Ras Suppressor-1 (RSU-1) in Cancer Cell Metastasis: Friend or Foe?

Metastasis to distant organs and not the primary tumor itself is usually the cause of death for cancer patients. Hence, studying the key molecules and molecular pathways involved in metastasis are essential. Metastasis is a complex process in which cancer cells detach from the original tumor, migrate, and invade through surrounding tissues and metastasize to other sites of the body through the circulation. The cell-extracellular matrix (ECM) adhesion proteins play a fundamental role in this process as cancer cells need to weaken their adhesions to dissociate from the ECM as well as the neighboring cells within the tumor and finally form new adhesions and invade surrounding tissues. Ras suppressor-1 (RSU-1) was originally identified as a suppressor of Ras-dependent oncogenic transformation and found to be localized to cell-ECM adhesions where it binds to PINCH-1, a focal adhesion involved in cell survival. Although RSU-1 was connected to cancer early on, little is known about its expression in various cancer types or its role in metastasis. In this article, we review the recent literature regarding the expression of RSU-1 in various cancer types and its potential role in metastasis, discussing interesting findings and issues that still need to be addressed.