True positive somatostatin receptor scintigraphy in primary breast cancer correlates with expression of sst2A and sst5

GRPr Theranostics: Current Status of Imaging and Therapy using GRPr Targeting Radiopharmaceuticals

Addressing molecular targets, that are overexpressed by various tumor entities, using radiolabeled molecules for a combined diagnostic and therapeutic (theranostic) approach is of increasing interest in oncology. The gastrin-releasing peptide receptor (GRPr), which is part of the bombesin family, has shown to be overexpressed in a variety of tumors, therefore, serving as a promising target for those theranostic applications. A large amount of differently radiolabeled bombesin derivatives addressing the GRPr have been evaluated in the preclinical as well as clinical setting showing fast blood clearance and urinary excretion with selective GRPr-binding. Most of the available studies on GRPr-targeted imaging and therapy have evaluated the theranostic approach in prostate and breast cancer applying bombesin derivatives tagged with the predominantly used theranostic pair of ⁶⁸Ga/¹⁷⁷Lu which is the focus of this review.

Theranostic Approach in Breast Cancer: A Treasured Tailor for Future Oncology

ABSTRACT

Breast cancer is the most frequent invasive malignancy and the second major cause of cancer death in female subjects mostly due to the considerable diagnostic delay and failure of therapeutic strategies. Thus, early diagnosis and possibility to monitor response to the treatment are of utmost importance. Identification of valid biomarkers, in particular new molecular therapeutic targets, that would allow screening, early patient identification, prediction of disease aggressiveness, and monitoring response to the therapeutic regimen has been in the focus of breast cancer research during recent decades. One of the intensively developing fields is nuclear medicine combining molecular diagnostic imaging and subsequent (radio)therapy in the light of theranostics. This review aimed to survey the current status of preclinical and clinical research using theranostic approach in breast cancer patients with potential to translate into conventional treatment strategies alone or in combination with other common treatments, especially in aggressive and resistant types of breast cancer. In addition, we present 5 patients with breast cancer who were refractory or relapsed after conventional therapy while presumably responded to the molecular radiotherapy with 177Lu-trastuzumab (Herceptin), 177Lu-DOTATATE, and 177Lu-FAPI-46.

Somatostatin receptor expression in non-classical locations - clinical relevance?

In-111 pentetreotide (Octreoscan) is a radiolabeled somatostatin analog with high binding affinity to somatostatin receptors (SSTR) used in somatostatin receptor scintigraphy (SRS). Pentetreotide labelled with In-111 is widely used due to its high affinity to SSTR 2 and 5. SSTR are expressed on neuroendocrine cells as well as several non-neural and non-endocrine cells with varying levels of density. We retrospectively reviewed articles and publications related to octreoscan accumulation in sites that classically do not have high concentrations of SSTR as well as in organs and tissues from diseases which are not usually diagnosed by octreoscan. The significance of a positive uptake as assessed by octreoscan in non-somatostatin receptor related diseases is not fully understood yet. Localization of octreotide in non-oncological disease states such as inflammation is due to presence of SSTR in activated immunological cells, over-expression by activated cells in the respective tissue and SSTR expression by blood vessels. In granulomatous diseases, over-expression of SSTR2 preferential binding sites were detected in epitheloid and giant cells. The purpose of the current study is to identify octreoscan localization in non-somatostatin receptor related disease sites to better understand the mechanism of this nonspecific accumulation which may help expand the clinical utilization of functional imaging utilizing somatostatin receptor scintigraphy in diagnosis and perhaps therapy.

Detection of somatostatin receptor subtypes 2 and 5 by somatostatin receptor scintigraphy and immunohistochemistry: Clinical implications in the diagnostic and therapeutic management of gastroenteropancreatic neuroendocrine tumors

Aims and background

Somatostatin receptor scintigraphy (SRS) is the standard method for the detection of somatostatin receptors (SSTRs). It is commonly used in gastroenteropancreatic neuroendocrine tumor (GEP-NET) staging, and represents the criterion of choice for treatment with somatostatin (SST) analogs. Immunohistochemistry (IHC) was reported as a reliable method for the detection of SSTRs with theoretically superior sensitivity over SRS.

Methods and study design

We retrospectively analyzed the sensitivity and specificity of IHC in the detection of SSTRs in a cohort of consecutive patients with GEP-NETs attending our Institute from 1997 to 2007. IHC analysis was restricted to SSTR2 and SSTR5, and the results were interpreted according to two different scoring systems. SRS was used as the gold standard.

Results

Forty-four patients were enrolled; 24 (55%) had foregut carcinoids, 9 (20%) midgut carcinoids, 2 (5%) hindgut carcinoids, and 9 (20%) had GEP-NETs of unknown primary sites. A high concordance rate between IHC and SRS was shown, irrespective of the IHC scoring system applied (73% and 70%). The sensitivity of IHC was 89.3% and 78.6% and the specificity 43.8% and 50%, depending on the scoring system used.

Conclusions

Although SSTR2 was shown to be expressed by IHC in up to 50% of tumors not visualized by SRS, SRS still remains the method of choice in the diagnostic and therapeutic management of GEP-NETs. More pathological and clinical data are needed to properly understand the clinical relevance of immunohistochemical detection of SSTR expression in the absence of tumor uptake at SRS.

Review: Receptor Targeted Nuclear Imaging of Breast Cancer

Receptor targeted nuclear imaging directed against molecular markers overexpressed on breast cancer (BC) cells offers a sensitive and specific method for BC imaging. Currently, a few targets such as estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), somatostatin receptor (SSTR), and the gastrin releasing peptide receptor (GRPR) are being investigated for this purpose. Expression of these targets is BC subtype dependent and information that can be gained from lesion visualization is dependent on the target; ER-targeting radiotracers, e.g., can be used to monitor response to anti-estrogen treatment. Here we give an overview of the studies currently under investigation for receptor targeted nuclear imaging of BC. Main findings of imaging studies are summarized and (potential) purposes of lesion visualization by targeting these molecular markers are discussed. Since BC is a very heterogeneous disease and molecular target expression can vary per subtype, but also during disease progression or under influence of treatment, radiotracers for selected imaging purposes should be chosen carefully.

Is there a role for peptide receptor radionuclide therapy in medullary thyroid cancer?

BACKGROUND

Medullary thyroid cancer (MTC) is a rare but potentially life-threatening disease with limited therapeutic options. As a neuroendocrine tumor, MTC expresses somatostatin receptors, and therefore, somatostatin-labeled radiopharmaceuticals could be used to treat patients with MTC.

OBJECTIVE

The aims of this study were to evaluate tumor shrinkage after Lu-DOTATATE treatment, to analyze the impact on quality of life as accessed by the SF-36 questionnaire, and to demonstrate a possible prognostic role for In-DTPA-octreotide uptake in patients with MTC.

PATIENTS AND METHODS

Patients with progressive MTC underwent evaluation using In-DTPA-octreotide. Patients who demonstrated In-DTPA-octreotide uptake were treated with 4 cycles of 200 mCi of Lu-DOTATATE and were evaluated using CT scans over 8 to 12 months of treatment.

RESULTS

Of the 16 patients initially enrolled, 9 (56.25%) had lesions that were observed in the In-DTPA-octreotide scans and were eligible for therapy with Lu-DOTATATE. Three patients had a partial response, 3 patients were classified as having stable disease and, 1 patient had a progressive disease. All responders indicated improvement in quality of life 6 to 12 months after therapy.

CONCLUSIONS

Treatment with Lu-DOTATATE seems to be an alternative therapy for somatostatin receptor-positive tumors, with very mild adverse effects and quality-of-life improvement, at least during a short-term period. Further studies are needed to determine long-term benefits and to identify which patients are more likely to respond to this modality of therapy.

The antiproliferative effects of somatostatin receptor subtype 2 in breast cancer cells

AIM

Somatostatin receptor subtype 2 (SSTR2) is the principal mediator of somatostatin's (SST) antiproliferative effects on normal and cancer cells. Therefore, we investigated whether the enhanced expression of SSTR2 could inhibit the proliferation of tumor cells, and, if so, the mechanisms that might be involved.

METHODS

SSTR2 expression levels were determined by qRT-PCR in several tumor cell lines. Then, a plasmid pIRES2-EGFP-SSTR2 (pSIG) was constructed and stably transfected into MCF-7 cells (MCF-7/pSIG). After SSTR2 overexpression was identified by qRT-PCR, immunofluorescence staining and a receptor binding assay, the MCF-7/pSIG cells were analyzed by PI staining for apoptosis and cell cycle arrest was tested by flow cytometry for epidermal growth factor receptor (EGFR) expression. The EGF-stimulated proliferation of MCF-7 cells was assayed by MTT.

RESULTS

The human breast cancer cell line MCF-7 expresses a lower level of SSTR2, thereby partly accounting for the decreased response to SST. The overexpression of SSTR2 in MCF-7 cells resulted in apoptosis, cytostasis and G(1)/S cell cycle arrest. Furthermore, the expression of EGFR, together with EGF-stimulated proliferation, was markedly decreased in the MCF-7/pSIG cells.

CONCLUSION

Enhanced SSTR2 expression played an antiproliferative role in MCF-7 cells through inducing apoptosis and G(1)/S cell cycle arrest, and also by decreasing EGFR expression, thereby counteracting the growth-stimulating effect of EGF. Our data seem to indicate that developing a new therapeutic agent capable of upregulating SSTR expression could potentially be a way to block tumor progression.Acta Pharmacologica Sinica (2009) 30: 1053-1059; doi: 10.1038/aps.2009.59.

The role of technetium-99m-labeled octreotide acetate scintigraphy in suspected breast cancer and correlates with expression of SSTR

PURPOSE

To evaluate the value of (99m)Tc-octreotide acetate (hereafter, (99m)Tc-octreotide) somatostatin receptor (SSTR) scintigraphy in the detection of primary breast cancer and to correlate with expression of SSTRs.

MATERIALS AND METHODS

Fifty-four female and 1 male patients (range, 17-77 years; mean age, 48 years) with palpable breast lesion were included in this study. (99m)Tc-octreotide and (99m)Tc-MIBI scintigraphy were undertaken in all patients, and the region of interest was drawn around each lesion. Tumor uptake was measured and expressed as the ratio of tumor to normal tissue activity (T/NT). Final clinical diagnosis was confirmed by histopathological analysis. Expression of SSTR1-5 mRNA was measured with RT-PCR in 15 patients with malignant neoplasm, and protein level of SSTR-2 and SSTR-5 was measured using immunohistochemical staining in 15 patients with malignant neoplasm and 18 patients with benign lesion.

RESULTS

Thirty-five patients were confirmed to have infiltrative ductal breast carcinoma, 1 patient with cellular cancer, 1 patient with adenocarcinoma and 18 patients had benign lesions. The sensitivity, specificity, positive predictive value and negative predictive value of (99m)Tc-octreotide in detection of primary lesion were 91.8%, 22.2%, 71.8% and 57.1%, respectively. No significant correlation was observed between T/NT of (99m)Tc-octreotide and (99m)Tc-MIBI. SSTR mRNA subtypes were variably expressed. SSTR3 was the most highly expressed, followed by SSTR1, SSTR2 and SSTR5; SSTR4 was the least expressed in the level of mRNA of SSTR. Significant correlation was shown between T/NT and the expression of SSTR2 mRNA (r=0.73, P<.01).

CONCLUSION

(99m)Tc-octreotide acetate scintigraphy was sensitive for the detection of primary lesion of breast cancer; however, nonspecific breast tissue uptake hampered the specificity and clinical value in the detection of lymph node metastasis. Five subtypes of SSTR mRNA and protein SSTR2 and SSTR5 were expressed variably in breast cancer due to tumor heterogeneity. (99m)Tc-octreotide imaging may hold promise in the evaluation of the level of SSTR2 in vivo.

Immunohistochemical localization of somatostatin receptor subtypes in benign and malignant adrenal tumours

BACKGROUND

Somatostatin mediates its action through five receptor subtypes (sst1-5) that are widely distributed in various endocrine tissues and tumours. Because of the inhibitory effects of somatostatin, long-acting analogues have been synthesized. In contrast to their well-established use in neuroendocrine and pituitary tumours, little is known about their potential use in adrenal tumours.

OBJECTIVE

We examined somatostatin receptor protein expression in adrenal tumours of various aetiologies. Immunostaining was performed with specific polyclonal antibodies for sst1-5.

DESIGN

Seven benign and eight malignant pheochromocytomas (PHEOs), eight aldosterone-secreting adenomas (APAs), nine cortisol-secreting adenomas (CPAs), seven nonfunctioning adrenal tumours (NFAs) and 25 adrenal carcinomas (CAs) as well as eight normal adrenal glands were investigated.

MEASUREMENTS

Staining pattern, distribution and subcellular localization of the somatostatin receptor subtypes were evaluated.

RESULTS

In the majority of normal cortices the expression of sst1-5 was limited to the reticular zone. The medulla was predominantly positive for sst3. Most cortical adenomas were positive for all five subtypes. However, in the majority of these tumours, less than 30% of cells were positively stained. A high expression of sst4 was found in CPAs but only very few cortical carcinomas exhibited sst immunostaining. All benign PHEOs were positive for sst3. The majority presented with more than 60% of tumour cells stained. By contrast, only six out of eight malignant PHEOs were positive for sst3.

CONCLUSIONS

Somatostatin receptor subtypes are expressed in PHEOs as well as in tumours of the adrenal cortex with tumour-specific distribution patterns. This may offer new diagnostic and therapeutic possibilities.

In Vitro and in Vivo Antitumor Effects of Cytotoxic Camptothecin-Bombesin Conjugates Are Mediated by Specific Interaction with Cellular Bombesin Receptors

Most human tumors overexpress or ectopically express peptide hormone/neurotransmitter receptors, which are being increasingly studied as a means to selectively deliver cytotoxic agents. Although a number of peptide ligand-constructs demonstrate tumor cytotoxicity, the role of specific tumoral receptor interaction in its mediation is unclear. To address this question, we synthesized camptothecin (CPT) bombesin (Bn) analogs, in which CPT was coupled via a novel carbamate linker, L2 [N-(N-methyl-amino-ethyl)-glycine carbamate], that were chemically similar but differed markedly in their potency/affinity for human Bn receptors. We then examined their ability to interact with Bn receptors and cause in vitro and in vivo tumor cytotoxicity. CPT-L2-[D-Tyr(6),beta-Ala(11),D-Phe(13),Nle(14)] Bn (6-14) (BA3) bound with high affinity and had high potency for all three human Bn receptor subtypes, whereas CPT-L2-[D-Tyr(6),beta-Ala(11), D-Phe(13),Nle(14)] Bn (6-14) [D-Phe-CPT-L2-BA3] had >1400-fold lower affinity/potency. (125)I-CPT-L2-BA3 but not (125)I-D-Phe-CPT-L2-BA3 was internalized by Bn receptor subtype-containing cells. CPT-L2-BA3 displayed significantly more cytotoxicity than D-Phe-CPT-L2-BA3 toward NCI-H1299 lung cancer cells in both 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide and clonogenic assays and more potently inhibited H1299 xenograft growth in nude mice. CPT-L2-BA3 was also metabolically more stable than its parent peptide and inhibited growth of a number of other tumor cell lines in vitro and in vivo. These results demonstrate that specific tumoral receptor interaction is important in mediating the ability of peptide ligand-cytotoxic constructs to cause cytotoxicity. Because many tumors overexpress Bn receptors, these results also demonstrate that CPT-L2-BA3 will be a useful agent for delivering receptor-mediated cytotoxicity to many different human tumors.

Value of immunohistochemistry for somatostatin receptor subtype sst2A in cancer tissues: lessons from the comparison of anti-sst2A antibodies with somatostatin receptor autoradiography

The somatostatin receptor sst2A is highly expressed at the cellular surface of neuroendocrine and other human tumor cells, allowing somatostatin receptor-targeted scintigraphic tumor imaging and tumor therapy. In vitro information on tumoral somatostatin receptor expression is provided mainly by receptor autoradiography, based on binding of radiolabeled somatostatin analogs to tumoral somatostatin receptors. Recent availability of anti-sst2A antibodies opens the possibility of sst2A assessment in human tumors with immunohistochemistry. The aim of the present study was to evaluate the usefulness of several commercial anti-sst2A antibodies for this purpose in comparison with the extensively characterized antibody R2-88 and with receptor autoradiography. sst2A immunohistochemistry was performed in 64 formalin-fixed tumors known to frequently express sst2A (pancreatic, gastrointestinal, pulmonary neuroendocrine tumors, breast carcinomas, meningiomas, pituitary adenomas, neuroblastomas, medulloblastomas, pheochromocytomas, and paragangliomas); receptor autoradiography could be performed simultaneously in 37 of these cases. The commercial antibody SS-800 clearly identified sst2A and correlated excellently with R2-88: compared with R2-88, SS-800 immunohistochemistry generally yielded the same tissular and subcellular staining distribution. Results of R2-88 and SS-800 immunohistochemistry correlated excellently with those obtained with receptor autoradiography; compared with receptor autoradiography, immunohistochemistry with both R2-88 and SS-800 resulted in a slightly lower tumoral sst2A incidence, but a higher resolution, with frequent identification of heterogeneous sst2A distribution at high magnification. Finally, not only membranous, but also cytoplasmic, sst2A immunostaining was simultaneously observed with both antibodies in some tumors. In conclusion, the commercially available SS-800 antibody promises to be useful for the routine immunohistochemical assessment of sst2A in formalin-fixed human tumors.

Biodistribution and dosimetry of (99m)Tc-depreotide (P829) in patients suffering from breast carcinoma

OBJECTIVE

This paper reports on the biodistribution and dosimetry of (99m)Tc-depreotide in patients.

METHODS

Whole body planar images were acquired 30 minutes, 1, 2, 4, 9, and 24 hours after intravenous injection of 555-740MBq (99m)Tc-depreotide in 5 breast cancer patients. Urine was collected up to 24 hours after injection, allowing for a calculation of renal clearance and an interpretation of whole body clearance. Time activity curves were generated for the thyroid, lungs, liver, spleen, kidneys, colon, thoracic vertebrae/sternum, and whole body by fitting the organ-specific geometric mean counts, obtained from regions of interest (ROIs). The Medical Internal Radiation Dose (MIRD) formulation was applied to calculate the absorbed radiation dose for various organs.

RESULTS

The whole body images show most of the activity distributed in the liver, spleen, and kidneys. Nearly all excretion of activity occurred by the renal system, and hepatobiliary excretion was negligible. Elimination of administered activity occurred predominantly through physical decay. The mean cumulative measured urinary excretion at 24 hours postinjection was 14.0% (standard deviation; 11.8%) of the administered activity. The highest absorbed dose was received by the kidneys, thyroid, and spleen. The average effective dose was estimated to be 1.15E-02mSv/MBq (standard deviation; 1.41E-03mSv/MBq).

CONCLUSION

The biodistribution of (99m)Tc-depreotide demonstrated low lung and myocardial uptake allowing early imaging of the supradiaphragmatic region and this with a dosimetry favorable for clinical whole body and single photon emission computed tomography (SPECT) imaging.

99mTc depreotide scan compared with 99mTc-MDP bone scintigraphy for the detection of bone metastases and prediction of response to hormonal treatment in patients with breast cancer

BACKGROUND

The purpose of this study was to determine the potential role of Tc depreotide scintigraphy for the evaluation of bone metastases compared with Tc methylenediphosphonate (MDP) bone scintigraphy and for the prediction of treatment response in breast cancer patients in whom first- or second-line hormonal therapy was to be initiated.

METHODS

Twelve patients with a diagnosis of advanced breast cancer were included. All patients underwent both a bone scan and a depreotide scan and at least one other conventional imaging procedure, including plain film radiography (n=11), computed tomography (n=6) or magnetic resonance imaging (n=5), for confirmation of metastatic disease. The mean time interval between the bone scan and the depreotide scan was 30.6 days. Follow-up data were retrieved from routine clinical evaluation by means of physical examination, imaging and blood analysis.

RESULTS

On a patient basis we found a sensitivity, specificity and accuracy of, respectively 100%, 50% and 83.3% for the bone scan and 62.5%, 100% and 75% for the depreotide scan in the diagnosis of bone metastasis. In eight patients with available follow-up data two with a positive depreotide scan remained stable and five of six patients with a negative depreotide scan had progressive disease.

CONCLUSION

In this small series of breast cancer patients Tc depreotide scintigraphy proves less sensitive but more specific as compared to Tc-MDP bone scintigraphy in measuring the extent of bone metastasis. On the other hand Tc depreotide scintigraphy elucidates, non-invasively, tumour characteristics and may be indicative for prognosis and response to hormonal treatment.

Neuroendocrine Basis of Human Disease

This paper is a short review of the traditionally obvious diseases of neuroendocrine origin (diabetes insipidus, Kallman syndrome, etc.), but also of the newly recognized participation of several peptides originally characterized in the hypothalamus and of their receptors, in a series of diseases, both in internal medicine and in psychiatry (rheumatoid arthritis, inflammation, carcinoids, anxiety, depression, etc.). The concept of neuropeptides is now vastly expanded, as these molecules and their several receptors are now known to be widely distributed throughout the brain and the periphery with increasing evidence of paracrine and autocrine modes of action.

Receptor-Mediated Tumor Targeting with Radiopeptides. Part 1. General Concepts and Methods: Applications to Somatostatin Receptor-Expressing Tumors

Radiolabeled peptides have become important tools in nuclear oncology, both as diagnostics and more recently also as therapeutics. They represent a distinct sector of the molecular targeting approach, which in many areas of therapy will implement the old "magic bullet" concept by specifically directing the therapeutic agent to the site of action. In this three-part review, we present a comprehensive overview of the literature on receptor-mediated tumor targeting with the different radiopeptides currently studied. Part I summarizes the general concepts and methods of targeting, the selection of radioisotopes, chelators, and the criteria of peptide ligand development. Then, the >400 studies on the application to somatostatin/somatostatin-release inhibiting factor receptor-mediated tumor localization and treatment will be reviewed, demonstrating that peptide radiopharmaceuticals have gained an important position in clinical medicine.

Oestrogen-mediated regulation of somatostatin receptor expression in human breast cancer cell lines assessed with 99mTc-depreotide

Investigating three somatostatin receptor (SSTR)-positive (+) human breast cancer cell lines, Xu et al. found a time- and dose-dependent up- or down-regulation of SSTR2 mRNA expression by 17beta-oestradiol (E(2)) or the anti-oestrogen tamoxifen, respectively, in the two oestrogen receptor-positive (ER+) cell lines but not in the oestrogen receptor-negative (ER-) cell line. This study aimed to confirm the findings of Xu et al. at the protein level by means of western blotting and saturation binding studies using (99m)Tc-depreotide (NeoSpect). The ER+/SSTR+ ZR75-1 and T47D and SSTR+/ER- MDA MB231 breast cancer cell lines were exposed to 1 n M E(2) or a combination of 1 n M E(2) plus 100 n M tamoxifen or ICI 182 780 (Faslodex) for 48 h. Exposed and non-exposed controls were incubated with increasing concentrations of (99m)Tc-depreotide (0.5 n M-15 n M) in the absence and the presence of 20 micro M of octreotide. Scatchard-Rosenthal plots were derived using commercially available software. SSTR subtypes responsible for E(2)-induced changes in (99m)Tc-depreotide binding were identified by means of western blotting. Mean K(d) values for (99m)Tc-depreotide were 13 n M, 7 n M and 4 n M for T47D, ZR75-1 and MDA MB231 cells, respectively. After stimulation with E(2), the ER+ cell line T47D demonstrated a mean increase of 81% ( P<0.05) in (99m)Tc-depreotide binding. Adding the partial agonist tamoxifen and full antagonist ICI 182 780 to E(2) blocked the induced increase in T47D cells, either reducing SSTR expression or restoring it to control levels. ZR75-1 cells stimulated with E(2) showed a mean decrease in (99m)Tc-depreotide binding of 36% as compared to control cells; this difference, however, proved to be not statistically significant. Similarly, B(max) values did not change in ZR75-1 cells exposed to E(2) in combination with an ER antagonist as compared to control cells. Finally, no influence of E(2) on (99m)Tc-depreotide binding was observed in the ER- cell line MDA MB231. Both SSTR2 and SSTR5 were expressed at high levels in T47D cells and ZR75-1 cells. SSTR5 drastically increased in the absence of E(2) and was restored to the original detection level after E(2) treatment. The presented findings support an oestrogen-dependent regulation of SSTR expression in breast cancer cell lines.

Frequent expression of immunoreactive somatostatin receptors in cervical and endometrial cancer

OBJECTIVE

A variety of human cancers has been shown to express somatostatin receptors which can be utilized for in vivo tumor targeting. Although the somatostatin receptor status of mammary and ovarian cancer has been studied in detail, somatostatin receptors have not been examined in other gynecological malignancies such as cervical or endometrial carcinoma.

METHODS

We have previously developed a panel of somatostatin receptor subtype-specific antibodies that effectively stain formalin-fixed, paraffin-embedded human tumor tissue. In the present study, we have used these antibodies to determine the somatostatin receptor status of 21 randomly selected cervical carcinomas and 28 randomly selected endometrial carcinomas.

RESULTS

In cervical carcinoma, the incidence of somatostatin receptor expression was sst2A (12/21, approximately 57%) > sst3 (9/21, approximately 43%) > sst1 (8/21, approximately 38%) > sst4 (0/21, 0%) = sst5 (0/21, 0%). In endometrial carcinoma, the incidence of somatostatin receptor expression was sst3 (12/28, approximately 43%) > sst2A (11/28, approximately 39%) > sst1 (9/28, approximately 32%) > sst4 (1/28, approximately 4%) = sst5 (1/28, approximately 4%). Somatostatin receptor-like immunoreactivity was in most cases located at the plasma membrane and completely blocked with antigenic peptide. The expression of somatostatin receptor subtypes was independent of patient age, diagnosis, tumor stage, and histological grade.

CONCLUSION

Our findings reveal a previously unappreciated high incidence of sst1, sst2A, and sst3 somatostatin receptors in human cervical and endometrial cancers and suggest that a subgroup of receptor-positive uterine carcinomas may be a potential target for diagnostic and therapeutic intervention with stable somatostatin analogs.