Combined cytogenetic and molecular genetic analyses of fifty-nine untreated human prostate carcinomas

Bioinformatic Tools Identify Chromosome-Specific DNA Probes and Facilitate Risk Assessment by Detecting Aneusomies in Extra-embryonic Tissues

Despite their non-diseased nature, healthy human tissues may show a surprisingly large fraction of aneusomic or aneuploid cells. We have shown previously that hybridization of three to six non-isotopically labeled, chromosome-specific DNA probes reveals different proportions of aneuploid cells in individual compartments of the human placenta and the uterine wall. Using fluorescence in situ hybridization, we found that human invasive cytotrophoblasts isolated from anchoring villi or the uterine wall had gained individual chromosomes. Chromosome losses in placental or uterine tissues, on the other hand, were detected infrequently. A more thorough numerical analysis of all possible aneusomies occurring in these tissues and the investigation of their spatial as well as temporal distribution would further our understanding of the underlying biology, but it is hampered by the high cost of and limited access to DNA probes. Furthermore, multiplexing assays are difficult to set up with commercially available probes due to limited choices of probe labels. Many laboratories therefore attempt to develop their own DNA probe sets, often duplicating cloning and screening efforts underway elsewhere. In this review, we discuss the conventional approaches to the preparation of chromosome-specific DNA probes followed by a description of our approach using state-of-the-art bioinformatics and molecular biology tools for probe identification and manufacture. Novel probes that target gonosomes as well as two autosomes are presented as examples of rapid and inexpensive preparation of highly specific DNA probes for applications in placenta research and perinatal diagnostics.

MAD2ΔC induces aneuploidy and promotes anchorage-independent growth in human prostate epithelial cells

The mitotic arrest deficient 2 (MAD2) is suggested to play a key role in a functional mitotic checkpoint because of its inhibitory effect on anaphase-promoting complex/cyclosome (APC/C) during mitosis. The binding of MAD2 to mitotic checkpoint regulators MAD1 and Cdc20 is thought to be crucial for its function and loss of which leads to functional inactivation of the MAD2 protein. However, little is known about the biological significance of this MAD2 mutant in human cells. In this study, we stably transfected a C-terminal-deleted MAD2 gene (MAD2DeltaC) into a human prostate epithelial cell line, Hpr-1 and studied its effect on chromosomal instability, cell proliferation, mitotic checkpoint control and soft agar colony-forming ability. We found that MAD2DeltaC was able to induce aneuploidy through promoting chromosomal duplication, which was a result of an impaired mitotic checkpoint and cytokinesis, suggesting a crucial role of MAD2-mediated mitotic checkpoint in chromosome stability in human cells. In addition, the MAD2DeltaC-transfected cells displayed anchorage-independent growth in soft agar after challenged by 7,12-dimethylbenz[A]anthracene (DMBA), demonstrating a cancer-promoting effect of a defective mitotic checkpoint in human cells. Furthermore, the DMBA-induced transformation was accompanied by a complete loss of DNA damage-induced p53 response and activation of the MAPK pathway in MAD2DeltaC cells. These results indicate that a defective mitotic checkpoint alone is not a direct cause of tumorigenesis, but it may predispose human cells to carcinogen-induced malignant transformation. The evidence presented here provides a link between MAD2 inactivation and malignant transformation of epithelial cells.

Aneuploidy of chromosome Y in prostate tumors and seminal vesicles: A possible sign of aging rather than an indicator of carcinogenesis?

Chromosome Y aneuploidies have been reported as one of the recurrent cytogenetic findings in prostate cancer (PCa) and many other solid and hematological tumors. We have studied this aneuploidy in 28 patients with PCa undergoing radical prostatectomy, one patient with benign hyperplasia (BPH) and four organ donors. A total of 72 samples have been studied: 17 tumors, 25 nontumor prostate tissues, 1 BPH, 21 seminal vesicles samples obtained along with the prostate when patients underwent radical prostatectomy and prostate tissues and seminal vesicles from four organ donors. We have also studied the aneuploidy of chromosome Y in peripheral blood from four of the patients and in seminal vesicles of 11 individuals with bladder cancer (BC). The study has been performed by Fluorescence in situ hybridization (FISH) in uncultured cells. Our results indicate that complete loss of chromosome Y is found in almost all the seminal vesicles both from patients with PCa and patients with BC (samples obtained from the tissue bank), and is more frequent in prostate tumors than in nontumor samples. The percentages of chromosome Y loss in the tissues analyzed are significatively higher than expected in lymphocytes considering the patient's age as reported in the literature. The high percentage of chromosome Y loss found in the nonmalignant seminal vesicles of these patients may be an indicator of an ageing process rather than a primary cytogenetic alteration in the carcinogenesis of the prostate. However, a contribution of this loss to chromosomal instability and therefore, to the multistep tumorigenic process, cannot be discarded.

Dual roles of E-cadherin in prostate cancer invasion

The role(s) of E-cadherin in tumor progression, invasion, and metastasis remains somewhat enigmatic. In order to investigate various aspects of E-cadherin biological activity, particularly in prostate cancer progression, our laboratory cloned unique subpopulations of the heterogeneous DU145 human prostatic carcinoma cell line and characterized their distinct biological functions. The data revealed that the highly invasive, fibroblastic-like subpopulation of DU145 cells (designated DU145-F) expressed less than 0.1-fold of E-cadherin protein when compared to the parental DU145 or the poorly invasive DU145 cells (designated DU145-E). Experimental disruption of E-cadherin function stimulated migration and invasion of DU145-E and other E-cadherin-positive prostate cancer cell lines, but did not affect the fibroblastic-like DU145-F subpopulation. Within the medium of parental DU145 cells, the presence of an 80 kDa E-cadherin fragment was detected. Subsequent functional analyses revealed the stimulatory effect of this fragment on the migratory and invasive capability of E-cadherin-positive cells. These results suggest that E-cadherin plays an important role in regulating the invasive potential of prostate cancer cells through an unique paracrine mechanism.

Gain of androgen receptor gene copies in primary prostate cancer due to X chromosome polysomy

BACKGROUND

Prostate cancer is an androgen dependent tumor. In advanced prostate cancers androgen deprivation has proved to be an effective therapy, but 25% show no response. In this study prostatectomy specimens from patients without preoperative therapy were analyzed to determine the possible mechanism of primary antiandrogen resistance.

METHODS

The number of androgen receptor (AR) gene copies and X-centromeres were investigated from 80 prostate cancer specimens by FISH analysis.

RESULTS

In 9 out of 80 prostate cancers additional X-chromosomes with the corresponding AR gene could be detected. Polysomy of the X-chromosome correlates with pathological classification and tumor volume.

CONCLUSIONS

Additional AR genes due to polysomy of the X-chromosome are present in a subgroup of primary prostate cancers prior to antiandrogen therapy. Because the growth of prostate cancers is androgen dependent, these specimens may have an advantage in low concentrations of androgens. This may be a factor for initial antiandrogen resistance.

Defining the region(s) of deletion at 6q16-q22 in human prostate cancer

Deletion of the long arm of chromosome 6 (6q) frequently occurs in many neoplasms, including carcinomas of the prostate and breast and melanoma, suggesting the location of a tumor-suppressor gene or genes at 6q. At present, however, the region of deletion has not been well defined, and the target gene of deletion remains to be identified. In this study, we analyzed 44 primary prostate cancers with 16 polymorphic markers for loss of heterozygosity (LOH) by using PCR-based techniques. We also examined 23 cell lines/xenografts of prostate cancer with 38 markers for LOH by the method of homozygosity mapping of deletion. LOH at 6q16 - q22 was detected in 21 of 44 (48%) primary tumors and in 12 of 23 (52%) cell lines/xenografts. Two regions of LOH were defined. One was 7.5 cM at 6q16 - q21 between markers D6S1716 and D6S1580, and the other was 4.3 cM at 6q22 between D6S261 and D6S1702. Whereas no correlation was found between LOH at 6q16-q22 and patient age at diagnosis or Gleason score, tumors at higher stage appear to have more frequent LOH. These findings suggest that deletion of 6q16 - q22 is a frequent event in prostate cancer, and that the deletion originates from two distinct regions. These results should be useful in identifying the target gene(s) of deletion at 6q.

Chromosomal changes in locally recurrent, hormone-refractory prostate carcinomas by karyotyping and comparative genomic hybridization

The genetic mechanisms of prostate cancer recurrence during hormonal therapy are largely unknown. So far, data from conventional karyotype analysis on hormone-refractory prostate carcinomas have not been published, mainly because of the difficulties in obtaining fresh hormone-refractory prostate carcinoma samples and getting metaphases from them. Here, we have studied chromosomal changes in 12 locally recurrent, hormone-refractory prostate carcinomas using karyotyping and CGH that revealed genetic aberrations in all tumors. Loss of the Y chromosome was the most common (89%) finding, and tetraploidy or near-tetraploidy was detected in all tumors. Also non-random translocations were found in 56% of the tumors. The present study indicates that clonal chromosomal aberrations in hormone-refractory prostate carcinomas are more common than in untreated primary tumors, and also, further studies on the frequency and significance of translocations in prostate carcinoma progression during hormonal therapy are warranted.

Clinical and experimental progression of a new model of human prostate cancer and therapeutic approach

We report the clinical evolution of a prostate cancer, metastasizing to lungs and bones, recurring locally, and escaping from anti-androgen therapy. Key event of biological progression of the patient's tumor was the coincidence of allelic imbalance accumulation and of bone metastases occurrence. The recurrent tumor was established as the transplantable xenograft PAC120 in nude mice, where it grew locally. PAC120 displayed the same immunophenotype of the original tumor (positive for keratin, vimentin, prostatic acid phosphatase, and Leu-7) and expressed human HOXB9, HOXA4, HER-2/neu, and prostate-specific antigen genes, as detected by reverse transcriptase-polymerase chain reaction. It formed lung micrometastases detected by mRNA expression of human genes. Cytogenetic analysis demonstrated numerous alterations reflecting the tumor evolution. PAC120 was still hormone-dependent; its growth was strongly inhibited by the new gonadotropin-releasing hormone antagonist FE 200486 but weakly by gonadotropin-releasing hormone superagonist D-Trp(6)-luteinizing-hormone releasing hormone (decapeptyl). Tumor growth inhibition induced by anti-hormone therapy was linked to the hormone deprivation degree, more important and more stable with FE 200486 than with D-Trp(6)-luteinizing-hormone releasing hormone. Surgical castration of mice led to tumor regressions but did not prevent late recurrences. Transition to hormone-independent tumors was frequently associated with a mucoid differentiation or with a neuroendocrine-like pattern. Independent variations of mRNA expression of HER-2/neu and prostate-specific antigen were observed in hormone-independent tumors whereas HOXB9 gene expression was constant. In conclusion, PAC120 xenograft, a new model of hormone-dependent prostate cancer retained the progression potential of the original tumor, opening the opportunity to study the hormone dependence escape mechanism.

Loss of the short arm of the Y chromosome in human prostate carcinoma

A change in Y chromosome number is one of the many cytogenetic abnormalities reported in human prostate tumors. However, reports in the literature have varied regarding the frequency of Y loss or gain and the significance of Y aneusomy with respect to the biology of the disease. We have conducted an analysis of the Y chromosome in malignant and benign hyperplastic human prostate epithelium in order to determine whether regional Y loss occurs in prostate cancer. To accomplish this we performed dual-color fluorescence in situ hybridization (FISH) on serial sections of paraffin-embedded prostate tumor tissues using either a Yp (SRY), Ycen (alpha-satellite) or Yq (satellite 3) probe, and an Xcen (alpha-satellite) probe that served as a control for hybridization and nuclear truncation. The results of our FISH analysis demonstrated loss of Yp in the malignant epithelium of 14/40 (35%) prostate tumor sections examined. We also found loss of Yq in 4/40 (10%) of the samples, with one of these exhibiting accompanying Yp loss. The remaining samples, 23/40 (58%), retained both Yp and Yq markers, with no evidence of either Ycen loss or Y gain in any of the tumor samples examined. In addition, Y loss was detected in the benign hyperplastic regions in nearly one-half of the tissue sections that exhibited Y loss in the malignant epithelium. These results demonstrate that regional chromosome Y loss occurs in prostate cancer, that loss of Yp is the most frequent event, and suggest that this loss may in some cases be a precursor to prostate malignancy.

Identification of a high frequency of chromosomal rearrangements in the centromeric regions of prostate cancer cell lines by sequential giemsa banding and spectral karyotyping

BACKGROUND

Currently, prostate cancer (CaP) cytogenetics is not well defined, largely because of technical difficulties in obtaining primary tumor metaphases.

METHODS AND RESULTS

We examined three CaP cell lines (LNCaP, DU145, PC-3) using sequential Giemsa banding and spectral karyotyping (SKY) to search for a common structural aberration or translocation breakpoint. No consistent rearrangement common to all three cell lines was detected. A clustering of centromeric translocation breakpoints was detected in chromosomes 4, 5, 6, 8, 11, 12, 14, and 15 in DU145 and PC-3. Both these lines were found to have karyotypes with a greater level of complexity than LNCaP.

CONCLUSION

The large number of structural aberrations present in DU145 and PC-3 implicate an underlying chromosomal instability and subsequent accumulation of cytogenetic alterations that confer a selective growth advantage. The high frequency of centromeric rearrangements in these lines indicates a potential role for mitotic irregularities associated with the centromere in CaP tumorigenesis.

Chromosomal basis of adenocarcinoma of the prostate

Prostate cancer is the most frequent malignancy and the second leading cause of cancer deaths among males in the Western world. The clinical course of the disease is highly complex, and genetic factors underlying tumorigenesis are poorly understood. The challenge that lies ahead is to identify the important gene(s) that causes adenocarcinoma of the prostate. Chromosomal findings by cytogenetic and molecular methods, including Southern blotting, microsatellite analysis, fluorescence in situ hybridization, and comparative genomic hybridization, revealed a high frequency of chromosomal aberrations of heterogeneous nature, including: -1, +1, -1q, +4, -6q, -7, +7, -8, -8p, -8q, +i(8q), -9, -9p, -10, +10, +11, -12, -13q, -16, -16q, +16, -17, +17, +17q, -18, +18, -18q, +19p, +20q, +X, -Xq, -Y, and +Y. Specific chromosomal regions of alterations were 1q24-25, 2cen-q31, 5cen-q23.3, 6q14-23.2, 7q22-q31, 8p12-21, 8p22, 8q24-qter, 10q22.1, 10q23-25, 11p11.2, 16q24, 17p13.1, 18q12.2, and Xq11-12. Recently, a predisposing gene for early onset has been localized on 1q42.2-43. The losses of heterozygosity at specific chromosomal loci from chromosomes 5q, 6q, 7q, 8p, 8q, 10q, 13q, 16q, 17p, 17q, and 18q are generally correlated with poor prognosis in advanced tumor stage. In addition, an abnormal function of known tumor suppressor genes from these regions have been observed in prostate cancer. Although, the amplification of the androgen receptor gene at Xq11-13 and HER-2/neu gene at 17q11.2-q12 are novel findings, no single gene has been implicated in harboring prostate cancer. Frequent inactivation of PTEN/MMAC1 tumor suppressor gene at 10q23, MXI-1 at 10q25, KAI-1 at 11p11.2, Rb at 13q14.2, and p53 at 17p13.1 and deregulation of c-myc oncogene at 8q24 have recently been the subject of intense scrutiny and debate.

Y chromosome enumeration in touch preparations from 42 prostate tumors by interphase fluorescence in situ hybridization analysis

A change in Y chromosome number is but one of the many cytogenetic abnormalities reported in human prostate tumors. However, reports in the literature have varied regarding the frequency of Y loss or gain, whether it is restricted to the cancerous tissue, and its relation to the biology of the disease. The most frequently used materials for analysis of Y enumeration have been metaphase spreads from short-term cell cultures of prostate tumor tissue and paraffin-embedded tissue sections. Analysis of Y chromosome number by using metaphase spreads on short-term cultures can be misleading owing to clonal cell selection during the establishment of these cultures. This may result in an incomplete representation of the loss/gain pattern in the tumor as a whole. Studies using paraffin-embedded tissue sections can be complicated by apparent chromosome loss due to nuclear truncation as a result of tumor sectioning. In an attempt to circumvent these problems, we have used touch preparations from human prostate tumors to search for Y chromosome loss. Fluorescence in situ hybridization analysis was conducted by using a whole chromosome Y paint, with an alpha-satellite chromosome 3 probe as a control, on tumor samples from 42 patients ages 40-75. The results demonstrated a gain of Y in a single prostate tumor sample, with no convincing evidence for loss of the entire Y chromosome in any of the other 41 samples examined. The results suggest that loss of the entire Y chromosome is an infrequent event in prostate cancer.

Chromosomal clues to the development of prostate tumors

BACKGROUND

Cytogenetic, molecular cytogenetic, and molecular studies of prostate cancer have revealed an enormous amount of data regarding chromosomal loci that are aberrant in prostate tumors.

METHODS

These data have been compared and condensed in this review to determine which chromosomes and chromosome sites have been most frequently reported.

RESULTS

Loss of the Y chromosome, gain of 7, 8, and X, and interstitial deletions on 6q, 7q, 8p, 10q, 13q, 16q, 17q, and 18q are the most prevalent.

CONCLUSIONS

A potential model for genetic control of tumor progression is presented, as are data regarding the evaluation of a new series of tumors.

S-phase fraction related to prognosis in localised prostate cancer. No specific significance of chromosome 7 gain or deletion of 7q31.1

A flow-cytometric (FCM) and fluorescence in situ hybridization (FISH) study was performed in 153 patients with clinically localised prostate cancer (PC) to evaluate retrospectively the prognostic significance of DNA ploidy, S-phase fraction (SPF) and chromosome 7 copy number. Deletions in 7q31.1 were analysed in a subset of 26 tumours. The mean follow-up time was 6 years (range 4-16 years). Twelve cases of benign prostatic hyperplasia (BPH) were studied as a control. Chromosome 7 enumeration and deletion studies were conducted using the alpha-satellite D7Z1 probe and a cosmid probe specific for the marker D7S522 on 7q31.1. Higher SPF was associated with shorter overall survival and shorter time to local progression and metastasis. Near diploid (DNA index 1.05-1.20) cases had a lower frequency of metastases and lower Gleason scores than aneuploid cases. Increased absolute chromosome 7 copy number (centromere count) was associated with higher Gleason score, higher SPF and shorter local progression-free and prostate cancer survival. Absolute chromosome 7 copy number was concordant with FCM DNA ploidy in the majority (75%) of cases. Relative gain or loss of chromosome 7 (centromere counts compared to ploidy) was infrequent, and no correlation was found with clinical parameters. Deletions in 7q31.1 were infrequent. Our results indicate that in localised PC (i) SPF is a prognostic factor, (ii) absolute chromosome 7 copy number is concordant with the ploidy status of the tumour (relative gain or loss of chromosome 7 is infrequent and has no independent prognostic value) and (iii) the frequency of deletions in 7q31.1 is low and not correlated with clinical outcome.

Allele loss in colorectal cancer at the Cowden disease/juvenile polyposis locus on 10q

The genes that are mutated in inherited cancer syndromes are often involved in the pathogenesis of sporadic cancers of the types that characterize those syndromes. In colorectal cancer such loci include the familial adenomatous polyposis (APC) gene and the hereditary nonpolyposis colorectal cancer (DNA mismatch repair) genes. Juvenile hamartomatous polyposis syndromes, which include Juvenile Polyposis and Cowden disease, also predispose to colorectal cancer. The gene for Cowden disease has recently been localized to chromosome 10q22-q23, and a juvenile polyposis locus, JP1, has been reported as mapping to the same location. We have studied up to 70 cases of sporadic colorectal cancer for allele loss at markers predominantly on the long arm of chromosome 10, including loci flanking the putative Cowden Disease/JP1 locus. Frequencies of allele loss of about 35% were found close to this locus, whereas low frequencies of allele loss were found elsewhere on 10q. Mutations at the putative Cowden Disease/JP1 locus may therefore be important in sporadic colorectal cancer and fine mapping of allele loss on 10q in sporadic colon cancers may help to refine the position of this gene.