Immunological aspects of chemical carcinogenesis

Distribution of coal and coal combustion related organic pollutants in the environment of the Upper Silesian Industrial Region

In this study, a large sample set (276) was separated into up to 15 groups, including coal, fly ash, total particulate matter, coal wastes, river sediments, and different water types. Grouping the sample set into these categories helped to identify the typical features of combustion or water-washing and compare them using newly developed polycyclic aromatic hydrocarbon diagnostic ratios. A wide range of organic pollutants were identified in samples, including aromatic and polycyclic hydrocarbons, nitrogen-heterocycles, sulphur-heterocycles + trithiolane, and polycyclic aromatic hydrocarbons substituted with oxygen functional groups. The distribution of compounds was significantly influenced by water washing or combustion. During the self-heating of coal wastes, secondary compounds such as chlorinated aromatics (chlorobenzene, chloroanthracene, etc.) or light sulphur compounds (e.g. benzenethiol and benzo[b]thiophene) were formed (synthesised). Since these compounds are generally absent in sedimentary organic matter, their origin may be connected with high-temperature formation in burning coal dumps. These compounds should be identified as persistent organic pollutants (POPs) in the environment. The newly defined diagnostic ratios have worked well in separating samples (petrogenic and pyrogenic) and have pointed out the effect of incomplete combustion on self-heated coal waste, ash from domestic furnaces, or water washing and biodegradation of the studied compounds.

Sensitization of Nude Mice Using Direct Liposome Transfer of Tumor Cell Antigens

Transplantable human squamous cell carcinoma cells were coincubated with 1,2-dimyristoylamido-1,2-deoxyphosphatidyl-choline (D14DPC) liposomes. These proteoliposomes and disrupted tumor cell suspensions were injected subcutaneously into two groups of nude mice, respectively, while the third group was untreated. Ten days previously, tumor had been implanted into both of the mice forefeet. In the seven-week old mice pretreated with the proteoliposomes, one of the tumors disappeared, while another tumor remained unchanged in size and the remaining two tumors regrew. Regrowth of the tumors was observed in both control groups. Their size and weight were significantly larger (p < 0.05) than those in the proteoliposome group. In all the 5-week old mice, the tumor masses grew but the size and weight of the tumor in the proteoliposome treated group were significantly smaller (p < 0.05) than those in the other two groups. The results showed the effectiveness of the proteoliposome treatment as a possible clinical application.

Chemical carcinogenesis

Understanding the relationship of chemicals to carcinogenesis has progressed significantly since the initial observations of Hill and Pott in the 1700's. Distinguishing between DNA-reactive chemicals and those which increase cancer risk by increasing cell proliferation has been a major breakthrough in delineating overall mechanisms. Competing processes for activation versus inactivation of chemicals occur at many levels, including metabolism, DNA repair, and cellular repair processes. These processes can be affected by other agents to decrease carcinogenesis (chemoprevention). Increasing knowledge of the multiple steps of carcinogenesis is leading to improved methods for screening chemicals for carcinogenic activity and for regulatory decision making. Improvements in assessment of modes of action involved in animal and in vitro models have led to more rational approaches to assessing relevance to humans. The advent of genomics and high-throughput technologies have contributed to investigations of mechanisms and is beginning to impact development of better methods for screening chemicals. Based on developments in basic research, epidemiology, and astute clinical observations, the major risk factors and etiologic agents have been identified for a majority of cancers, which is beginning to lead to methods to decrease cancer incidence overall and identify targets for early detection and treatment.

Umbuzeiro G, DeMarini DM. The Salmonella mutagenicity assay: the stethoscope of genetic toxicology for the 21st century

OBJECTIVES

According to the 2007 National Research Council report Toxicology for the Twenty-First Century, modern methods (e.g., "omics," in vitro assays, high-throughput testing, computational methods) will lead to the emergence of a new approach to toxicology. The Salmonella mammalian microsome mutagenicity assay has been central to the field of genetic toxicology since the 1970s. Here we document the paradigm shifts engendered by the assay, the validation and applications of the assay, and how the assay is a model for future in vitro toxicology assays.

DATA SOURCES

We searched PubMed, Scopus, and Web of Knowledge using key words relevant to the Salmonella assay and additional genotoxicity assays.

DATA EXTRACTION

We merged the citations, removing duplicates, and categorized the papers by year and topic.

DATA SYNTHESIS

The Salmonella assay led to two paradigm shifts: that some carcinogens were mutagens and that some environmental samples (e.g., air, water, soil, food, combustion emissions) were mutagenic. Although there are > 10,000 publications on the Salmonella assay, covering tens of thousands of agents, data on even more agents probably exist in unpublished form, largely as proprietary studies by industry. The Salmonella assay is a model for the development of 21st century in vitro toxicology assays in terms of the establishment of standard procedures, ability to test various agents, transferability across laboratories, validation and testing, and structure-activity analysis.

CONCLUSIONS

Similar to a stethoscope as a first-line, inexpensive tool in medicine, the Salmonella assay can serve a similar, indispensable role in the foreseeable future of 21st century toxicology.

Cancer vaccines as a therapeutic modality: The long trek

The development of cancer vaccines has been one of the several false dawns in which initial promising Phase I and Phase II clinical data have not been followed up with conclusive Phase III trials. In this review, we describe some of the successes and failures, and review the most likely reasons for Phase III failure, such as protocol changes, which are common between Phase II and III, and poorly defined patient groups. Nevertheless, significant survival results have been reported with autologous vaccines for colorectal, renal and, more recently, prostate cancer. In addition, it is becoming evident that immunotherapy is potentially synergistic with other treatment modalities, such as chemotherapy, which can reduce T-regulatory activity that inhibits the immune response to cancer vaccines. This potential for synergy should allow cancer vaccines to become part of the standard treatment regimen for many common tumours.

Effects of aflatoxin on lymphoid cells of weanling rat

Aflatoxin (AF), the hepatocarcinogenic food contaminant produced by the Aspergillus flavus group of fungi, is known to interact with various vital processes, including the immune function. Effects of long-term treatment of three dose levels of aflatoxin B1 (AFB1) on lymphoid cells of weanling rats were studied. AFB1 treatment caused a reduction in body weight gain, significantly (P less than 0.01) at the 700 microgram level. There was also a significant decrease in the weight of spleen and thymus in AFB1-treated animals in comparison to control. Similarly, AFB1 depleted cell populations of thymus and bone marrow and WBC and RBC counts. There was a marked reduction in the population and phagocytic capacity of macrophages due to AFB1 administration at dose levels of 350 and 700 micrograms kg-1 body weight. Macromolecular synthesis of DNA, RNA and protein in macrophages was affected, as there was significant inhibition in the incorporation of [3H]-thymidine, [3H]-uridine and [3H]-leucine. The hampered functioning of macrophages may be due to the cytotoxic action of AFB1.

Active specific chemoimmunotherapy of lymph-node metastasis from a poorly immunogenic murine fibrosarcoma

The fibrosarcoma MCA-SP, which was recently induced with methylcholanthrene (MCA) in C3H/HeJ mice, displays poor immunogenicity in in vivo prophylaxis. A cell variant MCA-SPN1, which bears a tumor-specific transplantation antigen (TSTA) cross-reactive with the parental line MCA-SP, was selected because of its proclivity for axillary lymph-node metastases. Although these lymph-node metastases were resistant to sinecomitant (post-excisional) immunity, they were susceptible to combined active and passive specific chemoimmunotherapy, using tumor-specific, 1-butanol-extracted, preparative isoelectric focusing-purified, TSTA (1 microgram weekly sc injections), cyclophosphamide (CY, a single intraperitoneal 20 mg/kg dose), and adoptive transfer of immune splenic T lymphocytes, which had been re-stimulated in vitro with extracted TSTA and interleukin-2. This triple regimen both reduced the incidence of spontaneous lymph-node metastases, and prolonged the survival of tumor-bearing, as well as tumor-resected hosts. The results from local adoptive transfer assay using T-lymphocyte subpopulations of spleen and lymph nodes in these treated hosts suggested that Lyt 2+ cytotoxic T-lymphocytes (CTL) mediated in vivo tumor-neutralization. Thus TSTA/CY/CTL therapy activates tumoricidal host responses effective against the poorly immunogenic MCA-SP tumor and its lymph-node metastases.

Cellular events during hepatocarcinogenesis in rats and the question of premalignancy

The cellular, biochemical, and genetic changes that occur in the liver of rats exposed to chemical hepatocarcinogens are reviewed. Multiple new cell types appear in the liver of carcinogen-treated rats including foci, nodules, ducts, oval cells, and atypical hyperplastic areas. The application of phenotypic markers for these cell types suggests that hepatocellular carcinomas may arise from more than one cell type, including a putative liver stem cell that proliferates following carcinogen exposure. Study of DNA, RNA, and proteins produced by hepatocellular carcinomas and putative premalignant cells has so far failed to identify a gene or gene product clearly associated with the malignant or premalignant phenotype. Understanding the cellular lineage from normal cell through putative premalignant cell to cancer is critical to understanding the process of carcinogenesis. Application of new immunological (monoclonal antibody, transplantation) and molecular biological (gene cloning, oncogene identification) approaches to this problem holds promise that the process of hepatocarcinogenesis will be better known in the near future.

Tumor-specific idiotopes on suppressor factors and suppressor cells revealed by monoclonal anti-idiotope antibodies

Two monoclonal anti-idiotope antibodies, previously found to induce tumor-specific cell-mediated immunity in mice, were examined for their relationship to tumor-associated suppressor factors (SF), produced in culture by spleen cells from tumor-bearing mice or present in sera from such mice. A leukocyte adherence inhibition assay was used to detect cellular immunoreactivity to tumor antigens and its inhibition by SF, using peritoneal cells from mice bearing tumor or sensitized with anti-idiotope antibody. The SF were specifically absorbed by the corresponding anti-idiotope antibodies coupled to a solid phase and were recovered by elution. They were also specifically neutralized by the addition of the respective antibodies to the assay system. Anti-idiotope antibody, used with complement to pretreat spleen cells from tumor-bearing mice, prevented these cells from producing SF in culture. Tumor antigen-reactive effector cells, suppressor cells, and SF thus share similar idiotopes, permitting their respective functions to be modulated by appropriate anti-idiotopes.

Glioma-associated antigens defined by monoclonal antibodies against an avian sarcoma virus-induced rat astrocytoma

S69-c15 is a highly immunogenic cell line derived from an avian sarcoma virus (ASV)-induced astrocytoma in F-344 rats. Monoclonal antibody (Mab) production was attempted by fusing F-344 rat splenocytes and mouse P3 X 63/Ag8.653 myeloma cells after a syngeneic immunization protocol. 336 fusion clones were screened by cell surface radioimmunoassay (CS-RIA) against the immunizing line S69-c15, rat kidney fibroblast line S203-c11 and Walker rat carcinoma line. Mabs 7G4, 9F1, 10E3 and 10E7 which reacted only with S69-c15 were chosen. Further analysis demonstrated that these Mabs reacted only with rat (13/23 astrocytomas, 2/4 gliomas, 1/11 neurinomas) or mouse (2/10 astrocytomas) neurogenic tumor cells induced by both viral and chemical agents. Reciprocal competition assays suggested that 7G4, 9F1 and 10E3 recognized the same epitope and that 10E7 reacted with a spatially close determinant. Antigen activity could not be found in adult rat tissues (brain, heart, lung, liver, kidney, spleen, thymus, intestine, muscle and peripheral nerve) and fetal brain (8, 12, 20 days gestation) by either absorption analysis or tissue staining. Preliminary characterization indicated that the epitope may be polypeptide-associated. Further antigen purification and tumor localization can be attempted with these Mabs.

Cytotoxic T cell lysis of H-2-negative murine sarcoma cells

The DOH cell line was established from C3H.OH (H-2Kd,Dk) embryonic fibroblasts transformed with Rous sarcoma virus (RSV) in vitro. When injected into syngeneic mice, DOH cells were very weakly tumorigenic and induced a cytotoxic immune response. Cytotoxic T lymphocytes (CTL) specifically lysed DOH cells but not other RSV-induced sarcoma cells, which shared the H-2Kd or H-2Dk antigen, respectively, with DOH. Serological and immunochemical analysis of H-2 antigens subsequently showed that DOH sarcoma cells did not express syngeneic H-2K and H-2D antigens. Surprisingly, a H-2Kk-specific monoclonal antibody (100-5) bound to DOH cells and was inhibitory for syngeneic CTL specific for DOH. In addition, DOH cells were lysed by alloreactive H-2Kk-specific CTL. The demonstration of immunogenic H-2-negative sarcoma cells suggests that either the H-2K antigens have been extensively altered or that hitherto unidentified major histocompatibility complex class I molecules are expressed on DOH sarcoma cells surfaces, acting as target antigens for tumor-specific CTL.

Persistent suppression of humoral and cell-mediated immunity in mice following exposure to the polycyclic aromatic hydrocarbon 7,12-dimethylbenz[a]anthracene

Carcinogen-induced immunosuppression has been implicated as an epigenetic mechanism in promoting the outgrowth and metastasis of neoplastic cells. It has previously been reported that the complete carcinogen 7,12-dimethylbenz[a]anthracene (DMBA) suppresses both humoral immunity (HI) and cell-mediated immunity (CMI) 3-5 days following exposure. Since persistent systemic immunosuppression may be more relevant in tumor outgrowth, assays quantitating HI and CMI, including those functions involved in tumor resistance, were performed 4 and 8 weeks following exposure to tumorigenic doses of DMBA. Adult B6C3F1 female mice were administered DMBA dissolved in corn oil subcutaneously at 5, 50 and 100 micrograms/g body weight in ten equal doses over 2 weeks (corn oil = vehicle control). The number of splenocytes producing IgM antibody to the T-dependent antigen, sheep erythrocytes, was suppressed up to 95% and 98% at 4 and 8 weeks, respectively. The IgG response was similarly depressed 75% and 98% at 4 and 8 weeks, respectively. Lymphoproliferation of splenocytes in response to the mitogens LPS, PHA and Con A were depressed up to 88%, 78% and 83% at 4 weeks and 63%, 63% and 67% respectively, at 8 weeks. In addition, alloantigen-induced proliferation of splenocytes in a one-way mixed lymphocyte culture was suppressed up to 90% at 8 weeks. The ability to generate cytotoxic T-lymphocytes (CTL) in vitro against P815 tumor cells was depressed at both time periods (88% and 60%, respectively) as was natural killer (NK) cell cytolysis of YAC-1 tumor targets (84% and 55%, respectively). The immunosuppression noted in these parameters was similar to that observed within 3-5 days following DMBA dosing. The persistent immunosuppression induced by the PAH carcinogen DMBA, including CTL and NK cell tumoricidal functions, may represent an important epigenetic mechanism contributing to tumor outgrowth or metastasis by this class of agents.

Mitomycin C-treated or irradiated concanavalin A-activated T cells augment the activation of cytotoxic T cells in vivo

The activation of cytotoxic T lymphocytes (CTL) in vivo after immunization of normal or cyclophosphamide-treated mice with allogeneic cells was strongly augmented by the administration of mitomycin C-treated or irradiated concanavalin A-activated spleen cells (Con A-spl). This effect of the Con A-spl was abrogated by treatment with Anti-Thy 1 antibody plus complement, and was therefore presumably mediated by activated "helper" T cells. (The term "helper" cell is only operationally defined in this context and indicates that the augmenting irradiation resistant T cells are obviously not CTL precursor cells). These observations indicated (i) that even the cytotoxic response against allogeneic stimulator cells suffers in vivo from insufficient "helper" T cell activity, and (ii) that the injection of Con A-spl may serve as a simple procedure to apply this "helper" activity in vivo. This procedure was at least as effective as the repeated injection of interleukin 2 (IL-2)-containing cell supernatants with up to four 30-unit doses of IL-2 per mouse. IL-2-containing cell supernatants were found to mediate similar effects only if injected into the footpads but not intravenously. This was in line with the reported observation that IL-2 has an extremely short half-life in vivo. The injection of Con A-spl was also found to augment the proliferative response in the regional lymph nodes.

The serologically unique cell surface antigen of Zajdela ascitic hepatoma is also its tumor-associated transplantation antigen

A unique cell surface antigen of a chemically induced rat hepatoma (Zajdela Ascitic Hepatoma, ZAH) has been identified serologically and purified to apparent homogeneity. ZAH cells, when injected subcutaneously or intradermally into syngeneic hosts, elicit a weak humoral antibody response directed against a single cell surface antigen. In spite of prolonged and extensive immunization, the syngeneic anti-tumor antibodies are solely of the IgM class. Antisera from such immunized animals lyse tumor cells in the presence of complement. These observations were utilized in developing methods for the identification and purification of the antigen. It was observed that administration of purified preparations of this antigen confers ZAH-specific tumor immunity in syngeneic animals. Hence the serologically unique antigen is also the tumor-associated transplantation antigen (TATA) of this tumor. This is the first reported purification of a TATA from a rat tumor. There is considerable earlier evidence for the existence of tumor-associated factors which elicit a strong suppressor-cell response in tumor-bearing rats. The availability of the purified TATA from a rat tumor provides, for the first time, a handle for the identification and further characterization of such molecular species.

Cell surface antigens of human ovarian and endometrial carcinoma defined by mouse monoclonal antibodies

Mouse monoclonal antibodies to several cell surface antigens of human ovarian and endometrial carcinomas have been produced. The distribution of the antigens was determined by mixed hemagglutination assays on 153 normal and malignant cell cultures of various types and by immuno-peroxidase staining of frozen sections of 27 normal adult and 24 fetal tissues. Five distinct antigens were characterized. MD144 antigen was detected on only a single ovarian carcinoma cell line and has the biochemical properties of a lipid. MH55 antigen is weakly expressed on ovarian and uterine cancer cell lines but not on other cells and tissues tested. MF61 antigen was detected on an ovarian carcinoma and some renal carcinoma cell lines but not on other cell lines tested. It was also detected by immunoperoxidase staining in the noncellular follicles of the thyroid and in uterine glandular epithelial cells. This antigen also has the properties of a lipid. MF116 antigen was detected on a proportion of ovarian, uterine, renal, and bladder carcinoma and neuroblastoma cell lines and on normal kidney epithelial cell cultures but not on other cell lines tested. It was not detected in sections of any normal tissue tested using the immunoperoxidase method. MF116 was readily detected in the spent culture medium but not in detergent-solubilized extracts of metabolically radiolabeled cells. This shed antigen is a glycoprotein of Mr 105,000 and isoelectric point lower than pH 4.0. MH94 antigen was detected on a proportion of ovarian, uterine, colon, breast, lung, cervical, and pancreatic carcinoma cell lines. In tissue sections it was detected in many but not all epithelia, predominantly in secretory epithelial cells. Antibody MH94 did not immunoprecipitate a detectable antigen.

Immunology of metastasis. Can the immune response cope with disseminated tumor?

The application of immunologic methods to the treatment of neoplasia has been a goal of research in tumor immunology. Unfortunately, no clearly defined success for such therapy has been achieved. However, the most recent advances in tumor biology have provided for a more valid conceptual framework upon which to plan further research in this area. The more general awareness of tumor progression and heterogeneity, particularly in the context of tumor metastasis, while imposing a sense of gloom regarding all therapeutic modalities, shifted immunologic thinking toward the development of nonspecific modalities. We herein propose that this 'shift' may be premature and that immunotherapy using cytolygic T cells could still be feasible. Our views are based on newer approaches for selecting immunogenic variants of malignant tumors and a better understanding of the relationship of the immune response to metastases.

Immunogenicity of cellular and acellular antigen preparations from a methylcholanthrene-induced mouse sarcoma

Inbred mice were immunized with various cellular and subcellular preparations from a syngeneic, methylcholanthrene-induced sarcoma to induce transplantation immunity against a subsequent challenge of viable cells from the same tumor. Only with conventional immunization procedures using radiation-attenuated tumor cells or viable tumor cells in admixture with bacillus Calmette-Guérin was transplantation immunity obtained. Neither native soluble tumor extracts prepared using several extraction methods, nor cross-linked preparations of these extracts gave rise to transplantation immunity. With few exceptions, however, the immunizing preparations resulted in the production of tumor-specific humoral antibody. The manner in which tumor antigens are presented to the host as well as the experimental system (animal strain; tumor) used appear to play an important role in the development of transplantation immunity against tumors.

Escape of tumours from immunological destruction

This paper reviews the mechanisms of tumour escape from immune destruction that have been delineated in the past 2 decades. Current evidence indicates that the principal escape mechanisms are (i) weak or absent immunogenicity (ii) immunosuppression by tumour antigens or antigen-antibody complexes (iii) induction of suppressor cells and (iv) production of immunosuppressive factors. A classification of tumour escape mechanisms is presented.

Immunotherapeutic effects of tumor-specific transplantation antigens released by 1-butanol

Active immunotherapy with materials extracted from a murine methylcholanthrene-induced sarcoma using single phase solutions of 2.5% 1-butanol evoked host resistance against supralethal burdens of neoplastic cells deposited subcutaneously or delivered hematogenously. After curative resection of progressing 1 cm tumors, postsurgical immunity against subsequent subcutaneous neoplastic challenges was potentiated by weekly injections of crude butanol extracts. In a conventional therapy model, hosts bearing progressing 4 mm subcutaneous tumors displayed neoplastic regression following chemoimmunotherapy with cyclosphosphamide and tumor extracts. Therapeutic effects were demonstrated not only against subcutaneous neoplasms, but also against hematogenously disseminated pulmonary and extrapulmonary metastases introduced by intravenous inoculation of sarcoma cells. These findings suggest that tumor extracts may afford potent therapeutic adjuvants for patients bearing a small body tumor burden but at high risk of disease recurrence.

Alterations in antigenic properties of normal epidermis adjacent to basal cell carcinomas

The expression of U-CYT antigens, tissue-specific cytoplasmic antigens of keratinocytes that are markers of the terminal differentiation of these cells, was studied in normal skin adjacent to malignant epidermal tumors. Ten basal-cell carcinomas were studied. In all cases, it was found that the expression of U-CYT antigens in normal epidermis gradually decreased with increasing proximity to the tumors and finally disappeared completely within the tumor tissue itself. This finding suggests that basal-cell carcinoma can alter the normal differentiation of adjacent nonmalignant cells.

Cell-mediated suppression of tumor immunity has a non-specific component. I. Evidence from transplantation tests

We have first demonstrated that the growth of a transplanted, 3-methyl-cholanthrene-induced BALB/c sarcoma, MCA-1425, in specifically immune syngeneic mice, was facilitated when the MCA-1425 tumor cells were injected together with either a mixture of irradiated MCA-1425 cells and thymus cells from mice immune to MCA-1425 or a mixture of irradiated cells from an antigenically different BALB/c sarcoma, MCA-1460, and thymus cells from mice immune to MCA-1460. We then performed Winn assays to study the induction of an immune response that could prevent the outgrowth of MCA-1425 cells in irradiated syngeneic recipients. Tumor immunity was found to be suppressed, if the mice immunized by a subcutaneous transplant of MCA-1425 cells and used as lymphocyte donors, were injected intraperitoneally with cells from either a different sarcoma, MCA-1460, or from 12-day BALB/c embryos. We tentatively attribute our finding to antigen-non-specific suppressor effector cells and postulate that an antigen-specific event is often involved in their induction.

Differential counts of B and T lymphocytes in the lymph nodes, circulating blood and spleen after inhalation of high concentrations of diesel exhaust

Inhalation of diluted diesel engine exhaust results in the deposition of submicron carbonaceous particles in the respiratory airways. The particles are phagocytized by the pulmonary alveolar macrophages and cleared from the respiratory tract via the mucociliary escalator or through lymphatic channels. Lung clearance via lymphatics results in accumulation of particles in the regional lymph nodes. Differential counts of B and T lymphocytes were performed to determine whether the deposited carbon particles in the lymphatic tissue can alter the subpopulation composition of various lymphoid compartments. In contrast to the effect of materials such as heavy metals, halogenated hydrocarbons or cigarette smoke condensate, all of which have been shown to alter B and T cell differential counts of lymphoid compartments under various test conditions, assays of lymphocytes from tracheobronchial lymph nodes, spleen and blood from guinea pigs exposed to diluted diesel exhaust with a particulate concentration of 1500 micrograms m-3 for up to 8 weeks revealed no significant changes when compared with age-matched controls. Furthermore, cell viability as measured by trypan blue exclusion in the exposed groups was comparable to that of the age-matched controls. These data indicate that, within the range of tested conditions, the deposited diesel particles do not exert major effects on the parameters of the immune system that were measured.

A survey of ethylnitrosourea-induced rat gliomas for the presence of tumour rejection antigens expressed in vivo

Transplanted lines of seven F-344 (Fischer) rat malignant gliomas induced transplacentally with ethylnitrosourea (ENU) were surveyed by in vivo immunoprotection assays for the presence of tumour rejection antigens. These gliomas were representative of commonplace histological types of human primary brain tumours and were analyzed in early transplantation passages. The classical tumour ligation method of immunizing animals was attempted with five glioma lines, but was found unusable in four of these because of a high incidence of local tumour recurrences and distant metastases. In most experiments the animals were immunized by repeated inoculations of heavily-irradiated tumour cells. Two gliomas, a glioblastoma multiforms and a mixed astrocytoma-ependymoma, demonstrated weak but statistically significant tumour rejection responses. Immunization with three other tumours, a mixed oligodendroglioma-astrocytoma and two glioblastomas multiforme, led to enhanced outgrowth of the challenge cell inocula. Neither a rejection nor an enhancement response was observed in assays of the remaining two neoplasms, a glioblastoma multiforme and a mixed astrocytoma-oligodendroglioma. Immunization with a 3-methylcholanthrene-induced urinary bladder carcinoma line, used as a control in assays of six gliomas, had no effect on the outgrowth of transplanted glioma cells. These results suggest that ENU-induced malignant rat gliomas do not uniformly elicit strong tumour-rejection responses in vivo.

Treatment of feline leukemia and reversal of FeLV by ex vivo removal of IgG: a preliminary report

Cats that were spontaneously infected with feline leukemia virus (FeLv) were treated with a combination of low-dose irradiation and extracorporeal immunosorption using formalin and heat-fixed S. aureus as a non-specific immunosorbent to remove plasma IgG and immune complexes. The treatment resulted in reduction of circulating lymphoblasts within two weeks and clinical improvement of three of the five animals. A reversal of the FeLV status is reported in five of five cats. Two of the five cats remain FeLV negative and completely tumor free seven and eight months post-therapy at the time of writing (July 1979). A third cat returned to an FeLV positive state but remained tumor free for 24 weeks. Another cat responded to the therapy by reduction of lymphoblasts and became FeLV negative but died of a hemorrhage during an immunosorption. The last cat's status was FeLV positive, then FeLV negative, and finally FeLV positive again. He died 20 weeks after initiation of therapy. During the treatment there was a weight gain in the three cats responding by tumor regression. The results are discussed in terms of a removal of some type of immunoinhibiting factors such as antigen-antibody complexes or suppressor molecules.

Leucocyte adherence inhibition test for the detection of cell-mediated immunity to malignant melanoma

A tube leucocyte adherence test was used to detect reactivity of melanoma patients to extracts of melanoma tissue. Breast cancer extracts were used as a control. Of 31 melanoma patients 22 gave a positive reaction (non-adherence index > 25%) to melanoma extracts whereas only three of 24 normal subjects did so. Fifteen of 16 patients with Stage 1 melanoma reacted but only seven of 15 patients with Stage 2 or Stage 3 disease did so. None of seven patients with breast cancer reacted to melanoma extract, but four of them reacted to breast cancer extract. None of four patients with benign breast disease reacted to either extract. It is concluded that leucocyte adherence inhibition is potentially useful in investigations of tumour-specific immune reactivity to melanoma and of melanoma antigens.

The undefined relationship between tumor antigens and histocompatibility antigens on cancer cells

The data pertaining to the possible relationship between histocompatibility antigens (HA) and tumor-specific transplantation or tumor surface antigen (TSTA or TSA) are reviewed. The HA profiles of certain experimental and human neoplasms have been found to be altered either from the quantitative (increased expression of some antigenic specificities and decreased expression or even lack of other HA) or qualitative point of view (appearance of alien, genetically inappropriate HA). The authors entertain the possibility that the persence of TSTA or TSA on cancer cells may be linked to alterations of the HA profile. Evidence in favour of the idea that tumor antigens may actually to alien MHC products, alien minor HA or modified HA, is reviewed. Findings on structural relationships between TSA and beta2-microglobulin are also summarized. In the authors' opinion, no definitive conclusions can be reached at the present time on the relationship between TSTA or TSA and HA of cancer cells.

New dimensions in the biology of cancer

A common thread interwoven throughout the literature of cancer biology is a wide-ranging abnormality of gene regulation, manifested by misprogramming of protein synthesis. This phenomenon encompasses virtually every means of identification of proteins, including antigens, hormones, growth factors, membrane components, and enzymes. Studies by the author and others of the activities of enzymes existing in multiple forms (termed isozymes) in a series of rat hepatomas ranging widely in growth rate, degree of differentiation, and other phenotypic properties has extended this concept and added to it a dimension of functional significance. Isozymes that are in high activity in adult liver and that are geared kinetically to catalyze specific hepatic functions are lost in varying degrees and generally depend on the growth rate and degree of differentiation. In fast growing, poorly differentiated hepatomas, these are replaced by high activities of isozymes that are normally low or absent in adult liver. In many instances, the isozymes that are expressed in poorly differentiated hepatomas are present also in fetal liver, thus pointing to reactivation of genes that were active in the fetus but were inactivated during normal embryonic development. The loss of isozymes that are under rigid host endocrine control, as well as other proteins that maintain the differentiated state, and the re-activation of genes coding for fetal or ectopic proteins are probably crucial factors in the initiation and maintenance of cellular proliferation.

Effector and enhancing lymphoid cells in plasmacytoma-bearing mice. I. Methodological studies on the Winn assay

Some parameters of the Winn assay for the detection of tumor-suppressing ("effector") and tumor-enhancing lymphoid cells were studied in BALB/c mice. Spleen cells of mice that were preimmunized with mitomycin-C-treated MOPC-104E plasmacytoma cells were inhibitory in this test system for both the MOPC-104E and the HOPC-I plasmacytomas, thus indicating cross-reactivity. Spleen cells taken from mice 6 days after the surgical removal of 15-day-old MOPC-104E tumors inhibited the growth of lethal doses of MOPC-104E cells in normal recipients, but no inhibition was observed 2 days after the removal of 18-day-old tumors. Spleen cells from mice bearing MOPC-104E for 13 days enhanced tumor growth. This enhancement was not influenced significantly by the wide dose range (from 10(5) to 3 x 10(7)) of MOPC-104E cells used to initiate tumors in the lymphoid cell donors, although tendency for stronger enhancing potential occurred after low tumor doses. When spleen cells from donors bearing MOPC-104E for 10 days were injected at the constant tumor-lymphocyte ratio of 1:30 with increasing numbers of tumor cells (from 5 x 10(5) to 2 x 10(6)), tumor inhibition occurred at the lowest dose only, while no significant effect was observed at higher tumor cell doses. When a constant dose (5 x 10(5)) of tumor cells was injected with spleen cells from 10-day tumor-bearers at tumor/lymphocyte ratios of 1:10, u:40 and 1:160, a significant tumor inhibition occurred only at the ratio of 1:40. The relevance of the Winn test to the study of immune mechanisms in tumor-bearing hosts is discussed.

Experimental inflammation and tumor growth: chemical carcinogenesis in adjuvant arthritic rats

Development and growth of primary (methylcholantrene or benzpyrene-induced) sarcomas in adjuvant arthritic rats were investigated and compared with the chemical carcinogenesis in normal healthy animals. When carcinogen and adjuvant were applied in the same time, tumor development and growth rate did not differ significantly from nonarthritic controls. When carcinogen was applied to rats with fully established arthritic disease, development and growth of tumors were significantly enhanced. In the latter case local and systemic adjuvant disease was more severe in tumor-bearing rats. Enhanced chemical carcinogenesis in arthritic rats can be explained by a defective immune responsiveness in the chronic stage of arthritis.

Tumour-related antigen specificities associated with 3-methylcholanthrene-treated rat embryo cells

Rat embryo cells were treated in vitro for 18 h with 10 micrograms/ml 3-methylcholanthrene (MCA). Syngenetic male rats were immunized with several inocula of treated cells to prepare antisera which were screened for membrane immunofluorescence reactivity against panels of established chemically-induced syngeneic rat tumours. Three separate antiserum pools raised against MCA-treated cells reacted with certain chemically-induced tumours, whereas antisera to control (DMSO-treated) cells were completely negative. The reactions observed were reproducible and highly specific for particular target tumours. Absorption studies indicated that each antiserum contained antibodies to several different antigens, present on different tumours. Antiserum prepared against extranuclear membrane from MCA-treated cells, rather than intact MCA-treated cells, was negative. This suggests that the antibody responses were directed against antigens arising subsequently to MCA treatment and injection into syngeneic hosts. It is postulated that carcinomgen treatment results in the acquisition of multiple neoantigens among a treated cell population, which represent an early change in a sequence of events leading to malignant transformation.

Theoretical mechanisms for synthesis of carcinogen-induced embryonic proteins: IV. The viruses

Speculations are developed for a mechanism by which oncogenic viruses can induce alterations in cells allowing them to express embryonic genes. It is suggested that if viral deoxyribonucleic acid, directly or via ribonucleic acid directed deoxyribonucleic acid polymerase activity becomes inserted at particular euchromatin - heterochromatin junctions of quasidifferentiated stem-like cells, then deheterochromatization may result, causing in turn derepression of genes for acidic protein phosphokinases. This sets into motion a series of events including altered acid protein repressors of embryonic genes which are repressed by uniquely weak type repressors. This explains how viruses can act as specific embryonic gene-inducing agents similar to chemical inducing agents such as the hepatocarcinogen ethinine.