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

Failure of Ploidy and Proliferative Fraction to Predict Long-Term Outcome After Prostatectomy

Background

Historically, ploidy and S phase percentage appeared to be promising predictors for prostate cancer recurrence. Lack of uniformity and consistency hampered their development. We evaluated ploidy and S phase for prostate cancer death in a cohort of patients with long-term follow-up.

Methods

We identified 127 patients that had ploidy and S phase determined at the time of their radical prostatectomy for prostate cancer. With 15 years of follow-up, we determined the risk of biochemical failure and risk of death from prostate cancer. We correlated the S phase and ploidy findings with standard pathology findings.

Results

A total of 107 (84%) had diploid and 20 (16%) had non-diploid cancers. The median S phase was 6.6%. There was no correlation of ploidy (P = 0.472) or S phase with preoperative PSA or Gleason score. On univariate analysis, EPE, margin positivity, seminal vesicle involvement, lymph node involvement, high Gleason score and PSA > 10 ng/mL were all predictive of biochemical failure. Ploidy and S phase were not. For prostate cancer death, only Gleason score was predictive.

Conclusions

With long-term follow-up in our cohort, Gleason score was predictive of prostate cancer death. Ploidy and S phase were not predictive for biochemical failure or prostate cancer mortality.

Cancer biomarker discovery: the entropic hallmark

Background

It is a commonly accepted belief that cancer cells modify their transcriptional state during the progression of the disease. We propose that the progression of cancer cells towards malignant phenotypes can be efficiently tracked using high-throughput technologies that follow the gradual changes observed in the gene expression profiles by employing Shannon's mathematical theory of communication. Methods based on Information Theory can then quantify the divergence of cancer cells' transcriptional profiles from those of normally appearing cells of the originating tissues. The relevance of the proposed methods can be evaluated using microarray datasets available in the public domain but the method is in principle applicable to other high-throughput methods.

Methodology/Principal Findings

Using melanoma and prostate cancer datasets we illustrate how it is possible to employ Shannon Entropy and the Jensen-Shannon divergence to trace the transcriptional changes progression of the disease. We establish how the variations of these two measures correlate with established biomarkers of cancer progression. The Information Theory measures allow us to identify novel biomarkers for both progressive and relatively more sudden transcriptional changes leading to malignant phenotypes. At the same time, the methodology was able to validate a large number of genes and processes that seem to be implicated in the progression of melanoma and prostate cancer.

Conclusions/Significance

We thus present a quantitative guiding rule, a new unifying hallmark of cancer: the cancer cell's transcriptome changes lead to measurable observed transitions of Normalized Shannon Entropy values (as measured by high-througput technologies). At the same time, tumor cells increment their divergence from the normal tissue profile increasing their disorder via creation of states that we might not directly measure. This unifying hallmark allows, via the the Jensen-Shannon divergence, to identify the arrow of time of the processes from the gene expression profiles, and helps to map the phenotypical and molecular hallmarks of specific cancer subtypes. The deep mathematical basis of the approach allows us to suggest that this principle is, hopefully, of general applicability for other diseases.

Flow cytometry evaluation of lead and cadmium effects on mouse spermatogenesis

Flow cytometry (FCM) is a powerful tool to evaluate cell DNA content and ploidy levels. We have assessed the accuracy of two protocols of nuclei isolation from paraffinized samples (P1 and P2) by comparing FCM results with those obtained using fresh material (F1-F3). After isolation, nuclei were stained with propidium iodide and quantitatively analysed by FCM for changes in germ cell ratios. Results obtained with Protocol P2 were similar to those obtained using the protocol that gave best results for fresh tissues (F2). Protocol P2 was then applied to paraffin embedded testicular samples from ICR-CD1 mice exposed to 1, 2 and 3 mg CdCl(2)/kg bw by single subcutaneous injection, and to 74 and 100 mg PbCl(2)/kg bw administered in four repeated doses. The highest doses of CdCl(2) decreased the number of haploid (1C) cells and increased the number of diploid (2C), S phase and tetraploid (4C) cells. Treatment with PbCl(2) did not induce significant changes in testicular cells subpopulations. These results support the usefulness of FCM in evaluating the effect of toxic substances on mouse spermatogenesis, using both fresh and paraffinized material.

Characteristics of prostate cancers detected at low PSA levels

BACKGROUND

When age-referenced PSA levels as recommended by Oesterling et al.1 were used as a biopsy criterion, only 25% of the cancers detected in a population based PSA Screening Project were organ-confined. This observation led to the decision to use low PSA levels as the sole indication for biopsy. Since 1995 age-referenced PSA levels of 1.25-3.25 ng/ml have been used in combination with a percentage free PSA cutoff of 18%. This PSA cutoff reduction led to a statistically significant migration to lower pathological stages with a decreased prostate cancer mortality in the years 1996-2001. However, concerns have been raised that screening with low PSA levels may detect clinically insignificant cancers.

MATERIALS AND METHODS

We evaluated prostate cancer patients with low PSA levels in terms of heterogeneity, clinical significance, multifocality, and tumor biology including ploidy and proliferation index.

RESULTS

Concerning heterogeneity the Gleason score of the needle biopsy failed to predict the Gleason score of the radical prostatectomy specimen in nearly 40% of prostate cancer patients; regarding multifocality 65% of patients with low PSA levels showed multifocal lesions and 36% exhibited tetraploid DNA distribution; more than 50% of tetraploid tumors were found in patients with tumor volumes of less than 0.5 cm(3). Ploidy correlated with the Ki-67 proliferation index, but not with tumor volume.

CONCLUSIONS

These results demonstrate that small prostate cancers with low PSA levels and low tumor volumes exhibit all features of prostate cancers with higher tumor volumes and show the characteristics of malignant cancers, i.e., multifocality, tetraploidy, and high proliferative activity.

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.

The prognostic value of p53 and DNA ploidy following radical prostatectomy

This study assesses the correlation of p53 immunoreactivity and DNA ploidy status with biochemical recurrence after radical prostatectomy. p53 protein expression and DNA ploidy were evaluated on 84 archival paraffin-embedded radical prostatectomy specimens. Patients were divided into two groups: those with low (38/84, 45%) and those with high (46/84, 55%) p53 immunoreactivity. The results were correlated with Gleason score, stage and serum PSA. Kaplan-Meier biochemical recurrence free survival and the Cox hazard-regression model were used for analysis. Multivariate analysis revealed p53, DNA ploidy, Gleason score, PSA and stage to be independent prognostic factors in this order. Kaplan-Meier analysis showed a significant difference in biochemical recurrence when p53 high expression and DNA aneuploidy were combined. The results of this study suggest that stratification for p53 expression and DNA ploidy status can provide additional prognostic information for patients with prostate carcinoma after radical prostatectomy.

Factors that influence the measurement of prostate cancer DNA ploidy and proliferation in paraffin embedded tissue evaluated by flow cytometry

DNA ploidy and proliferation have been shown in several studies to be prognostic markers for prostate cancer. Flow cytometry (FCM) is often used in the determination of ploidy and proliferation. However, FCM cannot readily distinguish among benign epithelium, stromal and inflammatory cells, high grade prostatic intraepithelial neoplasia (HGPIN), and cancer cells. In this study, we evaluated H&E histologic features of 322 radical prostatectomy formalin-fixed, paraffin-embedded tissue blocks used for determining DNA ploidy, percent S-phase (%S), and %S + %G2M by FCM. The microscopic findings included Gleason score, extent of cancer and HGPIN in the tissue block, and presence of a needle track. The amount of cancer in the block was expressed as a percentage of the total tissue surface area in quartiles: < or =25%, 26-50%, 51-75%, and > or =76%. The extent of HGPIN was recorded in rough 5% intervals. Needle track effect was defined as a combination of fibrohistiocytic reaction, fibrin clot, granuloma formation, and chronic inflammation. The associations between these histologic features and DNA ploidy and proliferation (%S and %S + %G2M) were assessed. In multivariate analyses, Gleason score, the amount of tumor in the tissue block, and the extent of HGPIN were significantly associated with ploidy. Gleason score was the only parameter significantly associated with the proliferation measure of %S. If we included %G2M as part of the proliferative fraction of the histogram, however, both Gleason score and the amount of tumor in the block were significantly associated with this measure of proliferation. The presence of a needle track was not significantly associated with DNA ploidy, %S, or %S + %G2M. In summary, prostate cancer DNA ploidy and proliferation results assessed by FCM in paraffin-embedded tissue blocks were associated with the Gleason score, amount of cancer in the tissue block, and extent of HGPIN. However, the presence of a needle track was not associated with the FCM results.