Evidence for the presence of an antitumor factor in serum of normal animals

Cytokine mRNA expression in whole blood samples from dogs with natural canine distemper virus infection

Cytokines are soluble polypeptides with many physiological functions and a special role during infection and inflammation. Little is known about cytokine regulation in naturally occurring viral diseases of animals. Especially the role of cytokines in the development and progression of lesions in canine distemper virus (CDV) infection in dogs is largely unknown. Whole blood samples from 14 dogs with CDV infection and three dogs suffering from non-distemper diseases were examined for mRNA of pro-inflammatory cytokines such as interleukin-1beta (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-12 (IL-12), tumor necrosis factor-alpha (TNF), interferon-gamma (IFN), and the anti-inflammatory transforming growth factor-beta1 (TGF) using reverse transcription polymerase chain reaction (RT-PCR). Blood samples from the three dogs that showed no clinical abnormalities during a pre-vaccination physical examination served as control. CDV infection was confirmed by post-mortem immunohistochemistry for CDV nucleoprotein. The degree of immunoreactivity and the number of virus antigen positive organs were expressed as antigen index. IFN transcripts were not identified in any dog and IL-8 transcripts were present in RNA isolates from all 20 dogs. None of the other cytokines was detected in control animals. IL-1 and IL-6 were each found in one non-distemper dog and TGF transcripts were amplified in two dogs with non-distemper disease. The following transcripts were found in variable numbers in distemper dogs: IL-1 (7/14 dogs), IL-6 (3/14 dogs), IL-12 (3/14 dogs), TNF (8/14 dogs), and TGF (10/14 dogs) with multiple cytokines in ten dogs. No cytokine transcripts were detected in three distemper dogs. There was no obvious correlation between cytokine mRNA expression and respiratory and gastrointestinal tract diseases. In the CNS, demyelination was frequently associated with IL-1, IL-12, TNF and TGF mRNA expression in the blood. IL-6 transcripts were found only in animals with early CNS lesions and TGF was the only detectable cytokine in an animal with chronic demyelination. Lack of detectable cytokine transcripts in whole blood samples was associated with a high antigen index and viremia, indicating that an overwhelming virus infection may suppress cytokine production, possibly due to paralysis of the immune system. Simultaneous occurrence of pro- and anti-inflammatory cytokines in whole blood preparation from most of the dogs with distemper, indicated a complex most likely disease stage dependent orchestrated cytokine expression.

Tumor necrosis factors

Tumor necrosis factor (TNF) is a well-described and characterized cytokine which can be elicited in the intact animal by endotoxin. This factor produces necrosis of subcutaneous tumors in the classic model: Meth A sarcoma in the Balb C mouse. It has been shown to be cytostatic or cytotoxic for a variety of human cancer cell lines, as well as to have effects against both mouse tumors and human cancers carried in the nude mouse. TNF is most likely produced by the macrophage. TNF has been cloned, and has been shown to have a molecular weight of 17,000 and to contain approximately 157 acids in its active form. The genes responsible for TNF are contained on chromosome 6 in man, which also contains genes of the major histocompatibility complex. Although there are similarities to lymphotoxin, which is produced by mitogen-stimulated lymphocytes, and to interleukin-1 (IL-1), which is also produced by macrophages, TNF has distinctive differences, primarily in its antiproliferative effects. TNF is also allied with the effects of cachexia and has been shown to be similar to, if not exactly the same as, cachectin. Although it appears that effects of TNF require expression of receptors to facilitate binding to the cell, there is not a quantitative relationship between receptors and the sensitivity. TNF cytotoxic effects appeared to be amplified by pretreatment of cells with chemotherapeutic agents such as Actinomycin D, Adriamycin, and Cytoxan as well as to have synergistic effects with gamma interferon, alpha interferon, and IL-2. Although initial phase I and phase II studies of TNF in man have shown the expected toxicity, there have been minimal antitumor effects. It is anticipated that with more sophisticated studies, perhaps combining TNF with either biological or chemotherapeutic agents, TNF's true role in cancer therapy may well unfold.

Human alpha 2-macroglobulin: a major serum factor cytotoxic for tumor cells

Human alpha 2-macroglobulin (alpha 2M) was established here as a major serum factor which inhibits the DNA synthesis of a mouse ovarian tumor cell line in culture. This inhibitory activity was species non-specific, dose-dependent and unaffected by serum concentrations in culture. alpha 2 M was cytotoxic to both murine and human tumor cell lines in culture, as determined by 2 different viability staining techniques, morphological observation and long-term in vitro culture. This report implicates alpha 2 M or an alpha 2 M-associated substance as a major cytotoxic serum factor that may be involved in endogenous cancer control processes in mammalian species.

Growth inhibitors in plasma derived human serum

It was reported previously that plasma derived human serum (PDS) inhibited the growth of cells established from malignant human breast tissues and the MCF-7 cell line but did not inhibit the growth of cells from nonmalignant mammary tissues, including the HBL-100 cell line. Plasma derived human serum was fractionated in the current study by molecular sieve chromatography on Sephadex G-100 in an effort to characterize the factor(s) responsible for inhibition. Plasma derived human serum contained several growth inhibitory fractions, which were designated G-1, G-2, G-3, and G-4. THe G-1 was associated with the lipoproteins and immunoglobulins of serum. The lipid portion of G-1 inhibited the growth of both MCF-7 and HBL-100 cells, whereas the protein fraction contained a low activity factor directed against MCF-7 cells only. The G-2 also inhibited MCF-7 cell growth at a low specific activity and was separated in the serum albumin fraction. The MCF-7 inhibitory activity in the G-3 fractions from individual donors fluctuated with the level of activity in the starting sera. The cell specific G-3 components were purified further by Sephadex G-100 superfine chromatography and gel electrophoresis. A tentative molecular weight of 50,000 was assigned to the G-3 inhibitor. The G-4 fraction consisted of small molecular weight materials migrating in advance of the column volume, which inhibited the growth of both cell lines.

Cellular and humoral factors in host susceptibility to Lewis lung carcinoma

Cellular and humoral anti-tumour reactivity in strains of mice highly susceptible (C57Bl/6) or less susceptible (C57Cl/6 x DBA/2 = B6D2F1) to Lewis lung carcinoma (LLC) was investigated. Natural killer cell activity in a 51Cr release assay against this tumour could be demonstrated with a good correlation to in vivo susceptibility. This has not been demonstrated earlier for solid, spontaneous tumours. T-cell deficiency (congenital athymic (nude mice)) did not affect the cumulative incidence of tumour take. However, the number of lung metastases was significantly reduced in nude mice. Treatment with antilymphocyte serum (ALS) increased the susceptibility to LLC in both strains. In a soft agar colony assay a marked reduction in the number of colonies was observed when tumour cells were incubated with serum from B6D2F1 mice as compared to serum from C57Bl/6 mice, prior to seeding. Apparently naturally occurring cellular, as well as humoral effector mechanisms are involved in host resistance to Lewis lung carcinoma in the mouse.

A protein fraction (NHG) from serum of normal humans which is cytotoxic for HeLa cells in culture

A fraction of the alpha-globulins (NHG) from normal human serum was cytotoxic for mouse L-cells in culture and Meth A tumors in mice. NHG inhibited the growth in vitro of human colon cancer (HT-29), melanoma (RPMI 7931) and a neuroblastoma cell line. Survival of HeLa S-3 cell colonies after 24 h exposure to 25, 50, 75 or 100 micrograms NHG/ml medium was 86%, 77%, 40% and 10%, respectively. Whole human serum or purified serum albumin had no anti-HeLa cell activity. These results confirm the presence of a protein in human serum with antitumor activity. An assay for NHG using HeLa S-3 tumor cells is described.