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PD-L1 (Programmed Death-Ligand 1), also known as CD274, is a 40 kDa type 1 transmembrane protein that has been speculated to play a major role in suppressing the immune system. Binding of PD-L1 to its ligand PD-1, which is expressed by various immune cell types including T cells, transmits an inhibitory signal that attenuates T cell function, expansion, and survival. Many tumors types can express PD-L1, including breast, ovarian, gastric, pancreatic, lung and renal cell carcinomas, and classical Hodgkin lymphoma. PD-L1 expression by tumor cells is thought to inhibit the local immune response to the tumor, at least in part by binding to T cell PD-1 and protecting the tumor from T-cell mediated immunity. Blockade of the PD-1/PD-L1 axis by humanized monoclonal antibodies against PD-1 and PD-L1 has emerged as a promising new cancer therapy. The anti-PD-1 antibodies nivolumab and pembrolizumab have received FDA approval for treating metastatic squamous NSCLC and metastatic melanoma, respectively. Expression of PD-L1 by tumors may predict response to these drugs. The main clinical indication for PD-L1 IHC is expected to be assessment of PD-L1 expression on tumor cells prior to the initiation of therapy targeting the PD-1 / PD-L1 axis. However, unforeseen clinical indications cannot be excluded. Subcellular Localization: membranous and cytoplasmic
Disease State: Melanoma
CPT Code(s): 88360 (reference only; CPTs may vary)
Turnaround Time: Within 1-2 business days of receipt
Schedule: Monday - Friday
• Formalin-fixed, paraffin-embedded (FFPE) tissue block or cell block - OR - • 1 unstained slide for each test requested plus 3-4 additional unstained slides cut at 4µm