SEC61A2 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 Sec61 translocon alpha 2 subunit encoded by SEC61A2 was among the genes whose expression was most different in the brain metastatic tumor tissues of patients with metastatic breast cancer. SEC61A2 messenger RNA was present at significantly increased quantities in metastasis to the brain when compared to normal breast tissues. SEC61A2 was also differentially expressed in primary tumors of the breast when compared to normal breast tissues. Up-regulation of SEC61A2 may be important for metastasis of primary tumor-derived cancer cells to the brain in humans with metastatic breast cancer, and these data suggest that a specific function of the Sec61 translocon may be important for central nervous system metastasis, or that the biosynthesis and transport of integral membrane and secreted proteins more broadly is in higher demand during this process.