodules, however their size, morphology and interaction with chick cells varied. MPM phenotypes including local invasion, fibroblast recruitment, tumour angiogenesis and vascular remodelling were evident. Bioluminescence imaging could be used to reliably estimate tumour burden pre- and post-treatment, correlating with tumour weight and Ki-67 staining. In conclusion, MPM-CAM models recapitulate important features of the disease and are suitable to assess drug targets using a broad range of MPM cell lines that allow histological or genetic stratification. They are amenable to multi-modal imaging, potentially offering a time and cost-efficient, 3Rs-compliant alternative to rodent xenograft models to prioritise candidate compounds from in vitro studies.

Preclinical Models and Resources to Facilitate Basic Science Research on Malignant Mesothelioma - A Review

Malignant mesothelioma is an aggressive cancer with poor prognosis, predominantly caused by human occupational exposure to asbestos. The global incidence of mesothelioma is predicted to increase as a consequence of continued exposure to asbestos from a variety of sources, including construction material produced in the past in developed countries, as well as those currently being produced in developing countries. Mesothelioma typically develops after a long latency period and consequently it is often diagnosed in the clinic at an advanced stage, at which point standard care of treatment, such as chemo- and radio-therapy, are largely ineffective. Much of our current understanding of mesothelioma biology, particularly in relation to disease pathogenesis, diagnosis and treatment, can be attributed to decades of preclinical basic science research. Given the postulated rising incidence in mesothelioma cases and the limitations of current diagnostic and treatment options, continued preclinical research into mesothelioma is urgently needed. The ever-evolving landscape of preclinical models and laboratory technology available to researchers have made it possible to study human disease with greater precision and at an accelerated rate. In this review article we provide an overview of the various resources that can be exploited to facilitate an enhanced understanding of mesothelioma biology and their applications to research aimed to improve the diagnosis and treatment of mesothelioma. These resources include cell lines, animal models, mesothelioma-specific biobanks and modern laboratory techniques/technologies. Given that different preclinical models and laboratory technologies have varying limitations and applications, they must be selected carefully with respect to the intended objectives of the experiments. This review therefore aims to provide a comprehensive overview of the various preclinical models and technologies with respect to their advantages and limitations. Finally, we will detail about a highly valuable preclinical laboratory resource to curate high quality mesothelioma biospecimens for research; the biobank. Collectively, these resources are essential to the continued advancement of precision medicine to curtail the increasing health burden caused by malignant mesothelioma.

Optimization of tumor spheroid model in mesothelioma and lung cancers and anti-cancer drug testing in H2052/484 spheroids

Advanced lung cancers and mesothelioma remain incurable diseases. Despite some promising new therapy strategies, predicting whether an individual patient will be sensitive to a given therapy is challenging. The purpose of this study is to establish and evaluate the efficiency of a three-dimensional spheroid model of human thoracic cancer in predicting the efficacy of drugs.

Human mesothelioma and lung tumor spheroids were established from cell lines and primary cells derived from the patient. The growth kinetics and cell viability of microtumors were assessed using spheroid size and intracellular ATP level. The sensitivity of the mesothelioma spheroids to the cisplatin or cisplatin/pemetrexed combination was determined.

We determined that studying the kinetics of the spheroid growth for 15 days after seeding 1000 cells/well in a 96-well plate was optimal. Monitoring the growth kinetic and intracellular ATP of spheroids allowed the identification of early changes in spheroid viability. Finally, we validated this model by measuring a dose-dependent reduction in the cell viability of mesothelioma H2052/484 spheroids treated with both first-line treatments, cisplatin and the cisplatin/pemetrexed combination. In conclusion, we have developed a three-dimensional spheroid model of thoracic tumor cells useful for tailoring the medical treatment to the specific characteristics of each patient.

Use of preclinical models for malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive cancer most commonly caused by prior exposure to asbestos. Median survival is 12-18 months, since surgery is ineffective and chemotherapy offers minimal benefit. Preclinical models that faithfully recapitulate the genomic and histopathological features of cancer are critical for the development of new treatments. The most commonly used models of MPM are two-dimensional cell lines established from primary tumours or pleural fluid. While these have provided some important insights into MPM biology, these cell models have significant limitations. In order to address some of these limitations, spheroids and microfluidic chips have more recently been used to investigate the role of the three-dimensional environment in MPM. Efforts have also been made to develop animal models of MPM, including asbestos-induced murine tumour models, MPM-prone genetically modified mice and patient-derived xenografts. Here, we discuss the available in vitro and in vivo models of MPM and highlight their strengths and limitations. We discuss how newer technologies, such as the tumour-derived organoids, might allow us to address the limitations of existing models and aid in the identification of effective treatments for this challenging-to-treat disease.

Single cell organization and cell cycle characterization of DNA stained multicellular tumor spheroids

Multicellular tumor spheroids (MCTSs) can serve as in vitro models for solid tumors and have become widely used in basic cancer research and drug screening applications. The major challenges when studying MCTSs by optical microscopy are imaging and analysis due to light scattering within the 3-dimensional structure. Herein, we used an ultrasound-based MCTS culture platform, where A498 renal carcinoma MCTSs were cultured, DAPI stained, optically cleared and imaged, to connect nuclear segmentation to biological information at the single cell level. We show that DNA-content analysis can be used to classify the cell cycle state as a function of position within the MCTSs. We also used nuclear volumetric characterization to show that cells were more densely organized and perpendicularly aligned to the MCTS radius in MCTSs cultured for 96 h compared to 24 h. The method presented herein can in principle be used with any stochiometric DNA staining protocol and nuclear segmentation strategy. Since it is based on a single counter stain a large part of the fluorescence spectrum is free for other probes, allowing measurements that correlate cell cycle state and nuclear organization with e.g., protein expression or drug distribution within MCTSs.

Imitating Hypoxia and Tumor Microenvironment with Immune Evasion by Employing Three Dimensional in vitro Cellular Models: Impressive Tool in Drug Discovery

The heterogeneous tumor microenvironment is exceptionally perplexing and not wholly comprehended. Different multifaceted alignments lead to the generation of oxygen destitute situations within the tumor niche that modulate numerous intrinsic tumor microenvironments. Disentangling these communications is vital for scheming practical therapeutic approaches that can successfully decrease tumor allied chemotherapy resistance by utilizing the innate capability of the immune system. Several research groups have concerned with a protruding role for oxygen metabolism along with hypoxia in the immunity of healthy tissue. Hypoxia in addition to hypoxia-inducible factors (HIFs) in the tumor microenvironment plays an important part in tumor progression and endurance. Although numerous hypoxia-focused therapies have shown promising outcomes both in vitro and in vivo these outcomes have not effectively translated into clinical preliminaries. Distinctive cell culture techniques have utilized as an in vitro model for tumor niche along with tumor microenvironment and proficient in more precisely recreating tumor genomic profiles as well as envisaging therapeutic response. To study the dynamics of tumor immune evasion, three-dimensional (3D) cell cultures are more physiologically important to the hypoxic tumor microenvironment. Recent research has revealed new information and insights into our fundamental understanding of immune systems, as well as novel results that have been established as potential therapeutic targets. There are a lot of patented 3D cell culture techniques which will be highlighted in this review. At present notable 3D cell culture procedures in the hypoxic tumor microenvironment, discourse open doors to accommodate both drug repurposing, advancement, and divulgence of new medications and will deliberate the 3D cell culture methods into standard prescription disclosure especially in the field of cancer biology which will be discussing here.

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

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

Argininosuccinate synthase 1 suppresses tumor progression through activation of PERK/eIF2α/ATF4/CHOP axis in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant cancers worldwide, and liver cancer has increased in mortality due to liver cancer because it was detected at an advanced stages in patients with liver dysfunction, making HCC a lethal cancer. Accordingly, we aim to new targets for HCC drug discovery using HCC tumor spheroids.

METHODS

Our comparative proteomic analysis of HCC cells grown in culture as monolayers (2D) and spheroids (3D) revealed that argininosuccinate synthase 1 (ASS1) expression was higher in 3D cells than in 2D cells due to upregulated endoplasmic reticulum (ER) stress responses. We investigated the clinical value of ASS1 in Korean patients with HCC. The mechanism underlying ASS1-mediated tumor suppression was investigated in HCC spheroids. ASS1-mediated improvement of chemotherapy efficiency was observed using high content screening in an HCC xenograft mouse model.

RESULTS

Studies of tumor tissue from Korean HCC patients showed that, although ASS1 expression was low in most samples, high levels of ASS1 were associated with favorable overall survival of patients. Here, we found that bidirectional interactions between ASS1 ER stress responses in HCC-derived multicellular tumor spheroids can limit HCC progression. ASS1 overexpression effectively inhibited tumor growth and enhanced the efficacy of in vitro and in vivo anti-HCC combination chemotherapy via activation of the PERK/eIF2α/ATF4/CHOP axis, but was not dependent on the status of p53 and arginine metabolism.

CONCLUSIONS

These results demonstrate the critical functional roles for the arginine metabolism-independent tumor suppressor activity of ASS1 in HCC and suggest that upregulating ASS1 in these tumors is a potential strategy in HCC cells with low ASS1 expression.

Cell spheroids as a versatile research platform: formation mechanisms, high throughput production, characterization and applications

Three-dimensional cell culture has tremendous advantages to closely mimic the in vivo architecture and microenvironment of healthy tissue and organs, as well as of solid tumors. Spheroids are currently the most attractive 3D model to produce uniform reproducible cell structures as well as a potential basis for engineering large tissues and complex organs. In this review we discuss, from an engineering perspective, processes to obtain uniform 3D cell spheroids, comparing dynamic and static cultures and considering aspects such as mass transfer and shear stress. In addition, computational and mathematical modelling of complex cell spheroid systems are discussed. The non-cell-adhesive hydrogel-based method and dynamic cell culture in bioreactors are focused in detail and the myriad of developed spheroid characterization techniques is presented. The main bottlenecks and weaknesses are discussed, especially regarding the analysis of morphological parameters, cell quantification and viability, gene expression profiles, metabolic behavior and high-content analysis. Finally, a vast set of applications of spheroids as tools for in vitro study model systems is examined, including drug screening, tissue formation, pathologies development, tissue engineering and biofabrication, 3D bioprinting and microfluidics, together with their use in high-throughput platforms.

EIF4G1 and RAN as Possible Drivers for Malignant Pleural Mesothelioma

For malignant pleural mesothelioma (MPM) novel therapeutic strategies are urgently needed. In a previous study, we identified 51 putative cancer genes over-expressed in MPM tissues and cell lines. Here, we deepened the study on nine of them (ASS1, EIF4G1, GALNT7, GLUT1, IGF2BP3 (IMP3), ITGA4, RAN, SOD1, and THBS2) to ascertain whether they are truly mesothelial cancer driver genes (CDGs) or genes overexpressed in an adaptive response to the tumoral progression (“passenger genes”). Through a fast siRNA-based screening, we evaluated the consequences of gene depletion on migration, proliferation, colony formation capabilities, and caspase activities of four MPM (Mero-14, Mero-25, IST-Mes2, and NCI-H28) and one SV40-immortalized mesothelial cell line (MeT-5A) as a non-malignant model. The depletion of EIF4G1 and RAN significantly reduced cell proliferation and colony formation and increased caspase activity. In particular, the findings for RAN resemble those observed for other types of cancer. Thus, we evaluated the in vitro effects of importazole (IPZ), a small molecule inhibitor of the interaction between RAN and importin-β. We showed that IPZ could have effects similar to those observed following RAN gene silencing. We also found that primary cell lines from one out of three MPM patients were sensitive to IPZ. As EIF4G1 and RAN deserve further investigation with additional in vitro and in vivo studies, they emerged as promising CDGs, suggesting that their upregulation could play a role in mesothelial tumorigenesis and aggressiveness. Furthermore, present data propose the molecular pathways dependent on RAN as a putative pharmacological target for MPM patients in the view of a future personalized medicine.

The Biology of Malignant Mesothelioma and the Relevance of Preclinical Models

Malignant mesothelioma (MM), especially its more frequent form, malignant pleural mesothelioma (MPM), is a devastating thoracic cancer with limited therapeutic options. Recently, clinical trials that used immunotherapy strategies have yielded promising results, but the benefits are restricted to a limited number of patients. To develop new therapeutic strategies and define predictors of treatment response to existing therapy, better knowledge of the cellular and molecular mechanisms of MM tumors and sound preclinical models are needed. This review aims to provide an overview of our present knowledge and issues on both subjects. MM shows a complex pattern of molecular changes, including genetic, chromosomic, and epigenetic alterations. MM is also a heterogeneous cancer. The recently described molecular classifications for MPM could better consider inter-tumor heterogeneity, while histo-molecular gradients are an interesting way to consider both intra- and inter-tumor heterogeneities. Classical preclinical models are based on use of MM cell lines in culture or implanted in rodents, i.e., xenografts in immunosuppressed mice or isografts in syngeneic rodents to assess the anti-tumor immune response. Recent developments are tumoroids, patient-derived xenografts (PDX), xenografts in humanized mice, and genetically modified mice (GEM) that carry mutations identified in human MM tumor cells. Multicellular tumor spheroids are an interesting in vitro model to reduce animal experimentation; they are more accessible than tumoroids. They could be relevant, especially if they are co-cultured with stromal and immune cells to partially reproduce the human microenvironment. Even if preclinical models have allowed for major advances, they show several limitations: (i) the anatomical and biological tumor microenvironments are incompletely reproduced; (ii) the intra-tumor heterogeneity and immunological contexts are not fully reconstructed; and (iii) the inter-tumor heterogeneity is insufficiently considered. Given that these limitations vary according to the models, preclinical models must be carefully selected depending on the objectives of the experiments. New approaches, such as organ-on-a-chip technologies or in silico biological systems, should be explored in MM research. More pertinent cell models, based on our knowledge on mesothelial carcinogenesis and considering MM heterogeneity, need to be developed. These endeavors are mandatory to implement efficient precision medicine for MM.

Differential Diagnosis of Malignant Pleural Mesothelioma on Cytology: A Gene Expression Panel versus BRCA1-Associated Protein 1 and p16 Tests

Pleural effusions are among the first clinical manifestations of malignant pleural mesothelioma (MPM) and often constitute the only available material for diagnosis. Although an MPM diagnosis can be reliable on cytology, the reported sensitivity is low (30% to 75%). Particularly, it can be hard to discriminate epithelioid MPM, the most common histotype, from reactive mesothelial hyperplasia (MH). Currently, BRCA1-associated protein 1 (BAP1) and CDKN2A (p16), evaluated by immunohistochemistry and fluorescent in situ hybridization, respectively, are the most valuable markers to discriminate MPM and MH. Both markers have a high specificity, but their sensitivity is not always satisfying, even when used together. We have recently developed a 117-gene expression panel, based on Nanostring technology, able to differentiate epithelioid MPM from MH pleural tissues better than BAP1 and p16. Herein, we evaluated the efficacy of the same panel on an independent retrospective cohort of 23 MPM and 11 MH pleural effusions (cell blocks and smears). The overall sensitivity and specificity of the panel were equal to 0.9565 and 1, respectively. Moreover, the panel performance was compared with BAP1 and p16 on 25 cell blocks. Sensitivity levels of gene panel, BAP1 alone, p16 alone, and BAP1 plus p16 were 1, 0.5882, 0.4706, and 0.7647, respectively. Specificity was always 1. Although further validation is needed, this gene panel could really facilitate patients' management, allowing a definitive MPM diagnosis directly on pleural effusions.

Apoptosis Induction and Alteration of Cell Adherence in Human Lung Cancer Cells under Simulated Microgravity

BACKGROUND

Lung cancer cells are known to change proliferation and migration under simulated microgravity. In this study, we sought to evaluate cell adherence, apoptosis, cytoskeleton arrangement, and gene expression under simulated microgravity.

METHODS

Human lung cancer cells were exposed to simulated microgravity in a random-positioning machine (RPM). Cell morphology and adherence were observed under phase-contrast microscopy, cytoskeleton staining was performed, apoptosis rate was determined, and changes in gene and protein expression were detected by real-time PCR with western blot confirmation.

RESULTS

Three-dimensional (3D)-spheroid formation was observed under simulated microgravity. Cell viability was not impaired. Actin filaments showed a shift in alignment from longitudinal to spherical. Apoptosis rate was significantly increased in the spheroids compared to the control. TP53, CDKN2A, PTEN, and RB1 gene expression was significantly upregulated in the adherent cells under simulated microgravity with an increase in corresponding protein production for p14 and RB1. SOX2 expression was significantly upregulated in the adherent cells, but protein was not. Gene expressions of AKT3, PIK3CA, and NFE2L2 remained unaltered.

CONCLUSION

Simulated microgravity induces alteration in cell adherence, increases apoptosis rate, and leads to upregulation of tumor suppressor genes in human lung cancer cells.

Short-term 3D culture systems of various complexity for treatment optimization of colorectal carcinoma

Three-dimensional (3D) cultures have the potential to increase the predictive value of pre-clinical drug research and bridge the gap towards anticipating clinical outcome of proposed treatments. However, their implementation in more advanced drug-discovery programs is still in its infancy due to the lack of reproducibility and low time- and cost effectiveness. HCT116, SW620 and DLD1 cells, cell lines with distinct mutations, grade and origin, were co-cultured with fibroblasts and endothelial cells (EC) in 3D spheroids. Clinically relevant drugs, i.e. 5-fluorouracil (5−FU), regorafenib and erlotinib, were administered individually to in CRC cell cultures. In this study, we established a robust, low-cost and reproducible short-term 3D culture system addressing the various complexities of the colorectal carcinoma (CRC) microenvironment. We observed a dose-dependent increase of erlotinib sensitivity in 3D (co-)cultures compared to 2D cultures. Furthermore, we compared the drug combination efficacy and drug-drug interactions administered in 2D, 3D and 3D co-cultures. We observed that synergistic/additive drug-drug interactions for drug combinations administered at low doses shifted towards additive and antagonistic when applied at higher doses in metastatic CRC cells. The addition of fibroblasts at various ratios and EC increased the resistance to some drug combinations in SW620 and DLD1 cells, but not in HCT116. Retreatment of SW620 3D co-cultures with a low-dose 3-drug combination was as active (88% inhibition, relative to control) as 5-FU treatment at high dose (100 μM). Moreover, 3D and 3D co-cultures responded variably to the drug combination treatments, and also signalling pathways were differently regulated, probably due to the influence of fibroblasts and ECs on cancer cells. The short-term 3D co-culture system developed here is a powerful platform for screening (combination) therapies. Understanding of signalling in 3D co-cultures versus 3D cultures and the responses in the 3D models upon drug treatment might be beneficial for designing anti-cancer therapies.

Three-Dimensional Cell Cultures in Drug Discovery and Development

The past decades have witnessed significant efforts toward the development of three-dimensional (3D) cell cultures as systems that better mimic in vivo physiology. Today, 3D cell cultures are emerging, not only as a new tool in early drug discovery but also as potential therapeutics to treat disease. In this review, we assess leading 3D cell culture technologies and their impact on drug discovery, including spheroids, organoids, scaffolds, hydrogels, organs-on-chips, and 3D bioprinting. We also discuss the implementation of these technologies in compound identification, screening, and development, ranging from disease modeling to assessment of efficacy and safety profiles.

Anticancer drug discovery using multicellular tumor spheroid models

INTRODUCTION

Despite the increasing financial outlay on cancer research and drug discovery, many advanced cancers remain incurable. One possible strategy for increasing the approval rate of new anticancer drugs for use in clinical practice could be represented by three-dimensional (3D) tumor models on which to perform in vitro drug screening. There is a general consensus among the scientific community that 3D tumor models more closely recapitulate the complexity of tumor tissue architecture and biology than bi-dimensional cell cultures. In a 3D context, cells are connected to each other through tissue junctions and show proliferative and metabolic gradients that resemble the intricate milieu of organs and tumors. Areas covered: The present review focuses on available techniques for generating tumor spheroids and discusses current and future applications in the field of drug discovery. The article is based on literature obtained from PubMed. Expert opinion: Given the relative simplicity of spheroid models with respect to clinical tumors, we must be careful not to overestimate the reliability of their drug-response prediction capacity. The next challenge is to combine our knowledge of co-culture methodologies with high-content imaging and advanced microfluidic technologies to improve the readout and biomimetic potential of spheroid-based models.

Malignant pleural mesothelioma and mesothelial hyperplasia: A new molecular tool for the differential diagnosis

Malignant pleural mesothelioma (MPM) is a rare asbestos related cancer, aggressive and unresponsive to therapies. Histological examination of pleural lesions is the gold standard of MPM diagnosis, although it is sometimes hard to discriminate the epithelioid type of MPM from benign mesothelial hyperplasia (MH).This work aims to define a new molecular tool for the differential diagnosis of MPM, using the expression profile of 117 genes deregulated in this tumour.The gene expression analysis was performed by nanoString System on tumour tissues from 36 epithelioid MPM and 17 MH patients, and on 14 mesothelial pleural samples analysed in a blind way. Data analysis included raw nanoString data normalization, unsupervised cluster analysis by Pearson correlation, non-parametric Mann Whitney U-test and molecular classification by the Uncorrelated Shrunken Centroid (USC) Algorithm.The Mann-Whitney U-test found 35 genes upregulated and 31 downregulated in MPM. The unsupervised cluster analysis revealed two clusters, one composed only of MPM and one only of MH samples, thus revealing class-specific gene profiles. The Uncorrelated Shrunken Centroid algorithm identified two classifiers, one including 22 genes and the other 40 genes, able to properly classify all the samples as benign or malignant using gene expression data; both classifiers were also able to correctly determine, in a blind analysis, the diagnostic categories of all the 14 unknown samples.In conclusion we delineated a diagnostic tool combining molecular data (gene expression) and computational analysis (USC algorithm), which can be applied in the clinical practice for the differential diagnosis of MPM.

Overexpressed genes in malignant pleural mesothelioma: implications in clinical management

Malignant pleural mesothelioma (MPM) is a very aggressive cancer poorly responsive to current therapies. MPM patients have a very poor prognosis with a median survival of less than one year from the onset of symptoms. The biomarkers proposed so far do not lead to a sufficiently early diagnosis for a radical treatment of the disease. Thus, the finding of novel diagnostic and prognostic biomarkers and therapeutic targets is needed. Gene overexpression has been frequently associated with a malignant phenotype in several cancer types; therefore the identification of overexpressed genes may lead to the detection of novel prognostic or diagnostic marker and to the development of novel therapeutic approaches, based on their inhibition. In the last years, several overexpressed genes have been identified in MPM through gene expression profiling techniques: among them it has been found a group of 51 genes that resulted overexpressed in more than one independent study, revealing their consistency among studies. This article reviews the clinical implications of confirmed overexpressed genes in MPM described so far in literature.

Embedded Spheroids as Models of the Cancer Microenvironment

To more accurately study the complex mechanisms behind cancer invasion, progression, and response to treatment, researchers require models that replicate both the multicellular nature and 3D stromal environment present in an in vivo tumor. Multicellular aggregates (i.e., spheroids) embedded in an extracellular matrix mimic are a prevalent model. Recently, quantitative metrics that fully utilize the capability of spheroids are described along with conventional experiments, such as invasion into a matrix, to provide additional details and insights into the underlying cancer biology. The review begins with a discussion of the salient features of the tumor microenvironment, introduces the early work on non-embedded spheroids as tumor models, and then concentrates on the successes achieved with the study of embedded spheroids. Examples of studies include cell movement, drug response, tumor cellular heterogeneity, stromal effects, and cancer progression. Additionally, new methodologies and those borrowed from other research fields (e.g., vascularization and tissue engineering) are highlighted that expand the capability of spheroids to aid future users in designing their cancer-related experiments. The convergence of spheroid research among the various fields catalyzes new applications and leads to a natural synergy. Finally, the review concludes with a reflection and future perspectives for cancer spheroid research.