Uremic toxins inhibit transport by breast cancer resistance protein and multidrug resistance protein 4 at clinically relevant concentrations.

During chronic kidney disease (CKD), there is a progressive accumulation of toxic solutes due to inadequate renal clearance. Here, the interaction between uremic toxins and two important efflux pumps, viz. multidrug resistance protein 4 (MRP4) and breast cancer resistance protein (BCRP) was investigated. Membrane vesicles isolated from MRP4- or BCRP-overexpressing human embryonic kidney cells were used to study the impact of uremic toxins on substrate specific uptake. Furthermore, the concentrations of various uremic toxins were determined in plasma of CKD patients using high performance liquid chromatography and liquid chromatography/tandem mass spectrometry. Our results show that hippuric acid, indoxyl sulfate and kynurenic acid inhibit MRP4-mediated [(3)H]-methotrexate ([(3)H]-MTX) uptake (calculated Ki values: 2.5 mM, 1 mM, 25 µM, respectively) and BCRP-mediated [(3)H]-estrone sulfate ([(3)H]-E1S) uptake (Ki values: 4 mM, 500 µM and 50 µM, respectively), whereas indole-3-acetic acid and phenylacetic acid reduce [(3)H]-MTX uptake by MRP4 only (Ki value: 2 mM and IC(50) value: 7 mM, respectively). In contrast, p-cresol, p-toluenesulfonic acid, putrescine, oxalate and quinolinic acid did not alter transport mediated by MRP4 or BCRP. In addition, our results show that hippuric acid, indole-3-acetic acid, indoxyl sulfate, kynurenic acid and phenylacetic acid accumulate in plasma of end-stage CKD patients with mean concentrations of 160 µM, 4 µM, 129 µM, 1 µM and 18 µM, respectively. Moreover, calculated Ki values are below the maximal plasma concentrations of the tested toxins. In conclusion, this study shows that several uremic toxins inhibit active transport by MRP4 and BCRP at clinically relevant concentrations.

Testicular germ cell cancer despite previous local radiotherapy to the testis.

BACKGROUND: Testicular intraepithelial neoplasia (TIN, also carcinoma in situ of the testis) is the uniform precursor of testicular germ cell cancer. Local radiotherapy to the testis with dosages of 18-20 Gy has been found to safely eradicate TIN and germ cells, too. Thus, the general assumption is that the development of invasive germ cell tumours can be prevented by this radiotherapy. PATIENTS AND METHODS: Herein, we report two patients with one-sided testicular tumour and biopsy-proven contralateral TIN. Both of them developed germ cell neoplasms in the remaining testis although local radiotherapy with 20 Gy had been applied to the testis. RESULTS: One patient developed pure seminoma 7 years after completion of radiotherapy, the other developed a combined tumour consisting of embryonal carcinoma and seminoma after 5 years. Treatment consisted of orchiectomy in each of the cases. Histologically, both had TIN in the testicular tissue surrounding the new growths. CONCLUSIONS: Pathogenetically, a small fraction of radioresistent TIN cells overcoming irradiation and progressing to full-blown germ cell cancer in the later course may be the histogenetic clue to explain these unexpected events. Other explanations, though less probable, could be technical radiotherapeutic failure due to targeting problems and a pre-existing radioresistent germ cell tumour in the irradiated testicle.

Endostatin inhibits angiogenesis by stabilization of newly formed endothelial tubes.

Endostatin decreased vascular endothelial growth factor (VEGF)-induced formation of endothelial tubes and microvessels sprouting from aortic rings and blocked their network. After cessation of treatment, the survival time of endostatin plus VEGF-treated tubes was approximately doubled in comparison to VEGF alone. Endostatin antibody blocked VEGF-induced endothelial tube formation and disrupted existing tubes. Endostatin immunostaining was localized between endothelium and basement membrane and in inter-endothelial junctions of new, but not of quiescent, blood vessels. In tumors grown in SCID mice, endostatin immunostaining was stronger accompanying blood vessel maturation and was significantly prominent in vessels of tumor marginal zone where angiogenesis is highly active. These data indicate a new antiangiogenic action of endostatin stabilizing and maturating endothelial tubes of newly formed blood vessels. Thus, strategies accelerating vascular stabilization and maturation could be promising in tumor therapy.

Human endogenous retrovirus (HERV)-K transcripts in gonadoblastomas and gonadoblastoma-derived germ cell tumours.

Gonadoblastomas are rare tumours of abnormal or dysgenetic gonads, often transforming to invasive seminomatous and nonseminomatous germ cell tumours (GCT). Because of the intimate association of noninvasive and invasive lesions, gonadoblastoma may provide clues as to the molecular pathogenesis of GCT. We studied the expression of the human endogenous retrovirus (HERV)-K gag gene in eight gonadoblastomas arising in phenotypically female patients, including two newborn girls. We also studied testicular biopsies with immature Sertoli cell nodules harbouring neoplastic germ cells, a lesion with morphological resemblance to gonadoblastoma. In five gonadoblastomas, invasive seminoma/dysgerminoma was noted, in two cases with formation of additional GCT components. HERV-K gag transcripts were found with moderate levels in gonocytes of all gonadoblastomas and in neoplastic germ cells in testicular Sertoli cell nodules. All invasive GCT except for teratomas displayed HERV-K transcripts. Thus, expression of HERV-K is induced during fetal or embryonal development and precedes invasive GCT formation. Although the specific role of HERV-K expression remains unknown, the findings place HERV-K expression in an appropriate time frame for it to have a role in the molecular pathogenesis of GCT and suggest a precursor-invasive tumour relationship for ovarian GCT equivalent to the more common carcinoma in situ of the testis and testicular GCT.

Angiogenic switch and vascular stability in human Leydig cell tumours.

The high degree of vascularisation, accompanied by the low malignancy of human Leydig cell tumours, offers an interesting model to study the neovascularisation and structural stabilisation of the vascular wall. We report here that Leydig cell tumours are characterised by an increased level of vascular endothelial growth factor (VEGF) in testicular veins, the presence of VEGF mRNA and of its receptor, KDR, and an absence of detectable VEGF receptor Flt-1, in blood vessels of tumour marginal zones and of peri-tumour areas. This is in contrast to the capillaries within normal Leydig cell clusters which demonstrate both Flt-1 and KDR. Ultrastructural destabilisation of the vascular wall, evident as a lack of basement membrane and of peri-endothelial cells was also present in nearly 85% of blood vessels of the peri-tumour areas. In contrast, approximately 89% of the blood vessels of the tumour centre region demonstrated a stabilised vascular wall including basement membrane and peri-endothelial cells. Local application of VEGF(165) to the normal testicular tissue induced significant ultrastructural destabilisation in the capillary walls which only expressed KDR. These results suggest an autocrine role of VEGF on endothelial cells of tumour blood vessels in a region-specific manner and implicate that VEGF interactions with KDR, in the absence of Flt-1, may be involved in vascular destabilisation. In addition, the finding that most (79%) of Leydig tumour blood vessels are stabilised may account for the low malignant potential of these tumours.

Immunohistochemical pattern of insulin-like growth factor (IGF) I, IGF II and IGF binding proteins 1 to 6 in carcinoma in situ of the testis.

AIM: To study the immunohistochemical localisation of insulin-like growth factor (IGF) I, IGF II, and IGF binding proteins 1-6 in intratubular germ cell neoplasia in the vicinity of solid germ cell tumours of the testis. METHODS: Testes were obtained from 13 patients (20-35 years old) who had undergone orchidectomy for treatment of a solid germ cell tumour. Tumour cells were verified histologically by their distinctive morphology and by visualisation of placental alkaline phosphatase immunoreactivity. RESULTS: The majority of carcinoma in situ (CIS) cells were immunopositive for IGF I, whereas no CIS cells stained for IGF II. Of all the IGF binding proteins investigated, CIS cells showed intense immunoreactivity for IGF binding protein 5 and lower expression of all other IGF binding proteins. CONCLUSIONS: These results suggest that the action of IGF binding protein 5 in CIS cells may modulate the activity of IGF I. This may be related to a proliferative advantage that could facilitate tumour development.

Mitotic frequency in different early stages of testicular seminoma.

The proliferation behaviour of early seminoma was studied by analysis of the mitotic frequency in defined stages of tumour development: Carcinoma in-situ, intratubular seminoma, intratubular seminoma with interstitial seminoma cells and solid seminoma. It was shown that the mitotic frequency increased during the process of tumour development and that tumour cells in different tissue compartments show a different proliferation behaviour. The first stage example (CIS) showed a mitotic frequency of 0.65% while the second stage example (intratubular seminoma) showed a mitotic frequency of 0.84%. The separated analysis of the third stage example (intratubular seminoma with interstitial seminoma cells) showed a mitotic frequency of 1.45% for the intratubular compartment and 0.72% for the interstitial compartment. The fourth stage example (solid seminoma) showed a mitotic frequency of 3.59%. The finding that mitotic frequencies differ in the examined stage examples are interpreted as an adaptation process of the tumour cells to a changed tissue micro-environment. Considering that little experimental data exists on the biological behaviour of early seminoma cells this study adds information to the present knowledge of their proliferation kinetics.

Carcinoma-in situ of the human testis: tumour cells are distributed focally in the seminiferous tubules.

The distribution of carcinoma-in-situ was investigated in the longitudinal course of human seminiferous tubules. Serial sections of tubular segments, measuring 9330 microns and 1600 microns in length respectively, were analysed. The tubules exhibited a local accumulation of tumour cells. Areas with abundant tumour cells followed areas that were free of tumour cells. The original coiled configuration of the seminiferous tubules was reconstructed with the help of a three-dimensional crepe rubber model. The model showed that tumour-bearing tubular segments lay close together, even if they were actually situated far distant from each other in the longitudinal course of the tubule. Consequently, distant tubular segments can be attached to a common area of the interstitial tissue. This corresponds to the observation that histological sections frequently show clustered CIS-tubules surrounded by tubules exhibiting spermatogenesis. It is a subject for debate whether the interstitial tissue connects tubular segments to functional testicular units.

The value of the AgNOR staining method in identifying carcinoma in situ testis.

An early and reliable diagnosis is necessary in order to have the chance of a curative therapy of Carcinoma in situ testis (Cis). Forty-six testicular biopsies were investigated to assess the value of the AgNOR staining method in comparison to placental alkaline phosphatase (PLAP) immunostaining. Both methods provided corresponding results and identical tumor cells were recognized in serial sections. The mean AgNOR counts per nucleus were 26.86 (19-52, SD: 2.68) for CIS cells, 8.18 (5-14, SD: 2.20) for spermatogonia and 12.96 (9-18, SD: 2.44) for Sertoli cells, without the counts overlapping within these three groups. Even single CIS cells are easily and reliably recognizable by their typical AgNOR pattern and their high AgNOR count per nucleus. The independent estimation of 9 testicular biopsies with the AgNOR staining method and the PLAP immunostaining correspondingly revealed 7 biopsies with CIS. Two biopsies lacked tumor cells. The AgNOR staining method can be recommended as an additional diagnostic tool in identifying CIS, because of the short and convenient staining procedure, low costs and the applicability on formalin-fixed and paraffin-embedded material.

Further practical experiences in the recognition and management of carcinoma in situ of the testis.

99 biopsies from the contralateral testis in patients with unilateral germ cell tumor were investigated using the semithin section technique. Four cases (4%) revealed a carcinoma in situ (CIS) pattern. Two patients underwent a local radiation (20 Gy), 2 patients received combination chemotherapy (cisplatin, etoposide and bleomycin; PEB). No tumor cells were found in control biopsies 4-8 months after therapy. Both biopsy specimens taken from radiated patients lacked also germ cells. In contrast, 1 patient who was treated with PEB and also another 1 presenting with a teratocarcinoma of apparently retroperitoneal origin and unilateral CIS revealed germ cells after chemotherapy. The present data suggest radiation therapy to be the first line treatment for CIS-bearing testes. In order to get informations about the distribution of CIS cells in the affected testes, one or two biopsies were additionally taken from macroscopically unsuspicious tissue surrounding various solid germ cell tumors (74 patients). 56 cases (76%) revealed CIS. Even considering the possibility of missing CIS, a screening biopsy is actually the only method for detecting early manifestations of germ cell tumors and should be performed routinely in contralateral testes of patients with germ cell tumors.

Carcinoma-in-situ cells in cultured human seminiferous tubules.

For the first time, early germ-cell derived tumour cells were studied in an in-vitro system of cultured seminiferous tubules. The intratubular tumour cells not only survived in culture for 7 days but were also able to multiply. Dividing tumour cells were identified in semi-thin sections and electron micrographs by morphological criteria. Additionally, mitotic activity was demonstrated by [3H]thymidine histo-autoradiography. There are numerous reports on cell lines established from solid non-seminomas, but up to now no references to seminoma cell lines or cultures of intratubular tumour cells are available. The culture of seminiferous tubules offers a tool in making carcinoma-in-situ cells accessible for experimental work.

Leydig cell mitoses in human testes bearing early germ cell tumors.

Numerous mitoses were noted in testicular tissue from adult men with early germ cell tumors. More than 15 Leydig cells undergoing mitosis were found in the interstitial compartment. The presence of specific crystalline intracytoplasmatic inclusions demonstrated for the first time that differentiated Leydig cells are capable of proliferation. Occasionally cells are difficult to discriminate during mitosis. To establish reference criteria, the light- and electron-microscopic features of the following mitotic cells were examined: Leydig cells, fibroblasts, perivascular cells, peritubular cells, and lymphocytes. Supplementary mitoses in germ cell tumors and in a case of Leydig cell tumor were investigated. In the literature, only single reports of mitoses in Leydig cells are available. The frequent incidence of Leydig cell mitosis in early germ cell tumors may be due to the presence of growth-promoting factors in the testicular tissue.