Sensory Neurotransmitter CGRP Modulates Oral Cancer Growth and Cancer-associated Immune Response

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      Head and neck squamous cell carcinoma (HNSCC) induces severe pain due in part to activation of primary afferent neurons by cancer-secreted mediators. Local neurotransmitter release (e.g., calcitonin gene-related peptide (CGRP)) from trigeminal neurons innervating the cancer has been linked to tumorigenesis. We hypothesize that CGRP exerts a dual effect on both cancer-associated pain and tumor progression, suggesting that CGRP may be a promising therapeutic target in HNSCC treatment. We used human tumor tissue and patient-reported outcomes to explore the relationship between CGRP+ sensory nerve innervation and cancer pain in patients. To determine CGRP receptor expression on tumor cells, immunohistochemistry and PCR were performed on human and mouse oral cancer cell lines. We used a syngeneic tongue tumor transplant mouse model of oral cancer and a global Calca knockout mouse (i.e. CGRP-KO) to investigate the impact of CGRP signaling on tumor growth and the associate immune response in vivo. We found prominent CGRP-immunoreactive sensory nerve presence innervating human HNSCC tumor tissue, which positively correlated to patient-reported pain (r2=0.357). Furthermore, human HNSCC cell lines expressed 3-fold more CGRP receptor, RAMP1, compared to a non-tumorigenic keratinocyte cell line. In tumor-bearing CGRP-KO mice, we found a significant reduction in tumor size at post-inoculation days 7 and 14 compared to wildtype. We also found a 4-fold increase in tumor infiltrating RAMP1-expressing CD4+ T cells, as well as a 5-fold increase cytotoxic CD8+ T cells and NK1.1+ NK cells in tumor tissue CGRP-KO mice compared to wildtype. This preliminary data suggests that CGRP signaling from sensory neurons may increase cancer associated pain and tumor progression. Further knowledge regarding the relationship between sensory neurons and cancer could allow for the repurposing clinically available nervous system drugs (e.g., anti-CGRP antibodies) for the treatment of cancer and cancer pain. Grant support from the Rita Allen Foundation.
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