High levels of MDM2 are not correlated with the presence of wild-type p53 in human malignant mesothelioma cell lines.

S Ungar,Bi Gerwin,K Mattson,A Van De Meeren,K Linnainmaa,L Tammilehto

doi:10.1038/bjc.1996.585

Abstract

Prior analysis of 20 human mesothelioma cell lines for p53 status revealed only two mutations and one p53 null cell line, although p53 expression was detected in most cell lines. In addition, mRNA and protein expression of the retinoblastoma gene product in human mesothelioma cell lines is similar to normal controls. We have tested for p53 induction after exposure to ionising radiation and demonstrate this induction and, to a lesser extent, p21(WAF1) induction, in both normal mesothelial cells and p53-positive mesothelioma cell lines. We postulated that high levels of MDM2 might alter p53 and retinoblastoma tumour-suppressor function in mesothelioma. However, Southern blot analysis for mdm2 indicated that no amplification had occurred in 18 mesothelioma cell lines tested. Steady-state mRNA and protein levels also did not indicate overexpression. These results indicate that high levels of MDM2 are not responsible for inactivating the functions of wild-type p53 or the retinoblastoma gene product during the pathogenesis of malignant mesothelioma.

Highlights

Summary Prior analysis of 20 human mesothelioma cell lines for p53 status revealed only two mutations and one p53 null cell line, p53 expression was detected in most cell lines
MRNA and protein expression of the retinoblastoma gene product in human mesothelioma cell lines is similar to normal controls
We have tested for p53 induction after exposure to ionising radiation and demonstrate this induction and, to a lesser extent, p2IWAFI induction, in both normal mesothelial cells and p53-positive mesothelioma cell lines

Summary

Methods

Human mesothelioma cell lines were cultured as described previously (LaVeck et al, 1988). OSACl, a sarcoma cell line lacking p53 mutation (Leach et al, 1993) but exhibiting a 30- to 40-fold mdm 2 gene amplification as well as overexpression of both mdm mRNA and protein (Oliner et al, 1992), was generously supplied by Dr Bert Vogelstein. This cell line, as well as human bronchial fibroblastic (HBF) cell strains, was maintained in Hut medium (Roswell Park Memorial Institute 1640 medium containing 10% fetal bovine serum; BioFluids, Rockville, MD, USA). Normal human bronchial epithelial (NHBE) cells were grown in LHC9 medium (BioFluids Inc.) as described previously (Lechner and LaVeck, 1985)

Results

Discussion

Conclusion