In light of the recent discovery of p53 point mutations in the affected Li-Fraumeni syndrome family members tested, RB overexpression may constitute a secondary event in Li-Fraumeni syndrome tumorigenesis.
The mechanistic role of the known tumor-suppressor genes Rb-1 and p53 in the development of human lung carcinomas is being investigated in this epithelial cell model of human bronchogenic carcinogenesis.
We conclude that p53 activation is an important event in human pancreatic tumorigenesis and that the CM1 antibody can detect a proportion of cases of overexpression of mutant p53 in archival pathological material.
Point mutations of the p53 tumor suppressor gene were detected in one of 10 squamous cell and one of 14 adenocarcinomas of the esophagus, a frequency that implicates this gene in tumorigenesis.
These results support the hypothesis that the inactivation of the normal functions of the tumor-suppressor proteins pRB and p53 are important steps in human cervical carcinogenesis, either by mutation or from complex formation with the HPV E6 and E7 oncoproteins.
Recently a 17p deletion and p53 gene mutations were reported in human gliomas, but the relationship of the timing of p53 gene mutation and oncogenesis of glioma is still obscure.
This study is the first report of p53 gene mutations in prostate cancer cells and suggests a functional role for the p53 gene in suppressing prostatic tumorigenesis.
Since mutation and overexpression of p53 are common in epithelial ovarian cancers, further studies are warranted to clarify the role of p53 in ovarian tumorigenesis.
Data concerning mutations of protooncogenes (H-, K-, and N-RAS) and tumor suppressor genes (retinoblastoma and p53 genes) in various common cancers are providing evidence of multiple genetic lesions that occur during the multistage process of carcinogenesis.
Based upon these results, we concluded that the p53 gene may play a role in the tumorigenesis of a limited number of parathyroid adenoma and thyroid cancers, and that the p53 mutation with an allelic loss of the p53 gene is an important factor in malignant tumorigenesis of the thyroid gland.
A previous report using cervical carcinoma cell lines suggests that the inactivation of two tumor suppressor gene products, p53 and pRB, either by complex formation with the E6 and E7 proteins of oncogenic human papillomaviruses (HPVs) or by mutation, may be an important step in cervical carcinogenesis (M. Scheffner et al., Proc.Natl.Acad.Sci.USA, 88: 5523-5527, 1991).
These observations further support the notion that germline p53 mutation plays a key role in the tumorigenesis of individuals with Li-Fraumeni syndrome.
The p53 tumour-suppressor gene is implicated in ovarian carcinogenesis, and our findings suggest that an important tumour-suppressor gene may be located in the region 17q23-qter.
We conclude from this study that mutational or other alterations of the p53 gene are not common in nasopharyngeal carcinogenesis and that a codon-280 mutation of p53 may be involved in less than 10% of NPC cases.
These results indicate that inactivation of the p53 gene through mutations and the allelic deletion may play an important role in gastric tumorigenesis.
On the basis of a previous report that genes on chromosome 17p were not deleted in MTCs and were relatively infrequently deleted in pheochromocytomas, our results suggest that the p53 gene is not involved in tumorigenesis of MTC or pheochromocytoma.
The discovery of the tumor suppressor genes, for which loss of function mutations are oncogenic as in the RB gene of the retinoblastoma and p53 gene, has introduced a new concept of oncogenesis which could be useful even in the cure of the neoplasms.