Abstract 917: CD82/KAI1 maintains the dormancy of long-term hematopoietic stem cells through interaction with DARC-expressing macrophages

Hematopoiesis is regulated by crosstalk between long-term repopulating hematopoietic stem cells (LT-HSCs) and supporting niche cells in the bone marrow (BM). Here, we examine the role of CD82/KAI1 (CD82 hereafter) in niche-mediated LT-HSC maintenance. We found that CD82 is expressed predominantly on LT-HSCs and rarely on other hematopoietic stem-progenitor cells (HSPCs). In Cd82 -/- mice, LT-HSCs were selectively lost as they exited from quiescence and differentiated. Mechanistically, CD82-based TGF-b1/Smad3 signaling leads to induction of CDK inhibitors and cell-cycle inhibition. The CD82 binding partner DARC/CD234 is expressed on macrophages and stabilizes CD82 on LT-HSCs, promoting their quiescence. When DARC + BM macrophages were ablated, the level of surface CD82 on LT-HSCs decreased, leading to cell-cycle entry, proliferation, and differentiation. A similar interaction appears to be relevant for human HSPCs. Thus, CD82 is a functional surface marker of LT-HSCs that maintains quiescence through interaction with DARC-expressing macrophages in the BM stem cell niche. Finally, we hope that further development of our study will allow us to improve leukemia treatment by awakening not only “good” stem cells to keep beneficial stem cell functions, but also “bad” stem cells (e.g. cancer stem cells) in order to increase the sensitivity to treatment and avoid relapse. Citation Format: Jae-Il Choi, Jin Hur, Hwan Lee, Pniel Nham, Cheong-Whan Chae, Young-Eun Choi, Taewan Kim, Ga-Young Lee, Sung Hee Baek, Hyo-Soo Kim. CD82/KAI1 maintains the dormancy of long-term hematopoietic stem cells through interaction with DARC-expressing macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 917. doi:10.1158/1538-7445.AM2017-917