| In order to determine the major regulators of fetal-maternal tolerance and reactivation which could be applicable for targeting tumors, there needs to be better definition of the changes occurring during gestation. For this thesis, plasma was measured for levels of hormones, cytokines, chemokines and angiogenic factors monthly throughout uncomplicated pregnancies from 48 primigravida mothers. Results demonstrated that many of the hormones, such as estrogen and progesterone increased though gestation along with IL-27, a pro-inflammatory cytokine that drives a Th1 immune response. There were also immunologic differences between women carrying a male fetus who had higher levels of inflammatory cytokines and angiogenic factors compared to women carrying a female fetus. This suggests that the immune environment at the fetal-maternal interface requires more strategies to tolerize the haploidentical male fetus. Lastly, levels of galectin-9, a molecule that binds to Th1 polarized cells and causes them to undergo apoptosis, was measured during pregnancy. Galectin-9 was elevated throughout gestation, dropping to normal levels 6 weeks postpartum. It was also noted that galectin-9 was significantly increased in the plasma of women carrying a male fetus compared to those carrying a female. Together, this points to galectin-9 as possible regulator of normal gestation and thus a potential target for study in cancer.;To test the idea that the physiological process of pregnancy could be studied and applied to oncology, galectin-9 was evaluated in a metastatic melanoma cohort. Most of what is known on galectin-9 has been determined in animal models; thus, human studies are merited. Similar to pregnancy, galectin-9 was significantly increased in the blood of metastatic melanoma patients compared to healthy controls. Considering anatomy of galectin-9 staining on tumors and placentas, our data demonstrated that the highest staining intensity for galectin-9 was around the edge of the tumor and the cells of the fetal maternal interface. Using plasma levels of galectin-9 in stage IV melanoma patients, a significant survival advantage at 2 years was demonstrated if patients had low levels of galectin-9 compared to those with high levels. Lastly, to determine if high versus low levels of galectin-9 correlated with relevant Th1/Th2 cells and cytokines, we measured cells and cytokines from patient blood. Patients with high galectin-9 levels had more Th2 biasing, as determined by cytokine secretion and cell phenotyping, compared to the low galectin-9 cohort. This suggests that galectin-9 has prognostic value in patients with melanoma; however, this finding should be validated in a true biomarker study.;Lastly, to understand how galectin-9 regulates immunity in vitro, we studied mechanisms in the context of human peripheral blood mononuclear cells (PBMCs). The known binding partner is T cell immunoglobulin mucin (Tim)-3 and the interaction has been shown to promote Th1 cell apoptosis in mouse models. Assays demonstrated galectin-9 inhibiting human T cell proliferation and promoting apoptosis both dependent and independent of Tim3. Incubation with galectin-9 resulted in the increase of Th2, tolerance promoting extracellular markers as well as the expansion of T regulatory cells independent of the Tim3 receptor. Following galectin-9 stimulation, Th2 pro-inflammatory cytokines increased; however, when the CD14+ monocyte population was removed cytokine production diminished significantly. Thus, galectin-9 seems to drive a Th2, pro-tumor immune response by promoting apoptosis of Th1 cells and encouraging Th2 cytokine production. Further studies into the myeloid population revealed that CD68 macrophages congregate around the edge of the tumor and that incubation of CD14+ human monocytes causes an increase in chemokines and cytokines known to induce a tumor promoting macrophage phenotype. Galectin-9 was found to upregulate M2 marker CD206 in THP-1 cells, a human monocyte cell line. This increase in CD206 was confirmed in our metastatic melanoma patients compared to healthy controls. (Abstract shortened by ProQuest.). |
