Mitochondrial DNA depletion in prostate epithelial cells promotes anoikis resistance and invasion through activation of PI3K/Akt2.

Neoplastic transformation of prostate epithelium involves aberrant activation of anti-apoptotic and pro-invasive pathways triggered by multiple poorly understood genetic events. We demonstrated earlier that depletion of mitochondrial DNA (mtDNA) induces prostate cancer progression. Here, using normal prostate epithelial PNT1A cells we demonstrate that mtDNA depletion prevents detachment-induced apoptosis (anoikis) and promotes migratory capabilities onto basement membrane proteins through upregulation of p85 and p110 phosphatidylinositol 3-kinase (PI3K) subunits, which results in Akt2 activation and phosphorylation of downstream substrates GSK3beta, c-Myc, MMP-9, Mdm2, and p53. Pharmacological or genetic PI3K inhibition, siRNA-mediated Akt2 depletion, as well as mtDNA reconstitution were sufficient to restore sensitivity to anoikis and curtail cell migration. Moreover, Akt2 activation induced glucose transporter 1 (GLUT1) expression, glucose uptake, and lactate production, common phenotypic changes seen in neoplastic cells. In keeping with these findings, several prostate carcinoma cell lines displayed reduced mtDNA content and increased PI3K/Akt2 levels when compared to normal PNT1A cells, and Akt2 downregulation prevented their survival, migration and glycolytic metabolism. On a tissue microarray, we also found a statistically significant decrease in mtDNA-encoded cytochrome oxidase I in prostate carcinomas. Taken together, these results provide novel mechanistic evidence supporting the notion that mtDNA mutations may confer survival and migratory advantage to prostate cancer cells through Akt2 signaling.

Neuroendocrine differentiation in prostatic carcinoma: an update on recent developments.

The most recent developments relating to neuroendocrine differentiation in prostate cancer are reviewed. In vivo and in vitro experimental models of neuroendocrine differentiation in prostate cancer are emphasized with a discussion of their fidelity to the actual human in vivo situation. The contribution of these models to our understanding of the process of neuroendocrine differentiation and the mechanisms by which neuroendocrine differentiation can affect prognosis is discussed. Finally, an hypothosis is proprosed integrating neuroendocrine differentiation into more traditional models of the evolution, differentiation pathways and progression of prostate cancer, particularly in the androgen independent state.

Calcitonin and calcitonin gene-related peptide in the human prostate gland.

BACKGROUND: Calcitonin-related peptides have been found in the human prostate, and calcitonin (CT) and calcitonin gene-related peptide (CGRP) have been demonstrated in subpopulations of neuroendocrine (NE) cells. The purpose of this study was to determine the concentrations of CT and CGRP as well as the densities of NE cells in normal prostates, benign prostatic hyperplasia (BPH), and carcinoma of the prostate (CAP). METHODS: In 42 specimens of radical prostatectomy, the number of CT- and CGRP-immunoreactive NE cells in areas of normal and BPH tissue was determined, and compared with CAP tissue using immunocytochemistry. In addition, by radioimmunoassay (RIA), tissue levels of CT and CGRP were analyzed in extracts from areas of normal, BPH, and CAP tissue, as verified by adjacent histologic sections. RESULTS: A significant decrease in CT-immunoreactive NE cells was observed in hyperplastic nodules of BPH in comparison to normal tissue. These findings were in parallel with a significant reduction in tissue CT level in BPH compared to normal tissue. There was also a marked, but statistically nonsignificant, reduction in CT levels in CAP tissue. In contrast, levels of CGRP in BPH and CAP tissue did not show any significant differences compared to normal tissue. CONCLUSIONS: CT and CGRP are present in NE cells of the human prostate. Calcitonin levels are significantly reduced in BPH, in parallel with a decreased number of CT-immunoreactive NE cells, whereas no significant changes in tissue levels of CGRP were observed. The functional significance of these findings is discussed.

Divergent neuroendocrine differentiation in prostatic carcinoma.

A rich variety of neuroendocrine cells are present in the normal prostate gland. Prostatic carcinoma may show divergent differentiation towards a neuroendocrine phenotype in the form of neuroendocrine small cell carcinoma or carcinoid-like tumors. Much more common is focal neuroendocrine differentiation in prostatic adenocarcinoma which may be pronounced in approximately 10% of adenocarcinomas. The prognostic significance of focal neuroendocrine differentiation in prostatic carcinoma is controversial but current evidence suggests an influence on prognosis related to hormone resistant tumors and/or a role in the conversion to a hormonal resistant phenotype. Chromogranin A appears to be the best overall tissue and serum marker of neuroendocrine differentiation. Chromogranin A serum levels may be useful in the assessment of the emergence of and/or progression of hormone resistant cancer.

Prognostic significance of neuroendocrine differentiation in clinically localized prostatic carcinoma.

Several recent studies have focused attention on neuroendocrine differentiation (NED) in prostatic carcinoma (PC). Clinical studies have shown PC with NED to behave aggressively and to be associated with poor prognosis. To evaluate NED as an independent prognostic factor, we conducted a retrospective study of 87 patients with clinically localized PC who underwent radical prostatectomy. The presence of neuroendocrine tumor cells was confirmed by positive immunostaining for serotonin, chromogranin A, and neuron-specific enolase. The correlation between NED and disease progression was assessed. Progression of cancer was demonstrated in 35 (40%) of the patients. The presence of NED was confirmed in 60 (69%) of cases, and of these patients 26 (43%) manifested evidence of disease progression. Disease progression was also manifest in nine (33%) of the 27 patients without evidence of NED. Thus, in the setting of clinically localized carcinoma of the prostate, NED does not appear to be a statistically significant independent prognostic factor.

Neuroendocrine differentiation in prostatic carcinoma: an update.

BACKGROUND: Neuroendocrine differentiation in prostatic carcinoma may be related to the growth and prognosis of prostate cancer, especially androgen-insensitive tumors. MATERIALS AND METHODS: This update reviews new investigations relating to neuroendocrine differentiation of prostatic carcinoma building on two previous review articles. All relevant publications are systematically reviewed. RESULTS: New developments include the detection of bombesin, calcitonin and serotonin receptors, as well as a clearer delineation of the role that neuroendocrine products play in the growth, invasiveness, and motility of prostate cancer. Prognostic studies are still somewhat contradictory, but those studies and studies related to serum/plasma levels of neuroendocrine products in prostate cancer suggest that neuroendocrine differentiation may be more important in androgen-independent tumors and metastatic tumors than in hormone-sensitive and locally recurrent tumors. New cell line xenograft and transgenic mouse models for neuroendocrine prostatic carcinoma are described and will provide the basis for further investigations into the role played by neuroendocrine differentiation in prostatic carcinoma. CONCLUSIONS: Neuroendocrine differentiation in prostatic carcinoma is of great potential significance but needs to be better defined before its significance can be accurately assessed.

Characterization of the cell-specific expression of parathyroid hormone-related protein in normal and neoplastic prostate tissue.

OBJECTIVES: Parathyroid hormone-related protein (PTHrP) is a primary factor in the pathogenesis of malignancy-associated hypercalcemia. By alternative splicing, the human PTHrP gene can generate three different species of mRNA that encode three initial translational isoforms of 139, 173, and 141 amino acids. We recently reported that PTHrP was present in normal prostatic neuroendocrine cells and was overexpressed in prostate cancer tissue as demonstrated by immunostaining. This study was undertaken to further clarify the complex expression of PTHrP gene in normal prostate tissue and prostate cancer. METHODS: PTHrP mRNA in samples prepared from normal prostate tissue, prostate cancer, and three prostate cancer cell lines, PC3, LNCaP, and DU145 was assessed using Northern hybridization. Expressed PTHrP isoforms were deduced from differential reverse transcription-polymerase chain reaction (RT-PCR) assays with exon-specific primers. Further localization of different species of PTHrP mRNA was performed using nonradioactive in situ hybridization with exon-specific probes on consecutive sections of normal and neoplastic prostate tissue. RESULTS: Northern hybridization showed that the PTHrP expression level was higher in prostate cancer than in normal prostate tissue. All three PTHrP isoforms could be detected in normal prostate tissues and prostate cancer with differential RT-PCR. Further analysis using in situ hybridization with exon-specific probes revealed that all three PTHrP isoforms were present in prostatic neuroendocrine cells and only PTHrP-1-139 isoform could be clearly detected in prostate cancer tissue. Two androgen-insensitive cell lines, PC3 and DU145, derived from a bone metastasis and a brain metastasis, respectively, expressed all three mRNA species encoding for the three isoforms, but DU145 cells expressed less than PC3 cells. Androgen-sensitive LNCaP cells exhibited a low level of expression of mRNA species encoding for PTHrP-1-139 and PTHrP-1-173, and no expression of PTHrP1-141 isoform. CONCLUSIONS: All three initial translational isoforms of PTHrP are produced by prostatic neuroendocrine cells. The mature products of PTHrP might exert their effects on other prostatic epithelial cells in a paracrine fashion and also participate in the homeostatic regulation of the ejaculate. In prostate cancer, differential expression of these three isoforms is evident and PTHrP-1-139 isoform is more abundant than the other two forms. These findings are valuable for designing future research studies to further elucidate the biological functions of PTHrP in normal prostatic glands and prostate cancer.

Neuroendocrine cells of the prostate and neuroendocrine differentiation in prostatic carcinoma: a review of morphologic aspects.

Neuroendocrine cells of the prostate are intraepithelial regulatory cells that secrete serotonin and a variety of peptide hormones. It is hypothesized that these cells regulate both growth and differentiation, as well as exocrine secretory activity through endocrine, paracrine, neurocrine, and lumenocrine mechanisms. Neuroendocrine differentiation in prostatic carcinoma occurs as pure neuroendocrine malignancies, such as small-cell carcinoma and carcinoid/carcinoid-like tumors, as well as focal neuroendocrine differentiation in a more conventional prostatic adenocarcinoma. Neuroendocrine differentiation in prostatic carcinoma may have diagnostic and prognostic significance.

Energy charge monitoring via magnetic resonance spectroscopy 31P in the perfused human placenta: effects of cadmium, dinitrophenol and iodoacetate.

Phosphorus 31 nuclear magnetic resonance spectroscopy as a non-invasive technique was applied to monitor the metabolic activity of the human placenta during perfusion in vitro. During control perfusions (n = 3) there was an initial increase in adenosine triphosphate (ATP) and a fall in inorganic phosphate (Pi). Thereafter, however, the level of both ATP and Pi remained constant throughout the perfusion period (11 h). Additional biochemical parameters such as glucose consumption, lactate production and the release of hormones, human chorionic gonadotrophin (hGC). measured in the perfusate samples, were also used to assess the viability of the placental tissue. As with ATP, all these biochemical parameters under the control conditions showed a stable rate of metabolic activity throughout the length of the experiments. In additional experiments, the effect of the metabolic inhibitor dinitrophenol (n = 2) and dinitrophenol (DNP) together with iodoacetic acid (IOA, n = 2) were studied. DNP (0.1 mM) alone showed a slight decrease of all parameters. In contrast, the addition of IOA (0.1 mM) with DNP (0.1 mM) not only blocked the production of ATP but also produced a substantial impact on placental metabolic activity. The effect of a toxic dose of cadmium (20 nmol/ml) was studied also (n = 3). This dose of cadmium demonstrated no effect on phosphorus metabolism. However, the rate of glucose consumption and the release of hCG were significantly reduced.

Immunoassay and immunohistology studies of chromogranin A as a neuroendocrine marker in patients with carcinoma of the prostate.

OBJECTIVES: Neuroendocrine differentiation in carcinoma of the prostate is characterized by the expression of neuroendocrine cell products such as chromogranin A (CgA). We studied serum levels and tissue staining for CgA in prostate cancer to assess their clinical value. METHODS: In 82 patients with prostate cancer, serum specimens were obtained at diagnosis and studied by both CgA and prostate-specific antigen (PSA) immunoassays. In 43 additional patients with prostate cancer, paraffin-embedded tissue from core biopsies or transurethral resections and serum samples were studied, respectively, by immunohistology and immunoassay for CgA. RESULTS: In serum samples from the 82 patients in whom CgA and PSA levels were measured, 26 of 82 (32%) had an elevated CgA (greater than 200 ng/mL), and 36 of 82 (44%) had an elevated PSA (greater than 4.0 ng/mL). Of the patients with Stage D2 cancer, 11 of 18 (61%) had an elevated CgA and 6 of 18 (33%) had an elevated PSA. Four of 5 patients with local recurrence had an elevated CgA, but only 1 patient had an elevated PSA. Of the 43 patients in whom serum and tissue CgA studies were performed, 12 (28%) had elevated serum CgA, and 15 of the 43 (35%) had CgA staining in their prostate tissue. Of the 14 of these patients with D2 disease (distant metastases), 9 (64%) had elevated serum levels of CgA and 6 (43%) had positive staining in their prostate tissue. Of the 9 patients with Stage D2 disease and elevated serum CgA, 6 had a normal serum PSA. CONCLUSIONS: Our studies complement those of others and indicate that CgA has potential as a clinically useful serum and tumor marker for prostate cancer. Serum CgA measurements can identify some patients with advanced disease who do not have elevated serum PSA. However, further studies in larger groups of patients are needed to define the clinical value of CgA as a marker for prostate cancer.

Neuroendocrine differentiation in prostatic malignancy.

BACKGROUND: The prostatic neuroendocrine cell is a regulatory cell that produces serotonin and peptide hormones. This cell is part of a more widely dispersed diffuse neuroendocrine regulatory system known as the APUD system. Focal neuroendocrine differentiation is seen in virtually all prostate carcinomas to one degree or another. Specific malignancies that are purely neuroendocrine include small cell carcinoma and carcinoid/carcinoid-like tumors. A variety of studies suggest a possible prognostic significance of neuroendocrine differentiation in prostate carcinoma. METHODS: The literature on the prostatic neuroendocrine cell and neuroendocrine differentiation in prostate carcinoma is reviewed. RESULTS: Based on analogy with other better studied elements of the diffuse neuroendocrine regulatory system or APUD system, as well as the morphology and specific products produced by neuroendocrine cells, it is likely that they play an important regulatory role in the prostate. Neuroendocrine differentiation may be of prognostic significance in prostate carcinoma. Mechanisms are not well characterized at this point, but the known growth factor activity of the neuroendocrine cell products, an increase in proliferation in cells surrounding neuroendocrine cells, and a lack of androgen receptor expression in neuroendocrine cells, suggest mechanisms by which they may be of prognostic significance. CONCLUSIONS: Neuroendocrine differentiation in prostate carcinoma may be of prognostic significance, but better methods to define neuroendocrine, differentiation are necessary. The therapeutic implications of neuroendocrine differentiation in prostate carcinoma may be of significance and need to be explored further.

Calcitonin receptor mRNA expression in the human prostate.

OBJECTIVES: A subpopulation of prostate neuroendocrine (NE) cells contain calcitonin (CT). It has been postulated that CT-producing cells in the prostate account for the high CT level in the semen, and may be involved in the regulation of other epithelial cells via a paracrine mechanism. The presence of CT binding sites in the plasma membrane fraction of prostate tissue has been demonstrated by radioligand binding assay. In the present study, we investigated the CT receptor gene expression in the human prostate, a key component of the autocrine/paracrine loop in the CT functional pathway. METHODS: Reverse transcription polymerase chain reaction (RT-PCR) was carried out to evaluate the CT receptor mRNA expression in normal prostate tissue. Subsequent DNA sequencing was used to verify RT-PCR amplified products and to determine the isoform of the receptor. To define the location of the CT receptor expression, nonradioactive in situ hybridization was performed with a digoxigenin-labeled probe complementary to the coding region of the CT receptor mRNA. A polyclonal antibody against CT was used to reveal the CT-secreting cells in the prostate. RESULTS: CT receptor MRNA expression was detected in the prostate tissue. Further analysis of the DNA sequence showed that CT receptor expressed in the prostate was the isoform without a 16-amino acid insert in the first intracellular domain. In situ hybridization revealed that CT receptor was present in the prostate NE cells. Immunocytochemical staining of mirror image sections showed that some CT-secreting cells also expressed CT receptor. CONCLUSIONS: CT receptor expression in the prostate, a key component in the CT functional pathway, is located in subsets of dispersed NE cells (CT secreting and CT nonsecreting), which indicates that prostate CT may play an important role in the autocrine/paracrine regulation of the prostate NE system.

Neuroendocrine differentiation in the precursors of prostate cancer.

OBJECTIVES: To review neuroendocrine differentiation in the precursors of prostatic carcinoma (prostatic intraepithelial neoplasia). METHODS: Background information is given on the prostatic neuroendocrine cell and neuroendocrine differentiation in prostatic carcinoma. Neuroendocrine differentiation in prostatic intraepithelial neoplasia is reviewed. RESULTS: Neuroendocrine differentiation occurs in prostatic intraepithelial neoplasia and is intermediate in degree between normal (which has the most cells with neuroendocrine differentiation) and carcinoma. CONCLUSION: Neuroendocrine differentiation in the precursors of prostatic carcinoma may play a role in the pathogenesis of cancer but is speculative at this time. Methods to better assess neuroendocrine differentiation are needed.

Immunohistochemical localization of parathyroid hormone-related protein in prostatic intraepithelial neoplasia.

Parathyroid hormone-related protein (PTHrP) is a regulatory protein hormone that has been associated with normal fetal growth and differentiation as well as fetal calcium regulation. Parathyroid hormone-related protein has been implicated in a variety of carcinomas as a major factor in the development of humoral hypercalcemia of malignancy and may also play a role as an autocrine growth factor. In a previous immunohistochemical study we found that all prostatic adenocarcinomas (CAP) express PTHrP. In the current study, we evaluated PTHrP in prostate intraepithelial neoplasia (PIN) in radical prostatectomy specimens. A validated mouse monoclonal antibody, 9H7, raised against fragment 109-141 of the carboxy-terminus of PTHrP was used for immunostaining. The results generally showed negative to weak staining of normal and hyperplastic tissue and strong staining in PIN. The staining intensity was further evaluated by computer based image analysis. The relative optical density in PIN (9.24 +/- 9.05) was significantly (P = .008) higher than that in normal gland (.00 +/- 3.6). These findings suggest that PTHrP may be involved in the pathogenesis of prostatic dysplasia, and its immunohistochemical evaluation may have diagnostic use in the evaluation of PIN.

Continuous measurement of ATP by 31P-NMR in term human dually perfused placenta in vitro: response to ischemia.

ATP was examined in dually perfused term human placentas by using 31P-nuclear magnetic resonance (NMR) spectroscopy. 31P-NMR spectra were acquired every 30 min starting approximately 30 min after establishing fetal and maternal perfusions, and maternal perfusate samples were obtained to monitor glucose utilization, lactate production, and human chorionic gonadotropin (hCG) and human placental lactogen (hPL) release. In continuous-perfusion experiments, placentas were perfused as long as 10 h. ATP increased and Pi fell after initiation of perfusion. Fetal volume loss was < 2 ml/h, and constant production of hCG, hPL, and lactate as well as constant utilization of glucose were observed. In additional experiments, ischemia was produced by halting maternal and fetal perfusion pumps after a 2-h control period. After 2, 3, or 4 h of ischemia, ATP decreased 46 +/- 17, 51 +/- 5, and 85% of control, respectively. When perfusion was reinitiated, ATP increased and was maintained for the duration of the experiment (an additional 2 h). Recovery of ATP after reperfusion was not paralleled by recovery in glucose utilization, lactate production, or hPL and hCG release. However, during the reperfusion period, fetal pressure was < 70 mmHg and fetal volume loss was < 2 ml/h. These investigations suggest that the dually perfused human placental lobule can maintain ATP for > or = 10 h. Although the perfused human placenta recovers ATP and maintains fetal perfusion volume after ischemia lasting up to 4 h, utilization of glucose, production of lactate, and production and release of hCG and hPL are impaired.

The prostatic endocrine-paracrine (neuroendocrine) regulatory system and neuroendocrine differentiation in prostatic carcinoma: a review and future directions in basic research.

Endocrine-paracrine (neuroendocrine, amine precursor uptake and decarboxylation [APUD]) cells of the prostato-urethral region are serotonin and peptide containing regulatory cells, which are part of a dispersed neuroendocrine regulatory system also known as the APUD system. These cells most likely regulate growth and differentiation, as well as the secretory functions of the prostate. Prostatic carcinoma exhibits neuroendocrine differentiation in 3 forms: 1) small cell neuroendocrine carcinoma, 2) carcinoid-like tumors and 3) conventional prostatic adenocarcinoma with focal neuroendocrine differentiation. Small cell carcinoma and carcinoid-like tumors are rather rare (1 to 2% of all prostatic malignancies) and generally pursue an aggressive course. Focal neuroendocrine differentiation in adenocarcinoma is extensive in 10% of the cases and may be present in virtually all adenocarcinomas to a minor degree. There are conflicting studies on the prognostic significance of focal neuroendocrine differentiation in prostatic carcinoma, although several suggest a poor prognosis. The finding that serum neuroendocrine markers predict initial insensitivity to or the development of resistance to hormonal suppression therapy, coupled with the recent observation that androgen receptor is not expressed in neoplastic neuroendocrine cells suggests that neuroendocrine differentiation directly results in resistance to hormonal manipulation therapy. Neuroendocrine differentiation in prostatic carcinoma raises the possibility of innovative modes of treatment. Future directions of research should concentrate on the quantitative analysis of serotonin and various peptides in prostatic malignancy, since high levels of constitutive secretion may not be appreciated by immunocytochemistry, as well as analysis of tumors for receptors to neuroendocrine products, which are necessary for these products to have a functional role. Finally, specific subtypes of neoplastic cells with neuroendocrine differentiation based on serotonin and peptide profiles should be analyzed.

Anomalous immunostaining of 'optically clear' nuclei in gestational endometrium. A potential pitfall in the diagnosis of pregnancy-related herpesvirus infection.

A distinctive morphologic alteration originally described as nuclear "clearing" has been observed in endometrial epithelium during pregnancy. Affected nuclei have a clear center and a rim of marginated chromatin, imparting a "glassy" appearance reminiscent of herpesvirus inclusions. We observed this change in gestational endometrium attached to the membranes of an otherwise normal-term placenta. Because of the morphologic suggestion of herpesvirus infection, immunoperoxidase studies using the avidin-biotin method were performed, resulting in intense staining of nuclear inclusions. An identical pattern of nuclear staining was also noted in negative controls. This anomalous staining reaction was replicated with the streptavidin-biotin method but not with the peroxidase-antiperoxidase method. Furthermore, nuclear staining was abolished after sequential preincubation with free avidin (0.05%) and free biotin (0.05%). Using the peroxidase-antiperoxidase method, positive nuclear staining was identified with monoclonal antibodies to biotin. Similar results were obtained in nine additional cases of optically clear nuclei associated with term placentas. We conclude that staining of optically clear nuclei is the result of avidin and streptavidin binding to intranuclear biotin. This anomalous staining pattern could potentially result in the misdiagnosis of herpesvirus infection.

Androgen receptor immunostaining and its tissue distribution in formalin-fixed, paraffin-embedded sections after microwave treatment.

We used microwave (MW) oven heat treatment to unmask human androgen receptor (AR) immunostaining in formalin-fixed, paraffin-embedded tissue. Prostate tissue was used as an AR-positive control. Tissue sections were boiled in citrate buffer in a conventional MW oven for 30 min, followed by immunostaining with a validated murine monoclonal antibody (MAb), F39.4.1, raised against a peptide included in the N-terminal domain of the 100 KD human AR. AR immunostaining was localized to the nuclei of prostate secretory epithelial cells but was weak or absent in basal cells and of variable intensity in the stromal cells. Slides exposed to less than 10 min of MW heat treatment or none at all manifested no AR immunoreactivity. Tissue morphology was well preserved. Immunohistochemical determination of AR status in a wide variety of human tissues was consistent with that previously reported by others using frozen sections. MW heat treatment of tissue samples in an excellent method of localizing AR antigenicity, enabling immunohistochemical evaluation of AR status in formalin-fixed, paraffin-embedded material.

Overexpression of human epidermal growth factor receptor and c-erbB-2 by neuroendocrine cells in normal prostatic tissue.

OBJECTIVE: It has been suggested that prostatic neuroendocrine (NE) cells play an important role in the growth and differentiation of the prostate by secreting various neuropeptides and serotonin. However, the mechanism by which NE cells themselves are regulated is virtually unknown. In the present study we evaluated the expression of the human epidermal growth factor receptor (EGFR) family (HER) in prostatic NE cells. METHODS: Formalin-fixed, paraffin-embedded tissue sections from twenty radical prostatectomy specimens were immunostained with validated rabbit polyclonal antibodies raised against human EGFR and c-erbB-2, using the streptavidin-peroxidase enzyme conjugate method. RESULTS: A strong immunoreactivity was observed with both antibodies in the cytosol of a few epithelial cells. These cells frequently had a dendritic appearance and were located in the acini and ducts. The EGFR-positive cells were predominant in most cases. Double immunostaining revealed the colocalization of both antigens with chromogranin A, a polypeptide that is expressed by most NE cells. Moreover, EGFR and c-erbB-2 appeared to be colocalized as well as independently expressed by different subpopulations of NE cells. CONCLUSIONS: The results suggest that prostatic NE cells might be regulated by the HER protein family, probably, in a ligand-specific fashion. This is the first report identifying a potential pathway regulating prostatic NE cells.