Chromosome 4 hyperploidy represents an early genetic aberration in premalignant Barrett's oesophagus

BACKGROUND AND AIMS

Characterisation of the underlying molecular mechanisms that promote Barrett's progression may ultimately lead to identification of potential predictive genetic markers that classify patients' malignant risk. In an attempt to understand these causative pathways, fluorescence in situ hybridisation (FISH) was used in this study to determine when specific genetic alterations arise during Barrett's associated neoplastic progression.

METHODS

Endoscopic cytology brushings were obtained from 28 patients with Barrett's metaplasia, 28 with dysplasia (20 low grade dysplasia (LGD) and eight with high grade dysplasia (HGD)), and seven with adenocarcinoma, together with paired control brushings from regions of normal proximal squamous cell epithelium. The exfoliated epithelial cells were washed and deposited onto slides. Probes specific for the centromeres of chromosomes 4, 8, 20, and Y, and locus specific probes for the tumour suppressor genes p16, p53, and Rb were subsequently hybridised.

RESULTS

Aneuploidy was found early in progression, with metaplastic tissues displaying increased copy numbers of chromosomes 4 and 8. Chromosome 4 hyperploidy was found in 89%, 90%, 88%, and 100% of metaplasias, LGD, HGD, adenocarcinomas, respectively, while chromosome 8 hyperploidy occurred in 71%, 75%, 100%, and 100% of patients with the respective staging. Loss of the p16 tumour suppressor gene also presented in metaplastic epithelium (7%) but most other genetic aberrations were only seen in HGD.

CONCLUSIONS

Genetic instability arises well before dysplasia in Barrett's oesophagus, with chromosome 4 and 8 hyperploidy representing the earliest and most common alterations identified. As these aberrations are widespread at all the premalignant stages, there may be genes on chromosomes 4 and 8 that are involved in both the initiation and progression of Barrett's oesophagus.

Increasing genome instability in adrenocortical carcinoma progression with involvement of chromosomes 3, 9 and X at the adenoma stage

The investigation of chromosomal aberrations in adrenocortical tumours has been limited by the difficulties of applying classical cytogenetics to tumours with low levels of proliferation. We have therefore applied the technique of interphase cytogenetics to paraffin-embedded archival specimens of 14 adrenocortical adenomas and 13 carcinomas. Hybridizations were performed using centromere-specific probes to chromosomes 3, 4, 9, 17, 18 and X, which have been shown to be altered in other types of tumours. Chromosomal imbalance was defined on the basis of changes in both chromosome index (CI) and signal distribution (SD). Where only one of these was altered, this was classified as a tendency to gain or loss. On the basis of the analysis of optimal hybridizations, carcinomas showed gains in all chromosomes studied, five of nine showing gains in multiple chromosomes. Gains were most common in chromosomes 3, 9 and, in particular X, eight of 11 showing gain, and one a tendency to gain. Chromosomal gain was seen less commonly in adenomas, but again chromosomes 3, 9 and X were involved. Losses were infrequent, only one carcinoma showing loss of chromosome 18, and adenomas showing a tendency to loss of chromosomes 4 (two cases), 17 (one case) and 18 (two cases). Our data suggest that changes in chromosomes 3, 9 and X are early events in adrenocortical tumorigenesis, and that there is increasing chromosomal instability with tumour progression.

Cellular characteristics of peripheral blood lymphocytes and tumour-infiltrating lymphocytes in patients with gynaecological tumours

Immunotherapy of gynaecological cancer with tumour-infiltrating lymphocytes (TIL) or peripheral blood lymphocytes (PBL) has become a valid treatment modality with varying degrees of success in obtaining an antitumour response. TIL consist of lymphocytes, mainly T cells and minor populations of natural killer cells or B cells. Conventional cytogenetic studies of tumour cells from patients with breast and ovarian cancer have shown multiple chromosomal abnormalities including chromosomes 7 and 12. This study was designed to analyse the surface further, as well as investigate the intracellular, characteristics of TIL by multicolour flow cytometry and the cytogenetic features by fluorescence in situ hybridization. Tumour cell, peripheral blood and TIL samples from 25 patients (15 ovarian tumours, 8 breast cancers, 1 uterine sarcoma, 1 cervical carcinoma) were analysed for their phenotype, the expression of major cytokines [interleukin-2 (IL-2), IL-4 and interferon gamma (IFN gamma)], their proliferation rate, their cytotoxic ability and for the presence of numerical aberrations of chromosomes 7 and 12. All the tumour cells showed a high frequency of numerical aberration in chromosomes 7 and 12, especially trisomies or tetrasomies and combined aberrations. Trisomies of both chromosomes also occured at a low percentage in TIL and PBL. The phenotyping of TIL and PBL revealed rather similar subsets of lymphocytes. In both, T cells were the major population, with TIL containing a slightly increased CD4/CD8 ratio. The cytokine pattern showed a predominance of IL-4 production in TIL and of IFN gamma in PBL, indicating that, in TIL, cellular immunity is downregulated, whereas in PBL the cytotoxic immune response predominates. This is in accordance with the cytotoxic ability of TIL, which is weakened in comparison to PBL. Cellular characteristics revealed some disadvantages in the use of TIL for cancer treatment, explaining ineffective clinical results. The search for specific antitumour lymphocytes requires carefully designed experiments in order to define effective anticancer cells and thereby improve immunologically mediated tumour therapy.

Signal amplification of FISH for automated detection using image cytometry

The purpose of this study was to improve the detection of FISH signals, in order that spot counting by a fully automated image cytometer be comparable to that obtained visually under the microscope. Two systems of spot scoring, visual and automated counting, were investigated in parallel on stimulated human lymphocytes with FISH using a biotinylated centromeric probe for chromosome 3. Signal characteristics were first analyzed on images recorded with a coupled charge device (CCD) camera. Number of spots per nucleus were scored visually on these recorded images versus automatically with a DISCOVERY image analyzer. Several fluochromes, amplification and pretreatments were tested. Our results for both visual and automated scoring show that the tyramide amplification system (TSA) gives the best amplification of signal if pepsin treatment is applied prior to FISH. Accuracy of the automated scoring, however, remained low (58% of nuclei containing two spots) compared to the visual scoring because of the high intranuclear variation between FISH spots.