C1R is differentially expressed in the brain metastases of patients with metastatic breast cancer.
Metastasis to the brain is a clinical problem in patients with breast cancer (1-3). We mined published microarray data (4, 5) to compare primary and metastatic tumor transcriptomes to discover genes associated with brain metastasis in patients with metastatic breast cancer. We found that the complement component 1, r subcomponent, encoded by C1R, was among the genes whose expression was most different in the brain metastases of patients with metastatic breast cancer as compared to normal breast tissues. C1R mRNA was present at significantly reduced quantities in brain metastatic tissues as compared to primary tumors of the breast. Down-regulation of C1R expression may contribute to metastasis of tumor cells from the breast to the brain in humans with metastatic breast cancer.