Recent advances on multiple tumorigenic cascades involved in prostatic cancer progression and targeting therapies

MicroRNA signature of stromal-epithelial interactions in prostate and breast cancers

Stromal-epithelial communication is an absolute necessity when it comes to the morphogenesis and pathogenesis of solid tissues, including the prostate and breast. So far, signalling pathways of several growth factors have been investigated. Besides such chemical factors, non-coding RNAs such as miRNAs have recently gained much interest because of their variety and complexity of action. Prostate and breast tissues being highly responsive to steroid hormones such as androgen and estrogen, respectively, it is not surprising that a huge set of available literature critically investigated the interplay between such hormones and miRNAs, especially in carcinogenesis. This review showcases our effort to highlight hormonally-related miRNAs that also somehow perturb the regular stromal-epithelial interactions during carcinogenesis in the prostate and breast. In future, we look forward to exploring how hormonal changes in the tissue microenvironment bring about miRNA-mediated changes in stromal-epithelial interactome in carcinogenesis and cancer progression.

Glucosinolates, Ca, Se Contents, and Bioaccessibility in Brassica rapa Vegetables Obtained by Organic and Conventional Cropping Systems

In northwest Spain and Portugal, there is a long tradition of cultivating B. rapa subsp. rapa to obtain turnip greens and turnip tops. Brassica rapa L. subsp. rapa (turnip greens and turnip tops) were grown under conventional and organic conditions in two Farms in southern Spain. Glucosinolatescontents were higher in Brassicas grown under conventional conditions than those grown under organic ones. Average Ca total and bioaccessible contents ranged between 14.6–23.4 mg/g; 8.9–12.0 mg/g for turnip greens and 6.4–8.9 mg/g; 4.3–4.8 mg/g for turnip tops. According to these concentrations, an intake of 100–200 g (fresh weight) of the studied Brassica rapa fulfills Ca dietary reference intakes (DRI) (considering the total content data) and complies with 72–100% Ca DRI percentage (considering the bioaccessible data). Se concentrations ranged between 0.061–0.073 µg/g and 0.039–0.053 µg/g for turnip greens and turnip tops respectively. Se bioaccessibility values were high, with percentages of around 90%. Finally, the total glucosinolate content ranged between 13.23–21.28 µmol/g for turnip greens and 13.36–20.20 µmol/g for turnip tops. In general, the bioaccessibility of the total glucosinolates analyzed in this study was high, with mean values of around 73% and 66% for turnip greens and turnip tops, respectively. Brassica rapa vegetables grown under both organic and conventional conditions in southern Spain are an excellent dietary source of Ca, Se, and glucosinolates with a high bioaccessibility.

CMTM5 inhibits the development of prostate cancer via the EGFR/PI3K/AKT signaling pathway

Prostate cancer (PCa) endangers the life and health of older men. Most PCa cases develop into castration-resistant PCa (CRPC) within 2 years. At present, the molecular mechanisms of the occurrence and development of PCa and its transformation to CRPC remain unknown. The present study aimed to investigate the role of CKLF-like Marvel transmembrane domain containing family member 5 (CMTM5) in PCa and its molecular mechanism in vitro. PCa tissues and paired adjacent normal prostate tissues from 70 patients were collected to examine the expression levels of CMTM5 and EGFR via immunohistochemistry, reverse transcription-quantitative PCR and western blotting. Then, CMTM5-overexpressing DU145 cells were constructed, and CMTM5 expression in these transfected cells and vector control cells was examined via western blotting. Cell Counting Kit-8 and plate clone formation assays were used to evaluate the proliferation and colony number of CMTM5-overexpressing cells and vector control cells. Then, cell migration and invasion were assessed using wound healing assay, Transwell assay and immunofluorescence analysis with DAPI staining. The effect of CMTM5 on apoptosis and its underlying molecular mechanism were examined using western blotting and flow cytometry. The results demonstrated that CMTM5 expression in PCa tissues and cell lines was significantly downregulated, while EFGR expression was significantly upregulated. The proportion of high CMTM5 expression in PCa tissues was significantly lower compared with that in normal prostate tissues. By contrast, the proportion of high EGFR expression in PCa tissues was significantly increased compared with that in normal prostate tissues. Moreover, CMTM5 overexpression significantly inhibited cell proliferation, migration and invasion, and promoted cell apoptosis compared with vector control cells in vitro. Furthermore, the regulation of PCa by CMTM5 was associated with the downregulation of PI3K/AKT and its downstream Bcl-2 expression, as well as the upregulation of Bax expression. In conclusion, CMTM5 may be an effective tumor suppressor gene for PCa, especially for castration-resistant PCa, by downregulating EGFR and PI3K/AKT signaling pathway components.

δ-Catenin Participates in EGF/AKT/p21Waf Signaling and Induces Prostate Cancer Cell Proliferation and Invasion

Prostate cancer (PCa) is the second most leading cause of death in males. Our previous studies have demonstrated that δ-catenin plays an important role in prostate cancer progression. However, the molecular mechanism underlying the regulation of δ-catenin has not been fully explored yet. In the present study, we found that δ-catenin could induce phosphorylation of p21^Waf and stabilize p21 in the cytoplasm, thus blocking its nuclear accumulation for the first time. We also found that δ-catenin could regulate the interaction between AKT and p21, leading to phosphorylation of p21 at Thr-145 residue. Finally, EGF was found to be a key factor upstream of AKT/δ-catenin/p21 for promoting proliferation and metastasis in prostate cancer. Our findings provide new insights into molecular controls of EGF and the development of potential therapeutics targeting δ-catenin to control prostate cancer progression.

miR-205: A Potential Biomedicine for Cancer Therapy

microRNAs (miRNAs) are a class of small non-coding RNAs that regulate the expression of their target mRNAs post transcriptionally. miRNAs are known to regulate not just a gene but the whole gene network (signaling pathways). Accumulating evidence(s) suggests that miRNAs can work either as oncogenes or tumor suppressors, but some miRNAs have a dual nature since they can act as both. miRNA 205 (miR-205) is one such highly conserved miRNA that can act as both, oncomiRNA and tumor suppressor. However, most reports confirm its emerging role as a tumor suppressor in many cancers. This review focuses on the downregulated expression of miR-205 and discusses its dysregulation in breast, prostate, skin, liver, gliomas, pancreatic, colorectal and renal cancers. This review also confers its role in tumor initiation, progression, cell proliferation, epithelial to mesenchymal transition, and tumor metastasis. Restoration of miR-205 makes cells more sensitive to drug treatments and mitigates drug resistance. Additionally, the importance of miR-205 in chemosensitization and its utilization as potential biomedicine and nanotherapy is described. Together, this review research article sheds a light on its application as a diagnostic and therapeutic marker, and as a biomedicine in cancer.

CMTM5-v1 inhibits cell proliferation and migration by downregulating oncogenic EGFR signaling in prostate cancer cells

Anomalous epidermal growth factor receptor (EGFR) signaling plays an important role in the progression of prostate cancer (PCa) and the transformation to castration-resistant PCa (CRPC). A novel tumor suppressor CKLF-like MARVEL transmembrane domain-containing member 5(CMTM5) has a MARVEL domain and may regulate transmembrane signaling. Thus, we postulated that CMTM5 could regulate EGFR and its downstream molecules to affect the biological behaviors of PCa cells. In this study, we found that CMTM5 was expressed in benign prostatic hyperplasia (BPH) tissues but was undetectable in PCa cells. However, the EGFR was upregulated in PCa cells, especially in two metastatic CRPC cell lines, PC3 and DU145. Furthermore, ectopic expression of CMTM5-v1 suppressed cell proliferation and migration and p-EGFR levels. Further investigation revealed that restoration of CMTM5-v1 inhibited not only EGF-mediated proliferation but also chemotactic migration by EGF in PC3 and DU145 cells. Moreover, mechanistic studies showed that CMTM5-v1 attenuated EGF-induced receptor signaling by repressing EGFR and Akt phosphorylation in PCa cells, which were essential for malignant features. Finally, CMTM5-v1can promote the sensitivity of PC3 cells to Gefetinib, a tyrosine kinase inhibitor (TKI) targeting the EGFR. These observations indicate that CMTM5-v1 suppressed PCa cells through EGFR signaling. The loss of CMTM5 may participate in the progression of PCa resulting from deregulated EGFR, and CMTM5 might be associated with the efficacy of TKIs in terms of their potent inhibition of EGFR and human epidermal growth factor-2 (HER2) activation.

Combined targeting of EGFR and HER2 against prostate cancer stem cells

Progression of prostate cancer has been associated with EGFR and HER2 activation and to tumor-initiating cells contribution toward chemotherapy resistance. We investigated the efficacy of a dual intervention against EGFR and HER2 to deplete the tumor-initiating cells, optimize the chemotherapy management and prevent the progression of castration-resistant prostate cancer (CRPC) cells. Using DU145, PC3, and 22Rv1 CRPC cell lines, biochemical analysis revealed activation of EGFR, HER2, MAPK, and STAT3 in DU145 and 22Rv1, and AKT and SRC in DU145 and PC-3. pSTAT3 nuclear staining was observed in DU145 xenografts and in 12 out of 14 CRPC specimens. The in vivo dual targeting of ErbB receptors with Cetuximab and Trastuzumab combined with chemotherapy caused an effective antitumor response in DU145 xenografted mice displaying STAT3 activation; conversely PC-3 bearing mice experienced tumor relapse. The potentiating of in vivo cytotoxic effect in DU145 model was accompanied by a significant decrease of prostatosphere-forming capacity assessed in vitro on residual tumor cells. Additionally, combined treatment in vitro with Cetuximab, Trastuzumab and chemotherapy negatively affected DU145 and 22Rv1 sphere formation, suggesting the critical function of ErbB receptors for tumor-initiating cells proliferation; no effect on PC-3 clonogenic potential was observed, indicating that other receptors than EGFR and HER2 may sustain PC3 tumor-initiating cells. These findings provided the preclinical evidence that the dual inhibition of EGFR and HER2 by targeting tumor-initiating cells may improve the efficacy of the current chemotherapy regimen, bringing benefits especially to castration-resistant patients with activated STAT3, and preventing disease progression.

Long non-coding RNAs in prostate cancer: Biological and clinical implications

Prostate cancer (PCa) is a major health issue in the Western world. Current clinical imperatives for this disease include better stratification of indolent versus aggressive disease to enable improved patient management, as well as the identification of more effective therapies for the prevention and treatment of metastatic and therapy-resistant PCa. The advent of next-generation transcriptomics led to the identification of an important class of molecules, long non-coding RNAs (lncRNAs). LncRNAs have critical functions in normal physiology, but their dysregulation has also been implicated in the development and progression of a variety of cancers, including PCa. Importantly, a subset of lncRNAs are highly prostate-specific, suggesting potential for utility as both biomarkers and therapeutic targets. In this review, we summarise the biology of lncRNAs and their mechanisms of action in the development and progression of prostate cancer. Additionally, we cast a critical eye over the potential for this class of molecules to impact on clinical practice.

The Tumor Microenvironments of Lethal Prostate Cancer

Localized prostate cancer (confined to the gland) generally is considered curable, with nearly a 100% 5-year-survival rate. When the tumor escapes the prostate capsule, leading to metastasis, there is a poorer prognosis and higher mortality rate, with 5-year survival dropping to less than 30%. A major research question has been to understand the transition from indolent (low risk) disease to aggressive (high risk) disease. In this chapter, we provide details of the changing tumor microenvironments during prostate cancer invasion and their role in the progression and metastasis of lethal prostate cancer. Four microenvironments covered here include the muscle stroma, perineural invasion, hypoxia, and the role of microvesicles in altering the extracellular matrix environment. The adaptability of prostate cancer to these varied microenvironments and the cues for phenotypic changes are currently understudied areas. Model systems for understanding smooth muscle invasion both in vitro and in vivo are highlighted. Invasive human needle biopsy tissue and mouse xenograft tumors both contain smooth muscle invasion. In combination, the models can be used in an iterative process to validate molecular events for smooth muscle invasion in human tissue. Understanding the complex and interacting microenvironments in the prostate holds the key to early detection of high-risk disease and preventing tumor invasion through escape from the prostate capsule.

Androgen receptor: what we know and what we expect in castration-resistant prostate cancer

Androgen deprivation therapy is an important therapy for prostate cancer (PCa) in aging men. Under the background of castration, it is inevitable that prostate cancer will develop into castration-resistant prostate cancer (CRPC), which has a high mortality rate, after 2-3 years. Androgen receptor (AR) plays a key role in PCa development and is essential to CRPC. More recent research studies have reported that the development of CRPC is largely due to altered mechanisms related to AR, so it is important for us to understand the roles of AR and detailed AR-related mechanisms in CRPC. The multiple AR-related mechanisms promoting the development of CRPC are as follows: (1) enhanced transformation and increased synthesis of intratumoral androgen; (2) AR overexpression, which enables CRPC to be hypersensitive to low levels of androgen; (3) AR cofactors, which enhanced AR transactivation; (4) AR-spliced variants, which mediated downstream gene expression without androgen; (5) the interaction between the AR pathway and classic tumor-related pathways; and» (6) AR mutations, which reduced AR specificity and enhanced AR transcription.

Cytochrome P450 1B1 inhibition suppresses tumorigenicity of prostate cancer via caspase-1 activation

Cytochrome P450 1B1 (CYP1B1) is recognized as a universal tumor biomarker and a feasible therapeutic target due to its specific overexpression in cancer tissues. Despite its up-regulation in prostate cancer (PCa), biological significance and clinicopathological features of CYP1B1 are still elusive. Here, we show that overexpression or hyperactivation of CYP1B1 stimulated proliferative, migratory and invasive potential of non-tumorigenic PCa cells. Attenuation of CYP1B1 with its specific small hairpin (sh) RNAs greatly reduced proliferation through apoptotic cell death and impaired migration and invasion in PCa cells. Intratumoral injection of CYP1B1 shRNA attenuated growth of pre-existing tumors. The antitumor effect of CYP1B1 shRNA was also observed in prostate tumor xenograft mouse models. Among the genes altered by CYP1B1 knockdown, reduction of caspase-1 (CASP1) activity attenuated the antitumor effect of CYP1B1 inhibition. Indeed, CYP1B1 regulates CASP1 expression or activity. Finally, CYP1B1 expression was increased in higher grades of PCa and overall survival was significantly reduced in patients with high levels of CYP1B1 protein. CYP1B1 expression was reversely associated with CASP1 expression in clinical tissue samples. Together, our results demonstrate that CYP1B1 regulates PCa tumorigenesis by inhibiting CASP1 activation. Thus, the CYP1B1-CASP1 axis may be useful as a potential biomarker and a therapeutic target for PCa.

Genetics of metastasis: melanoma and other cancers

Melanoma is a malignant neoplasm of melanocytes that accounts for the majority of skin cancer deaths despite comprising less than 5% of all cutaneous malignancies. Its incidence has increased faster than that of any other cancer over the past half-century and the annual costs of treatment in the United States alone have risen rapidly. Although the majority of primary melanomas are cured with local excision, metastatic melanoma historically carries a grim prognosis, with a median survival of 9 months and a long-term survival rate of 10%. Given the urgent need to develop treatment strategies for metastatic melanoma and the explosion of genetic technologies over the past 20 years, there has been extensive research into the genetic alterations that cause melanocytes to become malignant. More recently, efforts have focused on the genetic changes that drive melanoma metastasis. This review aims to summarize the current knowledge of the genetics of primary cutaneous and ocular melanoma, the genetic changes associated with metastasis in melanoma and other cancer types, and non-genetic factors that may contribute to metastasis.

Prostate cancer health disparities: An immuno-biological perspective

Prostate cancer (PCa) is the most commonly diagnosed malignancy in males, and, in the United States, is the second leading cause of cancer-related death for men older than 40 years. There is a higher incidence of PCa for African Americans (AAs) than for European-Americans (EAs). Investigations related to the incidence of PCa-related health disparities for AAs suggest that there are differences in the genetic makeup of these populations. Other differences are environmentally induced (e.g., diet and lifestyle), and the exposures are different. Men who immigrate from Eastern to Western countries have a higher risk of PCa than men in their native countries. However, the number of immigrants developing PCa is still lower than that of men in Western countries, suggesting that genetic factors are involved in the development of PCa. Altered genetic polymorphisms are associated with PCa progression. Androgens and the androgen receptor (AR) are involved in the development and progression of PCa. For populations with diverse racial/ethnic backgrounds, differences in lifestyle, diet, and biology, including genetic mutations/polymorphisms and levels of androgens and AR, are risk factors for PCa. Here, we provide an immuno-biological perspective on PCa in relation to racial/ethnic disparities and identify factors associated with the disproportionate incidence of PCa and its clinical outcomes.

GANT-61 and GDC-0449 induce apoptosis of prostate cancer stem cells through a GLI-dependent mechanism

Aberrant reactivation of the Sonic Hedgehog (SHH) signaling pathway promotes prostate cancer (PC) growth and progression by regulating cancer-related genes through its downstream effectors GLI1 and GLI2. Therefore, targeting the SHH-GLI pathway provides an alternative approach to avoid cancer progression. The aim of this study was to delineate the underlying molecular mechanisms by which GDC-0449 (a SMO receptor inhibitor) and GANT-61 (a GLI transcription factor inhibitor) regulate cellular proliferation and self-renewal in human PC stem cells (ProCSCs). Inhibition of the SHH signaling pathway by GANT-61 induced apoptosis with more efficacy than by GDC-0449 in ProCSCs and PC cell lines. GLI1 and GLI2 expression, promoter-binding activity and GLI-responsive luciferase reporter activity were all decreased with either GDC-0449 or GANT-61 treatment. Expression of Fas, DR4, DR5, and cleavage of caspase-3 and PARP were increased, whereas levels of PDGFR-α and Bcl-2 were reduced. Double knockout of GLI1 and GLI2 using shRNA abolished the effects observed with either GDC-0449 or GANT-61 treatment. Collectively, our results showed that GANT-61 and GDC-0449 induced ProCSC apoptosis by directly or indirectly inhibiting the activities of the GLI family transcription factors, may enhance the efficacy of PC treatment.

Crosstalk between Stem and Progenitor Cellular Mediators with Special Emphasis on Vasculogenesis

The cellular components and molecular processes of signaling during vasculogenesis have been investigated for decades. Considerable efforts have been made to unravel regulatory mechanisms of vasculogenesis through crosstalk between vasculogenic playmakers located in the vascular niche, namely hematopoietic stem cells, endothelial progenitor cells, and mesenchymal stem and progenitor cells. Recent studies have increased the knowledge about signaling events within vascular microenvironment that leads to vasculogenesis. Findings from these recent studies indicate the impact of cellular crosstalk through signaling pathways such as vascular endothelial growth factor signaling, wingless and Notch signaling in vasculogenesis and vascular development. In this review, we highlight the signaling signature between stem and progenitor cellular mediators during vasculogenesis. We further focus on hematopoietic stem cell-endothelial progenitor cell crosstalk during vasculogenesis and discuss their potential implications and benefits for therapeutic interventions and regenerative therapy.

Dual action of high estradiol doses on MNU-induced prostate neoplasms in a rodent model with high serum testosterone: Protective effect and emergence of unstable epithelial microenvironment

BACKGROUND

Estrogens are critical players in prostate growth and disease. Estrogen therapy has been the standard treatment for advanced prostate cancer for several decades; however, it has currently been replaced by alternative anti-androgenic therapies. Additionally, studies of its action on prostate biology, resulting from an association between carcinogens and estrogen, at different stages of life are scarce or inconclusive about its protective and beneficial role on induced-carcinogenesis. Thus, the aim of this study was to determine whether estradiol exerts a protective and/or stimulatory role on N-methyl-N-nitrosurea-induced prostate neoplasms.

METHODS

We adopted a rodent model that has been used to study induced-prostate carcinogenesis: the Mongolian gerbil. We investigated the occurrence of neoplasms, karyometric patterns, androgen and estrogen receptors, basal cells, and global methylation status in ventral and dorsolateral prostate tissues.

RESULTS

Histopathological analysis showed that estrogen was able to slow tumor growth in both lobes after prolonged treatment. However, a true neoplastic regression was observed only in the dorsolateral prostate. In addition to the protective effects against neoplastic progression, estrogen treatment resulted in an epithelium that exhibited features distinctive from a normal prostate, including increased androgen-insensitive basal cells, high androgens and estrogen receptor positivity, and changes in DNA methylation patterns.

CONCLUSIONS

Estrogen was able to slow tumor growth, but the epithelium exhibited features distinct from a normal prostatic epithelium, and this unstable microenvironment could trigger lesion recurrence over time.

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.

Mesenchymal Stem and Progenitor Cells in Regeneration: Tissue Specificity and Regenerative Potential

It has always been an ambitious goal in medicine to repair or replace morbid tissues for regaining the organ functionality. This challenge has recently gained momentum through considerable progress in understanding the biological concept of the regenerative potential of stem cells. Routine therapeutic procedures are about to shift towards the use of biological and molecular armamentarium. The potential use of embryonic stem cells and invention of induced pluripotent stem cells raised hope for clinical regenerative purposes; however, the use of these interventions for regenerative therapy showed its dark side, as many health concerns and ethical issues arose in terms of using these cells in clinical applications. In this regard, adult stem cells climbed up to the top list of regenerative tools and mesenchymal stem cells (MSC) showed promise for regenerative cell therapy with a rather limited level of risk. MSC have been successfully isolated from various human tissues and they have been shown to offer the possibility to establish novel therapeutic interventions for a variety of hard-to-noncurable diseases. There have been many elegant studies investigating the impact of MSC in regenerative medicine. This review provides compact information on the role of stem cells, in particular, MSC in regeneration.

Role of Long Noncoding RNAs in Neoplasia: Special Emphasis on Prostate Cancer

Recent advances in sequencing technology have dramatically improved the ability of investigators to study nucleic acid biology. Bolstered by these new and powerful techniques, the field of noncoding RNA (ncRNA) research, in particular, has witnessed a period of significant progress, wherein multiple new and unique species of ncRNA elements have been discovered and characterized. The current categories of ncRNAs include tRNA, rRNA, snoRNA, snRNA, piRNA, miRNA, and lncRNA, among others. The largest of these RNAs are the long noncoding RNAs (lncRNAs) that perform a diverse set of functions within the cell. Importantly, lncRNAs have recently been implicated in the pathogenesis of multiple types of cancer, including breast, lung, gastric, liver, and prostate. This reviews the major lncRNAs currently believed to play a role in human malignancies with a special emphasis on lncRNAs germane to cancer of the prostate gland. Continued investigation of lncRNA will likely prove to be exceedingly valuable, as they may provide novel therapeutic targets for the treatment of cancer. In addition, lncRNAs offer the potential to serve as diagnostic and prognostic biomarkers for cancer. The present state of lncRNA-based strategies for use in the management of cancer will also be highlighted.

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.

Over-expression of lipocalin 2 promotes cell migration and invasion through activating ERK signaling to increase SLUG expression in prostate cancer

BACKGROUND

Metastasis is the primary cause of prostate cancer (PCa) lethality and poses a huge clinical obstacle. Lipocalin 2 (LCN2), a member of the lipocalin family, is aberrantly expressed in some human cancers and has been implicated in the progression of some tumors. However, the role of LCN2 in the metastatic capacity of prostate cancer (PCa) is poorly understood.

METHODS

LCN2 expression was examined by RT-qPCR and/or immunoblotting in human prostate tissue specimens and prostate cancer cell lines LNCaP, C4-2, 22RV1, PC3, DU-145, and PC3MM2. LCN2 protein level in human serum samples was determined by ELISA. Lentiviruses-mediated over-expression of LCN2 and knockdown of LCN2 was conducted to evaluate the role of LCN2 in cell migratory and invasive capacities of prostate cancer cells. Cell migration and invasion was examined by transwell chamber assay. Knockdown of SLUG by lentivirus was performed to investigate its role in LCN2-promoted cell migration and invasion in vitro (22RV1 cell line) and metastasis in vivo (tail vein metastasis assay in nude mice). Role of ERK signaling in LCN2-mediated up-regulation of SLUG was assayed by using ERK inhibitor U0126.

RESULTS

We confirmed that LCN2 levels were correlated positively with invasive prostate cancer in human tissue and serum samples, and were also consistently associated with the invasive capacity of prostate cancer cell lines. The over-expression of LCN2 in 22RV1 cells (not highly invasive) promoted the epithelial-mesenchymal transition (EMT), increasing cell motility and invasiveness, while the knockdown of LCN2 in PC3 cells (highly invasive) inhibited EMT, decreasing cell motility and invasiveness. Among the multiple EMT transcription factors, LCN2 specifically induces the expression of SLUG, which was shown here to be required for the LCN2-induced increase in the invasive capacity of prostate cancer cells both in vitro and in vivo. Mechanistically, LCN2 promoted SLUG expression via activating ERK signaling pathway.

CONCLUSION

LCN2 plays an important role in promoting cell migration and invasion of prostate cancer by inducing EMT through the ERK/SLUG axis. Therefore, targeted inhibition of LCN2 may represent a therapeutic strategy to prevent the metastasis of prostate cancer.

Inhibition of LDHA suppresses tumor progression in prostate cancer

A key hallmark of cancer cells is their altered metabolism, known as Warburg effect. Lactate dehydrogenase A (LDHA) executes the final step of aerobic glycolysis and has been reported to be involved in the tumor progression. However, the function of LDHA in prostate cancer has not been studied. In current study, we observed overexpression of LDHA in the clinical prostate cancer samples compared with benign prostate hyperplasia tissues as demonstrated by immunohistochemistry and real-time qPCR. Attenuated expression of LDHA by siRNA or inhibition of LDHA activities by FX11 inhibited cell proliferation, migration, invasion, and promoted cell apoptosis of PC-3 and DU145 cells. Mechanistically, decreased Warburg effect as demonstrated by reduced glucose consumption and lactate secretion and reduced expression of MMP-9, PLAU, and cathepsin B were found after LDHA knockdown or FX11 treatment in PC-3 and DU145 cells. Taken together, our study revealed the oncogenic role of LDHA in prostate cancer and suggested that LDHA might be a potential therapeutic target.

Hepcidin regulation in prostate and its disruption in prostate cancer

Hepcidin is a circulating peptide hormone made by the liver that is a central regulator of systemic iron uptake and recycling. Here, we report that prostate epithelial cells also synthesize hepcidin, and that synthesis and secretion of hepcidin are markedly increased in prostate cancer cells and tissue. Prostatic hepcidin functions as an autocrine hormone, decreasing cell surface ferroportin, an iron exporter, increasing intracellular iron retention, and promoting prostate cancer cell survival. Synthesis of hepcidin in prostate cancer is controlled by a unique intersection of pathways that involves BMP4/7, IL6, Wnt, and the dual BMP and Wnt antagonist, SOSTDC1. Epigenetic silencing of SOSTDC1 through methylation is increased in prostate cancer and is associated with accelerated disease progression in patients with prostate cancer. These results establish a new connection between iron metabolism and prostate cancer, and suggest that prostatic dysregulation of hepcidin contributes to prostate cancer growth and progression.

Regulation of sonic hedgehog expression by integrin β1 and epidermal growth factor receptor in intestinal epithelium

We previously found that conditional deletion of integrin β1 in intestinal epithelium of mice caused early postnatal lethality and intestinal phenotypic changes including excessive proliferation and defective differentiation of intestinal epithelium due to loss of Hedgehog expression. Here, we link these defects to the Hedgehog (Hh) signaling pathway and show that loss of integrin β1 leads to excessive phosphorylation of MEK-1 and increased expression of ErbB receptors, including the epidermal growth factor receptor (EGFR). We show that increased EGFR signaling attenuates Hh abundance and that an EGFR inhibitor rescues conditional β1 integrin null pups from postnatal lethality. These studies link the loss of Hh expression in the intestinal epithelium of integrin β1-deficient mice to excessive EGFR/MAPK signaling, and identify a unique mechanism for crosstalk between stromal and epithelial signaling pathways that is critical for intestinal epithelial differentiation and function.

ErbB2 receptor immunoreactivity in prostate cancer: relationship to the androgen receptor, disease severity at diagnosis and disease outcome

Background

ErbB2 is a member of the epidermal growth factor family of tyrosine kinases that is centrally involved in the pathogenesis of prostate cancer and several studies have reported that a high expression of this protein has prognostic value. In the present study, we have investigated whether tumour ErbB2 immunoreactivity (ErbB2-IR) has clinically useful prognostic value, i.e. that it provides additional prognostic information to that provided by routine clinical tests (Gleason score, tumour stage).

Methodology/Principal Findings

ErbB2-IR was measured in a well-characterised tissue microarray of tumour and non-malignant samples obtained at diagnosis. Additionally, mRNA levels of ErbB2-IR in the prostate were determined in the rat following manipulation of circulating androgen levels. Tumour ErbB2-IR was significantly associated with the downstream signalling molecule phosphorylated-Akt and with the cell proliferation marker Ki-67. The significant association of tumour ErbB2-IR with the Gleason score at diagnosis was lost when controlled for the association of both parameters with Ki-67. In the rat prostate, mRNA for ErbB2 was inversely associated with circulating androgen levels. There was no association between ErbB2-IR and the androgen receptor (AR)-IR in the tumours, but an interaction between the two parameters was seen with respect to their association with the tumour stage. Tumour ErbB2-IR was confirmed to be a prognostic marker for disease-specific survival, but it did not provide significant additive information to the Gleason score or to Ki-67.

Conclusions/Significance

It is concluded that tumour ErbB2-IR is of limited clinical value as a prognostic marker to aid treatment decisions, but could be of pathophysiological importance in prostate cancer.

Quercetin, a natural dietary flavonoid, acts as a chemopreventive agent against prostate cancer in an in vivo model by inhibiting the EGFR signaling pathway

Prostate cancer incidence and mortality rates have increased over the past years. The purpose of the present study was to examine the molecular mechanism underlying the chemopreventive effects of quercetin on prostate cancer in an in vivo model. Sprague-Dawley male rats were divided into four groups, Group I: vehicle control (propylene glycol), Group II: chemically induced cancer model (MNU + T); Group III: chemically induced cancer model + quercetin (200 mg per kg b.w.); Group IV: quercetin (200 mg per kg b.w.). Serum levels of quercetin were assessed by high performance liquid chromatography (HPLC). EGFR, PI3K/Akt protein levels were significantly increased in chemically induced cancer rats, which were brought back to normalcy in both DLP & VP (dorsolateral prostate & ventral prostate) by quercetin supplementation. Also, the protein expression levels of proliferating cell nuclear antigen (PCNA), N-cadherin, vimentin, and cyclin D1 exhibited a significant increase in both DLP & VP of chemically induced cancer rats. However, simultaneous quercetin supplementation significantly decreased PCNA, N-cadherin, vimentin, and cyclin D1 protein levels compared to chemically induced cancer rats. The E-cadherin expression was decreased in chemically induced cancer animals. Simultaneous quercetin supplementation prevented it. Real time PCR was used to study the mRNA expression of snail, slug and twist. Quercetin significantly decreased snail, slug, and twist mRNA levels in chemically induced cancer rats. To conclude from the present study, quercetin was effective in preventing prostate cancer progression by inhibiting the EGFR signaling pathway and by regulating cell adhesion molecules in Sprague Dawley rats.

Overexpression of HepaCAM inhibits cell viability and motility through suppressing nucleus translocation of androgen receptor and ERK signaling in prostate cancer

BACKGROUND

HepaCAM is suppressed in a variety of human cancers, and involved in cell adhesion, growth, migration, invasion, and survival. However, the expression and function of HepaCAM in prostate cancer are still unknown.

METHODS

HepaCAM expression has been detected by RT-PCR, Western blotting and immunohistochemistry staining in prostate cell lines RWPE-1, LNCap, DU145, PC3, and in 75 human prostate tissue specimens, respectively. Meanwhile, the cell proliferation ability was detected by WST-8 assay. The role of HepaCAM in prostate cancer cell migration and invasion was examined by wound healing and transwell assay. And flow cytometry was used to observe the apoptosis of prostate cancer cells. Then we detected changes of Androgen Receptor translocation and ERK signaling using immunofluorescence staining and western blot after overexpression of HepaCAM.

RESULTS

The HepaCAM expression was significantly down-regulated in prostate cancer tissues and undetected in prostate cancer cells. However, the low HepaCAM expression was not statistically associated with clinicopathological characteristics of prostate cancer. Overexpression of HepaCAM in prostate cancer cells decreased the cell proliferation, migration and invasion, and induced the cell apoptosis. Meanwhile, HepaCAM prevented the androgen receptor translocation from the cytoplasm to the nucleus and down-regulated the MAPK/ERK signaling.

CONCLUSION

Our results suggested that HepaCAM acted as a tumor suppressor in prostate cancer. HepaCAM inhibited cell viability and motility which might be through suppressing the nuclear translocation of Androgen Receptor and down-regulating the ERK signaling. Therefore, it was indicated that HepaCAM may be a potential therapeutic target for prostate cancer.

KIF3a promotes proliferation and invasion via Wnt signaling in advanced prostate cancer

Aberrant activation of the Wnt/β-catenin signaling pathway is a critical event in advanced prostate cancer, but the genetic alterations that activate the Wnt signaling pathway in many other cancers are rarely observed in prostate cancer. Other molecular mechanisms that regulate the Wnt signaling pathway in prostate cancer remain to be identified. Here, it is demonstrated that KIF3a, a subunit of kinesin-II motor protein, functions as an agonist of the Wnt signaling pathway in prostate cancer. KIF3a is upregulated in the majority of human prostate cancer cell lines and primary tumor biopsies. The expression levels of KIF3a correlate with a higher Gleason score, tumor-node-metastasis stage, and metastatic status of prostate cancer. Moreover, exogenous expression of KIF3a promoted cell growth in the benign prostate cells, whereas silencing KIF3a in cancer cells decreased cell proliferation, anchorage-independent cell growth, and cell migration/invasion. Mechanistically, KIF3a increases CK1-dependent DVL2 phosphorylation and β-catenin activation in prostate cancer cells, leading to transactivation of the Wnt-signaling target genes such as cyclin D1, HEF1, and MMP9. These findings support the notion that upregulation of KIF3a is causal of aberrant activation of Wnt signaling in advanced prostate cancer through the KIF3a-DVL2-β-catenin axis.

IMPLICATIONS

Inactivation of KIF3a may improve survival of patients with advanced prostate cancer in which Wnt signaling is activated.

Snail mediates invasion through uPA/uPAR and the MAPK signaling pathway in prostate cancer cells

Epithelial-mesenchymal transition (EMT) is a process by which cancer cells acquire mesenchymal properties, such as induction of vimentin, while epithelial-associated genes like E-cadherin are lost. This enables cells to be more metastatic. Factors that are able to induce EMT include growth factors such as transforming growth factor-β (TGF-β) and epidermal growth factor, and transcription factors such as Snail. Snail-induced EMT promotes migration and invasion and we hypothesized that this may be mediated by the activity of urokinase-type plasminogen activator (uPA) and its receptor (uPAR). LNCaP, 22Rv1 and ARCaP human prostate cancer (CaP) cells stably transfected with empty vector control (Neo) or constitutively active Snail exhibited increased cell invasion. Superarray analysis revealed an upregulation in uPA and uPAR RNA expression in Snail-transfected ARCaP cells compared with that of a Neo control. In addition, the protein expression levels of Snail, uPA and uPAR were measured by western blot analysis which showed that overexpression of Snail increased uPA and uPAR protein levels. The activity of uPA in conditioned media was measured using an ELISA which revealed that uPA activity was elevated in LNCaP, 22Rv1 and ARCaP cells overexpressing Snail. Additionally, transient silencing of uPAR in ARCaP cells overexpressing Snail using short interfering RNA resulted in abrogation of Snail-mediated invasion. Snail overexpression was associated with increased extracellular-signal-regulated kinase activity, and antagonism of this activity with mitogen-activated protein (MAPK) inhibitor, UO126, inhibited cell invasion and decreased uPA activity. Therefore, Snail-mediated cell invasion in human CaP cells may occur via the regulation of uPA/uPAR and the MAPK signaling pathway.

Combined inhibition of epidermal growth factor receptor and cyclooxygenase-2 leads to greater anti-tumor activity of docetaxel in advanced prostate cancer

The epidermal growth factor receptor (EGFR) and cyclooxygenase-2(COX-2) play a critical role in disease progression, relapse and therapeutic resistance of advanced prostate cancer (PCa). In this paper, we evaluated, for the first time, the therapeutic benefit of blocking EGRF and/or COX-2 (using gefitinib and NS-398, respectively) in terms of improving the efficacy of the conventional clinical chemotherapeutic drug docetaxel in vitro and vivo. We showed that EGFR and COX-2 expression was higher in metastatic than non-metastatic PCa tissues and cells. Docetaxel, alone or in combination with gefitinib or NS-398, resulted in a small decrease in cell viability. The three drug combination decreased cell viability to a greater extent than docetaxel alone or in combination with gefitinib or NS-398. Docetaxel resulted in a modest increase in apoptotic cell in metastatic and non-metastatic cell lines. NS-398 markedly enhanced docetaxel-induced cell apoptosis. The combination of the three drugs caused even more marked apoptosis and resulted in greater suppression of invasive potential than docetaxel alone or in association with gefitinib or NS-398. The combination of all three drugs also resulted in a more marked decrease in NF-ΚB, MMP-9 and VEGF levels in PC-3M cells. These in vitro findings were supported by in vivo studies showing that docetaxel in combination with gefitinib and NS-398 was significantly more effective than any individual agent. Based on previous preclinical research, we conclude that simultaneously blocking EGFR and COX-2 by gefitinib and NS-398 sensitizes advanced PCa cells to docetaxel-induced cytotoxicity.

Knockdown of lipocalin-2 suppresses the growth and invasion of prostate cancer cells

BACKGROUND

Lipocalin-2 (LCN2) is a member of the lipocalin superfamily, and it has an important role in the regulation of cellular oncogenesis and apoptosis. However, the role for LCN2 in prostate cancer remains unclear.

METHOD

LCN2 expression has been determined by Western blotting, qRT-PCR, and immunohistochemistry in the human prostate cell lines PC3, DU145, LNCaP, and 22Rv, and in human prostate tissue array. In this study, we identified shRNA-LCN2 to determine the role of LCN2 in prostate-cancer cell proliferation, migration, and invasion. Cell proliferative ability was measured by MTT, colony-formation, and cell-cycle analysis. The role of LCN2 in prostate-cancer cell migration and invasion was analyzed by cell-migration assay and Matrigel invasion assay. The effect of LCN2 knockdown on prostate tumor growth was assessed in a subcutaneous xenograft model.

RESULTS

LCN2 protein and mRNA expression are higher in PC3 and DU145 cells than in LNCaP and 22Rv cells, and prostate cancer tissue correlated significantly with tumor differentiation (P < 0.017) and Gleason's grade (P < 0.02). LCN2 knockdown in PC3 and DU145 cells decreased cell proliferation, colony formation, cell cycle arrest, migration, and invasion. Conversely, LCN2 overexpression in 22Rv cells produced the opposite effect. Subcutaneous xenografts in mice models showed decreased tumor growth in the LCN2-knockdown mice.

CONCLUSIONS

Our results suggest that LCN2 might play an important role in regulation of proliferation and invasion of human prostate cancer, and that it can be a valuable marker of prostate cancer progression.

PTP1B: a simple enzyme for a complex world

Our understanding of the fundamental regulatory roles that tyrosine phosphatases play within cells has advanced significantly in the last two decades. Out-dated ideas that tyrosine phosphatases acts solely as the "off" switch counterbalancing the action of tyrosine kinases has proved to be flawed. PTP1B is the most characterized of all the tyrosine phosphatases and it acts as a critical negative and positive regulator of numerous signaling cascades. PTP1B's direct regulation of the insulin and the leptin receptors makes it an ideal therapeutic target for type II diabetes and obesity. Moreover, the last decade has also seen several reports establishing PTP1B as key player in cancer serving as both tumor suppressor and tumor promoter depending on the cellular context. Despite many key advances in these fields one largely ignored area is what role PTP1B may play in the modulation of immune signaling. The important recognition that PTP1B is a major negative regulator of Janus kinase - signal transducer and activator of transcription (JAK-STAT) signaling throughout evolution places it as a key link between metabolic diseases and inflammation, as well as a unique regulator between immune response and cancer. This review looks at the emergence of PTP1B through evolution, and then explore at the cell and systemic levels how it is controlled physiologically. The second half of the review will focus on the role(s) PTP1B can play in disease and in particular its involvement in metabolic syndromes and cancer. Finally we will briefly examine several novel directions in the development of PTP1B pharmacological inhibitors.

Angiogenin mediates androgen-stimulated prostate cancer growth and enables castration resistance

The androgen receptor (AR) is a critical effector of prostate cancer development and progression. Androgen-dependent prostate cancer is reliant on the function of AR for growth and progression. Most castration-resistant prostate cancer (CRPC) remains dependent on AR signaling for survival and growth. Ribosomal RNA (rRNA) is essential for both androgen-dependent and castration-resistant growth of prostate cancer cells. During androgen-dependent growth of prostate cells, androgen-AR signaling leads to the accumulation of rRNA. However, the mechanism by which AR regulates rRNA transcription is unknown. Here, investigation revealed that angiogenin (ANG), a member of the secreted ribonuclease superfamily, is upregulated in prostate cancer and mediates androgen-stimulated rRNA transcription in prostate cancer cells. Upon androgen stimulation, ANG undergoes nuclear translocation in androgen-dependent prostate cancer cells, where it binds to the rDNA promoter and stimulates rRNA transcription. ANG antagonists inhibit androgen-induced rRNA transcription and cell proliferation in androgen-dependent prostate cancer cells. Interestingly, ANG also mediates androgen-independent rRNA transcription through a mechanism that involves its constitutive nuclear translocation in androgen-insensitive prostate cancer cells, resulting in a constant rRNA overproduction and thereby stimulating cell proliferation. Critically, ANG overexpression in androgen-dependent prostate cancer cells enables castration-resistant growth of otherwise androgen-dependent cells. Thus, ANG-stimulated rRNA transcription is not only an essential component for androgen-dependent growth of prostate cancer but also contributes to the transition of prostate cancer from androgen-dependent to castration-resistant growth status.

IMPLICATIONS

The ability of angiogenin to regulate rRNA transcription and prostate cancer growth makes it a viable target for therapy.

Prostate stem cells in the development of benign prostate hyperplasia and prostate cancer: emerging role and concepts

Benign Prostate hyperplasia (BPH) and prostate cancer (PCa) are the most common prostatic disorders affecting elderly men. Multiple factors including hormonal imbalance, disruption of cell proliferation, apoptosis, chronic inflammation, and aging are thought to be responsible for the pathophysiology of these diseases. Both BPH and PCa are considered to be arisen from aberrant proliferation of prostate stem cells. Recent studies on BPH and PCa have provided significant evidence for the origin of these diseases from stem cells that share characteristics with normal prostate stem cells. Aberrant changes in prostate stem cell regulatory factors may contribute to the development of BPH or PCa. Understanding these regulatory factors may provide insight into the mechanisms that convert quiescent adult prostate cells into proliferating compartments and lead to BPH or carcinoma. Ultimately, the knowledge of the unique prostate stem or stem-like cells in the pathogenesis and development of hyperplasia will facilitate the development of new therapeutic targets for BPH and PCa. In this review, we address recent progress towards understanding the putative role and complexities of stem cells in the development of BPH and PCa.

Hedgehog signaling in prostate cancer and its therapeutic implication

Activation of Hedgehog (Hh) signaling is implicated in the development and progression of several tumor types, including prostate cancer, which is still the most common non-skin malignancy and the third leading cause of cancer-related mortality in men in industrialized countries worldwide. Several studies have indicated that the Hh pathway plays a crucial role in the development as well as in the progression of this disease to more aggressive and even therapy-resistant disease states. Moreover, preclinical data have shown that inhibition of Hh signaling has the potential to reduce prostate cancer invasiveness and metastatic potential. Clinical trials investigating the benefit of Hh inhibitors in patients with prostate cancer have recently been initiated. However, acquired drug resistance has already been observed in other tumor types after long-term Hh inhibition. Therefore, combining Hh inhibitors with ionizing radiation, chemotherapy or other molecular targeted agents could represent an alternative therapeutic strategy. In this review, we will highlight the role of Hh signaling in the development and progression of prostate cancer and summarize the different therapeutic applications of Hedgehog inhibition.

SIRT1 enhances matrix metalloproteinase-2 expression and tumor cell invasion in prostate cancer cells

BACKGROUND

Matrix metalloproteinase-2 (MMP2) has been shown to play an important role in cancer cell invasion and the expression of MMP2 is associated with the poor prognosis of prostate cancer; however, the mechanism of MMP2 expression is largely unknown. SIRT1 is a nicotinamide adenine dinucleotide-dependent histone deacetylase (class III HDAC) that has recently been shown to have implications in regulating cancer cell growth and apoptosis. The purpose of this study is to determine the role of SIRT1 in regulating MMP2 expression and tumor invasion in prostate cancer cells.

METHODS

The interfering RNAi was used to knockdown SIRT1 from prostate cancer cells. Immunoblots, RT-PCR, zymographic assays, co-immunoprecipitation, analysis and transwell assays were used to examine the effects of SIRT1 silencing on MMP2 expression and activity, on SIRT1 and MMP2 interaction, and on prostate cancer cell invasion. The immuno-histochemical assay was performed to study SIRT1 expression in prostate cancer tissues.

RESULTS

We show that SIRT1 associates and deacetylates MMP2 and SIRT1 regulates MMP2 expression by controlling MMP2 protein stability through the proteosomal pathway. Thus, we demonstrated a novel mechanism in that MMP2 expression can be regulated at the posttranslational level by SIRT1. Furthermore, we determined that SIRT1 inhibition reduced prostate cancer cell invasion and SIRT1 is highly expressed in advanced prostate cancer tissues.

CONCLUSIONS

SIRT1 is an important regulator of MMP2 expression, activity, and prostate cancer cell invasion. Overexpressed SIRT1 in advanced prostate cancer may play an important role in prostate cancer progression.

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.

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.

Epidermal growth factor promotes protein degradation of epithelial protein lost in neoplasm (EPLIN), a putative metastasis suppressor, during epithelial-mesenchymal transition

Aberrant expression of EGF receptors has been associated with hormone-refractory and metastatic prostate cancer (PCa). However, the molecular mechanism for EGF signaling in promoting PCa metastasis remains elusive. Using experimental models of PCa metastasis, we demonstrated that EGF could induce robust epithelial-mesenchymal transition (EMT) and increase invasiveness. Interestingly, EGF was found to be capable of promoting protein turnover of epithelial protein lost in neoplasm (EPLIN), a putative suppressor of EMT and tumor metastasis. Mechanistic study revealed that EGF could activate the phosphorylation, ubiquitination, and degradation of EPLIN through an extracellular signal-regulated kinase 1/2 (ERK1/2)-dependent signaling cascade. Pharmacological inhibition of the ERK1/2 pathway effectively antagonized EGF-induced EPLIN degradation. Two serine residues, i.e. serine 362 and serine 604, were identified as putative ERK1/2 phosphorylation sites in human EPLIN, whose point mutation rendered resistance to EGF-induced protein turnover. This study elucidated a novel molecular mechanism for EGF regulation of EMT and invasiveness in PCa cells, indicating that blockade of EGF signaling could be beneficial in preventing and retarding PCa metastasis at early stages.

SIRT1 induces EMT by cooperating with EMT transcription factors and enhances prostate cancer cell migration and metastasis

The epithelial-to-mesenchymal transition (EMT) is a crucial program for the invasion and metastasis of epithelial tumors that involves loss of cell-cell adhesion and increased cell mobility; however, mechanisms underlying this transition are not fully elucidated. Here, we propose a novel mechanism through which the nicotinamide adenine dinucleotide-dependent histone deacetylase SIRT1 regulates EMT in prostate cancer cells through cooperation with the EMT inducing transcription factor ZEB1. We found that forced expression of SIRT1 in non-transformed PZ-HPV-7 prostate epithelial cells disrupts the epithelial morphology concomitant with decreased expression of the epithelial marker, E-cadherin, and increased expression of mesenchymal markers. In contrast, silencing SIRT1 in metastatic prostate tumor cells restores cell-cell adhesion and induces a shift toward an epithelial morphology concomitant with increased expression of E-cadherin and decreased expression of mesenchymal markers. We also found that SIRT1 has a physiologically relevant role in endogenous EMT induced by EGF signaling in prostate cancer cells. We propose that the regulation of EMT by SIRT1 involves modulation of, and cooperation with, the EMT inducing transcription factor ZEB1. Specifically, we show that SIRT1 silencing reduces expression of ZEB1 and that SIRT1 is recruited to the E-cadherin proximal promoter by ZEB1 to deacetylate histone H3 and to reduce binding of RNA polymerase II, ultimately suppressing E-cadherin transcription. We thus identify a necessary role for ZEB1 in SIRT1-mediated EMT. Finally, we show that reduction of SIRT1 decreases prostate cancer cell migration in vitro and metastasis in vivo in immunodeficient mice, which is largely independent of any general effects of SIRT1 on prostate cancer growth and survival. We therefore identify SIRT1 as a positive regulator of EMT and metastatic growth of prostate cancer cells and our findings implicate overexpressed SIRT1 as a potential therapeutic target to reverse EMT and to prevent prostate cancer progression.

miR-23b represses proto-oncogene Src kinase and functions as methylation-silenced tumor suppressor with diagnostic and prognostic significance in prostate cancer

The miRNAs have great potential as biomarkers and therapeutic agents owing to their ability to control multiple genes and potential to influence cellular behavior. Here, we identified that miR-23b is a methylation-silenced tumor suppressor in prostate cancer. We showed that miR-23b expression is controlled by promoter methylation and has great promise as a diagnostic and prognostic biomarker in prostate cancer. High levels of miR-23b expression are positively correlated with higher overall and recurrence-free survival in patients with prostate cancer. Furthermore, we elucidated the tumor suppressor role of miR-23b using in vitro and in vivo models. We showed that proto-oncogene Src kinase and Akt are direct targets of miR-23b. Increased expression of miR-23b inhibited proliferation, colony formation, migration/invasion, and triggered G(0)-G(1) cell-cycle arrest and apoptosis in prostate cancer. Overexpression of miR-23b inhibited epithelial-to-mesenchymal transition (EMT) causing a decline in mesenchymal markers Vimentin and Snail and increasing the epithelial marker, E-cadherin. Depletion of Src by RNA interference conferred similar functional effects as that of miR-23b reconstitution. miR-23b expression caused a dramatic decrease in tumor growth in nude mice and attenuated Src expression in excised tumors compared with a control miR. These findings suggest that miR-23b is a methylation-silenced tumor suppressor that may be a useful biomarker in prostate cancer. Loss of miR-23b may confer proliferative advantage and promote prostate cancer migration and invasion, and reexpression of miR-23b may contribute to the epigenetic therapy for prostate cancer.

15-Lipoxygenase-1-mediated metabolism of docosahexaenoic acid is required for syndecan-1 signaling and apoptosis in prostate cancer cells

Fatty acid metabolism impacts multiple intracellular signaling pathways in many cell types, but its role in prostate cancer cells is still unclear. Our previous studies have shown that the n-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) induces apoptosis in human prostate cancer cells by a syndecan-1 (SDC-1)-dependent mechanism. Here, we examined the contribution of lipoxygenase (LOX)- and cyclooxygenase (COX)-mediated DHA metabolism to this effect. Pan-LOX inhibitor (nordihydroguaiaretic acid), 15-LOX inhibitor (luteolin) or 15/12-LOX inhibitor (baicalein) blocked the induced effect of DHA on SDC-1 expression and apoptosis in human prostate cancer cells, whereas 5-LOX inhibitor, AA861, was ineffective. Human prostate cancer cells lines (PC3, LNCaP and DU145 cells) expressed two 15-LOX isoforms, 15-LOX-1 and 15-LOX-2, with higher 15-LOX-1 and lower 15-LOX-2 expressions compared with human epithelial prostate cells. Knockdown of 15-LOX-1 blocked the effect of DHA on SDC-1 expression and caspase-3 activity, whereas silencing 15-LOX-2, 5-LOX, COX-1, COX-2 or 12-LOX had no effect. Moreover, the ability of DHA to inhibit the activity of the PDK/Akt (T308) signaling pathway was abrogated by silencing 15-LOX-1. These findings demonstrate that 15-LOX-1-mediated metabolism of DHA is required for it to upregulate SDC-1 and trigger the signaling pathway that elicits apoptosis in prostate cancer cells.

Variations in the exome of the LNCaP prostate cancer cell line

BACKGROUND

The LNCaP cell line is widely used as a model for prostate cancer. However, information on protein-changing mutations, genetic heterogeneity and genetic (in)stability is largely lacking for these cells.

METHODS

Next-generation sequencing of the LNCaP exome revealed many single nucleotide variants (SNVs). To help identify the mutations that are most likely drivers of the oncogenic process, we developed an in silico protocol, which can be adapted for other exome analyses.

RESULTS

We detected 1,802 non-synonymous SNVs and 218 small insertions and deletions in the LNCaP exome. We confirm the known mutations in the androgen receptor and the PTEN gene, but most other mutations remained undescribed until now. The presence of 38 out of 42 SNVs was confirmed in monoclonal as well as in polyclonal LNCaP derivatives. Moreover, most variants were also detectable in LNCaP mRNA.

CONCLUSIONS

We provide an extensive database of genetic variations in the protein-coding part of the genome of LNCaP cells, which should be taken into consideration when using LNCaP cells or its derivatives as models for prostate cancer. From the analysis of several LNCaP-derived cultures and clones, we can confirm that the cell line is heterozygous for a large number of variants and that both the variant and the wild-type allele can be simultaneously expressed as mRNA. The fact that the SNVs in the E-cadherin, CDK4, Notch1, and PlexinB1 genes are absent in some of the subclones strongly indicates a degree of genetic instability.

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

The progression of prostate cancers (PCs) to locally invasive, androgen-independent and metastatic disease states is generally associated with treatment resistance and disease relapse. The present study was undertaken to establish the possibility of using a combination of specific oncogenic products, including epidermal growth factor receptor (EGFR), pAkt, nuclear factor-kappaB (NF-κB) and macrophage inhibitory cytokine-1 (MIC-1) as biomarkers and therapeutic targets for optimizing the management of patients with localized PC at earlier disease stages. The immunohistochemical and immunofluorescence data have revealed that the expression levels of EGFR, Ser⁴⁷³-pAkt, NF-κB p65 and MIC-1 proteins were significantly enhanced in the same subset of 76 cases of prostatic adenocarcinoma specimens during the disease progression and these biomarkers were expressed in a small subpopulation of CD133⁺ PC cells and the bulk tumor mass of CD133⁻ PC cells. Importantly, all of these biomarkers were also overexpressed in 80–100% of 30 PC metastasis bone tissue specimens. Moreover, the results have indicated that the EGF-EGFR signaling pathway can provide critical functions for the self-renewal of side population (SP) cells endowed with stem cell-like features from highly invasive WPE1-NB26 cells. Of therapeutic interest, the targeting of EGFR, pAkt, NF-κB or MIC-1 was also effective at suppressing the basal and EGF-promoted prostasphere formation by SP WPE1-NB26 cells, inducing disintegration of SP cell-derived prostaspheres and decreasing the viability of SP and non-SP WPE1-NB26 cell fractions. Also, the targeting of these oncogenic products induced the caspase-dependent apoptosis in chemoresistant SP WPE1-NB26 cells and enhanced their sensibility to the cytotoxic effects induced by docetaxel. These findings suggest that the combined use of EGFR, pAkt, NF-κB and/or MIC-1 may represent promising strategies for improving the accuracy of current diagnostic and prognostic methods and efficacy of treatments of PC patients in considering the disease heterogeneity, thereby preventing PC progression to metastatic and lethal disease states.