OXTRHigh stroma fibroblasts control the invasion pattern of oral squamous cell carcinoma via ERK5 signaling

Worst pattern of invasion (WPOI) is a parameter used to quantify tumor invasiveness of oral squamous cell carcinoma (OSCC). Here the authors show that a fibroblast subset characterized by the expression of the oxytocin receptor is enriched in highly invasive WPOI 4-5 OSCC tumors and can be targeted to reduce the desmoplastic stroma and tumor metastasis. The Pattern Of Invasion (POI) of tumor cells into adjacent normal tissues clinically predicts postoperative tumor metastasis/recurrence of early oral squamous cell carcinoma (OSCC), but the mechanisms underlying the development of these subtypes remain unclear. Focusing on the highest score of POIs (Worst POI, WPOI) present within each tumor, we observe a disease progression-driven shift of WPOI towards the high-risk type 4/5, associated with a mesenchymal phenotype in advanced OSCC. WPOI 4-5-derived cancer-associated fibroblasts (CAFs(WPOI4-5)), characterized by high oxytocin receptor expression (OXTRHigh), contribute to local-regional metastasis. OXTRHigh CAFs induce a desmoplastic stroma and CCL26 is required for the invasive phenotype of CCR3(+) tumors. Mechanistically, OXTR activates nuclear ERK5 transcription signaling via G alpha q and CDC37 to maintain high levels of OXTR and CCL26. ERK5 ablation reprograms the pro-invasive phenotype of OXTRHigh CAFs. Therefore, targeting ERK5 signaling in OXTRHigh CAFs is a potential therapeutic strategy for OSCC patients with WPOI 4-5.