Abstract 3792: SKP2 supports cell proliferation and is regulated by Notch signaling in myoblasts and embryonal rhabdomyosarcoma

Background: Rhabdomyosarcoma (RMS) in a pediatric tumor of myogenic origin. It includes two subtypes: embryonal and alveolar. Embryonal RMS (ERMS) cells express key myogenic factors such as MyoD and Myogenin, but proliferate indefinitely and have lost the ability to terminally differentiate into skeletal myofibers. Differently from the alveolar tumors bearing specific chromosomal translocations, ERMS has cytogenetic aberrations and molecular deregulations of pathways regulating senescence, proliferation and differentiation. It has been shown that SKP2, an F-box protein and a component of the ubiquitin protein ligase complex SCFs (SKP1-cullin-F-box), is over-expressed in RMS primary samples and correlates with a dismal outcome. Therefore, we sought here to investigate the regulation of SKP2 and its role in ERMS. Methods: We modulated SKP2 expression through silencing, by using a siRNA validated in the literature, and forcing its expression through retroviral infection. In parallel, we investigate the effect of Notch signaling modulation on SKP2 expression. Results: SKP2 silencing resulted in cell cycle slowdown in both normal myoblasts and ERMS cells. Down-regulation of Notch1 led to SKP2 reduction while that of Notch3 supported SKP2 expression. Cosilencing SKP2 and Notch3 gave raise to myoblast-like structure formation in ERMS and facilitated myoblasts fusion. Finally, using a SKP2 inhibitor ERMS cell proliferation was completely blocked. Conclusion: Altogether, these preliminary experiments suggest that SKP2 could be regulated by Notch signaling in ERMS and that its inhibition hampers tumor cell proliferative capability. Note: This abstract was not presented at the meeting. Citation Format: Rossella Rota, Laura Adesso, Beatrice Conti, Roberta Ciarapica, Lavinia Raimondi, Maria De Salvo, Sonia Rodriguez, Nadia Carlesso, Lucio Miele, Franco Locatelli. SKP2 supports cell proliferation and is regulated by Notch signaling in myoblasts and embryonal rhabdomyosarcoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3792. doi:10.1158/1538-7445.AM2015-3792