TRPA1 and lip and oral cavity carcinoma: Polyunsaturated fatty acids (PUFAs) are a possible class of factors since human saliva from oral cancer patients has been reported to have elevated levels of certain TRP-active PUFAs (e.g., linoleic acid, arachidonic acid, HODE, and HETE), compared to normal control patients [20], and many of these PUFAs activate TRPV1 [12–19] or TRPA1 [12, 22–24].