Two of the earliest publications to use CyTOF to characterize melanoma patient samples utilized the Helios platform to characterize peripheral blood mononuclear cells (PBMCs) or immune profiles of tumor biopsies from patients treated with anti-PD-1 monotherapy, or combined anti-PD-1 and anti-CTLA-4 [62, 63]. The gene discussed is CTLA4; the disease is melanoma.