Mouse myeloma cell line secreting bifunctional fusion protein RM4/IFN-gamma [corrected] elicits antitumor CD8 MHC class I-restricted T cells that are cytolytic in vitro and tumoricidal in vivo

Vaccine of engineered tumor cells secreting stromal cell-derived factor-1 induces T-cell dependent antitumor responses

The CXC chemokine SDF-1 has been characterized as a T-cell chemoattractant both in vitro and in vivo. To determine whether SDF-1 expression within tumors can influence tumor growth, we transfected an expression vector pCI-SDF-1 for SDF-1 into J558 myeloma cells and tested their ability to form tumors in BALB/c. Production of biologically active SDF-1 (1.2 ng/mL) was detected in the culture supernatants of cells transfected with the expression vector pCI-SDF-1. J558 cells gave rise to a 100% tumor incidence, whereas SDF-1-expressing J558/SDF-1 tumors invariably regressed in BALB/c mice and became infiltrated with CD4(+) and CD8(+) T cells. Regression of the J558/SDF-1 tumors was dependent on both CD4(+) and CD8(+) T-cells. Our data also indicate that TIT cells containing both CD4(+) and CD8(+) T-cells within J558/SDF-1 tumors express the SDF-1 receptor CXCR4, and that SDF-1 specifically chemoattracts these cells in vitro. Furthermore, immunization of mice with engineered J558/SDF-1 cells elicited the most potent protective immunity against 0.5 x 10(6) cells J558 tumor challenge in vivo, compared to immunization with the J558 alone, and this antitumor immunity mediated by J558/SDF-1 tumor cell vaccination in vivo appeared to be dependent on CD8(+) CTL. Thus, SDF-1 has natural adjuvant activities that may augment antitumor responses through their effects on T-cells and thereby could be important in gene transfer immunotherapies for some cancers.

Molecular and immunophenotypical characterization of progressive and regressive leukemia cell lines

The P815 and P198 cell lines are clonally related mouse mastocytoma cell lines. They differ in their biologic behavior in that P815 is a progressive tumor cell line, whereas P198 is a regressive one. These cell lines have been extensively used as models for the study of tumor-host relationships and tumor immunology. Although some of their biological properties have been well documented, the molecular mechanisms underlying tumor progression or regression have not been completely elucidated. In this study, we characterized the growth behavior and immunophenotype of these two cell lines, and analyzed their gene profiles using a complementary deoxynucleic acid (cDNA) microarray composed of 514 immunologically relevant genes. Our data showed that the two cell lines exhibited quite dissimilar and contrasting growth characteristics when inoculated into syngeneic mice. P815 tumors grew unremittingly, while P198 tumors gradually regressed. From a molecular viewpoint, P815 cells showed a higher expression of genes promoting tumor growth, such as IGF-1, IL-8R, FGFR1, VEGF-A, and VEGF-B. On the other hand, P198 tumor cells expressed CD11b and CD80, which favor the recruitment of lymphocytes and antigen-presenting cells (APCs), as well as the elicitation of antitumor immunity. P198 tumor cells also depicted a higher expression of genes inhibiting tumor growth, such as TNF-alpha, SOCS-1, CIS1, 4-1BB, and GDF-10. In conclusion, our results contribute further information in the understanding of the molecular mechanisms associated with the regression and progression of P815 and P198 tumor cells.

Chimeric TNT-3 Antibody/Murine Interferon-γFusion Protein for the Immunotherapy of Solid Malignancies

Interferon-gamma (IFN-gamma) has been used in the experimental treatment of cancer with limited success. Despite direct cytotoxic effects on tumor cells and the ability to stimulate the antitumor activities of a variety of effector cells, IFN-gamma has not been found to produce impressive therapeutic responses partly because of inadequate sustained intratumoral concentrations and systemic toxicity. To overcome these obstacles, we have developed an antibody/murine IFN-gamma fusion protein (chTNT-3/muIFN-gamma), which utilizes the tumor necrosis therapy antibody, chTNT-3, to target murine IFN-gamma to necrotic regions of solid tumors implanted in immunocompetent BALB/c mice. The genetically engineered fusion protein was expressed in NS0 cells using the Glutamine Synthetase Gene Amplification Expression System. After purification, the fusion protein demonstrated both antigen targeting and cytokine activities as assessed by in vitro assays which, when compared to recombinant free IFN-gamma, demonstrated approximately 40-45% biologic activity by two separate assay determinations. Pharmacokinetic and biodistribution studies in mice demonstrated a relatively long whole body half-life of 32 h in vivo and significant intratumoral accretion, respectively. Most importantly, immunotherapeutic studies in the MAD109 syngeneic murine carcinoma of the lung demonstrated significant intratumoral infiltration by leukocytes, primarily by macrophages and CD4(-) CD8(-) Thy-1.2(+) lymphocytes. Additionally, intravenous administration of the fusion protein significantly decreased the number of metastatic foci in an experimental model of pulmonary metastasis without causing any observable toxicity. These studies demonstrate that chTNT3/muIFN-gamma can safely target syngeneic tumor models as part of a promising strategy for the targeted immunotherapy of solid tumors.

Antitumor immune responses derived from transgenic expression of CD40 ligand in myeloma cells

Tumor cells engineered to express immunogenes have been used for cancer vaccines to induce the antitumor immunity and study the antitumor immune mechanisms derived from the immunogene expression. In the present study, we engineered a mouse myeloma cell line J558 with a cloned CD40 ligand (CD40L) gene. We demonstrated that (i) the engineered J558/CD40L tumor cells expressing the CD40 ligand molecule lost their tumorigenicity in syngeneic mice, and (ii) the inoculation of J558/CD40L tumor cells further lead to the protective immunity against wild-type J558 tumors. In animal studies using T-cell subset depleted mice, we further showed that the primary rejection of J558/CD40L tumors did not require T cells, but was mainly mediated by NK cells, whereas the effector phase of the protective immunity is mediated by CD8+ T cells. In addition, our data, for the first time, showed that the inoculation of engineered J558/CD40L tumor cells is able to stimulate stronger activation of dendritic cells with enhanced expression of B7-1 and ICAM-1 molecules than the wild-type J558 tumor cells Taken together, we demonstrated the antitumor effect of engineered J558/CD40L tumor cells that is mediated by the activation of the host dendritic cells in vivo. Our data indicate that the introduction of co-stimulatory CD40 ligand molecule will be useful as a new strategy of immunogene therapy against tumors.

Lymphotactin expression by engineered myeloma cells drives tumor regression: mediation by CD4+ and CD8+ T cells and neutrophils expressing XCR1 receptor

The C chemokine lymphotactin has been characterized as a T cell chemoattractant both in vitro and in vivo. To determine whether lymphotactin expression within tumors could influence tumor growth, we transfected an expression vector for lymphotactin into SP2/0 myeloma cells and tested their ability to form tumors in BALB/c and nude mice. Transfection did not alter cell growth in vitro. Whereas SP2/0 cells gave rise to a 100% tumor incidence, lymphotactin-expressing SP2/0-Lptn tumors invariably regressed in BALB/c mice and became infiltrated with CD4(+) and CD8(+) T cells and neutrophils. Regression of the SP2/0-Lptn tumors was associated with a type 1 cytokine response and dependent on both CD4(+) and CD8(+) T cells, but not NK cells. Both SP2/0 and SP2/0-Lptn tumors grew in nude mice, but growth of the latter tumors was retarded and associated with heavy neutrophil responses; this retardation of SP2/0-Lptn tumor growth was reversed by neutrophil depletion of the mice. Our data also indicate that mouse neutrophils express the lymphotactin receptor XCR1 and that lymphotactin specifically chemoattracts these cells in vitro. Thus, lymphotactin has natural adjuvant activities that may augment antitumor responses via effects on both T cells and neutrophils and thereby could be important in gene transfer immunotherapies for some cancers.

Regression of engineered tumor cells secreting cytokines is related to a shift in host cytokine profile from type 2 to type 1

The precise role of the endogenous immune response in modulating cancer development remains unclear. In this study, three mouse tumor cell lines were used to elucidate the immune mechanisms for tumor regression versus tumor growth. These cell lines were (1) the poorly immunogenic VKCK cell line and (2) its two derived cell lines VKCK/RM4-tumor necrosis factor-alpha (TNF-alpha) and VKCK/RM4-interferon-gamma (IFN-gamma) engineered to secrete TNF-alpha and IFN-gamma, respectively. Our data showed that VKCK tumors grew aggressively in syngeneic BALB/c mice, and vaccination of irradiated VKCK cells failed to protect the mice from a subsequent challenge with the same tumor. In contrast, engineered VKCK tumor cells lost their tumorigenicity, and vaccination of engineered VKCK cells induced a protective immunity against VKCK cells that was mediated with VKCK-specific CD8+T cells. Susceptible mice developed a Th2-dominant response, whereas resistant mice developed a Th1-dominant response to VKCK. The T cell proliferative response and cytolytic activity against VKCK developed in both resistant and susceptible mice, but in the susceptible mice, these responses were much weaker compared with those in the resistant mice. Our results indicate that regression of tumor cells engineered to secrete cytokines TNF-alpha and IFN-gamma is related to a shift from a host type 2 to a type 1 cytokine profile. Our results further suggest that the failure of unmodified VKCK to generate efficacious T cells is not due to an inability to recognize tumor antigens but, rather, to the nature and magnitude of the antitumor immune response that develops. A better understanding of the mechanisms by which tumor cells modulate the host immune system may result in newer approaches for manipulating host-tumor interactions that favor the development of a protective antitumor immune response.

Antitumor vaccination with gene-transduced tumor cells expressing a fusion protein RM4/IFN-tau

Our previous studies showed that secretion of a fusion protein RM4/IFN-tau from a mouse myeloma cell line VKCK/RM4-IFN-tau curtailed its tumorigenicity. Inoculation of VKCK/RM4-IFN-tau tumor cells further induced a protective immunity against a secondary challenge of parental VKCK tumor cells, in which the predominant immune cellular components are CD8+ T cells. In this study, VKCK/RM4-IFN-tau cell line was again used to further characterize the protective immunity. We found that the reduced tumorigenicity of VKCK/RM4-IFN-tau was directly related to the amount of fusion protein secreted by tumor cells, and that CD8+ T cells derived from mice experienced with VKCK/RM4-IFN-tau tumor regression played an important role in the protective immunity in a chromium release assay in vitro and in an animal study in vivo by using T-cell subset depleted mice. Our animal studies also showed that not only the cytotoxic but also the memory T cells against the secondary challenge of parental VKCK cells could be adoptively transferred to normal BALB/c mice. In addition, our animal studies further showed that local vaccination of irradiated VKCK/RM4-IFN-tau cells was able to significantly inhibit established tumors in early stages in vivo. This study thus highlights the potential utility of this engineered VKCK/RM4-IFN-tau tumor cells secreting the fusion protein RM4/IFN-tau in cancer gene therapy.