Abstract: Objective To investigate the effect of ginseng-derived compound K (C-K) on apoptosis, immunosuppressive activity,
and pro-inflammatory cytokine production of myeloid-derived suppressor cells (MDSCs) from mice bearing colorectal cancer
xenograft. Methods Flow-sorted bone marrow MDSCs from Balb/c mice bearing CT26 tumor xenograft were treated with
either C-K or PBS for 96 h and examined for apoptosis with Annexin V/7-AAD, Cox-2 and Arg-1 expressions using qRT-PCR,
and supernatant IL-1β, IL-6, and IL-17 levels with ELISA. C-K- or PBS-treated MDSCs were subcutaneously implanted along
with CT26 tumor cells in WT Balb/c mice, and the tumor size and morphology were evaluated 21 days later. Results C-K
treatment significantly increased the percentages of early and late apoptotic MDSCs in vitro (P<0.01 and P<0.05, respectively),
decreased the expressions of immunosuppression-related genes Cox-2 (P<0.05) and Arg-1 (P<0.01), and suppressed the
production of IL-1β (P<0.05), IL-6 (P<0.01), and IL-17 (P<0.05) by the MDSCs . Compared with PBS-pre-treated cells,
C-K-pretreated MDSCs showed significantly attenuated activity in promoting CT26 tumor growth in mice (P<0.01).
Conclusion C-K can suppress the immunosuppresive effect of MDSCs to inhibit tumor cell proliferation in mice, which
suggests a new strategy of tumor therapy by targeting MDSCs.