Genetic alterations of chromosome 17 in human breast carcinoma studied by fluorescence in situ hybridization and molecular DNA techniques

Specificity of interphase fluorescence in situ hybridization for detection of chromosome aberrations in tumor pathology

Interphase fluorescence in situ hybridization (IFISH) is an interesting and intriguing cytogenetic approach in the study of tumor chromosomal abnormalities when metaphases are not available. This technique can be applied to different types of tumor nuclei, including imprinted nuclei (IM), nuclei obtained from conventional cytogenetic procedures (PB), frozen nuclei, paraffin-embedded nuclei (PE), and nuclei extracted from paraffin-embedded sections (EX). IFISH is a high-sensitivity approach in tumor studies that can give evidence of genetic aberrations present in a small percentage of cells that are likely to escape detection if only molecular techniques are applied. Despite its high sensitivity and versatility, IFISH is an indirect cytogenetic method and needs controls to have adequate specificity. This study includes present data obtained in IFISH experiments using different types of probes (alpha-satellite and YAC clones) hybridized on different types of normal control nuclei, such as PB, IM, EX, and PE nuclei, to define the threshold level for monosomy and trisomy of different chromosomal regions. My findings demonstrate that the cut-off values depend both on the types of probes and on the types of target nuclei. Therefore, even if IFISH is a versatile, high-sensitivity technique for detecting chromosomal abnormalities, the lack of accurate controls may result in the misdiagnosis of some abnormalities.

Patterns of aneusomy for three chromosomes in individual cells from breast cancer tumors

Multi-color fluorescence in situ hybridization (FISH) can determine the changes in the copy numbers of several chromosomes simultaneously and can therefore be used to identify aneusomic patterns in individual cells. Aneusomic patterns may be useful for determining the malignant nature of rare epithelial cells in the blood of cancer patients. Touch preparations from 74 primary breast tumors were evaluated for aneusomy of chromosomes 1, 8 and 17 by tri-color-FISH. In the first part of the analysis, percentages of aneusomy for individual chromosomes and their combinations were determined. In the second part of the analysis, aneusomic patterns for these three chromosomes were analyzed in individual tumor cells and compared to aneusomic patterns observed in leukocytes and in individual cells from benign and normal breast tissue to determine aneusomic patterns indicative of malignancy. Ninety-two percentage of the primary breast carcinomas showed aneusomy for one or more enumerator probes. Comparison with benign breast tissue identified six aneusomic patterns in individual carcinoma cells indicative for malignancy by statistical analysis and not observed in leukocytes. Hence, certain patterns of aneusomy in individual cells involving chromosomes 1, 8 and 17 are indicative of malignancy in individual breast tumor cells and may be useful for determining malignancy of rare epithelial cells in the blood of breast cancer patients.

Detection of numeric abnormalities of chromosome 17 and p53 deletions by fluorescence in situ hybridization in pleomorphic adenomas and carcinomas in pleomorphic adenoma. Correlation with p53 expression

BACKGROUND

A fluorescence in situ hybridization (FISH) technique using specific DNA probes allows for the detection of chromosomal aberrations and gene deletions and gains, even in interphase nuclei in human solid tumors. A high frequency of aberrations of chromosome 17 and mutation of the p53 gene have been reported in some human tumors. The correlation of p53 expression with abnormalities of chromosome 17 and p53 gene deletion in salivary gland tumors has not yet been investigated.

METHODS

The authors analyzed the numeric aberrations of chromosome 17 and p53 gene deletions in 11 paraffin embedded pleomorphic adenomas (PA) and 9 carcinomas in pleomorphic adenoma (CIPA), using FISH techniques. The centromere specific DNA probe for chromosome 17 and p53 cosmid DNA probe was used. The aberrations of chromosome 17 and p53 deletion were correlated with immunohistochemical detection of p53 protein.

RESULTS

Monosomy 17 was detected in 30.8% of CIPA cells and 29.6% of PA cells, and polysomy 17 was detected in 19.6% of CIPA cells and 9.6% of PA cells. p53 protein expression was observed in 6 of 9 CIPA specimens (66.7%) and 2 of 75 PA specimens (2.7%). Deletion of the p53 gene was frequent in p53 protein positive specimens. A statistically significant correlation existed between p53 protein expression and polysomy 17 (P = 0.0417).

CONCLUSIONS

It was observed that loss of chromosome 17 may occur in PA before its transformation to carcinoma. p53 expression was frequently associated with deletion of the p53 gene as detected by FISH. Polysomy 17 was more frequent in CIPA than PA and was associated with mutation of p53.