title: Down-regulation of DNA mismatch repair enhances initiation and growth of neuroblastoma and brain tumour multicellular spheroids.
abstract: Multicellular tumour spheroid (MCTS) cultures are excellent model systems for simulating the development and microenvironmental conditions of in vivo tumour growth. Many documented cell lines can generate differentiated MCTS when cultured in suspension or in a non-adhesive environment. While physiological and biochemical properties of MCTS have been extensively characterized, insight into the events and conditions responsible for initiation of these structures is lacking. MCTS are formed by only a small subpopulation of cells during surface-associated growth but the processes responsible for this differentiation are poorly understood and have not been previously studied experimentally. Analysis of gene expression within spheroids has provided clues but to date it is not known if the observed differences are a cause or consequence of MCTS growth. One mechanism linked to tumourigenesis in a number of cancers is genetic instability arising from impaired DNA mismatch repair (MMR). This study aimed to determine the role of MMR in MCTS initiation and development. Using surface-associated N2a and CHLA-02-ATRT culture systems we have investigated the impact of impaired MMR on MCTS growth. Analysis of the DNA MMR genes MLH1 and PMS2 revealed both to be significantly down-regulated at the mRNA level compared with non-spheroid-forming cells. By using small interfering RNA (siRNA) against these genes we show that silencing of MLH1 and PMS2 enhances both MCTS initiation and subsequent expansion. This effect was prolonged over several passages following siRNA transfection. Down-regulation of DNA MMR can contribute to tumour initiation and progression in N2a and CHLA-02-ATRT MCTS models. Studies of surface-associated MCTS differentiation may have broader applications in studying events in the initiation of cancer foci.
authors.affiliation: Centre for Biological Sciences, University of Southampton, Southampton, United Kingdom.
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Collins
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Hervé
authors.forename: C W
authors.initials: CW
authors.lastname: Keevil
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Blaydes
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Webb
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics*; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000235:genetics*; D000818:Animals; D001932:Brain Neoplasms / Q000235:genetics / Q000473:pathology*; D053843:DNA Mismatch Repair / Q000235:genetics*; D045643:DNA Repair Enzymes / Q000037:antagonists & inhibitors / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D015536:Down-Regulation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D009447:Neuroblastoma / Q000235:genetics / Q000473:pathology*; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018874:Spheroids, Cellular / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; C501485:Mlh1 protein, mouse; D009687:Nuclear Proteins; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D000251:Adenosine Triphosphatases; C094934:PMS2 protein, human; C499533:Pms2 protein, mouse; D000070976:Mismatch Repair Endonuclease PMS2; D000070957:MutL Protein Homolog 1; D045643:DNA Repair Enzymes