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[Cancer Research 59, 1152-1159, March 1, 1999]
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[Cancer Research 59, 1152-1159, March 1, 1999]
© 1999 American Association for Cancer Research

Tumor Biology

Gastrin-releasing Peptide Receptors in the Human Prostate

Relation to Neoplastic Transformation

Regula Markwalder and Jean Claude Reubi1

Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, CH-3010 Berne, Switzerland


   ABSTRACT
Top
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Bombesin-like peptides such as gastrin-releasing peptide (GRP) have been shown to play a role in cancer as autocrine growth factors that stimulate tumor growth through specific receptors. To search for potential clinical indications for GRP analogues, it is important to identify human tumor types expressing sufficient amounts of the respective receptors. In the present study, we have evaluated the expression of GRP receptors in human nonneoplastic and neoplastic prostate tissues using in vitro receptor autoradiography on tissue sections with 125I-Tyr4-bombesin as radioligand. GRP receptors were detected, often in high density, in 30 of 30 invasive prostatic carcinomas and also in 26 of 26 cases of prostatic intraepithelial proliferative lesions, corresponding mostly to prostatic intraepithelial neoplasias. Well-differentiated carcinomas had a higher receptor density than poorly differentiated ones. Bone metastases of androgen-independent prostate cancers were GRP receptor-positive in 4 of 7 cases. Conversely, GRP receptors were identified in only a few hyperplastic prostates and were localized in very low density in glandular tissue and, focally, in some stromal tissue. In all of the cases, the receptors corresponded to the GRP receptor subtype of bombesin receptors, having high affinity for GRP and bombesin and lower affinity for neuromedin B. These data demonstrate a massive GRP receptor overexpression in prostate tissues that are neoplastically transformed or, like prostatic intraepithelial neoplasias, are in the process of malignant transformation. GRP receptors may be markers for early molecular events in prostate carcinogenesis and useful in differentiating prostate hyperplasia from prostate neoplasia. Such data may not only be of biological significance but may also provide a molecular basis for potential clinical applications such as GRP-receptor scintigraphy for early tumor diagnosis, radiotherapy with radiolabeled bombesin-like peptide analogues, and chemotherapy with cytotoxic bombesin analogues.


   INTRODUCTION
Top
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Receptors for regulatory peptides have been shown over the last 15 years to be overexpressed in several types of human neoplasia. Somatostatin receptors are found in large quantities in most neuroendocrine tumors (1) , vasoactive intestinal peptide receptors are expressed in most epithelial tumors (2) , and cholecystokinin-B receptors are identified in medullary thyroid carcinomas and small cell lung cancers (3 , 4) . These in vitro observations have led to the development of diagnostic and radiotherapeutic applications, using radiolabeled peptides for in vivo receptor scintigraphy (5, 6, 7) or peptide radiotherapy (8) in tumor patients. Furthermore, peptides linked to cytotoxic drugs (9) or stable peptide agonists or antagonists (10) have been used for long-term targeted chemotherapy in animal tumor models.

GRP2 belongs to the family of bombesin-like peptides that includes the amphibian peptide bombesin as well as the mammalian counterparts GRP and neuromedin B (11) . These peptides have been shown to play a role in various tumor models and in human cancer. For instance, they were shown by the group of Rozengurt et al. (12) to be mitogenic in Swiss 3T3 cells. Moreover, Cuttitta et al. (13) showed that bombesin and GRP can stimulate small cell lung cancer growth and that this action is part of an autocrine feedback mechanism involving the expression of these peptides as well as their receptors in the tumor cells (14 , 15) . More recently, GRP and bombesin were shown to play a possible role in prostate cancers as well. For instance, it was shown that GRP can stimulate cell proliferation in the androgen-independent human prostatic carcinoma cell line PC3 and that antagonists of the GRP receptor inhibit the growth of a number of prostatic carcinoma models, either cancer cells in vitro or xenografts in syngeneic rats or nude mice (16, 17, 18, 19) .

GRP mediates its action through membrane-bound receptors. These receptors correspond to one of the subtypes of the bombesin-like peptide receptors, namely the GRP receptor, which is characterized by a high-affinity binding for GRP and bombesin and only a moderate affinity for neuromedin B. These receptors are members of the large superfamily of G-protein-coupled receptors with seven transmembrane domains. Bombesin-like peptide receptors seem to mediate the mitogenic action of bombesin-like peptides in neoplasias; therefore, the information about the presence of bombesin-like peptide receptors, in particular of GRP receptors, is crucial for the evaluation of the bombesin-like peptide action in tumors. GRP receptors have been detected in various types of tumor cell lines (20, 21, 22, 23) . To predict the potential implications of bombesin-like peptides in patients with prostatic cancers, it is mandatory to know the incidence and the density of GRP receptors in primary human tumor tissues. For such an evaluation, the method of choice is in vitro receptor autoradiography (24) . It allows the localization of peptide receptors in complex tumor samples obtained after surgical resection. In addition to prostatic carcinomas, such tissues usually contain normal prostate, hyperplastic prostate, and often PIN (25) . This morphological method, therefore, allows us to distinguish the receptor expression in the nonneoplastic prostate and its malignant counterparts in individual tissue samples.

The aim of the present study was the evaluation of the incidence and the density of GRP receptors in a large number of human prostatic samples containing normal prostate and various stages of prostatic neoplastic transformation. The method used was in vitro receptor autoradiography on tissue sections, using iodinated [Tyr4]-bombesin as radioligand.


   MATERIALS AND METHODS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Patient Tissues.
Prostate tissue samples (peripheral zone) were obtained from 50 patients, ages 52–86 years, with primary prostate (36 cases) or primary bladder (14 cases) cancer operated on at the Department of Urology, University Hospital (Berne, Switzerland). In the 14 patients with bladder cancer, we studied only the prostate tissue; 4 of them had prostate cancer in addition to bladder cancer. Several large samples of tissues were collected from the patients and kept frozen at -80°C for up to 1 year. The tumor characteristics are listed in Table 1Citation . In addition, seven samples of prostate cancer, metastatic to the bones and refractory to hormone treatment (androgen-independent), obtained previously from the University of Uppsala (26) , were investigated. The diagnosis and grading were reviewed and formulated by use of cryostat as well as paraffin-embedded sections, according to the guidelines issued by Mostofi (WHO; Ref. 27 ). All of the tumor samples were evaluated for their Gleason scores (28) . The high-grade PIN stage was also evaluated in cryostat sections and defined as atypical prostatic intraepithelial proliferation containing basal cells identified immunohistochemically by the presence of high molecular weight cytokeratins (i.e., 34ßE12 antibody) to make a distinction from invasive cribriform carcinomas (29 , 30) .


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  		Table 1 GRP receptor density in surgically resected human prostate samples from patients with prostate or bladder carcinomas

 
GRP Receptor Autoradiography.
Twenty-µm thick cryostat sections of the tissue samples were processed for GRP receptor autoradiography as described in detail previously for other peptide receptors (31) . The radioligand used was 125I-Tyr4-bombesin, known to specifically label GRP receptors (32) . For autoradiography, tissue sections were mounted on precleaned microscope slides and stored at -20°C for at least 3 days to improve adhesion of the tissue to the slide. Sections were then processed according to Vigna et al. (32) . They were first preincubated in 10 mM HEPES buffer (pH 7.4) for 5 min at room temperature. They were then incubated in 10 mM HEPES, 130 mM NaCl, 4.7 mM KCl, 5 mM MgCl2, 1 mM ethyleneglycol-bis (ß-aminoethylether)-N-N'-tetraacetic acid, 0.1% BSA, 100 µg/ml bacitracin (pH 7.4), and approximately 100 pM125I-Tyr4-bombesin-14 (2000 Ci/mmol; Anawa, Wangen, Switzerland) in the presence or absence of 1 µM bombesin for 1 h at room temperature. Additional sections were incubated in the presence of increasing amounts of nonradioactive bombesin, GRP, neuromedin B, or somatostatin to generate competitive inhibition curves. After incubation, the sections were washed four times for 2 min each in 10 mM HEPES with 0.1% BSA (pH 7.4) at 4°C. Finally, the slides were rinsed twice for 5 s each at 4°C in distilled water. The slides were then dried at 4°C under a stream of cold air. The slides were placed in apposition to [3H]Hyperfilms (Amersham, Little Chalfont, United Kingdom) and exposed for 7 days in X-ray cassettes.

The autoradiograms were quantified using a computer-assisted image processing system, as described previously. (31) . Tissue standards for iodinated compounds (Amersham) were used for this purpose. A tissue was defined as receptor-positive when the absorbance measured in the total binding section was at least twice that of the nonspecific binding section (in the presence of 10-6M bombesin).


   RESULTS
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
Table 1Citation summarizes the GRP receptor status in prostate tissues. The data obtained by quantitative receptor autoradiography from the resected prostate samples of all 36 of the prostate cancer and the 14 bladder cancer patients are listed. Four types of tissues were investigated: (a) invasive prostatic carcinoma; (b) high-grade PIN; (c) prostatic hyperplasia; and (d) prostatic stroma; however, not all of the samples contained invasive prostatic carcinoma and/or high-grade PIN tissue. In a few samples resected at the border of the carcinoma and devoid of neoplastic tissue, GRP receptors were quantified only in the stroma and hyperplastic glands.

Table 1Citation shows that neoplastic prostatic tissue expresses GRP receptors very frequently:

(a) All of the 30 cases with primary invasive prostatic carcinomas were found to express GRP receptors. In the majority (83%) of the cases, a high to very high density of receptors (>1000 dpm/mg tissue) was found (Table 1Citation , No. 1–21 and 37–40); in five cases (No. 12, 16, 19, 21, and 22) a heterogeneous distribution of the receptors within adjacent tumor regions was found. The only three available cases with high (i.e., 7–9) Gleason scores (No. 21, 24, and 26) were all associated with a very low density of GRP receptors. One case with the lowest levels of GRP receptors was identified as G3 grade with a Gleason score of 9; this patient did not have elevated levels of prostate-specific antigen in the serum (below 4 ng/ml), suggestive of a particularly poor differentiation or dedifferentiation of the tumor;

(b) All of the 26 tissue samples containing an area of PIN were GRP receptor-positive. All but one case (No. 45) had high to very high densities of GRP receptors. The PIN area quantified for GRP receptors consisted primarily of high-grade PIN, in particular PIN III, as a clearly identifiable stage (25) . PIN I, which is extremely difficult to distinguish from hyperplasia in cryostat sections (25) , may have been present in some of the cases but was not evaluated separately. In several cases, a heterogeneous distribution of GRP receptors was observed, with some PIN devoid of receptors located next to PIN with high receptor values (i.e., No. 44), possibly as a reflection of the different PIN stages (I, II, III) present in these samples.

In addition, Table 1Citation shows that nonneoplastic prostatic tissue only rarely expressed a measurable amount of GRP receptors, and normal prostatic glandular epithelium did not express GRP receptors; prostatic hyperplasia expressed GRP receptors in 23 of 50 cases; however, in all but two of these cases (No. 4 and 27), the density of the receptors was very low, <500 dpm/mg tissue. The prostatic stroma was GRP receptor-positive in 16 of 50 cases; however, in these positive cases, the prostatic stroma was only focally GRP receptor-positive, i.e., receptors were found in a restricted area of the whole prostatic stromal tissue; stromal values in Table 1Citation represent GRP receptor densities measured in stromal sites having the highest labeling found within a sample. Except for three cases (No. 13, 39, 44), the peak receptor density values obtained under these measurement conditions were below 1500 dpm/mg tissue.

Among the seven bone metastases of androgen-independent prostatic cancers [all of them of poor differentiation (G3)], four cases were GRP receptor-positive (respective values: 9402, 1226, 4800, and 600 dpm/mg tissue).

A comparison of the GRP receptor expression in malignant neoplastic prostatic tissue versus nonneoplastic prostatic tissue shows, as seen in Table 1Citation , that the receptor incidence is much higher in carcinoma tissue and high-grade PIN as compared with nodular hyperplastic prostate and stroma; also the receptor density, calculated as the mean of all of the values (Table 2)Citation , is much higher in prostate carcinoma and high-grade PIN as compared with prostatic hyperplasia. In every single case, the receptor density is usually considerably higher in the neoplastic GRP receptor-positive tissues than in the surrounding nonneoplastic GRP receptor-positive tissues.


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  		Table 2 Density of GRP receptors in prostatic hyperplasias, PIN, invasive prostatic carcinomas, and bone metastases of prostate cancer

 
Fig. 1Citation illustrates an example of a strongly GRP receptor-positive invasive prostatic carcinoma adjacent to a receptor-negative prostatic hyperplasia. Fig. 2Citation , A–C, illustrates a case consisting of an area of GRP receptor-positive high-grade PIN surrounded by receptor-negative normal prostate gland. Fig. 2 (D–F)Citation demonstrates high densities of GRP receptor expression in a high-grade PIN area with one adjacent PIN devoid of GRP receptors. Here, PIN is defined by the presence of basal cells positively immunostained for high molecular weight cytokeratins. Fig. 3Citation shows a GRP receptor-positive bone metastasis from an androgen-independent invasive prostatic carcinoma. Fig. 4Citation is an example of a focal area of GRP receptor-positive prostatic stroma surrounded by receptor-negative prostatic hyperplasia as well as additional receptor-negative stromal tissue.



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  		Fig. 1. High density of GRP receptors in an invasive prostatic carcinoma but not in the adjacent prostatic hyperplasia. A, H&E-stained section. Ca, carcinoma; ph, prostate hyperplasia. Bar, 1 mm. B, autoradiogram showing total binding of 125I-Tyr4-bombesin. Strong labeling of the carcinoma but not of the hyperplasia is seen. C, autoradiogram showing nonspecific binding of 125I-Tyr4-bombesin (in the presence of 10-6 M bombesin). D–E, details of stained section (A) at high magnification: D, carcinoma; E, hyperplasia. Bar, 0.1 mm.

 


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  		Fig. 2. GRP receptors in high-grade PIN. A–C, high density of GRP receptors in a high-grade PIN area but not in the surrounding normal prostate gland. A, H&E-stained section. P, prostate gland. Bar, 1 mm. B, autoradiogram showing total binding of 125I-Tyr4-bombesin. Strong and selective labeling of high-grade PIN is seen. Normal prostate is negative. C, autoradiogram showing nonspecific binding of 125I-Tyr4-bombesin. D–F, nonhomogeneous distribution of GRP receptors in a high-grade PIN area. D, section immunostained for high molecular weight cytokeratins showing basal cells (arrowhead) in PIN and normal prostate gland (P). Bar, 1 mm. E, autoradiogram showing total binding of 125I-Tyr4-bombesin. All of the PIN areas except one (*) are labeled. F, autoradiogram showing nonspecific binding. Insert, basal cell staining (arrowhead) for high molecular weight cytokeratins of the section seen in D at higher magnification. Bar, 0.01 mm.

 


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  		Fig. 3. GRP receptors in a bone metastasis of an androgen-independent prostatic carcinoma. A, H&E stained section. Ca, carcinoma; b, bone. Bar, 1 mm. B, autoradiogram showing total binding of 125I-Tyr4-bombesin. C, autoradiogram showing nonspecific binding.

 


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  		Fig. 4. Focal expression of GRP receptors in a stromal area of a prostatic cancer sample. A, H&E-stained section. *, stroma. ph, prostate hyperplasia. Bar, 1 mm. B, autoradiogram showing total binding of 125I-Tyr4-bombesin. Only a restricted area of the stroma is labeled (white star). Other stromal areas (black star), as well as prostate hyperplasia (ph), are negative. Several nonspecifically labeled prostate stones (arrowhead) are visible. C, autoradiogram showing nonspecific binding.

 
The receptor subtype identified in the prostatic invasive carcinoma and PIN corresponded to the GRP receptor subtype of the bombesin-like peptide receptor family; as shown in Fig. 5Citation , there was high-affinity binding for GRP and bombesin and lower affinity for neuromedin B. Unrelated peptides like somatostatin were inactive. The same receptor subtype was also identified in the bone metastasis (Fig. 5)Citation and in the prostatic stromal tissue (data not shown).



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  		Fig. 5. High affinity and specificity of the 125I-Tyr4-bombesin binding in displacement experiments. Sections of tissue samples with high-grade PIN (upper graph), prostate carcinoma (middle graph), and bone metastasis (lower graph) were incubated with 125I-Tyr4-bombesin and increasing concentrations of unlabeled bombesin (•), GRP ({blacksquare}), neuromedin B ({blacktriangleup}), and somatostatin ({diamondsuit}). High-affinity displacement of the trace is found with bombesin and GRP, whereas neuromedin B shows lower affinity. Somatostatin has no effect. Nonspecific binding was subtracted from all of the values. The observed rank order of potencies of these analogues is characteristic for the GRP receptor subtype.

 

   DISCUSSION
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
This is the first extensive evaluation of GRP receptors in primary human prostatic tumors using morphological methods such as receptor autoradiography. The main finding is a high incidence and a high density of GRP receptors not only in invasive prostatic carcinomas but also, most interestingly, in the earliest phase of neoplastic transformation of the prostate, namely the PIN (25) . This is in contrast to the absence or, at best, the low incidence and the low density of GRP receptors in nonneoplastic prostatic tissue, in particular in benign hyperplastic prostate. Such data suggest that GRP receptor expression is directly and strongly related to the neoplastic condition of the prostate with the most remarkable shift of expression of GRP receptors observed between the hyperplastic stage and the PIN stage. This study cannot establish with sufficient precision at which of the three PIN stages the overexpression of receptors begins. Indeed, the PIN stage detected in this study is primarily PIN III, which is clearly identifiable as such on cryostat-sectioned material. Low-grade PIN, because it is histologically difficult to identify in cryostat sections, has not been assessed separately and, therefore, no information is available on the receptor status of low-grade PIN.

High-grade PIN is defined as a moderate (PIN II) to severe (PIN III) intraductal dysplasia, containing numerous cells with large nucleoli identical to the cells found in prostatic carcinomas and characterized by the retention of the basal cells (25) . Present evidence from the literature supports the contention that high-grade PIN is a precursor of prostatic carcinoma. These lesions are highly associated with coexistent prostatic cancers and have similar DNA ploidy, antigenic composition, and kinetic potentialities (25) . It is recognized that detailed knowledge of PIN may have important impact on future patient care; therefore, a marker of this histological entity, such as GRP receptors, may be of considerable clinical interest.

The prostatic carcinomas examined in this study were mainly of a differentiated grade (G1 and G2 with Gleason scores of 3–6). There were only three poorly differentiated (G3 with Gleason scores of 7–9) prostatic carcinomas included in this study. Despite the uneven representation of the three differentiation grades G1, G2, and G3, it may be suggested, based on the low GRP receptor level in the few poorly differentiated prostatic carcinomas, that undifferentiated primary prostate carcinomas may not express or perhaps may have lost some of their GRP receptors. It is unclear yet whether the same general conclusion is valid for the androgen-independent bone metastases because they can sometimes express high levels of GRP receptors even though they are poorly differentiated. More G3 cases, both primary tumors and metastases, will be necessary for a more detailed evaluation of this aspect.

In a few cases a heterogeneous distribution of receptors was observed in histologically homogenous tumor areas. Heterogeneous receptor distribution was more often seen in tumors with a lower number of GRP receptors, reflecting possibly the presence of poorly differentiated tumor regions. It is also possible that the observed receptor heterogeneity is due to the presence of different tumor clones.

Several subtypes of the bombesin-like peptide receptors have been described: the neuromedin B receptor with high affinity for neuromedin B, the GRP receptor with high affinity for GRP but lower affinity for neuromedin B (33 , 34) , and the bombesin 3 receptor subtype, an orphan receptor for which no endogenous ligand has yet been found (35) . The pharmacological characterization of the receptor subtype in malignant neoplastic prostate tissues, as identified in the present study, points clearly toward the GRP receptor subtype, with very high affinity for GRP and bombesin and lower affinity for neuromedin B. This is in agreement with a recent in situ hybridization study evaluating the mRNAs for the three bombesin-like peptide receptor subtypes in prostatic tissues: only the GRP receptor subtype mRNA was detected both in nonmalignant and malignant prostate tissues (36) . The mRNA staining in cancerous tissue ranged widely from very intense to not detectable, whereas nonmalignant tissue displayed a low level of message (36) . These data may point toward an up-regulation of the GRP receptor expression in prostate neoplasia; gene up-regulations, for instance of the COSVIc gene, have recently been identified in prostate cancer, for which they may have diagnostic value (37) .

Although nonneoplastic prostatic tissues such as glandular hyperplasia and stroma were GRP receptor-negative in the majority of the cases, a few patients showed prostatic tissue or parts of prostatic tissue being weakly GRP receptor-positive. In those cases, the receptor density was usually several times lower in the nonneoplastic than in the neoplastic tissues. One possible explanation for the expression of a low density of receptors in prostatic hyperplasia may be the presence of an early phase of malignancy not readily detectable histologically in our cryostat sections. Alternatively, the GRP receptor expression seen in nonneoplastic prostate tissue in this study may be related to neuroendocrine elements known to be present in the normal prostate. Indeed, bombesin-like peptides and their receptors have been considered as markers of prostatic neuroendocrine tissues (38 , 39) . The very low level of receptors in hyperplastic glands could, therefore, represent GRP receptors located in the normal neuroendocrine cells of the glands (38 , 39) .

The observation of GRP receptors located in prostatic stroma is intriguing. The relative low incidence of cases with stromal GRP receptors as well as the focal distribution of these receptors suggest that it is not a general phenomenon, as compared for instance with the ubiquitous expression of somatostatin receptors in the smooth muscle cells of most of the prostatic tissue (40) . The stromal GRP receptor expression may be simply a local reaction to cancer; alternatively, it could be part of the physiological stromal-epithelial interactions, known to play a role in the prostate development (40 , 41) .

Even if the exact biological role of GRP receptors in the normal and neoplastic prostate is not yet established, the present in vitro receptor data have a number of important therapeutic and diagnostic implications. The very high GRP receptor density in prostatic invasive carcinomas and high-grade PIN suggests that prostate neoplasia represents an adequate type of cancer to perform GRP-related early clinical trials:

(a) Over the last several years, potent and selective bombesin antagonists have been developed (17 , 34 , 42) . Several of these antagonists are compounds which have been shown in various animal tumor models to strongly inhibit tumor growth (17 , 43) . Other bombesin analogues have been designed as carriers for the radicals doxorubicin and 2-pyrrolinodoxorubicin to create hybrid cytotoxic drugs (44) ; they were also shown to inhibit the growth of cancer cell lines, including PC3 human prostate cancer cells (44) . Therefore, the application of these types of compounds as long-term treatment of human prostate cancer may be considered as a future goal.

(b) In analogy to the diagnosis of somatostatin receptor-expressing tumors in vivo with somatostatin receptor scintigraphy, in vivo GRP receptor scintigraphy may be a potentially valuable tool to visualize prostate neoplasia with a noninvasive method. A high tumor:background ratio may be expected on the basis of the high GRP receptor density in these neoplastic tissues as compared with nonneoplastic prostate. In addition to the detection of invasive prostatic carcinoma, the possibility of detection of high-grade PIN is extremely attractive because it would represent an early detection of the tumor, just as the in vivo detection of distant metastases could be extremely useful. Radioligands that would make in vivo GRP receptor scintigraphy technically possible have recently been synthesized: these include primarily Technetium-labeled bombesin analogues (45, 46, 47) .

(c) As a logical consequence and further development, a radiotherapy comparable to that using 90Yttrium-labeled octreotide (8) , aiming at the destruction of GRP receptor-positive tumors, could possibly be envisaged using adequate bombesin analogues linked to ß emitters such as Rhenium-labeled bombesin analogues (45, 46, 47) . Not only the treatment of prostatic invasive carcinomas but also that of early neoplastic stages, such as high-grade PIN, would be of great potential interest.


   FOOTNOTES
 
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

1 To whom requests for reprints should be addressed, at Division of Cell Biology and Experimental Cancer Research, Institute of Pathology, University of Berne, Murtenstrasse 31, CH-3010 Berne, Switzerland. Phone: 41-31-632-3242; Fax: 41-31-632-8399; E-mail: reubi{at}patho.unibe.ch Back

2 The abbreviations used are: GRP, gastrin-releasing peptide; PIN, prostatic intraepithelial neoplasia. Back

Received 11/ 3/98. Accepted 1/ 4/99.


   REFERENCES
Top
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Reubi J. C. Neuropeptide receptors in health and disease: the molecular basis for in vivo imaging. J. Nucl. Med., 36: 1825-1835, 1995.[Free Full Text]
  2. Reubi J. C. In vitro identification of vasoactive intestinal peptide receptors in human tumors: implications for tumor imaging. J. Nucl. Med., 36: 1846-1853, 1995.[Abstract/Free Full Text]
  3. Reubi J. C., Waser B. Unexpected high incidence of cholecystokinin B/gastrin receptors in human medullary thyroid carcinomas. Int. J. Cancer, 67: 644-647, 1996.[Medline]
  4. Reubi J. C., Schaer J. C., Waser B. Cholecystokinin(CCK)-A, and CCK-B/gastrin receptors in human tumors. Cancer Res., 57: 1377-1386, 1997.[Abstract/Free Full Text]
  5. Krenning E. P., Kwekkeboom D. J., Pauwels S., Kvols L. K., Reubi J. C. Somatostatin receptor scintigraphy. Nucl. Med. Annu., 1995: 1-50, 1995.
  6. Virgolini I., Raderer M., Kurtaran A., Angelberger P., Banyai S., Yang Q., Li S., Banyai M., Pidlich J., Niederle B., Scheithauer W., Valent P. Vasoactive intestinal peptide-receptor imaging for the localization of intestinal adenocarcinomas and endocrine tumors. N. Engl. J. Med., 331: 1116-1121, 1994.[Abstract/Free Full Text]
  7. Behr T. M., Jenner N., Radetzky S., Béhe M., Gratz S., Yücekent S., Raue F., Becker W. Targeting of cholecystokinin-B/gastrin receptors in vivo: preclinical and initial clinical evaluation of the diagnostic and therapeutic potential of radiolabelled gastrin. Eur. J. Nucl. Med., 25: 424-430, 1998.[Medline]
  8. Otte A., Mueller-Brand J., Dellas S., Nitzsche E. U., Herrmann R., Maecke H. R. Yttrium-90-labelled somatostatin-analogue for cancer treatment. Lancet, 351: 417-418, 1998.[Medline]
  9. Nagy A., Schally A. V., Halmos G., Armatis P., Cai R., Csernus V., Kovacs M., Koppan M., Szepeshazi K., Kahan Z. Synthesis and biological evaluation of cytotoxic analogs of somatostatin containing doxorubicin or its intensely potent derivative, 2-pyrrolinodoxorubicin. Proc. Natl. Acad. Sci. USA, 95: 1794-1799, 1998.[Abstract/Free Full Text]
  10. Zia H., Hida T., Jakowlew S., Birrer M., Gozes Y., Reubi J. C., Fridkin M., Gozes I., Moody T. W. Breast cancer growth is inhibited by vasoactive intestinal peptide (VIP) hybrid, a synthetic VIP receptor antagonist. Cancer Res., 56: 3486-3489, 1996.[Abstract/Free Full Text]
  11. Erspamer V. Discovery, isolation, and characterization of bombesin-like peptides. Ann. NY Acad. Sci., 547: 3-9, 1988.[Medline]
  12. Rozengurt E. Bombesin stimulation of mitogenesis. Specific receptors, signal transduction and early events. Am. Rev. Respir. Dis., 142: S11-S15, 1990.[Medline]
  13. Cuttitta F., Carney D. N., Mulshine J., Moody T. W., Fedorko J., Fischler A., Minna J. D. Bombesin-like peptides can function as autocrine growth factors in human small-cell lung cancer. Nature (Lond.), 316: 823-825, 1985.[Medline]
  14. Carney D. N., Cuttitta F., Moody T. W., Minna J. D. Selective stimulation of small cell lung cancer clonal growth by bombesin and gastrin-releasing peptide. Cancer Res., 47: 821-825, 1987.[Abstract/Free Full Text]
  15. Moody T. W., Cuttitta F. Growth factor and peptide receptors in small cell lung cancer. Life Sci., 52: 1161-1173, 1993.[Medline]
  16. Bologna M. C., Festuccia C., Muzi P., Biordi L., Ciomei M. Bombesin stimulates growth of human prostatic cancer cells in vitro. Cancer (Phila.), 63: 1714-1720, 1989.[Medline]
  17. Pinski J., Reile H., Halmos G., Groot K., Schally A. V. Inhibitory effects of somatostatin analogue RC-160 and bombesin/gastrin-releasing peptide antagonist RC-3095 on the growth of the androgen-independent Dunning R-3327-AT-1 rat prostate cancer. Cancer Res., 54: 169-174, 1994.[Abstract/Free Full Text]
  18. Milovanovic S. R., Radulovic S., Groot K., Schally A. V. Inhibition of growth of PC-82 human prostate cancer cell line xenografts in nude mice by bombesin antagonist RC-3095 or combination of agonist [D-Trp6]-luteinizing hormone-releasing hormone and somatostatin analog RC-160. Prostate, 20: 269-280, 1992.[Medline]
  19. Jungwirth A., Pinski J., Galvan G., Halmos G., Szepeshazi K., Cai R. Z., Groot K., Vadillo-Buenfil M., Schally A. V. Inhibition of growth of androgen-independent DU-145 prostate cancer in vivo by luteinising hormone-releasing hormone antagonist cetrorelix and bombesin antagonists RC-3940-II and RC-3950-II. Eur. J. Cancer, 33: 1141-1148, 1997.
  20. Aprikian A. G., Han K., Chevalier S., Bazinet M., Viallet J. Bombesin specifically induces intracellular calcium mobilization via gastrin-releasing peptide receptors in human prostate cancer cells. J. Mol. Endocrinol., 16: 297-306, 1996.[Medline]
  21. Wu J. M., Hoang D. O., Feldman R. I. Differential activation of human gastrin-releasing peptide receptor-mediated responses by bombesin analogs. Mol. Pharmacol., 47: 871-881, 1995.[Abstract]
  22. Reile H., Armatis P. E., Schally A. V. Characterization of high-affinity receptors for bombesin/gastrin-releasing peptide on the human prostate cancer cell lines PC-3 and DU-145: Internalization of receptor bound 125-I-(Tyr4)bombesin by tumor cells. Prostate, 25: 29-38, 1994.[Medline]
  23. Feldman R. I., Bartholdi M. F., Wu J. M. Bombesin-like peptide receptor subtypes promote mitogenesis which requires persistent receptor signaling. Mol. Pharmacol., 50: 1346-1354, 1996.[Abstract]
  24. Reubi J. C. Relevance of somatostatin receptors and other peptide receptors in pathology. Endocrinol. Pathol., 8: 11-20, 1997.
  25. Epstein J. I. Prostatic intraepithelial neoplasia 2 Epstein J. I. eds. . Prostate Biopsy Interpretation, : 37-64, Lippincott-Raven Philadelphia 1995.
  26. Nilsson S., Reubi J. C., Kalkner K., Laissue J. A., Horisberger U., Olerud C., Westlin J. Metastatic hormone-refractory prostatic adenocarcinoma expresses somatostatin receptors and is visualized in vivo by (111In)-labeled DTPA-D-(Phe1)-octreotide scintigraphy. Cancer Res., 55 (Suppl.): 5805s-5810s, 1995.[Medline]
  27. Mostofi F. K. Grading of prostatic carcinoma. Cancer Chemother. Rep., 59: 111-117, 1975.[Medline]
  28. Gleason D. F., Veterans Administration Cooperative Urological Research Group. Histologic grading and clinical staging of prostatic carcinoma Tannenbaum M. eds. . Urologic Pathology: The Prostate, : 171-197, Lea & Febiger Philadelphia 1977.
  29. Bostwick D. G. High grade prostatic intraepithelial neoplasia. Cancer (Phila.), 75: 1823-1836, 1995.
  30. Rubin M. A., DeLaTaille A., Bagiella E., Olsson C. A., O’Toole K. M. Cribriform carcinoma of the prostate and cribriform prostatic intraepithlial neoplasia. Am. J. Surg. Pathol., 22: 840-848, 1998.[Medline]
  31. Reubi J. C., Kvols L. K., Waser B., Nagorney D., Heitz P. U., Charboneau J. W., Reading C. C., Moertel C. Detection of somatostatin receptors in surgical and percutaneous needle biopsy samples of carcinoids and islet cell carcinomas. Cancer Res., 50: 5969-5977, 1990.[Abstract/Free Full Text]
  32. Vigna S. R., Mantyh C. R., Giraud A. S., Soll A. H., Walsh J. H., Mantyh P. W. Localization of specific binding sites for bombesin in the canine gastrointestinal tract. Gastroenterology, 93: 1287-1295, 1987.[Medline]
  33. Battey J., Wada E. Two distinct receptor subtypes for mammalian bombesin receptors. Trends Neurosci., 14: 524-528, 1991.[Medline]
  34. Jensen R. T., Coy D. H. Progress in the development of potent bombesin receptor antagonists. Trends Pharmacol. Sci., 12: 13-19, 1991.[Medline]
  35. Mantey S. A., Weber H. C., Sainz E., Akeson M., Ryan R. R., Pradhan T. K., Searles R. P., Spindel E. R., Battey J. F., Coy D. H., Jensen R. T. Discovery of a high affinity radioligand for the human orphan receptor, bombesin receptor subtype 3, which demonstrates that it has a unique pharmacology compared with other mammalian bombesin receptors. J. Biol. Chem., 272: 26062-26071, 1997.[Abstract/Free Full Text]
  36. Bartholdi M. F., Wu J. M., Pu H., Troncoso P., Eden P. A., Feldman R. I. In situ hybridization for gastrin-releasing peptide receptor (GRP receptor) expression in prostatic carcinoma. Int. J. Cancer (Predict. Oncol.), 79: 82-90, 1998.[Medline]
  37. Wang F., Wang Y., Wong W., Liu A., Addivilona F. J., Liang P., Chen L. B., Kantoff P. W., Pardee A. B. Two differentially expressed genes in normal human prostate tissue and in carcinoma. Cancer Res., 56: 3634-3637, 1996.[Abstract/Free Full Text]
  38. Aprikian A. G., Cordon-Cardo C., Fair W. R., Reuter V. E. Characterization of neuroendocrine differentiation in human benign prostate and prostatic adenocarcinoma. Cancer (Phila.), 71: 3952-3965, 1993.[Medline]
  39. Di SantAgnese P. A. Neuroendocrine differentiation in carcinoma of the prostate. Cancer (Phila.), 70 (Suppl.): 254-268, 1992.[Medline]
  40. Reubi J. C., Waser B., Schaer J. C., Markwalder R. Somatostatin receptors in human prostate and prostate cancer. J. Clin. Endocrinol. Metab., 80: 2806-2814, 1995.[Abstract]
  41. Chung L. W., Gleave M. E., Hsieh J. T., Hong S. J., Zhau H. E. Reciprocal mesenchymal-epithelial interaction affecting prostate tumour growth and hormonal responsiveness. Cancer Surv., 11: 91-121, 1991.[Medline]
  42. de Castiglione R., Gozzini L. Bombesin receptor antagonists. Crit. Rev. Oncol. Hematol., 24: 117-151, 1996.[Medline]
  43. Moody T. W., Venugopal R., Zia R., Patierno S., Leban J. J., McDermed J. BW2258U89: a GRP antagonist which inhibits small cell lung cancer. Life Sci., 56: 521-529, 1995.[Medline]
  44. Nagy A., Armatis P., Cai R., Szepeshazi K., Halmos G., Schally A. V. Design, synthesis, and in vitro evaluation of cytotoxic analogs of bombesin-like peptides containing doxorubicin or its intensely potent derivative, 2-pyrrolinodoxorubicin. Proc. Natl. Acad. Sci. USA, 94: 652-656, 1997.[Abstract/Free Full Text]
  45. Baidoo K. E., Lin K., Zhan Y., Finley P., Scheffel U., Wagner H. N., Jr. Design, synthesis, and initial evaluation of high-affinity technetium bombesin analogues. Bioconjugate Chem., 9: 218-225, 1998.[Medline]
  46. Safavy A., Khazaeli M. B., Qin H., Buchsbaum D. J. Synthesis of bombesin analogues for radiolabeling with rhenium-188. Cancer (Phila.), 80 (Suppl.): 2354-2359, 1997.[Medline]
  47. Hoffman T. J., Li N., Sieckman G. L., Higginbotham C. A., Volkert W. A. Evaluation of radiolabeled (I-125 vs. Rh-105)bombesin analogue internalization in normal and tumor cell lines. Q. J. Nucl. Med., 41 (Suppl. 1): 5 1997.



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