Pathobiological implications of the expression of EGFR, pAkt, NF-κB and MIC-1 in prostate cancer stem cells and their progenies

Mass Spectrometry-Based Assessment of Prostate Cancer-Associated Crystalloids Reveals Enrichment for Growth & Differentiation Factor 15 (GDF15)

Intraluminal crystalloids are a common finding within malignant prostatic acini and are infrequently identified within benign glands. The proteomic composition of these crystalloids remains poorly understood and may provide insight regarding prostate cancer pathogenesis. Laser microdissection assisted liquid chromatography tandem mass spectrometry (LMD-LC-MS/MS) was performed to compare proteomic composition of corpora amylacea within benign acini (n=9), prostatic adenocarcinoma-associated crystalloids (n=8), benign (n=8), and malignant prostatic acini (n=6). The expression of candidate biomarkers was then measured in urine specimens from patients with (n=8) and without prostate cancer (n=10) using ELISA; and immunohistochemistry-based expression in adjacent prostate cancer and benign glands was assessed in 56 whole-slide sections from radical prostatectomy specimens. LMD-LC-MS/MS revealed enrichment for the C-terminal portion of growth and differentiation factor 15 (GDF15) in prostatic crystalloids. Although urinary GDF15 levels were higher in patients with prostatic adenocarcinoma compared to those without (median: 1561.2 vs 1101.3, arbitrary units), this did not meet statistical significance (p=0.07). Immunohistochemistry for GDF15 revealed occasional positivity in benign glands (median H-score: 30, n=56), and diffuse positivity in prostatic adenocarcinoma (median H-score: 200, n=56, p<0.0001). No significant difference was identified within different prognostic grade groups of prostatic adenocarcinoma, or within malignant glands with large cribriform morphology. Our results show that the C-terminal portion of GDF15 is enriched in prostate cancer-associated crystalloids, and higher GDF15 expression is seen in malignant rather than benign prostatic acini. Improved understanding of the proteomic composition of prostate cancer-associated crystalloids provides the rationale for evaluating GDF15 as a urine-based biomarker of prostate cancer.

C-reactive protein levels could be a prognosis predictor of prostate cancer: A meta-analysis

BACKGROUND

The relationship between the C-reactive protein (CRP) and prognosis in prostate cancer (PCa) has been widely discussed over the past few years but remains controversial.

MATERIAL AND METHODS

In our meta-analysis, we searched 16 reliable studies in the PubMed, Embase, and Cochrane Library databases. Otherwise, we have successfully registered on the INPLASY. We also performed random- and fixed-effects models to evaluate the hazard ratio (HR) and 95% confidence interval (CI), respectively.

RESULT

The result of our meta-analysis shows that elevated CRP levels were related to worse overall survival (OS) (HR = 1.752, 95% CI = 1.304-2.355, p = 0.000), cancer-specific survival (CSS) (HR = 1.663, 95% CI = 1.064-2.6, p = 0.026), and progression-free survival (PFS) (HR = 1.663, 95% CI = 1.064-2.6, p = 0.026) of PCa patients. There was significant heterogeneity, so we performed a subgroup analysis according to the staging of the disease and found the same result. Furthermore, the heterogeneity was also reduced, and no statistical significance.

CONCLUSION

Our study shows that the level of CRP could reflect the prognosis of prostate cancer patients. We find that PCa patients with high levels of CRP often have worse OS, CSS, and PFS, although the stages of the patients' disease are different. More studies are needed to verify this idea.

GDF15 promotes prostate cancer bone metastasis and colonization through osteoblastic CCL2 and RANKL activation

Bone metastases occur in patients with advanced-stage prostate cancer (PCa). The cell-cell interaction between PCa and the bone microenvironment forms a vicious cycle that modulates the bone microenvironment, increases bone deformities, and drives tumor growth in the bone. However, the molecular mechanisms of PCa-mediated modulation of the bone microenvironment are complex and remain poorly defined. Here, we evaluated growth differentiation factor-15 (GDF15) function using in vivo preclinical PCa-bone metastasis mouse models and an in vitro bone cell coculture system. Our results suggest that PCa-secreted GDF15 promotes bone metastases and induces bone microarchitectural alterations in a preclinical xenograft model. Mechanistic studies revealed that GDF15 increases osteoblast function and facilitates the growth of PCa in bone by activating osteoclastogenesis through osteoblastic production of CCL2 and RANKL and recruitment of osteomacs. Altogether, our findings demonstrate the critical role of GDF15 in the modulation of the bone microenvironment and subsequent development of PCa bone metastasis.

AKT in Bone Metastasis of Solid Tumors: A Comprehensive Review

Simple Summary

Bone metastasis is a frequent complication of solid tumors and leads to a reduced overall survival. Although much progress has been made in the field of tumor therapy in the last years, bone metastasis depicts a stage of the disease with a lack of appropriate therapeutical options. Hence, this review aims to present the role of AKT in bone metastasis of solid tumors to place the spotlight on AKT as a possible therapeutical approach for patients with bone metastases. Furthermore, we intended to discuss postulated underlying molecular mechanisms of the bone metastasis-promoting effect of AKT, especially in highly bone-metastatic breast, prostate, and lung cancer. To conclude, this review identified the AKT kinase as a potential therapeutical target in bone metastasis and revealed remaining questions, which need to be addressed in further research projects.

Abstract

Solid tumors, such as breast cancer and prostate cancer, often form bone metastases in the course of the disease. Patients with bone metastases frequently develop complications, such as pathological fractures or hypercalcemia and exhibit a reduced life expectancy. Thus, it is of vital importance to improve the treatment of bone metastases. A possible approach is to target signaling pathways, such as the PI3K/AKT pathway, which is frequently dysregulated in solid tumors. Therefore, we sought to review the role of the serine/threonine kinase AKT in bone metastasis. In general, activation of AKT signaling was shown to be associated with the formation of bone metastases from solid tumors. More precisely, AKT gets activated in tumor cells by a plethora of bone-derived growth factors and cytokines. Subsequently, AKT promotes the bone-metastatic capacities of tumor cells through distinct signaling pathways and secretion of bone cell-stimulating factors. Within the crosstalk between tumor and bone cells, also known as the vicious cycle, the stimulation of osteoblasts and osteoclasts also causes activation of AKT in these cells. As a consequence, bone metastasis is reduced after experimental inhibition of AKT. In summary, AKT signaling could be a promising therapeutical approach for patients with bone metastases of solid tumors.

Growth and differentiation factor 15 and NF-κB expression in benign prostatic biopsies and risk of subsequent prostate cancer detection

Growth and differentiation factor 15 (GDF‐15), also known as macrophage inhibitory cytokine 1 (MIC‐1), may act as both a tumor suppressor and promotor and, by regulating NF‐κB and macrophage signaling, promote early prostate carcinogenesis. To determine whether expression of these two inflammation‐related proteins affect prostate cancer susceptibility, dual immunostaining of benign prostate biopsies for GDF‐15 and NF‐κB was done in a study of 503 case‐control pairs matched on date, age, and race, nested within a historical cohort of 10,478 men. GDF‐15 and NF‐κB expression levels were positively correlated (r = 0.39; p < 0.0001), and both were significantly lower in African American (AA) compared with White men. In adjusted models that included both markers, the odds ratio (OR) for NF‐κB expression was statistically significant, OR =0.87; p = 0.03; 95% confidence interval (CI) =0.77–0.99, while GDF‐15 expression was associated with a nominally increased risk, OR =1.06; p = 0.27; 95% CI =0.96–1.17. When modeling expression levels by quartiles, the highest quartile of NF‐κB expression was associated with almost a fifty percent reduction in prostate cancer risk (OR =0.51; p = 0.03; 95% CI =0.29–0.92). In stratified models, NF‐κB had the strongest negative association with prostate cancer in non‐aggressive cases (p = 0.03), older men (p = 0.03), and in case‐control pairs with longer follow‐up (p = 0.02). Risk associated with GDF‐15 expression was best fit using nonlinear regression modeling where both first (p = 0.02) and second (p = 0.03) order GDF‐15 risk terms were associated with significantly increased risk. This modeling approach also revealed significantly increased risk associated with GDF‐15 expression for subsamples defined by AA race, aggressive disease, younger age, and in case‐control pairs with longer follow‐up. Therefore, although positively correlated in benign prostatic biopsies, NF‐κB and GDF‐15 expression appear to exert opposite effects on risk of prostate tumor development.

Catechol inhibits epidermal growth factor-induced epithelial-to-mesenchymal transition and stem cell-like properties in hepatocellular carcinoma cells

Epithelial-mesenchymal transition (EMT) is a major cellular process in which epithelial cells lose cell polarity and cell-cell adhesion and become motility and invasiveness by transforming into mesenchymal cells. Catechol is one of the natural compounds present in fruits and vegetables and has various pharmacological and physiological activities including anti-carcinogenic effects. However, the effects of catechol on EMT has not been reported. Epidermal growth factor (EGF) is one of the growth factors and is known to play a role in inducing EMT. The present study showed that catechol suppressed not only the morphological changes to the mesenchymal phenotype of epithelial HCC cells, but also the reduction of E-cadherin and the increment of Vimentin, which are typical hallmark of EMT. In addition, catechol suppressed EMT-related steps such as migration, invasion, anoikis resistance acquisition, and stem cell-like characterization through the EGFR-AKT-ERK signaling pathway during liver cancer metastasis. Therefore, these results suggest that catechol may be able to regulate the early metastasis of liver cancer in vitro.

Identification and characterization of biomarkers and their functions for docetaxel-resistant prostate cancer cells

Docetaxel treatment is a standard chemotherapy strategy for castration-resistant prostate cancer (CRPC), and patients with CRPC eventually develop resistance to treatment. However, little is understood regarding the underlying mechanism of resistance. The present study aimed to identify the underlying crucial genes and regulatory networks associated with docetaxel resistance in prostate cancer using bioinformatics analyses. For this purpose, one expression profile dataset (GSE33455), which included two docetaxel-sensitive and two docetaxel-resistant cell lines, was downloaded from the Gene Expression Omnibus database, and analyses of differential gene expression and function enrichment were performed. A protein-protein interaction (PPI) network was constructed, and the associated hub genes were investigated using the Search Tool for the Retrieval of Interacting Genes/Proteins and Cytoscape software. A total of 756 differentially expression genes (DEGs) were identified, including 509 downregulated and 247 upregulated genes. Enrichment analysis revealed that the DEGs were associated with the interferon-γ-mediated signaling pathway, protein binding, bicellular tight junctions and cancer pathways. Two modules were screened from the PPI network, and the corresponding genes were identified to be largely enriched in the interferon-γ-mediated signaling pathway and the negative regulators of the DExD/H-Box helicase 58/interferon induced with helicase C domain 1 signaling pathway, and enriched in cell-cell adhesion and the Rap1 signaling pathway. Among the ten hub genes, epidermal growth factor receptor, spleen tyrosine kinase (SYK), intracellular adhesion molecule 1 (ICAM1), interleukin (IL)6, CXC motif chemokine ligand 8 (CXCL8), cyclin dependent kinase 1 and CD44 molecule (CD44) were significantly differentially expressed in prostate cancer tissues compared with healthy tissues based on The Cancer Genome Atlas data. The Gene Expression Profiling Interactive Analysis database revealed that ICAM1 was positively associated with IL6 and CXCL8, and epidermal growth factor receptor was positively associated with CD44 and SYK. Additionally, ten hub genes, which were identified to be associated with the drug resistance of docetaxel in prostatic carcinoma in the present study, were predominantly associated with tumor progression and metastasis. Reverse transcription-quantitative PCR analysis performed on docetaxel-sensitive and docetaxel-resistant prostate cancer cell lines demonstrated that certain hub genes, including CDK1, 2′-5′-oligoadenylate synthetase 3, CXCL8 and CDH1, were highly expressed in the docetaxel-resistant cell lines, which confirmed the bioinformatics results. In conclusion, the present study identified a number of important genes that are associated with the molecular mechanism of docetaxel resistance by integrated bioinformatical analysis, and these genes and regulatory networks may assist with identifying potential gene therapy targets for CRPC. Further functional analyses are required to validate the current findings.

Growth differentiation factor 15 (GDF15): A survival protein with therapeutic potential in metabolic diseases

Growth Differentiation Factor 15 (GDF15), also known as NSAID activated gene-1 (NAG-1), is associated with a large number of biological processes and diseases, including cancer and obesity. GDF15 is synthesized as pro-GDF15, is dimerized, and is cleaved and secreted into the circulation as a mature dimer GDF15. Both the intracellular GDF15 and the circulating mature GDF15 are implicated in biological processes, such as energy homeostasis and body weight regulation. Although there have been many studies on GDF15, GFRAL, a member of the glial-derived neurotropic factor receptor α family, has only been recently identified as a receptor for mature GDF15. In this review, we focused on cancer and energy homeostasis along with obesity and body weight, and the effect of the identification of the GDF15 receptor in these investigations. In addition, the therapeutic potential of GDF15 as a pharmacological agent in obesity and other metabolic diseases was discussed.

Anticancer potential of novel curcumin analogs towards castrate-resistant prostate cancer

Prostate cancer is initially sensitive to hormone therapy; however, over time the majority of patients progress to a hormone-insensitive form classified as castration-resistant prostate cancer (CRPC). CRPC is highly metastatic and patients have a poor prognosis. Thus, new drugs for the treatment of this disease are required. In this study, we therefore examined the cytotoxic effects and anticancer mechanism(s) of action of second generation curcumin analogs towards CRPC cells. For this purpose, PC3 and DU145 cells were treated with a series of curcumin analogs at 0-10 µM for 72 h and cytotoxicity was determined by the sulforhodamine B (SRB) assay. Two compounds, 1-isopropyl-3,5-bis(pyridin-3-ylmethylene)-4-piperidone (RL118) and 1-methyl-3,5-[(6-methoxynaphthalen-2-yl)methylene]-4-piperidone (RL121), were found to have the most potent cytotoxic effect with EC50 values of 0.50 and 0.58 µM in the PC3 cells and EC50 values of 0.76 and 0.69 µM in the DU145 cells, respectively. Thus, further experiments were performed focusing on these two compounds. Flow cytometry was performed to determine their effects on the cell cycle and apoptosis. Both analogs increased the number of cells in the G2/M phase of the cell cycle and induced apoptosis. Specifically, in the PC3 cells, RL121 increased the number of cells in the G2/M phase by 86% compared to the control, while RL118 increased the number of cells in the G2/M phase by 42% compared to the control after 24 h. Moreover, both RL118 and RL121 induced the apoptosis of both cell lines. In the DU145 cells, a 38-fold increase in the number of apoptotic cells was elicited by RL118 and a 78-fold increase by RL121 compared to the control. Furthermore, the effects of both analogs on the expression of key proteins involved in cell proliferation were also determined by western blot analysis. The results revealed that both analogs inhibited the expression of nuclear factor (NF)-κB (p65/RelA), eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), p-4E-BP1, mammalian target of rapamycin (mTOR), p-mTOR, AKT and p-AKT. Thus, the findings of this study provide evidence that RL118 and RL121 have potent anticancer activity against CPRC cells, and both analogs warrant further investigation in vivo.

Expression of P-EGFR and P-Akt protein in esophageal squamous cell carcinoma and its prognosis

The phosphorylated epidermal growth factor receptor (P-EGFR) and phosphorylated Akt (P-Akt) protein in esophageal squamous cell carcinoma (ESCC) were studied, and its significance in clinical prognosis of patients was assessed. The expression of P-EGFR and P-Akt protein in 83 cases of ESCC and 83 normal esophageal tissues was determined by immunohistochemical staining. Log-rank test and correlation analysis were used to analyze the prognosis of ESCC. The positive expression of P-EGFR in ESCC was 88% (73/83 cases) compared with 41% in normal esophageal mucosa (34/83 cases) (P<0.05). The rate of P-Akt protein expression in ESCC was 90.4% (75/83 cases), compared with 27.7% seen in normal esophageal mucosa (23/83 cases) (P<0.05). The expression of P-EGFR and P-Akt protein was positively correlated with lymph node metastasis and degree of differentiation (P<0.05) irrespective of sex, age, tumor diameter and TNM stage (P>0.05). The expression of P-EGFR was positively correlated with that of P-Akt protein (r=0.674, P<0.01). P-EGFR expression was negatively correlated with survival time of patients with ESCC (r=−0.526, P<0.01). The Kaplan-Meier survival curves showed that the cumulative survival rate of P-EGFR-positive cases was significantly lower than that of the P-EGFR-negative cases (P<0.01). The expression of P-Akt was negatively correlated with survival in patients with ESCC (r=−0.473, P<0.01). The Kaplan-Meier survival curves showed that the cumulative survival rate of the P-Akt-positive cases was significantly lower than that of the P-Akt-negative cases (P<0.01). In conclusion, P-EGFR and P-Akt protein expression is closely related to the incidence of ESCC and mediates the development of invasive cancer and metastasis. It is used to determine the prognosis of ESCC, and may represent a new therapeutic target for the disease.

Combination of Carmustine and Selenite Inhibits EGFR Mediated Growth Signaling in Androgen-Independent Prostate Cancer Cells

Although aberrant androgen receptor (AR) signaling is a central mechanism for castration resistant prostate cancer (CRPC) progression, AR-independent growth signaling is also present in CRPC. The current therapeutic options for patients with CRPC are limited and new drugs are desperately needed to eliminate these crucial growth signaling pathways. We have previously shown that combination of carmustine and selenite effectively induces apoptosis and growth inhibition by targeting AR and AR-variants in CRPC cells. High levels of EGFR expression present in the CRPC cells mediates the cell proliferation via AR-independent growth signaling mechanisms. Therefore, in this study, we investigated whether the combination of carmustine and selenite could inhibit EGFR mediated growth signaling and induce apoptosis in androgen independent-AR negative prostate cancer cells. EGF exposure dose and time dependently increased phospho-EGFR (Tyr845, Tyr1068, and Tyr1045), pAkt (Ser473), and pERK1/2 (Thr204/Tyr202) protein expression levels in AIPC cells. Combination of carmustine and selenite treatment markedly suppressed EGF-stimulated proliferation and survival of AIPC cells and effectively induced apoptosis. The ROS generated by the combination of carmustine and selenite exhibited a strong inhibition on EGF stimulated EGFR and its downstream signaling molecules such as Akt, NF-kB, ERK1/2, and Cyclin D1. Individual agent treatment showed only partial effect. Overall, our findings demonstrated that the combination of carmustine and selenite treatment dramatically inhibits EGFR signaling, proliferation, and induces apoptosis in AIPC cells, suggesting a potential candidate for the treatment of CRPC. The results of the study further suggest that the combination of carmustine and selenite treatment can overcome EGFR mediated AR-independent growth response in CRPC during anti-androgen therapy. J. Cell. Biochem. 118: 4331-4340, 2017. © 2017 Wiley Periodicals, Inc.

Testis specific Y-like 5: gene expression, methylation and implications for drug sensitivity in prostate carcinoma

BACKGROUND

TSPYL5, a putative tumor suppressor gene, belongs to the nucleosome assembly protein family. The chromosomal location of the TSPYL5 gene is 8Q22.1, and its exact role in prostate cancer etiology remains unclear. Further TSPYL5 gene and protein expression in prostate carcinoma cells and diseased tissues including its susceptibility for epigenetic silencing is unknown. Also, not known is the variation in TSPYL5 protein expression with regards to progression of prostatic carcinoma and its possible role in drug sensitivity.

METHODS

TSPYL5, DNMT-1 and DNMT-B gene expression in DU145, LNCaP and RWPE-1 cells and prostate tumor tissues was analyzed by qRT-PCR and RT-PCR. Demethylation experiments were done by treating DU145 and LNCaP cells with 5-aza-2'-deoxycytidine in vitro. Methylation analysis of TSPYL5 gene was performed by methylation specific PCR and pyrosequencing. TSPYL5 protein expression in benign and diseased prostate tumor tissues was performed by immunohistochemistry and in the cells by Western blotting.

RESULTS

TSPYL5 was differentially expressed in non-tumorigenic prostate epithelial cells (RWPE-1), androgen independent (DU145), dependent (LNCaP) prostate carcinoma cells and tissues. Methylation-specific PCR and pyrosequencing analysis identified an inverse relationship between DNA methylation and expression leading to the silencing of TSPYL5 gene. Treatment of prostate carcinoma cells in which TSPYL5 was absent or low (DU145 and LNCaP) with the demethylating agent 5-aza-2'-deoxycytidine upregulated its expression in these cells. Immunohistochemical studies clearly identified TSPYL5 protein in benign tissue and in tumors with Gleason score (GS) of 6 and 7. TSPYL5 protein levels were very low in tumors of GS ≥ 8. TSPYL5 overexpression in LNCaP cells increased the cell sensitivity to chemotherapy drugs such as docetaxel and paclitaxel, as measured by the cellular viability. Furthermore, the cells also exhibited reduced CDKN1A expression with only marginal reduction in pAKT.

CONCLUSIONS

Decrease in TSPYL5 protein in advanced tumors might possibly function as an indicator of prostate tumor progression. Its absence due to methylation-induced silencing can lead to reduced drug sensitivity in prostate carcinoma.

Inhibition of hedgehog signaling improves the anti-carcinogenic effects of docetaxel in prostate cancer

The establishment of docetaxel-based chemotherapeutic treatments has improved the survival of castration-resistant prostate cancer (CRPC) patients. However, most patients develop resistance supporting the development of therapy. The current study was undertaken to establish the therapeutic benefit to target hedgehog signaling cascade using GDC-0449 to improve the efficacy of chemotherapeutic drug, docetaxel. Here, we show that the combination of GDC-0449 plus docetaxel inhibited the proliferation of WPE1-NB26 cells and PC3 cells via a blockade of G1 and G2M phases. The combined treatment significantly inhibited PC cell migration in vitro. Moreover, the apoptotic effect induced by GDC-0449 plus docetaxel on PC3 cells was mediated, at least partly, via the mitochondrial membrane depolarization, H₂O₂ production and caspase cascade activation. Interestingly, GDC-0449 was effective at inhibiting the prostasphere formation, inducing the prostasphere disintegration and apoptotic death of side population (SP) from PC3 cells and reversing the resistance of SP cells to docetaxel. In addition, GDC-0449 plus docetaxel also have shown a greater anti-tumoral growth inhibitory effect on PC3 cell xenografts. These findings support the use of the hedgehog inhibitor GDC-0449, which is currently in clinical trials, for improving the anticarcinogenic efficacy of docetaxel-based chemotherapeutic treatments against locally advanced, AI and metastatic PC.

Gene methylation of human ovarian carcinoma stromal progenitor cells promotes tumorigenesis

Background

This study aimed to investigate whether the DNA methylation of human ovarian carcinoma stromal progenitor cells (OCSPCs) could promote the tumorigenesis of ovarian carcinoma.

Methods

OCSPCs were first isolated from fresh tumor tissues and ascites of ovarian cancer patients. In vivo and in vitro experiments on the effect of the OCSPCs on tumorigenesis and the effects of DNA demethylation on the OCSPCs were then performed.

Results

The OCSPCs possessed self-renewal and multipotent differentiation capacity with elevated expressions of OCT4, NANOG, BMP2, BMP4, Rex-1, AC133 and TGF-β. The OCSPCs, when combined with tumor cells in vivo could promote tumor growth. The methylation profiles of tumor suppressor genes (TSGs) were significantly higher in the OCSPCs than in ovarian cancer cells (p < 0.001). 5-aza-2-dC could alter the methylation levels of TSGs in OCSPCs and also inhibit the tumor promoting capabilities of the OCSPCs by decreasing the proliferation of tumors cells. The expression levels of TSGs were re-expressed by 5-aza-2-dC to inhibit the self-renewal and growth of OCSPCs.

Conclusions

OCSPCs with decreased TSG expressions in the ovarian tumor microenvironment were able to promote tumorigenesis which could be reversed by DNA demethylation. DNA demethylation reversing the expression of TSGs in OCSPCs may represent a potential therapeutic target for ovarian cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0722-7) contains supplementary material, which is available to authorized users.

Novel roles of androgen receptor, epidermal growth factor receptor, TP53, regulatory RNAs, NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, and matrix metalloproteinase-9 in prostate cancer and prostate cancer stem cells

Approximately one in six men will be diagnosed with some form of prostate cancer in their lifetime. Over 250,000 men worldwide die annually due to complications from prostate cancer. While advancements in prostate cancer screening and therapies have helped in lowering this statistic, better tests and more effective therapies are still needed. This review will summarize the novel roles of the androgen receptor (AR), epidermal growth factor receptor (EGFR), the EGFRvIII variant, TP53, long-non-coding RNAs (lncRNAs), microRNAs (miRs), NF-kappa-B, chromosomal translocations, neutrophil associated gelatinase, (NGAL), matrix metalloproteinase-9 (MMP-9), the tumor microenvironment and cancer stem cells (CSC) have on the diagnosis, development and treatment of prostate cancer.

Overexpression of NRG1 promotes progression of gastric cancer by regulating the self-renewal of cancer stem cells

BACKGROUND

Gastric cancer stem cells (GCSCs) have been successfully isolated from patients. However, the molecular mechanisms underlying the self-renewal of GCSCs and their relationship with the microenvironment are poorly characterized.

METHODS

GCSCs and cancer-associated fibroblasts (CAFs) were cultured directly from gastric cancer patients. The self-renewal of GCSCs was assayed by sphere formation assay and in vivo tumorigenicity. Expression of neuregulin1 (NRG1) was examined by immunohistochemistry, real-time PCR and western blotting.

RESULTS

CAFs increased the self-renewal of GCSCs by secreting NRG1. NRG1 activated NF-κB signaling and this activation regulated GCSC self-renewal. Moreover, NF-κB-active GCSCs were tumorigenic, however NF-κB-inactive GCSCs were not. The overexpression of NRG1 in stromal cells and cancer cells was observed in the tumor tissues of gastric cancer patients and was associated with clinical stage lymph node metastasis and survival in gastric cancer patients. In addition, we also found that NRG1 can regulate the proliferation and invasion of gastric cancer cells.

CONCLUSIONS

These results indicate that NRG1, which can be secreted by CAFs or cancer cells, promotes progression of gastric cancer by regulating the self-renewal of GCSCs and its overexpression is associated with a prognosis of gastric cancer.

Prognostic role of vascular endothelial growth factor in prostate cancer: a systematic review and meta-analysis

The objective of this study was to perform a meta-analysis and literature review on the predictive role of vascular endothelial growth factor (VEGF) in prostate cancer. A detailed literature search was performed using PubMed and Embase databases for related research publications written in English. Methodological quality of the studies was also evaluated. Data was collected from studies comparing overall survival (OS), progression-free survival (PFS), disease-free survival (DFS), biomedical failure (BF) and cancer-specific survival (CSS) in patients with elevated VEGF levels and those having lower levels. The hazard ratio (HR) and its 95% confidence interval (CI) were used to assess the strength of associations. A total of 12 studies (n = 1,737) were included in this meta-analysis (4 for OS, 3 for CSS, 2 for DFS, 4 for BF, and 4 for PFS). For OS, DFS and PFS, the pooled HR for VEGF was not statistically significant at 1.30 (95% CI, 0.74-2.29), 0.80 (95% CI, 0.57-1.13) and 1.04 (95% CI, 0.93-1.16), respectively. However, for CSS and BF, the pooled HR was 2.32 (95% CI, 1.20-4.46) and 1.30 (95% CI, 1.06-1.59), respectively. Our results demonstrate that VEGF may have a critical prognostic value in patients with prostatic cancer.

Prognostic role of C-reactive protein in prostate cancer: a systematic review and meta-analysis

Several studies have reported that C-reactive protein (CRP), an inflammation biomarker, may be associated with the prognosis of prostate cancer (PCa). The objective of this systematic review is to summarize the predictive role of CRP for survival in PCa as reported in previous studies. Related studies were identified, and evaluated for quality through multiple search strategies. Data was collected from studies comparing overall and cancer-specific survival (CSS) in patients with elevated CRP levels and those having lower levels. However, for progression-free survival (PFS), data were collected according to the log of CRP. The hazard ratio (HR) and its 95% confidence interval (CI) were used to assess the strength of associations. A total of nine studies (n = 1,497) were evaluated in this meta-analysis (five for overall survival (OS), four for CSS and two for PFS). For OS and PFS, the pooled HR of CRP was statistically significant at 1.51 (95% CI, 1.28-1.79) and 1.50 (95% CI, 1.25-1.81), respectively. For CSS, the pooled HR was 1.91 (95% CI, 1.36-2.69) with higher CRP expression in PCa, which strongly indicates poorer survival in PCa. This study demonstrates that CRP may have a critical prognostic value in patients with prostatic cancer.

Combination simvastatin and metformin induces G1-phase cell cycle arrest and Ripk1- and Ripk3-dependent necrosis in C4-2B osseous metastatic castration-resistant prostate cancer cells

Castration-resistant prostate cancer (CRPC) cells acquire resistance to chemotherapy and apoptosis, in part, due to enhanced aerobic glycolysis and biomass production, known as the Warburg effect. We previously demonstrated that combination simvastatin (SIM) and metformin (MET) ameliorates critical Warburg effect-related metabolic aberrations of C4-2B cells, synergistically and significantly decreases CRPC cell viability and metastatic properties, with minimal effect on normal prostate epithelial cells, and inhibits primary prostate tumor growth, metastasis, and biochemical failure in an orthotopic model of metastatic CRPC, more effectively than docetaxel chemotherapy. Several modes of cell death activated by individual treatment of SIM or MET have been reported; however, the cell death process induced by combination SIM and MET treatment in metastatic CRPC cells remains unknown. This must be determined prior to advancing combination SIM and MET to clinical trial for metastatic CRPC. Treatment of C4-2B cells with combination 4 μM SIM and 2 mM MET (SIM+MET) led to significant G1-phase cell cycle arrest and decrease in the percentage of DNA-replicating cells in the S-phase by 24 h; arrest was sustained throughout the 96-h treatment. SIM+MET treatment led to enhanced autophagic flux in C4-2B cells by 72–96 h, ascertained by increased LC3B-II (further enhanced with lysosomal inhibitor chloroquine) and reduced Sequestosome-1 protein expression, significantly increased percentage of acidic vesicular organelle-positive cells, and increased autophagic structure accumulation assessed by transmission electron microscopy. Chloroquine, however, could not rescue CRPC cell viability, eliminating autophagic cell death; rather, autophagy was upregulated by C4-2B cells in attempt to withstand chemotherapy. Instead, SIM+MET treatment led to Ripk1- and Ripk3-dependent necrosis by 48–96 h, determined by propidium iodide-Annexin V flow cytometry, increase in Ripk1 and Ripk3 protein expression, necrosome formation, HMGB-1 extracellular release, and necrotic induction and viability rescue with necrostatin-1 and Ripk3-targeting siRNA. The necrosis-inducing capacity of SIM+MET may make these drugs a highly-effective treatment for apoptosis- and chemotherapy-resistant metastatic CRPC cells.

Altered gene products involved in the malignant reprogramming of cancer stem/progenitor cells and multitargeted therapies

Recent studies in the field of cancer stem cells have revealed that the alterations in key gene products involved in the epithelial-mesenchymal transition (EMT) program, altered metabolic pathways such as enhanced glycolysis, lipogenesis and/or autophagy and treatment resistance may occur in cancer stem/progenitor cells and their progenies during cancer progression. Particularly, the sustained activation of diverse developmental cascades such as hedgehog, epidermal growth factor receptor (EGFR), Wnt/β-catenin, Notch, transforming growth factor-β (TGF-β)/TGF-βR receptors and/or stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) can play critical functions for high self-renewal potential, survival, invasion and metastases of cancer stem/progenitor cells and their progenies. It has also been observed that cancer cells may be reprogrammed to re-express different pluripotency-associated stem cell-like markers such as Myc, Oct-3/4, Nanog and Sox-2 along the EMT process and under stressful and hypoxic conditions. Moreover, the enhanced expression and/or activities of some drug resistance-associated molecules such as Bcl-2, Akt/molecular target of rapamycin (mTOR), nuclear factor-kappaB (NF-κB), hypoxia-inducible factors (HIFs), macrophage inhibitory cytokine-1 (MIC-1) and ATP-binding cassette (ABC) multidrug transporters frequently occur in cancer cells during cancer progression and metastases. These molecular events may cooperate for the survival and acquisition of a more aggressive and migratory behavior by cancer stem/progenitor cells and their progenies during cancer transition to metastatic and recurrent disease states. Of therapeutic interest, these altered gene products may also be exploited as molecular biomarkers and therapeutic targets to develop novel multitargeted strategies for improving current cancer therapies and preventing disease relapse.

Targeting proapoptotic protein BAD inhibits survival and self-renewal of cancer stem cells

Emerging evidence suggests that the resistance of cancer stem cells (CSC) to many conventional therapies is one of the major limiting factors of cancer therapy efficacy. Identification of mechanisms responsible for survival and self-renewal of CSC will help design new therapeutic strategies that target and eliminate both differentiated cancer cells and CSC. Here we demonstrated the potential role of proapoptotic protein BAD in the biology of CSC in melanoma, prostate and breast cancers. We enriched CD44(+)/CD24(-) cells (CSC) by tumorosphere formation and purified this population by FACS. Both spheres and CSC exhibited increased potential for proliferation, migration, invasion, sphere formation, anchorage-independent growth, as well as upregulation of several stem cell-associated markers. We showed that the phosphorylation of BAD is essential for the survival of CSC. Conversely, ectopic expression of a phosphorylation-deficient mutant BAD induced apoptosis in CSC. This effect was enhanced by treatment with a BH3-mimetic, ABT-737. Both pharmacological agents that inhibit survival kinases and growth factors that are involved in drug resistance delivered their respective cytotoxic and protective effects by modulating the BAD phosphorylation in CSC. Furthermore, the frequency and self-renewal capacity of CSC was significantly reduced by knocking down the BAD expression. Consistent with our in vitro results, significant phosphorylation of BAD was found in CD44(+) CSC of 83% breast tumor specimens. In addition, we also identified a positive correlation between BAD expression and disease stage in prostate cancer, suggesting a role of BAD in tumor advancement. Our studies unveil the role of BAD in the survival and self-renewal of CSC and propose BAD not only as an attractive target for cancer therapy but also as a marker of tumor progression.

Nanoways to overcome docetaxel resistance in prostate cancer

Prostate cancer is the most common non-cutaneous malignancy in American men. Docetaxel is a useful chemotherapeutic agent for prostate cancer that has been available for over a decade, but the length of the treatment and systemic side effects hamper compliance. Additionally, docetaxel resistance invariably emerges, leading to disease relapse. Docetaxel resistance is either intrinsic or acquired by adopting various mechanisms that are highly associated with genetic alterations, decreased influx and increased efflux of drugs. Several combination therapies and small P-glycoprotein inhibitors have been proposed to improve the therapeutic potential of docetaxel in prostate cancer. Novel therapeutic strategies that may allow reversal of docetaxel resistance include alterations of enzymes, improving drug uptake and enhancement of apoptosis. In this review, we provide the most current docetaxel reversal approaches utilizing nanotechnology. Nanotechnology mediated docetaxel delivery is superior to existing therapeutic strategies and a more effective method to induce P-glycoprotein inhibition, enhance cellular uptake, maintain sustained drug release, and improve bioavailability.

Linking γ-aminobutyric acid A receptor to epidermal growth factor receptor pathways activation in human prostate cancer

Neuroendocrine (NE) differentiation has been attributed to the progression of castration-resistant prostate cancer (CRPC). Growth factor pathways including the epidermal growth factor receptor (EGFR) signaling have been implicated in the development of NE features and progression to a castration-resistant phenotype. However, upstream molecules that regulate the growth factor pathway remain largely unknown. Using androgen-insensitive bone metastasis PC-3 cells and androgen-sensitive lymph node metastasis LNCaP cells derived from human prostate cancer (PCa) patients, we demonstrated that γ-aminobutyric acid A receptor (GABA(A)R) ligand (GABA) and agonist (isoguvacine) stimulate cell proliferation, enhance EGF family members expression, and activate EGFR and a downstream signaling molecule, Src, in both PC-3 and LNCaP cells. Inclusion of a GABA(A)R antagonist, picrotoxin, or an EGFR tyrosine kinase inhibitor, Gefitinib (ZD1839 or Iressa), blocked isoguvacine and GABA-stimulated cell growth, trans-phospohorylation of EGFR, and tyrosyl phosphorylation of Src in both PCa cell lines. Spatial distributions of GABAAR α₁ and phosphorylated Src (Tyr416) were studied in human prostate tissues by immunohistochemistry. In contrast to extremely low or absence of GABA(A)R α₁-positive immunoreactivity in normal prostate epithelium, elevated GABA(A)R α₁ immunoreactivity was detected in prostate carcinomatous glands. Similarly, immunoreactivity of phospho-Src (Tyr416) was specifically localized and limited to the nucleoli of all invasive prostate carcinoma cells, but negative in normal tissues. Strong GABAAR α₁ immunoreactivity was spatially adjacent to the neoplastic glands where strong phospho-Src (Tyr416)-positive immunoreactivity was demonstrated, but not in adjacent to normal glands. These results suggest that the GABA signaling is linked to the EGFR pathway and may work through autocrine or paracine mechanism to promote CRPC progression.

Molecular biomarkers of cancer stem/progenitor cells associated with progression, metastases, and treatment resistance of aggressive cancers

The validation of novel diagnostic, prognostic, and predictive biomarkers and therapeutic targets in tumor cells is of critical importance for optimizing the choice and efficacy of personalized therapies. Importantly, recent advances have led to the identification of gene-expression signatures in cancer cells, including cancer stem/progenitor cells, in the primary tumors, exosomes, circulating tumor cells (CTC), and disseminated cancer cells at distant metastatic sites. The gene-expression signatures may help to improve the accuracy of diagnosis and predict the therapeutic responses and overall survival of patients with cancer. Potential biomarkers in cancer cells include stem cell-like markers [CD133, aldehyde dehydrogenase (ALDH), CD44, and CD24], growth factors, and their cognate receptors [epidermal growth factor receptor (EGFR), EGFRvIII, and HER2], molecules associated with epithelial-mesenchymal transition (EMT; vimentin, N-cadherin, snail, twist, and Zeb1), regulators of altered metabolism (phosphatidylinositol-3' kinase/Akt/mTOR), and drug resistance (multidrug transporters and macrophage inhibitory cytokine-1). Moreover, different pluripotency-associated transcription factors (Oct3/4, Nanog, Sox2, and Myc) and microRNAs that are involved in the epigenetic reprogramming and acquisition of stem cell-like properties by cancer cells during cancer progression may also be exploited as molecular biomarkers to predict the risk of metastases, systemic treatment resistance, and disease relapse of patients with cancer.

Branched chain amino acid suppresses hepatocellular cancer stem cells through the activation of mammalian target of rapamycin

Differentiation of cancer stem cells (CSCs) into cancer cells causes increased sensitivity to chemotherapeutic agents. Although inhibition of mammalian target of rapamycin (mTOR) leads to CSC survival, the effect of branched chain amino acids (BCAAs), an mTOR complex 1 (mTORC1) activator remains unknown. In this study, we examined the effects of BCAA on hepatocellular carcinoma (HCC) cells expressing a hepatic CSC marker, EpCAM. We examined the effects of BCAA and/or 5-fluorouracil (FU) on expression of EpCAM and other CSC-related markers, as well as cell proliferation in HCC cells and in a xenograft mouse model. We also characterized CSC-related and mTOR signal-related molecule expression and tumorigenicity in HCC cells with knockdown of Rictor or Raptor, or overexpression of constitutively active rheb (caRheb). mTOR signal-related molecule expression was also examined in BCAA-treated HCC cells. In-vitro BCAA reduced the frequency of EpCAM-positive cells and improved sensitivity to the anti-proliferative effect of 5-FU. Combined 5-FU and BCAA provided better antitumor efficacy than 5-FU alone in the xenograft model. Stimulation with high doses of BCAA activated mTORC1. Knockdown and overexpression experiments revealed that inhibition of mTOR complex 2 (mTORC2) or activation of mTORC1 led to decreased EpCAM expression and little or no tumorigenicity. BCAA may enhance the sensitivity to chemotherapy by reducing the population of cscs via the mTOR pathway. This result suggests the utility of BCAA in liver cancer therapy.

Diabetes protects from prostate cancer by downregulating androgen receptor: new insights from LNCaP cells and PAC120 mouse model

Type 2 diabetes has been associated with decreased risk of prostate cancer in observational studies, and this inverse association has been recently confirmed in several large cohort studies. However the mechanisms involved in this protective effect remain to be elucidated. The aim of the present study was to explore whether different features of type 2 diabetes (hyperinsulinemia, hyperglycemia and tumor necrosis factor alpha [TNF-α]) protect against the development of prostate cancer. For this purpose LNCaP cells were used for in vitro experiments and nude mice in which PAC120 (hormone-dependent human prostate cancer) xenografts had been implanted were used for in vivo examinations. We provide evidence that increasing glucose concentrations downregulate androgen receptor (AR) mRNA and protein levels through NF-κB activation in LNCaP cells. Moreover, there was a synergic effect of glucose and TNFα in downregulating the AR in LNCaP cells. By contrast, insulin had no effect on AR regulation. In vivo experiments showed that streptozotocin-induced diabetes (STZ-DM) produces tumor growth retardation and a significant reduction in AR expression in PAC120 prostate cancer mice. In conclusion, our results suggest that hyperglycemia and TNF-α play an important role in protecting against prostate cancer by reducing androgen receptor levels via NF-κB.

Cell mates: paracrine and stromal targets for prostate cancer therapy

After many years of limited treatment options for patients with metastatic castration-resistant prostate cancer (mCRPC), multiple systemic therapies are now available, providing patients with significant improvements in survival, symptom control and bone health. Most of the recent advances in this area have been based on better understanding of mCRPC biology, particularly with respect to the key role of androgen receptor signalling. However, most therapies are targeted towards the malignant epithelial cell component of the cancer and it should not be forgotten that cancer cells exist in close and symbiotic relationships with other components of the tumour. Paracrine and stromal signals are often critical to the growth of the cancer and represent new potential therapeutic targets that are separate from the malignant epithelial cells. The stroma produces numerous growth factors, including vascular endothelial growth factor family members, platelet-derived growth factors and fibroblast growth factors, which are all critical for tumour growth. Targeting prostate-cancer-associated fibroblasts in order to destroy the physical and functional scaffold of a cancer is also a logical approach. The interaction between prostate cancer and the immune system remains an active topic of basic and clinical research, with cytokines, chemokines and growth factors being potential targets for therapy. The biology of epithelial-mesenchymal transition and of circulating tumour cells might also provide insight into new therapeutic targets.

Increased chemosensitivity via targeting testicular nuclear receptor 4 (TR4)-Oct4-interleukin 1 receptor antagonist (IL1Ra) axis in prostate cancer CD133+ stem/progenitor cells to battle prostate cancer

Prostate cancer (PCa) stem/progenitor cells are known to have higher chemoresistance than non-stem/progenitor cells, but the underlying molecular mechanism remains unclear. We found the expression of testicular nuclear receptor 4 (TR4) is significantly higher in PCa CD133(+) stem/progenitor cells compared with CD133(-) non-stem/progenitor cells. Knockdown of TR4 levels in the established PCa stem/progenitor cells and the CD133(+) population of the C4-2 PCa cell line with lentiviral TR4 siRNA led to increased drug sensitivity to the two commonly used chemotherapeutic drugs, docetaxel and etoposide, judging from significantly reduced IC50 values and increased apoptosis in the TR4 knockdown cells. Mechanism dissection studies found that suppression of TR4 in these stem/progenitor cells led to down-regulation of Oct4 expression, which, in turn, down-regulated the IL-1 receptor antagonist (IL1Ra) expression. Neutralization experiments via adding these molecules into the TR4 knockdown PCa stem/progenitor cells reversed the chemoresistance, suggesting that the TR4-Oct4-IL1Ra axis may play a critical role in the development of chemoresistance in the PCa stem/progenitor cells. Together, these studies suggest that targeting TR4 may alter chemoresistance of PCa stem/progenitor cells, and this finding provides the possibility of targeting TR4 as a new and better approach to overcome the chemoresistance problem in PCa therapeutics.

Propagation of human prostate cancer stem-like cells occurs through EGFR-mediated ERK activation

Prostate cancer stem-like cells (PCSCs) are being intensely investigated largely owing to their contributions towards prostate tumorigenesis, however, our understanding of PCSC biology, including their critical pathways, remains incompletely understood. While epidermal growth factor (EGF) is widely used in maintaining PCSC cells in vitro, the importance of EGF-dependent signaling and its downstream pathways in PCSC self-renewal are not well characterized. By investigating DU145 sphere cells, a population of prostate cancer cells with stem-like properties, we report here that epidermal growth factor receptor (EGFR) signaling plays a critical role in the propagation of DU145 PCSCs. Activation of EGFR signaling via addition of EGF and ectopic expression of a constitutively-active EGFR mutant (EGFRvIII) increased sphere formation. Conversely, inhibition of EGFR signaling by using EGFR inhibitors (AG1478 and PD168393) and knockdown of EGFR significantly inhibited PCSC self-renewal. Consistent with the MEK-ERK pathway being a major target of EGFR signaling, activation of the MEK-ERK pathway contributed to EGFR-facilitated PCSC propagation. Modulation of EGFR signaling affected extracellular signal-related kinase (ERK) activation. Inhibition of ERK activation through multiple approaches, including treatment with the MEK inhibitor U0126, ectopic expression of dominant-negative MEK1(K97M), and knockdown of either ERK1 or ERK2 resulted in a robust reduction in PCSC propagation. Collectively, the present study provides evidence that EGFR signaling promotes PCSC self-renewal, in part, by activating the MEK-ERK pathway.

Gastric stem cells and gastric cancer stem cells

The gastric epithelium is continuously regenerated by gastric stem cells, which give rise to various kinds of daughter cells, including parietal cells, chief cells, surface mucous cells, mucous neck cells, and enteroendocrine cells. The self-renewal and differentiation of gastric stem cells need delicate regulation to maintain the normal physiology of the stomach. Recently, it was hypothesized that cancer stem cells drive the cancer growth and metastasis. In contrast to conventional clonal evolution hypothesis, only cancer stem cells can initiate tumor formation, self-renew, and differentiate into various kinds of daughter cells. Because gastric cancer can originate from gastric stem cells and their self-renewal mechanism can be used by gastric cancer stem cells, we review here how critical signaling pathways, including hedgehog, Wnt, Notch, epidermal growth factor, and bone morphogenetic protein signaling, may regulate the self-renewal and differentiation of gastric stem cells and gastric cancer stem cells. In addition, the precancerous change of the gastric epithelium and the status of isolating gastric cancer stem cells from patients are reviewed.

Marked improvement of cytotoxic effects induced by docetaxel on highly metastatic and androgen-independent prostate cancer cells by downregulating macrophage inhibitory cytokine-1

Background:

Overexpression of macrophage inhibitory cytokine-1 (MIC-1) frequently occurs during the progression of prostate cancer (PC) to androgen-independent (AI) and metastatic disease states and is associated with a poor outcome of patients.

Methods:

The gain- and loss-of-function analyses of MIC-1 were performed to establish its implications for aggressive and chemoresistant phenotypes of metastatic and AI PC cells and the benefit of its downregulation for reversing docetaxel resistance.

Results:

The results have indicated that an enhanced level of secreted MIC-1 protein in PC3 cells is associated with their acquisition of epithelial–mesenchymal transition features and higher invasive capacity and docetaxel resistance. Importantly, the downregulation of MIC-1 in LNCaP-LN3 and PC3M-LN4 cells significantly decreased their invasive capacity and promoted the antiproliferative, anti-invasive and mitochrondrial- and caspase-dependent apoptotic effects induced by docetaxel. The downregulation of MIC-1 in PC3M-LN4 cells was also effective in promoting the cytotoxic effects induced by docetaxel on the side population (SP) endowed with stem cell-like properties and the non-SP cell fraction from PC3M-LN4 cells.

Conclusion:

These data suggest that the downregulation of MIC-1 may constitute a potential therapeutic strategy for improving the efficacy of current docetaxel-based chemotherapies, eradicating the total mass of PC cells and thereby preventing disease relapse and the death of PC patients.

Dissociated primary human prostate cancer cells coinjected with the immortalized Hs5 bone marrow stromal cells generate undifferentiated tumors in NOD/SCID-γ mice

Reconstitution of tumor development in immunodeficient mice from disaggregated primary human tumor cells is always challenging. The main goal of the present study is to establish a reliable assay system that would allow us to reproducibly reconstitute human prostate tumor regeneration in mice using patient tumor-derived single cells. Using many of the 114 untreated primary human prostate cancer (HPCa) samples we have worked on, here we show that: 1) the subcutaneum represents the most sensitive site that allows the grafting of the implanted HPCa pieces; 2) primary HPCa cells by themselves fail to regenerate tumors in immunodeficient hosts; 3) when coinjected in Matrigel with rUGM (rat urogenital sinus mesenchyme), CAF (carcinoma-associated fibroblasts), or Hs5 (immortalized bone marrow derived stromal) cells, primary HPCa cells fail to initiate serially transplantable tumors in NOD/SCID mice; and 4) however, HPCa cells coinjected with the Hs5 cells into more immunodeficient NOD/SCID-IL2Rγ(-/-) (NSG) mice readily regenerate serially transplantable tumors. The HPCa/Hs5 reconstituted 'prostate' tumors present an overall epithelial morphology, are of the human origin, and contain cells positive for AR, CK8, and racemase. Cytogenetic analysis provides further evidence for the presence of karyotypically abnormal HPCa cells in the HPCa/Hs5 tumors. Of importance, HPCa/Hs5 xenograft tumors contain EpCAM(+) cells that are both clonogenic and tumorigenic. Surprisingly, all HPCa/Hs5 reconstituted tumors are undifferentiated, even for HPCa cells derived from Gleason 7 tumors. Our results indicate that primary HPCa cells coinjected with the immortalized Hs5 stromal cells generate undifferentiated tumors in NSG mice and we provide evidence that undifferentiated HPCa cells might be the cells that possessed tumorigenic potential and regenerated HPCa/Hs5 xenograft tumors.

Development of animal models underlining mechanistic connections between prostate inflammation and cancer

The characterization of animal models has indicated that the genetic, dietary and environmental factors and hormonal imbalance may influence the risk to develop prostate inflammatory lesions and prostate cancer (PC) confirming human epidemiologic data. It is now established that the prostate inflammatory response typically results in major changes in the local microenvironment of epithelial cells of the prostate gland, including an intense stromal remodeling, activation of fibroblasts, infiltration of immune cells such as mast cells, macrophages and B and T lymphocytes and collagen deposition. The immune cells recruited at prostate inflammatory lesions and myofibroblasts may contribute to the release of numerous pro-inflammatory cytokines and chemokines that in turn can promote the oxidative stress, genomic instability and proliferation of epithelial cells. The accumulation of additional genetic and/or epigenetic alterations in prostatic stem/progenitor cells may subsequently culminate to their malignant transformation and PC initiation and progression and more particularly with advancing age. The potential mechanistic relationships between the molecular events associated with the persistent inflammatory response and prostate carcinogenesis have important implications for optimizing the current therapies against different prostatic disorders and PCs.

Emergence of zebrafish models in oncology for validating novel anticancer drug targets and nanomaterials

The in vivo zebrafish models have recently attracted great attention in molecular oncology to investigate multiple genetic alterations associated with the development of human cancers and validate novel anticancer drug targets. Particularly, the transparent zebrafish models can be used as a xenotransplantation system to rapidly assess the tumorigenicity and metastatic behavior of cancer stem and/or progenitor cells and their progenies. Moreover, the zebrafish models have emerged as powerful tools for an in vivo testing of novel anticancer agents and nanomaterials for counteracting tumor formation and metastases and improving the efficacy of current radiation and chemotherapeutic treatments against aggressive, metastatic and lethal cancers.

Heterogeneity of neoplastic stem cells: theoretical, functional, and clinical implications

Accumulating evidence suggests that human cancers develop through a step-wise, but nonlinear process of cellular diversification and evolution. Recent mutational analyses indicate that this process is more complex and diverse than anticipated before whole-genome sequencing methods were readily available. Examples are also emerging now of genetically abnormal clones of cells that have acquired mutations with known oncogenic potential but, nevertheless, may show no manifestations of malignant change for many years. To accommodate these diverse realities, we suggest the term neoplastic refer to clones of cells that have any type of somatic aberrancy associated with an increased propensity to become malignant, and the derivative term neoplastic stem cell be adopted to identify the cells responsible for the long-term maintenance of such clones. Neoplastic clones would thus include those that never evolve further, as well as those that eventually give rise to fully malignant populations, and all stages in between. The term cancer stem cells would then be more appropriately restricted to cells generating subclones that have established malignant properties. More precise molecular understanding of the different stem cell states thus distinguished should contribute to the development of more effective prognostic and therapeutic tools for cancer diagnosis and treatment.

Hypoxia-inducing factors as master regulators of stemness properties and altered metabolism of cancer- and metastasis-initiating cells

Accumulating lines of experimental evidence have revealed that hypoxia-inducible factors, HIF-1α and HIF-2α, are key regulators of the adaptation of cancer- and metastasis-initiating cells and their differentiated progenies to oxygen and nutrient deprivation during cancer progression under normoxic and hypoxic conditions. Particularly, the sustained stimulation of epidermal growth factor receptor (EGFR), insulin-like growth factor-1 receptor (IGF-1R), stem cell factor (SCF) receptor KIT, transforming growth factor-β receptors (TGF-βRs) and Notch and their downstream signalling elements such as phosphatidylinositol 3′-kinase (PI3K)/Akt/molecular target of rapamycin (mTOR) may lead to an enhanced activity of HIFs. Moreover, the up-regulation of HIFs in cancer cells may also occur in the hypoxic intratumoral regions formed within primary and secondary neoplasms as well as in leukaemic cells and metastatic prostate and breast cancer cells homing in the hypoxic endosteal niche of bone marrow. The activated HIFs may induce the expression of numerous gene products such as induced pluripotency-associated transcription factors (Oct-3/4, Nanog and Sox-2), glycolysis- and epithelial-mesenchymal transition (EMT) programme-associated molecules, including CXC chemokine receptor 4 (CXCR4), snail and twist, microRNAs and angiogenic factors such as vascular endothelial growth factor (VEGF). These gene products in turn can play critical roles for high self-renewal ability, survival, altered energy metabolism, invasion and metastases of cancer cells, angiogenic switch and treatment resistance. Consequently, the targeting of HIF signalling network and altered metabolic pathways represents new promising strategies to eradicate the total mass of cancer cells and improve the efficacy of current therapies against aggressive and metastatic cancers and prevent disease relapse.

SRC kinase regulation in progressively invasive cancer

Metastatic progression is a multistep process that involves tumor growth and survival, motility and invasion, and subsequent proliferation in an inappropriate environment. The Src protein tyrosine kinase has been implicated in many of the biochemical pathways that drive these behaviors. Although Src itself is only rarely mutated in human tumors, its aberrant activity has been noted in various cancers and suggested to serve as a barometer of metastatic potential. With these features in mind, we examined Src kinase regulation at the structural, enzymatic, and expression levels as a function of progressively invasive prostate cancer cell lines. Surprisingly, both total Src content and kinase activity decrease with increasing cell line aggressiveness, an observation that appears to be inconsistent with the well-documented role of Src in the signaling pathways that drive growth and invasion. However, we do observe a direct correlation between Src kinase specific activity (total Src kinase activity/total Src content) and metastatic aggressiveness, possibly suggesting that in highly aggressive cell lines, key signaling enzymes are globally recruited to drive the cancerous phenotype. In addition, although the expected enhanced phosphorylation of Src at Tyr-416 (activation site) is present in the most aggressive prostate cancer cell lines, unexpectedly high phosphorylation levels at the Tyr-527 inhibitory site are observed as well. The latter, rather than representative of inhibited enzyme, is more indicative of primed Src responsive to local phosphorylated binding partners.

EGF signalling pathway regulates colon cancer stem cell proliferation and apoptosis

OBJECTIVES

Cancer stem cells (CSCs) compose a subpopulation of cells within a tumour that can self-renew and proliferate. Growth factors such as epidermal growth factor (EGF) and basic fibroblast growth factor (b-FGF) promote cancer stem cell proliferation in many solid tumours. This study assesses whether EGF, bFGF and IGF signalling pathways are essential for colon CSC proliferation and self-renewal.

MATERIAL AND METHODS

Colon CSCs were cultured in serum-free medium (SFM) with one of the following growth factors: EGF, bFGF or IGF. Characteristics of CSC gene expression were evaluated by real time PCR. Tumourigenicity of CSCs was determined using a xenograft model in vivo. Effects of EGF receptor inhibitors, Gefitinib and PD153035, on CSC proliferation, apoptosis and signalling were evaluated using fluorescence-activated cell sorting and western blotting.

RESULTS

Colon cancer cell HCT116 transformed to CSCs in SFM. Compared to other growth factors, EGF was essential to support proliferation of CSCs that expressed higher levels of progenitor genes (Musashi-1, LGR5) and lower levels of differential genes (CK20). CSCs promoted more rapid tumour growth than regular cancer cells in xenografts. EGFR inhibitors suppressed proliferation and induced apoptosis of CSCs by inhibiting autophosphorylation of EGFR and downstream signalling proteins, such as Akt kinase, extracellular signal-regulated kinase 1/2 (ERK 1/2).

CONCLUSIONS

This study indicates that EGF signalling was essential for formation and maintenance of colon CSCs. Inhibition of the EGF signalling pathway may provide a useful strategy for treatment of colon cancer.

Phospho-Akt immunoreactivity in prostate cancer: relationship to disease severity and outcome, Ki67 and phosphorylated EGFR expression

Background

In the present study, we have investigated the prognostic usefulness of phosphorylated Akt immunoreactivity (pAkt-IR) in prostate cancer using a well-characterised tissue microarray from men who had undergone transurethral resection due to lower urinary tract symptoms.

Methodology/Principal Findings

pAkt-IR in prostate epithelial and tumour cells was assessed using a monoclonal anti-pAkt (Ser⁴⁷³) antibody. Immunoreactive intensity was determined for 282 (tumour) and 240 (non-mlignant tissue) cases. Tumour pAkt-IR scores correlated with Gleason score, tumour Ki67-IR (a marker of cell proliferation) and tumour phosphorylated epidermal growth factor receptor (pEGFR)-IR. For cases followed with expectancy, a high tumour pAkt-IR was associated with a poor disease-specific survival, and the prognostic information provided by this biomarker was additive to that provided by either (but not both) tumour pEFGR-IR or Ki67-IR. Upon division of the cases with respect to their Gleason scores, the prognostic value of pAkt-IR was seen for patients with Gleason score 8–10, but not for patients with Gleason score 6–7.

Conclusions/Significance

Tumour pAkt-IR is associated with both disease severity and disease-specific survival. However, its clinical use as a biomarker is limited, since it does not provide prognostic information in patients with Gleason scores 6–7.