Endothelin-1 enhances the expression of the androgen receptor via activation of the c-myc pathway in prostate cancer cells

Implications of c-Myc in the pathogenesis and treatment efficacy of urological cancers

Urological cancers, including prostate, bladder, and renal cancers, are significant causes of death and negatively impact the quality of life for patients. The development and progression of these cancers are linked to the dysregulation of molecular pathways. c-Myc, recognized as an oncogene, exhibits abnormal levels in various types of tumors, and current evidence supports the therapeutic targeting of c-Myc in cancer treatment. This review aims to elucidate the role of c-Myc in driving the progression of urological cancers. c-Myc functions to enhance tumorigenesis and has been documented to increase growth and metastasis in prostate, bladder, and renal cancers. Furthermore, the dysregulation of c-Myc can result in a diminished response to therapy in these cancers. Non-coding RNAs, β-catenin, and XIAP are among the regulators of c-Myc in urological cancers. Targeting and suppressing c-Myc therapeutically for the treatment of these cancers has been explored. Additionally, the expression level of c-Myc may serve as a prognostic factor in clinical settings.

Targeting PHB1 to inhibit castration-resistant prostate cancer progression in vitro and in vivo

BACKGROUND

Castration-resistant prostate cancer (CRPC) is currently the main challenge for prostate cancer (PCa) treatment, and there is an urgent need to find novel therapeutic targets and drugs. Prohibitin (PHB1) is a multifunctional chaperone/scaffold protein that is upregulated in various cancers and plays a pro-cancer role. FL3 is a synthetic flavagline drug that inhibits cancer cell proliferation by targeting PHB1. However, the biological functions of PHB1 in CRPC and the effect of FL3 on CRPC cells remain to be explored.

METHODS

Several public datasets were used to analyze the association between the expression level of PHB1 and PCa progression as well as outcome in PCa patients. The expression of PHB1 in human PCa specimens and PCa cell lines was examined by immunohistochemistry (IHC), qRT-PCR, and Western blot. The biological roles of PHB1 in castration resistance and underlying mechanisms were investigated by gain/loss-of-function analyses. Next, in vitro and in vivo experiments were conducted to investigate the anti-cancer effects of FL3 on CRPC cells as well as the underlying mechanisms.

RESULTS

PHB1 expression was significantly upregulated in CRPC and was associated with poor prognosis. PHB1 promoted castration resistance of PCa cells under androgen deprivation condition. PHB1 is an androgen receptor (AR) suppressive gene, and androgen deprivation promoted the PHB1 expression and its nucleus-cytoplasmic translocation. FL3, alone or combined with the second-generation anti-androgen Enzalutamide (ENZ), suppressed CRPC cells especially ENZ-sensitive CRPC cells both in vitro and in vivo. Mechanically, we demonstrated that FL3 promoted trafficking of PHB1 from plasma membrane and mitochondria to nucleus, which in turn inhibited AR signaling as well as MAPK signaling, yet promoted apoptosis in CRPC cells.

CONCLUSION

Our data indicated that PHB1 is aberrantly upregulated in CRPC and is involved in castration resistance, as well as providing a novel rational approach for treating ENZ-sensitive CRPC.

Reciprocal regulation of CIP2A and AR expression in prostate cancer cells

Cancerous inhibitor of protein phosphatase 2A (CIP2A) is an oncoprotein overexpressed in human malignancies, including prostate cancer (PCa). In this study, we aimed to explore the oncogenic function of CIP2A in PCa cells and its underlying mechanism. We showed that 63.3% (38/60 cases) of PCa tissues exhibited a high CIP2A immunostaining, compared to 25% (3/12 cases) of BPH samples (p = 0.023). Furthermore, the protein level of CIP2A was positively correlated with patients' short survival time and nuclear AR levels in PCa tissues. Compared to PZ-HPV-7, an immortalized prostate cell line, androgen-sensitive LNCaP C-33, androgen-independent LNCaP C-81, or 22Rv1 cells exhibited a high CIP2A level, associated with high protein and phosphorylation levels of AR. While AR expression and activity modulated CIP2A expression, manipulating CIP2A expression in PCa cells regulated their AR protein levels and proliferation. The reduction of CIP2A expression also enhanced the sensitivity of PCa cells toward Enzalutamide treatment. Our data further showed that depletion of polo-kinase 1 (PLK1) expression or activity in C-81 or 22Rv1 cells caused reduced protein levels of c-Myc and AR. Notably, inhibition of PLK1 activity could abolish CIP2A-promoted expressions in c-Myc, AR, and prostate-specific antigen (PSA) in C-33 cells under an androgen-deprived condition, suggesting the role of PLK1 activity in CIP2A-promoted AR expression. In summary, our data showed the existence of a novel regulation between CIP2A and AR protein levels, which is critical for promoting PCa malignancy. Thus, CIP2A could serve as a therapeutic target for PCa.

RNF8 up-regulates AR/ARV7 action to contribute to advanced prostate cancer progression

Androgen receptor (AR) signaling drives prostate cancer (PC) progression. Androgen deprivation therapy (ADT) is temporally effective, whereas drug resistance inevitably develops. Abnormal expression of AR/ARV7 (the most common AR splicing variant) is critical for endocrine resistance, while the detailed mechanism is still elusive. In this study, bioinformatics and immunohistochemical analyses demonstrate that RNF8 is high expressed in PC and castration-resistant PC (CRPC) samples and the expression of RNF8 is positively correlated with the Gleason score. The high expression of RNF8 in PCs predicts a poor prognosis. These results provide a potential function of RNF8 in PC progression. Furthermore, the mRNA expression of RNF8 is positively correlated with that of AR in PC. Mechanistically, we find that RNF8 upregulates c-Myc-induced AR transcription via altering histone modifications at the c-Myc binding site within the AR gene. RNF8 also acts as a co-activator of AR, promoting the recruitment of AR/ARV7 to the KLK3 (PSA) promoter, where RNF8 modulates histone modifications. These functions of RNF8 are dependent on its E3 ligase activity. RNF8 knockdown further reduces AR transactivation and PSA expression in CRPC cells with enzalutamide treatment. RNF8 depletion restrains cell proliferation and alleviates enzalutamide resistance in CRPC cells. Our findings indicate that RNF8 may be a potential therapeutic target for endocrine resistance in PC.

Endothelin-1 induces changes in the expression levels of steroidogenic enzymes and increases androgen receptor and testosterone production in the PC3 prostate cancer cell line

Endothelin-1 (ET-1) is involved in the regulation of steroidogenesis. Additionally, patients with castration-resistant prostate cancer (PCa) have a higher ET-1 plasma concentration than those with localized PCa and healthy individuals. The aim of the present study was to evaluate the effect of ET-1 on steroidogenesis enzymes, androgen receptor (AR) and testosterone (T) production in PCa cells. The expression levels of endothelin receptors in prostate tissue from patients with localized PCa by immunohistochemistry, and those in LNCaP and PC3 cells were determined reverse transcription-quantitative PCR (RT-qPCR) and western blotting. Furthermore, the expression levels of ET-1 were determined in LNCaP and PC3 cells by RT-qPCR and western blotting. The ET-1 receptor activation was evaluated by intracellular calcium measurement, the expression levels of AR and enzymes participating in steroidogenesis [cytochrome P450 family 11 subfamily A member 1 (CyP11A1), cytochrome P450 family 17 subfamily A member 1, aldo-keto reductase family member C2 and 3β-hydroxysteroid dehydrogenase/isomerase 2 (3β HSD2)] were determined by western blotting and T concentration was determined by ELISA using PC3 cells. The present results revealed higher expression levels of endothelin A receptor (ET_AR) in tissues obtained from samples of patients with PCa with a low Gleason Score. No changes were identified for endothelin B receptor (ET_BR). PC3 cells expressed higher levels of ET-1 and ET_AR, while LNCaP cells exhibited higher expression levels of ET_BR. Blocking of ET_AR and endothelin B receptor decreased the expression levels of CyP11A1 and 3β HSD2 enzymes and AR in PC3 cells, as well as T secretion. These findings suggested that ET-1 has a potential role in modulating the intratumoral steroidogenesis pathway and might have relevance as a possible therapeutic target.

IKBKE activity enhances AR levels in advanced prostate cancer via modulation of the Hippo pathway

Resistance to androgen receptor (AR) targeting therapeutics in prostate cancer (PC) is a significant clinical problem. Mechanisms by which this is accomplished include AR amplification and expression of AR splice variants, demonstrating that AR remains a key therapeutic target in advanced disease. For the first time we show that IKBKE drives AR signalling in advanced PC. Significant inhibition of AR regulated gene expression was observed upon siRNA-mediated IKBKE depletion or pharmacological inhibition due to inhibited AR gene expression in multiple cell line models including a LNCaP derivative cell line resistant to the anti-androgen, enzalutamide (LNCaP-EnzR). Phenotypically, this resulted in significant inhibition of proliferation, migration and colony forming ability suggesting that targeting IKBKE could circumvent resistance to AR targeting therapies. Indeed, pharmacological inhibition in the CWR22Rv1 xenograft mouse model reduced tumour size and enhanced survival. Critically, this was validated in patient-derived explants where enzymatic inactivation of IKBKE reduced cell proliferation and AR expression. Mechanistically, we provide evidence that IKBKE regulates AR levels via Hippo pathway inhibition to reduce c-MYC levels at cis-regulatory elements within the AR gene. Thus, IKBKE is a therapeutic target in advanced PC suggesting repurposing of clinically tested IKBKE inhibitors could be beneficial to castrate resistant PC patients.

Genetic architecture of acne vulgaris

Acne vulgaris is a ubiquitary skin disease characterized by chronic inflammation of the pilosebaceous unit resulting from bacterial colonization of hair follicles by Propionibacterium acnes, androgen-induced increased sebum production, altered keratinization and inflammation. Here, we review our current understanding of the genetic architecture of this intriguing disease. We analysed genomewide association studies (GWAS) and candidate genes studies for acne vulgaris. Moreover, we included GWAS studies for the associated disease polycystic ovary syndrome (PCOS). Overall, the available data revealed sixteen genetic loci flagged by single nucleotide polymorphisms (SNPs), none of which has been confirmed yet by independent studies. Moreover, a GWAS for PCOS identified 21 susceptible loci. The genetic architecture is complex which has been revealed by GWAS. Further and larger studies in different populations are required to confirm or disprove results from candidate gene studies as well to identify signals that may overlap between different populations. Finally, studies on rare genetic variants in acne and associated diseases like PCOS may deepen our understanding of its pathogenesis.

Sulforaphane increases the efficacy of anti-androgens by rapidly decreasing androgen receptor levels in prostate cancer cells

Prostate cancer (PCa) cells utilize androgen for their growth. Hence, androgen deprivation therapy (ADT) using anti-androgens, e.g. bicalutamide (BIC) and enzalutamide (ENZ), is a mainstay of treatment. However, the outgrowth of castration resistant PCa (CRPC) cells remains a significant problem. These CRPC cells express androgen receptor (AR) and utilize the intratumoral androgen towards their continued growth and invasion. Sulforaphane (SFN), a naturally occurring isothiocyanate found in cruciferous vegetables, can decrease AR protein levels. In the present study, we tested the combined efficacy of anti-androgens and SFN in suppressing PCa cell growth, motility and clonogenic ability. Both androgen-dependent (LNCaP) and androgen-independent (C4-2B) cells were used to monitor the effects of BIC and ENZ, alone and in combination with SFN. Co-exposure to SFN significantly (p<0.005) enhanced the anti-proliferative effects of anti-androgens and downregulated expression of the AR-responsive gene, prostate specific antigen (PSA) (p<0.05). Exposure to SFN decreased AR protein levels in a time- and dose-dependent manner with almost no AR detected at 24 h with 15 µM SFN (p<0.005). This rapid and potent AR suppression by SFN occurred by both AR protein degradation, as suggested by cycloheximide (CHX) co-exposure studies, and by suppression of AR gene expression, as evident from quantitative RT-PCR experiments. Pre-exposure to SFN also reduced R1881-stimulated nuclear localization of AR, and combined treatment with SFN and anti-androgens abrogated the mitogenic effects of this AR-agonist (p<0.005). Wound-healing assays revealed that co-exposure to SFN and anti-androgens can significantly (p<0.005) reduce PCa cell migration. In addition, long-term exposures (14 days) to much lower concentrations of these agents, SFN (0.2 µM), BIC (1 µM) and/or ENZ (0.4 µM) significantly (p<0.005) decreased the number of colony forming units (CFUs). These findings clearly suggest that SFN may be used as a promising adjunct agent to augment the efficacy of anti-androgens against aggressive PCa cells.

Expression and functional role of orphan receptor GPR158 in prostate cancer growth and progression

Prostate cancer (PCa) is the second-leading cause of cancer-related mortality, after lung cancer, in men from developed countries. In its early stages, primary tumor growth is dependent on androgens, thus generally can be controlled by androgen deprivation therapy (ADT). Eventually however, the disease progresses to castration-resistant prostate cancer (CRPC), a lethal form in need of more effective treatments. G-protein coupled receptors (GPCRs) comprise a large clan of cell surface proteins that have been implicated as therapeutic targets in PCa growth and progression. The findings reported here provide intriguing evidence of a role for the newly characterized glutamate family member GPR158 in PCa growth and progression. We found that GPR158 promotes PCa cell proliferation independent of androgen receptor (AR) functionality and that this requires its localization in the nucleus of the cell. This suggests that GPR158 acts by mechanisms different from other GPCRs. GPR158 expression is stimulated by androgens and GPR158 stimulates AR expression, implying a potential to sensitize tumors to low androgen conditions during ADT via a positive feedback loop. Further, we found GPR158 expression correlates with a neuroendocrine (NE) differentiation phenotype and promotes anchorage-independent colony formation implying a role for GPR158 in therapeutic progression and tumor formation. GPR158 expression was increased at the invading front of prostate tumors that formed in the genetically defined conditional Pten knockout mouse model, and co-localized with elevated AR expression in the cell nucleus. Kaplan-Meier analysis on a dataset from the Memorial Sloan Kettering cancer genome portal showed that increased GPR158 expression in tumors is associated with lower disease-free survival. Our findings strongly suggest that pharmaceuticals targeting GPR158 activities could represent a novel and innovative approach to the prevention and management of CRPC.

Gene expression profiles of NO- and HNO-donor treated breast cancer cells: insights into tumor response and resistance pathways

Nitric oxide (NO) synthase 2 (NOS2), a major inflammatory protein, modulates disease progression via NO in a number of pathologies, including cancer. The role of NOS2-derived NO is not only flux-dependent, which is higher in mouse vs human cells, but also varies based on spatial and temporal distribution both within tumor cells and in the tumor microenvironment. NO donors have been utilized to mimic NO flux conditions and to investigate the effects of varied NO concentrations. As a wide range of effects mediated by NO and other nitrogen oxides such as nitroxyl (HNO) have been elucidated, multiple NO- and HNO-releasing compounds have been developed as potential therapeutics, including as tumor modulators. One of the challenges is to determine differences in biomarker expression from extracellular vs intracellular generation of NO or HNO. Taking advantage of new NO and HNO releasing agents, we have characterized the gene expression profile of estrogen receptor-negative human breast cancer (MDA-MB-231) cells following exposure to aspirin, the NO donor DEA/NO, the HNO donor IPA/NO andtheir intracellularly-activated prodrug conjugates DEA/NO-aspirin and IPA/NO-aspirin. Comparison of the gene expression profiles demonstrated that several genes were uniquely expressed with respect to NO or HNO, such as miR-21, HSP70, cystathionine γ-lyase and IL24. These findings provide insight into targets and pathways that could be therapeutically exploited by the redox related species NO and HNO.

Inhibition of RSK/YB-1 signaling enhances the anti-cancer effect of enzalutamide in prostate cancer

BACKGROUND

Previously, we have shown that Y-box binding protein-1 (YB-1) regulates androgen receptor (AR) expression and contributes to castration resistance. However, the mechanism of YB-1 activation remains unknown. In this study, we aimed to elucidate the mechanism and role of YB-1 activation in relation to castration resistance as well as enzalutamide resistance, with a view to developing a novel therapeutic concept for castration-resistant prostate cancer (CRPC) treatment.

METHODS

The expression and phosphorylation levels of ribosomal S6 kinase 1 (RSK1), YB-1 and AR were examined by quantitative PCR and Western blotting using prostate cancer cells. In addition, the effects of YB-1 inhibition using specific siRNA and small molecule inhibitor SL0101 on AR expression as well as combination treatment with enzalutamide and SL0101 were examined.

RESULTS

We found that androgen deprivation, as well as treatment with the next-generation anti-androgen enzalutamide, induced RSK1 and YB-1 activation followed by AR induction, which could be reversed by YB-1 shutdown and RSK inhibitor SL0101. SL0101 and enzalutamide exerted a synergistic tumor-suppressive effect on cell proliferation in androgen-dependent prostate cancer LNCaP cells, as well as castration-resistant C4-2 cells. Furthermore, the phosphorylation levels of RSK1 and YB-1 were elevated in castration- and enzalutamide-resistant cells, compared with their parental cells.

CONCLUSIONS

Taken together, these findings indicate that RSK1/YB-1 signaling contributes to castration as well as enzalutamide resistance, and that the therapeutic targeting of RSK1/YB-1 signaling would be a promising novel therapy against prostate cancer, especially CRPC when combined with enzalutamide.

A genome-wide association study of severe teenage acne in European Americans

Despite the family aggregation of severe teenage acne, the genetic basis of this common skin condition remains unclear. We conducted a genome-wide association study (GWAS) on severe teenage acne in 928 European Americans. The SNP rs4133274 on chromosome 8q24 (72 kb upstream of MYC) revealed the most significant association with severe teenage acne (p value = 1.7 × 10(-6)). The variant allele of this SNP (G allele) was associated with an increased risk of severe teenage acne with odds ratio of 4.01 (95 % confidence interval = 2.37-6.82). Upon further replication, our findings suggest new genetic basis of acne and may explain the association between acne and cancer risk observed in the epidemiological studies.

Regulation of several androgen-induced genes through the repression of the miR-99a/let-7c/miR-125b-2 miRNA cluster in prostate cancer cells

The androgen receptor (AR) stimulates and represses gene expression to promote the initiation and progression of prostate cancer. Here, we report that androgen represses the miR-99a/let7c/125b-2 cluster through AR and anti-androgen drugs block the androgen-repression of the miRNA cluster. AR directly binds to the host gene of the miR-99a/let7c/125b-2 cluster, LINC00478. Expression of the cluster is repressed or activated by chromatin remodelers EZH2 or JMJD3 in the presence or absence of androgen, respectively. Bioinformatics analysis reveals a significant enrichment of targets of miR-99a, let-7c and miR-125b in androgen-induced gene sets, suggesting that downregulation of the miR-99a/let7c/125b-2 cluster by androgen protects many of their target mRNAs from degradation and indirectly assists in the gene induction. We validated the hypothesis with 12 potential targets of the miR-99a/let7c/125b-2 cluster induced by androgen: 9 out of the 12 mRNAs are downregulated by the microRNA cluster. To ascertain the biological significance of this hypothesis, we focused on IGF1R, a known prostate cancer growth factor that is induced by androgen and directly targeted by the miR-99a/let7c/125b-2 cluster. The androgen-induced cell proliferation is ameliorated to a similar extent as anti-androgen drugs by preventing the repression of the microRNAs or induction of IGF1R in androgen-dependent prostate cancer cells. Expression of a microRNA-resistant form of IGF1R protects these cells from inhibition by the miR-99a/let7c/125b-2 cluster. These results indicate that a thorough understanding of how androgen stimulates prostate cancer growth requires not only an understanding of genes directly induced/repressed by AR, but also of genes indirectly induced by AR through the repression of key microRNAs.

Pro-survival and anti-apoptotic properties of androgen receptor signaling by oxidative stress promote treatment resistance in prostate cancer

Oxidative stress caused by an increase in reactive oxygen species levels or a decrease in cellular antioxidant capacity can evoke the modulation of various cellular events including androgen receptor (AR) signaling via direct or indirect interactions. In this review, we summarize the mechanisms of AR activation by oxidative stress including: i) AR overexpression; ii) AR activation by AR co-regulators or intracellular signal transduction pathways; iii) generation of AR mutations or splice variants; and iv) de novo androgen synthesis. AR signaling augmented by oxidative stress appears to contribute to pro-survival and anti-apoptotic effects in prostate cancer cells in response to androgen deprivation therapy. In addition, AR signaling suppresses anti-survival and pro-apoptotic effects in prostate cancer cells in response to various cytotoxic and tumor-suppressive interventions including taxanes and radiation through the modulation of βIII-tubulin and ataxia telangiectasia-mutated kinase expression respectively. Taken together, AR signaling appears to render prostate cancer cells refractory to various therapeutic interventions including castration, taxanes, and radiation, indicating that AR signaling is a comprehensive resistant factor and crucial target for prostate cancer treatment.

Biology of castration-recurrent prostate cancer

Although androgen-deprivation therapy is the standard therapy for advanced and metastatic prostate cancer, this treatment is only palliative. Prostate cancer recurs then grows despite low circulating testicular androgens, using several mechanisms that remain dependent on androgen-receptor signaling in most cases. This article reviews the diversity of mechanisms used for growth by castration-recurrent prostate cancer.

Oxidative stress and androgen receptor signaling in the development and progression of castration-resistant prostate cancer

Aberrant androgen receptor (AR) signaling plays a critical role in androgen-dependent prostate cancer (PCa), as well as in castration-resistant PCa (CRPC). Oxidative stress seems to contribute to the tumorigenesis and progression of PCa, as well as the development of CRPC, via activation of AR signaling. This notion is supported by the fact that there is an aberrant or improper regulation of the redox status in these disorders. Additionally, androgen-deprivation-induced oxidative stress seems to be involved in the pathogenesis of several disorders caused by androgen-deprivation therapy (ADT), including osteoporosis, neurodegenerative disease, and cardiovascular disease. Oxidative stress can be suppressed with antioxidants or via a reduction in reactive oxygen species production. Thus, developing new therapeutic agents that reduce oxidative stress might be useful in preventing the conversion of androgen-dependent PCa into CRPC, as well as reducing the adverse effects associated with ADT. The objective of this review is to provide an overview regarding the relationship between oxidative stress and AR signaling in the context of PCa and especially CRPC. Additionally, we discuss the potential use of antioxidant therapies in the treatment of PCa.

Increased androgen receptor transcription: a cause of castration-resistant prostate cancer and a possible therapeutic target

Few effective therapies exist for the treatment of castration-resistant prostate cancer (CRPC). Recent evidence suggests that CRPC may be caused by augmented androgen/androgen receptor (AR) signaling, generally involving AR overexpression. Aberrant androgen/AR signaling associated with AR overexpression also plays a key role in prostate carcinogenesis. Although AR overexpression could be attributed to gene amplification, only 10-20% of CRPCs exhibit AR gene amplification, and aberrant AR expression in the remaining instances of CRPC is thought to be attributed to transcriptional, translational, and post-translational mechanisms. Overexpression of AR at the protein level, as well as the mRNA level, has been found in CRPC, suggesting a key role for transcriptional regulation of AR expression. Since the analysis of the AR promoter region in the 1990s, several transcription factors have been reported to regulate AR transcription. In this review, we discuss the molecules involved in the control of AR gene expression, with emphasis on its transcriptional control by transcription factors in prostate cancer. We also consider the therapeutic potential of targeting AR expression.

Regulation of androgen receptor expression through angiotensin II type 1 receptor in prostate cancer cells

BACKGROUND

Although the local renin-angiotensin system (RAS) of the prostate gland is related to cell proliferation and angiogenesis, the detailed mechanism remains unclear. We examined the effects of the angiotensin II type 1 receptor (AT1R) on androgen receptor (AR) expression in prostate cancer cells.

METHODS

AR modulation by AT1R was examined by Western blot analysis, luciferase assay, and Immunocytochemical staining. The influence of AR expression by angiotensin II (Ang-II) and AT1R inhibition using siRNA was determined. Furthermore, using angiotensinogen or AT1R knockout (KO) mice, we performed quantitative real-time PCR to investigate the expression of AR.

RESULTS

Ang-II induced cell proliferation with enhancement of AR, prostate specific antigen (PSA), NF-κB, and c-myc, and the activity of AR and PSA promoter. Cell proliferation of LNCaP transfected with AT1R siRNA was decreased by 75% at 7 days by inhibition of AR, PSA, NF-κB, and c-myc. Immunocytochemical staining confirmed the suppression of AR translocation into the nucleus in AT1R siRNA cells. AT1R KO mice showed a decrease in AR expression in the prostate gland. We also found that the expression level of AT1R could modulate the transcriptional level of AR by affecting NF-κB and c-myc expression.

CONCLUSIONS

Knocking down of the AT1R protein resulted in significant inhibition of cell growth, associated with a marked decrease of AR protein. These results indicate that inhibition of AT1R has the potential to influence AR expression in prostate cells, and is anticipated to contribute to the development of novel therapeutic agents for prostate cancer.

Dynamics of plasma proteome during leptin-replacement therapy in genetically based leptin deficiency

The effects of leptin-replacement therapy on the plasma proteome of three unique adults with genetically based leptin deficiency were studied longitudinally during the course of recombinant human leptin-replacement treatment. Quantitative proteomics analysis was performed in plasma samples collected during four stages: before leptin treatment was initiated, after 1.5 and 6 years of leptin-replacement treatment, and after 7 weeks of temporary interruption of leptin-replacement therapy. Of 500 proteins reliably identified and quantitated in those four stages, about 100 were differentially abundant twofold or more in one or more stages. Synchronous dynamics of abundances of about 90 proteins was observed reflecting both short- and long-term effects of leptin-replacement therapy. Pathways and processes enriched with overabundant synchronous proteins were cell adhesion, cytoskeleton remodeling, cell cycle, blood coagulation, glycolysis, and gluconeogenesis. Plausible common regulators of the above synchronous proteins were identified using transcription regulation network analysis. The generated network included two transcription factors (c-Myc and androgen receptor) that are known to activate each other through a double-positive feedback loop, which may represent a potential molecular mechanism for the long-term effects of leptin-replacement therapy. Our findings may help to elucidate the effects of leptin on insulin resistance.

From pathogenesis to prevention of castration resistant prostate cancer

BACKGROUND

Significant progress in understanding the molecular basis of castration resistant prostate cancer (CRPCa) has been achieved in recent years. Despite this progress, CRPCa still remains a lethal disease. Early detection and prevention of CRPCa may provide a new strategy to improve survival of patients diagnosed with PCa at risk to fail standard androgen deprivation therapy (ADT).

METHODS

Herein, we review pathogenetic mechanisms implicated in PCa progression toward castration resistant disease that are detectable in hormone naive PCa to define relevant therapeutic targets for prevention.

RESULTS

Upregulation of androgen receptor (AR) expression has been recognized a major determinant for the development of CRPCa. This hypersensitive pathway is further boosted by the increase of intratumoral androgen synthesis. AR mutants bind promiscuous steroids, and may convert AR antagonists to agonists. Various non-hormonal growth factor receptors transactivate the AR, even in absence of androgens (outlaw pathway). Finally, PCa cells can bypass the AR through various mechanisms, including BCL-2, COX-2, neuroendocrine differentiation. Most of these pathogenetic factors involved in the development of CRPCa are detectable in hormone naive PCa tissue even at the time of initial diagnosis, and could be targeted by drugs currently available.

CONCLUSIONS

CRPCa is the end-stage of a multifactorial and heterogeneous disease process. Pathogenetic factors responsible for the development of the CRPCa phenotype are detectable in the patient's PCa tissue long before the clinical onset of the disease. This approach provides opportunity for early detection and prevention by targeting pathways relevant for the individual disease process.