SELL and cancer: Accordingly, two independent but complementary mechanisms are proposed to reduce LN trafficking in cancer: (1) MDSC-directed downregulation of lymphocyte L-selectin which we showed negatively impacts homing in HEV, and (2) elevated circulating sL-selectin which, at the concentrations detected in tumor-bearing mice (1 μg/mL in tumor-bearing mice compared to ~0.4 μg/mL in tumor-free controls), reportedly functions as a competitive antagonist of L-selectin-directed lymphocyte homing in vivo.