High dimensional analysis of immune signatures in melanoma patients

Checkpoint inhibitor therapy (CIT) has revolutionized cancer therapy. Notably, inhibition of programmed cell death protein 1 (PD-1) showed benefit in the treatment of metastatic melanoma and has even been promoted to first line therapy in advanced melanoma. Despite an increase in overall survival a minority of patients profits from CIT with anti-PD-1. Therefore, immune components or markers predicting responsiveness are urgently needed. Using phenotypic and functional markers we used high-dimensional single cell cytometry by time of flight (CyTOF), to measure blood samples from anti-PD-1 treated patients before and during therapy. CyTOF uses metal-tagged instead of fluorochrome-tagged antibodies, thus eliminating spectral overlap and, in combination with barcoding, enables the measurement of more than 30 parameters on a single cell in multiple samples in parallel. Due to the complexity of the data set and in order to reduce analytical bias we adapted a custom bioinformatic workflow. Using this approach we find immune signatures which allow us to separate responders from non-responders and might provide insights into the biology of immune therapy.