Project description:Genomic instability is a hallmark of cancer. Whether or not it also occurs in cancer-associated fibroblasts (CAFs) is a question of importance for the cancer/stromal cell co-evolution process. We find that DNA damage, telomere shortening and chromosome fusions occur at early times of CAF activation, as triggered by silencing of the CSL/RBP-J-κ gene in primary human dermal fibroblasts (HDFs) from multiple individuals. Similar alterations occur in skin Squamous Cell Carcinoma (SCC) - derived CAFs, in which CSL is down-modulated, versus HDFs from unaffected skin of the same patients. Mechanistically, CSL is part of a telomere protective complex with UPF1, KU70, and KU80 proteins, which fail to bind to telomeres in the absence of CSL. In CAFs, persistent genomic instability is associated with frequent amplification and overexpression of NOTCH1 gene, which is required to suppress DNA damage-induced ATM/P53 activation and growth arrest. These findings are of translational significance as, in an orthotopic model of skin SCC, genetic or pharmacological suppression of NOTCH1 activity suppresses cancer/stromal cell proliferation and expansion.
Project description:Kaposi's sarcoma-associated herpesvirus (KSHV) lytic switch protein, Rta, is a ligand-independent inducer of the Notch signal transduction pathway, and KSHV cannot reactivate from latency in cells null for the Notch target protein RBP-Jk. Here we show that Rta promotes DNA binding of RBP-Jk, a mechanism that is fundamentally different from that established for the RBP-Jk-activating proteins, Notch intracellular domain (NICD) and Epstein-Barr virus EBNA2. Although constitutively active RBP-Jk and NICD do not transactivate KSHV promoters independently, cotransfection of an Rta mutant lacking its transactivation domain robustly restores transcriptional activation. Cooperation requires intact DNA binding sites for Rta and RBP-Jk and trimeric complex formation between the three molecules in vitro. In infected cells, RBP-Jk is virtually undetectable on a series of viral and cellular promoters during KSHV latency but is significantly enriched following Rta expression during viral reactivation. Accordingly, Rta, but not EBNA2 and NICD, reactivates the complete viral lytic cycle.
Project description:BackgroundThis study explored the changes in expression of vascular smooth muscle cell (VSMC) markers and osteogenic markers, as well as the involvement of Notch1-RBP-Jk/Msx2 pathway in a rat model of diabetic nephropathy (DN) with vascular calcification.MethodsA rat model of DN with concomitant vascular calcification was created by intraperitoneal injection of streptozotocin followed by administration of vitamin D3 and nicotine. Biochemical analysis and histological examination of aortic tissue were performed. VSMC markers and osteogenic markers as well as target molecules in Notch1-RBP-Jk/Msx2 were determined by quantitative real-time polymerase chain reaction and immunohistochemical analysis.ResultsSerum calcium and phosphorus levels were significantly increased in model rats as compared to that in normal controls. Diabetic rats with vascular calcification exhibited mineral deposits in aortic intima-media accompanied by decreased expression of VSMC markers and increased expression of osteogenic markers. Notch1, RBP-Jk, Msx2, Jagged1, and N1-ICD were barely expressed in the aortic wall of normal rats. In contrast, these were significantly increased in the model group at all time points (8, 12, and 16 weeks), as compared to that in the normal rats.ConclusionActivation of the Notch1-RBP-Jk/Msx2 signaling pathway may be involved in the development and progression of vascular calcification in DN.
