Chromosomal clues to the development of prostate tumors

Y chromosome is moving out of sex determination shadow

Although sex hormones play a key role in sex differences in susceptibility, severity, outcomes, and response to therapy of different diseases, sex chromosomes are also increasingly recognized as an important factor. Studies demonstrated that the Y chromosome is not a ‘genetic wasteland’ and can be a useful genetic marker for interpreting various male-specific physiological and pathophysiological characteristics. Y chromosome harbors male‑specific genes, which either solely or in cooperation with their X-counterpart, and independent or in conjunction with sex hormones have a considerable impact on basic physiology and disease mechanisms in most or all tissues development. Furthermore, loss of Y chromosome and/or aberrant expression of Y chromosome genes cause sex differences in disease mechanisms. With the launch of the human proteome project (HPP), the association of Y chromosome proteins with pathological conditions has been increasingly explored. In this review, the involvement of Y chromosome genes in male-specific diseases such as prostate cancer and the cases that are more prevalent in men, such as cardiovascular disease, neurological disease, and cancers, has been highlighted. Understanding the molecular mechanisms underlying Y chromosome-related diseases can have a significant impact on the prevention, diagnosis, and treatment of diseases.

A review of studies examining the association between genetic biomarkers (short tandem repeats and single-nucleotide polymorphisms) and risk of prostate cancer: the need for valid predictive biomarkers

Prostate cancer (PCa) is a challenging polygenic disease because the genes that cause PCa remain largely elusive and are affected by several causal factors. Consequently, research continuously strives to identify a genetic marker which could be used as an indicator to predict the most vulnerable (i.e., predisposed) segments of the population to the disease or for the gene which may be directly responsible for PCa. To enhance the genetic etiology of PCa, this research sought to discover the key studies conducted in this field using data from the main journal publication search engines, as it was hoped that this could shed light on the main research findings from these studies, which in turn could assist in determining these genes or markers. From the research highlighted, the studies primarily used two kinds of markers: short tandem repeats or single-nucleotide polymorphisms. These markers were found to be quite prevalent in all the chromosomes within the research carried out. It also became apparent that the studies differed in both quantity and quality, as well as being conducted in a variety of societies. Links were also determined between the degree and strength of the relationship between these markers and the occurrence of the disease. From the studies identified, most recommended a larger and more diverse survey for the parameters which had not been studied before, as well as an increase in the size of the community (i.e., the population) being studied. This is an indication that work in this field is far from complete, and thus, current research remains committed toward finding genetic markers that can be used clinically for the diagnosis and screening of patients with PCa.

The Long Noncoding RNA TTTY15, Which Is Located on the Y Chromosome, Promotes Prostate Cancer Progression by Sponging let-7

BACKGROUND

The link between prostate cancer (PCa) development and aberrant expression of genes located on the Y chromosome remains unclear.

OBJECTIVE

To identify Y-chromosomal long noncoding RNAs (lncRNAs) with critical roles in PCa and to clarify the corresponding mechanisms.

DESIGN, SETTING, AND PARTICIPANTS

Aberrantly expressed lncRNAs on the Y chromosome were identified using transcriptome analysis of PCa clinical samples and cell lines. Biological functions and molecular mechanisms of the lncRNAs were revealed using in vitro and in vivo experimental methods.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Experiments and outcome measurements were performed in duplicate or triplicate. Wilcoxon signed-rank test was employed for comparison of RNA levels in clinical cohorts. Analysis of variance was employed for comparisons among multiple groups.

RESULTS AND LIMITATIONS

In most patients with PCa, TTTY15 was the most elevated lncRNA located on the Y chromosome. Knockout of this lncRNA by two different CRISPR-Cas9 strategies suppressed PCa cell growth both in vitro and in vivo. TTTY15 promoted PCa by sponging the microRNA let-7, consequently increasing CDK6 and FN1 expression. FOXA1 is an upstream regulatory factor of TTTY15 transcription.

CONCLUSIONS

The Y-chromosomal lncRNA TTTY15 was upregulated in most PCa tissues and could promote PCa progression by sponging let-7.

PATIENT SUMMARY

We found that TTTY15 levels were frequently elevated in prostate cancer (PCa) tissues compared with those in paracancerous normal tissues in a large group of PCa patients, and we observed a tumour suppressive effect after TTTY15 knockout using CRISPR/Cas9. These results may have therapeutic implications for PCa patients.

Chromosomal aberrations in benign prostatic hyperplasia patients

Purpose

To investigate the chromosomal changes in patients with benign prostatic hyperplasia (BPH).

Materials and Methods

A total of 54 patients diagnosed with clinical BPH underwent transurethral prostate resection to address their primary urological problem. All patients were evaluated by use of a comprehensive medical history and rectal digital examination. The preoperative evaluation also included serum prostate-specific antigen (PSA) measurement and ultrasonographic measurement of prostate volume. Prostate cancer was detected in one patient, who was then excluded from the study. We performed conventional cytogenetic analyses of short-term cultures of 53 peripheral blood samples obtained from the BPH patients.

Results

The mean (±standard deviation) age of the 53 patients was 67.8±9.4 years. The mean PSA value of the patients was 5.8±7.0 ng/mL. The mean prostate volume was 53.6±22.9 mL. Chromosomal abnormalities were noted in 5 of the 53 cases (9.4%). Loss of the Y chromosome was the most frequent chromosomal abnormality and was observed in three patients (5.7%). There was no statistically significant relationship among age, PSA, prostate volume, and chromosomal changes.

Conclusions

Loss of the Y chromosome was the main chromosomal abnormality found in our study. However, this coexistence did not reach a significant level. Our study concluded that loss of the Y chromosome cannot be considered relevant for the diagnosis of BPH as it is for prostate cancer. Because BPH usually occurs in aging men, loss of the Y chromosome in BPH patients may instead be related to the aging process.

Microchimeric Cells, Sex Chromosome Aneuploidies and Cancer

The phenomenon of feta-maternal microchimerisms inspires numerous questions. Many questions remain to be answered regarding this new avenue of genetics. The X and Y chromosomes have been associated with malignancy in different types of human tumors. We aimed to investigate the numerical aberrations of chromosomes X and Y in lung cancer (LC) and bladder cancer (BC) and review recent evidence for possible roles of microchimeric cells (McCs) in these cancers. We carried out cytogenetic analysis of the tumor and blood sampling in 52 cases of people with BC and LC, and also with 30 healthy people. A total of 48 (92.3 %) of the patients revealed sex chromosome aneuploidies (SCAs). A total SCAs was found in 9.8 % of 2282 cells that were analyzed as one or more cells in each case. The 68 and 95 SCAs were found in the 1952 (8.4 %) cells in peripheral blood, and 41 and 19 SCAs in the 330 (18.2 %) cells in the tumoral tissues respectively. There was a significant difference in the frequencies of SCAs between the patients and the control groups determined by the Fischer's Exact Test (p < 0.0001). The frequencies of SCAs were higher in the tumoral tissues than in the blood (p < 0.0001). There was a significant difference in the frequencies of SCAs between the tumor and blood tissues, and this was higher in the tumor tissue (p < 0.0001). In general, 78.9 % (41) of the 52 patients with LC and BC had X and Y chromosome monosomies. Largely a Y chromosome loss was present in 77.8 % of the men, and the 47, XXY karyotype was found in 33.3 % of them. The second most common SCA was monosomy X, and was found in 71.4 % of the women. McCs were observed in 26.9 % of the 52 patients, and the frequencies of McCs were higher in the blood than in the tissues (p < 0.0001). XY cells were identified in the lung and bladder tissues of the women who had been pregnant with boys, but not in those who had not. There was a significant difference in the frequencies of McCs between the LC and BC patients (p < 0.0005). We speculate that the microchimerism could have a general beneficial role in cancer, in which some sites may not be evident because of an allogeneic maternal immune reaction that hastens cancer development. A further understanding of McCs may help in anticipating its implications in cancer. Our results may suggest that SCAs may be contributing factors in the development of LC and BC, and aneuploidies of X and Y chromosomes play a role in the pathogenesis of cancers.

Identification of specific Y chromosomes associated with increased prostate cancer risk

BACKGROUND

Evidence supports the possibility of a role of the Y chromosome in prostate cancer, but controversy exists.

METHODS

A novel analysis of a computerized population-based resource linking genealogy and cancer data was used to test the hypothesis of a role of the Y chromosome in prostate cancer predisposition. Using a statewide cancer registry from 1966 linked to a computerized genealogy representing over 1.2 million descendants of the Utah pioneers, 1,000 independent sets of males, each set hypothesized to share the same Y chromosome as represented in genealogy data, were tested for a significant excess of prostate cancer.

RESULTS

Multiple Y chromosomes representing thousands of potentially at-risk males were identified to have a significant excess risk for prostate cancer.

CONCLUSIONS

This powerful and efficient in silico test of an uncommon mode of inheritance has confirmed evidence for Y chromosome involvement in prostate cancer.

Y chromosome haplogroups and prostate cancer in populations of European and Ashkenazi Jewish ancestry

Genetic variation on the Y chromosome has not been convincingly implicated in prostate cancer risk. To comprehensively analyze the role of inherited Y chromosome variation in prostate cancer risk in individuals of European ancestry, we genotyped 34 binary Y chromosome markers in 3,995 prostate cancer cases and 3,815 control subjects drawn from four studies. In this set, we identified nominally significant association between a rare haplogroup, E1b1b1c, and prostate cancer in stage I (P = 0.012, OR = 0.51; 95% confidence interval 0.30–0.87). Population substructure of E1b1b1c carriers suggested Ashkenazi Jewish ancestry, prompting a replication phase in individuals of both European and Ashkenazi Jewish ancestry. The association was not significant for prostate cancer overall in studies of either Ashkenazi Jewish (1,686 cases and 1,597 control subjects) or European (686 cases and 734 control subjects) ancestry (P_meta = 0.078), but a meta-analysis of stage I and II studies revealed a nominally significant association with prostate cancer risk (P_meta = 0.010, OR = 0.77; 95% confidence interval 0.62–0.94). Comparing haplogroup frequencies between studies, we noted strong similarities between those conducted in the US and France, in which the majority of men carried R1 haplogroups, resembling Northwestern European populations. On the other hand, Finns had a remarkably different haplogroup distribution with a preponderance of N1c and I1 haplogroups. In summary, our results suggest that inherited Y chromosome variation plays a limited role in prostate cancer etiology in European populations but warrant follow-up in additional large and well characterized studies of multiple ethnic backgrounds.

The genomic landscape of prostate cancer

Prostate cancer is a common malignancy in men, with a markedly variable clinical course. Somatic alterations in DNA drive the growth of prostate cancers and may underlie the behavior of aggressive versus indolent tumors. The accelerating application of genomic technologies over the last two decades has identified mutations that drive prostate cancer formation, progression, and therapeutic resistance. Here, we discuss exemplary somatic mutations in prostate cancer, and highlight mutated cellular pathways with biological and possible therapeutic importance. Examples include mutated genes involved in androgen signaling, cell cycle regulation, signal transduction, and development. Some genetic alterations may also predict the clinical course of disease or response to therapy, although the molecular heterogeneity of prostate tumors poses challenges to genomic biomarker identification. The widespread application of massively parallel sequencing technology to the analysis of prostate cancer genomes should continue to advance both discovery-oriented and diagnostic avenues.

Mitochondrial DNA haplogroup analysis reveals no association between the common genetic lineages and prostate cancer in the Korean population

Mitochondrial DNA (mtDNA) variation has recently been suggested to have an association with various cancers, including prostate cancer risk, in human populations. Since mtDNA is haploid and lacks recombination, specific mutations in the mtDNA genome associated with human diseases arise and remain in particular genetic backgrounds referred to as haplogroups. To assess the possible contribution of mtDNA haplogroup-specific mutations to the occurrence of prostate cancer, we have therefore performed a population-based study of a prostate cancer cases and corresponding controls from the Korean population. No statistically significant difference in the distribution of mtDNA haplogroup frequencies was observed between the case and control groups of Koreans. Thus, our data imply that specific mtDNA mutations/lineages did not appear to have a significant effect on a predisposition to prostate cancer in the Korean population, although larger sample sizes are necessary to validate our results.

Sex chromosome alterations associate with tumor progression in sporadic colorectal carcinomas

PURPOSE

The X and Y chromosomes have been associated with malignancy in different types of human tumors. This study attempts to determine the involvement of X chromosome and pseudoautosomal regions (PAR) in sporadic colorectal carcinogenesis.

EXPERIMENTAL DESIGN

An allelotyping of X chromosome in 20 premalignant and 22 malignant sporadic colorectal tumors (CRC) from female patients and an analysis of losses [loss of heterozygosity (LOH)] on PARs from 44 CRCs and 12 adenomas of male patients were carried out. In male tumors, a fluorescence in situ hybridization analysis was done to identify which sex chromosome was possibly lost.

RESULTS

The LOH frequency in female CRCs was 46% with higher incidence in patients with tumor recurrence than in those who were disease-free (P < 0.01) and with a significant difference from adenomas (11%; P < 0.0001). The LOH rate of PARs in male CRCs was 37% with a frequency significantly higher in patients with recurrence (P < 0.03). These results were maintained also when data from PARs of all 66 male and female patients were cumulated (P < 0.05). LOH in PARs was significantly correlated with LOH at 5q (P < 0.01) and 18q (P < 0.01), early and late events, respectively, in colorectal carcinogenesis. Fluorescence in situ hybridization analysis in male patients with extensive PAR LOH revealed a preferential loss of the Y chromosome.

CONCLUSIONS

Our data suggest a role for sex chromosome deletions in the malignant progression of sporadic CRCs and support the presence in the PARs of putative tumor suppressor genes involved in the progression of human sporadic CRCs.

Prostate cancer in fathers with fewer male offspring: the Jerusalem Perinatal Study cohort

Recent studies have suggested the involvement of loci on the Y chromosome in prostate cancer. We studied the relative risk (RR) of prostate cancer in relation to sex ratio of offspring in a cohort of 38,934 Israeli men who were followed from the birth of their offspring (in 1964 through 1976) until 2005. Cox models were used to adjust for changes in incidence over time, age, the man's year of birth, and social and ethnic variables. A total of 712 men were diagnosed with prostate cancer. Compared with men who had at least one son, men with only daughters had an increased risk of prostate cancer (adjusted RR = 1.40, 95% confidence interval [CI] = 1.20 to 1.64, P<.0001). In men with one, two, or three or more offspring, the relative risks associated with absence of sons were 1.25 (95% CI = 1.00 to 1.56), 1.41 (95% CI = 1.04 to 1.91), and 1.60 (95% CI = 1.05 to 2.43), respectively. Men with no daughters showed no statistically significantly altered risk, compared with men who had offspring of both sexes. The relative risk of prostate cancer decreased as the number of sons increased (P(trend)<.0001) but did not change with the number of daughters. These findings suggest that a Y chromosome locus may be involved in prostate cancer risk in this population.

Cancer du rein et deuxième cancer : Analyse critique de la littérature

This review was designed to determine whether patients with renal cell carcinoma (RCC) present an increased risk of developing a second cancer. Cancers statistically associated with RCC were determined by a review of epidemiological publications and the aetiological factors of these associations were then studied. The clinical implications of the results of this review are discussed at the end of this study. This review of the literature demonstrates an increased risk of bladder cancer and prostate cancer in patients with RCC, particularly in the case of the tubulopapillary subtype. The pathophysiology of these associations has not been clearly elucidated, but probably involves common genetic alterations. These epidemiological associations should be taken into account in the follow-up of patients with RCC.

Frequency of the TMPRSS2:ERG gene fusion is increased in moderate to poorly differentiated prostate cancers

BACKGROUND

Recent reports indicate that prostate cancers (CaP) frequently over-express the potential oncogenes, ERG or ETV1. Many cases have chromosomal rearrangements leading to the fusion of the 5' end of the androgen-regulated serine protease TMPRSS2 (21q22.2) to the 3' end of either ERG (21q22.3) or ETV1 (7p21.3). The consequence of these rearrangements is aberrant androgen receptor-driven expression of the potential oncogenes, ETV1 or ERG.

AIM

To determine the frequency of rearrangements involving TMPRSS2, ERG, or ETV1 genes in CaP of varying Gleason grades through fluorescence in situ hybridisation (FISH) on CaP tissue microarrays (TMAs).

METHODS

Two independent assays, a TMPRSS2 break-apart assay and a three-colour gene fusion FISH assay were applied to TMAs. FISH positive cases were confirmed by reverse transcriptase (RT) PCR and DNA sequence analysis.

RESULTS

A total of 106/196 (54.1%) cases were analysed by FISH. None of the five benign prostatic hyperplasia cases analysed exhibited these gene rearrangements. TMPRSS2:ERG fusion was found more frequently in moderate to poorly differentiated tumours (35/86, 40.7%) than in well differentiated tumours (1/15, 6.7%, p = 0.017). TMPRSS2:ETV1 gene fusions were not detected in any of the cases tested. TMPRSS2:ERG fusion product was verified by RT-PCR followed by DNA sequencing in 7/7 randomly selected positive cases analysed.

CONCLUSION

This study indicates that TMPRSS2:ERG gene rearrangements in CaP may be used as a diagnostic tool to identify prognostically relevant sub-classifications of these cancers.

Lack of association between Y-chromosomal haplogroups and prostate cancer in the Korean population

The Y chromosome has recently been suggested to have an association with prostate cancer risk in human populations. Since this chromosome is haploid and lacks recombination over most of its length, haplotypes constructed from binary markers throughout the chromosome can be used for association studies. To assess the possible Y-chromosomal contribution to prostate cancer risk, we have therefore analyzed 14 Y-chromosomal binary markers in 106 prostate cancer cases and 110 controls from the Korean population. In contrast to previous findings in the Japanese population, no statistically significant difference in the distribution of Y-chromosomal haplogroup frequencies was observed between the case and control groups of Koreans. Thus, our data imply that the previously reported associations between Y-chromosomal lineages and a predisposition to, or protection against, prostate cancer might be explained by statistical fluctuations, or by genetic effects that are seen only in some environments.

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.

Prostate cancer incidence varies among males from different Y-chromosome lineages

The incidence rate of prostate cancer in African-American males is two times higher than Caucasian men and ten times higher than Japanese men. The geographical specificity of Y haplogroups implies that males from different ethnic groups undoubtedly have various Y lineages with different Y-chromosomal characteristics that may affect their susceptibility or resistance to such a male-specific cancer. To confirm this hypothesis we studied the Y-chromosomal haplogroups of 92 Japanese prostate cancer patients comparing them with randomly selected 109 unrelated healthy Japanese male controls who were confirmed to be residents of the same geographical area. Males could be classified using three binary Y-chromosome markers (sex-determining region Y (SRY), YAP, 47z) into four haplogroups DE, O2b(*), O2b1, and untagged group. Our results confirmed that prostate cancer incidence varies among males from different Y-chromosome lineages. Males from DE and the untagged haplogroups are at a significantly higher risk to develop prostate cancer than O2b(*) and O2b1 haplogroups (P=0.01), odds ratio 2.17 and 95% confidence interval (1.16-4.07). Males from haplogroup DE are over-represented in the patient group showing a percentage of 41.3%. The underlying possible causes of susceptibility variations of different Y lineages for such a male-specific cancer tumorigenesis are discussed. These findings explain the lower incidence of prostate cancer in Japanese and other South East Asian males than other populations. To our knowledge, this is the first reliable study examining the association between prostate cancer and Y-chromosomal haplogroups, comparing prostate cancer patients with carefully selected matched controls.

Detection of Recurrent Copy Number Loss at Yp11.2 Involving TSPY Gene Cluster in Prostate Cancer Using Array-Based Comparative Genomic Hybridization

Prostate cancer is the second leading cause of cancer deaths among American men. The loss of Y chromosome has been frequently observed in primary prostate cancer as well as other types of cancer. Earlier, we showed that introduction of the human Y chromosome suppresses the in vivo tumorigenicity of the prostate cancer cell line PC-3. To further characterize the Y chromosome, we have developed a high-density bacterial artificial chromosome (BAC) microarray containing 178 BAC clones from the human Y chromosome. BAC microarray was used for array comparative genomic hybridization on prostate cancer samples and cell lines. The most prominent observation on prostate cancer specimens was a deletion at Yp11.2 containing the TSPY tandem gene array. Out of 36 primary prostate tumors analyzed, 16 (44.4%) samples exhibited loss of TSPY gene copies. Notably, we observed association between the number of TSPY copies in the blood and the incidence of prostate cancer. Moreover, PC-3 hybrids with an intact Yp11.2 did not grow tumors in nude mice, whereas PC-3 hybrids with a deletion at Yp11.2 grew tumors in nude mice.

Phenotypic characterization of telomerase-immortalized primary non-malignant and malignant tumor-derived human prostate epithelial cell lines

In vitro human prostate cell culture models are critical for clarifying the mechanism of prostate cancer progression and for testing preventive and therapeutic agents. Cell lines ideal for the study of human primary prostate tumors would be those derived from spontaneously immortalized tumor cells; unfortunately, explanted primary prostate cells survive only short-term in culture, and rarely immortalize spontaneously. Therefore, we recently have generated five immortal human prostate epithelial cell cultures derived from both the benign and malignant tissues of prostate cancer patients with telomerase, a gene that prevents cellular senescence. Examination of these cell lines for their morphologies and proliferative capacities, their abilities to grow in low serum, to respond to androgen stimulation, to grow above the agar layer, to form tumors in SCID mice, suggests that they may serve as valid, useful tools for the elucidation of early events in prostate tumorigenesis. Furthermore, the chromosome alterations observed in these immortalized cell lines expressing aspects of the malignant phenotypes imply that these cell lines accurately recapitulate the genetic composition of primary tumors. These novel in vitro models may offer unique models for the study of prostate carcinogenesis and also provide the means for testing both chemopreventive and chemotherapeutic agents.

Molecular changes in prostatic cancer

Prostate cancer is one of the most commonly diagnosed and potentially devastating cancers in men, throughout the world. However, the clinical manifestation of this disease varies greatly, from indolent tumours, requiring little or no treatment, to those aggressive cancers which require radical therapies. Prostate cancer, like all other cancers, develops and progresses as a consequence of an accumulation of genetic changes. While several putative genes have been isolated for the development of breast, ovarian and colon cancer, the aetiology and pathogenesis of prostate cancer remains poorly understood. In this review, we discuss important genetic markers in early, metastatic and hormone refractory prostate cancer which may, in the future, be used as markers for diagnosis and prognosis, as well as targets for therapeutic intervention.

The human Y chromosome suppresses the tumorigenicity of PC-3, a human prostate cancer cell line, in athymic nude mice

The loss of the Y chromosome is a frequent numerical chromosomal abnormality observed in human prostate cancer. In cancer, loss of specific genetic material frequently accompanies simultaneous inactivation of tumor suppressor genes. It is not known whether the Y chromosome harbors such genes. To address the role of genes on the Y chromosome in human prostate cancer, we transferred a tagged Y chromosome into PC-3, a human prostate cancer cell line lacking a Y chromosome. A human Y chromosome was tagged with the hisD gene and transferred to PC-3 by microcell-mediated chromosome transfer. Tumorigenicity of these PC-3 hybrids was tested in vivo and in vitro, and the results were compared with those of the polymerase chain reaction analyses conducted on the PC-3 hybrids using Y chromosome-specific markers. Among 60 mice injected with 12 different PC-3 hybrids (five mice per hybrid), tumor growth was apparent in only one mouse, whereas tumors grew in all mice injected with the parental PC-3 cells. An in vitro assay showed that the Y chromosome did not suppress anchorage-independent growth of PC-3 cells. We found that addition of the Y chromosome suppressed tumor formation by PC-3 in athymic nude mice, and that this block of tumorigenesis was independent of the in vitro growth properties of the cells. This observation suggests the presence of a gene important for prostate tumorigenesis on the Y chromosome.

Androgen receptor modifications in prostate cancer cells upon long-termandrogen ablation and antiandrogen treatment

To study the mechanisms whereby androgen-dependent tumors relapse in patients undergoing androgen blockade, we developed a novel progression model for prostate cancer. The PC346C cell line, established from a transurethral resection of a primary tumor, expresses wild-type (wt) androgen receptor (AR) and secretes prostate-specific antigen (PSA). Optimal proliferation of PC346C requires androgens and is inhibited by the antiandrogen hydroxyflutamide. Orthotopic injection in the dorsal-lateral prostate of castrated athymic nude mice did not produce tumors, whereas fast tumor growth occurred in sham-operated males. Three androgen-independent sublines were derived from PC346C upon long-term in vitro androgen deprivation: PC346DCC, PC346Flu1 and PC346Flu2. PC346DCC exhibited androgen-insensitive growth, which was not inhibited by flutamide. AR and PSA were detected at very low levels, coinciding with background AR activity in a reporter assay, which suggests that these cells have bypassed the AR pathway. PC346Flu1 and PC346Flu2 were derived by culture in steroid-stripped medium supplemented with hydroxyflutamide. PC346Flu1 strongly upregulated AR expression and showed 10-fold higher AR activation than the parental PC346C. PC346Flu1 proliferation was inhibited in vitro by R1881 at 0.1 nM concentration, consistent with a slower tumor growth rate in intact males than in castrated mice. PC346Flu2 carries the well-known T877A AR mutation, causing the receptor to become activated by diverse nonandrogenic ligands including hydroxyflutamide. Array-based comparative genomic hybridization revealed little change between the various PC346 lines. The common alterations include gain of chromosomes 1, 7 and 8q and loss of 13q, which are frequently found in prostate cancer. In conclusion, by in vitro hormone manipulations of a unique androgen-dependent cell line expressing wtAR, we successfully reproduced common AR modifications observed in hormone-refractory prostate cancer: downregulation, overexpression and mutation.

Are primary cultures realistic models of prostate cancer?

Primary cultures fill a unique niche among the repertoire of in vitro model systems available to investigate the biology of the normal and malignant human prostate. This review summarizes some of the properties of primary cultures, with special emphasis on two questions: are primary cultures from adenocarcinomas really comprised of cancer rather than normal cells, and do primary cultures faithfully retain characteristics of cells of origin?

Establishment and characterization of a primary androgen-responsive African-American prostate cancer cell line, E006AA

BACKGROUND

Establishment of human prostate cancer cell lines is essential to advance our understanding of complex processes associated with the initiation and progression of the disease. In the present study, we report the establishment of a primary African-American prostate cancer cell line (E006AA) as well as its associated stromal cells (S006AA).

METHODS

E006AA cell line was established as a spontaneously immortalized cells from a patient with a clinically localized prostate cancer. Extensive characterization of the cells was accomplished using androgen-dependent growth and sensitivity assays, Western analyses, RT-PCR/real-time PCR, cytogenetic analyses, and tumorigenicity in nude mice.

RESULTS

E006AA cell line shows androgen-dependent growth, expresses PSA and the androgen receptor (AR) with 26 CAG repeats in exon 1 of AR. Cytogenetic analyses revealed a hypertriploid karyotype with additional numerical gains in chromosomes 5, 6, 8, 10, 17, 20, 21 and a marker chromosome of unknown origin as well as structural abnormalities in chromosomes 4, 5, 8, 9, 11-14, 18, and 20. This cell line is not tumorigenic in nude mice. S006AA cell line, isolated from the same tumor specimen, also expresses AR and shows the morphological characteristics of smooth muscle cells of prostatic stroma.

CONCLUSIONS

These cell lines are the first available primary epithelial and stromal cells derived from an African-American patient with organ-confined prostate cancer and in conjunction with other established cell lines, could provide an in vitro model system to investigate early transforming events in prostate cancer.

Evaluation of genetic patterns in different tumor areas of intermediate-grade prostatic adenocarcinomas by high-resolution genomic array analysis

Prostate cancer is known for its highly heterogeneous histological appearance. Data concerning the cytogenetic content of areas with different histology are sparse. We have genetically evaluated 10 prostatic adenocarcinomas with intermediate histopathological grades (Gleason score 7) that showed two distinctive growth patterns with different pathologies, that is, Gleason grades 3 and 4 (G3 and G4). The G3 and G4 tumor specimens were taken from spatially separated regions within the cancer mass. Array-based comparative genomic hybridization (aCGH) was performed to obtain genotypes from the 10 pairs of G3 and G4 cancer areas. The cancer DNAs were retrieved from formalin-fixed and paraffin-embedded tissues allowing optimal recognition and selection of target cells. A genome-wide 2,400-element BAC array that provided high-resolution detection of both deletions and amplifications was used. In the 20 G3 and G4 areas, 252 genomic aberrations (88 gains, 164 deletions) were noted, of which 86 were concurrent in G3 and G4 areas (34% overlap). Ninety-five of the 252 alterations were defined by a single BAC clone (54 gains, 41 deletions). Overlapping changes were more frequent for deletions (46%) than for gains (13%). Frequent coinciding deletions (> or = 20% of tumors) were seen on 8p (60%), 6q (30%), 1p (20%), 2q (20%), proximal 8q (20%), 10q (20%), 13q (20%), 16q (20%), and 18q (20%). A frequent overlapping gain (> or = 20% of tumors) was detected on distal 13q (20%). The patterns of imbalance could be found to coincide in the G3 and G4 areas of the majority of cancers. Array-based CGH can be used as a tool for the evaluation of genetic patterns in prostate cancer.

A Y chromosomal influence on prostate cancer risk: the multi-ethnic cohort study

BACKGROUND

A Y chromosomal role in prostate cancer has previously been suggested by both cytogenetic findings and patterns of Y chromosomal gene expression. We took advantage of the well established and stable phylogeny of the non-recombining segment of the Y chromosome to investigate the association between Y chromosomal DNA variation and prostate cancer risk.

METHODS

We examined the distribution of 116 Y lineages in 930 prostate cancer cases and 1208 controls from four ethnic groups from a cohort study in Hawaii and California.

RESULTS

One lineage, found only among the Japanese group in our study, was associated with a statistically significant predisposition to prostate cancer (odds ratio (OR) = 1.63; 95% confidence interval (CI) 1.07 to 2.47), and, in particular, to high severity disease in younger individuals (OR = 3.89; 95% CI 1.34 to 11.31).

CONCLUSIONS

This finding suggests that a Y chromosomal factor contributes significantly to the development of prostate cancer in Japanese men.

Detection of Chromosomal Aberrations in Prostate Cancer by Fluorescence In Situ Hybridization (FISH)

PURPOSE

Fluorescence in situ hybridization (FISH) is a powerful tool for quantitative analysis of chromosomes and genes and can be applied in a variety of specimens, including cell cultures, isolated nuclei from fresh and fixed tissues, and histological tissue sections. For detection of numerical chromosome aberrations, we examined prostatic cancer samples at our department. In addition, we also observed primary and secondary aberrations taking part in the initiation and progression of tumours.

MATERIALS AND METHODS

FISH using chromosome-specific alpha-satellite DNA probes for chromosomes 7, 8, 9, 10, 17, X and Y was performed on 19 prostatic cancer and 19 benign prostatic hyperplasia (BPH) samples obtained from transurethral resection (TUR) and archival paraffin-embedded blocks.

RESULTS

Numerical aberrations were observed in 41% of the tumours studied. A range of aberrant copy numbers of chromosome 9 (68%), 7 (63%), 8 (58%), 17 (37%), Y (32%) and 10 (26%) was observed. We did not observe significant aberrations in BPH samples. In prostate cancer patients, chromosomes 7 (47%), 8 (58%) and 9 (63%) were monosomic by FISH. Monosomy 8 and 9 were significant differences (p>0.05) between prostate cancer and BPH patients.

CONCLUSIONS

FISH analysis could be observed an one of strongest methods of analysis in detecting numerical aberrations of individual chromosomes with application to paraffin-block samples, metaphase and, interphase nuclei. To our knowledge, this analysis is firstly studied in Turkish patients. Therefore, results of this analysis may be important for Turkish patients.

Spectral karyotype (SKY) analysis of human prostate carcinoma cell lines

BACKGROUND

Well-characterized in vitro model systems provide an invaluable tool for studying prostate cancer in the laboratory. Detailed karyotypes have been reported using modern techniques such as multiplex fluorescence in situ hybridization (M-FISH) and spectral karyotyping (SKY) for LNCaP, DU 145, NCI-H660, and PC-3 cell lines. However, karyotypic data for more recently established prostate carcinoma cell lines are still limited.

METHODS

Classical (G-banding) and SKY analyses were performed on ten prostate carcinoma cell lines: 22Rv1, CWR-R1, DuCaP, LAPC-4, MDA PCa 1, MDA PCa 2a, MDA PCa 2b, PC-346C, PSK-1, and VCaP.

RESULTS

Chromosomal abnormalities were identified in all cell lines, although the number and complexity varied greatly among them. PC-346C, established from a primary tumor, exhibited the lowest number (3) of clonal structural abnormalities, while DuCaP, established from a metastasis from a hormone-refractory patient, exhibited both the highest number (31) and largest complexity of structural abnormalities. In various subsets of these models, breakpoints were identified in chromosomal regions previously described as being involved in prostate cancer (e.g., 8p, 10q, 13q, and 16q).

CONCLUSIONS

The present study provides a comprehensive karyotypic analysis of a large number of prostate carcinoma cell lines, and offers a valuable resource for future investigations.

PROTEOME-3D: an interactive bioinformatics tool for large-scale data exploration and knowledge discovery

Comprehensive understanding of biological systems requires efficient and systematic assimilation of high-throughput datasets in the context of the existing knowledge base. A major limitation in the field of proteomics is the lack of an appropriate software platform that can synthesize a large number of experimental datasets in the context of the existing knowledge base. Here, we describe a software platform, termed PROTEOME-3D, that utilizes three essential features for systematic analysis of proteomics data: creation of a scalable, queryable, customized database for identified proteins from published literature; graphical tools for displaying proteome landscapes and trends from multiple large-scale experiments; and interactive data analysis that facilitates identification of crucial networks and pathways. Thus, PROTEOME-3D offers a standardized platform to analyze high-throughput experimental datasets for the identification of crucial players in co-regulated pathways and cellular processes.

A novel tumorigenic human prostate epithelial cell line (M2205): molecular cytogenetic characterization demonstrates C-MYC amplification and jumping translocations

The paucity of cell lines from early-stage prostate cancer tumors has hindered the recognition of genetic and cellular changes that are associated with the acquisition of tumorigenesis. We describe the chromosomal complement of a novel tumorigenic prostate epithelial cell subline, called M2205, that acquired only three new, consistent chromosomal changes (from those present in the SV40T antigen immortalized parental cell line, P69SV40TAg) when it attained tumor-forming potential. The consistent changes, which were fully characterized using GTG-banding, CBG-banding, silver staining, fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH), and spectral karyotyping (SKY), involved segmental jumping translocations and resulted in gains in the copy number of genes located on the distal long arm of chromosome 8 (8q22 to 8q24.3), including c-myc. Furthermore, the jumping translocations also resulted in ribosomal genes being present in multiple, tandem copies next to the chromatin from 8q. Given the relatively small number of cytogenetic changes present, this subline provides a means for better understanding the cellular changes associated with the acquired chromosomal imbalances. Further studies of this subline could also provide insight as to the mechanism or mechanisms leading to the formation of jumping translocations, as well as potential position effects resulting from the relocation of ribosomal genes next to other cellular genes or oncogenes.

Cytogenetics and molecular genetics of cancer of the prostate

Prostate cancer remains the most common male malignancy in Western countries and the second-leading cause of death from cancer in males. Progress in the understanding of molecular and genetic mechanisms leading to this disease has only recently begun to offer a glimpse of the genes, chromosomal sites, and proteins implicated in the development and progression of prostate tumors. This brief review addresses some of the key issues in prostate cancer research, including a discussion of both hereditary and sporadic cancers as well as specific genes and chromosomal loci that likely play a part in the etiology of this disease.

Down-regulation of Lsm1 is involved in human prostate cancer progression

Elucidation of genetic alterations is an approach to understanding the underlying molecular mechanisms of progression of human prostate cancers. We have searched for genes differentially expressed in advanced prostate cancers using cDNA-representational difference analysis, and thereby isolated the Lsm1 as one of down-regulated gene. An Lsm1 expression vector was transfected into PC3 cells, normally featuring down-regulated Lsm1, and four transfectants were established. No differences in morphology or cell proliferation were evident in comparison with parent PC3 or PC3/mock-transfectants. In contrast, significant suppression of invasive potential or metastatic ability of Lsm1 transfectants was observed in the Matrigel chemoinvasion assay and in nude mice, respectively. With human prostate cancers, almost all of informative prostatectomised cases without neoadjuvant therapy showed allelic retention in the Lsm1 region, whereas refractory cancers frequently showed allelic loss in this region. No critical gene mutations were found in open reading frame of Lsm1 in prostate cancers examined by PCR-SSCP analysis, including localised and refractory cancers. These results suggest that Lsm1 is deeply involved in prostate cancer progression through its down-regulation, independent of any gene mutation.

Down-regulation of human X-box binding protein 1 (hXBP-1) expression correlates with tumor progression in human prostate cancers

BACKGROUND

In our previous study, the gene encoding the human X-box binding protein 1 (hXBP-1) was isolated as a down-regulated gene in advanced prostate cancers using cDNA-representational difference analysis (RDA). In the present investigation, we characterized alterations of hXBP-1 in prostate cancer specimens.

METHODS

Expression patterns of hXBP-1 in a series of human prostate cancers were examined by Northern blotting, mRNA in situ hybridization or immunohistochemistry. Loss of heterozygosity (LOH) analysis using microsatellite markers and gene mutation analysis in the hXBP-1 region were also performed.

RESULTS

Expression of hXBP-1 was localized in epithelial and adenocarcinoma cells of the prostate. An inverse correlation between hXBP-1 expression and histological differentiation was found in a series of prostate cancers without hormonal therapy. Majority of refractory cancer cases exhibited weak hXBP-1 expression. No allelic loss or gene mutations were found in the hXBP-1 region and its open reading frame, respectively, in the prostate cancer examined.

CONCLUSIONS

These results suggest that reduction of hXBP-1 expression may be a useful marker for prostate adenocarcinoma differentiation and progression.

Aneusomy of chromosomes 7, 8, and 17 and amplification of HER-2/neu and epidermal growth factor receptor in Gleason score 7 prostate carcinoma: a differential fluorescent in situ hybridization study of Gleason pattern 3 and 4 using tissue microarray

Recent evidence shows that the proportion of poorly differentiated prostate carcinoma (Gleason pattern [GP] 4/5) is a surrogate factor for biochemical failure after radical prostatectomy (RP). However, little is known about specific molecular and cytogenetic changes in this aggressive component of localized prostate cancer. We constructed a tissue microarray containing areas of GP 3 and 4 from formalin-fixed radical prostatectomy specimens of 39 patients with Gleason score 7 carcinoma (>or=50% GP 4), known pathologic staging parameters (stage < T3b), and biochemical failure data (mean follow-up, 30 months; range, 5 to 74 months). Interphase fluorescent in situ hybridization (FISH) was performed on 5-microm microarray sections using pericentromeric probes to chromosomes 7, 8, and 17 and probes for the HER-2/neu and epidermal growth factor receptor (EGFR) genes. Low-level amplification of HER-2/neu was found in 26% of cases (3 to 5 signals per nucleus, corrected for chromosome 17 aneusomy). Aneusomy of chromosomes 7, 8, and 17 was identified in 21%, 15%, and 5% of cases, respectively. All aberrations occurred almost exclusively in GP 4 carcinoma (8 of 8 aneusomies 7, 2 of 2 trisomies 17, 9 of 10 HER-2/neu amplifications, and 5 of 6 aneusomies 8; P < .001). The presence of HER-2/neu amplification was associated with high tumor volume (>2.0 cm(3), P = 0.004). Among patients with negative surgical margins, gain of chromosome 7 was associated with biochemical failure after RP (P =.004, log-rank). Amplification of the EGFR gene occurred in only 1 case (3%). Significant differences in HER-2/neu amplification and gain of chromosomes 7, 8, and 17 were detected between GP 4 prostate carcinoma and GP 3. The frequency of aberrations increased with tumor volume. Chromosome 7 abnormalities may play an important role in cancer progression in margin-negative patients. EGFR amplification was rare, suggesting that this oncogene is not altered at the gene copy number level.

The TMPRSS2 gene encoding transmembrane serine protease is overexpressed in a majority of prostate cancer patients: detection of mutated TMPRSS2 form in a case of aggressive disease

The serine protease TMPRSS2 gene expression was studied by in situ hybridization using benign prostatic hyperplasia and prostate cancer tissue samples from 32 patients. Expression of TMPRSS2 gene was higher in cancer cells than that in benign cells in 84% of the specimens containing both benign and malignant tissues. The TMPRSS2 mRNA level was significantly increased in poorly differentiated (p = 0.014, n = 7) and untreated (p = 0.022, n = 13) primary prostate adenocarcinomas compared to benign tissues. In addition, androgen-deprivation therapy significantly decreased the expression of TMPRSS2 in benign prostate tissue (p = 0.07), which is in accordance with the androgen-inducible expression of the gene. The gene copy number of TMPRSS2, analyzed by competitively differential PCR, was duplicated in the malignant cells of about 38% of the prostate cancer patients analyzed. Thus, the increase in the gene copy number is probably not the primary reason for the detected overexpression of the TMPRSS2 gene. Mutations in the TMPRSS2 gene were screened using DNA isolated from paraffin-embedded prostate cancer tissues from 9 patients with aggressive prostate cancer and from 9 patients with nonaggressive disease. Thirteen exons covering the coding region were checked using enzymatic mutation detection and direct sequencing. One patient with aggressive prostate cancer carried a deletion and a stop codon in exon 11, leading to inactivation of the serine protease domain in TMPRSS2.

A novel human cancer culture model for the study of prostate cancer

Research into molecular and genetic mechanisms underlying prostate carcinogenesis would be greatly advanced by in vitro models of prostate tumors representing primary tumors. We have successfully established an immortalized human prostate epithelial (HPE) cell culture derived from a primary tumor with telomerase. The actively proliferating early passaged RC-58T cells were transduced through infection with a retrovirus vector expressing the human telomerase catalytic subunit (hTERT). A high level of telomerase was detected in RC-58T/hTERT cells but not RC-58T cells. RC-58T/hTERT cells are currently growing well at passage 50, whereas RC-58T cells senesced at passage 7. RC-58T/hTERT cells exhibit transformed morphology. More importantly, these immortalized cells showed anchorage-independent growth as they formed colonies in soft agar and grew above the agar layer. Expression of androgen-regulated prostate specific gene NKX3.1 and epithelial specific cytokeratin 8 (CK8) but not prostate specific antigen (PSA) and androgen receptor was detected in RC-58T/hTERT cells. Prostate stem cell antigen (PSCA) and p16 were also expressed in this cell line. RC-58T/hTERT cells showed growth inhibition when exposed to retinoic acid and transforming growth factor (TGF)-beta1 known potent inhibitors of prostate epithelial cell growth. A number of chromosome alterations were observed including the loss of chromosomes Y, 3p, 10p, 17p, 18q and the gain of chromosomes 16 and 20. These results demonstrate that this primary tumor-derived HPE cell line retained its transformed phenotypes and should allow studies to elucidate molecular and genetic alterations involved in prostate cancer. This is the first documented case of an established human prostate cancer cell line from a primary tumor of a prostate cancer patient with telomerase.

Prostatic expression of hensin, a protein implicated in epithelial terminal differentiation

OBJECTIVES

Hensin induces terminal differentiation in rabbit kidney collecting tubule cells. Rabbit hensin and human DMBT1 result from alternative splicing of the same gene. The human DMBT1 gene is located on chromosome 10q25-26, a region often deleted in prostate cancer. In this study we examined the potential role of this gene in terminal differentiation of prostate, as well as its role in prostatic carcinogenesis.

METHODS

We searched for deletions of this gene in prostatic cells cultured from cancer and benign tissues using PCR and cDNA cloning. The expression of hensin/DMBT1 in cultured cells and during prostate development was characterized by immunochemistry.

RESULTS

No deletions of hensin/DMBT1 similar to those found in glioblastomas, lung and esophageal cancers were observed in prostate cancer or BPH cells. Hensin/DMBT1 protein was localized in intracellular vesicles of epithelial cells in neonatal and 6-week-old mouse prostates. By 6 weeks, hensin/DMBT1 began to localize in the basal lamina of the prostate and vas deferens. In matured 6-month-old prostates, there was extensive deposition of hensin/DMBT1 in the basal lamina.

CONCLUSIONS

There is no evidence that hensin/DMBT1 is implicated in prostatic carcinogenesis. The localization of hensin/DMBT1 during maturation raises the possibility that hensin/DMBT1 is involved in terminal differentiation of the prostate and vas deferens.

Expression of the developmental and oncogenic PAX2 gene in human prostate cancer

PURPOSE

In the human prostate cancer cell lines LNCaP, DU145 and PC3, 27 primary prostate cancers, 10 benign prostatic hyperplasia specimens and 5 normal prostates we investigated the expression pattern of PAX2, a member of the PAX family of developmental control genes. PAX2 is expressed at high levels in developing undifferentiated cells of the urogenital system and is repressed upon terminal differentiation with no expression in normal adult cells. It is also been shown to be a proto-oncogene in mice and is expressed in human renal cell carcinoma.

MATERIALS AND METHODS

PAX2 expression was assessed at the RNA level by reverse transcriptase-polymerase chain reaction and Southern blot analysis using specific sets of nucleotides. The expression pattern of PAX2 was reconfirmed at the protein level by immunofluorescence in the cell lines, and by Western blot analysis in primary human prostate cancers and benign prostatic tissue.

RESULTS

Using reverse transcription-polymerase chain reaction combined with Southern hybridization PAX2 expression was detected in 52% of primary cancers and all 3 cell lines. PAX2 expression in these samples was confirmed at a protein level using immunoblotting and immunofluorescence. PAX2 messenger RNA was not detected in any benign or normal prostatic samples. Immunoblotting of protein from benign prostatic hyperplasia samples confirmed the lack of expression of PAX2 protein.

CONCLUSIONS

The expression of PAX2 in prostate cancer compared to nonmalignant prostates is statistically significant (Fisher's exact test p = 0.0004). These results suggest a possible role for PAX2 in prostate cancer. Although previous studies have suggested a role for PAX2 for supporting proliferation in undifferentiated cells, no correlation of PAX2 expression with Gleason score was found in prostate cancer.

Suppression of tumorigenicity in the human prostate cancer cell line M12 via microcell-mediated restoration of chromosome 19

Previously we immortalized human, nontransformed prostate epithelial cells with SV40 large T-antigen (SV40TAg) and derived increasingly aggressive sublines from the immortalized line. The progression of the tumorigenic sublines to metastatic capacity was accompanied by the formation of an unbalanced translocation between chromosomes 16 and 19, resulting in loss of 19p and proximal 19q. To test whether the tumorigenic and/or metastatic phenotype was causally related to this genetic alteration, we restored a neo-tagged human chromosome 19 to M12 cells by microcell-mediated transfer and assessed their growth. In vitro, the resultant hybrids grew more slowly in monolayer culture and showed a significant reduction in anchorage-independent growth as compared to M12neo controls. In vivo, all mice (13/13) injected subcutaneously (SC) with control M12neo cells developed tumors after 9-15 days. In contrast, 9/15 mice injected SC with microcell-transferred chromosome 19 hybrid cells failed to form tumors, with 6/15 producing very small tumors after 120 days. Analysis of three of these six tumors showed consistent, new chromosomal changes. Furthermore, in one of the tumors, loss of a chromosome 19 was noted in 40% of the cells. After intraprostatic injections of the hybrid cells, only 2/7 mice developed microscopic tumors, with no metastases. These data suggest the presence of a gene or genes on chromosome 19 that function to suppress growth.

Genetic abnormalities specifically associated with varying metastatic potential of prostate cancer cell lines as detected by comparative genomic hybridization

Established recently are two in vivo prostate tumor progression models in which subclones of the PC3M and LNCaP cell lines were selected for varying growth characteristics and metastatic potential after successive orthotopic implantation in the prostate of nude mice. In this study, we used comparative genomic hybridization (CGH) to compare the chromosomal abnormalities between the parental cell lines and their respective variants and to determine if specific chromosomal abnormalities can be identified that are associated with different growth properties. PC3M and its derivative cell lines PC3M-Pro4 and PC3M-LN4 shared gains of 8q22--qter, 10q21--q22, and Xq27--qter and loss of 13q33--qter. PC3M-Pro4, a derivative line that produced significantly larger tumors in the prostate, had a unique gain of 3q13. In contrast, PC3M-LN4, the derivative line that produced significantly larger metastatic tumors in the lymph nodes and had higher incidences of distant metastases, had a specific gain of 1q21--q22 and losses of 10q23--qter and 18q12--q21. In the second in vivo model, LNCaP and its derivative cell lines shared gain of 3q27--qter and loss on 13q21--qter. The derivative line that produced significantly larger tumors in the prostate, LNCaP-Pro5, had a unique gain on 13q12--q13. In comparison, LNCaP-LN3, a derivative line that had a significantly higher incidence of lymph node metastases and produced significantly larger metastatic tumors in the lymph nodes, had specific losses of 16q23--qter and 21q. Interestingly, some regions of loss (e.g., 10q23-->qter, 16q23-->qter, and 18q12-->q21) detected in the variant cell lines correlated well with abnormalities seen in clinical prostate cancer cases. Thus, our data suggest not only that these cell lines are relevant in vivo models for prostate cancer progression, but also that CGH is a valuable tool for uncovering chromosomal regions that are important for aggressive growth and metastasis of prostate cancer cells.

Human cell lines as an in vitro/in vivo model for prostate carcinogenesis and progression

BACKGROUND

The study of prostate carcinogenesis and tumor progression is made difficult by the lack of appropriate in vitro and in vivo models. High prevalence of prostatic intra-epithelial neoplasia and latent prostatic carcinoma, representing multiple steps in carcinogenesis to invasive carcinoma, are relevant targets for cancer prevention. From the RWPE-1, immortalized, non-tumorigenic, human prostate epithelial cell line, we have derived four tumorigenic cell lines with progressive malignant characteristics.

METHODS

Cell lines were derived by exposure of RWPE-1 to N-methyl-N-nitrosourea (MNU), selected and cloned in vivo and in vitro, and characterized by prostatic epithelial and differentiation markers, karyotype analysis, anchorage-independent growth, invasiveness, tumorigenicity, and pathology of the derived tumors.

RESULTS

Cytokeratins 8 and 18, androgen receptor, and prostate-specific antigen expression in response to androgen, confirm prostatic epithelial origin. RWPE-1 cells do not grow in agar and are not tumorigenic in mice, but the growth, tumorigenicity, and tumor pathology of the MNU cell lines correlate with their invasive ability. The WPE1-NA22 (least malignant) form small, well-differentiated, and WPE1-NB26 cells (most malignant) form large, poorly differentiated, invasive tumors. Overall, loss of heterozygosity for chromosomes 7q, 13q, 18q, and 22, and gain of 5, 9q, 11q, and 20, was observed. The MNU cell lines, in order of increasing malignancy are; WPE1-NA22, WPE1-NB14, WPE1-NB11, and WPE1-NB26.

CONCLUSIONS

This family of cell lines with a common lineage represents a unique and relevant model which mimics stages in prostatic intra-epithelial neoplasia (PIN) and progression to invasive cancer, and can be used to study carcinogenesis, progression, intervention, and chemoprevention.

Hypermethylation of the caveolin-1 gene promoter in prostate cancer

BACKGROUND

Hypermethylation of CpG islands in the promoter regions of tumor suppressor genes is one mechanism of tumorigenesis. Caveolin-1 (Cav-1), a gene coding for the structural component of cellular caveolae, is involved in cell signaling and has been proposed to be a tumor suppressor gene in several malignancies. This gene maps to 7q31.1, a site known to be deleted in some prostate tumors. We chose to examine the methylation status of the promoter region of Cav-1 to determine whether this gene could function as a tumor suppressor in prostate cancer

METHODS

Genomic DNA from both tumor and normal prostate epithelial cells was obtained from paraffin-embedded prostate sections by laser capture microdissection (LCM). The methylation status of 24 CpG sites at the 5' promoter region of Cav-1 was analyzed by bisulfite-direct-sequencing after amplification by PCR using primers specific for bisulfate modified DNA. Immunohistochemistry staining with a cav-1-specific antibody was also performed to evaluate the expression of the gene

RESULTS

Twenty of the 22 (90.9%) informative cases showed promoter hypermethylation in the tumor cell population when compared with adjacent normal prostate cells with an average Methylation Index (potential frequency of total possible methylated Cs) from tumor cells equal to 0.426 vs. 0.186 for normal cells (P = 0.001). While no association with Gleason grade was found, overall increased methylation correlated with PSA failure (P = 0.016), suggestive of clinical recurrence. Elevated immunoreactivity with a Cav-1 antibody was observed in tumor cells from 7 of 26 prostate samples tested; this was associated with a Gleason score but not correlated with PSA failure or Methylation Index

CONCLUSIONS

CpG sites at the 5' promoter of Cav-1 are more methylated in tumor than in adjacent normal prostate cells. Hypermethylation of the Cav-1 promoter supports the notion that Cav-1 may function as a tumor suppressor gene in prostate cancer and evidence is presented suggesting that methylation status of this gene is not only a marker for cancer but also may be predictive of outcome.

A common deletion at chromosomal region 17q21 in sporadic prostate tumors distal to BRCA1

Prostate cancer is the most common cancer in males in the United States, yet the etiology of this disease is still poorly understood. In previous work from our laboratory, one or more deleted regions were found in prostate tumors distal to the breast and ovarian cancer susceptibility gene (BRCA1) on chromosome 17. This suggested that genes at 17q21 may play a pivotal role in prostate cancer progression, and there may be new tumor suppressor genes at this locus. We now present a physical map built with P1, P1 artificial chromosome, and bacterial artificial chromosome clones encompassing a DNA sequence anchored by multiple STS markers. The analysis of prostate tumors indicated an 85-kb novel commonly deleted interval flanked by D17S1184-D17S183-D17S1203-D17S1860, which is at least 470 kb distal to the BRCA1 gene. Fifty-four of 126 prostrate cancer cases (43%) showed a deletion by a direct FISH technique using P1 probes in this region. Searching with clone end sequences in the sequence database BLAST, the deleted clone covered genomic DNA sequence that contained upstream binding factor (UBF), EPB3 genes, SHCL1, ASB-4-like sequence, and acidic protein-like sequence. PCR for the ESTs confirmed that these genes or ESTs are within the deletion region. Our results will be helpful for finding candidate tumor suppressor genes in prostate cancer.

Molecular cytogenetic analysis of prostatic adenocarcinomas from screening studies : early cancers may contain aggressive genetic features

No objective parameters have been found so far that can predict the biological behavior of early stages of prostatic cancer, which are encountered frequently nowadays due to surveillance and screening programs. We have applied comparative genomic hybridization to routinely processed, paraffin-embedded radical prostatectomy specimens derived from patients who participated in the European Randomized Study of Screening for Prostate Cancer. We defined a panel consisting of 36 early cancer specimens: 13 small (total tumor volume (Tv) < 0.5 ml) carcinomas and 23 intermediate (Tv between 0.5-1.0 ml) tumors. These samples were compared with a set of 16 locally advanced, large (Tv > 2.0 ml) tumor samples, not derived from the European Randomized Study of Screening for Prostate Cancer. Chromosome arms that frequently (ie, > or = 15%) showed loss in the small tumors included 13q (31%), 6q (23%), and Y (15%), whereas frequent (ie, > or = 15%) gain was seen of 20q (15%). In the intermediate cancers, loss was detected of 8p (35%), 16q (30%), 5q (26%), Y (22%), 6q, and 18q (both 17%). No consistent gains were found in this group. In the large tumors, loss was seen of 13q (69%), 8p (50%), 5q, 6q (both 31%), and Y (15%). Gains were observed of 8q (37%), 3q (25%), 7p, 7q, 9q, and Xq (all 19%). Comparison of these early, localized tumors with large adenocarcinomas showed a significant increase in the number of aberrant chromosomes per case (Rs = 0.36, P = 0.009). The same was true for the number of lost or gained chromosomes per case (Rs = 0.27, P: = 0.05; Rs = 0.48, respectively; P < 0.001). Interestingly, chromosomal alterations that were found in previous studies to be potential biomarkers for tumor aggressiveness, ie, gain of 7pq and/or 8q, were already distinguished in the small and intermediate cancers. In conclusion, our data show that chromosomal losses, more specifically of 6q and 13q, are early events in prostatic tumorigenesis, whereas chromosomal gains, especially of 8q, appear to be late events in prostatic tumor development. Finally, early localized tumors, as detected by screening programs, harbor cancers with aggressive genetic characteristics.