Comparative analysis of M-CSF and GM-CSF in human monocyte metabolic reprogramming and differentiation into tumor-associated macrophage-like cells

PROJECT SUMMARY A major component of the tumor microenvironment, tumor-associated macrophages (TAMs) play a critical role in the orchestration of immunosuppression, cancer cell proliferation, angiogenesis, and metastasis, as well as in resistance to cancer therapies. As the bulk of TAMs in established tumors arise from circulating monocytes,

targeting this differentiation process represents an attractive therapeutic strategy. Notably, the cytokines macrophage colony-stimulating factor (M-CSF) and granulocyte-macrophage colony-stimulating factor (GM- CSF) are both associated with TAM differentiation. Nonetheless, M-CSF and GM-CSF can also have distinct

functional effects as they stimulate different receptors and downstream signaling pathways. In recent years, studies in the emerging field of immunometabolism have demonstrated that changes in intracellular metabolism downstream of cytokine activation can actively regulate immune cell differentiation and function. Despite all this,

the differences in TAM-associated functions induced by M-CSF and GM-CSF in differentiated cells and whether early differential metabolic changes in monocytes contribute to these functional differences remain poorly understood. My preliminary data shows that GM-CSF derived macrophages have significantly higher expression

of the TAM markers CD206 and PD-L1 than M-CSF derived macrophages, and that these differences and others are already conspicuous in monocytes after only 7 hours of cytokine stimulation. Interestingly, my preliminary data also shows that GM-CSF, but not M-CSF, results in a transient 7-hour period of prominent glycolytic

oscillations in monocytes. Together, these results indicate that M-CSF and GM-CSF can produce unique effects on monocyte metabolism and TAM marker expression in differentiated cells. Considering previous studies and my preliminary findings, the central hypothesis of this proposal is that M-CSF and GM-CSF derived macrophages

exhibit significant differences in TAM-associated functional characteristics due to early differential metabolic changes in monocytes. I propose to test this hypothesis through the following specific aims: Aim 1: Characterize differences in TAM-associated functional attributes and their regulation between M-CSF and GM-CSF at early

and end points of differentiation of monocytes into TAM-like cells; Aim 2: Investigate whether differences in early metabolic changes induced by M-CSF and GM-CSF in monocytes contribute to differences in TAM marker expression in differentiated cells. These aims will be achieved through a combination of immunology, cancer

biology, genome-wide profiling, and cell metabolism techniques with human monocytes isolated from healthy

donor peripheral blood and differentiated in in vitro cultures to TAM-like cells. Collectively, the results of this work will advance our understanding of important functional differences between M-CSF and GM-CSF induced TAM- like cells and potentially reveal novel metabolic mechanisms that control TAM-associated functions, which may

ultimately improve TAM-targeting cancer therapeutics.