Tumor-Cell Number and Viability as Quality and Efficacy Parameters of Autologous Virus-Modified Cancer Vaccines in Patients With Breast or Ovarian Cancer

The April 1997 article entitled, "Tumor-Cell Number and Viability as Quality and Efficacy Parameters of Autologous Virus-Modified Cancer Vaccines in Patients With Breast or Ovarian Cancer" by Ahlert et al (J Clin Oncol 15:1354–1366, 1997) contained several errors. On page 1354, the affiliation should have read: from the Universität-Frauenklinik Heidelberg; Deutsches Krebsforschungszentrum Heidelberg, Abteilung 710; Forschungspraxis Technologiepark Heidelburg; Institute für medizinische Biometrie und Informatik, Universität Freiburg, Freiburg, Germany. Reference number 36 on page 1365 should have read:

36. Pomer S, Schirrmacher V, Thiele R, et al: Tumor response and 4-year survival data of patients with advanced renal cell carcinoma treated with autologous tumor vaccine and subcutaneous r-IL-2 and IFN-alpha 2b. Int J Oncol 6:941–954, 1995

In addition, Table 5 is reprinted here correctly in its entirety: Please see the PDF for table 5.

The activation domain of a hormone inducible HTLV-1 Rex protein determines colocalization with the nuclear pore

Human T-cell leukemia/lymphoma virus type 1 (HTLV-1) Rex is an essential regulatory protein that acts at the posttranscriptional level to promote expression of unspliced and singly spliced genes of the virus. Rex functions have been attributed to at least three separate domains of the protein determining nuclear/nucleolar accumulation and RNA binding (overlapping), multimerization, and nuclear export of Rex-responsive RNA. The steady-state intracellular localization of functional Rex molecules is mainly nucleolar. Fusions of wild-type Rex and the ligand binding domain of human estrogen receptor (ER) produced conditional molecules (ERRex and ERalaRex), which remained cytoplasmic in the absence of hormone and in response to hormone colocalized with the nuclear pore complex (NPC). These molecules induced in a hormone-dependent manner the expression of a Rex reporter plasmid and of the HTLV-1 Env protein and fusion of Env expressing cells. In contrast, activation domain mutants (ERRex delta and ERRexGly) translocated from the cytoplasm and acquired a diffuse nuclear localization. These mutants did not associate with the NPC and failed to show any of the expected Rex functions. Rex functions were perturbed by inactivating the RNA binding domain (mutant ERM2) or the oligomerization domain (mutant ERM7). However, these two mutant fusion proteins exhibited a hormone-dependent NPC colocalization. These observations provide in vivo evidence that intranuclear translocation of intact Rex to the NPC is dependent exclusively on a functional activation domain and is not influenced by binding to the target RNA.

ICE-proteases mediate HTLV-I Tax-induced apoptotic T-cell death

The Tax protein of Human T-cell leukemia virus type 1 (HTLV-1) is important for the T-cell immortalizing properties of this virus in vitro and is considered to be responsible for the early stages of leukemogenesis in infected hosts. Tax can upregulate expression of TNF-alpha and TNF-beta, as well as potentiate apoptosis in activated T-cells and in serum starved murine fibroblasts. To examine the role of CD95 (APO-1/Fas) and ICE-proteases in Tax-mediated active T-cell death, Jurkat T cells expressing (APO(S)) or lacking (APO(R)) cell surface expression of CD95 (APO-1/Fas) were genetically modified to express hormone-inducible HTLV-1 Tax constructs. Hormone-inducible action of Tax alone was sufficient to promote programmed cell death in CD95-expressing Jurkat T-cell clones. In contrast, clones lacking CD95 surface expression were resistant to the antiproliferative action of Tax. Both APO(S) and APO(R) clones exhibited Tax-dependent upregulation of CD95 ligand and TNF-alpha. Blocking experiments suggested that while the apoptotic action of Tax critically required ICE-protease function it was largely independent of cell surface interaction of CD95 ligand or TNF-alpha with their corresponding receptors. These observations strongly implicate ICE-proteases in Tax-induced T-cell death, and suggest a possible involvement of CD95 in this process.

Tumor-cell number and viability as quality and efficacy parameters of autologous virus-modified cancer vaccines in patients with breast or ovarian cancer

PURPOSE

We investigated quality and efficacy criteria of an autologous, physically and immunologically purified, Newcastle disease virus (NDV)-modified, irradiated tumor-cell vaccine (ATV-NDV) by analyzing three independent cohorts (a through c) of patients vaccinated between 1991 and 1995.

MATERIALS AND METHODS

Included were 63 patients with primary breast cancer (a), 27 with metastatic pretreated breast cancer (b), and 31 with metastatic pretreated ovarian cancer (c). In addition to vaccine, cohorts b and c received nonspecific immunotherapy as supportive treatment. After cryoconservation and purification, the vaccines varied in applied numbers of viable cells and dead cell contaminations. We retrospectively hypothesized that an immunogenic vaccine should contain at least 1.5 x 10(6) viable tumor cells and viability should be at least 33%. Each cohort was thus divided into two groups; one that received vaccine type A (A), fulfilling both criteria; and the other type B (B), missing one or both criteria.

RESULTS

Conventional prognostic factors were wall balanced between A and B in cohorts a and c. In cohort a, there was a benefit in survival (P = .026) and disease-free survival (P = .089) for A. In addition, in cohort a, the relative risk of dying in the group that received A as compared with B was 0.2 (univariate Cox model). There were also survival trends in favor of A versus B (P = .18 and P = .09, respectively) in cohorts b and c, with relative risks of 0.5 and 0.42, respectively. In cohort b, the survival benefit could not be ascribed to vaccine quality alone, because of prognostic imbalance in favor of A.

CONCLUSION

In cohort c, like in cohort a, the survival benefit for A may be ascribed to the ATV-NDV vaccine quality, since prognostic factors were not biased. This could imply clinical effectivity in breast and ovarian cancer with ATV-NDV high-quality vaccine. Furthermore, the data provide clinically relevant information for standardization and quality control of autologous tumor-cell vaccines. A randomized study is urgently needed.

Differences between graft-versus-leukemia and graft-versus-host reactivity. I. Interaction of donor immune T cells with tumor and/or host cells

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.

Induction of apoptosis by EGF receptor in rat mammary adenocarcinoma cells coincides with enhanced spontaneous tumour metastasis

The low metastatic MTC (13762NF) rat mammary adenocarcinoma cell line is devoid of epidermal growth factor receptor (EGFR). To test for a link between expression of EGFR and the ability of tumour cells to metastasise from their orthotopic site (spontaneous metastasis), stable subclones of this line (S+) that had been retrovirally transduced to express an ectopic full length HER1 were established and characterised. Proliferation, survival, and response to TGF-alpha were investigated and related to the tumorigenic growth and metastatic properties of the cells. S+ clones responded in vitro to ligand stimulation by growth inhibition and apoptosis. Upon orthotopic inoculation into the mammary fat pad of nude (nu/nu) mice, S+ clones showed retarded growth and apoptosed in situ, while MTC cells or neoR control cells showed no signs of apoptosis. Yet, S+ cells exhibited more spontaneous metastasis than the MTC parental cells or neoR control cells. Spontaneous metastasis requires cellular detachment (primary site) as well as attachment (secondary site) and growth in target organs. Neither the HER1 mediated increased ECM adhesion nor its negative effect on growth potential explains the observed effect. This is the first direct demonstration of the potential of EGFR to promote spontaneous metastasis of mammary adenocarcinoma cells from their orthotopic site.

Immunogenicity increase of autologous tumor cell vaccines by virus infection and attachment of bispecific antibodies

A new type of cancer vaccine for therapeutic application in cancer patients is described. It consists of three components. (1) autologous tumor cells, (2) Newcastle Disease Virus (NDV), to be used for infection and (3) bispecific antibodies (bsAb) which attach to the viral hemagglutinin neuraminidase (HN) molecule on the infected tumor cells. A standardized procedure has been developed for generating virus infected human autologous tumor cell vaccines (ATV-NDV) which includes cell dissociation, removal of leukocytes and cell debris, gamma-irradiation and cryopreservation. Infection with the non-virulent strain NDV Ulster is performed within 30 min of co-incubation. While virus infection already increased immunogenicity of the tumor vaccine, further augmentation of T cell stimulatory capacity is achieved by attachment of specially designed bi-specific antibodies (bs HN x CD28 or bs HN x CD3).

Dissection of tumour and host cells from target organs of metastasis for testing gene expression directly ex vivo

We report on a new methodology which allows the direct analysis ex vivo of tumour cells and host cells (lymphocytes, macrophages, endothelial cells) from a metastasised organ (liver or spleen) at any time point during the metastatic process and without any further in vitro culture. First, we used a tumour cell line transduced with the bacterial gene lacZ, which permits the detection of the procaryotic enzyme beta-galactosidase in eukaryotic cells at the single cell level thus allowing flow adhesion cell sorting (FACS) analysis of tumour cells from metastasised target organs. Second, we established a method for the separation and enrichment of tumour and host cells from target organs of metastasis with a high viability and reproducibility. As exemplified with the murine lymphoma ESb, this new methodology permits the study of molecules of importance for metastasis or anti-tumour immunity (adhesion, costimulatory and cytotoxic molecules, cytokines, etc.) at the RNA or protein level in tumour and host cells during the whole process of metastasis. This novel approach may open new possibilities of developing strategies for intervention in tumour progression, since it allows the determination of the optimal window in time for successful treatments. The possibility of direct analysis of tumour and host cell properties also provides a new method for the evaluation of the effects of immunisation with tumour vaccines or of gene therapy.

New insights into tumor-host interactions in lymphoma metastasis

The metastatic process is characterized by a complex series of sequential steps involving constant interactions (mutual "cross-talks") of metastasized tumor cells with their microenvironment (lymphocyte, macrophages, endothelial cells, etc.) in target organs. These interactions determine the outcome of metastasis (either the eradication of metastatic cells or their increased proliferation and invasion). Recently developed methods of tumor and host cell analysis at the molecular level allow better elucidation of molecular mechanisms of metastasis and of immune mechanisms involved in antitumor responses. Direct modulation of these processes will probably increase the success of clinical cancer treatment. Here we review data (a) on the expression of some costimulatory (MHC class II, CD80, sialoadhesin) and adhesion (LFA-1, ICAM-1, VLA-4) molecules on both metastasized tumor cells and host cells and (b) on the production of a cytotoxic molecule, nitric oxide, by in situ activated Kupffer and endothelial cells in the process of liver metastasis. This study was performed with well-characterized murine ESbL T lymphoma cells transduced with the bacterial lacZ gene, which allows detection and quantification of metastases at the single cell level throughout lymphoma growth and metastasis. Experimental results are discussed in the context of recent literature.

Liver endothelial cells: participation in host response to lymphoma metastasis

Interactions between metastasizing tumor cells and host cells in target organs determine the outcome of metastasis. This review discusses the dual role of activated host endothelial cells in the metastatic process. On one hand, the upregulation of the expression of particular adhesion molecules leads to increased tumor cell binding, and the stimulation of angiogenesis provides the vascular support for the growth of already established metastases. On the other hand, endothelial cells can contribute to host anti-metastatic responses, e.g. by production of the cytotoxic molecule nitric oxide (NO) from arginine with the help of the inducible nitric oxide synthase (iNOS). Using a well-characterized ESbL-lacZ mouse T lymphoma model with a typical three phasic growth profile, we showed during the period of growth retardation a stimulation of NO production by ex vivo isolated liver sinusoidal endothelial cells. The induction of NO synthesis in liver endothelial cells did not require the presence of Kupffer cells and appeared to be stimulated by and dependent on mature T lymphocytes. A breakdown of this NO synthesis coincided with the second tumor expansion phase.

Genetic separation of GvL and GvH reactivity in new recombinant-inbred tumor-resistant mouse strains

From a cross between a tumor-susceptible syngeneic mouse strain (DBA/2) and a tumor resistant MHC congenic strain (B10.D2) new recombinant inbred mouse strains were established over many generations of inbreeding and tumor resistance selection. The resistance selected against one DBA/2 derived malignant tumor (ESb) extended to other DBA/2 malignant tumors (SL 2, MDAY-D2) and was thus of more general significance. Since tumor resistance had an immunological basis and since the two parental strains differed in multiple minor histocompatibility antigens (H) as well as in viral superantigens (vSAGs) we determined specificities of cytotoxic T lymphocyte (CTL) responses in vitro. All CTL responses from tumor resistant strains showed not only antitumor reactivity but also rather strong anti-minor H reactivity. There was no relationship between cytolysis and the DBA/2 type vSAG-7 (Mls(a)) expression. We also tested the capacity of immune cells from 7 resistant lines to transfer graft versus leukemia and graft versus host reactivity to ESb tumor bearing DBA/2 mice. Immune cells from one subline were capable of transfering complete protection without development of chronic GVH over a period of 4 months. The resistant parental line B10.D2 and most of the other sublines also were able to transfer GvL reactivity but this was usually associated later with chronic GVH disease caused mortality. These results demonstrate the potential of this genetic approach to separate GvL from GvH reactivity.

Characterization of a murine lymphoma cell line by 31P-NMR spectroscopy: in vivo monitoring of the local anti-tumor effects of systemic immune cell transfer

The intradermal ESb-MP murine T-cell lymphoma in syngeneic DBA/2 mice has been used as a model for adoptive immunotherapy (ADI). Cultured ESb-MP cells were characterized in suspension by 31P-NMR spectroscopy (MRS) at 11.7 T, and solid primary tumors were examined by 31P-MRS in vivo at 7.0 Tesla using surface-coil techniques. Growing tumors contained relatively high levels of phosphomonoesters (PME, predominantly phosphoethanolamine), nucleotides (NTP) and Pi, low levels of phosphodiesters (PDE) and no phosphocreatine. Mean tissue pH was found to be 6.7-6.9. The spectra of ESb-MP cells cultured in RPMI medium (containing choline but no ethanolamine) also showed low PDE and no phosphocreatine at an intracellular pH of 7.4; however, only a trace amount of phosphoethanolamine was detected and significant levels of nucleoside mono- and diphosphates were observed. The complete ADI treatment protocol involved low-dose irradiation (5 Gy) followed by i.v. transfer of immune spleen cells from allogeneic B10.D2 donors and resulted in 100% remission (responders); no treatment or incomplete ADI (irradiation or immune cell transfer alone) resulted in no remissions (nonresponders). In vivo MRS could best discriminate between responders and non-responders on the basis of tissue pH, which increased in responders to 7.0 by day 5-6 after complete ADI. Following therapy, the sum of PME + Pi (both absolute and as a percent of total phosphates) decreased significantly only for responders but only after a visible decrease in tumor volume was apparent.

Dynamic expression changes in vivo of adhesion and costimulatory molecules determine load and pattern of lymphoma liver metastasis

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.

Induction of NO synthesis in macrophages by Newcastle disease virus is associated with activation of nuclear factor-kappa B

Newcastle disease virus (NDV) has received much attention recently because of its non-specific immune stimulating potential and its various anti-tumor activities. Here we describe that NDV induces synthesis of NO and causes an activation of nuclear factor-kappa B (NF-kappa B) in murine macrophages. These reactions were part of an activation process which included also stimulation of adenosine deaminase and inhibition of 5'-nucleotidase. NDV-mediated NO synthesis and NF-kappa B activation were blocked by an antioxidant (butylated hydroxyanisole), by an inhibitor of protein tyrosine kinase (genistein) and of protein kinase A (H-89), but not by an inhibitor of protein kinase C (staurosporin). These data suggest that signalling requirements of NF-kappa B activation and NO production in NDV-treated macrophages are similar.

A role for sialoadhesin-positive tissue macrophages in host resistance to lymphoma metastasis in vivo

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.

Newcastle disease virus-infected intact autologous tumor cell vaccine for adjuvant active specific immunotherapy of resected colorectal carcinoma

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.

Tumor vaccine design: concepts, mechanisms, and efficacy testing

This paper deals with the design of tumor vaccines for either prophylactic application, such as viral vaccines, or for therapeutic application in cancer patients. It discusses important aspects in the design of vaccines which come from experience in the fields of infectious diseases and autoimmunity. As examples of tumor vaccines which are presently being tested, virus-infected tumor cell vaccines and gene-transfected tumor cell vaccines are further discussed. Such live cell vaccines are compared with oncolysate vaccines or vaccines prepared from purified tumor antigens and adjuvants. Future perspectives of such approaches for biotherapy of cancer are also discussed.

Liver endothelial cells participate in T-cell-dependent host resistance to lymphoma metastasis by production of nitric oxide in vivo

Tumor growth and metastasis of lacZ-transduced murine lymphoma ESbL cells inoculated into syngeneic DBA/2 mice are characterized by a transient plateau phase with a constant tumor diameter and low metastatic load, indicating a host response against the tumor. Here we show that endothelial cells participate in a T-cell-dependent, anti-metastatic response by producing NO in situ. Liver endothelial cells were isolated and examined directly ex vivo without further manipulation. NO production in liver endothelial cells reached the highest level during the plateau phase but declined toward the end of it, followed by an overall breakdown of host response, leading to progressive tumor growth and high load of liver metastasis. Mice subjected to anti-tumor immunization and subsequent challenge with a tumorigenic dose of ESbL-lacZ cells showed, in comparison to non-immunized challenged controls, reduced liver metastasis and increased endothelial NO production. Adoptive transfer of anti-tumor immune spleen cells from semi-allogeneic B10.D2 mice into tumor-bearing animals during the plateau phase caused a regression of primary tumor and metastases, together with a preservation of the high level of NO synthesis in endothelial cells. In immuno-incompetent (SCID) mice, tumor growth and metastasis were progressive and there was no endothelial NO response. Pre-immunization of immuno-competent mice with both live and irradiated tumor cells at different sites of the body led to an induction of NO production by liver endothelial cells. These results reveal a novel role of endothelial cells in the suppression of lymphoma metastasis in the liver. The inducible endothelial cell NO response is apparently dependent and induced by mature T lymphocytes.

Biotherapy of cancer. Perspectives of immunotherapy and gene therapy

Prospects for a new biologically based strategy of cancer treatment are being discussed. While physically and chemically based therapies, such as radio- and chemotherapy, are not directed against cancer tissue only and have a suppressive effect on the immune system, immunotherapy and gene therapy, which are discussed here, try to be more selective and to stimulate rather than suppress antitumor immune mechanisms. On the basis of personal experience with these new technologies, good future prospects are predicted for the application of cancer vaccines and immune T lymphocytes for active specific immunization (ASI) and adoptive immunotherapy (ADI) respectively. While ASI strategies aim at micrometastases being affected by activated host immune T cells, and might find a place for postoperative adjuvant treatment in high-risk cancer patients, cellular therapies such as ADI do not require an intact host immune system and could therefore also find application in advanced stages of disease. In spite of the exciting new perspectives of immuno- and gene therapy for the cancer patient, this therapy is not yet a defined discipline and requires years of further research.

In-situ activated macrophages are involved in host-resistance to lymphoma metastasis by production of nitric-oxide

We studied nitric oxide (NO) production, adenosine deaminase (ADA) and 5'-nucleotidase (5-N) activity as a function of macrophage activation in the model of spontaneous metastasis of ESbL T lymphoma cells transduced with the lacZ gene. Liver and spleen macrophages were isolated and examined directly ex vivo without further experimental manipulation. Transient arrest of liver metastasis was accompanied by an increase of NO production and ADA activity and by a decrease of 5-N activity. An aggressive expansion of metastasis was correlated with a drop of NO production and ADA activity and with an increase of 5-N activity. To test the involvement of in situ activated Kupffer cells in an antimetastatic response, two immunotherapy protocols were used: i) active immunization with lymphoma cells and ii) adoptive transfer of antitumor immune spleen cells. Both treatments caused an upregulation of ADA activity and NO production in Kupffer cells, which correlated with host resistance against metastases.

Induction of CD44 expression by the Epstein-Barr virus latent membrane protein LMP1 is associated with lymphoma dissemination

Epstein-Barr Virus (EBV) is implicated in the pathogenesis of endemic Burkitt's lymphoma (BL), B-cell lymphomas occurring under immunosuppression, nasopharyngeal carcinoma and Hodgkin's disease. Two distinct patterns of latent EBV gene expression occur in EBV-associated lymphomas. BLs typically display expression of the nuclear antigen EBNAI only, whereas EBV-associated, non-Burkitt B-cell lymphomas express at least 9 latent viral genes (6 EBNAs and 3 latent membrane proteins), reminiscent of in vitro EBV-immortalized lymphoblastoid cell lines (LCL). BLs are characterized by local, extra-nodal growth, whereas EBV-associated B-cell lymphomas often disseminate to peripheral lymphoid tissue. We show here that BL cells forming local tumors after xenotransplantation into SCID mice disseminate to lymphoid tissue following introduction of the latent membrane protein I (LMP 1) gene. Introduction of LMP 1 into BL cells induced expression of CD44 on the cell surface, a molecule implicated in enhanced lymphoid tumor growth and dissemination. Introduction of CD44 into LMP 1-/CD44-BL cells was observed to confer the disseminated tumor growth pattern associated with LMP 1 expression. Taken together our results show that expression of LMP 1 may regulate expression of CD44 and play an important role in the behavior of EBV-based lymphomas.

Ligand mediated activation of ectopic EGF receptor promotes matrix protein adhesion and lung colonization of rat mammary adenocarcinoma cells

Increased expression of EGF receptor (EGFR) in metastases of human mammary carcinoma as compared to cells of the primary cancer suggests a contribution of EGFR to mammary carcinoma metastasis. To test for a positive causative link, we investigated 13762NF rat mammary adenocarcinoma cloned tumor cell lines of high (MTLn3) or low (MTC) metastatic potential. While MTC cells expressed barely detectable amounts of EGFR, MTLn3 cells expressed readily detectable levels of functional receptors. A full length cDNA of the human EGFR (HER) was introduced by infection with a retroviral vector into MTC cells. Expression of HER was stable and receptors were functional with respect to surface expression, ligand binding and EGF-stimulated phosphorylation. Independent clones of the transfectants were isolated and characterized. Ligand stimulation of MTC HER cells and derived clones led to enhanced adhesion of cells to extracellular matrix proteins. Implantation of cells intravenously into female nu/nu mice revealed ligand-dependent enhancement of lung colonizing potential of EGFR-expressing cells.

[Tumor vaccination in renal cell carcinoma with and without interleukin-2 (IL-2) as adjuvant. A clinical contribution to the development of effective active specific immunization]

Interleukin 2 (IL2) production is known to bypass T-helper-cell function in the generation of an antitumour response. The present analysis was designed to assess the effects of application of renal cancer vaccine with and without IL2 on delayed-type hypersensitivity (DTH) skin responses to the vaccine itself and tumour cell challenge. The renal cancer vaccine consisted of Newcastle disease virus (NDV)-infected autologous irradiated tumour cells and topical application of low-dose rIL2 (75,000 Cetus units). As a result, the coadministration of a supplement of rIL2 proved to be important for augmentation of DTH responsiveness to tumour cell challenge. Patients with aneuploid tumours vaccinated without rIL2 developed an anergy to the vaccine throughout vaccination. This effect could be reversed by the topical coapplication of this cytokine. While the treatment of renal cancer patients with IL2-based immunotherapy regimens appears to be effective in advanced renal cell carcinoma the IL2-supplemented vaccines should be tested to assess their benefit in the situation of "minimal disease" after surgery especially in high-risk patients with aneuploid tumours.

Immediate effects of reversible HTLV-1 tax function: T-cell activation and apoptosis

The tax protein of Human T-cell leukemia virus type 1 (HTLV-1) is important for the transforming properties of this virus in vitro and is considered to be responsible for the early stages of leukemogenesis in infected hosts. To address the early consequences of HTLV-1 tax function, we have constructed fusion proteins containing tax sequence either aminoterminal (taxER) or carboxy-terminal (ERtax) of the hormone binding domain of the human estrogen receptor (ER). Addition of estrogen or the antagonist hydroxytamoxifen to Jurkat T-cells expressing these constructs led to the trans-activation or responsive promoters and upregulation of cell surface markers CD28, CD69 and CD5 but not CD25 (IL2R-alpha subunit) or B7 (ligand for CD28). Additional stimulation of the T-cell receptor CD3 complex, led to the upregulation of CD25. B7 was upregulated by concomittent activation of ERtax and CD3 or CD28 pathways. These events were in part reversible upon withdrawal of hormone and inactivation of ERtax. Severe inhibition of proliferation, and apoptosis was observed with cells which had been subjected to short term (3 days) activation of the tax fusion proteins and the CD3 complex. Induction of ERtax activity for longer than 3 days promoted cell death independently of CD3 stimulation. Co-stimulation through the CD28 cell surface molecule did not suppress induction of apoptosis.

Augmentation of protective immunotherapy against metastatic esb lymphoma-cells by combining immune cell transfer with host irradiation, antigen restimulation and/or anti-tnf-alpha antibody treatment

To develop effective immunotherapies against disseminated metastatic tumor cells we have tried to improve the overall protective immunity effect by combining adoptive immune cell therapy (ADI) with other treatment modalities. In contrast to other groups who use in vitro cultured effector cells we use for ADI only in situ activated anti-tumor immune cells. The immunotherapy studies were performed with the lymphoma variant ESb which metastasizes to multiple visceral organs and can develop immune escape variants. In the absence of additional exogenous cytokines, peritoneal effector cells (PEC), generated from intra-pinna tumor immunized and i.p. re-stimulated mice, were able to transfer protective immunity and anti-tumor DTH reactivity into syngeneic mice with disseminated ESb tumor cells. We describe the protective immune capacity of PEC in comparison to immune cells from lymph nodes or spleens of immunized mice and test for possible synergistic interactions of the latter with PEC. The adoptive immunotherapy effect seen with immune PEC could be augmented by host irradiation and by combination with active specific immunization (ASI) using previously established virus modified tumor vaccines. In an attempt to study the possible role of cytokines in this system, we tested the effect of neutralizing antibodies to TNF-alpha and IFN-gamma on the therapeutic effect. Anti-TNF-alpha but not anti IFN-gamma antibody treatment augmented the immunotherapeutic effectiveness of immune PEC mediated ADI.

Effective anti-metastatic melanoma vaccination with tumor cells transfected with MHC genes and/or infected with Newcastle disease virus (NDV)

The therapeutic efficacy of active immunization with B16-F10.9 melanoma cells transfected with syngeneic major histocompatibility complex (MHC) class-I genes, modified by infection with Newcastle Disease virus (NDV) or modified by both treatments, was compared. B16-F10.9 tumor-bearing mice were treated at various stages of tumor growth and metastasis with irradiated, modified tumor-cell vaccines. Irradiated tumor cells and H-2Db transfectants did not stimulate anti-tumor immunity while H-2Kb transfectants and NDV-modified F10.9 cells showing low and high expression of MHC class-I genes efficiently prevented metastasis of small established tumors. NDV-modified parental-cell vaccines functioned optimally and improved overall survival by about 60%, also at early stages of metastasis establishment. A synergistic effect of H-2Kb expression and virus modification on rejection of micrometastases was observed in mice bearing advanced tumors. Postoperative vaccination of mice carrying multiple metastases with NDV-modified vaccines caused significant, but incomplete, reduction of metastatic tumor load. The therapeutic effect of NDV-modified tumor vaccines was dependent on multiple immune mechanisms. Depletion of CD8, CD4 or NK cells by in vivo treatment with monoclonal antibodies reversed the immunotherapeutic effects of the vaccine. Thus, tumor xenogenization and gene modification may act synergistically to vaccinate against advanced tumors, while single modalities can effectively vaccinate against metastasis at early stages of tumor growth.

Pattern and load of spontaneous liver metastasis dependent on host immune status studied with a lacZ transduced lymphoma

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.

Persistence of dormant tumor cells in the bone marrow of tumor cell-vaccinated mice correlates with long-term immunological protection

Live proliferation-competent and irradiated proliferation-incompetent L5178 murine lymphoma cells (Eb cell line) were compared for their potency to induce systemic anti-tumor immunity in syngeneic DBA/2 mice. The tumorigenic potential in vivo of live Eb cells was suppressed through local secretion of interleukin 4 (IL4) or alternatively by injection of parental cells at a site refractory to tumor growth. Inoculation of nontumorigenic doses of live Eb or Eb-IL4 cells led to long-lasting specific and systemic T-cell-mediated antitumor response requiring both CD4+ and CD8+ T lymphocytes. Irradiated cells offered only limited short-term protection, which could be marginally improved by IL4. The more effective protection offered by vaccination with live tumor cells correlated with rapid migration and persistence of tumor cells in the bone marrow of host animals after tumor cell inoculation. In contrast, irradiated Eb-lacZ cells had a short persistence. Tumor cells recovered from the bone marrow of host animals injected with live Eb-IL4 cells still expressed IL4. These observations indicate that in the course of vaccination with live Eb or Eb-IL4 cells, a fraction of these cells escaped destruction by host mechanisms and persisted in a dormant state in the bone marrow for long periods of time. Persistence of dormant tumor in the bone marrow correlated with the duration of anti-tumor immunity.

Adoptive transfer of protective immunity against a high metastatic tumor-cell variant by small numbers of tumor-specific in-situ activated peritoneal effector T-cells

We describe the generation and immunotherapeutic properties of syngeneic immune T cells activated in situ against the lymphoma variant ESb which metastasizes to multiple organs (liver, lung, spleen, bone) and can develop sophisticated immune escape mechanisms. Peritoneal effector cells (PEC) generated from intra-pinna tumor immunized and i.p. restimulated mice were able to transfer protective immunity in the absence of exogenous cytokines into normal or 5Gy irradiated or SCID mice which had been injected either s.c. or i.v. with 5x10(3) to 10(5) metastatic ESb tumor cells. Protective immunity was specific for ESb cells and could be followed by growth retardation of s.c. tumors as well as by prevention or retardation of death from metastases. Expression of protective immunity was independent of host T cells since it was similarly expressed in SCID-mice and sublethally irradiated mice. Preincubation in vitro for 24 h of the PEC before adoptive transfer led to pronounced decrease of protective immunity while the tumor specific cytotoxic T lymphocyte (CTL) activity was maintained or even enhanced. These results demonstrate i) that protective immunity in vivo requires more than tumor specific cytotoxic activity and ii) that in vitro culture of immune cells can change their in vivo functional properties.

Scattered micrometastases visualized at the single-cell level: detection and re-isolation of lacZ-labeled metastasized lymphoma cells

To study metastasis at the single-cell level we transduced highly metastatic ESb lymphoma cells with a retroviral expression vector containing the lacZ (bacterial beta-galactosidase) gene. This allowed single ESb-lacZ tumor cells to be detected in infiltrated target organs by means of X-Gal staining. Despite expression of the lacZ gene, the tumor cells were still tumorigenic, highly metastatic, unchanged in phenotype and therefore comparable to parental ESb cells. After spontaneous metastasis, whole-organ staining revealed metastatic foci at the surface of the liver. In histological liver sections, metastatic clusters and single dispersed tumor cells could be detected. In contrast to whole-organ staining, histological examination revealed scattered distribution of tumor cells throughout the organ, which was not evident with parental ESb cells. In addition, clusters with diffuse or dense (focal) appearance were found, in correlation with the whole-organ staining. Expression of the foreign lacZ gene allowed the metastatic spread of tumor cells to liver and spleen to be quantified approximately by FACS analysis. Furthermore, it was shown that the newly expressed beta-gal was expressed not only intercellularly but also at the cell surface. There it could be recognized by MAbs and cytotoxic T-cells (CTL). beta-gal did not affect CTL recognition of the ESb tumor-associated antigen. In conclusion, lacZ could be used as a genetic marker for a highly metastatic lymphoma, to define scattered metastatic spread in the liver at the single-cell level and to quantify the tumor load by FACS analysis.

Heat-stable antigen (CD24) as ligand for mouse P-selectin

Heat-stable antigen (HSA)/CD24 is a cell surface molecule expressed by many cell types in the mouse. The molecule has an unusual structure because of its small protein core and extensive glycosylation. In order to study the functional role of the HSA-associated glycoconjugates we have isolated different forms of HSA. Using lectin analysis we provide evidence for extensive heterogeneity in carbohydrate composition and sialic acid linkage. Several HSA forms were recognized by mouse P-selectin-IgG but not E-selectin-IgG in ELISA. As expected, P-selectin-IgG also bound to L2/HNK-1-positive neural glycoproteins (L2-glycoproteins) and sulfatides but not to gangliosides and other control glycoproteins. The binding of P-selectin-IgG to L2-glycoproteins and HSA required bivalent cations. The reactivity to HSA was sensitive to sialidase treatment whereas the binding to L2-glycoproteins was not. Studies with alpha 2-6 sialytransferase indicated that alpha 2-6 linked sialic acid was not involved in the P-selectin binding to HSA. Surprisingly, an L2/HNK-1 specific antibody was found to cross-react with some HSA glycoforms and its binding correlated with P-selectin-IgG reactivity. L2/HNK-1-positive or L2/HNK-1-negative HSA glycoforms were also analyzed after coating to polystyrene beads. Only the L2/HNK-1-positive HSA coated beads were reactive with P-selectin-IgG and could bind to activated bend3 endothelioma cells expressing P-selectin whereas the L2/HNK-1-negative HSA beads did not. It is suggested that in its L2/HNK-1 modified form the HSA molecule on leukocytes could represent a ligand for P-selectin on endothelial cells or platelets.

Successful immunotherapy of the highly metastatic murine ESb lymphoma with sensitized CD8+ T cells and IFN-alpha/beta

Daily IFN-alpha/beta therapy was totally ineffective in inhibiting the development of visceral metastases in DBA/2 mice injected i.v. with the ESb lymphoma regardless of the number of tumor cells injected. The finding that IFN-alpha/beta therapy increased the survival time of ESb-immunized mice rechallenged with ESb cells suggested that cooperation between the immune system and IFN-alpha/beta was important. Adoptive transfer of Esb-immune spleen cells (but not normal cells) together with IFN-alpha/beta treatment did inhibit the development of ESb metastases in immunocompetent DBA/2 mice. Either treatment alone was ineffective. The anti-metastatic effect was specific for the ESb lymphoma as spleen cells from ESb-immunized mice together with IFN-alpha/beta treatment did not inhibit the development of metastases in mice challenged with IFN-alpha/beta-resistant 3C18 FLC. Depletion of CD8+ T cells (but not CD4+ T cells or B lymphocytes) prior to transfer eliminated the protective effect of ESb-immune splenocytes in IFN-alpha/beta-treated mice. As few as 1 x 10(6) ESb-immune spleen cells highly enriched for CD8+ cells increased the survival time of IFN-alpha/beta-treated ESb-challenged DBA/2 mice. The combined therapy of ESb-specific immune cells and IFN-alpha/beta resulted in long-term immunity to this tumor.

Motility and invasive potency of murine T-lymphoma cells: effect of microtubule inhibitors

ESb and BW-O-Li1 are T-lymphoma cell lines that form metastases in various organs after injection into syngeneic mice. In vitro, both cell lines invade through a fibroblastic monolayer, but ESb cells do so much slower than BW-O-Li1. By the use of Fourier analysis of cell outlines, we can relate this difference in invasiveness to a difference in cell motility: ESb cells do not perform any conspicuous shape change, whereas BW-O-Li1 cells are actively protruding and retracting large pseudopodia. However, the low-motile ESb cells become as motile and deformable as BW-O-Li1 cells when they have eventually invaded under a fibroblastic monolayer. This indicates that ESb cells do have inherent capability for shape change. Treatment of ESb cells with the microtubule disrupting agent nocodazole concomitantly increases their shape change intensity, and their invasion rate through fibroblast monolayers. On the contrary, the microtubule stabilizing drug taxol inhibits both motility and invasion of BW-O-Li1 cells. Our observations suggest that the microtubule network can repress invasion-bound motility of lymphoid cells.

L1 adhesion molecule on mouse leukocytes: regulation and involvement in endothelial cell binding

L1 is a cell surface glycoprotein of the immunoglobulin superfamily which was initially shown to mediate adhesion between neural cells. Recently we have reported that L1 is expressed by bone marrow cells and the majority of mature lymphocytes (Kowitz et al., Eur. J. Immunol. 1992. 22: 1199-1205). To analyze the function of L1 on leukocytes we studied its regulation following cell activation. In vitro activation of B lymphocytes with lipopolysaccharide or T lymphocytes with phorbol 12-myristate 13-acetate/Ca2+ ionophore, concanavalin A or anti-CD3 monoclonal antibody as well as in vivo activation of V beta 8+ T cells with staphylococcal enterotoxin B (SEB) revealed a down-regulation of L1 within 48 h. A rapid loss of L1 expression was seen when mouse neutrophils were activated with PMA alone. This rapid loss paralleled the shedding of L-selectin. We also studied a possible role of L1 in the binding of leukocytes to endothelial cells. ESb-MP lymphoma cells with a high expression of L1 (L1hi) could bind to bend3 endothelioma cells without prior activation with inflammatory cytokines. The interaction was inhibited by anti-L1 antibodies. In contrast, ESb-MP cells with low L1 expression (L1lo) were only marginally bound. Latex beads coated with affinity-isolated L1 antigen were also able to bind to the endothelioma cells in a specific fashion. The binding of ESb-MP lymphoma cells required Ca2+ and Mg2+ ions and was sensitive to cold temperature. Since the endothelioma cells did not express L1 the binding mechanism studied here is distinct from the established L1-L1 homotypic interaction. It is possible that the novel L1-mediated adhesion pathway involves an unidentified ligand and could play a role in leukocyte migration.

Viral hemagglutinin augments peptide-specific cytotoxic T cell responses

In attempt to increase the induction of peptide-specific cytolytic T cells (CTL) we investigated the effect of the Newcastle disease virus (NDV) hemagglutinin-neuraminidase (HN) gene product on the activation of peptide-specific CTL. Spleen cells of CH3 mice immunized against the influenza nucleoprotein peptide 50-63 (NP 50-63) were restimulated in vitro (i) with peptide-pulsed syngeneic fibroblast cells (Ltk-) as antigen-presenting cells, which were in addition (ii) infected with NDV or (iii) stably transfected with the HN cDNA of NDV. A greater than sixfold increase in peptide-specific CTL responses was observed in cultures restimulated with peptide-pulsed Ltk- cells which co-expressed viral hemagglutinin due to either infection or transfection. A similar augmentation was seen in CTL responses against other types of antigen (major histocompatibility complex alloantigens, minor histocompatibility antigens or tumor antigens) when suboptimal cultures were stimulated with the respective antigen-presenting cells modified by NDV infection. These findings suggest that NDV or viral HN expressed on antigen-presenting cells or tumor cells can exert a T cell co-stimulatory function.

Expression of L1 cell adhesion molecule is associated with lymphoma growth and metastasis

The cell adhesion molecule (CAM) L1 is involved in homotypic and heterotypic adhesion between neural cells. It has recently also been identified on leucocytes. We have investigated the expression of L1 on hematopoietic tumor cell lines and found that several tumors including the ESb-MP lymphoma are positive for L1. A potential role for L1 in spontaneous metastasis formation was examined using these cells. From wild-type (wt) L1high lymphoma cells we selected by a fluorescence-activated cell sorter (FACS) stable L1low expression variants. Syngeneic DBA/2 mice injected subcutaneously with L1low clones showed faster primary tumor growth, developed visceral metastases significantly faster and died earlier than animals carrying L1high wt cells. L1 high revertants from the L1low variants showed again a reduced metastatic capacity and a malignancy similar to the wt cells. Expression of L1 on the tumor variants and revertants correlated directly with their homotypic aggregation behaviour in vitro. L1 expression correlated negatively with metastatic capacity. These results suggest that L1 molecules may contribute to the overall malignant potential of the lymphoma cells, presumably by interfering with cell-cell interactions critical for tumor growth and dissemination.

In vitro expansion and analysis of T lymphocyte microcultures obtained from the vaccination sites of cancer patients undergoing active specific immunization with autologous Newcastle-disease-virus-modified tumour cells

In order to understand further the effects of Newcastle-disease-virus(NDV)-modified tumour vaccines we investigated the feasibility of isolating lymphocytes from the site of injection of patients undergoing postoperative active specific immunization (ASI) with autologous NDV-modified tumour cells. Delayed-type-hypersensitivity(DTH)-like reactions from five cancer patients were surgically removed, minced and the tissue particles were digested with collagenase and DNase. Lymphoid cells recovered were expanded in a highly efficient limiting-dilution analysis system optimized for T cell growth [Moretta et al. (1983) J Exp Med 157: 743] and lymphocyte microcultures (clonal probability > 0.8) could be grown for up to 1 year. Analysis of the microcultures for phenotype and function showed that the majority were positive for CD4 (92%) and TCR alpha beta (96%). Concanavalin-A-induced production of interleukin-2 (IL-2), IL-6, interferon gamma and tumour necrosis factor alpha was detected in more than 70% of the microcultures. Lectin-dependent cytotoxicity was only very rarely observed. The general characteristics of the microcultures obtained support the notion of a DTH-like reaction taking place at the site of tumour cell challenge. The possibility of in vitro expansion and cultivation of T lymphocytes from ASI vaccination sites should help to elucidate further the role of these cells in active specific immunization against autologous tumour cells.

EGF receptor in neoplasia and metastasis

EGFR is a member of the tyrosine kinase family of cell surface receptors with a wide range of expression throughout development and in a variety of different cell types. The receptor can transmit signals to cells: i) upon interaction with ligands such as EGF, TGF alpha, amphiregulin or heparin binding EGF, ii) upon truncation or mutation of extracellular and/or intracellular domains, iii) upon amplification of a basal receptor activity (in the absence of ligand) through cooperation with other cellular signaling pathways or nuclear events (e.g. expression of v-erbA). The activated EGFR can exert pleiotropic functions on cells, depending on their tissue origin and state of differentiation. Under certain conditions it can also contribute to neoplasia and development of metastases. Such conditions can exist upon aberrant receptor/ligand expression and activation (e.g. in the wrong cell; at the wrong time; in the wrong amounts). Aberrant signalling can also occur through constitutive EGFR activation. Oncogenic potential of EGFR has been demonstrated in a wide range of experimental animals. EGFR is also implicated in human cancer, where it may contribute both to the initiation (glioblastoma) and progression (epithelial tumors) of the disease. EGFR may influence key steps in the processes of tumor invasion and dissemination. Involvement of EGFR in tumor spread may indicate a potential use of this receptor as a target for antimetastatic therapy.

Tumour-specific CTL response requiring interactions of four different cell types and recognition of MHC class I and class II restricted tumour antigens

This study demonstrates that a syngeneic specific cytotoxic T lymphocyte (CTL) response to a class I major histocompatibility complex (MHC) positive tumour requires dual processing and recognition of tumour antigens. One type of antigen is processed and expressed in association with class I MHC at the surface of intact tumour cells. It is recognized by CD8 alpha, beta TCR CTL in vitro and by protective immune T cells in vivo and thus functions as a tumour-associated transplantation antigen (TATA). The other type of antigen is processed and expressed by distinct host APC in association with class II MHC. This is recognized by immune CD4 T cells which function as essential helper cells in the generation of the CD8 CTL response. These conclusions are supported by cell depletion and reconstitution experiments as well as by blocking experiments with monoclonal antibodies using the highly metastatic class II negative murine lymphoma ESb as a model system. The existence of two types of cognate T cell responses in a syngeneic anti-tumour response was directly proved by the establishment of two types of tumour specific T cell lines which required as co-stimulator either MHC class II positive APC or IL-2. In suboptimal mixed lymphocyte tumour cell cultures either of these co-stimulator functions was found to be limiting the overall anti-tumour CTL response. The generation of the tumour specific CTL response could be blocked by monoclonal antibodies against all the molecules involved in the cognate interactions (i.e. class I MHC, CD8, class II MHC, CD4 and TCR) but not by anti-CD2 or anti-IgG. The strict requirement for helper cells and APC could be bypassed by the addition of recombinant IL-2 but optimal triggering of CD8 CTL-precursor required viable tumour stimulator cells. This well characterized in vitro assay may be useful (i) for monitoring the immune status of CD4 and CD8 immune T cells separately, for instance of tumour bearing and/or treated animals and (ii) for the development and testing of potent tumour cell vaccines with T cell stimulatory and/or co-stimulatory activities.

Preferential antibody targeting to small lymphoma metastases in the absence of the primary tumour

Targeting of spontaneous liver metastases of the ESb.MP murine lymphoma was achieved with anti-CD2 monoclonal antibody (MAb) 12-15A, which does not react with normal liver tissue. Using quantitative autoradiography on whole body sections of animals that had received a standard dose of 1.1 MBq of 125I-labelled monoclonal antibody, metastases accumulated up to > 90% of the injected dose per gram (id/g). The average uptake of primary tumour lesions was at a low level of 24 Bq/mg (corresponding to 2.2% id/g) because of highly non-uniform accumulation, while metastatic lesions were all above 50 Bq/mg. Uptake was particularly pronounced in animals tested after resection of the primary tumour: 85% of metastases showed levels above 300 Bq/mg, which was the upper limit of uptake in metastases of non-resected animals. These findings demonstrate the potential of the antibody approach with regard to attacking residual metastatic lesions after debulking.