MRC1 and malignant peripheral nerve sheath tumor: Since IL-6 overproduction in NF1-deficient models is mostly associated with increased infiltration and activation of myeloid-derived suppressor cells (MDSCs) [22], and previous observations that MSU-42011 reduced expression of CD206 tumor-promoting macrophage marker (Figure 1C) [29,30], we analyzed the levels of CD206 in MPNST flank tumors by IHC staining.