Apoptotic regulators in prostatic intraepithelial neoplasia (PIN): value in prostate cancer detection and prevention

MEIS1 and MEIS2 Expression and Prostate Cancer Progression: A Role For HOXB13 Binding Partners in Metastatic Disease

Purpose: Germline mutations within the MEIS-interaction domain of HOXB13 have implicated a critical function for MEIS-HOX interactions in prostate cancer etiology and progression. The functional and predictive role of changes in MEIS expression within prostate tumor progression, however, remain largely unexplored.Experimental Design: Here we utilize RNA expression datasets, annotated tissue microarrays, and cell-based functional assays to investigate the role of MEIS1 and MEIS2 in prostate cancer and metastatic progression.Results: These analyses demonstrate a stepwise decrease in the expression of both MEIS1 and MEIS2 from benign epithelia, to primary tumor, to metastatic tissues. Positive expression of MEIS proteins in primary tumors, however, is associated with a lower hazard of clinical metastasis (HR = 0.28) after multivariable analysis. Pathway and gene set enrichment analyses identified MEIS-associated networks involved in cMYC signaling, cellular proliferation, motility, and local tumor environment. Depletion of MEIS1 and MEIS2 resulted in increased tumor growth over time in vivo, and decreased MEIS expression in both patient-derived tumors and MEIS-depleted cell lines was associated with increased expression of the protumorigenic genes cMYC and CD142, and decreased expression of AXIN2, FN1, ROCK1, SERPINE2, SNAI2, and TGFβ2.Conclusions: These data implicate a functional role for MEIS proteins in regulating cancer progression, and support a hypothesis whereby tumor expression of MEIS1 and MEIS2 expression confers a more indolent prostate cancer phenotype, with a decreased propensity for metastatic progression. Clin Cancer Res; 24(15); 3668-80. ©2018 AACR.

5α-reductase 1 mRNA levels are positively correlated with TRAMP mouse prostate most severe lesion scores

Background

The contribution of 5α-reductase 1 and 5α-reductase 2 to prostate cancer development and progression is not clearly understood. TRAMP mice are a common prostate cancer model, in which 5α-reductase 1 and 5α-reductase 2 expression levels, along with prostate lesions scores, have not been investigated at different time points to further understand prostate carcinogenesis.

Method/Principal findings

To this end, 8-, 12-, 16-, and 20-week-old male C57BL/6TRAMP x FVB mice prostate most severe and most common lesion scores, 5α-reductase 1 and 5α-reductase 2 in situ hybridization expression, and Ki-67, androgen receptor, and apoptosis immunohistochemistry levels were measured. Levels of these markers were quantified in prostate epithelium, hyperplasia, and tumors sections. Mice developed low- to high-grade prostatic intraepithelial neoplasia at 8 weeks as the most severe and most common lesions, and moderate- and high-grade prostatic intraepithelial neoplasia at 12 and 16 weeks as the most severe lesion in all lobes. Moderately differentiated adenocarcinoma was observed at 20 weeks in all lobes. Poorly differentiated carcinoma was not observed in any lobe until 12-weeks-old. 5α-reductase 1 and 5α-reductase 2 were not significantly decreased in tumors compared to prostate epithelium and hyperplasia in all groups, while proliferation, apoptosis, and androgen receptor were either notably or significantly decreased in tumors compared with prostate epithelium and hyperplasia in most or all groups. Prostate 5αR1 levels were positively correlated with adjusted prostate most severe lesion scores.

Conclusion

Downregulation of androgen receptor and 5α-reductase 2, along with upregulation of 5α-reductase 1 in tumors may promote prostatic intraepithelial neoplasia and prostate cancer development in TRAMP mice.

XAF1 expression and regulatory effects of somatostatin on XAF1 in prostate cancer cells

Background

Somatostatin prevents cell proliferation by inducing apoptosis. Downregulation of the XAF1 transcript may occur during the development of prostate cancer. It is interesting to evaluate the potential regulatory effects of somatostatin on XAF1 expression during the development of prostate cancer cells.

Methods

XAF1 mRNA and protein expression in human prostate epithelial cells RWPE-1, androgen dependent prostate cancer LNCaP, and androgen independent DU145 and PC3 cells were evaluated using RT-PCR and Western blot. The regulation of XAF1 mRNA and protein expression by somatostatin and its analogue Octreotide was evaluated.

Results

Substantial levels of XAF1 mRNA and proteins were detected in RWPE-1 cells, whereas prostate cancer cells LNCaP, DU145 and PC3 exhibited lower XAF1 expression. Somatostatin and Octreotide up-regulated XAF1 mRNA and protein expression in all prostate cancer cell lines.

Conclusions

XAF1 down-regulation may contribute to the prostate cancer development. The enhanced XAF1 expression by somatostatin indicates a promising strategy for prostate cancer therapy.

Precursor Lesions of Prostate Cancer

Several morphological lesions have been proposed that may act as potential precursor lesions of prostate cancer. These are the morphologically distinct entities of focal atrophy or post-atrophic hyperplasia (PAH), atypical adenomatous hyperplasia (AAH) or adenosis, and prostatic intraepithelial neoplasia (PIN). The diagnostic criteria of low-and high-grade PIN (LGPIN and HGPIN, respectively) and of lesions suspicious for cancer (LSC) have been established. In the present review, we present the current knowledge about the precursor lesions of prostate cancer. We focus on the epidemiology, pathogenesis, clinical markers, and differential diagnosis of PIN. The similarities between HGPIN and prostate cancer are also discussed. Furthermore, potential markers and management strategies (that is, repeat biopsy, chemoprevention, radical prostatectomy, radiotherapy) are outlined along with updated recommendations.

Androgen-induced programs for prostate epithelial growth and invasion arise in embryogenesis and are reactivated in cancer. Oncogene. 2008;27:7180-7191. [PMID: 18794802 DOI: 10.1038/onc.2008.327]

Cancer cells differentiate along specific lineages that largely determine their clinical and biologic behavior. Distinct cancer phenotypes from different cells and organs likely result from unique gene expression repertoires established in the embryo and maintained after malignant transformation. We used comprehensive gene expression analysis to examine this concept in the prostate, an organ with a tractable developmental program and a high propensity for cancer. We focused on gene expression in the murine prostate rudiment at three time points during the first 48 h of exposure to androgen, which initiates proliferation and invasion of prostate epithelial buds into surrounding urogenital sinus mesenchyme. Here, we show that androgen exposure regulates genes previously implicated in prostate carcinogenesis comprising pathways for the phosphatase and tensin homolog (PTEN), fibroblast growth factor (FGF)/mitogen-activated protein kinase (MAPK), and Wnt signaling along with cellular programs regulating such 'hallmarks' of cancer as angiogenesis, apoptosis, migration and proliferation. We found statistically significant evidence for novel androgen-induced gene regulation events that establish and/or maintain prostate cell fate. These include modulation of gene expression through microRNAs, expression of specific transcription factors, and regulation of their predicted targets. By querying public gene expression databases from other tissues, we found that rather than generally characterizing androgen exposure or epithelial budding, the early prostate development program more closely resembles the program for human prostate cancer. Most importantly, early androgen-regulated genes and functional themes associated with prostate development were highly enriched in contrasts between increasingly lethal forms of prostate cancer, confirming a 'reactivation' of embryonic pathways for proliferation and invasion in prostate cancer progression. Among the genes with the most significant links to the development and cancer, we highlight coordinate induction of the transcription factor Sox9 and suppression of the proapoptotic phospholipid-binding protein Annexin A1 that link early prostate development to early prostate carcinogenesis. These results credential early prostate development as a reliable and valid model system for the investigation of genes and pathways that drive prostate cancer.

A cut-off based approach for gene expression analysis of formalin-fixed and paraffin-embedded tissue samples

Microarray analysis of formalin-fixed and paraffin-embedded (FFPE) tissue seems to be of importance for the detection of molecular marker sets in prostate cancer (PC). The compromised RNA integrity of FFPE tissue results in a high degree of variability at the probe level of microarray data as shown by degradation plot. We tested methods that reduce the variability by including all probes within 300 nucleotides, within 600 nucleotides, or up to a calculated breakpoint with reference to the 3'-end. Accepted PC pathways such as the Wnt signaling pathway could be observed to be significantly regulated within FFPE microarray datasets. The best representation of PC gene expression, as well as better comparability to meta-analysis and fresh-frozen microarray data, could be obtained with a 600-nucleotide cutoff. Beyond the specific impact for PC microarray data analysis we propose a cutoff of 600 nucleotides for samples for which the integrity of the RNA cannot be guaranteed.

Expression of nuclear Ki-67 antigen in prostatic high grade intraepithelial neoplasia and prostatic carcinoma

Background/Aim. Prostatic intraepithelial high grade neoplasia (PINHG) is accepted as preneoplastic lesion in prostatic carcinoma. One of the fundamental events in early oncogenesis is the disruption of proliferative activity. One of the numerous regulatory proteins is Ki-67 expressed in all proliferating cells. Index Ki-67 is considered to have prognostic significance. The aim of the study was to compare the level of proliferation in hyperplastic epithelium, prostatic carcinoma (Gleason score > 6) and PINHG. Methods. Micromorphological examination was done in 85 patients. Pathohistological analysis was performed on standard histologic specimens with the estimation of Gleason score and the presence of PINHG in its surroundings. Nuclear proliferative activity was analyzed immunohistochemically in 19 cases, using a monoclonal anti-Ki-67 antibody. Results. PINHG was found in prostatic carcinoma surrounding in 30% of the patients. In hyperplastic epithelia Ki-67 proliferative activity was 1,08, in PINHG 2,25 (p < 0,05), while in prostatic cancer, Ki-67 index was 17,64. Proliferative activity in prostatic carcinoma was significantly higher than in PINHG (p < 0,001) and hyperplasia (p < 0,001). Conclusion. This study confirmed that high grade PIN lesion predominately appears in the surrounding of poor or moderately differentiated prostate carcinoma, and that it represents progressive disorder of proliferation in preneoplastic and neoplastic prostatic epithelium. .

Akt-and CREB-mediated prostate cancer cell proliferation inhibition by Nexrutine, a Phellodendron amurense extract

Evidence from epidemiological studies suggests that plant-based diets can reduce the risk of prostate cancer. However, very little information is available concerning the use of botanicals in preventing prostate cancer. As a first step toward developing botanicals as prostate cancer preventives, we examined the effect of Nexrutine on human prostate cancer cells. Nexrutine is a herbal extract developed from Phellodendron amurense. Phellodendron extracts have been used traditionally in Chinese medicine for hundreds of years as an antidiarrheal, astringent, and anti-inflammatory agent. The present study investigated its potential antitumor effect on human prostate cancer cells. Our results suggest that it inhibits tumor cell proliferation through apoptosis induction and inhibition of cell survival signaling. The results of the present study indicate that Nexrutine treatment 1) inhibits the proliferation of both androgen-responsive and androgen-independent human prostate cancer cells through induction of apoptosis; 2) reduces levels of pAkt, phosphorylated cAMP response-binding protein (pCREB) and CREB DNA-binding activity; and 3) induces apoptosis in prostate cancer cells stably overexpressing Bcl-2. Further, Akt kinase activity was reduced in cells treated with Nexrutine, and ectopic expression of myristoylated Akt protected from Nexrutine induced inhibition of proliferation, implicating a role for Akt signaling.

Switch to full-length of XAF1 mRNA expression in prostate cancer cells by the DNA methylation inhibitor

X-linked inhibitor of apoptosis protein (XIAP) suppresses apoptotic cell death by binding to caspases and inhibiting their functions, while the XIAP-associated factor1 (XAF1), a zinc finger protein, antagonizes XIAP activities, thereby promoting apoptosis. The aberrant silence of the XAF1 gene has recently been found in various types of cancer cells, which is suggested to be one of the potential mechanisms underlying survival advantages of malignant cells. In the present study, we investigated the XAF1 expression in prostate cancer cells. Compared with normal tissues where a full-length of XAF1 mRNA is predominant, LNCaP and DU145 prostate cancer cell lines only expressed a short form of XAF1 transcripts, whereas PC3 cells exhibited a complete silence of the XAF1 gene. Inhibition of DNA methylation led to a switch to the full length of XAF1 mRNA expression in LNCaP and DU145 cells. The down-regulation of XAF1 expression was also observed in 6/8 tumor samples derived from patients with prostate cancer. Our findings suggest that splicing alterations or downregulation of the XAF1 transcript may occur during the development of prostate cancers due to the aberrant DNA methylation. The alternative splicing of XAF1 mRNA leads to formation of a truncated XAF1 protein with 19 amino acid deletion in its zinc finger domain, which likely affects its functional interaction with XIAP, and consequently, contributes to the pathogenesis of prostate cancers by disrupting balance of the apoptosis machinery.

Toremifene--a promising therapy for the prevention of prostate cancer and complications of androgen deprivation therapy

Deregulation of the estrogen axis in humans prompts a series of tissue-specific events. In the breast and prostate, alterations in estrogen signalling lead to genotypic and phenotypic molecular alterations that result in dysplastic cellular appearance, deregulated cell growth and carcinoma. In bone, decreased estrogen leads to increased osteoclastogenesis and bone resorption, decreased bone mineral density and a significant fracture risk. Toremifene is a selective estrogen receptor modulator that exerts pharmacological activity in the breast, bone and prostate. An intense interest in developing this agent for prostate cancer chemoprevention is based on the reduction of premalignant and malignant prostate lesions in a transgenic model of prostate cancer. Biological and clinical activity was demonstrated in Phase II trials by the prevention of progression to prostate cancer in men with high-grade prostate intraepithelial neoplasia and through suppression of bone turnover biomarkers and increased bone mineral density in men on androgen deprivation therapy for prostate cancer.

Alteration of proliferation and apoptotic markers in normal and premalignant tissue associated with prostate cancer

Background

Molecular markers identifying alterations in proliferation and apoptotic pathways could be particularly important in characterizing high-risk normal or pre-neoplastic tissue. We evaluated the following markers: Ki67, Minichromosome Maintenance Protein-2 (Mcm-2), activated caspase-3 (a-casp3) and Bcl-2 to determine if they showed differential expression across progressive degrees of intraepithelial neoplasia and cancer in the prostate. To identify field effects, we also evaluated whether high-risk expression patterns in normal tissue were more common in prostates containing cancer compared to those without cancer (supernormal), and in histologically normal glands adjacent to a cancer focus as opposed to equivalent glands that were more distant.

Methods

The aforementioned markers were studied in 13 radical prostatectomy (RP) and 6 cystoprostatectomy (CP) specimens. Tissue compartments representing normal, low grade prostatic intraepithelial neoplasia (LGPIN), high grade prostatic intraepithelial neoplasia (HGPIN), as well as different grades of cancer were mapped on H&E slides and adjacent sections were analyzed using immunohistochemistry. Normal glands within 1 mm distance of a tumor focus and glands beyond 5 mm were considered "near" and "far", respectively. Randomly selected nuclei and 40 × fields were scored by a single observer; basal and luminal epithelial layers were scored separately.

Results

Both Ki-67 and Mcm-2 showed an upward trend from normal tissue through HGPIN and cancer with a shift in proliferation from basal to luminal compartment. Activated caspase-3 showed a significant decrease in HGPIN and cancer compartments. Supernormal glands had significantly lower proliferation indices and higher a-casp3 expression compared to normal glands. "Near" normal glands had higher Mcm-2 indices compared to "far" glands; however, they also had higher a-casp3 expression. Bcl-2, which varied minimally in normal tissue, did not show any trend across compartments or evidence for field effects.

Conclusion

These results demonstrate that proliferation and apoptosis are altered not only in preneoplastic lesions but also in apparently normal looking epithelium associated with cancer. Luminal cell expression of Mcm-2 appears to be particularly promising as a marker of high-risk normal epithelium. The role of apoptotic markers such as activated caspase-3 is more complex, and might depend on the proliferation status of the tissue in question.