| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2160925 | Radiotherapy and Oncology | 2007 | 7 Pages |
Background and purposeIt has been proposed that radiation induced stimulation of ATM and downstream components involves activation of TGFβ-1 and that this may be due to TGFβ-1-receptor I-Smad signalling. Therefore, the aim of this study was to clarify the distinct role of TGFβ-1-receptor I-Smad signalling in mediating ATM activity following radiation exposure.Materials and methodsA549 cells were stably transfected with a conditionally regulatable TGFβ-1 antisense construct (Tet-on-system) to test clonogenic activity following irradiation. Phosphorylation profile of ATM, p53, and chk2 was determined in non-cycling, serum-starved cells by immunoblotting. Likewise, A549 wild type cells were used to identify cell cycle distribution as a function of irradiation with or without pretreatment with CMK, a specific inhibitor of furin protease involved in activation of latent TGFβ-1. Furthermore Western and immunoblot analyses were performed on serum-starved cells to investigate the dependence of ATM- and p53-stimulation on TGFβ-1-receptor I-Smad signalling by applying a specific TGFβ-1-receptor I inhibitor.ResultsKnock down of TGFβ-1 by an antisense construct significantly increased clonogenic cell survival following exposure to ionizing radiation. Likewise, CMK treatment diminished the radiation induced G1 arrest of A549 cells. Moreover, both TGFβ-1-knock down as well as CMK treatment inhibited the fast post-radiation phosphorylation of ATM, p53, and chk2. However, as shown by the use of a specific inhibitor TGFβ-1-receptor I-Smad signalling was not involved in this fast activation of ATM and p53.ConclusionsWe confirm that TGFβ-1 plays a critical role in the stimulation of ATM- and p53 signalling in irradiated cells. However, this fast stimulation seems not to be dependent on activation of TGFβ-1-receptor I-Smad signalling as recently proposed.
