PTDSS2 and neoplasm: We detected a dramatic increase in both monocytic MDSC (CD11b+Ly6C+) and PMN-MDSC (CD11b+Ly6G+) subpopulations in the sgATP11b-545 tumors compared with the 545 control tumors, and these populations were increased further in tumors expressing sgATP11b/OE-Ptdss2, whereas these populations were dramatically reduced when the tumor cells simultaneously harbored both sgATP11b and sgPtdss2 mutants (Figure 7, C and D), suggesting that increased PS induced by sgATP11b can cause the accumulation of MDSCs in mammary tissues and inhibit the actions of effector cells in the adaptive immune system.