PTEN and neoplasm: In conclusion, to further elucidate the mechanisms of radiosensitization in DNA-PK- and ATM-deficient tumor cells, studies on an extended panel of cell lines including genetically manipulated cell lines with PTEN- or p53-knockout, regarding the cell type-specific activation of p53, cell-cycle arrest, apoptosis and DNA repair will be the subject of future research in our laboratory.