TRPV4 and actinic keratosis: Fusi et al., 2014 showed that TRPA1 protein and mRNA expression levels are significantly increased in skin biopsies from patients with solar keratosis, a premalignant form of nonmelanoma skin cancer. Other studies have shown that TRPV4 stimulation leads to the release of IL-8, which in turn, downregulates TRPV4 expression in a human keratinocyte cell line (HaCaT), and the selective reduction of TRPV4 expression may represent an early biomarker of skin carcinogenesis (Fusi et al., 2014).