CD16+NKG2Ahigh Natural Killer cells infiltrate breast cancer draining lymph nodes

Abstract

Tumor-draining lymph nodes (TD-LNs) are the first site of metastasis of breast cancer (BC). Natural killer (NK) cells that infiltrate TD-LNs (including non-invaded (NI) or metastatic (M)-LNs from BC patients) and NK cells from healthy donor (HD)-LN were characterized, and their phenotype analyzed by flow cytometry. Low percentages of tumor cells invaded M-LNs, and these cells expressed ULBP2 and HLA class I molecules. Although NK cells from paired NI and M-LNs were similar, they expressed different markers compared to HD-LN NK cells. Compared to HD-LNs, TD-LN NK cells expressed activating DNAM-1, NKG2C and inhibitory NKG2A receptors, and exhibited elevated CXCR3 expression. CD16, NKG2A, and NKp46 expression were shown to be increased in stage IIIA BC patients. TD-LNs contained a large proportion of activated CD56brightCD16+ NK cells with high expression of NKG2A. We also showed that a subset of LN NK cells expressed PD-1, expression of which was correlated with NKp30 and NKG2C expression. LN NK cell activation status was evaluated by degranulation potential and lytic capacity towards BC cells. NK cells from TD-LNs degranulated after coculture with BC cell lines. Cytokine-activated TD-LN NK cells exerted greater lysis of BC cell lines than HD-LN NK cells and preferentially lysed the HLA class Ilow MCF-7 BC cell line. TD-LNs from BC patients, thus, contained activated lytic NK cells. The expression of inhibitory receptor NKG2A and checkpoint PD-1 by NK cells infiltrating BC-draining LNs supports their potential as targets for immunotherapies using anti-NKG2A and/or anti-PD-1.