Regression of an established tumor genetically modified to release granulocyte colony-stimulating factor requires granulocyte-T cell cooperation and T cell-produced interferon gamma.

Abstract

SummaryUsing the murine colon adenocarcinoma C-26 cell line, engineered to release granulocyte colonystimulating factor (G-CSF) (C-26/G-CSF), we studied the mechanisms responsible for inhibition of tumor take in syngeneic animals and of regression of an established tumor in sublethally irradiated mice injected with these cells. Immunocytochemistry and in situ hybridization, performed to characterize tumor-infiltrating lenkocytes and their cytokine expression, respectively, indicated that polymorphonudear leukocytes (PMN) were the major cells responsible for inhibition of tumor take and that they expressed mKNA for intedeukin lc~ (IL-lcz), IL-1/3, and tumor necrosis factor c~ (TNF-cz). Expression of interferon 3' (IFN-3') and of IL-4 was undetectable, consistent with the absence of T lymphocytes at the site of tumor injection. In mice injected with C-26/G-CSF cells after 600-tad irradiation, the tumors grew to "~1.5 cm in 30 d, regressing completely thereafter in 70-80% of mice. During the growing phase, tumors were infiltrated first by PMN (between days 15 and 20), then by macrophages, and last by T lymphocytes. Both CD4 + and CD8 + T cells were present but only CD8 depletion significantly abrogated tumor regression. Depletion of PMN by the RB6-8C5 antigranulocytes monoclonal antibody reduced the number of T cells infiltrating the tumor and prevented tumor regression. In situ hybridization performed at the beginning of tumor regression revealed the presence of mRNA for IL-la, IL-1/3, and TNF-ol, but also the presence of cells, with lymphoid morphology, expressing IFN-3'. Tumors from mice treated with recombinant IFN-3' (between days 20 and 35) were rejected faster, whereas mice treated with antibodies to IFN-3' (from day 20) died of progressive tumor. Cydosporin A treatment (started at day 20) also abrogated tumor regression. These results indicate that inhibition of tumor take and regression in this model occurs through different mechanisms that involve PMN and PMN-T cell interactions, respectively, as well as a combination of cytokines that, for tumor regression, require IFN-3'. Thus, gene transfer of a single cytokine gene such as G-CSF into tumor cells appears to be sufficient to trigger the cascade of cell interactions and cytokine production necessary to destroy a cancer nodule.

The Combined Action of IL-15 and IL-12 Gene Transfer Can Induce Tumor Cell Rejection Without T and NK Cell Involvement

“…Different from previous studies in tumor cytokine immuno/gene therapy, which emphasize the requirement of a cross-talk between specific and nonspecific immune mechanisms to obtain a complete tumor rejection (55,56), in this study we report evidence that the activation of macrophages by the synergistic action of IL-12 ϩ IL-15 may lead to an effective T-and NK-independent tumor growth inhibition. These data provide new insight on the cooperative activity of IL-12 and IL-15 in the stimulation of effective natural immunity response and could be relevant for the development of gene therapy strategies against MHC class I-negative tumors escaping from specific CTL control.…”

IL-12 Inhibition of Endothelial Cell Functions and Angiogenesis Depends on Lymphocyte-Endothelial Cell Cross-Talk

“…EC can no longer sustain neoangiogenesis and assume a phenotype more prone to tissue invasion by leukocytes that amplify vascular damage in vivo (73). These alterations of EC functions appear to form the basis of IL-12-mediated ischemichemorrhagic rejection of tumors in vivo.…”

Lymphotactin Expression by Engineered Myeloma Cells Drives Tumor Regression: Mediation by CD4+ and CD8+ T Cells and Neutrophils Expressing XCR1 Receptor

“…The effector phase of the tumor rejection was mediated by CD8 ϩ cells and not at all affected by CD4 ϩ cell depletion. Previous studies on tumor resistance following chemokine gene transfer neither defined the role of T cells nor analyzed the type 1 or type 2 nature of these responses (31)(32)(33)(34).…”