Psoriasin (S100A7) expression and invasive breast cancer

Alteration of psoriasin (S100A7) expression has previously been identified in association with the transition from preinvasive to invasive breast canc er. In this study we have examined persistence of psoriasin mRNA and protei n expression in relation to prognostic factors in a cohort of 57 invasive b reast tumors, comprising 34 invasive ductal carcinomas and 23 other invasiv e tumor types (lobular, mucinous, medullary, tubular). we first developed a n IgY polyclonal chicken antibody and confirmed specificity for psoriasin b y western blot in transfected cells and tumors. The protein was localized b y immunohistochemistry predominantly to epithelial cells, with both nuclear and cytoplasmic staining, as well as occasional stromal cells in psoriatic skin and breast tumors; however, in situ hybridization showed that psorias in mRNA expression was restricted to epithelial cells. In breast tumors, hi gher levels of psoriasin measured by reverse transcriptase-polymerase chain reaction and Western blot (93% concordance) were significantly associated with estrogen and progesterone receptor-negative status (P < 0.0001, P = 0. 0003), and with nodal metastasis in invasive ductal tumors (P = 0.035), but not with tumor type or grade. Psoriasin expression also correlated with in flammatory infiltrates (all tumors excluding medullary, P = 0.0022), These results suggest that psoriasin may be a marker of aggressive behavior in in vasive tumors and are consistent with a function as a chemotactic factor.