Evaluation of the potential of pyridine-derived hydrazones and their copper (II) complexes in Oncologic therapy: evaluation of the radiosensitizing potential

Cancer is one of the most challenging diseases in medicine, being the leading cause of death in economically developed countries and the second leading cause in developing countries. Among the modalities of cancer treatment, radiotherapy and chemotherapy are the most used, however, several tumors have radioresistance and resistance to chemotherapy in the clinic. In this sense, the use of combined therapies between chemotherapy and gamma radiation is one of the promising strategies for the treatment of cancer, since compounds with a potential radiosensitizer make the cancer cells more sensitive to the effects of radiotherapy, resulting in an increased cell death. The present work aimed to evaluate the in vitro cytotoxic effect of hydrazones derived from pyridine and its copper (II) complexes on brain tumor cells. Tumor lines used were glioblastoma multiform, wild type (U87) and glioblastoma multiform mutant P53 (T98). Cytotoxicity was also evaluated in human fetal lung fibroblast (MRC5) healthy cells. Considering that brain tumors have radioresistance, it was also proposed to evaluate, in tumor cells, the radiosensitizing potential of the most active compound and its respective copper (II) complex. For the accomplishment of the proposed objectives, different methodologies were used, for example, cytotoxicity was verified through the quantification of the metabolic viability using the MTT assay. Inhibition of proliferation was investigated in clonogenicity assays, whereas, cell cycle distribution and type of induced cell death was assessed by flow cytometry. In relation to cytotoxicity, the analysis of the results showed that the compounds evaluated were cytotoxic to U87 and T98 cells, and some of these compounds showed higher antitumor activity in vitro than cisplatin, an antineoplastic used in medical practice. The most potent compounds were H2AcPh, H2AcpClPh and H2AcpNO2Ph (hydrazones derived from 2-acetylpyridine) and their respective copper complexes, exhibiting IC50 on the order of micromolar. The analysis of cellular morphological alterations, chromosomal DNA and double staining with acridine orange / ethidium bromide suggest that these compounds induce programmed cell death in the cells. Analysis of the results also suggest that the compounds induce the generation of free radicals and that these are, at least in part, related to the activation of the cell signaling cascade that induces cell death observed in the treated cells. The evaluation of the radiosensitizer effect was performed with the hydrazone H2AcpClPh and its copper complex [Cu (2AcpCLPh) CL]. The evaluation of the results obtained showed that the compounds potentiated the effects of the radiation. Regarding the monotherapies, the combined treatment was able to decrease the metabolic viability and cell proliferation of the cells, as well as increase apoptotic cell death. It was also verified that the copper complex [Cu (2AcpCLPh) CL], in relation to its ligand, was more effective in enhancing the effects of radiation. Thus, the analysis of the results showed that, combined therapies of binders that present chelating activity and their metallic complexes with radiation are excellent therapeutic strategies for the radiosensitization of tumors. (author)