The uptake of alpha-foetoprotein by C-1300 mouse neuroblastoma cells

Anti-Gene IGF-I Vaccines in Cancer Gene Therapy: A Review of a Case of Glioblastoma

OBJECTIVE

Vaccines for the deadliest brain tumor - glioblastoma (GBM) - are generally based on targeting growth factors or their receptors, often using antibodies. The vaccines described in the review were prepared to suppress the principal cancer growth factor - IGF-I, using anti-gene approaches either of antisense (AS) or of triple helix (TH) type. Our objective was to increase the median survival of patients treated with AS and TH cell vaccines.

METHODOLOGY

The cells were transfected in vitro by both constructed IGF-I AS and IGF-I TH expression episomal vectors; part of these cells was co-cultured with plant phytochemicals, modulating IGF-I expression. Both AS and TH approaches completely suppressed IGF-I expression and induced MHC-1 / B7 immunogenicity related to the IGF-I receptor signal.

RESULTS

This immunogenicity proved to be stronger in IGF-I TH than in IGF-I AS-prepared cell vaccines, especially in TH / phytochemical cells. The AS and TH vaccines generated an important TCD8+ and TCD8+CD11b- immune response in treated GBM patients and increased the median survival of patients up to 17-18 months, particularly using TH vaccines; in some cases, 2- and 3-year survival was reported. These clinical results were compared with those obtained in therapies targeting other growth factors.

CONCLUSION

The anti-gene IGF-I vaccines continue to be applied in current GBM personalized medicine. Technical improvements in the preparation of AS and TH vaccines to increase MHC-1 and B7 immunogenicity have, in parallel, allowed to increase in the median survival of patients.

First report of the unique expression of RECAF (receptor for alfa feto-protein) in adult B-NHL/CLL patients

Background

Lymphoproliferative disorders (LPDs) are a heterogeneous group of diseases characterized by an uncontrolled production of monoclonal lymphocytes. RECAF is the receptor for alpha-fetoprotein, which is re-expressed on malignant cells, thus serving as a broad-spectrum tumor marker.

Methods

The current study is a retrospective study carried out on 200 archival bone marrow trephine biopsy specimens [60 normal control (NC), 38 pathological control (PC) and 102 lymphoproliferative diseases (LPD) specimens]. RECAF expression was assessed using immunohistochemistry.

Results

The percentage of cells that are positive for RECAF was significantly higher in the LPD group than in the NC group (P=0.007), while there was no significant difference between non-Hodgkin lymphoma (NHL) patients and PC regarding the number of RECAF positive cells (P=0.1). RECAF showed a unique expression pattern among the different subtypes of LPD. None of the hairy cell leukemia (HCL) expressed RECAF, while the highest percentage was seen in follicular lymphoma (FL) and diffuse large B cell lymphoma (DLBCL) (P=0.001). Compared to routine histopathology, RECAF was more sensitive in detecting bone marrow (BM) infiltration in FL, mantle cell lymphoma (MCL), and DLBCL (P=0.01).

Conclusion

RECAF is significantly expressed in the BM of NHL/chronic lymphocytic leukemia (CLL) patients. RECAF shows a unique expression pattern among the different subtypes of LPD. Furthermore, RECAF may help to detect bone marrow infiltration in lymphoma cells. This may help in the diagnosis, follow-up, and targeting of LPD.

Increased alpha-fetoprotein receptor in the serum of patients with early-stage breast cancer

The alpha-fetoprotein (afp) receptor (recaf) is an oncofetal antigen found in most types of cancer. Using a competitive radioimmunoassay, we measured the concentration of serum recaf in three sets of samples.Set 1 was blind and consisted of 119 normal subjects, 43 breast cancer patients (stages i and ii), and 20 patients with benign breast conditions. In this set, the assay discriminated normal from cancer samples with a receiver operating characteristic for the area under the curve (ROC(AUC)) of 0.983; with 95% specificity and 93% sensitivity at a cut-off of 4.6 K (arbitrary) recaf units; and with 72% sensitivity and 100% specificity at a cut-off of 7.3 K units. At 7.3 K units, the specificity for benign breast conditions was 85%, and the sensitivity was 72% (ROC(AUC) was 0.773). Carcinoembryonic antigen and cancer antigen 15-3 respectively showed 39% and 41% sensitivity, with 95% specificity in comparisons of normal with cancer samples, and 34% and 44% sensitivity, with 85% specificity in comparisons of benign with cancer samples. Set 2 consisted of 353 normal, 30 benign, and 64 cancer samples (stages ii and iii). The recaf assay sensitivity in discriminating normal from cancer samples was 97%, with 97% specificity. Benign compared with cancer samples showed 87% sensitivity, with 97% specificity. Set 3 included only 40 normal and 40 cancer samples. The assay sensitivity was 89%, with 100% specificity. Sets 2 and 3 were not tested with carcinoembryonic antigen and cancer antigen 15-3.These results strongly suggest that the recaf assay could be used for detecting breast cancer in its early stages.

Review of the adenocarcinoma cell surface receptor for human alpha-fetoprotein; proposed identification of a widespread mucin as the tumor cell receptor

The identification of a tumor cell receptor for alpha-fetoprotein (AFP) has long been sought in the field of medicine. The uptake and endocytosis of AFP by rat tumor cells in 1983 sparked a series of confirmatory reports which were extended to include multiple tumor types in rats, mice, and humans. The following year, French investigators characterized the binding properties of the AFP receptor but they did not purify and characterize the receptor. It was not until 1991-1992 that an AFP receptor was partially purified and characterized from both human monocytes and breast cancer cells. By 1993, monoclonal antibodies had been raised against the "AFP receptor" derived from breast cancer extracts with claims that the receptor was a widespread oncoprotein biomarker for cancer. To date, that receptor has yet to be identified due to its complex multimeric structure and carbohydrate composition. The present report will review the literature of the multiple AFP receptors previously including their cellular uptake, transmembrane passage, and partial biochemical characterization. . In addition, evidence derived from computer modeling, proteolytic/fragmentation cleavage patterns, domain structure analysis, and protein binding software analysis will be presented in a proposed identification of a widespread protein/gene family of transmembrane proteins which fits many, if not most, of the criteria attributed to the AFP receptor. The proposed receptor protein family is tentatively identified as an epithelial cell surface mucin constituting one (or more) of many classes of single-pass transmembrane proteins. Present data do not support the concept that the AFP receptor is a "universal" tumor receptor and/or biomarker, but rather a widespread mucin protein that functions primarily in protecting and lubricating epithelial mucosal layers, and engaging in signal transduction; the mucin only binds AFP as a molecule serving in a subordinate or ancillary function.

Review of the putative cell-surface receptors for alpha-fetoprotein: identification of a candidate receptor protein family

The identification of a receptor for alpha-fetoprotein (AFP) has long been sought in the field of medicine. The uptake and endocytosis of AFP by rat tumor cells in 1984 sparked a series of confirmatory reports and the original studies were then extended to include multiple tumor types in rats, mice, and humans. The following year, French investigators partially characterized the binding properties of the AFP receptor, but they were not able to purify the receptor. It was not until 1991-1992 that an AFP receptor was partially purified and characterized from both human monocytes and breast cancer cells. By 1993, a monoclonal antibody had been raised against the AFP receptor produced from a breast cancer extract with claims that the receptor was a widespread (universal) oncofetal biomarker for cancer. However, that receptor has yet to be cloned and/or purified due to its complex multimeric binding interactions and associations. The present report will review the literature of the multiple putative AFP receptors described to date, the cellular uptake and endocytosis of AFP, and the biochemical characterization of these putative cell-surface proteins. In addition, evidence derived from computer modeling, proteolytic degradation patterns, and amino acid sequence analysis will be presented in a proposed identification of a family of multi-ligand binding receptors; this family fits many, if not most, of the criteria required for an AFP receptor. The purposed receptor protein family is tentatively identified as the Scavenger receptors which comprise several classes of single- and double-pass integral transmembrane proteins. Present data do not support the concept that the AFP receptor is a "universal" tumor receptor and/or biomarker.

Cytoplasmic alpha-fetoprotein functions as a co-repressor in RA-RAR signaling to promote the growth of human hepatoma Bel 7402 cells

The role of AFP in the retinoic acid-RAR signaling pathway was investigated in human hepatoma Bel 7402 cells. The results showed that AFP and RAR-beta were co-localized and interacted in cytoplasm. AFP may inhibit translocation of RAR-beta into the nucleus via competitive binding to RAR-beta with ATRA, which was reversed by AFP-siRNA transfection. Our data suggest that the ATRA resistance of Bel 7402 cells is at least in part attributable to their high level of cytoplasmic AFP. Thus, by counteracting the effect of AFP, it may be possible to increase the sensitivity of tumor cells to ATRA.

Human alpha-fetoprotein contains potential heterodimerization motifs capable of interaction with nuclear receptors and transcription/growth factors

Alpha-fetoprotein (AFP) serum levels in man have long been utilized as a tumor marker and as a birth defect screening agent in the clinical laboratory. Although the physiological role of AFP has remained obscure, the stereotypic carrier/transport function of a fetal counterpart to albumin has been attributed to this oncofetal protein. However, reports from a multitude of investigators in the last decade have provided a rationale to reconsider and extend the biological role of AFP to include cell growth modulation during development. Previously, a leucine zipper-like (heptad) motif, which mimicked that found in the steroid/thyroid receptor superfamily, was postulated for portions of the third domain of AFP. The present report proposes the presence of additional potential heterodimerization sites for the nuclear receptor superfamily members and other growth factors in the second and third domains of human AFP.

Alpha-fetoprotein structure and function: relevance to isoforms, epitopes, and conformational variants

Mammalian alpha-fetoprotein (AFP) is classified as a member of the albuminoid gene superfamily consisting of albumin, AFP, vitamin D (Gc) protein, and alpha-albumin. Molecular variants of AFP have long been reported in the biomedical literature. Early studies identified isoelectric pH isoforms and lectin-binding variants of AFP, which differed in their physicochemical properties, but not in amino acid composition. Genetic variants of AFP, differing in mRNA kilobase length, were later extensively described in rodent models during fetal/perinatal stages, carcinogenesis, and organ regeneration. With the advent of monoclonal antibodies in the early 1980s, multiple antigenic epitopes on native AFP were detected and categorized, culminating in the identification of six to seven major epitopes. During this period, various AFP-binding proteins and receptors were reported to inhibit certain AFP immunoreactions. Concomittantly, human and rodent AFP were cloned and the amino acid sequences of the translated proteins were divulged. Once the amino acid composition of the AFP molecule was known, enzymatic fragments could be identified and synthetic peptide segments synthesized. Following discovery of the molten globule form in 1981, the existence of transitory, intermediate forms of AFP were acknowledged and their physiological significance was realized. In the present review, the various isoforms and variants of AFP are discussed in light of their potential biological relevance.

Alpha-fetoprotein in human fetal cerebrospinal fluid

Alpha-fetoprotein (AFP) is a fetal glycoprotein. It has been ascribed a regulatory function of growth factor responses and immune functions. The concentrations of AFP and albumin (ALB) are highly variable in fetal serum and CSF and change with gestational age. The AFP index=[AFP(CSF)/AFP(SERUM)]/[ALB(CSF)/ALB(SERUM)] was determined in six normal fetuses at gestational age 17-23 weeks and found to be independent of gestational age and close to unity, mean 0.90+/-0.11 (S.D.). The ratio of CSF-serum concentrations of AFP and ALB both decreased significantly (p<0.05) with gestational age. The mean fraction of AFP being non-reactive with concanavalin A was 1.7% in serum and 1.9% in CSF, suggesting a common hepatic origin of AFP in both compartments. In conclusion, the concentration of AFP in CSF seems to be determined largely by the serum-CSF concentration gradient in normal fetuses. This finding, combined with the remarkable constancy of the AFP index compared to the highly variable absolute concentrations of AFP in both serum and CSF should make the AFP index the marker of choice when analyzing for intrathecal AFP synthesis during development and in pathological conditions.

Expression of serum albumin and of alphafetoprotein in murine normal and neoplastic primitive embryonic structures

Alphafetoprotein (AFP), a major serum protein synthesized during the embryo-fetal and postnatal period (in the yolk sac, then in the liver), is also an oncoprotein. The intracellular presence of AFP and of serum albumin (SA) in normal and neoplastic neural crest and neural tube derivatives was previously demonstrated. In this work we have studied the comparative expression of AFP and SA in primitive neuroectoblastic structures of mouse embryos (6 and 7 days "post coitum") and mouse teratocarcinomas (derived from the PCC4 cell line). Using immunofluorescence technique, antibodies to SA gave a positive reaction in embryos of 7 days, while AFP was not detected during this period. By mRNA in situ hybridization, SA mRNA gave a strong signal in both 6 and 7 day embryos, whereas AFP mRNA gave a weak signal only in 7-day embryos. The distribution of SA and AFP and their mRNAs was investigated in primitive neuroectoblastic structures of the teratocarcinomas by in situ hybridization and immunostaining. Only SA protein was detectable by immunostaining. SA mRNA gave a strong signal in differentiating structures as well as in undifferentiated cell clusters. AFP mRNA was observed only in differentiating structure. Dot-blot hybridization indicated that the level of SA transcripts was at least 6-fold higher than that of AFP transcripts in the teratocarcinomas investigated. In teratocarcinoma-bearing mice injected intraperitoneally with 125I-radiolabeled SA and AFP, significant accumulations of both SA and AFP were demonstrated in the tumors, SA being about 3-fold higher than that of AFP after normalization to quantity of uptake in liver. External in vivo photoscanning confirmed this relationship of accumulated radiolabeled proteins. The last observation could be useful in vivo for diagnosis of teratocarcinoma. We conclude that the expression of SA relative to AFP and the external cellular uptake of SA relative to AFP are similar in normal embryonic developing tissues and in the corresponding morphologically neoplastic tissues of the teratocarcinomas. The same SA:AFP relationship constitutes an oncofetal marker of primitive neuroectoblastic structures.

Alpha-fetoprotein binding proteins: implications for transmembrane passage and subcellular localization

Alpha-fetoprotein (AFP) is an oncofetal protein classified in a super-family together with albumin and Vitamin-D binding (Gc) protein which present as globular proteins comprised of three domains. Several subdomain regions on AFP have been previously proposed to serve as dimerization interfaces for nuclear receptors or perhaps other co-factors/inhibitors. The cellular uptake and internalization of AFP together with its subcellular compartmentalization is now well documented in a variety of cell types. A myriad of reports have emerged which have detected, identified, and characterized various binding proteins associated with AFP in different cellular compartments. However, the literature is devoid of any attempts to summarize, categorize, and relate these proteins to the various physiological activities attributed to this fetal protein. It is conceivable that AFP could interact and/or bind cytoplasmic chaperone proteins that normally escort nuclear factors or transcription co-factors through the cytoplasm toward organelle interfaces. A dual concept proposing binding or escort proteins for AFP together with subdomain dimerization interfaces on the AFP molecule can be reconciled into a composite hypothesis to formulate a rationale for the growth regulating properties ascribed to AFP during the last decade. Thus, AFP might serve as a modulator/modifier of various cell growth regulatory pathways during embryonic and fetal development in vertebrates.

Chemistry and biology of alpha-fetoprotein

Alpha-Fetoprotein (AFP) is a product of specific fetal tissues and of neoplastic cells of hepatocyte or germ cell origin in adults. This protein belongs to a gene family that is phylogenetically most closely related to serum albumin. Its primary, secondary, and tertiary structural aspects appear similar to the three-domain concept proposed for the latter protein. The primary sequence of AFP departs most widely from serum albumin in the first 135 amino acid residues, with about 42% of the remaining 590 residues of the human proteins being identical. Some evidence exists that there are limited sequence differences in the AFP of a given animal species. AFP shows considerable charge heterogeneity that appears to relate mostly to its glycoid moiety. The proteins of some species such as the rat show more pronounced heterogeneities than that of humans. The variations in extent and type of glycosylations are evidenced by differences in the binding to various lectins. These interactions are being extensively explored in attempts to differentiate the sources of the protein produced by various normal and neoplastic cells and may provide valuable diagnostic methods. AFP, like serum albumin, shows relatively strong binding affinities for a variety of ligands. The most notable difference is the strong preferential binding of polyunsaturated fatty acids by AFP. This protein may play a role in transporting these substances to developing and to malignant cells. Various agents affect the synthesis of this protein both by specific fetal tissues and by neoplastic cells. Marked differences in the responses of cells, particularly those of neoplastic types, are indicative of variations in the genetic factors responsible for control of its synthesis. The subject of the genomic repression of the synthesis of AFP seen in fetal life upon maturation of the liver and the reoccurrence of synthesis upon malignant conversion of hepatocytes and of certain germ cells are of particular interest. The regulation of the closely related AFP and albumin genes is providing a powerful and attractive model to examine molecular events in the activation and inactivation of specific genes during development and in oncogenic processes. Extensive measurements of AFP during pregnancy and in the course of neoplasias, notably hepatoma, are being made to aid in following changes in such developments. Various specific physiological roles for this protein are also being proposed. One of these is its possible action in the regulation of immune processes.(ABSTRACT TRUNCATED AT 400 WORDS)

Specific uptake of alpha-fetoprotein by malignant human lymphoid cells

We have studied the ability of human B- and T-lymphoblastoid cell lines, as well as of peripheral lymphoid cells from leukemia patients, to take up alpha-fetoprotein (AFP) and other serum proteins. Two technical approaches have been employed, both using fluorescent protein derivatives (FITC-proteins): microscopic examination of labelled cells using epifluorescent illumination and quantitation of endocytosed proteins by fluorescence-activated cell sorting (FACS). Compared to human resting T-lymphocytes, all T- and B-cell lines tested exhibited positive staining for fluoresceinated AFP and transferrin (Tf) and a significant increase, up to 100-fold, of the number of AFP and Tf molecules endocytosed per cell. Labelling was prevented or strongly diminished by a 100-fold excess of unlabelled protein. Preliminary results with peripheral lymphoid cells harvested from leukemia patients showed the presence of AFP- and Tf-positive cells in the blood of all patients examined. Intensity of labelling was related to the type of leukemia cells and/or the degree of cell maturation. Most cell lines exhibited positive staining for alpha 2-macroglobulin (alpha 2M) and also, to a lesser extent, for serum Vitamin D3 binding protein (DBP). In contrast, no labelling was observed with FITC-serum albumin (FITC-Alb) or FITC-ovalbumin (FITC-OVA). Comparative uptake of several FITC-proteins by a single cell population revealed significant quantitative and qualitative differences.