MSR1 and neoplasm: Shp2f/fLysMCre MDSCs also exhibited lower expression of Msr1, which promotes neutrophil netosis, a protumorigenic process, and Xbp1, a classical marker of the unfolded protein response, which polarizes tumor-infiltrating myeloid cells to highly immunosuppressive MDSC20 (Fig. 4i,j and Supplementary Table 1).