Human Anti-Mouse Rae-1α/ beta /γ monoclonal Antibody, clone SFB689 [Biotin]

A major factor impeding the success of numerous therapeutic approaches in cancer is the immunosuppressive nature of the tumor microenvironment (TME). Hence, methods capable of reverting tumor immunosuppression through depletion or reprogramming of myeloid-derived suppressive cells (MDSCs) and regulatory T cells (Tregs) are of great clinical need. Here, we explore NKG2D-Fc as a modality to modulate antitumor immunity through the depletion of immunosuppressive MDSCs and Tregs in the TME. We have generated the NKG2D-Fc fusion protein and characterized its potential to mediate tumor control and overall survival in LL2 and MC38 murine models. Upon treatment of LL2 or MC38 tumor-bearing mice with NKG2D-Fc, we observe significant tumor control and enhanced survival compared to Fc control. When characterizing MDCSs and Tregs from tumor-bearing mice, we observe clear expression of NKG2D-ligand RAE1 gamma and subsequent binding of NKG2D-Fc fusion protein to both MDSCs and Tregs. Examining the immune profile of mice treated with NKG2D-Fc reveals significant depletion of MDSCs and Tregs in the TME, as well as an increase in NK cells likely due to the reversed suppressive TME. In conclusion, NKG2D-Fc induces antitumor immunity and tumor control through the depletion of MDSCs and Tregs, subsequently providing a niche for the infiltration and expansion of proinflammatory cells, such as NK cells. Strategies capable of modulating the immunosuppressive state in cancer are in high clinical demand. NKG2D-Fc is a simple, single tool capable of depleting both MDSCs and Tregs and should be further investigated as a therapeutic agent for the treatment of cancer.

In neuroblastoma cells, retinoic acid induces cell cycle arrest and differentiation through degradation of the F-box protein, Skp2, and stabilization of cyclin-dependent kinase inhibitor, p27. However, the mechanism responsible for retinoic acid-mediated Skp2 destabilization is unknown. Since Skp2 is degraded by anaphase-promoting complex (APC)(Cdh1), here we studied whether retinoic acid promotes differentiation of human SH-SY5Y neuroblastoma cells by modulating Cdh1. We found that retinoic acid induced the nuclear accumulation of Cdh1 that paralleled Skp2 destabilization and p27 accumulation. The mRNA and protein abundance of Rae1-a nuclear export factor that limits APC(Cdh1) activity in mitosis decreased upon retinoic acid-induced inhibition of neuroblastoma cell proliferation. Furthermore, either Rae1 overexpression or Cdh1 inhibition promoted Skp2 accumulation, p27 destabilization and prevented retinoic acid-induced cell cycle arrest and differentiation. Conversely, inhibition of Rae1 accelerated retinoic acid-induced differentiation. Thus, retinoic acid downregulates Rae1, hence facilitating APC(Cdh1)-mediated Skp2 degradation leading to the arrest of cell cycle progression and neuroblastoma differentiation.