Title: Sympathetic Modulation of Oral Cancer Proliferation and Nociception
Stella Park (Presenter)
New York University
Nicole Scheff, New York University
Brian Schmidt, New York University
John Dolan, New York University
Objectives: Oral cancer patients report severe functional pain. Oral cancer cells secrete mediators that activate neurons innervating the cancer microenvironment. Norepinephrine (NE), a key neurotransmitter released by
sympathetic neurons, is thought to dysregulate cytokines and cause pain during carcinogenesis. Previous data from the lab shows tumor necrosis factor-alpha (TNFα) is abundantly present in oral cancer microenvironment. We sought to test the hypothesis that sympathetic nerve fibers innervating the tongue release NE during oral carcinogenesis resulting in cancer proliferation, increased TNFα production, and pain.
Methods: To test this hypothesis, we used retrograde tracer, DiI, to identify sympathetic neurons innervating the mouse tongue. PCR was used to determine which adrenergic receptors are expressed in oral cancer and dysplastic oral keratinocyte (DOK) cell lines. Colorimetric proliferation and immunosorbent assays were used to determine NE-induced changes in cell growth and TNFα protein concentration, respectively.
Results: We identified DiI-positive sympathetic neurons in superior cervical ganglia and dense sympathetic fiber innervation in mouse tongue. Beta-2 adrenergic receptor (ADRβ2) was identified as most abundantly expressed in oral cancer cell lines (SCC4, HSC3) as well as a DOK. Exposure to 10μM NE resulted in 56.8±0.6% increase in HSC3 cell proliferation, but no significant change in DOK (10.4±1.8%). Elevated TNFα protein was also detected in response to 10μM NE in SCC4 and HSC3 cell line supernatants (130.9±25.3 and 142.2±12.5% respectively). However, 10μM NE treatment only resulted in 33.8±1.9% increase in DOK supernatant. Pre-treatment with ADRβ antagonist, propranolol, blocked NE-induced proliferation and increased TNFα in all cell lines.
Conclusions: Together these data suggest sympathetic neurons in the oral cancer microenvironment release NE which activates oral cancer cells to increase TNFα secretion and cause pain. Ongoing studies in an oral cancer animal model are testing therapeutic effects of propranolol on oral cancer pain and carcinogenesis.