Journal Article

Asbestos induction of extended lifespan in normal human mesothelial cells: interindividual susceptibility and SV40 T antigen

Lixin Xu, Barbara J. Flynn, Susan Ungar, Harvey I. Pass, Kaija Linnainmaa, Karin Mattson and Brenda I. Gerwin

in Carcinogenesis

Volume 20, issue 5, pages 773-783
Published in print May 1999 | ISSN: 0143-3334
Published online May 1999 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/20.5.773
Asbestos induction of extended lifespan in normal human mesothelial cells: interindividual susceptibility and SV40 T antigen

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Normal human mesothelial cells from individual donors were studied for susceptibility to asbestos-induction of apoptosis and generation of an extended lifespan population. Such populations were generated after death of the majority of cells and arose from a subset of mesothelial cultures (4/16) whereas fibroblastic cells (5/5) did not develop extended lifespan populations after asbestos exposure. All mesothelial cultures were examined for the presence of SV40 T antigen to obtain information on (i) the presence of SV40 T antigen expression in normal human mesothelial cells and (ii) the relationship between generation of an extended lifespan population and expression of SV40 T antigen. Immunostaining for SV40 T antigen was positive in 2/38 normal human mesothelial cultures. These cultures also had elevated p53 expression. However, the two isolates expressing SV40 T antigen did not exhibit enhanced proliferative potential or develop an extended lifespan population. Asbestos-generated extended lifespan populations were specifically resistant to asbestos-mediated but not to α-Fas-induced apoptosis. Deletion of p16Ink4a was shown in 70% of tumor samples. All mesothelioma cell lines examined showed homozygous deletion of this locus which extended to exon 1β. Extended lifespan cultures were examined for expression of p16Ink4a to establish whether deletion was an early response to asbestos exposure. During their rapid growth phase, extended lifespan cultures showed decreased expression of p16Ink4a relative to untreated cultures, but methylation was not observed, and p16Ink4a expression became elevated when cells entered culture crisis. These data extend the earlier observation that asbestos can generate extended lifespan populations, providing data on frequency and cell type specificity. In addition, this report shows that generation of such populations does not require expression of SV40 T antigen. Extended lifespan cells could represent a population expressing early changes critical for mesothelioma development. Further study of these populations could identify such changes.

Keywords: BSA, bovine serum albumin; DAPI, 4′-6-diamidine-2-phenylindole; DTT, dithiothreitol; ECL, enhanced chemiluminescence; ELP, extended proliferative lifespan populations; EMEM, Eagle's minimum essential medium; FITC, fluorescein isothiocyanate; LHC, Laboratory of Human Carcinogenesis; MM, mesothelial medium; NAIMA, North American Insulation Manufacturers Association; PBS, phosphate-buffered saline; PI, propidium iodide; PMSF, polymethylsulfonide fluoride; RB, retinoblastoma; TBST, Tris buffered saline plus Tween20; UICC, Union Internationale contre le Cancer.

Journal Article.  9364 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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