A Novel In Vitro Model of Human Mesothelioma for Studying Tumor Biology and Apoptotic Resistance

Lung Biology Center, Box 0854 University of California at San Francisco, San Francisco, CA 94143-0854, USA.
American Journal of Respiratory Cell and Molecular Biology (Impact Factor: 3.99). 01/2006; 33(6):541-8. DOI: 10.1165/rcmb.2004-0355OC
Source: PubMed


Like many tumors, malignant mesothelioma exhibits significant chemoresistance and resistance to apoptosis in vivo that is not seen in current in vitro models. To study the mechanisms of this multicellular resistance, biologically relevant in vitro models are necessary. Therefore, we characterized and tested human mesothelioma tissue grown in vitro as tumor fragment spheroids. After 5-10 d in culture, fragments from each of 15 human mesothelioma tumors rounded into spheroids. The tumor fragment spheroids maintained multiple characteristics of the original tumors for up to 3 mo including the presence of viable mesothelioma cells, macrophages, and a collagen-rich stroma. In 14-d-old spheroids, mesothelioma cells showed the same proliferation rate and expression of a death receptor, DR5, as in the original tumor. To determine responses to treatment, we treated tumor fragment spheroids grown from three separate tumors with agents, TNF-related apoptosis-inducing ligand (TRAIL) plus cycloheximide, that induced near total apoptosis in three human mesothelioma cell lines (M28, REN, MS-1) grown as monolayers (94 +/- 6% apoptosis; mean +/- SEM). Compared with mesothelioma cells in monolayers, mesothelioma cells in the spheroids were resistant to TRAIL plus cycloheximide (32 +/- 4% apoptosis; mean +/- SEM). Apoptotic resistance of mesothelioma cells was significantly reduced by inhibiting either the PI3K/Akt pathway with LY294002 (47 +/- 6% apoptosis) or the mTOR pathway with rapamycin (50 +/- 17% apoptosis). We conclude that human mesothelioma can be maintained in vitro in a biologically relevant model that exhibits apoptotic resistance, thereby permitting study of its tumor biology and of novel approaches to therapy.


Available from: Stephen Nishimura, Mar 10, 2015
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    • "OMSs are clearly distinct from the classical model of MCTS. OMSs, also designated as " biopsy spheroids " [45], " organotypic spheroids " [13], and " tumor fragment spheroids " [46], are generated directly from cut tissues, whereas MCTSs are established from single-cell suspensions of cancer cells. Ovarian carcinoma ascites fluids can lead to " spherules " [47] or " ovarian carcinoma ascites spheroids " [48], a specific term that prevents confusion with MCTSs from ovarian carcinoma cell lines. "
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    ABSTRACT: Three-dimensional (3D) in vitro models have been used in cancer research as an intermediate model between in vitro cancer cell line cultures and in vivo tumor. Spherical cancer models represent major 3D in vitro models that have been described over the past 4 decades. These models have gained popularity in cancer stem cell research using tumorospheres. Thus, it is crucial to define and clarify the different spherical cancer models thus far described. Here, we focus on in vitro multicellular spheres used in cancer research. All these spherelike structures are characterized by their well-rounded shape, the presence of cancer cells, and their capacity to be maintained as free-floating cultures. We propose a rational classification of the four most commonly used spherical cancer models in cancer research based on culture methods for obtaining them and on subsequent differences in sphere biology: the multicellular tumor spheroid model, first described in the early 70s and obtained by culture of cancer cell lines under nonadherent conditions; tumorospheres, a model of cancer stem cell expansion established in a serum-free medium supplemented with growth factors; tissue-derived tumor spheres and organotypic multicellular spheroids, obtained by tumor tissue mechanical dissociation and cutting. In addition, we describe their applications to and interest in cancer research; in particular, we describe their contribution to chemoresistance, radioresistance, tumorigenicity, and invasion and migration studies. Although these models share a common 3D conformation, each displays its own intrinsic properties. Therefore, the most relevant spherical cancer model must be carefully selected, as a function of the study aim and cancer type.
    Neoplasia (New York, N.Y.) 01/2015; 58(1). DOI:10.1016/j.neo.2014.12.004 · 4.25 Impact Factor
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    • "In recent years, multicellular spheroids (MCSs) have been widely used for drug-sensitivity and molecular mechanism studies to investigate the difference in biological characteristics and phenotypic expression not provided in monolayer cells. Many studies have revealed that resistance in MSCs was more closely associated with the natural resistance observed in patient tumors than the monolayer cells and supported in vitro models for the study of cytotoxic drugs.21–24 The present study used human HCC HepG2 MCSs to investigate the differential effects of celecoxib, a selective COX-2 inhibitor,25 combined with 5-FU or sorafenib or gefitinib on cell growth, apoptosis, and signaling pathways. "
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    ABSTRACT: Celecoxib, an inhibitor of cyclooxygenase-2 (COX2), was investigated for enhancement of chemotherapeutic efficacy in cancer clinical trials. This study aimed to determine whether celecoxib combined with 5-fluorouracil or sorafenib or gefitinib is beneficial in HepG2 multicellular spheroids (MCSs), as well as elucidate the underlying mechanisms. The human hepatocellular carcinoma cell line HepG2 MCSs were used as in vitro models to investigate the effects of celecoxib combined with 5-fluorouracil or sorafenib or gefitinib treatment on cell growth, apoptosis, and signaling pathway. MCSs showed resistance to drugs compared with monolayer cells. Celecoxib combined with 5-fluorouracil or sorafenib exhibited a synergistic action. Exposure to celecoxib (21.8 μmol/L) plus 5-fluorouracil (8.1 × 10(-3) g/L) or sorafenib (4.4 μmol/L) increased apoptosis but exerted no effect on COX2, phosphorylated epidermal growth-factor receptor (p-EGFR) and phosphorylated (p)-AKT expression. Gefitinib (5 μmol/L), which exhibits no growth-inhibition activity as a single agent, increased the inhibitory effect of celecoxib. Gefitinib (5 μmol/L) plus celecoxib (21.8 μmol/L) increased apoptosis. COX2, p-EGFR, and p-AKT were inhibited. Celecoxib combined with 5-fluorouracil or sorafenib or gefitinib may be superior to single-agent therapy in HepG2 MCSs. Our results provided molecular evidence to support celecoxib combination-treatment strategies for patients with human hepatocellular carcinoma. MCSs provided a good model to evaluate the interaction of anticancer drugs.
    OncoTargets and Therapy 02/2014; 7:353-63. DOI:10.2147/OTT.S56115 · 2.31 Impact Factor
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    • "Measurement of apoptosis in this complex tissue required dual immunostaining to identify the mesothelioma cells and thus to localize the cleaved caspase 3 characteristic of apoptosis to the mesothelioma cells, as we have previously reported [18]. Following treatment, tumor fragment spheroids were collected, fixed in 10% buffered formalin in PBS overnight at 4°C and embedded in 3% agar in PBS. "
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    PLoS ONE 12/2012; 7(12):e52753. DOI:10.1371/journal.pone.0052753 · 3.23 Impact Factor
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