Modulation of toll-like receptor 4 (TLR4) signaling as a novel strategy for macrophage-based prostate cancer immunotherapy

<p dir="ltr">Prostate cancer remains one of the most prevalent malignancies worldwide, with various treatment modalities available for clinically localized cases, including active surveillance, radical prostatectomy, and radiotherapy. Despite advancements in diagnostic methods such as magnetic resonance imaging (MRI) fusion biopsy, prostate cancer-associated mortality remains high. Immunotherapy has emerged as a promising treatment avenue, with innovative approaches such as immune checkpoint inhibitors, and adoptive cell therapies, including chimeric antigen receptor T (CAR-T) cells. However, the immunosuppressive tumor microenvironment and low genomic complexity of prostate cancer present significant challenges.</p><p dir="ltr">TLR4 plays a critical role in immune regulation, with both agonists and antagonists showing therapeutic potential in vaccine adjuvants and cancer immunotherapy. This study explored the role of novel synthetic TLR4 modulators (FP20 glycosylated agonists and FP7/FP12 antagonists) in modulating macrophage-mediated immune responses and prostate cancer cell fate. Findings from this study demonstrated that glyco-FP20 derivatives activated TLR4/ Myeloid Differentiation Primary-Response Protein 88 (MyD88) and TLR4/TIR-domain-containing adapter-inducing interferon-β (TRIF) signaling pathways in Tohoku Hospital Pediatrics (THP)-1-derived macrophages, leading to M1 macrophage polarization. In addition, these compounds induced proinflammatory cytokine release and promoted gasdermin D-dependent pyroptosis in THP-1 macrophages. Furthermore, results demonstrated that conditioned media from FP20-stimulated M1 macrophages induced a significant reduction in cancer cell viability and cell cycle inhibition in PC-3 prostate cancer cells. Further analysis of cell cycle inhibition demonstrated that this is associated with induction of senescence in PC-3 prostate cancer cells.</p><p dir="ltr">Conversely, TLR4 antagonists FP7 and FP12 exhibited anticancer properties by inhibiting prostate cancer cell viability and cell cycle progression, highlighting their potential to suppress TLR4-driven tumorigenic signaling. The results suggest that FP20 glycosylated derivatives could be developed as immunostimulatory agents for macrophage-based cancer immunotherapy, while FP7 and FP12 offer promising therapeutic strategies to counteract TLR4-mediated tumor progression. Together, these findings provide novel insights into the dual role of TLR4 modulators in prostate cancer treatment, supporting their further investigation as potential immunotherapeutic agents.</p>