Altered N-myc downstream-regulated gene 1 protein expression in African-American compared with caucasian prostate cancer patients

Genetic and biological drivers of prostate cancer disparities in Black men

Black men with prostate cancer have historically had worse outcomes than white men with prostate cancer. The causes of this disparity in outcomes are multi-factorial, but a potential basis is that prostate cancers in Black men are biologically distinct from prostate cancers in white men. Evidence suggests that genetic and ancestral factors, molecular pathways involving androgen and non-androgen receptor signalling, inflammation, epigenetics, the tumour microenvironment and tumour metabolism are contributing factors to the racial disparities observed. Key genetic and molecular pathways linked to prostate cancer risk and aggressiveness have potential clinical relevance. Describing biological drivers of prostate cancer disparities could inform efforts to improve outcomes for Black men with prostate cancer.

N-Myc Downstream Regulated Gene-1 May Play an Important Role in the Prognosis of Ovarian Cancer, in Its Association with Beta-Catenin

NDRG1 is a nickel- and calcium-inducible gene that plays important roles in the primary growth of malignant tumors, as well as in invasion and metastasis. This study investigated the associations of NDRG1 expression with cell adhesion and other clinicopathological factors in ovarian cancer. The clinical records of 123 women who underwent surgery for ovarian cancer in our institute were reviewed retrospectively. The expression of NDRG1, E-cadherin, and beta-catenin in surgical specimens were evaluated immunohistochemically. The NDRG1 expression level was significantly associated with beta-catenin expression, peritoneal metastasis outside the pelvic cavity, lymph node metastasis, and FIGO stages. The Kaplan-Meier analysis showed a significant association between the NDRG1 expression level and progression-free survival: high NDRG1 expression was related to poor survival. Our results suggest that the increased expression of NDRG1 is associated with cell adhesion and may be a poor prognostic indicator in women with ovarian cancer.

The Myc Family and the Metastasis Suppressor NDRG1: Targeting Key Molecular Interactions with Innovative Therapeutics

Cancer is a leading cause of death worldwide, resulting in ∼10 million deaths in 2020. Major oncogenic effectors are the Myc proto-oncogene family, which consists of three members including c-Myc, N-Myc, and L-Myc. As a pertinent example of the role of the Myc family in tumorigenesis, amplification of MYCN in childhood neuroblastoma strongly correlates with poor patient prognosis. Complexes between Myc oncoproteins and their partners such as hypoxia-inducible factor-1α and Myc-associated protein X (MAX) result in proliferation arrest and pro-proliferative effects, respectively. Interactions with other proteins are also important for N-Myc activity. For instance, the enhancer of zest homolog 2 (EZH2) binds directly to N-Myc to stabilize it by acting as a competitor against the ubiquitin ligase, SCFFBXW7, which prevents proteasomal degradation. Heat shock protein 90 may also be involved in N-Myc stabilization since it binds to EZH2 and prevents its degradation. N-Myc downstream-regulated gene 1 (NDRG1) is downregulated by N-Myc and participates in the regulation of cellular proliferation via associating with other proteins, such as glycogen synthase kinase-3β and low-density lipoprotein receptor-related protein 6. These molecular interactions provide a better understanding of the biologic roles of N-Myc and NDRG1, which can be potentially used as therapeutic targets. In addition to directly targeting these proteins, disrupting their key interactions may also be a promising strategy for anti-cancer drug development. This review examines the interactions between the Myc proteins and other molecules, with a special focus on the relationship between N-Myc and NDRG1 and possible therapeutic interventions. SIGNIFICANCE STATEMENT: Neuroblastoma is one of the most common childhood solid tumors, with a dismal five-year survival rate. This problem makes it imperative to discover new and more effective therapeutics. The molecular interactions between major oncogenic drivers of the Myc family and other key proteins; for example, the metastasis suppressor, NDRG1, may potentially be used as targets for anti-neuroblastoma drug development. In addition to directly targeting these proteins, disrupting their key molecular interactions may also be promising for drug discovery.

N-myc downstream regulated gene 1 (ndrg1) functions as a molecular switch for cellular adaptation to hypoxia

Lack of oxygen (hypoxia and anoxia) is detrimental to cell function and survival and underlies many disease conditions. Hence, metazoans have evolved mechanisms to adapt to low oxygen. One such mechanism, metabolic suppression, decreases the cellular demand for oxygen by downregulating ATP-demanding processes. However, the molecular mechanisms underlying this adaptation are poorly understood. Here, we report on the role of ndrg1a in hypoxia adaptation of the anoxia-tolerant zebrafish embryo. ndrg1a is expressed in the kidney and ionocytes, cell types that use large amounts of ATP to maintain ion homeostasis. ndrg1a mutants are viable and develop normally when raised under normal oxygen. However, their survival and kidney function is reduced relative to WT embryos following exposure to prolonged anoxia. We further demonstrate that Ndrg1a binds to the energy-demanding sodium-potassium ATPase (NKA) pump under anoxia and is required for its degradation, which may preserve ATP in the kidney and ionocytes and contribute to energy homeostasis. Lastly, we show that sodium azide treatment, which increases lactate levels under normoxia, is sufficient to trigger NKA degradation in an Ndrg1a-dependent manner. These findings support a model whereby Ndrg1a is essential for hypoxia adaptation and functions downstream of lactate signaling to induce NKA degradation, a process known to conserve cellular energy.

The Metastasis Suppressor NDRG1 Directly Regulates Androgen Receptor Signaling in Prostate Cancer

N-myc-downregulated gene 1 (NDRG1) has potent anticancer effects and inhibits cell growth, survival, metastasis, and angiogenesis. Previous studies suggested that NDRG1 is linked to the androgen signaling network, but this mechanistic relationship is unclear. Considering the crucial role of the androgen receptor (AR) in prostate cancer (PCa) progression, here we examined for the first time the effect of NDRG1 on AR expression, activation, and downstream signaling in LNCaP, 22Rv1, and C4-2B PCa cell types. We demonstrate that NDRG1 effectively promotes interaction of AR with the chaperone HSP90, which in turn stabilizes the AR while decreasing its androgen-mediated activation. The expression of NDRG1 suppressed: (1) AR activation, as measured by p-AR^Ser213 and p-AR^Ser81; (2) expression of a major AR transcriptional target, prostate-specific antigen (PSA); and (3) AR transcriptional activity, probably via inhibiting the c-Jun-AR interaction by reducing c-Jun phosphorylation (p-c-Jun^Ser63). NDRG1 was also demonstrated to inhibit multiple key molecules involved in androgen-dependent and -independent signaling (namely EGFR, HER2, HER3, PI3K, STAT3, and NF-κB), which promote the development of castration-resistant prostate cancer. We also identified the cysteine-rich secretory protein/antigen 5/pathogenesis related-1 (CAP) domain of NDRG1 as vital for inhibition of AR activity. Examining NDRG1 and p-NDRG1 in PCa patient specimens revealed a significant negative correlation between NDRG1 and PSA levels in prostatectomy patients that went on to develop metastasis. These results highlight a vital role for NDRG1 in androgen signaling and its potential as a key therapeutic target and biomarker in PCa.

The impact of racial residential segregation on prostate cancer diagnosis and treatment

OBJECTIVES

To examine the effects of racial residential segregation and structural racism on the diagnosis, treatment, and outcomes of patients with prostate cancer.

PATIENTS AND METHODS

This retrospective cohort study examined men diagnosed with prostate cancer between 2005 and 2015. We collected data from Black and White men, aged ≥30 years, living within the 100 most populous counties participating in the Surveillance, Epidemiology, and End Results programme, a nationally representative dataset. The racial Index of Dissimilarity, a validated measure of segregation, was the primary exposure of interest. Outcomes of interest included advanced stage at diagnosis (Stage IV), surgery for localised disease (Stage I-II), and 10-year overall and cancer-specific survival. Multivariable Poisson regression analyses with robust error variance estimated the relative risk (RR) of advanced stage at diagnosis and surgery for localised disease at differing levels of segregation. Survival analysis was performed using competing hazards analysis.

RESULTS

Multivariable models estimating stage at diagnosis showed that the disparities between Black and White men disappeared at low levels of segregation. Disparities in receiving surgery for localised disease persisted across all levels of segregation. In racially stratified analyses, segregation had no effect on stage at diagnosis or surgical resection for Black patients. White patients saw a 56% (RR 0.42, P < 0.001) reduced risk of presenting at advanced stage and 20% increased likelihood (RR 1.20, P < 0.001) of surgery for localised disease. Black patients in the lowest segregation areas had the lowest overall mortality, but the highest cancer-specific mortality.

CONCLUSIONS

Our study provides evidence that residential segregation has a significant impact on Black-White disparities in prostate cancer, likely through improved outcomes for White patients and worse outcomes for Black patients in more segregated areas. These findings suggest that mitigating segregation and the downstream effects of socioeconomic factors could alleviate these disparities.

Molecular functions of the iron-regulated metastasis suppressor, NDRG1, and its potential as a molecular target for cancer therapy

N-myc down-regulated gene 1 (NDRG1) is a known metastasis suppressor in multiple cancers, being also involved in embryogenesis and development, cell growth and differentiation, lipid biosynthesis and myelination, stress responses and immunity. In addition to its primary role as a metastasis suppressor, NDRG1 can also influence other stages of carcinogenesis, namely angiogenesis and primary tumour growth. NDRG1 is regulated by multiple effectors in normal and neoplastic cells, including N-myc, histone acetylation, hypoxia, cellular iron levels and intracellular calcium. Further, studies have found that NDRG1 is up-regulated in neoplastic cells after treatment with novel iron chelators, which are a promising therapy for effective cancer management. Although the pathways by which NDRG1 exerts its functions in cancers have been documented, the relationship between the molecular structure of this protein and its functions remains unclear. In fact, recent studies suggest that, in certain cancers, NDRG1 is post-translationally modified, possibly by the activity of endogenous trypsins, leading to a subsequent alteration in its metastasis suppressor activity. This review describes the role of this important metastasis suppressor and discusses interesting unresolved issues regarding this protein.

The expression and localization of N-myc downstream-regulated gene 1 in human trophoblasts

The protein N-Myc downstream-regulated gene 1 (NDRG1) is implicated in the regulation of cell proliferation, differentiation, and cellular stress response. NDRG1 is expressed in primary human trophoblasts, where it promotes cell viability and resistance to hypoxic injury. The mechanism of action of NDRG1 remains unknown. To gain further insight into the intracellular action of NDRG1, we analyzed the expression pattern and cellular localization of endogenous NDRG1 and transfected Myc-tagged NDRG1 in human trophoblasts exposed to diverse injuries. In standard conditions, NDRG1 was diffusely expressed in the cytoplasm at a low level. Hypoxia or the hypoxia mimetic cobalt chloride, but not serum deprivation, ultraviolet (UV) light, or ionizing radiation, induced the expression of NDRG1 in human trophoblasts and the redistribution of NDRG1 into the nucleus and cytoplasmic membranes associated with the endoplasmic reticulum (ER) and microtubules. Mutation of the phosphopantetheine attachment site (PPAS) within NDRG1 abrogated this pattern of redistribution. Our results shed new light on the impact of cell injury on NDRG1 expression patterns, and suggest that the PPAS domain plays a key role in NDRG1’s subcellular distribution.

The role of NDRG1 in the pathology and potential treatment of human cancers

N-myc downstream regulated gene 1 (NDRG1) has been well characterised to act as a metastatic suppressor in a number of human cancers. It has also been implicated to have a significant function in a number of physiological processes such as cellular differentiation and cell cycle. In this review, we discuss the role of NDRG1 in cancer pathology. NDRG1 was observed to be downregulated in the majority of cancers. Moreover, the expression of NDRG1 was found to be significantly lower in neoplastic tissues as compared with normal tissues. The most important function of NDRG1 in inhibiting tumour progression is associated with its ability to suppress metastasis. However, it has also been shown to have important effects on other stages of cancer progression (primary tumour growth and angiogenesis). Recently, novel iron chelators with selective antitumour activity (ie, Dp44mT, DpC) were shown to upregulate NDRG1 in cancer cells. Moreover, Dp44mT showed its antimetastatic potential only in cells expressing NDRG1, making this protein an important therapeutic target for cancer chemotherapy. This observation has led to increased interest in the examination of these novel anticancer agents.

Identification of cetrimonium bromide and irinotecan as compounds with synthetic lethality against NDRG1 deficient prostate cancer cells

The N-myc downstream regulated gene 1 (NDRG1) has been identified as a metastasis-suppressor gene in prostate cancer (PCa). Compounds targeting PCa cells deficient in NDRG1 could potentially decrease invasion/metastasis of PCa. A cell based screening strategy was employed to identify small molecules that selectively target NDRG1 deficient PCa cells. DU-145 PCa cells rendered deficient in NDRG1 expression by a lentiviral shRNA-mediated knockdown strategy were used in the primary screen. Compounds filtered from the primary screen were further validated through proliferation and clonogenic survival assays in parental and NDRG1 knockdown PCa cells. Screening of 3360 compounds revealed irinotecan and cetrimonium bromide (CTAB) as compounds that exhibited synthetic lethality against NDRG1 deficient PCa cells. A three-dimensional (3-D) invasion assay was utilized to test the ability of CTAB to inhibit invasion of DU-145 cells. CTAB was found to remarkably decrease invasion of DU-145 cells in collagen matrix. Our results suggest that CTAB and irinotecan could be further explored for their potential clinical benefit in patients with NDRG1 deficient PCa.

Nuclear MTA1 overexpression is associated with aggressive prostate cancer, recurrence and metastasis in African Americans

Metastasis-associated protein 1 (MTA1), a negative epigenetic modifier, plays a critical role in prostate cancer (PCa) progression. We hypothesized that MTA1 overexpression in primary tumor tissues can predict PCa aggressiveness and metastasis. Immunohistochemical staining of MTA1 was done on archival PCa specimens from University of Mississippi Medical Center and University of Iowa. We found that nuclear MTA1 overexpression was positively correlated with the severity of disease progression reaching its highest levels in metastatic PCa. Nuclear MTA1 overexpression was significantly associated with Gleason > 7 tumors in African Americans but not in Caucasians. It was also a predictor of recurrent disease. We concluded that MTA1 nuclear overexpression may be a prognostic indicator and a future therapeutic target for aggressive PCa in African American men. Our findings may be useful for categorizing African American patients with a higher probability of recurrent disease and metastasis from those who are likely to remain metastasis-free.

Prognostic significance of NDRG1 expression in oral and oropharyngeal squamous cell carcinoma

Human N-myc downstream-regulated gene 1 (NDRG1) is a metastasis suppressor gene with several potential functions, including cell differentiation, cell cycle regulation and response to hormones, nickel and stress. The purpose of this study was to investigate the immunoexpression of NDRG1 in oral and oropharyngeal squamous cell carcinomas searching for its role in the clinical course of these tumors. We investigated immunohistochemical expression of NDRG1 protein in 412 tissue microarray cores of tumor samples from 103 patients with oral and oropharyngeal squamous cell carcinomas and in 110 paraffin-embedded surgical margin sections. The results showed NDRG1 up-regulation in 101/103 (98.1 %) tumor samples, but no expression in any normal tissue sample. Western blot assays confirmed the immunohistochemical findings, suggesting that lower levels of NDRG1 are associated with a high mortality rate. NDRG1 overexpression was related to long-term specific survival (HR = 0.38; p = 0.009), whereas the presence of lymph-node metastasis showed the opposite association with survival (HR = 2.45; p = 0.013). Our findings reinforce the idea that NDRG1 plays a metastasis suppressor role in oral and oropharyngeal squamous cell carcinomas and may be a useful marker for these tumors.

Association of Differentiation-Related Gene-1 (DRG1) with Breast Cancer Survival and in Vitro Impact of DRG1 Suppression

Differentiation-related gene-1, DRG1, is a metastasis suppressor gene whose expression has been shown to be dysregulated in a number of malignancies. The current study examines the expression of DRG1 in a clinical breast cohort and its association with a number of clinical pathological factors using quantitative polymerase chain reaction. Additionally, DRG1 expression is targeted in vitro using ribozyme transgene technology to explore the function of DRG1 in two human breast cancer cell lines. Low levels of DRG1 were found in patients who developed metastasis (p = 0.036) and who died of breast cancer (p = 0.0048) compared to disease free patients. Knockdown of DRG1 also resulted in significantly increased invasion and motility, but decreased matrix-adhesion in MCF7 cells. Knockdown of DRG1 seemed to have minimal impact on the cellular functions of the MDA-MB-231 breast cancer cell line causing no significant differences in cell growth, invasion, motility or matrix-adhesion. Thus, DRG1 appears to be linked to development of metastasis and death in patients who died as a result of breast cancer and may be useful as a prognostic factor as its knockdown appears to be linked with increased invasion and motility and decreased adhesion in MCF7 breast cancer cells.

Emergent trends in the reported incidence of prostate cancer in Nigeria

BACKGROUND

To date there has not been any nationwide age-standardized incidence data reported for prostate cancer in Nigeria. We examined and integrated diverse trends in the age-specific incidence of prostate cancer into a comprehensive trend for Nigeria, and examined how best the existing data could generate a countrywide age-standardized incidence rate for the disease.

METHODS

Data were obtained from studies undertaken between 1970 and 2007 in referral hospital-based cancer registries. Records from at least one tertiary hospital in each of the six geopolitical zones of Nigeria were examined retrospectively. Data were also reported for the rural population in cross-sectional prospective studies. Age-standardized incidence rates and the annual incidence of disease were calculated.

RESULTS

Higher incidence rates for prostate cancer during this period were recorded for patients aged 60-69 years and 70-79 years, with a lower incidence rate for patients aged younger than 50 years. An exponential annual incidence rate of disease was observed in the 50-79 year age group and peaked at 70-79 years before dropping again at age 80 years. The results showed metastasis in more than half of these hospital-based prostate tumors.

CONCLUSION

Our results suggest that prostate cancer occurs at a relatively young age in Nigerians and that hospital-based registry reports may not appropriately reflect the incidence of the disease in Nigeria. A countrywide screening program is urgently needed. Finally, the difference in reported stages of disease found in Nigerians and African-Americans versus Caucasians suggests biological differences in the prognosis. Nigeria may thus typify one of the ancestral populations that harbor inherited genes predisposing African-Americans to high-risk prostate cancer.

Metastasis suppressors in human benign prostate, intraepithelial neoplasia, and invasive cancer: their prospects as therapeutic agents

Despite advances in diagnosis and treatment of prostate cancer, development of metastases remains a major clinical challenge. Research efforts are dedicated to overcome this problem by understanding the molecular basis of the transition from benign cells to prostatic intraepithelial neoplasia (PIN), localized carcinoma, and metastatic cancer. Identification of proteins that inhibit dissemination of cancer cells will provide new perspectives to define novel therapeutics. Development of antimetastatic drugs that trigger or mimic the effect of metastasis suppressors represents new therapeutic approaches to improve patient survival. This review focuses on different biochemical and cellular functions of metastasis suppressors known to play a role in prostate carcinogenesis and progression. Ten putative metastasis suppressors implicated in prostate cancer are discussed. CD44s is decreased in both PIN and cancer; Drg-1, E-cadherin, KAI-1, RKIP, and SSeCKS show similar expression between benign epithelia and PIN, but are downregulated in invasive cancer; whereas, maspin, MKK4, Nm23 and PTEN are upregulated in PIN and downregulated in cancer. Moreover, the potential role of microRNA in prostate cancer progression, the understanding of the cellular distribution and localization of metastasis suppressors, their mechanism of action, their effect on prostate invasion and metastasis, and their potential use as therapeutics are addressed.

Cholesterol and phytosterols differentially regulate the expression of caveolin 1 and a downstream prostate cell growth-suppressor gene

BACKGROUND

The purpose of our study was to show the distinction between the apoptotic and anti-proliferative signaling of phytosterols and cholesterol-enrichment in prostate cancer cell lines, mediated by the differential transcription of caveolin-1, and N-myc downstream-regulated gene 1 (NDRG1), a pro-apoptotic androgen-regulated tumor suppressor.

METHODS

PC-3 and DU145 cells were treated with sterols (cholesterol and phytosterols) for 72h, followed by trypan blue dye-exclusion measurement of necrosis and cell growth measured with a Coulter counter. Sterol induction of cell growth-suppressor gene expression was evaluated by mRNA transcription using RT-PCR, while cell cycle analysis was performed by FACS analysis. Altered expression of Ndrg1 protein was confirmed by Western blot analysis. Apoptosis was evaluated by real time RT-PCR amplification of P53, Bcl-2 gene and its related pro- and anti-apoptotic family members.

RESULTS

Physiological doses (16microM) of cholesterol and phytosterols were not cytotoxic in these cells. Cholesterol-enrichment promoted cell growth (P<0.05), while phytosterols significantly induced growth-suppression (P<0.05) and apoptosis. Cell cycle analysis showed that contrary to cholesterol, phytosterols decreased mitotic subpopulations. We demonstrated for the first time that cholesterols concertedly attenuated the expression of caveolin-1 (cav-1) and NDRG1 genes in both prostate cancer cell lines. Phytosterols had the opposite effect by inducing overexpression of cav-1, a known mediator of androgen-dependent signals that presumably control cell growth or apoptosis.

CONCLUSIONS

Cholesterol and phytosterol treatment differentially regulated the growth of prostate cancer cells and the expression of p53 and cav-1, a gene that regulates androgen-regulated signals. These sterols also differentially regulated cell cycle arrest, downstream pro-apoptotic androgen-regulated tumor suppressor, NDRG1 suggesting that cav-1 may mediate pro-apoptotic NDRG1 signals. Elucidation of the mechanism for sterol modulation of growth and apoptosis signaling may reveal potential targets for cancer prevention and/or chemotherapeutic intervention. Sterol regulation of NDRG1 transcription suggests its potential as biomarker for prediction of neoplasms that would be responsive to chemoprevention by phytosterols.

Prognostic value of NDRG1 and SPARC protein expression in breast cancer patients

An increasing number of studies have shown altered expression of secreted protein acidic and rich in cysteine (SPARC) and N-myc down-regulated gene (NDRG1) in several malignancies, including breast carcinoma; however, the role of these potential biomarkers in tumor development and progression is controversial. In this study, NDRG1 and SPARC protein expression was evaluated by immunohistochemistry on tissue microarrays containing breast tumor specimens from patients with 10 years of follow-up. NDRG1 and SPARC protein expression was determined in 596 patients along with other prognostic markers, such as ER, PR, and HER2. The status of NDRG1 and SPARC protein expression was correlated with prognostic variables and patient clinical outcome. Immunostaining revealed that 272 of the 596 cases (45.6%) were positive for NDRG1 and 431 (72.3%) were positive for SPARC. Statistically significant differences were found between the presence of SPARC and NDRG1 protein expression and standard clinicopathological variables. Kaplan-Meier analysis showed that NDRG1 positivity was directly associated with shorter disease-free survival (DFS, P < 0.001) and overall survival (OS, P < 0.001). In contrast, patients expressing low levels of SPARC protein had worse DFS (P = 0.001) and OS (P = 0.001) compared to those expressing high levels. Combined analysis of the two markers indicated that DFS (P < 0.001) and OS rates (P < 0.001) were lowest for patients with NDRG1-positive and SPARC-negative tumors. Furthermore, NDRG1 over-expression and SPARC down-regulation correlated with poor prognosis in patients with luminal A or triple-negative subtype breast cancer. On multivariate analysis using a Cox proportional hazards model, NDRG1 and SPARC protein expression were independent prognostic factors for both DFS and OS of breast cancer patients. These data indicate that NDRG1 over-expression and SPARC down-regulation could play important roles in breast cancer progression and serve as useful biomarkers to better define breast cancer prognosis.

NDRG3 is an androgen regulated and prostate enriched gene that promotes in vitro and in vivo prostate cancer cell growth

NDRG3 belongs to the N-myc down-regulated gene (NDRG) family that contains 4 paralogs: NDRG1, -2, -3 and -4. The function of NDRG3 and its relationship to cancer has not been studied. We herein report our examination of the expression and biological roles of NDRG3 in prostate cancers. We showed that NDRG3 expression is enriched in testis and prostate using gene expression data derived from massively parallel signature sequencing from 33 different human organs. We further showed that NDRG3 is expressed in both epithelial prostate cancer cells and prostatic stromal cells at both mRNA and proteins levels. We demonstrated that NDRG1 is significantly up-regulated by androgen in LNCaP cells. Over-expression of NDRG3 in stably transfected PC-3 cells increased their growth rates and migration capabilities when compared to parental or mock empty vector transfected PC-3 cells. In addition, we found that overexpresson of NDRG3 promoted the growth of xenograft tumors in nude mice. Finally, we found that NDRG3 expression was detected in 58.6% (41/70) of prostate cancer specimens compared to 13.2% (5/38) of benign prostatic hyperplasia specimens by immunohistochemistry. We showed by microarray and by RT-PCR that NDRG3 overexpression up-regulates the expression of many angiogenic chemokines including CXCL1 (chemokine ligand 1), CXCL3 (chemokine ligand 3) and CXCL5 (chemokine ligand 5), which may increase angiogenesis of tumors. Taken together, these results demonstrate that NDRG3 is a tumor promoter, the overexpression of which may contribute to the malignant phenotype of tumors.

Using proteomic approach to identify tumor-associated antigens as markers in hepatocellular carcinoma

Many studies have demonstrated that intracellular proteins, which are involved in carcinogenesis, can provoke autoantibody responses. Therefore, autoantibodies can be used clinically for cancer detection and for proteomic analysis in identification of tumor-associated antigens (TAAs) that are potentially involved in malignant transformation. Liver cancer, especially hepatocellular carcinoma (HCC), is one of the most common tumors in the world. The majority of people with HCC will die within 1 year of its detection. This high case fatality rate can partially be attributed to a lack of diagnostic methods that allow early detection. In the present study, sera from 20 patients with HCC, 30 patients with chronic hepatitis (CH), and 30 patients with liver cirrhosis (LC) as well as sera from 10 normal individuals were used in a proteomic approach to identify HCC-related TAAs. Thirty-four immunoreactive protein spots were excised from the two-dimensional gel electrophoresis (2DE), digested with trypsin, and subsequently analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Of 34 immunoreactive protein spots, 28 were identified. Seventeen of them were not only reactive with serum antibodies in HCC but also with antibodies in pre-HCC conditions, and 11 were only reactive with serum antibodies in HCC but not with antibodies in pre-HCC conditions. In the subsequent analysis, two representative proteins, HSP60 and HSP70, were selected as examples for the validation purpose. The results from immunoassay were consistent with the data from proteomic analysis, supporting our hypothesis that proteins identified with autoantibodies that have been present in precancer conditions may be not appropriate to use as TAA markers in cancer detection.

Evolutionary conservation of zinc finger transcription factor binding sites in promoters of genes co-expressed with WT1 in prostate cancer

BACKGROUND

Gene expression analyses have led to a better understanding of growth control of prostate cancer cells. We and others have identified the presence of several zinc finger transcription factors in the neoplastic prostate, suggesting a potential role for these genes in the regulation of the prostate cancer transcriptome. One of the transcription factors (TFs) identified in the prostate cancer epithelial cells was the Wilms tumor gene (WT1). To rapidly identify coordinately expressed prostate cancer growth control genes that may be regulated by WT1, we used an in silico approach.

RESULTS

Evolutionary conserved transcription factor binding sites (TFBS) recognized by WT1, EGR1, SP1, SP2, AP2 and GATA1 were identified in the promoters of 24 differentially expressed prostate cancer genes from eight mammalian species. To test the relationship between sequence conservation and function, chromatin of LNCaP prostate cancer and kidney 293 cells were tested for TF binding using chromatin immunoprecipitation (ChIP). Multiple putative TFBS in gene promoters of placental mammals were found to be shared with those in human gene promoters and some were conserved between genomes that diverged about 170 million years ago (i.e., primates and marsupials), therefore implicating these sites as candidate binding sites. Among those genes coordinately expressed with WT1 was the kallikrein-related peptidase 3 (KLK3) gene commonly known as the prostate specific antigen (PSA) gene. This analysis located several potential WT1 TFBS in the PSA gene promoter and led to the rapid identification of a novel putative binding site confirmed in vivo by ChIP. Conversely for two prostate growth control genes, androgen receptor (AR) and vascular endothelial growth factor (VEGF), known to be transcriptionally regulated by WT1, regulatory sequence conservation was observed and TF binding in vivo was confirmed by ChIP.

CONCLUSION

Overall, this targeted approach rapidly identified important candidate WT1-binding elements in genes coordinately expressed with WT1 in prostate cancer cells, thus enabling a more focused functional analysis of the most likely target genes in prostate cancer progression. Identifying these genes will help to better understand how gene regulation is altered in these tumor cells.

Cap43/NDRG1/Drg-1 is a molecular target for angiogenesis and a prognostic indicator in cervical adenocarcinoma

Cap43 is a nickel- and calcium-inducible gene that plays important roles in the primary growth of malignant tumors, as well as in invasion and metastasis, most likely through its ability to induce cellular differentiation. This study investigated associations of Cap43 expression with angiogenesis and other clinicopathological factors in cervical adenocarcinoma. The clinical records of 100 women who underwent surgery for cervical adenocarcinoma were reviewed retrospectively. Microvessel density and the expression of Cap43 and VEGF in the surgical specimens were evaluated immunohistochemically. The Cap43 expression level was significantly associated with angiogenesis, tumor diameter, stromal invasion, lymphovascular space invasion, lymph node metastasis, and histopathological differentiation. Kaplan-Meier analysis showed a significant association between the Cap43 expression level and survival: high Cap43 expression was related to poor survival. Our results suggest that increased expression of Cap43 is associated with angiogenesis and may be a poor prognostic indicator in women with cervical adenocarcinoma.

Correlation of N-myc downstream-regulated gene 1 expression with clinical outcomes of colorectal cancer patients of different race/ethnicity

AIM: To evaluate the role of N-myc downstream-regulated gene 1 (NDRG1) expression in prognosis and survival of colorectal cancer patients with different ethnic backgrounds.

METHODS: Because NDRG1 is a downstream target of p53 and hypoxia inducible factor-1α (HIF-1α), we examined NDRG1 expression together with p53 and HIF-1α by immunohistochemistry. A total of 157 colorectal cancer specimens including 80 from Japanese patients and 77 from US patients were examined. The correlation between protein expression with clinicopathological features and survival after surgery was analyzed.

RESULTS: NDRG1 protein was significantly increased in colorectal tumor compared with normal epithelium in both Japanese and US patient groups. Expression of NDRG1 protein was significantly correlated with lymphatic invasion, venous invasion, depth of invasion, histopathological type, and Dukes' stage in Japanese colorectal cancer patients. NDRG1 expression was correlated to histopathological type, Dukes' stage and HIF-1α expression in US-Caucasian patients but not in US-African American patients. Interestingly, Kaplan-Meier survival analysis demonstrated that NDRG1 expression correlated significantly with poorer survival in US-African American patients but not in other patient groups. However, in p53-positive US cases, NDRG1 positivity correlated significantly with better survival. In addition, NDRG1 expression also correlated significantly with improved survival in US patients with stages III and IV tumors without chemotherapy. In Japanese patients with stages II and III tumors, strong NDRG1 staining in p53-positive tumors correlated significantly with improved survival but negatively in patients without chemotherapy.

CONCLUSION: NDRG1 expression was correlated with various clinicopathological features and clinical outcomes in colorectal cancer depending on the race/ethnicity of the patients. NDRG1 may serve as a biological basis for the disparity of clinical outcomes of colorectal cancer patients with different ethnic backgrounds.

A conditionally immortalized cell line model for the study of human prostatic epithelial cell differentiation

In the normal human prostate, undifferentiated proliferative cells reside in the basal layer and give rise to luminal secretory cells. There are, however, few epithelial cell lines that have a basal cell phenotype and are able to differentiate. We set out to develop a cell line with these characteristics that would be suitable for the study of the early stages of prostate epithelial cell differentiation. We produced a matched pair of conditionally immortalized prostate epithelial and stromal cell lines derived from the same patient. The growth of these cells is temperature dependent and differentiation can be induced following a rise in culture temperature. Three-dimensional co-cultures of these cell lines elicited gland-like structures reminiscent of prostatic acini. cDNA microarray analysis of the epithelial line demonstrated changes in gene expression consistent with epithelial differentiation. These genes may prove useful as markers for different prostate cell types. The cell lines provide a model system with which to study the process of prostatic epithelial differentiation and stromal-epithelial interactions. This may prove to be useful in the development of differentiation-targeted prostate cancer therapies.

The tumor metastasis suppressor gene Drg-1 down-regulates the expression of activating transcription factor 3 in prostate cancer

The tumor metastasis suppressor gene Drg-1 has been shown to suppress metastasis without affecting tumorigenicity in immunodeficient mouse models of prostate and colon cancer. Expression of Drg-1 has also been found to have a significant inverse correlation with metastasis or invasiveness in various types of human cancer. However, how Drg-1 exerts its metastasis suppressor function remains unknown. In the present study, to elucidate the mechanism of action of the Drg-1 gene, we did a microarray analysis and found that induction of Drg-1 significantly inhibited the expression of activating transcription factor (ATF) 3, a member of the ATF/cyclic AMP-responsive element binding protein family of transcription factors. We also showed that Drg-1 attenuated the endogenous level of ATF3 mRNA and protein in prostate cancer cells, whereas Drg-1 small interfering RNA up-regulated the ATF3 expression. Furthermore, Drg-1 suppressed the promoter activity of the ATF3 gene, indicating that Drg-1 regulates ATF3 expression at the transcriptional level. Our immunohistochemical analysis on prostate cancer specimens revealed that nuclear expression of ATF3 was inversely correlated to Drg-1 expression and positively correlated to metastases. Consistently, we have found that ATF3 overexpression promoted invasiveness of prostate tumor cells in vitro, whereas Drg-1 suppressed the invasive ability of these cells. More importantly, overexpression of ATF3 in prostate cancer cells significantly enhanced spontaneous lung metastasis of these cells without affecting primary tumorigenicity in a severe combined immunodeficient mouse model. Taken together, our results strongly suggest that Drg-1 suppresses metastasis of prostate tumor cells, at least in part, by inhibiting the invasive ability of the cells via down-regulation of the expression of the ATF3 gene.

The prognostic value of hemoglobin change after initiating androgen-deprivation therapy for newly diagnosed metastatic prostate cancer: A multivariate analysis of Southwest Oncology Group Study 8894

BACKGROUND

The objective of this study was to characterize changes in hemoglobin (HGB) levels after the initiation of androgen-deprivation therapy (ADT) in patients with previously untreated, metastatic prostate cancer who were enrolled in a large clinical trial.

METHODS

The multivariate associations between 3-month change in HGB and baseline characteristics were evaluated with a linear regression model. The associations between 3-month change in HGB level and time-to-event outcomes, including overall survival and progression-free survival, were evaluated by using proportional hazards regression models.

RESULTS

Quartiles of baseline HGB levels were < or =12.0 g/dL, from 12.1 to 13.7 g/dL, from 13.8 to 14.7 g/dL, and >14.7 g/dL. Overall, 3 months after initiating ADT, the mean HGB level declined 0.54 g/dL (standard deviation [SD], 1.68 g/dL); however, the mean HGB level increased by 0.99 g/dL (SD, 1.83 g/dL) in patients who had baseline HGB levels <12 g/dL and decreased 1.04 g/dL (SD, 1.28 g/dL) in patients who had baseline HGB levels > or =12 g/dL. After adjusting for potential confounders, including baseline HGB level, a decline in HGB after 3 months of ADT was associated independently with shorter survival (hazards ratio [HR], 1.10 per 1 g/dL decline; P = .0035) and shorter progression-free survival (HR, 1.08 per 1 g/dL decline; P = .013). An unexpected finding was that the effect of baseline HGB on overall and progression-free survival varied significantly by race.

CONCLUSIONS

In a sample of men with newly diagnosed, metastatic prostate cancer, a decline in HGB level after 3 months of ADT was associated with shorter survival and progression-free survival after adjusting for disease status and other baseline covariates. Although race alone was not a strong predictor of death or disease progression, the effect of the baseline HGB level on overall and progression-free survival varied significantly by race.

Prostatic tissue testosterone and dihydrotestosterone in African-American and white men

OBJECTIVES

To compare tissue androgen levels in the prostate gland of African-American and white men, looking for a possible explanation of the increased incidence of cancer in the former.

METHODS

The subjects were 25 African-American and 36 white men, undergoing prostate biopsy consecutively, in whom cancer was absent. Biopsy cores (18 gauge) from the peripheral zone were homogenized, subjected to ether extraction, and separation by chromatography. Tissue testosterone and dihydrotestosterone (DHT) levels were determined by radioimmunoassay.

RESULTS

The groups were matched for mean age (67.6 +/- 9.6 years), prostate volume (37.9 +/- 21.0 cm3), body mass index (28.2 +/- 4.2 kg/m2), and serum prostate-specific antigen (2.8 to 3.4 ng/mL) and testosterone (330 +/- 114 ng/dL) levels (P = NS for all measures). No significant difference in tissue testosterone (median 0.8 ng/g) or DHT (median 4.6 ng/g) was found between groups (P = NS). Furthermore, the tissue DHT/testosterone ratio (approximately 5) was not significantly different between the two groups (P = NS).

CONCLUSIONS

Prostatic tissue levels of testosterone and DHT were similar in African-American and white men; thus, the present data do not support a hypothesis of increased androgenic activity in African-American men. Because the ratio of DHT/testosterone in prostatic tissue was similar in the two groups, the possibility of increased 5-alpha-reductase activity in African-American men did not seem likely. Using needle biopsy specimens, both absolute values and the ratio of the androgens in prostatic tissue were similar to those found in previous studies using surgically excised glands. Thus, quick-frozen biopsy cores appear to be a valuable tissue source for evaluating the androgen status within the prostate.

Cellular differentiation determines the expression of the hypoxia-inducible protein NDRG1 in pancreatic cancer

N-myc downstream-regulated gene-1 (NDRG1) is a recently described hypoxia-inducible protein that is upregulated in various human cancers. Pancreatic ductal adenocarcinoma, called pancreatic cancer, is a highly aggressive cancer that is characterised by its avascular structure, which results in a severe hypoxic environment. In this study, we investigated whether NDRG1 is upregulated in these tumours, thus providing a novel marker for malignant cells in the pancreas. By immunohistochemistry, we observed that NDRG1 was highly expressed in well-differentiated cells of pancreatic cancer, whereas the poorly differentiated tumour cells were negative. In addition, hyperplastic islets and ducts of nonquiescent pancreatic tissue were positive. To further explore its selective expression in tumours, two well-established pancreatic cancer cell lines of unequal differentiation status were exposed to 2% oxygen. NDRG1 mRNA and protein were upregulated by hypoxia in the moderately differentiated Capan-1 cells; however, its levels remained unchanged in the poorly differentiated Panc-1 cell line. Taken together, our data suggest that NDRG1 will not serve as a reliable marker of tumour cells in the pancreas, but may serve as a marker of differentiation. Furthermore, we present the novel finding that cellular differentiation may be an important factor that determines the hypoxia-induced regulation of NDRG1.

Differences in clinicopathologic features of prostate cancer between black and white patients treated in the 1990s and 2000s

OBJECTIVES

We have previously reported on the disparity in the clinicopathologic features of prostate cancer between black and white patients at our equal-access institution during the 1990s. The goal of this study was to determine whether the worse clinicopathologic features of prostate cancer in black patients have persisted in the 2000s.

METHODS

We examined 362 men (224 black and 138 white) treated with radical prostatectomy at the Veterans Affairs Medical Center in New York. We compared the clinicopathologic variables between 227 patients treated during the 1990s (group 1) and 135 treated in the 2000s (group 2).

RESULTS

In group 1, black patients were significantly younger (P < 0.001) and had a greater prostate-specific antigen (PSA) level (P = 0.001), Gleason score (P = 0.005), and stage (P = 0.03) than white patients. In group 2, black patients continued to have significantly greater PSA levels (P = 0.04) and Gleason scores (P = 0.005) than white patients. Comparing only the black patients, those in group 2 had significantly lower PSA levels (P < 0.001) and stage (P = 0.03), but had worse Gleason scores (P = 0.03) than those in group 1. On multivariate analysis, black patients were significantly more likely to have a worse Gleason score (P = 0.005) than white patients.

CONCLUSIONS

Our data have demonstrated a narrowing of the differences in pathologic stage between black and white patients in the 2000s. However, black men have continued to have worse Gleason scores and greater PSA levels than white patients. These findings suggest that there may be different patterns of molecular alterations in black men that may contribute to the poor tumor differentiation. Additional research is underway to better characterize these underlying molecular mechanisms.

Loss of neutral endopeptidase and activation of protein kinase B (Akt) is associated with prostate cancer progression

BACKGROUND

Neutral endopeptidase (NEP) is a cell-surface peptidase that can regulate the activation of Akt kinase through catalytic-dependent and independent mechanisms. NEP expression is absent in approximately 50% of prostate cancers. The authors investigated whether NEP loss in vivo would result in Akt phosphorylation and potentially contribute to prostate cancer progression by examining the interaction of NEP, Akt, and phosphatase and tensin homolog (PTEN) in a prostate xenograft model and in clinical specimens from patients with prostate cancer.

METHODS

Using a tetracycline-repressible expression system to express NEP in a tumor animal xenograft model, the effects of NEP were tested on tumor growth, Akt phosphorylation, and PTEN expression. The clinical relevance of NEP, phosphorylated Akt, and PTEN protein expression also was investigated in 204 patients who had undergone radical prostatectomy.

RESULTS

The results indicated that the induction of NEP expression inhibited established xenograft tumor growth, diminished Akt phosphorylation, and increased PTEN protein levels. In humans, prostate cancers with complete loss of NEP expression were significantly more likely to express phosphorylated Akt (P = .02). Moreover, patients who had prostate cancers with concomitant loss of NEP and expression of phosphorylated Akt had an increased, independent risk of prostate-specific antigen (PSA) recurrence (P = .03). In the study cohort, loss of PTEN protein expression did not correlated significantly with phosphorylated Akt or with patients' clinical outcome.

CONCLUSIONS

The findings from this investigation demonstrated that NEP loss leads to Akt activation and contributes to the clinical progression of prostate cancer.

Racial Disparity of Epidermal Growth Factor Receptor Expression in Prostate Cancer

Purpose

The epidermal growth factor receptor (EGFR) plays a critical role in prostate cancer (PC) signal transduction and is the target of a novel class of anticancer agents. Despite recent reports of interethnic variation in response to EGFR inhibitors, limited information exists regarding differences in expression of EGFR in PC patients. This has therapeutic relevance because a better understanding of the molecular basis underlying the ethnic variability will help in the design of individualized treatment regimens using EGFR inhibitors.

Patients and Methods

We investigated EGFR expression in a well-characterized cohort of PC patients to determine the association between EGFR expression and race. Tumor tissues from 202 radical prostatectomies performed between 1990 and 2000 at the Veterans Administration Medical Center (New York, NY) were studied (142 African Americans, 60 whites; median age, 67 years; stage T2, n = 130; stage ≥ T3, n = 72; Gleason score < 7, n = 110; Gleason score ≥ 7, n = 92). Membrane-specific EGFR expression was evaluated immunohistochemically.

Results

EGFR overexpression, defined as complete membrane staining in more than 10% of tumor cells, was observed in 75 of 202 patients (37%). There was a significant association between EGFR overexpression and African American race (P = .0006), higher pretreatment prostate-specific antigen (PSA; P = .02), and stage (P = .02), but not Gleason score (P = .33). The association between African American race and EGFR overexpression remained significant in a multivariate model after controlling for grade, stage, and pretreatment PSA simultaneously (P = .003).

Conclusion

Our data demonstrate that race contributes significantly to variability of EGFR expression in prostate cancer. Racial background may have an impact on the design of clinical trials to test the efficacy of anti-EGFR agents.