Autophagy-Mediated Antitumor Effects of BCG and Imiquimod in Oral Squamous Cell Carcinoma

Abstract Autophagy and Toll-like receptor (TLR) signaling are both implicated in cancer progression, but whether they act as tumor suppressors or promoters remains unclear. To explore this relationship, we investigated the role of autophagy downstream of therapeutic TLR activation in oral squamous cell carcinoma (OSCC). Using the FDA- approved TLR agonists Bacillus Calmette-Guérin (TLR2/4) and imiquimod (TLR7), we assessed their effects in vitro on SCC-4 cells and in vivo in a chemically induced OSCC hamster model. Both agents, alone or in combination with each other or with Monophosphoryl Lipid-A induced robust autophagy, as measured by LC3B staining in vitro and flow cytometry in vivo. Autophagy induction correlated with reduced tumor volume and prolonged survival, with outcomes comparable to cisplatin, the current standard chemotherapeutic, but with less treatment-associated morbidity and mortality. Autophagy was also associated with cisplatin antitumor effects. Notably, imiquimod produced the most pronounced and sustained autophagic and antitumor effects. To our knowledge, this is the first study to directly link the therapeutic efficacy of TLR agonists in OSCC to autophagy modulation, providing both mechanistic and translational insights into their potential as immunotherapeutic agents.