ABSTRACT
Increased cancer risk associated with germ-line p53 mutation was linked to a deficit in the ability to maintain genomic stability. Accordingly, normal fibroblasts from cancer-prone individuals accumulate genomic aberrations with concomitant loss of wild-type p53 allele during in vitro culture. We tested whether such changes also occur in EBV-immortalized lymphoblastoid cells. Both normal and p53 germ-line mutant lymphoblastoid cells maintained functional p53 and genomic stability during long term in vitro culture. These unexpected differences between fibroblastic and lymphoblastic cells suggest that phenotypic expression of p53 deficiency is cell type specific. This could contribute to selective tissular localization of tumours observed in patients with Li-Fraumeni syndrome despite the presence of a mutant p53 allele in all cells.
Subject(s)
Breast Neoplasms/genetics , Cyclins/metabolism , DNA Damage , Genes, p53/physiology , Tumor Suppressor Protein p53/metabolism , Alleles , B-Lymphocytes/metabolism , Breast Neoplasms/metabolism , Cell Line , Cyclin-Dependent Kinase Inhibitor p21 , G1 Phase/genetics , Humans , Karyotyping , Mutation , S Phase/genetics , Tumor Cells, CulturedABSTRACT
Among obese insulin resistant subjects plasminogen activator inhibitor 1 (PAI 1) levels are closely associated with fasting insulin levels in cross sectional as well as intervention studies. Insulin concentration by itself does not seem to modulate PAI 1 levels at least in acute conditions. PAI 1 levels could be more directly related to the insulin resistant state than to hyperinsulinaemia. To elucidate further this phenomenon we compared insulin, triglyceride and PAI 1 levels in twenty control subjects and in three groups of patients presenting insulin resistance 14 obese subjects, 6 patients with Cushing disease and 7 with acromegaly. None of the tested subjects was diabetic. Fasting insulin levels were elevated in obese (21.4 +/- 8.0) hypercortisolic (20.3 +/- 11.0) and acromegalic patients (16.1 +/- 5.0) compared to controls (9.2 +/- 3.0 microU/ml, m +/- SD). PAI activity and PAI 1 antigen levels were elevated in the obese group only (34.3 +/- 13.0 for PAI 1 activity) and not in the others: 10.2 +/- 10.0, 7.0 +/- 4.6 I U/l for hypercortisolic and acromegalic patients respectively (normal controls 9.7 +/- 5.4). Triglyceride levels were also elevated among obese subjects 2.2 +/- 1.3 vs 1.1 +/- 0.4 mM/l in the controls; they were slightly higher than normal but not significantly in the hypercortisolic (1.5 +/- 0.6) and acromegalic (1.43 +/- 0.6 mM/l) patients. The mechanism of insulin resistance is different in the three conditions studied here. This may explain why elevated PAI 1 concentration are restricted to the common form of insulin resistance as seen in obese subjects. Therefore insulin resistant state per se is not associated with elevated PAI 1 levels.
