Differential expression of melanocortin 2 receptor accessory protein 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 melanocortin 2 receptor accessory protein, MRAP, when comparing primary tumors of the breast to the tissue of origin, the normal breast. MRAP was also differentially expressed in the brain metastases of patients with metastatic breast cancer. MRAP 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 MRAP in primary tumors of the breast was correlated with overall survival in patients with luminal A subtype cancer, demonstrating a relationship between primary tumor expression of a differentially expressed gene and patient survival outcomes influenced by PAM50 molecular subtype. MRAP may be of relevance to initiation, maintenance or progression of cancers of the female breast.