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Mouse models for hepatocellular carcinoma (HCC) provide an experimental ground to dissect the genetic and biological complexities of human liver cancer and enhance our ability to gain insights into the relevance of candidate cancer genes. We examined, using spectral karyotyping (SKY) and array-based CGH (aCGH), seven cell lines derived from HCC spontaneously developed in transgenic c-Myc animals (c-Myc), and four cell lines established from tumors induced in nude mice by inoculation with the original c-Myc cells (nuMyc). All of those cell lines exhibited gain of material from chromosomes 5, 6, 8, 10, 11, 15 and 19, and DNA copy-number loss from chromosomes 2, 4, 7, 9, 12, 14, and X. In addition, several recurrent chromosome reorganizations were found including del(3), t(3;8), del(4) t(4;11), t(6;5), del(7), del(8), del(9), t(10;14), del(11) and del(16). Chromosome breakpoints underlying rearrangements clustered in the regions previously identified as important for the early stages of c-Myc induced hepatocarcinogenesis. The results strongly suggest the importance of recurrent breakage and loss of chromosomes 4, 9 and 14, and gain of chromosomes 15 and 19 in mouse liver neoplasia. Genomic changes observed in c-Myc HCC cell lines are also recurrent in HCC developed in a different other transgenic mouse models, in mouse spontaneous HCC and derivative cell lines, as well as in preneoplastic liver lesions induced with chemical carcinogens. Overall, our results demonstrate selective, non-random genomic changes involving chromosomal regions homologous to those implicated in human HCC.

The etiology and genetic alterations of follicular thyroid carcinoma are not well understood. By targeting a mutation (PV) into the thyroid hormone receptor beta gene (TRbetaPV mouse), we created a knock-in mutant TRbeta(PV/PV) mouse that spontaneously develop follicular thyroid carcinoma with progression to metastasis similar to human follicular thyroid carcinoma. This mouse model provides a valuable tool to ascertain the nature and the extent of genomic rearrangements that occur during carcinogenesis of the thyroid. Spectral karyotyping analysis (SKY) of seven cell lines derived from thyroid tumors developed in TRbeta(PV/PV) mice showed that all of them had abnormal karyotypes, with chromosome number ranging from near-diploid (39-42 chromosomes) to hypotetraploid (63-79 chromosomes). These seven cell lines also exhibited a variety of structural chromosomal aberrations, including common recurrent translocations and deletions. This SKY analysis shows that the development and progression of follicular thyroid carcinoma in knock-in TRbeta(PV/PV) mutant mice comprise recurrent structural and numerical genomic changes, some of which mimic those described in human thyroid cancer.

Contrast-enhanced, look-up-table (LUT)-inverted digital images of DAPI-banded chromosomes after fluorescence in situ hybridization (FISH) permit direct regional chromosomal localization of the fluorescent signals of single-copy gene probes. Improved quality and resolution of chromosome banding allowed a refined localization of the erb B-3 protooncogene from chromosome band 12813 to subbands 12q13.2-13.3. This procedure can be used for direct and precise mapping of single-copy genes on both normal and cancer-cell-rearranged chromosomes.

In the search for specific chromosomal alterations in human hepatocellular carcinomas (HCC), we analyzed two new HCC cell lines and identified nonrandom changes by combined G-banding and fluorescence in situ hybridization (FISH). Cell line 7703 was established from an HCC deriving from a patient in the Qidong region of China, where the incidence of HCC is very high and is associated with hepatitis-B virus infection and exposure to aflatoxin. This line has a highly rearranged karyotype eliciting complex rearrangements involving the majority of chromosomes. The second line, SK-Hep-1, derived from a liver adenocarcinoma, is less heterogeneous, having few altered chromosomes. We have characterized the majority of structural and numerical alterations and identified in both lines unbalanced translocations with the breakpoints nonrandomly involving regions 1p36 and 3p14 and gain of chromosome 6p and 8q. While gain of 6p and 8q are recurrent in HCC, translocations of 1p and 3p are described for the first time. Damage and recombination at the breakpoint sites on chromosomes 1 and 3 might have resulted in activation of proto-oncogene, formation of new oncogenic chimeric genes, or loss of tumor suppressor genes. Published by Elsevier Science Inc.

Chromosomal abnormalities are the hallmark of cancer cells. Recurring and highly consistent structural and numerical alterations have been identified in a large number of leukemias, lymphomas, and solid tumors. The identification of recurrent genetic alterations and the isolation of molecular markers have clinical applications in the diagnosis and prognosis of neoplasia and in the detection of minimal residual disease that are essential for designing the most effective therapeutic approach. Polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) are powerful techniques for detection of genomic alterations. The battery of FISH methods and DNA probes that are available can resolve virtually any chromosomal alterations regardless of their complexity. Combined chromosome banding, multifluor or spectral karyotype, and comparative genomic hybridization (CGH) allow identification of structural and numerical alterations on a global basis, mapping of the DNA copy number on the entire tumor genome, complete derivation of complex rearrangements, and localization of the breakpoints of translocations and deletions. Regions of recurrent alterations can be microdissected, amplified, microclone libraries constructed and probes localized on extended chromosomes or chromatin fibers for construction of high resolution physical maps that are critical for positional cloning and gene identification. In this review we attempted to cover the current trends in cancer molecular cytogenetics, and to outline the importance of molecular chromosome analysis in the understanding of oncogenesis and its clinical applications.

The target specificity of viral integration is essential to determining the biologic significance of this integration to various pathologic conditions, including cancer. In this study the chromosomal features of several human papillomavirus (HPV)-16 integration sites mapped by in situ hybridization in human keratinocyte lines were visualized directly by G-banding and differential labeling with bromodeoxyuridine of later replicating domains. G-negative chromosomal bands exhibiting late replication were selectively targeted by HPV-16, suggesting that the structural and functional relationship of the state of chromatin condensation and replication is critical in accessibility to virus integration.