IDENTIFYING THE COMBINATION OF THE TRANSCRIPTIONAL REGULATORY SEQUENCES ON PROSTATE SPECIFIC ANTIGEN AND HUMAN GLANDULAR KALLIKREIN GENES

Two New Components from an Association of Marine Sponges Poecillastra sp. and Jaspis sp. and Their Inhibitory Effects on Biomarkers for Benign Prostatic Hyperplasia

Benign prostatic hyperplasia (BPH), characterized by the enlargement of the prostate gland and subsequent lower urinary tract symptoms, poses a significant health concern for aging men with increasing prevalence. Extensive efforts encompassing in vitro and in vivo models are underway to identify novel and effective agents for the management and treatment of BPH. Research endeavors are primarily channeled toward assessing the potential of compounds to inhibit cell proliferation, curb inflammation, and display anti-androgenic activity. Notably, through screening aimed at inhibiting 5-alpha reductase type 2 (5αR2) in human prostatic cells, two acyl compounds (1 and 2) were isolated from a bioactive fraction sourced from an association of marine sponges Poecillastra sp. and Jaspis sp. The complete structure of 1 was determined as (Z)-dec-3-enony (2S, 3S)-capreomycidine, ascertained by JBCA and ECD comparison. While the absolute configurations of 2 remained unassigned, it was identified as a linkage of a 2, 7S*-dihydoxy-9R*-methyloctadecanoyl group with the 2-amino position of a tramiprosate moiety referred to as homotaurine. Evaluation of both compounds encompassed the assessment of their inhibitory effects on key biomarkers (5αR2, AR, PSA, and PCNA) associated with BPH in testosterone propionate (TP)-activated LNCap and RWPE-1 cells.

Androgen Receptor Upregulates Mucosa-Associated Lymphoid Tissue 1 to Induce NF-κB Activity via Androgen-Dependent and -Independent Pathways in Prostate Carcinoma Cells

The androgen-dependent or -independent pathways are regarded as primary therapeutic targets for the neoplasm of the prostate. Mucosa-associated lymphoid tissue 1 (MALT1) acting as a paracaspase in the regulation of nuclear factor κB (NF-κB) signal transduction plays a central role in inflammation and oncogenesis in cancers. This study confirmed the potential linkages between androgen and NF-κB activation by inducing MALT1 in the androgen receptor-full length (ARFL)-positive LNCaP and 22Rv1 prostate cancer cells. Although androgen did not stimulate MALT1 expression in AR-null or ectopic ARFL-overexpressed PC-3 cells, the ectopic overexpression of the AR splicing variant 7 (ARv7) upregulated MALT1 to activate NF-κB activities in 22Rv1 and PC-3 cells. Since the nuclear translocation of p50 and p65 was facilitated by ARv7 to motivate NF-κB activity, the expressions of MALT1, prostate-specific antigen (PSA), and N-myc downstream regulated 1 (NDRG1) were therefore induced in ectopic ARv7-overexpressed prostate cancer cells. Ectopic ARv7 overexpression not only enhanced 22Rv1 or PC-3 cell growth and invasion in vitro but also the tumor growth of PC-3 cells in vivo. These results indicate that an androgen receptor induces MALT1 expression androgen-dependently and -independently in ARFL- or ARv7-overexpressed prostate cancer cells, suggesting a novel ARv7/MALT1/NF-κB-signaling pathway may exist in the cells of prostate cancer.

The Antitumor Effect of Caffeic Acid Phenethyl Ester by Downregulating Mucosa-Associated Lymphoid Tissue 1 via AR/p53/NF-κB Signaling in Prostate Carcinoma Cells

Caffeic acid phenethyl ester (CAPE), a honeybee propolis-derived bioactive ingredient, has not been extensively elucidated regarding its effect on prostate cancer and associated mechanisms. The mucosa-associated lymphoid tissue 1 gene (MALT1) modulates NF-κB signal transduction in lymphoma and non-lymphoma cells. We investigated the functions and regulatory mechanisms of CAPE in relation to MALT1 in prostate carcinoma cells. In p53- and androgen receptor (AR)-positive prostate carcinoma cells, CAPE downregulated AR and MALT1 expression but enhanced that of p53, thus decreasing androgen-induced activation of MALT1 and prostate-specific antigen expressions. p53 downregulated the expression of MALT in prostate carcinoma cells through the putative consensus and nonconsensus p53 response elements. CAPE downregulated MALT1 expression and thus inhibited NF-κB activity in p53- and AR-negative prostate carcinoma PC-3 cells, eventually reducing cell proliferation, invasion, and tumor growth in vitro and in vivo. CAPE induced the ERK/JNK/p38/AMPKα1/2 signaling pathways; however, pretreatment with the corresponding inhibitors of MAPK or AMPK1/2 did not inhibit the CAPE effect on MALT1 blocking in PC-3 cells. Our findings verify that CAPE is an effective antitumor agent for human androgen-dependent and -independent prostate carcinoma cells in vitro and in vivo through the inhibition of MALT1 expression via the AR/p53/NF-κB signaling pathways.

The Effects of Aronia melanocarpa Extract on Testosterone-Induced Benign Prostatic Hyperplasia in Rats, and Quantitative Analysis of Major Constituents Depending on Extract Conditions

This study aimed to investigate the beneficial effects of A. melanocarpa on testosterone propionate (TP)-induced benign prostatic hyperplasia (BPH) in Wistar rats. Moreover, the bioactive constituents in the extract were determined using LC/MS and HPLC analyses. The dried fruits of A. melanocarpa were extracted using accelerated solvent extraction (ASE) under different extract conditions (temperature, 30 C or 100 C; extract solvent, 60% or 100% ethanol) to yield four extracts (T1~T4). Of the four A. melanocarpa extracts, T1 extracted under the condition of 100% ethanol/low temperature (30 C) exhibited the greatest inhibitory activity on TP-induced prostatic hyperplasia in rats. The administration of T1 (100 mg/kg body weight, p.o.) for six weeks attenuated TP-induced prostate enlargement and reduced the levels of dihydrotestosterone (DHT) and 5α-reductase in both serum and prostate tissue. The suppression of PCNA mRNA expression in prostate tissue was remarkable in T1-treated rats. In LC/MS analysis, the levels of main anthocyanins and phenolics were significantly higher in T1 than in the other extracts. Furthermore, the quantitative study showed that the contents of cyanidin-3-glucose and cyanidin-3-xylose in T1 exhibited 1.27~1.67 and 1.10~1.26 folds higher compared to those in the other extracts. These findings demonstrated that A. melanocarpa extract containing anthocyanins as bioactive constituents attenuated the development of testosterone-induced prostatic hyperplasia, and suggested that this extract has therapeutic potential to treat prostate enlargement and BPH.

Capillarisin blocks prostate-specific antigen expression on activation of androgen receptor in prostate carcinoma cells

BACKGROUND

Capillarisin (Cap), an active ingredient of Artemisia capillaris extracts, has known for its anti-inflammatory, antioxidant, and anticancer properties. Functions of Cap in prostate cancer are not clear. We investigate effects of Cap on downregulation of prostate specific antigen (PSA) via modulation of androgen receptor (AR) in prostate carcinoma cells.

METHODS

Cell proliferation was measured by water-soluble tetrazolium-1 (WST-1) cell proliferation assays. The PSA and AR expressions were assessed by immunoblotting and RT-qPCR assays. Effects of Cap on PSA expressions were determined by ELISA, immunoblotting, and reporter assays. Co-immunoprecipitation and immunoblotting assays were used to define the effects of Cap on dissociation of AR-heat shock protein 90 (Hsp90) interaction.

RESULTS

Cap inhibited LNCaP cell growth in a dose- and/or time-dependent way without inducing poly ADP-Ribose Polymerase (PARP) cleavage. Cap not only effectively suppressed AR and PSA protein expressions, but also attenuated activations of synthetic androgen (R1881) on PSA promoter activity dose- and time-dependently. The Cap pretreatment abrogated effects of R1881 on AR activity by reducing AR translocation to the nucleus. Immunoblotting assays indicated that Cap promoted a degradation of AR proteins dose-dependently in either cycloheximide pretreated-LNCaP cells or AR-ectopic expressed PC-3 cells. Pretreatment of MG132, a proteasome inhibitor, attenuated effect of Cap on AR degradation. Cap lessened AR stability by dissociation of AR-Hsp90 interaction.

CONCLUSIONS

Our results indicated that Cap inhibited growth of LNCaP cells. Cap effectively suppressed androgen activation on AR-mediated transactivation, which is AR-dependent through AR degradation and dissociation of AR-Hsp90 in prostate carcinoma cells.

Exponential rise in prostate-specific antigen (PSA) during anti-androgen withdrawal predicts PSA flare after docetaxel chemotherapy in patients with castration-resistant prostate cancer

PURPOSE

To investigate the relationship between rising patterns of prostate-specific antigen (PSA) before chemotherapy and PSA flare during the early phase of chemotherapy in patients with castration-resistant prostate cancer (CRPC).

MATERIALS AND METHODS

This study included 55 patients with CRPC who received chemotherapy and in whom pre-treatment or post-treatment PSA levels could be serially obtained. The baseline parameters included age, performance, Gleason score, PSA level, and disease extent. PSA doubling time was calculated using the different intervals: the conventional interval from the second hormone manipulation following the nadir until anti-androgen withdrawal (PSADT1), the interval from the initial rise after anti-androgen withdrawal to the start of chemotherapy (PSADT2), and the interval from the nadir until the start of chemotherapy (PSADT3). The PSA growth patterns were analyzed using the ratio of PSADT2 to PSADT1.

RESULTS

There were two growth patterns of PSA doubling time: 22 patients (40.0%) had a steady pattern with a more prolonged PSADT2 than PSADT1, while 33 (60.0%) had an accelerating pattern with a shorter PSADT2 than PSADT1. During three cycles of chemotherapy, PSA flare occurred in 11 patients (20.0%); of these patients, 3 were among 33 (9.1%) patients with an accelerating PSA growth pattern and 8 were among 22 patients (36.4%) with a steady PSA growth pattern (p=0.019). Multivariate analysis showed that only PSA growth pattern was an independent predictor of PSA flare (p=0.034).

CONCLUSION

An exponential rise in PSA during anti-androgen withdrawal is a significant predictor for PSA flare during chemotherapy in CRPC patients.

Serum alkaline phosphatase differentiates prostate-specific antigen flare from early disease progression after docetaxel chemotherapy in castration-resistant prostate cancer with bone metastasis

PURPOSE

A transient rise in prostate-specific antigen (PSA) after the initiation of chemotherapy, called as PSA flare, has been frequently reported in patients with castration-resistant prostate cancer (CRPC) but there has been no way to differentiate PSA rises in CRPC. We investigated whether bone-related serum markers differentiate PSA flare from progression in CRPC patients with bone metastasis.

METHODS

We reviewed CRPC patients with bone metastasis who received systemic chemotherapy from 2002 to 2008. Pretreatment baseline and follow-up data including age, performance score, PSA, Gleason score, alkaline phosphatase (ALP), calcium level, and hemoglobin were evaluated. Pretreatment parameters and follow-up serum parameters after the first cycle of chemotherapy were included in statistical analyses.

RESULTS

PSA increased in 38 patients (45.8 %) at the first evaluation after chemotherapy. Among the PSA rises, PSA increased continuously or did not decrease to the stabilization level by the third evaluation in 22 (26.5 %) patients, while PSA decreased to the stabilization or response level by the third evaluation in 16 (19.3 %). PSA flare occurred in 17 (20.5 %). The univariate analyses showed that no baseline parameters were associated with PSA flare, but the initial ALP decrease, changed ALP ratio, and median calcium level were significantly associated with PSA flare (p = 0.001, p = 0.008 and p = 0.012, respectively). Multivariate logistic regression analysis showed that a change in the ALP level is an independent predictive factor for PSA flare (p = 0.017).

CONCLUSIONS

ALP is a useful biomarker to differentiate PSA flare from early PSA progression during docetaxel chemotherapy in CRPC patients with bone metastasis.

Topoisomerase inhibitors modulate gene expression of B-cell translocation gene 2 and prostate specific antigen in prostate carcinoma cells

Camptothecin (CPT) and doxorubicin (DOX) have been demonstrated to have potent anti-tumor activity. The B-cell translocation gene 2 (BTG2) is involved in the regulation of cell cycle progression. We evaluated the molecular mechanisms of CPT and DOX on cell proliferation and the expressions of BTG2 and prostate specific antigen (PSA) in prostate carcinoma cells. Our results indicated that CPT or DOX treatments induced Go/G1 cell cycle arrest in LNCaP cells and apoptosis at higher dosage. Immunoblot and transient gene expression assay indicated that CPT or DOX treatments induced p53 and BTG2 gene expression, with the later effect dependent on the p53 response element within BTG2 promoter area since mutation of the p53 response element from GGGAAAGTCC to GGAGTCC or from GGCAGAGCCC to GGCACC by site-directed mutagenesis abolished the stimulation of CPT or DOX on the BTG2 promoter activity, which is also supported by our results that cotreatments of pifithrin-α, an inhibitor of p53 dependent transcriptional activation, blocked the induction of CPT or DOX on BTG2 gene expression. CPT or DOX also downregulated the protein expressions of androgen receptor (AR) and PSA. Transient gene expression assays suggested that CPT or DOX’s attenuation of PSA promoter activity is dependent on both the androgen and p53 response elements within of the PSA promoter. Our results indicated that CPT and DOX attenuate cell proliferation via upregulation of BTG2 gene expression through the p53-dependent pathway. The CPT and DOX block the PSA gene expression by upregulation of p53 activity and downregulation of androgen receptor activity.

Kallikreins on steroids: structure, function, and hormonal regulation of prostate-specific antigen and the extended kallikrein locus

The 15 members of the kallikrein-related serine peptidase (KLK) family have diverse tissue-specific expression profiles and putative proteolytic functions. The kallikrein family is also emerging as a rich source of disease biomarkers with KLK3, commonly known as prostate-specific antigen, being the current serum biomarker for prostate cancer. The kallikrein locus is also notable because it is extraordinarily responsive to steroids and other hormones. Indeed, at least 14 functional hormone response elements have been identified in the kallikrein locus. A more comprehensive understanding of the transcriptional regulation of kallikreins may help the field make more informed hypotheses about the physiological functions of kallikreins and their effectiveness as biomarkers. In this review, we describe the organization of the kallikrein locus and the structure of kallikrein genes and proteins. We also focus on the transcriptional regulation of kallikreins by androgens, progestins, glucocorticoids, mineralocorticoids, estrogens, and other hormones in animal models and human prostate, breast, and reproductive tract tissues. The interaction of the androgen receptor with androgen response elements in the promoter and enhancer of KLK2 and KLK3 is also summarized in detail. There is evidence that all kallikreins are regulated by multiple nuclear receptors. Yet, apart from KLK2 and KLK3, it is not clear whether all kallikreins are direct transcriptional targets. Therefore, we argue that gaining more detailed information about the mechanisms that regulate kallikrein expression should be a priority of future studies and that the kallikrein locus will continue to be an important model in the era of genome-wide analyses.

A coregulatory role for the mediator complex in prostate cancer cell proliferation and gene expression

Androgen receptor (AR) signaling pathways are important for the survival and proliferation of prostate cancer cells. Because AR activity is facilitated by distinct coregulatory factors and complexes, it is conceivable that some of these proteins might also play a role in promoting prostate oncogenesis. The multisubunit Mediator complex is an important coactivator for a broad range of regulatory transcriptional factors including AR, yet its role in prostate cancer is unclear. Here, we used RNA interference to knock down the expression of two integral Mediator components, MED1/TRAP220 and MED17, in prostate cancer cells. MED1/TRAP220 plays a particularly important role in androgen signaling in that it serves as a direct binding target for AR. We found that the knockdown of either subunit markedly decreases transcription from transiently transfected androgen-responsive reporter genes, as well as inhibits androgen-dependent expression of endogenous AR target genes. We show for the first time that loss of either MED1/TRAP220 or MED17 in prostate cancer cells significantly decreases both androgen-dependent and -independent cellular proliferation, inhibits cell cycle progression, and increases apoptosis. Furthermore, we show that MED1/TRAP220 is overexpressed in both AR-positive and -negative prostate cancer cells lines, as well as in 50% (10 of 20) of the clinically localized human prostate cancers we examined, thus suggesting that MED1/TRAP220 hyperactivity may have implications in prostate oncogenesis. In sum, our data suggest that Mediator plays an important coregulatory role in prostate cancer cell proliferation and survival, and therefore, may represent a new target for therapeutic intervention.

Advances in preclinical investigation of prostate cancer gene therapy

Treating recurrent prostate cancer poses a great challenge to clinicians. Research efforts in the last decade have shown that adenoviral vector-based gene therapy is a promising approach that could expand the arsenal against prostate cancer. This maturing field is at the stage of being able to translate many preclinical discoveries into clinical practices. At this juncture, it is important to highlight the promising strategies including prostate-targeted gene expression, the use of oncolytic vectors, therapy coupled to reporter gene imaging, and combined treatment modalities. In fact, the early stages of clinical investigation employing combined, multimodal gene therapy focused on loco-regional tumor eradication and showed promising results. Clinicians and scientists should seize the momentum of progress to push forward to improve the therapeutic outcome for the patients.

Specific targeting of gene therapy to prostate cancer using a two-step transcriptional amplification system

Significant advances in gene therapy have been made as a result of the improvement of gene delivery systems, discovery of new therapeutic genes, better understanding of mechanisms of disease progression, exploration and improvement of tissue-specific gene regulatory sequences, and development of better prodrug/enzyme systems. This review discusses adenoviral-based and prostate-specific cancer gene therapy--emphasizing tissue-specific promoter choices to increase gene therapy safety and specificity--and the development of prostate-targeted vectors, with a focus on the two-step transactivation system for amplifying gene expression, specifically in prostate cancer cells. Several examples will be discussed for the scientific basis and therapeutic applications. In addition, prostate cancer gene therapy clinical trials and future directions in this field will also be described briefly.