Toll-like receptors: versatile players in tumor

Toll-like receptors (TLRs) are a class of pattern-recognition receptors first identified for their role in detecting microbial pathogens and initiating innate immune responses. Beyond pathogen defense, TLRs serve as crucial mediators connecting innate and adaptive immunity and contribute to processes such as tissue repair and remodeling. Owing to their functional versatility, TLRs are involved in multiple stages of tumor progression, presenting both anti- and pro-tumor effect. Here we review the functions of TLRs in physiologic activities, as well as their roles in tumor biology including tumorigenesis, tumor progression, tumor microenvironment, treatment sensitivity, tumor recurrence and patient prognosis. TLRs function as a context-dependent interface where host homeostasis and tumor subversion compete; the additive, synergistic, or antagonistic integration of their signals ultimately determines whether the balance tips toward tumor suppression or progression.