PDCD1 and melanoma: In melanoma patients, baseline CD8+ levels within the tumor are associated with response to PD-1 therapy, whereas with the anti-CTLA-4 agent ipilimumab, response is better correlated with post-treatment increases in tumor-infiltrating lymphocytes (TILs) rather than baseline levels.11–13 This is to say, an inflamed tumor phenotype can promote response, but treatment-induced modulation of a less immunogenic tumor may yield similar results, highlighting opportunities for therapeutic intervention.