The neuroendocrine prostate: characterization and quantitation of calcitonin in the human gland

Role of Seminal Plasma Proteins in Effective Zygote Formation- A Success Road to Pregnancy

Seminal plasma proteins contributed by secretions of accessory glands plays a copious role in fertilization. Their role is overlooked for decades and even now, as Artificial Reproduction Techniques (ART) excludes the plasma components in the procedures. Recent evidences suggest the importance of these proteins starting from imparting fertility status to men, fertilization and till successful implantation of the conceptus in the female uterus. Seminal plasma is rich in diverse proteins, but a major part of the seminal plasma is constituted by very lesser number of proteins. This makes isolation and further research on non abundant protein a tough task. With the advent of much advanced proteomic techniques and bio informatics tools, studying the protein component of seminal plasma has become easy and promising. This review is focused on the role of seminal plasma proteins on various walks of fertilization process and thus, the possible exploitation of seminal plasma proteins for understanding the etiology of male related infertility issues. In addition, a compilation of seminal plasma proteins and their functions has been done.

Sperm proteins in teleostean and chondrostean (sturgeon) fishes

Sperm proteins in the seminal plasma and spermatozoa of teleostean and chondrostean have evolved adaptations due to the changes in the reproductive environment. Analysis of the composition and functions of these proteins provides new insights into sperm motility and fertilising abilities, thereby creating possibilities for improving artificial reproduction and germplasm resource conservation technologies (e.g. cryopreservation). Seminal plasma proteins are involved in the protection of spermatozoa during storage in the reproductive system, whereas all spermatozoa proteins contribute to the swimming and fertilising abilities of sperm. Compared to mammalian species, little data are available on fish sperm proteins and their functions. We review here the current state of the art in this field and focus on relevant subjects that require attention. Future research should concentrate on protein functions and their mode of action in fish species, especially on the role of spermatozoa surface proteins during fertilisation and on a description of sturgeon sperm proteins.

Calcitonin increases invasiveness of prostate cancer cells: Role for cyclic AMP-dependent protein kinase A in calcitonin action

Calcitonin (CT) is synthesized and secreted in prostate epithelium, and its secretion from malignant prostates is several-fold higher than from benign prostates. CT receptor (CTR) is expressed in malignant prostate epithelium, and its activation stimulates growth of prostate cancer (PC) cells via activation of adenylyl cyclase and calcium/phospholipid pathways. To identify the role of "CT System" in prostate cancer, we tested the expression of CT and CTR mRNAs in invading tumor cells of prostate cancer specimens. The effect of CT on in vitro invasion of PC cell lines and on activation of gelatinases was also examined. The cells of primary tumors and those invading stroma co-expressed CT/CTR mRNAs. Exogenously added CT increased in vitro invasion of PC cell lines and caused a rapid, several-fold but transient increase in protein kinase A activity. In contrast, anti-CT serum caused a dose-dependent inhibition of in vitro invasion of PC-3M cells. CT also increased the concentration and activities of MMP-2 and MMP-9. Rp.cAMP, a competitive inhibitor of cAMP-dependent protein kinase A, myristoylated protein kinase A inhibitory peptide (PKI) as well as the expression of dominant negative form of PKA all attenuated basal in vitro invasion of PC-3M cells, and CT could not increase in vitro invasiveness in their presence. These results suggest that overexpression of "CT System" in invasive PC tumors significantly contributes to increased invasiveness of prostate cancer cells. The action of CT may be mediated by protein kinase A signaling, which subsequently leads to increased cell invasion and secretion of gelatinases.

Calcitonin receptor gene expression in K562 chronic myelogenous leukemic cells

BACKGROUND: The peptide hormone calcitonin (CT) can significantly effect the proliferation rate of CT receptor (CTR) positive human cancer cells. We wish to identify additional human cancers expressing CTRs and assay the effects of CT on their growth rates and signal transduction pathways. RESULTS: The expression of the human calcitonin receptor (hCTR) gene in the chronic myelogenous leukemia cell line K562 was examined. RT-PCR on total RNA extracted from K562 cells detected the presence of hCTR mRNA. Further analysis demonstrated that multiple hCTR isoforms were present. Incubation of K562 cells with salmon calcitonin (sCT), but not amylin, caused an increase in intracellular levels of cAMP similar to that induced by forskolin treatment. We further demonstrated that butyrate induced erythroid differentiation of K562 cells caused a significant decrease in hCTR mRNA levels. However, phorbol myristate acetate (PMA) induced megakaryocytic differentiation of these cells had no significant effect on hCTR mRNA levels. We demonstrated that exposure to various concentrations of sCT had no effect on the cellular proliferation of K562 cells in vitro. CONCLUSION: Chronic myelogenous k562 cells express multiple CTR isoforms. However, CT does not effect K562 proliferation rates. It is likely that the small increase in intracellular levels of cAMP following CT treatment is not sufficient to interfere with cellular growth.

Neuroendocrine expression in node positive prostate cancer: correlation with systemic progression and patient survival

PURPOSE

Neuroendocrine cells are ubiquitous but uncommon in benign and neoplastic prostate epithelium, and they are considered important for regulating cell growth and differentiation. The predictive value of neuroendocrine immunoreactivity for patient outcome after radical prostatectomy is uncertain. In this study we determined the expression of 2 important neuroendocrine markers, chromogranin and serotonin, in benign epithelium, primary prostate cancer and lymph node metastases, and correlated cellular expression with patient outcome.

MATERIALS AND METHODS

We studied 196 patients with node positive prostate adenocarcinoma who underwent bilateral pelvic lymphadenectomy and radical prostatectomy at Mayo Clinic between 1987 and 1992. Mean followup was 6.8 years (range 0.3 to 11). The cellular expression of chromogranin and serotonin in matched samples of benign tissue, primary prostate cancer and lymph node metastases from the same patients was evaluated by immunohistochemical staining using commercially available monoclonal antibodies. Results were correlated with patient age, pathological findings (Gleason score, DNA ploidy and cancer volume) and patient outcome, including clinical progression, cancer specific and all cause survival.

RESULTS

Chromogranin immunoreactivity was greater in benign prostatic epithelium and primary cancer cases (99% each) than in those of lymph node metastases (37.5%) (pairwise comparisons with metastases p <0.001). The mean incidence of immunoreactive cells in benign epithelium, primary cancer and metastases was 6% (median 5%), 6% (median 3%) and 2.2% (median 0%), respectively. Serotonin immunoreactivity was greatest in benign prostate epithelium cases (98.5%) with less in primary cancer (95%) and lymph node metastases (21.5%) (pairwise comparisons p <0.001). The mean incidence of immunoreactive cells in benign epithelium, primary cancer and metastases was 2.2% (median 3%), 2.4% (median 2%) and 0.4% (median 0%), respectively. Chromogranin expression was invariably greater than that of serotonin for all 3 diagnostic categories (p <0.0001). There was a marginally significant positive trend in the level of chromogranin expression in benign prostatic epithelium and systemic progression (p = 0.05) but no significant association with cancer specific or all cause survival (p >0.1). No significant association was observed of chromogranin expression in primary cancer or lymph node metastases with any patient outcomes (p >0.1). There was a significant association of the level of serotonin expression in benign prostatic epithelium with cancer specific survival (p = 0.03) but no significant association with systemic progression or all cause survival (p > 0.1). There were positive trends in the association of serotonin immunoreactivity in primary cancer with systemic progression (p = 0.09) and cancer specific survival (p = 0.05) but not with all cause survival (p >0.1). No significant association was observed of serotonin expression in lymph node metastases with any patient outcomes (p >0.1).

CONCLUSIONS

Benign prostatic epithelium and primary prostate cancer express a significantly greater number of chromogranin and serotonin immunoreactive cells than lymph node metastases, suggesting that decreased expression of neuroendocrine markers is involved in cancer progression. However, neuroendocrine expression was marginally useful for predicting the outcome in patients with node positive prostate cancer treated with radical prostatectomy.

Calcitonin is a prostate epithelium-derived growth stimulatory peptide

Locally secreted growth factors and neuropeptides may play an important role in sustaining the growth of hormone-independent prostate cancer. Our previous studies have shown that calcitonin-like immunoreactive peptide (CTI) is secreted by primary prostate cells in culture, and its secretion from malignant prostate cells is significantly higher than benign cells. Exogenously added calcitonin (CT) induces DNA synthesis in serum-starved prostate cancer LNCaP and PC-3M cells. Present studies extended these findings by cloning cDNAs for CT and CT receptor (CT-R) from prostate cancer cells and studying the expression of CT and CT-R mRNA in prostate cancer cell lines and primary prostate tumor specimens. The results have shown that PC-3 cells expressed CT, and not CT-R, mRNA, whereas CT-R, but not CT, mRNA was expressed by LNCaP cells. Conditioned media from PC-3 cells induced DNA synthesis of LNCaP cells, and this mitogenic response was abolished by anti-CT serum. Highly aggressive PC-3M cells co-expressed CT and CT-R mRNAs. CT also induced a twofold increase in DNA synthesis of primary prostate cells and anti-CT serum caused a 56% decline. In-situ hybridization histochemistry of archival prostate specimens has selectively localized CT and CT-R mRNA in basal epithelium of benign and low grade PC specimens, and these mRNAs were not detected in either luminal epithelium or stroma. In contrast, CT and CT-R mRNA were detected throughout the luminal epithelium of moderate and high-grade PC specimens. Most epithelial cells of low and moderately differentiated tumors expressed either CT or CT-R mRNA, suggesting that CT may serve as a paracrine factor. In contrast, CT and CT-R mRNAs were co-expressed by most tumor cells in advanced PC specimens. The cells expressing CT-R mRNA in primary tumors also co-expressed PCNA. These results, when combined with mitogenic actions of CT on primary prostate cells as well as PC cell lines, strongly support the role for CT in sustaining the growth of cancer cells.

Effect of seminal plasma calcitonin levels on sperm mobility

This study investigated the effect of the seminal and blood plasma calcitonin levels on the sperm motility in idiopathic infertile patients. The number of sperm cells and their motility were evaluated in the spermiograms of 52 idiopathic infertile patients. The levels of seminal plasma calcitonin were studied with double antibody technique using a DPC kit. Fifty-two patients were divided into 2 groups according to the motility rates of sperm and 20 healthy volunteers were assigned to a control group. The difference between the groups was evaluated by using Kruskall-Wallis and Mann-Whitney U tests, and the correlation of seminal and blood calcitonin levels with sperm motility were determined. The difference in motility rates between the 3 groups was statistically significant (p = .000, p < .05). Blood plasma calcitonin levels were in normal ranges in all cases and no significant difference was found among the 3 groups (chi2 = 2.7219, p = .2589, p > .05). While sperm motility was correlated with seminal calcitonin levels (r = .8581), blood calcitonin levels did not show a correlation with sperm motility rate (r = -.0265). Moreover, there was no correlation between seminal and blood plasma levels of calcitonin (r = -.0010). Motility rates decreased in the patients with low seminal calcitonin levels and seminal calcitonin levels had a significant effect on sperm motility.

Calcitonin and calcitonin receptors: bone and beyond

Calcitonin (CT), a 32 amino acid peptide hormone produced primarily by the thyroid, and its receptor (CTR) are well known for their ability to regulate osteoclast mediated bone resorption and enhance Ca2+ excretion by the kidney. However, recent studies now suggest that CT and CTRs may play an important role in a variety of processes as wide ranging as embryonic/foetal development and sperm function/physiology. In this review article, CT and CTR gene transcription, signal transduction and function are addressed. The effects of CT on the physiology of a variety of organ systems are discussed and the relationship between polymorphisms in the CTR gene and bone mineral density (BMD)/osteoporosis is examined. Recent studies demonstrating the ability of receptor activity modifying proteins (RAMPs) to post-translationally modify the calcitonin receptor-like receptor (CRLR) are detailed and studies employing transgenic mouse technology to determine the temporal and tissue specific transcriptional activity of the CTR gene in vivo are discussed.

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.

Neuroendocrine cells in the prostate of the rat, guinea pig, cat, and dog

BACKGROUND

The neuroendocrine (NE) cells in the human prostate gland probably have a local regulatory role in both prostatic growth and differentiation as well as in the exocrine secretory process. Moreover, NE cells may be involved in the pathogenesis of both prostatic cancer and hyperplasia. To enhance the knowledge of the physiological and pathophysiological role of NE cells in the prostate gland, we wanted to establish an experimental animal model.

METHODS

All lobes of the prostatic complex of rats with different serum levels of testosterone, as well as the prostate of the guinea pig, cat, and dog, were studied. Prostatic tissue fixed in different fixatives was studied with regard to NE cells by using cytochemical and immunohistochemical staining techniques, as well as Northern blotting and reverse transcriptase polymerase chain reaction (RT-PCR) for detection of rat chromogranin A (CgA) mRNA.

RESULTS

The present study indicates the absence of NE cells in the rat prostatic complex. No expression of CgA RNA was detectable either by Northern blotting or by RT-PCR. Only a few argyrophil cells in the prostatic complex of guinea pig were detected in tissue fixed in Bouin's solution.

CONCLUSIONS

Rat, guinea pig, cat, and dog are not suitable animals in physiological studies of NE cells in the prostate gland.

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.

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 peptides in the prostate

Circulating androgens are required for normal growth and maintenance of function of the prostate. However, the prostate also contains neuroendocrine peptides, found either in nerve terminals or in prostatic neuroendocrine cells, which are likely to regulate prostate growth or function. The neuronal peptides are likely to participate in the regulation of the synthesis and secretion of prostatic secretory products. While the function of the neuroendocrine cells is undefined, there is evidence for growth-regulating effects of several neuroendocrine cell peptides. Since neuroendocrine differentiation has been correlated with tumor grade and poor prognosis in prostate cancer, the peptide products of the neuroendocrine cells may influence cancer cell replication as well. Recent evidence in other tissues suggests that peptide hormone receptor second-messenger systems may interact with steroid receptors to modulate their actions. These findings raise the possibility that prostatic neuroendocrine peptides may modulate the response of prostate to androgens.

Neuroendocrine cells in the normal, hyperplastic and neoplastic prostate

Neuroendocrine cells can be demonstrated in normal, hyperplastic and neoplastic prostatic tissues. The products secreted by these cells can be used as tissue and/or serum markers but may also have biological effects. Neuroendocrine cells in prostate cancer most probably do not contain the androgen receptor and are therefore primarily androgen independent. Some of the neuropeptides secreted by the neuroendocrine cells may act as growth factor by activation of membrane receptors in an autocrine-paracrine fashion or by ligand-independent activation of the androgen receptor in neighboring non-neuroendocrine cells. Evidence is accumulating from experiments with tumor models that neuropeptides indeed can influence the growth of prostatic tumor cells. Future research on neuroendocrine differentiation may answer some questions concerning the biological behavior of clinical prostatic tumors.

Immunohistochemical localization of chromogranins A and B and secretogranin II in normal, hyperplastic and neoplastic prostate

Routinely processed normal, hyperplastic and neoplastic prostatic tissue was immunohistochemically investigated with antibodies against chromogranin A and B and secretogranin II. In normal and hyperplastic prostates all three peptides were immunolocalized in scattered neuroendocrine cells situated within the glandular epithelium. In 17 prostatic carcinomas with pronounced neuroendocrine differentiation and in a case of prostatic carcinoid, chromogranin B was the major component whereas chromogranin A and secretogranin II were virtually absent in poorly differentiated (grade III) tumours. Neuroendocrine differentiation in prostatic cancer is most likely to be associated with a poor clinical outcome; thus, chromogranin B appears to be a useful marker in the histopathological diagnosis of these neoplasms.

Relationship of neuroendocrine cells of prostate and serotonin to benign prostatic hyperplasia

Neuroendocrine (NE) cells containing neurosecretory granules, rich in various peptide hormones and biogenic amines such as serotonin (5-HT), are components of the human prostate epithelium. The NE cells probably subserve a paracrine or local regulatory role in both prostatic growth and differentiation as well as the exocrine secretory process. Neuroendocrine cells may be involved in the etiology of benign prostatic hyperplasia (BPH). In this study the number of NE cells in areas of BPH was compared with normal tissue using 5-HT immunocytochemistry. In addition, using high-performance liquid chromatography with electrochemical detection (HPLC-ECD), tissue levels of 5-HT and its metabolite 5-hydroxy-indoleacetic acid (5-HIAA) were analyzed in prostatic tissue extracts including 25 cases of BPH and 16 cases of normal tissue verified by adjacent histologic sections. Compared with normal prostate our results demonstrated a marked decrease in 5-HT immunoreactive NE cells in the vast majority of larger hyperplastic nodules of BPH. These findings were corroborated by quantitative analysis where a significant reduction in the tissue 5-HT levels in BPH (0.539 +/- 0.09 SE) compared with normal (1.75 +/- 0.22 SE) (p < 0.05) was found. When smaller nodules of BPH were studied, abundant NE cells, equal or increased in number compared with those in adjacent normal prostatic tissue, were seen. The small apparently developing BPH nodules and ductal-like structures contained NE cells which may be growth foci near the periphery of some hyperplastic nodules. These findings particularly in small hyperplastic nodules suggest that NE cells and their products involved in controlling cell proliferation through a paracrine hormonal mechanism and may be involved in the pathogenesis of BPH. Serotonin (5-HT) and NE peptides may represent that elusive local "missing link" often alluded to in various theories relating to the development of early nodular hyperplasia in BPH.

Neuroendocrine differentiation in carcinoma of the prostate. Diagnostic, prognostic, and therapeutic implications

Endocrine-paracrine cells of the prostate (also known as APUD or neuroendocrine cells) constitute, in addition to the basal and exocrine secretory cells, a third population of highly specialized epithelial cells in the prostate gland. These endocrine-paracrine cells contain, and most likely secrete, serotonin and calcitonin, as well as variety of other peptides. Little is known of the functional role of these cells, but they probably subserve a paracrine or local regulatory role. They may also regulate via endocrine, lumencrine, or neurocrine mechanisms. These endocrine-paracrine cells probably play a significant role during prostatic growth and differentiation as well as regulating the secretory process of the mature gland. Neuroendocrine differentiation in prostatic carcinoma occurs in the form of the relatively rare small cell carcinoma and carcinoid or carcinoid-like tumor, but most commonly as focal neuroendocrine differentiation in a conventional prostatic adenocarcinoma that is a very frequent, if not ubiquitous phenomenon, and reflects tumor cell heterogeneity mimicking the normal differentiation process. The world's literature on neuroendocrine differentiation in prostatic carcinoma is reviewed. Neuroendocrine differentiation in all types of prostatic carcinoma appears to correlate with a poor prognosis. This correlation is probably multifactorial and may relate to a positive correlation with grade, a direct resistance to hormonal manipulation, and/or autocrine/paracrine growth factor activity due to the secretion of neuroendocrine products. Neuron-specific enolase and chromogranin, as well as other neuroendocrine products, may be useful as serum markers in patients with prostatic carcinoma with neuroendocrine differentiation. New therapeutic strategies need to be developed to treat these tumors. This includes the use of specialized protocols that have been effective against neuroendocrine carcinomas arising in other organ systems.

Neuroendocrine differentiation in human prostatic carcinoma

Endocrine-paracrine (APUD, neuroendocrine) cells are located in the prostatic ductal and acinar epithelium. These cells are of the open and closed type and have dendritic processes. There is a wide range of secretory granule morphology presumably indicating a variety of different cell "types." Secretory immunoreactive peptides include serotonin, calcitonin (and related peptides), somatostatin, bombesin-like, thyroid-stimulating hormone-like (beta chain), and alpha-glycoprotein chain-like. These cells may function by endocrine, paracrine, neurocrine, and lumencrine mechanisms and play an important regulatory role both during growth and differentiation of the prostate as well as in the secretory process of the mature gland. Neuroendocrine differentiation in prostatic carcinoma is a frequent occurrence and manifests itself in several forms, including (1) small cell carcinoma, (2) carcinoid and carcinoid-like tumors, and (3) conventional adenocarcinoma with focal neuroendocrine differentiation. This latter pattern is the most common, and there is evidence that all or nearly all prostatic adenocarcinomas show at least some focal neuroendocrine differentiation. A review of the world's literature on this topic is included. Neuroendocrine differentiation generally portends a poorer prognosis but may also correlate directly with the grade. There is some evidence to suggest that neoplastic cells with neuroendocrine differentiation are resistant to hormonal therapy. Eutopic and ectopic hormone production may allow screening for prostatic carcinoma and/or monitoring for recurrence of prostatic carcinomas. Finally, the more basic implications of endocrine-paracrine cells and neuroendocrine differentiation are speculated on in reference to prostatic carcinogenesis and autocrine/paracrine tumor growth factor activity.

Presence of calcitonin-like immunoreactivity (iCT) in human prostate gland: evidence for iCT secretion by cultured prostate cells

Immunoreactive calcitonin (iCT) has been detected in human prostate tissue extracts as well as seminal plasma. The present studies were undertaken to examine whether iSCT (immunoreactive salmon CT-like human peptide) co-exists with iHCT (thyroid CT-like substance) in human prostate tissue extracts, and whether these substances are secreted by primary prostate cells in culture. Since the local secretion of these substances seems to increase in some neoplasms, a second objective of the study was to examine whether basal secretion of iCTs from primary prostate cells is increased in carcinoma. The present results have shown that both iHCT and iSCT were present in prostate tissue extracts. The mean iHCT levels in extracts of benign hyperplastic prostates (BPH) were 0.59 ng/g prostate, and these were significantly lower than iHCT concentrations in prostatic carcinoma (PC) (2.53 ng/g). No significant differences in their iSCT contents were observed. However, the results from culture of over 90 individual prostate tissue specimens from BPH or PC indicate that primary prostate cells secreted detectable quantities of iSCT and the basal release of this material from PC prostate cultures was almost four-fold higher than that from BPH prostate cultures. These results suggest that a CT-like immunoreactive material is secreted by primary prostate cells in culture, and the basal secretion of this material is significantly higher in PC cells as compared to BPH cells. Endogenous secretion of prostatic CT, and the elevation of its expression in PC suggest that it may serve as a regulatory factor in the pathophysiology of the prostate gland.