Koebnerisin is also known as protein S1-A7A (S1A7A), S1 calcium-binding protein A7-like 1 (S1A7L1) or S1 calcium-binding protein A15 (S1A15). Human S1A7A / S1A15 is a novel member of the S1 family of EF-hand calcium-binding proteins and was recently identified in psoriasis, where it is significantly upregulated in lesional skin. S1A7 is expressed by both normal cultured and malignant keratinocytes and malignant breast epithelial cells within ductal carcinoma in situ, suggesting an association with abnormal pathways of differentiation. S1A7 plays a role in the pathogenesis of inflammatory skin disease, as a chemotactic factor for hematopoietic cells. It also plays a role in early stages of breast tumor progression in association with the development of the invasive phenotype. The association of the 11.2 kDa S1A7A / S1A15 with psoriasis suggests that it contributes to the pathogenesis of the disease and could provide a molecular target for therapy.