title: In vitro chemo- and radio-resistance in small cell lung cancer correlates with cell adhesion and constitutive activation of AKT and MAP kinase pathways.
abstract: Most small cell lung cancer (SCLC) patients relapse within 12 months of starting combination chemotherapy plus radio-therapy, due to the development of acquired chemo- and radio-resistance. This phenomenon relates to the induction of tumour differentiation, resulting in apoptosis-resistant, morphologically variant (v-SCLC) cells, which lack the neuroendocrine expression of classic (c-) SCLC cells. In this study spontaneously adherent SCLC sublines were shown by differential gene expression analysis to provide an in vitro model of variant differentiation in SCLC, with down-regulation of neuroendocrine markers and up-regulation of epithelial differentiation markers cyclin D1, endothelin, the cell adhesion molecules CD 44 and integrin subunits alpha2, beta3 and beta4. The sensitivity of adherent SCLC sublines to etoposide, cyclophosphamide and gamma radiation was significantly diminished relative to parent suspension cell lines. Western blot analysis using phosphorylation-specific antibodies to Akt and MAP kinase revealed markedly elevated activation in adherent SCLC sublines, paralleled by increased levels of phosphorylated Bad protein and activated NF-kappaB. Subcultivation of the adherent sublines on uncoated surfaces reversed their adherent phenotype immediately and under these conditions Akt activity reverted to low levels. These results suggest that c-SCLC cells can differentiate spontaneously to v-SCLC and that the associated cellular adhesion may trigger Akt-dependent inhibition of apoptosis in SCLC cells, thus leading to acquired chemo- and radio-resistance.
authors.affiliation: Department of Haematology and Oncology, Centre for Internal Medicine, University Hospital, Philipps-Universität Marburg, D35033 Marburg, Germany.
authors.forename: Alison C
authors.initials: AC
authors.lastname: Kraus
authors.forename: Ines
authors.initials: I
authors.lastname: Ferber
authors.forename: Sven-Oliver
authors.initials: SO
authors.lastname: Bachmann
authors.forename: Hannah
authors.initials: H
authors.lastname: Specht
authors.forename: Anja
authors.initials: A
authors.lastname: Wimmel
authors.forename: Markus W
authors.initials: MW
authors.lastname: Gross
authors.forename: Juergen
authors.initials: J
authors.lastname: Schlegel
authors.forename: Guntram
authors.initials: G
authors.lastname: Suske
authors.forename: Marcus
authors.initials: M
authors.lastname: Schuermann
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D001483:Base Sequence; D018288:Carcinoma, Small Cell / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology* / Q000532:radiotherapy; D002448:Cell Adhesion; D017931:DNA Primers; D005720:Gamma Rays; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000473:pathology* / Q000532:radiotherapy; D020935:MAP Kinase Signaling System; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D017931:DNA Primers; D011518:Proto-Oncogene Proteins; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt