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CASE REPORT |
, ERß1, ERß2) in human Leydig cell tumorDepartments of Cell Biology and 1 Pharmaco-Biology, Faculty of Pharmacy, University of Calabria, 87030 Arcavacata di Rende (CS), Italy and 2 Department of Internal Medicine, University of Modena and Reggio Emilia, Policlinico, 411000 Modena, Italy
(Correspondence should be addressed to S Andò who is now at Dipartimento di Biologia Cellulare, Università degli Studi della Calabria, Arcavacata di Rende, 87030 Cosenza, Italy; Email: sebastiano.ando{at}unical.it)
Abstract
A Leydig cell tumor is a rare neoplasm, deriving from the interstitial cells, whose pathogenesis has not been still defined. Leydig cells of normal adult testis are known as physiological targets for estrogens. However, some studies on transgenic rodents suggest a role of estrogens in the development of Leydig cell hyperplasia and Leydig cell tumor. Therefore, with the aim to evaluate a possible link between estrogens and testicular tumorigenesis, this study investigated the expression of aromatase and estrogen receptors (ER
, ERß1, ERß2) in testes from two patients with Leydig cell tumor. A strong immunoreactivity for aromatase, ERß1, and ERß2, together with a detectable ER immunostaining, was revealed in tumoral tissues. These findings were confirmed by western blot analysis of tumor extracts detecting a 55 kDa P450arom, a 67 kDa ER band, a 59 kDa ERß1 band, and a 53 kDa ERß2 band. The pattern of ER expression in neoplastic cells appears different from that of control Leydig cells exhibiting only ERß1 and ERß2 isoforms. The authors hypothesize how the high estrogen production could play a role in the neoplastic transformation of Leydig cells, while the exclusive presence of ER in tumoral cells could amplify estradiol-17ß signaling contributing to the tumor cell growth and progression.
Introduction
A Leydig cell tumor is a rare neoplasm of the male gonadal interstitium, accounting for 2–3% of all testicular tumors (1). It is usually observed in adult men (30–60 years) but it may also occur in prepubertal boys. This tumor is generally associated with endocrine disturbance, as adulthood gynecomastia and precocious puberty in children (2, 3). A Leydig cell tumor is commonly benign, but ~10% malignant variants have been reported in adults. A malignant neoplasm is characterized by large size, marked nuclear pleomorphism, high mitotic rate, extensive necrosis, and vascular invasion (4, 5).
Estrogen receptor (ER) expression has been reported by different authors in normal Leydig cells of adult testis (6–8) indicating these cells as physiological targets for estrogens. Furthermore, cytochrome P450 aromatase, the enzyme catalyzing androgen aromatization into estrogens, has been detected in Leydig cells of normal human testis (9), suggesting a paracrine action of estrogens, locally produced, in the steroidogenesis control (10).
However, estrogens are able to regulate cell growth and apoptosis (11, 12); therefore, these hormones could also be involved in testicular neoplastic proliferation. A possible involvement of estrogens in tumorigenesis in the human male gonad has been suggested by the increased incidence of testicular germ cell tumors after prenatal or occupational estrogen exposure (13–17). Conversely, the link between estrogens the and tumoral process is scarcely known in human testicular tumors originating from the gonadal stroma. However, some studies on transgenic rodents suggested a role of estrogens in the development of Leydig cell hyperplasia and Leydig cell tumor (18, 19).
The aim of the present work was to investigate the expression of aromatase and ER isoforms, ER, ERß1, and ERß2, in testes from two patients with a Leydig cell tumor, a rare neoplasm deriving from the interstitial cells.
Materials and methods
Patients
The investigation was performed on formalin-fixed and paraffin-embedded testis tissues from two male patients with Leydig cell tumors (aged 31 and 33 years). Control testicular tissues were obtained from two male patients (aged 29 and 35 years) showing testes with a sarcoidosis granulomatous-like lesion. The archival cases were provided by the Department of Medicine and Medical Specialties, University of Modena and Reggio Emilia, Policlinico, Italy. The patients showed gynecomastia, normal follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and testosterone (T) serum levels but high estradiol-17ß (E2) levels, as well as oligoasthenozoospermia, before therapeutic orchidectomy. After orchidectomy, sperm motility and E2 levels of patients were in the normal ranges (see collected data in Table 1
).
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Morphological analysis
Paraffin-embedded sections, 5 µm thick, were deparaffinized, dehydrated, and stained by hematoxylin–eosin.
Antibodies
Anti-aromatase primary antibody was mouse monoclonal MCA2077 (Serotec, Oxford, UK), which recognizes epitope mapping at the C-terminus region of the human native P450arom. Anti-ER primary antibody was mouse monoclonal F-10 (Santa Cruz Bio-technology, Santa Cruz, CA, USA), which recognizes epitope mapping at the C-terminus region of the human native ER. Anti-ERß1 primary antibody was mouse monoclonal MCA1974S (Serotec), which recognizes epitope mapping at the C-terminus regions of human native ERß1. Anti-ERß2 primary antibody was mouse monoclonal MCA2279S (Serotec), which recognizes epitope mapping at the C-terminus regions of human native ERß2. Rabbit polyclonal anti-ß-actin (Santa Cruz Biotechnology) was also used as a loading control. Biotinylated goat anti-mouse IgG (Vector Laboratories Inc., Burlingame, CA, USA) and goat anti-mouse horseradish peroxidase-conjugated IgG (Amersham) were used as secondary antibodies.
Immunohistochemical analysis
Paraffin-embedded sections, 5 µm thick, were mounted on slides precoated with poly-lysine, and then they were deparaffinized and dehydrated (7–8 serial sections). Immunohistochemical experiments were performed after heat-mediated antigen retrieval (20). Hydrogen peroxide (3% in distillate water) was used, for 30 min, to inhibit endogenous peroxidase activity, while normal goat serum (10%) was utilized, for 30 min, to block the nonspecific binding sites.
Immunodetection was carried out using mouse monoclonal anti-aromatase (1:50), anti-ER (1:50), anti-ERß1, and anti-ERß2 (1:100) primary antibodies at 4 °C overnight. Then, a biotinylated goat anti-mouse IgG was applied (1:600) for 1 h at RT, followed by the avidin–biotin/horseradish peroxidase complex (ABC/HRP; Vector Laboratories). Immunoreactivity was visualized by using the diaminobenzidine chromogen (DAB; Zymed Laboratories, San Francisco, CA, USA). P450arom sections were also counterstained with hematoxylin. The primary antibody was replaced by normal rabbit serum in negative control sections. Absorption controls have utilized primary antibodies preabsorbed with an excess (5 nmol/ml) of the purified respective blocking peptides (Santa Cruz Bio-technology), at 4 °C for 48 h.
Rat ovary was used as a positive control for P450arom and ER, while control human testis was used as a positive control for both ERß1 and ERß2.
Scoring system The immunostained slides were examined by light microscopy using the ‘Allred score’ (21), which combines a proportion score and an intensity score. A proportion score was assigned representing the estimated proportion of positively stained tumor cells (0, none; 1,<1/100; 2, 1/100 to <1/100; 3, 1/10 to <1/3; 4, 1/3 to 2/3; 5, >2/3). An intensity score was assigned by the average estimated intensity of staining in positive cells (0, none; 1, weak; 2, moderate; 3, strong). Proportion and intensity scores were added to obtain a total score that ranged from 0 to 8.
Protein extraction
Protein extraction from formalin-fixed paraffin-embedded sections was carried out according to Ikeda (22). Briefly, 50 µm testis sections were deparaffinized in xylene, dehydrated in graded ethanol, immersed in distilled water, and air dried. Then, the neoplastic area was recovered from the glass slides, cut into small pieces and placed in Eppendorf tubes. Two hundred microliters of RIPA buffer, pH 7.6 (1 M NaH2PO4, 10 mM Na2HPO4, 154 mM NaCl, 1% Triton X-100, 12 mM C24H39O4Na, 0.2% NaN3, 0.95 mM NaF, 2 mM PMSF, 50 mg/ml aprotinin, 50 mM leupeptin; Sigma Chemical) containing 0.2% SDS, were added to each tube and the contents were incubated at 100 °C for 20 min, followed by incubation at 60 °C for 2 h. After incubation, tissue lysates were centrifuged at 15 000 g for 20 min at 4 °C and the supernatants were stored at –80 °C until biochemical analysis.
Western blot analysis
Tissue lysates were quantified using the Bradford protein assay reagent (23). Equal amounts of protein (50 µg) were boiled for 5 min, separated under denaturing conditions by SDS–PAGE on 10% polyacrylamide Tris-glycine gels and electroblotted onto nitro-cellulose membranes. Nonspecific sites were blocked with 5% nonfat dry milk in 0.2% Tween-20 in Tris-buffered saline (TBS-T) for 1 h at room temperature and incubated overnight with anti-aromatase (1:500), anti-ER (1:500), anti-ERß1(1:500), anti-ERß2 (1:500), and anti-actin (1:1000) primary antibodies. The antigen–antibody complexes were then detected by incubation of the membranes for 1 h at 22 °C with the horseradish peroxidase-conjugated secondary antibody (1:7000). The bound secondary antibodies were located with the ECL Plus western blotting detection system (Amersham) according to the manufacturer’s instructions. Each membrane was exposed to the film for 2 min.
Protein extracts from a rat ovary and control human testis were used as positive controls as in immunohistochemical analysis. Negative controls were prepared using tissue lysates, where antigens were previously removed by preincubation with specific antibodies (1 h at room temperature) and subsequently immuno-precipitated with protein A/G agarose.
Results
Histological study
H–E staining showed similar cell arrangement of neoplastic Leydig cells in the two testis specimens with unilateral Leydig cell tumors (sized 1.4x1.1 cm and 4x4 cm). Tumoral samples revealed large, vacuolated Leydig cells arranged in multiple clusters with pseudo-tubular appearance. Mild nuclear pleomorphism and occasional mitotic figures were observed (Fig. 1A and B).
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. Immunohistochemistry
P450arom
The cytoplasm of vacuolated neoplastic Leydig cells has shown a strong P450arom immunoreactivity (total score 8) in both the samples, while immunonegative nuclei displayed only the blue counter-staining (Fig. 1A1 and B1). Control testes have shown an intense P450arom immunoreactivity exclusively in interstitial Leydig cells (total score 8), while the cells of tubular compartment were immunonegative (Fig. 1C1). Negative controls (not shown) and the absorption controls (inserts) were all immunonegative.
Estrogen receptors
Neoplastic Leydig cells of both samples showed a moderate ER immunoreactivity in the nuclei (total score 5) and a weak immunostaining (total score 4) was also observed in the cytoplasm (Fig. 1A2 and B2). Control testis sections were all ER immunonegative (Fig. 1C2).
A strong nuclear ERß1 (total score 7) immunoreactivity was observed in neoplastic Leydig cells of both samples as well as a weak (total score 4) signal has been detected in their cytoplasm (Fig. 1A3 and B3). The control testis showed a strong ERß1 immunostaining (total score from 5 to 7) in the cells of both the tubular and interstitial compartments (Fig. 1C3).
Neoplastic Leydig cells show a very intense ERß2 immunoreactivity (total score 8) in the nuclei, while their cytoplasm was moderately stained (total score 5; Fig. 1A4 and B4). In the control testis, ERß2 signal (total score from 5 to 8) was mainly revealed in Leydig cells, Sertoli cells, spermatogonia, and spermatocytes (Fig. 1C4).
Negative controls (not shown) and the absorption controls (inserts) were all immunonegative.
Western blot analysis
Using an antibody against P450arom, the western blot of tumoral tissues revealed a single band corresponding to a molecular mass of ~55 kDa (Fig. 2: lanes 1 and 2) consistent with the human P450arom size and co-migrating with the ovary extract band (positive control; Fig. 2: C+). Furthermore, using an antibody specific to ER, the western blot of neoplastic tissues showed a single band at ~67 kDa (Fig. 2: lanes 1 and 2), with the same mobility of ovary extract (positive control; Fig. 2: C+). Conversely, no protein band was observed in the western blot of control testes (Fig. 3: lanes 1 and 2) except for ovary extract (positive control; Fig. 3: C+). In addition, using antibodies specific to ERß1 and ERß2, two bands were detected, at ~59 kDa and ~53 kDa respectively (Fig. 2: lanes 1 and 2). The two bands migrated as in control testis extracts (Fig. 2: C+). All the negative control lanes were unlabeled (Fig. 2: C–).
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The biological significance of estrogen-induced testicular tumorigenesis has been suggested by the in vivo model overexpressing aromatase transgenic mice (19). Half of these males were infertile and some of them showed larger than normal testis and Leydig cell hyperplasia/ Leydig cell tumor. Furthermore, aromatase was markedly immunolocalized in the cytoplasm of interstitial cells, and its immunoreactivity appeared to be strongest in the testes with more advanced stages of neoplasia. The same transgenic animals exhibited circulating estrogen levels at least twice higher than those of control animals, and the levels of aromatase mRNA in their testicular tissues were fourfold higher when compared with controls. It is worth mentioning how ER protein in testicular tissue of aromatase transgenic animals was very high with respect to the undetectable levels of control animals. So the authors suggest how an enhanced synthesis of estrogens in tumoral tissues led to an upregulation of ER expression.
Human Leydig cell tumor is a rare testicular neoplasm where the estrogen involvement in tumorigenesis process has scarcely been investigated. In our patients, a strong aromatase expression in tumoral tissues was revealed by immunostaining and western blotting. This finding agrees with a single previous report (24) showing the aromatase immunolocalization in Leydig cell tumors. Furthermore, aromatase expression in control human testicular tissue confirmed Turner’s report in normal testes (25). The enhanced endogenous synthesis of estrogens by Leydig cell tumors was reflected in both patients by a dramatic increase of circulating estrogen levels, resulting in a more than twofold higher level than those of normal adult male, and by the low testosterone levels (at the lower limit of normal range).
We may reasonably assume how the ratio between the free fraction levels of the two steroids is furthermore increased in the target tissues. The diminished sperm count and motility of both patients may not only be related to altered testicular tropism, parenchymal compression and increased local temperature ipsilateral to the tumor (26), but also to the detrimental effects of high circulating estrogen levels on the counter-lateral gonad activity. In the normal adult male, 80% of the plasma estradiol originates from aromatization of testosterone and androstenedione in fat, striated muscle, and other tissues including bone and brain, while 20% in the circulation is secreted by the testis. So, it is reasonable to argue that the excessive increase of estradiol circulating levels, observed in the two patients with Leydig cell tumor, is the consequence of an enhanced rate of testicular secretion. This is confirmed by the evidence that estradiol, as well as circulating E2/T ratio levels, drops dramatically following surgical treatment, while for one of the two patients the persistence of a conspicuous bilateral gynecomastia led to bilateral mastectomia.
Following orchidectomy, the two patients exhibited a moderate increase of sperm count and a remarkable augmentation of sperm motility. The latter event may be reconducted to the restored circulating testosterone levels likely affecting the entire male genital tract.
The expression of ER isoforms in Leydig cell tumors is, to date, unknown. In fact, only a single work showed the ER immunolocalization in cryostat sections of Leydig cell tumors (24), but these data were obtained before the ERß discovery.
Immunohistochemical and western blot analysis of tumoral tissues revealed the expression of ER and of the two ERß isoforms, ERß1 and ERß2, in the neoplastic Leydig cells of both patients. So, the pattern of ERs expression in tumoral cells appears different from that of control Leydig cells, exhibiting only ERß1 and ERß2 as previously reported (8, 27).
There is a growing body of evidence suggesting that ER and ERß can be expressed together in the same cell type and independently expressed in another. Therefore, homodimers (ER–ER/ERß–ERß) or heterodimers (ER–ERß) can be formed (28). The binding affinity of ER–ER/ ER–ERß dimers for a consensus DNA estrogen response element is reported to be higher than that of the ERß–ERß homodimer (29). Thus, the presence of ER could reinforce the estradiol-induced tumor cell proliferation.
Finally, the present report demonstrates that neoplastic Leydig cells are potential estrogen biosynthesis sites and display a modified ER expression pattern. Therefore, it appears reasonable to suggest that the high estrogen levels, measured in the two patients, could play a role in the neoplastic transformation of Leydig cells, while the exclusive presence of ER in tumoral cells could amplify E2 signaling, contributing to the tumor cell growth and progression.
Acknowledgements
The authors thank Dr Francesco Romeo for the pathological–anatomical support. Financial support: this work was supported by PRIN 2004 prot. no. 0067227 and A I R C.
References
and ß in the human reproductive organs. Journal of Clinical Endocrinology and Metabolism 2000 85 4835–4840. and ß proteins in the testes and male reproductive system of human and non-human primates. Molecular Human Reproduction 2001 7 227–236.
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