ERbeta impedes prostate cancer EMT by destabilizing HIF-1alpha and inhibiting VEGF-mediated snail nuclear localization: implications for Gleason grading

Differential expression of estrogen receptor α, β1, and β2 in lobular and ductal breast cancer

The role of estrogen receptor (ER) α as a target in treatment of breast cancer is clear, but those of ERβ1 and ERβ2 in the breast remain unclear. We have examined expression of all three receptors in surgically excised breast samples from two archives: (i): 187 invasive ductal breast cancer from a Japanese study; and (ii) 20 lobular and 24 ductal cancers from the Imperial College. Samples contained normal areas, areas of hyperplasia, and in situ and invasive cancer. In the normal areas, ERα was expressed in not more than 10% of epithelium, whereas approximately 80% of epithelial cells expressed ERβ. We found that whereas ductal cancer is a highly proliferative, ERα-positive, ERβ-negative disease, lobular cancer expresses both ERα and ERβ but with very few Ki67-positive cells. ERβ2 was expressed in 32% of the ductal cancers, of which 83% were postmenopausal. In all ERβ2-positive cancers the interductal space was filled with dense collagen, and cell nuclei expressed hypoxia-inducible factor 1α. ERβ2 expression was not confined to malignant cells but was strong in stromal, immune, and endothelial cells. In most of the high-grade invasive ductal cancers neither ERα nor ERβ was expressed, but in the high-grade lobular cancer ERβ was lost and ERα and Ki67 expression were abundant. The data show a clear difference in ER expression between lobular and ductal breast cancer and suggest (i) that tamoxifen may be more effective in late than in early lobular cancer and (ii) a potential role for ERβ agonists in preventing in situ ductal cancers from becoming invasive.

Prostate cancer: the need for biomarkers and new therapeutic targets

Prostate cancer (PCa) incidence and mortality have decreased in recent years. Nonetheless, it remains one of the most prevalent cancers in men, being a disquieting cause of men's death worldwide. Changes in many cell signaling pathways have a predominant role in the onset, development, and progression of the disease. These include prominent pathways involved in the growth, apoptosis, and angiogenesis of the normal prostate gland, such as androgen and estrogen signaling, and other growth factor signaling pathways. Understanding the foundations of PCa is leading to the discovery of key molecules that could be used to improve patient management. The ideal scenario would be to have a panel of molecules, preferably detectable in body fluids, that are specific and sensitive biomarkers for PCa. In the early stages, androgen deprivation is the gold standard therapy. However, as the cancer progresses, it eventually becomes independent of androgens, and hormonal therapy fails. For this reason, androgen-independent PCa is still a major therapeutic challenge. By disrupting specific protein interactions or manipulating the expression of some key molecules, it might be possible to regulate tumor growth and metastasis formation, avoiding the systemic side effects of current therapies. Clinical trials are already underway to assess the efficacy of molecules specially designed to target key proteins or protein interactions. In this review, we address that recent progress made towards understanding PCa development and the molecular pathways underlying this pathology. We also discuss relevant molecular markers for the management of PCa and new therapeutic challenges.

Epithelial-mesenchymal plasticity in carcinoma metastasis

Tumor metastasis is a multistep process by which tumor cells disseminate from their primary site and form secondary tumors at a distant site. Metastasis occurs through a series of steps: local invasion, intravasation, transport, extravasation, and colonization. A developmental program termed epithelial-mesenchymal transition (EMT) has been shown to play a critical role in promoting metastasis in epithelium-derived carcinoma. Recent experimental and clinical studies have improved our knowledge of this dynamic program and implicated EMT and its reverse program, mesenchymal-epithelial transition (MET), in the metastatic process. Here, we review the functional requirement of EMT and/or MET during the individual steps of tumor metastasis and discuss the potential of targeting this program when treating metastatic diseases.

Insight into the mechanisms of action of estrogen receptor β in the breast, prostate, colon, and CNS

Estrogen and its receptors (ERs) influence many biological processes in physiology and pathology in men and women. ERs are involved in the etiology and/or progression of cancers of the prostate, breast, uterus, ovary, colon, lung, stomach, and malignancies of the immune system. In estrogen-sensitive malignancies, ERβ usually is a tumor suppressor and ERα is an oncogene. ERβ regulates genes in several key pathways including tumor suppression (p53, PTEN); metabolism (PI3K); survival (Akt); proliferation pathways (p45(Skp2), cMyc, and cyclin E); cell-cycle arresting factors (p21(WAF1), cyclin-dependent kinase inhibitor 1 (CDKN1A)), p27(Kip1), and cyclin-dependent kinases (CDKs); protection from reactive oxygen species, glutathione peroxidase. Because they are activated by small molecules, ERs are excellent targets for pharmaceuticals. ERα antagonists have been used for many years in the treatment of breast cancer and more recently pharmaceutical companies have produced agonists which are very selective for ERα or ERβ. ERβ agonists are being considered for preventing progression of cancer, treatment of anxiety and depression, as anti-inflammatory agents and as agents, which prevent or reduce the severity of neurodegenerative diseases.

VEGF targets the tumour cell

The function of vascular endothelial growth factor (VEGF) in cancer is not limited to angiogenesis and vascular permeability. VEGF-mediated signalling occurs in tumour cells, and this signalling contributes to key aspects of tumorigenesis, including the function of cancer stem cells and tumour initiation. In addition to VEGF receptor tyrosine kinases, the neuropilins are crucial for mediating the effects of VEGF on tumour cells, primarily because of their ability to regulate the function and the trafficking of growth factor receptors and integrins. This has important implications for our understanding of tumour biology and for the development of more effective therapeutic approaches.

The roles of HLH transcription factors in epithelial mesenchymal transition and multiple molecular mechanisms

Epithelial-to-mesenchymal transition (EMT) is presently recognized as an important event and the initiating stage for tumor invasion and metastasis. Several EMT inducers have been identified, among which the big family of helix-loop-helix (HLH) transcription factors are rising as a novel and promising family of proteins in EMT mediation, such as Twist1, Twist2, E47, and HIFs, etc. Due to the variety and complexities of HLH members, the pathways and mechanisms they employ to promote EMT are also complex and characteristic. In this review, we will discuss the roles of various HLH proteins in the regulation and sustenance of the EMT and multiple cellular mechanisms, attempting to provide a novel and broadened view towards the link between HLH proteins and EMT.

Suppression of ERβ signaling via ERβ knockout or antagonist protects against bladder cancer development

Epidemiological studies showed that women have a lower bladder cancer (BCa) incidence, yet higher muscle-invasive rates than men, suggesting that estrogen and the estrogen receptors, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ), may play critical roles in BCa progression. Using in vitro cell lines and an in vivo carcinogen N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN)-induced mouse BCa model, we found that ERβ plays a positive role in promoting BCa progression. Knockdown of ERβ with ERβ-shRNA in ERβ-positive human BCa J82, 647v and T24 cell lines led to suppressed cell growth and invasion. Mice lacking ERβ have less cancer incidence with reduced expression of the proliferation marker Ki67 in BBN-induced BCa. Consistently, our results show that non-malignant urothelial cells with ERβ knockdown are more resistant to carcinogen-induced malignant transformation. Mechanism dissection found that targeting ERβ suppressed the expression of minichromosome maintenance complex component 5 (MCM5), a DNA replication licensing factor that is involved in tumor cell growth. Restoring MCM5 expression can partially reverse ERβ knockdown-mediated growth reduction. Supportively, treating cells with the ERβ-specific antagonist, 4-[2-Phenyl-5,7-bis(trifluoromethyl) pyrazolo[1,5-a]pyrimidin-3-yl]phenol (PHTPP), reduced BCa cell growth and invasion, as well as MCM5 expression. Furthermore, we provide the first evidence that BCa burden and mortality can be controlled by PHTPP treatment in the carcinogen-induced BCa model. Together, these results demonstrate that ERβ could play positive roles in promoting BCa progression via MCM5 regulation. Targeting ERβ through ERβ-shRNA, PHTPP or via downstream targets, such as MCM5, could serve as potential therapeutic approaches to battle BCa.

Down-regulation of RE-1 silencing transcription factor (REST) in advanced prostate cancer by hypoxia-induced miR-106b~25

Clinically aggressive prostate cancer (PCa) is linked to androgen resistance, metastasis, and expression of neuroendocrine markers. To understand mechanism(s) of neuroendocrine differentiation (NED) of PCa epithelia, we compared neuronal differentiation occurring during embryogenesis, in primary cultures of neural crest (NC) cells, and NED in PCa cell lines (LNCaP and PC3). We demonstrate, hypoxia promotes neuronal and neuroendocrine differentiation of NC cells and PCa cells, respectively, by inducing the miR-106 b~25 cluster. In turn, miR-106b~25 comprised of miR-106b, miR-93 and miR-25, down-regulates the transcriptional repressor REST, which represses neuron-specific protein-coding and miRNA genes. In prostate tumors of high Gleason score (≥ 8), an inverse trend was observed between REST and miR-106b~25 induction. Employing miRNA PCR arrays, we identified miRNAs up-regulated by hypoxia in LNCaP cells and REST-knockdown in NC cells. Significantly, a subset of miRNAs (miR-9, miR-25, miR-30d and miR302b) is up-regulated in high Gleason score (≥ 8) PCa, suggesting a mechanism by which NED contributes to PCa malignancy. We propose that loss of REST and induction of this set of microRNAs can serve as potential novel clinical markers of advanced PCa.

Slug is a key mediator of hypoxia induced cadherin switch in HNSCC: correlations with poor prognosis

OBJECTIVES

According to recent studies, the function of Slug in hypoxia induced cadherin switch differs from cancer to cancer. Whether Slug is an essential mediator of the tumor hypoxia induced cadherin switch in head and neck squamous cell carcinoma (HNSCC) and the prognostic role of Slug in HNSCC patients are not elucidated. The aim of this study is to investigate the role of the Slug in cadherin switch induced by hypoxia in HNSCC.

MATERIALS AND METHODS

Two HNSCC cell lines and 119 HNSCC specimens were selected for the present experiments. E/N-cadherins expression and tumor cell invasion responding to hypoxia/HIF-1α overexpression and the silence of Slug/SnaI2 gene were detected in vitro. HNSCC specimens were analyzed by immunohistochemistry staining to correlate the expressions of Slug, HIF-1α and E/N-cadherins with clinical outcomes.

RESULTS AND CONCLUSION

Our research evidenced that Slug was extremely elevated in the HNSCC cells in response to hypoxia/HIF-1α overexpression. Suppressing Slug expression impaired HIF-1α induced cadherin switch and tumor invasion. In HNSCC tissues, relatively high expression of Slug was detected to be associated with endogenous HIF-1α overexpression, cadherin switch, the risk of lymph node metastasis, and a more advanced TNM stage. Additionally, aberrant Slug expression combined with HIF-1α overexpression and cadherin switch was significantly correlated with shorter HNSCC patient survival. In conclusion, Slug is necessary for hypoxia-induced cadherin switch in HNSCC and may be used as a potential risk marker in predicting HNSCC clinical outcomes.

Differential expression of estrogen receptor beta isoforms in prostate cancer through interplay between transcriptional and translational regulation

Estrogen receptor β (ERβ) and its isoforms have different putative functions and expression patterns in prostate cancer. Current studies on 5'-most exons, 0K and 0N, show that their respective promoters are actively involved in transcription. These data, however, do not explain why ERβ isoforms are differentially expressed in normal and cancerous tissues, since 0K and 0N transcripts are detectable in clinical specimens. Various combinations of 5' untranslated exons, termed exon 0Xs, associate with promoter 0K only and exon 0Xs accommodate upstream open reading frames (uORFs) reducing protein expression. Moreover, ERβ1, 2, and 5 are transcriptionally linked to promoter 0K; exon 0Xs are spliced only into ERβ2 and ERβ5 transcripts, suggesting that their expressions are regulated post-transcriptionally by exon 0Xs. This study reveals that expression of ERβ1 is regulated primarily at the transcriptional level, whereas that of ERβ2 and ERβ5 is controlled by the interplay between transcriptional and post-transcriptional regulation.

Ridaifen-SB8, a novel tamoxifen derivative, induces apoptosis via reactive oxygen species-dependent signaling pathway

Tamoxifen is an anticancer agent widely used for treatment of estrogen receptor (ERα)-positive breast cancer. We previously developed a novel synthesis of tamoxifen and its derivatives, named Ridaifens (RIDs). Some of them, including RID-SB8, exhibited a stronger anticancer activity than tamoxifen in ERα-positive MCF-7 cells while having lost the affinity for ERα, suggesting an ERα-independent anticancer mode of action. In this study, we investigated the underlying mechanism by which RID-SB8 exerts anticancer activity. As expected, anticancer activity of RID-SB8 was not influenced upon knockdown of ERα expression in MCF-7 cells. RID-SB8 exerted similar anticancer effects on thirteen ERα-negative cancer cell lines including human gliosarcoma SF539 cells. In SF539 cells, RID-SB8 triggered loss of mitochondrial membrane potential (ΔΨ(m)) and progression of apoptosis accompanied by activation of caspases and translocation of apoptosis-inducing factor (AIF) to the nucleus. Furthermore, it induced reactive oxygen species (ROS), and a ROS scavenger, N-acetylcysteine (NAC), canceled loss of ΔΨ(m) and progression of apoptosis triggered by RID-SB8. Using fifteen human cancer cell lines, we demonstrated a significant correlation between RID-SB8 concentration required for ROS production and that required for cytotoxic effect across these cell lines, but such correlation was not observed for tamoxifen. Finally, the selective induction of ROS and cytotoxic effect on cancer cells by RID-SB8 were confirmed. From these results, we concluded that RID-SB8 exerts an anticancer effect via a mode of action distinct from tamoxifen, and that RID-SB8 could become a promising anticancer lead compound which selectively induces ROS formation and apoptosis in cancer cells.

Lapatinib induces p27(Kip1)-dependent G₁ arrest through both transcriptional and post-translational mechanisms

Lapatinib, a dual EGFR/HER2 tyrosine kinase inhibitor, has been shown to have potent antitumor effects against human breast cancer. Recent studies have shown that lapatinib upregulates p27(Kip1) (here after referred to as p27) expression and induces G₁ cell cycle arrest in various types of cancer cells. However, the regulation of p27 in lapatinib-induced cell cycle arrest is not well studied. Here we demonstrate that lapatinib-induced cell growth inhibition and G₁ cell cycle arrest in HER2-overexpressing human breast cancer cells were dependent on p27. We also show that lapatinib-induced upregulation of p27 expression was mediated through both transcriptional and post-translational mechanisms. On the one hand, lapatinib treatment led to increased FOXO3a expression and enhanced p27 transcription. On the other hand, lapatinib treatment resulted in increased DYRK1B expression, which correlated with increased p27 phosphorylation at Ser10 and decreased p27 degradation. Interestingly, we found that ERβ1 but not ERβ2 expression also upregulated p27 and enhanced lapatinib-induced cell proliferation inhibition and G₁ cell cycle arrest in HER2-overexpressing breast cancer cells. Taken together, our results suggest that lapatinib induces p27 expression via both transcriptional and post-translational upregulations, leading to cell cycle arrest and cell proliferation inhibition, and that its effect on breast cancer cells may be modified by ER expression status.

Hypoxia-dependent modification of collagen networks promotes sarcoma metastasis

Intratumoral hypoxia and expression of hypoxia-inducible factor-1α (HIF-1α) correlate with metastasis and poor survival in patients with sarcoma. We show here that hypoxia controls sarcoma metastasis through a novel mechanism wherein HIF-1α enhances expression of the intracellular enzyme procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (PLOD2). We show that loss of HIF-1α or PLOD2 expression disrupts collagen modification, cell migration, and pulmonary metastasis (but not primary tumor growth) in allograft and autochthonous LSL-Kras(G12D/+); Trp53(fl/fl) murine sarcoma models. Furthermore, ectopic PLOD2 expression restores migration and metastatic potential in HIF-1α-deficient tumors, and analysis of human sarcomas reveals elevated HIF1A and PLOD2 expression in metastatic primary lesions. Pharmacologic inhibition of PLOD enzymatic activity suppresses metastases. Collectively, these data indicate that HIF-1α controls sarcoma metastasis through PLOD2-dependent collagen modification and organization in primary tumors. We conclude that PLOD2 is a novel therapeutic target in sarcomas and successful inhibition of this enzyme may reduce tumor cell dissemination.

SIGNIFICANCE

Undifferentiated pleomorphic sarcoma (UPS) is a commonly diagnosed and particularly aggressive sarcoma subtype in adults, which frequently and fatally metastasizes to the lung. Here, we show the potential use of a novel therapeutic target for the treatment of metastatic UPS, specifi cally the collagen-modifying enzyme PLOD2.

PROX1 promotes hepatocellular carcinoma metastasis by way of up-regulating hypoxia-inducible factor 1α expression and protein stability

Hepatocellular carcinoma (HCC) is one of the most common cancers and the third leading cause of death from cancer worldwide. HCC has a very poor prognosis because of tumor invasiveness, frequent intrahepatic spread, and extrahepatic metastasis. The molecular mechanism of HCC invasiveness and metastasis is poorly understood. The homeobox protein PROX1 is required for hepatocyte migration during mouse embryonic liver development. In this study, we show that high PROX1 protein expression in primary HCC tissues is associated with significantly worse survival and early tumor recurrence in postoperative HCC patients. Knockdown of PROX1 expression in HCC cells inhibited cell migration and invasiveness in vitro and HCC metastasis in nude mice while overexpression of PROX1 in HCC cells promoted these processes. PROX1's pro-metastasis activity is most likely attributed to its up-regulation of hypoxia-inducible factor 1α (HIF-1α) transcription and stabilization of HIF-1α protein by recruiting histone deacetylase 1 (HDAC1) to prevent the acetylation of HIF-1α, which subsequently induces an epithelial-mesenchymal transition response in HCC cells. We further demonstrated the prognostic value of using the combination of PROX1 and HDAC1 levels to predict postoperative survival and early recurrence of HCC.

CONCLUSION

PROX1 is a critical factor that promotes HCC metastasis.

TGF-β modulates ovarian cancer invasion by upregulating CAF-derived versican in the tumor microenvironment

TGF-β has limited effects on ovarian cancer cells, but its contributions to ovarian tumor growth might be mediated through elements of the tumor microenvironment. In the present study, we tested the hypothesis that TGF modulates ovarian cancer progression by modulating the contribution of cancer-associated fibroblasts (CAF) that are present in the microenvironment. Transcriptome profiling of microdissected stromal and epithelial components of high-grade serous ovarian tumors and TGF-β-treated normal ovarian fibroblasts identified versican (VCAN) as a key upregulated target gene in CAFs. Functional evaluations in coculture experiments showed that TGF-β enhanced the aggressiveness of ovarian cancer cells by upregulating VCAN in CAFs. VCAN expression was regulated in CAFs through TGF-β receptor type II and SMAD signaling. Upregulated VCAN promoted the motility and invasion of ovarian cancer cells by activating the NF-κB signaling pathway and by upregulating expression of CD44, matrix metalloproteinase-9, and the hyaluronan-mediated motility receptor. Our work identified a TGF-β-inducible gene signature specific to CAFs in advanced high-grade serous ovarian tumors, and showed how TGF-β stimulates ovarian cancer cell motility and invasion by upregulating the CAF-specific gene VCAN. These findings suggest insights to develop or refine strategies for TGF-β-targeted therapy of ovarian cancer.

Infiltrating bone marrow mesenchymal stem cells increase prostate cancer stem cell population and metastatic ability via secreting cytokines to suppress androgen receptor signaling

Although the contribution of the bone marrow mesenchymal stem cells (BM-MSCs) in cancer progression is emerging, their potential roles in prostate cancer (PCa) remain unclear. Here, we showed that PCa cells could recruit BM-MSCs and consequently the metastatic ability of PCa cells was increased. We also found that the increased metastatic ability of PCa cells could be due to the increased PCa stem cell population. Mechanism dissection studies found that the upregulation of Chemokine ligand 5 (CCL5) expression in BM-MSCs and PCa cells, after MSCs infiltrated into the PCa cells, subsequently downregulated androgen receptor (AR) signaling, which was due to inhibition of AR nuclear translocation. Interruption of such signaling led to suppression of the BM-MSCs-induced PCa stem cell population increase and thereby inhibited the metastatic ability of PCa cells. The PCa stem cell increase then led to the upregulation of matrix metalloproteinase 9, ZEB-1, CD133 and CXCR4 molecules, and enhanced the metastatic ability of PCa cells. Therefore, we conclude that the BM-MSCs-mediated increased metastatic ability of PCa cells can be due to the PCa stem cell increase via alteration of the CCL5-AR signaling pathway. Together, these results uncover the important roles of BM-MSCs as key components in the prostate tumor microenvironment to promote PCa metastasis and may provide a new potential target to suppress PCa metastasis by blocking BM-MSCs infiltration into PCa.

TGF-β signalling and its role in cancer progression and metastasis

The transforming growth factor-β (TGF-β) system signals via protein kinase receptors and SMAD mediators to regulate a large number of biological processes. Alterations of the TGF-β signalling pathway are implicated in human cancer. Prior to tumour initiation and early during progression, TGF-β acts as a tumour suppressor; however, at later stages, it is often a tumour promoter. Knowledge about the mechanisms involved in TGF-β signal transduction has allowed a better understanding of cancer progression, invasion, metastasis and epithelial-to-mesenchymal transition. Furthermore, several molecular targets with great potential in therapeutic interventions have been identified. This review discusses the TGF-β signalling pathway, its involvement in cancer and current therapeutic approaches.

Hedgehog signaling regulates hypoxia induced epithelial to mesenchymal transition and invasion in pancreatic cancer cells via a ligand-independent manner

Background

Hypoxia plays a vital role in cancer epithelial to mesenchymal transition (EMT) and invasion. However, it is not quite clear how hypoxia may contribute to these events. Here we investigate the role of Hedgehog (Hh) signaling in hypoxia induced pancreatic cancer EMT and invasion.

Methods

Pancreatic cancer cells were cultured under controlled hypoxia conditions (3% O2) or normoxic conditions. HIF-1α siRNA, cyclopamine (a SMO antagonist) and GLI1 siRNA were used to inhibit HIF-1α transcription or Hh signaling activation. The effect of hypoxia and Hh signaling on cancer cell EMT and invasion were evaluated by Quantitative real-time PCR analysis, Western blot analysis and invasion assay.

Results

Here, we show that non-canonical Hh signaling is required as an important role to switch on hypoxia-induced EMT and invasion in pancreatic cancer cells. Moreover, our data demonstrate hypoxia induces EMT process as well as invasion, and activates the non-canonical Hh pathway without affecting sonic hedgehog homolog (SHH) expression. Moreover, these effects are reversible upon HIF-1α siRNA interference with unchanged SHH and patched1 (PTCH1) level. Furthermore, our data demonstrate that hypoxia induced invasion and EMT process are effectively inhibited by Smoothened (SMO) antagonist cyclopamine and GLI1 siRNA. In addition, GLI1 interference inhibited EMT progress with significantly suppressed vimentin expression, whereas inhibition of SMO through cyclopamine could not reduce vimentin level. This data indicate that hypoxia could trigger other factors (such as TGF-β, KRAS or RTK) bypassing SMO to activate GLI1 directly.

Conclusions

Our findings suggest that Hh signaling modulates hypoxia induced pancreatic cancer EMT and invasion in a ligand-independent manner. Thus, Hh signaling may represent a promising therapeutic target for preventing pancreatic cancer progression.

Stabilization of Snail through AKT/GSK-3β signaling pathway is required for TNF-α-induced epithelial-mesenchymal transition in prostate cancer PC3 cells

Metastasis induced by chronic inflammation has been considered as a major challenge during cancer therapy. Epithelial-mesenchymal transition (EMT) is associated with cancer invasion and metastasis promoted by pro-inflammatory cytokine TNFα. However, the mechanisms underlying TNFα-induced EMT in prostate cancer cells is not entirely clear. Here we showed that EMT induced by longstanding stimulation with TNFα in prostate cancer PC3 cells is mediated by up-regulation of the transcriptional repressor Snail. TNFα-mediated EMT was characterized by acquiring mesenchymal fusiform morphology, increasing the expression of Vimentin and decreasing the expression of E-cadherin. Exposure to TNFα increased the expression of transcription factor Snail via post-transcriptional regulation process and induced Snail nuclear localization in PC3 cells. Moreover, overexpressed Snail in PC3 cells induced EMT. Conversely, suppressing Snail expression abrogated TNFα-induced EMT, suggesting that Snail plays a crucial role in TNFα-induced EMT in prostate cancer cells. Finally, we showed that TNFα time-dependently activated NF-κB, AKT, ERK, p38 MAPK signaling pathways, and elevated Snail stability by activating AKT pathway that subsequently inhibited GSK-3β activity. Taken together, these results reveal that stabilization of Snail via AKT/GSK-3β signaling pathway is required for TNFα-induced EMT in prostate cancer cells. This study offers a better understanding of TNFα-induced metastasis and provides an effective therapeutic strategy for prostate cancer treatment.

Local endocrine, paracrine and redox signaling networks impact estrogen and androgen crosstalk in the prostate cancer microenvironment

Androgen receptor (AR) signaling is essential for the initial development and progression of prostate cancer (PCa) as well as the growth and survival of castration-resistant tumors. However, AR action may be opposed by estrogen receptor beta (ERß) that responds to androgen metabolites produced in the prostate. The balance between the activity of these two receptors is not only influenced by the steroidogenic capacity of the prostatic microenvironment but also by its redox status and local paracrine signals such as transforming growth factor-beta (TGF-ß). In this review, we highlight the studies that revealed select roles for AR and ERß in distinct compartments of the prostate cancer microenvironment. We also discuss new work that identified stromal-epithelial crosstalk through TGF-ß1 signaling that drives the production of reactive oxygen species in stromal cells thereby selectively limiting the anti-tumor activity of ERß in cancer cells. Therefore, any new therapeutic approaches that seek to limit AR but enhance ERß activity in PCa, must take into account potential adaptive changes in the tumor microenvironment that utilize paracrine signals and altered redox balance to divert local androgen metabolites towards AR at the expense of ERß.

Chemoprevention of BBN-Induced Bladder Carcinogenesis by the Selective Estrogen Receptor Modulator Tamoxifen

Bladder cancer is the fifth most frequent tumor in men and ninth in women in the United States. Due to a high likelihood of recurrence, effective chemoprevention is a significant unmet need. Estrogen receptors (ERs), primarily ERβ, are expressed in normal urothelium and urothelial carcinoma, and blocking ER function with selective ER modulators such as tamoxifen inhibits bladder cancer cell proliferation in vitro. Herein, the chemoprotective potential of tamoxifen was evaluated in female mice exposed to the bladder-specific carcinogen, N-butyl-N-(4-hydroxybutyl) nitrosamine (BBN). Carcinogen treatment resulted in a 76% tumor incidence and increased mean bladder weights in comparison to controls. In contrast, mice receiving tamoxifen concurrent (8-20 weeks) or concurrent and subsequent (8-32 weeks) to BBN administration had no change in bladder weight and only 10% to 14% incidence of tumors. Non-muscle-invasive disease was present in animals treated with tamoxifen before (5-8 weeks) or after (20-32 weeks) BBN exposure, while incidence of muscle-invasive bladder carcinoma was reduced. ERβ was present in all mice and thus is a potential mediator of the tamoxifen chemoprotective effect. Surprisingly, ERα expression, which was detected in 74% of the mice exposed to BBN alone but not in any controlmice, was correlated with tumor incidence, indicating a possible role for this receptor in carcinogen-induced urothelial tumorigenesis. Thus, these data argue that both ERα and ERβ play a role in modulating carcinogen-induced bladder tumorigenesis. Administration of tamoxifen should be tested as a chemopreventive strategy for patients at high risk for bladder cancer recurrence.

A bi-faceted role of estrogen receptor β in breast cancer

Despite over 15 years of research, the exact role, if any, played by estrogen receptor β (ERβ) in human breast cancer remains elusive. A large body of data both in vitro and in vivo supports its role as an antiproliferative, pro-apoptotic factor especially when co-expressed with ERα. However, there is a smaller body of data associating ERβ with growth and survival in breast cancer. In clinical studies and most often in cell culture studies, the pro-growth and pro-survival activity of ERβ occurs in ERα-negative breast cancer tissue and cells. This bi-faceted role of ERβ is discussed in this review.

Estrogen receptor β expression and androgen receptor phosphorylation correlate with a poor clinical outcome in hormone-naive prostate cancer and are elevated in castration-resistant disease

Patients with advanced prostate cancer (PC) are usually treated with androgen withdrawal. While this therapy is initially effective, nearly all PCs become refractory to it. As hormone receptors play a crucial role in this process, we constructed a tissue microarray consisting of PC samples from 107 hormone-naïve (HN) and 101 castration-resistant (CR) PC patients and analyzed the androgen receptor (AR) gene copy number and the protein expression profiles of AR, Serin210-phosphorylated AR (pAR(210)), estrogen receptor (ER)β, ERα and the proliferation marker Ki67. The amplification of the AR gene was virtually restricted to CR PC and was significantly associated with increased AR protein expression (P<0.0001) and higher tumor cell proliferation (P=0.001). Strong AR expression was observed in a subgroup of HN PC patients with an adverse prognosis. In contrast, the absence of AR expression in CR PC was significantly associated with a poor overall survival. While pAR(210) was predominantly found in CR PC patients (P<0.0001), pAR(210) positivity was observed in a subgroup of HN PC patients with a poor survival (P<0.05). Epithelial ERα expression was restricted to CR PC cells (9%). ERβ protein expression was found in 38% of both HN and CR PCs, but was elevated in matched CR PC specimens. Similar to pAR(210), the presence of ERβ in HN patients was significantly associated with an adverse prognosis (P<0.005). Our results strongly suggest a major role for pAR(210) and ERβ in HN PC. The expression of these markers might be directly involved in CR tumor growth.

BIBF 1120 (nintedanib), a triple angiokinase inhibitor, induces hypoxia but not EMT and blocks progression of preclinical models of lung and pancreatic cancer

Signaling from other angiokinases may underlie resistance to VEGF-directed therapy. We evaluated the antitumor and biologic effects of BIBF 1120 (nintedanib), a tyrosine kinase inhibitor that targets VEGF receptor, platelet-derived growth factor receptor, and fibroblast growth factor receptor in preclinical models of lung and pancreatic cancer, including models resistant to VEGF-targeted treatments. In vitro, BIBF 1120 did not show antiproliferative effects, nor did it sensitize tumor cells to chemotherapy. However, in vivo BIBF 1120 inhibited primary tumor growth in all models as a single agent and in combination with standard chemotherapy. Analysis of tumor tissue posttreatment revealed that BIBF 1120 reduced proliferation (phospho-histone 3) and elevated apoptosis (cleaved caspase-3) to a greater extent than chemotherapy alone. Furthermore, BIBF 1120 showed potent antiangiogenic effects, including decreases in microvessel density (CD31), pericyte coverage (NG2), vessel permeability, and perfusion, while increasing hypoxia. Despite the induction of hypoxia, markers of epithelial-to-mesenchymal transition (EMT) were not elevated in BIBF 1120-treated tumors. In summary, BIBF 1120 showed potent antitumor and antiangiogenic activity in preclinical models of lung and pancreatic cancer where it induced hypoxia but not EMT. The absence of EMT induction, which has been implicated in resistance to antiangiogenic therapies, is noteworthy. Together, these results warrant further clinical studies of BIBF 1120.

Junctional adhesion molecule-A regulates vascular endothelial growth factor receptor-2 signaling-dependent mouse corneal wound healing

Inflammation and angiogenesis are integral parts of wound healing. However, excessive and persistent wound-induced inflammation and angiogenesis in an avascular tissue such as the cornea may be associated with scarring and visual impairment. Junctional adhesion molecule A (Jam-A) is a tight junction protein that regulates leukocyte transmigration as well as fibroblast growth factor-2 (FGF-2)-induced angiogenesis. However its function in wound-induced inflammation and angiogenesis is still unknown. In this study, we report spontaneous corneal opacity in Jam-A deficient mice associated with inflammation, angiogenesis and the presence of myofibroblasts. Since wounds and/or corneal infections cause corneal opacities, we tested the role of Jam-A in wound-induced inflammation, angiogenesis and scarring by subjecting Jam-A deficient mice to full thickness corneal wounding. Analysis of these wounds demonstrated increased inflammation, angiogenesis, and increased number of myofibroblasts thereby indicating that Jam-A regulates the wound-healing response by controlling wound-induced inflammation, angiogenesis and scarring in the cornea. These effects were not due to inflammation alone since the inflammation-induced wound-healing response in Jam-A deficient mice was similar to wild type mice. In order to determine the molecular mechanism associated with the observed aberrant corneal wound healing in Jam-A deficient mice, we assessed the expression of the components of vascular endothelial growth factor A (VEGF-A)/vascular endothelial growth factor receptor- 2(VEGFR-2) signaling pathway. Interestingly, we observed increased levels of VEGF-A mRNA in Jam-A deficient eyes. We also observed nuclear localization of phosphorylated SMAD3 (pSMAD3) indicative of TGFβ pathway activation in the Jam-A deficient eyes. Furthermore the increased wound-induced corneal inflammation, angiogenesis, and scarring in Jam-A deficient mice was attenuated by treatment with DC101, an anti-vascular endothelial growth factor receptor-2 (VEGFR-2) antibody. Our results suggest that in the absence of Jam-A, the VEGF-A/VEGFR-2 pathway is upregulated, thereby augmenting wound induced corneal inflammation, angiogenesis, and myofibroblast accumulation leading to scarring.

High circulating estrogens and selective expression of ERβ in prostate tumors of Americans: implications for racial disparity of prostate cancer

Although estrogen receptor beta (ERβ) has been implicated in prostate cancer (PCa) progression, its potential role in health disparity of PCa remains elusive. The objective of this study was to examine serum estrogens and prostate tumor ERβ expression and examine their correlation with clinical and pathological parameters in African American (AA) versus Caucasian American (CA) men. The circulating 17β-estradiol (E2) was measured by enzyme immunoassay in blood procured from racially stratified normal subjects and PCa patients. Differential expression profile analysis of ERβ was analyzed by quantitative immunohistochemistry using ethnicity-based tissue microarray encompassing 300 PCa tissue cores. In situ ERβ expression was validated by quantitative reverse transcription-PCR in matched microdissected normal prostate epithelium and tumor cells and datasets extracted from independent cohorts. In comparison with normal age-matched subjects, circulating E2 levels were significantly elevated in all PCa patients. Further analysis demonstrates an increase in blood E2 levels in AA men in both normal and PCa in comparison with age- and stage-matched counterparts of CA decent. Histochemical score analysis reveals intense nuclear immunoreactivity for ERβ in tumor cores of AA men than in CA men. Gene expression analysis in microdissected tumors corroborated the biracial differences in ERβ expression. Gene expression analysis from independent cohort datasets revealed correlation between ERβ expression and PCa progression. However, unlike in CA men, adjusted multivariate analysis showed that ERβ expression correlates with age at diagnosis and low prostate-specific antigen recurrence-free survival in AA men. Taken together, our results suggest that E2-ERβ axis may have potential clinical utility in PCa diagnosis and clinical outcome among AA men.

STAT3 mediates TGF-β1-induced TWIST1 expression and prostate cancer invasion

TGF-β1 induces epithelial-mesenchymal transition (EMT) to stimulate cancer cell progression, and TWIST1 is a critical regulator of EMT. In the present study, we determined the underlying mechanisms of TGF-β1-induced TWIST1 expression and its effect on prostate cancer cell invasion. TGF-β1 stimulated STAT3 phosphorylation and HIF-1α expression. Silencing either STAT3 or HIF-1α efficiently attenuated TGF-β1-induced TWIST1 expression. Further ectopic expression of a dominant negative mutant of STAT3 reduced TGF-β1-induced TWIST1 expression. In addition, STAT3 and HIF-1α up-regulated TWIST1 expression by direct binding to a TWIST1 promoter. Strikingly, STAT3 also enhanced TGF-β1-induced TWIST1 expression through HIF-1α stabilization. Collectively, we demonstrate a mechanistic cascade of TGF-β1 up-regulating STAT3 activation and HIF-1α stabilization and subsequent TWIST1 expression, leading to prostate cancer invasion.

DDB2 suppresses epithelial-to-mesenchymal transition in colon cancer

Colon cancer is one of the deadliest cancers worldwide because of its metastasis to other essential organs. Metastasis of colon cancer involves a complex set of events, including epithelial-to-mesenchymal transition (EMT) that increases invasiveness of the tumor cells. Here, we show that the xeroderma pigmentosum group E (XPE) gene product, damaged DNA-binding protein (DDB)-2, is downregulated in high-grade colon cancers, and it plays a dominant role in the suppression of EMT of the colon cancer cells. Depletion of DDB2 promotes mesenchymal phenotype, whereas expression of DDB2 promotes epithelial phenotype. DDB2 constitutively represses genes that are the key activators of EMT, indicating that DDB2 is a master regulator of EMT of the colon cancer cells. Moreover, we observed evidence that DDB2 functions as a barrier for EMT induced by hypoxia and TGF-β. Also, we provide evidence that DDB2 inhibits metastasis of colon cancer. The results presented here identify a transcriptional regulatory pathway of DDB2 that is directly linked to the mechanisms that suppress metastasis of colon cancer.

Hypoxia-inducible factor and vascular endothelial growth factor are targets of dietary soy during acute stroke in female rats

Dietary soy and soy isoflavones are neuroprotective in experimental cerebral ischemia. Because these isoflavones have estrogenic properties, we hypothesized that, like estrogens, they would inhibit acute vascular injury and the detrimental acute increase in hypoxia-induced vascular endothelial growth factor (VEGF) that leads to cerebral edema after stroke. Mature ovariectomized female Sprague Dawley rats were fed soy-free or soy-containing diets for 4 weeks followed by 90 minutes of transient middle cerebral artery occlusion. Similar to estrogens, dietary soy significantly reduced cerebral edema and vascular apoptosis 24 hours after stroke. Soy also inhibited the ischemia-induced increase in cortical VEGF and VEGF receptor (VEGFR)-2 protein expression observed 4 and 24 hours after stroke, although mRNA levels increased. The reduction in VEGF/VEGFR-2 was associated both with decreases in receptor phosphorylation and signaling to AKT and endothelial nitric oxide synthase. Furthermore degradation of the VEGFR-2 was increased with dietary soy. The primary ischemic stimulus for VEGF, hypoxia-inducible factor 1α (HIF1α), was similarly reduced by dietary soy 4 hours after transient middle cerebral artery occlusion in both the cortex and striatum. The inhibition of HIF1α activity was further confirmed by a significant decrease in the HIF1α-activated apoptotic mediator BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (Nip3-like protein X). These data suggest that soy isoflavones target events early in the ischemic cascade as part of their neuroprotective actions and counterbalance some of the detrimental effects of the endogenous response to cerebral injury.

Loss of the polycomb protein Mel-18 enhances the epithelial-mesenchymal transition by ZEB1 and ZEB2 expression through the downregulation of miR-205 in breast cancer

The epithelial-mesenchymal transition (EMT) is the pivotal mechanism underlying the initiation of cancer invasion and metastasis. Although Mel-18 has been implicated in several biological processes in cancer, its function in the EMT of human cancers has not yet been studied. Here, we demonstrate that Mel-18 negatively regulates the EMT by epigenetically modulating miR-205. We identified miR-205 as a novel target of Mel-18 using a microRNA microarray analysis and found that Mel-18 increased miR-205 transcription by the inhibition of DNA methyltransferase-mediated DNA methylation of the miR-205 promoter, thereby downregulating its target genes, ZEB1 and ZEB2. Furthermore, the loss of Mel-18 promoted ZEB1- and ZEB2-mediated downregulation of E-cadherin transcription and also enhanced the expression of mesenchymal markers, leading to increased migration and invasion in MCF-7 cells. In MDA-MB-231 cells, Mel-18 overexpression restored E-cadherin expression, resulting in reduced migration and invasion. These effects were reversed by miR-205 overexpression or inhibition. A tumor xenograft with Mel-18 knockdown MCF-7 cells consistently showed increased ZEB1 and ZEB2 expression and decreased E-cadherin expression. Taken together, these results suggest that Mel-18 functions as a tumor suppressor by its novel negative control of the EMT, achieved through regulating the expression of miR-205 and its target genes, ZEB1 and ZEB2.

Estrogen receptor β sustains epithelial differentiation by regulating prolyl hydroxylase 2 transcription

Estrogen receptor β (ERβ) promotes the degradation of hypoxia inducible factor 1α (HIF-1α), which contributes to the ability of this hormone receptor to sustain the differentiation of epithelial and carcinoma cells. Although the loss of ERβ and consequent HIF-1 activation occur in prostate cancer with profound consequences, the mechanism by which ERβ promotes the degradation of HIF-1α is unknown. We report that ERβ regulates the ligand (3β-adiol)-dependent transcription of prolyl hydroxylase 2 (PHD2) also known as Egl nine homolog 1 (EGLN1), a 2-oxoglutarate-dependent dioxygenase that hydroxylates HIF-1α and targets it for recognition by the von Hippel-Lindau tumor suppressor and consequent degradation. ERβ promotes PHD2 transcription by interacting with a unique estrogen response element in the 5' UTR of the PHD2 gene that functions as an enhancer. PHD2 itself is critical for maintaining epithelial differentiation. Loss of PHD2 expression or inhibition of its function results in dedifferentiation with characteristics of an epithelial-mesenchymal transition, and exogenous PHD2 expression in dedifferentiated cells can restore an epithelial phenotype. Moreover, expression of HIF-1α in cells that express PHD2 does not induce dedifferentiation but expression of HIF-1α containing mutations in the proline residues that are hydroxylated by PHD2 induces dedifferentiation. These data describe a unique mechanism for the regulation of HIF-1α stability that involves ERβ-mediated transcriptional regulation of PHD2 and they highlight an unexpected role for PHD2 in maintaining epithelial differentiation.

GLI1 regulates a novel neuropilin-2/α6β1 integrin based autocrine pathway that contributes to breast cancer initiation

The characterization of cells with tumour initiating potential is significant for advancing our understanding of cancer and improving therapy. Aggressive, triple-negative breast cancers (TNBCs) are enriched for tumour-initiating cells (TICs). We investigated that hypothesis that VEGF receptors expressed on TNBC cells mediate autocrine signalling that contributes to tumour initiation. We discovered the VEGF receptor neuropilin-2 (NRP2) is expressed preferentially on TICs, involved in the genesis of TNBCs and necessary for tumour initiation. The mechanism by which NRP2 signalling promotes tumour initiation involves stimulation of the α6β1 integrin, focal adhesion kinase-mediated activation of Ras/MEK signalling and consequent expression of the Hedgehog effector GLI1. GLI1 also induces BMI-1, a key stem cell factor, and it enhances NRP2 expression and the function of α6β1, establishing an autocrine loop. NRP2 can be targeted in vivo to retard tumour initiation. These findings reveal a novel autocrine pathway involving VEGF/NRP2, α6β1 and GLI1 that contributes to the initiation of TNBC. They also support the feasibility of NRP2-based therapy for the treatment of TNBC that targets and impedes the function of TICs.

Epithelial-mesenchymal transition (EMT) induced by TNF-α requires AKT/GSK-3β-mediated stabilization of snail in colorectal cancer

Chronic inflammation-promoted metastasis has been considered as a major challenge in cancer therapy. Pro-inflammatory cytokine TNFα can induce cancer invasion and metastasis associated with epithelial-mesenchymal transition (EMT). However, the underlying mechanisms are not entirely clear. In this study, we showed that TNFα induces EMT in human HCT116 cells and thereby promotes colorectal cancer (CRC) invasion and metastasis. TNFα-induced EMT was characterized by acquiring mesenchymal spindle-like morphology and increasing the expression of N-cadherin and fibronectin with a concomitant decrease of E-cadherin and Zona occludin-1(ZO-1). TNFα treatment also increased the expression of transcription factor Snail, but not Slug, ZEB1 and Twist. Overexpression of Snail induced a switch from E-cadherin to N-cadherin expression in HCT116 cells, which is a characteristic of EMT. Conversely, knockdown of Snail significantly attenuated TNFα-induced EMT in HCT116 cells, suggesting that Snail plays a crucial role in TNFα-induced EMT. Interestingly, exposure to TNFα rapidly increased Snail protein expression and Snail nuclear localization but not mRNA level upregulation. Finally, we demonstrated that TNFα elevated Snail stability by activating AKT pathway and subsequently repressing GSK-3β activity and decreasing the association of Snail with GSK-3β. Knockdown of GSK-3β further verified our finding. Taken together, these results revealed that AKT/GSK-3β-mediated stabilization of Snail is required for TNFα-induced EMT in CRC cells. Our study provides a better understanding of inflammation-induced CRC metastasis.

Estrogen receptor β agonists affect growth and gene expression of human breast cancer cell lines

Expression of estrogen receptor β (ERβ) has been described to reduce growth of cancer cell lines derived from hormone-dependent tumors, like breast cancer. In this study we tested to what extent two ERβ agonists, androgen derivative 3β-Adiol and flavonoid Liquiritigenin, would affect growth and gene expression of different ERβ-positive human breast cancer cell lines. Under standard cell culture conditions, we observed 3β-Adiol to inhibit growth of MCF-7 cells in a dose-dependent manner, whereas growth of BT-474 and MCF-10A cells was suppressed by the maximum concentration (100 nM) only. When treated in serum-free medium, all cell lines except of MDA-MB-231 were responsive to 1 nM 3β-Adiol, and ZR75-1 cells exhibited a dose-dependent antiproliferative response. Providing putative mechanisms underlying the observed growth-inhibitory effect, expression of Ki-67 or cyclins A2 and B1 was downregulated after 3β-Adiol treatment in all responsive lines. In contrast, treatment with lower doses of Liquiritigenin did not affect growth. In MCF-7 cells, the highest dose of this flavonoid exerted proliferative effects accompanied by increased expression of cyclin B1, PR and PS2, indicating unspecific activation of ERα. In conclusion, the ERβ agonists tested exerted distinct concentration-dependent and cell line-specific effects on growth and gene expression. The observed inhibitory effects of 3β-Adiol on breast cancer cell growth encourage further studies on the potential of this and other ERβ agonists as targeted drugs for breast cancer therapy.

The lysine specific demethylase-1 (LSD1/KDM1A) regulates VEGF-A expression in prostate cancer

Recurrent prostate cancer remains a major clinical challenge. The lysine specific demethylase-1 (LSD1/KDM1A), together with the JmjC domain-containing JMJD2A and JMJD2C proteins, have emerged as critical regulators of histone lysine methylation. The LSD1-JMJD2 complex functions as a transcriptional co-regulator of hormone activated androgen and estrogen receptors at specific gene promoters. LSD1 also regulates DNA methylation and p53 function. LSD1 is overexpressed in numerous cancers including prostate cancer through an unknown mechanism. We investigated expression of the LSD1 and JMJD2A in malignant human prostate specimens. We correlated LSD1 and JMJD2A expression with known mediators of prostate cancer progression: VEGF-A and cyclin A1. We show that elevated expression of LSD1, but not JMJD2A, correlates with prostate cancer recurrence and with increased VEGF-A expression. We show that functional depletion of LSD1 expression using siRNA in prostate cancer cells decreases VEGF-A and blocks androgen induced VEGF-A, PSA and Tmprss2 expression. We demonstrate that pharmacological inhibition of LSD1 reduces proliferation of both androgen dependent (LnCaP) and independent cell lines (LnCaP: C42, PC3). We show a direct mechanistic link between LSD1 over-expression and increased activity of pro-angiogenic pathways. New therapies targeting LSD1 activity should be useful in the treatment of hormone dependent and independent prostate cancer.

Estrogen inhibits colon polyp formation by reducing angiogenesis in a carcinogen-induced rat model

Objective. To study the effects of estrogen on colon polyp formation, proliferation, and angiogenesis on a rat model of colon cancer induced by dimethylhydrazine (DMH). Methods. Thirty-six female ovariectomized (OVX) rats were randomly divided into 3 groups: (I) control group (administrated with vehicles weekly), (II) DMH group (administrated with DMH weekly), and (III) DMH + E2 group (administrated with DMH and 17β-estradiol weekly). The incidence, volumes, and multiplicity of colon polyps in each group were evaluated. The microvessel density (MVD), the expressions of Proliferating Cell Nuclear Antigen (PCNA), and the expressions of HIF-1 α and VEGF in polyps were detected in each group. Results. Estrogen reduced the multiplicity, volumes, and the PCNA expressions of DMH-induced colon polyps. The MVD in DMH + E2 group was significantly lower than that in DMH group. Estrogen treatment decreased the HIF-1 α and VEGF expressions at both mRNA and protein level. Conclusion. Estrogen replacement was protective for ovariectomized rats from DMH-induced carcinogenesis, and one of the mechanisms for this was due to estrogen's inhibitive effects on blood vessel formation by downregulating VEGF and HIF-1 α expressions.

Hypoxia-regulated target genes implicated in tumor metastasis

Hypoxia is an important microenvironmental factor that induces cancer metastasis. Hypoxia/hypoxia-inducible factor-1α (HIF-1α) regulates many important steps of the metastatic processes, especially epithelial-mesenchymal transition (EMT) that is one of the crucial mechanisms to cause early stage of tumor metastasis. To have a better understanding of the mechanism of hypoxia-regulated metastasis, various hypoxia/HIF-1α-regulated target genes are categorized into different classes including transcription factors, histone modifiers, enzymes, receptors, kinases, small GTPases, transporters, adhesion molecules, surface molecules, membrane proteins, and microRNAs. Different roles of these target genes are described with regards to their relationship to hypoxia-induced metastasis. We hope that this review will provide a framework for further exploration of hypoxia/HIF-1α-regulated target genes and a comprehensive view of the metastatic picture induced by hypoxia.

The "Sharp" blade against HIF-mediated metastasis

Hypoxia-inducible factors (HIFs) control cellular adaptation to oxygen deprivation. Cancer cells engage HIFs to sustain their growth in adverse conditions, thus promoting a cellular reprograming that includes metabolism, proliferation, survival and mobility. HIFs overexpression in human cancer biopsies correlates with high metastasis and mortality. A recent report has elucidated a novel mechanism for HIFs regulation in triple-negative breast cancer. Specifically, the basic helix-loop-helix (bHLH), Sharp-1, serves HIF1α to the proteasome and promotes its O₂-indendpendet degradation, counteracting HIF-mediated metastasis. These findings shed light on how HIFs are manipulated during cancer pathogenesis.

ERbeta1 represses basal breast cancer epithelial to mesenchymal transition by destabilizing EGFR

Introduction

Epithelial to mesenchymal transition (EMT) is associated with the basal-like breast cancer phenotypes. Sixty percent of basal-like cancers have been shown to express wild-type estrogen receptor beta (ERβ1). However, it is still unclear whether the ERβ expression is related to EMT, invasion and metastasis in breast cancer. In the present study, we examined whether ERβ1 through regulating EMT can influence invasion and metastasis in basal-like cancers.

Methods

Basal-like breast cancer cells (MDA-MB-231 and Hs578T), in which ERβ1 was either overexpressed or down-regulated were analyzed for their ability to migrate and invade (wound-healing assay, matrigel-coated Transwell assay) as well as for the expression of EMT markers and components of the EGFR pathway (immunoblotting, RT-PCR). Co-immunoprecipitation and ubiquitylation assays were employed to examine whether ERβ1 alters epidermal growth factor receptor (EGFR) protein degradation and the interaction between EGFR and the ubiquitin ligase c-Cbl. The metastatic potential of the ERβ1-expressing MDA-MB-231 cells was evaluated in vivo in a zebrafish xenotransplantation model and the correlation between ERβ1 and E-cadherin expression was examined in 208 clinical breast cancer specimens by immunohistochemistry.

Results

Here we show that ERβ1 inhibits EMT and invasion in basal-like breast cancer cells when they grow either in vitro or in vivo in zebrafish. The inhibition of EMT correlates with an ERβ1-mediated up-regulation of miR-200a/b/429 and the subsequent repression of ZEB1 and SIP1, which results in increased expression of E-cadherin. The positive correlation of ERβ1 and E-cadherin expression was additionally observed in breast tumor samples. Down-regulation of the basal marker EGFR through stabilization of the ubiquitin ligase c-Cbl complexes and subsequent ubiquitylation and degradation of the activated receptor is involved in the ERβ1-mediated repression of EMT and induction of EGFR signaling abolished the ability of ERβ1 to sustain the epithelial phenotype.

Conclusions

Taken together, the results of our study strengthen the association of ERβ1 with the regulation of EMT and propose the receptor as a potential crucial marker in predicting metastasis in breast cancer.

Heat stress induces epithelial plasticity and cell migration independent of heat shock factor 1

Current cancer therapies including cytotoxic chemotherapy, radiation and hyperthermic therapy induce acute proteotoxic stress in tumour cells. A major challenge to cancer therapeutic efficacy is the recurrence of therapy-resistant tumours and how to overcome their emergence. The current study examines the concept that tumour cell exposure to acute proteotoxic stress results in the acquisition of a more advanced and aggressive cancer cell phenotype. Specifically, we determined whether heat stress resulted in an epithelial-to-mesenchymal transition (EMT) and/or the enhancement of cell migration, components of an advanced and therapeutically resistant cancer phenotype. We identified that heat stress enhanced cell migration in both the lung A549, and breast MDA-MB-468 human adenocarcinoma cell lines, with A549 cells also undergoing a partial EMT. Moreover, in an in vivo model of thermally ablated liver metastases of the mouse colorectal MoCR cell line, immunohistological analysis of classical EMT markers demonstrated a shift to a more mesenchymal phenotype in the surviving tumour fraction, further demonstrating that thermal stress can induce epithelial plasticity. To identify a mechanism by which thermal stress modulates epithelial plasticity, we examined whether the major transcriptional regulator of the heat shock response, heat shock factor 1 (HSF1), was a required component. Knockdown of HSF1 in the A549 model did not prevent the associated morphological changes or enhanced migratory profile of heat stressed cells. Therefore, this study provides evidence that heat stress significantly impacts upon cancer cell epithelial plasticity and the migratory phenotype independent of HSF1. These findings further our understanding of novel biological downstream effects of heat stress and their potential independence from the classical heat shock pathway.

Enhancing integrin function by VEGF/neuropilin signaling: implications for tumor biology

This review advances the hypothesis that the ability of integrins to engage their extracellular matrix ligands and signal can be regulated in tumor cells by vascular endothelial growth factor (VEGF), a major angiogenic factor that also has direct effects on the function of tumor cells. More specifically, we will discuss how neuropilins (NRPs), a distinct class of VEGF receptors, enable the function of specific integrins that contribute to tumor initiation and progression.

Therapeutic targeting of angiotensin II receptor type 1 to regulate androgen receptor in prostate cancer

BACKGROUND

With the limited strategies for curative treatment of castration-resistant prostate cancer (CRPC), public interest has focused on the potential prevention of prostate cancer. Recent studies have demonstrated that an angiotensin II receptor blocker (ARB) has the potential to decrease serum prostate-specific antigen (PSA) level and improve performance status in CRPC patients. These facts prompted us to investigate the direct effects of ARBs on prostate cancer growth and progression.

METHODS

Transgenic rat for adenocarcinoma of prostate (TRAP) model established in our laboratory was used. TRAP rats of 3 weeks of age received ARB (telmisartan or candesartan) at the concentration of 2 or 10 mg/kg/day in drinking water for 12 weeks. In vitro analyses for cell growth, ubiquitylation or reporter gene assay were performed using LNCaP cells.

RESULTS

We found that both telmisartan and candesartan attenuated prostate carcinogenesis in TRAP rats by augmentation of apoptosis resulting from activation of caspases, inactivation of p38 MAPK and down-regulation of the androgen receptor (AR). Further, microarray analysis demonstrated up-regulation of estrogen receptor β (ERβ) by ARB treatment. In both parental and androgen-independent LNCaP cells, ARB inhibited both cell growth and AR-mediated transcriptional activity. ARB also exerted a mild additional effect on AR-mediated transcriptional activation by the ERβ up-regulation. An intervention study revealed that PSA progression was prolonged in prostate cancer patients given an ARB compared with placebo control.

CONCLUSION

These data provide a new concept that ARBs are promising potential chemopreventive and chemotherapeutic agents for prostate cancer.

Current concepts and significance of estrogen receptor β in prostate cancer

An increasing amount of evidence points at important roles for estrogen receptors in prostate carcinogenesis and progression. Of the two estrogen receptors, estrogen receptor β is the most prominent within the prostate gland. Although there is much yet to be known, the findings from the discovery of the receptor in 1996 until now point at a role of the receptor in maintaining differentiation and reducing cellular proliferation in the prostate. Moreover, estrogen receptor β is the main target for phytoestrogens, perhaps at least partially explaining the difference in incidence of prostate cancer in the Western world compared to Asia where the intake of soy-based, phytoestrogen-rich food is higher. The tumor suppressive capability of estrogen receptor β makes it a promising drug target for the treatment and prevention of prostate cancer. This review will focus on different aspects of estrogen receptor signaling and prostate cancer.

Estrogen receptors β1 and β2 have opposing roles in regulating proliferation and bone metastasis genes in the prostate cancer cell line PC3

The estrogen receptor (ER)β1 is successively lost during cancer progression, whereas its splice variant, ERβ2, is expressed in advanced prostate cancer. The latter form of cancer often metastasizes to bone, and we wanted to investigate whether the loss of ERβ1 and/or the expression of ERβ2 affect such signaling pathways in prostate cancer. Using PC3 and 22Rv1 prostate cancer cell lines that stably express ERβ1 or ERβ2, we found that the ERβ variants differentially regulate genes known to affect tumor behavior. We found that ERβ1 repressed the expression of the bone metastasis regulator Runx2 in PC3 cells. By contrast, RUNX2 expression was up-regulated at the mRNA level by ERβ2 in PC3 cells, whereas Slug was up-regulated by ERβ2 in both PC3 and 22Rv1 cells. In addition, the expression of Twist1, a factor whose expression strongly correlates with high Gleason grade prostate carcinoma, was increased by ERβ2. In agreement with the increased Twist1 expression, we found increased expression of Dickkopf homolog 1; Dickkopf homolog 1 is a factor that has been shown to increase the RANK ligand/osteoprotegerin ratio and enhance osteoclastogenesis, indicating that the expression of ERβ2 can cause osteolytic cancer. Furthermore, we found that only ERβ1 inhibited proliferation, whereas ERβ2 increased proliferation. The expression of the proliferation markers Cyclin E, c-Myc, and p45(Skp2) was differentially affected by ERβ1 and ERβ2 expression. In addition, nuclear β-catenin protein and its mRNA levels were reduced by ERβ1 expression. In conclusion, we found that ERβ1 inhibited proliferation and factors known to be involved in bone metastasis, whereas ERβ2 increased proliferation and up-regulated factors involved in bone metastasis. Thus, in prostate cancer cells, ERβ2 has oncogenic abilities that are in strong contrast to the tumor-suppressing effects of ERβ1.