Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

DNA-damage recognition and cellular responses to DNA damaging treatments

We have analyzed how different types of DNA damages i.e., ionizing radiation and DNA cross linking platinum agents are detected by the Non-homologous end joining (NHEJ)-and Homologous recombination repair (HRR) systems in vitro and in vivo in tumour cell lines.

We have studied the NHEJ DNA double strand break (DSBs) repair efficiency and fidelity in cell extracts from NSCLC cells sensitive and resistant to radiotherapy using an in vitro functional assay using restriction enzyme-generated double strand breaks with different end structures (compatible and incompatible ends) in a pBR322 plasmid.

Results show that neither repair efficiency of DNA DSBs nor fidelity of NHEJ correlated with sensitivity to radiation i.e. to SF2 values. Moreover, no correlation between NHEJ key protein levels and SF2 value was observed in either NSCLC or SCLC subtypes.

The role of NHEJ components, DNA dependent kinase (DNA-PKcs) and KU86 in cisplatin and oxaliplatin-induced cellular sensitivity has been studied. Results show that mutation of DNA-PKcs or deficiency in KU86 results in increased sensitivity to platinum drugs i.e., cisplatin and oxaliplatin.

Moreover the sensitivity to oxaliplatin was higher in DNA-PKcs deficient cells than in cells missing KU86 suggesting that these subunits of DNA-PK may have different function with regard to oxaliplatin-induced cell signalling. The influence of p53 on the HRR protein Rad 51 protein level and sub cellular localisation in response to ionising radiation has been assessed in human colon cancer cell lines deficient or proficient in p53. We found that p53 has a role in Rad 51 clearance post radiation and that nucleoli might be sites of Rad 51 degradation.


Rolf LEWENSOHN, (Research Director)
Tel.: +46-851773188
Fax: +46-851775042