Influence of head and neck cancer exosomes on macrophage polarization.

BACKGROUND

Tumor cells within the tumor microenvironment (TME) release exosomes that influence macrophage phenotypes, either pro-tumorigenic or anti-tumorigenic. This mechanism, especially in head and neck squamous cell carcinoma (HNSCC), remains poorly understood. This study investigates the role of HNSCC exosomes in macrophage polarization.

METHODOLOGY

Exosomes were isolated from HPV16-positive (93VU147T, UDSCC2) and HPV-negative (OCT1) HNSCC cell lines. These exosomes were characterized for their potential to modulate macrophage polarization. Uptake of PKH-26 labeled exosomes by macrophages was monitored via confocal microscopy. Changes in macrophage polarization were assessed using quantitative real-time PCR and immunoblotting. Exosomal transcripts and proteome cargo was examined for polarization associated mediators.

RESULTS

HPV-negative exosomes showed higher uptake by THP1 resting macrophages (M0). Exosomes from HPV-positive cells induced a mixed macrophage phenotype (M1 and M2), whereas HPV-negative exosomes favored M1 polarization. Immunoblotting analysis revealed that this polarization was driven by the activation of transcription factors STAT1, NF-κB, and AP1. Transcriptomic analysis of HNSCC exosomes revealed reads for AP1 (c-Jun, c-Fos, FosB, Fra1, Fra2) and NF-κB (p50/105, p52/100, RelA, RelB, c-Rel), along with their known upstream mediators MEK1--7, JNK1-3, JAK1-3, TYK2, IKKα, and IKKβ. Splice variants of macrophage polarization markers, including iNOS and TGFβ, were also identified, though none of the exosomal proteome component corresponded to these factors.

CONCLUSION

HPV-negative exosomes are efficiently internalized by macrophages, promoting M1 polarization likely via modulation of STAT1, NF-κB, and AP1 signaling. These findings provide novel insights into role of tumor exosomes in modulation of macrophage-mediated TME dynamics in HNSCC.