Dominguez, Ana Lucía

Abstract IL-9 is a Th2 cytokine associated with T regulatory cell function, parasite expulsion and allergic airway inflammation. In many tumors IL-9 contributes to the establishment of a tolerogenic / immunosuppressive environment or acts directly to drive tumor growth, whereas in melanomas it inhibits tumor growth. Little is known about the effect of IL-9 in breast cancer biology. Here we show that IL-9 is a key factor in establishing a permissive growth environment for two murine breast cancer cells lines: TUBO cells that express Her2/neu and 4T1 cells that resemble aggressive, triple-negative breast cancers. We observed that TUBO cells were rejected by 78%, and 4T1 cells by 68% of IL-9 -/- (IL-9ko) mice, and that in the remaining mice the tumors developed later and grew slower than in WT mice. Tumor rejection is CD8+ T cell dependent and is capable of producing a memory response against tumor rechallenge. Delayed depletion of CD8+ T cells in mice that had rejected 4T1 cells showed no tumor growth in 63 % of the mice, suggesting that in these mice the tumor had been completely eradicated and was not held in stasis by immune surveillance. Furthermore we found a 3.7 fold increase (p=0.007) in the number of activated CD8+ T cells derived from IL-9ko mice rejecting tumors as compared to CD8+ T cells from tumor bearing WT mice. More importantly, the transfer of activated splenocytes from IL-9ko mice led to tumor rejection in WT mice (p<0.001). Moreover, WT mice treated with neutralizing anti-IL-9 evidenced slower 4T1 tumor growth compared to untreated and isotype control antibody treated mice. These data suggest that IL-9 neutralization should be examined as an adjuvant to immunotherapeutic or chemotherapeutic approaches. Supported by the NCI : CA155295 Citation Format: Dominique B. Hoelzinger, Ana Lucia Dominguez, Peter A. Cohen, Sandra J. Gendker. IL-9 is involved in the establishment of a tolerogenic milieu that prevents anti-tumor immunity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3640. doi:10.1158/1538-7445.AM2014-3640

Abstract The tolerogenic cytokine IL9 promotes T regulatory cell function and allergic airway inflammation, but it has not been extensively studied in cancer. In this report, we used IL9-deficient mice to investigate the effects of IL9 in multiple models of breast and colon cancer development. Eliminating endogenous IL9 enabled sensitization of host T cells to tumors, leading to their early rejection without the requirement of vaccines or immunomodulatory therapies. Notably, IL9-deficient mice acquired immunologic memory, which actively protected from residual disease and tumor rechallenge, an effect linked to activation of CD8+ T cells. Depletion of either CD8+ or CD4+ T cells abolished the benefits of IL9 loss to tumor control. Adoptive transfer experiments showed that T cells from tumor-rejecting IL9-deficient mice retained their effector competency in wild-type animals. Moreover, neutralizing IL9 antibody phenocopied the effects of IL9 gene deletion by slowing tumor progression in wild-type animals. Our results show the ability of IL9 to function as an inhibitor of adaptive immunity that prevents the formation of immunologic memory to a growing tumor, highlighting the potential for IL9 neutralization as a unique tool for cancer immunotherapy. Cancer Res; 74(23); 6845–55. ©2014 AACR.

Regulatory T cells (T reg cells) are characterized by the expression of the forkhead lineage-specific transcription factor Foxp3, and their main function is to suppress T cells. While evaluating T reg cells, we identified a population of Foxp3-positive cells that were CD11b+F4/80+CD68+, indicating macrophage origin. These cells were observed in spleen, lymph nodes, bone marrow, thymus, liver, and other tissues of naive animals. To characterize this subpopulation of macrophages, we devised a strategy to purify CD11b+F4/80+Foxp3+ macrophages using Foxp3-GFP mice. Analysis of CD11b+F4/80+Foxp3+ macrophage function indicated that these cells inhibited the proliferation of T cells, whereas Foxp3− macrophages did not. Suppression of T cell proliferation was mediated through soluble factors. Foxp3− macrophages acquired Foxp3 expression after activation, which conferred inhibitory properties that were indistinguishable from natural Foxp3+ macrophages. The cytokine and transcriptional profiles of Foxp3+ macrophages were distinct from those of Foxp3− macrophages, indicating that these cells have different biological functions. Functional in vivo analyses indicated that CD11b+F4/80+Foxp3+ macrophages are important in tumor promotion and the induction of T reg cell conversion. For the first time, these studies demonstrate the existence of a distinct subpopulation of naturally occurring macrophage regulatory cells in which expression of Foxp3 correlates with suppressive function.

Abstract Intratumoral accumulation of T regulatory cells (Tregs) creates an immunosuppressive environment that reduces the efficacy of antitumor immunotherapy. The immunosuppressive milieu within tumors is largely brought about by the presence of Tregs, which maintain self-tolerance by directly inhibiting T cells, NK cells, and dendritic cells. Depletion of Tregs enhances antitumor immune responses; however, current depletion therapies also affect the function of CD4 and CD8 T effector cells. Previous studies from our laboratory indicate that intratumoral delivery of CpG-ODN strongly reduces the levels of Tregs within the tumor, which is mainly mediated by IL-6. Because IL-6 promotes growth of some human cancers, alternate pathways to inactivate Tregs were sought through microarray analysis, resulting in gene candidates that can be exploited to modulate the function of Tregs. Analysis of these candidates indicates that neutralization of chemokine (C-C motif) ligand 1 (CCL1) prevented de novo conversion and suppressive function of Tregs without affecting the function of T effector cells. The combination of CpG-ODN and anti-CCL1 treatments induced complete rejection of tumors in BALB-neuT tolerant mice, and result in the generation of long-term protective memory responses. Tumor rejection correlated with changes in the lymphocyte composition within the tumor; we observed decreased Treg numbers and a concomitant accumulation of tumoricidal cells such as CD8+NKG2D+ and NK cells. These studies demonstrate that neutralization of CCL1 can be used as an adjuvant to antitumor immunotherapy, as a means of reversing the immunosuppressive function of Tregs without compromising T cell effector function.

Abstract T cell responses are compromised in the elderly. The B7-CD28 family receptors are critical in the regulation of immune responses. We evaluated whether the B7-family and CD28-family receptors were differentially expressed in dendritic cells, macrophages, and CD4+ and CD8+ T cells from young and old mice, which could contribute to the immune dysfunction in the old. Although most of the receptors were equally expressed in all cells, >85% of the old naive CD8+ T cells expressed B7-H1 compared with 25% in the young. Considering that B7-H1 negatively regulates immune responses, we hypothesized that expression of B7-H1 would downregulate the function of old CD8+ T cells. Old CD8+ T cells showed reduced ability to proliferate, but blockade of B7-H1 restored the proliferative capacity of old CD8+ T cells to a level similar to young CD8+ T cells. In vivo blockade of B7-H1 restored antitumor responses against the B7-H1− BM-185–enhanced GFP tumor, such that old animals responded with the same efficiency as young mice. Our data also indicate that old CD8+ T cells express lower levels of TCR compared with young CD8+ T cells. However, following antigenic stimulation in the presence of B7-H1 blockade, the levels of TCR expression were restored in old CD8+ T cells, which correlated with stronger T cell activation. These studies demonstrated that expression of B7-H1 in old CD8+ T cells impairs the proper activation of these cells and that blockade of B7-H1 could be critical to optimally stimulate a CD8 T cell response in the old.

Abstract We have shown that neu transgenic mice are immunotolerant and that immunizations with dendritic cells (DC) pulsed with neu-derived antigens were not able to control tumor growth in these animals. We tested whether, by modulating the tumor microenvironment with Toll-like receptor ligands, it could be possible to induce the activation of antitumor responses in neu mice. Our results indicate that only intratumoral (i.t.) injections of CpG-ODN induce an antitumor response in neu mice. To target the CpG-ODN to the tumor site anywhere within the body, we chemically conjugated an anti–Her-2/neu monoclonal antibody (mAb) with CpG-ODN. The anti–neu-CpG hybrid molecule retained its ability to bind to Her-2/neu+ tumors, activate DCs, and induce antitumor responses. Our results indicated that injections of anti–neu-CpG induced the rejection of primary tumors in 100% of BALB/c mice and only in ∼30% of BALB-neuT mice. After challenging the BALB/c and BALB-neuT mice, we observed that BALB/c mice developed a protective memory response; in contrast, BALB-neuT mice succumbed to the challenge. After injections of anti–neu-CpG, T regulatory cells (T-reg) were drastically reduced at the tumor site, but a large number were still present in the lymphoid organs. When BALB-neuT mice were treated with anti–neu-CpG plus anti-GITR mAb, but not with anti-CD25 mAb, 100% of the BALB-neuT mice rejected the primary tumor and developed a protective memory response indicating the critical role of T-regs in regulating the repertoire against self antigens. Taken together, these results indicate that CpG-ODN–targeted therapy and depletion of T-regs optimally activate a primary response and generate a protective memory response against self-tumor antigens. [Cancer Res 2008;68(18):7530–40]

AbstractCancer statistics show a disproportionately higher burden of tumors in the old. Most of the studies evaluating vaccination strategies have not taken into consideration the effect that aging has on the immune system. For the first time, we describe an animal tumor model in which self-tolerance and aging are present at the same time. FVB-Her-2/neu mice which are tolerant to neu antigens crossed with HLA-A2/Kb mice (A2xneu) develop spontaneous tumors when they are more than 22 months old. Analysis of CD8+ T-cell–specific responses in A2xneu mice indicated that the priming activity of old A2xneu mice to induce an immune response was diminished compared with young animals. Following intratumoral injections of CpG-ODN, ∼30% of young A2xneu mice rejected the tumor; however, no antitumor effect was observed in old A2xneu mice. Analysis of T regulatory cells (Treg) indicated that there are significantly more Tregs in old animals. After CpG-ODN vaccination plus Treg depletion, 70% of young A2xneu mice rejected the tumor. The same treatment prolonged survival in old A2xneu mice, but none of the animals rejected the tumor. Even though CpG-ODN injections plus Treg depletion could rescue the antitumor responses against self-tumor antigens in young tolerant mice, the same therapy is not as effective in old tolerant hosts. Relevant tumor models such as the A2xneu mice in which self-tolerance and aging are present at the same time are critical to allow the optimization of vaccination strategies to effectively stimulate immune responses against self-tumor antigens in the young and the old. [Cancer Res 2008;68(13):5423–31]