Morphometrically estimated variation in nuclear size. A useful tool in grading prostatic cancer

Reduction in Nuclear Size by DHRS7 in Prostate Cancer Cells and by Estradiol Propionate in DHRS7-Depleted Cells

Increased nuclear size correlates with lower survival rates and higher grades for prostate cancer. The short-chain dehydrogenase/reductase (SDR) family member DHRS7 was suggested as a biomarker for use in prostate cancer grading because it is largely lost in higher-grade tumors. Here, we found that reduction in DHRS7 from the LNCaP prostate cancer cell line with normally high levels of DHRS7 increases nuclear size, potentially explaining the nuclear size increase observed in higher-grade prostate tumors where it is lost. An exogenous expression of DHRS7 in the PC3 prostate cancer cell line with normally low DHRS7 levels correspondingly decreases nuclear size. We separately tested 80 compounds from the Microsource Spectrum library for their ability to restore normal smaller nuclear size to PC3 cells, finding that estradiol propionate had the same effect as the re-expression of DHRS7 in PC3 cells. However, the drug had no effect on LNCaP cells or PC3 cells re-expressing DHRS7. We speculate that separately reported beneficial effects of estrogens in androgen-independent prostate cancer may only occur with the loss of DHRS7/ increased nuclear size, and thus propose DHRS7 levels and nuclear size as potential biomarkers for the likely effectiveness of estrogen-based treatments.

A Cell-Free Assay Using Xenopus laevis Embryo Extracts to Study Mechanisms of Nuclear Size Regulation

A fundamental question in cell biology is how cell and organelle sizes are regulated. It has long been recognized that the size of the nucleus generally scales with the size of the cell, notably during embryogenesis when dramatic reductions in both cell and nuclear sizes occur. Mechanisms of nuclear size regulation are largely unknown and may be relevant to cancer where altered nuclear size is a key diagnostic and prognostic parameter. In vivo approaches to identifying nuclear size regulators are complicated by the essential and complex nature of nuclear function. The in vitro approach described here to study nuclear size control takes advantage of the normal reductions in nuclear size that occur during Xenopus laevis development. First, nuclei are assembled in X. laevis egg extract. Then, these nuclei are isolated and resuspended in cytoplasm from late stage embryos. After a 30 - 90 min incubation period, nuclear surface area decreases by 20 - 60%, providing a useful assay to identify cytoplasmic components present in late stage embryos that contribute to developmental nuclear size scaling. A major advantage of this approach is the relative facility with which the egg and embryo extracts can be biochemically manipulated, allowing for the identification of novel proteins and activities that regulate nuclear size. As with any in vitro approach, validation of results in an in vivo system is important, and microinjection of X. laevis embryos is particularly appropriate for these studies.

New Insights into Mechanisms and Functions of Nuclear Size Regulation

Nuclear size is generally maintained within a defined range in a given cell type. Changes in cell size that occur during cell growth, development, and differentiation are accompanied by dynamic nuclear size adjustments in order to establish appropriate nuclear-to-cytoplasmic volume relationships. It has long been recognized that aberrations in nuclear size are associated with certain disease states, most notably cancer. Nuclear size and morphology must impact nuclear and cellular functions. Understanding these functional implications requires an understanding of the mechanisms that control nuclear size. In this review, we first provide a general overview of the diverse cellular structures and activities that contribute to nuclear size control, including structural components of the nucleus, effects of DNA amount and chromatin compaction, signaling, and transport pathways that impinge on the nucleus, extranuclear structures, and cell cycle state. We then detail some of the key mechanistic findings about nuclear size regulation that have been gleaned from a variety of model organisms. Lastly, we review studies that have implicated nuclear size in the regulation of cell and nuclear function and speculate on the potential functional significance of nuclear size in chromatin organization, gene expression, nuclear mechanics, and disease. With many fundamental cell biological questions remaining to be answered, the field of nuclear size regulation is still wide open.

cPKC regulates interphase nuclear size during Xenopus development

During Xenopus development, increased nuclear cPKC activity and decreased nuclear association of lamins mediate nuclear scaling.

Dramatic changes in cell and nuclear size occur during development and differentiation, and aberrant nuclear size is associated with many disease states. However, the mechanisms that regulate nuclear size are largely unknown. A robust system for investigating nuclear size is early Xenopus laevis development, during which reductions in nuclear size occur without changes in DNA content. To identify cellular factors that regulate nuclear size during development, we developed a novel nuclear resizing assay wherein nuclei assembled in Xenopus egg extract become smaller in the presence of cytoplasmic interphase extract isolated from post-gastrula Xenopus embryos. We show that nuclear shrinkage depends on conventional protein kinase C (cPKC). Increased nuclear cPKC localization and activity and decreased nuclear association of lamins mediate nuclear size reductions during development, and manipulating cPKC activity in vivo during interphase alters nuclear size in the embryo. We propose a model of steady-state nuclear size regulation whereby nuclear expansion is balanced by an active cPKC-dependent mechanism that reduces nuclear size.

Mechanisms of nuclear size regulation in model systems and cancer

Changes in nuclear size have long been used by cytopathologists as an important parameter to diagnose, stage, and prognose many cancers. Mechanisms underlying these changes and functional links between nuclear size and malignancy are largely unknown. Understanding mechanisms of nuclear size regulation and the physiological significance of proper nuclear size control will inform the interplay between altered nuclear size and oncogenesis. In this chapter we review what is known about molecular mechanisms of nuclear size control based on research in model experimental systems including yeast, Xenopus, Tetrahymena, Drosophila, plants, mice, and mammalian cell culture. We discuss how nuclear size is influenced by DNA ploidy, nuclear structural components, cytoplasmic factors and nucleocytoplasmic transport, the cytoskeleton, and the extracellular matrix. Based on these mechanistic insights, we speculate about how nuclear size might impact cell physiology and whether altered nuclear size could contribute to cancer development and progression. We end with some outstanding questions about mechanisms and functions of nuclear size regulation.

Mechanisms of intracellular scaling

Cell size varies widely among different organisms as well as within the same organism in different tissue types and during development, which places variable metabolic and functional demands on organelles and internal structures. A fundamental question is how essential subcellular components scale to accommodate cell size differences. Nuclear transport has emerged as a conserved means of scaling nuclear size. A meiotic spindle scaling factor has been identified as the microtubule-severing protein katanin, which is differentially regulated by phosphorylation in two different-sized frog species. Anaphase mechanisms and levels of chromatin compaction both act to coordinate cell size with spindle and chromosome dimensions to ensure accurate genome distribution during cell division. Scaling relationships and mechanisms for many membrane-bound compartments remain largely unknown and are complicated by their heterogeneity and dynamic nature. This review summarizes cell and organelle size relationships and the experimental approaches that have elucidated mechanisms of intracellular scaling.

Organ-specific enhancement of metastasis by spontaneous ploidy duplication and cell size enlargement

Aneuploidy is commonly observed in breast cancer and is associated with poor prognosis. One frequent type of aneuploidy, hypertetraploidy, may derive from ploidy duplication of hyperdiploid cells. However, the pathological consequences of ploidy duplication in breast cancer progression have not been characterized. Here, we present an experimental system demonstrating spontaneous appearance of hypertetraploid cells from organ-specific metastatic variants of the MDA-MB-231 breast cancer cell line through ploidy duplication in vitro and in vivo. The hypertetraploid progenies showed increased metastatic potential to lung and brain, but not to bone, which may be partially explained by the distinct capillary structures in these organs that confer differential lodging advantages to tumor cells with enlarged size. Our results suggest a potential mechanistic link between ploidy duplication and enhancement of metastatic potentials, as was observed in previous clinical studies of breast cancer.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Prognostic value of DNA ploidy and nuclear morphometry in prostate cancer treated with androgen deprivation

OBJECTIVES

To assess the prognostic value of flow cytometry and nuclear morphometry in prostate cancer after androgen deprivation treatment.

METHODS

A total of 127 patients with a prostate cancer diagnosis who had undergone androgen suppression were retrospectively studied. The DNA content by flow cytometry and nuclear morphometry was studied from biopsy specimens. In the patients with Stage M0, two multivariate analyses by the Cox proportional regression model were performed to determine whether the experimental variables (DNA content and nuclear area) added independent information to the classic prognostic factors (Gleason score and stage). Using the statistical analysis results, risk groups were created.

RESULTS

T and M categories, Gleason score, DNA ploidy, and mean nuclear area proved to have prognostic value in the univariate analysis. For the group of patients free of metastasis (M0), it was possible to create low, intermediate, and high-risk groups using stage and Gleason score with statistically significant differences in survival. Multivariate analysis, combining the classic and experimental variables, selected Gleason score and DNA content as prognostic independent factors. Also, risk groups with statistically significant differences in survival were created. However, the net result of combining both kinds of factors was at least as valuable as the combination of stage and Gleason score in predicting survival.

CONCLUSIONS

The determination of DNA ploidy and mean nuclear area do not add enough independent information to improve the predictive value to justify their use in this group of patients treated with hormonal therapy.

Analysis of the mechanism of discrepant nuclear morphometric results comparing preoperative biopsy and prostatectomy specimens

OBJECTIVES

To explore the mechanism for the differing nuclear morphometric results between needle biopsy and surgical specimens of the prostate.

METHODS

In experiment 1, a comparison of mean nuclear area (MNA), volume-weighted mean nuclear volume (MNV), and form factor (FF) for prostatic epithelial cells was performed between preoperative needle biopsy and prostatectomy specimens from 5 patients with benign prostatic hyperplasia (BPH). In experiment 2, a scheduled, sequential ex vivo needle sampling from the enucleated prostates (at 0, 2, 6, and 24 hours after surgical resection) was also performed for 7 patients with BPH. The prostatectomy specimens were left unfixed for 2 hours until the second needle sampling was done. Nuclear morphometric parameters were measured on the needle-sampled as well as on the prostatectomy specimens.

RESULTS

MNA, MNV, and FF of BPH cells measured on preoperative biopsy specimens were smaller than those of surgical specimens in all 5 of the cases. The results of nuclear morphometry on the materials obtained by ex vivo needle sampling of prostates before and during fixation revealed that the MNA, MNV, and FF for BPH cells of 0-hour specimens were significantly smaller than those for needle samples at 2, 6, and 24 hours after surgical resection as well as those for prostatectomy specimens.

CONCLUSIONS

The present study provided further evidence that the ischemic damage caused by delayed fixation could result in a substantial change of the nuclear morphology of prostate cells. An immediate start, as well as a rapid completion, of the fixation procedure seems critical for an accurate nuclear morphometry of prostatectomy specimens.

Prognostic value of nuclear morphometry on needle biopsy from patients with prostate cancer: is volume-weighted mean nuclear volume superior to other morphometric parameters?

OBJECTIVES

To compare the prognostic value of stereologically estimated volume-weighted mean nuclear volume (MNV) with other nuclear morphometric parameters using pretreatment needle-biopsy specimens of prostate cancer.

METHODS

The MNV, mean nuclear area, form factor, and coefficients of variation for nuclear area (VNA) and form factor were measured on pretreatment needle biopsy specimens from 66 patients with prostate cancer (clinical Stage B, n = 9; Stage C, n = 14; and Stage D, n = 43), all of whom underwent androgen deprivation therapy. The prognostic value of those morphometric parameters, as well as Gleason score and clinical stage, was examined in terms of cause-specific patient survival using univariate and multivariate analysis (Cox proportional hazard model).

RESULTS

Univariate analysis of the nuclear morphometric parameters revealed that MNV, mean nuclear area, VNA, coefficient of variation for form factor, and clinical stage were significant prognostic factors for cause-specific patient survival. However, when the patients with Stage D disease were selectively analyzed for survival, only the VNA was a significant prognostic parameter. Furthermore, the multivariate analysis, including the morphometric parameters, clinical stage, and Gleason score revealed that only VNA and clinical stage were independent variables.

CONCLUSIONS

The present comparative study could not demonstrate any prognostic superiority of MNV over other nuclear morphometric parameters in patients with prostate cancer.

Comparison of nuclear morphometric results between needle biopsy and surgical specimens from patients with prostate cancer

OBJECTIVES

To compare nuclear morphometric values and Gleason scores between biopsy and radical prostatectomy specimens in patients with clinically localized prostate cancer.

METHODS

The mean nuclear area (MNA), volume-weighted mean nuclear volume (MNV), and form factor (FF) were measured on the 18-gauge needle biopsy and radical prostatectomy specimens of 25 patients with clinically localized prostate cancer. The correlation between biopsy and surgical specimens was investigated for MNA, MNV, FF, and Gleason scores.

RESULTS

The average values for the MNA, MNV, and FF of the biopsy specimens (36.2 microm2, 366 microm3, and 0.86, respectively) were significantly smaller than those of the prostatectomy specimens (51.4 microm2, 646 microm3, and 0.91) by Student's paired t test. The Pearson correlation of morphometric parameters between the biopsy and surgical specimens was significant only for FF. A comparison of histologic grading between the biopsy and surgical specimens revealed identical Gleason scores in 32% and identical grades (on a three-grade system) in 68% of all the cases.

CONCLUSIONS

Discrepant nuclear morphometric results were observed between biopsy and surgical specimens of localized prostate cancer. The reason for such differing results is unclear but may be caused by artifacts associated with tissue sampling and processing. It is recommended that data obtained by biopsy should be considered separately from that obtained from surgical specimens.

High and low risk prostate carcinoma determined by histologic grade and proliferative activity

BACKGROUND

Histologic grade of differentiation is a strong prognostic factor for prostate carcinoma. However, most tumors fall in the intermediate group. Nuclear and nucleolar morphometry and analysis of the argyrophilic nucleolar organizer regions (AgNORs) were performed to improve prognosis, especially for patients with intermediate histologic grade tumors.

METHODS

Core needle biopsies from 65 patients with primary prostate carcinoma at diagnosis were studied. Patients received only hormone therapy. Formalin fixed and paraffin embedded sections were stained with the method of Ploton. The mean AgNOR count was calculated in 100 tumor cells for each case. Nuclear and nucleolar areas from 100 cells were measured with an automated image analyzer. One-way analysis of variance and uni- and multivariate survival analyses were used for statistical evaluation.

RESULTS

In the whole series, World Health Organization (WHO) tumor grade, nuclear and nucleolar areas, and AgNOR counts were correlated with survival time. By multivariate analysis, only AgNOR counts retained independent prognostic significance. In WHO Grade 2 carcinoma, the 5-year survival rate for patients with AgNOR/cell < or = 7.84 was 77%, but was only 12% for those with higher counts (P < 0.0001). These survival rates were similar to those obtained when patients with WHO Grade 1 carcinoma and Grade 2 carcinoma plus low AgNOR counts were compared with patients with Grade 3 carcinoma and Grade 2 carcinoma plus high AgNOR counts. In Gleason intermediate Grade 6 and 7 carcinomas, the 5-year survival rate for patients with AgNOR/cell < or = 7.84 was 71%, but was only 7% for those having higher counts (P = 0.0001).

CONCLUSIONS

Nuclear and nucleolar areas, as well as AgNOR counts, supplement histologic grading in the prognostic assessment of prostate carcinoma in patients receiving only hormone therapy. AgNOR count also is a prognostic factor for patients with intermediate grade tumors. The combination of histologic grade and proliferative activity allows the stratification of patients into low and high risk groups.

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.

Nuclear morphometry is of independent prognostic value only in T1 prostatic adenocarcinomas

A series of 325 patients with prostatic adenocarcinoma followed-up for over 13 years was subjected to histomorphometric analysis for the following prognostic factors: the Gleason score and 10 nuclear morphometric factors (mean nuclear area, nuclear perimeter, shortest and longest nuclear axis, form factor and their SDs), using the IBAS 1&2 image analyzer. Nuclear factors, Gleason score (P = 0.0013-0.0148), and T-category (P = 0.004-0.0107) were significantly interrelated, while the M-category was independent of the morphometric parameters. Nuclear factors (P = 0.0003-0.5), Gleason score (P < 0.0001), T-category (P < 0.0001) and M-category (P < 0.0001) predicted the disease outcome. In T1-2M0 tumors, the T-category (P = 0.0001), Gleason score (P < 0.0001), SD of nuclear area (P = 0.057), SD of nuclear perimetry (P = 0.039), mean shortest nuclear axis (P = 0.030), SD of the shortest nuclear axis (P = 0.0045), SD of the longest nuclear axis (P = 0.009), and nuclear form factor (P = 0.0123) were significant prognostic factors. In the multivariate survival analysis, the nuclear area had independent prognostic significance only in T1 tumors, whereas in other subcategories, the clinical stage, Gleason score, and patient age included all the available prognostic information. The results indicate that nuclear morphometric measurements are of borderline significance only in evaluating the intrinsic malignancy of prostatic adenocarcinoma.

Stereological analysis of the synovial membrane in rheumatic disorders: diagnostic value of volume-weighted mean nuclear volume estimation

Quantitative evaluation of nuclear size of synoviocytes was performed on 48 synovial biopsies in various rheumatic disorders: osteoarthritis (n = 10), rheumatoid arthritis (11), and chronic non-specific synovitis (14). Thirteen tissue specimens from non-inflammatory synovial membrane were included as a control group. Using the point-sampled intercepts method, unbiased stereological estimates of volume-weighted mean nuclear volume (nuclear upsilon v) were obtained. A slight increase in nuclear volume was observed in osteoarthritis in comparison with the control group with an overlap in 90% of cases. However, in rheumatoid arthritis there was a significant increase of nuclear upsilon v. Significant differences were found between rheumatoid arthritis and the control and osteoarthritis groups (P < or = 0.001). In biopsies from patients diagnosed as chronic non-specific synovitis the averaged nuclear upsilon v values were between those in osteoarthritis and rheumatoid arthritis with a wide range of data. Similar, but less significant differences were demonstrated between rheumatic disorders when using mean nuclear area. Further analysis of chronic non-specific synovitis patients in combination with nuclear upsilon v estimates as a simple, unbiased, complementary tool are required to better establish the diagnostic value of nuclear stereology in the diagnosis of rheumatic disorders.

Nuclear quantitative grading by discriminant analysis of renal cell carcinoma samples. A patient survival evaluation

Specimens from 60 cases of renal cell carcinoma (RCC) were graded employing quantitative nuclear data combined with multivariate discriminant analysis. Evaluation of patient survival was analysed with respect to quantitative microscopic and qualitative features. Both morphometric and stereological estimators were used to establish the nuclear size and form pattern of the RCC specimens. Tumoural dedifferentiation paralleled progressive increases in nuclear elongation and in two- and, especially, three-dimensional--mean nuclear volume (MNV)--size parameters. Using stepwise discriminant analysis, 85.0 per cent of the specimens were correctly classified when differentiating grade 2 and 3 tumours. It is concluded that simple and realistic estimates of MNV are the best discriminator for objective grading in patients with RCC. Univariate survival analysis demonstrated the important significance of several features such as MNV, clinical stage, and nuclear discriminant and histopathological tumour grades. Nuclear form factor PE, area, and perimeter were also significant. A prognosis study based on the Cox model using a stepwise selection of parameters showed that only MNV has an independent prognostic role when examining all investigated quantitative parameters. The clinical stage was the best prognostic feature when all quantitative and qualitative characteristics were included in the analysis.

Computer-based image analysis of prostate cancer: comments with emphasis on use of commercially available systems

This review is concerned with computer-based image analysis (CBIA) in prostate cancer. The emphasis is placed on evaluating extent and grade of prostate cancer. The quest for reproducibility in these evaluations has provided an important area of possible application for CBIA studies. Commercially available CBIA systems allow an opportunity for increased efforts in studying the merits of CBIA in prostate cancer. Many CBIA systems with various capabilities are currently on the market. They can be described as either "general" or "dedicated" CBIA systems and are exemplified by two systems: the Werner Frei Imlab/Imtool (Werner Frei Associates, Venice, CA) and the CAS 200 (Cell Analysis Systems, Inc, Lombard, IL), respectively. "General" systems are composed of individual components with data being stored and analyzed using a personal computer (Werner Frei Imlab/Imtool). "Dedicated" systems are integrated systems, usually with little variability of either software or hardware specifications (CAS 200). It is helpful to be cognizant of the contrasting abilities provided by these two systems when evaluating which CBIA system would be most appropriate for a particular application in the study of prostate cancer.