Interleukin-12 (IL-12)-mediated immune responses are critical for the control of malignant development. Tumors can actively resist detrimental immunity of the host via many routes. Prostaglandin E 2 (PGE 2 ) is one of the major immune-suppressive factors derived from many types of tumors. Here, we show that systemic administration of recombinant IL-12 could therapeutically control the growth of aggressive TS/A and 4T1 mouse mammary carcinomas. However, PGE 2 produced by tumors potently inhibits the production of endogenous IL-12 at the level of protein secretion, mRNA synthesis, and transcription of the constituent p40 and p35 genes. The inhibition can be reversed by NS-398, a selective inhibitor of the enzymatic activity of cyclooxygenase 2 in PGE 2 synthesis. Moreover, PGE 2 -mediated inhibition of IL-12 production requires the functional cooperation of AP-1 and AP-1 strongly suppresses IL-12 p40 transcription. Blocking PGE 2 production in vivo results in a marked reduction in lung metastasis of 4T1 tumors, accompanied by enhanced ability of peritoneal macrophages to produce IL-12 and spleen lymphocytes to produce interferon-γ. This study contributes to the elucidation of the molecular mechanisms underlying the interaction between a progressive malignancy and the immune defense apparatus.

IL-12 is a major activator of tumor-killing NK cells and CTL. IFN-γ mediates most of the well-known immunological activities of IL-12. In this study, we report IFN-γ-independent activities induced by therapeutic application of rIL-12 in restricting tumor growth and metastasis in the 4T1 murine mammary carcinoma model. IFN-γ-deficient mice carrying 4T1 tumor exhibit no gross defect in the number of tumor-infiltrating lymphocytes but have exaggerated angiogenesis in the tumor. Administration of IL-12 is able to constrict blood vessels in the tumor in the absence of IFN-γ, and retains certain therapeutic efficacy even when applied late during tumor progression. IL-12 exposure in vivo does not irreversibly alter the immunogenicity of the tumor. Finally, global gene expression analysis of primary tumors reveals IL-12-induced molecular patterns and changes, implicating a number of novel genes potentially important for IFN-γ-independent immune responses against the tumor, for IL-12-mediated antiproliferation, antimetastasis, and antiangiogenesis activities.

Interleukin-12 (IL-12) has potent antitumor activities via natural killer cells and cytotoxic T lymphocytes. However, the molecular mechanisms whereby IL-12 induces tumoricidal activities are poorly understood. Here, we report the genome-wide analysis of gene expression in a primary murine mammary carcinoma model that resembles human breast cancer, following the therapeutic application of recombinant IL-12, which restricted tumor growth and metastasis. IL-12 was able to curtail neovascularization in the tumor as well as enhance the number of tumor-infiltrating lymphocytes. Comprehensive examination of global gene expression revealed IL-12-induced molecular changes associated with tumor regression and reduced lung metastasis, thus providing a high-resolution snapshot of a host response against a developing malignancy and a rich source of potential targets for therapeutic intervention of breast cancer. © 2004 Wiley-Liss, Inc. mammary carcinoma; metastasis; angiogenesis Tumors often possess a number of potential recognition sites for immunologic effector cells, which, in theory, could make them susceptible to immune surveillance. Nevertheless, most of such tumors grow progressively in their natural hosts or syngeneic recipients, without being controlled effectively by the immune system. The lack of apparent immunogenicity of tumors in situ might be due to special properties of the tumor cells, e.g., lack of costimulatory molecules, downregulation of MHC molecules, or production of immunosuppressive factors 1,2 or due to intrinsic tolerance mechanisms of the immune system. 3 Two principal types of cells are immunologically potent tumor-killing effectors: NK and CTL. A major activator of both cell types is Interleukin-12 (IL-12). NK cells kill tumors by intrinsic and nonspecific mechanisms hinged on a lack of MHC molecules on the surface of the tumor. CTL, on the other hand, recognizes specific antigenic peptides that are derived from the tumor and presented to them by antigen-presenting cells such as dendritic cells (DCs). In recent years, immunotherapy has been rekindled that attempts to either mark the tumor by upregulating the surface antigens for enhanced interaction with immune effector cells 2,4 or by directly activating DC, T and NK cells for their heightened "scouting" capacity and increased cytolytic potency. IL-12 is a factor belonging to the latter class. 5 IL-12 has powerful anti-tumor and anti-metastatic activities against many murine tumors as well as human tumors. 6 Recent encouraging developments in clinical applications of IL-12 for human T cell lymphoma, 7,8 B cell non-Hodgkin lymphoma, 9 melanoma 10 -14 and renal carcinoma 15 and SIV-infection model in rhesus macaques 16 strongly underscore the importance of understanding the cellular and molecular mechanisms of IL-12me-diated anti-tumor responses. The potent anti-malignancy activities of IL-12 are thought to be mediated through similar mechanisms that are used by IL-12 against infectious agents, i.e., via the activation of NK cells for the bu...

Chemoradiotherapy is a multimodal therapy routinely used as a primary treatment for advanced esophageal cancer. However, it is beneficial only to patients who respond. To identify pretreatment markers predicting response and survival, we examined the expression of cell cycle regulatory molecules, p53, p21(Waf1/Cip1) cyclin D1, and CDC25B, in biopsy specimens from 76 patients with stage III and stage IV squamous cell carcinoma. Overexpression of p53, p21, cyclin D1 and CDC25B was observed in 58%, 30%, 28%, and 32% of patients, respectively. The expression of p21 correlated significantly with response to chemoradiotherapy (P = 0.0001). Survival of patients with p21-expressing tumors was better than that of patients with p21-negative tumors (P = 0.013). Expression of other genes was not significantly correlated with treatment response and survival. In patients with p53-negative tumors, survival of those patients with p21-positive tumors was significantly higher than that of those with p21-negative tumors (P = 0.0452), but no significant difference was found in patients with p53-positive tumors. Multivariate analysis revealed that p21 expression was an independent variable among pretreatment parameters in predicting survival. These results suggest that p21 expression is potentially useful for predicting the response to chemoradiotherapy and survival of patients with advanced esophageal squamous cell cancer.

Thus, our results demonstrate that, by using B7.1 gene-transfected tumour cell lines, we effectively induced autologous tumour-specific CTL. These results will provide us with new tools for adoptive immunotherapy for colon cancer patients.