p53 mutations are confined to the comedo type ductal carcinoma in situ of the breast. Immunohistochemical and sequencing data.
ABSTRACT Mutations in the p53 tumor suppressor gene have been identified in breast and many other carcinomas. It is not clear, however, when these mutations occur during breast carcinogenesis. Overexpression of 53 protein has been reported in some ductal carcinoma in situ (DCIS) lesions. To further study the overexpression of p53 in DCIS of the breast and correlate these findings with changes at the molecular level, we performed p53 immunostaining and direct sequencing in noncomedo and comedo DCIS.
Archival blocks were obtained on cases of noncomedo DCIS, (including encysted, noninvasive papillary carcinoma) and comedo DCIS. Immunohistochemical staining with the p53 antibody DO7 was performed on all cases. Polymerase chain reaction (PCR) amplification of exons 5, 6, and 7 of the p53 gene was performed and the PCR products were directly sequenced. Four comedo DCIS cases that were p53 immunopositive were further screened for p53 mutations by PCR/single strand conformation polymorphism in exons 8 and 9 of the p53 gene. One of these cases showing a mobility shift was directly sequenced.
We examined 39 lesions including comedo DCIS (N = 12) and noncomedo DCIS (N = 27), the latter including 17 encysted noninvasive papillary carcinomas. Immunostaining with DO7 was positive in 4 of 12 comedo DCIS lesions (33%) while all noncomedo lesions including encysted noninvasive papillary carcinomas were negative. Direct sequencing of PCR products confirmed wild-type DNA in exons 5 and 6 in all noninvasive papillary carcinomas, 3 randomly selected noncomedo DCIS lesions, and 4 p53 antibody-positive comedo DCIS lesions. In these latter 4 cases, wild-type DNA sequences were preserved in exon 7 for all cases. A single case had a conformational shift in exon 8 within the four cases screened in exons 8 and 9. Direct DNA sequencing of this exon revealed a G to A point mutation resulting in an arginine-to-histidine substitution at codon 273 of the protein.
Our results suggest that mutant p53 protein accumulation in preinvasive lesions is limited to comedo (high grade) DCIS and that p53 positivity by immunohistochemistry does not correlate in all cases with specific p53 mutations in exons 5 to 9, the most highly conserved regions of this gene.
SourceAvailable from: Roy A Jensen[Show abstract] [Hide abstract]
ABSTRACT: Background. There is increasing evidence linking development and progression of cancer to an accumulation of mutations at the genomic level. The most frequently mutated gene known to date in sporadic breast cancer appears to be the tumor suppressor gene p53. This study was designed to determine the frequency of p53 gene mutations in primary breast cancer, to correlate the presence of p53 mutations with established clinicopathologic parameters, including the estrogen receptor (ER) and progesterone receptor (PR) status, and to assess the prognostic significance of p53 mutations regarding patient survival.Methods. We examined the p53 gene in genomic DNA samples from 192 primary breast cancers. Using denaturant gradient gel electrophoresis, the authors analyzed exons 5–9 in all tumors for mutations and performed DNA sequencing in 20 tumors to identify the exact nature of the p53 mutations.Results. p53 gene alterations were identified in 43 of the 192 tumors (22%), the majority localized in exons 5 and 6. DNA sequencing showed mostly missense mutations resulting from G or C substitutions. p53 mutations were found more often in tumors of younger women (P = 0.002), Afro-American women (P = 0.05), and in tumors lacking ER (P = 0.03), PR (P = 0.04), or both (P = 0.06). There were no significant correlations with family history, tumor size, histologic grade or type, nodal status, or disease stage. The overall survival rates showed no significant difference between patients with mutant and wild-type p53 tumors. The same was true when the comparison was limited to node-negative patients or patients with ER-positive or ER-negative tumors. Finally, there was no significant difference in survival between patients with tumors harboring mutations in exons 5 and 6 versus exons 7–9.Conclusions. The results of this and other studies demonstrate a consistent relationship between ER-positive tumors and wild-type p53 on one hand and ER-negative cancers and p53 mutations on the other. Our data do not support a significant prognostic role for p53 mutations in predicting survival.Cancer 04/1994; 73(8):2147 - 2156. DOI:10.1002/1097-0142(19940415)73:8<2147::AID-CNCR2820730820>3.0.CO;2-5 · 4.90 Impact Factor
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ABSTRACT: For a variety of technical reasons it is rarely possible to study cytogenetic abnormalities in ductal carcinoma in situ (DCIS) using traditional techniques. However, by combining molecular biology and computerized image analysis it is possible to carry out cytogenetic analyses on formalin-fixed, paraffin-embedded tissue, using comparative genomic hybridization (CGH). The purpose of this study was to identify the prevalence of chromosomal amplifications and deletions in high-grade DCIS and to look specifically for unique or consistent abnormalities in this pre-invasive cancer. Twenty-three cases of asymptomatic, non-palpable, screen-detected, high-grade DCIS were examined using CGH on tumour cells obtained from histology slides. All cases showed chromosomal abnormalities. A wide variety of amplifications and deletions were spread across the genome. The most frequent changes were gains of chromosomes 17 (13 of 23), 16p (13 of 23), and 20q (9 of 23) and amplifications of 11q13 (22 of 23), 12q 24.1–24.2 (12 of 23), 6p21.3 (11 of 23), and 1q31-qter (6 of 23). The most frequent deletions were on 13q 21.3–q33 (7 of 23), 9p21 (4 of 23), and 6q16.1 (4 of 23). These findings indicate that high-grade DCIS is, from a cytogenetic viewpoint, an advanced lesion. There was no absolutely consistent finding in every case, but amplification of 11q13 was found in 22 of the 23 cases. The precise significance of this is unknown at present. This region of chromosome 11q harbours a number of known oncogenes, including cyclinD1 and INT2. It is likely that many of these findings are the result of accumulated chromosomal abnormalities, reflecting an unstable genome in established malignancy. Copyright © 1999 John Wiley & Sons, Ltd.The Journal of Pathology 03/1999; 187(4):403 - 409. DOI:10.1002/(SICI)1096-9896(199903)187:4<403::AID-PATH284>3.0.CO;2-J · 7.33 Impact Factor
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ABSTRACT: The elucidation of molecular alterations that occur during human breast cancer progression may contribute to the development of preventative strategies. Using in situ hybridizations on a cohort of 94 biopsy lesions, quantitatively increased cyclin D mRNA expression levels were observed in only 18% of benign lesions, which confer no or slightly increased breast cancer risk, and 18% of premalignant atypical ductal hyperplasias, which confer a four to fivefold increase in breast cancer risk. The transition to carcinoma was accompanied by frequent cyclin D mRNA overexpression in 76% of low-grade ductal carcinomas in situ, 87% of higher grade comedo ductal carcinomas in situ and 83% of infiltrating ductal breast carcinomas. The data identify a molecular event that may separate benign and premalignant human breast lesions from any form of breast carcinoma.Nature Medicine 11/1995; 1(12):1257-1260. DOI:10.1038/nm1295-1257 · 28.05 Impact Factor