Optimization of an assay to measure chemosensory changes that accompany oral cancer

Introduction

Oral cancer patients suffer severe mechanical and function related pain. Some patients report increased sensitivity to spicy, pungent and acidic foods. Pain is attributed to neuronal sensitization by the release of chemical mediators from the cancer and cancer microenvironment. Pain mediators activate and sensitize multiple transient receptor potential (TRP) ion channels including TRP ankyrin 1 (TRPA1). TRPA1 is co-expressed and localized with other TRP channels to a subpopulation of primary sensory neurons of the trigeminal ganglia detecting noxious thermal, mechanical and chemical stimuli. This study was designed to evaluate chemosensory changes due to sensitization of the TRPA1 ion channel in preclinical models.

Materials and Methods

A two bottle choice drinking assay was used to evaluate aversion to the TRPA1 agonist, allyl isothiocyanate (AITC), which is responsible for the pungent taste of mustard, horseradish and wasabi. Fifty, naive wild type female mice (C57BL/6) were single housed. Liquid intake over 5 day periods was measured from two drinking bottles one with AITC dissolved in dimethyl sulfoxide (DMSO), and the other vehicle (0.25% DMSO). Five AITC concentrations (0.06 mM, 0.1 mM, 0.25 mM, 0.5 mM and 1mM) were tested (n = 10 mice per group). Positions of the bottles were exchanged daily to avoid habituation.

Results

Naive female mice demonstrated statistically significant aversion to AITC concentrations 0.25 mM (p= 0.0001), 0.5 mM (p ≤ 0.0001) and 1mM (p ≤ 0.0001), two way ANOVA, Tukey's multiple comparisons test . Mice offered lower AITC concentrations did not show significant aversion.

Conclusions

Naive mice demonstrated significant aversion to AITC concentrations ≥ 0.25 mM. Additional testing is being performed in tongue cancer bearing mice. Aversion to a non-aversive concentration of AITC (≤ 0.1 mM) is expected to identify the change in chemosensitivity and difference between sensitive vs. non sensitive cancers.