Deficiency of DNA-repair

The cell uses the DNA to keep those information, which are vital to function properly.  It is essential to maintain the integrity of the DNA, the stability of the genome. Since DNA damages, caused by external or internal factors, are continuously produced, DNA-repair mechanisms should be ready to identify and eliminate the damages. Either the repair system is successful and the cell can continue its duty, or, if the damages are unrepaired, the programed cell death (apoptosis) is activated according to the rule, that it is prohibited to transfer genomic/epigenomic damages into the daughter cells. It is true that the severness of the damages are not the same. The most important is the identifi cation and repair of those damages which can make genomic instability increasing the risk of cancer development. This may happen when the repair system is insuffi cient, sometimes due to inherited mutations (e.g. BRCA1 mutations can increase the risk of breast cancer, ovarian cancer etc.). Among the damages the DNA double strand breaks are rather common, and also, that the breaks are intended to be repaired in most cases. However, if such repair fails, the cell, here the cancer cell, due to the overhelming damages will dye. This phenomenon is the synthetic lethality. An example: „cooperation” of inherited BRCA1 mutation and PARP-inhibition, can lead to clinical response using PARP inhibitors, as oliparib. New agents and clinical trials intend to take advantage from synthetic lethality.