Background
Extensive attention has been given to the role of myeloid-derived suppressor cells (MDSCs) in driving tumor progression and treatment failure. Preclinical studies have identified multiple agents that eliminate MDSCs. However, none have been authorized in the cliniccal ues due to the safety reasons. In the present study, we investigated the efficacy and mechanism of sulforaphane (SFN) to eliminate MDSCs in the tumor microenvironment (TME).
Methods
We monitored SFN effect on tumor growth and the percents or apoptosis of immune cell subsets in mice models bearing LLC or B16 cells. Flow cytometry, quantitative reverse transcription-PCR, immunohistochemistry, ELISA, immunofluorescence, imaging flow cytometry and western blot were performed to validate the role of SFN on MDSCs function in vivo and in vitro. RNA sequencing was then used to interrogate the mechanisms of how SFN regulated MDSCs function. Tumor xenograft models were established to evaluate the involvement of IL-12RB2/MMP3/FasL induced MDSCs apoptosis in vivo. We verified the effect of SFN on MDSCs and CD8+ T cells in the blood samples from a phase I clinical trial (KY-2021–0350).
Results
In this study, we elucidated that SFN liberated CD8+ T-cell antitumor ability by reducing MDSCs abundance, leading to repressed tumor growth. SFN treatment suppressed MDSCs accumulation in the peripheral blood and tumor sites of mice, but had no effect on the bone marrow. Mechanistically, SFN activates IL-12RB2, which stimulates the MMP3/FasL signaling cascade to trigger caspase 3 cleavage and induce apoptosis in MDSCs. Clinically, SFN treatment eliminates peripheral MDSCs and increases the percentage and activation of CD8+ T cells.
Conclusions
Collectively, we uncovered the role of SFN in eliminating MDSCs to emancipate CD8+ T cells through IL-12RB2/MMP3/FasL induced apoptosis, thus providing a strategy for targeting MDSCs to control tumors and improve clinical efficacy.