Androgen-dependent Prostate Cancer Research Articles

The experimental study of ^131I labeling prostate stem cell antigen monoclonal antibody in the treat-ment of nude mice bearing orthotopic implantation of prostate carcinomar

Objective To study the distribution, radioimmunoimaging and anti-tumor effect of ^131I labeling prostate stem cell antigen monoclonal antibody （^131I-PSCA-McAb） in nude mice bearing orthotopic implantation of prostate carcinoma. Methods Thirty-six male nude mice were randomly divided into 2 groups： LNCap cell group （androgen dependent prostate cancer） and PC3 cell group （androgen independent prostate cancer）. Each group were then subdivided into 3 subgroups： experimental group （were intrave noused 1311-PSCA-McAb 200 μg）, monoclonal control group （were intravenoused PSCA-McAb 200 μg）, iodic control group （ were intravenoused 1311 200 μg）. Continuous images of nude mice bearing LNCap cell and PC3 cell were carried out respectively at 1, 4, 8, 12 and 24 h after drugs injection. Transplantation tumor images were then observed and the radioactivity ratio of tumor/non-tumor （T/NT） was calculated. 48 h later, nude mice were sacrificed and the apoptosis of tumor tissues were measured by TdT-mediated dUTP nick end labeling （TUNEL）. Results The models of nude mice bearing orthotopic implantation of prostate carcinoma were successfully established. The peak uptake of ^131I_PSCA.McAb in orthotopic tumor of prostate carcinoma was at 8h after injection with a T/NT ratio of 4.37 ± 0. 76 （LNCap cell group） and 4. 21±0. 71 （PC3 cell group） respectively. The number of TUNEL positive cells in experimental group was larger than that of the two other control groups. Conclusion ^131 I-PSCA-McAb could effectively target PSCA and inhibit the growth of tumor, therefore was a promising radioimmunotherapy radiophamaceutical for prostate carcinoma. Key words: Models of orthotopic implantation of prostate cancer; ^131I labeling prostate stem cellantigen monoclonal antibody; Cell apoptosis; Radioimmunotherapy

Effects of selective inhibitors of the isoprenoid biosynthetic pathway on androgen‐dependent and independent prostate cancer cells (842.6)

The isoprenoid biosynthetic pathway (IBP) provides substrates, such as geranylgeranyl diphosphate (GGDP), which are used to post‐translationally modify proteins that are key regulators of malignant cell properties such as proliferation, migration, and invasion. Clinically relevant IBP inhibitors, including statins and nitrogenous bisphosphonates, affect these malignant cell properties. However, they broadly deplete all mevalonate derivatives, thus affecting farnesylated proteins and cholesterol. XZ‐1‐269 and XZ‐4‐37 were developed as selective inhibitors of GGDP synthase to reduce protein GGation. In the androgen‐dependent prostate cancer (PCa) cell line LNCaP and the highly metastatic androgen‐independent PCa cell line PC3, lovastatin and XZ‐1‐269 more potently reduce protein GGation and cell viability than digeranyl bisphosphonate, XZ‐4‐37, and zoledronate. In the androgen‐independent PCa cell line 22Rv1, all compounds are less potent in reducing protein GGation and cell viability than in LNCaP and PC3 cells. Our findings detail novel compounds for selectively reducing protein GGation in three prostate cancer cell lines. Further work defining the isoprenoid proteins involved in advancing PCa will identify new targets for therapeutic intervention.Grant Funding Source: Supported by NIH Pharmacological Sciences Training Grant T32 GM067795

Antischistosomal versus Antiandrogenic Properties of Aryl Hydantoin Ro 13-3978

In the early 1980s, the antischistosomal aryl hydantoin Ro 13-3978 (AH01), a close structural analogue of the androgen receptor antagonist nilutamide, was discovered. Administration of 100 mg/kg oral doses of AH01 to mice infected with adult and juvenile Schistosoma mansoni produced 95% and 64% total worm burden reductions, confirming its high activity against adult worms, and showing that AH01 is also effective against juvenile infections. AH01 had no measureable interaction with the androgen receptor in a ligand competition assay, but it did block dihydrotestosterone-induced cell proliferation in an androgen-dependent human prostate cancer cell line. For AH01, nilutamide, and three closely related aryl hydantoin derivatives, there was no correlation between antischistosomal activity and androgen receptor interaction.

The NLR-related protein NWD1 is associated with prostate cancer and modulates androgen receptor signaling

Prostate cancer (PCa) is among the leading causes of cancer-related death in men. Androgen receptor (AR) signaling plays a seminal role in prostate development and homeostasis, and dysregulation of this pathway is intimately linked to prostate cancer pathogenesis and progression. Here, we identify the cytosolic NLR-related protein NWD1 as a novel modulator of AR signaling. We determined that expression of NWD1 becomes elevated during prostate cancer progression, based on analysis of primary tumor specimens. Experiments with cultured cells showed that NWD1 expression is up-regulated by the sex-determining region Y (SRY) family proteins. Gene silencing procedures, in conjunction with transcriptional profiling, showed that NWD1 is required for expression of PDEF (prostate-derived Ets factor), which is known to bind and co-regulate AR. Of note, NWD1 modulates AR protein levels. Depleting NWD1 in PCa cell lines reduces AR levels and suppresses activity of androgen-driven reporter genes. NWD1 knockdown potently suppressed growth of androgen-dependent LNCaP prostate cancer cells, thus showing its functional importance in an AR-dependent tumor cell model. Proteomic analysis suggested that NWD1 associates with various molecular chaperones commonly related to AR complexes. Altogether, these data suggest a role for tumor-associated over-expression of NWD1 in dysregulation of AR signaling in PCa.

Inhibition of Protein Kinase C/Twist1 Signaling Augments Anticancer Effects of Androgen Deprivation and Enzalutamide in Prostate Cancer

The progression of prostate cancer to metastatic and castration-resistant disease represents a critical step. We previously showed that the transcription factor Twist1, which promotes epithelial-mesenchymal transition, was involved in castration-resistant progression. Similarly, protein kinase C (PKC) has been implicated in both metastatic progression and castration resistance in prostate cancer. In this study, we aimed to elucidate the role of PKC/Twist1 signaling in castration resistance, and to apply this information to the development of a novel therapeutic concept using PKC inhibitor Ro31-8220 against prostate cancer using various prostate cancer cell lines. Androgen deprivation and the next-generation antiandrogen enzalutamide induced PKC activation and Twist1 expression, which were reversed by the PKC inhibitor Ro31-8220. Ro31-8220 suppressed cell proliferation in androgen-dependent prostate cancer LNCaP cells, which was augmented by its combination with androgen deprivation or enzalutamide. The favorable anticancer effects of the combination of Ro31-8220 and enzalutamide were also observed in castration-resistant C4-2 and 22Rv1 cells. Furthermore, PKC phosphorylation was elevated in castration-resistant and enzalutamide-resistant cells compared with their parental cells, leading to persistent sensitivity to Ro-31-8220 in castration- and enzalutamide-resistant cells. Taken together, these findings indicate that PKC/Twist1 signaling contributes to castration resistance as well as enzalutamide resistance in prostate cancer, and suggest that therapeutics targeting PKC/Twist1 signaling, such as PKC inhibitors, represent a promising novel therapeutic strategy for prostate cancer, especially castration-resistant prostate cancer, when combined with enzalutamide.

Preclinical efficacy of growth hormone-releasing hormone antagonist MIA-602 for androgen-dependent and castration-resistant human prostate cancer.

221 Background: Advanced hormone-sensitive prostate cancer (PCa) responds to androgen deprivation therapy (ADT). However, therapeutic options for castration-resistant disease are limited. As growth hormone-releasing hormone receptor (GHRH-R) and ligand GHRH are regulated in an autocrine fashion in PCa, GHRH-R inhibition represents a novel approach to PCa treatment. We investigated the effects of a new, highly potent GHRH antagonist, MIA-602, on growth of androgen-dependent and castration-resistant PCa cells in vitro/in vivo. Methods: All three cell lines used in this study expressed androgen receptors (ARs). 22Rv1 cells are castration-resistant and also express clinically relevant AR splice variants. LNCaP and VCaP lines are androgen dependent models that progress to castration resistance following ADT. Protein and mRNA levels of GHRH-R and its biologically active splice variant, SV1, were evaluated in cell lines and tumors by immunoblot and real-time RT-PCR. The influence of MIA-602 on cell proliferation and tumor formation was examined. Results: GHRH-R and SV1 were present in 22Rv1, LNCaP, and VCaP. LNCaP and VCaP cells expressed higher levels of GHRH-R protein compared to 22Rv1. However, 22Rv1 expressed higher levels of SV1. Inhibition of GHRH-R using MIA-602 decreased cell proliferation in vitro of 22Rv1, LNCaP, and VCaP PCa cell lines respectively by 70.4%, 60.7% and 20.3% (P<0.05 for all). MIA-602 decreased 22Rv1 xenograft volumes in mice by 63% after 3 weeks of treatment. VCaP showed a substantial inhibition of xenograft growth following therapy with MIA-602 in vivo. MIA-602 effectively inhibited VCaP xenografts as a single agent or in combination with ADT by surgical castration. Conclusions: The effectiveness of the novel Miami class GHRH antagonist, MIA-602, in inhibiting growth of androgen-dependent and castration-resistant PCa models in vitro and in vivo was demonstrated. The inhibitory effect of GHRH antagonists appear to be due to effects exerted through GHRH receptors on cancer cells and/or possibly by indirect mechanisms. Further investigations of GHRH antagonists for PCa treatment are warranted.

In vitro efficacy of MAGMAS inhibition in prostate cancer.

281 Background: Prostate cancer is the second most common cancer worldwide in males. The initial treatment in advanced cases is medical or surgical castration. The outlook declines when prostate cancer advances independently, despite the aforementioned castration. Within the last ten years, a handful of new agents have proven effective in this castration-resistant phase, but finding more effective, novel ways of treating advanced prostate cancer is warranted. MAGMAS (mitochondria-associated, granulocyte-macrophage colony stimulating factor (GM-CSF) signaling molecule) is a protein ubiquitously expressed in eukaryotic cells that plays a key role in embryonal development in a variety of species. Overexpression of MAGMAS has anti-apoptotic effects, as GM-CSF is a growth factor essential for survival, proliferation and differentiation of cells. MAGMAS and GM-CSF receptor levels have been shown to be overexpressed in prostate cancer, but do not correlate with pathological grade or clinical stage. The purpose of our study was to evaluate the efficacy of a MAGMAS inhibitor, synthesized by Dr Bhaskar Das, in androgen-dependent and androgen-independent prostate cancer cell lines, as well as in a normal prostate cell line as another control. Methods: The different cell lines were treated with MAGMAS inhibitor at various concentrations in vitro. For analysis, we used MTT Cell Proliferation assay at 24 and 48 hours, per manufacturer’s protocol. We tested MAGMAS inhibitor effect on apoptosis/necrosis, cell migration and microtubule destabilization as well. Results: After prostate cancer cell lines were treated with MAGMAS inhibitor in vitro, cell proliferation and migration decreased, apoptosis and necrosis were induced, and microtubules were destabilized, all showing more impressive results in the androgen-independent cells. MAGMAS inhibition did not affect cell proliferation in the normal prostate cells. Conclusions: In vitro studies show MAGMAS inhibition proves efficacious in both androgen-dependent and androgen-independent prostate cancer cell lines. This will be evaluated further in a xenograft mouse model.

MiR-361-5p acts as a tumor suppressor in prostate cancer by targeting signal transducer and activator of transcription-6(STAT6)

Castration-resistant prostate cancer (CRPC), whose pathogenesis is known to be regulated by microRNAs (miRNAs), has a poor prognosis. In our present study, we found that the expression of miR-361-5p in CRPC was lower than in androgen-dependent prostate cancer (ADPC), indicating that miR-361-5p may play an important role in the progression of ADPC to CRPC. The role of miR-361-5p in prostate cancer (PCa) has not been evaluated until date. Our findings suggest that miR-361-5p is a suppressor in CRPC. Signal transducer and activator of transcription-6 (STAT6), a direct target of miR-361-5p, enhances the expression of B-cell lymphoma-extra large (Bcl-xL), while miR-361-5p inhibits its expression through STAT6. Therefore, miR-361-5p has great clinical significance in preventing the malignant progression of PCa.

Genetics, Structure, Function, Mode of Actions and Role in Cancer Development of CYP17

Most prostate and breast cancers are hormone dependent. The inhibition of steroid 17α-hydroxylase/17,20- lyase (CYP17), which is a crucial enzyme for steroid hormone biosynthesis, is widely used to treat androgen-dependent prostate cancer (PC). CYP17 has dual enzymatic activity: 17alpha-hydroxylase activity (utilizing delta4- C21 steroids as substrates) and the 17,20-lyase activity (using delta5- C21 steroids as substrates). The steroid biosynthetic pathway is directed to either the production of corticosteroids or sex hormones depending on the activity of CYP17. In this review, the current information on the genetics, molecular structure, substrate specificity and inhibitors of CYP17 is analyzed and discussed.

Synthesis of bufalin derivatives with inhibitory activity against prostate cancer cells

Bufalin possesses a strong anti-cancer effect, but the cardiac toxicity targeting the Na+, K+-ATPase limits its application. Here, two bufalin derivatives, bufadienolactam (1) and secobufalinamide (2), were synthesised by treating bufalin with ammonium acetate in dimethylformamide solution. Their structures were elucidated by extensive spectroscopic methods. The structure of compound 2 was further confirmed by single-crystal X-ray diffraction analysis. Compounds 1 and 2 expressed strong inhibitory activities against androgen-dependent prostate cancer cells (IC50 values about 10 μM), but only weak inhibition on Na+, K+-ATPase (Ki about 70 μM), indicating that they might be potential anti-prostate cancer agents without severe cardiac toxicity.

Nrf1 and Nrf2 Transcription Factors Regulate Androgen Receptor Transactivation in Prostate Cancer Cells

Despite androgen deprivation therapy (ADT), persistent androgen receptor (AR) signaling enables outgrowth of castration resistant prostate cancer (CRPC). In prostate cancer (PCa) cells, ADT may enhance AR activity through induction of oxidative stress. Herein, we investigated the roles of Nrf1 and Nrf2, transcription factors that regulate antioxidant gene expression, on hormone-mediated AR transactivation using a syngeneic in vitro model of androgen dependent (LNCaP) and castration resistant (C4-2B) PCa cells. Dihydrotestosterone (DHT) stimulated transactivation of the androgen response element (ARE) was significantly greater in C4-2B cells than in LNCaP cells. DHT-induced AR transactivation was coupled with higher nuclear translocation of p65-Nrf1 in C4-2B cells, as compared to LNCaP cells. Conversely, DHT stimulation suppressed total Nrf2 levels in C4-2B cells but elevated total Nrf2 levels in LNCaP cells. Interestingly, siRNA mediated silencing of Nrf1 attenuated AR transactivation while p65-Nrf1 overexpression enhanced AR transactivation. Subsequent studies showed that Nrf1 physically interacts with AR and enhances AR’s DNA-binding activity, suggesting that the p65-Nrf1 isoform is a potential AR coactivator. In contrast, Nrf2 suppressed AR-mediated transactivation by stimulating the nuclear accumulation of the p120-Nrf1 which suppressed AR transactivation. Quantitative RT-PCR studies further validated the inductive effects of p65-Nrf1 isoform on the androgen regulated genes, PSA and TMPRSS2. Therefore, our findings implicate differential roles of Nrf1 and Nrf2 in regulating AR transactivation in PCa cells. Our findings also indicate that the DHT-stimulated increase in p65-Nrf1 and the simultaneous suppression of both Nrf2 and p120-Nrf1 ultimately facilitates AR transactivation in CRPC cells.

Effects of Sulforaphane and 3,3′-Diindolylmethane on Genome-Wide Promoter Methylation in Normal Prostate Epithelial Cells and Prostate Cancer Cells

Epigenetic changes, including aberrant DNA methylation, result in altered gene expression and play an important role in carcinogenesis. Phytochemicals such as sulforaphane (SFN) and 3,3′-diindolylmethane (DIM) are promising chemopreventive agents for the treatment of prostate cancer. Both have been shown to induce re-expression of genes, including tumor suppressor genes silenced in cancer cells, via modulation of epigenetic marks including DNA methylation. However, it remained unclear the effects SFN and DIM on DNA methylation at a genomic scale. The goal of this study was to determine the genome-wide effects of SFN and DIM on promoter methylation in normal prostate epithelial cells and prostate cancer cells. Both SFN and DIM treatment decreased DNA methyltransferase expression in normal prostate epithelial cells (PrEC), and androgen-dependent (LnCAP) and androgen-independent (PC3) prostate cancer cells. The effects of SFN and DIM on promoter methylation profiles in normal PrEC, LnCAP and PC3 prostate cancer cells were determined using methyl-DNA immunoprecipitation followed by genome-wide DNA methylation array. We showed widespread changes in promoter methylation patterns, including both increased and decreased methylation, in all three prostate cell lines in response to SFN or DIM treatments. In particular, SFN and DIM altered promoter methylation in distinct sets of genes in PrEC, LnCAP, and PC3 cells, but shared similar gene targets within a single cell line. We further showed that SFN and DIM reversed many of the cancer-associated methylation alterations, including aberrantly methylated genes that are dysregulated or are highly involved in cancer progression. Overall, our data suggested that both SFN and DIM are epigenetic modulators that have broad and complex effects on DNA methylation profiles in both normal and cancerous prostate epithelial cells. Results from our study may provide new insights into the epigenetic mechanisms by which SFN and DIM exert their cancer chemopreventive effects.

The role of sLZIP in cyclin D3-mediated negative regulation of androgen receptor transactivation and its involvement in prostate cancer

Androgen and the androgen receptor (AR) have important roles in prostate cancer (PCa) development, and androgen ablation has been the main therapeutic option for the treatment of PCa. However, the transition mechanism from androgen-dependent to -independent PCa after androgen depletion remains unclear. We investigated the distinct roles of small leucine zipper protein (sLZIP) in proliferation of androgen-dependent and -independent PCa cells. Cyclin D3 is known to interact with AR and attenuates the ligand-dependent function of AR in PCa cells. sLZIP regulates the transcription of cyclin D3 by binding directly to the AP-1 region in the cyclin D3 promoter. sLZIP represses AR transcriptional activity by interaction with AR that is phosphorylated by cyclin D3/cyclin-dependent kinase11(p58), leading to the suppression of androgen-dependent proliferation of PCa cells. The expression level of sLZIP is elevated in androgen-independent PCa cells and advanced human prostate tumors. Knockdown of endogenous sLZIP suppresses proliferation of androgen-independent PCa cells. LNCaP cells transformed to androgen-independent PCa cells exhibit increased expressions of sLZIP and cyclin D3. Tumor formation is inhibited in nude mouse xenografts from two androgen-independent PCa cells that are stably transfected with sh-sLZIP. Our findings indicate that sLZIP negatively regulates AR transactivation in androgen-dependent PCa cells and functions as a positive regulator in tumor progression of androgen-independent PCa. sLZIP contributes to the malignant phenotype of PCa and constitutes a novel therapeutic target for human PCa.

Preclinical efficacy of growth hormone-releasing hormone antagonists for androgen-dependent and castration-resistant human prostate cancer

Advanced hormone-sensitive prostate cancer responds to androgen-deprivation therapy (ADT); however, therapeutic options for recurrent castration-resistant disease are limited. Because growth hormone-releasing hormone (GHRH) and GHRH receptor (GHRH-R) are regulated in an autocrine fashion in prostate cancer, inhibition of GHRH-R represents a compelling approach to treatment. We investigated the effects of the latest series of improved, highly potent GHRH antagonists--MIA-602, MIA-606, and MIA-690--on the growth of androgen-dependent as well as castration-resistant prostate cancer (CRPC) cells in vitro and in vivo. GHRH-R and its splice variant, SV1, were present in 22Rv1, LNCaP, and VCaP human prostate cancer cell lines. Androgen-dependent LNCaP and VCaP cells expressed higher levels of GHRH-R protein compared with castration-resistant 22Rv1 cells; however, 22Rv1 expressed higher levels of SV1. In vitro, MIA-602 decreased cell proliferation of 22Rv1, LNCaP, and VCaP prostate cancer cell lines by 70%, 61%, and 20%, respectively (all P < 0.05), indicating direct effects of MIA-602. In vivo, MIA-602 was more effective than MIA-606 and MIA-690 and decreased 22Rv1 xenograft tumor volumes in mice by 63% after 3 wk (P < 0.05). No noticeable untoward effects or changes in body weight occurred. In vitro, the VCaP cell line was minimally inhibited by MIA-602, but in vivo, this line showed a substantial reduction in growth of xenografts in response to MIA-602, indicating both direct and systemic inhibitory effects. MIA-602 also further inhibited VCaP xenografts when combined with ADT. This study demonstrates the preclinical efficacy of the GHRH antagonist MIA-602 for treatment of both androgen-dependent and CRPC.

Cytokine effects on cell viability and death of prostate carcinoma cells.

We analyzed the effects of IL-13, IFN-γ, and IL-1β on cell viability and death of LNCaP and PC-3 cells and major signaling pathways involved in these effects. Significant increase of LNCaP cell death (apoptotic and necrotic) and increased levels of active caspase 3 were observed in cells treated with inhibitors of ERK 1/2 (UO126) and p38 (SB203580) prior to IL-1β treatment in comparison to cells treated with UO126, SB203580, or IL-1β alone. Significant increase of LNCaP but not PC-3 cell death was detected after treatment with LY-294002 (inhibitor of phosphatidylinositol 3-kinase). No significant increase of LNCaP and PC-3 cell death was observed after treatment with SP600125 (inhibitor of JNK), SB203580 (inhibitor of p38), UO126 (inhibitor of ERK 1/2), or BAY 11-7082 (inhibitor of NF-κB). Reduced c-FLIPL expression was observed in LNCaP cells treated with LY-294002. The significant potentiation of LNCaP cell death by inhibition of ERK 1/2, p38, and PI3-K pathways may provide a rationale for therapeutic approach in androgen-dependent prostate cancer.

Resveratrol Inhibits Hypoxia-Inducible Factor-1^|^alpha;-Mediated Androgen Receptor Signaling and Represses Tumor Progression in Castration-Resistant Prostate Cancer

Androgen-dependent prostate cancer inevitably progresses to incurable castration-resistant prostate cancer (CRPC) after androgen deprivation therapy. Because castration-induced hypoxia-inducible factor (HIF)-1α enhances the transcriptional activity of androgen receptor (AR) at low androgen levels mimicking the castration-resistant stage, HIF-1α is expected to be a promising target for suppression of growth of CRPC. We investigated the effect of resveratrol (3,4',5-trihydroxy-trans-stilbene) on the growth of human prostate cancer LNCaP xenografts in castrated male BALB/cSlc-nu/nu mice (5 wk old). The mice were administered a control diet or a resveratrol diet (4 g/kg diet) for 40 d. The resveratrol diet significantly suppressed tumor growth compared to the control diet. In LNCaP xenografts, dietary resveratrol decreased the protein level of HIF-1α, but not the AR coactivator β-catenin, and reduced the mRNA levels of androgen-responsive genes. In the control group, β-catenin was predominantly localized in the nucleus with HIF-1α in LNCaP xenografts, whereas dietary resveratrol inhibited the nuclear accumulation of β-catenin. In hypoxic LNCaP cells at a low androgen level mimicking the castration-resistant stage, hypoxia-induced nuclear accumulation of β-catenin was inhibited by resveratrol. Furthermore, resveratrol repressed the expression level of HIF-1α even in the presence of a proteasome inhibitor and suppressed hypoxia-enhanced AR transactivation. These results indicate that dietary resveratrol represses nuclear localization of β-catenin by decreasing the HIF-1α expression, perhaps in a proteasome-independent manner, and inhibits β-catenin-mediated AR signaling; this contributes to suppression of tumor growth of CRPC.

Androgen receptor as a driver of therapeutic resistance in advanced prostate cancer.

The role of the androgen receptor (AR) signaling axis in the progression of prostate cancer is a cornerstone to our understanding of the molecular mechanisms causing castration-resistant prostate cancer (CRPC). Resistance of advanced prostate cancer to available treatment options makes it a clinical challenge that results in approximately 30,000 deaths of American men every year. Since the historic discovery by Dr. Huggins more than 70 years ago, androgen deprivation therapy (ADT) has been the principal treatment for advanced prostate cancer. Initially, ADT induces apoptosis of androgen-dependent prostate cancer epithelial cells and regression of androgen-dependent tumors. However, the majority of patients with advanced prostate cancer progress and become refractory to ADT due to emergence of androgen-independent prostate cancer cells driven by aberrant AR activation. Microtubule-targeting agents such as taxanes, docetaxel and paclitaxel, have enjoyed success in the treatment of metastatic prostate cancer; although new, recently designed mitosis-specific agents, such as the polo-kinase and kinesin-inhibitors, have yielded clinically disappointing results. Docetaxel, as a first-line chemotherapy, improves prostate cancer patient survival by months, but tumor resistance to these therapeutic agents inevitably develops. On a molecular level, progression to CRPC is characterized by aberrant AR expression, de novo intraprostatic androgen production, and cross talk with other oncogenic pathways. Emerging evidence suggests that reactivation of epithelial-mesenchymal-transition (EMT) processes may facilitate the development of not only prostate cancer but also prostate cancer metastases. EMT is characterized by gain of mesenchymal characteristics and invasiveness accompanied by loss of cell polarity, with an increasing number of studies focusing on the direct involvement of androgen-AR signaling axis in EMT, tumor progression, and therapeutic resistance. In this article, we discuss the current knowledge of mechanisms via which the AR signaling drives therapeutic resistance in prostate cancer metastatic progression and the novel therapeutic interventions targeting AR in CRPC.

Metabolomic profiling identifies biochemical pathways associated with castration-resistant prostate cancer.

Despite recent developments in treatment strategies, castration-resistant prostate cancer (CRPC) is still the second leading cause of cancer-associated mortality among American men, the biological underpinnings of which are not well understood. To this end, we measured levels of 150 metabolites and examined the rate of utilization of 184 metabolites in metastatic androgen-dependent prostate cancer (AD) and CRPC cell lines using a combination of targeted mass spectrometry and metabolic phenotyping. Metabolic data were used to derive biochemical pathways that were enriched in CRPC, using Oncomine concept maps (OCM). The enriched pathways were then examined in-silico for their association with treatment failure (i.e., prostate specific antigen (PSA) recurrence or biochemical recurrence) using published clinically annotated gene expression data sets. Our results indicate that a total of 19 metabolites were altered in CRPC compared to AD cell lines. These altered metabolites mapped to a highly interconnected network of biochemical pathways that describe UDP glucuronosyltransferase (UGT) activity. We observed an association with time to treatment failure in an analysis employing genes restricted to this pathway in three independent gene expression data sets. In summary, our studies highlight the value of employing metabolomic strategies in cell lines to derive potentially clinically useful predictive tools.

Prolonged androgen deprivation leads to overexpression of calpain 2: Implications for prostate cancer progression

Understanding the molecular mechanism of prostate cancer progression from androgen dependence to independence may lead to developing more effective treatments against prostate cancer. Herein, our previous in vitro model was employed to assess the effects of continuous androgen-deprivation on developing the metastatic phenotype from androgen-dependent prostate cancer cells (LNCaP). The results indicated that long-term androgen deprivation resulted in overexpression of calpain 2 and increased expression of filamin A (FlnA), but not for calpain 1. The enhanced activity of calpain 2 was confirmed by the accumulation of cleaved FlnA fragments, which could be effectively blocked by calpeptin (an inhibitor of calpain 2). Therefore, the combination of calpain 2 inhibitor and androgen deprivation may provide new therapeutic strategy for patients to prevent or postpone prostate cancer progression.

Pao Pereira Extract Suppresses Castration-Resistant Prostate Cancer Cell Growth, Survival, and Invasion Through Inhibition of NFκB Signaling

Pao extract, derived from bark of Amazonian tree Pao Pereira, is commonly used in South American medicine. A recent study showed that Pao extract repressed androgen-dependent LNCaP prostate cancer cell growth. We hypothesize that Pao extract asserts its anticancer effects on metastatic castration-resistant prostate cancer (CRPC) cells. Pao extract suppressed CRPC PC3 cell growth in a dose- and time-dependent manner, through induction of apoptosis and cell cycle arrest. Pao extract treatment induced cell cycle inhibitors, p21 and p27, and repressed PCNA, Cyclin A and Cyclin D1. Furthermore, Pao extract also induced the upregulation of pro-apoptotic Bax, reduction of anti-apoptotic Bcl-2, Bcl-xL, and XIAP expression, which were associated with the cleavage of PARP protein. Moreover, Pao extract treatment blocked PC3 cell migration and invasion. Mechanistically, Pao extract suppressed phosphorylation levels of AKT and NFκB/p65, NFκB DNA binding activity, and luciferase reporter activity. Pao inhibited TNFα-induced relocation of NFκB/p65 to the nucleus, NFκB/p65 transcription activity, and MMP9 activity as shown by zymography. Consistently, NFκB/p65 downstream targets involved in proliferation (Cyclin D1), survival (Bcl-2, Bcl-xL, and XIAP), and metastasis (VEGFa, MMP9, and GROα/CXCL1) were also downregulated by Pao extract. Finally, forced expression of NFκB/p65 reversed the growth inhibitory effect of Pao extract. Overall, Pao extract induced cell growth arrest, apoptosis, partially through inhibiting NFκB activation in prostate cancer cells. These data suggest that Pao extract may be beneficial for protection against CRPC.