PD-L1 importance in malignancies comprehensive insights into the role of PD-L1 in malignancies: from molecular mechanisms to therapeutic opportunities

The phenomenon of upregulated programmed death-ligand 1 (PD-L1) expression is common in numerous human malignancies. The overexpression of PD-L1 significantly contributes to immune evasion because its interaction with the PD-1 receptor on activated T lymphocytes impairs anti-tumour immunity by neutralizing T cell stimulatory signals. Furthermore, beyond its immunological interface, PD-L1 possesses intrinsic capabilities that directly modulate oncogenic processes, fostering cancer cell proliferation and survival. This dual function of PD-L1 challenges the efficacy of immune checkpoint inhibitors and highlights its possible application as a direct target for therapy. Recent discoveries concerning the cancer cell-intrinsic signalling pathways of PD-L1 have significantly enhanced our understanding of the pathological implications linked to its tumour-specific expression. These entail the orchestration of tumour proliferation and viability, maintenance of cancer stem cell-like phenotypes, modulation of immune responses, as well as impacts on DNA repair mechanisms and transcriptional regulation. This review aims to deliver an exhaustive synthesis of PD-L1's molecular underpinnings alongside its clinical implications in a spectrum of cancers, spanning both solid neoplasms and haematological disorders. It underscores the necessity for an integrated understanding of PD-L1 in further refining therapeutic strategies and improving patient outcomes.