Psoriasin (S100A7) expression and invasive breast cancer

Abstract

Alteration of psoriasin (S100A7) expression has previously been identified in association with the transition from preinvasive to invasive breast cancer. In this study we have examined persistence of psoriasin mRNA and protein expression in relation to prognostic factors in a cohort of 57 invasive breast tumors, comprising 34 invasive ductal carcinomas and 23 other invasive tumor types (lobular, mucinous, medullary, tubular). We first developed an IgY polyclonal chicken antibody and confirmed specificity for psoriasin by Western blot in transfected cells and tumors. The protein was localized by 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 psoriasin mRNA expression was restricted to epithelial cells. In breast tumors, higher 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 inflammatory infiltrates (all tumors excluding medullary, P = 0.0022). These results suggest that psoriasin may be a marker of aggressive behavior in invasive tumors and are consistent with a function as a chemotactic factor.

Figure 1.

Western blot analysis of cell lines and tumors to demonstrate anti-psoriasin IgY antibody specificity. A: A protein band (approx 11.7 kd) detected using a chicken IgY anti-psoriasin antibody in a psoriasin-transfected MDA-MB-231 breast cell line and two tumors (10049, 12434), but absent in tumor 13402 and wild-type MDA-MB-231 cells. B: Detection of several S100-like proteins, using a commercial polyclonal S100 antibody applied to the same samples, in addition to weak detection of the same (approx 11.7 kd) protein band seen in A.

Figure 2.

Immunohistochemical and in situ hybridization analysis of the cellular distribution and patterns of expression of psoriasin within psoriatic skin and breast carcinoma. Psoriasin protein is localized in hyperplastic epidermis of skin to both nuclei (A, white arrow) and cytoplasm (A, black arrow) of keratinocytes. Similar nuclear and cytoplasmic staining is seen in breast epithelial tumor cells (C, black arrow; case 8965). Psoriasin protein is also detected within occasional stromal inflammatory cells (C, white arrow). E: H&E-stained section from the same region of the tumor shown in C. Psoriasin mRNA expression in skin is restricted to epithelial cells in suprabasal layers of epidermis (B) and scattered invasive epithelial tumor cells in breast tumors (D), detected using antisense probe (B and D) compared to sense probe (F). Original magnification for all panels at the microscope, ×200.

Figure 3.

RT-PCR analysis of psoriasin mRNA expression in invasive breast tumors. Psoriasin (upper black arrow) and GAPDH (lower open arrow) from duplicate PCRs of 10 representative tumors. Control lanes include estradiol-treated MCF7-E2 cells, a tumor control 12077c, and wild-type MDA-MB-231 cells.

Figure 4.

Western blot analysis of psoriasin protein expression in invasive breast tumors. Psoriasin (black arrow) is detected in 3/12 representative tumors and within the positive control (CL7FD3).