{
  "abstract": "Background Immune checkpoint inhibitors (ICIs) have revolutionized melanoma treatment, yet many patients fail to respond. Tumor-infiltrating lymphocytes (TILs), which can recognize and attack cancer cells, often become ineffective when tumor cells express programmed death-ligand (PD-L1) that binds to the programmed cell death protein 1 (PD-1) receptor on the surface of TILs. 1 2 Antibodies targeting PD-1or PD-L1 can block this interaction, restoring immune-mediated tumor killing.3 The goal of this study is to evaluate whether spatial colocalization of PD-1/PD-L1, defined as the overlap of PD-1+ immune cells and PD-L1+ tumor cells in direct proximity, can serve as a predictive biomarker of response to ICIs. We hypothesize that patients who benefit from ICIs will exhibit higher levels of PD-1/PD-L1 spatial colocalization in the tumor microenvironment, indicating immune engagement at the time of treatment.Methods We conducted a retrospective analysis of samples from 111 melanoma patients treated with anti-PD-1 therapy to quantify PD-1/PD-L1 interactions and to assess their association with clinical outcomes. QuPath was used for quantitative immunofluorescence analysis after a staining protocol was performed on two independent retrospective melanoma cohorts on tissue microarrays where all patients have received anti-PD-1 therapy. Visualization included: 1) DAPI staining for cell nuclei, 2) S100b & HMB45, which are common biomarkers for both melanocytes & melanomas, 3) PD-L1, and 4) PD-1. 1 We quantified PD-1/PD-L1 colocalization within the tumor compartment by calculating the normalized pixel area overlap between these targets and correlated with PFS (progression-free survival). We identified the optimal cut-point in the training sets derived from a 15-fold cross-validation and validated it in the corresponding testing set.Results In a 15-fold cross-validation, a best cut-point of 3734 px/mm 2 demonstrated better response associated with higher pixel overlap in the training set, with p = 6.3e-07 and an average hazard ratio (HR) of 0.76 ± 0.098 for the 15 sets, as well as the testing set, where p = 0.037 and the HR average for the sets = 0.83 ± 0.32. Figure 1 displays the PFS curve of a fold from the testing set for which the best cut-point yielded significant results.Conclusions Our findings show that measuring the area of interaction between PD-1 and PD-L1 within the tumor compartment is associated with better PFS. With further validation, this assay may serve as a robust biomarker to identify patients most likely to benefit from ICIs in clinical settings.References Gavrielatou N, et al. Association of PD-1/PD-L1 co-location with immunotherapy outcomes in non-small cell lung cancer. Clin Cancer Res. 2022 Jan 15;28(2):360–7.Waldman AD, Fritz JM, Lenardo MJ. A guide to cancer immunotherapy: from T cell basic science to clinical practice [Internet]. Nat Rev Immunol. 2020;20(11):651–68. Available from: https://www.nature.com/articles/s41577-020-0306-5Liu Y, et al. Immune cell PD-L1 colocalizes with macrophages and is associated with outcome in PD-1 pathway blockade therapy. Clin Cancer Res. 2020 Feb 15;26(4):970–7.Abstract 453 Figure 1Testing set PFS (Low vs High pixel overlap in px/mm2). Kaplan Meier analysis displaying PFS data in the testing set with high overlapping pixel area (red), and low overlapping pixel area (blue) in tumor compartment, as defined by the optimal cut-point of 3734 px/mm2",
  "authors": [
    {
      "affiliations": [
        "Yale University, New Haven, CT, USA"
      ],
      "name": "Parmees Fazeli"
    },
    {
      "affiliations": [
        "NEC Laboratories America, Princeton, NJ, USA",
        "Yale University School of Medicine, Department of Pathology, New Haven, CT, USA",
        "Yale University, Department of Molecular Biophysics and Biochemistry, New Haven, CT, USA"
      ],
      "name": "Jonathan Warrell"
    },
    {
      "affiliations": [
        "Yale University School of Medicine, Department of Pathology, New Haven, CT, USA"
      ],
      "name": "David L Rimm"
    },
    {
      "affiliations": [
        "Yale University School of Medicine, Department of Pathology, New Haven, CT, USA"
      ],
      "name": "Thazin N Aung"
    }
  ],
  "title": "453 Colocalization of PD-1 and PD-L1 in the tumor compartment predicts checkpoint inhibitor response in melanomas",
  "uid": "ae084342-c656-5ee5-ac87-148002652e61"
}