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

Tobacco smoking-associated genome-wide DNA methylation changes in the EPIC study

AIM

Epigenetic changes may occur in response to environmental stressors, and an altered epigenome pattern may represent a stable signature of environmental exposure.

MATERIALS & METHODS

Here, we examined the potential of DNA methylation changes in 910 prediagnostic peripheral blood samples as a marker of exposure to tobacco smoke in a large multinational cohort.

RESULTS

We identified 748 CpG sites that were differentially methylated between smokers and nonsmokers, among which we identified novel regionally clustered CpGs associated with active smoking. Importantly, we found a marked reversibility of methylation changes after smoking cessation, although specific genes remained differentially methylated up to 22 years after cessation.

CONCLUSION

Our study has comprehensively cataloged the smoking-associated DNA methylation alterations and showed that these alterations are reversible after smoking cessation.

Tobacco smoking leads to extensive genome-wide changes in DNA methylation

Environmental factors such as tobacco smoking may have long-lasting effects on DNA methylation patterns, which might lead to changes in gene expression and in a broader context to the development or progression of various diseases. We conducted an epigenome-wide association study (EWAs) comparing current, former and never smokers from 1793 participants of the population-based KORA F4 panel, with replication in 479 participants from the KORA F3 panel, carried out by the 450K BeadChip with genomic DNA obtained from whole blood. We observed wide-spread differences in the degree of site-specific methylation (with p-values ranging from 9.31E-08 to 2.54E-182) as a function of tobacco smoking in each of the 22 autosomes, with the percent of variance explained by smoking ranging from 1.31 to 41.02. Depending on cessation time and pack-years, methylation levels in former smokers were found to be close to the ones seen in never smokers. In addition, methylation-specific protein binding patterns were observed for cg05575921 within AHRR, which had the highest level of detectable changes in DNA methylation associated with tobacco smoking (–24.40% methylation; p = 2.54E-182), suggesting a regulatory role for gene expression. The results of our study confirm the broad effect of tobacco smoking on the human organism, but also show that quitting tobacco smoking presumably allows regaining the DNA methylation state of never smokers.

Specific immunoassays for placental alkaline phosphatase as a tumor marker

Human placental (hPLAP) and germ cell (PLAP-like) alkaline phosphatases are polymorphic and heat-stable enzymes. This study was designed to develop specific immunoassays for quantifying hPLAP and PLAP-like enzyme activity (EA) in sera of cancer patients, pregnant women, or smokers. Polyclonal sheep anti-hPLAP antibodies were purified by affinity chromatography with whole hPLAP protein (ICA-PLAP assay) or a synthetic peptide (aa 57–71) of hPLAP (ICA-PEP assay); the working range was 0.1–11 U/L and cutoff value was 0.2 U/L EA for nonsmokers. The intra- and interassay coefficients of variation were 3.7%–6.5% (ICA-PLAP assay) and 9.0%–9.9% (ICA-PEP assay). An insignificant cross-reactivity was noted for high levels of unheated intestinal alkaline phosphatase in ICA-PEP assay. A positive correlation between the regression of tumor size and EA was noted in a child with embryonal carcinoma. It can be concluded that ICA-PEP assay is more specific than ICA-PLAP, which is still useful to detect other PLAP/PLAP-like phenotypes.

A new highly specific monoclonal antibody against placental alkaline phosphatase: a potential marker for the early detection of testis tumour

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.

The combined use of high performance liquid chromatography and immuno-biochemical techniques for protein isolation: a new approach for identification of an individual protein from a pool of proteins

HPLC was used in combination with immuno-bead separation technique for identification of an individual protein from a pool of proteins. This was carried out using an in-house monoclonal antibody (ATC2) specific for placental alkaline phosphatase (PLAP) as a primary antibody for conjugation to CNBr beads. The phosphatase activity (ALP) of PLAP was measured by colorimetric assay (MEDC). The data from this study has so far indicated that: 1. HPLC analysis of molecules following isolation with ATC2-conjugated beads showed high degree of purity. This could be achieved using protein mixtures prepared from lysates of tumour cell lines or tumour fragments. 2. HPLC-isolated PLAP maintained phosphatase activity. 3. Out of the four dissociation reagents used, diethyl amine (DEA) was found to be the best reagent for dissociation of antigen, ie PLAP, but not mAb from CNBr beads. 4. The profile of ALP activity was different for samples prepared from testis and kidney fragments, both in terms of the HPLC peak profile as well as the sensitivity. These data confirmed that the immuno-bead separation technique in conjunction with HPLC were powerful tools for identifying an individual protein from a pool of proteins. These approaches are being used for the identification of PLAP molecules, as a tumour marker in patients suspected of testicular malignancies with equivocal ultrasound.

Human placental alkaline phosphatase: expression in Pichia pastoris, purification and characterization of the enzyme

The soluble form of human placental alkaline phosphatase (PLAP) was expressed in the methylotrophic yeast Pichia pastoris and the expression product was purified and characterized. Yeast-derived PLAP (yPLAP) was secreted into the medium to the level of 2 mg/liter. yPLAP displayed kinetic properties similar to those reported earlier for the membrane-bound PLAP. Purified yPLAP had specific activity of 774 U/mg and appeared in two subunit sizes, ca. 62 and 65 kDa. This difference was due to heterogenous N-glycosylation. Purified yPLAP appeared as multiple forms in isoelectric focusing in pI range of 4.2 to 5.2. The expression system is discussed in comparison to previously reported expression systems.

Serum placental-type alkaline phosphatase activity in women with squamous and glandular malignancies of the reproductive tract

AIM

To investigate serum placental-type alkaline phosphatase (PLAP-type) activities in women with squamous and glandular malignancies of the reproductive tract using an immunoradiometric assay.

METHODS

PLAP-type immunoreactivity was measured in 180 women with non-ovarian malignancies of the reproductive tract and the values were compared with those from 334 controls. The cases comprised 18 vulval, nine vaginal, 103 cervical, 46 endometrial, and five fallopian tube cancers.

RESULTS

Serum PLAP-type activities were no different from controls in patients with squamous cell tumours. Women with adenocarcinoma of the cervix, endometrium, and fallopian tube had increased values: women with endometrial cancer had a median value nearly four times greater than that of controls. There was no direct correlation between PLAP-type activities and stage of disease in patients with endometrial cancer, but values reverted to normal after treatment.

CONCLUSIONS

Serum PLAP-type measurements are of no value in the management of patients with squamous cell tumours of the female reproductive tract. Raised activities can, however, be found in glandular tumours, in particular endometrial cancer where serum PLAP-type measurements may be of value in predicting remission.

Production of placental alkaline phosphatase (PLAP) and PLAP-like material by epithelial germ cell and non-germ cell tumours in vitro

Placental and placental-like alkaline phosphatase (PLAP) levels in the culture media of 87 cell lines of neoplastic and 'normal' origin were measured by a conventional immunosorbent enzymatic assay (IAEA) and by a new immunoradiometric assay (IRMA). The IRMA detected immunoreactive PLAP in 37 of 80 (46%) human epithelial and germ cell cultures, while the IAEA detected PLAP in only 25 (33%). Of the 52 non-germ cell tumour cultures, the IRMA detected expression in 24 (46%) and the IAEA in only 16 (31%). In 17 cases (21%) the IRMA recorded levels double that of the IAEA, while in five cultures (6%) the reverse was true. The IRMA was much more robust than the IAEA and had considerably lower inter- and intra-assay coefficients of variation (3.75-8.5% vs 5.2-46%). Detection of PLAP(-like) expression by IAEA is dependent on neoplastic expression of enzymatically functional molecules and quantification assumes constant enzyme kinetics. PLAP-like material has a higher catalytic rate constant than PLAP and thus will give higher values on a stoichiometric basis in an IAEA. The higher detection rate and levels of PLAP-like material in neoplastic cultures when measured by the IRMA clearly demonstrate ectopic expression of non-enzymatic PLAP and PLAP-like genes. The incidence of PLAP(-like) expression by non-germ cell and possible germ cell tumours has been underestimated and its utility as a tumour marker should be re-examined using assays which measure antigen mass rather than phosphatase activity.

Expression of placental alkaline phosphatase in gastric and colorectal cancers. An immunohistochemical study using the prepared monoclonal antibody

The authors developed monoclonal antibodies (MoAb) against human placental alkaline phosphatase (PLAP). Four specific MoAb reacting only with PLAP and two nonspecific MoAb reacting equally with isozymes of alkaline phosphatase (hepatic, intestinal, and placental) were obtained. Immunohistochemical staining with the specific MoAb showed that the cell membrane and cytoplasm of cancer cells were stained in gastric and colorectal carcinoma. The incidence of PLAP positivity was 23% (25 of 107) of all gastric carcinomas. Among gastric carcinomas, the 42% (13 of 31) positivity of highly differentiated carcinoma (papillary adenocarcinoma and well-differentiated tubular adenocarcinoma) was a significantly higher rate than that found in poorly differentiated carcinoma (poorly differentiated adenocarcinoma and signet-ring cell carcinoma, five of 41, 12%). The incidence of PLAP positivity was 11% (four of 35) in colorectal carcinoma. In contrast, gastric adenoma, intestinal metaplasia, and noncancerous tissue adjacent to cancer did not show staining. These results indicated that expression of PLAP was apt to occur in more highly differentiated gastric carcinoma and was highly specific for carcinoma in the gastrointestinal tract, although its incidence was not high.

Expression of human placenta alkaline phosphatase in placenta during pregnancy

To clarify the expression of PLAP during the course of pregnancy, the amount of PLAP mRNA and its activity in normal placental villi were measured. Both PLAP and its mRNA were found in placentae of as early as 7 weeks of gestation, and they continued to increase throughout pregnancy. But they showed different patterns of increase. The amount of PLAP mRNA began to increase dramatically around 13th week and probably continued to increase gradually until term. PLAP activity per gram of villi showed a gradual increase from around 13th week and a marked increase was observed after about 20th week. PLAP levels in sera from pregnant women were also measured, and they showed a pattern of increase imilar to that of PLAP activity per gram of villi. The continuous increase in the expression of PLAP throughout pregnancy suggests that PLAP may play a role in feto-maternal metabolism and placental differentiation.

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.

Analysis of serum placental alkaline phosphatase activity in testicular cancer and cigarette smokers

Serum PLAP/PLAP-like enzymes are elevated in testicular cancer patients and also in heavy smokers. Such elevations were measurable with anti-PLAP polyclonal and monoclonal antibodies, and an antigenic heterogeneity was demonstrated in the circulating enzymes. Thus polyclonal antibody revealed more of tumor PLAP-like antigen while a monoclonal antibody H7 detected PLAP of smokers better. PLAP of smokers and PLAP-like enzyme of cancer (seminoma) patients showed similar characteristics with respect to glycosylation pattern, charge and hydrophobicity. By these properties they were differentiated from PLAP of placenta.

Is placental alkaline phosphatase (PLAP) a useful marker for seminoma?

The usefulness of placental alkaline phosphatase (PLAP) as a tumour marker was assessed in 1578 serum samples from 236 patients with seminoma. Smoking habits were known for all but 7 patients (22 samples). Smoking was associated with significantly higher mean levels of PLAP in disease-free patients (28.8 [S.E. 2.1] U/l vs. 15.9 [1.3] U/l in non-smokers). Mean PLAP levels were higher in patients with active disease (78.6 [23.5] U/l in non-smokers and 47.2 [18.5] U/l in smokers). The median values showed a similar trend. However, there was considerable overlap between the various groups and differences between mean and median values indicated that PLAP values were distributed asymmetrically. The predictive value of PLAP as a tumour marker was consequently much less than superficial inspection of these values might suggest. In 97 patients on surveillance, only 2 out of 11 patients who relapsed had elevated PLAP at the time of clinically detectable relapse. With the upper limit of normal PLAP quoted by our laboratory (35 U/l), specificity and sensitivity were, respectively, 88% and 45% (all patients) and 96% and 47% (non-smokers). The sensitivity and specificity of PLAP were assessed in more detail for a series of threshold values (normal vs. abnormal) with a graphical method. Only in non-smokers did PLAP seem useful and even in this group the positive predictive value of an "abnormal" test may be low; less than 50% in clinically relevant circumstances. Serum PLAP assay cannot usefully stand alone as a marker for seminoma and its routine estimation contributes little to follow-up.

New cancer markers

In recent years many new and improved cancer markers have become available. From a clinical point of view, the most useful of the new markers include CA 19-9 for pancreatic adenocarcinoma, CA 125 for epithelial ovarian cancer, CA 15-3 for breast cancer, prostate specific antigen for prostatic adenocarcinoma, placental alkaline phosphatase for testicular seminomas and neuron-specific enolase for small cell carcinoma of lung. None of these new markers are specific for cancer. Furthermore, none are organ specific, except prostate specific antigen for prostatic tissue. The main application of these markers is in monitoring patients with the specific malignancies indicated. Whether routine use of any of these new markers leads to higher quality of life or enhanced survival remains to be determined.

Monoclonal antibodies to enzymes

The production, identification, and utilisation of monoclonal antibodies to enzymes are reviewed. Such antibodies may be produced in vitro by the mouse-hybridoma technique, may occur naturally in vivo as enzyme-binding immunoglobulins and may be produced in the laboratory from the lymphocytes of patients whose sera contains such immunoglobulins. The diagnostic application of monoclonal antibodies to enzymes is considered, with special reference to their use in the measurement of the MB-isoenzyme of creatine kinase, pancreatic isoamylase, prostatic acid phosphatase, and the isoenzymes of alkaline phosphatase.

The place of surgery in the management of germ cell tumours in childhood

Because of their rarity and the availability of effective, if toxic, treatment, germ cell tumours should be managed by a team familiar with their behaviour and response to therapy. Treatment decisions from the time of presentation onwards should be made by surgeon and oncologist together, and, where the diagnosis is made unexpectedly after emergency surgery, early consultation is necessary to establish the best approach to treatment for that individual patient. Mutual recognition of the possibilities and problems of each modality of treatment will lead to their use together in the most effective way.

Serum placental-like alkaline phosphatase (PLAP): a novel combined enzyme linked immunoassay for monitoring ovarian cancer

A new combined enzyme linked immunoassay (ELISA) was developed to measure both serum placental-like alkaline phosphatase (PLAP) activity (PLAPA) and concentration (PLAPC) in the same microtitre plate using an Imperial Cancer Research Fund monoclonal antibody, designated H17E2. PLAP A and PLAP C were determined together with an existing marker, CA125 in 397 serial samples from 87 patients with epithelial ovarian cancer. Retrospective assessment showed the sensitivity to increase from 73% with CA125 alone, to 88% using CA125 and PLAP A, and to 93% with all three markers in 261 samples from the patients with known active disease at the time of sampling. When the results for all 397 samples were included in the analysis, however, the specificity, sensitivity, accuracy and predictive powers of this monoclonal antibody were not sufficiently high to assist in the prospective follow up of patients with ovarian cancer. This was due to a significant number of false positive and false negative results. Our data indicate that PLAP A or PLAP C estimation with H17E2 may, therefore, only be of value in the management of those patients with known active disease who are already known to be "marker positive" for this antigen.

Production of monoclonal antibodies to placental alkaline phosphatase: preliminary characterisation includes identification of one antibody reactive with routinely fixed histological preparations

We describe the production and preliminary characterisation of a set of monoclonal antibodies (MAbs) raised against placental alkaline phosphatase (PLAP). Different forms of antigen presentation, PLAP or PLAP-like expressing whole cells, placental membranes or purified PLAP were used to immunise BALB/c mice. Initial screening was carried out against the immunising material by ELISA, against fresh frozen placental sections by immunostaining and against purified PLAP using an enzyme capture assay. The most successful fusions were those following whole cell immunisation, producing 27 antibodies that all reacted with both the placental and testicular form of enzyme. These all showed a broadly similar pattern of reactivity when tested against a range of human malignant cell lines. Further characterisation identified one antibody, 8B6, as strongly reactive with formalin-fixed paraffin-embedded placental sections. This antibody also performed well when tested against a range of normal and malignant routinely fixed tissue sections. Of 14 antibodies analysed for immunoglobulin isotype, 10 were of the IgGI subclass. In competitive binding studies with 7 antibodies to discriminate epitopes, at least 4 distinct binding sites were identified. By Scatchard analysis on 4 of these antibodies, binding constants of 3 were within the range 3.5-5.3 x 10(-9)M. Unusually the 4th antibody appeared to recognise 2 separate antigen sites with binding constants of 2.1 and 7.5 x 10(-9)M. In a preliminary study to compare patterns of reactivity of a selection of the new antibodies with a limited number of sera from smokers and seminoma patients, results indicate their potential for further typing within the placental group of enzymes.

Monoclonal antibodies to placental alkaline phosphatase: preclinical evaluation in a human xenograft tumour model of F(ab')2 and Fab fragments

Six new placental alkaline phosphatase monoclonal antibodies (MAbs) have been evaluated in order to select a potentially clinically useful antibody fragment for use in immunoscintigraphy or therapy. Initially, 3 antibodies were identified by trial pepsin digestion as likely to give satisfactory F(ab')2 yield. The corresponding intact antibodies were then compared for ability to localise human xenograft tumours in athymic mice. Of the best of these, designated 3F6, F(ab')2 and Fab fragments were then evaluated in similar xenograft experiments. In intact antibody biodistribution comparisons, 3F6 showed good tumour retention and satisfactory specific/non-specific ratios at 8 days. In similar fragment biodistribution experiments 3F6 F(ab')2 gave the highest tumour/blood ratio (10) and tumour/organ ratios (19) and the best specific/non-specific localisation. This fragment also showed higher absolute uptake in the tumour than intact antibody, 18.9% and 14.4% respectively of the injected dose. As expected, fragments showed much faster blood clearance rates than whole antibody. For Fab the in vivo instability by 6 hr was also demonstrated.

Independent expression in serum of three tumour-associated antigens: CA 125, placental alkaline phosphatase and HMFG2 in ovarian carcinoma

Circulating levels of CA 125, the HMFG2 antigen and placental alkaline phosphatase were measured in patients with epithelial ovarian cancer. In 37 patients the antigens were assayed before operation and 161 follow-up samples from 41 patients were assayed at different times during treatment. These three human tumour-associated antigens were expressed independently of each other. Measurement of all three antigens, compared with measurement of CA 125 alone, resulted in a statistically significant improvement in the detection rate of patients with localized disease from 18% to 69%.

Catalytic and immunologic activities of placental-like alkaline phosphatase in clinical studies. The value of PLAP in follow-up of ovarian cancer

Placental-like alkaline phosphatase (PLAP) was measured by its catalytic activity (CA), using an amplified enzyme-linked immunoassay, and by its immunologic activity (IA), using an enzyme-linked immunosorbent assay. In both assays the same monoclonal anti-PLAP antibody was used as the primary reagent. This antibody reacts with the main epitope on PLAP that is common to PLAP of ovarian and testicular origin, as well as of PLAP that is induced by smoking. Determinations of CA and IA of PLAP were carried out in serum samples from 101 patients with epithelial ovarian cancer (49 patients with progressive or recurrent disease, 52 patients with no evidence of disease), 20 patients with testicular cancer (8 non-seminoma testis, 12 seminoma testis) and 61 healthy controls. Smoking status was taken into consideration. The main findings from this study are: 1. In prolonged follow-up of patients who were treated for ovarian cancer, progressive or recurrent disease was never accompanied by rising values of CA or IA of PLAP. Therefore in this study, PLAP was not a good monitor for this disease. 2. In all instances where expression of PLAP was reflected by raised serum levels of these antigens, the measurement of the catalytic activity proved to be a more sensitive parameter than that of the immunologic activity. The value of PLAP measurements in the follow-up of patients with testicular cancer remains to be elucidated.

The management of testicular seminoma: Edinburgh 1970-1981

One hundred and fifty two patients with seminoma of the testis presenting to a regional centre between 1970 and 1981 have been reviewed. One hundred and forty three of these patients were treated primarily with radiotherapy. The actuarial survival of all 152 patients was 84.4% at 5 years and 83.3% at 10 years. The following factors significantly influenced survival: clinical stage; T-stage of the primary tumour; date of first treatment. Patients treated after 1979 had a better prognosis than patients treated before 1973. A group of patients with an actuarial survival of 100% at 5 years could be identified: they were in clinical stage I after lymphography and had T1 primary tumours. We could find no clear relationship between tumour size, duration of symptoms and clinical stage at presentation. We conclude that radiation therapy still has an important role to play in the management of seminoma of the testis. We recommend prophylactic retroperitoneal irradiation for patients in clinical stage I, primary treatment with radiotherapy for patients in clinical stages IIA and IIB, and primary treatment with chemotherapy for patients in clinical stages IIC, III and IV.

Monoclonal antibodies to human trophoblast and sperm antigens: report of two WHO-sponsored workshops, June 30, 1986--Toronto, Canada

Two WHO-sponsored workshops were recently held to obtain a consensus view from researchers active in the field of reproductive immunology on the current status of the application of monoclonal antibodies to studies of molecular events underlying reproduction and to determine the feasibility of using this approach to identify trophoblast- or sperm-specific antigens that might represent suitable candidates for the development of antifertility vaccines. A total of 66 mouse monoclonal antibodies reacting with human sperm and 45 monoclonal antibodies reacting with human trophoblast membrane components were submitted by 29 laboratories. These were evaluated in coded form by 42 laboratories with the appropriate expertise in biochemistry, immunohistology and tests of reproductive cell function. The majority of both anti-sperm and anti-trophoblast monoclonal antibodies cross-reacted with cellular elements in non-reproductive tissues. However, at least five monoclonal antibodies (two anti-trophoblast and three anti-sperm) appeared to demonstrate sufficient specificity to warrant further investigation as reagents for the identification of antifertility vaccine candidates.

Limitations to the use of surveillance as an option in the management of stage I seminoma

Improved definition of seminoma using step sections and tumour markers makes such patients a more selected group than when radiotherapy was first introduced. This and the improvements in radiological staging and the exquisite sensitivity of metastatic seminoma to chemotherapy justifies reappraisal of the role of prophylactic radiotherapy. To investigate this, twenty-six patients have been entered onto a programme of prospective biochemical and radiological surveillance. Though only four (15%) have relapsed, and all easily salvaged by chemotherapy, the relative difficulty and lateness of establishing the diagnosis makes this approach unsuitable for service use. Whether given the chemosensitivity of seminomas, radiotherapy would remain the treatment of choice compared to short courses of adjuvant carboplatin requires testing in a randomized trial.

Placental-type alkaline phosphatase in cervical neoplasia

Monoclonal antibodies reactive with placental-type alkaline phosphatase have formed the basis of methods for detection of this oncodevelopmental antigen in patients with pre-invasive and invasive cervical neoplasia, with or without evidence of papilloma virus infection. Disease-related elevations of placental-type alkaline phosphatase were not observed in patients' sera. Solubilised cervical smears or biopsy material, and cervical mucus swabs, often contained substantial amounts of this isoenzyme; however, there was no significant difference between any of the patient and control groups. Thus, serological and smear test assays for placental-type alkaline phosphatase were not useful in differential diagnosis of cervical lesions. However, its presence in most biopsy specimens, often at high levels, indicated possible application for in vivo radioimmunoimaging studies of invasive or metastatic cervical cancer.

Two gene duplication events in the evolution of the human heat-stable alkaline phosphatases

There are at least three alkaline phosphatase (AP) isoenzymes in man: a heat-stable placental enzyme (PLAP), a less heat-stable intestinal form (IAP), and the very heat-labile AP enriched in liver, bone and kidney. In addition to these enzymes, there is a heat-stable activity in the thymus and testis that is similar but not identical to the PLAP (the PLAP-like enzyme). Previous work has demonstrated a close structural relatedness among the IAP, PLAP and PLAP-like enzymes. Thus, it is possible that there are three human genes encoding heat-stable AP enzymes. To test this hypothesis, we have used a PLAP cDNA clone to screen a human genomic library cloned into the phage vector lambda EMBL-3. Three sets of clones were isolated, each bearing a distinct coding region homologous to the PLAP cDNA probe. Nucleotide sequence analysis of the 5' ends of these genes allowed comparison of their derived peptide sequences and positive identification of two of the genes. One of the genes encodes the PLAP (the PLAP-1 gene), another encodes the IAP, and a third closely resembles the PLAP-1 gene, but is distinct from it (the PLAP-2 gene). The PLAP-2 gene is highly homologous (greater than 95%) with the PLAP-1 except in the first exon, where sequences encoding the hydrophobic signal peptide are nearly identical with the same region of the IAP gene. These results demonstrate the existence of a small family of PLAP-related genes which is the result of at least two duplication events during the descent of man.

A new immunoassay using monoclonal antibodies HMFG1 and HMFG2 together with an existing marker CA125 for the serological detection and management of epithelial ovarian cancer

A new method with a low pH step to dissociate serum complexes has been developed to measure serum levels of antigens associated with ovarian cancer. The antigens are detected by monoclonal antibodies HMFG1 and HMFG2 and have been compared to an existing ovarian cancer associated antigen detected by the antibody CA125. Elevated HMFG1 was found in 56%, and elevated HMFG2 in 65% of 924 sera from 85 patients with ovarian cancer. CA125 was elevated in 85% of these sera. When the three markers were used in conjunction, 95% of sera from patients with ovarian cancer were positive--compared with 7% in sera from healthy control subjects. Therefore, the combination of HMFG1, HMFG2 and CA125 increases the diagnostic accuracy. If all three markers are normal in a patient previously treated for ovarian cancer then no further positive information regarding disease status can be obtained by ultrasound and CT scanning.

A highly sensitive assay method for human placental alkaline phosphatase involving a monoclonal antibody bound to a paper disk

A monoclonal antibody which is specific for human placental alkaline phosphatase and does not cross-react at all with intestinal alkaline phosphatase was prepared, and a procedure for the determination of placental alkaline phosphatase activity in serum was developed involving this monoclonal antibody bound to a paper disk. The minimum amount of placental alkaline phosphatase detectable by this method is 0.0025 King-Armstrong unit. Good correlation with the heat-treatment method was obtained. Therefore this proposed method can be used as a routine clinical test for the determination of serum placental alkaline phosphatase.

Serum and tissue tumour markers in seminomas

The serum expression of the tumour markers hydroxybutyric dehydrogenase (HBD), beta human chorionic gonadotrophin (beta HCG), alphafetoprotein (alpha FP) and placental alkaline phosphatase (PLAP) has been assessed in a consecutive series of 50 patients with pure seminoma. In pre-orchiectomy sera from 15 patients with stage I disease, HBD was elevated in 5, beta HCG in 3, alpha FP in 1 and PLAP in 1 (of 3 only). In 27 patients with stage 2 or 3 disease, prior to chemotherapy, serum HBD was elevated in 19, beta HCG in 11, alpha FP in 2 and PLAP in 10 (of 18). The presence of beta HCG was investigated immunocytochemically in primary tumour tissue from 39 patients. It was demonstrated in 6 of 21 tumours from patients with stage I disease and 5 of 18 with stage 2 or 3 disease.

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.