People with acne will find this JCI paper of interest. 13-cis retinoic acid can be used to treat acne, as it can kill human sebaceous-gland cells by apoptosis. The molecule is teratogenic, though, making it necessary to look for alternatives. As the mechanism of action of 13-cis retinoic acid is unknown, Amanda Nelson and her colleagues tried to elucidate it, hoping to identify new targets for the treatment of the bothersome skin condition. Using transcriptional profiling of skin cells from people with acne and cultured sebaceous glands, they found that lipocalin-2 was distinctively upregulated by treatment with 13-cis retinoic acid. They also found that the apoptotic effect of 13-cis retinoic acid indeed depended on the expression of neutrophil gelatinase–associated lipocalin (NGAL), the protein encoded by lipocalin-2; by using siRNA to lipocalin-2, they blocked the apoptotic effect, and by adding recombinant NGAL, they promoted it.