Interferon-stimulated neutrophils identified in preclinical models may serve as a potential biomarker for immunotherapy response in human
Despite the remarkable success of immunotherapy, only ~20-30% of cancer patients display an extended durable response. Pre-existing biomarkers for immunotherapy outcome are significantly limited in their predictive power. While mice are the most widely used and cost-effective model to study human disease, translating preclinical biomarkers into clinical practice faces significant obstacles – in part due to the lack of diverse or appropriate models. Here, to improve translatability and identify novel biomarkers, we showcase an approach encompassing several  pre-clinical models - each capturing one possible mechanistic aspect of immunotherapy response, such as tumor- and host-dependency, in order to reflect the variability seen in human cancers. Using this approach, we identify interferon-stimulated, Ly6Ehi neutrophils as a pre-treatment, blood-borne biomarker for anti-PD1 response in mice. We subsequently validate this result in cohorts of immunotherapy-treated non-small cell lung cancer (NSCLC) and melanoma patients, where the abundance of Ly6Ehi neutrophils predicts anti-PD1 response and further validated these results using available datasets for other cancers. Moreover, we demonstrate that these cells sensitize otherwise resistant tumors to anti-PD1 therapy, in part by directly activating cytotoxic T cells and contributing to tumor cell killing, while operate upstream of T cells in the immunotherapy response. Collectively, our study identifies a new and functionally active biomarker to predict immunotherapy outcome with potential clinical relevance. Overall design: GR1+ myeloid cells were isolated from non-responding or responding 4T1, breast carcinoma murine tumors (5 mice pooled per sample) using magnetic beads and analyzed using scRNAseq.