Biomedical subjects

A Porgador

Publications and source records attributed to A Porgador.

29 records · Page 2Linked to original sources

PubMed1995

Combined vaccination with major histocompatibility class I and interleukin 2 gene-transduced melanoma cells synergizes the cure of postsurgical established lung metastases.

We have analyzed and compared in detail the malignant phenotypes of, the immune mechanisms induced by, and the immunotherapeutic potentials of B16-F10.9 melanoma cells manipulated by gene transfer to express syngeneic H-2Kb molecules or to secrete the cytokines interleukin 2 (IL-2) or IL-6. Local tumor growth in the footpad of transduced cells is mainly retarded by expression of H-2Kb and IL-2 genes and less by expression of IL-6. Mice given injections intrafootpad of tumorigenic doses of transduced clones manifested significantly reduced postsurgical spontaneous metastasis. After i.v. inoculation, mice given injections of F10.9-Kb expressors did not develop experimental lung metastases; mice given injections of F10.9-IL-6 secretors developed reduced metastatic loads; whereas mice given injections of F10.9-IL-2 secretors developed high loads of lung metastases. On the basis of injections into nude mice, in vivo depletions of CD4+, CD8+, and NK1.1+ cells, and in vitro CTL and natural killer (NK) assays, we show that all F10.9-modified cells induce CD8+ tumor-specific CTL activity and that F10.9-IL-2 secretors also induce nonspecific NK/lymphokine-activated killer cell activity. Vaccinations with F10.9-modified cells were capable of significantly reducing metastatic spread from small established F10.9 footpad tumors. However, in mice carrying preestablished lung metastases, a highly therapeutic effect was achieved only when H-2Kb expressors and IL-2 secretors were combined in vaccination, whereas individual vaccines or other combinations had marginal effects. This higher efficiency of the combined vaccine is due to the combined effect of efficient CTL induction and NK/lymphokine-activated killer cell activity as concluded from depletion of CD8+ and NK1.1 cells during immunotherapy. Thus, the cure of established metastasis can be achieved by the synergistic effects of vaccination with class I and IL-2-transduced tumor cells.

Animals↗

PubMed1995

Bone marrow-generated dendritic cells pulsed with a class I-restricted peptide are potent inducers of cytotoxic T lymphocytes.

It has previously been shown that bone marrow-generated dendritic cells (DC) are potent stimulators in allogeneic mixed leukocyte reactions and are capable of activating naive CD4+ T cells in situ in an antigen-specific manner. In this study we have investigated whether bone marrow-generated DC are capable of inducing antigen-specific CD8+ T cell responses in vivo. Initial attempts to induce specific cytotoxic T lymphocyte (CTL) responses in mice injected with bone marrow-generated DC pulsed with ovalbumin (OVA) peptide were frustrated by the presence of high levels of nonspecific lytic activity, which obscured, though not completely, the presence of Ag-specific CTL. Using conditions that effectively differentiate between antigen-specific and nonspecific lytic activity, we have shown that bone marrow-generated DC pulsed with OVA peptide are potent inducers of OVA-specific CTL responses in vivo, compared with splenocytes or RMA-S cells pulsed with OVA peptide, or compared with immunization with free OVA peptide mixed with adjuvant. Antibody-mediated depletion experiments have shown that the cytotoxic effector cells consist primarily of CD8+ cells, and that induction of CTL in vivo is dependent on CD4+ as well as on CD8+ T cells. These results provide the basis for exploring the role of bone marrow-generated DC in major histocompatibility class I-restricted immune responses, and they provide the rationale for using bone marrow-generated DC in CTL-mediated immunotherapy of cancer and infectious diseases.

Adjuvants, Immunologic↗

PubMed1994

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.

Animals↗

PubMed1993

Antimetastatic vaccination of tumor-bearing mice with two types of IFN-gamma gene-inserted tumor cells.

IFN-gamma genes were introduced through retroviral vectors into the high metastatic, low H-2Kb class I expressor, and poorly immunogenic 3LL-D122 clone. Two types of IFN-gamma infectants were isolated: IFN-gamma high secretors (128 to 256 IU/ml) and IFN-gamma non- or very low secretors (< 2 IU/ml). Both manifested high expression of MHC class I Ag. IFN-gamma secretors showed significant decrease in tumorigenicity and metastatic growth, whereas IFN-gamma nonsecretors retain tumorigenicity and were more metastatic than parental D122 cells. However, both groups, when inoculated in an irradiated form, induced similar high levels of CTL and protected mice to the same degree against a subsequent graft of parental cells. This indicates that enhanced expression of MHC class I and related genes caused by IFN-gamma is the major participant in CTL induction. Immunization of mice carrying an established tumor of parental D122 cells with IFN-gamma infectants is capable of almost completely preventing lung metastasis. Immunotherapy of tumor-bearing hosts is more effective when IFN-gamma secreting cells are used as immunogens, indicating that mechanisms, in addition to CTL, are stimulated by secreted IFN-gamma. Moreover, immunization with IFN-gamma high secretors of postoperative mice, carrying established micrometastases, almost completely cured these mice. Support for the participation of non-T cell effectors in the response to IFN-gamma secretors derives from the reduced tumorigenicity of these cells in CD1 nude mice. These data provide a rationale for the use of IFN-gamma gene-transferred tumor cells as a modality for cancer therapy.

Animals↗

PubMed1993

Anti-metastatic vaccination of tumor-bearing mice with IL-2-gene-inserted tumor cells.

IL-2 gene was introduced through retroviral vectors into the highly malignant and poorly immunogenic 3LL-D122 clone. Both high and low D122-IL-2 secretors showed elimination of tumorigenicity in syngeneic immune-competent mice; however, in nude mice only the high IL-2 secretor showed reduced tumorigenicity as compared with parental D122 cells. Also, following intravenous inoculation, only the high IL-2 secretor showed reduced generation of metastases, whereas the low IL-2 secretors were as highly metastatic as parental cells. These results seem to indicate that low levels of IL-2 secreted by tumor cells are sufficient to activate T cells, while higher levels are needed in order to activate non-T-cell effectors. D122-IL-2 secretors induced high levels of anti-tumor CTL, while their sensitivity to the lytic activity of these CTL was similar to the sensitivity of D122 cells, thus indicating that the elevation of immunogenicity of IL-2 secretors was essentially due to the secreted IL-2. In accordance with CTL induction, pre-immunization with IL-2 secretors protected mice against subsequent challenge of parental cells. Moreover, immunization in an "immunotherapy protocol" i.e., vaccination of mice carrying an established tumor of parental D122 cells with inactivated D122-IL2 infectants, almost completely eliminated the generation of lung metastases by D122 cells, thus providing a rationale for the use of IL-2 gene transferred tumor cells as a modality for treatment of metastasis.

Animals↗

PubMed1993

Abrogation of B16 melanoma metastases by long-term low-dose interleukin-6 therapy.

We investigated the antitumor effects of human recombinant interleukin-6 (hrIL-6) on the highly metastatic B16 melanoma clone F10.9. These tumor cells were found to have very low levels of IL-6 receptors and in vitro IL-6 had no effect on cell proliferation or on the expression of MHC class I antigens. However, in vivo IL-6 was active against the metastatic growth of this tumor in mice, presumably through indirect immune effects. Low-dose IL-6 (1-10 micrograms/day), in three daily injections, 4 days a week, for 3 weeks, strongly inhibited the formation of experimental lung metastases following intravenous tumor cell inoculation. IL-6 therapy could be started even 10 days after tumor injection, when metastases are already established. Moreover, IL-6 treatment of mice bearing F10.9 tumors in the footpads resulted in complete protection against pulmonary spontaneous metastasis and in long-term survival. Histology confirmed the absence of micrometastases in most of the IL-6-treated animals. Analysis of the cytolytic activity of splenocytes at different times during therapy of tumor-bearing mice revealed significant lysis (up to 42%) of the melanoma F10.9 cells in the mice receiving IL-6 but not in the control mice.

Animals↗

PubMed1993

Immunotherapy via gene therapy: comparison of the effects of tumor cells transduced with the interleukin-2, interleukin-6, or interferon-gamma genes.

We have comparatively analyzed the immune mechanisms induced by and the immunotherapeutic potentials of a highly metastatic clone of the Lewis lung carcinoma, D122, transduced with the interleukin-2 (IL-2), IL-6, or interferon-gamma (IFN-gamma) genes. All of the D122 cytokine gene-transduced cells induced antitumor CD8+ cytotoxic T lymphocytes (CTLs), as can be judged from in vivo depletion of CD8+ cells and in vitro CTL assays. In vivo depletion of CD4+ cells did not affect the malignant phenotypes of the different D122 gene-modified cells, but in vivo depletion of natural killer (NK) cells resulted in increased malignancy of both D122 cells and D122 gene-modified cells. In accordance with the effects of in vivo NK depletion, D122 as well as D122 derivative cells were sensitive to lysis by polyinosinic-polycytidylic acid (poly I:C)-induced activity. We discuss the immune responses generated by the different D122 gene-modified cells in view of their in vivo behavior in syngeneic and nude mice. We also performed comparative analysis of the capacity of vaccinations with irradiated D122 gene-modified cells to cure established micrometastases of parental D122 cells in tumor-operated mice. Vaccinations with D122-IL-2 or -IL-6 secretors did not generate a significant effect. Also, vaccinations with D122-IFN-gamma cells, which showed increased major histocompatibility complex class I expression but did not secrete detectable levels of IFN-gamma, did not cure established micrometastases. Only vaccination with D122-IFN-gamma high secretors efficiently cured postoperated mice carrying established micrometastases. We discuss the relevance of these results to the application of immunotherapy via cytokine gene therapy of human malignancy.

Animals↗

PubMed1992

Interleukin 6 gene transfection into Lewis lung carcinoma tumor cells suppresses the malignant phenotype and confers immunotherapeutic competence against parental metastatic cells.

To investigate the influence of interleukin 6 (IL-6) production on malignancy of tumor cells we transfected cells of the high-metastatic, low-immunogenic D122 clone of the Lewis lung carcinoma with a mammalian expression vector containing the human IL-6 complementary DNA. In vitro, IL-6 positive transfectants showed growth inhibition that was directly correlated with the levels of IL-6 production. The in vitro growth arrest did not seem to be a function of an autocrine system mediated via the secreted human IL-6 acting on the tumor cell surface receptors since neutralizing antibodies to human IL-6 did not prevent the growth inhibition. Neither did exogenous human recombinant IL-6 affect the growth of D122 cells. In vivo, IL-6 positive transfectants showed reduction of tumorigenicity and significant suppression of metastatic competence in syngeneic, immunocompetent mice. In mature T-cell deficient nude mice, the IL-6 transfectants showed some arrest of local growth but no suppression of lung metastasis. It seems therefore that the reduction of metastatic competence of IL-6 transfectants is primarily a function of stimulation by the transfectants of host T-cell immune responses. Immunization with inactivated high-positive IL-6 transfectants induced high levels of anti-tumor cytotoxic T-lymphocytes and protected mice against metastatic growth of a subsequent graft of parental tumor cells. Moreover, reduction of metastatic growth of parental highly metastatic D122 cells was also achieved when immunization of mice was begun after establishment of the primary parental tumors. Thus, inactivated IL-6 transfectants were effective when used as a cellular vaccine for experimental immunotherapy of metastasis.

Adolescent↗

PubMed1991

Immunization by gamma-IFN-treated B16-F10.9 melanoma cells protects against metastatic spread of the parental tumor.

B16-F10.9 is a highly metastatic clone of the B16-F10 melanoma line, that expresses low levels of MHC class-I antigens. F10.9 cells transfected with H-2Kb are highly immunogenic and consequently exhibit a low metastatic phenotype. Treatment with gamma-IFN elevated H-2Kb and H-2Db cell surface expression of F10.9 cells to levels much higher than did transfection of these genes. Yet, following intravenous injection, the gamma-IFN treated cells generated high loads of lung metastases. However, when tested for their immunogenic effect, they elicited CTL and were sensitive to CTL. Immunization with both the positive transfectant KI and the gamma-IFN-treated F10.9 cells protected in vivo against metastatic spread of a subsequent transplant of parental F10.9 cells. The protection elicited by KI transfectants was more effective than the protection by gamma-IFN-treated cells.

Animals↗

PubMedDate not supplied

H-2Kb transfection of B16 melanoma cells results in reduced tumourigenicity and metastatic competence.

The metastatic B16 mouse melanoma shows a low cell surface expression of H-2Kb and H-2Db class I antigens on cells of both the high-metastatic line B16-F10 and the low-metastatic line B16-F1. Similarly, newly generated clones of these lines, having different metastatic properties, all express low levels of major histocompatibility antigens. One of these clones, the high-metastatic F10.9, was transfected with H-2Kb genes to generate H-2Kb-expressing transfectants. The resulting clones showed reduced tumourigenicity and a low metastatic phenotype. Unlike the parental cells, H-2Kb-positive transfectants are potent inducers and sensitive targets of H-2Kb-restricted syngeneic cytotoxic T cells. Immunization of mice with H-2Kb-positive transfectants conferred protection against a subsequent challenge with Kb-positive transfectants but had only a small effect on growth and metastatic spread of parental cells.

Animals↗

PubMedDate not supplied

Immunotherapy of tumor metastasis via gene therapy.

Active cellular immunotherapy of cancer, via gene-modified tumor cells, may develop to an effective treatment modality. Here we discuss some of the cytokines used in gene transfer, the importance of MHC class I expression on tumor cells used as vaccines, the relevance of experimental tumor systems to human tumors, and the use of live versus irradiated vaccines. Possible methods for effective gene transfer and possible protocols for immunotherapy studies are presented. Our studies in two highly metastatic murine tumors, the Lewis lung carcinoma (3LL) and the B16 melanoma, and immune mechanisms involved in immunotherapy of metastasis are summarized.

Animals↗