Advances on tumor-associated tertiary lymphoid structures in immunotherapy

Tertiary lymphoid structures (TLS) are ectopic lymphoid structures found in non-lymphoid tissues under chronic inflammatory conditions in recent years. Similar to lymph nodes, TLS primarily consist of B lymphocytes, T lymphocytes, and dendritic cells. TLS are also the direct sites where antitumor immune responses are initiated. Within tumors, TLS promote the aggregation of immune cells, particularly effector T cells and B cells, to the tumor microenvironment, providing an important local site for cellular and humoral antitumor immune responses. This underscores their potential to predict favorable patient prognosis and positive responses to immune therapies. This review provides an overview of assessing and characterizing tumor-associated TLS, detailing their structural elements, composition, and the factors driving their formation. Furthermore, it explores TLS as promising biomarkers in tumor immunotherapy and their prospective clinical applications. The review also addresses the challenges and future prospects of TLS in the context of tumor immunotherapy.