epidermal-growth-factor and Ataxia-Telangiectasia

Previous studies have shown that tumor-driving glioma stem cells (GSC) may promote radio-resistance by constitutive activation of the DNA damage response started by the ataxia telangiectasia mutated (ATM) protein. We have investigated whether GSC may be specifically sensitized to ionizing radiation by inhibiting the DNA damage response. Two grade IV glioma cell lines (BORRU and DR177) were characterized for a number of immunocytochemical, karyotypic, proliferative and differentiative parameters. In particular, the expression of a panel of nine stem cell markers was quantified by reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry. Overall, BORRU and DR177 displayed pronounced and poor stem phenotypes, respectively. In order to improve the therapeutic efficacy of radiation on GSC, the cells were preincubated with a nontoxic concentration of the ATM inhibitors KU-55933 and KU-60019 and then irradiated. BORRU cells were sensitized to radiation and radio-mimetic chemicals by ATM inhibitors whereas DR177 were protected under the same conditions. No sensitization was observed after cell differentiation or to drugs unable to induce double-strand breaks (DSB), indicating that ATM inhibitors specifically sensitize glioma cells possessing stem phenotype to DSB-inducing agents. In conclusion, pharmacological inhibition of ATM may specifically sensitize GSC to DSB-inducing agents while sparing nonstem cells.

Topics: Ataxia Telangiectasia; Cell Line, Tumor; DNA Breaks, Double-Stranded; Enzyme Inhibitors; Epidermal Growth Factor; Fibroblast Growth Factors; Flow Cytometry; Gene Expression Regulation, Neoplastic; Glial Fibrillary Acidic Protein; Humans; Intermediate Filament Proteins; Karyotyping; Mutation; Neoplastic Stem Cells; Nerve Tissue Proteins; Nestin; Neuroblastoma; Radiation, Ionizing

To determine if cells from the cancer-prone autosomal recessive disorder ataxia telangiectasia (A-T) are defective in responding to stimuli other than ionizing-radiation (IR) damage.. The induction of c-jun transcripts by IR, by phorbol 12-myristate 13-acetate (PMA), interleukin 1 (IL-1) and epidermal growth factor (EGF) in normal and A-T lymphoblasts was measured.. Treatment with PMA increased c-jun transcripts in a dose- and time-dependent manner two- to three-fold more in A-T than in normal cells. Similarly, treatment with EGF and IL-1 also increased c-jun transcripts more in A-T than in normal lymphoblasts. In contrast, exposure to gamma-radiation increased c-jun transcripts at least twofold more in normal than in A-T lymphoblasts.. These findings indicate that A-T cells are not only defective in responding to IR damage, but also in responding to mitogenic stimuli like IL-1 and EGF. Furthermore, these findings implicate ATM, the gene responsible for the A-T disorder, in the induction of c-jun transcripts by PMA, EGF or IL-1.

Topics: Ataxia Telangiectasia; Ataxia Telangiectasia Mutated Proteins; Cell Cycle Proteins; Cell Line; DNA-Binding Proteins; Epidermal Growth Factor; Gamma Rays; Gene Expression Regulation; Genes, jun; Humans; Interleukin-1; Lymphocytes; Mitogens; Protein Serine-Threonine Kinases; Proteins; Radiation Tolerance; RNA, Messenger; Tetradecanoylphorbol Acetate; Tumor Suppressor Proteins

The ATDC gene was originally identified by its ability to complement the radiosensitivity defect of an ataxia telangiectasia (AT) fibroblast cell line. Because hypersensitivity to ionizing radiation is an important feature of the AT phenotype, we reasoned that ATDC may function generally in the suppression of radiosensitivity. Previous work in our laboratory focused on radiosensitization mechanisms in human squamous carcinoma (SC) cells, especially A431 cells. To establish a basis for investigating the role of ATDC in radiation-responsive signaling pathways in human SC cells, we characterized ATDC message and protein expressions in A431 cells. ATDC message expression was also compared among human epidermoid cells (A431 cells, HaCaT spontaneously immortalized human keratinocytes and normal human epidermal keratinocytes) and a normal human fibroblast cell line (LM217). We made the following major observations: (i) the relative abundance of ATDC message is substantially higher in the epidermoid cells than in the fibroblast cell line, which has a message level comparable to those reported for other fibroblast lines; (ii) ATDC is constitutively phosphorylated on serine/threonine in A431 cells; (iii) in A431 cells, ATDC is a substrate for the serine/threonine protein kinase C (PKC) but not the epidermal growth factor (EGF) receptor tyrosine kinase; and (iv) EGF decreases ATDC message and protein expressions in A431 cells after a 24-hr exposure. The phosphorylation studies suggest that the ability of ATDC to modulate cellular radiosensitivity may be mediated in part through a PKC signaling pathway.

Topics: Ataxia Telangiectasia; Base Sequence; Carcinoma, Squamous Cell; Cell Line, Transformed; Cell Transformation, Viral; DNA-Binding Proteins; DNA, Complementary; Epidermal Growth Factor; Fibroblasts; G1 Phase; Gene Expression Regulation, Neoplastic; Humans; Keratinocytes; Molecular Sequence Data; Neoplasm Proteins; Phosphorylation; Protein Kinase C; Protein Processing, Post-Translational; Recombinant Fusion Proteins; Recombinant Proteins; RNA, Messenger; RNA, Neoplasm; Simian virus 40; Skin; Transcription Factors; Tumor Cells, Cultured

Topics: Animals; Ataxia Telangiectasia; Cattle; Cell Division; Cell Survival; Cells, Cultured; Culture Media; Epidermal Growth Factor; Fibroblast Growth Factors; Fibroblasts; Growth Substances; Humans; Insulin; Peptides