title: A novel in vitro model of human mesothelioma for studying tumor biology and apoptotic resistance.
abstract: 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.
authors.affiliation: Lung Biology Center, Box 0854 University of California at San Francisco, San Francisco, CA 94143-0854, USA.
authors.forename: Ki-Up
authors.initials: KU
authors.lastname: Kim
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Wilson
authors.forename: Keith S
authors.initials: KS
authors.lastname: Abayasiriwardana
authors.forename: Rodney
authors.initials: R
authors.lastname: Collins
authors.forename: Lars
authors.initials: L
authors.lastname: Fjellbirkeland
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Xu
authors.forename: David M
authors.initials: DM
authors.lastname: Jablons
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Nishimura
authors.forename: V Courtney
authors.initials: VC
authors.lastname: Broaddus
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D058534:Class I Phosphatidylinositol 3-Kinases; D003094:Collagen / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008264:Macrophages / Q000166:cytology / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000378:metabolism; D008654:Mesothelioma / Q000378:metabolism / Q000473:pathology*; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism*; D015398:Signal Transduction; D018874:Spheroids, Cellular / Q000378:metabolism / Q000473:pathology*; D017154:Stromal Cells / Q000378:metabolism / Q000473:pathology; D053221:TNF-Related Apoptosis-Inducing Ligand; D058570:TOR Serine-Threonine Kinases; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D014408:Biomarkers, Tumor; D002867:Chromones; D058534:Class I Phosphatidylinositol 3-Kinases; D003094:Collagen; D003513:Cycloheximide; D008562:Membrane Glycoproteins; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053221:TNF-Related Apoptosis-Inducing Ligand; D058570:TOR Serine-Threonine Kinases; D014409:Tumor Necrosis Factor-alpha; C505639:TNFRSF10B protein, human; C505653:TNFSF10 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C546842:MTOR protein, human; C484760:PIK3CA protein, human