MicroRNA-155 governs SHIP-1 expression and localization in NK cells and regulates subsequent infiltration into murine AT3 mammary carcinoma.

Wendy M Kandell,William A Adams,Jinhong Liu,Nhan Tu,Julie Y Djeu,Tina So,Erika A Eksioglu,Sarah S Donatelli,Yin-Kai Chen,Xianghong Chen,Thu Le Trinh,Danielle L Gilvary,Pingyan Cheng,Alexandra R Calescibetta,Sheng Wei,Fabrizio Mattei

doi:10.1371/journal.pone.0225820

Wendy M Kandell, William A Adams + Show 14 more

Open Access

https://doi.org/10.1371/journal.pone.0225820

Copy DOI

Abstract

NK cell migration and activation are crucial elements of tumor immune surveillance. In mammary carcinomas, the number and function of NK cells is diminished, despite being positively associated with clinical outcome. MicroRNA-155 (miR-155) has been shown to be an important regulator of NK cell activation through its interaction with SHIP-1 downstream of inhibitory NK receptor signaling, but has not been explored in regard to NK cell migration. Here, we explored the migratory potential and function of NK cells in subcutaneous AT3 in mice lacking miR-155. Without tumor, these bic/miR-155-/- mice possess similar numbers of NK cells that exhibit comparable surface levels of cytotoxic receptors as NK cells from wild-type (WT) mice. Isolated miR-155-/- NK cells also exhibit equivalent cytotoxicity towards tumor targets in vitro compared to isolated WT control NK cells, despite overexpression of known miR-155 gene targets. NK cells isolated from miR-155-/- mice exhibit impaired F-actin polymerization and migratory capacity in Boyden-chamber assays in response chemokine (C-C motif) ligand 2 (CCL2). This migratory capacity could be normalized in the presence of SHIP-1 inhibitors. Of note, miR-155-/- mice challenged with mammary carcinomas exhibited heightened tumor burden which correlated with a lower number of tumor-infiltrating NK1.1+ cells. Our results support a novel, physiological role for SHIP-1 in the control of NK cell tumor trafficking, and implicate miR-155 in the regulation of NK cell chemotaxis, in the context of mammary carcinoma. This may implicate dysfunctional NK cells in the lack of tumor clearance in mice.

Highlights

Natural Killer (NK) cells are a subset of lymphocytes that produce pro-inflammatory cytokines such as IFNγ and perforin, and kill target cells through an array of germline encoded receptors
While previous studies have shown that CCL2 is required for NK cell-mediated clearance of viral infections [10], information about NK cell chemotaxis in the context of breast tumor challenge is limited compared to T cell trafficking in the disease, and NK trafficking in other tumor types such as colon [11]
Our results were similar to the findings cited, whereby the percentage of splenic NK cells was equivalent in miR-155-/- and WT mice, as assessed by NK1.1/DX5 co-expression [1] (S1A and S1B Fig), suggesting that miR-155 does not play a role in NK cell development or homeostasis

Summary

Introduction

Natural Killer (NK) cells are a subset of lymphocytes that produce pro-inflammatory cytokines such as IFNγ and perforin, and kill target cells through an array of germline encoded receptors. NK cell activation is a finely tuned balance between positive (activating) and negative (inhibitory) signals Ligands for these activating receptors are found on malignant or virally infected cells, which frequently downregulate MHC [1]. A robust NK cell response in cancer patients correlates with a positive prognosis [2, 3], and these clinical data translate to animal studies showing that NK cell depletion or inactivation increases tumor burden and worsens prognosis [4, 5]. This highlights the important role of NK cells in anti-tumoral defense. While previous studies have shown that CCL2 is required for NK cell-mediated clearance of viral infections [10], information about NK cell chemotaxis in the context of breast tumor challenge is limited compared to T cell trafficking in the disease, and NK trafficking in other tumor types such as colon [11]

Methods

Results

Conclusion