Tumor invasion in draining lymph nodes is associated with Treg accumulation in breast cancer patients.. Tumor invasion in draining lymph nodes is associated with Treg accumulation in breast cancer patients.

Tumor-draining lymph node (TDLN) invasion by metastatic cells in breast cancer correlates with poor prognosis and is associated with local immunosuppression, which can be partly mediated by regulatory T cells (Tregs). Here, we study Tregs from matched tumor-invaded and non-invaded TDLNs, and breast tumors. We observe that Treg frequencies increase with nodal invasion, and express higher levels of co-inhibitory/stimulatory receptors than effector cells. Also, while Tregs show conserved suppressive function in TDLN and tumor, conventional T cells (Tconvs) in TDLNs proliferate and produce Th1-inflammatory cytokines, but are dysfunctional in the tumor. We describe a common transcriptomic signature shared by Tregs from tumors and nodes, including CD80, which is significantly associated with poor patient survival. TCR RNA-sequencing analysis indicates trafficking between TDLNs and tumors and ongoing Tconv/Treg conversion. Overall, TDLN Tregs are functional and express a distinct pattern of druggable co-receptors, highlighting their potential as targets for cancer immunotherapy. Overall design: TCR-β sequencing of sorted CD4+ Tconv (CD4+FOXP3-CD45RA-) and Treg (CD4+FOXP3hiCD45RA-) from breast cancer patients. Tconvs and Tregs were purified and processed from matched non-invaded lymph node (N=5) and invaded lymph node (N=5), as well as tumors when possible (N=3 for Tconvs and N=2 for Tregs).