Harald Blegen

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).

Genomic changes defining the genesis, progression, and malignancy potential in solid human tumors: a phenotype/genotype correlation.

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.

Advanced-stage cervical carcinomas are defined by a recurrent pattern of chromosomal aberrations revealing high genetic instability and a consistent gain of chromosome arm 3q

We have analyzed 30 cases of advanced‐stage cervical squamous cell carcinoma (stages IIb–IV) by comparative genomic hybridization (CGH). The most consistent chromosomal gain in the aneuploid tumors was mapped to chromosome arm 3q in 77% of the cases. Acquisition of genetic material also occurred frequently on 1q (47%), 5p (30%), 6p (27%), and 20 (23%). Recurrent losses were mapped on 2q (33%), 3p (50%), 4 (33%), 8p (23%), and 13q (27%). High‐level copy number increases were mapped to chromosome 8, chromosome arms 3q, 5p, 8q, 12p, 14q, 17q, 19q, 20p, and 20q, and chromosomal bands 3q26‐27, 9p23‐24, 11q22‐23, and 12p13. In the majority of the cases, the presence of high‐risk human papilloma virus genomes was detected. High proliferative activity was accompanied by crude aneuploidy. Increased p21/WAF‐1 activity, but low or undetectable expression of TP53 were representative for the immunophenotype. This study confirms the importance of a gain of chromosome arm 3q in cervical carcinogenesis and identifies additional, recurrent chromosomal aberrations that are required for progression from stage I tumors to advanced‐stage carcinomas. Genes Chromosom. Cancer 19:233–240, 1997. Published 1997 Wiley‐Liss, Inc.

Mevalonic acid is limiting for N-linked glycosylation and translocation of the insulin-like growth factor-1 receptor to the cell surface. Evidence for a new link between 3-hydroxy-3-methylglutaryl-coenzyme a reductase and cell growth.

Depletion of mevalonic acid (MVA), obtained by inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase using lovastatin, depressed the biosynthesis of dolichyl-phosphate and the rate of N-linked glycosylation and caused growth arrest in the melanoma cell line SK-MEL-2. The growth arrest was partially prevented by addition of high concentrations of insulin-like growth factor-1 (IGF-1) to the cells, indicating that MVA depletion may inhibit cell growth through decreasing the number of IGF-1 receptors (IGF-1R) at the cell surface. Such a decrease in receptor number might be a result of a lowered translocation of de novo synthesized receptors to the cell membrane which in turn might be a result of a decreased N-linked glycosylation of the receptor proteins. We could also demonstrate that IGF-1R became underglycosylated and that the amount of de novo synthesized IGF-1R proteins at the cell membrane was drastically decreased upon MVA depletion. Analysis of receptor proteins cross-linked with IGF-1, as well as binding assays and immunocytostaining confirmed that the number of functional membrane-bound IGF-1R was substantially reduced. The N-linked glycosylation and the expression of de novo synthesized IGF-1R proteins at the cell surface as well as the number of IGF-1 binding sites were completely restored upon replenishment of MVA. These effects of MVA were efficiently abrogated by the glycosylation inhibitor tunicamycin. The translocation of IGF-1R to the cell membrane was shown to take place just prior to initiation of DNA synthesis in arrested cells stimulated with MVA. Additionally, there was a clear correlation between IGF-1 binding and initiation of DNA synthesis with regard to the MVA dose requirement. It was confirmed that inhibition of HMG-CoA reductase activity and N-linked glycosylation also depressed the expression of functional IGF-1R in other cell types (i.e. hepatoblastoma cells and colon cancer cells). Our data suggest that this mechanism is involved in MVA-regulated cell growth.

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.

Primary carcinoma of the fallopian tube: comparative genomic hybridization reveals high genetic instability and a specific, recurring pattern of chromosomal aberrations.

SummaryPrimary fallopian tube carcinoma (PFTC) is a rare and highly aggressive tumor. Twelve cases of PFTC (stages IA to IV) were analyzed by comparative genomic hybridization. The most consistent DNA gain was mapped to chromosome arm 3q in 11 of 12 cases. In six cases, the gain of 3q was present as a high level copy number increase (amplification) with a consensus region mapped to 3q26.2-qter. In the 12 cases, other frequent gains were located on chromosome arms 1q (in 11 cases), 2q (in 10), 7q (in 9), 8q (in 9), 5p (in 8), 6p (in 7), 12p (in 7), and 14q (in 6). Frequent copy number losses occurred on chromosome arms 16q (in 8 cases), 22q (in 7), 6q (in 6), 8p (in 6), 18q (in 6), Xq (in 6), 1p (in 5), and 17p (in 5). All chromosomes were involved in chromosomal aberrations and the average number of copy alterations per case was 19.7. None of the 12 carcinomas revealed the presence of human papillomavirus (HPV) genomes. All of the cases exhibited crude aneuploidy. Strong p53 immunoreactivity could be observed in 10 of 12 cases while p21/WAFl expression was low or undetectable. These results indicate that PFTC is a genomically highly unstable cancer, an observation that is in agreement with the poor prognosis associated with this tumor. A high frequency of 3q-gains has also been observed in HPV-related carcinomas of the uterine cervix. However, none of the PFTC was HPV-related, suggesting that the 3q-gain is independent from HPV DNA.

DNA Amplifications and Aneuploidy, High Proliferative Activity and Impaired Cell Cycle Control Characterize Breast Carcinomas with Poor Prognosis

In order to explore whether specific cytogenetic abnormalities can be used to stratify tumors with a distinctly different clinical course, we performed comparative genomic hybridization (CGH) of tumors from patients who were diagnosed with metastatic disease after an interval of less than 2 years or who remained free from distant metastases for more than 10 years. All patients presented with distant metastases after mastectomy indicating that none of the patients in this study was cured and free of remaining tumor cells. Tumors in the group of short‐term survivors showed a higher average number of chromosomal copy alterations compared to the long‐term survivors. Of note, the number of sub‐chromosomal high‐level copy number increases (amplifications) was significantly increased in the group of short‐term survivors. In both short‐ and long‐term survivors recurrent chromosomal gains were mapped to chromosomes 1q, 4q, 8q, and 5p. Copy number changes that were more frequent in the group of short‐term survivors included gains of chromosome 3q, 9p, 11p and 11q and loss of 17p. Our results indicate that low‐ and high grade malignant breast adenocarcinomas are characterized by a specific pattern of chromosomal copy number changes. Furthermore, immunohistochemical evaluation of the expression levels of Ki‐67, p27KIP1, p21WAF1, p53, cyclin A and cyclin E revealed a correlation between increased proliferative activity and poor outcome.

Frequent co-amplification of two different regions on 17q in aneuploid breast carcinomas

Chromosome 17q is highly susceptible to rearrangement mutations in breast cancer. c-erbB-2 at 17q11.2 approximately q21.1 is frequently amplified, as is a region at 17q22 approximately q24. As a step in the search for the target gene(s) of the 17q22-q24 amplification we determined whether the placental lactogen (PL) genes at 17q23 were amplified in 59 breast carcinomas. These genes were selected as their upregulation could theoretically be involved in breast cancer tumorigenesis. Amplification of the PL genes, and also of c-erbB-2, was detected using semi-quantitative PCR. The reliability of this method was confirmed since c-erbB-2 results obtained using PCR, Southern blotting and immunohistochemistry were in good agreement. The PL genes were amplified in 13 (22%) of the tumors. Furthermore, the PL and c-erbB-2 genes were frequently co-amplified although there is a non-amplified region between them. Expression of PL was investigated in 26 tumors and was detected in 16 of these cases including all 10 tumors with amplification of the PL genes. The tumors with PL gene amplification were all aneuploid. A trend was seen towards an increased incidence of lymph node involvement for tumors with amplification of the PL genes and for tumors with co-amplification of PL and c-erbB-2, which suggests a possible association with high malignancy.

Pronounced chromosomal instability and multiple gene amplifications characterize ulcerative colitis–associated colorectal carcinomas

Patients with ulcerative colitis have a significantly increased lifetime risk for the development of colorectal carcinomas. While genetic and genomic changes during carcinogenesis have been thoroughly studied in sporadic colorectal cancers, less is known about ulcerative colitis-associated colorectal carcinomas. The aim of this study was to extend the identification of specific genomic imbalances to ulcerative colitis-associated colorectal carcinomas and to establish a comprehensive map of DNA gains and losses by investigating 23 tumor specimens from 23 patients. The molecular cytogenetic characterization was performed using comparative genomic hybridization; immunohistochemistry was used to measure proliferative activity and laminin-5 expression as a marker for invasiveness. The results indicate that these tumors are invariably aneuploid, with a high proliferative activity and increased invasive potential. The average number of copy alterations correlates with increased cyclin A levels (P=0.044), which is an independent predictor of risk of carcinoma development in ulcerative colitis. Despite severe genetic instability, the general pattern of specific chromosomal aberrations that defines sporadic colorectal carcinomas is maintained in ulcerative colitis-associated malignancies. High-level copy number increases (amplifications) are dispersed throughout the genome. Strikingly, these amplifications are much more frequent than in sporadic carcinomas and map to chromosomal regions that have not been described before.

Recurrent fallopian tube carcinoma : TP53 mutation and clinical course

Primary fallopian tube carcinoma is a rare, aggressive gynecological cancer; little is known about its cause. Previous studies have indicated that p53 immunopositivity is correlated with short-term survival in primary fallopian tube carcinoma. We examined p53 and p21/WAF1 immunostaining and TP53 mutation in exons 5 to 8 by single-stranded conformation polymorphism and constant denaturant gel electrophoresis in nine cases of primary fallopian tube carcinoma and their metastases/recurrences from patients who survived for between a few months and more than 20 years after diagnosis. We found that 1.) p53 immunopositivity without detectable p21/WAF1 immunostaining did not correlate with TP53 mutations in the conserved domains; 2.) mutations in TP53 occurred in two metastases/recurrences but not in their corresponding primary tumors; 3.) in two cancers, a TP53 mutation was observed in the primary tumor but not in the metastases/recurrences; 4.) constant denaturant gel electrophoresis seems to be more sensitive than single-stranded conformation polymorphism in detecting TP53 mutations; and 5.) in the nine cases studied, p53 immunoreactivity and/or TP53 mutation analysis did not correlate with tumor progression, survival, or response to treatment.