Attribution 4.0 International (CC BY 4.0)2022-08-222022-08-222020-02-11Sridharan, S., & Basu, A. (2020). Distinct Roles of mTOR Targets S6K1 and S6K2 in Breast Cancer. International journal of molecular sciences, 21(4), 1199. https://doi.org/10.3390/ijms210411991422-0067https://hdl.handle.net/20.500.12503/31596The mechanistic target of rapamycin (mTOR) is a master regulator of protein translation, metabolism, cell growth and proliferation. It forms two complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2). mTORC1 is frequently deregulated in many cancers, including breast cancer, and is an important target for cancer therapy. The immunosuppressant drug rapamycin and its analogs that inhibit mTOR are currently being evaluated for their potential as anti-cancer agents, albeit with limited efficacy. mTORC1 mediates its function via its downstream targets 40S ribosomal S6 kinases (S6K) and eukaryotic translation initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1). There are two homologs of S6K: S6K1 and S6K2. Most of the earlier studies focused on S6K1 rather than S6K2. Because of their high degree of structural homology, it was generally believed that they behave similarly. Recent studies suggest that while they may share some functions, they may also exhibit distinct or even opposite functions. Both homologs have been implicated in breast cancer, although how they contribute to breast cancer may differ. The purpose of this review article is to compare and contrast the expression, structure, regulation and function of these two S6K homologs in breast cancer.http://creativecommons.org/licenses/by/4.0/Rps6kb1Rps6kb2S6k1S6k2breast cancermTORAnimalsBreast Neoplasms / geneticsBreast Neoplasms / metabolismBreast Neoplasms / pathologyEnzyme ActivationFemaleGene AmplificationGene Expression Regulation, NeoplasticHumansProtein Interaction MapsRibosomal Protein S6 Kinases, 70-kDa / analysisRibosomal Protein S6 Kinases, 70-kDa / geneticsRibosomal Protein S6 Kinases, 70-kDa / metabolismTOR Serine-Threonine Kinases / analysisTOR Serine-Threonine Kinases / geneticsTOR Serine-Threonine Kinases / metabolismArticle© 2020 by the authors.214