Advances in establishment and analysis of three-dimensional tumor spheroid-based functional assays for target validation and drug evaluation

Three-dimensional (3D) tumor spheroid invasion assay

Invasion of surrounding normal tissues is generally considered to be a key hallmark of malignant (as opposed to benign) tumors. For some cancers in particular (e.g., brain tumors such as glioblastoma multiforme and squamous cell carcinoma of the head and neck – SCCHN) it is a cause of severe morbidity and can be life-threatening even in the absence of distant metastases. In addition, cancers which have relapsed following treatment unfortunately often present with a more aggressive phenotype. Therefore, there is an opportunity to target the process of invasion to provide novel therapies that could be complementary to standard anti-proliferative agents. Until now, this strategy has been hampered by the lack of robust, reproducible assays suitable for a detailed analysis of invasion and for drug screening. Here we provide a simple micro-plate method (based on uniform, self-assembling 3D tumor spheroids) which has great potential for such studies. We exemplify the assay platform using a human glioblastoma cell line and also an SCCHN model where the development of resistance against targeted epidermal growth factor receptor (EGFR) inhibitors is associated with enhanced matrix-invasive potential. We also provide two alternative methods of semi-automated quantification: one using an imaging cytometer and a second which simply requires standard microscopy and image capture with digital image analysis.

Pathophysiologically relevant in vitro tumor models for drug screening

The alarming rate of failure of clinical trials is a major hurdle in cancer therapy that partly results from the inadequate use of in vitro tumor models for the screening of promising hits and leads in preclinical studies. 2D cultures of cancer cell lines that are primarily used for drug screening do not adequately recapitulate tumor microenvironment (TME) complexities compared with 3D cancer cell cultures and tumor-derived primary cell cultures. In this review, we focus on the potential use of in vitro tumor models that reproduce in vivo tumor complexities for effective drug selection in the preclinical stages of drug development.

Three-dimensional models of cancer for pharmacology and cancer cell biology: capturing tumor complexity in vitro/ex vivo

Cancers are complex and heterogeneous pathological "organs" in a dynamic interplay with their host. Models of human cancer in vitro, used in cancer biology and drug discovery, are generally highly reductionist. These cancer models do not incorporate complexity or heterogeneity. This raises the question as to whether the cancer models' biochemical circuitry (not their genome) represents, with sufficient fidelity, a tumor in situ. Around 95% of new anticancer drugs eventually fail in clinical trial, despite robust indications of activity in existing in vitro pre-clinical models. Innovative models are required that better capture tumor biology. An important feature of all tissues, and tumors, is that cells grow in three dimensions. Advances in generating and characterizing simple and complex (with added stromal components) three-dimensional in vitro models (3D models) are reviewed in this article. The application of stirred bioreactors to permit both scale-up/scale-down of these cancer models and, importantly, methods to permit controlled changes in environment (pH, nutrients, and oxygen) are also described. The challenges of generating thin tumor slices, their utility, and potential advantages and disadvantages are discussed. These in vitro/ex vivo models represent a distinct move to capture the realities of tumor biology in situ, but significant characterization work still remains to be done in order to show that their biochemical circuitry accurately reflects that of a tumor.

Culturing Uveal Melanoma Cells

A major challenge in cancer research is the use of appropriate models with which to study a specific biological question. Cell lines have long been used to study cellular processes and the effects of individual molecules because they are easy to use, grow rapidly, produce reproducible results and have a strong track record in research. In uveal melanoma in particular, the absence of animal models that faithfully replicate the behavior of the human disease has propagated the generation and use of numerous cell lines by individual research groups. This in itself, however, can be viewed as a problem due to the lack of standardization when characterizing these entities to determine how closely they reflect the genetic and phenotypic characteristics of this disease. The alternative is to use in vitro primary cultures of cells obtained directly from uveal melanoma patient samples, but this too has its difficulties. Primary cell cultures are difficult to use, hard to obtain and can show considerable heterogeneity. In this article, we review the following: (1) the uveal melanoma cell lines that are currently available, discussing the importance of establishing a bank of those that represent the molecular heterogeneity of uveal melanoma; (2) the methods used to isolate and perform short-term cultures of primary uveal melanoma cells, and (3) the establishment of 3D tissue culture models that bridge the gap between 2D in vitro systems and in vivo models with which to dissect cancer biology and perform therapeutic screens.

In vitro microtumors provide a physiologically predictive tool for breast cancer therapeutic screening

Many anti-cancer drugs fail in human trials despite showing efficacy in preclinical models. It is clear that the in vitro assays involving 2D monoculture do not reflect the complex extracellular matrix, chemical, and cellular microenvironment of the tumor tissue, and this may explain the failure of 2D models to predict clinical efficacy. We first optimized an in vitro microtumor model using a tumor-aligned ECM, a tumor-aligned medium, MCF-7 and MDA-MB-231 breast cancer spheroids, human umbilical vein endothelial cells, and human stromal cells to recapitulate the tissue architecture, chemical environment, and cellular organization of a growing and invading tumor. We assayed the microtumor for cell proliferation and invasion in a tumor-aligned extracellular matrix, exhibiting collagen deposition, acidity, glucose deprivation, and hypoxia. We found maximal proliferation and invasion when the multicellular spheroids were cultured in a tumor-aligned medium, having low pH and low glucose, with 10% fetal bovine serum under hypoxic conditions. In a 7-day assay, varying doses of fluorouracil or paclitaxel had differential effects on proliferation for MCF-7 and MDA-MB-231 tumor spheroids in microtumor compared to 2D and 3D monoculture. The microtumors exhibited a tumor morphology and drug response similar to published xenograft data, thus demonstrating a more physiologically predictive in vitro model.

Improvement of anti-tumor abilities on human non-small cell lung carcinoma by micellization and cross-linking of N-(2-hydroxypropyl) methacrylamide copolymers

Non-small cell lung carcinoma is one of the most frequently occurred cancers with a very high rate of recurrence. Self-assembly N-(2-hydroxypropyl) methacrylamide (HPMA) micelles and cross-linked micelles were developed to improve antitumor ability of linear HPMA copolymer. The characters of HPMA micelles were investigated and compared using human non-small cell lung carcinoma 3-D culture model and nude mice xenograft model. Cross-linked micelles showed highest cytotoxicity on A549 cell monolayers after a short time treatment in vitro. Moreover, both of the two micelles exhibited better in vitro anti-tumor activity on A549 tumor spheroids than linear HPMA conjugates especially the cross-linked micelles. On BALB/c nude mice bearing A549 xenograft tumors, the cross-linked micelles exhibited the greatest tumor accumulation and the best anti-tumor activity due to the highly improved stabilities and the more pronounced enhanced permeability and retention (EPR) effect, which were followed by the non-cross-linked micelles. Meanwhile, neither the two micelles nor the linear HPMA copolymers showed significant toxicity on the main organs of mice while free doxorubicin (DOX) showed obvious cardiac toxicity. All the results suggested that micellization improved the anti-tumor activity of HPMA copolymers on A549 human non-small cell lung carcinoma, furthermore, cross-linked HPMA copolymer micelles with pH-sensitivity and biodegradability showed more excellent anti-tumor activity.

Quantitative determination of irinotecan and the metabolite SN-38 by nanoflow liquid chromatography-tandem mass spectrometry in different regions of multicellular tumor spheroids

A new and simple method was developed to evaluate the distribution of therapeutics in three-dimensional multicellular tumor spheroids (MCTS) by combining serial trypsinization and nanoflow liquid chromatography-tandem mass spectrometry (nLC-MS/MS). This methodology was validated with quantitative measurements of irinotecan and its bioactive metabolite, SN-38, in distinct spatial regions of HCT 116 MCTS. Irinotecan showed a time-dependent permeability into MCTS with most of the drug accumulating in the core after 24 h of treatment. The amount of SN-38 detected was 30 times lower than that of the parent drug, and was more abundant in the outer rim and intermediate regions of MCTS where proliferating cells were present. This method can be used to investigate novel and established drugs. It enables investigation of drug penetration properties and identification of metabolites with spatial specificity in MCTS. The new approach has great value in facilitating the drug evaluation process.

Acquired resistance to EGFR tyrosine kinase inhibitors alters the metabolism of human head and neck squamous carcinoma cells and xenograft tumours

BACKGROUND

Acquired resistance to molecularly targeted therapeutics is a key challenge in personalised cancer medicine, highlighting the need for identifying the underlying mechanisms and early biomarkers of relapse, in order to guide subsequent patient management.

METHODS

Here we use human head and neck squamous cell carcinoma (HNSCC) models and nuclear magnetic resonance (NMR) spectroscopy to assess the metabolic changes that follow acquired resistance to EGFR tyrosine kinase inhibitors (TKIs), and which could serve as potential metabolic biomarkers of drug resistance.

RESULTS

Comparison of NMR metabolite profiles obtained from control (CAL(S)) and EGFR TKI-resistant (CAL(R)) cells grown as 2D monolayers, 3D spheroids or xenograft tumours in athymic mice revealed a number of differences between the sensitive and drug-resistant models. In particular, we observed elevated levels of glycerophosphocholine (GPC) in CAL(R) relative to CAL(S) monolayers, spheroids and tumours, independent of the growth rate or environment. In addition, there was an increase in alanine, aspartate and creatine+phosphocreatine in resistant spheroids and xenografts, and increased levels of lactate, branched-chain amino acids and a fall in phosphoethanolamine only in xenografts. The xenograft lactate build-up was associated with an increased expression of the glucose transporter GLUT-1, whereas the rise in GPC was attributed to inhibition of GPC phosphodiesterase. Reduced glycerophosphocholine (GPC) and phosphocholine were observed in a second HNSCC model probably indicative of a different drug resistance mechanism.

CONCLUSIONS

Our studies reveal metabolic signatures associated not only with acquired EGFR TKI resistance but also growth pattern, microenvironment and contributing mechanisms in HNSCC models. These findings warrant further investigation as metabolic biomarkers of disease relapse in the clinic.

The multifactorial role of the 3Rs in shifting the harm-benefit analysis in animal models of disease

Ethics on animal use in science in Western society is based on utilitarianism, weighing the harms and benefits to the animals involved against those of the intended human beneficiaries. The 3Rs concept (Replacement, Reduction, Refinement) is both a robust framework for minimizing animal use and suffering (addressing the harms to animals) and a means of supporting high quality science and translation (addressing the benefits). The ambiguity of basic research performed early in the research continuum can sometimes make harm-benefit analysis more difficult since anticipated benefit is often an incremental contribution to a field of knowledge. On the other hand, benefit is much more evident in translational research aimed at developing treatments for direct application in humans or animals suffering from disease. Though benefit may be easier to define, it should certainly not be considered automatic. Issues related to model validity seriously compromise experiments and have been implicated as a major impediment in translation, especially in complex disease models where harms to animals can be intensified. Increased investment and activity in the 3Rs is delivering new research models, tools and approaches with reduced reliance on animal use, improved animal welfare, and improved scientific and predictive value.

A computer-assisted 3D model for analyzing the aggregation of tumorigenic cells reveals specialized behaviors and unique cell types that facilitate aggregate coalescence

We have developed a 4D computer-assisted reconstruction and motion analysis system, J3D-DIAS 4.1, and applied it to the reconstruction and motion analysis of tumorigenic cells in a 3D matrix. The system is unique in that it is fast, high-resolution, acquires optical sections using DIC microscopy (hence there is no associated photoxicity), and is capable of long-term 4D reconstruction. Specifically, a z-series at 5 μm increments can be acquired in less than a minute on tissue samples embedded in a 1.5 mm thick 3D Matrigel matrix. Reconstruction can be repeated at intervals as short as every minute and continued for 30 days or longer. Images are converted to mathematical representations from which quantitative parameters can be derived. Application of this system to cancer cells from established lines and fresh tumor tissue has revealed unique behaviors and cell types not present in non-tumorigenic lines. We report here that cells from tumorigenic lines and tumors undergo rapid coalescence in 3D, mediated by specific cell types that we have named “facilitators” and “probes.” A third cell type, the “dervish”, is capable of rapid movement through the gel and does not adhere to it. These cell types have never before been described. Our data suggest that tumorigenesis in vitro is a developmental process involving coalescence facilitated by specialized cells that culminates in large hollow spheres with complex architecture. The unique effects of select monoclonal antibodies on these processes demonstrate the usefulness of the model for analyzing the mechanisms of anti-cancer drugs.

Evaluation of chemotherapeutics in a three-dimensional breast cancer model

PURPOSE

Utilization of miniaturized three-dimensional (3D) cell culture-based assays enables investigation into the anticancer activity of drug candidates and further elucidation of the anticancer profile of standard-of-care chemotherapeutic agents against tumor cells. Drug discovery assays established using 3D cell culture, which better recapitulate the tumor microenvironment, may more accurately reflect the antitumor activity of compounds.

METHODS

Several standard-of-care anticancer drugs, epirubicin, paclitaxel and vinorelbine, were evaluated against a panel of breast cancer cell lines grown in a 3D cell culture microenvironment in the presence of extracellular matrix. A comparison of this antitumor activity in 3D conditions was made with that observed in traditional two-dimensional (2D) monolayer conditions.

RESULTS

Examination of the above mentioned drugs against breast tumor cells cultured in 3D conditions demonstrated significantly altered potency and efficacy in comparison with cells propagated in a 2D monolayer system. The differences observed were cell line-dependent and drug-specific; the triple-negative cell line MDA-MB-231 and the endocrine receptor-positive cell line MCF-7 consistently displayed resistance to therapeutics with distinct modes of action (i.e., topoisomerase II and microtubules) in 3D cell culture in comparison with ErbB2 receptor-positive BT-474 cells.

CONCLUSION

The data presented herein demonstrates the cellular viability and physical changes observed within the 3D spheroid following exposure to drug, which is not always reflected in 2D cell culture models.

Magnetic flattening of stem-cell spheroids indicates a size-dependent elastocapillary transition

Cellular aggregates (spheroids) are widely used in biophysics and tissue engineering as model systems for biological tissues. In this Letter we propose novel methods for molding stem-cell spheroids, deforming them, and measuring their interfacial and elastic properties with a single method based on cell tagging with magnetic nanoparticles and application of a magnetic field gradient. Magnetic molding yields spheroids of unprecedented sizes (up to a few mm in diameter) and preserves tissue integrity. On subjecting these spheroids to magnetic flattening (over 150g), we observed a size-dependent elastocapillary transition with two modes of deformation: liquid-drop-like behavior for small spheroids, and elastic-sphere-like behavior for larger spheroids, followed by relaxation to a liquidlike drop.

Engineering a High-Throughput 3-D In Vitro Glioblastoma Model

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumor in adults because of its highly invasive behavior. The existing treatment for GBM, which involves a combination of resection, chemotherapy, and radiotherapy, has a very limited success rate with a median survival rate of <1 year. This is mainly because of the failure of early detection and effective treatment. We designed a novel 3-D GBM cell culture model based on microwells that could mimic in vitro environment and help to bypass the lack of suitable animal models for preclinical toxicity tests. Microwells were fabricated from simple and inexpensive polyethylene glycol material for the control of in vitro 3-D culture. We applied the 3-D micropatterning system to GBM (U-87) cells using the photolithography technique to control the cell spheroids' shape, size, and thickness. Our preliminary results suggested that uniform GBM spheroids can be formed in 3-D, and the size of these GBM spheroids depends on the size of microwells. The viability of the spheroids generated in this manner was quantitatively evaluated using live/dead assay and shown to improve over 21 days. We believe that in vitro 3-D cell culture model could help to reduce the time of the preclinical brain tumor growth studies. The proposed novel platform could be useful and cost-effective for high-throughput screening of cancer drugs and assessment of treatment responses.

Comparison of 2D- and 3D-culture models as drug-testing platforms in breast cancer

It is becoming recognized that screening of oncology drugs on a platform using two-dimensionally (2D)-cultured cell lines is unable to precisely select clinically active drugs; therefore three-dimensional (3D)-culture systems are emerging and show potential for better simulating the in vivo tumor microenvironment. The purpose of this study was to reveal the differential effects of chemotherapeutic drugs between 2D- and 3D-cultures and to explore their underlying mechanisms. We evaluated differences between 2D- and 3D-cultured breast cancer cell lines by assessing drug sensitivity, oxygen status and expression of Ki-67 and caspases. Three cell lines (BT-549, BT-474 and T-47D) developed dense multicellular spheroids (MCSs) in 3D-culture, and showed greater resistance to paclitaxel and doxorubicin compared to the 2D-cultured cells. An additional three cell lines (MCF-7, HCC-1954, and MDA-MB‑231) developed only loose MCSs in 3D, and showed drug sensitivities similar to those found in the 2D-culture. Treatment with paclitaxel resulted in greater increases in cleaved-PARP expression in the 2D-culture compared with the 3D-culture, but only in cell lines forming dense 3D-MCSs, suggesting that MCS formation protected the cells from paclitaxel-induced apoptosis. Hypoxia was observed only in the dense 3D-MCSs. BT-549 had fewer cells positive for Ki-67 in 3D- than in 2D-culture, suggesting that the greater G0-dormant subpopulation was responsible for its drug resistance in the 3D-culture. BT-474 had a lower level of caspase-3 in the 3D- than in the 2D-culture, suggesting that the 3D-environment was anti-apoptotic. Finally, we compared staining for Ki-67 and caspases in the 2D- and 3D-primary‑cultured cells originating from a patient-derived xenograft (PDX), fresh PDX tumor, and the patient's original tumor; 2D-cultured cells showed greater proportions of Ki-67-positive and caspase-3-positive cells, in agreement with the view that 3D-primary culture better represents characteristics of tumors in vivo. In conclusion, 3D-cultured cells forming dense MCSs may be better than 2D-cultured cells in simulating important tumor characteristics in vivo, namely hypoxia, dormancy, anti-apoptotic features and their resulting drug resistance.

PTEN deletion potentiates invasion of colorectal cancer spheroidal cells through 3D Matrigel

PTEN (phosphatase and tensin homolog), a tumour suppressor negatively regulating the PI3K signalling pathway, is the second most frequently mutated gene in human cancers. Decreased PTEN expression is correlated with colorectal cancer metastases and poor patient survival. Three dimensional (3D) multicellular spheroid models have been postulated to bridge the gap between 2D cell models and animal models for cancer research and drug discovery. However, little is known about the impact of PTEN deletion on the invasion of colon cancer spheroidal cells through a 3D extracellular matrix, and current techniques are limited in their ability to study in vitro 3D cell models in real-time. Here, we investigated the migration and invasion behaviours of the colon cancer cell line HCT116 and its PTEN-/- isogenic cell line using three different in vitro assays, wound healing, transwell invasion, and label-free single cell 3D(2) invasion assays enabled by a resonant waveguide grating (RWG) biosensor. Light microscopic and RWG imaging showed that PTEN deletion influences the spheroid formation of HCT116 cells at high seeding density, and accelerates the spontaneous transfer from the spheroid to substrate surfaces. In vitro migration and invasion assays showed that PTEN knockout increases the 2D migration speed of HCT116 cells, and the invasion rate of individual cells through Matrigel or cells in the spheroid through 3D Matrigel; moreover, the PI3K inhibitor treatment drastically reduces the invasiveness of both cell lines. This study suggests that PTEN knockout potentiates the invasiveness of colorectal cancer spheroidal cells through a 3D extracellular matrix, and the label-free single cell assay is a powerful tool for investigating cancer cell invasion, in particular using 3D cell models.

Cell migration in paediatric glioma; characterisation and potential therapeutic targeting

BACKGROUND

Paediatric high grade glioma (pHGG) and diffuse intrinsic pontine glioma (DIPG) are highly aggressive brain tumours. Their invasive phenotype contributes to their limited therapeutic response, and novel treatments that block brain tumour invasion are needed.

METHODS

Here, we examine the migratory characteristics and treatment effect of small molecule glycogen synthase kinase-3 inhibitors, lithium chloride (LiCl) and the indirubin derivative 6-bromoindirubin-oxime (BIO), previously shown to inhibit the migration of adult glioma cells, on two pHGG cell lines (SF188 and KNS42) and one patient-derived DIPG line (HSJD-DIPG-007) using 2D (transwell membrane, immunofluorescence, live cell imaging) and 3D (migration on nanofibre plates and spheroid invasion in collagen) assays.

RESULTS

All lines were migratory, but there were differences in morphology and migration rates. Both LiCl and BIO reduced migration and instigated cytoskeletal rearrangement of stress fibres and focal adhesions when viewed by immunofluorescence. In the presence of drugs, loss of polarity and differences in cellular movement were observed by live cell imaging.

CONCLUSIONS

Ours is the first study to demonstrate that it is possible to pharmacologically target migration of paediatric glioma in vitro using LiCl and BIO, and we conclude that these agents and their derivatives warrant further preclinical investigation as potential anti-migratory therapeutics for these devastating tumours.

3D cell culture systems: advantages and applications

Cell cultures are important material of study for the variety of advantages that they offer. Both established continuous cell lines and primary cell cultures continue to be invaluable for basic research and for direct applications. Technological advancements are necessary to address emerging complex challenges and the way cells are cultured in vitro is an area of intense activity. One important advancement in cell culture techniques has been the introduction of three dimensional culture systems. This area is one of the fastest growing experimental approaches in life sciences. Augmented with advancements in cell imaging and analytical systems, as well as the applications of new scaffolds and matrices, cells have been increasingly grown as three dimensional models. Such cultures have proven to be closer to in vivo natural systems, thus proving to be useful material for many applications. Here, we review the three dimensional way of culturing cells, their advantages, the scaffolds and matrices currently available, and the applications of such cultures in major areas of life sciences.

Three-dimensional cell culture systems and their applications in drug discovery and cell-based biosensors

Three-dimensional (3D) cell culture systems have gained increasing interest in drug discovery and tissue engineering due to their evident advantages in providing more physiologically relevant information and more predictive data for in vivo tests. In this review, we discuss the characteristics of 3D cell culture systems in comparison to the two-dimensional (2D) monolayer culture, focusing on cell growth conditions, cell proliferation, population, and gene and protein expression profiles. The innovations and development in 3D culture systems for drug discovery over the past 5 years are also reviewed in the article, emphasizing the cellular response to different classes of anticancer drugs, focusing particularly on similarities and differences between 3D and 2D models across the field. The progression and advancement in the application of 3D cell cultures in cell-based biosensors is another focal point of this review.

Labile ruthenium(ii) complexes with extended phenyl-substituted terpyridyl ligands: synthesis, aquation and anticancer evaluation

The present study demonstrated that the anticancer activities of labile Ru(ii) complexes can be efficiently tuned by chelating with different phenyl-substituted terpyridyl ligands.

Development of a screen to identify selective small molecules active against patient-derived metastatic and chemoresistant breast cancer cells

Introduction

High failure rates of new investigational drugs have impaired the development of breast cancer therapies. One challenge is that excellent activity in preclinical models, such as established cancer cell lines, does not always translate into improved clinical outcomes for patients. New preclinical models, which better replicate clinically-relevant attributes of cancer, such as chemoresistance, metastasis and cellular heterogeneity, may identify novel anti-cancer mechanisms and increase the success of drug development.

Methods

Metastatic breast cancer cells were obtained from pleural effusions of consented patients whose disease had progressed. Normal primary human breast cells were collected from a reduction mammoplasty and immortalized with human telomerase. The patient-derived cells were characterized to determine their cellular heterogeneity and proliferation rate by flow cytometry, while dose response curves were performed for chemotherapies to assess resistance. A screen was developed to measure the differential activity of small molecules on the growth and survival of patient-derived normal breast and metastatic, chemoresistant tumor cells to identify selective anti-cancer compounds. Several hits were identified and validated in dose response assays. One compound, C-6, was further characterized for its effect on cell cycle and cell death in cancer cells.

Results

Patient-derived cells were found to be more heterogeneous, with reduced proliferation rates and enhanced resistance to chemotherapy compared to established cell lines. A screen was subsequently developed that utilized both tumor and normal patient-derived cells. Several compounds were identified, which selectively targeted tumor cells, but not normal cells. Compound C-6 was found to inhibit proliferation and induce cell death in tumor cells via a caspase-independent mechanism.

Conclusions

Short-term culture of patient-derived cells retained more clinically relevant features of breast cancer compared to established cell lines. The low proliferation rate and chemoresistance make patient-derived cells an excellent tool in preclinical drug development.

Mesenchymal stem cell spheroids exhibit enhanced in-vitro and in-vivo osteoregenerative potential

Background

Mesenchymal stem cells (MSCs) are a favored cell source for regenerative medicine because of their multilinage potential. However, the conventional monolayer technique used to culture MSCs, inadequately overcomes their low differentiation capacity. Culture of MSCs in multicellular spheroids, more accurately mimics the in-vivo microenvironment; thus, resolving this problem. In this study, we assessed whether the osteoregenerative potential of MSC spheroids is greater than that of monolayer MSCs.

Results

MSC spheroids were generated from rat MSCs (rMSCs) using low-binding plates. Real-time reverse transcription-polymerase chain reaction and immunocytochemical analysis indicated that osteogenic properties were accelerated in MSC spheroids compared with monolayer rMSCs when treated with an osteoblast-inducer reagent for 7 days. Moreover, increased calcium deposition was visualized in MSC spheroids using Alizarin red staining. In a rat calvarial defect model, micro-computed tomography and histological assays showed that MSC spheroid-engrafted defects experienced enhanced bone regeneration.

Conclusions

Our in-vitro and in-vivo results reveal that MSCs in the spheroid culture exhibit enhanced osteoregenerative efficiency compared with monolayer MSCs.

Three-dimensional in vitro tumor models for cancer research and drug evaluation

Cancer occurs when cells acquire genomic instability and inflammation, produce abnormal levels of epigenetic factors/proteins and tumor suppressors, reprogram the energy metabolism and evade immune destruction, leading to the disruption of cell cycle/normal growth. An early event in carcinogenesis is loss of polarity and detachment from the natural basement membrane, allowing cells to form distinct three-dimensional (3D) structures that interact with each other and with the surrounding microenvironment. Although valuable information has been accumulated from traditional in vitro studies in which cells are grown on flat and hard plastic surfaces (2D culture), this culture condition does not reflect the essential features of tumor tissues. Further, fundamental understanding of cancer metastasis cannot be obtained readily from 2D studies because they lack the complex and dynamic cell-cell communications and cell-matrix interactions that occur during cancer metastasis. These shortcomings, along with lack of spatial depth and cell connectivity, limit the applicability of 2D cultures to accurate testing of pharmacologically active compounds, free or sequestered in nanoparticles. To recapitulate features of native tumor microenvironments, various biomimetic 3D tumor models have been developed to incorporate cancer and stromal cells, relevant matrix components, and biochemical and biophysical cues, into one spatially and temporally integrated system. In this article, we review recent advances in creating 3D tumor models employing tissue engineering principles. We then evaluate the utilities of these novel models for the testing of anticancer drugs and their delivery systems. We highlight the profound differences in responses from 3D in vitro tumors and conventional monolayer cultures. Overall, strategic integration of biological principles and engineering approaches will both improve understanding of tumor progression and invasion and support discovery of more personalized first line treatments for cancer patients.

Comparison between polypyridyl and cyclometalated ruthenium(II) complexes: anticancer activities against 2D and 3D cancer models

The aim of this study was to illustrate the dramatically different anticancer activities between coordinatively saturated polypyridyl (1 a-4 a) and cyclometalated (1 b-4 b) ruthenium(II) complexes. The cyclometalated complexes 1 b-4 b function as DNA transcription inhibitors, exhibiting switch-on cytotoxicity against a 2D cancer cell monolayer, whereas the polypyridyl complexes 1 a-4 a are relatively inactive. Moreover, complexes 1 b-4 b exhibit excellent cytotoxicity against 3D multicellular tumor spheroids (MCTSs), which serve as an intermediate model between in vitro 2D cell monolayers and in vivo 3D solid tumors. The hydrophobicity, efficient cell uptake, and nucleus targeting ability, as well as the high DNA binding affinity of complexes 1 b-4 b, likely contribute to their enhanced anticancer activity. We surmise that cyclometalation could be a universal approach to significantly enhance the anticancer activity of substituted polypyridyl Ru(II) complexes. We also suggest that 3D MCTSs may be a more practical platform for anticancer drug screening than 2D cancer monolayer approaches.

A co-culture model with brain tumor-specific bioluminescence demonstrates astrocyte-induced drug resistance in glioblastoma

BACKGROUND

Although several studies suggest that stromal fibroblasts mediate treatment resistance in several cancer types, little is known about how tumor-associated astrocytes modulate the treatment response in brain tumors. Since traditionally used metabolic assays do not distinguish metabolic activity between stromal and tumor cells, and since 2-dimensional co-culture system does not recreate the formidable complexity of the microenvironment within 3-dimensional structures such as solid tumor tissue, we instead established a glioblastoma (GBM) cell-specific bioluminescent assay for direct measurements of tumor cell viability in the treatment of clinical relevant drugs.

METHODS

Using lentiviral transfection, we established a panel of human GBM cell lines constitutively expressing a fusion transgene encoding luciferase and the enhanced green fluorescence protein (eGFP). We then initiated co-cultures with immortalized astrocytes, TNC-1, and the eGFP/Luc GBM cell lines. Next, we treated all eGFP/Luc GBM cell lines with Temozolomide (TMZ) or Doxorubicin, comparing co-cultures of glioblastoma (GBM) cells and TNC-1 astrocytes with mono-cultures of eGFP/Luc GBM cells. Cell viability was quantitated by measuring the luciferase expression.

RESULTS

Titration experiments demonstrated that luciferase expression was proportional to the number of eGFP/Luc GBM cells, whereas it was not influenced by the number of TNC-1 cells present. Notably, the presence of TNC-1 astrocytes mediated significantly higher cell survival after TMZ treatment in the U251, C6, A172 cell lines as well as the in vivo propagated primary GBM tumor cell line (P3). Moreover, TNC-1 astrocytes mediated significantly higher survival after Doxorubicin treatment in the U251, and LN18 glioma cell lines.

CONCLUSION

Glioma cell-specific bioluminescent assay is a reliable tool for assessment of cell viability in the brain tumor cell compartment following drug treatment. Moreover, we have applied this assay to demonstrate that astrocytes can modulate chemo sensitivity of GBM tumor cells. These effects varied both with the cell line and cytotoxic drug that were used, suggesting that several mechanisms may be involved.

Three-dimensional in vitro co-culture model of breast tumor using magnetic levitation

In this study, we investigate a novel in vitro model to mimic heterogeneous breast tumors without the use of a scaffold while allowing for cell-cell and tumor-fibroblast interactions. Previous studies have shown that magnetic levitation system under conventional culturing conditions results in the formation of three-dimensional (3D) structures, closely resembling in vivo tissues (fat tissue, vasculature, etc.). Three-dimensional heterogeneous tumor models for breast cancer were designed to effectively model the influences of the tumor microenvironment on drug efficiency. Various breast cancer cells were co-cultured with fibroblasts and then magnetically levitated. Size and cell density of the resulting tumors were measured. The model was phenotypically compared to in vivo tumors and examined for the presence of ECM proteins. Lastly, the effects of tumor stroma in the 3D in vitro model on drug transport and efficiency were assessed. Our data suggest that the proposed 3D in vitro breast tumor is advantageous due to the ability to: (1) form large-sized (millimeter in diameter) breast tumor models within 24 h; (2) control tumor cell composition and density; (3) accurately mimic the in vivo tumor microenvironment; and (4) test drug efficiency in an in vitro model that is comparable to in vivo tumors.

Kaposi's sarcoma herpesvirus microRNAs induce metabolic transformation of infected cells

Altered cell metabolism is inherently connected with pathological conditions including cancer and viral infections. Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS). KS tumour cells display features of lymphatic endothelial differentiation and in their vast majority are latently infected with KSHV, while a small number are lytically infected, producing virions. Latently infected cells express only a subset of viral genes, mainly located within the latency-associated region, among them 12 microRNAs. Notably, the metabolic properties of KSHV-infected cells closely resemble the metabolic hallmarks of cancer cells. However, how and why KSHV alters host cell metabolism remains poorly understood. Here, we investigated the effect of KSHV infection on the metabolic profile of primary dermal microvascular lymphatic endothelial cells (LEC) and the functional relevance of this effect. We found that the KSHV microRNAs within the oncogenic cluster collaborate to decrease mitochondria biogenesis and to induce aerobic glycolysis in infected cells. KSHV microRNAs expression decreases oxygen consumption, increase lactate secretion and glucose uptake, stabilize HIF1α and decreases mitochondria copy number. Importantly this metabolic shift is important for latency maintenance and provides a growth advantage. Mechanistically we show that KSHV alters host cell energy metabolism through microRNA-mediated down regulation of EGLN2 and HSPA9. Our data suggest that the KSHV microRNAs induce a metabolic transformation by concurrent regulation of two independent pathways; transcriptional reprograming via HIF1 activation and reduction of mitochondria biogenesis through down regulation of the mitochondrial import machinery. These findings implicate viral microRNAs in the regulation of the cellular metabolism and highlight new potential avenues to inhibit viral latency.

Kaposi's sarcoma (KS) is the most common cancer in HIV-infected untreated individuals. Kaposi's sarcoma-associated herpesvirus (KSHV) is the infectious cause of this neoplasm. The discovery of KSHV and its oncogenic enigmas has enlightened many fields of tumor biology and viral oncogenesis. The metabolic properties of KS significantly differ from those of normal cells and resemble cancer cells in general, but the mechanisms employed by KSHV to alter host cell metabolism are poorly understood. Our work demonstrates that KSHV microRNAs can alter cell metabolism through coherent control of independent pathways, a key feature of microRNA-mediated control of cellular functions. This provides a fresh perspective for how microRNA-encoding pathogens shape a cell's metabolism to create an optimal environment for their survival and/or replication. Indeed, we show that, in the case of KSHV, viral microRNA-driven regulation of metabolism is important for viral latency. These findings will evoke new and exciting approaches to prevent KSHV from establishing latency and later on KS.

3-Dimensional culture systems for anti-cancer compound profiling and high-throughput screening reveal increases in EGFR inhibitor-mediated cytotoxicity compared to monolayer culture systems

3-dimensional (3D) culture models have the potential to bridge the gap between monolayer cell culture and in vivo studies. To benefit anti-cancer drug discovery from 3D models, new techniques are needed that enable their use in high-throughput (HT) screening amenable formats. We have established miniaturized 3D culture methods robust enough for automated HT screens. We have applied these methods to evaluate the sensitivity of normal and tumorigenic breast epithelial cell lines against a panel of oncology drugs when cultured as monolayers (2D) and spheroids (3D). We have identified two classes of compounds that exhibit preferential cytotoxicity against cancer cells over normal cells when cultured as 3D spheroids: microtubule-targeting agents and epidermal growth factor receptor (EGFR) inhibitors. Further improving upon our 3D model, superior differentiation of EC50 values in the proof-of-concept screens was obtained by co-culturing the breast cancer cells with normal human fibroblasts and endothelial cells. Further, the selective sensitivity of the cancer cells towards chemotherapeutics was observed in 3D co-culture conditions, rather than as 2D co-culture monolayers, highlighting the importance of 3D cultures. Finally, we examined the putative mechanisms that drive the differing potency displayed by EGFR inhibitors. In summary, our studies establish robust 3D culture models of human cells for HT assessment of tumor cell-selective agents. This methodology is anticipated to provide a useful tool for the study of biological differences within 2D and 3D culture conditions in HT format, and an important platform for novel anti-cancer drug discovery.

Bimodal tumor-targeting from microenvironment responsive hyaluronan layer-by-layer (LbL) nanoparticles

Active targeting of nanoscale drug carriers can improve tumor-specific delivery; however, cellular heterogeneity both within and among tumor sites is a fundamental barrier to their success. Here, we describe a tumor microenvironment-responsive layer-by-layer (LbL) polymer drug carrier that actively targets tumors based on two independent mechanisms: pH-dependent cellular uptake at hypoxic tumor pH and hyaluronan-directed targeting of cell-surface CD44 receptor, a well-characterized biomarker for breast and ovarian cancer stem cells. Hypoxic pH-induced structural reorganization of hyaluronan-LbL nanoparticles was a direct result of the nature of the LbL electrostatic complex, and led to targeted cellular delivery in vitro and in vivo, with effective tumor penetration and uptake. The nanoscale drug carriers selectively bound CD44 and diminished cancer cell migration in vitro, while co-localizing with the CD44 receptor in vivo. Multimodal targeting of LbL nanoparticles is a powerful strategy for tumor-specific cancer diagnostics and therapy that can be accomplished using a single bilayer of polyamine and hyaluronan that, when assembled, produce a dynamic and responsive cell-particle interface.

Label-free single cell kinetics of the invasion of spheroidal colon cancer cells through 3D Matrigel

This article reports label-free, real-time, and single-cell quantification of the invasion of spheroidal colon cancer cells through three-dimensional (3D) Matrigel using a resonant waveguide grating (RWG) imager. This imager employs a time-resolved swept wavelength interrogation scheme to monitor cell invasion and adhesion with a temporal resolution up to 3 s and a spatial resolution of 12 μm. As the model system, spheroids of human colorectal adenocarcinoma HT-29 cells are generated by culturing the cells in 96-well round-bottom ultralow attachment plates. 3D Matrigel is formed by its gelation in 384-well RWG biosensor microplates. The invasion and adhesion of spheroidal HT29 cells is initiated by placing individual spheroids onto the Matrigel-coated biosensors. The time series RWG images are obtained and used to extract the optical signatures arising from the adhesion after the cells are dissociated from the spheroids and invade through the 3D Matrigel. Compound profiling shows that epidermal growth factor accelerates cancer cell invasion, while vandetanib, a multitarget kinase inhibitor, dose-dependently inhibits invasion. This study demonstrates that the label-free imager can monitor in real-time the invasion of spheroidal cancer cells through 3D matrices.

Multiplexing spheroid volume, resazurin and acid phosphatase viability assays for high-throughput screening of tumour spheroids and stem cell neurospheres

Three-dimensional cell culture has many advantages over monolayer cultures, and spheroids have been hailed as the best current representation of small avascular tumours in vitro. However their adoption in regular screening programs has been hindered by uneven culture growth, poor reproducibility and lack of high-throughput analysis methods for 3D. The objective of this study was to develop a method for a quick and reliable anticancer drug screen in 3D for tumour and human foetal brain tissue in order to investigate drug effectiveness and selective cytotoxic effects. Commercially available ultra-low attachment 96-well round-bottom plates were employed to culture spheroids in a rapid, reproducible manner amenable to automation. A set of three mechanistically different methods for spheroid health assessment (Spheroid volume, metabolic activity and acid phosphatase enzyme activity) were validated against cell numbers in healthy and drug-treated spheroids. An automated open-source ImageJ macro was developed to enable high-throughput volume measurements. Although spheroid volume determination was superior to the other assays, multiplexing it with resazurin reduction and phosphatase activity produced a richer picture of spheroid condition. The ability to distinguish between effects on malignant and the proliferating component of normal brain was tested using etoposide on UW228-3 medulloblastoma cell line and human neural stem cells. At levels below 10 µM etoposide exhibited higher toxicity towards proliferating stem cells, whereas at concentrations above 10 µM the tumour spheroids were affected to a greater extent. The high-throughput assay procedures use ready-made plates, open-source software and are compatible with standard plate readers, therefore offering high predictive power with substantial savings in time and money.

Hybrid Nanomaterial Complexes for Advanced Phage-guided Gene Delivery

Developing nanomaterials that are effective, safe, and selective for gene transfer applications is challenging. Bacteriophages (phage), viruses that infect bacteria only, have shown promise for targeted gene transfer applications. Unfortunately, limited progress has been achieved in improving their potential to overcome mammalian cellular barriers. We hypothesized that chemical modification of the bacteriophage capsid could be applied to improve targeted gene delivery by phage vectors into mammalian cells. Here, we introduce a novel hybrid system consisting of two classes of nanomaterial systems, cationic polymers and M13 bacteriophage virus particles genetically engineered to display a tumor-targeting ligand and carry a transgene cassette. We demonstrate that the phage complex with cationic polymers generates positively charged phage and large aggregates that show enhanced cell surface attachment, buffering capacity, and improved transgene expression while retaining cell type specificity. Moreover, phage/polymer complexes carrying a therapeutic gene achieve greater cancer cell killing than phage alone. This new class of hybrid nanomaterial platform can advance targeted gene delivery applications by bacteriophage.

Arrestin2 modulates androgen receptor activation

Androgen receptor (AR) has a pivotal role in the growth and survival of prostate cancer (PCa). Arrestin2 (Arr2) is a ubiquitous scaffolding/adaptor protein first characterized as a regulator of G protein-coupled receptor signaling. In this study, we report that Arr2 additionally functions as a positive regulator of AR expression and function in PCa cells. Expression level of Arr2 correlates with that of AR, and knockdown of Arr2 inhibits the expression of AR and its effectors prostate-specific antigen, transmembrane protease serine 2, FK506-binding protein 51 and fatty acid synthase. Mechanistically, the knockdown of Arr2 attenuates the binding of AR to androgen response elements and consequently decreases transcription of AR-regulated genes. The inhibition of AR by Arr2 knockdown occurs in both androgen-dependent and castration-resistant PCa (CRPC) cells, although the effect is more prominent in CRPC. Arr2 knockdown inhibits the in vitro CRPC cell proliferation, prostasphere growth and invasion, as well as the in vivo prostate tumor formation, local invasion and distant metastasis. These results illustrate a new role for Arr2 in the expression and activation of AR and its potential relevance as a target for therapeutic intervention and monitoring of disease progression.

Biological activity of a series of cisplatin-based aliphatic bis(carboxylato) Pt(IV) prodrugs: how long the organic chain should be?

The biological properties of a series of cisplatin-based Pt(IV) prodrug candidates, namely trans,cis,cis-[Pt(carboxylato)2Cl2(NH3)2], where carboxylato=CH3(CH2)nCOO(-) [(1), n=0; (2), n=2; (3), n=4; (4), n=6] having a large interval of lipophilicity are discussed. The stability of the complexes was tested in different pH conditions (i.e. from 1.0 to 9.0) to simulate the hypothetical conditions for an oral route of administration, showing a high stability (>90%). The transformation into their active Pt(II) metabolites was demonstrated in the presence of ascorbic acid, with a pseudo-first order kinetics, the half-time of which smoothly decreases as the chain length of carboxylic acid increases. Their antiproliferative activity has been evaluated in vitro on a large panel of human cancer cell lines. As expected, the potency increases with the chain length: 3 and 4 resulted by far more active than cisplatin on all cell lines of about one or two orders of magnitude, respectively. Both complexes retained their activity also on cisplatin-resistant cell line, and exhibited a progressive increase of the selectivity compared with non-tumor cells. These results were confirmed with more prolonged treatment (up to 14days) studied on multicellular tumor spheroids (MCTSs). In this case the Pt(IV) complexes exert a protracted antiproliferative action, even if the drug is removed from the culture medium. Finally, in a time-course experiment of the total platinum evaluation in mice blood (after a single oral administration of the title complexes), 2 gave the best results, representing a good compromise between lipophilicity and water solubility, that increase and decrease respectively on passing from 1 to 4.

Imaging of human differentiated 3D neural aggregates using light sheet fluorescence microscopy

The development of three dimensional (3D) cell cultures represents a big step for the better understanding of cell behavior and disease in a more natural like environment, providing not only single but multiple cell type interactions in a complex 3D matrix, highly resembling physiological conditions. Light sheet fluorescence microscopy (LSFM) is becoming an excellent tool for fast imaging of such 3D biological structures. We demonstrate the potential of this technique for the imaging of human differentiated 3D neural aggregates in fixed and live samples, namely calcium imaging and cell death processes, showing the power of imaging modality compared with traditional microscopy. The combination of light sheet microscopy and 3D neural cultures will open the door to more challenging experiments involving drug testing at large scale as well as a better understanding of relevant biological processes in a more realistic environment.

Optimization of Aqueous Biphasic Tumor Spheroid Microtechnology for Anti-Cancer Drug Testing in 3D Culture

Tumor spheroids are three-dimensional clusters of cancer cells that exhibit characteristics of poorly perfused tumors and hence present a relevant model for testing the efficacy of anti-cancer compounds. The use of spheroids for drug screening is hindered by technological complexities for high throughput generation of consistent size spheroids individually addressable by drug compounds. Here we present and optimize a simple spheroid technology based on the use of an aqueous two-phase system. Cancer cells confined in a drop of the denser aqueous dextran phase are robotically dispensed into a microwell containing the immersion aqueous polyethylene glycol phase. Cells remain within the drop and form a viable spheroid, without a need for any external stimuli. The size of resulting spheroids is sensitive to volume variations of dispensed drops from the air displacement pipetting head of a commercial liquid handling robot. Therefore, we parametrically optimize the process of dispensing of dextran phase drops. For a given cell density, this optimization reproducibly generates consistent size spheroids in standard 96-well plates. In addition, we evaluate the use of a commercial biochemical assay to examine cellular viability of cancer cell spheroids. Spheroids show a dose-dependent response to cisplatin similar to a monolayer culture. However unlike their two-dimensional counterpart, spheroids exhibit resistance to paclitaxel treatment. This technology, which uses only commercially-available reagents and equipment, can potentially expedite anti-cancer drug discovery. Although the use of robotics makes the ATPS spheroid technology particularly useful for drug screening applications, this approach is compatible with simpler liquid handling techniques such as manual micropipetting and offers a straightforward method of 3D cell culture in research laboratories.

Dimerization of the kinase ARAF promotes MAPK pathway activation and cell migration

The RAF family of kinases mediates RAS signaling, and RAF inhibitors can be effective for treating tumors with BRAF(V600E) mutant protein. However, RAF inhibitors paradoxically accelerate metastasis in RAS-mutant tumors and become ineffective in BRAF(V600E) tumors because of reactivation of downstream mitogen-activated protein kinase (MAPK) signaling. We found that the RAF isoform ARAF has an obligatory role in promoting MAPK activity and cell migration in a cell type-dependent manner. Knocking down ARAF prevented the activation of MAPK kinase 1 (MEK1) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) and decreased the number of protrusions from tumor cell spheroids in three-dimensional culture that were induced by BRAF(V600E)-specific or BRAF/CRAF inhibitors (GDC-0879 and sorafenib, respectively). RAF inhibitors induced the homodimerization of ARAF and the heterodimerization of BRAF with CRAF and the scaffolding protein KSR1. In a purified protein solution, recombinant proteins of the three RAF isoforms competed for binding to MEK1. In cells in culture, overexpressing mutants of ARAF that could not homodimerize impaired the interaction between ARAF and endogenous MEK1 and thus prevented the subsequent activation of MEK1 and ERK1/2. Our findings reveal a new role for ARAF in directly activating the MAPK cascade and promoting tumor cell invasion and suggest a new therapeutic target for RAS- and RAF-mediated cancers.

The effect of co-delivery of paclitaxel and curcumin by transferrin-targeted PEG-PE-based mixed micelles on resistant ovarian cancer in 3-D spheroids and in vivo tumors

Multicellular 3D cancer cell culture (spheroids) resemble to in vivo tumors in terms of shape, cell morphology, growth kinetics, gene expression and drug response. However, these characteristics cause very limited drug penetration into deeper parts of the spheroids. In this study, we used multi drug resistant (MDR) ovarian cancer cell spheroid and in vivo tumor models to evaluate the co-delivery of paclitaxel (PCL) and a potent NF-κB inhibitor curcumin (CUR). PCL and CUR were co-loaded into the polyethylene glycol-phosphatidyl ethanolamine (PEG-PE) based polymeric micelles modified with transferrin (TF) as the targeting ligand. Cytotoxicity, cellular association and accumulation into the deeper layers were investigated in the spheroids and compared with the monolayer cell culture. Comparing to non-targeted micelles, flow cytometry and confocal imaging proved significantly deeper and higher micelle penetration into the spheroids with TF-targeting. Both in monolayers and in spheroids, PCL cytotoxicity was significantly increased when co-delivered with CUR in non-targeted micelles or as single agent in TF-targeted micelles, whereas TF-modification of co-loaded micelles did not further enhance the cytotoxicity. In vivo tumor inhibition studies showed good correlation with the 3D cell culture experiments, which suggests the current spheroid model can be used as an intermediate model for the evaluation of co-delivery of anticancer compounds in targeted micelles.

Galium verum aqueous extract strongly inhibits the motility of head and neck cancer cell lines and protects mucosal keratinocytes against toxic DNA damage

Galium verum, also known as Lady's Bedstraw, is an herbaceous plant native to Europe and Asia, and has been used in traditional medicine as an anticancer medicine applied in most cases as a decoction. The influence of a Galium verum decoction on the head and neck cancer cell lines HLaC78 and FADU was analyzed and proved to be toxic in high doses on both cell lines. Cytotoxicity appeared to be influenced by expression of p-glycoprotein (MDR-1) in the carcinoma cell lines. Mucosal keratinocytes, although void of MDR-1 expression, showed only low sensitivity against high Galium concentrations. Sublethal doses of Galium extract acted as strong inhibitors of motility, as shown by a spheroid-based invasion analysis on Matrigel-coated surfaces. Inhibition of invasion was significantly more pronounced in the invasive HLaC78 cell line. mRNA expression analysis of matrix metalloproteinases MMP-2 and MMP-9 and their inhibitors TIMP-1/-2 revealed significant TIMP-1 upregulation after an 8-h Galium exposition in FADU cells. Gelatinolytic activity, however, was not influenced by Galium extract in HLaC78, in the FADU cells MMP-2/-9 activity was slightly increased after incubation with Galium extract. In primary mucosal keratinocytes, Galium decoction protected DNA against benz[a]pyrene, one of the most DNA toxic agents in cigarette smoke. In conclusion Galium extract may be useful as a preventive and/or a concomitant therapeutic approach in head and neck cancer.

Microstructured multi-well plate for three-dimensional packed cell seeding and hepatocyte cell culture

In this article, we present a microstructured multi-well plate for enabling three-dimensional (3D) high density seeding and culture of cells through the use of a standard laboratory centrifuge to promote and maintain 3D tissue-like cellular morphology and cell-specific functionality in vitro without the addition of animal derived or synthetic matrices or coagulants. Each well has microfeatures on the bottom that are comprised of a series of ditches/open microchannels. The dimensions of the microchannels promote and maintain 3D tissue-like cellular morphology and cell-specific functionality in vitro. After cell seeding with a standard pipette, the microstructured multi-well plates were centrifuged to tightly pack cells inside the ditches in order to enhance cell-cell interactions and induce formation of 3D cellular structures during cell culture. Cell-cell interactions were optimized based on cell packing by considering dimensions of the ditches/open microchannels, orientation of the microstructured multi-well plate during centrifugation, cell seeding density, and the centrifugal force and time. With the optimized cell packing conditions, we demonstrated that after 7 days of cell culture, primary human hepatocytes adhered tightly together to form cord-like structures that resembled 3D tissue-like cellular architecture. Importantly, cell membrane polarity was restored without the addition of animal derived or synthetic matrices or coagulants.

Establishment of highly tumorigenic human colorectal cancer cell line (CR4) with properties of putative cancer stem cells

Background

Colorectal cancer (CRC) has the third highest mortality rates among the US population. According to the most recent concept of carcinogenesis, human tumors are organized hierarchically, and the top of it is occupied by malignant stem cells (cancer stem cells, CSCs, or cancer-initiating cells, CICs), which possess unlimited self-renewal and tumor-initiating capacities and high resistance to conventional therapies. To reflect the complexity and diversity of human tumors and to provide clinically and physiologically relevant cancer models, large banks of characterized patient-derived low-passage cell lines, and especially CIC-enriched cell lines, are urgently needed.

Principal Findings

Here we report the establishment of a novel CIC-enriched, highly tumorigenic and clonogenic colon cancer cell line, CR4, derived from liver metastasis. This stable cell line was established by combining 3D culturing and 2D culturing in stem cell media, subcloning of cells with particular morphology, co-culture with carcinoma associated fibroblasts (CAFs) and serial transplantation to NOD/SCID mice. Using RNA-Seq complete transcriptome profiling of the tumorigenic fraction of the CR4 cells in comparison to the bulk tumor cells, we have identified about 360 differentially expressed transcripts, many of which represent stemness, pluripotency and resistance to treatment. Majority of the established CR4 cells express common markers of stemness, including CD133, CD44, CD166, EpCAM, CD24 and Lgr5. Using immunocytochemical, FACS and western blot analyses, we have shown that a significant ratio of the CR4 cells express key markers of pluripotency markers, including Sox-2, Oct3/4 and c-Myc. Constitutive overactivation of ABC transporters and NF-kB and absence of tumor suppressors p53 and p21 may partially explain exceptional drug resistance of the CR4 cells.

Conclusions

The highly tumorigenic and clonogenic CIC-enriched CR4 cell line may provide an important new tool to support the discovery of novel diagnostic and/or prognostic biomarkers as well as the development of more effective therapeutic strategies.

Cancer stem cell differentiation: TGFβ1 and versican may trigger molecules for the organization of tumor spheroids

Cancer stem cells (CSCs) have the ability to self-renew similar to normal stem cells. This process is linked with metastasis and resistance to chemotherapy and radiotherapy. In the present study, we constructed an in vitro differentiation model for CSCs. CSCs isolated and proliferated for one passage were maintained as monolayers or spheroid-forming cells with serum included media for differentiation process. Differentiation of adhesion molecules and cellular ultrastructural properties were investigated and compared in both monolayer and spheroid cultures. CD133+/CD44+ cancer-initiating cells were isolated from DU-145 human prostate cancer cell line monolayer cultures and propagated as tumor spheroids and compared with the remaining heterogeneous cancer cell bulk population. Microarray-based gene expression analysis was applied to determine genes with differential expression and protein expression levels of candidates were analyzed by immunohistochemistry. Electron microscopy showed detailed analysis of morphology. TGFβ1 was found to be significantly upregulated in monolayer CSCs. High expression levels of VCAN, COL7A1, ITGβ3, MMP16, RPL13A, COL4A2 and TIMP1 and low expression levels of THBS1, MMP1 and MMP14 were detected when CSCs were maintained as serum-grown prostate CSC spheroids. Immunohistochemistry supported increased immunoreactivity of TGFβ1 in monolayer cultures and VCAN in spheroids. CSCs were found to possess multipotential differentiation capabilities through upregulation and/or downregulation of their markers. TGFβ1 is a triggering molecule, it stimulates versican, Col7A1, ITGβ3 and, most importantly, the upregulation of versican was only detected in CSCs. Our data support a model where CSCs must be engaged by one or more signaling cascades to differentiate and initiate tumor formation. This mechanism occurs with intracellular and extracellular signals and it is possible that CSCc themselves may be a source for extracellular signaling. These molecules functioning in tumor progression and differentiation may help develop targeted therapy.

Advanced cell culture techniques for cancer drug discovery

Human cancer cell lines are an integral part of drug discovery practices. However, modeling the complexity of cancer utilizing these cell lines on standard plastic substrata, does not accurately represent the tumor microenvironment. Research into developing advanced tumor cell culture models in a three-dimensional (3D) architecture that more prescisely characterizes the disease state have been undertaken by a number of laboratories around the world. These 3D cell culture models are particularly beneficial for investigating mechanistic processes and drug resistance in tumor cells. In addition, a range of molecular mechanisms deconstructed by studying cancer cells in 3D models suggest that tumor cells cultured in two-dimensional monolayer conditions do not respond to cancer therapeutics/compounds in a similar manner. Recent studies have demonstrated the potential of utilizing 3D cell culture models in drug discovery programs; however, it is evident that further research is required for the development of more complex models that incorporate the majority of the cellular and physical properties of a tumor.

Development of a magnetic 3D spheroid platform with potential application for high-throughput drug screening

Three-dimensional (3D) cell culture has become increasingly adopted as a more accurate model of the complex in vivo microenvironment compared to conventional two-dimensional (2D) cell culture. Multicellular spheroids are important 3D cell culture models widely used in biological studies and drug screening. To facilitate simple spheroid manipulation, magnetic spheroids were generated from magnetically labeled cells using a scaffold-free approach. This method is applicable to a variety of cell types. The spheroids generated can be targeted and immobilized using magnetic field gradients, allowing media change or dilution to be performed with minimal disruption to the spheroids. Cells in magnetic spheroids showed good viability and displayed typical 3D morphology. Using this platform, a 28 day study was carried out using doxorubicin on magnetic MCF-7 spheroids. The results provided a proof-of-principle for using magnetic tumor spheroids in therapeutic studies. They can offer beneficial insights that help to bridge the gap between in vitro and in vivo models. Furthermore, this platform can be adapted for high-throughput screening in drug discovery.

Stress-induced cleavage of Myc promotes cancer cell survival

Evasion of apoptosis is critical in Myc-induced tumor progression. Here we report that cancer cells evade death under stress by activating calpain-mediated proteolysis of Myc. This generates Myc-nick, a cytoplasmic, transcriptionally inactive cleavage product of Myc. We found conversion of Myc into Myc-nick in cell lines and tissues derived from multiple cancers. In colon cancer, the production of Myc-nick is enhanced under stress conditions such as hypoxia and nutrient deprivation. Under these conditions, ectopic expression of Myc-nick promotes anchorage-independent growth and cell survival at least in part by promoting autophagy. Myc-nick also delays colon cancer cell death after treatment with chemotherapeutic drugs such as etoposide, cisplatin, and imatinib. Furthermore, colon cancer cells expressing a cleavage-resistant form of Myc undergo extensive apoptosis but are rescued by overexpression of Myc-nick. We also found that ectopic expression of Myc-nick results in the induction of the actin-bundling protein fascin, formation of filopodia, and increased cell motility-all mediators of tumor metastasis. Myc-nick-induced survival, autophagy, and motility require Myc box II (MBII), a region of Myc-nick that recruits acetyltransferases that in turn modify cytoplasmic proteins, including α-tubulin and ATG3. Our results suggest that Myc-nick-induced survival and motility contribute to colon cancer progression and metastasis.

3D tumor models: history, advances and future perspectives

ABSTRACT: 

Evaluation of cancer therapeutics by utilizing 3D tumor models, before clinical studies, could be more advantageous than conventional 2D tumor models (monolayer cultures). The 3D systems mimic the tumor microenvironment more closely than 2D systems. The following review discusses the various 3D tumor models present today with the advantages and limitations of each. 3D tumor models replicate the elements of a tumor microenvironment such as hypoxia, necrosis, angiogenesis and cell adhesion. The review introduces application of techniques such as microfluidics, imaging and tissue engineering to improve the 3D tumor models. Despite their tremendous potential to better screen chemotherapeutics, 3D tumor models still have a long way to go before they are used commonly as in vitro tumor models in pharmaceutical industrial research.

The need for complex 3D culture models to unravel novel pathways and identify accurate biomarkers in breast cancer

The recent cataloging of the genomic aberrations in breast cancer has revealed the diversity and complexity of the disease at the genetic level. To unravel the functional consequences of specific repertoires of mutations and copy number changes on signaling pathways in breast cancer, it is crucial to develop model systems that truly recapitulate the disease. Here we discuss the three-dimensional culture models currently being used or recently developed for the study of normal mammary epithelial cells and breast cancer, including primary tumors and dormancy. We discuss the insights gained from these models in regards to cell signaling and potential therapeutic strategies, and the challenges that need to be met for the generation of heterotypic breast cancer model systems that are amenable for high-throughput approaches.

3D cell culture systems modeling tumor growth determinants in cancer target discovery

Phenotypic heterogeneity of cancer cells, cell biological context, heterotypic crosstalk and the microenvironment are key determinants of the multistep process of tumor development. They sign responsible, to a significant extent, for the limited response and resistance of cancer cells to molecular-targeted therapies. Better functional knowledge of the complex intra- and intercellular signaling circuits underlying communication between the different cell types populating a tumor tissue and of the systemic and local factors that shape the tumor microenvironment is therefore imperative. Sophisticated 3D multicellular tumor spheroid (MCTS) systems provide an emerging tool to model the phenotypic and cellular heterogeneity as well as microenvironmental aspects of in vivo tumor growth. In this review we discuss the cellular, chemical and physical factors contributing to zonation and cellular crosstalk within tumor masses. On this basis, we further describe 3D cell culture technologies for growth of MCTS as advanced tools for exploring molecular tumor growth determinants and facilitating drug discovery efforts. We conclude with a synopsis on technological aspects for on-line analysis and post-processing of 3D MCTS models.