Detection of mutations in the p53 gene in human head and neck carcinomas by single strand conformation polymorphism analysis.
ABSTRACT Using the polymerase chain reaction (PCR)-based single strand conformation polymorphism (SSCP) analysis, we have examined the highly conserved regions of the p53 gene in 58 biopsy samples of head and neck tumors. Mutations were found in 13/58 (23%) tumor specimens, but not in 6 normal tissues. Ten of 13 mutations were due to single base changes and the remaining 3 were 1- or 8-base deletion mutants. These mutations were clustered in exons 5 and 7 and resulted in amino acid changes. Our results seem to indicate that mutations in the p53 gene contribute to a significant number of cases of the head and neck tumors including 20% of nasopharyngeal carcinoma biopsies. The relationship of Epstein-Barr virus or human papillomavirus and p53 gene mutations in this group of cancers was also analyzed and discussed.
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ABSTRACT: In this study, we analyzed 53 oral squamous-cell carcinomas among Indians for the presence of alterations in the tumor-suppressor gene p53 by PCR-SSCP and sequencing methods. Our results showed that 21% (II/53) of oral carcinomas analyzed carried mutations within the exons 5–8 of the p53 gene. We have identified II single-base pair substitutions consisting of 10 mis-sense mutations and one at the splice acceptor site, and one deletion mutation involving 4 consecutive bases. The majority of the base substitutions were transitions (5 TA to CG and 5 GC to AT), while only one transversion (TA to GC) was observed. Probable hot-spots for the mutation induction were identified at codons 149 and 274, which have not been observed before in head-and-neck cancers. The mutational spectrum might have originated from base alkylations at guanine and thymine residues, caused by some alkylating agents. The present results are thus consistent with the involvement of tobacco-related nitrosoamines in the etiology of oral squamous-cell carcinoma. © 1996 Wiley-Liss, Inc.International Journal of Cancer 05/1996; 66(3):297 - 300. · 6.20 Impact Factor
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ABSTRACT: Tonsillar squamous cell carcinomas (a total of 14) were examined both for the presence of human papillomavirus (HPV) DNA and for p53 alterations. General primer-mediated HPV polymerase chain reaction (GP-PCR) revealed the presence of HPV DNA in 12/14 cases. Subsequent typing by HPV type-specific PCR and sequence or hybridization analysis of GP-PCR products revealed DNA from HPV 16 in seven cases, from HPV 33 in two cases, and from HPV 7, HPV 16/33 and HPV 33/59 each in a single case. p53 immunohistochemistry performed on nine HPV containing tonsillar carcinomas using polyclonal serum CM-1 showed elevated p53 levels in four cases. These included 3/5 HPV 16 containing carcinomas and the HPV 33/59 containing carcinoma. Analysis of p53 mutations using denaturing gradient gel electrophoresis (DGGE) of GC-clamped PCR products of exons 5 to 8 showed p53 gene alterations in 3/13 cases, including 2/11 HPV positive cases and 1/2 HPV negative cases. The alterations included a silent point mutation within exon 8 of an HPV 16 containing carcinoma, a 1 bp deletion within exon 8 of an HPV 33 containing carcinoma, and a missense mutation within exon 7 of one of the HPV negative carcinomas. There was evident discrepancy between p53 immunohistochemistry and gene analysis. Four HPV containing cases showing elevated p53 levels did not reveal the presence of exon 5 to 8 alterations affecting the amino acid code, suggesting the presence of mutations occurring in other exons or non-mutational p53 stabilization. The data indicate that HPV and elevated p53 can coexist in tonsillar carcinomas and that despite the low frequency of p53 mutations the presence of HPV is not exclusively related to the absence of mutated p53.Journal of General Virology 11/1994; 75 ( Pt 10):2769-75. · 3.13 Impact Factor
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ABSTRACT: We have examined a series of 37 oropharyngeal squamous cell carcinomas for the presence of HPV 6/11, 16, and 18 DNA by polymerase chain reaction (PCR)/Southern blotting and for p53 alterations by immunohistochemistry and mutation screening with temperature gradient gel electrophoresis (TGGE). HPV sequences were found in a total of 26 of 37 cancers (70.3%), most frequently HPV 16 (20/37) followed by HPV 18 (11/37). Double infections with HPV 16 and 18 were present in 5 tumours. p53 accumulation was detectable immunohistochemically in 21 of 37 carcinomas (56.8%). There were remarkable differences in the distribution of immunoreactive tumour cells in relation to the tumour grade. A mutation screening for p53 by TGGE, directed to the amplified exons 5-8, revealed p53 mutations in 14 of 37 carcinomas (37.8%). Mutations in two different exons were present in 3 tumours, 11 tumours being hit once. Exon 7 was mutated in 6 carcinomas, exons 5 and 8 in 4 cases, and exon 6 in 3 cases. When grouping the tumours with p53 mutation according to their HPV state, HPV-positive cases showed slightly more mutations (11/26) than HPV-negative cases (3/11). Only 5 of 37 carcinomas (13.5%) contained neither HPV DNA nor p53 alterations. Our results indicate that high-risk HPV and p53 mutations frequently coexist in oropharyngeal carcinomas, in contrast to genital tumours, notably carcinomas of the cervix uteri. This may reflect different pathways in carcinogenesis in squamous cell epithelium from different sites.Archiv für Pathologische Anatomie und Physiologie und für Klinische Medicin 02/1995; 427(2):153-7. · 2.68 Impact Factor