Bone marrow-derived myeloid cells can accumulate within tumors and foster cancer outgrowth. Local immune-neoplastic interactions have been intensively investigated, but the contribution of the systemic host environment to tumor growth remains poorly understood. Here, we show in mice and cancer patients ( = 70) that lung adenocarcinomas increase bone stromal activity in the absence of bone metastasis. Animal studies reveal that the cancer-induced bone phenotype involves bone-resident osteocalcin-expressing (Ocn) osteoblastic cells. These cells promote cancer by remotely supplying a distinct subset of tumor-infiltrating SiglecF neutrophils, which exhibit cancer-promoting properties. Experimentally reducing Ocn cell numbers suppresses the neutrophil response and lung tumor outgrowth. These observations posit osteoblasts as remote regulators of lung cancer and identify SiglecF neutrophils as myeloid cell effectors of the osteoblast-driven protumoral response.

Infiltration and dysfunction of immune cells have been documented in many types of cancers. We previously reported that plasmacytoid dendritic cells (pDC) within primary breast tumors correlate with an unfavorable prognosis for patients. The role of pDC in cancer remains unclear but they have been shown to mediate immune tolerance in other pathophysiologic contexts. We postulated that pDC may interfere with antitumor immune response and favor tolerance in breast cancer. The present study was designed to decipher the mechanistic basis for the deleterious impact of pDC on the clinical outcome. Using fresh human breast tumor biopsies (N ¼ 60 patients), we observed through multiparametric flow cytometry increased tumor-associated (TA) pDC (TApDC) rates in aggressive breast tumors, i.e., those with high mitotic index and the so-called triple-negative breast tumors (TNBT). Furthermore, TApDC expressed a partially activated phenotype and produced very low amounts of IFN-a following toll-like receptor activation in vitro compared with patients' blood pDC. Within breast tumors, TApDC colocalized and strongly correlated with TA regulatory T cells (TATreg), especially in TNBT. Of most importance, the selective suppression of IFN-a production endowed TApDC with the unique capacity to sustain FoxP3 þ Treg expansion, a capacity that was reverted by the addition of exogenous IFN-a. These findings indicate that IFNa-deficient TApDC accumulating in aggressive tumors are involved in the expansion of TATreg in vivo, contributing to tumor immune tolerance and poor clinical outcome. Thus, targeting pDC to restore their IFN-a production may represent an attractive therapeutic strategy to overcome immune tolerance in breast cancer. Cancer Res; 72(20); 5188-97. Ó2012 AACR.

In ovarian cancer, the immune system fails to eradicate established tumors partly due to the induction of immune tolerance within tumor microenvironment. In this study, we investigated the contribution of plasmacytoid dendritic cells (pDC) in the establishment of immune tolerance in a cohort of 44 ovarian cancer patients. In the tumor and malignant ascites, CD4 þ CD123 þ BDCA2 þ pDC were the most abundant dendritic cell subset; however, they were profoundly depleted in peripheral blood. The presence of pDC in primary ovarian cancer, but not ascites, was an independent prognostic factor associated with early relapse. Following chemotherapy, we observed a partial restoration of blood pDC levels in patients in complete remission. These findings show preferential recruitment of pDC into tumors where they express a partially mature phenotype that may reflect an in situ activation. Importantly, compared with pDC found in ascites or blood, tumor-associated pDC (TApDC) produced less IFN-a, TNF-a, IL-6, macrophage inflammatory protein-1b, and RANTES in response to toll-like receptor stimulation, and alterations in pDC functions were mainly mediated through tumor-derived TNF-a and TGF-b. Unlike ascites-derived pDC, TApDC induced IL-10 production from allogeneic naive CD4 þ T lymphocytes, suggesting the existence of a paracrine immunosuppressive loop. Taken together, our findings indicate that both local and systemic dysfunction of pDC play a critical role in the progression of ovarian cancer via induction of immune tolerance. Cancer Res; 71(16); 5423-34. Ó2011 AACR.

Neutrophils are an essential part of the innate immune system. To study their importance, experimental studies often aim to deplete these cells, generally by injecting anti-Ly6G or anti-Gr1 antibodies. However, these approaches are only partially effective, transient or lack specificity. Here we report that neutrophils remaining after anti-Ly6G treatment are newly derived from the bone marrow, instead of depletion escapees. Mechanistically, newly generated, circulating neutrophils have lower Ly6G membrane expression, and consequently reduced targets for anti-Ly6G-mediated depletion. To overcome this limitation, we develop a double antibody-based depletion strategy that enhances neutrophil elimination by anti-Ly6G treatment. This approach achieves specific, durable and controlled reduction of neutrophils in vivo, and may be suitable for studying neutrophil function in experimental models.

Understanding the immune compartment of tumors facilitates the development of revolutionary new therapies. We used a Kras(G12D)-driven mouse model of lung cancer to establish an immune signature and identified a contribution of Gr1 neutrophils to disease progression. Depletion experiments showed that Gr1 cells (1) favor tumor growth, (2) reduce T cell homing and prevent successful anti-PD1 immunotherapy, and (3) alter angiogenesis, leading to hypoxia and sustained Snail expression in lung cancer cells. In turn, Snail accelerated disease progression and increased intratumoral Cxcl2 secretion and neutrophil infiltration. Cxcl2 was produced mainly by neutrophils themselves in response to a factor secreted by Snail-expressing tumor cells. We therefore propose a vicious cycle encompassing neutrophils and Snail to maintain a deleterious tumor microenvironment.

Human breast tumors are infiltrated by memory CD4 þ T cells along with increased numbers of regulatory T

In breast carcinomas, patient survival seems to be negatively affected by the recruitment of regulatory T cells (T reg ) within lymphoid aggregates by CCL22. However, the mechanisms underpinning this process, which may be of broader significance in solid tumors, have yet to be described. In this study, we determined how CCL22 production is controlled in tumor cells. In human breast carcinoma cell lines, CCL22 was secreted at low basal levels that were strongly increased in response to inflammatory signals [TNF-a, IFN-g, and interleukin (IL)-1b], contrasting with CCL17. Primary breast tumors and CD45þ infiltrating immune cells appeared to cooperate in driving CCL22 secretion, as shown clearly in cocultures of breast tumor cell lines and peripheral blood mononuclear cells (PBMC) or their supernatants. We determined that monocyte-derived IL-1b and TNF-a are key players as monocyte depletion or neutralization of these cytokines attenuated secretion of CCL22. However, when purified monocytes were used, exogenous human IFN-g was also required to generate this response suggesting a role for IFN-g-producing cells within PBMCs. In this setting, we found that human IFN-g could be replaced by the addition of (i) IL-2 or K562-activated natural killer (NK) cells or (ii) resting NK cells in the presence of anti-MHC class I antibody. Taken together, our results show a dialogue between NK and tumor cells leading to IFN-g secretion, which in turn associates with monocyte-derived IL-1b and TNF-a to drive production of CCL22 by tumor cells and subsequent recruitment of T reg . As one validation of this conclusion in primary breast tumors, we showed that NK cells and macrophages tend to colocalize within tumors. In summary, our findings suggest that at early times during tumorigenesis, the detection of tumor cells by innate effectors (monocytes and NK cells) imposes a selection for CCL22 secretion that recruits T reg to evade this early antitumor immune response.

The production of CD73-derived adenosine (Ado) by Tregs has been proposed as a resistance mechanism to anti-PD-1 therapy in murine tumor models. We reported that human Tregs express the ectonucleotidase CD39, which generates AMP from ATP, but do not express the AMPase CD73. In contrast, CD73 defined a subset of effector CD4 T cells (Teffs) enriched in polyfunctional Th1.17 cells characterized by expression of CXCR3, CCR6, and MDR1, and production of IL17A/IFNγ/IL22/GM-CSF. CD39 Tregs selectively targeted CD73 Teffs through cooperative degradation of ATP into Ado inhibiting and restricting the ability of CD73 Teffs to secrete IL17A. CD73 Teffs infiltrating breast and ovarian tumors were functionally blunted by Tregs expressing upregulated levels of CD39 and ATPase activity. Moreover, tumor-infiltrating CD73 Teffs failed to express inhibitory immune checkpoints, suggesting that CD73 might be selected under pressure from immune checkpoint blockade therapy and thus may represent a nonredundant target for restoring antitumor immunity. Polyfunctional CD73 T-cell effectors lacking other immune checkpoints are selectively targeted by CD39 overexpressing Tregs that dominate the breast tumor environment. .