Myeloid‑derived suppressor cell accumulation induces Treg expansion and modulates lung malignancy progression
Yinghua Wan, Xiangdong Mu, Jingquan Zhao, Li Li, Wenshuai Xu, Mingqiang Zhang
Abstract
Myeloid‑derived suppressor cells (MDSCs) are a heterogeneous family of myeloid cells that suppress T cell immunity in tumor‑bearing hosts. The present study aimed to examine roles of T and MDSC subsets in lung malignancy. The study analyzed 102 cases with lung malignancy and 34 healthy individuals. Flow cytometry was performed for identification of T cell and MDSC subsets and their phenotypic characteristics in peripheral blood. The lung malignancy cases exhibited lower frequencies of granulocyte‑like MDSCs (G‑MDSCs) expressing PD‑L2 and PD‑L1 than healthy controls (P=0.013 and P<0.001, respectively). Additionally, there was a higher frequency of monocyte‑like MDSCs (M‑MDSCs) expressing PD‑L1 in the peripheral blood of patients with lung malignancy than healthy controls (P<0.001). The frequencies of G‑MDSCs and M‑MDSCs were positively correlated with proportions of PD‑1<sup>+</sup> and CTLA‑4<sup>+</sup> regulatory T cells (Tregs). <em>In</em> <em>vitro</em> co‑culture assay demonstrated M‑MDSCs of lung malignancy enhanced naive T cell apoptosis and promoted Treg subset differentiation compared with M‑MDSCs of healthy controls. The findings suggested accumulation of MDSC subsets in lung malignancy and MDSCs expressing PD‑L2 and PD‑L1 induced Treg expansion by binding to PD‑1 on the surface of Tregs.