More than 60% of all breast neoplasias are ductal carcinomas expressing estrogen (ER) and progesterone receptors (PR). By contrast, most of the spontaneous, chemically or mouse mammary tumor virus induced tumors, as well as tumors arising in genetically modified mice do not express hormone receptors. We developed a model of breast cancer in which the administration of medroxyprogesterone acetate to BALB/c female mice induces mammary ductal carcinomas with a mean latency of 52 weeks and an incidence of about 80%. These tumors are hormone-dependent (HD), metastatic, express both ER and PR, and are maintained by syngeneic transplants. The model has been further refined to include mammary carcinomas that evolve through different stages of hormone dependence, as well as several hormone-responsive cell lines. In this review, we describe the main features of this tumor model, highlighting the role of PR as a trigger of key signaling pathways mediating tumor growth. In addition, we discuss the relevance of this model in comparison with other presently used breast cancer models pointing out its advantages and limitations and how, this model may be suitable to unravel key questions in breast cancer.

Synthetic progesterone used in contraception drugs (progestins) can promote breast cancer growth, but the mechanisms involved are unknown. Moreover, it remains unclear whether cytoplasmic interactions between the progesterone receptor (PR) and estrogen receptor alpha (ERa) are required for PR activation. In this study, we used a murine progestin-dependent tumor to investigate the role of ERa in progestin-induced tumor cell proliferation. We found that treatment with the progestin medroxyprogesterone acetate (MPA) induced the expression and activation of ERa, as well as rapid nuclear colocalization of activated ERa with PR. Treatment with the pure antiestrogen fulvestrant to block ERa disrupted the interaction of ERa and PR in vitro and induced the regression of MPA-dependent tumor growth in vivo. ERa blockade also prevented an MPA-induced increase in CYCLIN D1 (CCND1) and MYC expression. Chromatin immunoprecipitation studies showed that MPA triggered binding of ERa and PR to the CCND1 and MYC promoters. Interestingly, blockade or RNAi-mediated silencing of ERa inhibited ERa, but not PR binding to both regulatory sequences, indicating that an interaction between ERa and PR at these sites is necessary for MPA-induced gene expression and cell proliferation. We confirmed that nuclear colocalization of both receptors also occurred in human breast cancer samples. Together, our findings argued that ERa-PR association on target gene promoters is essential for progestin-induced cell proliferation. Cancer Res; 72(9); 2416-27. Ó2012 AACR.

During mammalian pregnancy, the immune system defies a double challenge: to tolerate the foreign growing fetus and to fight off infections that could affect both mother and fetus. Minimal disturbances to the fine equilibrium between immune activation and tolerance would compromise fetal survival. Here, we show that regulatory B10 cells are important for pregnancy tolerance in mice. The frequency of these cells increases during normal murine pregnancies, while mice presenting spontaneous abortion do not show elevated levels of regulatory B10 cells. When B10 cells are transferred to the abortion-prone mice, dendritic cells are kept in an immature state, and regulatory T cells increase, thus avoiding immunological rejection of the fetuses. In vitro, we could identify IL-10 secreted by B10 cells as the main mediator of these salutary effects. Our data add an important piece of information to the complex immune crosstalk during pregnancy. This study opens novel lines of work to better understand how to help women who have trouble in maintaining a pregnancy.

Pregnancy hides an immunological riddle combining two antagonistic characteristics of immunology: the existence of a tolerance that allows the gestation of a semiallogeneic fetus and proper protection against pathogens threatening the health of the immunocompromised mother. Despite the fundamental role that B cells play in orchestrating an immune response, their behavior in the context of pregnancy has been barely investigated. Here we demonstrate that numbers of pre/pro and immature B cells were progressively diminished in the bone marrow (BM) of pregnant mice, leading to a reduced influx of B cells in blood and spleen. Correspondingly, lower levels of B cell-activating factor of the TNF family were observed in serum of pregnant mice. In contrast to immature B cells, mature B cells were accumulated in the BM during pregnancy. Accordingly, higher numbers of mature B cells were observed in the lymph nodes draining the uterus as well as in the peritoneal cavity of pregnant mice, both tissues in close contact with the fetuses. Despite an increase in spleen size, pregnant mice showed lower numbers of splenic B cells, which was mirrored by lower numbers of immature and FO B cells. However, marginal zone B cells in the spleen increased during pregnancy. Additionally, serum IgM, IgA, and IgG3 titers were elevated in pregnant mice. Collectively, our data show how the B cell compartment adapts to the presence of the semiallogeneic fetus during gravidity.

The immunosuppressive strategies devised by neuroblastoma (NB), the most common solid extracranial childhood cancer, are poorly understood. Here, we identified an immunoevasive program triggered by NB through secretion of galectin-1 (Gal-1), a multifunctional glycan-binding protein. Human and mouse NB cells express and secrete Gal-1, which negatively regulates T cell and dendritic cell function. When injected subcutaneously in syngeneic A/J mice, knockdown transfectants expressing low amounts of Gal-1 (NXS2/L) showed reduction of primary tumor growth by 83-90% and prevented spontaneous liver metastases in contrast to NXS2 cell variants (NXS2/H, NXS2 wildtype) expressing high amounts of Gal-1. Splenocytes from mice receiving Gal-1 knockdown NXS2/L cells secreted higher amounts of IFN-c and displayed enhanced cytotoxic T-cell function compared to NXS2/H or NXS2 controls. Immunohistochemical analysis revealed a six-to tenfold increase in the frequency of CD4 1 and CD8 1 T cells infiltrating tumors from mice receiving knockdown transfectants. This effect was confirmed by in vitro migration assays. Finally, supernatants of NXS2/H or NXS2 cells suppressed dendritic cell (DC) maturation and induce T cell apoptosis, whereas these effects were only marginal on DCs and T cells exposed to supernatants from NXS2/L cells. These results demonstrate a novel immunoinhibitory role of the Gal-1-glycan axis in NB, highlighting an alternative target for novel immunotherapeutic modalities.Neuroblastoma (NB) is the most common extracranial solid malignancy in childhood. 1 This neuroendocrine tumor arising from neural crest cells is responsible for over 10-15% of pediatric cancer deaths. 1 The disease exhibits extreme heterogeneity, resulting in most recent stratification into very low, low, intermediate or high risk. 2 NB of lower risk groups occur during the first 18 months of life, and good outcomes are typical after surgery. 2 In contrast, high-risk NB, notably characterized by the amplification of NB-derived myelocytomatosis viral related oncogene (N-MYC), is resistant even to the most intensive treatment protocols available. 3,4 This suggests the need of more effective therapeutic strategies targeting nontraditional targets and lacking toxicity for treating high-risk aggressive NB.The introduction of monoclonal antibodies or chimeric T cells engineered to express chimeric antigen receptors targeting the GD2 antigen together with the implementation of dendritic cell (DC)-based vaccination have validated the critical function of the immune system in promoting NB regression. 5 Treatment with IL-2, GM-CSF, CD40 agonists or CTLA-4 blockade, in combination with other traditional approaches, has successfully improved immune effector functions in high-risk NB patient. 5,6 However, the success of these adjuvant immunotherapeutic approaches is hindered by a number of strategies used by tumors or tumor-associated stroma cells to elude immune recognition or thwart immune

During pregnancy, the maternal immune system faces a double dilemma: tolerate the growing semi-allogeneic fetus and at the same time protect the mother and the progeny against pathogens. This requires a fine and extremely regulated equilibrium between immune activation and tolerance. As professional antigen presenting cells, B cells and in particular B-1a B cells, can activate or tolerize T cells and thus participate in the generation or regulation of the immune response. B-1a B cells were involved in the humoral immune response leading to pre-eclampsia, one of the main medical complications during pregnancy. Here we demonstrated that B-1a B cells are additionally involved in cellular immune mechanisms associated with pregnancy complications. Using a mouse model of pregnancy disturbances, we showed that B-1a B cells from animals suffering pregnancy disturbances but not from those developing normal pregnancies induce the differentiation of naïve T cells into Th17 and Th1 cells. This differential role of B-1a B cells during pregnancy seems to be associated with the co-stimulatory molecule CD86 as normal pregnant mice showed lower percentages of CD86 expressing B-1a B cells as compared to pregnant mice developing pregnancy disturbances or to non-pregnant animals. Our data bring to light a new and not explored role of B-1a B cells in the context of pregnancy.

No abstract

Introduction Previous data from our laboratory suggested that progesterone receptors (PRs) are involved in progestinindependent growth of mammary carcinomas. To investigate this possibility further, we studied the effects of PR antisense oligodeoxynucleotides (asPR) on in vivo tumor growth.