Discovery of a perinecrotic 60 kDa MDM2 isoform within glioma spheroids and glioblastoma biopsy material

• Published in: Neuropathology and applied neurobiology 2005-04, Vol.31 (2), p.191-202
• Main Authors: Bell, H. S., Whittle, I. R., Bader, S. A., Wharton, S. B.
• Format: Article
• Language: English
• Subjects: Antineoplastic agents; Apoptosis - physiology; bcl-2-Associated X Protein; Biological and medical sciences; Blotting, Western; Brain Neoplasms - metabolism; Brain Neoplasms - pathology; Cell Line, Tumor; Chemotherapy; Gene Expression; Genes, p53 - physiology; glioblastoma; Glioblastoma - metabolism; Glioblastoma - pathology; Glioma - metabolism; Glioma - pathology; Humans; Immunohistochemistry; Isoenzymes - metabolism; MDM2; Medical sciences; necrosis; Necrosis - physiopathology; Neurology; Nuclear Proteins - metabolism; Oxidative Stress - physiology; p53; Pharmacology. Drug treatments; Polymerase Chain Reaction; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-bcl-2 - biosynthesis; Proto-Oncogene Proteins c-mdm2; Proto-Oncogene Proteins p21(ras) - biosynthesis; Sarcoidosis. Granulomatous diseases of unproved etiology. Connective tissue diseases. Elastic tissue diseases. Vasculitis; spheroid; Spheroids, Cellular - metabolism; Transfection
• ISSN: 0305-1846; 1365-2990
• DOI: 10.1111/j.1365-2990.2004.00627.x

Necrosis in glioblastoma is often associated with high levels of Fas (APO‐1), HIF‐1α and PARP expression. The presence of such molecules suggests a regulative element to cell death within this tissue, which may involve p53. We aimed to establish whether p53 and its downstream targets Bax, MDM2 and p21 play a role in perinecrotic cell death in glioblastoma. Following sequencing of the p53 gene in U87 and U373 glioma cell lines, p53 was found to be reactive in the p53 wild‐type line U87 in response to hypoxia but not in the p53 mutant line, U373. Although no  increase  in  perinecrotic  p53  expression  was  detected in spheroid cultures derived from these lines, a 60 kDa MDM2 isoform lacking a C‐terminal domain showed perinecrotic localization, irrespective of p53 status. Similar findings were observed surrounding regions of necrosis in 80% of glioblastoma biopsies examined. Increasing levels of wild‐type p53 did not affect cell death in U87 spheroid cultures but killed all U373 cells 3 days post transfection. Dominant negative p53 did not affect cell death in U373 and U87 spheroid cultures. Although p53 accumulation appeared not to be important for the onset of cell death both in spheroid and biopsy cases, high levels of perinecrotic 60 kDa MDM2 may have implications for glioma cell death susceptibility in both p53 mutant and wild‐type tumour cell populations.