Mouse anti-IL6 Monoclonal antibody, clone DD421

Although thousands of breast cancer cells disseminate and home to bone marrow until primary surgery, usually less than a handful will succeed in establishing manifest metastases months to years later. To identify signals that support survival or outgrowth in patients, we profile rare bone marrow-derived disseminated cancer cells (DCCs) long before manifestation of metastasis and identify IL6/PI3K-signaling as candidate pathway for DCC activation. Surprisingly, and similar to mammary epithelial cells, DCCs lack membranous IL6 receptor expression and mechanistic dissection reveals IL6 trans-signaling to regulate a stem-like state of mammary epithelial cells via gp130. Responsiveness to IL6 trans-signals is found to be niche-dependent as bone marrow stromal and endosteal cells down-regulate gp130 in premalignant mammary epithelial cells as opposed to vascular niche cells. PIK3CA activation renders cells independent from IL6 trans-signaling. Consistent with a bottleneck function of microenvironmental DCC control, we find PIK3CA mutations highly associated with late-stage metastatic cells while being extremely rare in early DCCs. Our data suggest that the initial steps of metastasis formation are often not cancer cell-autonomous, but also depend on microenvironmental signals. Metastatic dissemination in breast cancer patients occurs early in malignant transformation, raising questions about how disseminated cancer cells (DCC) progress at distant sites. Here, the authors show that DCCs in bone marrow are activated via IL6-trans-signaling and thereby acquire stemness traits relevant for metastasis formation.

Neutrophils with immunosuppressive activity are polymorphonuclear myeloid-derived suppressor cells (MDSCs) and may contribute to the resistance to cancer immunotherapy. A major gap for understanding and targeting these cells is the paucity of cell line models with cardinal features of human immunosuppressive neutrophils and their normal counterparts, especially in an isogenic manner. To address this issue, we employ the human promyelocytic cell line HL60 and use DMSO and cytokines (granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin 6 (IL6)) to induce the formation of either neutrophils or MDSCs. The induced MDSCs are CD11b(+) CD33(+) HLA-DR-/low and are heterogeneous for CD15 and CD14 expression. The induced MDSCs abrogate IL2 production and activation-induced cell death of the human T cell line Jurkat stimulated by CD3/CD28 antibodies, whereas the induced neutrophils enhance IL2 production from Jurkat cells. The induced MDSCs upregulate the expression of C/EBP beta, STAT3, VEGFR1, FATP2 and S100A8. Lastly, the immunosuppressive activity of the induced MDSCs is inhibited by all-trans retinoic acid and STAT3 inhibitor BP-1-102 through cellular differentiation and dedifferentiation mechanisms, respectively. Together, our study establishes a human isogenic cell line system for neutrophils and MDSCs and this system is expected to facilitate future studies on the biology and therapeutics of human immunosuppressive neutrophils.