Oleanolic Acid Modulates DNA Damage Response tomCamptothecin Increasing Cancer Cell Death

DNA damage is one of the main causes of tumor development. Different sources, both endogenous and exogenous, could be affect the stability of double helix of DNA. A detrimental DNA damage is the Double-Strand -Break, which is repaired by two principal mechanisms, the Non Homologous End Joining (NHEJ) or the Homologous Recombination (HR) process, to preserve genome stability. NHEJ is an error prone mechanism generating high number of insertions or deletions to repair the damaged DNA during the whole cell cycle; on the other hand, the HR is restricted to the S/G2 cell cycle phases, given its dependency on the presence of the sister chromatid for the correct DNA repair. Although the resolution of the HR intermediates leads to error-free repair or the mutagenic pathways (Single Strand Annealing and Alternative End-Joining), but the regulation of this processes is actually under investigation. In this work we used a Fermented grape extract, named Ethyl Acetate (OA ETOH), to evaluate its effect on DNA damage response, alone and combined with Camptothecin. From OA ETOH we isolated two main molecules: Oleanolic Acid (OA) and Linoleic Acid (CLA). We decided to focus our attention on the Oleanolic Acid because it is known that Oleanolic acid in combination with Olaparib and radiotherapy, significantly inhibits cell proliferation if compared with the not treated samples. We demonstrated, in HeLa cells, that combination treatment between Oleanolic Acid with Camptothecin increased phosphorylation of Replication Protein A 32 Serine 4/8 (RPA32 S4/8) protein, a marked of DNA end resection, respect to Camptothecin alone. Furthermore, we evaluated which DNA repair mechanisms could be potentially involved in the repair of the lesions after the combination treatment with Camptothecin and Oleanolic Acid. We demonstrated that this treatment activates Single strand Annealing through the chromatin loading of DNA excision repair protein ERCC-1 and Ligase 1 (LIG1) proteins. By describing the role of Oleanolic Acid in the modulation of DNA repair, we demonstrated that Oleanolic Acid potentially favours an increased activity of Camptothecin in HeLa cell line, leading a new possible strategy for cancer therapy.