Introduction:

Tumor microenvironment (TME) remodeling is one of the major research subjects in oncology. Several strategies can be implemented to modulate the tumor microenvironment, particularly in reprogramming myeloid cells to stimulate their anti-cancer activities. Indeed, myeloid cells constitute the major component of TME. Hence, it is important to identify the molecular signatures associated to cancer-promoting myeloid cells. Here, we defined the phenotype and proteome of tumor associated myeloid cells. Moreover, we identified the relationships between myeloid-derived suppressor cells (MDSCs) and tumor associated macrophages (TAM). The proteomic atlas of tumor-associated cells revealed important routes to reprogram cancer-associated myeloid cells.

Methods:

We used an ex vivo differentiation system for MDSCs and TAM by from C57BL/6J mouse bone marrow cells in cancer-polarized conditioning medium (1). Three global experiments of quantitative mass spectrometry (shotgun proteomics) were performed. Construction of functional interactomes maps from up- or down-regulated proteins was conducted with the Ingenuity Pathway Analysis (IPA) Tool from Quiagen. Targeted proteins were evaluated using western blot. We evaluated the effect at differentiation, maturation and immunosuppressive level in MDSCs and TAMs of several compounds. Markers were evaluated by cytometry and western blot.

Results:

We confirmed morphological and phenotypic differences in ex vivo differentiated myeloid populations. High-throughput proteomics uncovered protein expression patterns characteristic of populations modelling tumor-infiltrating subsets, as a result of cancer-derived factors.

Therefore, we evaluated several compounds for reprogramming tumor-associated cells. A resemblance to activated myeloid cells and a greater rise of macrophages and DC were observed. In addition, changes in cytokine secretion were detected. Moreover, the immunosuppressive functions of MDSCs decreased which led to enhanced CD4 cells proliferation and increased CD4 ability to release more IFN-gamma and IL2.

Conclusions:

In the present study, we identified differences in proteomic signatures between MDSCs and TAMs related to lineage, and cancer-driven polarization. Moreover, these result permit us develop strategies to reprogram myeloid cells cancer associated.