Single-cell transcriptomic unveils tumor-mediated reprogramming of neutrophils and their unique vulnerability that...

Neutrophils are protumorigenic and prometastatic in tumor-bearing mice. Comprehensive single-cell RNA sequencing analyses on various tissues of naïve and tumor-bearing MMTV-PyMT (mouse mammary tumor virus-polyoma middle T antigen) mice unraveled a neutrophil reprogramming process and uncovered a strategy to selectively target reprogrammed neutrophils. Transcriptional reprogramming of neutrophils in tumor-bearing mice is initiated in the bone marrow (BM) by granulocyte colony-stimulating factor (G-CSF). Among the seven neutrophil clusters in the BM, the abundance of one cluster is markedly increased whereas another cluster is diminished in tumor-bearing mice. This reprogramming endures across tissue types including blood, tumor microenvironment, and the metastatic niche in the lungs. Thus, in all tissues tested, neutrophils derived from tumor-bearing mice are transcriptionally distinct from those derived from naïve mice. Among the genes that are markedly induced are members of the Ifitm family. We leverage this facet to selectively target reprogrammed neutrophils through treatment with Rapalink-1-an mTOR (mechanistic target of rapamycin) inhibitor-whose intake is greatly enhanced by IFITM proteins. Reprogrammed neutrophils selectively uptake Rapalink-1, which selectively eradicate them in vivo and normalized the neutrophil-to-lymphocyte ratio in tumor-bearing mice without affecting naïve neutrophils. Last, Rapalink-1 inhibited metastasis of a Rapalink-1-resistant tumor. Thus, Rapalink-1 not only could affect the primary tumor but also selectively eliminates tumor-reprogrammed neutrophils to diminish metastasis.