Original PaperChromosomal abnormality in hepatocellular carcinoma by comparative genomic hybridisation in Taiwan
Introduction
Hepatocellular carcinoma (HCC) is one of the leading malignancies in the world[1]. In Taiwan, it ranks first in terms of cancer mortality2, 3. Different aetiological factors such as hepatitis viral infection, dietary aflatoxins, or chemical carcinogens are associated with the development of liver cancer2, 3, 4, 5. Nevertheless, the molecular mechanism remains to be clarified.
The genesis of human cancers is a multistep process reflecting cumulative genetic alterations that include the activation of oncogenes or the inactivation of tumour suppressor genes6, 7. Traditionally, cytogenetics have been used to detect the genetic changes of cancer[8]. Chromosomal aberrations have been reported in leukaemia for many years7, 8. For solid tumours, the identification of chromosomal aberrations is in its infancy because of technical difficulties in obtaining sufficient numbers of dividing cells9, 10, 11. Molecular genetic studies of isolated tumour DNA have been more successful and have been used to detect common regions of allelic loss, mutation, or amplification12, 13. In HCC, by using restriction fragment length polymorphism (RFLP), loss of heterozygosity (LOH) on chromosome 1p, 4q, 5q, 8p, 11p, 13q, 16q and 17p has been described14, 15, 16, 17, 18. Microsatellite analysis provides another simple way to study systematically genetic changes in tumour tissue19, 20, 21, 22. However, genome-wide surveys of LOH are tedious and time consuming[23].
Recently, a new molecular cytogenetic method has been developed[11]. This method, comparative genomic hybridisation (CGH), is capable of detecting and mapping relative DNA sequence copy number between genomes. Tumour DNA and DNA from non-neoplastic tissue are labelled with different fluorochromes and then simultaneously hybridised into normal metaphase spread chromosomes. An image acquisition system is used to quantitate signal intensities contributed by tumour and reference DNA along the entire length of each chromosome. Regions of amplification and deletion are demonstrated as quantitative alterations.
CGH adapts molecular biological techniques for simultaneous analysis of the entire genome24, 25, 26, 27, 28. As no specific probes or previous knowledge of aberrations are required, CGH is especially suitable for the identification and mapping of previously unknown DNA copy number changes that may highlight the locations of important genes in neoplasia. Furthermore, the possibility that more than one locus is involved in tumour initiation and progression can be assessed26, 29, 30. Genomic DNA from tumour specimens is used so that genetic alterations identified with CGH are not artifactually altered by propagation in cell culture24, 27. In this study, we used CGH to identify the gains or losses in DNA sequence copy number in 40 HCC patients.
Section snippets
Patients
Primary HCC tissues and non-neoplastic liver tissues were obtained from 40 HCC patients who underwent surgical resection in National Taiwan University Hospital. The diagnosis of HCC was confirmed by histology. A total of 40 HCC patients were included in this study (Table 1). One patient (case 29) had two operations for primary and recurrent HCCs and there were two tumours in each operation. Another patient (case 30) had two small tumours. Therefore, a total of 44 tumours were studied. The
Gains and losses of DNA sequence in HCC detected by CGH
Of the 40 HCC patients analysed, 30 HCC patients (75%, 30/40) clearly showed a number of chromosomal alterations, whilst the remaining 10 HCCs had no detectable changes (Table 1 and Table 2). Among the 30 HCC patients who had chromosomal aberrations, 21 HCCs had both gains and losses, seven HCCs had gains only, whilst two HCCs had losses only (Table 1). After analysing the 24 chromosomes, a total of 15 chromosomes had abnormalities (Fig. 1). Among the 15 chromosomes which had aberrations, eight
Discussion
In the 44 HCCs studied by CGH, 77% of the tumours showed losses and gains of DNA sequences in at least one chromosome arm. Furthermore, most of the changes involved many different chromosomal regions. Losses were prevalent on chromosome regions 16q (43%), 17p (20%), 13q (20%), 4q (15%) and 8p (15%). Gains frequently occurred on 8q (30%), 1q (20%), 6p (20%) and 17q (18%). These results suggest that the genetic changes of HCC are highly complex. Similar complexity has been reported in a variety
Acknowledgements
This study was supported by grants from the Department of Health and National Science Council, Executive Yuan and Liver Disease Prevention and Treatment Research Foundation, Taiwan, Republic of China.
References (40)
- et al.
Hepatitis C and B viruses in hepatitis B surface antigen negative hepatocellular carcinoma
Gastroenterology
(1992) - et al.
Comparative genomic hybridization: a new tool in cancer pathology
Human Pathol.
(1996) The chromosomal analysis of human solid tumors. A triple challenge
Cancer Genet. Cytogenet.
(1989)- et al.
A genetic model for colorectal tumorigenesis
Cell
(1990) - Linsell DA, Higginson J. The geographic pathology of liver cell cancer. In Cameron HM, Linsell DA, Warwick GP, eds....
Hepatitis B virus as the etiologic agent in hepatocellular carcinoma-epidemiologic considerations
Hepatology
(1982)- Chen DS. Hepatitis B virus infection, its sequelae, and prevention in Taiwan. In Okuda K, Ishak KG, eds. Neoplasms of...
- et al.
Mutation of p53 gene in hepatocellular carcinoma in Taiwan
Cancer Res.
(1992) - et al.
Genomic components of carcinogenesis
Clin. Chem.
(1993) The molecular biology of carcinogenesis
Cancer
(1993)
Developments in cytogenetics and oncogenes in acute leukemia
Curr. Opin. Oncol.
Comparative genomic hybridization for molecular cytogenetic analysis of solid tumors
Science
Amplification of cellular oncogenes: a predictor of clinical outcome in humans
Genes Chromosom. Cancer
Deletions in human chromosome arms 11p and 13q in primary hepatocellular carcinomas
Cytogenet. Cell. Genet.
Rearrangement of a common cellular DNA domain on chromosome 4 in human primary liver tumors
J. Virol.
Frequent loss of heterozygosity on chromosomes 16 and 4 in human hepatocellular carcinoma
Jpn. J. Cancer Res.
Allele loss on chromosome 16 associated with progression of human hepatocellular carcinoma
Proc. Natl. Acad. Sci. USA
Interstitial chromosomal deletion within 4q11-q13 in a human hepatoma cell line
Cancer Res.
Microsatellite instability in cancer of the proximal colon
Science
Frequent genetic alterations at the distal region of chromosome 1p in human hepatocellular carcinomas
Cancer Res.
Cited by (53)
Molecular markers as a prognostic system for hepatocellular carcinoma
2011, Journal of Advanced ResearchCitation Excerpt :The frequently deleted chromosome regions by loss of heterozygosity (LOH) in HCCs contain many tumour suppressor genes and some oncogenes, (p53, Rb, p16, PTEN, DLC1, and IGF2R) [14,31]. LOH at chromosome 1p is usually seen in early, small or well-differentiated HCC [32], whereas LOH at chromosomes16p and 17p is more frequently associated with HCCs in advanced stages, aggressive tumours, and poor prognosis [33]. By comparative genomic hybridization (CGH), chromosome 8p, 17p and 19p are associated with HCC metastases [32].
The basal body gene, RPGRIP1L, is a candidate tumour suppressor gene in human hepatocellular carcinoma
2009, European Journal of CancerCitation Excerpt :Among these alterations, LOH on chromosome 16q has been reported to occur more frequently in HCCs of poor differentiation or larger size, and with metastasis.17,19 Recently, in the analysis of chromosomal abnormality in HCC6 and in a comprehensive analysis of LOH,8 we also observed that two of the most commonly affected areas spanned the region near the sequence tag site (STS) markers D16S415 and D16S419.8,20 The high incidence of LOH observed at an early stage of tumour development led us to speculate that candidate tumour suppressor genes located in this region may play an important role in early hepatocellular carcinoma.
Diverse cellular transformation capability of overexpressed genes in human hepatocellular carcinoma
2004, Biochemical and Biophysical Research CommunicationsClinicopathologic significance of genetic alterations in hepatocellular carcinoma
2003, Cancer Genetics and Cytogenetics