Ingredients of a skin cancer cream that were assumed to be inactive may contribute to its ability to stimulate the immune system when applied to mouse skin, according to a report in this week’s Nature Communications. The findings raise the possibility that the combination of both the active drug and the vehicle cream contributes to its therapeutic success in humans.
A widely available cream this is used to alleviate non-melanoma skin cancer consists of the immune stimulating drug imiquimod dissolved in a vehicle cream. Imiquimod activates inflammatory pathways in the skin that are thought to prime the immune system into attacking tumour cells. Maries van den Broek and her team found that in mice, the cream activates additional immune pathways, some of which are stimulated by the vehicle cream alone. They conclude that the full effects of the drug in mouse skin depend on both imiquimod and the vehicle cream being present. The contribution of the vehicle to this treatment’s effects on non-melanoma skin cancer, and on several other skin conditions including external genital warts and actinic keratoses - for which the drug has been approved - has not yet been tested.