Details

Autor(en) / Beteiligte

• Toulany, Mahmoud
• Kasten-Pisula, Ulla
• Brammer, Ingo
• Wang, Shaomeng
• Chen, Jianyong
• Dittmann, Klaus
• Baumann, Michael
• Dikomey, Ekkehard
• Rodemann, H Peter

Titel

Blockage of Epidermal Growth Factor Receptor-Phosphatidylinositol 3-Kinase-AKT Signaling Increases Radiosensitivity of K-RAS Mutated Human Tumor Cells In vitro by Affecting DNA Repair

Ist Teil von

• Clinical cancer research, 2006-07, Vol.12 (13), p.4119-4126

Ort / Verlag

United States: American Association for Cancer Research

Erscheinungsjahr

2006

Quelle

MEDLINE

Beschreibungen/Notizen

• Purpose: It is known that blockage of epidermal growth factor receptor (EGFR)/phosphatidylinositol 3-kinase (PI3K) activity enhances radiation sensitivity of human tumor cells presenting a K- RAS mutation. In the present study, we investigated whether impaired repair of DNA double-strand breaks (DSB) is responsible for the radiosensitizing effect of EGFR and PI3K inhibition in K- RAS mutated (K- RAS mt ) cells. Experimental Design: The effect of the EGFR tyrosine kinase inhibitor BIBX1382BS (BIBX) on cellular radiosensitivity was determined in K- RAS mt (A549) and K- RAS wt (FaDu) cell lines by clonogenic survival assay. Radiation-induced phosphorylation of H2AX (Ser 139 ), ATM (Ser 1981 ), and DNA-dependent protein kinase catalytic subunit (DNA-PKcs; Thr 2609 ) was analyzed by immunoblotting. Twenty-four hours after irradiation, residual DSBs were quantified by identification of γH2AX foci and frequency of micronuclei. Results: BIBX reduced clonogenic survival of K- RAS mt -A549 cells, but not of K- RAS wt -FaDu cells, after single-dose irradiation. Analysis of the radiation-induced H2AX phosphorylation revealed that BIBX, as well as the PI3K inhibitor LY294002, leads to a marked reduction of P-H2AX in K- RAS mt -A549 and MDA-MB-231 cells, but not in K- RAS wt -FaDu and HH4ded cells. Likewise, radiation-induced autophosphorylation of DNA-PKcs at Thr 2609 was only blocked in A549 cells by these two inhibitors and AKT1 small interfering RNA transfection. However, neither in K- RAS mt nor in K- RAS wt cells the inhibitors did affect radiation-induced ATM phosphorylation. As a consequence of inhibitor treatment, a significant enhancement of both residual DSBs and frequency of micronuclei was apparent only in A549 but not in FaDu cells following radiation. Conclusion: Targeting of the EGFR-dependent PI3K-AKT pathway in K- RAS -mutated A549 cells significantly affects postradiation survival by affecting the activation of DNA-PKcs, resulting in a decreased DSB repair capacity.