Programmed Death-Ligand 1 (PD-L1) is an immune checkpoint molecule expressed on antigen-presenting cells and various cancer cells, critically involved in modulating T-cell-mediated immune responses. Its interaction with programmed cell death protein 1 (PD-1) on activated T cells delivers inhibitory signals that suppress cytotoxic activity and promote immune tolerance-a mechanism exploited by malignancies to evade immune surveillance. Elevated PD-L1 expression has been documented across multiple tumor types including non-small cell lung carcinoma, melanoma, and gastrointestinal cancers, correlating with advanced disease progression and poorer prognostic outcomes.
VEGFA (Vascular endothelial growth factor A), also known as VPF, VEGF or MVCD1, is the most potent growth factor for endothelial cells and belongs to the PDGF/VEGF growth factor family. In humans, it is encoded by the VEGFA gene localizing at the chromosome 6p21.1. VEGF-A, as well as VEGF-C, and -D are found in the lung. During the embryonic and pseudoglandular stages, it is expressed in epithelial and mesenchymal compartments, then becoming more restricted to the epithelium as development process. VEGFA encodes a heparin-binding protein existing as a disulfide-linked homodimer. This growth factor is involved in inducing proliferation and migration of vascular endothelial cells. It is essential for physiological and pathological angiogenesis and considered as a powerful vascular permeability-enhancing agent.