RESUMO
OBJECTIVE: Glioblastomas are a kind of cancer with high resistance to treatments, requiring more efficient alternatives of treatment. X-linked inhibitor of apoptosis (XIAP) is highly expressed in gliomas and, due to its inhibition of caspases, can participate in resistance to therapy. Here we test the sensitization of glioma cells with XIAP gene knockdown (KD) to drugs used in chemotherapy. METHODS: We silenced XIAP expression in U87MG glioblastoma using stable shRNA, and cells were treated with taxol, BCNU, temozolomide, cisplatin, etoposide, resveratrol (Rsv), vincristine and doxorubicin. We analyzed cell viability, cell cycle, apoptosis and senescence. RESULTS: XIAP KD cells were more sensitive to etoposide, Rsv, vincristine and doxorubicin compared to wild-type (WT) cells. Doxorubicin 1 µM and vincristine 100 nM induced higher activation of caspases after 24 h and doxorubicin induced a higher degree of senescence induction in XIAP KD cells in relation to WT cells. Phospho-p53 and phospho-H2Ax Western blot indicate subsequent DNA damage as an important effector of doxorubicin-induced death. CONCLUSIONS: This study suggests that XIAP inhibitors may sensitize gliomas to certain drugs and induce death and that the mechanisms of sensitization involve apoptosis, senescence and p53 signaling.
Assuntos
Neoplasias do Sistema Nervoso Central/tratamento farmacológico , Neoplasias do Sistema Nervoso Central/genética , Glioma/tratamento farmacológico , Glioma/genética , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/genética , Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Apoptose/genética , Caspases/metabolismo , Senescência Celular/efeitos dos fármacos , Senescência Celular/genética , Dano ao DNA , Doxorrubicina/farmacologia , Resistencia a Medicamentos Antineoplásicos , Etoposídeo/farmacologia , Técnicas de Silenciamento de Genes , Humanos , RNA Interferente Pequeno , Proteína Supressora de Tumor p53/metabolismo , Vincristina/farmacologia , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/metabolismoRESUMO
5-Fluorouracil (5-FU) is an antineoplasic drug widely used to treat cancer. Its cytotoxic effect has been principally ascribed to the misincorporation of fluoronucleotides into DNA and RNA during their synthesis, and the inhibition of thymidylate synthase (TS) by FdUMP (one of the 5-FU active metabolites), which leads to nucleotide pool imbalance. In the present study, we compared the ability of 5-FU and FdUMP to induce apoptosis and to influence the cell cycle progression in human colon SW620 adenocarcinoma cells in regards to their genotoxic and clastogenic activities. Our study demonstrates that 5-FU induces SSB, DSB and apoptosis earlier than FdUMP. Interestingly, while both drugs are able to induce apoptosis, their effect on the cell cycle progression differed. Indeed, 5-FU induces an arrest in G1/S while FdUMP causes an arrest in G2/M. Independently of the temporal difference in strand breaks and apoptosis induction, as well as the differential cell cycle modulation, both drugs presented similar clastogenic effects. The different pattern of cell cycle arrest suggests that the two drugs induce different types of primary DNA lesions that could lead to the activation of different checkpoints and recruit different DNA repair pathways.