In this study, we assess the apparent generation effect on cancer incidence in ten extended families with P53 germline mutation, identified through probands diagnosed with childhood sarcoma.
We analyzed the loss of heterozygosity (LOH) and the presence of mutations for a series of genes implicated in DSB repair by non-homologous end-joining in five radiation-induced sarcomas devoid of both active Tp53 and Rb1.
Among genes governing the apoptosis pathway, overexpression of the bcl2 family or mutations of p53 have recently been reported to be involved in drug resistance in sarcoma.
Germline mutations of the p53 coding region are present in approximately 50-70% of patients with Li-Fraumeni Syndrome (LFS), a rare hereditary disorder of familial and intraindividual clustering of different malignancies such as sarcoma (index tumor), breast cancer, brain tumors, leukemias, and adrenocortical carcinomas, the latter usually in young children.
These results suggest that p53 abnormality occurs during advanced stages of sarcoma and are related to patient prognosis, and it is possible that aberrations in mismatch repair activity are related to sarcoma tumorigenesis.
We also analyzed P53 status, because this parameter has been found to have a significant prognostic impact in other sarcomas with chromosomal translocations.
The results support the hypothesis that the prevention of irradiation induced G2/M arrest but not the induction of apoptosis plays a critical role in determining radiosensitivity in sarcoma cell lines with p53 mutations.
Because these rare tumors also respond poorly to standard chemotherapy and bear a 50% 5-year mortality rate, we investigated the possible therapeutic benefits of p53 gene restoration in sarcomas.
The different incidence of TP53 abnormalities in the 2 types of sarcoma may reflect differences of the molecular processes through which the 2 types of tumor develop.
We examined the effect of overexpression of p21(waf1) on cytotoxicity of paclitaxel, a microtubule stabilizer, using a tetracycline-inducible expression system in human sarcoma cells (SaOs-2) that lack both functional retinoblastoma protein and p53.
A high proliferative index was demonstrated in 27.5% (11/40) of the tumours (2 MFH, 4 leiomyosarcomas, 1 rhabdomyosarcoma, 1 osteosarcoma, 2 Ewing's sarcomas and 1 unclassified sarcoma). p53 overexpression was associated with high tumour grade (p < 0.05) and MIB-1 expression was correlated with reduced survival (p < 0.05), but p53 overexpression was not significantly associated with either MIB-1 score or with overall survival of the patients.