Relationship of success in classical immunotherapy to the relative immunorejective strength of the tumor

Six tumors of varying immunorejective strengths were used to compare the response of their isogenic hosts to standardized regimens of immunoprophylaxis and immunotherapy. The tumors were generated spontaneously or induced chemically [with 9,10-dimethyl-1,2-benzanthracene (CAS: 57-97-6)], virally (with murine leukemia virus), or radiogenically (with strontium-90). The hosts were C57BL/6J or BALB/cByJ mice. Immunoprophylaxis and immunotherapy were performed with isogenic irradiated tumor cells, with Corynebacterium parvum, or with both. The results of challenge experiments were quantified as the doses of viable tumor cells that produced 50% tumor deaths for immunized and for control mice. The results for these quantitative "classical" immunoprophylaxis and immunotherapy experiments were consistent with two theses: that only immunorejective tumors give positive results with classical immunotherapy and that classical immunoprophylaxis is more effective than classical immunotherapy when identical materials are used for immunizations. These results have important consequences for the clinical use of classical immunotherapy.

Potential uses of interleukin 2 in cancer therapy

Interleukin 2 (IL 2) has several potential uses in cancer therapy including: the augmentation of specific T cell mediated anti-tumor immunity and the activation of non-specific cytolytic effector cells, termed lymphokine-activated killer (LAK) cells. The current review will present data from our laboratory demonstrating in animal models the feasibility of both potential approaches. Studies to be reviewed show that: IL 2 can induce the proliferation and expansion in number of tumor-reactive T cells in vitro; T cells grown in culture in IL 2 can be effective reagents in vivo for specific tumor therapy; the administration of exogenous IL 2 can induce the growth and augment the function of cultured T cells in vivo; however, as a corollary, T cells cultured long-term in vivo with IL 2 are functionally limited in vivo without the administration of exogenous IL 2 in vivo; by contrast, T cells grown in vitro with specific antigen, as opposed to IL 2, as the major stimulus for proliferation are able to proliferate rapidly in vivo, distribute widely in host lymphoid organs, and mediate therapy of disseminated murine leukemia; importantly, such antigen-driven long-term cultured T cells can survive long-term in vivo and provide specific immunologic memory, and, the administration of low-dose IL 2 in vivo can induce the growth of antigen-driven long-term cultured T cells in vivo and thereby increase the number of functional memory T cells; the culture of lymphoid cells in high concentrations of IL 2 can induce LAK cells in vitro capable of lysing leukemia in vitro; LAK cells generated in vitro can mediate a small but detectable anti-tumor effect in vivo against disseminated leukemia as an adjunct to chemotherapy; and, high-dose IL 2 administered in vivo can activate LAK cells in vivo and cure disseminated murine leukemia. Therefore, it is highly likely that IL 2 can become an effective reagent for the therapy of human cancer.

Growth inhibition of a B cell leukemia: evidence implicating an anti-idiotype immune response for protective tumor immunity

BCL1, a spontaneous surface IgM (mu lambda)-positive (sIgM+) B cell leukemia of BALB/c (Igha) origin rarely grows in the Ig heavy chain (Igh) congenic mouse C.B-20 (Ighb) but is highly metastatic and lethal in the host strain of origin. Previous studies indicated that BCL1 tumor immunity in C.B-20 mice was associated with a T cell-mediated immune response against H-40, a minor histocompatibility (H) antigen controlled by a gene linked to the Igh locus. However, we observed that BCL1 leukemia grew progressively in BAB-14 (Igha/b) mice, a strain capable of generating an anti-H-40 immune response. This suggested that anti-H-40 immunity was insufficient for protection and implied that an Igh-V (variable) region gene product was also important for BCL1 growth inhibition. We therefore evaluated the role of two possible Igh-V region-linked gene products in BCL1 growth inhibition; namely, an Igh-V region-linked minor H antigen or alternatively the BCL1 IgM idiotype (Id). We could find no evidence for an Igh-V region-linked minor H antigen because immunosuppressed (500 R) CB-20 mice reconstituted with C.B-20 anti-BAB-14 splenocytes were susceptible to BCL1 growth, whereas recipients reconstituted with C.B-20 anti-BALB/c splenocytes were resistant to BCL1 challenge. In contrast, C.B-20 mice immunized against purified BCL1 IgM protein could adoptively confer BCL1 tumor immunity. C.B-20 mice immunized against other BALB/c IgM myeloma proteins containing either lambda or kappa light chains failed to protect C.B-20 mice suggesting that recognition of a unique determinant (Id) and not an allotype was crucial for tumor immunity. The BCL1 mu-chain appeared to make the major contribution to the idiotypic determinant because a hybridoma product composed of BCL1 mu-chains and BALB/c kappa-chains still elicited BCL1 immunity. Adoptive transfer of C.B-20 anti-BCL1 Id splenocytes into irradiated recipients that prevented an anti-H-40 response due to H-40 tissue expression failed to adoptively confer BCL1 immunity. Thus, these data suggest that BCL1 growth inhibition requires a T cell-mediated response against both H-40 and the BCL1 Id; these responses must be elicited concurrently in the tumor-bearing host to achieve protective BCL1 immunity.

Anti-tumor effects of interferon in mice injected with interferon-sensitive and interferon-resistant friend leukemia cells. IV. Definition of optimal treatment regimens

Mouse interferon alpha/beta exerted a similar anti-tumor effect in DBA/2 mice injected i.p. with Friend erythroleukemia cells (FLC) either sensitive or resistant to interferon as determined by both in vitro and in vivo assays. Using this tumor system we attempted to define optimal treatment regimens for interferon administration. Interferon was most effective when injected at the site of tumor inoculation rather than at a distant site. Two factors seemed of especial importance: the amount of interferon injected and the frequency of interferon administration. Thus, for daily administration of interferon, the antitumor effect was directly related to the amount of interferon injected. For a given total dose of interferon, repeated administration of small doses of interferon was more effective than administration of a larger dose at more widely spaced intervals. The anti-tumor efficacy of interferon was independent of the number of FLC inoculated when 10(2) to 10(5) FLC were injected, but interferon treatment was less effective when 10(6) or 10(7) FLC were injected. The relevance of these results to the use of interferon in patients with cancer is discussed.

Monoclonal antibody therapy of spontaneous AKR T-cell leukemia

We have previously shown that monoclonal antibodies against the Thy 1.1 differentiation antigen can inhibit the outgrowth of a lethal inoculum of transplanted AKR T-leukemic cells. In the present report we have extended these studies to examine antibody therapy of aged AKR/J mice with spontaneous leukemia. Infusion of anti-Thy 1.1 antibody in frankly leukemic mice led to uniform early mortality from cell lysis and agglutination. In contrast, anti-Thy 1.1 antibody therapy of mice in remission following treatment with cyclophosphamide prolonged remission duration (P less than 0.001) and modestly prolonged survival (P less than 0.01) compared to treatment with irrelevant antibody or chemotherapy alone. The major cause of failure was relapse of leukemia. In 85% (47 of 55) of cases relapse was due to cells that continued to express Thy 1.1, but in 15% of these relapsing animals all leukemic cells failed to express the target antigen. Our results suggest that monoclonal antibody against a normal T-cell antigen can add to the antileukemic effects obtained with chemotherapy alone. Nevertheless, the clinical benefit of unmodified antibody was modest, and antibodies conjugated to cytotoxic agents may be needed to overcome the limitations of unmodified antibodies.

[Basic study on interferon-beta: Part IV. Antitumor effect on nude mouse-transplanted human tumors]

The effects of human interferon-beta (IFN-beta, MR-21) on the growth of xenografted human tumors in nude mice were examined. IFN-beta was administered to mice with malignant melanoma (SK-MEL-28 and Sk-14) intratumorally at a dose of 1 X 10(5)-3 X 10(5) IU/mouse, with acute leukemia (CCRF-HSB-2) intratumorally at a dose of 3 X 10(5) IU/mouse, with glioblastoma (U-373 MG) intravenously or intratumorally at a dose of 1 X 10(5)-6 X 10(5) IU/mouse, or with uterine cervical tumor (HeLa S3) intravenously at a dose of 0.3 X 10(5)-1 X 10(5) IU/mouse. IFN-beta inhibited the growth of all of these tumors in a dose-dependent manner.

Antigen-driven long term-cultured T cells proliferate in vivo, distribute widely, mediate specific tumor therapy, and persist long-term as functional memory T cells

Mice bearing disseminated syngeneic FBL-3 leukemia were treated with cyclophosphamide plus long term-cultured T cells immune to FBL-3. The cultured T cells for therapy had been induced to grow in vitro for 62 d by intermittent stimulation with irradiated FBL-3. At the time of therapy, such antigen-driven long term-cultured T cells were greatly expanded in number, proliferated in vitro in response to FBL-3, and were specifically cytotoxic. Following adoptive transfer, donor T cells persisting in the host were identified and counted using donor and host mice congenic for the T cell marker Thy-1. The results show that antigen-driven long term-cultured T cells proliferated rapidly in vivo, distributed widely in host lymphoid organs, and were effective in tumor therapy. Moreover, the already rapid in vivo growth rate of donor T cells could be augmented by administration of exogenous IL-2. When cured mice were examined 120 d after therapy, donor L3T4+ T cells and donor Lyt-2+ T cells could be found in large numbers in host ascites, spleen, and mesenteric and axillary lymph nodes. The persisting donor T cells proliferated in vitro, and became specifically cytotoxic in response to FBL-3, demonstrating that antigen-driven long term-cultured T cells can persist long term in vivo and provide immunologic memory.

Properties of mouse leukemia viruses: XX. Variation of AKR Substrains in response to antibody therapy

In previous reports in this series, we have demonstrated that treatment of young AKR mice with IgG prepared against the viral envelope glycoprotein suppresses the development of spontaneous leukemia. Moreover, animals exhibiting high anti-viral antibody titers can transfer protection to their offspring. In this report we have extended the studies to another strain of AKR mice and find that the ability to transfer protection to offspring was not obtained. Foster nursing experiments were therefore conducted and their outcomes are indicative that maternal factors may be responsible for this phenomenon.

Combined prophylactic suppression of graft-versus-host and host-versus-graft reactions following treatment of prospective bone marrow recipients with rat IgG 2b anti-mouse T cell antibodies

A new approach to avoid typical complications from bone marrow transplantation into MHC different mice was studied. Rat monoclonal anti-Thy-1 antibodies of the IgG 2b isotype were identified, which inhibit T lymphocytes in vivo so that transplanted donor T cells as well as residual T cells of the conditioned marrow recipient were suppressed. A single injection of these antibodies after irradiation and before marrow transplantation did not only prevent graft-versus-host mortality but suppressed also host-versus-graft reactivity so that the radiation dose necessary for engraftment of donor cells differing in H-2, IA (both haplotypes) major histocompatibility antigens could be reduced to 6.0 Gy. In addition an anti-T leukemic cell effect from the injected monoclonal T cell antibodies was observed.

Cloned fragment of diphtheria toxin linked to T cell-specific antibody identifies regions of B chain active in cell entry

The role of discrete domains of diphtheria toxin (DT) B chain in cytosol entry and cytotoxicity was investigated by linking a monoclonal antibody recognizing the human T cell-specific antigen T3 (UCHT1) to diphtheria toxin (UCHT1-DT), DT A subunit (UCHT1-DTA), or to a genetically engineered form of DT (UCHT1-MspSA) lacking the C-terminal 17-kDa portion of the B subunit. The N-terminal 21-kDa region of DT B chain increased toxicity of UCHT1-DTA 100-fold (UCHT1-MspSA) while addition of the C-terminal 17-kDa region (UCHT1-DT) increased toxicity 100-fold more. The cytotoxicity was dependent upon antibody binding as demonstrated by blocking toxicity with excess UCHT1. The differences in toxicity between these reagents were not due to differences in ADP-ribosylation activity of DT A chain, binding activity of the antibody moiety, extent of DT nicking, or the cross-linking method, so we conclude that the large differences in toxicity were due to the presence of different B chain domains. The large increase in toxicity by the C-terminal region of DT B did not appear to be caused by DT receptor binding. The lysosomotropic agent NH4Cl blocked the cytotoxic effect of DT, UCHT1-DT, and UCHT1-MspSA but not UCHT1-DTA.

Manipulation of graft-versus-host disease for a graft-versus-leukemia effect after allogeneic bone marrow transplantation in AKR mice with spontaneous leukemia/lymphoma

Graft-versus-host (GVH) disease can result in a beneficial graft-versus leukemia (GVL) effect after bone marrow transplantation in patients with malignant disease. In this report, we used bacteria-free AKR (H-2k) mice bearing advanced spontaneous T cell leukemia/lymphoma as a moel to evaluate the GVH and GVL effects of bone marrow transplantation using fully incompatible SJL (H-2s) donors. A therapeutic GVL effect, accompanied by increased leukemia-free survival, was obtained only when 0.5 X 10(6) allogeneic lymphocytes (lymph node cells) were added to the marrow inoculum. Transplantation of allogeneic bone marrow without added lymph node cells (or use of syngeneic cells) resulted in a significant increase in leukemia relapse; increasing the dose of allogeneic lymph node cells to 2.0 X 10(6) resulted in significantly higher GVH-associated mortality. Survival and therapeutic benefits were obtained only when the intensity of the GVH reaction was carefully controlled by manipulation of alloreactive lymphocytes present in the marrow. These results suggest, indirectly, that T cell depletion may abolish any GVL effect of marrow transplantation, even if the donor is mismatched with the host at the major histocompatibility complex. The frequency in the spleen of cytotoxic T lymphocytes (CTL) reactive against host alloantigens was estimated using limiting-dilution microcytotoxicity assays at various times after transplantation of allogeneic bone marrow with and without added lymph node cells. The average frequency of CTL was highest in mice that were given marrow plus lymph node cells and tested within the first four weeks after transplantation. The level of CTL activity measured in vitro was dependent on the dose of lymphocytes injected and correlated with both the GVL and GVH effects in vivo. Down-regulation of CTL activity against host, but not third-party, alloantigens in vitro was observed under limiting dilution assay conditions, leading to the suggestion that host-specific regulatory cells may be present in these allogeneic bone marrow chimeras.

Induction of leukemia regression in mice by immunotherapeutic transfer of T-lymphocytes

The erythroleukemia induced in susceptible mice by Friend virus (FV) is a progressive, lethal disease. A variant strain of Friend virus (regressing FV) produces a histopathologically identical leukemia except that the disease spontaneously regresses in 50% of leukemic mice. Normal T-cell and macrophage function are required for regression to occur and in animals that are going to regress, specifically reactive T-cells are found in the spleen. Passive transfer of sensitized T-cells from regressing FV immunized or regressed mice caused regression of the conventional lethal leukemia induced by FV. To expand the effector cell populations, characterize them and improve their therapeutic efficacy, sensitized T-cells were cultured in vitro. The T-cells, isolated from regressed or immunized mice, were grown and expanded in vitro with interleukin 2 and antigen (mitomycin C treated regressing FV-infected cell lines). The T-cells demonstrated high levels of in vitro cytotoxicity against FV antigens but exhibited no blastogenic response to the same antigens. When fully FV-induced leukemic mice (14 days post virus inoculation; spleen weight, greater than 0.75 g) were given one injection of 5 X 10(6) in vitro cultured T-cells and no other treatment the mice experienced permanent regressions of their disease. From T-cell cultures depleted of specific cell populations with monoclonal antisera, helper Lyt-1+ cells were shown to be responsible for permanent regressions (cures), whereas cytotoxic Lyt-2+ cells caused temporary leukemia remissions. This model thus provides an experimental system of highly effective passive cellular immunotherapy against an autochthonous, fully developed leukemia, requiring no adjunctive treatment for activity.

[Ability of sera from mice treated with Ge-132, an organo-germanium compound, to inhibit experimental murine ascites tumors]

Serum specimens from mice treated orally with Ge-132 (100 mg/kg) exhibited antitumor activity against Ehrlich (allogeneic) and RL 1 (syngeneic) ascites tumors in BALB/c mice. Sera obtained from mice 24 hours after Ge-132 administration displayed the highest antitumor effect and the antitumor activity was dose-dependent. Sera prepared from mice 12, 36 or 48 hours after Ge-132 treatment had no protective effect. Circulating interferon (IFN) was induced at 24 hours after administration. The antiviral activity of serum from Ge-132-treated mice was inactivated by treatment with trypsin, low pH, and anti-IFN-gamma antiserum. The inactivated preparations of serum IFN induced by Ge-132 did not show antitumor activity when administered to mice bearing Ehrlich ascites tumors. These results suggest that the antitumor activity in the sera of Ge-132-treated mice may have been expressed through IFN-gamma which was induced by Ge-132.

Influence of antibody isotype on passive serotherapy of lymphoma

We assessed the in vivo anti-tumor effectiveness of monoclonal antibodies of different isotypes. Starting with a hybridoma cell secreting an IgG3 anti-Thy-1.1 antibody, we isolated three variant hybridoma cell lines secreting anti-Thy-1.1 antibody of the IgG1, IgG2a, and IgG2b isotypes. Each antibody displayed identical antigen binding properties, but differed in their ability to mediate in vitro lysis of Thy-1.1+ AKR/J SL2 lymphoma cells. In assays of complement dependent cytotoxicity, the relative activity of each antibody isotype was IgG2a = IgG2b greater than IgG3 greater than IgG1. In assays of antibody-dependent cell-mediated cytotoxicity when using non-immune spleen cells as effectors, the relative activities were IgG2a greater than or equal to IgG2b greater than IgG1 greater than IgG3. Infusion of equivalent amounts of each antibody (1.5 mg) in AKR/Cum (Thy-1.2+) mice inoculated subcutaneously with 3 X 10(5) AKR/J SL2 lymphoma cells resulted in significant inhibition of tumor growth only in mice treated with IgG2a antibody. However, the antibodies were cleared at different rates, with the IgG2a antibody having the slowest clearance. When antibody doses were adjusted to achieve equivalent serum levels 24 hr after infusion, all of the antibody isotypes exhibited at least some anti-tumor activity, although IgG2a antibody was again the most effective. These studies demonstrate that the difference in anti-tumor activity between antibodies of different isotypes may result from differences both in their serum clearance rate and their ability to interact with host effector mechanisms.

Induction of tumor-inhibitory macrophages with a novel synthetic immunomodulator, 3,6-bis(2-piperidinoethoxy)acridine trihydrochloride (CL 246,738)

3,6-bis(2-piperidinoethoxy)acridine trihydrochloride (CL 246,738) has been investigated for its immunomodulatory effect on murine macrophages. Incubation of macrophages harvested from the peritoneal cavities of normal mice with the compound for 48 to 72 hr rendered these cells inhibitory to the growth of tumor cells in vitro. Activation of tumor-inhibitory macrophages occurred over a range of concentrations (0.025 to 0.1 micrograms/ml) producing no direct inhibitory effects on tumor cells. Treatment of effector cells with carrageenan abrogated the effect, whereas treatment with anti-Thy-1.2 antibody and C did not, suggesting that the primary effectors were macrophages rather than T lymphocytes. These activated macrophages also manifested in vitro tumor cytolysis. In vivo studies indicated that peritoneal macrophages from mice treated with single oral doses of 100 to 400 mg/kg of the compound were also inhibitory to tumor cell growth in vitro. Effector macrophages became demonstrable in mice as early as 1 day after drug administration, reached peak activity at day 12, and disappeared by day 31, indicating a rapid onset but long-persisting effect. The tumor cytostatic activity of these macrophages was augmented by endotoxin at the dose of endotoxin that, in itself, had no effect. The addition of protease inhibitors, N-alpha-p-tosyl-L-lysine chloromethyl ketone and aprotinin, to cultures markedly diminished the cytostatic effect, suggesting that the release of neutral protease(s) could account for the inhibitory effects of the macrophages. On the other hand, hydrogen peroxide and arginase seemed excluded as the mechanism of action because the effect was not sensitive to treatment with catalase and exogenous arginine. The present findings indicate that CL 246,738 is an orally active immunopotentiator capable of inducing tumor-inhibitory macrophages both in vitro and in vivo.

Adoptive immunotherapy of intracerebral murine lymphomas: role of different lymphoid populations

In an attempt to elucidate the cellular mechanisms responsible for the therapeutic activity of systemic immunotherapy in an adoptive transfer system, lymphoma cells were implanted i.c. It was found that, upon peripheral injection of cytotoxic T-lymphocytes with specificity for the tumor, the cells reached and infiltrated the diseased brain but did not accumulate selectively in the malignant graft. In order to accomplish significant tumor inhibition, the infused lymphocytes, largely expressing the Lyt-1+2+ phenotype, apparently cooperated with radioresistant phagocytic cells present in histocompatible hosts and athymic mice.

Leukemia X fibroblast hybrid cells prolong the lives of leukemic mice

ASL-1 leukemia X LM(TK-) fibroblast hybrid cells prolong the livers of leukemic (A/JXC3H/HeJ)F1 mice. The hybrid cells, like the fibroblast cells used in forming the hybrid, have lost malignant growth properties in immunocompetent recipients and are rejected. Mice receiving hybrid cells along with ASL-1 cells exhibit immunity toward the leukemia cells; approximately 50% of the animals injected with 10(6) or more hybrid cells along with ASL-1 cells survive more than 60 days; animals in the control group injected with leukemia cells alone invariably die in shorter intervals. The immunity generated is persistent for at least 6 months. Some leukemic mice receiving doses of combination chemotherapy which are insufficient to cure them of the disease survive for prolonged and at times indefinite periods if they are injected with hybrid cells. The immunity generated in mice receiving hybrid cells is directed toward a leukemia-associated antigen of leukemia cells expressed by hybrid cells as well. In mixed lymphocyte culture a heightened stimulation of spleen cells from hybrid cell-injected mice toward ASL-1 cells is observed.