The ROS1 gene belongs to the sevenless subfamily of tyrosine kinase insulin receptor genes. A literature review identified a ROS1fusion in 2.54% of the patients with lung adenocarcinoma and even higher frequencies in spitzoid neoplasms and inflammatory myofibroblastic tumors. At present, 26 genes were found to fuse with ROS1, some of them already known to fuse with RET and ALK. All the fusion proteins retain the ROS1 kinase domain, but rarely its transmembrane domain. Most of the partners have dimerization domains that are retained in the fusion, presumably leading to constitutive ROS1 tyrosine kinase activation. Some partners have transmembrane domains that are retained or not in the chimeric proteins. Therefore, different ROS1fusions have distinct subcellular localization, suggesting that they may activate different substrates in vivo.
Since the identification of the BCR–ABL1 fusion gene generated by the (9;22)(q34;q11) translocation in chronic myeloid leukemia, fusion genes have long been considered as the hallmark of hematological neoplasia. It is only more recently that fusion genes have been started to be identified in solid tumors [1–3].
Receptor tyrosine kinases (RTKs) are important regulators of signal transduction and cellular communication. They act as the cell surface receptors for a number of important growth factors and hormones and play crucial roles in development and cancer by regulating cellular proliferation, differentiation, migration and death.
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