Analyzing the influence of kinase inhibitors on DNA repair by differential proteomics of chromatin-interacting proteins and nuclear phospho-proteins.

The combination of radiotherapy and pharmacological inhibition of cellular signal transduction pathways offers promising strategies for enhanced cancer cell inactivation. However, the molecular effects of kinase inhibitors especially on DNA damage detection and repair after X-irradiation have to be understood to facilitate the development of efficient and personalized treatment regimens. Therefore, we applied differential proteomics for analyzing inhibitor-induced changes in either chromatin-bound or phosphorylated nuclear proteins.

Radiosensitization of HNSCC cells by EGFR inhibition depends on the induction of cell cycle arrests.

The increase in cellular radiosensitivity by EGF receptor (EGFR) inhibition has been shown to be attributable to the induction of a G1-arrest in p53-proficient cells. Because EGFR targeting in combination with radiotherapy is used to treat head and neck squamous cell carcinomas (HNSCC) which are predominantly p53 mutated, we tested the effects of EGFR targeting on cellular radiosensitivity, proliferation, apoptosis, DNA repair and cell cycle control using a large panel of HNSCC cell lines. In these experiments EGFR targeting inhibited signal transduction, blocked proliferation and induced radiosensitization but only in some cell lines and only under normal (pre-plating) conditions.

Quantitative proteomics unveiled: Regulation of DNA double strand break repair by EGFR involves PARP1.

Background: EGFR inhibition blocks DNA double strand break (DSB) repair but the detailed mechanisms are still unclear. We asked whether EGFR inhibition blocks DSB repair by reducing the X-ray-induced phosphorylation of repair proteins using a phosphoproteomic approach.

Materials And Methods: Using UT-SCC5 and SAS head and neck cancer cells we established a differential phosphoproteomic approach for quantitative analysis of DNA repair proteins by stable isotope labeling with amino acids.

In tumor cells regulation of DNA double strand break repair through EGF receptor involves both NHEJ and HR and is independent of p53 and K-Ras status.

Purpose: The purpose of this study was to examine whether the epidermal growth factor receptor (EGFR) may be used as a general target to modulate DNA double strand break (DSB) repair in tumor cells.

Material And Methods: Experiments were performed with human tumor cell lines A549, H1299 and HeLa and primate cell line CV1. EGF, ARG and TGFα were used for EGFR activation, cetuximab or erlotinib for inhibition.