Characterization of 10 marker chromosomes in a prostatic cancer cell line by in situ hybridization

Methodologies in cancer cytogenetics and molecular cytogenetics

Various types of cytogenetic and molecular cytogenetic approaches, including conventional banding, fluorescence in situ hybridization (FISH), fiber-FISH, comparative genomic hybridization (CGH), matrix array CGH, chromosome microdissection, and microcell-mediated chromosome transfer are summarized. The rationale, advantage, and limitations of each approach are discussed with respect to research and clinical applications in human neoplasia.

Karyotypic similarity identified by multiplex-FISH relates four prostate adenocarcinoma cell lines: PC-3, PPC-1, ALVA-31, and ALVA-41

Recently developed molecular cytogenetic techniques for karyotyping are providing new and important insights regarding the chromosomal changes that occur in solid tumors. We used multiplex-FISH to analyze four adenocarcinoma cell lines, PC-3, PPC-1, ALVA-31, and ALVA-41, in which the characterization of a large number of rearranged chromosomes was partially or substantially inconclusive by G-banding. Although the original descriptions of these lines depict them as distinct entities established from different patients, this study demonstrates that these four lines share numerous, highly rearranged chromosomes, strongly supporting the conclusion that they are derived from the same patient material. Our analysis indicates that PPC-1, ALVA-31, and ALVA-41 were derived from PC-3 through mechanisms involving clonal progression represented by sequential changes and clonal diversion represented by differing patterns of changes. Extensive cellular heterogeneity was detected in all four lines, and most rearrangements included segments derived from multiple chromosomes. Each line also showed a set of unique derivative chromosomes. However, a limited number of metaphase cells (approximately 10) was analyzed for each line, and numerous single-cell abnormalities were detected in all of them. Therefore, it is plausible that the number of clonal, shared, and/or unique rearrangements has been underestimated. These cell lines have been utilized as models for understanding the biology of prostate cancer and reportedly differ in their cell physiology. Rather than detracting from their value, a complete understanding of the interrelationships of these lines to one another may provide the opportunity to define the molecular changes that have led to their individual malignant phenotypes.

Functional evidence for the presence of tumor suppressor gene on chromosome 10p15 in human prostate cancers

Loss of heterozygosity on chromosome 10p was observed frequently in human prostate cancers. Studies have demonstrated that the introduction of the short arm of human chromosome 10 into a human prostate cancer cell line, PPC-1, by microcell-mediated chromosome transfer (MMCT), suppressed the malignant phenotype, suggesting the presence of a prostate tumor suppressor gene(s) within a region of 17 cM at distal 10p. To narrow down the candidate region harboring the tumor suppressor gene, a series of 10p fragments were transferred into PPC-1 cells by MMCT using a panel of hamster-human hybrid cells containing various portions of 10p. Four of the six hybrid cells obtained showed decreased tumorigenicity when injected subcutaneously into athymic nude mice. Tumors developed only at six of 40 injection sites for these four hybrid cells. In contrast, the other two hybrid cells, as well as parental PPC-1 cells, were judged to be fully tumorigenic because tumors appeared at a total 26 of 32 sites for the two hybrid cells and 15 of 16 sites for PPC-1. Allelotyping of 10p combined with fluorescence in situ hybridization in these hybrid cells suggested that a prostate tumor suppressor gene was located within a fragment of approximately 1.2 Mb flanked by D10S1172 and D10S226 on 10p15.1.

Molecular cytogenetic studies of a serially transplanted primary prostatic carcinoma xenograft (CWR22) and four relapsed tumors

BACKGROUND

Established cell lines or xenografts from prostatic carcinoma have been infrequently studied cytogenetically. CWR22 and CWR22-R are xenografts that are unique in offering one strongly androgen-dependent and several relapsed strains of a human prostate cancer that can be investigated in the laboratory. We report on the cytogenetic characterization of the hormone-dependent CWR22, and the relapsed CWR22-R serially transplanted xenografts, in our laboratory.

METHODS

We utilized a suspension harvest of the xenograft tissue to optimize our yield for metaphase chromosome studies and analyzed the hormone-dependent CWR22 and four relapsed CWR22-R xenografts. These studies were accomplished using standard G-banded analysis and fluorescence in situ hybridization (FISH). A variety of DNA probes including alpha-satellite DNA probes, and chromosomal libraries, were utilized for the FISH analysis.

RESULTS

Utilizing both standard cytogenetic analysis and FISH studies we have more precisely defined the CWR22 xenograft: 49,XY,+i(1)(q10),-2, der(4)t(2;4)(p21;q33), +7,+8,+12[7]/50,XY,idem, +der(2)t(2;4)(p21;q33)del(2)(q13q33)[13]. Four relapsed xenografts, CWR22R-2152, CWR22R-2524, CWR22R-2274, and CWR22R-2272 were also studied. Each of these lines demonstrated a different karyotype.

CONCLUSIONS

The CWR22 karyotype offers the simplest reported karyotype for a prostate cancer tissue culture cell line or xenograft; this makes CWR22 an attractive candidate for studies of genetic changes associated with the relapse of prostate cancer treated with androgen withdrawal. Four separate, serially transplanted, relapsed CWR22-R xenografts were detected, each with a separate karyotype.

Analysis of 14q+ derivative chromosomes in non-Hodgkin's lymphomas by fluorescence in-situ hybridization

The most common chromosomal abnormality observed in non-Hodgkin's lymphomas (NHL) involves the structural alteration of the q arm of chromosome 14. It is not always possible, however, to fully analyse such derivative chromosomes by Giemsa-banding. Therefore, we have applied the fluorescence in-situ hybridization (FISH) technique of chromosome painting to elucidate the origins of the der(14) chromosomes in 8 cases of NHL. In 2 NHL the der(14) appeared to be the product of the t(14;18)(q32;q21) translocation, but were not accompanied by the reciprocal der(18) chromosome. In 3 cases the breakpoint was at 14q32 but the translocated material appeared not to be from chromosome 18 and in 2 cases the breakpoint was centromeric to 14q32. One case with a t(14;18)(q32;q21) was also analysed as a control. Dual painting was carried out with paints for chromosome 14 and either chromosome 3, 8, 10, 11, 18 or 19. In the control and 2 other cases the translocated material was demonstrated to be from chromosome 18, in two cases it was from chromosome 3 and in 1 case there was an unusual insertion of chromosome 11 material. We were unable to identify the origins of the translocated material in 1 NHL and in the final case the apparent der(14) was demonstrated not to contain chromosome 14 material. These data demonstrated the utility of the FISH technique for analysing malignant cell karyotypes, and in particular indicated the potential of this approach for identifying cases containing putative NHL associated oncogenes that may have been translocated adjacent to the immunoglobulin locus at 14q32.

Identification of chromosomal structural alterations in human ovarian carcinoma cells using combined GTG-banding and repetitive fluorescence in situ hybridization (FISH)

In order to identify chromosomal structural alterations in the ovarian carcinoma cell line MLS/P, fluorescence in situ hybridization with centromeric probes for chromosomes 1, 8, 9, 13/21, 14/22, 15, 17, and X and whole chromosome painting probes for chromosomes 1, 3, 4, 5, 7, 8, 9, 10, 12, 13, 14, 17, 19, 22, and X were performed subsequent to GTG-banding. This combined approach identified 14 of the 18 clonal structurally rearranged chromosomes, with the X chromosome involved in three aberrations. In contrast, only eight of the 14 rearrangements were identifiable by G-banding alone. These results indicate that the combined G-banding and FISH approach can significantly improve the cytogenetic analysis of human neoplasia.

Cytogenetic analysis by chromosome painting

Chromosome painting is a term used to describe the direct visualisation using in situ hybridisation of specific chromosomes in metaphase spreads and in interphase nuclei. Chromosome painting, coupled with fluorescence in situ hybridisation (FISH), is now used routinely to enhance the identification of chromosomal rearrangements, the assignment of breakpoints, and the determination of the origin of extra chromosomal material. Amplification of small numbers of flow-sorted chromosomes by the polymerase chain reaction allows labelled chromosome paints to be generated in a matter of days. These technologies have enabled the development of reverse chromosome painting, in which the paint is produced from sorted aberrant chromosomes and hybridised back onto normal metaphase spreads to identify directly the composition of the aberrant chromosome. Reverse chromosome painting is able to identify not only the chromosomal origin of marker chromosomes but also the regions and breakpoints involved. In some cases, such as interstitial translocations and complex marker chromosomes, the combination of conventional (forward) chromosome painting and reverse chromosome painting combine to provide a definitive analysis of the rearrangement. With the availability of chromosome paints and painting kits from a variety of commercial sources, multicolour chromosome painting has now become a routine method of analysis in the clinical cytogenetic laboratory.

Characterization of two marker chromosomes in a patient with acute nonlymphocytic leukemia by two-color fluorescence in situ hybridization

A patient with acute nonlymphocytic leukemia (ANLL), M5b according to French-American-British (FAB) classification, showed monosomy 16, an extra 1p-, and a 21q+. These derivative chromosomes could not be defined by GTG-banding. For better characterization, we performed two-color fluorescence in situ hybridization (FISH) experiments applying DNA libraries from sorted human chromosomes, chromosome-specific repetitive probes, and a band-specific YAC-clone. With these FISH studies the karyotype could be characterized as 46,XY, +der(1)t(1;21)(p11;?), -16,der(21)t(16;21) (p11.1;q22).

Identification of some marker chromosomes in acute leukemias by fluorescence in situ hybridization

Four patients with acute leukemia are presented in whom conventional karyotypic analysis had revealed complex numerical and structural changes including unidentifiable (marker) chromosomes. It is demonstrated that the application of fluorescence in situ hybridization (FISH) may contribute to the identification of such anomalies.

Molecular cytogenetics: Diagnosis and prognostic assessment

This review describes molecular cytogenetic techniques for detection and characterization of genetic aberrations associated with human disease. The techniques of fluorescence in situ hybridization, primed in situ labeling and comparative genome hybridization are described, as are probes for repeated sequences, whole chromosomes and specific loci. Also reviewed are applications of these technologies to pre- and neonatal diagnosis and to the characterization of human malignancies.