Regulation of DNA repair and drug sensitivity by cytokines in immunocompetent cells

点击翻译按钮获取中文摘要

Cytokines are important intercellular mediators of biological processes including the immune response. Whether cytokines have an impact on DNA repair has been studied by us using as a model system freshly isolated human monocytes, which were matured by GM-CFS/IL-4 into macrophages and dendritic cells (DCs). We observed that human monocytes do not express detectable amounts of the DNA repair proteins XRCC1, Ligase III, PARP-1 and DNA-PKCS. During cytokine-stimulated differentiation of monocytes into macrophages or DCs the expression of these repair proteins is upregulated. The regulation occurs for XRCC1, PARP-1 and DNA-PKCS on gene/mRNA level. Lack of expression of the repair proteins results in a defect in base excision and DNA doble-strand break repair and hypersensitivity of monocytes to monofunctional alkylating agents, including temozolomide, ionising radiation and oxidative agents. Our preliminary data revealed that also mouse monocytes lack XRCC-1, Ligase III, PARP-1 and DNA-PKCS, indicating this is a general biological phenomenon. - In this grant proposal we wish to extend the previous studies in both human and mouse system. We wish to elucidate when and how during maturation of CD34+ cells into monocyte precursors XRCC1, PARP-1 and DNA-PKCS become downregulated, whether the repair proteins are also lacking in established monocyte-like human cells, whether they become upregulated durig differentiation and how the corresponding repair genes are regulated. In mice, we wish to determine the monocyte precursor in the bone marrow in which downregulation of XRCC1, Ligase III, PARP-1 and DNA-PKCS occurs. Further, we want to assess whether mouse monocytes are also hypersensitive to genotoxicants, including ROS, whether other genes are differentially regulated and subject to upregulation following cytokine stimulation of monocytes and, finally, whether hypersensitivity of monocytes results in depletion of monocytes and the descending population, i.e. macrophages, following whole body irradiation and treatment with alkylating agents, including the anticancer drug temozolomide.