Gene from a psoriasis susceptibility locus primes the skin for inflammation.

Psoriasis is a common complex genetic disease characterized by hyperplasia and inflammation in the skin; however, the relative contributions of epidermal cells and the immune system to disease pathogenesis remain unclear. Linkage studies have defined a psoriasis susceptibility locus (PSORS4) on 1q21, the epidermal differentiation complex, which includes genes for small S100 calcium-binding proteins. These proteins are involved in extracellular and intracellular signaling during epithelial host defense, linking innate and adaptive immunity. Inflammation-prone psoriatic skin constitutively expresses elevated concentrations of S100A7 (psoriasin) and S100A15 (koebnerisin) in the epidermis. Here, we report that genetically modified mice expressing elevated amounts of doxycycline-regulated mS100a7a15 in skin keratinocytes demonstrated an exaggerated inflammatory response when challenged by exogenous stimuli such as abrasion (Koebner phenomenon). This immune response was characterized by immune cell infiltration and elevated concentrations of T helper 1 (T(H)1) and T(H)17 proinflammatory cytokines, which have been linked to the pathogenesis of psoriasis and were further amplified upon challenge. Both inflammation priming and amplification required mS100a7a15 binding to the receptor of advanced glycation end products (RAGE). mS100a7a15 potentiated inflammation by acting directly as a chemoattractant for leukocytes, further increasing the number of inflammatory cells infiltrating the skin. This study provides a pathogenetic psoriasis model using a psoriasis candidate gene to link the epidermis and innate immune system in inflammation priming, highlighting the S100A7A15-RAGE axis as a potential therapeutic target.

Highly homologous hS100A15 and hS100A7 proteins are distinctly expressed in normal breast tissue and breast cancer.

Human S100A7 (psoriasin) is considered a marker for specific stages of breast cancer. hS100A15 is almost identical to hS100A7 and difficult to discriminate. We developed specific probes to distinguish hS100A7 and hS100A15, and demonstrate their differential distribution in normal breast tissue. Further, hS100A7 and S100A15 transcripts are elevated in ER/PR negative breast cancers, but hS100A15 protein is detected in all cancer specimens while hS100A7 protein is sporadically expressed. The differential regulation, expression and distribution of hS100A7 and hS100A15 and their reported distinct functions are compelling reasons to discriminate among these proteins in normal breast and breast cancers.