KRT14 and actinic keratosis: A transgenic human papillomavirus type 38 (HPV38) mouse model (Tg38), which expresses E6 and E7 of β-HPV38 in the skin under the control of the keratinocyte K14 promoter (K14 HPV38 E6/E7), did not show any spontaneous formation of cancer lesions under physiological conditions, whereas after UV exposure, Tg38 mice developed actinic keratosis-like lesions, which are considered a precursor of cSCC in humans.