ROS1 (69D6) Mouse mAb #3266

ROS1, an orphan receptor tyrosine kinase of the insulin receptor family, was initially identified as a homolog of v-ros from the UR2 sarcoma virus (1). ROS1 consists of a large extracellular domain that is composed of six fibronectin repeats, a transmembrane domain, and a C-terminal kinase domain. Being an orphan receptor, the functions of ROS1 are not well known, though it has been shown to play an important role in differentiation of epididymal epithelium (2). The first oncogenic fusion of ROS1, FIG-ROS1, was initially identified by research studies in glioblastoma (3), and subsequent studies have found this fusion in cholangiocarcinoma (4), ovarian cancer (5), and non-small cell lung cancer (NSCLC) (6). Investigators have found additional oncogenic ROS1 fusion proteins in NSCLC (at a frequency of ~1.6%), where the ROS1 kinase domain is fused to the amino-terminal region of several different proteins, including CD74 and SLC34A2 (6-8). ROS1 fusion proteins activate the SHP-2 phosphatase, PI3K/Akt/mTOR, Erk, and Stat3 pathways (3,4,9). There are two autophosphorylation sites (Tyr2274, Tyr2334) downstream of the kinase domain of ROS1, either of which may serve as biomarkers of ROS1 kinase activity, including that of ROS1 fusion proteins (10).