Comparative analysis of paracrine immunotherapy in experimental brain tumors

Local delivery of cytokines has been shown to have a potent antitumor activity against a wide range of malignant brain tumors. In this study, the authors examined the efficacy of treating central nervous system (CNS) tumors by transfecting poorly immunogenic B16/F10 melanoma cells with interleukin (IL)-2, IL-4, or granulocytemacrophage-colony stimulating factor (GM-CSF) gene, and using these cells to deliver the cytokine locally at the site of the CNS tumor. The object was to determine which cytokine would possess the greatest antitumor activity and to further elucidate its mechanism of action. METHODS: The transfected B16/F10 cells were irradiated to prevent replication and injected intracranially into C57BL/6 mice (10 mice per group) along with nonirradiated, nontransfected B16/F10 (wild-type) melanoma cells. Sixty percent of mice treated with IL-2 (p 120 days). The median survival for animals treated with GM-CSF was 22 days with no long term survivors (p = 0.01 compared with control). Control animals that received only wild-type cells had a median survival of 18 days (range 15-20 days). Histopathological examination of brains from animals killed at different times showed minimal infiltration of tumor cells in the IL-2 group, moderate infiltration of tumor cells in the IL-4 group, and gross tumor invasion and tissue necrosis in the GM-CSF group. Animals treated with IL-2 showed a strong CD8 T cell-mediated response, whereas IL-4 evoked a prominent eosinophilic infiltrate in the area of the tumor. CONCLUSIONS: High levels of locally expressed IL-2 rather than IL-4 or GM-CSF stimulate a strong immunological cytotoxic antitumor response that leads to significant prolongation of survival in mice challenged with B16/F10 intracranial melanoma tumor cells. Consequently, IL-2 may be a superior candidate for use in paracrine immunotherapy

Major histocompatibility complex class II-restricted presentation of a cytosolic antigen by autophagy.

Biochemical and functional studies have demonstrated major histocompatibility complex (MHC) class II-restricted presentation of peptides derived from cytosolic proteins, but the underlying processing and presentation pathways have remained elusive. Here we show that endogenous presentation of an epitope derived from the cytosolic protein neomycin phosphotransferase II (NeoR) on MHC classII is mediated by autophagy. This presentation pathway involves the sequestration of NeoR into autophagosomes, and subsequent delivery into the lytic compartment. These results identify endosomes/lysosomes as the processing compartment for cytosolic antigens and furthermore link endogenous antigen presentation on MHC class II with the process of cellular protein turnover by autophagy

Paracrine immunotherapy with interleukin-2 and local chemotherapy is synergistic in the treatment of experimental brain tumors

Potent immune responses against malignant brain tumors can be elicited by paracrine intracranial (i.c.) immunotherapy with interleukin (IL)-2. Additionally, i.c. delivery of carmustine via biodegradable polymers has been shown to significantly prolong survival in both animal models and clinical trials. In this study, we show that the combination of paracrine immunotherapy, with nonreplicating genetically engineered tumor cells that produce IL-2, and local delivery of chemotherapy by biodegradable polymers prolongs survival in a synergistic manner in mice challenged intracranially with a lethal murine brain tumor. Animals receiving IL-2-transduced cells and polymers containing 10% 1,3-bis(2-chloroethyl)-1-nitrosourea had significantly improved survival compared with animals receiving IL-2-transduced cells or 10% 1,3-bis(2-chloroethyl)-1-nitrosourea alone. Median survival for the control group was 19 days. Survival in animals receiving IL-2-transduced cells and 1% carboplatin-containing polymers was also significantly improved compared with either therapy alone. Histopathological examination on day 14 of animals receiving combination treatment showed rare degenerating tumor cells. In addition to tissue necrosis surrounding the polymer, a marked inflammatory reaction was observed. In long-term survivors (all animals receiving combination treatment), no tumor was observed and the inflammatory reaction was completely resolved. The brains of animals receiving combination therapy showed both tissue necrosis due to local chemotherapy and strong inflammation due to paracrine immunotherapy. The demonstration of synergy between paracrine IL-2 and local i.c. delivery of antineoplastic drugs is novel and may provide a combined treatment strategy for use against both primary and metastatic i.c. tumors

Immunostimulatory monoclonal antibodies for cancer therapy

Increasing immune responses with immunostimulatory monoclonal antibodies (mAbs) directed to immune-receptor molecules is a new and exciting strategy in cancer therapy. This expanding class of agents functions on crucial receptors, either antagonizing those that suppress immune responses or activating others that amplify immune responses. Complications such as autoimmunity and systemic inflammation are problematic side effects associated with these agents. However, promising synergy has been observed in preclinical models using combinations of immunostimulatory antibodies and other immunotherapy strategies or conventional cancer therapies. Importantly, mAbs of this type have now entered clinical trials with encouraging initial results

Diverse CD8+ T-cell responses to renal cell carcinoma antigens in patients treated with an autologous granulocyte-macrophage colony-stimulating factor gene-transduced renal tumor cell vaccine.

A phase I clinical trial with granulocyte-macrophage colony-stimulating factor tumor cell vaccines in patients with metastatic renal cell carcinoma (RCC) showed immune cell infiltration at vaccine sites and delayed-type hypersensitivity (DTH) responses to autologous tumor cells indicative of T-cell immunity. To further characterize RCC T-cell responses and identify relevant RCC-associated antigens, we did a detailed analysis of CD8+ T-cell responses in two vaccinated RCC patients who generated the greatest magnitude of DTH response and also displayed a strong clinical response to vaccination (>90% reduction in metastatic tumor volume). Three separate CD8+ T-cell lines (and subsequent derived clones) derived from patient 24 recognized distinct RCC-associated antigens. One recognized a shared HLA-A*0201-restricted antigen expressed by both renal cancer cells and normal kidney cells. This recognition pattern correlated with a positive DTH test to normal kidney cells despite no evidence of impairment of renal function by the patient's remaining kidney after vaccination. A second line recognized a shared HLA-C7-restricted antigen that was IFN-γ inducible. A third line recognized a unique HLA-A*0101-restricted RCC antigen derived from a mutated KIAA1440 gene specific to the tumor. In addition, two independent CTL lines and three clones were also generated from patient 26 and they recognized autologous tumor cells restricted through HLA-A*0205, HLA-A/B/C, and HLA-B/C. These results show that paracrine granulocyte-macrophage colony-stimulating factor tumor vaccines may generate a diverse repertoire of tumor-reactive CD8+ T-cell responses and emphasize the importance of polyvalency in the design of cancer immunotherapies

The Bacteroides fragilis Toxin Gene Is Prevalent in the Colon Mucosa of Colorectal Cancer Patients

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