Placental alkaline phosphatase, alphafetoprotein and carcinoembryonic antigen in testicular tumors. Tissue typing by means of cytologic smears

Placental alkaline phosphatase levels in cerebrospinal fluid can have a decisive role in the differential diagnosis of intracranial germ cell tumors

OBJECTIVE

Placental alkaline phosphatase (PLAP) in CSF can provide a very high diagnostic value in cases of intracranial germ cell tumors (GCTs), especially in pure germinomas, to the level of not requiring histological confirmation. Unlike other tumor markers, reliable data analysis with respect to the diagnostic value of PLAP serum or CSF levels has not been available until now. This is the first systematic and comprehensive study examining the diagnostic value of CSF PLAP in patients with intracranial GCTs.

METHODS

From 2004 to 2014, 74 patients (average age 19.6 ± 10.6 years) with intracranial GCTs were evaluated using PLAP from their CSF and histological samples. Chemiluminescent enzyme immunoassay was utilized to measure CSF PLAP in the following tumor sites: pineal (n = 32), pituitary stalk, suprasellar (n = 16), basal ganglia (n = 15), intraventricular (n = 9), and cerebellar (n = 5) regions. In addition to classifying GCT cases, all patients underwent tumor biopsy for correlation with tumor marker data.

RESULTS

PLAP in combination with other tumor markers resulted in extremely high sensitivity and specificity of the diagnostic value of intracranial GCTs. Intracranial GCT cases were classified into 1) germinomas, both "pure" and syncytiotrophoblastic giant cell types (n = 38); 2) nongerminomatous GCTs, choriocarcinomas (n = 9) and teratomas (n = 4); and 3) nongerminomas, other kinds of tumors (n = 23). Consequently, all patients received chemoradiation therapy based on elevation of PLAP and the histopathological results. It was also speculated that the level of PLAP could show the amount of intracranial germ cell components of a GCT. PLAP was 100% upregulated in all intracranial germinoma cases. The absence of CSF PLAP proved that the tumor was not a germinoma.

CONCLUSIONS

The current study is the first systematic and comprehensive examination of the diagnostic value of the tumor marker PLAP in pediatric patients with intracranial GCT. Using the level of PLAP in CSF, we were able to detect the instances of intracranial germinoma with very high reliability, equivalent to a pathological diagnosis.

Radioimmunoscintigraphy of Gynecologic Tumors with 131I-Labeled Anti-Plap Monoclonal Antibodies

Radioimmunoscintigraphy (RIS) was performed in 20 patients with gynecologic tumors, 14 ovarian, 5 cervical, and one endometrial carcinoma. One murine monoclonal antibody (mab) against placental alkaline phosphatase (H7) was used after radiolabeling with 131I. The labeling procedure yielded antibodies with specific activity varying between 60 and 73 MBq/mg mab. Each patient received 57 to 100 MBq of the preparation. RIS was performed 7 to 35 days later. Patients with ovarian adenocarcinoma had an accumulation of activity on RIS at tumor sites (79%, 11/14) verified by ultrasonography, CT, and clinical examination. A low or absent accumulation of activity was seen in patients with cervical tumors. The patient with an endometrial adenocarcinoma was seen to have an activity accumulation at RIS corresponding to tumor sites determined by ultrasound and/or CT. It is concluded that RIS using monoclonal antibodies against placental alkaline phosphatase can provide information which will supplement that gained from other investigations of patients with ovarian adenocarcinomas.

Investigation of quinoline-4-carboxylic acid as a highly potent scaffold for the development of alkaline phosphatase inhibitors: synthesis, SAR analysis and molecular modelling studies

The present study is directed towards the development of quinoline-4-carboxylic acid derivatives as potential alkaline phosphatase inhibitors.

Influence of the diversified structural variations at the imine functionality of 4-bromophenylacetic acid derived hydrazones on alkaline phosphatase inhibition: synthesis and molecular modelling studies

Putative binding mode of 4g inside the active pocket of h-PLAP.

Role of biochemical markers in testicular cancer: diagnosis, staging, and surveillance

Testis cancer is one of the few solid organ malignancies for which reliable serum tumor markers are available to help guide disease management. Human chorionic gonadotropin, alpha fetoprotein, and lactate dehydrogenase play crucial roles in diagnosis, staging, prognosis, monitoring treatment response, and surveillance of seminomatous and nonseminomatous germ cell tumors. Herein we discuss the clinical applications of germ cell tumor markers, the limitations of these markers in the management of this disease, and additional serum molecules that have been identified with potential roles as novel germ cell tumor markers.

Design and synthesis of selective inhibitors of placental alkaline phosphatase

Placental Alkaline Phosphatase (PLAP) is a tissue-restricted isozyme of the Alkaline Phosphatase (AP) superfamily. PLAP is an oncodevelopmental enzyme expressed during pregnancy and in a variety of human cancers, but its biological function remains unknown. We report here a series of catechol compounds with great affinity for the PLAP isozyme and significant selectivity over other members of the AP superfamily. These selective PLAP inhibitors will provide small molecule probes for the study of the pathophysiological role of PLAP.

Structural evidence of functional divergence in human alkaline phosphatases

The evolution of the alkaline phosphatase (AP) gene family has lead to the existence in humans of one tissue-nonspecific (TNAP) and three tissue-specific isozymes, i.e. intestinal (IAP), germ cell (GCAP), and placental AP (PLAP). To define the structural differences between these isozymes, we have built models of the TNAP, IAP, and GCAP molecules based on the 1.8-structure of PLAP(1) and have performed a comparative structural analysis. We have examined the monomer-monomer interface as this area is crucial for protein stability and enzymatic activity. We found that the interface allows the formation of heterodimers among IAP, GCAP, and PLAP but not between TNAP with any of the three tissue-specific isozymes. Secondly, the active site cleft was mapped into three regions, i.e. the active site itself, the roof of the cleft, and the floor of the cleft. This analysis led to a structural fingerprint of the active site of each AP isozyme that suggests a diversification in substrate specificity for this isozyme family.

Specific determination of germ cell alkaline phosphatase for early diagnosis and monitoring of seminoma: performance and limitations of different analytical techniques

Two-dimensional electrophoresis, ion-exchange chromatography and immunoassay were evaluated in order to improve the diagnostic specificity of the germ cell specific isoenzyme of alkaline phosphatase (GCAP) for the detection of seminoma. Assessment of GCAP is hampered by its structural heterogeneity and low serum concentration. The structural heterogeneity of GCAP from seminoma tissue could be clearly visualized by two-dimensional electrophoresis. We inferred that it depended on allelic amino acid substitutions, varying sialylation and differential cleavage of the membrane anchor. The allelic variability of GCAP affects the accuracy of immunological measurements. However, immunoassay was found to be the only technique sensitive enough to assess GCAP in serum. The elevated GCAP levels in 15% of healthy blood donors were shown to be correlated with smoking. Further studies clarifying how to interpret the values measured in smokers are prerequisite for the introduction of GCAP as a serum marker for seminoma. In the future, GCAP might be utilized for the detection of carcinoma in situ (CIS) cells in ejaculate. Assessment of the enhanced expression of cellular GCAP by CIS cells exfoliated into ejaculate could be a means for noninvasive, early diagnosis that presumably will not be hampered by the patient's smoking habits.

Biology of human alkaline phosphatases with special reference to cancer

The current information on the cloning and sequencing of four alkaline phosphatase genes (PLAP, GCAP, IAP, TNAP) has been reviewed. It has provided insights into their evolutionary history and the mechanisms of catalysis and of uncompetitive inhibition. The oncodevelopmental biology of the germ cell and its excessive GCAP eutopic expression in neoplasia are noted, and there is reason to suggest that the enzyme may serve to guide migratory cells and to transport specific molecules such as fat and immunoglobulins across membranes. The hyperexpression of all four genes has been observed in various human tumors and in their cell lines, particularly cancers of the testis and ovary. The membrane APs have been investigated as targets for immunolocalization and immunotherapy.

Regulation of the expression of alkaline phosphatase in a human breast-cancer cell line

Treatment of the cultured human breast-cancer cells BC-M1 with dexamethasone induced a placental-type alkaline phosphatase (ALP). Both the ALP activity and the mRNA level in the cells were increased. The induction of ALP activity by dexamethasone was time- and dose-dependent. The accumulation of ALP mRNA was inhibited by both actinomycin D and cycloheximide, indicating that its induction is a complex event and may involve other regulatory proteins. Retinoic acid showed opposing effects with dexamethasone on the expression of alkaline phosphatase. Retinoic acid (RA) and phorbol 12-myristate 13-acetate also substantially reduced the dexamethasone-induced expression of ALP. Studies on thermostability and sensitivity to various amino acid inhibitors indicated that the BC-M1 ALP is most similar to the placental form. Northern hybridization analysis also revealed that ALP mRNA transcripts in BC-M1 and term placenta are similar in size and are distinct from that of the placental-like mRNA transcript in choriocarcinoma cells. Analysis of the degradation of BC-M1 ALP mRNA showed a similar half-life of 27 h in the untreated and in dexamethasone- or RA-treated cells. These findings demonstrated that the induction of ALP in BC-M1 cells by dexamethasone is mainly due to the increase in the transcription of the ALP gene.

Characterisation of the differential expression of marker antigens by normal and malignant endometrial epithelium

In order to examine the production of marker proteins, a reproducible method has been established for culturing purified epithelial cells from normal and malignant endometrium. We have examined the differential expression of secretory proteins using immunohistochemistry in frozen tissue sections, immunocytochemistry in cell cultures derived from the same specimens and protein assays on the culture supernatants. Placental protein 14 (PP14) was produced by normal premenopausal epithelium but not by the post-menopausal or malignant endometrial epithelium. In contrast, placental alkaline phosphatase (PLAP) was produced by endometrial cancers and the endometrial adenocarcinoma-derived cell line Ishikawa, but not by the normal endometrial epithelium. Other markers such as CA-125, which was produced by both normal and malignant endometrium but not by the cell line, and human chorionic gonadotrophin (beta-hCG), which was produced by Ishikawa cells but not by any of the fresh tissues, were less cancer specific. Placental alkaline phosphatase is a direct product of endometrial cancers that can be readily assayed in serum using this two-site assay to test its clinical usefulness in monitoring patients at risk for endometrial cancer.

Control of alkaline phosphatase activity in C3H10T1/2 cells: role of retinoic acid and cell density

The enzyme alkaline phosphatase (AP) has been shown to be lost or inappropriately expressed during carcinogenesis in some tissues. Because retinoic acid (RA) appears to play a role in the normal regulation of the enzyme (RA up-regulates AP in a variety of cell types) we have suggested that altered AP expression in some cancers may be caused by a defect in the ability of the cells to respond normally to retinoid. We have begun to use the chemically transformable mouse embryo fibroblast cell, C3H10T1/2, to investigate this possibility. In this initial study we characterized AP regulation in normal C3H10T1/2 cells and show that: (1) 10(-7) M RA increases AP activity within 3-4 h in serum-free medium; (2) serum inhibits short-term induction (0-8 h) in a concentration-dependent manner (10% serum causes complete inhibition); (3) during long-term RA exposure (24 h and 48 h), induction can be detected in serum-containing medium; (4) AP induction is dose related at RA concentrations from 10(-10) M to 10(-6) M in serum-free medium; (5) 10(-5) M RA is ineffective at inducing AP in serum-free medium during 8 h but is the most effective concentration in serum-containing medium during 24 h and 48 h exposures; (6) AP inducibility by RA requires near-confluent cell densities; and (7) when cultures become confluent, cells become constitutive for AP and no longer require RA for enzyme expression. The effects of serum and cell density on AP inducibility by RA and implications of the RA up-regulation of AP for teratogenesis are discussed.

Placental-like alkaline phosphatase as a marker of carcinoma-in-situ of the testis. Comparison with monoclonal antibodies M2A and 43-9F

In an immunohistochemical study of 59 routinely processed tissue specimens from 48 adult testes with isolated carcinoma-in-situ (CIS) changes and of 66 specimens from adult testes without neoplasia, placental-like alkaline phosphatase (PlAP) was shown to be a reliable marker of CIS cells preceding the development of a testicular tumour. Thus, a positive reaction was encountered in all 36 biopsies treated with formaldehyde, or Bouin's or Stieve's fluid. However, only 11 of 23 specimens fixed with Cleland's fluid were immunoreactive for PlAP. None of the non-malignant components of seminiferous tubules, including the large abnormal spermatogonia, reacted with the antibody against PlAP. Besides the antibody against PlAP, monoclonal antibodies M2A and 43-9F were tested on CIS specimens fixed with the above-mentioned fixatives. In the 17 specimens fixed with Stieve's or Bouin's fluid, a positive reaction was obtained in all sections with all three antibodies tested. However, for each antibody at least two specimens gave a weak staining reaction. When all three immunostainings were performed, in each case at least one of them gave a moderate or strong reaction, thus making CIS cells easily detectable. In the samples fixed with Cleland's fluid, a negative reaction was found in one to three specimens, depending on the antibody used. However, at least one of the three antibodies gave a positive reaction if all three immunostainings were applied. In only one of the formaldehyde-fixed paraffin specimens did CIS cells react with the monoclonal antibody 43-9F, whereas M2A gave no positive reaction at all if this method of fixation was used. Thus, the sensitivity of the immunohistochemical staining procedure in the detection of CIS is dependent on the fixative used and increases when immunostainings with all three markers are performed simultaneously.

Isoenzymes of alkaline phosphatases in seminomas. An immunohistochemical and biochemical study

Placental alkaline phosphatase (the PLAP-like isoenzyme) and liver alkaline phosphatase (LAP) were demonstrated immunohistochemically by use of monoclonal antibodies in the tumor cells of twelve seminomas and one seminoma metastasis. Intestinal alkaline phosphatase (IAP) was not found. The PLAP-like and LAP enzymes showed high catalytic activities compared to normal testis. This is the first occasion that LAP has been demonstrated by immunochemistry in seminoma cells. The results suggest that demonstration of these tumor enzymes may be useful markers for seminomas in histopathological specimens.

The expression of placental alkaline phosphatase (PLAP) and PLAP-like enzymes in normal and neoplastic human tissues. An immunohistological survey using monoclonal antibodies

The immunohistological expression of placental alkaline phosphatase (PLAP) and PLAP-like enzyme was studied in frozen sections from a wide variety (n = 254) of normal and malignant tissues using monoclonal antibodies reactive with PLAP (H317) and PLAP/PLAP-like enzyme (H17E2; H315). PLAP/PLAP-like reactivity was seen in normal thymus, and foetal and neonatal testis, and in 21 out of 22 malignant germ cell tumours (GCTs), but was also found in normal endocervix, normal Fallopian tube and in 28 out of 167 non-GCTs (particularly in ovarian and proximal gastrointestinal tract tumours). Positivity for true PLAP (as demonstrated with H317) was seen in term placenta, in endocervix, and in Fallopian tube (but not in other normal tissues) and was commonly found in ovarian and proximal gastrointestinal tract tumours. Reactivity with H317 was unusual in malignant GCTs (2 out of 22 cases). These findings confirm that PLAP/PLAP-like positivity is a highly sensitive immunohistological marker for malignant GCTs, but one which by itself is of only moderate specificity. Furthermore, expression of true PLAP is rare in GCTs and favours instead an origin from the ovary or proximal gastrointestinal tract. The results also indicate that the predominant heat-stable alkaline phosphatase species in normal foetal and neonatal testis, and in thymus has a similar immunohistological profile to that found in malignant GCTs, and is a PLAP-like enzyme ("germ cell alkaline phosphatase") distinct from true PLAP. The occurrence of this marker in GCTs would appear to reflect increased eutopic production of an enzyme present in trace amount in corresponding normal tissues rather than a genuine example of ectopic expression.

A difference in the regulation of mRNA expression between the phenotypic and the embryonic alkaline phosphatase genes in human cancer cells

The steady-state levels of mRNAs encoding alkaline phosphatase isoenzymes were examined in two human breast carcinoma cell lines. MDA-MB-157 cells expressed the phenotypic breast alkaline phosphatase and BT20 cells expressed the nonphenotypic placental alkaline phosphatase isoenzyme, frequently reexpressed in neoplasms. Dexamethasone (DEX), which elicits a general effect on phosphatase expression, and 1,25-dihydroxy vitamin D3 (1,25(OH)2D3), a promoter of cell differentiation that correspondingly effects embryonic phosphatase expression, were chosen as perturbing agents for these experiments. RNA blot analysis showed a single RNA species of approximately 2.6 kb under all treatment conditions in BT20 cells and a single RNA species of 2.6 kb under each condition in MDA-MB-157 cells. The results showed that the expression of both the AP isoenzyme mRNA phenotypic of breast produced by MDA-MB-157 cells and the embryonic alkaline phosphatase isoenzyme (PLAP) mRNA produced by BT20 cells was increased by treatment with DEX. By comparison 1,25(OH)2D3 caused an increase in the tissue-unspecific AP mRNA in the MDA-MB-157 cells, but caused a decrease in PLAP mRNA levels in BT20 cells. The level of each isoenzyme mRNA species is altered by either hormone in a dose- and time-dependent manner in both cell lines. In BT20 cells, treatment with cycloheximide showed that ongoing protein synthesis is not required to potentiate the PLAP mRNA response to DEX, but is required for the action of 1,25(OH)2D3. However, protein synthesis is required for the action of both hormones in the MDA-MB-157 cells which make the breast phenotypic AP. These data demonstrate that the DEX- and 1,25(OH)2D3-regulated expression of both of these alkaline phosphatase isoenzymes occurs via a complex mechanism involving control of mRNA abundance, not translational control of constant message levels.

Heat-stable alkaline phosphatase as a marker for human and monkey type-I pneumocytes

The expression of the heat-stable isoenzyme of alkaline phosphatase in the human and monkey (Macaca mulatta, M. fascicularis) lung was investigated at the light- and electron-microscopic level, using cytochemical techniques and immunocytochemical procedures based on monoclonal and polyclonal antibodies against human term-placental alkaline phosphatase. Both in man and monkey, the enzyme was present in type-I pneumocytes. In the monkey, the enzyme was found in all type-I cells. In man, strong staining was observed only in some type-I cells and in certain cuboidal respiratory bronchiolar cells. Staining was localized on the apical and basal plasma membrane, in apical and basal caveolae, and in the underlying basement membrane. The level of heat-stable alkaline phosphatase expression in the human lung was 10-fold lower than in the monkeys studied. In human fetal lung, the onset of heat-stable alkaline phosphatase expression was associated with the development of the alveolar epithelium from 17-20 weeks gestation onward. It is concluded that: (1) heat-stable alkaline phosphatase is a specific constituent of type-I pneumocytes in man and monkeys; and (2) its subcellular localization may explain its rapid appearance in the circulation under certain conditions.

Alkaline phosphatase isozymes: recent progress

The past few years have witnessed the reports of significant new events in alkaline phosphatase (AP) isozymes. The cloning of the relevant genes and their nucleotide sequencing have all been accomplished. As a group, the genes for the intestinal, germ cell and placental isozymes have considerable sequence similarity; it is noteworthy that they occupy vicinal positions on chromosome 2, while the tissue unspecific AP gene is located on chromosome 1. The latter makes evolutionary lineage and instances of coordinate expression understandable. Another new development is the demonstration of a phosphatidyl inositol glycan tail on the C-terminus of these chromosome-2 AP genes. This is the major membrane insertion mechanism for AP, which is a cell surface membrane enzyme. This information may be helpful in understanding the phenomenon of the depletion of intestinal mucosal AP during fat absorption. Finally, a discussion has been focussed on recent studies on seminoma and AP, including immunodetection and immunoradiotherapy.

Placental-like alkaline phosphatase in seminoma

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.

Alkaline phosphatase isozymes in non-malignant intestinal and hepatic diseases

Human alkaline phosphatase isozymes--the tissue-unspecific, the intestinal, and the placental alkaline phosphatases--were determined in sera by use of isozyme-specific monoclonal antibodies. The clinical utility of serum determinations of alkaline phosphatase isozymes was evaluated in patients with diseases of the gastrointestinal tract and the liver. No elevations of the different serum isozymes were observed in the intestinal diseases investigated (active Crohn's disease and ulcerative colitis). For non-malignant diseases of the liver the alkaline phosphatase isozymes presented characteristic patterns. Patients with cirrhosis due to hepatocellular diseases had markedly elevated levels of intestinal alkaline phosphatase and moderate serum activities of tissue-unspecific and placental alkaline phosphatases. In patients with liver disease with cholestatic features tissue-unspecific and placental isozyme levels were high, but the intestinal isozyme remained normal, whereas primary biliary cirrhosis was associated with high levels of the tissue-unspecific enzyme and moderate elevations of intestinal and placental alkaline phosphatases. It can be concluded that, in addition to tissue-unspecific alkaline phosphatase, intestinal and placental isozymes contribute to the total alkaline phosphatase activity for patients with liver disease. The results suggest that specific methods for the identification of alkaline phosphatase isozymes could be of value.

Human teratocarcinomas

Teratocarcinomas are one of the commonest forms of cancer in young adult men. Cell lines derived from these tumors, and particularly the cell lines composed of their embryonal carcinoma (EC) stem cells, may provide useful information concerning the development and subsequent pathology of teratocarcinomas in humans. In addition, it is likely that human EC cells resemble early embryonic cells and can be used as an in vitro counterpart of such cells from the human embryo. Several common properties of human EC cells have been identified, and a human EC cell line, TERA-2, that is capable of extensive somatic differentiation has been cloned. In nude mice, TERA-2 EC cells form tumors containing neural elements and glandular structures that resemble primitive gut. In culture, these EC cells can be induced to differentiate by exposure to retinoic acid and hexamethylenebisacetamide (HMBA). Differentiation is marked by the disappearance of several cell surface antigens characteristic of human EC cells, and the appearance of other antigens on the various subsets of differentiated derivatives. In retinoic acid-induced cultures, these differentiated derivatives include neurons and cells permissive for the replication of cytomegalovirus, a virus that can cause birth defects in humans. On the other hand, HMBA appears to activate an alternative pathway of differentiation for TERA-2 EC cells, although the identity of the resulting cells remains to be elucidated. In addition to providing a tool for analyzing the evolution of teratocarcinomas in human patients, the TERA-2 EC cells may provide us with insights into the mechanisms of cellular differentiation in the human embryo and a model in which to investigate how teratogenic agents such as HCMV can disrupt these processes.

Placental alkaline phosphatase as a tumor marker for primary intracranial germinoma

A sensitive enzyme-linked immunosorbent assay (ELISA) was used in a retrospective study of placental alkaline phosphatase (PLAP) levels in serum, cerebrospinal fluid (CSF), and intratumoral cyst fluid in primary intracranial germinoma. The ELISA showed no cross-reactivity with intestinal alkaline phosphatase except in very high concentrations, after samples had been heat-treated. Three patients with germinoma were studied for serum PLAP levels and in all the levels were elevated (3.78, 0.52, and 2.11 IU/liter). Two of the germinoma patients were studied for PLAP levels in the CSF, and both had elevated levels (0.83 and 9.83 IU/liter). The intratumoral cyst fluid in one case of germinoma was tested for PLAP and the level was found to be very high (603 IU/liter). These PLAP levels decreased concomitantly with the reduction in tumor size during irradiation. Serum PLAP levels were measured in 40 control adult male individuals and in the CSF of 20 nonpregnant patients with subarachnoid hemorrhage. The upper normal limits were 0.20 and 0.11 IU/liter in the serum and the CSF, respectively. All PLAP levels measured in the serum of patients with various brain tumors were 0.18 IU/liter or less. This study strongly suggests that PLAP is a clinically useful tumor marker for primary intracranial germinoma.

Seminoma-derived Nagao isozyme is encoded by a germ-cell alkaline phosphatase gene

A full-length placental alkaline phosphatase (PLAP) cDNA was used to identify and clone the PLAP-like Nagao isozyme gene from human genomic libraries. The entire nucleotide sequence of the gene reveals the existence of 11 exons interrupted by 10 small introns (76-427 base pairs). Putative regulatory sequences have been identified in the promoter regions as well as dispersed in the introns. The deduced amino acid sequence of the Nagao isozyme indicates that the mature molecule is composed of 513 amino acids, of which 12 residues are different from the sequence of PLAP (98% homology). A sequence derived from exon III of the Nagao isozyme gene was used to synthesize a peptide (NH2-Lys-Leu-Gly-Pro-Glu-Thr-Phe-Leu-Ala-COOH) that contains two mutations with respect to the corresponding PLAP sequence. This peptide elicited rabbit polyclonal antibodies that reacted specifically with the seminoma Nagao isozyme but not with PLAP in electrophoretic transfer blots. These results indicate that the tumor, and possibly the normal testis, Nagao isozyme is encoded by a gene referred to as germ-cell alkaline phosphatase gene that differs from the PLAP gene expressed by syncitiotrophoblastic cells.

Testicular cancer

Testicular cancer, which predominantly occurs in young men, has become increasingly common; it is presently the most common malignancy in men aged 20-34. Despite a lack of knowledge of aetiology, empirical advances, particularly in the management of patients with advanced disease, have been dramatic. Prior to the development of effective chemotherapy in the 1970s, less than 10% of men with metastatic non-seminomatous germ cell tumours were cured; nowadays approximately 90% of patients are potentially curable. The introduction of effective chemotherapy has led to a reappraisal of surgery and radiotherapy in the management of early stage disease and the introduction of a policy of surveillance in patients without evidence of metastases at the time of removal of the primary tumour. Following chemotherapy, surgery is required in approximately 25% of patients with advanced disease to excise residual masses, which in one-fifth of cases will show evidence of residual malignancy. In a proportion of patients, testicular cancer develops on a background of long-standing infertility, whereas in many men there is temporary oligospermia, despite a previous history of fertility. The majority of patients with prior evidence of spermatogenesis recover this function following chemotherapy and there is no evidence that children fathered by such patients have an increased risk of malformation. Despite physician optimism and excellent prospects for cure, significant psycho-social morbidity is associated with the diagnosis and treatment of testicular cancer. Factors contributing to this are being identified and will lead, hopefully, to the minimisation of such problems by appropriate intervention.

Patterns of seminoma tissue markers and deletions

Seminomas and control tissues were analyzed for several tumor markers. Very high levels of placental alkaline phosphatase (PLAP)-like enzyme levels were found in all 18 seminomas studied. The majority of the seminomas were of phenotype I, thus differing from palcental PLAP. The mean amount of enzyme protein as measured by monoclonal antibodies, was 100 times higher than in non-malignant tissues and 10 times lower than in placental tissue. The specific enzymatic activity in seminomas was about half of that observed in placenta. Similarly, the specific activity of PLAP-like enzymes in sera of patients with seminoma was only about half of that found in pregnancy sera. HCG was strongly elevated in 3 seminomas, but not obviously related to PLAP. Thirteen of the 17 pure seminomas had HCG over 100 IU/g, which was not seen in normal testes. Liver alkaline phosphatase (LAP) and intestinal alkaline phosphatase (IAP) were high in seminomatous tissues, the mean increases being 60-fold and 20-fold, respectively. The highest IAP levels were found in 2 yolk-sac tumors. Ferritin was moderately elevated in seminomas, but high in several control tissues. Carcinoembryonic antigen (CEA) was not elevated and alpha-fetoprotein (AFP) was not detected at all in pure seminomas. A decrease in carbohydrate antigen 50 (CA-50) content was noted in seminomas as compared to normal testes, yolk-sac tumors and choriocarcinomas. Defects in tumor-related enzymes may account for increase of PLAP and decrease of CA-50.

Enzyme-linked coagulation assay. IV. Sensitive sandwich enzyme-linked immunosorbent assays using Russell's viper venom factor X activator-antibody conjugates

We have applied the enzyme-linked coagulation assay (ELCA) system to the development of an amplified immunoassay using the clotting cascade to enhance sensitivity of detection of immune complexes. The factor X-activating enzyme of Russell's viper venom was detectable using ELCA in amounts as low as 0.25 fg per assay. Monoclonal antibodies to beta-hCG, placental alkaline phosphatase (PLAP), and the P-24 antigen of HTLV-III were labeled with this enzyme or peroxidase and used for "sandwich" immunoassays using another monoclonal antibody (beta-hCG, PLAP) or polyclonal patient IgG (P-24 antigen) bound to a polylysine-glutaraldehyde-coated plate as a "capture" reagent. After the immunobinding step, the plate was washed and substrate consisting of a mixture of factors X, V, and II in buffer containing calcium and lipid was incubated for various lengths of time. The mixture was transferred to another plate coated with fibrinogen and containing peroxidase-fibrinogen in EDTA solution to measure the amount of thrombin generated. Using this protocol, we were able to measure the presence of 2-10 pg/ml of beta-hCG and PLAP (5-30 amol per sample). All three model antigens were detectable at concentrations 2-3 orders of magnitude less using RVV-XA-labeled antibodies and ELCA than they were using peroxidase-labeled antibodies. The assay has considerable potential as a general immunoassay amplification system, yielding a "color test" for antigens of interest with a detection limit not readily attainable using other chromogenic methodologies.

Identification of testicular atypical germ cells by an immunohistochemical technique for placental alkaline phosphatase

The identification of atypical testicular germ cells is often difficult by by routine histologic examination. By immunohistochemical detection of placental alkaline phosphatase (PLAP) and by periodic acid Schiff staining of glycogen, atypical germ cells were easily identified in testicular samples. Forty-one fetal and adult testes were used for a preliminary study, and 121 testes from infants and adults with either cryptorchidism or germ cell tumors were studied for the presence of atypical germ cells. Two types of clear germ cells were differentiated histochemically, and one with PLAP-positive cell surfaces and glycogen-rich cytoplasm was considered to be atypical. The alkaline phosphatase of atypical germ cells appeared to be similar to that found in a few germ cells of early fetal testes. The atypical germ cells seemed to be multi-potential malignant cells capable of developing not only into seminoma but also into other germ cell tumors. Only in yolk sac tumor of infants were the atypical germ cells absent from tumor-adjacent seminiferous tubules.

Placental-like alkaline phosphatase reactivity in human tumors: an immunohistochemical study of 520 cases

Placental-like alkaline phosphatase (PLAP) activity has been reported in various human neoplasms of both somatic and germ cell types. The expression of PLAP was examined with a polyclonal antibody and the immunoperoxidase technique in formalin-fixed, paraffin-embedded sections of 37 germ cell neoplasms and 483 somatic tumors. The expression of keratin and epithelial membrane antigen (EMA) was concurrently assessed to determine whether these stains were helpful in distinguishing germ cell neoplasms from somatic tumors that might mimic them microscopically. All germ cell lesions were reactive for PLAP, but so were 62 somatic carcinomas, usually in female müllerian, intestinal, and lung cancers and less often in carcinomas of the breast and kidney. PLAP-reactive somatic tumors exhibited EMA and keratin positivity in the absence of prior protease digestion, whereas germ cell neoplasms failed to do so. Malignant mesotheliomas were nonreactive for PLAP, as were carcinomas of the nasopharynx, adrenals, liver, pancreas, stomach, prostate, and urinary bladder. PLAP is a highly sensitive but nonspecific immunohistologic marker of germ cell differentiation. However, non-protease-enhanced stains for keratin and EMA allow separation of germ cell and somatic carcinomas, despite their shared capacity for PLAP expression. In somatic neoplasms, PLAP immunoreactivity might be of potential use in predicting possible primary sources for metastatic tumors of unknown origin.

Pst I restriction fragment length polymorphism of the human placental alkaline phosphatase gene in normal placentae and tumors

The structure of the human placental alkaline phosphatase gene from normal term placentae was studied by restriction enzyme digestion and Southern blot analysis using a cDNA probe to the gene for the placental enzyme. The DNA digests fall into three distinct patterns based on the presence and intensity of an extra 1.1-kilobase Pst I band. The extra 1.1-kilobase band is present in 9 of 27 placenta samples, and in 1 of these samples the extra band is present at double intensity. No polymorphism was revealed by digestion with restriction enzymes EcoRI, Sma I, BamHI, or Sac I. The extra Pst I-digestion site may lie in a noncoding region of the gene because no correlation was observed between the restriction fragment length polymorphism and the common placental alkaline phosphatase alleles identified by starch gel electrophoresis. In addition, because placental alkaline phosphatase is frequently re-expressed in neoplasms, we examined tissue from ovarian, testicular, and endometrial tumors and from BeWo choriocarcinoma cells in culture. The Pst I-DNA digestion patterns from these cells and tissues were identical to those seen in the normal ovary and term placentae. The consistent reproducible digestion patterns seen in DNA from normal and tumor tissue indicate that a major gene rearrangement is not the basis for the ectopic expression of placental alkaline phosphatase in neoplasia.

Pathobiology of intracranial germ-cell tumors: immunochemical, immunohistochemical, and electron microscopic investigations

In an attempt to clarify the pathobiology of intracranial germ-cell tumors, we studied 56 patients with these tumors, both clinically and pathologically. Our evaluations included immunochemical, immunohistochemical, and electron microscopic observations. Thirty tumors originated in the pineal region, ten in the suprasellar region, nine in the basal ganglia, and two in other regions. Five had double sites of origin. Histologically, there were 39 germinomas, six teratomas, four embryonal carcinomas, two choriocarcinomas and five mixed tumors. Among tumors tested immunochemically, serum carcinoembryonic antigen (CEA) was positive in 3.4%, serum alpha-fetoprotein (AFP) in 25.8%, and serum human chorionic gonadotropin (HCG) in 32.1%. In CSF, CEA was positive in 14.3%, AFP in 26.3%, and HCG in 75%. One third of germinomas were positive for serum HCG, and 88.9% for CSF HCG. One half of teratomas were positive for CEA of CSF. In immunohistochemical testing, the positive rates for CEA, AFP, HCG, and placental alkaline phosphatase (PLAP) were 26.9%, 11.5%, 24.1%, and 55.6%, respectively. Most teratomas were positive for CEA and the reactions were prominent in gland-like structures. HCG-positive syncytial cells were found in three germinomas and two embryonal carcinomas as well as in choriocarcinomas. The majority of germinomas were positive for PLAP and the reactive sites were tumor cell membranes and cytoplasm. On electron microscopy, germinomas were least differentiated, followed in order by embryonal carcinomas, choriocarcinomas, and teratomas. Further clinical and pathological studies will be necessary for a better understanding of the biology of these tumors.

Carcinoma-in-situ of the testis: possible origin from gonocytes and precursor of all types of germ cell tumours except spermatocytoma

Based on evidence from morphological and histochemical studies and from clinical experience, the following hypotheses are proposed: carcinoma-in-situ (CIS) germ cells are malignant gonocytes; these CIS gonocytes have some capacity to regress into more primitive, totipotent embryonic cells which can give rise to all types of nonseminomatous germ cell tumours; the tumour germ cells of classical seminomas are malignant gonocytes derived from CIS gonocytes which have lost their ability to regress into totipotent embryonic cells; the ability of CIS gonocytes to regress into totipotent embryonic cells decreases with age, whereas the capacity to form classical seminoma cells is preserved; the transformation of CIS gonocytes into invasive tumours is dependent on factors such as gonadotrophins and/or testicular steroids; the pathogenesis of classical and spermatocytic seminoma are unrelated. As a consequence of these hypotheses an alternative nomenclature for carcinoma-in-situ, seminoma and dysgerminoma is suggested.

Placental-like alkaline phosphatase. Re-evaluation of the tumor marker with exclusion of smokers

This report demonstrates that smoking is a major factor of nonspecific elevation of the tumor marker placental-like alkaline phosphatase (PLAP). In 98 healthy nonsmokers the mean of the enzyme activity was determined as 0.068 U/L (range, +/- 2 SD 0-0.144 U/L) compared to a mean of 0.378 U/L (range, +/- 2 SD 0-1.02 U/L) in 65 smokers. In view of this finding the usefulness of PLAP as a tumor marker was re-evaluated in 286 patients with various neoplasms and a negative smoking history. Of these patients, 23% and 50% had elevated values for PLAP and carcinoembryonic antigen, respectively. When compared to the range of PLAP in normal smokers only 4.1% of the patients showed elevated values. An increased incidence of elevated PLAP was found in patients with tumors of the lung, pancreas, stomach, colon/rectum, ovaries, and in 2 of 3 seminomas. It was concluded from the data that PLAP is a useful tumor marker for selected neoplasms provided its use is confined to nonsmokers.

Vasitis nodosa--a site of arrest of malignant germ cells

A 40-year-old man, with a history of vasectomy 11 years previously, presented with a tumour in his right testis. At orchidectomy a seminoma was found, together with a nodule on the vas deferens. Histological examination of this area in the vas identified the lesion of vasitis nodosa and also showed it to be the site of proliferating germ cells. The pathogenesis of this lesion is discussed.

Diagnosis of germinal neoplasm in the thalamus and basal ganglia

Germinal neoplasms originating in the thalamus and basal ganglia were histologically verified by stereotactic biopsies in five cases and by other methods in three cases. Immunoperoxidase staining was performed on the tumors using antibodies against human chorionic gonadotropin and placental alkaline phosphatase. The presence of human chorionic gonadotropin was demonstrated in one germinoma and two mixed tumors, but not in three germinomas. Placental alkaline phosphatase was demonstrated to be present in four germinomas and one mixed tumor. Stereotactic biopsy specimens can be studied immunohistochemically, and the placental isoenzyme of alkaline phosphatase appears to be a new tumor marker for germinoma.

Radiotherapy for stage I seminoma testis: results of treatment and complications

The results of treatment by infradiaphragmatic lymph node irradiation and orchiectomy in 232 patients with Stage I testicular seminoma seen between 1963 and 1983 are reported. Of this group, only five (2%) patients relapsed and none died from seminoma. Contralateral testicular tumours occurred in 12 patients and five developed second non-testicular malignancies. The acute and late morbidity of radiotherapy was low although 15 patients developed peptic ulceration. There was a significant association between prior abdominal surgery and a history of dyspepsia with ensuing peptic ulceration. Future management policy is discussed on the basis of these observations.

Phenotypes of placental-type alkaline phosphatase in seminoma sera as defined by monoclonal antibodies

PLAP-like enzymes could be detected in serum of patients with primary testicular tumors, in particular seminomas. The use of a panel of monoclonal antibodies (MAbs) permitted typing into 6 different testicular serum phenotypes, of which one appeared similar to a placental type (II) and 2 have not been previously described. Most tumor sera belonged to type I, as described for seminoma tissues. With a more advanced tumor the mean serum PLAP-like levels increased. After operation, after radiotherapy or with no evidence of disease lower or non-detectable enzyme levels were found. In typing the tissue PLAP-like antigen in serum of the same patient or sera from recurrences of a seminoma in the same patient, the same phenotypes of PLAP-like antigen were usually but not always found. None of the 6 phenotypes appeared to confer a poorer prognosis. We conclude that the expression of PLAP-like antigen is eutopic and is enhanced by testicular malignancy, especially in seminoma cells.

Immunohistochemical study of placental alkaline phosphatase in primary intracranial germ-cell tumors

Indirect immunoperoxidase staining by the peroxidase-antiperoxidase (PAP) technique was carried out on 23 human primary intracranial germ-cell tumors (17 germinomas, one embryonal carcinoma, one yolk-sac tumor, three teratomas, and one teratoma with embryonal carcinoma) and on six human primary pineal non-germ-cell tumors (one pineocytoma, two pineoblastomas, two astrocytomas, and one glioblastoma multiforme). The technique used specific rabbit antisera against placental alkaline phosphatase (PLAP), alpha-fetoprotein (AFP), and human chorionic gonadotropin (HCG). Thirteen of 17 intracranial germinomas (76.5%) showed positive staining for PLAP mainly on the tumor cell membrane. In six primary intracranial non-seminomatous germ-cell tumors, there was weak positive staining indicating the presence of PLAP in only a few cells of one embryonal carcinoma, and in some glandular epithelial cells of one teratoma; this staining was limited to the cytoplasm. None of the other six primary pineal non-germ-cell tumors showed any positive PLAP reaction. From these results, PLAP was shown to be very useful in histopathology as a diagnostic tumor marker of intracranial germinoma. Positive AFP staining was seen in several yolk-sac tumor cells and a few embryonal carcinoma cells. However, no intracranial germinomas and non-germ-cell tumors of the pineal region showed positive reaction. As for HCG, only one suprasellar germinoma and one pineal embryonal carcinoma among 29 specimens contained a few positive-staining tumor cells.

Serum marker potential of placental alkaline phosphatase-like activity in testicular germ cell tumours evaluated by H17E2 monoclonal antibody assay

A monoclonal antibody (H17E2) was used in a solid-phase localisation of enzyme activity (ILEA) assay to evaluate placental-like alkaline phosphatase (PLAP) as a serum marker of testicular germ cell tumours. Single or repeated assays were performed on 213 normal blood donor and a smaller number of term pregnancy and testicular cancer sera. The detection limit of PLAP by this system was 0.14 O.D. units equivalent to 0.04iul-1. Of 50 patients with established metastatic disease tested before treatment, 88% of 16 with seminoma, 54% of 13 with mixed seminoma and malignant teratoma and 33% of 21 with malignant teratoma had serum PLAP greater than 0.2 O.D. units. This compared to an incidence of 2% in non-smokers and of 29% in smokers who had been free of disease for more than 12 months. In 15 of 22 successfully treated patients, pre-treatment serum PLAP exceeded 0.2 O.D. units (mean 0.69 O.D.) and varying (53-97%) reductions in the initial levels occurred with treatment. These results with monoclonal antibody ILEA assay suggest that measurement of PLAP levels will be useful in the management of patients with germ cell tumours, particularly seminoma.

Placental alkaline phosphatase as a tumour marker in seminoma using the H17 E2 monoclonal antibody assay

Serum samples from 62 patients with seminoma were assayed for placental alkaline phosphatase-like activity using the monoclonal antibody H17 E2, in order to evaluate its utility as a serum tumour marker. Fifteen of 16 patients (94%) with active seminoma had elevated serum PLAP levels. Sixteen of 46 (35%) of patients considered to be in remission had elevated PLAP levels (false positive rate 35%). Fifteen false positive results were considered attributable to concomitant smoking, and if these patients are excluded, only one false positive case was detected. In 7 out of 7 patients sequential PLAP assays reflected clinical response to treatment.

Eutopic expression of placental-like alkaline phosphatase in testicular tumors

Very high levels of placental-like alkaline phosphatases (PLAP-like enzymes) were observed in tissues from 13 typical seminomas. Four tumors with seminoma components contained these enzymes to varying degrees, and other testicular tumors had them in smaller or non-detectable amounts. Analysis using monoclonal antibodies produced against the common placental alkaline phosphatase (PLAP) phenotypes and enzyme inhibition studies with amino acids and peptides showed the PLAP-like enzymes present in seminoma to be similar to those PLAP-like enzymes which are expressed in lower amounts in two embryonal carcinomas and in trace amounts in normal testicular tissue. These similarities suggest that the increased expression of PLAP-like enzymes in seminomas results from enhanced eutopic expression of enzymes found in normal testis.

Tumour and cellular localization by use of monoclonal and polyclonal antibodies to placental alkaline phosphatase

Monoclonal and polyclonal antibodies against placental alkaline phosphatase (PLAP) were evaluated for tumour immunolocalization of human PLAP-producing Hep 2 tumours in nude mice. The antibodies were labelled with 125I and injected i.p. in mice with developing Hep 2 tumours. The distribution of 125I-anti PLAP in various tissues showed that the labelled antibody was enriched in the tumour, the mean concentration ratio being 7.1 and 6.8 for polyclonal and monoclonal antibodies, respectively. A PLAP negative tumour (RD) showed a mean ratio of 1.2. There was a positive correlation between PLAP content and uptake of labelled antibody in the tumours. Hep 2 tumour cells in tissue culture showed 100% positivity for PLAP, while imprints of the tumour after passage in nude mice showed 40-50% positivity. PLAP offers potential as a useful marker for localizing tumours in humans.

Multiple biochemical tumor markers in seminoma. A double-blind study

The value of certain biochemical tumor markers have been well established in nonseminomatous testicular cancer. However, the lack of frequent tumor markers in the sera of patients with seminoma has prompted us to embark on this double blind study. The authors studied 89 patients with the histologic diagnosis of seminoma utilizing placental alkaline phosphatase (PLAP), gamma-glutamyl transpeptidase (gamma GT), human chorionic gonadotropin (hCG), and alpha-fetoprotein (AFP). It was found that 12/30 patients (40%) with active tumor had elevated serum PLAP and 10/30 (33%) of these patients had elevated serum levels of GGT. Eighty percent of the patients with clinically active tumors had detectable serum levels of one or more of these biochemical markers. Since the frequency of the previous tumor markers have been scarce in seminoma, these serial utilization of these biochemical markers should assist the clinician to detect and monitor seminoma patients more efficaciously. However, the false-positive, false-negative, rates, and biologic half lifes of these markers should be taken in account.