Immunotherapy I: Cyclosine gene transfer strategies

Effects of irradiated tumor vaccine and infusion of granulocyte-macrophage colony-stimulating factor and interleukin-12 on established gliomas in rats

PURPOSE

We investigated granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-12 (IL-12) infused into the injection site of irradiated tumor vaccine (TV) as therapy for gliomas.

METHODS

Rats with subcutaneous RT-2 gliomas were treated with irradiated TV and/or subcutaneous infusion of GM-CSF and/or IL-12 via osmotic minipump 5 days after tumor-cell inoculation. Cytotoxic T lymphocyte (CTL) and natural killer (NK) cell activity were analyzed to investigate immune responses. Rats with intracerebral gliomas were treated with irradiated TV and infused GM-CSF/IL-12 3 days after tumor-cell inoculation. Tumor growth rates and animal survival were followed. Survivors were re-challenged with wild-type RT-2 cells subcutaneously or intracerebrally to study long-term anti-tumor immunity.

RESULTS

Rats with subcutaneous gliomas treated with GM-CSF and IL-12 or TV plus GM-CSF or IL-12 did not have increased survival rate (P>0.2), but did have prolonged survival time (P<0.05); in contrast, rats treated with TV plus GM-CSF/IL-12 had increased survival rate (P<0.05) and prolonged survival time (P<0.05) compared with controls. These treatment strategies showed enhanced CTL and NK cell activities. Rats with intra-cerebral gliomas treated with TV plus GM-CSF/IL-12 did not have increased survival rate (P=0.11), but did have prolonged survival time (P<0.0001). Survivors in each group were re-challenged with wild-type RT-2 cells, and all had long-term survival.

CONCLUSIONS

Irradiated TV plus continuous localized infusion of GM-CSF/IL-12 may induce a tumor-specific anti-tumor immune response on established subcutaneous or intra-cerebral gliomas, and such a treatment strategy deserves consideration as adjuvant treatment for glioma.

Induction of T-Cell Apoptosis in Rats by Genetically Engineered Glioma Cells Expressing Granulocyte-Macrophage Colony-Stimulating Factor and B7.1

PURPOSE

To evaluate antitumor effects on intracerebral gliomas of genetically engineered tumor vaccines expressing granulocyte-macrophage colony-timulating factor (GM-CSF), B7.1, or both (combination).

EXPERIMENTAL DESIGN

A rat glioma cell line, RT-2, was engineered with a retroviral vector to express GM-CSF, B7.1, or combination. Tumorigenicity of engineered cells and therapeutic effects of s.c. given irradiated or live tumor vaccines on parental intracerebral gliomas were studied. Immune cell infiltration induced at vaccine and tumor sites was examined by histologic and immunohistochemical staining. Apoptosis of T cells from vaccine sites was analyzed with fluorescence-activated cell sorting.

RESULTS

Engineered RT-2 cells exhibited reduced s.c. tumorigenicity in rats with reduced tumor growth and prolonged animal survival time compared with control rats. Rats with intracerebral gliomas s.c. treated with irradiated or live GM-CSF-expressing vaccines had 60% and 100% survival rates, respectively, significantly better than the control groups (P < 0.05). In contrast, rats treated with vaccines expressing B7.1 or the combination had no or mild therapeutic effects. Studies revealed less T-cell infiltration at both vaccine and tumor sites in rats treated with vaccines expressing B7.1 or the combination than in rats treated with a vaccine expressing GM-CSF. Cell sorting analyses revealed higher proportions of apoptotic T cells at vaccine sites of rats treated with the combination than those treated with vaccine expressing GM-CSF.

CONCLUSIONS

Combination of GM-CSF- and B7.1-expressing tumor vaccines exerted no synergistic, or even worse, therapeutic effects on gliomas compared with single GM-CSF-secreting tumor vaccine. The worse therapeutic effects of the GM-B7.1-expressing tumor vaccine than the GM-CSF-expressing tumor vaccine were related to the reduced T-cell amount and increased T-cell apoptosis in the former.

Biologic and therapeutic role of HER2 in cancer

Overexpression of the human epidermal growth factor-2 (HER2) oncogene in human breast carcinomas has been associated with a more aggressive course of disease. The reason for this association is still unclear, although it has been suggested to rest in increased proliferation, vessel formation, and/or invasiveness. Alternatively, prognosis may not be directly related to the presence of the oncoprotein on the cell membrane, but instead to the breast carcinoma subset identified by HER2 overexpression and characterized by a peculiar gene expression profile. HER2 has also been associated with sensitivity to anthracyclins and resistance to endocrine therapy, suggesting that tyrosine kinase receptor and hormone receptor pathways represent two major proliferation pathways exclusively active in breast carcinomas, one sensitive to chemotherapeutic drugs and the other to antiestrogens. HER2 currently represents one of the most appropriate targets for specific therapy. Indeed, trastuzumab, a monoclonal antibody directed against the extracellular domain of HER2, is therapeutically active in HER2-positive breast carcinomas. However, a consistent number of HER2-positive tumors is not responsive to HER2-driven therapy, indicating the need for a better understanding of the mechanism of action of this new biological drug in vivo. While preclinical studies suggest antibody-dependent cell cytotoxicity as the major mechanism, determination of NK activity at the time of treatment remains mandatory, especially in patients treated with immunosuppressive drugs. The efficacy of prophylactic vaccination has been fully demonstrated in preclinical models, whereas ongoing studies of active immunotherapy using a variety of vaccination regimens against HER2 in tumor-bearing mice and patients have met with only moderate success.

Immunology and immunotherapy of human cancer: present concepts and clinical developments

Immunotherapy of cancer is entering into a new phase of active investigation both at the pre-clinical and clinical level. This is due to the exciting developments in basic immunology and tumour biology that have allowed a tremendous increase in our understanding of mechanisms of interactions between the immune system and tumour cells. This review briefly summarizes the state of the art in basic tumour immunology before discussing the clinical applications of the new concepts in the clinical setting. Clinical approaches are diverse but can now be based on strong scientific rationales. The analysis of the available clinical results suggests that, despite some disappointments, there is room for optimism that both active immunotherapy (vaccination) and adoptive immunotherapy may soon become part of the therapeutic arsenal to combat cancer in a more efficient way.

Specific and nonspecific immunity in the prevention of spontaneous tumours

Antitumour vaccines cannot cure established tumours. However, tumour cells engineered to release cytokines can halt progression to cancer by inhibiting the angiogenic phenotype of pretumoural cells and activating tumour-associated leukocytes, thus they might prove useful in immunizing those at risk of cancer.

Paracrine effects of IL-4 transfection on TS/A adenocarcinoma cells mediate reduced in vivo growth

The in vitro/in vivo growth capacity and phenotype of TS/A and the IL4-transfected TS/A-IL4 cell lines were studied by cell cycle analysis, expression of ICAM-1/CD54, transferrin receptor/CD71 and E-cadherin and by histology of the primary tumors. TS/A-IL4, unlike the TS/A line, shows in vitro a marked increase in the fibroblastoid cell type and a decreased E-cadherin expression. Administration of conditioned medium containing IL4 obtained from the TS/A-IL4 cell line, stimulates CD54 expression in the TS/A cell line. TS/A-IL4 tumors grow more slowly in vivo and are ultimately rejected. These processes are accompanied by a marked increase in collagen and extracellular matrix proteins and increased recruitment and degranulation of mast cells. The paracrine effect of IL4, released by the transfected tumor cells, might be responsible for the reduced in vivo growth of the TS/A cell line in the presence of TS/A-IL4 cells.

Gene therapy of glioblastoma multiforme via combined expression of suicide and cytokine genes: a pilot study in humans

Retrovirus-mediated gene therapy is a particularly attractive approach for glioblastoma multiforme (GBM), given the poor prognosis of this tumour and its localized proliferation in post-mitotic tissue. In this study we assessed, for the first time in humans, the therapeutic potential of a newly designed bicistronic Moloney vector (pLIL-2-TK), combining the expression of a suicide gene (thymidine kinase, tk) with an immunomodulatory gene (human interleukin 2, IL-2). Evidence of transgene activity in the treated tumours is presented.

Expression of B7 co-stimulatory molecules by B16 melanoma results in a natural killer cell-dependent local anti-tumour response, but induces T-cell-dependent systemic immunity only against B7-expressing tumours

In an attempt to enhance the anti-tumour immune response, the co-stimulatory molecules B7-1 or B7-2 were expressed on the surface of B16 melanoma cells. B7-expressing tumours grew more slowly in both syngeneic immunocompetent mice and athymic T cell-immunodeficient nude mice. The delay in growth of B7-expressing tumours was dependent on natural killer (NK) cells, as reductions in tumour growth rates were minimized in mice depleted of NK cells. Systemic immunity to B16 melanoma was examined by vaccination with irradiated tumour cells. Inoculation with irradiated B16 B7-1 cells failed to protect against a subsequent challenge with live parental B16 cells, but conferred partial protection against challenge with live B16 B7-1 cells. In contrast to the local anti-tumour reaction, this protective response was dependent on T cells. The results presented here reveal some of the mechanisms involved in the in vivo response to a poorly immunogenic tumour modified to express co-stimulatory molecules.