The induction of enhanced antitumor effect against a nonimmunogenic tumor by highly immunogenic variants obtained by mutagen treatment

Nonimmunogenic 1767-3 fibrosarcoma was treated with the mutagen N-methyl-N'-nitro-N-nitrosoguanidine, and stable variant cell clones (M-clones) were obtained that were able to elicit an immunological rejection response in syngenic C3H mice. Mice immunized with some M-clones were protected against a challenge from the original nonimmunogenic fibrosarcoma. Furthermore, when spleen cells of immunized syngenic mice were restimulated in vitro with M-clones, cytotoxic T lymphocytes (CTL) were obtained that were able to lyse not only M-clones but also the original nonimmunogenic tumor. These in vivo and in vitro results demonstrate the immunogenicity of M-clones and the existence of a singular antigenic specificity between the original nonimmunogenic tumor and M-clones. For the purpose of application of this mutagen treatment to cancer therapy, we combined it with lymphokine-activated killer (LAK) adoptive immunotherapy (AIT). With interleukin 2 and in vitro stimulation with highly immunogenic variant clones, we tried to induce transfer cells that had not only nonspecific LAK cells but also CTL with specific immunity against the original nonimmunogenic tumor. Successful results were obtained in the LAK AIT models. These findings indicate that an immunotherapy of human cancers that are thought to be weakly or nonimmunogenic may be possible by the application of this approach to LAK AIT.     

Specificity of antigens on UV radiation-induced antigenic tumor cell variants measured in vitro and in vivo

In vitro exposure of nonimmunogenic murine tumor cells to UV radiation (UVR) generates highly antigenic variants that are immunologically rejected by normal, syngeneic mice. The purpose of this study was to determine whether these antigenic variants cross-react immunologically with the parental tumor and whether the UVR-associated antigen unique to UVR-induced tumors is also present on the variants. Antigenic (regressor) variants and nonimmunogenic (progressor) clones derived from UV-irradiated cultures of the C3H K1735 melanoma and SF19 spontaneous fibrosarcoma cell lines were used to address these questions. In an in vivo immunization and challenge assay, the antigenic variants did not induce cross-protection among themselves, but each induced immunity against the immunizing variant, the parent tumor cells, and nonimmunogenic clones derived from UV-irradiated parent cultures. Therefore, the variants can be used to induce in mice a protective immunity that prevents the growth of the parent tumor and nonimmunogenic clones, but not other antigenic variants. In contrast, immunization with cells of the parental tumor or the nonimmunogenic clones induced no protective immunity against challenge with any of the cell lines. Utilizing the K1735 melanoma-derived cell lines in vitro, T-helper (Th) cells isolated from tumor-immunized mice were tested for cross-reactivity by their ability to collaborate with trinitrophenyl-primed B-cells in the presence of trinitrophenyl-conjugated tumor cells. Also, the cross-reactivity of cytotoxic T-lymphocytes from tumor-immunized mice was assessed by a 4-h 51Cr-release assay. Antigenic variants induced cytotoxic T-lymphocytes and Th activity that was higher than that induced by the parent tumor and nonimmunogenic clones from the UVR-exposed parent tumor and cross-reacted with the parental tumor cells and nonimmunogenic clones, but not with other antigenic variants. Furthermore, upon transplantation, the UVR-induced antigenic variants grew in UV-irradiated and immunosuppressed mice, but not in untreated mice indicating that the variants expressed the determinant recognized by suppressor T-cells present in UV-irradiated mice. These results demonstrate that highly antigenic cells generated by the in vitro exposure of two different murine tumors to UV radiation express a determinant shared with the parental tumor cells and nonimmunogenic clones, a unique variant-specific determinant and the suppressor cell-defined determinant present on UVR-induced tumors. Based on these results, two models are proposed to explain the make-up of the antigenic determinants present on the UVR-induced antigenic variants.     

In situ augmentation of class I major histocompatibility antigen expression on immunogenic variants of a spontaneous murine mammary carcinoma

The relationship between expression of cell surface glycoproteins encoded by the major histocompatibility complex (MHC) and immunogenicity of a recently obtained spontaneous murine mammary adenocarcinoma (designated CBA.SP1) was examined. Immunogenic and nonimmunogenic variant clones were isolated from a subclone of the parent tumor after treatment with the mutagen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or the DNA hypomethylating agent and "gene activator," 5-aza-2'-deoxycytidine (5-aza-dCyd). All clones from the untreated tumor population were tumorigenic in normal syngeneic recipients. In contrast, immunogenic variant clones, isolated at high frequencies after drug treatment [ranging from 5% (5-aza-dCyd treated) to greater than 90% (MNNG treated)], were rejected in normal syngeneic mice but grew progressively in T-cell deficient nude mice. Consistent with our previous report (J. Natl. Cancer Inst., 75: 291, 1985), all 5-aza-dCyd induced immunogenic clones expressed elevated levels of class I (particularly Dk) MHC antigens. However some (three out of nine) nonimmunogenic clones also showed enhanced class I MHC expression, implying that not all high MHC expressors were immunogenic. In contrast to 5-aza-dCyd induced variants, only 50% of MNNG induced immunogenic variants showed elevated levels of Dk or Dk and Kk antigens in vitro. Strong augmentation of class I MHC antigens in situ was observed on all immunogenic, but not nonimmunogenic, clones following transplant into syngeneic mice; no increase in MHC expression on variants during progressive growth in athymic nude mice occurred. Although no class II (Ak or Ek) antigens were detected on the parent line or any of the immunogenic variants, a strong infiltration of host I-A bearing cells occurred during immune rejection of SP1 variants. These results are consistent with the hypothesis that induction of class I MHC antigen expression on certain low MHC expressing tumors, although not the sole requirement for immunogenicity, can facilitate immune rejection of the SP1 tumor and, conversely, that the reduced level of MHC observed in certain clinical cancers may significantly affect the immunological aspects of the tumor-host relationship.     

Immunogenic neoplastic clones derived in vitro from an originally non-immunogenic BALB/c fibrosarcoma

A non-immunogenic fibrosarcoma (SDC2), obtained by spontaneous neoplastic transformation of BALB/c fibroblasts cultured within a diffusion chamber kept in the peritoneal cavity of (BALB/c x C3Hf)F1 mice, was maintained in tissue culture for 10 passages. Three different clones were then derived from the in vitro neoplastic population. Each of the clones, the original in vivo tumor, and its in vitro line taken at the 10th passage (before cloning) were tested for the presence of individual tumor-associated tramsplantation antigens (TATA) by in vivo growth and excision assay. Contrary to the original SDC2 neoplasm, its in vitro line and 2 out of 3 clones (CL1-SDC2 and CL3-SDC2) were immunogenic, whereas the other clone (CL6-SDC2) displayed no immunogenicity. In addition, CL1-SDC2 and CL3-SDC2 were able to induce a reciprocal cross-protection in in vivo transplantation tests, thus showing common TATA; no cross-reactions were found between these clones and 2 other chemically-induced immunogenic sarcomas. The results suggest an antigenic heterogeneity in the original population of the nonimmunogenic SDC2 sarcoma, with the presence of antigenic but sub-immunogenic neoplastic cells.     

Interleukin-12 enhances the antitumor activity of cytotoxic T lymphocytes against lung adenocarcinoma engrafted in severe combined immunodeficient mice

Background. Through a number of biologic activities, interleukin 12 (IL-12) has proven to be a potential antitumor cytokine in mice bearing a variety of malignancies. However, in clinical trials in humans, the eradication of solid tumors remains difficult. Methods. A lung cancer cell line (PC-9)-specific cytotoxic T lymphocytes (CTL) were generated by multiple stimulations, with irradiated PC-9 cells, of regional lymph node lymphocytes obtained from patients with lung cancer whose cells expressed the same HLA-A locus haplotype as PC-9 (HLA-A24). Severe combined immunodeficient (SCID) mice bearing a subcutaneous graft of PC-9 were then intravenously injected with anti-PC-9-specific CTLs. Under these conditions, the in-vivo effect of recombinant human (rh) IL-2 and rh IL-12 was evaluated, based on tumor growth. Results. Mice that received either rh IL-2 or rh IL-12 exhibited no inhibitory effect on tumor growth. However, mice that received adoptive immunotherapy (AIT) alone exhibited a significant inhibition of tumor growth in the PC-9 graft in comparison to untreated mice. When mice were treated with AIT combined with rh IL-2 + rh IL-12 administration, tumor growth was significantly suppressed. A significant difference was observed in the growth of the PC-9 graft between AIT + IL-2 + IL-12 treatment and AIT + IL-2 treatment. Four of eight mice in the AIT + IL-2 + IL-12-treated group showed complete tumor regression. Conclusion. IL-12 showed a synergistic effect with adoptive immunotherapy, using CTL in a tumor-engrafted SCID model. These results are therefore considered to provide a sufficient rationale for IL-2 + IL-12-based immunotherapy using CTL transfer for patients with lung cancer. Received: June 30, 1999 / Accepted: May 10, 2000     

Mice vaccination with interleukin 12-transduced colon cancer cells potentiates rejection of syngeneic non-organ-related tumor cells

Cell-based gene therapy after cytokine gene transfer is being investigated for autologous and allogeneic vaccination in cancer therapy. Here we show that mice vaccinated with 3-5 x 10(6) interleukin 12 (IL-12) gene-transduced CT26 colon cancer cells developed a long-lasting antitumor immune memory able to reject not only parental cells but also syngeneic, LM3 mammary, and MCE fibrosarcoma tumorigenic cells. In contrast, mice vaccinated with 0.5-1 x 10(6) CT26 cells transduced with pBabe neo IL-12 retrovirus cells (CT26-IL12) were only able to reject parental cells. An increase in the total circulating levels of IgG2a and a clear shift toward a systemic Th1 response developed, regardless of the amount of injected CT26-IL12 cells. On the contrary, a strong increase in anti-CT26-specific IgG2a levels was observed only when 3-5 x 10(6) CT26-IL12 cells were injected. Immunocompetent mice vaccinated with 3-5 x 10(6) CT26-IL12 cells developed local nodules for a few days, which then ceased growing. These nodules comprised mainly blood vessels, suggesting that an angiogenic process was taking place. CD8+ T cells were responsible for the anti-LM3 tumor cell memory, whereas CD4+ T cells were not involved. Splenocytes and lymphocytes obtained from mice immunized against CT26 cells were able to kill LM3 cells in vitro. Adoptive transfer of lymphocytes obtained from animals immunized against CT26 colon cancer cells suppressed LM3 mammary tumor growth in tumor-bearing mice. The present studies raised the possibility of isolating CTL clones and identifying CTL epitopes shared by different tumor cell types, which can be a target for cancer therapy.     

Antitumor efficacy of lymphokine-activated killer cells and recombinant interleukin 2 in vivo: successful immunotherapy of established pulmonary metastases from weakly immunogenic and nonimmunogenic murine tumors of three district histological types

We have recently shown that the systemic administration of lymphokine activated killer cells (LAK cells) plus relatively low doses of recombinant interleukin 2 (RIL-2) or the administration of high doses of RIL-2 alone can reduce the number of established pulmonary metastases from the weakly immunogenic MCA-105 sarcoma in mice. We have now analyzed the therapeutic efficacy of these treatments on both weakly and nonimmunogenic tumors of three distinct histological types in two different mouse strains. In all experiments, LAK cells were administered i.v. on days 3 and 6 and RIL-2 was injected i.p. from days 3 through 8 after tumor induction. The MCA-101 sarcoma was completely nonimmunogenic as defined by its inability to successfully immunize C57BL/6 mice. Nevertheless, administration of LAK cells plus 7,500-10,000 units RIL-2 was highly effective in reducing the number of established 3-day pulmonary metastases from this sarcoma [at 7,500 units RIL-2, mean number of metastases 37 +/- 11 (SE); P less than 0.05; at 100,000 units, 2 +/- 1; P less than 0.05] when compared to Hanks' balanced salt solution treated control animals (116 +/- 9). Likewise, RIL-2 alone at doses of 20,000 units/injection or greater had significant antimetastatic effects (77 +/- 12; P less than 0.05). Established 3-day pulmonary metastases from the MCA-38 adenocarcinoma in C57BL/6 mice and the M-3 melanoma in C3H mice were also susceptible to adoptive immunotherapy with LAK cells plus RIL-2 and with high dose RIL-2 alone. Treatment of mice with LAK cells alone or with low doses of RIL-2 alone (less than or equal to 20,000 units/injection) had little if any antitumor effects. LAK cells were tested for cytolytic activity in vitro against tumor target cells of a variety of histological types; there was no discernible relationship between susceptibility to lysis by LAK cells in vitro and therapeutic efficacy in vivo. These findings have thus demonstrated that the successful immunotherapy of established pulmonary metastases with LAK cells plus RIL-2 or with high dose RIL-2 alone includes: tumors that are immunogenic and nonimmunogenic; tumors of distinct histological types such as sarcoma, adenocarcinoma, and melanoma; and tumors in at least two different mouse strains, C57BL/6 and C3H, and that there is little correlation between the in vitro lysability of tumor cells by LAK effectors and the susceptibility of these same tumors to successful immunotherapy in vivo.     

Susceptibility of human and murine drug-resistant tumor cells to the lytic activity of rIL2 - activated lymphocytes (LAK)

This article surveys the available data on the sensitivity of drug-resistant tumor cells to recombinant interleukin 2 (rIL2)-activated lymphocytes (LAK). In our own study, three different experimental systems were used: 1. in vitro treatment of tumor cells with an anticancer drug followed by the use of surviving cells as targets of LAK; 2. use of pairs of drug-resistant and drug-sensitive cell sublines; 3. analysis of several tumor clones obtained from the same tumor. The antitumor activity of LAK was evaluated both by the 51Cr release and the human tumor clonogenic assay (HTCA). In all the experimental systems used, drug-resistant tumor cells were found to be significantly lysed by LAK, with a consistent trend towards a higher susceptibility than their drug-sensitive counterparts. A positive correlation between the sensitivity to LAK and the ID50 for doxorubicin (Dx) was found in 44 melanoma clones analyzed, suggesting that spontaneously drug-resistant clones have a higher sensitivity to LAK than the drug-sensitive clones. Drug-resistant cells were also more sensitive to antibody and complement-mediated lysis, whereas the higher lysis of drug-resistant tumor cells exerted by LAK was maintained in a lectin dependent cytotoxicity assay. These data offer a rationale for combining chemotherapy with adoptive immunotherapy in the treatment of cancer. Moreover, studying the reasons for the higher LAK sensitivity of drug-resistant tumor cells may provide insights into the mechanisms by which tumor cells can resist LAK action.     

Augmentation by tumor necrosis factor alpha of the systemic therapeutic effect of lymphokine-activated killer cells in adoptive immunotherapy of murine tumor

The therapeutic effect of a combined modality of lymphokine-activated killer (LAK) cells and tumor necrosis factor alpha (TNF alpha) on MBL-2 tumor in C57BL/6 mice was studied. Murine LAK cells induced from splenocytes by interleukin 2 (IL2) could lyse MBL-2 target cells in vitro. but no enhancement of the LAK activity was found by the treatment of LAK cells with TNF alpha in vitro. However, the treatment of MBL-2 with TNF alpha enhanced the sensitivity to LAK cells. Moreover, administration of TNF alpha to mice bearing solid MBL-2 tumor led to increased tumor vascular permeability within 1 h, and resulted in the enhanced accumulation of systemically transferred LAK cells in tumor tissue. Based on these results, we treated MBL-2-bearing mice with TNF alpha and then with LAK cells 1 h later. No therapeutic effect was observed when tumor-bearing mice were treated with TNF alpha alone or LAK cells plus IL2. However, adoptive immunotherapy using LAK cells and TNF alpha had therapeutic effects, i.e., growth inhibition of tumor nodules and prolongation of survival. These results indicated that appropriately timed pretreatment of tumor-bearing mice with TNF alpha augmented the anti-tumor efficacy of LAK cells.     

Comparison of tumor-associated transplantation antigens of sublines of methylcholanthrene-induced murine tumors passaged separately in vivo for over a decade

Two sublines of the methylcholanthrene-induced P815 mastocytoma, which had been passaged in vivo in separate institutions for over a decade, were compared for the expression of tumor-associated antigens in common. In cytotoxicity assays in vitro, the sublines were found to differ in expression of tumor-associated antigen(s) that were recognized by cytotoxic lymphocytes. However, in assays of tumor rejection in vivo, the sublines were found to express tumor-associated transplantation antigens in common. Both sublines were capable of inducing reciprocal cross-protection against the growth of a challenge implant of tumor cells of either subline, and both sublines were capable of inducing immunity that upon transfer of spleen cells from immunized mice to appropriate immunodeficient recipients would result in the complete regression of already established tumors of either subline. Similarly, two sublines of the methylcholanthrene-induced Meth-A fibrosarcoma that had been passaged separately in vivo for over a decade were also found to induce reciprocal cross-protection against a subsequent implant of cells of either subline. These results indicate that the expression of tumor-associated transplantation antigens by two methylcholanthrene-induced immunogenic tumors is quite stable and suggest that the generation of tumor-associated transplantation antigen variant cells occurs infrequently. Therefore, an explanation for the progressive growth of immunogenic tumors based on the emergence of nonimmunogenic variants is unlikely, and the probability that the emergence of antigenic variants will lead to the failure of specific adoptive immunotherapy is low. Furthermore, the results indicate that the specificity of the immune response of mice to tumors as defined by transplantation immunity in vivo and lymphocyte cytotoxicity in vitro may be quite different. Therefore, using antigenic differences defined by in vitro cytotoxicity assays to explain the behavior of immunogenic tumors in vivo should be done with caution.     

Augmentation by Tumor Necrosis Factor α of the Systemic Therapeutic Effect of Lymphokine-activated Killer Cells in Adoptive Immunotherapy of Murine Tumor

The therapeutic effect of a combined modality of lymphokine-activated killer (LAK) cells and tumor necrosis factor α (TNFα) on MBL-2 tumor in C57BL/6 mice was studied. Murine LAK cells induced from splenocytes by interleukin 2 (IL2) could lyse MBL-2 target cells in vitro , but no enhancement of the LAK activity was found by the treatment of LAK cells with TNFα in vitro. However, the treatment of MBL-2 with TNFα enhanced the sensitivity to LAK cells. Moreover, administration of TNFα to mice bearing solid MBL-2 tumor led to increased tumor vascular permeability within 1 h, and resulted in the enhanced accumulation of systemically transferred LAK cells in tumor tissue. Based on these results, we treated MBL-2-bearing mice with TNFα and then with LAK cells 1 h later, No therapeutic effect was observed when tumor-bearing mice were treated with TNFα alone or LAK cells plus IL2. However, adoptive immunotherapy using LAK cells and TNFα had therapeutic effects, i.e. growth inhibition of tumor nodules and prolongation of survival. These results indicated that appropriately timed pretreatment of tumor-bearing mice with TNFα augmented the anti-tumor efficacy of LAK cells.     

Activation of mononuclear cells to be used for hybrid monoclonal antibody-induced lysis of human ovarian carcinoma cells

Recently we reported that cytotoxic T-cell clones can be retargeted to unrelated tumor cells by bispecific monoclonal antibodies (MAbs), anti-CD3 and anti-ovarian carcinoma (alpha OC/TR) (Mezzanzanica et al., 1988). In the perspective of in vivo tumor immunotherapy, as an alternative to cytotoxic T lymphocytes (CTL) from T-cell clones, since human peripheral blood mononuclear cells (PBMCs) without stimulation were quite ineffective, a suitable in vitro activation method was developed to render PBMCs lytic for relevant targets in the presence of the bispecific hybrid MAb alpha OC/TR. This activation protocol was applied to PBMCs from 9 healthy donors (HD) and 6 ovarian carcinoma patients (P) and to tumor-associated lymphocytes (TAL) from 4 ovarian carcinoma P. The method consisted of in vitro stimulation with phytohemagglutinin (PHA) for 2 days, followed by culture with a low dose of recombinant human interleukin-2 (rIL-2) for 6 to 10 days. The antibody-mediated lysis of CTL from HD PBMCs was found to be specifically directed against cells expressing the relevant ovarian tumor antigen when different tumor cell lines and short-term cultures of tumor and normal cells were tested. The antibody-mediated lysis of CTL from P PBMCs or TAL was efficient both on autologous and allogeneic ovarian tumor cells, whereas no reactivity with autologous normal cells was observed and LAK activity was only evident in 1 out of 4 cases. The hybrid antibody induced cytotoxic activity of CTL from P was, however, lower than that of CTL from HD.     

Enhanced expression of class I major histocompatibility complex gene (Dk) products on immunogenic variants of a spontaneous murine carcinoma

Both immunogenic and nonimmunogenic variant clones were isolated from a recently obtained spontaneous murine adenocarcinoma after treatment (xenogenization) with either the mutagen ethyl methanesulfonate or the DNA hypomethylating agent, and "gene activator," 5-azacytidine. Clonal analysis of the untreated tumor population confirmed that immunogenic variants arose as a consequence of the xenogenization protocol. At a dose of 10(6) cells per mouse, nonimmunogenic variants, like the parental tumor line, grew progressively in normal syngeneic recipients. In contrast, immunogenic variants were rejected in normal syngeneic mice and grew progressively only in T-cell-deficient nude mice. Serologic analysis of the respective clonal variants revealed that immunogenic variants expressed substantially elevated (fourfold to tenfold) levels of class I H-2Dk antigen relative to parental or nonimmunogenic cell lines. Two variants exhibiting marginal immunogenicity expressed high and low levels of major histocompatibility complex (MHC) antigen, respectively suggesting that elevated MHC expression, although possibly a contributing factor, did not account for the immunogenic phenotype in all cases. Finally, the immunogenic phenotype of two variants decayed with time in culture. Clones in the process of reversion lost their elevated Dk gene expression and became progressively more tumorigenic in normal syngeneic mice. Together, these data are consistent with a hypothesis that elevated MHC expression can contribute to the immunogenic phenotype of originally low MHC-expressing tumors and that the reduced level of MHC observed in certain clinical cancers may have significant implications with regard to immunologic aspects of the tumor-host relationship.     

Antitumor efficacy of lymphokine-activated killer cells and recombinant interleukin-2 in vivo: survival benefit and mechanisms of tumor escape in mice undergoing immunotherapy

The studies described in this paper showed that the combination of i.v.-transferred lymphokine-activated killer (LAK) cells and i.p. injections of recombinant interleukin-2 (RIL-2) was highly effective in vivo in reducing established pulmonary metastases of natural killer cell-resistant, MCA-105 sarcoma and B16 melanoma in mice. A 3-day in vitro incubation of normal C57BL/6 splenocytes in medium containing pure RIL-2 generated LAK cells that, when combined with RIL-2, reduced the mean number of established pulmonary micrometastases of the B16 melanoma and of the MCA-105 sarcoma from 179 and 140, respectively (in groups treated with Hanks' balanced salt solution alone), to 12 (P = 0.01) and 6 (P = 0.01), respectively. This combined immunotherapy also consistently resulted in significant prolongation of survival in mice with established, 3-day or 10-day pulmonary metastases of the MCA-105 sarcoma. Mice autopsied at time of death revealed a massive involvement of tumor in the lungs and liver in the group receiving Hanks' balanced salt solution alone compared to a small number of residual large lung or liver metastases in the group receiving LAK cells plus RIL-2. Experiments were designed to test whether variants existed in the original tumor cell inoculum that were resistant to killing by LAK cells and thus could account for the metastases that "escaped" the combined immunotherapy of LAK cells plus RIL-2 in vivo. Metastases of the MCA-105 sarcoma that escaped the combined therapy of LAK cells plus RIL-2 were dissected from the organs of mice upon autopsy and directly tested for susceptibility in vitro to lysis by LAK cells in 4-h and 18-h 51Cr release assays. Target cells derived from the metastases were lysed to an equivalent extent as those prepared from a fresh MCA-105 sarcoma that was growing s.c. In addition, successful reduction of pulmonary metastases established by the i.v. infusion of MCA-105 sarcoma cells obtained from metastases that escaped a prior round of therapy with LAK cells and RIL-2 could be achieved in vivo by the combined immunotherapy as well as by high doses of RIL-2 alone. Culture adapted, natural killer cell-resistant B16 melanoma cells surviving two successive treatments with LAK cells in vitro remained as susceptible to LAK cell lysis as untreated B16 melanoma cells in 18-h 51Cr release assays.(ABSTRACT TRUNCATED AT 400 WORDS)     

Antimetastasis effect of lymphokine-activated killer (LAK) cells on fibrosarcoma in WKA rats

Treating WKA rats with fibrosarcoma with LAK cells, antimetastasis effect was studied. The results indicated that splenocytes incubated by IL-2 could produce lytic activity to WKA rats with fibrosarcoma in vitro. Passive infusion of LAK cells lead to a marked reduction in the number of metastatic nodules in the lung. After intravenous injection of LAK cells, cancer cells in the lung speedily disappeared. LAK cell administration for 3 times gave better result than once only (P less than 0.01). In this paper, the possibility of LAK cells used as an adoptive immunotherapy for human neoplasms is briefly discussed.     

Immunogenicity of the tumor determines the outcome of immunotherapy with interleukin-2, ABPP, and cyclophosphamide of micro- and macrometastatic intraperitoneal tumor

We have shown previously that interleukin-2 (IL-2) and the interferon inducer ABPP can induce lymphokine activated killer (LAK) cell activity in vivo after intraperitoneal (i.p.) administration. The antitumor effects of various immunotherapy regimens with IL-2, LAK cells, ABPP, and cyclophosphamide (CY) on microscopic (day 3) and on macroscopic (day 8) i.p. tumors, differing in histology and immunogenicity, were studied in C57BL6 mice. The immunogenic sarcomas MCA-105, -106, and the colon adenocarcinoma MCA-38, and the nonimmunogenic sarcomas MCA-101, -102 were used. After i.p. inoculation of 1 X 10(5) tumor cells i.p. on day 0, therapy with IL-2 +/- LAK cells consisted of 1 X 10(8) LAK cells, i.p., on day 3 and IL-2, 10k to 25k U, i.p., b.i.d., on days 3 to 7. Treatment with ABPP +/- CY consisted of CY, 50 mg/kg, i.p., on day 3 and/or 8 ABPP, 250 mg/kg on days 3, 4 and/or 8, 9. In the treatment of micrometastases, IL-2 + LAK cell therapy was effective against all tumors. Therapy with low dose IL-2 alone was effective only against immunogenic tumors. Combined therapy with CY was very effective against the immunogenic tumors and prolonged survival significantly. Only marginal antitumor effects were seen against nonimmunogenic tumors. In the setting of advanced tumor, chemoimmunotherapy was only successful against immunogenic tumors. These observations demonstrate that the immunogenicity of the tumor is of major importance in the outcome of immunotherapy, especially in the setting of advanced disease. This indicates that, apart from LAK cells, the in vivo activation of other cytotoxic effector cells is important in the rejection of immunogenic tumors.     

ANTITUMOR EFFECTS OF HUMAN IL-15 GENE MODIFIED LUNG CANCER CELL LINE

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树突状细胞与肿瘤细胞融合后诱导T细胞介导的抗肿瘤效应

目的：研究树突状细胞（DC）与肿瘤细胞（SP2／0）融合作为肿瘤疫苗免疫小鼠后抑制肿瘤生长的作用及其机理。方法：BALB／C小鼠DC与SP2／0细胞体外融合,形成的杂交瘤分2次免疫接种同基因小鼠皮下,然后用SP2／0细胞攻击免疫的小鼠,观察肿瘤的生长情况及免疫小鼠脾细胞特异性CTL功能。结果：DC－SP2／0杂交瘤接种小鼠能产生明显的抗肿瘤效应,其拮抗SP2／0细胞攻击的能力明显强于用灭活的死SP2／0细胞与DC混合,和单用死SP2／0细胞免疫的小鼠及用生理盐水的对照组小鼠。DC－SP2／0杂交瘤免疫接种小鼠的脾细胞特异性CTL杀伤活性强于其它各组小鼠。结论：DC与肿瘤细胞融合后作为肿瘤疫苗接种可在体内产生明显的抗肿瘤免疫,其机理主要是特异性CTL的作用。     

Effect of immunotherapy with allogeneic lymphokine-activated killer cells and recombinant interleukin 2 on established pulmonary and hepatic metastases in mice

The adoptive transfer of lymphokine-activated killer (LAK) cells in conjunction with the systemic administration of recombinant interleukin 2 (RIL-2) results in the regression of established pulmonary and hepatic micrometastases from a variety of immunogenic and nonimmunogenic murine tumors in syngeneic C57BL/6 mice. Recent studies have shown that this therapeutic approach can mediate the regression of cancer in humans as well. Because of the practical difficulties in obtaining syngeneic or autologous LAK cells for the therapy of cancer in humans we have now evaluated the antitumor efficacy of allogeneic LAK cells generated from different strains of mice. The in vitro lysis of fresh tumor targets by LAK cells is not a major histocompatibility complex-restricted phenomenon since LAK cells of BALB/c-H-2d, DBA/2-H-2d, and C3H-H-2k origin all exhibited lytic activity when tested against allogeneic MCA-102-H-2b tumor cells in short term 51Cr release assays. In vivo, the i.v. transfer of allogeneic LAK cells combined with i.p. injections of RIL-2 reduced the number of established pulmonary metastases induced by either MCA-105 or MCA-101 tumors which are syngeneic to C57BL/6 hosts. The extent of reduction of these pulmonary metastases by the allogeneic LAK cells was directly dependent upon the dose of RIL-2 given; increasing doses of systemically administered RIL-2 resulted in increasingly greater reduction in the numbers of established 3-day pulmonary sarcoma metastases. In dose titration experiments, adoptive transfer of at least 2 doses of 10(8) allogeneic LAK cells was necessary to achieve significant antitumor effect in vivo. Allogeneic LAK cells were also successful in mediating significant regression of hepatic micrometastases. Again, the i.v. transfer of allogeneic LAK cells had a smaller therapeutic benefit compared to i.v. transfer of syngeneic LAK cells. When allogeneic LAK cells were injected intraportally, however, they were as effective as syngeneic LAK cells. Allogeneic LAK cells had little, if any, therapeutic effect on established pulmonary and hepatic metastases when administered to recipients previously immunized to the histocompatibility antigens on the donor cells. Taken together, our results indicate that allogeneic LAK cells from several strains of mice are effective in lysing fresh MCA-102 tumor in vitro and that when given i.v. in sufficient numbers, in conjunction with RIL-2, they can mediate significant reduction in the number of established pulmonary and hepatic micrometastases in nonalloimmunized C57BL/6 mice.(ABSTRACT TRUNCATED AT 400 WORDS)     

Inhibition of tumor-specific cytotoxic T-lymphocyte responses by transforming growth factor beta 1.

Transforming growth factor beta (TGF-beta) is a potent immunosuppressive cytokine that is produced by neoplastic and normal cells. It has not been demonstrated directly, however, that TGF-beta can inhibit antigen-specific T-cell responses to tumor cells in vitro. We show here that generation of antitumor cytotoxic T-lymphocyte (CTL) activity in mixed-lymphocyte tumor cultures of splenocytes from DBA/2 mice immunized with the syngeneic P815 mastocytoma + Corynebacterium parvum was consistently and profoundly inhibited when 0.675 to 10 ng/ml of TGF-beta were added on Day 0 of culture. TGF-beta added on Day 1 or later had little or no effect. In contrast to the results with P815 immune mice, mixed-lymphocyte tumor cultures established with splenocytes from P815 tumor-bearing hosts showed variable degrees of inhibition by TGF-beta, depending on the stage of the ongoing in vivo immune response. Addition of recombinant murine tumor necrosis factor alpha (1,000 or 10,000 units/ml) partially reversed inhibition of CTL responses by TGF-beta, while recombinant interleukin 2 nearly completely reversed the suppression. These data indicate that one level at which TGF-beta may act to inhibit mixed-lymphocyte tumor cultures is that of cytokine production. To determine whether TGF-beta also has any direct effect on CTL, P815-specific CTL clones derived from tumor-bearing host mice were utilized. We found that proliferation of rested CTL clones in response to tumor cells + interleukin 2 was inhibited by 5 ng/ml of TGF-beta, while the interleukin 2-dependent reactivation of cytolytic activity was not affected by TGF-beta. In contrast to rested CTL, when TGF-beta was added to cultures of previously activated CTL, proliferation was not inhibited. These data demonstrate that TGF-beta has profound inhibitory effects on the in vitro generation of effector CTL from tumor-specific murine splenocytes, and this inhibition may be an indirect result of suppressed cytokine production as well as a direct antiproliferative effect on CTL.