(195) Trigeminal Ganglia Neurons Support Oral Carcinogenesis through Neurotransmitter Release in a Mouse Model of Tongue Squamous Cell Carcinoma

Tongue cancer patients suffer severe, chronic pain driven by oral cancer-induced activation of sensory neurons innervating the oral cavity. However, the impact of sensory neurotransmission on oral carcinogenesis is understudied. Local neurotransmitter release from sensory neurons innervating the cancer has been linked to cancer growth and immune suppression. We hypothesize that oral cancer-induced neurotransmitter release from trigeminal sensory neurons (TGNs) promotes oral cancer proliferation and suppresses the immune response. To investigate sensory neuron subtypes that may impact cancer in the oral cavity, we characterized TGNs that innervate the tongue using a retrograde tracer, DiI, and immunohistochemistry for neuropeptides. We used a colorimetric MTS assay kit to quantify cancer cell proliferation in response to supernatant from TGN cultures. Using flow cytometry, we tested whether pharmacologic inhibition of peripheral sensory neurons impacted inflammation in response to oral cancer. We found that a majority of TGNs innervating the tongue are peptidergic and express neurotransmitters calcitonin-gene related peptide (CGRP, 64.3±13.2%) and substance P (SP, 44.1± 9.9%). Oral cancer cell line, HSC-3, exposed to TGN culture supernatant for 48 hours had a 2.00±0.04-fold increase in proliferation compared to Dulbecco's Modified Eagle Medium (DMEM) cell culture media. HSC-3 cell culture supernatant injection (50µl) into the tongue of C57Bl/6 female mice resulted in infiltration of CD45+ immune cells (9.10±1.2% of total live cells). Temporary nerve block with 1% bupivacaine injection into the lingual nerve prior to a 50µl injection of HSC-3 supernatant into the tongue resulted in significantly more CD45+ immune cell infiltration (21.66±3.4%) compared to HSC-3 supernatant without pharmacologic nerve block. These results suggest neurotransmitter-induced increase in oral cancer cell proliferation and neurotransmitter-induced suppression of the cancer-evoked immune response. Understanding the nerve-cancer interaction may improve strategies to treat oral cancer and pain by targeting sensory neurons.