Nerve Types and Classification of Neurons Innervating Oral Cancer.

PURPOSE Although the association between neural invasion and poor survival in oral cavity squamous cell carcinoma (OSCC) is known, innervating nerve types have not been definitively established; this has confounded mechanistic and translational studies. Therefore, we investigated innervation in human OSCC and further explored these findings in mice. EXPERIMENTAL DESIGN Sensory, sympathetic, and parasympathetic nerves were identified by immunohistochemistry and linked to neural phenotypes in 71 patients. Additionally, we investigated sensory innervation of OSCC using neuronal tracing with transcriptomic profiling, and transgenic mice. RESULTS In OSCC, most nerves are exclusively sensory or sensory mixed with other types. The presence of exclusively sensory nerves and mixed sensory and sympathetic nerves was significantly increased within the tumor bulk compared to the margin, whereas mixed sympathetic and parasympathetic nerves were decreased. The proportion of exclusively sensory, and mixed sensory and sympathetic PNI+ (perineural invasion) nerves was significantly higher, whereas the proportion of mixed sympathetic and parasympathetic nerves was significantly lower than PNI(-) nerves. Classification of tumor-innervating trigeminal sensory neurons in mice revealed an increase in Calca+ peptidergic nociceptors and reduction in low-threshold mechanoreceptors. Using transgenic reporter mice to verify innervation, we identified that mouse tongue SCC is innervated by Pirt+ and Calca+ nociceptors. CONCLUSIONS This study is the first comprehensive characterization of nerve types in OSCC with classification of innervating trigeminal sensory neurons. Our findings emphasize the importance of sensory innervation in OSCC and are highly relevant for mechanistic and translational studies on treatment strategies.