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Two years after testicular resection was carried out in a 40-year-old man that revealed mixed germ cell tumor of more than one histological type (seminoma, embryonal cell carcinoma, and yolk sac tumor), he presented with an asymptomatic pulmonary nodule in his left lower lobe. Video-assisted thoracoscopic partial resection of the tumor revealed a 24 × 20 mm teratoma with somatic-type malignancy in which pleomorphic rhabdomyosarcoma was a major element. One year later, asymptomatic tumor recurrence occurred at both edges of the stapler line as 22 × 20 mm and 10 × 5 mm nodules composed only of pleomorphic rhabdomyosarcoma. Throughout the course there was no abdominal lymph node swelling detected by computed tomography (CT) and tumor markers were normal. Adjuvant chemotherapy was started after the tumor recurrence. Currently, the patient is still undergoing chemotherapy 5 months after the tumor recurrence. In conclusion, despite the fact that primary pulmonary rhabdromyosarcoma is a rare neoplasm, metastatic pulmonary germ cell tumor with somatic-type malignancy showing predominantly rhabdomyosarcomatous differentiation should be considered in the differential diagnosis of such lesions of the lung. [ABSTRACT FROM AUTHOR]

Background. Among salivary glands, the parotid gland is the most common site for secondary neoplastic involvement, and carcinomas and melanomas are the two most common secondary tumors. Methods. We present a case of testicular seminoma metastasizing to the parotid gland. The patient, who had a remote history of testicular seminoma, was initially seen with a parotid mass. A primary parotid lesion was anticipated, and excisional biopsy was performed. The diagnosis of testicular seminoma metastasizing to the parotid gland was established on the basis of histologic findings and was confirmed by immunohistochemical analysis. Results. Metastatic and primary seminomas have the same morphologic features and cellular composition, and granulomatous reaction is often present in both neoplasms. Extragonadal seminoma often occurs in the midline (presacral, retroperitoneal, anterior mediastinal, and pineal regions); when present in any other locations, the tumor should be considered to be metastatic. Placenta alkaline phosphatase is a useful immunohistochemical stain to confirm the diagnosis, and cytokeratin immunohistonegativity rules out carcinomas or epithelioid sarcomas. Conclusions. To our knowledge, this is the first published case of metastatic testicular seminoma to the parotid gland. Cytomorphologic features of seminoma and the presence of granulomatous giant cells are important diagnostic clues. Two other neoplasms with granulomatous reactions, nasopharyngeal carcinoma and epithelioid sarcoma, should be considered in the differential diagnosis. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX–XXX, 2005 [ABSTRACT FROM AUTHOR]

The activity of human placental alkaline phosphatase (PLAP) is downregulated by a number of effectors such as l-phenylalanine, an uncompetitive inhibitor, 5′-AMP, an antagonist of the effects of PLAP on fibroblast proliferation and by p-nitrophenyl-phosphonate (PNPPate), a non-hydrolysable substrate analogue. For the first two, such regulation may be linked to its biological function that requires a reduced and better-regulated hydrolytic rate. To understand how such disparate ligands are able to inhibit the enzyme, we solved the structure of the complexes at 1.6Å, 1.9Å and 1.9Å resolution, respectively. These crystal structures are the first of an alkaline phosphatase in complex with organic inhibitors. Of the three inhibitors, only l-Phe and PNPPate bind at the active site hydrophobic pocket, providing structural data on the uncompetitive inhibition process. In contrast, all three ligands interact at a remote peripheral site located 28Å from the active site. In order to extend these observations to the other members of the human alkaline phosphatase family, we have modelled the structures of the other human isozymes and compared them to PLAP. This comparison highlights the crucial role played by position 429 at the active site in the modulation of the catalytic process, and suggests that the peripheral binding site may be involved in the functional specialization of the PLAP isozyme. [Copyright &y& Elsevier]

A 19-year-old man with mild mental retardation was diagnosed as having metastatic choriocarcinoma and a testicular tumor. Histopathological examination of the resected testis revealed the presence of a small lesion of mature teratoma but no trace of choriocarcinoma. The remaining seminiferous tubules were atrophic and lined by large atypical germ cells, which were diagnosed as intratubular germ cell neoplasia of the unclassified type (IGCNU). A small area with prominent tubules was also observed. Within this lesion, the tubules were dilated and contained several layers of cells with central necrosis. Immunohistological comparison of staining for several biological markers (Ki-67, c-kit and placental alkaline phosphatase) between cells in the atrophic tubules and those in the dilated tubules indicated a progression of the latter cells to cells with a more proliferative ability. In the opposite testis, examined at autopsy after death due to metastatic choriocarcinoma, all seminiferous tubules were lined by Sertoli cells only. It was therefore assumed that the germ cell tumor of the combined histological type had primarily arisen in the background of IGCNU, and that choriocarcinoma had spontaneously regressed. The early onset of these testicular neoplastic lesions strongly indicates their occurrence under the genetic background of gonadal dysplasia, the Sertoli cell-only syndrome. The possible relation of gonadal disease to mental retardation in this patient is also discussed. [ABSTRACT FROM AUTHOR]

Background: In vitro, Trypanosoma cruzi invades a wide variety of mammalian cells by an unique process that is still poorly understood. Trypomastigotes adhere to specific receptors on the outer membrane of host cells before intracellular invasion, causing calcium ion mobilization and rearrangement of host cell microfilaments.Objective: To test if placental alkaline phosphatase (PLAP), a trophoblast plasma membrane protein anchored by a glycosylphosphatidylinositol molecule, is involved in the transplacental transmission of this parasite.Method: We cultured HEp2 cells with the parasite and studied PLAP and actin microfilaments. The results were correlated with invasion rate.Results: Human HEp2 tumour cells express PLAP. HEp2 cells infected with trypomastigotes showed alteration in their alkaline phosphatase activity and a different pattern of actin organization, compared to control cells. Perturbation of PLAP from HEp2 cells before infection with T. cruzi trypomastigotes decreased the invasion rate.Conclusion: Placental alkaline phosphatase could be involved in the internalization of T. cruzi into HEp2 cells, via activation of tyrosine kinase and rearrangement of actin microfilaments. [ABSTRACT FROM AUTHOR]

We report the case of a 17-yr-old male with ambiguous genitalia, 45,X/46,XY mosaic karyotype, and Y chromosome microdeletions. The patient underwent a testicular biopsy at the age of 6 with normal findings. A second biopsy at the age of 17 established the diagnosis of intratubular germ cell neoplasia (ITGCN), which was treated with bilateral orchidectomy. This case report deals with three important issues regarding ITGCN: First, although a prepubertal biopsy can be performed in order to provide evidence for future fertility, it is very unreliable for making a diagnosis of ITGCN. Second, because ITGCN tends to be a generalized procedure that affects both testes in a uniform pattern, a small number of biopsies, even a single one, could be adequate for diagnostic purposes in the majority of cases. Third, although the population that requires screening for ITGCN remains controversial, the early postpubertal period could be the optimum time for a testicular biopsy. [ABSTRACT FROM AUTHOR]

Peptide phage display is a method by which large numbers of diverse peptides can be screened for binding to a target of interest. Even when successful, the rate-limiting step is usually validation of peptide bioactivity using living cells. In this paper, we describe an integrated system of vectors that expedites both the screening and the characterization processes. Library construction and screening is performed using an optimized type 3 phage display vector, mJ1, which is shown to accept peptide libraries of at least 23 amino acids in length. Peptide coding sequences are shuttled from mJ1 into one of three families of mammalian expression vectors for cell physiological studies. The vector pAL1 expresses phage display-derived peptides as Gal4 DNA binding domain fusion proteins for transcriptional activation studies. The vectors pG1, pG1N, and pG1C express phage display-derived peptides as green fluorescent protein fusions targeted to the entire cell, nucleus, or cytoplasm, respectively. The vector pAP1 expresses phage display-derived peptides as fusions to secreted placental alkaline phosphatase. Such enzyme fusions can be used as highly sensitive affinity reagents for high-throughput assays and for cloning of peptide-binding cell surface receptors. Taken together, this system of vectors should facilitate the development of phage display-derived peptides into useful biomolecules. [Copyright &y& Elsevier]

Cholesterol and glycosphingolipid-rich membrane rafts, which are rich in GPI-anchored proteins and are distinct from caveolae, are believed to serve as platforms for signal transduction events and protein recycling. GPI-anchored proteins with diverse functions as well as caveolin may be recovered in a membrane fraction insoluble in cold non-ionic detergent. This study tests for possible heterogeneity in the protein composition of the lipid rafts and detergent-insoluble membrane complexes by examining the two GPI-anchored homologous human folate receptors (FR)-a and -b, the GPI-anchored human placental alkaline phosphatase (PLAP), and caveolin (control) in transfected CHO cells. Both FR and PLAP showed the equal distribution of cell-surface vs. sequestered (recycling) protein typical of GPI-proteins. Quantitative affinity purification of detergent-insoluble complexes using biotinylated folate or specific antibodies demonstrated a strong association of the homologous FR-a and FR-b in the same detergent-insoluble complex and separate complexes containing either PLAP or caveolin. Immunogold localization experiments using antibody crosslinking to produce larger aggregates of GPI-anchored proteins for visualization by electron microscopy also showed a clear separation between FR- and PLAP-rich membrane microdomains. Thus, even though functionally diverse and heterologous GPI-anchored proteins are known to share endocytic and recycling vesicles, they may be segregated in distinct lipid rafts on the basis of their ecto(protein) domains facilitating clustering, compartmentalization and homotypic protein interactions. [ABSTRACT FROM AUTHOR]

To determine the frequency of mutation in different cell types of mammals, transgenic mice that allow mutant cells to be visualized in situ were used. These mice carry a defective allele of the human placental alkaline phosphatase (PLAP) gene. The allele does not produce enzyme because the reading frame is shifted by an insertion of 7 G:C basepairs. The insertion is adjacent to four existing G:C basepairs, so the allele has a tract of 11 Gs. The G11 PLAP allele was studied in wildtype mice and in mice deficient in mismatch-repair (MMR) due to lack of either Pms2 or Mlh1. PLAP+ cells were counted in brain, heart, kidney, and liver. In wildtype mice, there was an average of between 5 and 30 PLAP+ events per million cells. No cells with alkaline phosphatase activity were detected in tissues from mice lacking the PLAP gene. In MMR-deficient mice, the number of PLAP+ allele was increased by at least three-order of magnitude in brain, heart and kidney, but <10-fold in liver. These data show that MMR is vital to maintaining repeat stability in brain, heart and kidney cells. The reason for the different results in the liver is not clear. Cells in the liver were shown to be capable of expressing of PLAP enzyme and PLAP mRNA was present in this organ. [Copyright &y& Elsevier]

Congenital Chagas disease, due to the intracellular parasite Trypanosoma cruzi, is associated with premature labor, miscarriage, and placentitis. Human enzyme placental alkaline phosphatase (PLAP) (EC 3.1.3.1.) is membrane-anchored through glycosylphosphatidylinositol (GPI). PLAP is present in plasma in late pregnancy, 36 to 40 weeks; there are lower levels in maternal Chagas disease. Infants born to such mothers may have congenital Chagas disease. Human placental villi (PV) were treated with phospholipase-C (PL-C) and then cultured with T. cruzi to determine the effect of the parasites on PLAP activity as an in vitro model. There is less PLAP activity after treatment by PL-C and during culture with T. cruzi. Pretreatment of PV with PL-C before culture with T. cruzi yielded essentially normal specific activity of PLAP and prevented or greatly reduced infective penetration of villi by parasites. The results are consistent with a pathogenetic role for placental alkaline phosphatase in congenital Chagas disease. Receptor activation of membrane attachment to PLAP may be a device used by T. cruzi to enable parasite invasion of human trophoblast. [Copyright &y& Elsevier]

Seminoma arising in patients with Klinefelter's syndrome is extremely rare; to our knowledge, only three cases have been reported in the English language literature. We report a case of intrapelvic seminoma in a 39-year-old man with Klinefelter's syndrome. Gross examination revealed that the tumor was a solid and irregular mass measuring 90 mm in diameter. The cut surfaces of this ill-defined tumor were yellow–white with necrotic foci. Histologically, the tumor cells were separated into lobules by branching, fibrous septa containing lymphocytes. In some parts of the tumor, a cord-like arrangement of tumor cells was present. Immunohistochemically, the tumor cells were strongly and diffusely positive for antiplacental alkaline phosphatase antibody along their cytoplasmic membranes, but negative for both chorionic gonadotrophin and α-fetoprotein. Based on these findings, we diagnosed this tumor as a seminoma. The testes when examined were found to be atrophic bilaterally, but with no tumor lesions. Chromosomal analysis yielded a 47XXY karyotype, compatible with Klinefelter's syndrome. These findings indicate a case of primary intrapelvic seminoma in Klinefelter's syndrome. The patient underwent intensive radiation therapy postoperatively, and he demonstrated no evidence of recurrence or metastasis during the 13-month period following surgery. [ABSTRACT FROM AUTHOR]

Objective To develop specific monoclonal antibodies (mAbs) against human germ cell tumours. Materials and methods A single-cell suspension obtained from tumour tissue fragments (consisting of both tumour and normal compartments) from a patient with seminoma was used as an immunogen. Spleen cells from immunized mice were used to develop mAbs. Tissue specificity, biochemical characteristics and competitive studies were analysed using immunocytochemical staining, dot blots and a Western blot analysis, to identify target antigen(s). Results The immunization protocol led to the development of 107 hybridomas, 90 of which were negative against the original tissue biopsies. The remaining 17 showed positivity against various tissue compartments. One selected mAb (ATC2) showed specific staining on germ cell tumours but not on normal tissues, and positive staining with some human tumour cell lines. The target antigen for ATC2 was confirmed to be placental alkaline phosphatase (PLAP) based on: Western blot analysis compared with commercially available PLAP; comparison of the data with another well-known anti-PLAP mAb (H17E2, although the two mAbs recognized different antigenic epitopes); heat resistance characteristics; high-performance liquid chromatography of the ATC2 target antigen and purified PLAP. Conclusion The selected mAb ATC2 has high specificity for human germ cell tumours, the target antigen for ATC2 being PLAP, although the antigenic epitope(s) differ from those recognized by H17E2. Thus ATC2 may be useful for monitoring serum levels of PLAP in patients with testis cancer and may be relevant for detecting cancer cells in the semen of individuals with suspected testis cancer, particularly in those with equivocal findings on ultrasonography. [ABSTRACT FROM AUTHOR]

The objective of our study was to test if a tumor expressing a transgene coding for a membrane-bound protein is amenable to immunotherapy by antibodies to the same protein. To this end, we have established an Ehrlich ascites tumor (EAT) cell line, EAT-DAP, stably expressing human, membrane-bound placental alkaline phosphatase (PLAP) by infecting EAT cells (EATC) with the retroviral vector DAP and selecting neomycin-resistant cells. EATC and EAT-DAP cells grew at similar rates in vitro, and produced ascites tumor in Swiss-Webster mice with similar efficiency. We have treated mice bearing EAT-DAP ascites tumor with a mouse monoclonal antibody to human PLAP or with a monoclonal antibody to human C proteins of the heterogenous ribonucleoprotein complex (hnRNP). The average survival of mice treated with anti-hnRNP was 16.4 ± 1.1 days (n = 8). Treatment with anti-PLAP prolonged the survival of mice; in 4 mice average survival was 23.3 ± 5.7 days. Four animals, however, survived for 60 days when they were killed and had no visible signs of tumor. These data support the notion that passive immunotherapy using antibodies against a membrane protein, expressed in tumor cells transduced by a viral vector coding for that protein, may be effective in controlling tumor growth. Copyright © 2000 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Placental alkaline phosphatase (PLAP) is one of the cellular phosphatases (ALP) expressed in patients with testis cancers, particularly in seminomas. Using various techniques including Western blot and high-performance liquid chromatography (HPLC) systems and ATC2, a newly developed specific anti-PLAP monoclonal antibody (Mab), the presence of active form of PLAP in lysates prepared from testis tumour fragment and tumour cell lines, was studied. This was carried out following isolation of PLAP from biological samples using CNBr Sepharose-conjugated ATC2 beads. The results showed that: (1) The target for the newly developed Mab ATC2 was PLAP. (2) The ATC2-conjugated bead system was an efficient method for isolating pure PLAP. (3) Diethylamine (DEA), in contrast to urea and glycine, was the most efficient for separation of PLAP from ATC2-conjugated beads, as the isolated molecule did not lose any phosphatase activity and there was very little uncoupling of the ATC2 Mab from the beads. (4) ATC2-conjugated CNBr beads could pick up PLAP from a solution containing standard PLAP and lysates prepared from tumour cell lines or testis tissue fragments positive for the PLAP. (5) HPLC profile of testis tumour lines and testis tumours showed two distinct peaks with ALP activity, one at retention time 7– 8 min (corresponding to 95 kDa molecule) and one at 12–13 min corresponding to 70 kDa molecule). These data demonstrated the potential use of various biochemical methods in combination with HPLC for isolation of the fully functional molecules with ALP activity from different samples including lysates prepared from patients with testis cancer. The nature of ALP activity at 95 kDa is being investigated as no such molecule has been reported previously. These techniques might have an important implication for an early detection of germ cell tumours, particularly in patients with equivocal ultrasound.Copyright © 2000 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

A case of tubular seminoma in a 33-year-old man is reported. The tumor occurred in his right testis, measuring 7 × 6 × 6 cm in size. Microscopically, most of the tumor cells were arranged in solid or hollow tubular patterns. The tumor cells had round nuclei with vesicular chromatin and clear or granular cytoplasm, characteristic features of seminoma cells. A classic seminoma component and intratubular atypical germ cells occupying approximately 5% of the tumor area were noted. Immunohistochemical staining revealed that the tumor cells were diffusely placental alkaline phosphatase and vimentin positive, and focally cytokeratin positive. These findings are consistent with a tubular seminoma. The differential diagnoses are discussed. [ABSTRACT FROM AUTHOR]

A 56-year-old male treated for a gastric yolk sac tumor with an adenocarcinomatous component is described. A mixed area of reticular and glandular neoplastic components was morphologically identified in this tumor. Immunohistochemically, the yolk sac tumor expressed alpha-fetoprotein (AFP), placental alkaline phosphatase (PLAP), and cytokeratin, but was negative for carcinoembryonic antigen (CEA). The adenocarcinoma was positive for CEA and cytokeratin, partially positive for PLAP, and negative for AFP. In the mixed area, the tumor cells were positive for cytokeratin, weakly expressed AFP and PLAP, and sporadically stained for CEA both in the reticular and glandular components. This area was identified as a transitional area of the yolk sac tumor and adenocarcinoma. These findings demonstrate that the yolk sac and adenocarcinomatous components are closely related. It also suggests that the tumor arose from multipotential neoplastic mucosal epithelial cells with both yolk sac and gastric mucosal phenotypes. [ABSTRACT FROM AUTHOR]

Detergent extracts of human trophoblast plasma membanes (TrPM) and of other fetal tissues from the same conceptus were prepared and the proteins separated by use of isoelectric focusing. A major band of isoelectric point (pI) 4.1 was present in TrPM together with minor bands of (pI) 49, 59, 73, 78 and 7.9. These bands were absent from non-trophoblastic fetal tissues. The pI 4.1 protein reacted with an 125I-labelled IgG fraction of a heterologous antiserum raised against TrPM and was found to have an apparent molecular weight of 100,000. This protein did not appear to be placental alkaline phosphatase, SP1, transferrin or human chorionic gonadotrophin. Many neoplastic cell lines tested also revealed a major protein band of pI 4.1 but it has not been established that this was the same protein as found in the TrPM preparations. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the effect of natural interferon (IFN) on the expression of placental alkaline phosphatase (PLAP) in a human seminoma xenograft in severe combined immunodeficient mice. Mice were injected intramuscularly with 3 × 105 U/mouse of IFN, twice a day, for five consecutive days. A significant increase in PLAP level of the xenografts followed IFN treatment. A radiolabeled anti-PLAP monoclonal antibody (MAb) was intravenously injected on the first day of IFN administration in order to determine if IFN has the potential to enhance the efficacy of an anti-PLAP MAb in the detection of seminoma. Enhanced retention of the anti-PLAP MAb was observed at 7 and 11 days after MAb administration. Thus, IFN treatment appears to have some effect on the efficacy of the anti-PLAP MAb in the detection of seminoma xenografts. [ABSTRACT FROM AUTHOR]

To evaluate the ability of an anti-placental alkaline phosphatase (PLAP) monoclonal antibody (MAb) to localize to PLAP-expressing tumors, we established a model of testicular tumor with metastasis to lymph nodes and liver in severe combined immunodeficient (SCID) mice. 131I-labeled or 125I-labeled MAb was simultaneously administered via the intravenous or lymphatic route, respectively. Preferential accumulation of MAb in PLAP-expressing tumors at primary as well as metastatic sites was demonstrated. The percentage of the injected dose of MAb found in the tumor was generally higher when MAb was administered intravenously. Identical tumor/blood ratios were found with the two routes of administration. These data suggest that intravenous administration of a radiolabeled MAb is superior to lymphatic administration for tumor imaging and radioimmunotherapy. [ABSTRACT FROM AUTHOR]

Tumor marker identification in testicular cancer has contributed to early detection and monitoring of non-seminomatous disease. A placental alkaline phosphatase-like (PLAP-like) enzyme derived from seminomas has recently been focused upon as a possible marker for this disease. The biochemistry of the PLAP-like enzyme is reviewed, as well as its occurrence in tissue and sera from healthy persons and patients with testicular cancer. [ABSTRACT FROM AUTHOR]

FL-amnion cells have mainly two alkaline phosphatase (AP) isozymes, of which the faster migrating one (FL-APF) on 5 % polyacrylamide gel electrophoresis has proved to be identical to the Kasahara isozyme, a tumor-associated AP of intestinal type. But the other slower migrating one (FL-APs) remains to be characterized. Immunological and enzymic examination of purified FL-APS revealed that it is a hybrid form of AP consisting of one subunit with a molecular weight of 66,200 coming from the same subunit as that of FL-APF and another one with a molecular weight of 58,000 from placental AP subunit with modified glycosylation. Copyright © 1991 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Placental alkaline phosphatase (PLAP) was measured by an immunoradiometric assay using the monoclonal antibody C2 (PLAP-C2). Serum samples of 135 patients with epithelial ovarian cancer were analyzed, and the results were compared with CA125 levels. CA125 and PLAP-C2 were elevated in 85 and 43% of the patients, respectively. Only 1 patient with normal CA125 and evidence of disease at the time of sampling had an elevated PLAP-C2. Fifty-three patients with measurable tumor were followed longitudinally during chemotherapy. Correct correlation with disease evolution was observed in 95% of the patients for CA125 and in 59% for PLAP-C2. The PLAP-C2 assay did not add significantly to the predictive value of CA125 in the diagnosis and follow-up of epithelial ovarian cancer. Copyright © 1992 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Three monoclonal antibodies and their Fab and Fab2′ fragments with specificity against human placental alkaline phosphatase (PLAP) were evaluated for tumour immunolocalization of human PLAP-producing Hela Hep 2 tumours in nude mice. The antibodies and their fragments were labelled with 125I and injected intraperitoneally in mice with developing Hep 2 tumours. The animals were followed individually for 14 days with repetitive computerized gamma-camera recordings, which enable quantitation of several crucial parameters, i.e. the time-dependent antibody uptake in the tumours, decrease in background activity and tumour/background ratio. Excellent radioimmunolocalization was obtained with both the intact PLAP-specific immunoglobulins and their fragments but not with the nonspecific antibodies. No background subtraction had to be used. As much as 15 % of the initially injected dose could be visualized in the tumours and for the uncleaved mab up to 80% of the radioactivity in the animals was retained in the tumours after 14 days, a considerably longer observation time than usually reported in such tumour xenograft models. The Fab and Fab2′ fragments were found to be excreted fast with less than 5 % of the injected dose remaining in the animals after 48 h, but still with positive specific localization to the tumours after an initial high uptake in the kidneys. The results are encouraging and indicate significant potentials of the PLAP-antiPLAP mab system for immunolocalization studies in patients. Copyright © 1989 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Electrophoretic patterns of seminoma- and normal-testis-derived alkaline phosphatase isozymes, the placental alkaline phosphatase (PLAP)-like enzyme and the tissue-nonspecific (liver) alkaline phosphatase (LAP), were studied on starch gel and isoelectric focusing (IEF). Different migration patterns of the PLAP-like enzyme were observed with respect to both seminomas and normal testes on starch gel electrophoresis. On IEF, seminomas showed different staining patterns among different tumors; however, a common main activity was focused at pis of 4.3-4.6, corresponding to pIs of PLAP. Normal testes showed two enzyme-staining regions, at pIs of 4.1 and 5.0-5.2, which were discriminated from pIs of PLAP and the PLAP-like enzyme in seminoma. The PLAP-like enzyme in seminoma was differentiated from PLAP by digestion with neuraminidase. Neuraminidase treatment simplified the distribution patterns of the PLAP-like enzyme in normal testis, but did not alter the pattern of microheterogeneity in seminoma. Two factors other than sialylation, namely structural modification of the carbohydrate moiety and variation of hydrophobicity, were shown to contribute to the microheterogeneity of the PLAP-like enzyme in seminoma. LAP in seminoma and in normal testis also showed marked electrophoretic heterogeneity and differences in pI distributions from LAP of liver. However, the migration patterns after desialylation were very similar to each other. The findings imply that electrophoretic heterogeneity demonstrated in LAP in seminoma and in normal testis is caused by a difference in sialic acid content in the molecule, and the heterogeneity of the PLAP-like enzyme in seminoma is considerable. Copyright © 1989 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

The expression of placental alkaline phosphatase in 116 ovarian epithelial tumours was examined in formalin-fixed tissues used for routine histopathologic examination. In the total material, 51 % of the tumours displayed positive immunoreactivity, as described by the monoclonal anti-placental alkaline phosphatase antibody C2, with similar incidence (46-67%) in the four major groups of the adenocarcinomas, i.e., serous, mucinous, endometrioid and mesonephric tumours. By use of a histochemical staining index the mucinous and mesonephric tumours demonstrated a more intense staining (2.1 and 2.6) compared to the serous and endometrioid tumours (0.9 and 1.5). The relevance of the findings is discussed in relation to the use of monoclonal antibody technologies for radioimmunolocalization and radioimmunotherapy. Copyright © 1989 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

A panel of monoclonal antibodies against different keratin Polypeptides, epithelial glycoproteins, placental alkaline Phosphatase and collagen type IV was used to evaluate immunohistochemically the expression of the target antigens in 30 different human testicular germ-cell tumours of various types. Antikeratin antibodies detecting markers of different routes of epithelial differentiation revealed remarkable similarity of differential expression of various keratins in epithelial struetures of teratomas and combined tumours as compared with normal human epithelial tissues. A considerable proportion of embryonal Carcinoma cells stained positively for keratins 8,18 and 19, while a minor subpopulation of tumour cells in embryonal carcinomas, some seminomas and many atypical intratubular cells expressed keratins 8 and 18 but usually lacked keratin 19. Antibody RICEO-MFG-06.3, specific for epithelial glycoproteins, gave negative results with seminomas as opposed to positivity in all but two nonseminomatous tumours. All but two neoplasms showed positivity for placental alkaline Phosphatase, thus supporting its reliability as a marker of germ-cell tumours. It is concluded that the monoclonal antibody RICEO-MFG-06.3 and especially the keratin-19-speeifie antibodies BAI6 and BAI7 can be helpful in distinguishing embryonal Carcinoma from seminoma and, together with antibodies to other keratins, in the study of the origin and histogenesis of testicular germ-cell tumours. Copyright © 1987 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

(1) Two sets of monoclonal antibodies (mAbs) specific for human placental alkaline phosphatase (PLAP) were compared. One set of four mAbs was generated against solubilized and purified PLAP; the other set of seven mAbs was generated against the malignant cell line Hela TCRC-1 in which PLAP is an ectopically synthesized membrane-bound enzyme. Double immunodiffusion and competitive enzyme-linked immunosorbent assays were used to examine the relative spatial arrangement of the antigenic determinants to which each of the eleven mAbs binds. (2) Significant differences in immunoreactivity of the antibodies were demonstrated. The mAbs to the solubilized and purified enzyme bound in either of two regions of the molecule. By contrast, all of the mAbs to PLAP as presented on the tumor cell surface bound in only one of these two regions. One of the major antigenic determinants on the solubilized enzyme is apparently unavailable for recognition by immunoreactive cells during immunization with whole cells. Furthermore, when mAbs are generated to this region using purified PLAP as the immunogen, they do not recognize membrane-bound PLAP. (3) The 'hidden' determinant can be exposed in vitro after partial solubilization using butanol to extract the enzyme from HeLa TCRC-1 cells and subsequent treatment with 0.5% Nonidet P-40 detergent. The results of this study have implications for the potential use of mAbs in studies of other cell surface antigens and in tumor immunolocalization and drug targeting. Copyright © 1987 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objective To investigate the significance of placental alkaline phosphatase (PLAP) as a tumour marker for seminoma. Patients and methods A total of 673 serum samples from 116 patients with testicular germ cell tumours (78 seminomas and 38 non-seminomas) were analysed for several markers including PLAP, total alkaline phosphatase (AL-P), alpha fetoprotein (AFP), beta human chorionic gonadotrophin (HCG-B), and lactic dehydrogenase (LDH). Results Serum PLAP was increased initially in about 50% of patients with seminoma, and the mean magnitude of elevation was about five times the normal value. There was no significant correlation between PLAP and LDH or between PLAP and HCG-B. Therefore, a combination of these three markers was of value, and resulted in a positive identification rate of 82% of patients with seminoma. False-positive results for PLAP appeared in 1.6% of 673 samples investigated. Conclusion The monitoring of serum PLAP might be of value, as fluctuations in this marker provide information about disease status and prognosis. [ABSTRACT FROM AUTHOR]

In cocultures of human plancental alkaline phosphatase(PLAP)-positive MO tumor cells and human peripheral blood mononuclear cells (PBMC), also containing a heteroconjugate (7E8-OKT3) synthesized between the anti-PLAP monoclonal antibody 7E8 and the anti-CD3 antibody OKT3, and supplemented with low levels of recombinant interleukin-2 (rIL-2), T cells are progressively activated, resulting in tumor cell lysis. To unravel the contribution of PBMC subsets to the generation of this targetable cytotoxicity, PBMC subsets were studied after their isolation by cell sorting, either from fresh PBMC or from PBMC peractivated with OKTe3 and rIL-2. Whereas no targetable cytotoxicity was found in Fc-receptor-bearing CD3-cells, tumor cells were lysed by CD3 T cells (mostly CD8) isolated from pre-activated PBMC. When isolated from fresh PBMC, neither the CD8 T cell subset, nor the total CD3 T cell population developed significant targetable cytotoxicity, even in the presence of rIL-2. Thus, additional cell types are essential for the CD8 T cell activation. Indeed. CD4 T cells isolated from pre-activated but not from fresh PBMC were capable of eliciting cytotoxicity in fresh CD8 T cells. The non-targeted monocytes were found to be the activators of the CD4 T cells. In summary, targeting T cells to the surface of a tumor cell is not sufficient per se to achieve activation and lysis. The progressive tumor cell lysis by targeted T cells seems to be initiated by non-targeted monocytes activating CD4 T cells, these cells in turn promoting CD8 T cell activation, necessary for the development of cytotoxicity. [ABSTRACT FROM AUTHOR]

Significant improvements in tumor/nontumor ratio can be achieved by injections of nonlabeled anti-idiotypic monoclonal antibodies (MAbs) during radioimmunolocalization and radioimmunotherapy using MAbs to target experimental tumors. The in vivo effects of an anti-idiotypic MAb (αH7) against a radioiodinated, high affinity, low dissociation rate, monoclonal antiplacental alkaline phosphatase antibody (H7) was investigated. Following in vivo injection of the anti-idiotypic MAb, the radioactivity in experimental tumors was found to decrease only 25% while the reduction of corresponding radioactivity in nontumor tissues amounted to 65-85%, compared to the group receiving no anti-idiotypic MAbs. These results indicate that it is possible to partially clear the circulation and nontumor tissues from excess of radiolabeled idiotypic antibody, without significant decrease in specific tumor localization, increasing the tumor/ nontumor ratio three- to fourfold. Circulating nontumor targeting radiolabeled antibodies is one of the major limiting factors in radioimmunotherapy today. Injection of anti-idiotypic MAbs could selectively significantly reduce the radiation dose to radiosensitive tissues, i.e., bone marrow and intestine, thus improving efficiency in radioimmunoscintigraphy and radioimmunotherapy. [ABSTRACT FROM AUTHOR]

The evolution of the gonads during intra-uterine development has been followed by immunohistochemical demonstration of placental-like alkaline phosphatase (PLAP) at the germ-cell level. PLAP immunopositivity was restricted to the limited period when germ cells were not surrounded by granulosa or Sertoli cells. Abnormal fetuses or neonates presenting with chromosomal anomalies frequently had disorganized gonads where germ cells retained their membrane PLAP immunopositivity. This abnormal immunopositivity is similar to that expressed by abnormal germ cells in testicular in situ carcinoma, in gonadoblastoma (case of 45,XO/ 46,XY mosaic) and in seminoma. The pattern of positivity for other germ-cell tumours was highly variable. We suggest that in abnormal gonads, dysgenetic or neoplastic, an early embryonic property is retained by abnormal germ cells. Its importance in the process of neoplastic induction remains to be defined. [ABSTRACT FROM AUTHOR]