The transition of normal epithelium to invasive carcinoma occurs sequentially. In colorectal and cervical carcinogenesis, this transition is reflected by histomorphologically defined grades of increasing dysplasia that untreated may progress to invasive disease. In an attempt to understand the role of chromosomal aberrations during tumorigenesis we have applied comparative genomic hybridization using DNA extracted from defined stages of colorectal and cervical tumors, from low‐ and high‐grade astrocytic tumors and from diploid and aneuploid breast carcinomas. Genetic instability, as measured by the number of chromosomal copy alterations per case, increases significantly at the transition from precursor lesions to invasive carcinomas and continues to increase with tumor stage. Aggressive tumors have a higher number of copy alterations per case. High‐level copy number changes (amplifications) become more prevalent in advanced‐stage disease. Subtractive karyograms of chromosomal gains and losses were used to map tumor stage‐specific chromosomal aberrations and clearly showed that nonrandom chromosomal aberrations occur during disease progression. In colorectal and cervical tumors, chromosomal copy number changes were correlated with nuclear DNA content, proliferative activity, expression levels of the tumor suppressor gene TP53, and the cyclin‐dependent kinase inhibitor p21/WAF1, as well as the presence of viral genomes. Here we summarize and review the results of this comprehensive phenotype/genotype correlation and discuss the relevance of stage‐specific chromosomal aberrations with respect to diagnostic applications. Genes Chromosomes Cancer 25:195–204, 1999. Published 1999 Wiley‐Liss, Inc.

Ductal carcinoma in situ (DCIS) is a precursor lesion of invasive ductal carcinoma (IDC) of the breast. To understand the dynamics of genomic alterations in this progression, we used four multicolor fluorescence in situ hybridization probe panels consisting of the oncogenes COX2, MYC, HER2, CCND1, and ZNF217 and the tumor suppressor genes DBC2, CDH1, and TP53 to visualize copy number changes in 13 cases of synchronous DCIS and IDC based on single-cell analyses. The DCIS had a lower degree of chromosomal instability than the IDC. Despite enormous intercellular heterogeneity in DCIS and IDC, we observed signal patterns consistent with a nonrandom distribution of genomic imbalances. CDH1 was most commonly lost, and gain of MYC emerged during progression from DCIS to IDC. Four of 13 DCISs showed identical clonal imbalances in the IDCs. Six cases revealed a switch, and in four of those, the IDC had acquired a gain of MYC. In one case, the major clone in the IDC was one of several clones in the DCIS, and in another case, the major clone in the DCIS became one of the two major clones in the IDC. Despite considerable chromosomal instability, in most cases the evolution from DCIS to IDC is determined by recurrent patterns of genomic imbalances, consistent with a biological continuum.

Invasive cervical carcinomas frequently reveal additional copies of the long arm of chromosome 3. The detection of this genetic aberration in diagnostic samples could therefore complement the morphological interpretation. We have developed a triple-color DNA probe set for the visualization of chromosomal copy number changes directly in thin-layer cervical cytology slides by fluorescence in situ hybridization. The probe set consists of a BAC contig that contains sequences for the RNA component of the human telomerase gene (TERC) on chromosome band 3q26, and repeat sequences specific for the centromeres of chromosomes 3 and 7 as controls. In a blinded study, we analyzed 57 thin-layer slides that had been rigorously screened and classified as normal (n ‫؍‬ 13), atypical squamous cells (ASC, n ‫؍‬ 5), low-grade squamous intraepithelial lesions (LSIL, n ‫؍‬ 14), and highgrade squamous intraepithelial lesions ( Cytologic screening 1 has greatly reduced incidence and mortality of cervical cancer in industrialized nations.2 In developing countries, however, cervical cancer remains a health problem of tremendous proportions. If detected in a timely manner, cervical cancer precursors, especially high-grade squamous intraepithelial lesions (HSILs) can be effectively treated, sparing patients the morbidity and mortality resulting from invasive cancer. Despite its success as a public health measure, a single cytologic examination is relatively insensitive, poorly reproducible and frequently yields equivocal results. Inadequate sampling, the scarcity of aberrant cells in some samples and the subjectivity of morphological interpretation are recognized limitations of cytology. 2,3 In addition, equivocal and mild cytologic abnormalities are extremely common in young women, but most of these lesions regress spontaneously, even when caused by oncogenic types of human papillomaviruses, 4,5 which play a crucial role in the pathogenesis of cervical cancer. 6,7 This has prompted efforts to discover other biomarkers and other screening techniques with the potential to supplement cytologic screening. 8 -13