Aminopeptidase N regulated by zinc in human prostate participates in tumor cell invasion

Identification of markers of prostate cancer progression using candidate gene expression

BACKGROUND

Metastatic prostate cancer (PCa) has no curative treatment options. Some forms of PCa are indolent and slow growing, while others metastasise quickly and may prove fatal within a very short time. The basis of this variable prognosis is poorly understood, despite considerable research. The aim of this study was to identify markers associated with the progression of PCa.

METHODS

Artificial neuronal network analysis combined with data from literature and previous work produced a panel of putative PCa progression markers, which were used in a transcriptomic analysis of 29 radical prostatectomy samples and correlated with clinical outcome.

RESULTS

Statistical analysis yielded seven putative markers of PCa progression, ANPEP, ABL1, PSCA, EFNA1, HSPB1, INMT and TRIP13. Two data transformation methods were utilised with only markers that were significant in both selected for further analysis. ANPEP and EFNA1 were significantly correlated with Gleason score. Models of progression co-utilising markers ANPEP and ABL1 or ANPEP and PSCA had the ability to correctly predict indolent or aggressive disease, based on Gleason score, in 89.7% and 86.2% of cases, respectively. Another model of TRIP13 expression in combination with preoperative PSA level and Gleason score was able to correctly predict recurrence in 85.7% of cases.

CONCLUSION

This proof of principle study demonstrates a novel association of carcinogenic and tumourigenic gene expression with PCa stage and prognosis.

Decreased zinc and downregulation of ZIP3 zinc uptake transporter in the development of pancreatic adenocarcinoma

Pancreatic adenocarcinoma is an untreatable deadly cancer. The factors involved in its early development remain unknown; which contributes to the absence of biomarkers for early detection of malignancy or at-risk subjects, and the absence of efficacious therapeutic agents. Because zinc changes are implicated in some cancers, we determined if it might be involved in the development of pancreatic adenocarcinoma. With in situ Dithizone and Zinquin staining of normal pancreas and adenocarcinoma tissue sections, we show for the first time, a consistent major loss of zinc in ductal and acinar epithelium in adenocarcinoma compared to the normal epithelium. This decrease in zinc is evident in well-differentiated through poorly-differentiated stages of malignancy. Immunohistochemistry identified ZIP3 as the basilar membrane zinc uptake transporter in normal ductal/acinar epithelium; and that the transporter is absent in adenocarcinoma. In situ Rt-PCR revealed that ZIP3 gene expression is silenced in adenocarcinoma. The ZIP3 down regulation accompanied the loss of zinc in early and progressing malignancy. RREB1 transcription factor was down regulated along with ZIP3; and might be involved in the silencing of ZIP3 expression. Zinc treatment was cytotoxic to malignant Panc1 cells. The combination of concurrent zinc, ZIP3, and RREB-1 changes represent early events in the development of adenocarcinoma; and suggest that zinc might be a tumor suppressor of pancreatic cancer. This report provides the clinical foundation for further mechanistic studies that will provide important insight into pancreatic carcinogenesis, and can lead to the development of effective early biomarkers and effective therapeutic agents for pancreatic cancer.

Activity screening and structure-activity relationship of the hit compounds targeting APN/CD13

Aminopeptidase N (APN) plays an important role in tumor progression, which participates in the progress such as proliferation, attachment, angiogenesis, and tumor invasion. All of this makes APN as a good chemical therapeutic anti‐tumor target. In this study, a series of chemically synthesized APN inhibitors were tested for the anti‐tumor activities, and three most effective compounds were chosen according to the MTT assay. Then, the enzyme inhibitory, anti‐tumor, specificity, angiogenesis, and invasion were determined to evaluate the activity of these three compounds. All compounds can markedly inhibit the enzyme activity of APN, angiogenesis of endothelial cells, and the invasion of ES‐2 cells. And it had little effect on the viability of K562 which express low level of APN. This data indicated that the tested compounds were APN hit compounds. We also did kinetic assay to determine the inhibition constant and constructed a three‐dimensional quantitative structure–activity relationship model to analyze the structure–activity relationship to direct the further design of novel APN inhibitors as anti‐tumor agents. These data demonstrate that the tested compounds can be developed as novel candidates of anticancer agent.

Aminopeptidase N (EC 3.4.11.2) inhibitors (2006 - 2010): a patent review

INTRODUCTION

Aminopeptidase N (APN/CD13) acts as an exopeptidase and has been studied for decades. In recent years, it has been seen not only as a tumor-related target but also as a potential functional protein in various other physiological or pathological processes, such as analgesia, virus infection and inflammation.

AREAS COVERED

In this review, APN inhibitors in the patents publicized during 2006 - 2010 are introduced. Readers will gain information on the patent inhibitors, including chemical structures, original sources or synthetic methods, biological assays and application potential.

EXPERT OPINION

It is difficult to identify compounds that interact with the function not relevant with peptide-hydrolysis of APN in the enzyme activity assay, and such compounds have not been reported in the patents during the past 5 years. The progress of protein-small molecule interaction detecting means, such as surface plasmon resonance, will possibly help develop such compounds for the treatment of relevant diseases or new molecular probes in mechanism investigation.

Heterologous expression and purification of Vibrio proteolyticus (Aeromonas proteolytica) aminopeptidase: a rapid protocol

Metalloaminopeptidases (mAPs) are enzymes that are involved in HIV infectivity, tumor growth and metastasis, angiogenesis, and bacterial infection. Investigation of structure-function relationships in mAPs is a prerequisite to rational design of anti-mAP chemotherapeutics. The most intensively studied member of the biomedically important dinuclear mAPs is the prototypical secreted Vibrio proteolyticus di-zinc aminopeptidase (VpAP). The wild-type enzyme is readily purified from the supernatant of cultures of V. proteolyticus, but recombinant variants require expression in Escherichia coli. A greatly improved system for the purification of recombinant VpAP is described. A VpAP-(His)(6) polypeptide, containing an N-terminal propeptide, and a C-terminal (His)(6) adduct, was purified by metal ion affinity chromatography from the supernatant of cultures of E. coli. This single step replaced the sequence of (NH(4))(2)SO(4) fractionation, and anion-exchange and hydrophobic interaction chromatographic separations of earlier methods. Traditionally, recombinant VpAP proenzyme has been treated with proteinase K and with heat (70 degrees C), to remove the N- and C-terminal regions, and yield the mature active enzyme. This method is unsuitable for VpAP variants that are unstable towards these treatments. In the new method, the hitherto noted, but not fully appreciated, ability of VpAP to autocatalyze the hydrolysis of the N-terminal propeptide and C-terminal regions was exploited; extensive dialysis of the highly purified VpAP-(His)(6) full-length polypeptide yielded the mature active protein without recourse to proteinase K or heat treatment. Purification of variants that have previously defied isolation as mature forms of the protein was thus carried out.

Reduced activity of CD13/aminopeptidase N (APN) in aggressive meningiomas is associated with increased levels of SPARC

Meningiomas are the second most common brain tumors in adults, and meningiomas exhibit a tendency to invade adjacent structures. Compared with high-grade gliomas, little is known about the molecular changes that potentially underlie the invasive behavior of meningiomas. In this study, we examined the expression and function of the membrane alanyl-aminopeptidase [mAAP, aminopeptidase N (APN), CD13, EC3.4.11.2] zinc-dependent ectopeptidase in meningiomas and meningioma cell lines, based on its prior association with tumor invasion in colorectal and renal carcinomas. We found a significant reduction of APNmRNA and protein expression, as well as enzymatic activity, in high-grade meningiomas. While meningioma tumor cell proliferation was not affected by either pharmacologic APN inhibition or siRNA-mediated APN silencing, APN pharmacologic and siRNA knockdown significantly reduced meningioma cell invasion in vitro. Next, we employed pathway-specific cDNA microarray analyses to identify extracellular matrix and adhesion molecules regulated by APN, and found that APN-siRNA knockdown substantially increased the expression of secreted protein, acidic and rich in cysteine (SPARC)/osteonectin. Finally, we demonstrated that SPARC, which has been previously associated with meningioma invasiveness, was increased in aggressive meningiomas. Collectively, these results suggest that APN expression and enzymatic function is reduced in aggressive meningiomas, and that alterations in the balance between APN and SPARC might favor meningioma invasion.

Vitamin and mineral use and risk of prostate cancer: the case-control surveillance study

BACKGROUND

Many studies have evaluated the association between vitamin and mineral supplement use and the risk of prostate cancer, with inconclusive results.

METHODS

The authors examined the relation of use of multivitamins as well as several single vitamin and mineral supplements to the risk of prostate cancer risk among 1,706 prostate cancer cases and 2,404 matched controls using data from the hospital-based case-control surveillance study conducted in the United States. Odds ratios (OR) and 95% confidence intervals (CI) for risk of prostate cancer were estimated using conditional logistic regression model.

RESULTS

For use of multivitamins that did not contain zinc, the multivariable odds ratios of prostate cancer were 0.6 for 1-4 years, 0.8 for 5-9 years, and 1.2 for 10 years or more, respectively (p for trend = 0.70). Men who used zinc for ten years or more, either in a multivitamin or as a supplement, had an approximately two-fold (OR = 1.9, 95% CI: 1.0, 3.6) increased risk of prostate cancer. Vitamin E, beta-carotene, folate, and selenium use were not significantly associated with increased risk of prostate cancer.

CONCLUSION

The finding that long-term zinc intake from multivitamins or single supplements was associated with a doubling in risk of prostate cancer adds to the growing evidence for an unfavorable effect of zinc on prostate cancer carcinogenesis.

Overexpression of the zinc uptake transporter hZIP1 inhibits nuclear factor-kappaB and reduces the malignant potential of prostate cancer cells in vitro and in vivo

PURPOSE

Intracellular zinc levels and expression of the zinc uptake transporter, hZIP1, are markedly down-regulated in prostate adenocarcinomatous tissue compared with normal prostate tissue. Our previous studies have shown that zinc inhibits nuclear factor-kappaB (NF-kappaB) activity and reduces the malignant potential of prostate cancer cells in vitro. In this study, we investigate the functional effect of hZIP1 overexpression on NF-kappaB activity and tumorigenic potential in human prostate cancer cells in vitro and in vivo.

EXPERIMENTAL DESIGN

NF-kappaB activity in PC-3 prostate cancer cells was examined by Western blotting and luciferase assay. ELISA was used to examine the expression of tumorigenic cytokines. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, adhesion, and invasiveness assays were used to assess the malignant potential of tumor cells. The effect of hZIP1 overexpression on prostate tumor progression in vivo was assessed using a xenograft model.

RESULTS

Overexpression of the hZIP1 transporter in PC-3 cells results in significant inhibition of NF-kappaB activity in the presence of physiologic levels of zinc. NF-kappaB inhibition coincides with a reduction in expression of several NF-kappaB controlled prometastatic and antiapoptotic factors as well as sensitization of the cells to etoposide and tumor necrosis factor-mediated apoptosis-inducing ligand-mediated cell death. Moreover, overexpression of the hZIP1 transporter induces regression of prostate tumor growth in a xenograft model.

CONCLUSIONS

Our results show that hZIP1 overexpression has a functional effect on the malignant potential of prostate cancer cells via inhibition of NF-kappaB-dependent pathways and support the concept that hZIP1 may function as a tumor suppressor gene in prostate cancer.

Depletion of intracellular zinc increases expression of tumorigenic cytokines VEGF, IL-6 and IL-8 in prostate cancer cells via NF-kappaB-dependent pathway

BACKGROUND

Zinc accumulation diminishes early in the course of prostate malignancy and continues to decline during progression toward hormone-independent growth. In contrast, constitutive levels of NF-kappaB activity increase during progression of prostate cells toward greater tumorigenic potential. We have reported previously that physiological levels of zinc suppress NF-kappaB activity in prostate cancer cells and reduce expression of pro-angiogenic and pro-metastatic cytokines VEGF, IL-6, IL-8, and MMP-9 associated with negative prognostic features in prostate cancer.

METHODS

Intracellular zinc levels were examined by atomic absorption spectroscopy. NF-kappaB activity was examined by TransAm and Luciferase reporter assays, and Western blot analysis of p50 nuclear translocation. VEGF, IL-6 and IL-8 levels were assessed by ELISA.

RESULTS

Selective zinc deficiency induced by the membrane-permeable zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)-ethylenediamine (TPEN) increases activation of NF-kappaB and up-regulates expression of the NF-kappaB controlled pro-angiogenic and pro-metastatic cytokines VEGF, IL-6 and IL-8 in androgen-independent PC-3 and DU-145 prostate cancer cells. Pre-incubation with I kappaB alpha dominant mutant adenovirus efficiently blocks expression of these cytokines in zinc deficient cells indicating that the observed effects are NF-kappaB dependent.

CONCLUSIONS

Our findings suggest that zinc deficiency may contribute to the tumor progression via augmented expression of the NF-kappaB-dependent pro-tumorigenic cytokines.

Aminopeptidase N (APN)/CD13 inhibitor, Ubenimex, enhances radiation sensitivity in human cervical cancer

Background

Radiotherapy can be used to treat all stages of cervical cancer. For improving local control via radiotherapy, it is important to use additional antitumor agents. Aminopeptidase N (APN)/CD13, a 150-kDa metalloproteinase, is a multifunctional cell surface aminopeptidase with ubiquitous expression. Recent studies have suggested that APN/CD13 plays an important role in tumor progression in several human malignancies.

Methods

We investigated whether the suppression of APN/CD13 using Ubenimex, an inhibitor of APN/CD13 activity, may affect tumor radiosensitivity in cervical cancer cells both in vitro and in vivo. Cell surface APN/CD13 activity in HeLa cells was calculated using alanine-p-nitroanilido as a substrate. For colony formation assays, single-dose radiation and/or Ubenimex were administered to each dish of HeLa cells, and these dishes were cultured for 14 days. Molecular changes of apoptosis were determined by Western blot. Apoptosis was evaluated by Annexin-V PI staining (flow cytometry analysis) and the Tunel method. Moreover, we investigated the effect of combining Ubenimex and low-dose radiation on tumor growth using nude mice.

Results

We demonstrated that Ubenimex enhanced the effectiveness of radiotherapy, acting as a radiosensitizer both in vitro and in vivo. In colony formation assays, a significant decline in clonogenic survival was observed in Ubenimex-treated cells. Mice treated with a combination of radiation and Ubenimex showed a significant prolongation of the tumor-doubling time compared with the control, Ubenimex, or radiation-alone groups. We also showed that ubenimex enhanced radiation-induced apoptosis in vitro and in vivo.

Conclusion

Although further studies are needed, this report suggests that Ubeniemx acts as a radiosensitizer in cervical cancer treatment, and that the inhibition of APN/CD13 activity may represent a new approach for improving the therapeutic efficacy of radiotherapy for uterine cervical cancer.

Clinical significance of aminopeptidase N in non-small cell lung cancer

PURPOSE

The aim of our study is to investigate the mechanism of metastasis, to detect novel metastasis-associated molecules, and to evaluate the molecules from the point of view of clinical application. A monoclonal antibody MH8-11, which we established, recognizes a glycoprotein that is identical to aminopeptidase N (APN/CD13). APN/CD13 degrades the extracellular matrix, while it is also involved in cell motility and improves angiogenesis.

EXPERIMENTAL DESIGN

We investigated the expression of APN/CD13 in 194 cases of non-small cell lung cancer (NSCLC) by immunohistochemical analyses and reverse transcription-PCR assay to determine the significance of this prognostic factor; 95 tumors were stage I, 36 were stage II, 39 were stage IIIA, and 24 were stage IIIB. Moreover, we investigated that the relationship between the expression of APN/CD13 and angiogenesis and prognosis for patients with NSCLC.

RESULTS

We found a correlation between the expression of APN/CD13 and angiogenesis (r = 0.659; P < 0.0001). In the 194 patients with NSCLC, we found 68 patients to be APN/CD13+ and 126 patients to be APN/CD13-. The 5-year survival rate in patients with APN/CD13+ tumors was significantly lower than in those whose tumors had negative APN/CD13 (48.3% versus 67.1%; P = 0.0001).

CONCLUSION

Our data suggest the expression of APN/CD13 for patients with NSCLC to be associated with a poor prognosis and angiogenesis. This is the first study to show the relationship between the expression of APN/CD13 and the prognosis of patients with NSCLC. The inhibition of APN/CD13 may be an effective new molecular target therapy for patients with NSCLC.

Aminopeptidase N in arterial hypertension

Aminopeptidase N (APN) or CD13 is a conserved type II integral membrane zinc-dependent metalloprotease in the M1 family of ectoenzymes. APN is abundant in the kidneys and central nervous system. Identified substrates include Angiotensin III (Ang III); neuropeptides, including enkephalins and endorphins; and homones, including kallidan and somatostatin. It is developmentally expressed, a myelomonocytic marker for leukemias, and a receptor for coronovirus. There is evolving support for APN in the regulation of arterial blood pressure and the pathogenesis of hypertension. In rodent strains, intracerebraventricular (i.c.v.) infusions of APN reduces, while inhibitors of APN activity have a pressor effect on blood pressure. Dysregulation of central APN has been linked to the pathogenesis of hypertension in the spontaneously hypertensive rat. There is evidence that renal tubule APN inhibits Na flux and plays a mechanistic role in salt-adaptation. A functional polymorphism of the ANP gene has been identified in the Dahl salt-sensitive rat. Signaling by APN impacting on blood pressure is likely mediated by regulation of the metabolism of Ang III to Ang IV. Whether APN regulates arterial blood pressure in humans or is a therapeutic target for hypertension are subjects for future exploration.

NMR-based metabolomics approach to target biomarkers for human prostate cancer

In the era of genomics and proteomics, metabolomics offers a unique way to probe the underlying biochemistry of malignant transformations. In the context of oncological metabolomics, the study of the global variation of metabolites involved in the development and progression of cancers, few existing techniques offer as much potential to discover biomarkers as nuclear magnetic resonance techniques. The most fundamental magnetic resonance methodologies with regard to human prostate cancer are magnetic resonance spectroscopy and magnetic resonance spectroscopic imaging. Recent in vivo explorations have examined crucial metabolites that may indicate cancerous lesions and have the potential to direct treatment; while ex vivo studies of prostatic fluids and tissues have defined novel diagnostic parameters and indicated that magnetic resonance methodologies will be paramount in future prostate cancer management.

Trace elemental analysis of normal, benign hypertrophic and cancerous tissues of the prostate gland using the particle-induced X-ray emission technique

Trace elemental analysis was carried out in the tissue samples of normal, benign hypertrophic and carcinoma prostate using the particle-induced X-ray emission technique. A proton beam of 3 MeV energy was used to excite the samples. The elements Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, and Br were identified and their concentrations were estimated. It is observed that in benign tissues the concentrations of Cl, K, Zn, and Se are lower (P<0.05) and those of Cr, Fe, Ni, and Cu are higher (P<0.05 ) than in normal tissues. The concentrations of K, Ca, Zn, Se, and Br are lower (P<0.01) and those of Ti, Cr, Mn, Fe, Ni, and Cu are significantly higher (P<0.0005) in cancerous tissues than in normal tissues. Free radicals generated by elevated levels of Cr, Fe, Ni, and Cu possibly initiate and promote prostate cancer by oxidative DNA damage. The excess Cu levels in cancerous tissues support the fact that Cu promotes cancer through angiogenesis. The higher levels of Fe observed in cancerous tissues might be a consequence of tumor growth through angiogenesis. Significantly higher levels of Ni and Cr observed in carcinoma tissues support the well-established role of Ni and Cr as carcinogens. It is likely that the observed low levels of Zn and Se in cancerous tissues lead to the development of prostate cancer owing to a decrease in antioxidative defense capacity and impaired immune function of cells and also suggest that the inability to retain high levels of Zn and Se may possibly be an important factor in the development and progression of malignant prostate cells. In order to substantiate the observed elevated or deficient levels of trace elements in initiating, promoting, and inhibiting prostate cancer, several cellular and molecular studies are required.

hZip2 and hZip3 zinc transporters are down regulated in human prostate adenocarcinomatous glands

BACKGROUND

The normal human prostate glandular epithelium has the unique function of accumulating high levels of zinc. In prostate cancer this capability is lost as an early event in the development of the malignant cells. The mechanism and factors responsible for the ability of the normal epithelial cells to accumulate zinc and the loss of this capability in the malignant cells need to be identified. We previously reported that Zip1 is an important zinc uptake transporter in prostate cells and is down regulated in the malignant cells in situ along with the depletion of zinc levels. In this report we investigated the expression of two other Zip family zinc transporters, Zip2 and Zip3 in malignant versus nonmalignant (normal and BPH) glands. Zip2 and Zip3 relative protein levels were determined by immunohistochemistry analysis of human prostate tissue sections.

RESULTS

Normal and BPH glandular epithelium consistently exhibited the strong presence of both Zip 2 and Zip3; whereas both transporters consistently were essentially non-detectable in the malignant glands. This represents the first report of the expression of Zip3 in human prostate tissue; and more importantly, reveals that ZiP2 and Zip3 are down regulated in malignant cells in situ as we also had demonstrated for Zip1. Zip2 and Zip3 transporter proteins were localized predominantly at the apical cell membrane, which is in contrast to the Zip1 localization at the basolateral membrane. Zip2 and Zip3 seemingly are associated with the re-uptake of zinc from prostatic fluid.

CONCLUSION

These results coupled with previous reports implicate Zip2 and Zip3 along with Zip1 as important zinc uptake transporters involved in the unique ability of prostate cells to accumulate high cellular zinc levels. Zip1 is important for the extraction of zinc from circulation as the primary source of cellular zinc. Zip 2 and Zip3 appear to be important for retention of the zinc in the cellular compartment. The down regulation of all three transporters in the malignant cells is consistent with the loss of zinc accumulation in these cells. Since zinc imposes tumor suppressor effects, the silencing of the gene expression for these transporters is a required event for the manifestation of the malignant activities of the neoplastic cells. This now provides new insights into the genetic/molecular events associated with the development of prostate cancer; and supports our concept of Zip1, and now Zip2 and Zip3, as tumor suppressor genes and zinc as a tumor suppressor agent.

Experimental evidence for a metallohydrolase mechanism in which the nucleophile is not delivered by a metal ion: EPR spectrokinetic and structural studies of aminopeptidase from Vibrio proteolyticus

Metallohydrolases catalyse some of the most important reactions in biology and are targets for numerous chemotherapeutic agents designed to combat bacterial infectivity, antibiotic resistance, HIV infectivity, tumour growth, angiogenesis and immune disorders. Rational design of inhibitors of these enzymes with chemotherapeutic potential relies on detailed knowledge of the catalytic mechanism. The roles of the catalytic transition ions in these enzymes have long been assumed to include the activation and delivery of a nucleophilic hydroxy moiety. In the present study, catalytic intermediates in the hydrolysis of L-leucyl-L-leucyl-L-leucine by Vibrio proteolyticus aminopeptidase were characterized in spectrokinetic and structural studies. Rapid-freeze-quench EPR studies of reaction products of L-leucyl-L-leucyl-L-leucine and Co(II)-substituted aminopeptidase, and comparison of the EPR data with those from structurally characterized complexes of aminopeptidase with inhibitors, indicated the formation of a catalytically competent post-Michaelis pre-transition state intermediate with a structure analogous to that of the inhibited complex with bestatin. The X-ray crystal structure of an aminopeptidase-L-leucyl-L-leucyl-L-leucine complex was also analogous to that of the bestatin complex. In these structures, no water/hydroxy group was observed bound to the essential metal ion. However, a water/hydroxy group was clearly identified that was bound to the metal-ligating oxygen atom of Glu152. This water/hydroxy group is proposed as a candidate for the active nucleophile in a novel metallohydrolase mechanism that shares features of the catalytic mechanisms of aspartic proteases and of B2 metallo-beta-lactamases. Preliminary studies on site-directed variants are consistent with the proposal. Other features of the structure suggest roles for the dinuclear centre in geometrically and electrophilically activating the substrate.

Zinc as an anti-tumor agent in prostate cancer and in other cancers

Human prostate glandular epithelial cells have the unique capability of accumulating high levels of zinc. This is essential to inhibit m-aconitase activity so that citrate can accumulate for secretion into prostatic fluid, which is a major function of the prostate gland. As a result, the Krebs cycle is truncated with the consequence of the lost ATP production that would result from citrate oxidation. The cellular accumulation of zinc also inhibits mitochondrial terminal oxidation and respiration. In addition to these metabolic effects, zinc accumulation exhibits anti-proliferative effects via its induction of mitochondrial apoptogenesis. Zinc accumulation also inhibits the invasive/migration activities in malignant prostate cells. The anti-proliferative effects and the effects on invasion and migration occur through zinc activation of specific intracellular signaling pathways. Consequently, these effects impose anti-tumor actions by zinc. The ability of prostate cells to accumulate zinc is due to the expression and activity of the zinc uptake transporter, ZIP1. To avoid the anti-tumor effects of zinc, in prostate cancer the malignant prostate cells exhibit a silencing of ZIP1 gene expression accompanied by a depletion of cellular zinc. Therefore we regard ZIP1 as a tumor suppressor gene in prostate cancer. In addition to prostate cells, similar tumor suppressor effects of zinc have been identified in several other types of tumors.

Differential expression of CD10 in prostate cancer and its clinical implication

BACKGROUND

CD10 is a transmembrane metallo-endopeptidase that cleaves and inactivates a variety of peptide growth factors. Loss of CD10 expression is a common, early event in human prostate cancer; however, CD10 positive cancer cells frequently appear in lymph node metastasis. We hypothesize that prostate tumors expressing high levels of CD10 have a more aggressive biology with an early propensity towards lymph node metastasis.

METHODS

Eighty-seven patients, 53 with and 34 without pathologically organ confined prostate cancer at the time of radical prostatectomy (RP), were used for the study. Fourteen patients with lymph node metastasis found at the time of surgery were identified and included in this study. Serial sections from available frozen tumor specimens in OCT were processed for CD10 immunohistochemistry. Cancer glands were graded for the presence and intensity of CD10 staining, and overall percentage of glands staining positive was estimated. Clinical characteristics including pre- and post-operative PSA and Gleason score were obtained. A similar study as a control for the statistical analysis was performed with CD13 staining. For statistical analysis, strong staining was defined as > 20% positivity based on the observed maximum separation of the cumulative distributions.

RESULTS

CD10 expression significantly correlated with Gleason grade, tumor stage, and with pre-operative serum PSA. Seventy percent of RP specimens from patients with node metastasis showed strong staining for CD10, compared to 30% in the entire cohort (OR = 3.4, 95% CI: 1.08-10.75, P = 0.019). Increased staining for CD10 was associated with PSA recurrence after RP. CD13 staining did not correlate significantly with any of these same clinical parameters.

CONCLUSION

These results suggest that the expression of CD10 by prostate cancer corresponds to a more aggressive phenotype with a higher malignant potential, described histologically by the Gleason score. CD10 offers potential clinical utility for stratifying prostate cancer to predict biological behavior of the tumor.

Involvement of aminopeptidase N in enhanced chemosensitivity to paclitaxel in ovarian carcinoma in vitro and in vivo

Aminopeptidase N (APN/CD13), a 150-kDa metalloproteinase, is a multifunctional cell surface aminopeptidase with ubiquitous expression. Recent studies have suggested that APN/CD13 plays an important role in tumor progression in several human malignancies. In the current study, we investigated the role of APN/CD13 in paclitaxel (PAC)-resistance of ovarian carcinoma (OVCA) cells. We first examined the correlation between APN/CD13 expression and IC50 values of PAC in a variety of OVCA cell lines. Next we investigated whether suppression of APN/CD13 using bestatin, an inhibitor of APN/CD13 activity or the siRNA technique influenced PAC-sensitivity in ES-2 cells, which highly express APN/CD13. Moreover, we investigated the effect of bestatin on peritoneal metastasis using nude mice. We found a negative correlation between APN/CD13 expression and chemosensitivity to PAC in various carcinoma cell lines. Subsequently, we found a significant increase in PAC-sensitivity of APN/CD13 expressing OVCA cells by suppression of this enzyme, using the addition of bestatin or the siRNA technique. Furthermore, in a peritoneal metastasis model using nude mice, combination treatment with PAC and bestatin caused a synergistic increase of survival time compared with PAC alone treatment. (mean survival time: 37.7 +/- 7.0 s and 27.1 +/- 6.6 days, respectively). The present findings showed that APN/CD13 may be involved in decreased sensitivity to PAC in OVCA cells and that the mechanism of this effect involves its enzyme activity at least in part. APN/CD13 may be a therapeutic target for the treatment of OVCA in combination with chemotherapy.

Synergistic inhibition of the enzymatic activity of aminopeptidase N by divalent metal ion chelators

Membranes of HEK293 cells that were transfected with human aminopeptidase N (AP-N, CD13, EC 3.4.11.2) and purified soluble porcine kidney AP-N were used to study inhibition of its enzyme activity by divalent cation chelators. Whereas pre-incubation for 10 min with ethylenediaminetetraacetic acid (EDTA), did not or only weakly affected the enzyme activity, the bidentate chelator 1,10-phenanthroline produced a complete and concentration-dependent inhibition of AP-N. The corresponding curves had Hill slopes of 2.50 +/- 0.23 and 2.73 +/- 0.01 for soluble and recombinant AP-N respectively. EDTA increased the potency of 1,10-phenanthroline till a limit, at which Hill slopes became close to unity. In the absence of EDTA, the inhibition by 1,10-phenanthroline was only weakly affected by the substrate concentration. On the other hand, competition between 1,10-phenanthroline and the substrate took place in the presence of EDTA. Similar findings were reported for the related metallopeptidase cystinyl aminopeptidase and point towards a model in which 1,10-phenanthroline inhibit enzyme activity by decreasing the free Zn2+ concentration. Moreover, EDTA is capable of removing a modulatory ion from an allosteric site at the enzyme, facilitating the direct interaction between 1,10-phenanthroline and the catalytic Zn2+. Compatible with this model, Ca2+ may bind to this allosteric site resulting in the potentiation of Zn2+-mediated re-activation of the enzyme activity in the presence of EDTA and 1,10-phenanthroline.

CD13/Aminopeptidase N overexpression by basic fibroblast growth factor mediates enhanced invasiveness of 1F6 human melanoma cells

CD13/Aminopeptidase N (CD13) is known to play an important role in tumour cell invasion. We examined whether basic fibroblast growth factor (bFGF) is involved in the regulation of CD13 expression in human melanoma cells. 1F6 human melanoma cells were stably transfected with constructs encoding either the 18 kDa (18kD) or all (ALL) bFGF isoform proteins. We observed highly increased CD13 mRNA and protein expression in the 1F6 clones regardless of the overexpression of either the 18kD or all isoform proteins. Neutral aminopeptidase activity was increased five-fold and could be inhibited by bestatin and the CD13-neutralising antibody WM15. The enhanced invasion through Matrigel, but not migration in a wound assay, was efficiently abrogated by both bestatin and WM15. Upregulation of CD13 expression was the result of increased epithelial and myeloid promoter activity up to 4.5-fold in 1F6-18kD and 1F6-ALL clones. Interestingly, in a panel of human melanoma cell lines, a significant correlation (r²=0.883, P<0.05) between bFGF and CD13 mRNA and protein expression was detected. High bFGF and CD13 expression were clearly related with an aggressive phenotype. Taken together, our data indicate that high bFGF expression upregulates CD13 expression in human melanoma cells by activating both the myeloid and the epithelial CD13 promoter. In addition, we show that high bFGF and CD13 expression results in enhanced invasive capacity and metastatic behaviour of human melanoma cells.

Incadronate inhibits aminopeptidase N expression in prostatic PC-3 cells

Bone metastasis is an important cause of morbidity in advanced prostate cancer. Bisphosphonates are widely used for the treatment and prevention of osteoporosis, but recently have been observed to be effective in controlling prostate cancer metastasis. Since aminopeptidase N (AP-N) is known to be involved in the metastasis of prostate cancer, we investigated the effect of bisphosphonate on AP-N expression. Incadronate induced inhibition of AP-N mRNA and protein expression in PC-3 cells. The inhibitory effect of AP-N mRNA expression was also observed in the cells treated with pravastatin and other nitrogen-containing bisphosphonates, which inhibit the key enzyme in the isoprenoid biosynthesis pathway. The decrease of AP-N mRNA expression induced by incadronate was inhibited by co-incubation with geranylgeranyl diphosphate (GGPP). Moreover, GGTI-286 treatment also resulted in reduced AP-N mRNA expression. The translocation of small G protein Rap1 from the cytosol to the membrane was inhibited by incadronate and pravastatin, respectively. These above results indicate that the decrease in AP-N expression elicited by bisphosphonate is related to the inhibition of the mevalonate pathway.

Zinc and prostate cancer: a critical scientific, medical, and public interest issue (United States)

The role of zinc in the development and progression of prostate malignancy and its potential application in the prevention and treatment of prostate cancer (PCa) are contemporary critical issues for the medical/scientific community and the public-at-large. The overwhelming clinical and experimental evidence provides a compelling rational basis for the expectation and concept that prostate zinc accumulation is an important factor in the development and progression of prostate malignancy; and that zinc could be efficacious in the prevention and treatment of PCa. In contrast, various epidemiologic studies have produced divergent and conflicting results regarding the efficacy of dietary and supplemental zinc against PCa. Before reaching any definitive conclusions regarding this complex issue, one should have a complete understanding of the clinical and experimental evidence associated with the involvement of zinc in the normal and malignant prostate. Also, an understanding of interacting effects of confounding factors on the absorption, assimilation, and bioavailability of supplemental dietary zinc is important. The purpose of this review is to present the current state of the clinical and experimental information regarding zinc relationships in the normal prostate and in the pathogenesis PCa. The evidence in support of a potential beneficial effect of zinc supplement versus potential harmful effects on PCa is assessed. A discussion of the divergent results of the epidemiologic studies is presented along with a description of important factors and conditions that impact or mask the effects of dietary zinc on PCa development and progression. We also hope to bring more attention to the medical and research community of the critical need for concerted clinical and basic research regarding zinc and PCa, for the development of appropriate human prostate models to investigate these relationships, for further appropriately designed epidemiologic studies, and for future well-controlled clinical trials.

Aminopeptidase-N/CD13 (EC 3.4.11.2) inhibitors: chemistry, biological evaluations, and therapeutic prospects

Aminopeptidase N (APN)/CD13 (EC 3.4.11.2) is a transmembrane protease present in a wide variety of human tissues and cell types (endothelial, epithelial, fibroblast, leukocyte). APN/CD13 expression is dysregulated in inflammatory diseases and in cancers (solid and hematologic tumors). APN/CD13 serves as a receptor for coronaviruses. Natural and synthetic inhibitors of APN activity have been characterized. These inhibitors have revealed that APN is able to modulate bioactive peptide responses (pain management, vasopressin release) and to influence immune functions and major biological events (cell proliferation, secretion, invasion, angiogenesis). Therefore, inhibition of APN/CD13 may lead to the development of anti-cancer and anti-inflammatory drugs. This review provides an update on the biological and pharmacological profiles of known natural and synthetic APN inhibitors. Current status on their potential use as therapeutic agents is discussed with regard to toxicity and specificity.

CD13 (aminopeptidase N) can associate with tumor-associated antigen L6 and enhance the motility of human lung cancer cells

Cancer metastasis is a multiple-step process that involves the regulated interaction of diverse cellular proteins. We recently reported that the expression of tumor-associated antigen L6 (TAL6) promoted the invasiveness of lung cancer cells and was inversely correlated with disease-free survival of squamous lung carcinoma patients. We now report that CD13 (aminopeptidase N) can associate with TAL6 and can enhance cancer cell migration. CD13 was shown by coimmunoprecipitation to associate in vitro with TAL6 on several cancer cell lines and to associate in vivo by antibody-mediated copatching immunofluorescence. CD13 was selectively expressed on highly invasive CL1-5 lung cancer cells as compared to poorly invasive CL1-0 lung cancer cells. The role of CD13 aminopeptidase activity in regulating cell motility was investigated with chemical inhibitors, specific antibodies and a catalytically inactive CD13 protein. Inhibition of CD13 aminopeptidase activity by nontoxic concentrations of leuhistin modestly decreased the migration of CL1-5 cells. In contrast, binding of CD13 by specific antibodies significantly reduced both the migration and the invasion of CL1-5 cells. Poorly invasive CL1-0 cells that stably expressed CD13 displayed significantly (p < or = 0.0005) enhanced cell migration (300% of control). Expression of an enzymatically inactive CD13 mutant on CL1-0 cells also significantly (p < or = 0.0005) enhanced cell migration (200% of control). Our results show that TAL6 and CD13 can form a complex on lung cancer cells, that these molecules can modulate cell migration and invasion and that the influence of CD13 on cell motility did not strictly depend on its aminopeptidase activity.

Cells of human aminopeptidase N (CD13) transgenic mice are infected by human coronavirus-229E in vitro, but not in vivo

Aminopeptidase N, or CD13, is a receptor for serologically related coronaviruses of humans, pigs, and cats. A mouse line transgenic for the receptor of human coronavirus-229E (HCoV-229E) was created using human APN (hAPN) cDNA driven by a hAPN promoter. hAPN-transgenic mice expressed hAPN mRNA in the kidney, small intestine, liver, and lung. hAPN protein was specifically expressed on epithelial cells of the proximal convoluted renal tubules, bronchi, alveolar sacs, and intestinal villi. The hAPN expression pattern within transgenic mouse tissues matched that of mouse APN and was similar in mice heterozygous or homozygous for the transgene. Primary embryonic cells and bone marrow dendritic cells derived from hAPN-transgenic mice also expressed hAPN protein. Although hAPN-transgenic mice were resistant to HCoV-229E in vivo, primary embryonic cells and bone marrow dendritic cells were infected in vitro. hAPN-transgenic mice are valuable as a source of primary mouse cells expressing hAPN. This hAPN-transgenic line will also be used for crossbreeding experiments with other knockout, immune deficient, or transgenic mice to identify factors, in addition to hAPN, that are required for HCoV-229E infection.

Reduced growth, increased vascular area, and reduced response to cisplatin in CD13-overexpressing human ovarian cancer xenografts

PURPOSE

Expression of aminopeptidase N/CD13 can be detected in several solid tumor types. Thus far, the role of CD13 in ovarian cancer has not been studied. We have investigated the expression pattern and biological function of CD13 in ovarian cancer.

EXPERIMENTAL DESIGN

First, we studied the expression of CD13 in ovarian cancer tissue of 15 patients representing three different histological types (5 patients each) by immunohistochemistry. We then stably transfected the IGROV-1 human ovarian cancer cell line with a CD13 expression vector and examined the biological effect of CD13 in vitro and in vivo.

RESULTS

The expression of CD13 in ovarian cancer was associated with the histological subtype: CD13 expression in tumor cells was observed in 80-100% of the patients with a serous or mucinous carcinoma and in only 20% of the clear cell carcinoma patients. In all patients' tumor samples, CD13-positive blood vessels were present. CD13 overexpression in IGROV-1 cells did not affect in vitro cell growth and sensitivity to doxorubicin, cisplatin, or gemcitabine. CD13 overexpression reduced invasion in Matrigel, which appeared to be independent of the aminopeptidase activity of CD13. Furthermore, the growth rate of IGROV-1/CD13 xenografts was reduced. The area of the vessel lumens was enlarged in a small percentage of vessels in the CD13-overexpressing xenografts. In addition, the CD13-overexpressing tumors were less sensitive to cisplatin.

CONCLUSIONS

CD13 is expressed in tumor as well as endothelial cells in human ovarian cancer. Our results suggest that CD13 overexpression affects ovarian cancer growth, vascular architecture, and response to chemotherapy. Further elucidation of the mechanism of the observed effects of CD13 is warranted to better understand its role in the pathophysiology of ovarian cancer.

Prevention and treatment of erectile dysfunction using lifestyle changes and dietary supplements: what works and what is worthless, part II

It seems naïve to believe that some plants or herbs do not contain specific compounds that could benefit patients with ED. Many supplements have not been investigated in a laboratory or clinical research setting before commercial sale, however,which creates a complex situation. If efficacy is or is not demonstrated through adequate research, then the benefit or lack thereof cannot be mentioned on the label. Furthermore, clinicians and the public cannot be made aware of which compounds or supplements are effective because no general standards for sale exist under the current guidelines. Dietary supplements have received a tremendous amount of publicity. The large and growing market for ED treatment seems to have contributed partly to the promotion of numerous supplements and their apparent benefits. Whether these dietary supplements have merit is questionable. Some supplements may produce results opposite to those advertised. Other supplements may be enjoying the benefits of the placebo effect. Because a placebo response of 25% to 50% has been recorded in clinical trials with effective agents, it is understandable that some supplements enjoy financial success despite the limited research espousing their use. If one to two of four individuals or one of three individuals who try a dietary supplement gain some benefit for their ED, the market for these supplements will remain extraordinary. On a larger scale, of 100,000 men who try a supplement, approximately 25,000 to 50,000 will claim some success. The challenge for clinicians is to discuss the placebo response properly and the need for good research before any intervention, especially supplements, can be advocated for general use. Table 2 summarizes some popular ED supplements and general conclusions that can be drawn from clinical investigations. Some dietary supplements may have an active ingredient that benefits patients with certain types of ED. An exciting area of future dietary supplement research is the ability of certain agents to have a synergistic effect with prescription agents for ED, thereby improving response rates in men that have failed approved ED therapy initially, especially with oral agents. Randomized clinical trials are the best method of determining which dietary supplements will become a part of conventional medicine. Therefore, more randomized trials for dietary supplements are needed so that they may have the opportunity to become a part of the mainstream milieu, which means that more funding needs to be made available for ED research. The coming years of research should bring enormous excitement and objectivity to this area of medicine.

Evidence that the prostate-specific antigen (PSA)/Zn2+ axis may play a role in human prostate cancer cell invasion

Prostate-specific antigen (PSA), which is used as a marker for the diagnosis and monitoring of prostate cancer, is a kallikrein protease which could potentially play a role in human prostate cancer cell invasion. Zinc ions are effective inhibitors of a number of proteases. The enzymatic activity of purified PSA was strongly inhibited by Zn(2+). The ability of LNCaP cells which express and secrete PSA to invade Matrigel was strongly suppressed by Zn(2+) at a concentration similar to that inhibiting the activity of purified PSA. Zn(2+) effectively inhibited the degradation of Matrigel by purified PSA. These results suggest that Zn(2+) in human prostate may suppress the invasion and metastasis of prostate cancer cells through the regulation of the proteolytic activity of PSA. Loss of inhibition of the proteolytic activity of PSA by Zn(2+) in prostate tumors could contribute to invasion.

Membrane alanyl aminopeptidase

This chapter focuses on the structural chemistry of membrane alanyl aminopeptidase (mAAP). The early history of mAAP relates to its role as Cys-Gly dipeptidase or cysteinyl-glycinase. It was proposed that this peptidase activity present in apparently purified RNA preparations contributed to polypeptide biosynthesis by acting in reverse in a sequential fashion. mAAP has a broad substrate specificity removing N-terminal amino acids (Xaa-Xbb-) from almost all unsubstituted oligopeptides and from an amide or arylamide. mAAP is a type II integral membrane protein located on the plasma membrane as an ectoenzyme. The pI is approximately 5. mAAP is widely distributed among species and tissues although it is of greatest abundance in brush border membranes of the kidney, in the mucosal cells of the small intestine and in the liver. It is also present in the lung where it is identical to the pI46 type II alveolar epithelial cell antigen and is located on endothelial cells in blood vessels. On polarized epithelial cells, mAAP is localized to the apical domain and is targeted there through an apical sorting signal thought to be located in the catalytic head group region of the protein.

Tumor cytosol dipeptidyl peptidase III activity is increased with histological aggressiveness of ovarian primary carcinomas

OBJECTIVE

Proteolytic enzymes have been implicated in the progression of various human malignancies, including ovarian cancer. The enhanced expression of dipeptidyl peptidase III (DPP III) was found in endometrial carcinomas of various histological types and grade. The aim of this study was to assess activity of DPP III in ovarian tissue specimens and to correlate it with clinico-pathological data.

METHODS

DPP III hydrolytic activity toward Arg-Arg-2-naphthylamide was determined in 108 ovarian tissue cytosol specimens of 79 patients. The data obtained for 41 ovarian primary carcinoma specimens were stratified according to clinical stage, histological grade and type, and age of the patients.

RESULTS

Median DPP III activity expressed as milliunits per milligram protein was 6 in normal ovarian tissues (n = 29), 6.5 in benign ovarian tumors (n = 19), 19.5 in primary ovarian carcinomas (n = 41), 12.5 in nonepithelial primary ovarian tumors (n = 7), and 22.1 in metastatic ovarian malignancies (n = 12). A significant rise in median DPP III specific activity was observed in malignant ovarian tumors (of epithelial, nonepithelial, and metastatic origin), but not in benign ovarian tumors, compared to the activity in normal tissue. A significant difference of DPP III expression was found between the group of normal tissues and tumors of clinical stage I and II, of grade 2 and 3, of serous and mucinous histologic type.

CONCLUSIONS

DPP III activity of benign ovarian tumors equaled that in normal ovarian tissue. In malignant neoplasms of the ovary it increased with growing histologic grade.

Synthesis and biological evaluation of novel flavone-8-acetic acid derivatives as reversible inhibitors of aminopeptidase N/CD13

The cell surface aminopeptidase N (APN/CD13), overexpressed in tumor cells, plays a critical role in angiogenesis. However, potent, selective, and, particularly, noncytotoxic inhibitors ot this protein are lacking, and the present work was undertaken with the aim of developing a new generation of noncytotoxic inhibitors that bind to APN/CD13. In this context, we have synthesized a series of novel flavone-8-acetic acid derivatives. Among the herein described and evaluated compounds, the 2',3-dinitroflavone-8-acetic acid (19b) proved to be the most efficient and exhibited an IC(50) of 25 microM which is 2.5 times higher than that of bestatin (1), the natural known inhibitor of APN/CD13. However, in contrast to bestatin (1), the dinitroflavone 19b did not induce any cytotoxicity to cultured human model cells. The presence of other substituents such as NO(2) or OCH(3) groups at the 3'- or 4'-position of the B phenyl group, or the existence of steric constraints (compounds 24 and 29), did not improve selectivity and potency. The flavone 19b affinity for APN/CD13 is not recovered with other proteases such as matrix metalloproteinase-9 (MMP-9), angiotensin converting enzyme (ACE/CD143), neutral endopeptidase (NEP/CD10), gamma-glutamyl transpeptidase (CD224), or the serine proteases dipeptidyl peptidase IV (DPPIV/CD26) or cathepsin G.

Leukotriene A4 hydrolase in rat and human esophageal adenocarcinomas and inhibitory effects of bestatin

BACKGROUND

Esophageal adenocarcinoma (EAC) is increasing at the most rapid rate of any cancer in the United States. An esophagogastroduodenal anastomosis (EGDA) surgical model in rats mimics human gastroesophageal reflux and results in EAC. Leukotriene A4 hydrolase (LTA4H), a protein overexpressed in EAC in this model, is a rate-limiting enzyme in the biosynthesis of leukotriene B4 (LTB4), a potent inflammatory mediator. We used this model and human EAC and non-tumor tissues to elucidate the expression pattern of LTA4H and to evaluate it as a target for chemoprevention.

METHODS

LTA4H expression was examined by western blotting and immunohistochemistry. The functional role of LTA4H in carcinogenesis was investigated by use of an LTA4H inhibitor, bestatin, in the rat EGDA model. All statistical tests were two-sided.

RESULTS

LTA4H was overexpressed in all 10 rat EACs examined, compared with its level in normal rat tissue; it was also overexpressed in four of six human EAC tumor samples, compared with its level in adjacent non-tumor tissue. In tissue sections from 20 EGDA rats and 92 patients (86 with EAC, one with dysplasia, and five with columnar-lined esophagus), LTA4H was expressed in infiltrating inflammatory cells and overexpressed in the columnar cells of preinvasive lesions and cancers, especially in well-differentiated EACs, as compared with the basal cells of the normal esophageal squamous epithelium. Bestatin statistically significantly inhibited LTB4 biosynthesis in the esophageal tissues of EGDA rats (without bestatin = 8.28 ng/mg of protein; with bestatin = 4.68 ng/mg of protein; difference = 3.60, 95% CI = 1.59 to 5.61; P = .002) and reduced the incidence of EAC in the EGDA rats from 57.7% (15 of 26 rats) to 26.1% (6 of 23 rats) (difference = 31.6%, 95% CI = 0.3% to 56.2%; P = .042).

CONCLUSION

LTA4H overexpression appears to be an early event in esophageal adenocarcinogenesis and is a potential target for the chemoprevention of EAC.

Zinc supplement use and risk of prostate cancer

The high concentration of zinc in the prostate suggests that zinc may play a role in prostate health. We examined the association between supplemental zinc intake and prostate cancer risk among 46 974 U.S. men participating in the Health Professionals Follow-Up Study. During 14 years of follow-up from 1986 through 2000, 2901 new cases of prostate cancer were ascertained, of which 434 cases were diagnosed as advanced cancer. Supplemental zinc intake at doses of up to 100 mg/day was not associated with prostate cancer risk. However, compared with nonusers, men who consumed more than 100 mg/day of supplemental zinc had a relative risk of advanced prostate cancer of 2.29 (95% confidence interval = 1.06 to 4.95; P(trend) =.003), and men who took supplemental zinc for 10 or more years had a relative risk of 2.37 (95% confidence interval = 1.42 to 3.95; P(trend)<.001). Although we cannot rule out residual confounding by supplemental calcium intake or some unmeasured correlate of zinc supplement use, our findings, that chronic zinc oversupply may play a role in prostate carcinogenesis, warrant further investigation.

The Drosophila slamdance gene: a mutation in an aminopeptidase can cause seizure, paralysis and neuronal failure

We report here the characterization of slamdance (sda), a Drosophila melanogaster "bang-sensitive" (BS) paralytic mutant. This mutant exhibits hyperactive behavior and paralysis following a mechanical "bang" or electrical shock. Electrophysiological analyses have shown that this mutant is much more prone to seizure episodes than normal flies because it has a drastically lowered seizure threshold. Through genetic mapping, molecular cloning, and RNA interference, we have demonstrated that the sda phenotype can be attributed to a mutation in the Drosophila homolog of the human aminopeptidase N (APN) gene. Furthermore, using mRNA in situ hybridization and LacZ staining, we have found that the sda gene is expressed specifically in the central nervous system at particular developmental stages. Together, these results suggest that the bang sensitivity in sda mutants is caused by a defective APN gene that somehow increases seizure susceptibility. Finally, by using the sda mutation as a sensitized background, we have been able to identify a rich variety of sda enhancers and other independent BS mutations.