Differential expression of peptidase inhibitor 16 in cancers of the breast.

Breast cancer affects women at relatively high frequency (1). We mined published microarray datasets (2, 3) to determine in an unbiased fashion and at the systems level genes most differentially expressed in the primary tumors of patients with breast cancer. We report here significant differential expression of the gene encoding the peptidase inhibitor 16, PI16, when comparing primary tumors of the breast to the tissue of origin, the normal breast. PI16 mRNA was present at significantly lower quantities in tumors of the breast as compared to normal breast tissue. Analysis of human survival data revealed that expression of PI16 in primary tumors of the breast was correlated with overall survival in patients with basal subtype cancer, demonstrating a relationship between primary tumor expression of a differentially expressed gene and patient survival outcomes influenced by molecular subtype. PI16 may be of relevance to initiation, maintenance or progression of cancers of the female breast.