title: Multidrug resistance characterization in multicellular tumour spheroids from two human lung cancer cell lines.
abstract: BACKGROUND
  Most of the knowledge about the mechanisms of multidrug resistance in lung cancer has been achieved through the use of cell lines isolated from tumours cultivated either in suspensions of isolated cells or in monolayers and following exposition to different cytostatic agents. However, tumour cell lines growing as multicellular tumour spheroids (MTS) frequently develop multicellular resistance in a drug-independent form. The aim of this study was to characterize the phenotypic and functional differences between two human NSCLC cell lines (INER-37 and INER-51) grown as traditional monolayer cultures versus as MTS.
  
  
  METHODS
  After 72 hours treatment with anticancer drugs, chemosensitivity in monolayers and tumour spheroids cultures was assessed using MTT assay. Reverse transcription-polymerase chain reaction was employed to detect the mRNAs of multidrug resistance-related genes. The expression of P-gp was analyzed by immunohistochemical staining and cell cycle profiles were analyzed using FACS.
  
  
  RESULTS
  The results indicate that when grown as MTS each lung cancer cell line had different morphologies as well as and abrogation of cell proliferation with decrease of the G2/M phase. Also, MTS acquired multicellular resistance to several chemotherapeutic agents in only a few days of culture which were accomplished by significant changes in the expression of MDR-related genes.
  
  
  CONCLUSIONS
  Overall, the MTS culture changed the cellular response to drugs nevertheless each of the cell lines studied seems to implement different mechanisms to acquire multicellular resistance.
authors.affiliation: Departamento Bioquímica y Medicina Ambiental., Instituto Nacional de Enfermedades Respiratorias, Clza. Tlalpan, 4502, Col Sec. XVI., Mexico, 14080 Mexico.
authors.forename: Raúl
authors.initials: R
authors.lastname: Barrera-Rodríguez
authors.affiliation: Jefe del Serv. Neumología. Hospital Central Del Sur, Pemex, Mexico, Mexico.
authors.forename: Jorge Morales
authors.initials: JM
authors.lastname: Fuentes
keywords: Drug cytotoxicity; Lung cancer; Multicellular resistance; Multicellular tumour cancer spheroids; Multidrug resistance genes; Three-dimensional culture