DNA heterogeneity determined by flow cytometry in prostatic adenocarcinoma--necessitating multiple site analysis

Exploring the intratumoral heterogeneity of DNA ploidy in prostate cancer

BACKGROUND

Prostate cancer is morphologically and molecularly heterogeneous. Genomic heterogeneity might be mirrored by variability in DNA ploidy. Aneuploidy is a hallmark of genomic instability and associated with tumor aggressiveness. Little attention has been paid to the biological significance of the diploid tumor cell population that often coexists with aneuploid populations. Here, we investigated the role of DNA ploidy in tumor heterogeneity and clonal evolution.

METHODS

Three radical prostatectomy specimens with intratumoral heterogeneity based on nuclear features on H&E were selected. DNA content of each subpopulation was determined by DNA image cytometry and silver in situ hybridization (SISH). Genomic evolution was inferred from array comparative genomic hybridization (aCGH). Additionally, immunohistochemistry was used to examine the stemness-associated marker ALDH1A1.

RESULTS

Nuclear morphology reliably predicted DNA ploidy status in all three cases. In one case, aCGH analysis revealed several shared deletions and one amplification in both the diploid and the aneuploid population, suggesting that these populations could be related. In the other two cases, a statement about relatedness was not possible. Furthermore, ALDH1A1 was expressed in 2/3 cases and exclusively observed in their diploid populations.

CONCLUSIONS

In this proof-of-concept study, we demonstrate the feasibility to predict the DNA ploidy status of distinct populations within one tumor by H&E morphology. Future studies are needed to further investigate the clonal relationship between the diploid and the aneuploid subpopulation and test the hypothesis that the aneuploid population is derived from the diploid one. Finally, our analyses pointed to an enrichment of the stemness-associated marker ALDH1A1 in diploid populations, which warrants further investigation in future studies.

[Cell ploidy: predictive factor of locally advanced prostate cancer]

OBJECTIVE

This study was designed to demonstrate that the study of cell ploidy on biopsies of clinically localized prostate cancers can contribute to the diagnosis of a tumour extending beyond the prostatic capsule and can complete imaging for local staging.

METHODS

Analysis of the histological results of 140 patients operated for clinically localized prostate cancer distinguished two groups of patients in whom the initial tumour was Gleason score 6 or 7. The first group was composed of 33 patients whose tumour was classified as pT3 and the second group was composed of 24 patients whose tumour was classified as pT2. The cell ploidy study was performed on biopsies and operative specimens in the two groups.

RESULTS

In the pT3N0M0 group, 72% of tumours presented an aneuploid contingent versus 16% of tumours of the pT2N0M0 group. A strong correlation was demonstrated between cell ploidy and tumour stage (p = 0.0002) and a highly significant correlation was observed between tumour stage and the presence of a tumour contingent with ploidy greater than 5C (p = 0.0009).

CONCLUSION

The presence of an aneuploid contingent on biopsies of clinically localized prostate cancer significantly increases the risk of a more advanced tumour. This technique could therefore constitute a simple complementary tool in the staging of prostate cancer in combination with transrectal MRI, but this needs to be confirmed by other studies.

The significance of tumor heterogeneity for prediction of DNA ploidy of prostate cancer

OBJECTIVE

In a previous study, we mapped the ploidy heterogeneity of prostate cancer using flow cytometry in 676 tumor samples from 50 radical prostatectomy specimens. Ploidy heterogeneity was common (42% of tumors) and was found in all non-diploid tumors. The volume of non-diploid tumor was estimated and found to predict extra-prostatic extension and seminal vesicle invasion. The aim of this study was to evaluate the impact of tumor heterogeneity on preoperative ploidy assessment.

MATERIAL AND METHODS

In 50 men at least six core biopsies were taken before prostatectomy. Sections from biopsies with cancer were Feulgen-stained for image cytometry. After exclusion of biopsies with insufficient material, 123 histograms from 48 men (mean 2.6; range 1-7) remained for analysis.

RESULTS

In 32 men, biopsies were diploid. In 16 men, at least one biopsy was non-diploid (14 tetraploid, two aneuploid) and 10 of them also had diploid biopsies. In 34 men (71%), the prostatectomy specimens were correctly predicted as being either diploid (48%) or non-diploid (23%). The sensitivity and specificity of biopsies for predicting non-diploid cancer were 55% and 82%, respectively, and the positive and negative predictive values were 69% and 72%, respectively. The ploidy status of tumors with and without ploidy heterogeneity was correctly predicted in 55% and 82% of cases, respectively (p=0.04). Biopsies underestimated ploidy in 9/20 tumors (45%) with heterogeneous ploidy status. Underestimation mainly occurred when one or two cores were analyzed.

CONCLUSIONS

Preoperative prediction of the ploidy status of prostate cancer is hampered by tumor heterogeneity. Analysis of multiple biopsies is important for correct preoperative ploidy estimation.

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.

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.

Androgen receptor expression and DNA content of paraffin-embedded archival human prostate tumors

BACKGROUND

Androgen receptors (AR) are expressed in human prostate cells and immunohistochemistry has been used for qualitative analysis of AR expression in prostate tumor cells. Quantitative and multiparametric analysis of receptor expression could be of diagnostic and prognostic value in the management of patients on antiandrogen therapy. Multiparametric flow cytometric methods have been developed for analysis of hormone receptor expression and DNA content in nuclei isolated from formalin-fixed/paraffin-embedded human solid tumors. The present study was undertaken for analysis of AR expression and DNA content in archival human prostate tumors.

METHODS

AR expression and DNA content were measured in nuclei isolated by enzyme digestion from thick sections cut from 51 paraffin-embedded human prostate tumors. AR expression in different subpopulations was studied by gated analysis. The relationship among AR activity, DNA content, and histopathological grade was analyzed.

RESULTS

Distinct aneuploid populations were observed in 23% of tumors examined. AR activity was observed in all the specimens and the percentage of AR- positive nuclei in the 48 samples analyzed was <10% (n = 4), 11-50% (n = 39), and >51% (n = 5). Tumor subpopulations with aneuploid DNA content had higher AR expression (percent AR-positive cells and mean log fluorescence) than the diploid subpopulations. No strong correlation was seen between AR expression and histopathological grade of the tumors.

CONCLUSIONS

Flow cytometric analysis of archival prostate tumor can be used for rapid determination of aneuploid DNA content and AR expression in subpopulations of nuclei isolated from formalin-fixed/paraffin-embedded prostate tumor blocks.

Impact of different variables on the outcome of patients with clinically confined prostate carcinoma: prediction of pathologic stage and biochemical failure using an artificial neural network

BACKGROUND

The advent of advanced computing techniques has provided the opportunity to analyze clinical data using artificial intelligence techniques. This study was designed to determine whether a neural network could be developed using preoperative prognostic indicators to predict the pathologic stage and time of biochemical failure for patients who undergo radical prostatectomy.

METHODS

The preoperative information included TNM stage, prostate size, prostate specific antigen (PSA) level, biopsy results (Gleason score and percentage of positive biopsy), as well as patient age. All 309 patients underwent radical prostatectomy at the University of Colorado Health Sciences Center. The data from all patients were used to train a multilayer perceptron artificial neural network. The failure rate was defined as a rise in the PSA level > 0.2 ng/mL. The biochemical failure rate in the data base used was 14.2%. Univariate and multivariate analyses were performed to validate the results.

RESULTS

The neural network statistics for the validation set showed a sensitivity and specificity of 79% and 81%, respectively, for the prediction of pathologic stage with an overall accuracy of 80% compared with an overall accuracy of 67% using the multivariate regression analysis. The sensitivity and specificity for the prediction of failure were 67% and 85%, respectively, demonstrating a high confidence in predicting failure. The overall accuracy rates for the artificial neural network and the multivariate analysis were similar.

CONCLUSIONS

Neural networks can offer a convenient vehicle for clinicians to assess the preoperative risk of disease progression for patients who are about to undergo radical prostatectomy. Continued investigation of this approach with larger data sets seems warranted.

Stage B Prostate Cancer: Correlation of DNA Ploidy Analysis With Histological and Clinical Parameters

BACKGROUND: The ability to accurately predict tumor behavior and patient survival is a problem in managing patients with prostate cancer. Prognostic variables in predicting death from tumor include prostate-specific antigen (PSA) level, histological grade, and clinical stage. Observer subjectivity is inherent in determining grade and stage; thus, criteria that are more objective are needed to identify patients for appropriate treatment. METHODS: The authors correlated flow cytometric nuclear DNA ploidy with Gleason score, PSA level, and recurrence risk in patients who underwent radical retropubic prostatectomy and bilateral pelvic lymphadenectomy between 1987 and 1993 for histopathologic stage B prostate cancer (T2, N0, M0). RESULTS: Of the tumors analyzed, 64% were DNA diploid with a low proliferative fraction, 25% were DNA diploid with a high proliferative fraction, and 11% were DNA aneuploid. DNA aneuploidy was associated with high Gleason grade (7-10). All Gleason grade 10 tumors were DNA aneuploid. Both DNA aneuploidy and high proliferative fraction (S+G2M) were statistically correlated with high Gleason grade and adverse prognosis but not with PSA level or patient age. CONCLUSIONS: A direct relationship is shown between both DNA aneuploidy and a high proliferation index with aggressive biological behavior in stage B prostatic cancer. Objective tumor criteria are needed to choose treatment more selectively for individual patients.

Study of free and complexed prostate-specific antigen in mice bearing human prostate cancer xenografts

BACKGROUND

Our objective was to evaluate five preclinical prostate cancer (CaP) xenograft models to determine whether (1) prostate-specific antigen (PSA) formed complexes in murine serum, (2) the percentage of free PSA (f-PSA) was characteristic of a given xenograft line, and (3) the percentage of f-PSA was similar to that in the patient at time of tumor harvest. Our fourth objective was to identify which murine serpin(s) bind(s) to PSA in vivo.

METHODS

Xenografts were established from metastatic foci. The percentage of f-PSA, and total PSA (t-PSA) in serum of animals bearing CaP xenografts was determined by immunoassay. Size exclusion high-performance liquid chromatography and Western blots were used to evaluate the presence of PSA complexes in murine serum. Edman degradation was used to determine the N-terminal sequence of complexed proteins.

RESULTS

PSA was detected as both free and complexed forms in murine serum from all mice bearing the CaP xenografts. Three xenografts (related sublines) produced PSA that resulted in low mean percentages of f-PSA (1.9-6.4%). In sera from the other two xenografts, the mean percentages of f-PSA were high (>25%); patient sera, where available at time of tumor acquisition, were in agreement. Western blots showed that murine protease inhibitors formed complexes with PSA. Edman degradation yielded a sequence with 80% homology over 15 amino acids with that of murine alpha1-protease inhibitor (alpha1-PI).

CONCLUSIONS

Our data have shown that the majority of PSA secreted by these CaP xenografts complexes in murine serum with a protease inhibitor with high homology to murine alpha1-PI and that the percentage of f-PSA is a characteristic of each xenograft line tested, which is in agreement with patient values at time of tumor harvest. These CaP xenografts offer opportunities for study of human PSA biology and phenomenology.

Molecular heterogeneity in prostate cancer: can TP53 mutation unravel tumorigenesis?

While prostate cancer is the most common malignant visceral neoplasm of men, its etiology remains largely unknown and its clinical course unpredictable. Molecular genetics of prostate cancer has become a fruitful area of investigation and might provide clues to understanding these phenomena. Mutation of the TP53 tumor suppressor gene (encoding the p53 protein) has been commonly reported as a critical event in human carcinogenesis, but recent findings in prostate cancer research call into question the correlation between TP53 mutation and prognosis for patients with this tumor. Whole-mount analysis has begun to address the histologic significance of the focal evolution of TP53 mutation in a pre-existing cancer and to reveal its role throughout the process of tumor progression. This model might also apply to other tumors.

The cellular basis of tumor progression

Variability in disease presentation and course is a hallmark of cancer. Variability is seen among similarly diagnosed cancers in different patients or animal hosts and in the same cancer at different periods of time. This latter type of variability, termed "tumor progression," was defined by Foulds in a series of six rules that describe the independent behavior of individual cancers and the independent evolution of different cancer characteristics. Tumor progression is believed to result from variability among subpopulations of tumor cells within individual cancers and from selection of these subpopulations by conditions within the cancer environment, such that different subpopulations come to prominence over the course of cancer development and growth. Interactions among subpopulations, however, modulate tumor behavior as well as tumor evolution. The leading hypothesis for the origin of tumor subpopulations is the genetic instability of cancer cells. There are a number of possible mechanisms of genetic instability, some internal to cancer cells (mutation, amplification, mutator phenotypes, DNA repair deficiencies) and some present in the tumor microenvironment (endogenous mutagens). There are also potential epigenetic mechanisms of variability, including alterations in gene regulation, differentiation, adaptation, and cell fusion. Regardless of mechanism, the heterogeneity of tumor subpopulations poses a number of challenges to the practice of cancer research, including the design of reproducible and meaningful experiments. Tumor heterogeneity also has significant consequences for the clinical assessment of tumor prognosis and the development of effective treatment regimens.

A DNA cytometric proliferation index improves the value of the DNA ploidy pattern as a prognosticating tool in patients with carcinoma of the prostate

OBJECTIVES

A still controversial issue is whether the results of a cytometric assessment of the DNA distribution pattern of the nuclei of the neoplastic parenchymal cells of a prostatic adenocarcinoma has additional prognostic value to that of the stage and grade of the disease. To increase the accuracy of the DNA ploidy assessments. Image cytometry (ICM) has been used and combined with the determination of an ICM proliferation index (PI) to increase its value as an additional prognosticating tool.

METHODS

We investigated 96 patients, followed up since diagnosis in 1980/1981 until death or, in 11 surviving patients, for an average of 14.5 years. Survival analysis was made by the conventional Kaplan-Meier method. Fine-needle aspiration biopsy was used as the major diagnostic tool. The neoplastic cell nuclei were classified as ICM DNA diploid, tetraploid, or aneuploid by means of the ploidy-establishing peak in the ICM DNA histograms, as well as the fraction of tumor cells in the S-phase. Scattered cells to the right of the ploidy-establishing peak, the S-phase fraction, and those in the G2M area of the ICM DNA histograms were counted as percent of the total number of tumor cells; this percentage was defined as the PI. Arbitrarily, tumors with a PI less than 5% were classified as having a low proliferation rate, those with a PI greater than 10% were considered highly proliferating, and those with a PI between 5% and 10% as carcinomas with an intermediate proliferation potency.

RESULTS

By univariate analyses, clinical stage, cytodiagnostic grade, cytometric DNA ploidy pattern and PI all had significant prognostic value. By multivariate analyses, the PI was found to add prognostic information to that of the ICM DNA ploidy pattern variable, giving it an increase in its statistical P value from 0.002 to 0.0005. As a consequence, the combination of these two variables was found to give rise to three new patient groups with regards to their prognosis: DNA group I had tumors with a diploid ICM DNA pattern with a low PI; DNA group II had tumors with a diploid or tetraploid ICM DNA tumor cell nuclei pattern with an intermediate PI; and DNA group III had a diploid or tetraploid ICM DNA pattern with high PI and all tumors with an aneuploid pattern. By multivariate analysis, including tumor grade and clinical stage, these new DNA groups (P = 0.0004) and M stage disease (P = 0.0006) were the only significant prognostic variables.

CONCLUSIONS

A DNA cytometric PI improves the prognosticating value of DNA ploidy. Patients with prostatic adenocarcinomas, classified as DNA group I, have a low risk of death from their neoplastic disease with deferred or hormonal treatment only.

Intratumoral nuclear morphologic heterogeneity in prostate cancer

OBJECTIVES

Tumor heterogeneity can be measured by quantifying variance of nuclear characteristics by image analysis. Heterogeneity of cell nuclear features correlated with increased local progression in prostate cancer. In the present study, the influence of tumor heterogeneity on prostate-specific antigen (PSA) recurrence after radical retropubic prostatectomy was analyzed and tumor heterogeneity was compared in patients with and without neoadjuvant hormonal therapy.

METHODS

Retrospectively, radical prostatectomy material of 44 patients without and 12 patients with neoadjuvant hormonal treatment with a postoperative follow-up of at least 4 years was studied. Each prostatectomy specimen was systematically embedded in paraffin, and each tumor area within the prostate was marked and analyzed by an image analysis system for 32 nuclear features comprising nuclear shape, size, DNA content, and chromatin pattern. Several clinical features were available: preoperative serum PSA, hemoglobin concentration, Karnofsky score, tumor stage, and Gleason score.

RESULTS

Increased tumor heterogeneity, as expressed by differences in karyometric values between tumor areas in nuclear shape and chromatin pattern within the tumor, was significantly correlated with earlier PSA recurrence rate. As compared with nonpretreated patients, hormonally pretreated specimens showed smaller and less heterogeneous tumors. In particular, chromatin pattern heterogeneity was decreased in patients who underwent preoperative hormonal treatment compared with patients who were not pretreated. However, decreased heterogeneity was accompanied by a higher percentage of aneuploid areas per tumor in the pretreated patients. Cox regression analysis showed that karyometric determination of nuclear shape heterogeneity in combination with preoperative PSA level could predict time to PSA recurrence after radical prostatectomy in patients without hormonal pretreatment.

CONCLUSIONS

Increase in karyometric tumor heterogeneity in nuclear shape and chromatin pattern was correlated with a shorter PSA recurrence-free interval after radical prostatectomy. Preoperative PSA and karyometric tumor heterogeneity were the best predictors of PSA recurrence in a multivariate analysis. Intratumoral heterogeneity was decreased in patients with prostate cancer who underwent neoadjuvant hormonal therapy.