Faculty Bibliography

Polymorphonuclear neutrophils (PMNs) are increasingly recognized to influence solid tumor development, but why their effects are so context dependent and even frequently divergent remains poorly understood. Using an autochthonous mouse model of uterine cancer and the administration of respiratory hyperoxia as a means to improve tumor oxygenation, we provide in vivo evidence that hypoxia is a potent determinant of tumor-associated PMN phenotypes and direct PMN-tumor cell interactions. Upon relief of tumor hypoxia, PMNs were recruited less intensely to the tumor-bearing uterus, but the recruited cells much more effectively killed tumor cells, an activity our data moreover suggested was mediated via their production of NADPH oxidase-derived reactive oxygen species and MMP-9. Simultaneously, their ability to promote tumor cell proliferation, which appeared to be mediated via their production of neutrophil elastase, was rendered less effective. Relieving tumor hypoxia thus greatly improved net PMN-dependent tumor control, leading to a massive reduction in tumor burden. Remarkably, this outcome was T cell independent. Together, these findings identify key hypoxia-regulated molecular mechanisms through which PMNs directly induce tumor cell death and proliferation in vivo and suggest that the contrasting properties of PMNs in different tumor settings may in part reflect the effects of hypoxia on direct PMN-tumor cell interactions.

Problem: Neutrophils are increasingly recognized to influence solid tumor development, but the basis of their context-dependent and frequently divergent effects remains poorly understood. Method of Study: In vivo analysis of an autochthonous mouse model of endometrial cancer.
Result(s): Previously, we found that neutrophils oppose tumor development in a mouse model of PTEN deficiency-induced endometrial cancer (Blaisdell et al., Cancer Cell, 28:785, 2015). We now find that tumor hypoxia is a major determinant of PMN function in this tumor microenvironment. When tumors were rendered less hypoxic, tumor-associated PMN phenotypes were altered and the cells more effectively killed tumor cells through their production of reactive oxygen species and MMP-9. Simultaneously, they less effectively induced tumor cell proliferation through their production of neutrophil elastase. Relieving tumor hypoxia thus greatly improved net PMN-dependent tumor control.
Conclusion(s): These studies may have clinical implications and suggest that the contrasting properties of PMNs in different tumor settings may reflect the effects of tissue hypoxia on the multiple, simultaneously manifested facets of tissue PMN biology

Uncovering the causes of pregnancy complications such as preterm labor requires greater insight into how the uterus remains in a noncontractile state until term and then surmounts this state to enter labor. Here, we show that dynamic generation and erasure of the repressive histone modification tri-methyl histone H3 lysine 27 (H3K27me3) in decidual stromal cells dictate both elements of pregnancy success in mice. In early gestation, H3K27me3-induced transcriptional silencing of select gene targets ensured uterine quiescence by preventing the decidua from expressing parturition-inducing hormone receptors, manifesting type 1 immunity, and most unexpectedly, generating myofibroblasts and associated wound-healing responses. In late gestation, genome-wide H3K27 demethylation allowed for target gene upregulation, decidual activation, and labor entry. Pharmacological inhibition of H3K27 demethylation in late gestation not only prevented term parturition, but also inhibited delivery while maintaining pup viability in a noninflammatory model of preterm parturition. Immunofluorescence analysis of human specimens suggested that similar regulatory events might occur in the human decidua. Together, these results reveal the centrality of regulated gene silencing in the uterine adaptation to pregnancy and suggest new areas in the study and treatment of pregnancy disorders.

The bacterial pathogen Listeria monocytogenes causes a food-borne systemic disease in pregnant women that can lead to preterm labor, stillbirth, or severe neonatal disease. Colonization of the maternal decidua appears to be an initial step in the maternal component of the disease as well as bacterial transmission to the placenta and fetus. Host-pathogen interactions in the decidua during this early stage of infection remain poorly understood. Here, we assessed the dynamics of L. monocytogenes infection in primary human decidual organ cultures and in the murine decidua in vivo. A high inoculum was necessary to infect both human and mouse decidua, and the data support the existence of a barrier to initial colonization of the murine decidua. If successful, however, colonization in both species was followed by significant bacterial expansion associated with an inability of the decidua to mount appropriate innate cellular immune responses. The innate immune deficits included the failure of bacterial foci to attract macrophages and NK cells, cell types known to be important for early defenses against L. monocytogenes in the spleen, as well as a decrease in the tissue density of inflammatory Ly6Chi monocytes in vivo. These results suggest that infectivity of the decidua is not the result of enhanced recruitment of L. monocytogenes to the gestational uterus, but rather to compromised local innate cellular immune responses.

Successful pregnancy requires delicate control over the immunological and inflammatory properties of the maternal/fetal interface. For example, inflammation within the pregnant uterus is likely to be a major instigator of preterm birth, while inadequate immune surveillance of the maternal/fetal interface likely increases the risk of fetal and placental infection. We will discuss our recent work on the molecular and cellular pathways that regulate immune cell trafficking and inflammation within the pregnant mouse uterus. This work points to the seminal importance of the decidua, i.e. the specialized endometrial stromal tissue that encases the implanted embryo, and in particular an epigenetic program active in decidual stromal cells that we previously found transcriptionally silences the expression of chemokine genes that control effector T cell trafficking. Our recent results suggest that this program also silences a multitude of other important genes, including ones whose misexpression might be expected to generate uterine inflammation and lead to a variety of pregnancy complications including preterm birth

Polymorphonuclear neutrophils (PMNs) are largely considered to foster cancer development despite wielding an arsenal of cytotoxic agents. Using a mouse model of PTEN-deficient uterine cancer, we describe a surprising inhibitory role for PMNs in epithelial carcinogenesis. By inducing tumor cell detachment from the basement membrane, PMNs impeded early-stage tumor growth and retarded malignant progression. Unexpectedly, PMN recruitment and tumor growth control occurred independently of lymphocytes and cellular senescence and instead ensued as part of the tumor's intrinsic inflammatory response to hypoxia. In humans, a PMN gene signature correlated with improved survival in several cancer subtypes, including PTEN-deficient uterine cancer. These findings provide insight into tumor-associated PMNs and reveal a context-specific capacity for PMNs to directly combat tumorigenesis.

Successful pregnancy requires delicate control over the maternal immune cells that reside at the maternal/ fetal interface. On the one hand, immune cell-mediated inflammation at the maternal/fetal interface is likely to be a major instigator of preterm birth, while immunogenic recognition of fetal/placental antigens by professional antigen presenting cells runs the risk of inducing T cell responses that might induce fetal demise. On the other hand, inadequate immune surveillance of the maternal/fetal interface might be expected to increase the risk of fetal and placental infection. We will discuss recent our recent work on the molecular and cellular pathways that regulate immune cell trafficking and inflammation within the pregnant mouse uterus. This work points to the seminal importance of the decidua, i.e. the specialized endometrial stromal tissue that directly encases the implanted embryo, and in particular an epigenetic program active in decidual stroma cell is that transcriptionally silences expression of genes that regulate inflammation and leukocyte trafficking. For example, as a result of this program, effector T cells are unable to accumulate within the maternal/fetal interface even under conditions of local inflammation. We are currently attempting to elucidate the breadth and overall significance of the silencing program towards reproductive success, and to determine the exact molecular pathways that induce its activity in decidual stromal cells. Together, our results have major implications for the immunology of pregnancy its complications