PERK+ macrophages drive immunotherapy resistance in lymph node metastases of oral squamous cell carcinoma

Neoadjuvant anti-PD-1 immunotherapy combined with chemotherapy has shown promising pathological responses in various cancers, including oral squamous cell carcinoma (OSCC). However, the pathological response of lymph node (LN) metastases remains poorly understood. This study aims to systematically evaluate the pathological response rates (pRRs) of LN metastases in OSCC patients and identify potential targets to improve therapeutic outcomes. We assessed the pRRs of LN metastases and matched primary tumors (PTs) in OSCC patients enrolled in a randomized, two-arm, phase II clinical trial (NCT04649476). Single-cell and spatial transcriptomics and multiplex immunohistochemistry were performed to analyze the tumor microenvironment and identify potential therapeutic targets in LN metastases. A neoadjuvant orthotopic OSCC mouse model was established to evaluate the therapeutic potential of these targets. We observed significant heterogeneity in pathological regression of LN metastases, with lower pRRs compared to PTs. pRRs in LN metastases were correlated with overall and disease-free survival in OSCC patients. We identified an abundance of macrophages in LN metastases exhibiting an unfolded protein response and activated PERK signaling. These macrophages contributed to an extracellular matrix-enriched microenvironment through interactions with fibroblasts, which hindered T cell-mediated cytotoxicity. Pharmacological inhibition of the PERK pathway significantly enhanced anti-PD-1 therapy in LN metastases and PTs in the mouse model. Our study confirms that the pathological response of LN metastases in OSCC patients undergoing neoadjuvant immunotherapy or immunochemotherapy is inferior to that of PTs. It suggests targeting the PERK pathway in macrophages could be a potential strategy to enhance treatment outcomes.