Topical probiotics for actinic keratoses: Alteration of actinic keratoses microbiome to reduce the risk of malignant progression.. Human normal and actinic keratosis skin rRNA samples

Cutaneous squamous cell carcinoma (cSCC) is an extremely common cancer strongly associated with UV exposure, and is typically preceded by premalignant actinic keratoses (AK). Staphylococcus aureus has been isolated in abundant proportions from AK and cSCC lesions, whereby it causes a large inflammatory response on the skin and secrete toxins resulting in DNA damage, which could potentiate tumorigenesis. Topical probiotics may reduce the rate of malignant transformation through reintroducing a normal skin microbiome, therefore decreasing inflammation. Therefore, the aim of this study was to modulate the skin microbiome of premalignant actinic keratosis lesions to restore microbial eubiosis through the application of topical probiotics.This was a double blind, split-body, pilot study conducted by The University of Queensland Frazer Institute at the Princess Alexandra Hospital Dermatology Clinic. Study participants applied one of four topical treatments, with swabs of an identified forearm AK and a corresponding section of normal skin (NS) on the other forearm taken prior to ointment application, on day 0 (V1), 14 (V2), 21 (V3), and 3-6-months post-treatment (V4). Swab samples were sequenced using SSU rRNA sequencing. The study demonstrated that topical probiotics are a viable alternative to improve microbial diversity and reduce Staphylococcal load on AK lesions, potentially aiding in the prevention of malignant progression.