EGF prevents the neuroendocrine differentiation of LNCaP cells induced by serum deprivation: the modulator role of PI3K/Akt

Upregulation of human GD3 synthase (hST8Sia I) gene expression during serum starvation-induced osteoblastic differentiation of MG-63 cells

In this study, we have firstly elucidated that serum starvation augmented the levels of human GD3 synthase (hST8Sia I) gene and ganglioside GD3 expression as well as bone morphogenic protein-2 and osteocalcin expression during MG-63 cell differentiation using RT-PCR, qPCR, Western blot and immunofluorescence microscopy. To evaluate upregulation of hST8Sia I gene during MG-63 cell differentiation by serum starvation, promoter area of the hST8Sia I gene was functionally analyzed. Promoter analysis using luciferase reporter assay system harboring various constructs of the hST8Sia I gene proved that the cis-acting region at -1146/-646, which includes binding sites of the known transcription factors AP-1, CREB, c-Ets-1 and NF-κB, displays the highest level of promoter activity in response to serum starvation in MG-63 cells. The -731/-722 region, which contains the NF-κB binding site, was proved to be essential for expression of the hST8Sia I gene by serum starvation in MG-63 cells by site-directed mutagenesis, NF-κB inhibition, and chromatin immunoprecipitation (ChIP) assay. Knockdown of hST8Sia I using shRNA suggested that expressions of hST8Sia I and GD3 have no apparent effect on differentiation of MG-63 cells. Moreover, the transcriptional activation of hST8Sia I gene by serum starvation was strongly hindered by SB203580, a p38MAPK inhibitor in MG-63 cells. From these results, it has been suggested that transcription activity of hST8Sia I gene by serum starvation in human osteosarcoma MG-63 cells is regulated by p38MAPK/NF-κB signaling pathway.

Neuroendocrine differentiation: a risk fellow in colorectal cancer

BACKGROUND

Neuroendocrine differentiation (NED) is often found in colorectal cancer (CRC) and may have unique biological behavior, which has not been previously delineated. Here, we explore the relationship between CRC, NED, and clinicopathological factors. We also offer a preliminary explanation of the mechanism underlying the malignant biological behavior of NED in CRC.

METHODS

Between 2013 and 2015, 394 CRC patients who underwent radical operations were selected for analysis. The relationship between NED and clinicopathological factors was analyzed. To further clarify the pivotal role of NED in CRC, we performed bioinformatic analyses and identified genes that may be involved in NED, which were obtained from in silico data from The Cancer Genome Atlas (TCGA) database. Then, we conducted functional enrichment analyses and confirmed the critical pathways for intensive study. Moreover, we detected the expression of key proteins by immunohistochemistry and analyzed the correlation of their expression with NED.

RESULTS

The statistical analysis showed that CRC with NED was positively correlated with lymph node metastasis. Through bioinformatic analysis, we found that chromogranin A (CgA) was positively correlated with invasion and lymph node metastasis. ErbB2 and PIK3R1, which are key proteins in the PI3K-Akt signaling pathway, were closely related to NED. Furthermore, we determined that the PI3K-Akt signaling pathway likely plays a critical role in the NED of CRC.

CONCLUSIONS

CRC with NED is associated with lymph node metastasis. The PI3K-Akt signaling pathway, which is closely related to CRC, may be the mechanism promoting the malignant biological behavior of CRC with NED.

Claudin-3 Loss of Expression Is a Prognostic Marker in Castration-Resistant Prostate Cancer

Castration-resistant prostate cancer (CRPC) development is the foremost concern after treatment of patients with high risk with locally advanced or metastatic prostate cancer. Androgen receptor (AR) is the main driver of CRPC development, through its interaction with epigenetic modifier genes, placing epigenetics modifications in the forefront of CRPC development. Comparing the DNA methylation and expression profile of androgen-sensitive and -refractory prostate cancer cells, we describe the epigenetic silencing of claudin-3 (CLDN3) in AR positive cells resistant to androgen deprivation (LNCaP-abl). CLDN3 silencing was associated with DNA methylation, loss of histone acetylation and H3K27 methylation, and was re-expressed by the combined treatment with the epigenetic modulators Aza and SAHA. From a functional point of view, CLDN3 loss was associated with increased cellular invasion. Immunohistochemical analysis showed decreased CLDN3 expression in samples from CRPC patients. Interestingly, CLDN3 expression was significantly decreased in samples from patients with high total Gleason score (≥8) and locally advanced tumors. Finally, CLDN3 loss of expression was associated with worse disease-free survival and time to clinical progression. In conclusion, our findings strongly indicate that epigenetic silencing of CLDN3 is a common event in CRPC that could be useful as a molecular marker for the prognosis of prostate cancer patients and to discriminate aggressive from indolent prostate tumors.

Interplay of Epidermal Growth Factor Receptor and Signal Transducer and Activator of Transcription 3 in Prostate Cancer: Beyond Androgen Receptor Transactivation

Prostate cancer (PCa) is one of the most common cancers in the world and causes thousands of deaths every year. Conventional therapy for PCa includes surgery and androgen deprivation therapy (ADT). However, about 10-20% of all PCa cases relapse; there is also the further development of castration resistant adenocarcinoma (CRPC-Adeno) or neuroendocrine (NE) PCa (CRPC-NE). Due to their androgen-insensitive properties, both CRPC-Adeno and CRPC-NE have limited therapeutic options. Accordingly, this study reveals the inductive mechanisms of CRPC (for both CRPC-Adeno and CRPC-NE) and fulfils an urgent need for the treatment of PCa patients. Although previous studies have illustrated the emerging roles of epidermal growth factor receptors (EGFR), signal transducer, and activator of transcription 3 (STAT3) signaling in the development of CRPC, the regulatory mechanisms of this interaction between EGFR and STAT3 is still unclear. Our recent studies have shown that crosstalk between EGFR and STAT3 is critical for NE differentiation of PCa. In this review, we have collected recent findings with regard to the involvement of EGFR and STAT3 in malignancy progression and discussed their interactions during the development of therapeutic resistance for PCa.

Increased Expression of AKT3 in Neuroendocrine Differentiated Prostate Cancer Cells Alters the Response Towards Anti-Androgen Treatment

Patients with advanced prostate carcinoma are often treated with an androgen deprivation therapy but long-term treatment can result in a metastatic castration-resistant prostate cancer. This is a more aggressive, untreatable tumor recurrence often containing areas of neuroendocrine differentiated prostate cancer cells. Using an in vitro model of NE-like cancer cells, it could previously be shown that neuroendocrine differentiation of LNCaP cells leads to a strong deregulation of mRNA and miRNA expression. We observe elevated RNA and protein levels of AKT Serine/Threonine Kinase 3 (AKT3) in neuroendocrine-like LNCaP cells. We used prostate resections from patients with neuroendocrine prostate cancer to validate these results and detect a co-localization of neuroendocrine marker genes with AKT3. Analysis of downstream target genes FOXO3A and GSK3 strengthens the assumption AKT3 may play a role in neuroendocrine differentiation. Overexpression of AKT3 shows an increased survival rate of LNCaP cells after apoptosis induction, which in turn reflects the significance in vivo or for treatment. Furthermore, miR-17, -20b and -106b, which are decreased in neuroendocrine-like LNCaP cells, negatively regulate AKT3 biosynthesis. Our findings demonstrate AKT3 as a potential therapeutic target and diagnostic tool in advanced neuroendocrine prostate cancer and a new mRNA-miRNA interaction with a potential role in neuroendocrine differentiation of prostate cancer.

Anticancer Effects and Mechanisms of Action of Plumbagin: Review of Research Advances

Plumbagin (PLB), a natural naphthoquinone constituent isolated from the roots of the medicinal plant Plumbago zeylanica L., exhibited anticancer activity against a variety of cancer cell lines including breast cancer, hepatoma, leukemia, melanoma, prostate cancer, brain tumor, tongue squamous cell carcinoma, esophageal cancer, oral squamous cell carcinoma, lung cancer, kidney adenocarcinoma, cholangiocarcinoma, gastric cancer, lymphocyte carcinoma, osteosarcoma, and canine cancer. PLB played anticancer activity via many molecular mechanisms, such as targeting apoptosis, autophagy pathway, cell cycle arrest, antiangiogenesis pathway, anti-invasion, and antimetastasis pathway. Among these signaling pathways, the key regulatory genes regulated by PLB were NF-kβ, STAT3, and AKT. PLB also acted as a potent inducer of reactive oxygen species (ROS), suppressor of cellular glutathione, and novel proteasome inhibitor, causing DNA double-strand break by oxidative DNA base damage. This review comprehensively summarizes the anticancer activity and mechanism of PLB.

EGFR-upregulated LIFR promotes SUCLG2-dependent castration resistance and neuroendocrine differentiation of prostate cancer

Neuroendocrine (NE) differentiation is a well-recognized phenotypic change of prostate cancer after androgen deprivation therapy (ADT), and it ultimately develops into an aggressive subset of this disease. However, the contribution of signaling pathways that lead to metabolic disorders and NE differentiation of prostate cancer remains unclear. In this study, we identified that ADT induced upregulation of the succinate-CoA ligase GDP-forming beta subunit (SUCLG2), which regulates succinate metabolism and NE differentiation of prostate cancer. We demonstrated a connection that upregulation of epidermal growth factor receptor (EGFR)-leukemia inhibitory factor receptor (LIFR) signaling induced SUCLG2 expression in prostate cancer cells. The LIFR is upregulated by nuclear EGFR, which acts as a transcriptional regulator, directly binds to the LIFR promoter, and drives NE differentiation and glycolysis of prostate cancer. LIFR upregulation is associated with SUCLG2, which increased succinate synthesis and enzymatic activities of mitochondrial nucleoside diphosphate kinase (NDPK) in prostate cancer cells. Knockdown of SUCLG2 suppressed NE differentiation in cultured cells and reduced prostate tumor growth in a xenograft model. Analysis of prostate tissue samples showed increased intensity of nuclear EGFR associated with the LIFR and SUCLG2 in castration-resistant prostate cancer tumors. Our study provides a mechanism whereby ADT upregulates EGFR-LIFR signaling that activates SUCLG2, which subsequently stimulates the metabolic changes associated with NE differentiation and aggressive prostate cancer phenotype.

SNHG16 promotes tumorigenesis and cisplatin resistance by regulating miR-338-3p/PLK4 pathway in neuroblastoma cells

Background

Long noncoding RNA small nucleolar RNA host gene 16 (lncRNA SNHG16) has been revealed to be involved in the tumorigenesis of neuroblastoma. However, the role of SNHG16 in regulating cisplatin sensitivity in neuroblastoma remains largely unknown.

Methods

The expression of SNHG16, microRNA (miR)-338-3p and polo-like kinase 4 (PLK4) mRNA was measured using quantitative real-time polymerase chain reaction. The protein levels of PLK4, multidrug resistance protein 1 (MRP1), multidrug-resistance gene 1-type p-glycoprotein (P-gp) and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway-related proteins were detected by Western blot. The half maximal inhibitory concentration (IC50) value, cell proliferation, migration and invasion were analyzed using Cell Counting Kit-8 assays or Transwell assay. Apoptotic cells were measured by Flow cytometry. The interaction between miR-338-3p and SNHG16 or PLK4 was confirmed by dual-luciferase reporter and RNA immunoprecipitation assay. In vivo experiments were conducted through the murine xenograft model.

Results

SNHG16 was up-regulated, while miR-338-3p was down-regulated in cisplatin-resistant neuroblastoma tissues and cells. SNHG16 silencing weakened cisplatin resistance, reflected by the reduction of IC50 value, down-regulation of MRP-1 and P-gp protein expression, suppression of proliferation, migration and invasion, as well as enhancement of apoptosis in SNHG16 deletion cisplatin-resistant neuroblastoma cells. Besides that, SNHG16 could regulate PLK4 expression by sponging miR-338-3p and SNHG16/miR-338-3p/PLK4 axis could affect the activation of PI3K/AKT pathway in cisplatin-resistant neuroblastoma cells. MiR-338-3p inhibition attenuated SNHG16 deletion-mediated impairment on cisplatin resistance and PLK4 overexpression reversed the decrease of cisplatin-resistance induced by miR-338-3p re-expression. Furthermore, SNHG16 knockdown contributed to the anti-tumor effect of cisplatin in neuroblastoma in vivo.

Conclusion

SNHG16 contributed to the tumorigenesis and cisplatin resistance in neuroblastoma possibly through miR-338-3p/PLK4 pathway, indicating a novel insight for overcoming chemoresistance in neuroblastoma patients.

Propofol Inhibits the Migration and Invasion of Glioma Cells by Blocking the PI3K/AKT Pathway Through miR-206/ROCK1 Axis

Background

Propofol has been identified to perform anti-tumor functions in glioma. However, the molecular mechanisms underlying propofol-induced prevention on migration and invasion of glioma cells remain unclear.

Methods

Cell proliferation, invasion and migration were measured by 3-(4,5)-dimethylthiahiazo(−z-y1)-3,5-di-phenytetrazoliumromide assay and transwell assay, respectively. The expression of microRNA (miR)-206 and Rho-associated coiled coil-containing protein kinase 1 (ROCK1) was detected by quantitative real-time polymerase chain reaction. Western blot was used to measure the activation of the PI3K/AKT pathway. The interaction between miR-206 and ROCK1 was analyzed using the dual-luciferase reporter assay, RNA immunoprecipitation assay, and pull-down assay.

Results

Propofol treatment inhibited the migration, invasion, and PI3K/AKT pathway activation in glioma cells. MiR-206 was decreased in glioma tissues and cells, while propofol exposure induced the upregulation of miR-206 in glioma cells. Besides that, we also found overexpressed miR-206 enhanced propofol-mediated inhibition on the migration, invasion, and PI3K/AKT pathway activation of glioma cells. Subsequently, ROCK1 was confirmed to be a target of miR-206. ROCK1 was elevated in glioma tissues and cells, but was reduced by propofol exposure in glioma cells. The rescue assay indicated that the miR-206/ROCK1 axis was involved in propofol-induced inhibition on the migration, invasion, and PI3K/AKT pathway activation in glioma cells.

Conclusion

Propofol inhibited the migration and invasion of glioma cells by blocking the PI3K/AKT pathway through the miR-206/ROCK1 axis, suggesting an effective clinical implication for the anesthetic to prevent the metastasis of glioma.

Inhibition of epidermal growth factor receptor stimulates prolactin expression in primary culture of the mouse pituitary gland

The roles of epidermal growth factor (EGF) in the regulation of prolactin (PRL) gene expression in the normal pituitary gland remain poorly understood. In the present study, the effects of EGF and an inhibitor of the EGF receptor, erlotinib, on PRL gene expression were examined both in the pituitary tumour cell line GH3 and in a primary culture of the mouse pituitary gland under similar experimental conditions. The results showed that EGF stimulated PRL expression in GH3 cells, but not in normal cells. Erlotinib was found to counteract EGF in GH3 cells inhibiting the PRL expression enhanced by EGF. By contrast, erlotinib induced an elevation in the PRL mRNA levels in the primary culture of the adult pituitary gland and the initiation of PRL production in the culture of the foetal pituitary gland in which PRL production had not yet occurred. Western blot analyses showed that EGF induced and erlotinib inhibited the activation of extracellular regulated protein kinase equally in GH3 and normal cells. These results suggest that the consequences of EGF receptor activation in normal PRL cells contradict those in adenomatous PRL cells.

Casticin inhibits breast cancer cell migration and invasion by down-regulation of PI3K/Akt signaling pathway

Casticin is one of the major active components isolated from Fructus viticis Increasing studies have revealed that casticin has potential anticancer activity in various cancer cells, but its effects on breast cancer cell migration and invasion are still not well known. Therefore, the ability of cell migration and invasion in the breast cancer MDA-MB-231 and 4T1 cells treated by casticin was investigated. The results indicated that casticin significantly inhibited cell migration and invasion in the cells exposed to 0.25 and 0.50 µM of casticin for 24 h. Casticin treatment reduced matrix metalloproteinase (MMP) 9 (MMP-9) activity and down-regulated MMP-9 mRNA and protein expression, but not MMP-2. Casticin treatment suppressed the nuclear translocation of transcription factors c-Jun and c-Fos, but not nuclear factor-κB (NF-κB), and decreased the phosphorylated level of Akt (p-Akt). Additionally, the transfection of Akt overexpression vector to MDA-MB-231 and 4T1 cells could up-regulate MMP-9 expression concomitantly with a marked increase in cell invasion, but casticin treatment reduced Akt, p-Akt, and MMP-9 protein levels and inhibited the ability of cell invasion in breast cancer cells. Additionally, casticin attenuated lung metastasis of mouse 4T1 breast cancer cells in the mice and down-regulated MMP-9 expression in the lung tissues of mice treated by casticin. These findings suggest that MMP-9 expression suppression by casticin may act through inhibition of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway, which in turn results in the inhibitory effects of casticin on cell migration and invasion in breast cancer cells. Therefore, casticin may have potential for use in the treatment of breast cancer invasion and metastasis.

The deregulation of miR-17/CCND1 axis during neuroendocrine transdifferentiation of LNCaP prostate cancer cells

Prostate carcinoma contain foci of neuroendocrine transdifferentiation, resulting in an increase of androgen-independent neuroendocrine-like (NE) tumor cells, whose number significantly correlates with tumor aggressiveness and thus lower survival rate. Neuroendocrine transdifferentiation of prostate cancer cells and a potential role of miRNAs within this process are poorly understood. MicroRNAs are small non-coding RNAs which post-transcriptionally regulate gene expression. The aim of this project was to identify new genes and miRNAs involved in neuroendocrine transdifferentiation. LNCaP prostate cancer cells were differentiated to NE-like cancer cells and microarray analyses were performed. Microarray results have been validated for the eight most deregulated mRNAs and microRNAs via qRT-PCR and analyzed with different algorithms to predict new targets for deregulated microRNAs. The induced CyclinD1 gene could be validated as new target gene for the repressed miR-17 family containing miR-17, miR-20a, miR-20b, miR-106a and miR-106b via reporter gene assays and Western Blot. Functional analysis of miR-17 family shows a high influence on cell proliferation, colony forming ability and apoptosis in LNCaP cells. Our data demonstrate wide changes in mRNA and microRNA expression during neuroendocrine transdifferentiation of LNCaP cells and confirm new mRNA-miRNA interactions with potential roles in NE-transdifferentiation of prostate carcinoma.

MicroRNA-652 induces NED in LNCaP and EMT in PC3 prostate cancer cells

MicroRNAs (miRNAs) are small noncoding RNA molecules that post-transcriptionally regulate gene expression. Dysregulation of miRNAs is frequently associated with disease and, in particular, is involved in prostate cancer progression. Next generation miRNA sequencing identified a panel of five miRNAs associated with prostate cancer recurrence and metastasis. High expression of one of these five miRNAs, miR-652, correlated significantly with an increased rate of prostate cancer biochemical recurrence. Overexpression of miR-652 in prostate cancer cells, PC3 and LNCaP, resulted in increased growth, migration and invasion. Prostate cancer cell xenografts overexpressing miR-652 showed increased tumorigenicity and metastases. We found that miR-652 directly targets the B" regulatory subunit, PPP2R3A, of the tumor suppressor PP2A, inducing epithelial-mesenchymal transition (EMT) in PC3 cells and neuroendocrine-like differentiation (NED) in LNCaP cells. The mesenchymal marker N-cadherin increased and epithelial marker E-cadherin decreased in PC3 cells overexpressing miR-652. In LNCaP cells and xenografted tumors, overexpression of miR-652 increased markers of NED, including chromogranin A, neuron specific enolase, and synaptophysin. MiR-652 may contribute to prostate tumor progression by promoting NED through decreased PP2A function. MiR-652 expression could serve as a biomarker for aggressive prostate cancer, as well as provide an opportunity for novel therapy in prostate cancer.

Alterations of androgen receptor-regulated enhancer RNAs (eRNAs) contribute to enzalutamide resistance in castration-resistant prostate cancer

Enzalutamide is a second-generation anti-androgen for treatment of castration-resistant prostate cancer (CPRC). It prolongs survival of CRPC patients, but its overall survival benefit is relatively modest (4.8 months) and by 24 months most patients progress on enzalutamide. To date, however, the molecular mechanisms underlying enzalutamide resistance remain elusive. Herein, we report enzalutamide treatment-induced alterations of androgen receptor (AR)-regulated enhancer RNAs (AR-eRNAs) and their roles in enzalutamide-resistant growth and survival of CRPC cells. AR chromatin immunoprecipitation and high throughput sequencing (ChIP-seq) and RNA-seq analyses revealed that 188 and 227 AR-eRNAs were differentially expressed in enzalutamide-resistant LNCaP and C4-2 cells, respectively. The AR-eRNAs upregulated in C4-2 cells and downregulated in LNCaP cells were selected through meta-analysis. Expression of AR-eRNAs and related mRNAs in the loci of FTO, LUZP2, MARC1 and NCAM2 were further verified by real-time RT-PCR. Silencing of LUZP2 inhibited, but silencing of MARC1 increased the growth of enzalutamide-resistant C4-2 cells. Intriguingly, meta-analysis showed that expression of LUZP2 mRNA increased in primary tumors compared to normal prostate tissues, but decreased again in metastatic CRPC. Our findings suggest that eRNA alteration profiling is a viable new approach to identify functional gene loci that may not only contribute to enzalutamide-resistant growth of CRPC, but also serve as new targets for CRPC therapy.

Induction of Neuroendocrine Differentiation in Prostate Cancer Cells by Dovitinib (TKI-258) and its Therapeutic Implications

Prostate cancer (PCa) remains the second-leading cause of cancer-related deaths in American men with an estimated mortality of more than 26,000 in 2016 alone. Aggressive and metastatic tumors are treated with androgen deprivation therapies (ADT); however, the tumors acquire resistance and develop into lethal castration resistant prostate cancer (CRPC). With the advent of better therapeutics, the incidences of a more aggressive neuroendocrine prostate cancer (NEPC) variant continue to emerge. Although de novo occurrences of NEPC are rare, more than 25% of the therapy-resistant patients on highly potent new-generation anti-androgen therapies end up with NEPC. This, along with previous observations of an increase in the number of such NE cells in aggressive tumors, has been suggested as a mechanism of resistance development during prostate cancer progression. Dovitinib (TKI-258/CHIR-258) is a pan receptor tyrosine kinase (RTK) inhibitor that targets VEGFR, FGFR, PDGFR, and KIT. It has shown efficacy in mouse-model of PCa bone metastasis, and is presently in clinical trials for several cancers. We observed that both androgen receptor (AR) positive and AR-negative PCa cells differentiate into a NE phenotype upon treatment with Dovitinib. The NE differentiation was also observed when mice harboring PC3-xenografted tumors were systemically treated with Dovitinib. The mechanistic underpinnings of this differentiation are unclear, but seem to be supported through MAPK-, PI3K-, and Wnt-signaling pathways. Further elucidation of the differentiation process will enable the identification of alternative salvage or combination therapies to overcome the potential resistance development.

FOXA1 inhibits prostate cancer neuroendocrine differentiation

Neuroendocrine prostate cancer (NEPC) has increasingly become a clinical challenge. The mechanisms by which neuroendocrine (NE) cells arises from prostate adenocarcinoma cells are poorly understood. FOXA1 is a transcription factor of the forkhead family that is required for prostate epithelial differentiation. In this study, we demonstrated that FOXA1 loss drives NE differentiation, demarcated by phenotypical changes and NEPC marker expressions. Mechanistically, this is mediated by FOXA1 binding to the promoter of interleukin 8 (IL-8), a chemokine previously shown elevated in NEPC, to directly inhibit its expression. Further, IL-8 upregulation activates the MAPK/ERK pathway, leading to ERK phosphorylation and enolase 2 (ENO2) expression. IL-8 knockdown or ERK inhibition, on the other hand, abolished FOXA1 loss-induced NE differentiation. Analysis of xenograft mouse models confirmed FOXA1 loss in NEPC tumors relative to its adenocarcinoma counterparts. Importantly, FOXA1 is downregulated in human NEPC tumors compared to primary and castration-resistant prostate cancers, and its expression is negatively correlated with that of ENO2. These findings indicate that FOXA1 transcriptionally suppresses IL-8, the expression of which would otherwise stimulate the MAPK/ERK pathway to promote NE differentiation of prostate cancer cells. Our data strongly suggest that FOXA1 loss may play a significant role in enabling prostate cancer progression to NEPC, whereas IL-8 and MAPK/ERK pathways may be promising targets for therapeutic intervention.

IGFBP3 and MAPK/ERK signaling mediates melatonin-induced antitumor activity in prostate cancer

Treatment of prostate cancer (PCa), a leading cause of cancer among males, lacks successful strategies especially in advanced, hormone-refractory stages. Some clinical studies have shown an increase in neuroendocrine-like cells parallel to the tumor progression but their exact role is a matter of debate. The prostate is a well-known target for melatonin, which reduces PCa cells proliferation and induces neuroendocrine differentiation. To evaluate the mechanisms underlying the indole effects on neuroendocrine differentiation and its impact on PCa progression, we used a cell culture model (LNCaP) and a murine model (TRAMP). Persistent ERK1/2 activation was found in both, melatonin and androgen-deprived cells. Melatonin blocked nuclear translocation of androgen receptor (AR), thus confirming anti-androgenic actions of the indole. However, using a comparative genome microarray to check the differentially expressed genes in control, melatonin, or androgen-deprived cells, some differences were found, suggesting a more complex role of the indole. By comparing control cells with those treated with melatonin or depleted of androgen, a cluster of 26 differentially expressed genes (±2.5-fold) was found. Kallikreins (KLK)2 and KLK3 (PSA) were dramatically downregulated by both treatments whereas IGFBP3 and IGF1R were up- and downregulated, respectively, in both experimental groups, thus showing a role for IGF in both scenarios. Finally, melatonin prolonged the survival of TRAMP mice by 33% when given at the beginning or at advances stages of the tumor. Serum IGFBP3 was significantly elevated by the indole in early stages of the tumor, confirming in vivo the role of the IGF signaling in the oncostatic action of the indole.

Wnt3a suppresses Wnt/β-catenin signaling and cancer cell proliferation following serum deprivation

Canonical Wnt/β-catenin signaling is often aberrantly activated in tumor cells and required for tumor growth. The internalization of Wnt co-receptor low-density lipoprotein receptor-related protein 6 (LRP6) induced by Wnt ligands is commonly thought to be critical for Wnt/β-catenin signaling activation. However, in contrast to theses previous studies, we here show that persistent excessive stimulation with a canonical Wnt ligand Wnt3a could induce a long-term decreased expression level of membrane LRP6, which prevented nuclear β-catenin accumulation and tumor cell;proliferation. Importantly, Wnt3a was robustly upregulated following serum deprivation. The upregulated Wnt3a under serum deprivation was responsible for LRP6 internalization, decreased accumulation of nuclear β-catenin, and further inhibition of tumor cell proliferation. It has well been known that insufficient blood supply during tumor development occurs frequently, causing a worsening environment for tumor growth. Therefore, these results reveal a novel inhibitory role of Wnt3a on canonical Wnt/β-catenin signaling and cancer cell proliferation when there is an insufficient blood supply during tumor development, which might be a potential mechanism for tumor evasion within a worsening environment.

Neuroendocrine differentiation in prostate cancer: a mechanism of radioresistance and treatment failure

Neuroendocrine differentiation (NED) in prostate cancer is a well-recognized phenotypic change by which prostate cancer cells transdifferentiate into neuroendocrine-like (NE-like) cells. NE-like cells lack the expression of androgen receptor and prostate specific antigen, and are resistant to treatments. In addition, NE-like cells secrete peptide hormones and growth factors to support the growth of surrounding tumor cells in a paracrine manner. Accumulated evidence has suggested that NED is associated with disease progression and poor prognosis. The importance of NED in prostate cancer progression and therapeutic response is further supported by the fact that therapeutic agents, including androgen-deprivation therapy, chemotherapeutic agents, and radiotherapy, also induce NED. We will review the work supporting the overall hypothesis that therapy-induced NED is a mechanism of resistance to treatments, as well as discuss the relationship between therapy-induced NED and therapy-induced senescence, epithelial-to-mesenchymal transition, and cancer stem cells. Furthermore, we will use radiation-induced NED as a model to explore several NED-based targeting strategies for development of novel therapeutics. Finally, we propose future studies that will specifically address therapy-induced NED in the hope that a better treatment regimen for prostate cancer can be developed.

Salivary mucins induce a Toll-like receptor 4-mediated pro-inflammatory response in human submandibular salivary cells: are mucins involved in Sjögren's syndrome?

OBJECTIVES

A hallmark characteristic of SS patients is the ectopic presence of the mucins MUC5B and MUC7 in the extracellular matrix of salivary glands that have lost apical-basolateral acinar-cell polarity. This study aims to determine whether exogenous salivary mucins induce gene expression of pro-inflammatory cytokines, as well as to evaluate whether the Toll-like receptor-4 (TLR4) pathway is involved in this response.

METHODS

Differentiated human submandibular gland (HSG) cells were stimulated with mucins or oligosaccharide residues at different concentrations and for different periods of time. The expression of pro-inflammatory cytokines and their receptors was determined by semi-quantitative real time PCR (sqPCR). TLR4-mediated responses induced by mucin were evaluated with the Toll-IL-1 receptor domain containing adaptor protein (TIRAP) inhibitory peptide or using anti-hTLR4 blocking antibody. TLR4-receptor expression was also determined in SS patients, controls and HSG cells.

RESULTS

Mucins induced a significant increase in CXCL8, TNF-α, IFN-α, IFN-β, IL-6 and IL-1β, but not B cell activating factor (BAFF). Cytokine induction was mediated by TLR4, as shown using TIRAP or using anti-hTLR4 antibody. Sugar residues present in MUC5B, such as sulpho-Lewis (SO3-3Galβ1-3GlcNAc), also induced cytokines. Unexpectedly, mucins induced MUC5B, but not MUC7 expression.

CONCLUSION

Salivary mucins were recognized by TLR4 in epithelial cells initiating a pro-inflammatory response that could attract inflammatory cells to amplify and perpetuate inflammation and thereby contribute to the development of a chronic state characteristic of SS. The ectopic localization of MUC5B and MUC7 in the salivary gland extracellular matrix from SS patients and the current results reveal the importance of salivary epithelial cells in innate immunity, as well as in SS pathogenesis.

SRPK1 contributes to malignancy of hepatocellular carcinoma through a possible mechanism involving PI3K/Akt

Protein kinases are important regulators in biologic processes. Aberrant expression of protein kinases often causes diseases including cancer. In the present study, we found that the serine-arginine protein kinase 1 (SRPK1) might be involved in hepatocellular carcinoma (HCC) proliferation from a kinome screen using a loss-of-function approach. In clinical samples, SRPK1 was frequently up-regulated in HCCs as compared with adjacent non-tumor tissues at both mRNA and protein levels. Functional studies indicated that overexpression of wild-type SRPK1 promoted HCC cell proliferation, while forced expression of the kinase-dead mutant of SRPK1 or RNA interference against SRPK1 suppressed cell growth and malignancy as measured in soft agar assay. The kinase-dead mutant of SRPK1 also inhibited subcutaneous xenografts' growth of HCC cells in nude mice. Furthermore, western bolt analysis showed overexpression of wild-type SRPK1 enhanced Akt phosphorylation and knockdown of SRPK1 by RNA interference attenuated Akt phosphorylation induced by epidermal growth factor. Meanwhile, overexpression of wild-type SRPK1 also induced a concurrent increase in the total tyrosine phosphorylation of phosphotidylinositol-3 kinase p110α subunit, indicating a functional link between SRPK1 and PI3K/Akt signaling. Our findings suggest that SRPK1 plays an oncogenic role and could be a potential therapeutic target in HCC.

Involvement of Src in the Adaptation of Cancer Cells under Microenvironmental Stresses

Protein-tyrosine phosphorylation, which is catalyzed by protein-tyrosine kinase (PTK), plays a pivotal role in a variety of cellular functions related to health and disease. The discovery of the viral oncogene Src (v-Src) and its cellular nontransforming counterpart (c-Src), as the first example of PTK, has opened a window to study the relationship between protein-tyrosine phosphorylation and the biology and medicine of cancer. In this paper, we focus on the roles played by Src and other PTKs in cancer cell-specific behavior, that is, evasion of apoptosis or cell death under stressful extracellular and/or intracellular microenvironments (i.e., hypoxia, anoikis, hypoglycemia, and serum deprivation).

In vitro model of metastasis to bone marrow mediates prostate cancer castration resistant growth through paracrine and extracellular matrix factors

The spread of prostate cancer cells to the bone marrow microenvironment and castration resistant growth are key steps in disease progression and significant sources of morbidity. However, the biological significance of mesenchymal stem cells (MSCs) and bone marrow derived extracellular matrix (BM-ECM) in this process is not fully understood. We therefore established an in vitro engineered bone marrow tissue model that incorporates hMSCs and BM-ECM to facilitate mechanistic studies of prostate cancer cell survival in androgen-depleted media in response to paracrine factors and BM-ECM. hMSC-derived paracrine factors increased LNCaP cell survival, which was in part attributed to IGFR and IL6 signaling. In addition, BM-ECM increased LNCaP and MDA-PCa-2b cell survival in androgen-depleted conditions, and induced chemoresistance and morphological changes in LNCaPs. To determine the effect of BM-ECM on cell signaling, the phosphorylation status of 46 kinases was examined. Increases in the phosphorylation of MAPK pathway-related proteins as well as sustained Akt phosphorylation were observed in BM-ECM cultures when compared to cultures grown on plasma-treated polystyrene. Blocking MEK1/2 or the PI3K pathway led to a significant reduction in LNCaP survival when cultured on BM-ECM in androgen-depleted conditions. The clinical relevance of these observations was determined by analyzing Erk phosphorylation in human bone metastatic prostate cancer versus non-metastatic prostate cancer, and increased phosphorylation was seen in the metastatic samples. Here we describe an engineered bone marrow model that mimics many features observed in patients and provides a platform for mechanistic in vitro studies.

EGF promotes neuroendocrine-like differentiation of prostate cancer cells in the presence of LY294002 through increased ErbB2 expression independent of the phosphatidylinositol 3-kinase-AKT pathway

An increased neuroendocrine (NE) cell population in prostate cancer is associated with more aggressive disease and recurrence after androgen-deprivation therapy, although the mechanism responsible is unknown. In this study, we report that the treatment of LNCaP cells with epidermal growth factor (EGF) in the presence of LY294002, an inhibitor of the phosphoinositol 3'-kinase (PI3K)-AKT pathway, induced an increase of levels and activity of ErbB2. Under these conditions, we also observed cell survival and NE differentiation. When we treated with wortmannin, another PI3K inhibitor, or we knocked down PI3K or AKT isoforms in the presence of EGF, ErbB2 up-regulation was not observed, suggesting that the increase of ErbB2 induced by EGF plus LY294002 is not mediated by the PI3K-Akt pathway. Other targets of LY294002 were also discounted. We also show that ErbB2 up-regulation is directly involved in neuroendocine differentiation but not in cell survival as ErbB2 levels increased in parallel with NE differentiation marker levels, whereas ErbB2 knockdown reduced them; other NE differentiation inducers also increased the ErbB2 levels and the immunohistochemical analysis of prostate cancer samples showed colocalization of ErbB2 and chromogranin A. We found that, in LNCaP cells, EGF in combination with LY294002 increased ErbB2 levels by a PI3K/AKT-independent mechanism and that this increase was associated with the acquisition of a NE phenotype. These results suggest that is worth reconsidering ErbB2 as a drug target in prostate cancer and this should be kept in mind when designing new clinical schedules for the treatment of this disease.

Regulation of neuroendocrine differentiation by AKT/hnRNPK/AR/β-catenin signaling in prostate cancer cells

Current diagnostic tools cannot predict clinical failure and androgen-independent disease progression for patients with prostate cancer (PC). The survival signaling pathways of prostate cells play a central role in the progression of tumors to a neuroendocrine (NE) phenotype. NE cells demonstrate attributes that suggest that they are an integral part of the signaling cascade leading to castration-resistant PC. In this study, making use of in vitro neuroendocrine differentiation (NED) of human LNCaP and mouse TRAMP-C2 cells after androgen withdrawal, and of the transgenic adenocarcinoma of mouse prostate (TRAMP) model, we characterized a sequence of molecular events leading to NED and identified a number of markers that could be detectable by routine analyses not only in castration resistant PC but also in hormone naïve PC at the time of initial diagnosis. We found that NED associates with AKT activation that in turn regulates heterogeneous nuclear ribonucleoprotein K (hnRNP K), androgen receptor (AR) and β-catenin levels. Addition of molecules targeting membrane-bound receptors and protein kinases blocks NE differentiation in LNCaP and TRAMP-C2 cells. The extent of AKT phosphorylation and hnRNP K, AR and β-catenin levels may have a potential value as prognostic indicators discriminating between androgen-responsive and unresponsive cells and could be used as molecular targets to monitor the anti-tumor action of new therapeutic protocols based on antireceptor agents and/or neuroendocrine hormone antagonists.

Androgen-responsive and -unresponsive prostate cancer cell lines respond differently to stimuli inducing neuroendocrine differentiation

The treatment of advanced prostate cancer (CaP) with androgen deprivation therapy inevitably renders the tumours castration resistant and incurable. Under these conditions, neuroendocrine differentiation (NED) of CaP cells occurs and neuropeptides released by neuroendocrine cells facilitate tumour progression. Pharmacological strategies aiming to prevent or delay NED during androgen ablation could, therefore, increase the effectiveness of the therapy. Mechanisms and pathways inducing NED in CaP are poorly understood and data are often discordant. In the present study, we used several CaP cell lines (androgen-responsive: LNCaP, PC3-AR, 22RV1 and -irresponsive: DU145 and PC3) to evaluate NED after androgen deprivation or treatment with epidermal growth factor (EGF). NED was determined by neuron-specific enolase and chromogranin A expression and by the occurrence of morphological changes in the cells. Androgen-deprivation conditions induced NED in LNCaP and PC3-AR, but not in 22Rv1, PC3 and DU145 cells. LNCaP and PC3-AR cells also became resistant to thapsigargin-induced apoptosis. In all the AR-positive cell lines, androgen deprivation caused a decrease in androgen receptor expression indicating that it is downregulated irrespective of NED induction. Treatment with EGF induced NED in DU145 cells and the EGF receptor inhibitor gefinitib prevented the process. On the contrary, no effect of EGF was demonstrated in LNCaP or 22Rv1 cells. CaP cell lines did not respond univocally to treatments inducing NED, suggesting that studies on this topic should be performed in a wide spectrum of cell models which can be more indicative of the tumour variability in vivo.

The War on Cancer rages on

In 1971, the "War on Cancer" was launched by the US government to cure cancer by the 200-year anniversary of the founding of the United States of America, 1976. This article briefly looks back at the progress that has been made in cancer research and compares progress made in other areas of human affliction. While progress has indeed been made, the battle continues to rage on.

Knockdown of protein tyrosine phosphatase SHP-1 inhibits G1/S progression in prostate cancer cells through the regulation of components of the cell-cycle machinery

SHP-1, a haematopoietic cell-specific tyrosine phosphatase, is also expressed in human prostate. In this study, we report that SHP-1 depletion in PC-3 cells induced by small interfering RNAs causes G1 phase cell-cycle arrest accompanied by changes in some components of the cell-cycle machinery. SHP-1 knockdown increases p27(Kip1) (p27) protein stability, its nuclear localization and p27 gene transcription. These effects could be mediated by PI3K-AKT pathway as SHP-1 interacts with PI3K regulating its activity and p110 catalytic subunit phosphorylation. The increase in p27 protein stability could also because of reduced cyclin-dependent kinase (CDK2) activity. SHP-1 knockdown decreases the CDK6 levels, inducing retinoblastoma protein hypophosphorylation, downregulation of cyclin E and thereby a decrease in the CDK2 activity. However, the codepletion of SHP-1 and p27 does not produce re-entry into the cycle, implying that p27 is not required to maintain cell-cycle arrest induced by SHP-1 depletion. The maintenance of the PC-3 cell anti-proliferative response after p27 loss could be because of mislocalization of CDK2 induced by SHP-1 knockdown. This study shows that SHP-1 depletion promotes cell-cycle arrest by modulating the activity of cell-cycle regulators and suggests that SHP-1 may be required for the proper functioning of events governing cell-cycle progression.

Highly efficient capture and enumeration of low abundance prostate cancer cells using prostate-specific membrane antigen aptamers immobilized to a polymeric microfluidic device

Prostate tumor cells over-express a prostate-specific membrane antigen (PSMA) that can be used as a marker to select these cells from highly heterogeneous clinical samples, even when found in low abundance. Antibodies and aptamers have been developed that specifically bind to PSMA. In this study, anti-PSMA aptamers were immobilized onto the surface of a capture bed poised within a PMMA, microchip, which was fabricated into a high-throughput micro-sampling unit (HTMSU) used for the selective isolation of rare circulating prostate tumor cells resident in a peripheral blood matrix. The HTMSU capture bed consisted of 51 ultra-high-aspect ratio parallel curvilinear channels with a width similar to the prostate cancer cell dimensions. The surface density of the PSMA-specific aptamers on an ultraviolet-modified PMMA microfluidic capture bed surface was determined to be 8.4 x 10(12) molecules/cm(2). Using a linear velocity for optimal cell capture in the aptamer-tethered HTMSU (2.5 mm/s), a recovery of 90% of LNCaP cells (prostate cancer cell line; used as a model in this example) was found. Due to the low abundance of these cells, the input volume required was 1 mL and this could be processed in approximately 29 min using an optimized linear flow rate of 2.5 mm/s. Captured cells were subsequently released intact from the affinity surface using 0.25% w/w trypsin followed by counting individual cells using a contact conductivity sensor integrated into the HTMSU that provided high detection and sampling efficiency (approximately 100%) and did not require staining of the cells for enumeration.

Combined analysis of EGF+61G>A and TGFB1+869T>C functional polymorphisms in the time to androgen independence and prostate cancer susceptibility

Proliferative mechanisms involving the epidermal growth factor (EGF) and transforming growth factor beta (TGF-beta(1)) ligands are potential alternative pathways for prostate cancer (PC) progression to androgen independence (AI). Thus, the combined effect of EGF and TGFB1 functional polymorphisms might modulate tumor microenvironment and consequently its development. We studied EGF+61G>A and TGFB1+869T>C functional polymorphisms in 234 patients with PC and 243 healthy individuals. Intermediate- and high-proliferation genetic profile carriers have increased risk for PC (odds ratio (OR)=3.76, P=0.007 and OR=3.98, P=0.004, respectively), when compared with low proliferation individuals. Multivariate analysis showed a significantly lower time to AI in the high proliferation group, compared with the low/intermediate proliferation genetic profile carriers (HR=2.67, P=0.039), after adjustment for age, metastasis and stage. Results suggest that combined analysis of target genetic polymorphisms may contribute to the definition of cancer susceptibility and pharmacogenomic profiles. Combined blockage of key molecules in proliferation signaling pathways could be one of the most promising strategies for androgen-independent prostate cancer.

Neoplasia: the second decade

This issue marks the end of the 10-year anniversary of Neoplasia where we have seen exciting growth in both number of submitted and published articles in Neoplasia. Neoplasia was first published in 1999. During the past 10 years, Neoplasia has dynamically adapted to the needs of the cancer research community as technologies have advanced. Neoplasia is currently providing access to articles through PubMed Central to continue to facilitate rapid broad-based dissemination of published findings to the scientific community through an Open Access model. This has in part helped Neoplasia to achieve an improved impact factor this past year, demonstrating that the manuscripts published by Neoplasia are of great interest to the overall cancer research community. This past year, Neoplasia received a record number of articles for review and has had a 21% increase in the number of published articles.

Osteoblast-induced EGFR/ERBB2 signaling in androgen-sensitive prostate carcinoma cells characterized by multiplex kinase activity profiling

Bone metastases in prostate cancer are predominantly osteoblastic. To study regulatory mechanisms underlying the establishment of prostate cancer within an osteoblastic microenvironment, human androgen-sensitive prostate carcinoma cells (LNCaP) were treated with culture medium conditioned by human osteoblast-derived sarcoma cells (OHS), and activated signalling pathways in the carcinoma cells were analyzed using microarrays with tyrosine kinase substrates. Network interaction analysis of substrates with significantly increased phosphorylation levels revealed that signalling pathways mediated by EGFR and ERBB2 were activated in LNCaP cells under OHS influence but also by androgen treatment. Activation of EGFR/ERBB2 signalling was also found in LNCaP cells in cocultures with OHS cells or osteoblastic cells that had been differentiated from human mesenchymal stem cells. Our experimental data suggests osteoblast-directed induction of signalling activity via EGFR and ERBB2 in prostate carcinoma cells and may provide a rationale for the use of EGFR or ERBB2 inhibition in systemic prevention or treatment of metastatic prostate cancer in the androgen-sensitive stage of the disease.

Altered fibroblast growth factor receptor 4 stability promotes prostate cancer progression

Fibroblast growth factor receptor 4 (FGFR-4) is expressed at significant levels in almost all human prostate cancers, and expression of its ligands is ubiquitous. A common polymorphism of FGFR-4 in which arginine (Arg(388)) replaces glycine (Gly(388)) at amino acid 388 is associated with progression in human prostate cancer. We show that the FGFR-4 Arg(388) polymorphism, which is present in most prostate cancer patients, results in increased receptor stability and sustained receptor activation. In patients bearing the FGFR-4 Gly(388) variant, expression of Huntingtin-interacting protein 1 (HIP1), which occurs in more than half of human prostate cancers, also results in FGFR-4 stabilization. This is associated with enhanced proliferation and anchorage-independent growth in vitro. Our findings indicate that increased receptor stability and sustained FGFR-4 signaling occur in most human prostate cancers due to either the presence of a common genetic polymorphism or the expression of a protein that stabilizes FGFR-4. Both of these alterations are associated with clinical progression in patients with prostate cancer. Thus, FGFR-4 signaling and receptor turnover are important potential therapeutic targets in prostate cancer.