Neuroendocrine differentiation in the progression of prostate cancer

Neuroendocrine (NE) cells originally exist in the normal prostate acini and duct, regulating prostatic growth, differentiation and secretion. Clusters of malignant NE cells are found in most prostate cancer (PCa) cases. NE differentiation (NED) is the basic character of the prostate, either benign or malignant. NE cells hold certain peptide hormones or pro-hormones, which affect the target cells by endocrine, paracrine, autocrine and neuroendocrine transmission in an androgen-independent fashion due to the lack of androgen receptor. NED is accessed by immunohistochemical staining or measurement of serum levels of NE markers. The extent of NED is associated with progression and prognosis of PCa. Chromogranin A (CGA) is the most important NE marker. In metastatic PCa, pretreatment serum CGA levels can be a predictor for progression and survival after endocrine therapy. It is recommended to measure longitudinal change in serum CGA. The NE pathway can also be a therapeutic target.     

Citrate in the diagnosis of prostate cancer

BACKGROUND: One of the major current problems involved in prostate cancer (PCa) is the unavailability of sensitive, accurate, and preferably noninvasive procedures for the diagnosis of PCa. Moreover, procedures are needed which will permit the early detection, staging, location, and estimation of the volume of malignancy, and preferably a mapping of the prostate for follow-up of progression and regression of the malignancy. METHODS: The unique citrate relationships of the prostate, coupled with recent developments and technological advancements in magnetic resonance spectroscopy (MRS) for the in situ determination of citrate levels, now provides an excellent diagnostic procedure which can achieve all these goals. There exist strong, compelling basic and clinical studies in support of the employment of 1H MRS measurements of citrate and other associated metabolites in the diagnosis of PCa. RESULTS: This review provides the background leading to the current status of MRS citrate analysis, summarizes the data from clinical trials, and describes the applications of the procedure for the diagnosis of PCa and follow-up of patients. The use of MRS studies in defining the functional, as well as pathological relationships of the prostate, is also discussed. CONCLUSIONS: This review is intended to be informative to the prostate- and oncology-interested community, and, hopefully, to engender much-needed interest and support in future research regarding the prostate relationships described in this report.     

前列腺增生和前列腺癌血清锌浓度对比研究

目的：微量元素锌对前列腺的结构与功能有着重要的影响,并可成为诊断前列腺疾病的一项重要检测手段。方法：本研究选择３０例良性前列腺增生病人,平均年龄６２．４岁;１２例前列腺癌病人,平均年龄６５．６岁,测定其血清锌含量。结果：血清锌平均浓度良性前列腺增生组为（２０４．３２±１０９．０４）μｍｏｌ／Ｌ,前列腺癌组为（９７．６５±６３．１６）μｍｏｌ／Ｌ,二者差异显著（Ｐ＜０．０１）。结论：由于前列腺增生（ＢＰＨ）及前列腺癌时前列腺结构、功能的不同改变而导致血清锌的浓度差异,故测定血清锌浓度对前列腺增生与前列腺癌的鉴别诊断有一定的参考价值。     

Cell lines used in prostate cancer research: a compendium of old and new lines--part 1

PURPOSE: This is part 1 of a 2-part review. Research into the molecular mechanisms underlying the various aspects of prostate cancer (PCa) requires the use of in vivo and in vitro model systems. In the last few years many new cell lines have been established by investigators from primary tissue sources and clonal derivatives of previously established lines. Therefore, the purpose of this 2-part review is to catalogue the current human cell lines developed for PCa research, as reported in the literature. Part 1 includes tissue culture cell lines derived from metastases, primary tumors and nonadenocarcinomas that were established without the use of transgenes. It also includes a section describing lines that have been contaminated with other lines, shown not to be of prostatic origin or whose identity is being challenged. MATERIALS AND METHODS: Prostate cell lines included in this review were identified by extensive searching of the literature using several strategies, including PubMed searches and book chapter reviews. RESULTS: In total we describe the derivation, phenotype, genotype and characterization of molecular markers expressed by approximately 200 lines and sublines used in PCa research, including those derived from primary tumors, metastases and normal prostate tissue. We paid particular attention to the expression of prostate specific antigen, androgen receptor, cytokeratins and other molecular markers used to indicate the status of PCa and the prostatic lineage of a given line. In an attempt to provide PCa researchers with a resource of information regarding new and established cell lines we have also created an online database of these PCa cell lines freely accessible via the World Wide Web at http://www.CaPCellLines.com. The web based interface allows researchers to peruse and print information regarding cell lines, add new cell lines and update or add new information regarding established cell lines. CONCLUSIONS: This compendium of cell lines currently used in PCa research combined with access to our on-line database provides researchers with a continually updated and valuable resource for investigating the molecular mechanisms of PCa.     

COX-2、Ki-67联合检测对良恶性前列腺病变鉴别诊断的价值分析

目的 探讨环氧合酶-2(COX-2)、细胞增殖核抗原Ki-67(Ki-67)联合检测对良恶性前列腺病变的鉴别诊断价值。方法 选取2017年1月至2019年6月本院收治的168例良恶性前列腺病变患者,将其中83例前列腺癌(PCa)患者设为PCa组,85例良性前列腺病变患者[良性前列腺增生（BPH）患者40例、前列腺上皮内瘤(PIN)患者45例]设为BPH+PIN组。检测两组前列腺病变组织的COX-2、Ki-67表达水平;分析前列腺组织中的COX-2、Ki-67表达水平与PCa临床病理特征的关系;采用受试者工作特征（ROC）曲线评价前列腺病变组织COX-2、Ki-67 mRNA表达水平对PCa的诊断和鉴别价值。结果 PCa组患者的前列腺组织中COX-2、Ki-67 mRNA及蛋白阳性表达率水平均高于BPH+PIN组（均P<0.001）;PCa组患者的前列腺组织中COX-2、Ki-67表达水平与临床分期、远处转移、淋巴结转移、浸润深度、分化程度有明显相关性（均P<0.05）,与年龄、组织类型无相关性（均P>0.05）;前列腺病变组织的COX-2、Ki-67 mRNA诊断PCa的曲线下面积（AUC）分别为0.885、0.868,灵敏度分别为83.13%、78.31%,特异度分别为91.76%、92.94%;两者联合鉴别PCa的灵敏度（95.18%）高于两项单独检测,而特异度（90.59%）低于两项单独检测。结论 前列腺病变组织中的COX-2联合Ki-67对PCa具有较高的诊断价值,可提高诊断灵敏度,且具有较高准确度,有助于临床鉴别良恶性前列腺病变。     

Testosterone and Prostate Cancer: Revisiting Old Paradigms

Context

Androgens are vital for growth and maintenance of the prostate; however, the notion that pathologic prostate growth, benign or malignant, can be stimulated by androgens is a commonly held belief without scientific basis. Therefore, the current prostatic guidelines for testosterone therapy (TT) appear to be overly restrictive and should be reexamined.

Objective

To review the literature addressing the possible relationship between testosterone and prostate cancer (PCa) and to summarize the main aspects of this issue.

Evidence acquisition

A Medline search was conducted to identify original articles, review articles, and editorials addressing the relationship between testosterone and the risk of PCa development, as well as the impact of TT on PCa development and its natural history in men believed to be cured by surgery or radiation.

Evidence synthesis

Serum androgen levels, within a broad range, are not associated with PCa risk. Conversely, at time of PCa diagnosis, low rather than high serum testosterone levels have been found to be associated with advanced or high-grade disease. The available evidence indicates that TT neither increases the risk of PCa diagnosis nor affects the natural history of PCa in men who have undergone definitive treatment without residual disease. These findings can be explained with the saturation model (which states that prostatic homeostasis is maintained by a relatively low level of androgenic stimulation) and with the observation that exogenous testosterone administration does not significantly increase intraprostatic androgen levels in hypogonadal men. It must, however, be recognized that the literature remains limited regarding the effect of TT on PCa risk. Nonetheless, the current European Association of Urology guidelines state that in hypogonadal men who were successfully treated for PCa, TT can be considered after a prudent interval.

Conclusions

Although no controlled studies have yet been performed and there is a paucity of long-term data, the available literature strongly suggests that TT neither increases the risk of PCa diagnosis in normal men nor causes cancer recurrence in men who were successfully treated for PCa. Large prospective studies addressing the long-term effect of TT are needed to either refute or corroborate these hypotheses.     

Novel role of zinc in the regulation of prostate citrate metabolism and its implications in prostate cancer

The prostate gland of humans and many other animals has the major function of accumulating and secreting extraordinarily high levels of citrate. This specialized metabolic process of “net citrate production” is the result of unique metabolic capabilities of the secretory epithelial cells. Most importantly, in prostate cancer (Pca) the capability for net citrate production is lost. In addition to citrate, the normal and BPH (benign prostatic hyperplasia) prostate also accumulates the highest levels of zinc in the body. As with citrate, in Pca the ability for high zinc accumulation is diminished. These and other correlations between zinc and citrate in the prostate have been indicative of an important role of zinc in the regulation of citrate metabolism in normal and malignant prostate epithelial cells. The link between zinc and citrate metabolism has now been established. The intramitochondrial accumulation of high zinc levels inhibits mitochondrial (m-) aconitase activity, which inhibits citrate oxidation. This essentially truncates the Krebs cycle and markedly decreases the cellular energy (ATP) production normally coupled to citrate oxidation. It is also clear that zinc accumulation in citrate-producing prostate epithelial cells is regulated by testosterone and by prolactin. These relationships form the basis for a new concept of the role of zinc and citrate-related energy metabolism in prostate malignancy. The inability of malignant prostate cells to accumulate high zinc levels results in increased citrate oxidation and the coupled ATP production essential for the progression of malignancy. The concept offers new approaches to the treatment of Pca. Prostate 35:285–296, 1998. © 1998 Wiley-Liss, Inc.     

Prolactin and testosterone regulation of mitochondrial zinc in prostate epithelial cells

The prostate gland of many animals accumulates extremely high levels of zinc and citrate. Evidence currently exists in support of a concept that zinc might be an important regulator of m-aconitase and citrate oxidation of prostate epithelial cells. No information concerning the mitochondrial levels of zinc has been available. The roles of testosterone and prolactin in the regulation of zinc have not been established. In this report, we determined the levels of tissue and mitochondrial zinc of rat lateral prostate (LP), ventral prostate (VP), dorsal prostate (DP), liver, and kidney. The results demonstrate that the mitochondrial zinc levels of the prostate cells were higher than levels of nonprostatic cells. The LP contained severalfold higher zinc levels than DP and VP. The effects of testosterone and prolactin in vivo and in vitro on the zinc levels were also determined. Both hormones significantly increased cellular and mitochondrial zinc levels of LP cells; decreased the zinc levels of VP cells; and had no effect on the zinc levels of DP, liver, or kidney cells. These effects are direct and physiological effects of the hormones on the targeted prostate epithelial cells. The hormonal effects on mitochondrial zinc of LP and VP epithelial cells correlate perfectly with their effects on citrate oxidation. The results support the concept that mitochondrial zinc is an inhibitor of m-aconitase and citrate oxidation; and that prolactin and testosterone regulation of mitochondrial zinc provides a mechanism for their regulation of citrate oxidation in citrate-producing prostate epithelial cells. Prostate 30:26–32, 1997 © 1997 Wiley-Liss, Inc.     

Effect of testosterone administration to men with prostate cancer is unpredictable: a word of caution and suggestions for a registry

To assess the evidence for the concept that the androgen receptor of prostate cancer (PCa) cells becomes saturated when testosterone values exceed castrate levels, so that testosterone administration in hypogonadal men with untreated PCa does not stimulate tumour growth. To propose basic criteria for administration of testosterone to untreated patients with PCa and, as this is a rare clinical situation, to encourage the establishment of an international registry for these patients. Men with a diagnosis of PCa and symptomatic testosterone deficiency received testosterone therapy (TTh). Patients were assessed quarterly. Prostate-specific antigen (PSA) velocity was used as the criterion to discontinue therapy and a return to nadir PSA levels allowed re-initiation of testosterone supplementation. The responses to testosterone supplementation were varied according to each individual and were unpredictable. While some men showed little change after years of treatment, others exhibited a rapid and significant increase in PSA levels. In others, the use of intermittent therapy resulted in synchronous changes in PSA levels. Interruption of TTh invariably translated into a decrease in PSA to pre-therapy levels. Available evidence regarding the effect of testosterone administration to hypogonadal men with untreated PCa is too limited to be considered reliable. In addition, the response to this treatment appears to be varied and unpredictable. Hypogonadism associated with untreated PCa is not common, therefore, we propose the establishment of an international registry as the quickest way to establish the basic parameters for consideration of TTh in this situation and recommendations for follow-up. Until credible evidence becomes available, the current restrictions regarding the administration of testosterone to men with PCa should remain in place.     

Pilot and feasibility study of serum chemokines as markers to distinguish prostatic disease in men with low total serum PSA

BACKGROUND: The incidence and prevalence of both benign prostatic hypertrophy (BPH) and prostate cancer (PCa) increase with the aging process. Our laboratory recently showed that the chemokines CXCL5 and CXCL12, which normally function as inflammatory mediators, are secreted at higher levels by aging prostate stromal fibroblasts and elicit proliferative responses from both prostate stromal fibroblast and epithelial cells. Because both CXCL5 and CXCL12 are secreted molecules, we hypothesized that their levels in patient serum might serve as biomarkers to distinguish between BPH and PCa. METHODS: Serum CXCL5 and CXCL12 levels were determined using sandwich ELISAs for 51 men demonstrating low serum PSA values of < or =10 ng/ml who underwent diagnostic needle biopsy for the detection of PCa. The bivariate relationship of circulating chemokine levels, age, and disease status in the prostate was tested using the Wilcoxon rank-sum test. RESULTS: Total serum CXCL12 levels were significantly higher for men who were biopsy positive compared to those who were biopsy negative for cancer and histological prostatitis (P = 0.050). Among men who were biopsy negative for PCa, total serum CXCL5 levels were inversely associated with prostate volume and were significantly higher in men with concomitant BPH and histological prostatitis compared to those without evidence of prostatic disease (P < 0.003). CONCLUSIONS: The results of this pilot and feasibility study suggest that serum or plasma CXCL5 and CXCL12 levels may potentially distinguish between BPH and PCa among patients presenting with low serum PSA, and may be useful toward facilitating decisions to perform diagnostic needle biopsy in this patient population.     

前列腺雄激素调节基因:一个新的雄激素非依赖性前列腺癌治疗的潜在靶点(英文)

目的:初步研究前列腺雄激素调节基因(PAR)与雄激素—雄激素受体信号转导通路的关系及其在前列腺癌细胞恶性转化过程中的作用,探讨通过抑制 PAR 基因治疗雄激素非依赖性前列腺癌的可能性。方法:用 RT-PCR 检测 LNCaP、PC3细胞中 PAR 基因 mRNA 表达水平的差异。分别用 RT-PCR 检测双氢睾酮对LNCaP、PC3及稳定转染了 pcDNA3-AR 的 PC3细胞株 PC3-AR 的 PAR 基因 mRNA 表达的调节作用,并观察这一调节作用是否可被雄激素受体拮抗剂氟他胺阻断。进一步用 RNA 干扰技术下调 PC3细胞 PAR 的表达,用细胞计数、软琼脂克隆形成实验、流式细胞术研究 PAR 基囚表达下调对 PC3细胞生长的抑制作用。结果:PC3细胞 PAR 基因 mRNA 的表达是 LNCaP 细胞的3倍;双氢睾酮可调节 LNCaP 和 PC3-AR 细胞株PAR 基因 mRNA 表达水平,此种对 PAR 表达的调节作用可被氟他胺阻断:双氢睾酮对 PC3细胞 PAR 基因mRNA 表达无明显影响。RNA 干扰可抑制 PC3细胞 PAR 基因表达,使细胞增殖受抑制,细胞周期阻滞于G_2-M 期,凋亡增加。结论:PAR 可能是雄激素—雄激素受体信号转导通路下游的与雄激素非依赖性前列腺癌恶性表型密切相关的癌基因,有望成为其基冈和药物治疗的靶点。     

Measurement of serum zinc improves prostate cancer detection efficiency in patients with PSA levels between 4 ng/mL and 10 ng/mL

Aim： To investigate whether the measurement of serum zinc may improve the detection of prostate cancer （PCa） in men who had total prostate-specific antigen （PSA） levels higher than 4.1 ng/mL. Methods： A mass screening for PCa of 3940 men over 50 years old was undertaken using total serum PSA. Of the 190 men （4.8 %） with elevated PSA, 143 （3.6 %） underwent a transrectal ultrasonography （TRUS）-guided biopsy of the prostate, and 42 men （1% of total and 29.3 % of men undergoing biopsy） were found to have cancer. The areas under the receiver operating characteristic curves （ROC-AUC） were used to compare the diagnostic power of cancer detection by means of serum zinc, and free PSA/total PSA ratio （fit）. Results： The men with levels of serum zinc that ranged from 40 ng/mL-60 ng/mL, had an age-adjusted odds ratios（OR） of 5.0. A cutoff value of 100 gg/mL for-serum zinc concentration provided a sensitivity of 90.5 % and a specificity of 32.7 % in elevated PSA range, and a sensitivity of 93.3 % and specificity of 27.1% in gray zone, respectively. In the gray zone ranges of 4.1 ng/mL-10.0 ng/mL, the ROC-AUC for zinc was 73.0 % higher than 62.7 % of f/t PSA ratio and 56.7 % of total PSA. Conclusion： PCa displays a lower serum zinc concentration. The measurement of zinc levels improves PCa detection in the gray zone compared with the f/t PSA ratio and total PSA. （Asian J Androl 2005 Sep; 7： 323-328）     

Activation of the thromboxane A2 pathway in human prostate cancer correlates with tumor Gleason score and pathologic stage

OBJECTIVE: We investigated the potential involvement of the thromboxane A(2) (TXA(2)) pathway in human prostate cancer (PCa). METHODS: Expression of cyclooxygenase-2 (COX-2), TXA(2) synthase (TXS), and TXA(2) receptors (TPRs), the main actors of the TXA(2) pathway, was analyzed on serial tissue sections from 46 human PCa specimens. RESULTS: The expression levels of COX-2, TXS, and TPRs were significantly higher in malignant than in corresponding nontumoral prostatic epithelial cells. Increased immunoreactivity for these antigens was also observed in high-grade prostate intraepithelial neoplasia (HGPIN) glands. COX-2, TXS, and TPR proteins usually displayed a coordinated overexpression pattern in PCa lesions, as assessed in serial tissue sections. Increased levels of these proteins in the tumors were all significantly associated with higher Gleason scores and pathologic stages. CONCLUSIONS: Proteins specifically involved in the TXA(2) pathway are up-regulated in human PCa and their level of expression is associated with tumor extraprostatic extension and loss of differentiation. Our study is the first to examine simultaneously all key proteins involved in this pathway including TXA(2) receptors and results suggest that the TXA(2) pathway may be a potential target for PCa prevention/therapy.     

Prostate cancer antigen-1 as a potential novel marker for prostate cancer

Aim： To examine the expression of prostate cancer antigen-1 （PCA-1） in prostate cancer （PCa） and to validate it as a potential marker for diagnosis of PCa. Methods： In situ hybridization analysis of PCA-1 mRNA expression was performed on 40 benign prostate hyperplasia （BPH）, 16 high-grade prostatic intraepithelial neoplasm （HG-PIN）, 74 PCa and 34 other malignant carcinoma specimens. The level of PCA- 1 expression was semiquanfitatively scored by assessing both the percentage and intensity of PCA- 1 positive staining cells in the specimens. We then compared the PCA-1 expression between BPH, HG-PIN and PCa and evaluated the correlation of PCA-1 expression level with clinical parameters of PCa. Results： PCA-1 mRNA was expressed in the majority of both PCa and HG-PIN specimens but not in BPH and other malignant carcinoma. The expression level of PCA-1 increased along with a high Gleason score （P 〈 0.05）, and was unrelated to other clinical parameters of PCa （all P 〉 0.05）. Conclusion： The data suggest that PCA-1 might be a novel diagnostic marker for PCa, and that increased PCA-1 expression might denote more aggressive variants of PCa.     

Complex Mechanisms in Prostatic Inflammatory Response

ContextThe immunology of the prostate has developed into a new field of research in urology. The leukocyte population increases are not yet fully understood, but it has been demonstrated that most resected prostate tissue shows signs of inflammatory response.ObjectiveThis article reviews recent findings and discusses the complex mechanisms involved in the prostatic inflammatory response and the immunologic functions of the prostate, and the roles the prostatic inflammatory response in the cause of prostate disease such as benign prostatic hyperplasia (BPH).Evidence acquisitionWe performed a search of the medical literature with PubMed, using keywords such as prostate cancer, inflammation of the prostate, leukocytes, estrogen, and cytokine and genetic expression of inflammation. Articles and data were reviewed as to their relevance, and inclusion and exclusion criteria were determined prospectively.Evidence synthesisEvidence showing that inflammation of the prostate plays a role in prostate cancer (PCa) is mounting. Different types of inflammation exist and are distinguished according to the distribution and location of leukocytes and the histology of the surrounding tissue. Most resected prostate tissue shows signs of inflammatory response, and a relationship between T-cell infiltration and stromal proliferation can be found. Evidence for the importance of estrogen and proinflammatory cytokine interleukin (IL; IL-6, IL-8, IL-15, IL-17) also can be found. Early stages of investigation of the immunologic function of the prostate show that both prostatic epithelial and stromal cells express members of the toll-like receptor family and are therefore capable of recognizing foreign incoming antigens.ConclusionsAlthough this area of study is new, the immunology and inflammatory responses of the prostate are seen as important components of further study of prostate diseases such as PCa and BPH. Data supporting the role of immunology and activated leukocytes in malignant cells are also an important finding and can possibly lead to new knowledge about malignant cells.     

XAGE-1 b基因在良性前列腺增生症与前列腺癌中的表达及其意义

目的 观察XAGE-1b基因在良性前列腺增生症和前列腺癌中的表达,探讨其数值对良性前列腺增生症和前列腺癌各项指标的临床意义.方法 运用实时荧光定量聚合酶链反应(PCR)方法检测38例前列腺癌病理组织以及40例良性前列腺增生症组织XAGE-1b的基因表达水平.结果 XAGE-1b在前列腺癌组织中表达值为8.299 50±0.97116,在良性前列腺增生症组织中表达值为3.007 80±0.91600,差异有统计学意义(P＜0.05).XAGE-1b表达值随着Gleason评分、临床分期和肿瘤恶性程度升高而表达增强(P＜0.05).结论 XAGE-1b基因高表达值有助于前列腺癌的诊断和指导前列腺癌的恶性程度分期.

Abstract：

Objective To study the XAGE-1 b mRNA expression in prostate cancer (PCa) tissues and benign prostate hyperplasia (BPH) tissues,and explore the diagnostic values of XAGE-1 b mRNA expression level in PCa and BPH.Methods A sensitive,real-time quantitative polymerase chain reaction (PCR) assay was developed to compare the expression difference of XAGE-1b mRNA in PCa and BPH tissues,by testing 38 samples of PCa and 40 samples of BPH.Results The expression level of XAGE-1 b in PCa tissue was 8.299 50 ± 0.971 16,and 3.007 80 ± 0.916 00 in BPH tissue ( P＜0.05 ).The XAGE-1 b expression levels were increased with the increase of the Gleason score,clinical stage and malignant grade (P＜0.05).Conclusion The high expression of of XAGE-1 b mRNA can afford a reliable and helpful information for diagnosis of PCa and BPH,and PCa malignant grade.     

Expression of pro-angiogenic growth factors VEGF,EGF and bFGF and their topographical relation to neovascularisation in prostate cancer

The aim of the study was to quantify the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) in prostate cancer and adjacent non-tumorous tissue in a standardized experimental set-up and to evaluate the paracrine effects of three endothelial stimuli on neovascularisation. Immunohistochemical staining of prostate cancer (PCa) specimens for VEGF, bFGF, EGF and the endothelial marker CD31 was performed (n=56). Sections were analyzed for growth factor-positive cancer/epithelial cells as well as staining intensity in (I) malignant and (II) non-tumorous tissue. Within PCa the topographic relationship (TR) of maximum microvessel density (MWD) and maximum expression of each growth factor was assessed. The number of VEGF- and EGF-positive cells in PCa was significantly enhanced compared with non-tumorous tissue (p<0.0001), whereas there was no difference in staining intensity. In contrast, the staining intensity of bFGF sections revealed a stronger expression in non-tumorous tissue compared with PCa (p<0.0001). In benign glands, VEGF, EGF and bFGF expression is chiefly restricted to basal cells. VEGF and EGF displayed a close TR in 65 and 57% of cases, respectively, whereas bFGF revealed a close TR in only 43% of PCa specimens. The results outline the relationship of the investigated growth factors and angiogenesis in PCa, which is strongest for VEGF and EGF. The relevance of VEGF and EGF is underlined by the increased number of positive cancer cells. Although previously reported to be a pro-angiogenic growth hormone, bFGF appears to play an assimilably minor role in the angiogenesis of PCa.This project was supported by a grant from the Reinhard Nagel Trust, Germany     

Zinc and metallothionein levels and expression of zinc transporters in androgen-independent subline of LNCaP cells

Zinc levels in the prostate have been reported to be associated with the development and progression of malignant prostate cells. To investigate the reason why the zinc content decreases during the progression of prostate cancer to an androgen-independent state, we compared the expression levels of metallothionein and zinc transporters between androgen-responsive LNCaP cells and its androgen-independent subline, AIDL cells. AIDL cells showed lower zinc levels than LNCaP cells and comparable levels of androgen receptor expression to LNCaP cells, consistent with some clinical aspects of androgen-independent prostatic cancer. AIDL cells exhibited a lower expression of zinc transporter 1 (ZnT1) and higher expression of ZnT3 than LNCaP cells. The content of metallothionein, which is a major zinc-binding protein, was significantly lower in AIDL cells than in LNCaP cells. Furthermore, the expression of ZnT3 mRNA was decreased by incubating LNCaP cells in medium containing hormone-stripped fetal calf serum and increased by addition of synthetic androgen R1881 to the medium, whereas the intracellular zinc levels were not affected under these conditions. These findings suggest that factors such as ZnT1 and metallothioneins other than ZnT3 are associated with the low intracellular zinc content in AIDL cells.     

Inhibitory effect of zinc on human prostatic carcinoma cell growth.

BACKGROUND: Normal human prostate accumulates the highest levels of zinc of any soft tissue in the body. In contrast, the zinc level in prostate cancer is markedly decreased from the level detected in nonprostate tissues. Despite these relationships, the possible role of zinc in the growth of normal and malignant prostate has not been determined. METHODS: Growth inhibition and various regulatory responses were investigated in two human prostate carcinoma cell lines (LNCaP and PC-3), treated with or without zinc. RESULTS: Incubation of the prostate carcinoma cell lines with physiological levels of zinc resulted in the marked inhibition of cell growth. A lower 50% inhibition of cell growth (IC50) value for zinc (about 100 ng/ml) was detected in LNCaP cells, which are androgen-responsive, whereas androgen-independent PC-3 cells exhibited a higher IC50 for zinc (about 700 ng/ml). Incubation with 1 microg/ml zinc resulted in maximum inhibition of growth in both cell lines. These inhibitory effects of zinc correlated well with the accumulation of zinc in the cells. Simultaneously, cell flow cytometric analyses revealed a dramatic increase of the cell population in G2/M phase, in both LNCaP (2.3-fold vs. control) and PC-3 (1.9-fold vs. control), and a decreased proportion of cells in S phase (LNCaP, -51.4%; PC-3, -23%), indicating a G2/M phase arrest. The cell growth inhibition and G2/M arrest in these cells were accompanied by an increase in apoptosis, as demonstrated by the characteristic cell morphology and further confirmed by cellular DNA fragmentation. The specificity of zinc-induced apoptosis was identified by ethylenediamine-tetraacetic acid (EDTA)-chelation, which abolished the zinc effect on cellular DNA fragmentation. The zinc-induced G2/M phase arrest and apoptosis were accompanied by increased mRNA levels of p21(Waf1/Cip1/Sdi1) in both LNCaP (p53+/+) and PC-3 (p53-/-) cells. CONCLUSIONS: These results suggest that zinc inhibits human prostatic carcinoma cell growth, possibly due to induction of cell cycle arrest and apoptosis. There now exists strong evidence that the loss of a unique capability to retain high levels of zinc is an important factor in the development and progression of malignant prostate cells.