Alpha-fetoprotein

Chinese expert consensus statement on the clinical application of AFP/AFP-L3%/DCP using GALAD and GALAD-like algorithm in HCC

BACKGROUND

Primary hepatocellular carcinoma (HCC) is one of the most prevalent world-wide malignancies. Half of the newly developed HCC occurs in China. Optimizing the strategies for high-risk surveillance and early diagnosis are pivotal for improving 5-year survival. Constructing the scientific non-invasive detection technologies feasible for medical and healthcare institutions is among the key routes for elevating the efficacies of HCC identification and follow-up.

RESULTS

Based on the Chinese and international guidelines, expert consensus statements, literatures and evidence-based clinical practice experiences, this consensus statement puts forward the clinical implications, application subjects, detection techniques and results interpretations of the triple-biomarker (AFP, AFP-L3%, DCP) based GALAD, GALAD like models for liver cancer.

CONCLUSIONS

The compile of this consensus statement aims to address and push the reasonable application of the triple-biomarker (AFP, AFP-L3%, DCP) detections thus to maximize the clinical benefits and help improving the high risk surveillance, early diagnosis and prognosis of HCC.

Levels of alpha-fetoprotein during pregnancy and early infancy in normal and disease states

Alpha-fetoprotein (AFP) was 1 of the first serum protein markers to serve in the dual capacities of tumor marker and fetal defect marker, ie, an oncofetal protein, in the clinical laboratory. Although the serum-marker capacity of AFP has long been used, less is known of the fluid compartments of this oncofetal protein during fetal and perinatal development. In this review, the biologic activities of AFP are discussed in light of its presence in the various biologic fluid compartments: fetal serum, amniotic fluid, cord blood, urine, and maternal serum. AFP concentrations within the biologic fluids are considered in the context of gestational age, sex, body weight, and anatomic location. Discussion follows concerning the relationships and roles of AFP in various developmental disorders such as hypothyroidism, folate deficiencies, autoimmune disorders, acquired immunodeficiency disorder (AIDS), congenital heart defects, cystic fibrosis, preeclampsia/hypertension, and platelet aggregation disorders. Based on its presence in so many types of birth defects, malformations, and congenital anomalies, AFP can be seen to serve as a form of molecular "duct tape" during pregnancy and postnatal development.

Alpha-fetoprotein gene expression in early and full-term human trophoblast

Alpha-fetoprotein (AFP) is a major serum glycoprotein synthesized during fetal life mainly by the yolk sac and the fetal liver. At term, it reaches high concentrations in the maternal intervillous blood, which is in direct contact with the placental trophoblastic microvillous membrane, and this suggests the placental origin of the AFP at the fetal-maternal interface. We used several experimental approaches to investigate the expression of AFP gene and fetal protein production in early gestation and term placentas. RT-PCR and immunological studies clearly identified AFP messenger RNA and AFP protein in the placental villi from first trimester of pregnancy. The AFP gene was also expressed in highly purified cytotrophoblasts from early placentas, and enzymo-immunoassay showed that AFP protein was synthesized and secreted by early cytotrophoblasts. AFP was also detected in the cytoplasm of these cells by immuno-cytochemistry. However, none of these methods detected any expression of the AFP gene in full-term placental villi or in cultured trophoblasts. These findings demonstrate that both AFP mRNA and protein are present in trophoblastic cells early in pregnancy. The absence of AFP gene expression in term placental villi also suggests, that the AFP at the fetal-maternal interface is attributable to a notable transplacental passage of AFP from fetal blood in late pregnancy.

Elevated maternal serum AFP and normal ultrasound: what next?

Given the discovery of intracranial changes observed in fetuses with open spina bifida, the wisdom of routinely performing amniocentesis on persons with unexplained maternal serum alpha-fetoprotein elevations is now being questioned. The detection rate for spina bifida with a targeted ultrasound examination is greater than 95%. Yet one must also consider the sensitivity of ultrasound in detecting other anomalies, such as ventral wall defects and fetal karyotype anomalies. Although the sensitivity of ultrasound for neural tube defects has improved dramatically in recent years, it cannot detect all chromosome or structural anomalies that may be detected by amniocentesis. Therefore, patients should be made aware of their specific risks following a targeted ultrasound and offered the option of amniocentesis.

Human alpha-fetoprotein purified from amniotic fluid enhances growth factor-mediated cell proliferation in vitro

Using a primary monolayer culture of porcine granulosa cells (pGC) as an in vitro cell proliferation assay, we have examined the growth-promoting activity of alpha-fetoprotein (AFP) purified from term cord blood and midtrimester amniotic fluid. Increasing concentrations (2.5-20%) of crude human cord blood (CB) increased pGC proliferation, while identical concentrations of crude amniotic fluid (AF) were ineffective. When the cell system was maximally stimulated, AF dose dependently decreased cell proliferation. AFP purified from AF and CB (1.25-5.0 micrograms/ml) was not mitogenic alone, but, in the presence of epidermal growth factor (EGF) + insulin-like growth factor (IGF-I) (10 ng/ml each), AFP dose dependently increased cell proliferation to nearly double that of EGF + IGF-I alone. The response of pGC to the proliferative effects of AF-AFP and CB-AFP were identical at each dose of AFP tested. These results indicate that although crude, pooled midtrimester AF does not display the mitogenic activity seen in cord blood, AFP purified from pooled AF significantly synergizes with growth factors to increase cell proliferation markedly.

Characterization of human alpha fetoprotein charge microheterogeneity during fetal development

Aliquotes of human amniotic fluid (AF), fetal serum (FS), and cord blood (CB) were obtained as by-products of routine clinical diagnostic procedures at term or in the second trimester of pregnancy. When samples of CB were applied to a pH 5.5-4 chromatofocusing gradient, three isoforms of AFP could be resolved; a pl 4.57 form (isoform IA, 52% AFP), a pl 4.27 form (isoform IB, 43% AFP), and one species that was bound to the column but could be eluted with 1.0 M NaCl (isoform II, pl less than 4.00, 5% AFP). Term AF displayed a profile similar to that observed in term CB. When samples of 15-20-week gestation AF were chromatofocused, the immunoreactive AFP recovered was distributed between isoform IA and IB (60%) and isoform II (40%). FS and AF obtained from same pregnancy (23-26 weeks) displayed an identical chromatofocusing profile. Aliquotes of AF subjected to conA revealed 83% reactive variants compared with greater than 95% reactive variants for CB. FS displayed a conA profile identical to CB. When individual CB charge isoforms were isolated and subjected to conA analysis, greater than 97% of the AFP bound to conA. In contrast, when AFP isoform IA and IB were isolated from midgestation AF, approximately 22% of the AFP did not bind to the lectin while 100% of isolated AFP isoform II eluted as the reactive variant. These data suggest that human AFP exists as at least three charge and two lectin variants and that the charge profile may change during fetal development.

Colon cancer in pregnancy with elevated maternal serum alpha-fetoprotein level at presentation

A case of colon cancer in pregnancy is presented in which the maternal serum alpha-fetoprotein level was elevated. Failure to evaluate colon cancer as a cause of the elevated maternal serum alpha-fetoprotein may have accounted for the poor outcome.

The relationship between maternal serum and amniotic fluid alpha-fetoprotein in women undergoing early amniocentesis

alpha-Fetoprotein levels were measured on 148 paired samples from the maternal serum and amniotic fluid in women greater than or equal to age 35, who were undergoing early amniocentesis (12 to 14 weeks) for chromosomal analysis. These 148 women were white, weighed less than 200 pounds, had no serious medical problems, and did not have a fetal abnormality detected by ultrasonography or karyotype analysis. There was a significant rise in the maternal serum alpha-fetoprotein concentration from 12 to 14 weeks' gestation. Amniotic fluid alpha-fetoprotein peaked at 13 weeks and then significantly declined by 14 weeks' gestation. Similar to reports from normal pregnancies at 16 and 17 weeks, we found no correlation between the maternal serum and amniotic fluid alpha-fetoprotein levels between 12 and 14 weeks. Amniotic fluid alpha-fetoprotein levels cannot be predicted by levels in the maternal serum in pregnancies between 12 and 14 weeks' gestation.

Plasma protein binding of drugs in pregnancy and in neonates

Plasma protein binding of drugs has important implications for drug disposition and action since it is the first, and controlling, step in drug distribution. Physiological changes in pregnancy include significant changes in plasma composition which affect drug binding and subsequent drug response; the extent of these changes depends on the stage of gestation. Both albumin and alpha 1-acid glycoprotein fractions are reduced, and consequently the binding of both acidic and basic drugs may be affected. This may lead to difficulties in maintaining adequate plasma concentrations of highly protein-bound drugs, since the measurement of total drug concentration in plasma may no longer be a valid indicator for dose adjustment. The newborn infant displays a continually changing plasma profile. The presence of fetal proteins and endogenous substrates known to interfere with drug binding can lead to unexpected complications due to a higher than expected 'free' drug fraction. Furthermore, a decrease in the affinity of albumin for bilirubin during this period may lead to bilirubin displacement by drugs such as diazepam, sulphonamides and salicylate, resulting in clinical jaundice which would not occur beyond the neonatal period. Plasma composition and its effect on drug binding should be taken into account when prescribing highly protein bound drugs with narrow therapeutic: toxic ratios.

A comparison between the composition of maternal peripheral plasma and plasma collected from the retroplacental compartment at caesarean section. A study on protein and steroid hormones and binding proteins

In the pregnant uterus unique immunological conditions must prevail. Since compounds of possible fetoplacental origin may modulate the local maternal immunological response, higher concentrations of such compounds in the vicinity of the conceptus might be expected. We have measured the concentrations of several compounds in peripheral and retroplacental plasma, mainly by immunological methods, from women delivered by caesarean section in pregnancy week 38-40. Significantly higher (P less than 0.001) retroplacental concentrations were found for human placental lactogen, prolactin, alpha-fetoprotein, tissue polypeptide antigen, non-conjugated estriol and progesterone. Peripheral plasma levels were significantly higher for cortisol (P less than 0.01), transcortin (P less than 0.001) and sex-hormone binding globulin (P less than 0.002). No difference was found for albumin, alpha 2-macroglobulin, estradiol, placental alkaline phosphatase and human chorionic gonadotrophin. Significant correlations between retroplacental and maternal peripheral plasma levels were found for progesterone, cortisol, estradiol, estriol, transcortin, sex-hormone binding globulin, prolactin, human placental lactogen, human chorionic gonadotrophin, placental alkaline phosphatase, albumin and alpha 2-macroglobulin. There were also significant correlations between estradiol and sex-hormone binding globulin as well as transcortin in peripheral maternal plasma.

Type III congenital cystic adenomatoid malformation of the lung: another cause of elevated alpha fetoprotein?

In this report we document the first observation of highly elevated alpha fetoprotein (AFP) levels in the amniotic fluid of a 23-week gestation male fetus with cystic adenomatoid lung malformation (CCAML) Type III and caudal regression. The increase of AFP levels may be related to the presence of tumor-like lung masses of embryonic origin.

Inhibition by alpha-fetoprotein fractions of hemagglutination reactions between A and B antigens of human red blood cells and specific antisera

It is shown that fetal alpha-fetoprotein (AF)-rich fractions, isolated by chemical methods, can inhibit the agglutination reaction of human AB red blood cells (RBC) with specific antisera. Hemagglutination was not inhibited by other amniotic fluid or umbilical cord serum proteins in equivalent concentrations or by other pregnancy-associated hormones. The inhibitory effect is related to the amount of antibodies and AF fractions. It seems that AF interferes with the interaction between the antibody and the cell-surface antigens by preventing the binding of the antibodies to the cells. It is suggested that the ability of AF to inhibit hemagglutination reactions in vitro may play a role during pregnancy on the immune reaction between anti-A and anti-B antibodies and the corresponding RBC antigens, as well as on the manifestations or hemolytic disease of the newborn.

Suppressive effect of pregnancy on the development of experimental allergic encephalomyelitis in rabbits

In the present study we have investigated the influence of pregnancy on the induction and development of experimental autoimmune encephalomyelitis (EAE) in rabbits in relation to the time of gestation. Randomly bred rabbits were immunized with encephalitogenic bovine brain homogenate in complete Freund's adjuvant before or during pregnancy. The appearance of EAE was delayed and occurred only after delivery, abortion, or fetal resorption. The incidence of the disease was lower and the duration longer. The levels of antibodies to myelin basic protein, an autoantigen of EAE, as measured by solid phase radioimmunoassay, were lower in the pregnant rabbits as compared to the nonpregnant animals. The suppressive influence of pregnancy on the induction and the development of EAE confirms previous reports demonstrating amelioration of autoimmune diseases and other immunological reactions during the second half of human pregnancy. This effect might be partially attributed to the increased level of alpha-fetoprotein (AFP) and/or other pregnancy-associated factors in maternal serum.

Human alpha-fetoprotein-rich fraction inhibits galactocerebroside antibody-mediated lysis of oligodendrocytes in vitro

Polyclonal rabbit antiserum to galactocerebroside (anti-GalC) produces titer-dependent lysis of cultured Percoll-isolated bovine and rat oligodendrocytes. In this study anti-GalC produced complement-dependent lysis of 76% of the bovine cells and 65% of the rat cells maintained for 3 to 6 days in vitro. With the concomitant addition of human umbilical cord serum fractions containing fetal alpha-fetoprotein (AFP), lysis was decreased to 31% and 39%, respectively. Control antisera (anti-complete Freund's adjuvant/albumin) showed a cytotoxicity index of 15% for bovine cells and 23% for rat cells. Neither albumin, nor normal human serum, nor any of several pregnancy-associated hormones reduced the lysis produced by anti-GalC. AFP-rich fraction reduced oligodendrocyte lysis when mixed with anti-GalC or complement, but not when first incubated with the cells. Similar findings were obtained when AFP was assayed in specific oligodendrocyte radioimmunoassays utilizing anti-GalC antibody. Our experiments indicate that AFP activity may result from its binding to anti-GalC antibody; it is possible that the Fc portion of the antibody is involved. These data provide in vitro evidence of a possible immunosuppressive role of AFP in the central nervous system.

Diagnostic value of tumoral markers in serous effusions: carcinoembryonic antigen, alpha1-acidglycoprotein, alpha-fetoprotein, phosphohexose isomerase, and beta 2-microglobulin

In order to discriminate between benign and malignant effusions, the value of carcinoembryonic antigen (CEA), alpha 1-acidglycoprotein (AGP), alpha-fetoprotein (AFP), phosphohexose isomerase (PHI), and beta 2-microglobulin (B2M) has been estimated in serous effusions in a group of 106 patients, 30 with a malignant and 76 with a benign effusion. Mean CEA and AGP levels in malignant effusions were significantly higher than in benign effusions; no significant differences of mean PHI, AFP and B2M levels of benign and malignant effusions were found. CEA level estimations were useful for confirming malignancy in 27% of malignant effusions but in only 7.5% of all effusions, and AGP and PHI for excluding it in 37.5 and 36.0% of all effusions, respectively. With the combination of CEA with AGP or PHI, a correct diagnosis was achieved in only 45 and 44% of all effusions, respectively. The combination of AFP or B2M with CEA, AGP or PHI did not improve the discriminative value for differentiating malignant and benign effusions.

Influence of alpha-fetoprotein on the in vitro and in vivo immune response to acetylcholine receptor

Alpha-fetoprotein (AFP) derived from amniotic fluid and both maternal and umbilical cord sera but not from hepatoma, blocks the binding of serum acetylcholine receptor (AChR) antibody from patients with myasthenia gravis (MG) and animals with experimental autoimmune MG (EAMG) to AChR preparations as measured by a radioimmunoassay. AFP also inhibits the AChR and mitogen induced in vitro proliferative response of lymphocytes obtained from animals with EAMG. Laboratory animals repeatedly injected with AFP fail to develop EAMG in response to sensitization with AChR. Animals with established EAMG show clinical improvement in response to AFP treatment. AChR antibodies are suppressed in such AFP-treated animals. AFP is present in increased amounts during pregnancy and thus could contribute to remissions during the second half of pregnancy in patients with MG. The rapid decrease in levels of AFP during the post-partum period may also be partly responsible for relapses seen during this period. AFP may also be responsible for the appearance of transitory neonatal MG only sometime after birth and in only a minority of cases.

alpha-Fetoprotein in the routine clinical laboratory: evaluation of a simple radioimmunoassay and review of current concepts in its clinical application

We have assessed the clinical utility of a radioimmunoassay for alpha-fetoprotein (AFP). The method, which relies on ammonium sulfate precipitation for the separation of "bound" and "free" radiolabeled antigen, can be completed in one working day. The assay is specific for AFP, has a sensitivity of < 10 ng/ml, and has intra- and inter-assay precision of 5--8% and 9--11%, respectively. We have conducted a three-year study of 472 pregnancies in which physicians wished to detect neural tube defects, and of 400 non-pregnant patients to assess the value of serum AFP as a marker for certain benign and malignant diseases. Six of 6 fetal open neural-tube defects (NTD's) and 3 of 3 intrauterine fetal deaths were correctly identified by their association with marked AFP elevations in both maternal serum and amniotic fluid. Thirty non-pregnant patients were found to have AFP elevations greater than 20 ng/ml. Malignancies associated with these elevations were hepatoma, germ cell tumors, Wilms' tumor, and carcinoma of unknown origin. Carcinoma metastatic to the liver was not associated with AFP elevations. In AFP-associated tumors we found serial measurements of serum AFP to be of value in assessing therapeutic response. Benign diseases associated with AFP elevations included neonatal hepatitis, viral hepatitis, fulminant toxic hepatitis, and cryptogenic cirrhosis.

Inhibitory effect of alpha-fetoprotein on the binding of myasthenia gravis antibody to acetylcholine receptor

The binding of myasthenia gravis antibody acetylcholine receptor (AcChoR) as measured in vitro by Radioimmunoassay with 125I-labeled alpha-bungarotoxin (alpha-BuTx), can be blocked by amniotic fluid, maternal serum, and umbilical cord serum. This inhibitory effect is due to alpha-fetoprotein present in high concentrations in amniotic fluid and serum, as shown by: (i) selective removal of several components from amniotic fluid and serum; (ii) selective addition of different components present in amniotic fluid and serum, including alpha-fetoprotein, to be radioimmunoassay; (iii) correlation between the inhibitory effect of both amniotic fluid and serum and between the amounts of alpha-fetoprotein they contain; (iv) blocking of the alpha-fetoprotein in vitro suggests a similar effect in vivo in pregnant women with myasthenia gravis. This effect may explain in part the variability in the development of neonatal myasthenia gravis in the babies, due to transplacental transfer of maternal anti-AcChoR antibody, only after delivery and only in the minority of the cases. It also may explain the appearnace of remissions in females with myasthenia gravis during the second and third trimesters of pregnancy. Similar phenomena observed during pregnancy in other autoimmune and immunopathogenic diseases also might be attributed to activity of alpha-fetoprotein.

Significance in neonatal myasthenia gravis of inhibitory effect of amniotic fluid on binding of antibodies to acetylcholine receptor

The effect of amniotic fluid on the binding of anti-acetylcholine receptor (anti-AChR) antibodies from myasthenia gravis (MG) patients to AChR preparations was examined by radioimmunoassay using 125I-labelled alpha-bungarotoxin. Human amniotic fluid from healthy women in their second trimester inhibited the in-vitro interaction between antibody and antigen. This finding suggests that during pregnancy there is a similar inhibitory effect in MG on the in-vivo binding of maternal anti-AChR antibodies, transferred through the placenta, to AChR at the fetal neuromuscular junction. The presence of feto-placental inhibitory factors may explain the development of transitory muscular weakness only after birth and only in the minority of the babies born to myasthenic mothers.

Inhibition of blastic transformation and immunoglobulin release in lymphocytes cultured in the presence of alpha-fetoprotein (AFP)

Blastic transformation of phytohemagglutinin-stimulated lymphocytes in cultures containing various concentrations of homogenous alpha-fetoprotein (AFP) was studied. It was found that AFP in concentrations of 4-12 microgram/ml inhibits both blastic transformation and immunoglobulin release (IgA, IgG) in lymphocyte cultures. It is suggested that AFP plays an important role in immunoregulation during the fetal life.

Bovine fetus-specific serum proteins. Purification and characterization of alpha1-fetoprotein and immunological identification of alpha2- and beta-fetoproteins

Bovine alpha1-fetoprotein was isolated from fetal calf serum by successive procedures of concanavalin A-Sepharose chromatography, DEAE-Sephadex chromatography, SP-Sephadex chromatography and preparative disc polyacrylamide gel electrophoresis. The bovine alpha1-fetoprotein preparation was considered homogeneous by several physicochemical and immunochemical criteria. Bovine alpha1-fetoprotein has a molecular weight of 68 000 with an amino acid composiotn similar to that of other mammalian alhpa1-fetoprotein. In addition, bovine alpha1-fetoprotein was shown to exist as two distinct variants on the basis of carbohydrate heterogeneity. alpha2-Fetoprotein and a new beta-fetoprotein were immunologically identified in fetal calf serum. These fetoproteins, like alpha1-fetoprotein, were not detectable in non-pregnant cow serum by immunoelectrophoresis.

Radioimmunoassay of ovine alpha-fetoprotein

Highly purified ovine alpha-fetoprotein (AFP) was used both for radioisotope labelling and as the reference standard in the double antibody radioimmunoassay of ovine AFP. The sensitivity of the assay is 2 ng/ml which is about 8000 times more sensitive than radialimmunodiffusion assay. The assay is of sufficient sensitivity to quantitate AFP in normal adult sheep serum, pregnancy serum, amniotic fluid and fetal lamb serum.

alpha-Fetoprotein values in monkey (Macaca mulatta) pregnancy

The pregnant rhesus monkey's (Macaca mulatta) potential as a model for understanding the dynamics of alpha-fetoprotein (AFP) metabolism in human pregnancy was evaluated. AFP levels in maternal and fetal serum and amniotic fluid were determined by radioimmunoassay. Significant correlations were found between decreasing maternal serum, fetal serum and amniotic fluid AFP concentrations and increasing gestational age. However, these data are not consistent with the AFP changes reported in human pregnancy. It appears that this animal has limited applicability as a model in this aspect of human pregnancy.

Watery diarrhea syndrome in an adult with ganglioneuroma-pheochromocytoma: identification of vasoactive intestinal peptide, calcitonin, and catecholamines and assessment of their biologic activity

A case of adult ganglioneuroma-pheochromocytoma with an associated watery diarrhea syndrome is reported. High levels of vasoactive intestinal peptide (VIP) were found in preoperative serum and in tumor tissue. The serum VIP levels fell to normal, and the watery diarrhae syndrome completely ceased following removal of the tumor. In addition to containing VIP, the tumor was rich in catecholamines, and calcitonin. Peptide hormone-containing extracts and catecholamine extracts from the tumor both activated the adenyl cyclase system and increased lipolytic activity in a preparation of isolated rat fat cells. The findings in this patient further link VIP with neural crest tissues, and suggest the importance of determining catecholamine levels in patients with the watery diarrhea syndrome.

Immunochemical purification and characterization of ovine alpha-fetoprotein

Ovine alpha-fetoprotein was successfully isolated from fetal sheep serum by using rabbit anti-ovine alpha-fetoprotein linked to an agarose immunoadsorbent column. Antibody used in this affinity chromatography column was produced by immunizing a rabbit with highly purified alpha-fetoprotein-antibody complex to yield a monospecific antiserum to ovine alpha-fetoprotein. Following affinity chromatography, alpha-fetoprotein was further purified by preparative polyacrylamide disc gel electrophoresis ultimately yielding a 105-fold purification. The purified alpha-fetoprotein was homogeneous on analytical polyacrylamide disc gel electrophoresis. Ovine alpha-fetoprotein was found to be immunochemically related to human alpha-fetoprotein and to exhibit a molecular weight and amino acid composition similar to other mammalian alpha-fetoproteins.