Topical kinase inhibitors induce regression of cutaneous squamous cell carcinoma

Actinic keratoses (AKs) and squamous cell carcinoma in situ (SCCIS) are precursor lesions for cutaneous squamous cell carcinoma (cSCC), the second most common form of cancer. Current topical therapies for AKs and SCCIS promote skin inflammation to eradicate lesions and do not directly target the biological mechanisms driving growth. We hypothesized that topical small molecule inhibitors targeting kinases promoting keratinocyte growth in AKs and SCCIS could induce regression of these lesions with less inflammation. To test this hypothesis, we determined the efficacy of topical dasatinib, 5-fluorouracil and BEZ-235 in inducing regression of cSCCs in the K14-Fyn Y528 transgenic mouse model. Topical dasatinib induced regression of cSCC with less inflammation, no ulceration and no mortality compared to 5-fluorouracil. Topical BEZ-235 induced cSCC regression similar to dasatinib without erythema or ulceration. These data indicate that topical small molecule kinase inhibitors targeting drivers of AK/SCCIS/cSCC growth represent a promising therapeutic approach to treat these common skin lesions.