Cancer, differentiation and embryonic antigens: some central problems

Carcino-Evo-Devo, A Theory of the Evolutionary Role of Hereditary Tumors

A theory of the evolutionary role of hereditary tumors, or the carcino-evo-devo theory, is being developed. The main hypothesis of the theory, the hypothesis of evolution by tumor neofunctionalization, posits that hereditary tumors provided additional cell masses during the evolution of multicellular organisms for the expression of evolutionarily novel genes. The carcino-evo-devo theory has formulated several nontrivial predictions that have been confirmed in the laboratory of the author. It also suggests several nontrivial explanations of biological phenomena previously unexplained by the existing theories or incompletely understood. By considering three major types of biological development-individual, evolutionary, and neoplastic development-within one theoretical framework, the carcino-evo-devo theory has the potential to become a unifying biological theory.

The "life code": A theory that unifies the human life cycle and the origin of human tumors

Tumors arise from the transformation of normal stem cells or mature somatic cells. Intriguingly, two types of tumors have been observed by pathologists for centuries: well-differentiated tumors and undifferentiated tumors. Well-differentiated tumors are architecturally similar to the tissues from which they originate, whereas undifferentiated tumors exhibit high nuclear atypia and do not resemble their tissue of origin. The relationship between these two tumor types and the human life cycle has not been clear. Here I propose a unifying theory that explains the processes of transformation of both tumor types with our life cycle. Human life starts with fertilization of an egg by a sperm to form a zygote. The zygote undergoes successive rounds of cleavage division to form blastomeres within the zona pellucida, with progressive decreases in cell size, and the cleaved blastomeres then compact to form a 32-cell or a "64n" morula [n = 1 full set of chromosomes]. Thus early embryogenesis can be interpreted as a progressive increase in ploidy, and if the zona pellucida is considered a cell membrane and cleavage is interpreted as endomitosis, then the 32-cell morula can be considered a multinucleated giant cell (or 64n syncytium). The decrease in cell size is accompanied by an increase in the nuclear-to-cytoplasmic (N/C) ratio, which then selectively activates a combined set of embryonic transcription factors that dedifferentiate the parental genome to a zygotic genome. This process is associated with a morphologic transition from a morula to a blastocyst and formation of an inner cell mass that gives rise to a new embryonic life. If the subsequent differentiation proceeds to complete maturation, then a normal life results. However, if differentiation is blocked at any point along the continuum of primordial germ cell to embryonic maturation to fetal organ maturation, a well-differentiated tumor will develop. Depending on the level of developmental hierarchy at which the stem cell differentiation is blocked, the resulting tumor can range from highly malignant to benign. Undifferentiated tumors are derived from mature somatic cells through dedifferentiation via a recently described reprogramming mechanism named the giant cell life cycle or the giant cell cycle. This mechanism can initiate "somatic embryogenesis" via an increase in ploidy ranging from 4n to 64n or more, similar to that in normal embryogenesis. This dedifferentiation mechanism is initiated through an endocycle and is followed by endomitosis, which leads to the formation of mononucleated or multinucleated polyploid giant cancer cells (PGCCs), that is, cancer stem-like cells that mimic the blastomere-stage embryo. The giant cell life cycle leads to progressive increases in the N/C ratio and awakens the suppressed embryonic reprogram, resulting in mature somatic transformation into undifferentiated tumors. Thus, the increase in ploidy explains not only normal embryogenesis for well-differentiated tumors but also "somatic embryogenesis" for undifferentiated tumors. I refer to this ploidy increase as the 'life code". The concept of the "life code" may provide a simple theoretical framework to guide our immense efforts to understand cancer and fight this disease.

Nomenclature for cellular plasticity: are the terms as plastic as the cells themselves?

It is now recognized that cell identity is more fluid, and tissues more plastic, than previously thought. The plasticity of cells is relevant to diverse fields, most notably developmental and stem cell biology, regenerative medicine, and cancer biology. To date, a comprehensive and uniform nomenclature to define distinct cell states and their injury-induced interconversions has been elusive. The first Keystone Symposium devoted exclusively to cellular plasticity in regeneration and tumorigenesis was held on January 2019 in Keystone, Colorado, and featured a workshop on terminology in the cell plasticity field. Definitions for terms such as plasticity, de- and transdifferentiation, reversion, and paligenosis were discussed. Here, we summarize the content and tenor of the symposium and nomenclature-focused workshop with regard to terms in the field. We outline the challenges with current definitions and recommend best practices and approaches to developing an accurate and acceptable nomenclature in the future.

The Role of Metabotropic Glutamate Receptor 1 Dependent Signaling in Glioma Viability

Glioma refers to malignant central nervous system tumors that have histologic characteristics in common with glial cells. The most prevalent type, glioblastoma multiforme, is associated with a poor prognosis and few treatment options. On the basis of reports of aberrant expression of mGluR1 mRNA in glioma, evidence that melanoma growth is directly influenced by glutamate metabotropic receptor 1 (mGluR1), and characterization of β-arrestin-dependent prosurvival signaling by this receptor, this study investigated the hypothesis that glioma cell lines aberrantly express mGluR1 and depend on mGluR1-mediated signaling to maintain viability and proliferation. Three glioma cell lines (Hs683, A172, and U87) were tested to confirm mGluR1 mRNA expression and the dependence of glioma cell viability on glutamate. Pharmacologic and genetic evidence is presented that suggests mGluR1 signaling specifically supports glioma proliferation and viability. For example, selective noncompetitive antagonists of mGluR1, CPCCOEt and JNJ16259685, decreased the viability of these cells in a dose-dependent manner, and glutamate metabotropic receptor 1 gene silencing significantly reduced glioma cell proliferation. Also, results of an anchorage-independent growth assay suggested that noncompetitive antagonism of mGluR1 may decrease the tumorigenic potential of Hs683 glioma cells. Finally, data are provided that support the hypothesis that a β-arrestin-dependent signaling cascade may be involved in glutamate-stimulated viability in glioma cells and that ligand bias may exist at mGluR1 expressed in these cells. Taken together, the results strongly suggest that mGluR1 may act as a proto-oncogene in glioma and be a viable drug target in glioma treatment.

Non-Specifically Bound Immunoglobulins on Mouse Placental Cells

There seem to be some similarities between escape mechanisms employed by embryos and cancer cells from the maternal or tumor bearer's immune system. In the present study, we investigated the presence of hemagglutinins on placental cells and their relationship to circulating antibodies in mice immunized against sheep erythrocytes before mating. The results obtained demonstrated that placental cells may fix large quantities of maternal immunoglobulins. The hemagglutinins are probably fixed on placental cells by the Fc, since the combining sites of the antibody were free and able to react with the antigen in the « rosette » test. It was also demonstrated that placental tissue may fix up to 1/4 of the maternal circulating antibodies, while only 1/200 of them were transmitted to the fetuses. Some theoretical implications of the presence in the placenta of antibodies not directed against feto-placental antigens are also discussed.

Cancer Is to Embryology as Mutation Is to Genetics: Hypothesis of the Cancer as Embryological Phenomenon

Despite numerous advances in cell biology, genetics, and developmental biology, cancer origin has been attributed to genetic mechanisms primarily involving mutations. Embryologists have expressed timidly cancer embryological origin with little success in leveraging the discussion that cancer could involve a set of conventional cellular processes used to build the embryo during morphogenesis. Thus, this "cancer process" allows the harmonious and coherent construction of the embryo structural base, and its implementation as the embryonic process involves joint regulation of differentiation, proliferation, cell invasion, and migration, enabling the human being recreation of every generation. On the other hand, "cancer disease" is the representation of an abnormal state of the cell that might happen in the stem cells of an adult person, in which the mechanism for joint gene regulating of differentiation, proliferation, cell invasion, and migration could be reactivated in an entirely inappropriate context.

Oncofetal antigen/immature laminin receptor protein in pregnancy and cancer

The 37-kDa immature laminin receptor protein (iLRP) is a speciesconserved, universal immunogenic protein that is expressed in all thus-far examined embryonic and early fetal cells of inbred and outbred rodents. It has also been identified in human concepti. It is altered through normal maturation processes to become a non-immunogenic 67-kDa dimeric mature laminin receptor protein (mLRP) in mid-to late gestation in the mammalian fetus. This antigen ceases to be expressed as an active autoimmunogen in the full-term fetus and in the normal differentiating tissues and organs of the neonate or adult organism, apparently due to dimerization, but it is re-expressed as an immunogenic monomer in tumor cells. In this review, we highlight the known mechanisms of immune responses with particular emphasis on the possible role of the 37-kDa oncofetal antigen/immature laminin receptor (OFA/iLRP) in both pregnancy and cancer.

Heat Shock Protein Vaccines: From Bench to Bedside

Heat shock proteins (HSPs) are immunogenic, with the specificity of the immune response provided by the peptides that they chaperone. Binding of cell surface receptors by HSPs is central to the elicitation of the innate and adaptive immune responses obtained after vaccination and also plays a physiologic role in cross-priming. These effects of HSPs have been exploited in prophylaxis and therapy of cancer and infectious disease. The data obtained from murine studies have been translated into ongoing clinical trials of cancer of which the most recent results are provided here.

The flip side of immune surveillance: immune dependency

The growths of many and perhaps all tumors may be stimulated rather than inhibited by a quantitatively low level of immunity. The reason tumors have antigens may be that tumors do not develop in vivo in the absence of at least a minimal immune reaction; in this sense, cancer may be considered an autoimmune disease. This review, based largely on the work of our own laboratory, outlines the data showing that the titration of anti-tumor immunity exhibits the phenomenon of hormesis, i.e. the dose-response curve is non-linear such that low levels of immunity are generally stimulatory but larger quantities of the same immune reactants may inhibit tumor growth. Evidence is also reviewed that suggests that the immune response may vary qualitatively and quantitatively during progression, such that there seems to be, during oncogenesis, a very low level of immune reaction that aids initial tumor growth, followed by a larger reaction that may cause remission of early neoplasms, followed, if the neoplasm survives, by a relative immunologic tolerance to the tumor that may be dependent, at least in part, on suppressor cells. This knowledge may help to explain some clinical observations concerning the relationships among tumor types and the organ distribution of metastases.

Host recognition of fetal antigens: do they induce specific antibodies?

The purpose of this study was to ascertain whether the protection afforded to adult mice against the induction and growth of 3-methylcholanthrene-induced tumours by prior exposure to syngeneic fetal cells has an immunological basis. Adult CBA mice were inoculated with fetal cells according to a variety of protocols and the sera were tested for their ability to bind to fetal and adult tissue cells, using a staphylococcal protein A binding assay. All 10 sera tested showed some degree of binding though this varied from strong to weak, and there was some cross-reactivity with adult thymic cells but relatively little with adult spleen cells. Absorption studies were carried out with one of these sera and with two others raised against testicular and thymic cells, respectively. The absorption patterns obtained so far suggest that fetal cells possess at least three, and possibly up to five, distinct antigens. Although none of the anti-fetal sera were produced with a sensitizing protocol identical with that used in in vivo protection, some of them were so close as to suggest that protection is associated with, and perhaps causally related to, these IgG antibodies. The in vitro evidence presented here, together with the in vivo data of P. B. Medawar & R. Hunt, shows that antigens are shared between fetal cells and adult thymic and testicular cells. It therefore lends support to the notion that the production of a vaccine against anaplastic neoplasms, using immunogens derived from adult tissues, is within the realms of possibility.

Antibodies to fetal antigens associated with rodent tumours

Fetal antigens associated with a range of carcinogen-induced and naturally arising rat tumours have been identified by reaction with antibodies induced by sensitizing rats for fetal cells in various ways, including by multiparity and by immunizing syngeneic WAB/Not rats with fetal tissues. Antibodies recognizing fetal antigens have potential applications in addition to their use for typing tumour-associated products. These applications include their use as carriers for targeting antitumour agents such as cytotoxic drugs and immunomodulating agents. Accordingly, several methods for producing antibodies directed against 'oncofetal' antigens have been examined, including the development of anti-fetal antibody-secreting hybridomas.

Embryonic antigens in malignancy and pregnancy: common denominators in immune regulation

There is mounting that the majority of malignant tumours of humans and rodents carry embryonic determinants (EA) associated with the cell membrane. The evolutionary and developmental purpose of these determinants seems to be related to their biochemical and structural role in the cell membrane. True EAs are uniquely expressed on germinal, embryonic and some fetal cell membranes and are not expressed in adult tissues nor in regenerating tissues. The immunological role of EA in fetal development in utero is still obscure. It is known that maternal IgG and cytotoxic T lymphocytes are produced in response to EA expressed in utero. Immunoregulatory interactions between suppressor, helper and cytotoxic T lymphocytes sensitized to EA during pregnancy have been detected in mice and hamsters bearing a variety of tumours. The same immunological events may occur in humans. The biological product of the retrogenic process that leads to the expression of EA in the emerging malignant cell clone seems to be intimately associated with the promotion of tumour-protective immune responses in the host which mimic the immune responses in pregnancy aimed at protecting the EA+ fetus from maternal immune attack. The description of the immunoregulatory perturbations generated by EA during the induction of cancer may eventually provide effective and predictable attack points for immunological intervention in the control of malignancy. This paper describes methods for detecting EA and considers some immunoregulatory traits found in response to EA expression.

Heat shock proteins: the 'Swiss Army Knife' vaccines against cancers and infectious agents

The ability of heat shock proteins to: (a) chaperone peptides, including antigenic peptides; (b) interact with antigen presenting cells through a receptor; (c) stimulate antigen presenting cells to secrete inflammatory cytokines; and (d) mediate maturation of dendritic cells, makes them a one-stop shop for the immune system. These properties also permit the utilization of heat shock proteins for development of a new generation of prophylactic and therapeutic vaccines against cancers and infectious diseases.

Heat shock proteins: the fountainhead of innate and adaptive immune responses

The ability of heat shock proteins to (1) chaperone peptides, including antigenic peptides; (2) interact with antigen-presenting cells through a receptor; (3) stimulate antigen-presenting cells to secrete inflammatory cytokines; and (4) mediate maturation of dendritic cells, makes them a unique starting point for generation of immune responses. These properties also permit the use of heat shock proteins for development of a new generation of prophylactic and therapeutic vaccines against cancers and infectious diseases.

Heat shock proteins: the fountainhead of innate and adaptive immune responses

The ability of heat shock proteins to (1) chaperone peptides, including antigenic peptides; (2) interact with antigen-presenting cells through a receptor; (3) stimulate antigen-presenting cells to secrete inflammatory cytokines; and (4) mediate maturation of dendritic cells, makes them a unique starting point for generation of immune responses. These properties also permit the use of heat shock proteins for development of a new generation of prophylactic and therapeutic vaccines against cancers and infectious diseases.

Purification and partial characterization of 200 kDa oncofetal antigen from radiation induced murine lymphocytic lymphoma

1. A 200 kDa glycoprotein (gp200) oncofetal antigen was purified from solubilized membranes of a radiation-induced murine lymphocytic lymphoma cell line (XR11-5T), grown in syngeneic RFM mice, by successive gel chromatography of the active fraction on lentil lectin agarose, Q- and S-Sepharose and Superose-12 using an FPLC system. 2. A murine monoclonal antibody 115, produced by the syngeneic immunization of adult male C57BL/6N mice with 12-day mouse fetal cells, was used in a slot blot antibody assay to follow up the active fractions. 3. The purified glycoprotein has a pI of 5.4. 4. Treatment of radiolabeled gp200 with neuraminidase caused a slight reduction in size due to the removal of sialic acid groups and a shift in pI to 6.3. 5. Treatment of gp200 with different glycosidases shows that gp200 is susceptible to N- and O-glycanase but not to endoglycosaminidase H. 6. On extraction of gp200 with Triton X-114 it partitions exclusively into the detergent-rich fraction consistent with being an integral membrane protein.

T cell response to embryonal carcinoma F9 cells: induction and characterization of T cell receptor alpha beta+ double-negative cytotoxic T lymphocytes

We investigated the mechanism of T cell response to murine embryonal carcinoma F9 cells. Thy-1+, CD4-, CD8- (double-negative) cytotoxic effector cells were induced in spleen cells obtained from immune A.BY mice to F9 cells, and the cytotoxic activity was major histocompatibility complex (MHC)-unrestricted. Furthermore, CD4+ T cells were essential for the induction of double-negative cytotoxic T lymphocytes directed to F9 cells. Most of the double-negative cytotoxic T lymphocyte lines obtained by long-term culture of the effector cells had CD3 molecule and T-cell receptor beta chain on their cell surface, and the CD3 molecule was found to be involved in target cell recognition. The T cell receptor alpha beta+ double-negative cytotoxic T lymphocyte line (2A5) also lysed various tumor cells in a non-MHC-restricted manner, but did not lyse concanavalin A-stimulated blasts of 129 strain, from which F9 cells had originated. These results indicate that T cell receptor alpha beta+ double-negative cytotoxic T lymphocytes induced by F9 cells recognize a common antigen(s) expressed on F9 cells and other tumor cells but not minor histocompatibility antigens.

A long-term study of mortality in men who have undergone vasectomy

BACKGROUND

Vasectomy is a reliable and widely accepted method of contraception, but there is some uncertainty and few data about a possible long-term adverse effect on health.

METHODS

We examined the relation between vasectomy and mortality rates from cardiovascular disease, cancer, and all causes in a retrospective cohort of husbands of members of the Nurses' Health Study. In 1989 we obtained data by questionnaire on 14,607 men who had undergone vasectomy as of 1976 and 14,607 men who had not.

RESULTS

Among the men who were free of cancer at the start of the study, 1052 died: 446 of cardiovascular disease, 341 of cancer, and 265 of other causes. Vasectomy was associated with reductions in mortality from all causes (age-adjusted relative risk, 0.85; 95 percent confidence interval, 0.76 to 0.96) and mortality from cardiovascular disease (relative risk, 0.76; 95 percent confidence interval, 0.63 to 0.92). Vasectomy was unrelated to mortality from all forms of cancer (relative risk, 1.01; 95 percent confidence interval, 0.82 to 1.25). Among men who had a vasectomy at least 20 years earlier, the procedure had no relation to mortality from all causes (relative risk, 1.11; 95 percent confidence interval, 0.92 to 1.33) or that from cardiovascular disease (relative risk, 0.85; 95 percent confidence interval, 0.63 to 1.16). However, mortality from cancer was increased in men who had a vasectomy at least 20 years earlier (relative risk, 1.44; 95 percent confidence interval, 1.07 to 1.92). The excess risk of cancer in these men was due primarily to lung cancer. None of the observed associations were confounded by smoking habits, body-mass index, alcohol consumption, or educational level.

CONCLUSIONS

Vasectomy is not associated with an increase in overall mortality or mortality from cardiovascular disease. Our study also found no increase in overall mortality from cancer after vasectomy, but there was an apparent increase in the risk of cancer 20 or more years after vasectomy that requires further study.

Immunological screening of a glycoprotein antigen expressed by Zajdela ascites hepatoma cells on normal rat tissues and tumour cells

Expression of the glycoprotein MII2 antigen originally identified in Zajdela ascites hepatoma cells was investigated in several normal rat tissues and in more or less differentiated tumours using biochemical and immunological approaches. SDS-polyacrylamide gel electrophoresis followed by fluorography or immunoblotting with an antiserum raised against the purified MII2 antigen revealed that this antigen was absent from normal liver cells. ELISA assays, indirect immunofluorescence and immunoprecipitation experiments using the same antiserum showed that this glycoprotein was not expressed in various normal tissues such as liver, spleen, lung, pancreas, intestine and stomach, but it was unexpectedly detected in kidney and thymic tissues. However, the molecular weight of the antigens immunoprecipitated from kidney and thymus was lower than the one of MII2 (Mr of 60,000 versus 110,000-160,000 for purified MII2). No staining was observed in embryonic rat liver at 10 and 20 days of development. Moreover, this antigen was present on the surface of Morris hepatoma 7777, another rapidly proliferating and poorly differentiated hepatocellular carcinoma. In contrast, this antigen was not detected on the surface of in vitro Zajdela hepatoma cells (ZHC) or of partially differentiated hepatomas (Faza) which have recovered some hepatic functions. In addition, the MII2 antigen was found on the human non-hepatic HT-29 tumour cell line, under its undifferentiated form (HT-29 G+ subline). The possible relationships between the expression of this antigen and both the malignant transformation process and the differentiation process are discussed.

Isolation and partial characterization of a soluble oncofetal antigen from murine and human amniotic fluids

A soluble (cell-free) oncofetal antigen (OFA) was detected in murine and human amniotic fluids by immunostaining with the murine monoclonal antibody (MAb 115) produced by syngeneic immunization with mid-gestational mouse fetal cells. OFA was purified from the amniotic fluids by ammonium sulfate precipitation at 30-70% saturation, followed by successive gel chromatography of the OFA-containing fraction on Sephacryl-S300 HR, Q- and S-Sepharoses and lentil lectin agarose. The fraction eluted from the lentil lectin column gave a single band on SDS-PAGE of the same molecular weight as the membrane-bound OFA found on both fetal and tumor tissues of humans and several rodents. Both soluble and membrane-bound OFAs share several chemical characteristics, including binding to lentil lectin and wheat-germ agglutinin, molecular weight (44 kDa) and pI (6.8). Mild periodate oxidation of OFA did not affect its binding to MAb 115 in an enzyme-linked immunosorbent assay, indicating that the reactive epitope is a peptide.

Stress-induced proteins in immune response to cancer

Chemically induced tumors of inbred mice elicit immunity in animals in which the tumors are induced and in other animals of the same inbred stock. The immunity is specific for each tumor: even two tumors induced in one animal with the same carcinogen are not cross-reactive. Immunity to cancer has since been observed in the case of sarcomas and carcinomas induced by a number of chemical and physical carcinogens and in several species, including mice, rats, and guinea pigs. The nature of molecules which mediate immunity to tumors is a central question in cancer immunology. A small number of such molecules have been biochemically defined. Of these, some are viral antigens expressed in tumor cells, while the relationship of some others to viral antigens is unclear. A surprising majority of nonviral tumor antigens have turned out to bear homology with stress-induced proteins. Four families of such molecules are discussed: the gp96 (hsp100) and p84/86 (hsp90) antigens of chemically induced mouse sarcomas, hsp70 antigens of tumors obtained by transfection of normal rat fetal fibroblasts with an H-ras oncogene, and the albuminoid antigens of murine melanomas and a rat histiocytoma. (Albumin-like antigens are included among the stress-induced proteins because albumin, though constitutively expressed in adult tissues, is heat shock inducible in fetal liver.) Each of these antigens is a moderately abundant protein, present not only in tumors but also in normal tissues. Administration of each of these antigen preparations from the tumor, but not from normal tissue, renders the animal immune to challenge with live cells of the tumor from which the antigens are prepared. And yet, no structural differences in the antigens have been observed between normal tissues and tumors. It is suggested that these stress-induced proteins may not be tumor antigens per se, but may be carriers of immunogenic moieties such as short peptides. The stress-induced proteins may therefore serve either as antigen-presenting molecules like the MHC-encoded molecules or as accessory molecules in the presentation of antigens by MHC molecules. The ability of stress-induced proteins to bind to a variety of molecules, including peptides, is consistent with this possibility.

Photoimmunology: the mechanisms involved in immune modulation by UV radiation

Ultraviolet radiation (UVR) may be the most prevalent agent that man encounters in his environment. As a result, certain biological adaptations take advantage of the beneficial effects of UVR exposure, e.g. the photoactivation steps involved in vitamin D metabolism. In this regard, UVR plays an important role in maintaining our good health; however, it must be noted that UVR is potentially the most harmful naturally occurring agent in our environment. Thus, it appears that several mechanisms have evolved to protect us against the detrimental effects of UVR overexposure. Although epidermal melaninization or "tanning" may be the most obvious example of these processes, we would argue that adoptive mechanisms within the immune system also provide protection against UVR-induced skin damage. It is now known that UVR affects the distribution and functional activities of various immunocompetent cells within the skin, as well as modifying the production of inflammatory and hematopoietically active cytokines. This review will focus on the known mechanisms involved in the immune modulatory effects of UVR and how adoptive immune responses to UVR-induced skin damage contribute to specific pathological processes.

Decrease in glucokinase and glucose-6-phosphatase and increase in hexokinase in putative preneoplastic lesions of rat liver

Preneoplastic liver lesions were produced in female Wistar rats by oral administration of 2-acetylaminofluorene for 165 days succeeded by a carcinogen-free standard diet up to 420 days. During the treatment numerous altered hepatic foci (AHF) and hyperplastic nodules (HN) were detected histochemically by a focal decrease or lack of adenosine-5-triphosphatase and glucose-6-phosphatase (G-6-Pase) activities. In addition, the immunohistochemically demonstrable amount of L-type pyruvate kinase was clearly reduced. The histochemically demonstrated decrease of G-6-Pase was substantiated by microbiochemical determination of the enzyme activity in microdissected material. Moreover, during the experimental period a continuous decrease in glucokinase and an increase in hexokinase was detected microbiochemically within AHF and HN. These alterations indicate a shift in the carbohydrate metabolism from gluconeogenesis to glucose utilization and pentose-phosphate-pathway for biosynthesis of nucleic acids. Beside other oncofetal markers, HK may be used as indicator of the early stages of liver carcinogenesis.

Appearance of serum antibodies to rat yolk-sac carcinomas during the latent period prior to primary tumor development

Rat yolk-sac tumors were induced by intraperitoneal (i.p.) displacement of the visceral yolk sac in fetectomized W/Fu rats. Serum was obtained from each female rat prior to the pregnancy preceding the tumor-inducing procedure and then once a month during the induction period. The sera were analyzed for the presence of antibodies binding to cultured cells of one of the yolk-sac tumors. Sera were also assayed for complement-dependent cytotoxic antibodies on tumor cells. In rats that developed tumors, antibodies reacting specifically with the target tumor cells could be detected in all of 10 rats. Antibodies appeared before tumor detection in all animals but one, and in 6 rats as early as 11 to 25 weeks prior to tumor detection. Nine rats developed antibodies demonstrable in the binding assay and in 6 of those the antibodies appeared 8 to 25 weeks before the tumor became palpable. Analysis of the isotypes of the Ig that bound to tumor cells showed that IgG1 and IgG2b were most frequently present. In one rat IgG2a antibodies appeared one month before tumor detection followed by IgG1 and IgG2b antibodies detectable 4 weeks later. IgG2c and IgM antibodies were not detected in any of the rats. At dilution 1/10, sera of all 10 rats showed specific cytotoxicity to the tumor cells in the presence of added rabbit complement. In 9 of these animals antibodies were demonstrated 1 to 4 months prior to tumor detection.

5'-structural analysis of genes encoding polymorphic antigens of chemically induced tumors

We have proposed that the distinct tumor rejection antigens of chemically induced sarcomas in inbred mice belong to a family of Mr 96,000 glycoproteins (gp96). An identical 14-amino acid sequence was found at the amino terminus of gp96 from two antigenically distinct BALB/c sarcomas. Oligonucleotide probes derived from this sequence permitted isolation of 5' cDNA and genomic fragments coding for gp96. Three short exons interrupted by relatively long introns were identified at the 5' terminus of the gp96 gene. The first exon encodes a signal peptide, which is consistent with gp96 being a cell surface antigen. Southern blot analysis indicated that the gp96 family is encoded by a single gene, and 3-kilobase transcripts were detected in all normal and tumor cells tested. Nucleotide and deduced amino acid sequences from 311 base paris at the 5' terminus showed no homology with any known protein. The availability of molecular probes for the gp96 system permits analysis of the structural polymorphism of these antigens.

Differentiation-linked leukemogenesis in lymphocytes

Most human lymphoid malignancies preserve a pattern of gene expression reflecting their proliferative activity and the development level of clonal expansion and maturation arrest. Characteristics of leukemia and other cancer cells frequently considered to reflect aberrant differentiation may more often reflect clonal selection of cell types that are normally infrequent and transitory. The differentiation status of progenitor or mature lymphoid cells influences which genetic elements are at risk of being exploited, via mutation, recombination, or deletion, for clonal advantage. These alterations may frequently arise spontaneously as a consequence of the unique developmental and functional programs of lymphoid cells and have as a major phenotypic consequence the stabilization of transitory cellular phenotypes.

Tumor rejection antigens of chemically induced sarcomas of inbred mice

Chemically induced sarcomas of inbred mice are immunogenic in syngeneic hosts, and preimmunization with tumor cells leads to resistance to subsequent tumor transplants. The tumor rejection antigens (TRAs) that mediate this reaction are highly specific for each tumor; cross-protection between different syngeneic sarcomas is rare. Isolated membrane and cytosol fractions from two antigenically distinct BALB/c sarcomas, Meth A and CMS5, have TRA activity, and biochemical characterization of the active components from the cytosol and plasma membranes of these two tumors identified a glycoprotein of Mr 96,000. Immunization with unfractionated Meth A cytosol frequently leads to tumor enhancement, but the tumor-enhancing activity (TEA) is lost on fractionation and TRA activity becomes demonstrable. As Meth A and CMS5 lack expression of murine leukemia virus (MuLV) antigens or transcripts, MuLV-related antigens cannot be involved in the TEA or TRA activities of these tumors. In contrast to the lack of cross-reactivity between Meth A and CMS5 TRAs in transplantation tests, rabbit antiserum prepared against the Meth A Mr 96,000 antigen reacted with the CMS5 Mr 96,000 antigen. In view of the biochemical and antigenic similarities of Meth A and CMS5 TRAs, we propose that structurally related but distinct Mr 96,000 glycoproteins are expressed in chemically induced sarcomas and that these molecules are responsible for the individually specific immunogenicity of these tumors.

The implications of embryonic gene expression in neoplasia

The discovery that human as well as animal tumors generally expressed oncofetal antigens (OFAs) and that these antigens generate a variety of immune responses in the tumor-bearing host is of potential major significance in tumor biology. The concept of the reexpression of embryonic or fetal antigens (EAs) encoded by DNA, which is silent in adults but is essential in metazoan development, may mesh with the exciting concept of cancer causation. While this scenario is still only speculative, it provides an interesting forum for reviewing the current data concerning the role of OFAs in cancer processes. The literature describing OFAs and their embryonic counterparts, the EAs, in modern tumor and fetal immunobiology has become extensive and, unfortunately, is quite scattered. This article seeks to synthesize this complicated data base into a cogent presentation focusing on the immunological role of EAs and OFAs in fetal survival in utero and in tumor progression and regression, respectively. The immunogenicity and characteristics of the immune responses to EAs and OFAs will be presented and placed in perspective to the rapidly unraveling story of protooncogenes and oncogenes in tumor induction.

Distribution of type 1 and 2 blood group chains in normal and pathological odontogenic epithelium defined by monoclonal antibodies specific for Lea and H type 2

This study describes the distribution of type 1 and type 2 blood group carbohydrate chains in human normal and pathological odontogenic epithelia and in epithelia of human oral mucosa. Odontogenic epithelium was examined from 12 fetal tooth germs, 25 ameloblastomas, 13 odontogenic keratocysts, 13 follicular cysts and 13 radicular cysts. Oral mucosal epithelia was studied from 12 fetuses and 10 adults. Cell surface carbohydrates were detected using antibodies with reactivity for the blood group antigens A, B, type 1 chain Lea and type 2 chain H by an immunofluorescence technique. The expression of Lea and H type 2 chain in fetal palatal epithelium and only H type 2 chain in adult palatal epithelium suggests that a change in synthesis of blood group chains occurs during development. Type 2 blood group chains (antigen H) were found in fetal tooth germs, type 1 (Lea) in ameloblastomas and both type 1 and type 2 in odontogenic cysts. These results indicate that a modulation in synthesis of blood group carbohydrates has occurred in ameloblastomas and odontogenic cysts as compared with the cells from which the lesions presumably are developed. It is suggested that ameloblastomas may be distinguished from odontogenic cysts by the inability of ameloblastomas to synthesize type 2 blood group chains and antigens A and B.

Inhibition of precartilaginous chick somites by oncogenic virus

Infection of embryonic chicken notochord-somite explants with Rous sarcoma virus inhibited the in vitro differentiation of somites into cartilage. Visual inspection of the explants revealed that viral infection reduced the size of cartilage nodule formation. Formation of the complex of sulfated proteoglycans with hyaluronic acid was inhibited by RSV infection, and sedimentation analysis of the sulfated proteoglycans showed that very little fast sedimenting proteoglycans were synthesized by RSV-infected explants. The infected explants primarily synthesize a slowly sedimenting sulfated proteoglycan which was chondroitinase resistant. These slow-sedimenting sulfated proteoglycans lack the ability to associate with hyaluronic acid and appear to be noncartilaginous. These effects of RSV are apparently due to the src gene of this virus since the mutant td108, which lacks part of the src gene, has no detectable influence on the chondrogenic differentiation of somite explants. Similarly, infection with RAV-2 as well as with uv-irradiated virus had no detectable effect. The inhibition of synthesis of fast sedimenting proteoglycans was observed at 41 degrees C with explants infected with tsNY68, suggesting that residual activity of transforming gene of this virus at the non-permissive temperature is sufficient for this inhibition in the explants.

Rapid induction of foci escaping density-dependent inhibition in baby mouse skin cultures

Mesenchymal cells from primary BMS (baby mouse skin) cultures formed secondary monolayers subject to density-dependent inhibition. The monolayers remained quiescent but in good condition for 6-8 weeks if given weekly medium changes. Exposure of the primary cultures to fluorescent light and/or oxygen produced "altered" cells that gave rise in the secondary cultures to foci of up to 10(4) cells after 15 days. These foci overgrew the background BMS cells. The rate of growth, morphology, and arrangement of the altered cells varied greatly between foci but much less within a focus, which usually showed one or more characters of neoplastic cells. The initiation of foci was apparently not transmissible by an infectious agent.

S-100 protein in granular cell tumors (granular cell myoblastomas)

Outside the central nervous system S-100 is found only in Schwann cells and satellite cells of ganglia. It has also been demonstrated in Schwannomas and neurofibromas but is absent from soft tissue tumors of non-neural origin. S-100 protein was looked for in granular cell myoblastomas using an immunohistochemical technique in an attempt to further elucidate the histogenesis of these tumors. All tumor cells in the ten tumors studied were intensely stained with antiserum to S-100 including one with some malignant features. These results support the idea that granular cell myoblastomas arise from Schwann cells.

Hereditary adenomatosis of the colon and rectum: relevance to cancer promotion and cancer control in humans

We propose that SF derived from normal-appearing biopsies of ACR gene carriers exist in an initiated state as the result of a dominant mutation. Based on our studies with the ACR cell system, we further suggest that, although an initiated state is essential to cancer development, not all initiated cells necessarily develop into cancerous cells. The genetic makeup of an initiated cell has been established through linkage between abnormal phenotypic markers and pedigree profiles and through cell hybridization, including initial analysis of gene products. We believe that it is consistent with an autosomal dominant trait. In contrast, cells from patients who are homozygous for chromosomal breakage syndromes, including those with xeroderma pigmentosum, represent an experiment of nature which presumably underlies factors associated with cancer promotion in humans. We have demonstrated that ACR cells can be differentially transformed by oncogenic viruses, a carcinogen (MNNG), and gamma-ray irradiation, and that they can proliferate in vitro after exposure to a tumor promoter (TPA. This simple experimental model provides a novel system for the study of tumor promotion in vitro. We further suggest that, through the use of TPA, various stages associated with cancer development in humans, i.e., initiation through promotion and progression, can be identified in vitro. Attempts to apply these results in vivo are currently in progress. The apparent susceptibility of ACR cells to further transformation by oncogenic viruses and chemical and physical agents indicates that genetic information residing within these cells, probably in the form of a relatively limited and specific number of DNA sequences associated with the ACR mutation, renders them more sensitive to these three distinct classes of carcinogens. We submit that, through our tests on SF, and ACR gene carriers within recognized ACR clusters can be diagnosed at present with sufficient certainty to warrant immediate action. In addition, it seems that the time has arrived for a major undertaking to screen for persons who are likely to be at increased risk of cancer, perhaps through walk-in clinics. An underlying assumption in these studies is that predisposition to cancer, in general, is associated with an autosomal dominant trait in obligatory heterozygote gene carriers.

Differentiation of the mammary gland and susceptibility to carcinogenesis

It has been demonstrated that in humans certain factors such as early menarche, late pregnancy, and nulliparity are associated with a higher risk of developing breast cancer, while early pregnancy acts as a protective factor. Induction of mammary cancer in rats by administration of the chemical carcinogen 7,12-dimethylbenz(a)anthracene reveals that the same factors influencing human breast cancer risk also affect the susceptibility of the rat mammary gland to the chemical carcinogen. Nulliparous rats and rats undergoing pregnancy interruption are more susceptible to developing carcinomas. This fact has been attributed to the incomplete differentiation of the gland at the time of carcinogen administration. Parous rats are resistant to the carcinogenic effect of DMBA, which is explained by the complete development of the gland attained during pregnancy and lactation. This development is manifested by the differentiation of terminal end buds into secretory units, which have a smaller proliferative compartment; the epithelial cells of these secretory units have a longer cell cycle, less avidity for binding DMBA, and possess a more efficient DNA excision repair capacity.

Heterogeneity of tumorigenicity phenotype in murine tumors. I. Characterization of regressor and progressor clones isolated from a nonmutagenized ultraviolet regressor tumor

We have shown that both regressor and progressor clones can be isolated from a UV regressor tumor, RD-1024. Although the daughter clones are characterized by differences in tumorigenic potential in normal transplant hosts, they nevertheless seem to express the same major tumor rejection antigens, because immunization with either the regressor parent tumor, RD-1024, or with regressor Cl 8 protects against subsequent challenge with progressor C1 4 or Cl 9. Consistent with the in vivo-generated data is the evidence that draining lymph node cells with functional specificity for regressor Cl 8 are capable of cross-reactive cytotoxicity in an in vitro chromium release assay. We have demonstrated an indirect interaction occurring in vivo between regressor and progressor cells, in that Cl 8 cells have the ability to influence the outcome of simultaneous or sequential challenge with Cl 4 or Cl 9 cells. Because 500 rad of gamma irradiation has been shown to compromise the ability of mice to respond to a primary challenge with tumor, an immunological mechanism is implicated in the ultimate rejection of progressor tumor in a doubly challenged host. The importance of these results lies in the knowledge that these interacting subpopulations have been isolated directly from a tumor growing in vivo and that no selection pressure has been exerted on the cells greater than the short in vitro culture period necessary for the isolation and expansion of individual clones. The apparent immunoregulatory potential in a tumor-bearing animal is thus seen to be modified in accordance with the phenotypic heterogeneity of the cells within that tumor.