Neural Transcription Factors in Disease Progression.

Progression to the malignant state is fundamentally dependent on transcriptional regulation in cancer cells. Optimum abundance of cell cycle proteins, angiogenesis factors, immune evasion markers, etc. is needed for proliferation, metastasis or resistance to treatment. Therefore, dysregulation of transcription factors can compromise the normal prostate transcriptional network and contribute to malignant disease progression.The androgen receptor (AR) is considered to be a key transcription factor in prostate cancer (PCa) development and progression. Consequently, androgen pathway inhibitors (APIs) are currently the mainstay in PCa treatment, especially in castration-resistant prostate cancer (CRPC). However, emerging evidence suggests that with increased administration of potent APIs, prostate cancer can progress to a highly aggressive disease that morphologically resembles small cell carcinoma, which is referred to as neuroendocrine prostate cancer (NEPC), treatment-induced or treatment-emergent small cell prostate cancer. This chapter will review how neuronal transcription factors play a part in inducing a plastic stage in prostate cancer cells that eventually progresses to a more aggressive state such as NEPC.

Hsp27 regulates EGF/ß-catenin mediated epithelial to mesenchymal transition in prostate cancer.

Increased expression of the molecular chaperone Hsp27 is associated with the progression of prostate cancer (PCa) to castration-resistant disease, which is lethal due to metastatic spread of the prostate tumor. Metastasis requires epithelial to mesenchymal transition (EMT), which endows cancer cells with the ability to disseminate from the primary tumor and colonize new tissue sites. A wide variety of secreted factors promote EMT, and while overexpression and constitutive activation of epidermal growth factor (EGF) signaling is associated with poor prognosis of PCa, a precise role of EGF in PCa progression to metastasis remains unclear. Here, we show that Hsp27 is required for EGF-induced cell migration, invasion and MMPs activity as well as the expression of EMT markers including Fibronectin, Vimentin and Slug with concomitant decrease of E-cadherin. Mechanistically, we found that Hsp27 is required for EGF-induced AKT and GSK3ß phosphorylation and ß-catenin nuclear translocation. Moreover, silencing Hsp27 decreases EGF dependent phosphorylation of ß-catenin on tyrosine 142 and 654, enhances ß-catenin ubiquitination and degradation, prevents ß-catenin nuclear translocation and binding to the Slug promoter. These data suggest that Hsp27 is required for EGF-mediated EMT via modulation of the ß-catenin/Slug signaling pathway. Together, our findings underscore the importance of Hsp27 in EGF induced EMT in PCa and highlight the use of Hsp27 knockdown as a useful strategy for patients with advanced disease.

PEG10 is associated with treatment-induced neuroendocrine prostate cancer.

Neuroendocrine (NE) differentiation of advanced prostate adenocarcinoma following androgen receptor (AR) axis-directed therapy is becoming increasingly recognized. Several models of this transdifferentiation provide insight into its molecular pathogenesis and have highlighted the placental gene PEG10 for further study. Using our unique model of enzalutamide resistance (ENZR) and NE differentiation, we studied PEG10/AR interplay in enzalutamide treatment-resistant cell lines 42DENZR and 42FENZR compared to LNCaP and castration-resistant 16DCRPC cells. ENZR cell lines with positive terminal NE marker status also displayed higher baseline expression of PEG10 compared to LNCaP and 16DCRPC. Antagonism of AR activity increased PEG10 expression followed by an increase in terminal NE markers. Conversely, stimulating AR activity via androgen supplementation reversed PEG10 and NE marker expression in a time and dose-dependent manner. These results were supported by human data showing that PEG10 expression is highest in NEPC and that AR-dependent gene, PSA, is negatively correlated with PEG10 in adenocarcinoma. Further, ChIP assay confirmed binding of activated AR to the PEG10 enhancer, decreasing PEG10 expression. While PEG10 did not drive NEPC, its knockdown reduced NE markers in our cell lines. Moreover, PEG10 knockdown in vitro- and in vivo-attenuated tumor growth. Overall, these observations indicate that PEG10 is an AR-repressed gene which modulates NE markers in ENZR cells and targeting PEG10 in advanced prostate cancer with NE features is a rational and viable option.

Galiellalactone inhibits the STAT3/AR signaling axis and suppresses Enzalutamide-resistant Prostate Cancer.

Most prostate cancer patients will progress to a castration-resistant state (CRPC) after androgen ablation therapy and despite the development of new potent anti-androgens, like enzalutamide (ENZ), which prolong survival in CRPC, ENZ-resistance (ENZR) rapidly occurs. Re-activation of the androgen receptor (AR) is a major mechanism of resistance. Interrogating our in vivo derived ENZR model, we discovered that transcription factor STAT3 not only displayed increased nuclear localization but also bound to and facilitated AR activity. We observed increased STAT3 S727 phosphorylation in ENZR cells, which has been previously reported to facilitate AR binding. Strikingly, ENZR cells were more sensitive to inhibition with STAT3 DNA-binding inhibitor galiellalactone (GPA500) compared to CRPC cells. Treatment with GPA500 suppressed AR activity and significantly reduced expression of Cyclin D1, thus reducing cell cycle progression into S phase and hindering cell proliferation. In vivo, GPA500 reduced tumor volume and serum PSA in ENZR xenografts. Lastly, the combination of ENZ and GPA500 was additive in the inhibition of AR activity and proliferation in LNCaP and CRPC cells, providing rationale for combination therapy. Overall, these results suggest that STAT3 inhibition is a rational therapeutic approach for ENZR prostate cancer, and could be valuable in CRPC in combination with ENZ.

Chaperoning the Cancer: The Proteostatic Functions of the Heat Shock Proteins in Cancer.

BACKGROUND: Protein homeostasis (proteostasis) is vital for the survival of cells in physiological and pathological conditions. Particularly, cancer cells are in constant state of cellular stress due to rapid proliferation and decreased quality control in proteosynthesis and therefore, are exceedingly dependent on the homeostasis pathways. Among the complex biological mechanisms regulating proteostasis are the highly conserved molecular chaperones, heat shock proteins (HSPs). HSPs assist cell survival by catalysing the proper folding of proteins, modulation of the apoptotic machinery and finally regulating the protein degradation machinery, providing either the stability or the degradation of selected proteins under stress conditions. Inevitably, HSPs are upregulated in malignancies and participate in different hallmarks of cancer, with indispensable roles in the onset and progression of the disease. Moreover, high levels of HSPs contribute to poor prognosis and treatment resistance in various cancers. Therefore these molecular chaperones present as attractive targets for anti-cancer therapy. OBJECTIVE: This review describes how HSPs regulate different hallmarks of cancer and provides an overview on the most relevant patents which have recently appeared in the literature. METHODS: The patents were extracted from Google Patents (2012-2016) while the clinical trial results were mined from www.clinicaltrial.gov. RESULTS AND CONCLUSION: Review of literature shows that the proteostatic functions of HSPs can modify different hallmarks of cancer. Moreover, targeting HSPs (notably HSP27, HSP70 and HSP90) exhibited positive results in clinical trials so far. However, more studies should be designed to optimize the efficacy of mono or combination therapy in various malignancies.

The Master Neural Transcription Factor BRN2 Is an Androgen Receptor-Suppressed Driver of Neuroendocrine Differentiation in Prostate Cancer.

Mechanisms controlling the emergence of lethal neuroendocrine prostate cancer (NEPC), especially those that are consequences of treatment-induced suppression of the androgen receptor (AR), remain elusive. Using a unique model of AR pathway inhibitor-resistant prostate cancer, we identified AR-dependent control of the neural transcription factor BRN2 (encoded by POU3F2) as a major driver of NEPC and aggressive tumor growth, both in vitro and in vivo Mechanistic studies showed that AR directly suppresses BRN2 transcription, which is required for NEPC, and BRN2-dependent regulation of the NEPC marker SOX2. Underscoring its inverse correlation with classic AR activity in clinical samples, BRN2 expression was highest in NEPC tumors and was significantly increased in castration-resistant prostate cancer compared with adenocarcinoma, especially in patients with low serum PSA. These data reveal a novel mechanism of AR-dependent control of NEPC and suggest that targeting BRN2 is a strategy to treat or prevent neuroendocrine differentiation in prostate tumors. SIGNIFICANCE: Understanding the contribution of the AR to the emergence of highly lethal, drug-resistant NEPC is critical for better implementation of current standard-of-care therapies and novel drug design. Our first-in-field data underscore the consequences of potent AR inhibition in prostate tumors, revealing a novel mechanism of AR-dependent control of neuroendocrine differentiation, and uncover BRN2 as a potential therapeutic target to prevent emergence of NEPC. Cancer Discov; 7(1); 54-71. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 1.

Molecular chaperone Hsp27 regulates the Hippo tumor suppressor pathway in cancer.

Heat shock protein 27 (Hsp27) is a molecular chaperone highly expressed in aggressive cancers, where it is involved in numerous pro-tumorigenic signaling pathways. Using functional genomics we identified for the first time that Hsp27 regulates the gene signature of transcriptional co-activators YAP and TAZ, which are negatively regulated by the Hippo Tumor Suppressor pathway. The Hippo pathway inactivates YAP by phosphorylating and increasing its cytoplasmic retention with the 14.3.3 proteins. Gain and loss of function experiments in prostate, breast and lung cancer cells showed that Hsp27 knockdown induced YAP phosphorylation and cytoplasmic localization while overexpression of Hsp27 displayed opposite results. Mechanistically, Hsp27 regulates the Hippo pathway by accelerating the proteasomal degradation of ubiquitinated MST1, the core Hippo kinase, resulting in reduced phosphorylation/activity of LATS1 and MOB1, its downstream effectors. Importantly, our in vitro results were supported by data from human tumors; clinically, high expression of Hsp27 in prostate tumors is correlated with increased expression of YAP gene signature and reduced phosphorylation of YAP in lung and invasive breast cancer clinical samples. This study reveals for the first time a link between Hsp27 and the Hippo cascade, providing a novel mechanism of deregulation of this tumor suppressor pathway across multiple cancers.

Effect of herbal medicine achillea millefolium on plasma nitrite and nitrate levels in patients with chronic kidney disease: a preliminary study.

INTRODUCTION: Increased plasma nitric oxide concentration has been supposed as one of the possible mechanisms of bleeding tendency in patients who suffer chronic kidney disease. Nitric oxide-scavenging properties have been reported with some Achillea species. This study was designed to find any possible effect of Achillea millefolium on plasma nitric oxide concentration in these patients. MATERIALS AND METHODS: Thirty-one chronic kidney disease patients were included in this randomized controlled trial, of whom16 received 1.5 g of powdered A millefolium flower 3 days a week for 2 months, and 15 received placebo for the same period. Plasma samples were collected before and after the study period to estimate the effect of A millefolium on plasma nitric oxide metabolites (nitrite and nitrate). RESULTS: Although not statistically significant, plasma nitrite and nitrate concentrations decreased after 2 months' administration of A millefolium (0.82 ± 0.51 µmol/L to 0.63 ± 0.42 µmol/L and 50.55 ± 17.92 µmol/L to 44.09 ± 17.49 µmole/L, respectively). These concentrations were slightly increased in the placebo group after the study period. CONCLUSIONS: Countercurrent to the placebo group, plasma nitric oxide metabolites were marginally decreased after A millefolium administration in chronic kidney disease patients. Higher doses or longer duration of plant administration may make these changes more significant.

Concomitant chemopreventive and antibacterial effects of some Iranian plants from the genus Cousinia (Asteraceae)

During the past several years, various species of Cousinia (Asteraceae) have been authenticated in Iran. However, data concerning their biological activities remain limited. The main purpose of this research was to assess potential cytotoxicity and matrix metalloproteinases (MMP) inhibitory effects of seven ethanol extracts of Cousinia using a cell line model (Fibrosarcoma-WEHI 164). We further investigated the antibacterial activity of these Cousinia ethanol extracts, using disk diffusion method. Among the ethanol extracts, the total extract of C. sulabadensis elicited significant inhibition of MMP activity in a dose-response fashion (49.2 ± 0.51, p < 0.05). However, this extract exhibited the lowest cytotoxicity effect at all tested concentrations. The concentration necessary to produce a 50 percent cell death rate (IC50) with C. shulabadensis was 304.5 ± 0.61 μg/mL. The calculated IC50 for cytotoxicity of the other Cousinia species extracts ranged between 18.4 ± 0.59 to 87.9 ± 0.58 μg/mL. The highest antibacterial activity was observed for the total extract of Cousinia phyllocephala. In conclusion, this study supports that Cousinia species display a remarkable inhibition of matrix metalloproteinases activity. The concomitant MMP-inhibitory and low cytotoxicity effects observed in C. sulabadensis might coin this extract for future potential anti-invasive herbal medicine studies.

Durante os últimos anos, várias espécies de Cousinia (Asteraceae) têm sido identificadas no Irã. No entanto, dados acerca de suas atividades biológicas permanecem limitados. O principal propósito desta pesquisa foi avaliar a potencial citotoxidade e os efeitos inibitórios de metaloproteinases da matriz (MMP) de sete extratos etanólicos de Cousinia utilizando um modelo de linhagem celular (Fibrosarcoma-WEHI 164). Além disso, investigamos a atividade antibacteriana destes extratos etanólicos de Cousinia, utilizando o método de difusão em disco. Dentre os extratos etanólicos, o extrato total de C. sulabadensis promoveu inibição significativa da atividade de MMP de maneira dose-resposta (49,2 ± 0,51, p < 0,05). Todavia, este extrato exibiu o menor efeito de citotoxicidade em todas as concentrações testadas. A concentração necessária para produzir uma taxa de 50 por cento de morte celular (IC50) com C. shulabadensis foi 304,5 ± 0,61 μg/mL. A IC50 calculada para a citotoxicidade dos outros extratos de espécies de Cousinia situou-se entre 18,4 ± 0,59 e 87,9 ± 0,58 μg/mL. A maior atividade antibacteriana foi observada para o extrato total de Cousinia phyllocephala. Em conclusão, este estudo corrobora que espécies de Cousinia mostram uma notável inibição da atividade de metaloproteinases da matriz. Os concomitantes efeitos inibitórios de MMP e baixa citotoxicidade observados em C. sulabadensis devem direcionar este extrato para futuros estudos de potenciais fitoterápicos anti-invasivos.