Ingenol mebutate induces profound inflammatory and wound healing responses in uninvolved and actinic keratosis skin

We studied the transcriptomic profile of actinic keratosis (AK) skin compared to matched samples from uninvolved skin (US) before and after treatment with ingenol mebutate gel. We found that AK has a distinct mRNA profile that separates it from uninvolved skin. In particular, numerous genes associated with epidermal development and keratinocyte differentiation, such as LCE3D, SPRR1A, PI3 and several genes in the keratin family were highly expressed in AK0 skin, but not in US0, in line with the hyperkeratosis characteristic for AK. Topical application of ingenol mebutate had a profound effect on the gene expression profile, and interestingly, many more genes were affected in US than in AK. Enrichment analysis revealed that the main responses to ingenol mebutate treatment of both US and AK were inflammatory response, response to wounding, and wound healing. 30 skin biopsies were analysed; 5 from each of 6 AK patients. Before initiation of treatment, baseline biopsies were taken from one AK lesion (AK0) and from uninvolved skin (US0). A third biopsy was taken after day 1 application of ingenol mebutate from one AK lesion (AK1). The fourth and fifth biopsies were obtained one day after the second topical application with ingenol mebutate from an AK lesion (AK2) and from uninvolved skin (US2), respectively.