Transcriptomic signatures designed to predict melanoma patient responses to PD-1 blockade have been reported but rarely validated.,We now show that intra-patient heterogeneity of tumor responses to PD-1 inhibition limit the predictive performance of these signatures.,We reasoned that resistance mechanisms will reflect the tumor microenvironment, and thus we examined PD-1 inhibitor resistance relative to T-cell activity in 94 melanoma tumors collected at baseline and at time of PD-1 inhibitor progression.,Tumors were analyzed using RNA sequencing and flow cytometry, and validated functionally.,These analyses confirm that major histocompatibility complex (MHC) class I downregulation is a hallmark of resistance to PD-1 inhibitors and is associated with the MITFlow/AXLhigh de-differentiated phenotype and cancer-associated fibroblast signatures.,We demonstrate that TGFß drives the treatment resistant phenotype (MITFlow/AXLhigh) and contributes to MHC class I downregulation in melanoma.,Combinations of anti-PD-1 with drugs that target the TGFß signaling pathway and/or which reverse melanoma de-differentiation may be effective future therapeutic strategies.,A significant proportion of patients develop innate or acquired resistance to immune checkpoint inhibitors.,Here, the authors show that resistance to anti-PD-1 blockade is associated with TGF-beta driven major histocompatibility complex I (MHCI) down-regulation and a de-differentiated phenotype in melanoma patients.
Treatment with programmed death receptor-1 (PD-1) antibodies is associated with high response rates in patients with advanced melanoma.,Reliable markers for early response and outcome are still sparse.,We evaluated 66 consecutive patients with advanced/metastatic melanoma treated with nivolumab or pembrolizumab between 2013 and 2014.,The main objectives of this study were to investigate whether, first, serum lactate dehydrogenase (LDH) at baseline (normal vs above the upper limit of normal) correlates with overall survival (OS), and, second, whether the change of LDH during treatment predicts response before the first scan and OS in patients with an elevated baseline LDH.,After a median follow-up of 9 months, patients with an elevated baseline LDH (N=34) had a significantly shorter OS compared with patients with normal LDH (N=32; 6-month OS: 60.8% vs 81.6% and 12-month OS: 44.2% vs 71.5% (log-rank P=0.0292).,In those 34 patients with elevated baseline LDH, the relative change during treatment was significantly associated with an objective response on the first scan: the 11 (32%) patients with partial remission had a mean reduction of −27.3% from elevated baseline LDH.,In contrast, patients with progressive disease (N=15) had a mean increase of +39%.,Patients with a relative increase over 10% from elevated baseline LDH had a significantly shorter OS compared with patients with ⩽10% change (4.3 vs 15.7 months, log-rank P<0.00623).,LDH could be a useful marker at baseline and during treatment to predict early response or progression in patients with advanced melanoma who receive anti-PD-1 therapy.