Kerstin Heselmeyer

Comparative genomic hybridization reveals a specific pattern of chromosomal gains and losses during the genesis of colorectal tumors

Comparative genomic hybridization was used to screen the DNA extracted from histologically defined tissue sections from consecutive stages of colorectal carcinogenesis for chromosomal aberrations. No aberrations were detected in normal epithelium (n = 14). Gain of chromosome 7 occurred as a single event in low‐grade adenomas (n = 14). In high‐grade adenomas (n = 12), an overrepresentation of chromosomes 7 and 20 was present in 30% of the cases analyzed. The transition to colon carcinomas (n = 16) was characterized by the emergence of multiple chromosomal aberrations. Chromosomes 1, 13, and 20 and chromosome arms 7p and 8q were frequently gained, whereas chromosome 4 and chromosome arms 8p and 18q were recurrently underrepresented. The same tissue sections that were used for CGH were analyzed by means of DNA‐ploidy measurements and immunohistochemical staining to quantify proliferative activity and p21/WAF‐I and TP53 expression. We observed that crude aneuploidy and increased proliferative activity are early events in colorectal carcinogenesis, followed by TP53 overexpression and the acquisition of recurrent chromosomal gains and losses during the progression from high‐grade adenomas to invasive carcinomas. Genes Chromosom Cancer (1996).

Tumor cytogenetics revisited: comparative genomic hybridization and spectral karyotyping.

Abstract Fluorescence in situ hybridization techniques allow the visualization and localization of DNA target sequences on the chromosomal and cellular level and have evolved as exceedingly valuable tools in basic chromosome research and cytogenetic diagnostics. Recent advances in molecular cytogenetic approaches, namely comparative genomic hybridization and spectral karyotyping, now allow tumor genomes to be surveyed for chromosomal aberrations in a single experiment and permit identification of tumor-specific chromosomal aberrations with unprecedented accuracy. Comparative genomic hybridization utilizes the hybridization of differentially labeled tumor and reference DNA to generate a map of DNA copy number changes in tumor genomes. Comparative genomic hybridization is an ideal tool for analyzing chromosomal imbalances in archived tumor material and for examining possible correlations between these findings and tumor phenotypes. Spectral karyotyping is based on the simultaneous hybridization of differentially labeled chromosome painting probes (24 in human), followed by spectral imaging that allows the unique display of all human (and other species) chromosomes in different colors. Spectral karyotyping greatly facilitates the characterization of numerical and structural chromosomal aberrations, therefore improving karyotype analysis considerably. We review these new molecular cytogenetic concepts, describe applications of comparative genomic hybridization and spectral karyotyping for the visualization of chromosomal aberrations as they relate to human malignancies and animal models thereof, and provide evidence that fluorescence in situ hybridization has developed as a robust and reliable technique which justifies its translation to cytogenetic diagnostics.

A recurrent pattern of chromosomal aberrations and immunophenotypic appearance defines anal squamous cell carcinomas

Squamous cell carcinomas of the anus are rare neoplasias that account for about 3% of large bowel tumours. Infections with human papillomaviruses are frequently detected in these cancers, suggesting that pathogenic pathways in anal carcinomas and in carcinomas of the uterine cervix are similar. Little is known regarding recurrent chromosomal aberrations in this subgroup of squamous cell carcinomas. We have applied comparative genomic hybridization to identify chromosomal gains and losses in 23 cases of anal carcinomas. A non-random copy number increase of chromosomes 17 and 19, and chromosome arm 3q was observed. Consistent losses were mapped to chromosome arms 4p, 11q, 13q and 18q. A majority of the tumours were aneuploid, and most of them showed increased proliferative activity as determined by staining for Ki-67 antigen. p53 expression was low or undetectable, and expression of p21/WAF-1 was increased in most tumours. Sixteen cancers were satisfactorily tested for the presence of HPV by consensus L1-primer polymerase chain reaction; nine were HPV positive, of which eight were positive for HPV 16.

The relationship between aneuploidy and p53 overexpression during genesis of colorectal adenocarcinoma

This paper describes the investigation of nuclear DNA content and p53 immunoreactivity in normal mucosa (n=25), mildly (n=15), moderately (n=28) and severely atypical (n=22) colorectal adenomas and in colorectal adenocarcinomas (n=116). Twenty-seven per cent of the mildly atypical, 43% of the moderately, 77% of the severely atypical adenomas and 91% of the colorectal carcinomas were distinctly aneuploid. In the aneuploid lesions p53 immunoreactivity was not observed in mildly atypical adenomas, whereas 17% of the moderately atypical, 24% of the severely atypical adenomas and 66% of the adenocarcinomas were p53 positive. None of the diploid lesions were p53 immunoreactive. These data are interpreted to indicate that genomic instability as reflected by crude aneuploidy occurs early during genesis of colorectal carcinoma and represents a high risk factor for p53-gene mutation.

DNA content and PCNA immunoreactivity in oral precancerous and cancerous lesions

Thirty-three dysplastic lesions showing varying degrees of atypia located in the oral cavity and 83 squamous cell carcinomas located in the oral cavity and tongue (n = 56) or in the lips (n = 27) were analysed by means of proliferating cell nuclear antigen (PCNA) immunoreactivity and image cytometric DNA measurements. The results show that in dysplastic lesions increasing cellular atypia correlated to elevated proliferative activity and aneuploidy occurring in the basal cell layers. In highly differentiated squamous carcinomas increased PCNA immunoreactivity and aneuploidy was preferentially observed focally (grade 1 tumours) or in the invasive zones (grade 2 tumours). In contrast, more poorly differentiated carcinomas (grade 3 and 4 tumours) showed strongly elevated proliferative activity and aneuploidy throughout the entire tumour mass.

The Relationship Between Proliferating Cell Nuclear Antigen (PCNA), Nuclear DNA Content and Mutant p53 During Genesis of Cervical Carcinoma

Proliferating cell nuclear antigen (PCNA), nuclear DNA content and mutant p53 overexpression were studied by means of image cytometry and immunohistochemistry respectively in normal mucosa (n = 10), in mild (n = 16), moderate (n = 9) and severe (n = 17) atypical lesions, as well as in squamous cell carcinomas (n = 36) of the cervix uteri. The results show that increasing histopathological atypia in the cervical mucosa was correlated to an initial increase of PCNA followed by distinct aneuploidy and p53 overexpression. The data are suggested to contribute to a better understanding of the genesis of cervical carcinoma, and to indicate that the coexistence of both distinct aneuploidy and p53 immunoreactivity can be used to decide if a cell population is neoplastic, whereas the absence of p53 overexpression does not necessarily exclude neoplasia. This diagnostic procedure can be suggested to improve early detection of intraepithelial squamous neoplasia.