Role of natural killer cells in the destruction of circulating tumor emboli

The mechanism of action of a synthetic immunomodulator, 3,6-bis(2-piperidinoethoxy)acridine trihydrochloride (CL 246,738), in natural killer cell activation in animals

CL 246,738 is a low molecular weight, synthetic immunomodulator. The present study was done to determine the interaction among interferon (IFN), macrophages, and natural killer (NK) cells in mice following oral administration of CL 246,738. Splenic NK activity as evidenced by lysis of YAC-1 lymphoma cells in vitro was found to be augmented by the compound not only in normal mice, but also in immunodeficient beige and nude mice. Lytic activity remained elevated from one to seven days after a single treatment and the peak activation varied depending on the source of NK cells. NK cell activity associated with the peritoneal exudate cell population peaked at day 1 and returned to normal by day 2, whereas NK cell activity of peripheral blood lymphocytes peaked at day 3 and remained significantly elevated until day 7. Liver associated NK activity peaked at day 4 and remained significantly elevated at day 7 after treatment with CL 246,738. Lung associated NK activity was elevated by day 1 after treatment, peaked at day 4 and returned to normal by day 7 after drug administration. The drug was also effective in inducing IFN in all mouse strains tested. When these drug-treated mice were given antibody to IFN-(alpha + beta) but not to IFN-(beta), both IFN levels and NK cell activity decreased, suggesting the importance of IFN-(alpha) in this system. Furthermore, mice that had received carrageenan prior to, but not after CL 246,738 administration showed reduced serum IFN titers as well as decreased NK cell activity, indicating that macrophages played an intermediate role in immune enhancement by the drug.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of subchronic d-fenfluramine on splenic immune functions in young and old male and female Fischer 344 rats

The present study was designed to demonstrate age- and sex-related differences in immune functions, and to determine whether subchronic elevations in serotonin (5-HT) availability in vivo would alter immune functions assessed subsequently in vitro. Male and female F344 rats (5 and 21 months of age) were administered the 5-HT releaser and reuptake inhibitor, d-fenfluramine (d-Fen), in their drinking water for 30-38 days then killed. The young animals received a higher dose (1.8 mg/kg/day) of d-Fen than the old rats (0.6 mg/kg/day) in order to compensate for age-related decreases in drug biotransformation and clearance. Brain and spleen d-Fen and metabolite concentrations, however, were considerably higher in the young than in the old rats. d-Fen treatment did not affect body weight or fluid intake. Although substantial sex differences in immune function were not discerned, age-related decreases were observed in absolute splenic cellularity, recombinant interleukin-2 (rIL-2) stimulated natural killer (NK) cytotoxicity, LPS stimulated B-cell mitogenesis, and in the level of Ox19 (CD5) positive cells. d-Fen caused an increase in absolute spleen weight and a decrease in absolute splenic cellularity only in the old rats of both sexes. Spleen cells from young male and old female rats receiving d-Fen had relatively more large granular lymphocytes and enhanced baseline and rIL-2 activated killing of YAC-1 cells than their vehicle matched or opposite sex counterparts. The drug also increased Con A-induced T-cell proliferation in young males and LPS induced B-cell proliferation in old females. d-Fen decreased Ox39 (CD25) levels by 19%, but did not affect any of the other phenotypes examined. The results suggest that 5-HT has a selective stimulatory effect on young male and old female NK activity, and that old female rats are more sensitive to the immunological effects of d-Fen than old male rats.

Immune-competent cells of regional lymph nodes in colorectal cancer patients: II. Immunohistochemical analysis of Leu-7+ cells

Distribution of Leu-7+ cells in cancer tissues and regional lymph nodes was immunohistochemically examined to estimate the role of NK cells in colorectal cancer patients. Leu-7+ cells were rarely observed both in the primary and distant metastatic lesions, but the number of these cells was large in the germinal center of the lymph nodes. Studies of Leu-7+ cell population in the lymph node indicated that intermediate nodes in n0 and n1 groups showed significantly higher values than those in the control group. Comparative study of the population in identical patients revealed a significantly higher rate in the intermediate nodes than in the paracolic nodes both in n0 and n1 groups. These data suggest that Leu-7+ cells might be related to the defense mechanism of regional lymph nodes against tumor.

Hyperplasia of mouse duodenal crypts and its control by NK cells during the initial phase of DMH carcinogenesis

The possible regulatory role of NK cells on early events in chemical carcinogenesis remains undefined. The present study examined whether NK cells control 1,2-dimethylhydrazine (DMH)-induced hyperplasia of the duodenal crypt in CD1 mice. Mice receiving chronic DMH treatment showed a dose-dependent hyperplasia confined to the proliferative zone, with a parallel increase in mitotic and 3H-TdR-labelled cells and significant suppression of splenic NK activity. Complete ablation of splenic NK activity with anti-asialo GM-I antibody (alpha AGM-I) treatment slightly enhanced hyperplasia. Halving of the DMH dose for 2 weeks led to regression of hyperplasia, which was totally prevented by alpha AGM-I treatment. The alpha AGM-I treatment alone did not influence crypt size in normal mice. Finally, a stimulation of NK activity with Poly I:C treatment in DMH-treated mice caused regression of the DMH-induced hyperplasia. Our results suggest that hyperplastic cells with possible genetic alterations induced by the carcinogen express target structures for NK cells, but that simultaneous carcinogen-induced suppression of NK activity hampers their containment, allowing progression of hyperplasia to neoplasia, possibly owing to additional genetic changes.

Orthotopic implantation is essential for the selection, growth and metastasis of human renal cell cancer in nude mice [corrected]

Human neoplasms are heterogeneous for a variety of biological properties that include invasion and metastasis. The presence of a small subpopulation of cells with a highly metastatic phenotype has important clinical implications for diagnosis and therapy of cancer. For this reason, it is important to develop an animal model for the selection and isolation of metastatic variants from human neoplasms and for testing the metastatic potential of human tumor cells. We have implanted human renal cell carcinoma (HRCC) cells (obtained from a surgical specimen) into different organs of nude mice and then recovered the tumors and established each in culture. The 5 established lines differed in their biological-metastatic properties and had a unique karyotype, indicating that growth at different organs selects for different subpopulations of HRCC. Moreover, the HRCC did not metastasize unless they were implanted orthotopically. These findings indicate that the appropriate nude mouse model for studying the biology and therapy of HRCC must be based on the orthotopic implantation of tumor cells.

Natural cell-mediated immunity in the rabbit

Susceptibility and resistance to tumors represent the interplay of many factors. One factor felt to govern the development of tumors is natural killer and natural cytotoxic cellular activity. The constitutional resistance of rabbits to spontaneous tumor development raises questions regarding the activity of natural cell-mediated immunity in this species. We therefore examined the ability of rabbit spleen, lymph node, and peripheral blood lymphocytes to mediate natural killer cell (NK) and natural cytotoxic cell (NC) activity in vitro. Using classical approaches to the study of NK and NC activity, we found no evidence of these activities in leporine spleen, lymph node, and peripheral blood lymphocytes. Preincubation of these cells with IL-2 did not induce such activity. Antibody-dependent cell-mediated cytotoxic reactivity (ADCC), which is believed to be mediated by NK cells, was also undetectable in rabbit lymphocytes. As controls, lymphocytes from other species were capable of mediating NK, NC, and ADCC functions normally in these experiments. Finally, we were unable to identify a population of large granular lymphocytes, the cells believed to mediate NK activity in other animals. Therefore, we could not demonstrate in the rabbit either natural cell-mediated immunity or the population of cells usually associated with natural cell-mediated immunity. If such activity exists in rabbits, it is different from that seen in other animals. More likely, the basis for the natural resistance of rabbits to tumor development must be sought elsewhere.

MHC restricted and non-restricted killer lymphocytes

Cytotoxic lymphocytes are either MHC-restricted (cytotoxic T-cells) or nonrestricted (natural killer NK-cells), although cells of the monocyte/macrophage lineage are also cytotoxic, and lymphocytes or phagocytic cells expressing Fc-receptors for immunoglobulin can function as antibody-dependent killer cells (referred to as antibody-dependent cellular cytotoxicity: ADCC). Antigen-specific T-lymphocytes recognise their target antigen in the context of MHC class I components, focusing their attack only against those cells expressing the relevant antigen specificity on their cell surface. A more primitive and alternative mechanism exists whereby NK-cells, classified as large granular lymphocytes (LGL), are able to kill in a non-specific manner, not requiring prior sensitisation to antigen. Both antigen-specific T-cells and LGL mediate their cytotoxicity through the release of cytotoxic molecules at the target-effector cell interface. LGL also have a regulatory role in the immune system through the release of cytokines, and can be distinguished from T-lymphocytes by the expression of distinct phenotypic markers (CD16+, CD56+) and they lack CD3 antigen expression or rearranged alpha/beta or gamma/delta T-cell receptor gene products. Cytotoxic activity is positively regulated by interleukin-2 (IL-2) and interferon (IFN), whilst prostaglandins and transforming growth factor-beta (TGF beta) diminish activation and effector pathways. Cytotoxicity mediated by NK- and T-cell populations are principally involved in the defence against microbial infections and neoplasia; the abrogation of cytotoxicity either by direct interaction of 'suppressor factors' with effector cells, or indirectly by reducing cytokine production can inevitably lead to the proliferation of the disease.

Effects of a stable prostacyclin analogue on platelet activity and on host immunocompetence in mice

The stable prostacyclin (PGI2) analogue, iloprost, is a potent inhibitor of both tumor cell-induced platelet aggregation and of experimental metastasis in mice. To explore possible mechanisms of antimetastatic effect of iloprost, we measured the effect of this drug on both platelet aggregation and immunocompetence in the mouse. Iloprost (4 x 10(-8) M) inhibited platelet aggregation as induced by a mixture of collagen and epinephrine for at least 180 minutes of incubation, and completely reversed platelet aggregation when added during the second wave of aggregation. In addition, aggregation of platelets obtained from iloprost-treated mice (0.2 mg/kg) was completely inhibited for at least 90 minutes of incubation. Moreover, iloprost pretreatment in vivo counteracted tumor cell-induced thrombocytopenia. Thus, mouse platelets were equally sensitive to the inhibitory effect of iloprost on aggregation as platelets of other species including humans. Effects of iloprost on parameters of host immunocompetence that may influence tumor growth and metastasis formation were also evaluated. Iloprost treatment increased significantly macrophage cytostasis to tumor cells, natural killer (NK) lytic activity of spleen cells and T-cell mediated cytotoxicity ex vivo. These results suggested that the antimetastatic effect of iloprost in the mouse may be attributable to multiple mechanisms including inhibition of platelet aggregation and stimulation of certain host immune functions.

Neoadjuvant immunotherapy with interferon of the spontaneously metastasizing murine B16F10L melanoma

We have previously demonstrated that administration of interferon a/b (IFN) for 4-5 days after challenge with a transplantable Moloney sarcoma virus-induced tumor completely inhibited tumor development. In the present study, we examined the therapeutic effects of IFN on mortality induced by metastatic dissemination of the B16F10L murine melanoma. IFN was administered at various times in relation to the surgical removal of primary tumor: days -5 to -1 prior to tumor excision (neo-adjuvant protocol), or for 5 days after tumor excision, beginning on days 1, 6 or 11 after excision of the primary tumor (adjuvant protocols). The neo-adjuvant protocol was superior to all other protocols, significantly increasing percentage survival (56% vs. 0%) and median survival time (greater than 84 days vs. 33 days) compared to untreated controls, as well as to all adjuvant protocols. In contrast, IFN treatment on days 1 to 5 after excision of the primary tumor decreased median survival time of cases compared to untreated controls (20 days vs. 33 days). Both IFN-induced inhibition and enhancement of metastatic dissemination were dose-dependent, with higher amounts of IFN producing greater inhibition or enhancement. The superior therapeutic efficacy of the neo-adjuvant IFN treatment was associated with increased spleen and lung-derived natural killer cell cytolytic activity (on days -4, 0 and 2) followed by a later (day 13) increase in lung-associated cytolytic T-cell responses.

N-methylformamide affects spontaneous metastases of 3LL lines and increases natural killer activity of tumor-bearing mice

The antitumor activity of the polar solvent N-methylformamide (NMF) was evaluated on three lines derived from the Lewis lung carcinoma (3LL), endowed with different metastatic potential. Two administration schedules were tested, these being repeated regimens of NMF (200 mg/kg per dose) for 12 consecutive days, starting 24 h or 6-10 days after tumor implantation (early or late treatment, respectively). The results of the present work can be summarized as follows: (1) NMF regimens did not greatly affect tumor growth behavior of 3LL lines; conversely, they markedly influenced their spontaneous colonizing ability in the lungs, either by delaying early metastatic spread or by reducing the number and size of pulmonary metastases already implanted. (2) A significant increase of NK cell activity during and after early treatment with NMF was observed in the more-metastasizing lines, thus suggesting the possibility of an immunomodulating effect of NMF.

Reduction of metastasis in a murine mammary tumour model by heparin and polyinosinic-polycytidylic acid

A murine mammary tumour model has been used to test the efficacy of a combination of heparin and the interferon inducer, poly I:C on spontaneous metastasis from a s.c. primary tumour and on experimental metastasis following i.v. injection of tumour cells. This treatment has no effect on the growth of primary tumours, but lung metastases arising from these tumours were reduced. When tumour cells were injected i.v. the number of lung colonies was significantly reduced and survival time extended. Short-term treatment did not prevent the subsequent growth of extravasated, but dormant tumour cells, although mice treated for 8 or 12 weeks survived at least 6 months without any sign of lung colonies. Several mechanisms may contribute to the overall effect of this treatment; a reduction in the mitotic indices of lung colonies (observed in poly I:C treated mice) and also NK cells appeared to be important for the effectiveness of poly I:C since the reduction in experimental metastasis was abrogated by concomitant treatment with anti-asialo GM1 serum.

Antimetastatic effect of defibrinogenation with batroxobin depends on the natural killer activity of host in mice

Using batroxobin, a thrombin-like enzyme found in snake venom, the effects of defibrinogenation on artificial lung metastasis in mice were studied. The role of natural killer (NK) cells in the inhibitory effects of defibrinogenation on metastasis was also investigated. Artificial lung metastasis experiments were performed by inoculating either B16-F10 cells or B16-BL/6 cells, highly metastatic strains of B16 melanoma cells, into C57BL/6 mice via the tail vein. The administration of batroxobin significantly inhibited lung metastasis, as did NK activity augmented by poly (I).poly (C) were administered, lung metastasis was more markedly inhibited. When NK activity was suppressed by administration of anti-(asialo GM1) antibody, lung metastasis was markedly increased. When batroxobin was administered with anti-(asialo GM1) antibody, no inhibitory effects on lung metastasis, such as those seen with batroxobin alone, were observed. The administration of batroxobin had no effect at all on spleen lymphocyte NK activity. These results indicated that defibrinogenation due to batroxobin inhibits lung metastasis, and these effects depend on NK activity of the host.

Inhibition of lung colonization of mouse colon 26 adenocarcinoma by recombinant mouse interferon beta through a modification of platelet function

Recombinant murine interferon beta (MuIFN-beta) given i.v. efficiently inhibited both pulmonary arrest and formation of lung colonies of NL-17, a highly metastatic variant of mouse colon adenocarcinoma 26. NL-17 was rather resistant to MuIFN-beta in vitro and was highly resistant to natural killer cells of mice even though they were treated in vivo with MuIFN-beta. Platelets isolated from MuIFN-beta-treated mice showed reduced aggregating activity induced by NL-17. Since lung colonization by NL-17 is influenced by platelet aggregation, the inhibition of colonization by MuIFN-beta could be partly mediated through modification of platelet function in vivo. The effect of MuIFN-beta on platelet function and its subsequent inhibition of lung colony formation give new insights into the action of recombinant MuIFN-beta.

Opposing influence of age on the growth and colony-forming ability of mouse melanoma B16 and mammary adenocarcinoma: correlation with natural killer activity

C57B1 and CBA mice of different ages (6, 12, 26 or 35 weeks) received intramuscular inocula of melanoma B16 or mammary adenocarcinoma (MCa), respectively. Median survival time was shorter, the younger the recipients. Tumor enlargement was correspondingly retarded in older mice. This was associated with decrease of natural killer (NK) activity in the spleens. However, the cytotoxicity against fresh syngeneic tumor cells, increased with age in CBA mice. In contrast to the growth of intramuscular tumors, the ability of intravenously injected B16 or MCa cells to form nodules in the lungs was significantly superior in old animals (35 weeks or more), with low levels of NK activity, than in young ones (6 weeks) with high levels of NK activity. Stimulation of NK activity by poly(I).poly(C) reduced the number of MCa colonies by 50% in the lungs of old mice, but had no effect on colony-forming ability in young animals. The observed association of tumor growth with age and NK activity levels may reflect (a) an interplay of tumor-inhibiting and tumor-promoting effects of NK cells, changing with age, and (b) the accessibility of tumor cells, inoculated intramuscularly or captured in the lungs, to these influences.

The in vivo clearance of Ha-ras transformants by natural killer cells

The experiments in this study were designed to test the hypothesis that natural killer (NK) cells play a role in host surveillance against early neoplastic changes in the malignant process. C3H 10T1/2 mouse fibroblasts were transfected with a pSV2-neo plasmid vector which contains EJ, the mutated c-Ha-ras, regulated by its own promoter. Control cells were transfected with pSV2-neo alone and did not contain the ras gene. Oncogene-transfected cells were compared with control cells for lung colony formation following tail vein injection into C3H mice. Intravenous injection of ras-transfected 10T1/2 cells induced marked lung colony formation in vivo, whereas C3H 10T1/2 parental lines or 10T1/2 cells transfected with pSV2-neo alone induced no lung colonies in C3H mice. The colonising potential of ras transfectants could be decreased by augmentation of NK activity by injection of polyinosinic cytidylic acid and increased by depletion of NK effectors with anti-asialo GM1. Experiments with beige mice demonstrated that the mortality of syngeneic, NK-deficient C3H-bg/bg mice injected with ras tranfectants was significantly greater than similarly treated NK-normal C3H(-)+/bg littermate controls. The results support the view that NK cells are capable in vivo of recognizing early defined stages in the neoplastic process initiated by oncogenes.

NK sensitivity and lung clearance of MHC-class-I-deficient cells within a heterogeneous fibrosarcoma

The present study examines clonal variations in NK sensitivity in a methylcholanthrene-induced fibrosarcoma. Previous studies of clones from this tumor have shown considerable heterogeneity in H-2 expression, and an association between deleted or low levels of class-I products and increased tumorigenicity after subcutaneous implantation in immunocompetent syngeneic mice. Here, fibrosarcoma clones with no or low expression of MHC-class-I products were found to be sensitive to NK-mediated lysis, while clones with high levels of MHC-class-I expression were relatively resistant. One H-2+ (G2) and one H-2- (B9) clone were chosen for more detailed studies. Cold-target competition assays and conjugate cytotoxicity assays in agarose showed that splenic effector cells bound equally well to the H-2+ and H-2- tumor clone, although only the latter was sensitive to NK cell lysis. Treatment with 50 U/ml of rIFN-gamma for 48 hr increased the levels of H-2 expression and made both clones more resistant to NK-mediated lysis. In vivo studies with radiolabelled tumor cells showed that cells from the H-2+ clone survived better than cells from the H-2- clone in the pulmonary capillary bed after i.v. inoculation. This difference disappeared in mice treated with anti-asialo GM1 serum, known to deplete NK cell activity.

Modulation of metastatic ability by inhibition of cholesterol synthesis

Synvinolin (MK-733), a potent inhibitor of 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMG-CoA reductase) depressing de novo synthesis of cholesterol, was given to BN472 tumor cells in culture medium, 2 days prior to i.v. injection of the cells into syngeneic rats. Another group of rats received cells cultured under the same conditions but without synvinolin. Two different types of culture medium were used, a 'complete' medium (Hybridoma) and a medium (RPMI 1640) to which 1 per cent of fetal calf serum (FCS) was added. Tumor cells cultured in the presence of synvinolin showed significantly lower cholesterol values than untreated cells. Tumor cells treated with synvinolin had a decreased ability to form metastatic nodules when compared with control cells. The results supply further evidence for the suggestion that cholesterol modulates the ability of mononuclear cells to eliminate tumor cells, although it cannot be excluded that alteration of cell growth plays an important role as well.

Differential activity of a tissue-specific extinguisher locus in hepatic and nonhepatic cells

Tissue-specific extinguisher 1 (Tse-1) is a genetic locus on mouse chromosome 11 that can repress expression of several liver genes in trans. This locus is clearly active in fibroblasts, as hepatoma cells retaining fibroblast chromosome 11 are extinguished for both tyrosine aminotransferase and phosphoenolpyruvate carboxykinase gene expression. To assess the activity of Tse-1 in other tissues, we transferred mouse chromosome 11 from several different cell types into rat hepatoma recipients. Tse-1 was active in nonhepatic cell lines derived from each primary germ layer, but Tse-1 activity was not apparent in hybrids between hepatoma cells and primary mouse hepatocytes. These differences in the genetic activity of murine Tse-1 were apparently heritable in cis.

Eicosanoid synthesis by alveolar macrophages in rats with malignant mammary tumors: differences in rats treated with and without carrageenan implants

Eicosanoid synthesis by alveolar macrophages (AM), harvested from tumor bearing animals, was measured after tumor inoculation in rats treated with or without carrageenan (carra), an immunomodulating agent. After incubation of the cells with [14]C-arachidonic acid and the Ca-ionophore A23187, samples were measured by high pressure liquid chromatography (HPLC). From the HPLC profiles the lypoxygenase products, 12-hydroxyeicosatetraenoic acid (12-HETE), 15-HETE, and leukotriene-B4 (LTB4) were determined as well as the cyclooxygenase products, prostaglandin (PG)E2, PGF2 alpha and TXB2. After tumor inoculation AM-synthesis of lipoxygenase products tended to increase to values twice those of the base line values, whereas cyclooxygenase products showed subnormal values. In the non treated animals, 10 days after tumor inoculation, statistically significant increases in 12- and 15-HETE, LTB4 and PGE2 were observed when compared with carra treated animals. Later measurements did not show these differences in AM metabolism. AM metabolism was (negatively) correlated with the number of macrophages, which was particularly evident in the correlation with 12-HETE synthesis.

Suppression of human natural killer cell activity by amino sugars

In the present study we investigated the effect of amino sugars on human natural killer (NK) activity against K562, a human myeloid leukemia cell line, and Molt-4, a human T lymphoma cell line. The presence of amino sugars such as D-mannosamine, D-galactosamine, and D-glucosamine [6-25 mM (in the case of D-mannosamine, 1.5-12.5 mM)] in a 4-hr chromium-51 (Cr) release assay significantly inhibited NK activity of large granular lymphocytes (LGL) without affecting effector cell viability or spontaneous release from target cells. Sugars with acetylated amino residues (N-acetyl-D-mannosamine, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine) showed much smaller NK inhibition. Among the amino sugars tested, D-mannosamine was the strongest suppressor. When either LGL or K562 cells were pretreated with amino sugars and used in the 4-hr 51Cr release assay, only the pretreatment of effector cells resulted in the reduction of NK activity. The binding capacity of LGL to K562 cells, determined by a conjugate assay, was not reduced by the amino sugars enough to explain the strong inhibition of NK activity by these amino sugars, although some inhibitory effect on the binding of LGL to K562 cells was observed in some cases. In contrast, the polarization of the effector cell cytoskeleton, one of the energy-dependent steps, was significantly impaired. The cellular ATP level of LGL was also significantly reduced and the reduction of cellular ATP correlated well with the degree of the inhibition of NK cytotoxicity. These results suggest that the suppression of NK activity by amino sugars is due to the reduction of the ATP-based energy supply of the effector cells and that amino sugars, especially D-mannosamine, should be recognized as potent suppressors of natural cell-mediated immunity.

In vivo and in vitro modulation of NK and ADCC activities of mouse spleen cells by peptidoglycan monomer (PGM)

The ability of peptidoglycan monomer (PGM), an immunomodulator obtained from Brevibacterium divaricatum, to modulate NK and ADCC activities of spleen cells was tested in mice with constitutively weak (C57B1) or strong NK activity (CBA, C3H). In weak reactors, i.v. injection of PGM enhanced the NK and ADCC activity as effectively as a known stimulator, poly I.C, and the dynamics of the response was comparable. In strong reactors, PGM caused two peaks of the ADCC response, and one peak of NK stimulation (after an initial decline), whereas poly I.C caused more or less persistent stimulation of both activities. Incubation of spleen cells with PGM was generally less effective than the treatment in vivo. No alteration of NK activity was recorded at high effector-to-target ratio (E:T), and at low ones, PGM caused suppression. This was true both for weakly and strongly reactive cells. ADCC was either unchanged (CBA spleen cells), stimulated (C3H), or suppressed at high E:T and enhanced at low E:T (C57B1). PGM apparently activates an interlocked regulatory mechanism, and the final outcome probably depends on relative concentrations of regulatory and effector cells and on their per cell activities. Hence the effect varied with the time interval between treatment and assay, with strain-related constitutive reactivity, and with the E:T ratio.

Natural resistance in mice against Friend cells injected intravenously. III. Comparison between in vivo and in vitro passaged interferon-sensitive (745) and interferon-resistant (3Cl8) cell clones

In vitro (FLC-Vt) or in vivo (FLC-V) passaged Friend erythroleukaemia cells of DBA/2 origin were tested for susceptibility to natural resistance (NR) in vivo or to NK cell activity in vitro. Scarcely oncogenic FLC-Vt cells were highly susceptible to in vivo NR (measured as rapid organ clearance or growth inhibition in lethally irradiated mice) or to in vitro NK attack. Conversely, highly oncogenic FLC-V cells were weakly susceptible to NR and to NK as well. These data seem to point out that natural immunity, which is up-regulated by endogenous or exogenous interferons, can play a significant role in surveillance against mouse leukaemic cells of retrovirus origin.

Differential activity of a tissue-specific extinguisher locus in hepatic and nonhepatic cells

Tissue-specific extinguisher 1 (Tse-1) is a genetic locus on mouse chromosome 11 that can repress expression of several liver genes in trans. This locus is clearly active in fibroblasts, as hepatoma cells retaining fibroblast chromosome 11 are extinguished for both tyrosine aminotransferase and phosphoenolpyruvate carboxykinase gene expression. To assess the activity of Tse-1 in other tissues, we transferred mouse chromosome 11 from several different cell types into rat hepatoma recipients. Tse-1 was active in nonhepatic cell lines derived from each primary germ layer, but Tse-1 activity was not apparent in hybrids between hepatoma cells and primary mouse hepatocytes. These differences in the genetic activity of murine Tse-1 were apparently heritable in cis.

Radioimmunolocation of hepatic and pulmonary metastasis of human colon adenocarcinoma

We have established a large library of monoclonal antibodies against a human hepatoma cell line called FOCUS. One such monoclonal antibody (SF-25) detects a 125-kilodalton cell surface antigen found on FOCUS cells. As both the liver and the colon are of endodermal origin, we examined the possibility of expression in colon adenocarcinomas. This antigen was found in all 23 colon adenocarcinoma tissues surgically obtained but was absent in the adjacent normal mucosal counterpart as determined by a direct radioimmunohistologic technique. In the present study, we have established a model for human metastatic colon adenocarcinoma using the LS 180 cell line. Athymic mice were further immunosuppressed by intravenous injection of anti-NK cell antibodies (antiasialo GM1). After 24 h, mice were injected with LS 180 cells either via the tail vein or into the spleen followed by splenectomy. Macroscopic pulmonary and lymphatic metastasis developed within 2-3 wk after injection of cells and 9 of 10 mice died with advanced metastatic disease 2-3 wk later. In addition, macroscopic hepatic metastases were evident in 4 of 5 mice 3-4 wk after intrasplenic injection. Both hepatic as well as pulmonary and lymphatic tumor spread was localized by nuclear imaging with 125I-SF-25. Furthermore, micrometastases were detected by autoradiography 5-10 days later. Monoclonal antibody SF-25 is a potential candidate for tumor localization and the experimental metastatic colon cancer animal model may be useful for treatment evaluation of monoclonal antibody SF-25 either alone or in combination with other monoclonal antibodies when conjugated to radionucleotides and chemotherapeutic agents.

Isolation and characterization of low- and high-metastatic clones from murine RCT (Radiological, Chiba, and Toyama) sarcoma

We have established low- and high-metastatic clones, named RCT(-) and RCT(+) cells, respectively, from the RCT (Radiological, Chiba, and Toyama) sarcoma spontaneously developed in a C3H/He male mouse by the limiting-dilution method in vitro or by the combination of the lung passages and limiting-dilution methods. After 20 serial passages in vitro, the metastatic potential of each clone did not alter. Morphologically, both cells were spindle-shaped, but RCT(+) cells were slightly thicker and larger than RCT(-) cells. The organization of actin-containing filaments was slightly poorer in RCT(+) cells than that in RCT(-) cells. Marked differences were observed in their growth characteristics and adhesiveness to plastic or collagen-coated surfaces, that is, RCT(+) cells grew more slowly but could adhere more rapidly and firmly to the surfaces than RCT(-) cells. RCT(+) cells were agglutinated by all lectins used but several lectins could not agglutinate RCT(-) cells. These results could be a reflection of the difference in oligosaccharide residues on the surface of each cell and, in part, might reflect the difference in organization of the actin-containing filaments that regulate the mobility of lectin receptors. No significant difference between these cell clones was noted in their sensitivity to natural-killer-cell-mediated cytotoxicity in vitro. RCT(-) and RCT(+) cells are considered to be the most useful experimental model for the study of the certain sarcomas.

Effects of the immunomodulator PSK on growth of human prostate adenocarcinoma in immunodeficient mice

Tumor growth alterations were studied using an immunomodulator, PSK. Four human prostate tumor lines were grown in two types of immunodeficient mice. Two of the lines were selected because they are able to metastasize to lungs in host animals. Outbred NIH Swiss athymic mice having normal natural killer cells and athymic Beige mice deficient in natural killer cells were used as animal hosts. PSK treatment was given to tumor-bearing hosts to some animals soon after solid tumors were injected and to others after solid tumors were well-established. Low dose cyclophosphamide was given to some animals to decrease host natural killer cells and polyinosinic-polycytidylic acid (poly I:C) was given to other animals to increase natural killer cell activity. Measurement of tumor doubling times, host survival and metastatic capabilities showed that either poly I:C or PSK treatment in NIH Swiss animals soon after tumor cells were injected significantly increased tumor doubling times and host survival and decreased the incidence and number of metastatic lung lesions. Two of the tumor lines incapable of metastasizing in NIH Swiss mice were metastatic in the Beige athymic, natural killer-cell-deficient animals.

The relationship between MHC antigen expression and metastasis

From the studies summarized here a complex picture of the role played by MHC products in determining tumorigenicity and metastasis is emerging. In order to be able to understand this relationship better, it is necessary to consider several factors. 1. Each tumor system or neoplastic tissue is unique, and its behavior reflects the influence of cell-specific characteristics, as well as its ability to modulate other cells and tissues--including cells belonging to the immune system--and also to be modulated by other cells and soluble factors. 2. Since metastasis formation is a multistep process in which only small subpopulations of tumor cells with complex and defined phenotypes are able to colonize secondary tissues, elimination of even one single phenotypic component of this structured process can easily reverse the metastatic capacity of the cells. Acquisition of metastatic ability, on the other hand, would be a more difficult task, since any new characteristic expressed by the cells or induced experimentally, such as gene transfection or results of IFN treatment, must be expressed in a temporal manner and in concert with other cellular characteristics. Therefore, an experimental protocol measuring a specific element in determining metastasis can easily produce conflicting results, depending on the type of cells and genetic background of the host studied. 3. The level of specific MHC products on tumor cells is one among many other cell characteristics that may determine the metastatic potential of cells. Moreover, each of the class 1 MHC products, and the relationship among them, including other than the classical K, L, or D products (Brickell et al., 1983), should be regarded as independent entities, with possible different regulatory roles in cell-cell recognition, in a general sense, which may be involved in determining invasiveness and homing as well as recognition by the immune system. 4. Both specific T-cell and nonspecific natural mediated immunity (which is much less understood) are involved in the selection of the metastatic cell population. 5. Immunogenicity of tumors is not necessarily determined by high levels of MHC antigen expression; it is also dependent on the level of TSA. Thus, immunoselection mediated by T lymphocytes during metastasis formation could be directed against both MHC and TSA antigens. Therefore, low expression of MHC antigens by metastatic cells as a result of immunoselection is not always observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Non-cytotoxic asialo-GM1-positive cells exert antimetastatic activity

Metastasis can be inhibited by asialo-GM1-positive spleen cells, and in this paper we show that there are two such spleen cell populations. One population is adherent and non-cytotoxic to YAC cells, whereas the other population is non-adherent and cytotoxic to YAC cells. Both cell populations exert an antimetastatic activity in cyclophosphamide-treated mice that are inoculated with LL2 Lewis lung carcinoma cells. We conclude that the antimetastatic activity is not only exerted by cytotoxic asialo-GM1-positive cells (apparently natural killer cells), but also by adherent, non-cytotoxic asialo-GM1+, Thy1.2-, IgG- cells. This means that the latter exert their antimetastatic activity by a non-cytotoxic mechanism.

Inhibition of lymphokine-activated killer cell generation by cultured tumor cell lines in vitro

The co-culture of human peripheral blood mononuclear cells (PBMC) with high concentrations of interleukin 2 normally generates lymphokine-activated killer (LAK) cells capable of indiscriminate lysis of tumor targets. However, the addition of certain cell-line-derived tumor cells to the LAK generation cultures within the first 48 h of culture initiation resulted in the suppression of the LAK cytotoxicity measured after 3-4 days of culture. Suppression could be achieved with tumor cell:PBMC ratios as low as 1:50 when tumor cells were derived from melanoma and colorectal cancer (G361, COLO320, HT-29), but suppression was not observed with cells from the breast cancer cell line SKBr3. No suppression of LAK generation was observed with normal epithelial cells from colon or breast, with autologous or allogeneic lymphoblasts, or with allogeneic vascular endothelial cells. Suppression was independent of the removal of adherent cells from PBMC, could not be prevented by indomethacin and was not attributable to interleukin 2 absorption/adsorption by tumor cells. The suppressive activity of some tumor cells could be augmented by preculture in recombinant gamma interferon. Serum-free supernatants from G361, COLO320 and HT-29 (but not SKBr3 or endothelial cells) were also highly suppressive towards the generation of LAK cells. The elaboration by tumor cells of factors capable of inhibiting LAK generation may partially explain the failure of LAK/interleukin 2 therapy in some experimental and clinical protocols.

Growth and metastasis of human tumors in nude mice following tumor-cell inoculation into a vascularized polyurethane sponge matrix

Growth and metastasis of human tumor cells in immunodeficient nude mice were improved when tumor cells were inoculated within a vascularized artificial polyurethane sponge matrix. The sponges had been implanted 7-10 days earlier and were vascularized at the time of cell injection. All cell lines tested, including colon carcinoma-derived lines from primary tumors (HT29, PT3 and PT4) or from liver metastasis (LM3), and a metastatic variant from a melanoma (MeWo-Met) grew in a high percentage (78-94%) of the inoculated sponge grafts. When growth in sponge grafts is compared with growth at a subcutaneous site, the sponge matrix appears to increase tumorigenicity, at least for some cell lines. Regular formation of metastases was observed when cells had been injected into sponges. Most metastases were found in a second sponge graft implanted at a contralateral site, but some were also found at other s.c. sites. In vivo depletion of NK cells by pre-treatment with cyclophosphamide could not further enhance the formation of metastasis. Tumor cells from fresh surgical specimens could be propagated in sponge matrix grafts and subsequently established as cell lines in tissue culture.

Relation of H-2 expression on murine RCT(+) sarcoma cells to lung colonization and sensitivity to NK cells

Murine RCT(+) sarcoma cells were sorted using a fluorescence-activated cell sorter with regard to the expression of H-2 antigens and then an increased H-2-expressing subclone was established, and named RCT(+)H-2+. The experimental metastasis of RCT(+) cells was compared with that of RCT(+)H-2+ cells by counting pulmonary colonies on the 21st day after i.v. inoculation of tumor cells (5-10 x 10(4)/mouse). When mice were inoculated with RCT(+) cells, mean numbers of pulmonary colonies were 2.1(range 0-6), 2.8(range 0-7) using 5 x 10(4) and 1 x 10(5) cells, respectively. On the other hand, in the mice inoculated with RCT(+)H-2+ cells, figures obtained were 7.0(range 4-16), 31.9(range 13-79), using 5 x 10(4) and 1 x 10(5) cells, respectively. The survival rate of RCT(+)H-2+ cells was higher than that of RCT(+) cells, when this was assayed in the early stage after i.v. injection of 51Cr-labeled cells (1 x 10(5) cells/mouse). In addition, RCT(+)H-2+ cells were more resistant than RCT(+) cells to lysis mediated by natural killer cells. These data suggest that an increase in metastatic ability was paralleled by an increase in the H-2 antigen expression and a decrease in sensitivity to the natural killer cells.

Effects of low dose perioperative interferon on the surgically induced suppression of antitumour immune responses

General surgical procedures are followed by a period of generalized immunosuppression that may favour the deposition of metastases seeded at operation in patients with malignant disease. In an attempt to prevent the suppression of host-antitumour immune mechanisms following surgery we have studied the immunological effects of low-dose perioperative interferon-alpha (r-HuIFN alpha). Patients were randomly allocated pre-operatively to the control (n = 15) or treatment group (n = 15). Patients in the treatment arm received a 1-week course of subcutaneous recombinant human interferon-alpha 2a (Roferon-A) at a dose of 2 megaunits daily starting on the evening before surgery. Natural killer cell, lymphokine activated killer cell cytotoxicities and endogenous interleukin 2 production were measured 1 day before surgery and on the first, third, fifth and tenth postoperative days. Treatment with r-HuIFN alpha did not prevent the postoperative impairment of interleukin 2 production or lymphokine activated killer cell cytotoxicity. However it prevented the fall in natural killer cell activity normally observed following surgery. This may have important consequences in controlling metastatic dissemination of tumour in this vulnerable period.

Tumor cells are protected from NK-cell-mediated lysis by adhesion to endothelial cells

We have examined the effect of various cell monolayers on the ability of mouse spleen cells to lyse tumor cell targets (natural cytotoxicity reaction). Natural killer (NK) cell activity was reduced by as much as 75% depending on the cell substrate, with the greatest protection afforded by endothelial cells. Cell adhesion to the underlying cell monolayer was directly correlated with the degree of protection from lysis. Since it has previously been shown that tumor cells manifest selective adhesion to endothelial cells from those organs to which they are likely to metastasize, the experiments suggest a means by which natural surveillance mechanisms might be circumvented during the metastatic process.

Trichinella pseudospiralis larvae express natural killer (NK) cell-associated asialo-GM1 antigen and stimulate pulmonary NK activity

Natural killer (NK) cell function was evaluated in mice infected with either Trichinella pseudospiralis or T. spiralis larvae. T. pseudospiralis-infected mice consistently demonstrated augmented pulmonary NK cell-mediated clearance of YAC-1 tumor cells in vivo but failed to display enhanced splenic NK cell-mediated lysis of the same tumor cells in vitro. Attempts to alter NK cell function in vivo by the injection of anti-asialo-GM1 antibody resulted in anaphylaxis and death of the hosts infected with T. pseudospiralis but not of mice infected with T. spiralis. Immunofluorescence studies demonstrated that larvae of both species bound large quantities of anti-asialo-GM1 antibody but did not react with another NK-associated antibody, anti-NK-1.1. Even though anti-asialo-GM1 antibody reacted with larvae of both species, intravenous injection of antibody elicited anaphylaxis only in hosts that were infected with T. pseudospiralis.

Physiological relationships among stress, viruses, and cancer in experimental animals

Anxiety-induced psychoneural stimulation, via the hypothalamic-pituitary axis, activates the adrenal cortex to release corticosteroids, which elicit various alterations of corticoid-sensitive cell-mediated immunologic processes. Stress sensitive murine tumor-host experimental models have been utilized to demonstrate various effects of stress upon aspects of tumor development. Although many of the observed anxiety-induced alterations of tumor-related parameters can be interpreted in terms of corticoid-induced modifications of immune functions, other observations are more difficult to interpret, and may be caused in part by corticosteroid-independent modulation of lymphocyte functions. In the case of tumors induced by oncogenic viruses, anxiety-induced plasma corticoid elevations may also act independently of the immune system to stimulate tumor development via hormone binding sites on proviral DNA. Rigorously controlled environmental and experimental conditions are fundamental for the demonstration and interpretation of stress-related phenomena. Technical prerequisites include protective animal facilities, special handling procedures, the use of nontraumatic stressors, and the recognition of vital psychosocial, coping and timing factors. Various biologic factors, such as sex, genetic substrain differences and common interfering viral infections, must also be controlled or taken into consideration.

Role of concomitant resistance in the development of murine lung metastases

An attempt was made to explain the distinct lung metastatic patterns of 2 mammary adenocarcinomas with a common BALB/c origin: M3, which does not induce spontaneous metastases, and MM3 with an almost 100% incidence. No difference between the 2 tumors was detected with respect to host mononuclear cell content, degree of immunogenicity or lung-colony-forming ability. Conversely, there was a marked difference in the capacity to induce concomitant resistance: M3-bearing mice induced stronger and earlier resistance against i.v. challenge of both M3 and MM3 tumor cells than MM3-bearing mice; this resistance was expressed as lower number of lung metastases and lower tumor-cell proliferation in metastatic nodules. M3 was also able to control the development of spontaneous metastases: metastases developed in all M3-excised mice, compared with none in M3-bearing mice, while MM3-bearing mice also bearing a secondary M3 tumor developed fewer metastases than mice bearing MM3 only. This anti-metastatic effect does not appear to depend on classical immunological mechanisms since no difference could be detected between the 2 tumors in response to T cells, NK, macrophages or antibodies.

Inhibition of experimental metastasis with indomethacin: role of macrophages and natural killer cells

The metastatic capacity of murine mammary tumor line 410.4 is greatly increased by treatment of the host with asialo-GM1 antiserum (5-fold), 2-chloroadenosine (4-fold) or k-carrageenan (2.5-fold). This suggests that both NK cells and macrophages contribute to control of metastatic dissemination. The metastatic potential of these cells is associated with the synthesis of high levels of prostaglandin E2 (PGE2) (1). When line 410.4 cells are cultured in vitro in the presence of the prostaglandin synthesis inhibitor indomethacin (INDO) 1 microM) their subsequent lung colonization ability (experimental metastasis) is reduced by 50-90% as compared to solvent-treated cells. The inhibitory effect of INDO is highly dependent on the presence of asGM1 positive cells, and is compromised to a lesser extent by treatments directed towards macrophages. The INDO-mediated inhibition is neither due to differential arrest of tumor cells in the lung nor does it appear to be due to shifts in the replication cycle.

Investigation of the biological effects of anti-cell adhesive synthetic peptides that inhibit experimental metastasis of B16-F10 murine melanoma cells

The experimental metastasis of B16-F10 murine melanoma cells is blocked by the anti-cell adhesive pentapeptide Gly-Arg-Gly-Asp-Ser (GRGDS) derived from the central cell-binding domain of fibronectin. In this report, we show that peptide treatment substantially extends the survival time for mice injected intravenously with B16-F10 cells (8/8 vs. 0/8 mice alive at 150 d), thereby demonstrating the potential efficacy of GRGDS treatment in protection against metastatic colonization. We have also examined the specificity of GRGDS activity by testing a series of related homologues for their effects on experimental metastasis. The overall profile of the relative inhibitory activities of these peptides closely matched their previously established capacity to disrupt adhesion in vitro. Lung retention studies with radiolabeled B16-F10 cells revealed an accelerated rate of cell loss from the lung 0-6 h after coinjection with the active peptide GRGDS. This early effect of GRGDS was consistent with its short circulatory half-life, which was found to be 8 min. Taken together, these results suggest that peptide-mediated inhibition of pulmonary colonization is due to interference with B16-F10 cell adhesion to structures in the target organ. Possible peptide interference in tumor cell-blood cell interactions was examined in order to assess (a) possible biological side-effects of peptide treatment and (b) whether such interactions might be an alternative mechanism for GRGDS-mediated inhibition of pulmonary colonization. GRGDS was found to retain full inhibitory activity when coinjected with B16-F10 cells into mice in which platelet function was impaired by acetylsalicylic acid treatment or into thrombocytopenic mice treated with antiplatelet serum (76-93% inhibition of colony formation). These data suggest that platelet involvement in the effects of the peptide is minimal. Similarly, GRGDS was also found to be a potent inhibitor of experimental metastasis in natural killer (NK) cell-deficient beige mice (86% inhibition), thereby discounting the possibility that GRGDS artifactually enhanced NK cell activity. We conclude as a result of these studies that cell-binding fibronectin peptides are specific inhibitors of experimental metastasis that prolong survival, that they appear to function by blocking the adhesion of B16-F10 cells to structures in the target organ, and that they do not appear to act through side effects on certain metastasis-related blood cell functions. In the future, derivatives of fibronectin peptides may be potentially useful prophylactic agents for interfering with the process of metastasis.

Tumor necrosis can facilitate the appearance of metastases

The non-metastatic murine mammary adenocarcinoma M3 and its metastatic variant MM3 were used to evaluate the role of intratumoral necrosis in cell detachment and metastasis. Accelular extracts from necrotic areas of both tumors increased in vitro cellular detachment from M3 but not from MM3 fragments. Furthermore, the in vivo inoculation of the necrotic extracts within non-metastatic M3 tumors gave rise to pulmonary metastases. Histological studies revealed in M3 a central necrosis limited by an uninterrupted peripheral ring of well preserved cells, while in MM3 necrotic and non-necrotic areas alternated. It is concluded that the distribution of necrosis within the primary tumor by facilitating cell detachment is, at least in part, responsible for the development of metastases.

Influence of host defenses on the hepatic colonization of B16F10 melanoma cells

To investigate the significance of host immunity in metastasis we have simultaneously evaluated metastatic development and the tumoricidal action of host defenses in an experimental system for liver metastasis which involves the intrasplenic injection of B16F10 melanoma cells in syngeneic mice. In addition, three experimental groups were treated with immunosuppressive doses of cyclosporin A (CsA) during the following periods of the malignant process: 1st-5th days, 1st-12th days and 7th-12th days. Analysis of cytolytic effects of macrophages, NK cells and T-lymphocytes on tumor cells reveals a decay in antitumor immunity from the 7th day to the 12th day and a marked resistance of B16F10 melanoma cells derived from hepatic metastases to T-lymphocytes and NK cells. The 1st-5th day CsA treatment of tumor-bearing mice produced a reduction in both T-lymphocyte and macrophage reactions against tumor cells and a significant increase in the 7th day micrometastasis incidence in the liver. Once micrometastases have been established the CsA-treatment suppression on the 5th day allows the tumor growth rate in these mice to become the same as in controls. However, the 7th-12th day CsA treatment produces a clear inhibitory effect on focal metastatic development which may correspond to the in vitro antiproliferative effect of CsA, detected on cultured B16F10 melanoma cells.

Interferon treatment markedly inhibits the development of tumor metastases in the liver and spleen and increases survival time of mice after intravenous inoculation of Friend erythroleukemia cells

To investigate the effect of interferon treatment on the development of tumor metastases, DBA/2 mice were injected i.v. with 2 X 10(6) Friend erythroleukemia cells (FLC) (equivalent to about 5 X 10(5) LD50). FLC multiplied rapidly in the liver and spleen and all untreated or control treated mice died between 7 and 12 days. Daily treatment of mice with potent preparations of mouse interferon alpha/beta was initiated 3 to 72 hr after i.v. inoculation of tumor cells, at times when FLC were already present in the liver and spleen. Interferon treatment resulted in a 100 to 1,000-fold inhibition of the multiplication of FLC in the liver and spleen and a marked increase in mean survival time. Small numbers of tumor cells persisted in the liver and spleen in some interferon-treated mice and could be recovered by bioassay several weeks after tumor inoculation. Most interferon-treated mice died with tumor in the ensuing months. Three of 34 interferon-treated mice were considered cured as they were alive at 386, 325 and 284 days after tumor inoculation. Daily treatment of tumor-inoculated mice with human recombinant interferons alpha D and alpha BDDD, which had antiviral activity on mouse cells in culture, also increased the survival time of mice injected i.v. with FLC. The use of the interferon-resistant 3C18 line of FLC suggests that the marked inhibition of development of established liver and spleen metastases was not due to a direct effect of interferon on the tumor cells, but was host-mediated.

Stimulation of natural killer cytotoxicity by long-term treatment with double-stranded polynucleotides without induction of hyporesponsiveness

Treatment of Wistar/AG rats with a single i.p. injection of 1 mg/kg of synthetic double-stranded polynucleotides, either polyadenylic-polyuridylic acid (rAn.rUn), or a mismatched analogue of polyinosinic-polycytidylic acid (rIn.r(C12U)n), enhanced the cytotoxicity of natural killer (NK) cells among peripheral blood leukocytes and lung intracapillary leukocytes (LICL). The enhancement reached a peak 24 h after treatment and returned to control values after 4 days. In rats given repeated injections of double-stranded polynucleotides (2 per week), the NK cytotoxicity expressed by LICL reached more than ten times (in lytic units) the control levels between day 8, after 3 injections, and day 360, after 100 injections. No hyporesponsiveness was observed. Moreover, NK activity was frequently and significantly higher in rats given multiple injections than in those given a single injection. In rats with experimentally induced P77 lung fibrohistiocytoma colonies, repeated injections of rIn.r(C12U)n stimulated NK activity and reduced the number of metastatic nodules from 172 to 19. The same significant reduction (from 172 to 27) was also observed in animals given repeated injections of rAn.rUn. However, with two models of spontaneous metastases, significant reduction in lung metastases (M37 bronchioloalveolar carcinoma) or lack of effect (S4T19 rhabdomyosarcoma) were observed.

Molecular, cellular, and tissue responses following photodynamic therapy

Photodynamic therapy (PDT) is being utilized in the treatment of a wide variety of malignant tumors. Results using PDT have been encouraging, and controlled clinical trials are currently being performed. The procedure exploits both the tumor-localizing and -photosensitizing properties of hematoporphyrin derivative or its purified component, Photofrin II. When this porphyrin mixture is administered systemically, it is retained preferentially in tumor tissue as compared to surrounding normal tissue. Localized tumor destruction induced by PDT results from the photochemical generation of cytotoxic oxygen species within the tumor. This review will provide a summary of historical and current research pertaining to molecular, cellular, and tissue responses induced by PDT. Emphasis is placed on information related to the chemistry of current photosensitizers, subcellular targets, preclinical treatment parameters, and clinical responses following PDT.

Can cancer chemotherapy enhance the malignant behaviour of tumours?

Cancer chemotherapy is currently undergoing an intensive reappraisal because of its unimpressive performance against the major common cancers. There are a number of possible reasons for this lack of success; one considered here is that under some circumstances anti-neoplastic drug treatment actually increases the malignant behaviour of tumours. Support for this idea comes mainly from experimental studies in which drug treatments increased metastatic spread. Investigation of this phenomenon shows that drug induced modifications of the host, including immunosuppression and vascular damage, can indeed facilitate metastasis. In addition, new data are presented demonstrating that the direct action of drugs on the tumour cells themselves can have similar enhancing effects. The possible mechanisms underlying such direct effects are discussed and the ability of anti-cancer drugs to cause genetic mutations, amplify genes, and alter gene expression are considered. While the nature and extent of this facilitation of tumour malignancy is not fully understood, it is suggested that this possibility should be considered in the design of treatment protocols.

Lung natural killer and interleukin-2 activity in lung cancer. A pulmonary compartment of augmented natural killer activity occurs in patients with bronchogenic carcinoma

Studies were performed to determine if natural killer (NK) cell and interleukin-2 (IL-2) activities are increased in lungs that harbor malignancy. The NK activity (ability to lyse 51Cr-K562 cells) in bronchoalveolar lavage mononuclear cells (BAC) and washed whole blood cells (Blood) was measured in 8 patients with bronchogenic carcinoma and 8 healthy control subjects. The mean NK activity by BAC from the patients with bronchogenic carcinoma was 2.81 lytic units, and from the control subjects it was 0.19 lytic units (p less than 0.001). When the data were expressed as a ratio of NK activity for BAC/Blood, the mean ratio was 0.98 in patients with cancer compared with 0.12 in control subjects (p less than 0.003). IL-2 activity was bioassayed in recovered bronchoalveolar lavage fluid (BAL) using 3H-thymidine uptake by IL-2-dependent T-cells. The concentration of IL-2 was expressed as units per microgram albumin and also as units multiplied by a dilution factor. The median concentration of IL-2 in BAL from the patients with bronchogenic carcinoma was 10.5 units x 10(-3)/micrograms albumin (range, 3.7 to 229), and from the healthy control subjects it was 0.37 units x 10(-3)/micrograms albumin (range 0.26 to 0.70) (p less than 0.001). When IL-2 activity was expressed as total number of IL-2 units in recovered lavage fluid times a dilution factor (volume of saline used for lavage/volume of lavage fluid recovered), the median number of IL-2 units was 4.7 for the patients with bronchogenic carcinoma and 0.085 for the control subjects (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Interferon-induced alterations in metastatic capacity, class-1 antigen expression and natural killer cell sensitivity of melanoma cells

Pre-treatment of B16 melanoma cells with recombinant interferon-gamma (IFN-gamma) markedly increased their lung-colonising capacity following i.v. injection into syngeneic mice as compared with control cells. A similar enhancement was observed following the injection of treated cells into athymic nude mice but not in athymic mice carrying the beige mutation. Pre-treatment of syngeneic mice with anti-asialo GM1 antibody effectively abrogated any interferon-induced increase in experimental metastatic activity. The same IFN-gamma treatment significantly increased resistance of B16 cells to splenic natural killer (NK) cell activity as determined by in vitro assays. IFN-alpha/beta pre-treatment of B16 cells decreased sensitivity to NK-cell-mediated lysis to a lesser extent than IFN-gamma and had no detectable effect upon the subsequent metastatic activity of the tumor cells. Class-I antigen expression was altered by these IFN treatments, with IFN-gamma causing dramatic increases in expression of H-2Db antigen, in a pattern consistent with the possibility that increased H-2 antigen expression on B16 cells led to decreased NK-cell sensitivity which was reflected by an increase in experimental metastatic capacity.

Growth of a human carcinoma (HEp3) in nude mice: rapid and efficient metastasis

Our aim was to identify conditions which would permit the development of spontaneous metastasis of a human tumor in nude mice in a rapid and predictable manner and to explore ways to quantitate metastasis. Using a human squamous carcinoma--HEp3--we determined that invasiveness and metastasis were influenced by the host. HEp3 cells grew very rapidly and without a significant lag period in Balb/c and NIH(S)-II nude mice kept in aseptic conditions; a much longer lag period was observed in NIH-Swiss mice kept in conventional conditions. The HEp3 tumor displayed a highly invasive behavior in N-NIH(S)-II mice, in which it invaded the body wall, gaining access to the peritoneal cavity. Microinvasion was noted in all strains of mice inoculated with HEp3 cells. To prolong survival of the mice until metastases became evident, primary tumors were excised when they weighed 1-2 gm. N-NIH(S)-II and Balb/c nude mice, maintained in germ-free conditions, were most receptive to the development of metastases-lung metastases developed in 80% of these mice. Over 60% of all metastases were present within 4 weeks following the removal of the primary. Only 26% of tumor bearing NIH-Swiss developed lung metastases. Lung metastases were observed in some mice in the absence of local microinvasion, local tumor recurrence, and regardless of the presence of lymph node involvement. They were also noted in mice from which primary tumors were not excised. We compared three methods of lung metastasis detection: histology, detection of tumor cells in the cultures of lung minces, and the measurement of the levels of human urokinase-type plasminogen activator directly in the lysates of lungs. The detection of tumor cells in cultures of lung minces appeared to be the most sensitive of these methods and the determination of enzyme in lung lysates seemed to hold most promise for a quantitative approach. These data indicate that, the type of tumor, as well as the genetic background and the maintenance conditions of the host, have to be carefully selected to ensure the successful outcome of the particular tumor-host interaction being studied. Adherence to these guidelines allowed us, in the case of the HEp3 tumor, to develop a rapid, predictable, and efficient model in which to study factors affecting metastasis of this human tumor.