Date of Award
Master of Science
Molecular Biology Microbiology and Biochemistry
Lymphatic metastasis in breast cancer (BC) is one of the most important prognostic factors for patient survival. The escaped tumor cells reach distant vital organs and their unopposed expansion in these organs may cause mortality to patient. Tumor cells are transported to lymph node (LN) exclusively by tumor lymphatic vessels (LV). Increased tumor lymphangiogenesis, i.e., the formation of new LV is currently thought to be promoted by soluble factors such as VEGF-C and –D that activate VEGFR-3 expressed in lymphatic endothelial cells (LEC). These factors are secreted by malignant, tumor-infiltrating immune and stromal cells and create a favorable environment for formation of new vessels. However, emerging evidence suggests that tumor lymphangiogenesis is also promoted by Myeloid-derived Lymphatic Endothelial Cell Progenitors (M-LECP). We recently showed that M-LECP are abundant in mouse and human breast tumors and that their density strongly correlates with both lymphatic formation and nodal metastasis. Characterization of M-LECP showed that nearly all these cells express typical markers of the M2-type of macrophages such as CD163, CD204, and CD209. These cells are consider to be strongly immunosuppressive as exemplified by their inhibition of mobilization, activation, and survival of the key defenders against cancer cells, cytotoxic CD8+ T lymphocytes. Here, we compare the in vitro differentiation of M-LECP derived from bone marrow (BM) myeloid precursors primed with CSF-1 followed by secondary stimulants such as LPS, an immunomodulatory ligand for TLR4, and IL-4, IL-13, and IL-10 downstream targets of this receptor that are known to promote M2-macrophage development. Expression of these stimulants was analyzed by qPCR, flow cytometry, and ELISA during M-LECP differentiation. Our study describes the expression and functionality of these Th2 cytokines and their receptors during M-LECP differentiation. We found that each of the Th2 pathways singularly promotes M-LECP differentiation but there is an absent additive effect. We also found that IL-10 but no other Th2 cytokines is upregulated along with its receptor and contributes to the expression of the lymphatic properties similarly to LPS. To our knowledge, the role of IL-10 in development of lymphatic phenotype through differentiation of M-LECP has not been reported previously. Lastly, we show recruitment of M-LECP in a mouse BC model and the co-expression of the Th2 cytokine receptors in these cells. These studies have a potential to identify new regulators of M-LECP production in the bone marrow that could serve as biomarkers and targets for inhibiting tumor lymphatic formation, and by extension, lymph node metastasis.
This thesis is only available for download to the SIUC community. Current SIUC affiliates may also access this paper off campus by searching Dissertations & Theses @ Southern Illinois University Carbondale from ProQuest. Others should contact the interlibrary loan department of your local library or contact ProQuest's Dissertation Express service.