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Context. Dust formation, i.e. the condensation of solid particles from a gas phase, occurs in astrophysical environments that are sufficiently cool and offer a sufficiently high density of condensable species. Since many astrophysical systems in which dust forms have turbulent features and the dust formation rates depend significantly on temperature, we investigate the influence of temperature fluctuations on dust condensation in dust-driven AGB winds. Aims. We present an approach for the time-dependent stochastic description of astrophysical dust formation and apply this in developing a fast algorithm, which is well suited for implementation into numerical models of dynamical AGB winds. The influence of the fluctuations on the dynamical structure is then investigated for a large sample of wind parameters. Methods. We employ a mathematical method, which describes the dust formation under the influence of random temperature fluctuations as a stochastic process. A system of Fokker-Planck equations for the one-point distribution function of the conjoint temporal development of temperature and dust results. Gas-box studies of this system have led us to a simplified microturbulent description for the implementation into time-dependent numerical wind models. Results. A method for the investigation of temperature fluctuations on dust formation is presented, which can be adapted to a variety of astrophysical situations. For dust-driven AGB winds, a microturbulent description turns out to be admissible. In AGB winds, rms-temperature fluctuations of 20–60 K can result in increased mass loss rates of 10–30% depending on the details of the physical model assumptions. Conclusions. The presented method for the treatment of temperature fluctuations with respect to dust formation has been succesfully applied to dynamical AGB winds. We suggest how to apply the method to other astrophysical systems. The influence of the fluctuations on the dynamics of dust-driven AGB winds is remarkable, but not overwhelming.

In this paper, we examine the mass loss mechanism of C-rich AGB stars by means of spherically symmetric model calculations, which combine hydrodynamics, grey radiative transfer (with constant gas and variable dust opacity) and time- dependent dust formation (based on equilibrium chemistry and modified classical nucleation theory) with a time-independent non-LTE description of the state functions of the gas, in particular concerning the radiative heating and cooling function. According to our models, the dissipative heating by shock waves created by the stellar pulsation does not lead to a long-lasting increase of the gas temperatures close to the star, because the radiative cooling is too effective. The gas results to be mostly in radiative equilibrium (RE), except for some narrow but hot post-shock cooling zones. Consequently, the dust formation and wind acceleration proceeds in a similar way as described by Fleischer et al. (1992) and we find a dust-driven wind triggered by the stellar pulsation, but no evidence for a purely pulsation-driven mass loss. Several new effects occur in the models which are causally connected with the non-LTE state functions. In particular, the dissociation/re-formation of H2 consumes/liberates so much energy that the radiative relaxation towards RE can be significantly delayed in regions where the phase transition H H2 takes place. These regions may stay in non-RE for a considerable fraction of the stellar pulsation period. The radiative cooling behind the strongest, dissociative shock waves (>20 km s −1 ) usually proceeds in a two-step process where the initially rapid cooling by permitted atomic lines down to ≈6000 K is followed by a second phase of intense radiative cooling below ≈3000 K, as soon as the first molecules (e.g. CO) have formed. In the meantime, the gas cools slowly by forbidden metal emission lines, or by adiabatic expansion. This re-increase of the radiative cooling function with decreasing gas temperature causes a radiative instability which may temporarily lead to a coexistence of cool molecule-rich and warm molecule-poor regions in the radiative relaxation zone.

Dendritic cell (DC)-based tumor vaccines have been tested extensively to treat cancer patients. However, the results of several DC-based clinical trials have been disappointing. Amelioration of such a modality for cancer treatment seems warranted, i.e. by improving DC immunogenicity and polarization. The goal of our study was to evaluate the potential for immune activation of human DCs by incubating them in vitro with the Newcastle Disease Virus (NDV), a paramyxovirus with strong immunostimulatory properties.In vitro infection with NDV of human monocyte-derived DCs--generated from peripheral monocytes cultured with IL-4 and GM-CSF--induces the generation of viral M gene transcripts and RIG-I expression within DCs. Expression of both genes was increased upon co-stimulation with LPS. Surprisingly, LPS and NDV had opposite effects on induction of interferon (IFN)-alpha. Furthermore, NDV induced DC maturation (as measured by TNF-alpha production and CD80 cell surface expression) only in the presence of LPS. Most interestingly, an optimal combination of NDV and LPS caused polarization of the DCs to Th1 type cytokines with a high ratio of interleukin (IL)-12 to IL-10.These in vitro results provide a means and protocol for maturation and activation of DCs with enhanced and sustained T helper type 1-polarizing capacity. Such pretreated DCs may significantly improve DC-based cancer immunotherapy. The data encourage the use of RNA-based viral vectors as potential novel and powerful gene transfer modality for cytoplasmic gene expression in professional antigen-presenting cells (APC) to overcome immunosuppression in cancer patients.

The nature of the cooperation between platelets and tumor cells during the process of blood-borne metastasis is essentially unknown. In previous in vitro studies we showed that platelets participated in the formation of gaps in the endothelial cell lining, and that concomitantly heparan sulfate glycosaminoglycans were degraded by the platelet heparitinase, released on activation of platelets. In the current study we show that the ability to degrade proteoheparan sulfate derived from endothelial extracellular matrix is gradually eliminated when the number of human platelets is decreased from 5 x 10(7) to 10(6) cells/mL. When aliquots of conditioned media or lysates of either Eb or heat-inactivated ESb mouse lymphoma cells (both of which showed no heparanase activity) were added to freeze-thawed lysates of 10(6) platelets, a reappearance of platelet heparitinase activity was observed. A similar activation was not elicited by lysates of several normal mammalian cells. These data suggest that in its native form, a fraction of the platelet heparitinase is stored in an inactive form that can be activated by a factor secreted by lymphoma, but not by normal cells. Partial characterization of the heparitinase-activating factor showed that it is a heat-stable polyanionic molecule, devoid of proteolytic activity and resistant to both proteolytic and chondroitinase digestions. Activation of platelet heparitinase was also observed on coincubation with chondroitinases ABC and AC, suggesting that the inactive form of platelet heparitinase could result from a complex formation with a chondroitinase-sensitive proteoglycan. The lymphoma-derived heparitinase activating factor itself is, however, not a chondroitinase, because activity of chondroitinase could not be detected in Eb and ESb cells. A possible mechanism by which tumor cells recruit and regulate the activity of platelet heparitinase, and its relevance to the progression of blood borne metastasis, is discussed.

In a murine tumor model, complete tumor remission is achievable at even advanced metastasized stages by transfer of immune T cells from donor B10.D2 (H-2d, Mls(b)) into tumor-bearing DBA/2 (H-2d, Mls(a)) mice. We showed previously that this graft-versus-leukemia (GvL) effect is dependent on synergistic interactions of transferred CD4+ and CD8+ T cells with host sialoadhesin (SER)-positive macrophages. We now show that the CD40-CD40L (CD154) interaction is involved in the induction of inducible nitric oxide synthase (iNOS) expression during adoptive immunotherapy (ADI). We demonstrate that during ADI, the level of CD40 expression in the liver becomes significantly augmented in comparison to livers of tumor-bearing, untreated animals. CD40 expression is found mostly on SER+ macrophages and to a lesser extent on dendritic cells (DCs). In GvL animals, more SER+ macrophages express iNOS than untreated animals. iNOS expressing cells are found in close proximity to apoptotic cells, at early time points of the therapy in areas of metastasis, and at late stages around portal veins, where CD4+ and CD8+ T lymphocytes form clusters with SER+ macrophages. Blocking of CD40L in vivo at days 5 and 20, when all iNOS+ cells express CD40, leads to significantly reduced CD40 and iNOS expression as well as to a marked inhibition of the therapeutic effect. These data provide functional and in situ evidence that the increased CD40 and iNOS expression observed during ADI contribute to the eradication of liver metastases and to the clearance of donor lymphocytes from the liver.

Cytokines with immunostimulating effects have the capacity to induce tumor immunity in animal models, whereas some cytokines interfere with tumor growth based on their angiostatic effects. Despite these capabilities, cytokines, such as IFN-, IFN-, tumor necrosis factor, interleukin (IL)-1, and IL-2, have had limited clinical efficacy and many undesirable side effects. In preclinical models, cytokines can even promote tumor growth and increase metastatic spread. Although chemokines have had limited clinical evaluation, studies of animal models show that they can also have tumor-suppressive or tumor-enhancing effects. In mice, chemokines, such as IP-10, RANTES, and TCA3, have resulted in tumor regression and immunity to subsequent tumor challenge. Those chemokines that are angiostatic (e.g., PF4, IP-10, and MIG) can also induce tumor regression by reducing the tumor blood supply. Conversely, IL-8, which is angiogenic, can promote tumor growth. Our studies show that nasopharyngeal cell line cells (FADU) show a chemotactic as well as a proliferative response to MCP-1. In addition, a variant murine T cell lymphoma cell line Esb-MP, unlike the parental variant Esb, was selectively chemoattracted by murine MCP-1/JE. When injected s.c. into mice, the Esb-MP variant metastasized to the kidney with much higher frequency than the Esb variant. Both cultured kidneys from normal mice and a mesangial cell line constitutively produced chemoattractants that acted on Esb-MP but not Esb parental cells. Purification to homogeneity of these chemoattractants led to the identification of RANTES and JE. These results demonstrate that some chemokines may promote tumor growth and organ-specific metastatic spread of those tumors that have adapted and become responsive to chemokines. Finally, tumors appear to use numerous adaptive mechanisms to subvert and suppress the immune system. More effective therapy with cytokines and chemokines will require better characterization of the means by which tumors develop resistance to cytokines and overcome the immune system. Only then can we develop appropriate therapeutic approaches to antagonize cancer-induced immunosuppression.

T-cell-mediated antitumor effects play an important role clinically in allogeneic graft-versus-leukemia (GvL) reactivity, whereas T-cell-mediated antihost effects are associated with a risk of developing graft-versus-host (GvH) disease. GvL and GvH were compared in an animal tumor model system after the systemic transfer of allogeneic antitumor immune T lymphocytes from B10.D2 [H-2d; minor lymphocyte-stimulating antigen (Mls)b] mice into ESb-MP tumor-bearing or normal DBA/2 (H-2d; Mls(a)) mice. Here we demonstrate that this T-cell-mediated therapy involves the formation of clusters of donor CD4 and CD8 T cells with host macrophages, in particular, with a subpopulation expressing the lymphocyte adhesion molecule sialoadhesin. DBA/2 mice and the derived tumor ESb-MP express viral superantigen 7 (Mls(a)), an endogenous viral superantigen that is absent from B10.D2 mice. To test the contribution of viral superantigen 7-reactive Vbeta6 donor T cells in the GvL-mediated eradication of liver metastases, we performed immunohistological and transmission electron microscopy studies. Vbeta6+ CD4 and CD8 T cells from B10.D2 donors formed tight clusters with host sialoadhesin-positive macrophages, and transmission electron microscopy pictures revealed direct membrane-membrane interactions between T cells and macrophages. Clusters were more abundant and consisted of more cells in tumor-bearing hosts (GvL model) than in non-tumor-bearing hosts (GvH model). In addition, Vbeta6 T cells within the clusters showed a strong proliferation activity, indicating stimulation. Moreover, in an in vitro tumor cytostasis assay, primed as well as nonprimed purified Vbeta6 T cells from donor mice were able to inhibit the proliferation of superantigen-expressing ESb-MP lymphoma cells. This suggests that the transferred superantigen-reactive Vbeta6 T cells contribute to the eradication of metastases. The observed cell clusters might be sites for antigen presentation and the activation of tumor-reactive T cells.

This study demonstrates that systemic interleukin 2 (IL-2) can decrease the homing of syngeneic immune T cells to the target organ of metastases and accelerate unwanted side effects of allogeneic immune T cells. As a tumor system, we used the well-characterized highly aggressive DBA/2 mouse leukemia ESb and its less aggressive adhesion variant, ESb-MP. Systemic IL-2 treatment was performed with recombinant human interleukin-2 (Proleukin), which was slowly released via an implanted osmotic pump or was modified with polyethylene glycol (PEG-IL-2) to achieve constant plasma levels. Allogeneic B10.D2 antitumor immune spleen cells (ISPL cells) exerted strong graft-versus-leukemia (GvL) reactivity after adoptive transfer into late-stage ESb-MP tumor-bearing DBA/2 mice. Mls(a) superantigen-reactive vbeta6 donor T cells were not eliminated or tolerized by in vivo priming with the tumor cells and were present in active proliferation in liver infiltrates. When exogenous PEG-IL-2 or Proleukin was applied in addition to ISPL cells in such mice, the strong GvL-mediated protective immunity was converted into a fatal graft-versus-host disease. IL-2 treatment alone had no toxic effect and caused a moderate protection effect in the absence of an effect on local tumor growth. Potentiation of GvH reactivity of B10.D2 ISPL by PEG-IL-2 was proven in non-tumor-bearing DBA/2 mice, in which graft-versus-host disease was characterized by: (a) heavy hepatic lymphocytic infiltration, (b) irreversible increase of serum glutamate-oxalacetate-transaminase and glutamate-pyruvate-transaminase levels, (c) weight loss, and (d) death. Antagonistic effects of systemic IL-2 on GvL were observed with syngeneic DBA/2 anti-ESb immune peritoneal effector cells (PECs). There was a detrimental effect of systemic IL-2 on liver target organ infiltration by immune T cells causing, at day 6 after transfer, a drop from 20-30 CD4 or CD8 T cells per liver lobule in the PEC group to5 in the PEC plus IL-2 group. The results emphasize the importance of a better understanding of IL-2 function in vivo and of its interaction with immune cell function to improve protocols for optimal application in the clinic to achieve maximal GvL effects.

A spontaneously metastasizing, well-defined mouse lymphoma was chosen as an in vivo model to study the effect of tumor-host interaction on gene expression in liver sinusoidal endothelial cells. Forty-nine bovine aortic endothelial cell (BAEC) genes, recently isolated by a differential screening approach of a cDNA library enriched for tumor necrosis factor-alpha (TNF-alpha) suppressed genes, were investigated. Four of these genes were finally selected because they were affected differentially by host immuno-competence, TNF-alpha, and tumor cells. Sequence analysis showed them to encode the bovine polyubiquitin (A4), elongation factor 1alpha (B2), the acidic ribosomal phosphoprotein PO (C3), and the ribosomal protein S2 (E10). Gene expression was analyzed by dot-blot or Northern blot analysis. TNF-alpha and tumor cell conditioned supernatant suppressed the genes additive in BAEC but not in other endothelial cells except for bovine capillary endothelial cells. Ex vivo-isolated liver endothelial cells of tumor-bearing syngeneic DBA/2 mice showed strong downregulation of these four genes in comparison to normal control values. In contrast, endothelial cells of tumor-bearing immuno-incompetent Balb/c (nu/nu) mice showed no downregulation but upregulation of these genes. Consistently, all four genes were also downregulated when BAEC were incubated with supernatants derived from ex vivo-isolated liver metastases from immuno-competent but not from -incompetent mice. Thus, the expression of a group of genes involved in protein translation and processing was more profoundly altered in endothelial cells in vivo than in vitro, suggesting that microenviromental factors and cell-cell and cell-matrix interactions play an important role.

The production and functional testing of two new bispecific (bs) hybrid antibodies [Abs; bs Ab hemagglutinin-neuraminidase (HN) x CD3 and bs Ab HN x CD28] designed for cancer vaccine modification are described. They allow distinct modifications of the human tumor cell vaccine ATV-NDV, an autologous tumor cell vaccine already modified by infection with Newcastle disease virus. The bs Abs use the viral HN molecule as a common foreign anchoring molecule for attachment to the tumor cells and allow the introduction of anti-CD3 or anti-CD28 T-cell-stimulatory molecules. The bs Abs attached to tumor target cells were able to cross-link CTL effector cells and up-regulate T-cell activation markers on autologous cancer patient-derived CD4 and CD8 T lymphocytes. This strategy of combining a cellular vaccine with a bs Ab is highly specific, quick, and economical and has broad-range applications. Five ng or less of target cell-bound bs Ab HN x CD28 were effective at augmenting T-cell-mediated antitumor cytotoxicity.

This study elucidates a basically new mechanism of function of a virus-modified tumor cell vaccine which has been successful in mouse tumor models (metastatic ESb lymphoma and B16-F10 melanoma) in preventing or delaying metastatic spread and improving survival and which is being tested in clinical studies. Modification of tumor cells by a low dose of Newcastle disease virus (NDV), which caused this therapy effect, led to an augmentation of the tumor-specific cytotoxic CD8 T-cell (CTL) response and to increased CD4 T-helper activity in the absence of an antiviral T-cell response. When various noninfectious NDV preparations, which, according to newly established quantitative tests, had lost one or several of the viral functions, were tested, noninfectious virus particles with inactive fusion proteins and virus inactivated by UV light, which could fuse but could not replicate, were as active as infectious NDV in the tumor-specific CTL response. In contrast, NDV inactivated by heat treatment (NDV-HI) had no effect on the CTL response. NDV-HI, even when added to the cultures in excess, did not modulate the antitumor CTL response, which argues against a nonspecific adjuvant effect. There was no mitogenic effect of NDV. Because NDV-HI was not able to bind to the tumor cell surface and because hemagglutinin-neuraminidase c-DNA transfectants increased antigen-presenting function as virus-modified cells do, we propose that the NDV effect in the CTL response is caused by the introduction of functional viral hemagglutinin-neuraminidase molecules (1000 per virus particle) into the tumor cell surface, thereby facilitating cell-cell interactions through their cell-binding and neuraminidase activity.

Graft-versus-leukemia (GVL) and Graft-versus-host (GVH) reactions were compared after systemic transfer of allogeneic antitumor immune T lymphocytes from B10.D2 (H-2d; Mls(b)) into DBA/2 (H-2d; Mis(a)) mice. Before immune cell transfer, recipient DBA/2 mice were sublethally irradiated with 5 Gy to prevent host-versus-graft reactivity. Recipients were either bearing syngeneic metastatic ESb lymphomas (GVL system) or were normal, non-tumor-bearing mice (GVH system). We previously reported that this adoptive immunotherapy protocol (ADI) had pronounced GVL activity and led to immune rejection of even advanced metastasized cancer. In this study, monoclonal antibodies were used for immunohistochemical analysis of native frozen tissue sections from either spleen or liver to distinguish donor from host cells, to differentiate between CD4 and CD8 T lymphocytes, and to stain sialoadhesin-positive macrophages at different time points after cell transfer. The kinetics of donor cell infiltration in spleen and liver differed in that the lymphoid organ was infiltrated earlier (days 1 to 5 after transfer) than the nonlymphoid organ (days 5 to 20). After reaching a peak, donor cell infiltration decreased gradually and was not detectable in the spleen after day 20 and in the liver after day 30. The organ-infiltrating donor immune cells were mostly T lymphocytes and stained positive for CD4 or CD8 T-cell markers. A remarkable GVL-associated observation was made with regard to a subset of macrophages bearing the adhesion molecule sialoadhesin (SER+ macrophages). In the livers of tumor-bearing mice, their numbers increased between days 1 and 12 after ADI by a factor greater than 30. Double-staining for donor cell marker and SER showed that the sialoadhesin-expressing macrophages were of host origin. The SER+ host macrophages from GVL livers were isolated by enzyme perfusion and rosetting 12 days after ADI, when they reached peak values of about 60 cells per liver lobule, and were tested, without further antigen addition, for their capacity to stimulate an antitumor CD8 T-cell response. The results of this immunologic analysis suggest that these cells in the liver function as scavengers of the destroyed metastases and as antigen-processing and -presenting cells for antitumor immune T cells.

Although intradermal primary tumor growth and spontaneous liver metastasis of ESbL-lacZ lymphoma in syngeneic DBA/2 mice are progressive and malignant, they are characterized by a transient plateau period with a constant tumor diameter and a low number of metastasized cells in the liver. This period, which was shown to be immune dependent, was followed by a second expansion phase characterized by a preferential localization of tumor cells in the periportal areas of liver lobules (mosaic phenotype). To elucidate possible mechanisms leading to the plateau period as well as for the mosaic-like metastasis pattern, we investigated, using flow cytometry analysis, alterations in costimulatory and adhesion molecule expression in liver sinusoidal cells as well as in tumor cells isolated directly ex vivo throughout the kinetics of metastasis. In tumor and sinusoidal cells, we found up-regulation in the expression of MHC class II and B7 molecules during the plateau period. These molecules, which facilitate cell-mediated immune responses, were again down-regulated during the final exponential tumor growth and metastasis. In the final expansion phase, in which the mosaic phenotype of liver metastasis is seen, we detected a significant increase of leukocyte function-associated antigen-1/intercellular adhesion molecule-1 expression in both tumor and sinusoidal cells, suggesting tumor cell-sinusoidal cell interactions. vascular cell adhesion molecule-1/very late activated antigen-4 did not show any modification during the whole metastatic process. In vivo application of monoclonal antibodies directed to leukocyte function-associated antigen-1 and intercellular adhesion molecule-1 appeared to block the spread of metastasis, while no effect was seen with monoclonal antibodies directed to vascular cell adhesion molecule-1 and very late activated antigen-4. This study reveals in situ expression changes of cell surface molecules in tumor and host cells during metastasis. The changes seen during the plateau phase and during the second expansion phase differ, suggesting associations with mechanisms of immune control and tumor immune evasion, respectively.

Sialoadhesin (SER) is a newly described macrophage-restricted adhesion molecule with a sequence similarity to CD22 on B cells and to myelin-associated glycoprotein on Schwann cells. We describe here a functional role of SER+ spleen macrophages in antigen processing and presentation to T lymphocytes. In two syngeneic murine tumour systems (ESb-MP and lacZ transduced ESbL T-lymphoma cells), the activation state of SER+ macrophages (tested by activity of marker enzymes adenosine deaminase and 5'-nucleotidase) correlated with the arrest of lymphoma metastasis. Furthermore, this macrophage subpopulation became activated upon anti-tumour immunization as well as upon adoptive transfer of immune T lymphocytes into tumour-bearing hosts. We suggest that in situ-activated SER+ macrophages contribute to host resistance against metastasis.

An active specific immunization (ASI) procedure with two types of autologous tumor cell vaccines (ATVs) is tested for adjuvant immunotherapy of resected colorectal carcinoma to provide preliminary information on local immunological skin responses, side effects, and 2-year survival rates. For vaccine preparation, the tumor-derived freshly isolated and cryopreserved cells were thawed, purified by Percoll density centrifugation, and depleted of tumor-infiltrating lymphocytes by immunomagnetic beads. After inactivation by 200 Gy, the cells of this ATV were either infected by Newcastle disease virus (NDV) or they were admixed with Bacillus Calmette Guérin (BCG) organisms. Vaccination was performed in the arm beginning 6-8 weeks after operation, three times at 2-week intervals. Of 57 patients that received ASI, 48 were treated by virus-infected ATV (ATV-NDV) and 9 were treated with the BCG-admixed vaccine (ATV/BCG). The mean value of delayed hypersensitivity skin reactions from ATV-NDV-treated patients was 18 mm for the first vaccination and 26 and 29 mm for the succeeding ones. Although the application of ATV-NDV was associated with only mild side effects, the ATV/BCG vaccine led to long-lasting ulcers and to more serious side effects. The 2-year survival rate obtained with ATV-NDV was 97.9%, whereas the survival rate with ATV/BCG was 66.7%. The mean survival of 661 patients from a historical control was 73.8%. These data suggest that the type and quality of the tumor vaccine for ASI treatment is important. The findings with ATV-NDV necessitate corroboration in a prospective, randomized controlled study.

Detection of disseminated leukemia within organ is often very difficult and might lead to underestimation of the metastatic load. Therefore, we transduced the mouse ESb T lymphoma with the bacterial lacZ gene, which allowed us to follow metastasis at the single cell level. Intradermal primary tumor growth of lacZ transduced ESbL cells (L-CI.5s) comprised three phases: an initial expansion phase (day 0 to 9, increase from 0 to 8 mm, tumor diameter), a plateau phase (day 9 to 20, constant diameter of 8 mm and necrosis), and a second expansion phase (day 20 to 30, increase from 8 to 15 mm). Liver metastasis could already be detected at day 3 and maintained at that level until day 23, where exponential expansion started. A distinct mosaic-like metastasis pattern developed, with preferential localization of tumor cells to the periportal areas of the liver in immunocompetent animals. In contrast, in immunocompromised mice, primary tumor growth and metastasis were progressive and metastasis appeared as diffuse or focal/clustered. Healthy animals surviving a tumor cell inoculum of a variant cell ESbL-CI.5) with a reduced metastatic potential carried low levels of possibly dormant tumor cells in the bone marrow. Thus, this study showed that host immunocompetence determines to a large extent kinetics and load of spontaneous liver metastases and even influences the pattern and localization of disseminated lymphoma cells.

In this study, we describe the origin and characterization of a new metastatic tumor cell line (p11-R-Eb) obtained after i.p. passages of the nonmetastatic Eb lymphoma cells into DBA/2 mice. The p11-R-Eb cells exhibited the same morphology and in vitro growth properties and chromosome markers as the original Eb cells. FACS analysis of the p11-R-Eb cells also revealed a close similarity to the Eb cells. Moreover, the p11-R-Eb cells were specifically killed by anti-Eb cytotoxic lymphocytes. In spite of all these characteristics of the Eb line, p11-R-Eb cells metastasized to the liver when injected i.v. or s.c. in DBA/2 mice. Peritumoral interleukin (IL)-2 treatment resulted in a potent antitumor response in DBA/2 mice transplanted s.c. with p11-R-Eb cells. In contrast, the same IL-2 regimen did not significantly increase the survival time of mice transplanted with the highly metastatic ESb cell line. Combined IL-1/IL-2 treatments of established p11-R-Eb tumors resulted in a synergistic antitumor effect and in tumor regression in 70% of the injected mice. Similarly, combined peritumoral treatment with IL-1 and interferon-alpha/beta, which were poorly effective or ineffective as single cytokine therapy, resulted in a marked antitumor effect, and 30% of the mice were cured. Spleen cells from IL-1/IL-2-treated p11-R-Eb-cell-injected mice showed a marked antitumor activity when assayed in a Winn assay with homologous tumor cells. This antitumor activity was eliminated by preincubation of spleen cells with antibodies to CD4 and complement and markedly inhibited by anti-asialo GM1 antibodies. P11-R-Eb cells represent, therefore, a new tumor model which may be useful for investigating the relevant mechanisms which need to be activated to achieve a potent antitumor response to cytokine therapy in the DBA/2 mouse host.

Expression and function of epidermal growth factor receptor (EGFR) was investigated in a metastatic cell clone (MTLn3) derived from the 13762NF rat mammary adenocarcinoma. No receptor phosphorylation could be identified in intact cells or in membrane preparations, while EGF-dependent phosphorylation of substrates occurred in intact cells. Indications for active suppression of receptor phosphorylation came from the fact that EGFRs bound in immunocomplexes or associated with the cytoskeleton of detergent treated cells were able to undergo basal and EGF-induced phosphorylation in vitro. Cross-linking experiments with 125I-EGF, as well as [35S]methionine labeling followed by immunoprecipitation with receptor specific antibodies readily detected in MTLn3 cells the expected 170-kDa EGFR protein. In addition, two proteins with molecular masses of 420-480 and 95 kDa specifically bound 125I-EGF on intact MTLn3 and sparse cultures of A431 cells. Phosphorylation of the 420-480 kDa molecule could be identified in immunocomplexes of EGFRs isolated from MTLn3 and sparse A431 cells, but the 95-kDa receptor molecule was never phosphorylated. While the presence of alternative forms of EGFR in the highly metastatic cell clone MTLn3 was unexpected, our observations of inefficient receptor autophosphorylation are in agreement with other recent reports and suggest that in MTLn3 cells EGFR-mediated signal transduction can be an event independent from receptor autophosphorylation.

In this report, we investigated the expression and activation of proteolytic enzymes by mouse T-lymphoma cell lines of differing metastatic potential. In contrast to the low metastatic Eb line, the metastatic variants ESb and ESb-MP secreted urokinase-type plasminogen activator (u-PA), which was present in the culture supernatant predominantly in the active form (ESb, 96%; ESb-MP, 80%). All three T-lymphoma variants expressed a mainly cell surface-associated proteinase, which proved to be immunologically and enzymatically related to the murine T-cell-associated serine proteinase-1 (MTSP-1). Intact lymphoma cells were able to activate the recombinant human proenzyme of u-PA (pro-u-PA) by a plasmin-independent mechanism, because plasmin contamination of the cells was not detectable. When ESb-MP cells were cultured in the presence of inhibitors of MTSP-1, such as antithrombin III, Pro-Phe-Arg-chloromethylketone, or aprotinin, the ratio of endogenously activated murine u-PA to inactive pro-u-PA in conditioned medium was significantly reduced (from 80% to 15%). The most potent inhibitor, antithrombin, did not inhibit plasmin-catalyzed pro-u-PA activation. These results suggest a novel autocrine mechanism of plasmin-independent pro-u-PA activation for metastatic T lymphomas by the production of an MTSP-1-related proteinase. The ability to initiate the proteolytic cascade of plasminogen activation in the absence of plasmin might contribute to the metastatic behavior of these cells observed in vivo.

This study evaluates the cell surface expression of urokinase-type plasminogen activator (u-PA) and the capacity to bind exogenous urokinase as possible parameters for the distinction of various types of human lung tumours. Twelve different tumour cell lines including four small cell carcinoma, two large cell carcinoma, three squamous cell carcinoma, one adenocarcinoma and two mesothelioma cell lines of lung origin were investigated. Surface expression of endogenous u-PA was determined in a cellular radioimmunoassay (CRIA) using the u-PA-specific monoclonal antibody 98/6. To estimate additional u-PA binding capacity, exogenous two-chain, 54 kDa u-PA was employed in the CRIA. The influence of phorbol ester (PMA) treatment on expression and binding of these molecules was studied. Three different groups of lung tumour cell lines could be distinguished according to their expression of u-PA and u-PA-binding ability: (i) non small cell lung carcinoma (NSCLC) cell lines of squamous cell carcinoma/adenocarcinoma origin expressed small amounts of u-PA and bound little u-PA. Large cell carcinoma cell lines expressed high amounts of u-PA and bound large amounts of u-PA. In general, expression of u-PA and u-PA binding was enhanced after PMA treatment. (ii) Mesothelioma cell lines did not express u-PA, but were able to bind u-PA. (iii) Small cell carcinoma (SCLC) lines were devoid of surface-expressed u-PA and could not bind u-PA, both under untreated and PMA-treated conditions. It could thus be demonstrated that these three groups of lung tumour cell lines differ in their ability to express u-PA and to bind external u-PA. This may reflect the different in vivo growth behaviour and origin of the respective tumour groups. Images Figure 1

The nature of the cooperation between platelets and tumor cells during the process of blood-borne metastasis is essentially unknown. In previous in vitro studies we showed that platelets participated in the formation of gaps in the endothelial cell lining, and that concomitantly heparan sulfate glycosaminoglycans were degraded by the platelet heparitinase, released on activation of platelets. In the current study we show that the ability to degrade proteoheparan sulfate derived from endothelial extracellular matrix is gradually eliminated when the number of human platelets is decreased from 5 x 10(7) to 10(6) cells/mL. When aliquots of conditioned media or lysates of either Eb or heat-inactivated ESb mouse lymphoma cells (both of which showed no heparanase activity) were added to freeze-thawed lysates of 10(6) platelets, a reappearance of platelet heparitinase activity was observed. A similar activation was not elicited by lysates of several normal mammalian cells. These data suggest that in its native form, a fraction of the platelet heparitinase is stored in an inactive form that can be activated by a factor secreted by lymphoma, but not by normal cells. Partial characterization of the heparitinase-activating factor showed that it is a heat-stable polyanionic molecule, devoid of proteolytic activity and resistant to both proteolytic and chondroitinase digestions. Activation of platelet heparitinase was also observed on coincubation with chondroitinases ABC and AC, suggesting that the inactive form of platelet heparitinase could result from a complex formation with a chondroitinase-sensitive proteoglycan. The lymphoma-derived heparitinase activating factor itself is, however, not a chondroitinase, because activity of chondroitinase could not be detected in Eb and ESb cells. A possible mechanism by which tumor cells recruit and regulate the activity of platelet heparitinase, and its relevance to the progression of blood borne metastasis, is discussed.

The apathogenic Newcastle disease virus (NDV) strain Ulster has been used successfully as an adjuvant component for active specific immunotherapy of malignant mouse lymphoma, and in nude mice it was shown to be able to lead to retardation of the s.c. growth of xenotransplanted human melanoma cells. In order to improve in vivo effectiveness of virotherapy of human tumors without significantly increasing the risk of unspecific viral replication in host cells, we adapted the virus for growth in a human melanoma line (MeWo M). For this purpose NDV Ulster was mutagenized and a variant was selected which could replicate and reinfect the tumor line. The mutant (NDV 1E 10) performed late lysis on the melanoma line. Replication was found to be at least 100 times more efficient in MeWo M than in 6 of 8 other human tumor cell lines of different tissue origin. In 10 of 11 murine cell lines, NDV 1E 10 did not replicate via multicycles. Chick embryonic fibroblasts were permissive for nonlytic replication. Neither the virulent wild-type NDV Italian nor the avirulent strain NDV Ulster shared these specific replication properties with the new variant. We also established MeWo melanoma sublines with different metastatic capacities and tested them as targets for NDV 1E 10 infection. The MeWo subpopulations exhibited comparatively small differences in permissivity for multicyclic replication, but the more metastatic MeWo Met, like allogeneic melanoma lines, was more resistant to lysis. NDV Italian, in contrast, showed no differences in replication and lysis on any of the tested melanoma lines. Trypsin-activation experiments suggested an incomplete cleavage of mutant envelope glycoprotein F by the permissive cell line and, thus, mechanisms of specific infection and replication not requiring fully activated envelope glycoproteins.

Two Fc receptor-dependent tests were investigated to study the question of a relationship between Fc receptors and known cell surface antigens, in particular I region-associated (Ia) antigens: (a) a rosette assay with antibody-coated erythrocytes (EA) as indicator cells and normal mouse lymphoid cells as source of rosette-forming cells, and (b) a cytotoxicity test with antibody-coated erythrocytes as target cells and normal mouse spleen cells as a source of cytotoxic cells (K cells). EA rosettes were specifically inhibited by antibodies reacting with Ia antigens. Various other antisera reacting with antigens on B lymphocytes, like anti-Ly 4.2 (raised in H-2 identical mice), rabbit antimouse B-cell serum, or rabbit antimouse immunoglobulin, also specifically inhibited the rosettes. No inhibition occurred in the presence of allogeneic or xenogeneic antisera reacting with T lymphocytes. K-cell cytotoxicity was specifically inhibited by each of the antisera (reacting with either B cells or T cells). F(ab')2 fragments of anti-Ia antibodies could still specifically inhibit EA rosettes but they could not inhibit K-cell cytotoxicity. Similar results were obtained with F(ab')2 fragments of anti-immunoglobulin antibodies. These results indicate that the mechanism of inhibition of Fc receptors in the two tests was different. In neither of the tests could we find any evidence for a unique association between the Fc receptors and Ia antigens. The Fc receptors on K cells did not seem to be associated at all with Ia antigens.

SUMMARY The ability of mouse alloantibody to inhibit EA rosette formation and antibodydependent cell-mediated cytotoxicity (ADCC) was used to study the expression of H-2K, Ia and H-2D antigens in various tissues. As previously reported antisera against each of these groups of antigens inhibited B lymphocyte EA rosette formation. Continuing studies confirmed these observations but established that quantitative differences may exist in the ease with which antibody against antigens in each region can inhibit EA rosettes: anti H-2D and anti-Ia seemed stronger relative to their cytotoxic titres than anti H-2K. Possible reasons for this are discussed. When rosette forming cells from other tissues were studied, (bone marrow cells, peritoneal macrophages and tumour cells), they were inhibited by anti H-2K and anti H-2D sera but not by anti Ia sera, presumably reflecting the restricted distribution of Ia antigens in those tissues. Inhibition of ADCC by various antisera reflected qualitatively and quantitatively the expression of H-2 antigens in various tissues : whereas effector cell activity in spleen, bone marrow, or peritoneal cell populations was inhibited by anti H-2 or anti-Ia sera, the amount of inhibition observed with anti-Ia was much less when the tissue expressed little Ia antigen (bone marrow) than when it expressed abundant Ia antigen (spleen). The ability of cytotoxicity inhibition to detect antibody coated cells was used to assess the relative amount of Ia antigen on thymus and on lymph node cells, showing significant amounts of Ia antigen on thymus cells. Fc receptor inhibition studies may thus be useful as new approaches to the study of the expression of the antigens of the major histocompatibility complex.

In order to study the possible role of the T-lymphocyte growth factor, Interleukin 2 (IL-2), and/or of the IL-2 receptor in the autonomous growth of leukaemic cells, 15 mouse leukaemic cell lines of various aetiology were analyzed for (i) IL-2 receptor expression and (ii) for the capacity to secrete IL-2. Several but not all of the cell lines tested were IL-2 receptor positive. The cells constitutively expressing IL-2 receptors at their surface could not be stimulated to secrete IL-2. Cell producing and secreting IL-2 did not express detectable amounts of IL-2 receptors at their surface. It has been demonstrated that proliferation of the leukaemic cells was independent of exogenous IL-2. The monoclonal anti-IL-2 receptor antibody AMT-13 inhibited IL-2 dependent proliferation of activated normal T-lymphocytes but failed to inhibit the growth of IL-2 receptor expressing leukaemic cells. The results argue against the autocrine stimulation hypothesis but do not exclude the possibility of involvement of functionally altered IL-2 receptors on autonomous cell growth.

Plasma membrane fragments from two variants of a murine lymphoma, Eb and ESb, with different metastatic capacity were investigated. Plasma membranes were isolated from tumor cells recovered from the peritoneal cavity. They differed in their lipid composition, indicating a more fluid state of the plasma membranes derived from the highly metastatic tumor line ESb. Extracellular membrane vesicles could be isolated from the ascites of the tumor-bearing mice. The shedding capacity of ESb cells was much higher than that of Eb cells. The extracellular membranes by chemical analysis and the measurement of marker enzymes proved to be derived from the plasma membranes. However, they differed from the plasma membranes from which they were derived in several aspects: the lipid to protein ratio was diminished; the activities of some plasma membrane-associated enzymes were lower while others were identical in plasma membranes and extracellular membranes; the content of saturated fatty acids in phospholipids was enhanced in extracellular membranes. These effects were more pronounced in the highly metastasizing tumor line ESb. It is thus concluded that shedding of extracellular membranes is not a random process. The biochemical differences found in the plasma membranes and the extracellular membranes of the two tumor lines are discussed with respect to the different metastatic capacity of the tumors.

Even though many studies suggest that proteoglycans with their structurally determinative polysaccharide chains, the glycosaminoglycans (GAGs), are important mediators of cellular interactions, little is known about expression and possible functions of these macromolecules expressed by tumour cells during the transition from low to highly metastatic behaviour. Therefore, we investigated the cellular expression and secretion of GAGs in a syngeneic tumour system of DBA/2 mice consisting of a methylcholanthrene-induced low metastatic T lymphoma (Eb), its highly metastatic spontaneous variant (ESb), and a low metastatic derivative of ESb (ESb-MP), selected by its adherent growth properties. The [35S]-sulphate-labelled GAGs were isolated from in vitro cultivated cells and further characterized by separation on Sepharose CL 6B, on Mono-Q ion exchange chromatography, and alkali- and enzymatic digestion. In contrast to Eb-cells which produce chondroitin/dermatan sulphate (CS/DS) and heparan sulphate (HS) (cellular extract: CS/DS 67%, HS 33%; culture medium: CS/DS 61%, HS 39%) ESb- and ESb-MP-cells only express and secrete CS/DS. For ESb cells the CS portions consisted of 42% chondroitin-4-sulphate (CS-4) and 58% chondroitin-6-sulphate (CS-6), for ESb-MP cells of 23% CS-4 and 77% CS-6, for Eb cells of 16% CS-4 and 84% CS-6. The cell surface GAGs of the adherent variant ESb-MP contained a significantly higher portion of DS (65%) compared to ESb cells (25%). GAGs of all tumour cell lines studied had a mol. wt ranging from 35-40 kD compared to GAG molecular weight standards. Ion exchange chromatography indicated that differences in charge density between GAGs of these cell lines were minimal. These findings suggest that the different biological behaviour of the cell lines cannot be attributed to altered size and charge density of their GAG chains. However, highly metastatic ESb-cells secreted significantly more GAG than low metastatic Eb- and ESb-MP-cells. The possible consequences of the enhanced secretion of CS/DS by ESb-cells are discussed in terms of the postulated role of CS/DS in cellular adhesion, growth regulation and interactions with the immune system.

Water-soluble multimeric complexes of Friend leukemia virus envelope glycoprotein gp85 bind specifically to C57BL/6 mouse spleen leukocytes. Such complexes were used to isolate cell surface receptors for the virus, using an immunoprecipitation technique. The putative rceptor has a molecular weight of 14,000. Mouse H-2 histocompatibility antigens, which are receptors for Semliki Forest virus, are not receptors for Friend leukemia virus.

A low metastatic, thioguanine-resistant murine T lymphoma line (EbTGR) was hybridized in vitro, with the help of polyethylene glycol, with syngeneic bone marrow-derived macrophages. Two HAT-resistant hybrid lines (Eb-F1 and Eb-F2) were obtained from independent fusion cultures. A cytogenetic analysis revealed that most of the macrophage chromosomes except No. 12 had segregated or become rearranged 60 d after fusion, a time at which the cell lines had become stabilized in culture. Syngeneic mice inoculated subcutaneously with the tumor macrophage hybrid lines developed, very quickly, visceral metastases and died after less than 2 wk, while those inoculated with the parental line lived for greater than 6 wk and developed only localized, large primary tumors. The metastatic hybridomas expressed a similar tumor antigen as a spontaneous, in vivo derived, high metastatic variant (ESb) of the same tumor. This suggests that ESb cells might have arisen from a spontaneous fusion with a host macrophage.

Serum levels of cell-free interleukin-2 receptors were elevated above normal in mice bearing the IL-2R positive T-cell lymphoma Eb or its highly metastatic variant ESb. Although ESb cells expressed less IL-2R molecules than Eb cells on their cell surface, serum receptor levels were raised more quickly in ESb than in Eb tumour bearing animals. Elevated IL-2R serum levels were a sensitive tumour marker in animals bearing the aggressive variant ESb but not in animals bearing the low metastatic line Eb. Peritoneal ascites tumour-bearing animals had higher serum IL-2R levels than corresponding animals with subcutaneously growing tumours. Thus, serum IL-2R levels in tumour-bearing animals were dependent on the tumour line and influenced by the site and mode of tumour growth.

A new quantitative method for the study of tumor cell invasion in vitro is presented. It is intended to facilitate the study of the mechanisms of invasion using an isolated basement membrane without the involvement of stromal structures or using defined protein gels. Cells are allowed to migrate through the pores of a Nuclepore polycarbonate filter into a protein gel on a nitrocellulose filter, or they may have to penetrate a cell-derived extracellular matrix (ECM) to reach the gel. Experiments with a nonmetastatic mouse lymphoma (Eb) and its two metastatic variants (ESb and ESb-MP) showed that the metastatic lines penetrated a Matrigel (a gel containing the components of a basement membrane) much better than the nonmetastatic cell line, but only the most metastatic line (ESb) was able to penetrate into a native collagen I gel. The presence of an ECM on the polycarbonate filter reduced the number of cells invading a fibrin gel, demonstrating that the dense, fibrillar structure of the cell-derived ECM was a barrier to the tumor cells. The metastatic lines penetrated the ECM to a 4- to 6-fold higher extent than the nonmetastatic cell line. It is concluded that in order to metastasize efficiently, the tumor cells must be able to penetrate many different kinds of barriers.

We have analyzed cell surface-bound carbohydrates in two different model systems for metastasis composed of closely related tumor cell lines with differing metastatic potential. The first system studied was that of the DBA/2-derived T-lymphoma lines (Eb/ESb) and some recently established sublines of ESb with altered metastatic behavior (ESb-M and ESb-MR). The second system consisted of the highly metastatic MDAY-D2 cells, a wheat germ agglutinin-resistant low metastatic subline MDW40, and two metastatic revertants from the latter. The cells were stained with fluorescein isothiocyanate-conjugated lectins and analyzed by flow cytofluorography. All low-metastatic tumor lines expressed receptor sites for the lectins soybean agglutinin (SBA) and Vicia villosa (VV). The metastatic lines had the respective lectin binding sites blocked by sialic acid (SA). A good correlation was found within the cell lineages Eb leads to ESb leads to ESb-M leads to ESb-MR and MDAY-D2 leads to MDW40 leads to MDW40M1 between reactivity of SBA and VV and metastatic potential. The amount of neuraminidase-accessible SA was similar for all cell types (except MDW40) indicating differences in the positioning of SA. For high-metastatic ESb cells, the sialylation of SBA and VV receptor sites was paralleled by a relative decrease of SA associated with receptor sites for peanut agglutinin. Low-metastatic Eb cells, in contrast, had their peanut agglutinin receptor sites sialylated but expressed asialylated SBA and VV receptor sites. Eb cells were also found to have 2-fold higher activities in galactose-specific sialyltransferases. It is proposed that the differences in positioning of SA on the cell surface leading to masking or unmasking of terminal sugars could influence the metastatic potential of tumor cells.

Glycolipids of murine lymphoma cell lines with low metastatic (Eb) and high metastatic (ESb) potentials have been investigated. The Eb cell line was characterized by a high quantity of gangliotriaosylceramide (Gg3), gangliotetraosylceramide (Gg4), GM1b, and a new type of disialoganglioside, termed GD1 alpha. In contrast, the high metastatic ESb cell line was characterized by the absence of these glycolipids and instead by the presence of GM3, GM2, GM1a, GD1a, and GD1b gangliosides. A clear cell surface reactivity with monoclonal antibody anti-Gg3 (2D4) was observed only in Eb cells. Thus, Eb cells are distinct from ESb cells in their ability to add the GalNAc residue to LacCer, supplying Gg3 for synthesis of a series of glycolipids via an asialogangliotetraosyl pathway, while ESb cells are capable of synthesizing GM3, which initiates synthesis of ganglio-series gangliosides GM2, GM1a, GD1a, and GD1b. While disialogangliosides of ESb cells were identified as GD1a and GD1b, a disialoganglioside isolated from Eb cells was characterized as having a novel structure (referred to as GD1 alpha) as follows: (formula; see text) Thus, Eb and ESb cells are clearly different in their qualitative sialylation patterns, i.e., the position of sialic acid residues. Cell surface labeling with galactose-oxidase/NaB[3H]4 revealed a high exposure of Gg3 and Gg4 at the Eb cell surface, while both labels were absent in ESb cells. In contrast, ESb cells showed a substantial label at GM1a, which was greatly enhanced after sialidase treatment.

Eb lymphoma cells were subjected to treatment in vitro with the alkylating mutagen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and then cloned by limiting dilution. When tested in vivo for tumorigenicity in groups of syngeneic DBA/2 mice, 6 from 18 clones were found to be strongly reduced (tum- phenotype). The other clones showed only moderate or no change in tumorigenicity compared to the untreated control. All clones were able to grow in 400-rad-irradiated mice. Mice in which MNNG clones had regressed were able to generate tumor-specific cytolytic T-lymphocytes in vitro. Limiting dilution analysis indicated that 3 of 4 MNNG clones analyzed in detail displayed additional antigenic determinants that were detected by cytolytic T-lymphocytes. These data thus provided evidence for increased immunogenicity of some of the MNNG clones. Membrane proteins of MNNG clones and original Eb cells were compared biochemically after metabolic labeling with [35S]methionine, TX114 solubilization, and electrophoretic separation. Two-dimensional gel maps revealed a general quantitative decrease in the expression of membrane proteins in MNNG clones. In addition, several proteins were only found in MNNG clones but not in untreated cells. Two membrane proteins of molecular weight 22,000 and 38,000 were greatly increased in expression in all MNNG clones but could be detected at a low level in the original Eb cells. MNNG is known to be a strong mutagenic agent, but it can also interfere with DNA methylation and cause transcriptional activation of genes. We suggest that amplified cell surface structures may be the consequence of such transcriptional activation and could be involved in altered immunogenicity.

Inhibition of cell-dependent antibody-mediated cytotoxicity has been investigated as a new assay for antibody against cell surface antigens. The cytotoxicity system consisted of effector cells (normal mouse spleen cells), target cells ((61)Cr-labeled chicken erythrocytes), and antitarget cell antibody. Addition of antibody against cell surface antigens in the effector cell population regularly inhibited the cytotoxicity measured in this system. This cytotoxicity inhibition assay (CIA) detected antibody with a variety of specificities: anti-H-2, anti-Thy 1.2, anti-immunoglobulin, and antimouse bone marrow-derived lymphocyte antigen. When the inhibition by anti-H-2 sera was analyzed using effector cells from congenic mice, the activity was found to be directed against specificities mapping in the H-2K, H-2D, and I regions of the H-2 complex, correlating well with the specificities characterized by complement-dependent assays. A comparison between the sensitivity of the CIA and complement-dependent lysis revealed that the CIA was 2-11 times more sensitive for anti-H-2 antisera and 20-780 times more sensitive for certain antisera against subpopulations of the spleen cells (i.e., T cells or B cells). The CIA proved to be precise, sensitive, and reliable. It may become a very useful antibody assay in various species including man.

A new microradioassay for the detection and quantification of disseminated tumor cells in blood and organ samples of tumor-bearing animals has been worked out in a murine total system for tumor metastasis. In contrast to previous prelabeling or in situ labeling procedures, the basis of this assay is a postlabeling in vitro of tumor cell-containing material with [3H]thymidine. Percoll gradient fractionation and autoradiography revealed that most of the isotope was incorporated into tumor cells. Titration curves with tumor cells from tissue culture were run in parallel and allowed to calculate from the radioactivity of a sample that actual number of proliferating tumor cells. The postlabeling assay correlated fairly well with an agar colony test which measure the clonogenic or stem cell potential of a tumor cell population. About 70% of syngeneic animals which had been inoculated s.c. with ESb tumor cells showed increased [3H]thymidine uptake in their blood, particularly at certain time intervals (11 and 21 days). None of these animals lived for more than 2 days longer. The advantages of the new microradioassay and its possible prognostic significance will be discussed.

Cloned lines of the methylcholanthrene-induced DBA/2 low-metastatic T-lymphoma Eb line and its highly metastatic variant ESb line were compared for the ability to degrade proteoglycans in the subendothelial extracellular matrix (ECM) produced by cultured endothelial cells. The ECM was metabolically labeled with Na2(35)SO4, and the tumor cell-mediated release of labeled degradation products was analyzed by gel filtration. More than 90% of the labeled material released upon incubation of ESb cells with the ECM, either when exposed or covered with vascular endothelial cells, was in the form of low-Mr, heparan sulfate-containing fragments (Mr approximately 10(4)) compared to high-Mr sulfated proteoglycans (mostly excluded from Sepharose 6B) released by incubation with the low-metastatic Eb cells. The same high- and low-Mr degradation products were obtained by incubation of the ECM with a serum-free medium conditioned by the low (Eb)- and high (ESb)-metastatic sublines, respectively. The high-Mr proteoglycans released by incubation of the ECM with Eb-conditioned medium was further degraded into Mr 10(4) glycosaminoglycan fragments upon a subsequent incubation with ESb-conditioned medium. These fragments were smaller than glycosaminoglycan side chains released by treatment of the ECM with papain or alkaline borohydride, suggesting an ESb-specific endoglycosidase activity. The higher ability of the ESb over the Eb cells to solubilize the glycosaminoglycan scaffolding of the sub-endothelial ECM may, among other properties, facilitate their hematogenous dissemination and extravasation.

Matrix heparan sulphate, but not endothelial cell surface heparan sulphate, is degraded by highly metastatic mouse lymphoma cells

Cellular adhesion is important during metastasis, as metastatic cells must escape from the primary site into lymph and blood systems, there to adhere specifically to sites in distant organs. We have recently selected monoclonal antibodies which prevent adherence of B 16 mouse melanoma cells to tissue culture dishes, and also markedly reduce experimental lung metastasis in mice when injected before or with the tumour cells. Here, we investigated which step in the metastatic process may be affected by the antibodies. The possible inhibitory effect of antibody on tumour cell adherence to vascular endothelial monolayers and to purified components of the underlying extracellular matrix-fibronectin, laminin and collagen type IV - was studied using in vitro assays. We found that the antibodies significantly blocked attachment to laminin, suggesting that specific basement membrane components play an important role in attracting or otherwise modifying the behaviour of metastatic tumour cells.

Spleen cells from mice immunized against ovalbumin (OA) or dinitrophenylated mouse serum albumin (DM) were found to be specifically cytotoxic in vitro towards target cells (chicken red blood cells) coated with these antigens. Inhibition of specific cytotoxicity was observed when free soluble antigen was added to the incubation mixtures. DM-immune cell cytotoxicity could be specifically and completely inhibited by DNP-lysine and was thus shown to be hapten specific. Complete and specific inhibition was also observed for OA-immune cell cytotoxicity using OA as inhibitor, but compared with the inhibition curves obtained with DNP-lysine, the OA cytotoxicity inhibition curves were shifted by a factor of about one hundred towards lower molar inhibitor concentrations. Very similar results were observed when the serum antibodies of DM- and OA-immune animals were analyzed by passive hemagglutination inhibition. With increasing time after immunization, both cytotoxicity inhibition curves and agglutination inhibition curves, shifted to lower antigen or hapten concentrations. Specific cytotoxicity against antigen-coated target cells was induced in nonimmune spleen cells (a) by serum from immune animals, and (b) by supernatants from in vitro immune cell cultures. In both instances, the factor which induced antigen-specific cytotoxic activity could be absorbed on anti-mouse Ig columns, thus demonstrating its immunoglobulin nature. The ability of target cell bound antibodies to induce cytotoxicity in nonimmune spleen cells was restricted to the 7S antibody class.

Immune cells induced by bovine serum albumin (BSA) and its methylated derivative (MBSA) have been compared in a cooperative cell transfer system for their content of BSA-specific antibody-forming cell precursors (AFCP, B) and BSA-specific helper (T) cells. When MBSA immune cells were transferred together with hapten-primed cells into recipient mice which were stimulated by a hapten-BSA conjugate, their cooperative secondary anti-hapten response was as good as in case of transferred BSA immune cells. Their secondary anti-BSA response, however, was markedly reduced (reduction factor > 30). Hapten-MBSA conjugates had the same capacity to react with BSA-specific helper cells in the cooperative secondary anti-hapten response as hapten-BSA conjugates but had a reduced ability to react with BSA-specific AFCP cells. In spite of the pronounced reduction of the B cell response, MBSA had the same threshold dose as BSA for activating BSA-specific T cells. These data suggest that B and T cells recognize different epitopes on the BSA molecule, only those recognized by B cells being affected by the methylation procedure.