Immunohistochemical quantitation of androgen receptor expression using color video image analysis

Inhibition of dihydrotestosterone synthesis in prostate cancer by combined frontdoor and backdoor pathway blockade

Androgen deprivation therapy (ADT) is palliative and prostate cancer (CaP) recurs as lethal castration-recurrent/resistant CaP (CRPC). One mechanism that provides CaP resistance to ADT is primary backdoor androgen metabolism, which uses up to four 3α-oxidoreductases to convert 5α-androstane-3α,17β-diol (DIOL) to dihydrotestosterone (DHT). The goal was to determine whether inhibition of 3α-oxidoreductase activity decreased conversion of DIOL to DHT. Protein sequence analysis showed that the four 3α-oxidoreductases have identical catalytic amino acid residues. Mass spectrometry data showed combined treatment using catalytically inactive 3α-oxidoreductase mutants and the 5α-reductase inhibitor, dutasteride, decreased DHT levels in CaP cells better than dutasteride alone. Combined blockade of frontdoor and backdoor pathways of DHT synthesis provides a therapeutic strategy to inhibit CRPC development and growth.

Roles for the backdoor pathway of androgen metabolism in prostate cancer response to castration and drug treatment

Almost all men who present with advanced prostate cancer (CaP) and many men who fail potentially curative therapy are treated with androgen deprivation therapy (ADT). ADT is not curative and CaP recurs as the lethal phenotype. The goal of this review is to describe the evolution of adrenal androgen blockade, how new androgen measurement methods have furthered understanding of androgen metabolism, and how further understanding of the backdoor pathway of androgen metabolism may lead to interventions that extend survival even more.

20(S)-protopanaxadiol-aglycone downregulation of the full-length and splice variants of androgen receptor

As a public health problem, prostate cancer engenders huge economic and life-quality burden. Developing effective chemopreventive regimens to alleviate the burden remains a major challenge. Androgen signaling is vital to the development and progression of prostate cancer. Targeting androgen signaling via blocking the production of the potent ligand dihydrotestosterone has been shown to decrease prostate cancer incidence. However, the potential of increasing the incidence of high-grade prostate cancers has been a concern. Mechanisms of disease progression after the intervention may include increased expression of androgen receptor (AR) in prostate tissue and expression of the constitutively active AR splice variants (AR-Vs) lacking the ligand-binding domain. Thus, novel agents targeting the receptor, preferentially both the full-length and AR-Vs, are urgently needed. In the present study, we show that ginsenoside 20(S)-protopanaxadiol-aglycone (PPD) effectively downregulates the expression and activity of both the full-length AR and AR-Vs. The effects of PPD on AR and AR-Vs are manifested by an immediate drop in proteins followed by a reduction in transcripts, attributed to PPD induction of proteasome-mediated degradation and inhibition of the transcription of the AR gene. We further show that although PPD inhibits the growth as well as AR expression and activity in LNCaP xenograft tumors, the morphology and AR expression in normal prostates are not affected. This study is the first to show that PPD suppresses androgen signaling through downregulating both the full-length AR and AR-Vs, and provides strong rationale for further developing PPD as a promising agent for the prevention and/or treatment of prostate cancer.

Thioredoxin Reductase 1 Expression and Castration-recurrent Growth of Prostate Cancer

INTRODUCTION

Many genes are differentially expressed between androgen-dependent and androgen-independent prostate cancer (CaP). Differential expression analysis and subtractive hybridization previously identified nine genes expressed in intact mice bearing CWR22 tumors and castrated mice bearing recurrent CWR22 tumors but not in regressed tumors. The objectives of this study were to develop an immunostaining method to dual-label foci of proliferating tumor cells [the origin of castration-recurrent CaP (CR-CaP)], to determine which of the nine candidate proteins were differentially expressed in proliferating versus nonproliferating cells at the onset of growth after castration, and to test preclinical findings using clinical specimens of androgen-stimulated benign prostate (AS-BP) and CaP (AS-CaP) and CR-CaP.

METHODS

Paraffin-embedded, bromodeoxyuridine-injected CWR22 tumors were hydrated, antigen-retrieved using high heat and high pressure, labeled for each of the nine antigens of interest, visualized using peroxidase, and counterstained with hematoxylin. Mean optical density was calculated for proliferating and nonproliferating areas using automated (nuclear staining) or manual (cytoplasmic staining) image analysis. Prostate tissue microarray sections were immunostained and visually scored.

RESULTS

Immunohistochemistry revealed higher nuclear expression of thioredoxin reductase 1 (TrxR1) in proliferating cells than nonproliferating cells (P < .005). There were no statistical differences between cell types in the expression of other proteins. TrxR1 expression was higher (P < .01) in CR-CaP compared with AS-BP or AS-CaP.

CONCLUSIONS

Increased TrxR1 expression in CR-CaP was consistent with increased TrxR1 and BrdU expression at the onset of growth in the CWR22 model. Thioredoxin reductase 1 should be targeted in an attempt to delay or prevent CaP recurrence after castration.

Automation of immunohistochemical evaluation in breast cancer using image analysis

AIM: To automate breast cancer diagnosis and to study the inter-observer and intra-observer variations in the manual evaluations.

METHODS: Breast tissue specimens from sixty cases were stained separately for estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2/neu). All cases were assessed by manual grading as well as image analysis. The manual grading was performed by an experienced expert pathologist. To study inter-observer and intra-observer variations, we obtained readings from another pathologist as the second observer from a different laboratory who has a little less experience than the first observer. We also took a second reading from the second observer to study intra-observer variations. Image analysis was carried out using in-house developed software (TissueQuant). A comparison of the results from image analysis and manual scoring of ER, PR and HER-2/neu was also carried out.

RESULTS: The performance of the automated analysis in the case of ER, PR and HER-2/neu expressions was compared with the manual evaluations. The performance of the automated system was found to correlate well with the manual evaluations. The inter-observer variations were measured using Spearman correlation coefficient r and 95% confidence interval. In the case of ER expression, Spearman correlation r = 0.53, in the case of PR expression, r = 0.63, and in the case of HER-2/neu expression, r = 0.68. Similarly, intra-observer variations were also measured. In the case of ER, PR and HER-2/neu expressions, r = 0.46, 0.66 and 0.70, respectively.

CONCLUSION: The automation of breast cancer diagnosis from immunohistochemically stained specimens is very useful for providing objective and repeatable evaluations.

A role for the androgen-receptor in clinically localized and advanced prostate cancer

Earlier studies of androgen-receptor (AR) expression using frozen prostate tissue, and later studies using archived specimens, produced the consensus that ligand-stabilized AR is nuclear, AR expression is similar in benign epithelia and stroma, AR expression is greater in secretory epithelia than basal cells, and AR expression is more variable in prostate cancer (CaP) than in benign prostatic hyperplasia (BPH). Accurate measurement of AR expression remains technically challenging but necessary to evaluate the relevance of AR to clinical CaP. Recent studies demonstrated that AR expression in epithelia and stroma may be prognostic in clinically localized CaP, and AR expression may play a role in racial differences in CaP mortality and predict response to androgen deprivation therapy. High levels of AR and AR-regulated gene expression indicate a central role for AR in growth regulation of castration-recurrent CaP. New treatments for the lethal phenotype of CaP require better understanding of AR transactivation during androgen deprivation therapy.

Quantitative image analysis of immunohistochemical stains using a CMYK color model

Background

Computer image analysis techniques have decreased effects of observer biases, and increased the sensitivity and the throughput of immunohistochemistry (IHC) as a tissue-based procedure for the evaluation of diseases.

Methods

We adapted a Cyan/Magenta/Yellow/Key (CMYK) model for automated computer image analysis to quantify IHC stains in hematoxylin counterstained histological sections.

Results

The spectral characteristics of the chromogens AEC, DAB and NovaRed as well as the counterstain hematoxylin were first determined using CMYK, Red/Green/Blue (RGB), normalized RGB and Hue/Saturation/Lightness (HSL) color models. The contrast of chromogen intensities on a 0–255 scale (24-bit image file) as well as compared to the hematoxylin counterstain was greatest using the Yellow channel of a CMYK color model, suggesting an improved sensitivity for IHC evaluation compared to other color models. An increase in activated STAT3 levels due to growth factor stimulation, quantified using the Yellow channel image analysis was associated with an increase detected by Western blotting. Two clinical image data sets were used to compare the Yellow channel automated method with observer-dependent methods. First, a quantification of DAB-labeled carbonic anhydrase IX hypoxia marker in 414 sections obtained from 138 biopsies of cervical carcinoma showed strong association between Yellow channel and positive color selection results. Second, a linear relationship was also demonstrated between Yellow intensity and visual scoring for NovaRed-labeled epidermal growth factor receptor in 256 non-small cell lung cancer biopsies.

Conclusion

The Yellow channel image analysis method based on a CMYK color model is independent of observer biases for threshold and positive color selection, applicable to different chromogens, tolerant of hematoxylin, sensitive to small changes in IHC intensity and is applicable to simple automation procedures. These characteristics are advantageous for both basic as well as clinical research in an unbiased, reproducible and high throughput evaluation of IHC intensity.

Java Web Start based software for automated quantitative nuclear analysis of prostate cancer and benign prostate hyperplasia

Background

Androgen acts via androgen receptor (AR) and accurate measurement of the levels of AR protein expression is critical for prostate research. The expression of AR in paired specimens of benign prostate and prostate cancer from 20 African and 20 Caucasian Americans was compared to demonstrate an application of this system.

Methods

A set of 200 immunopositive and 200 immunonegative nuclei were collected from the images using a macro developed in Image Pro Plus. Linear Discriminant and Logistic Regression analyses were performed on the data to generate classification coefficients. Classification coefficients render the automated image analysis software independent of the type of immunostaining or image acquisition system used. The image analysis software performs local segmentation and uses nuclear shape and size to detect prostatic epithelial nuclei. AR expression is described by (a) percentage of immunopositive nuclei; (b) percentage of immunopositive nuclear area; and (c) intensity of AR expression among immunopositive nuclei or areas.

Results

The percent positive nuclei and percent nuclear area were similar by race in both benign prostate hyperplasia and prostate cancer. In prostate cancer epithelial nuclei, African Americans exhibited 38% higher levels of AR immunostaining than Caucasian Americans (two sided Student's t-tests; P < 0.05). Intensity of AR immunostaining was similar between races in benign prostate.

Conclusion

The differences measured in the intensity of AR expression in prostate cancer were consistent with previous studies. Classification coefficients are required due to non-standardized immunostaining and image collection methods across medical institutions and research laboratories and helps customize the software for the specimen under study. The availability of a free, automated system creates new opportunities for testing, evaluation and use of this image analysis system by many research groups who study nuclear protein expression.

Androgen receptor expression and cellular proliferation during transition from androgen-dependent to recurrent growth after castration in the CWR22 prostate cancer xenograft

Androgen receptor expression was analyzed in the CWR22 human prostate cancer xenograft model to better understand its role in prostate cancer recurrence after castration. In androgen-dependent tumors, 98.5% of tumor cell nuclei expressed androgen receptor with a mean optical density of 0.26 +/- 0.01. On day 2 after castration androgen deprivation decreased immunostained cells to 2% that stained weakly (mean optical density, 0.16 +/- 0.08). Cellular proliferation measured using Ki-67 revealed <1% immunostained cells on day 6. Androgen receptor immunostained cells increased to 63% on day 6 and 84% on day 32 although immunostaining remained weak. Cellular proliferation was undetectable beyond day 6 after castration until multiple foci of 5 to 20 proliferating cells became apparent on day 120. These foci expressed increased levels of prostate-specific antigen, an androgen receptor-regulated gene product. In tumors recurrent 150 days after castration androgen receptor-immunostaining intensity was similar to CWR22 tumors from intact mice although the percentage of cells immunostained was more variable. The appearance of proliferating tumor cells that expressed androgen receptor and prostate-specific antigen 120 days after castration suggests that these cells represent the origin of recurrent tumors.