The ability of interleukin (IL)-12 to prevent tumors when administered to individuals with a genetic risk of cancer was studied in two lines of transgenic mice expressing rat HER-2/neu oncogene in the mammary gland. Female BALB/c (H-2^d) mice carrying the activated HER-2/ neu oncogene show no morphological abnormalities of the mammary gland until 3 wk of age. They then progress through atypical hyperplasia to in situ lobular carcinoma and at 33 wk of age all 10 mammary glands display invasive carcinomas. Adult FVB mice (H-2^q) carrying the HER-2/neu protooncogene develop mammary carcinomas with a longer latency (38-49 wk) and a lower multiplicity (mean of 2.6 tumors/mice). Treatment with IL-12 (5 daily intraperitoneal injections, 1 wk on, 3 wk off; the first course with 50 ng IL-12/day, the second with 100 ng IL-12/day) begun at 2 wk of age in BALB/c mice and at 21 wk of age in FVB mice markedly delayed tumor onset and reduced tumor multiplicity. Analogous results were obtained in immunocompetent and permanently CD8⁺ T lymphocyte–depleted mice. In both transgenic lines, tumor inhibition was associated with mammary infiltration of reactive cells, production of cytokines and inducible nitric oxide synthase, and reduction in microvessel number, in combination with a high degree of hemorrhagic necrosis.

Background: Numerous animal model studies have examined the ability of genetically engineered tumor cells to release cytokines and to elicit an immune memory against the parental tumor. Often only a single cytokine is studied, and few comparative studies have been conducted. Purpose: We evaluated the antitumor efficacy of adenocarcinoma cells engineered to release interleukin (IL)-12 in a mouse model system. The efficacy of this cytokine was compared with that of other cytokines released by engineered adenocarcinoma cells and that of exogenous IL-12 administered both locally and intraperitoneally. Methods: BALB/cAnCr mice were inoculated with syngeneic parental mammary adenocarcinoma (TSA) cells in quantities sufficient to lead to tumors in all inoculated mice. TSA cells engineered to release IL-12 (TSA-IL12) were also injected into normal and selectively immunosuppressed BALB/cAnCr mice. Tumor incidence, growth, and rejection patterns were evaluated by the measurement of neoplastic masses and by the study of the histologic and ultrastructural features of the tumor site. The effects of local or intraperitoneal administration of recombinant IL-12 (rIL-12) on tumor-bearing animals were also studied. Results: Most mice rejected TSA-IL12 cells through a CD8-positive, T-lymphocyte-dependent reaction associated with macrophage infiltration, vessel damage, and necrosis. The systemic immunity of mice that had rejected TSA-IL12 cells to a subsequent challenge with parental TSA cells was less efficient than that elicited by TSA cells engineered to release IL-4 or IL-10 but equivalent to that elicited by TSA cells engineered to release IL-2, IL-7, and interferon alfa. Compared with TSA cells engineered to produce other cytokines, TSA-IL12 cells were the most efficient in curing mice with established TSA tumors; injection of 0.1 million proliferating cells contralaterally to the tumor growth area cured five of 15 mice bearing 1-day-old tumors; injection of the same dose of proliferating cells into the tumor growth area cured two of 20 tumor-bearing mice. However, two 5-day courses with a nontoxic dose (0.1 µg) of rIL-12 given intraperitoneally cured a similar proportion of these animals (six of 20). Only two of 20 mice with 7-day-old TSA tumors were cured by vaccination with proliferating TSA-IL12 cells, whereas 24 of 30 mice with such tumors were cured by intraperitoneal administration of rIL-12. Conclusions: TSA cells engineered to release IL-12 are rejected by most mice; the ensuing immune memory for TSA parental cells, however, was less efficient than that elicited by proliferating TSA cells engineered to release other cytokines (e.g., IL-4, IL-10, and possibly interferon gamma). The immune reaction elicited by TSA-IL12 cells was the most efficient in curing mice with established TSA tumors; notably though, the same or a better cure rate was obtained with rIL-12 given intraperitoneally.

Dendritic cells (DCs) are a heterogeneous group of professional antigen-presenting cells functioning as sentinels of the immune system and playing a key role in the initiation and amplification of innate and adaptive immune responses. DC development and functions are acquired during a complex differentiation and maturation process influenced by several factors present in the local milieu. A common feature at pathologic sites is represented by hypoxia, a condition of low pO2, which creates a unique microenvironment affecting cell phenotype and behavior. Little is known about the impact of hypoxia on the generation of mature DCs (mDCs). In this study, we identified by gene expression profiling a significant cluster of genes coding for immune-related cell surface receptors strongly up-regulated by hypoxia in monocyte-derived mDCs and characterized one of such receptors, TREM-1, as a new hypoxia-inducible gene in mDCs. TREM-1 associated with DAP12 in hypoxic mDCs, and its engagement elicited DAP12-linked signaling, resulting in ERK-1, Akt, and IκBα phosphorylation and proinflammatory cytokine and chemokine secretion. Finally, we provided the first evidence that TREM-1 is expressed on mDCs infiltrating the inflamed hypoxic joints of children affected by juvenile idiopathic arthritis, representing a new in vivo marker of hypoxic mDCs endowed with proinflammatory properties.

TS/A is a spontaneous adenocarcinoma, apparently not immunogenic in BALB/cnAnCr mice. TS/A cells are unable to stimulate a syngeneic antitumor response either in vitro or in vivo. To evaluate the immunogenic potential of IL-2-releasing neoplastic cells, we used an expression vector to introduce the cDNA coding for murine IL-2 into TS/A cells. Six clones releasing between 30 and 6800 U of IL-2/10(5) cells/ml/48 h have been isolated. Both low (30 U, B1.30) and high (6000 U, B4.6000) IL-2-releasing clone are capable of stimulating a proliferative and cytotoxic response in syngeneic cultures. While the B1.30 clone grows in 60% of syngeneic mice with a delayed pattern, the five clones that release higher levels of IL-2 are promptly rejected. Rejection is associated with neutrophil infiltration, the intensity of which is directly proportional to the amount of IL-2 released. NK cells and CD4+ lymphocytes are uninfluential, whereas CD8+ lymphocytes play only a minor role. This neutrophil-dominated rejection leaves a long-lasting, tumor-specific, T lymphocyte-mediated immune memory. For its induction, CD4+ lymphocytes are required. Their specific activation appears to depend on both the amount of IL-2 released and the granulocyte-mediated reaction that may lead to a more efficient presentation of tumor-associated Ag. These data support the notion that, after transduction of IL-2 gene, cancer cells may elicit an immune antitumor response, and stress the potential use of IL-2 as a component of new tumor vaccines.

The cDNA coding for mouse IL-10 (mIL-10) was transduced into the parental cells of a spontaneous adenocarcinoma of BALB/c mice (TSA-pc), and clones secreting small, medium, and large quantities of IL-10 were selected. In vivo, both low and high producer clones do not display an enhanced ability to grow in H-2 and non-H-2 incompatible mice. Instead, the intensity of their rejection increases in function of the amount of mIL-10 released. After an initial growth period in syngeneic mice, high producer clones undergo complete rejection due to the combined action of CD8+ lymphocytes, NK cells, and neutrophils. After this rejection, mice are immune to a subsequent challenge with TSA-pc. This memory rests on a strong lytic activity of CD8+ CTL and granulocytes. Following the rejection, mice also develop anti-TSA Ab that guide the granulocytes in TSA-pc memory reaction. A direct comparison shows that although TSA clones engineered to release IL-2 activate CTL and no anti-TSA Ab, those engineered to release IL-4 activate a strong Ab response but not CTL. The kind of cytokine released by the tumors appears to determine the type of response. However, IL-10 high producer cells do not deviate the immune memory, neither toward a Th1 nor a Th2. Both the CTL activity and the Ab responses induced by IL-10 high producer cells are the strongest so far observed in the TSA system.