Autophagy interplays with apoptosis and cell cycle regulation in the growth inhibiting effect of Trisenox in HEP-2, a laryngeal squamous cancer.

Laryngeal squamous cell carcinoma (LSCC) is the most common among several types of head and neck cancers. Current treatments have a poor effect on early and advanced cases, and further investigations for novel agents against LSCCs are desirable. In this study, we elucidate the cytotoxic enhancing effect of arsenic trioxide (As2O3) combined with L-buthionine sulfoximine (BSO) in LSCC. The effect of BSO with As2O3 or Cisplatin (CDDP) on cell viability was examined using 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The reactive oxygen species (ROS) levels, cell cycle, and apoptosis were measured by flow cytometry using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA), propidium iodide (PI) and annexin V/PI. The acidic vacuolar organelles were visualized by fluorescence microscope and quantified using flow cytometry. Neither CDDP nor As2O3 when used alone reduced the cell viability. BSO was found to enhance only As2O3 sensitivity, leading to G2/M arrest and autophagy with no correlation of ROS induction. This result suggests that modulation of glutathione enhances autophagy, which interplays with apoptosis. In this study, we obtained initial preclinical evidence for the potential efficacy of these drugs in a combined therapy protocol.

A paradoxical chemoresistance and tumor suppressive role of antioxidant in solid cancer cells: a strange case of Dr. Jekyll and Mr. Hyde.

Modulation of intracellular antioxidant concentration is a double-edged sword, with both sides exploited for potential therapeutic benefits. While antioxidants may hamper the efficacy of chemotherapy by scavenging reactive oxygen species and free radicals, it is also possible that antioxidants alleviate unwanted chemotherapy-induced toxicity, thus allowing for increased chemotherapy doses. Under normoxic environment, antioxidants neutralize toxic oxidants, such as reactive oxygen species (ROS), maintaining them within narrow boundaries level. This redox balance is achieved by various scavenging systems such as enzymatic system (e.g., superoxide dismutases, catalase, and peroxiredoxins), nonenzymatic systems (e.g., glutathione, cysteine, and thioredoxin), and metal-binding proteins (e.g., ferritin, metallothionein, and ceruloplasmin) that sequester prooxidant metals inhibiting their participation in redox reactions. On the other hand, therapeutic strategies that promote oxidative stress and eventually tumor cells apoptosis have been explored based on availability of chemotherapy agents that inhibit ROS-scavenging systems. These contradictory assertions suggest that antioxidant supplementation during chemotherapy treatment can have varied outcomes depending on the tumor cellular context. Therefore, understanding the antioxidant-driven molecular pathways might be crucial to design new therapeutic strategies to fight cancer progression.

Histone deacetylase inhibitor potentiates chemotherapy-induced apoptosis through Bim upregulation in Burkitt's lymphoma cells.

PURPOSE: Although polychemotherapy regiments have improved clinical outcome for Burkitt's lymphoma (BL) patients, salvage treatment of patients with refractory disease remains very poor. Combined therapies protocols have been emerging to improve treatment strategies to circumvent responseless BL patients. We evaluate the cell death effect of histone deacetylase inhibitor (HDACI) combined with etoposide (VP-16) and cisplatin (CDDP) on BL cell lines. METHODS: 3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay was performed to assess drug toxicity. To establish the concentrations and time of incubation for the combined treatment, a kinetic analysis was performed for each drug on BL41 and Raji BL cell lines for 24, 48 and 72 h. Apoptosis was assessed by flow cytometry using Annexin V/propidium iodide (PI) and cleaved caspase 3 labeling assays. Caspase 9 activation and levels of Bcl-2 family proteins were analyzed by Western blot. RESULTS: The doses of NaB (1.0 mM), CDDP (1.0 and 2.5 µM), and VP-16 (0.1 and 0.3 µM) after 24 h of incubation were chosen for the evaluation of combined therapy. The apoptotic effects on BL cell lines of NaB/VP-16 and NaB/CDDP were followed by upregulation of Bim protein (P < 0.05), activation of caspase-3 and caspase-9, followed by Mcl-1 downregulation (P < 0.05). However, Bim overexpression was not correlated with Bcl-2 inhibition (P > 0.05) and was accompanied by increase in Bax expression (P < 0.05). The combination effects of NaB/VP-16 and NaB/CDDP were found to be synergistic and additive, respectively, in both the cell lines. CONCLUSIONS: The study provides strong evidence for the synergistic effects of the association with HDCI and chemotherapy in BL cells.

Histone deacetylase inhibitor potentiates chemotherapy-induced apoptosis through Bim upregulation in Burkitt's lymphoma cells

PURPOSE: Although polychemotherapy regiments have improved clinical outcome for Burkitt's lymphoma (BL) patients, salvage treatment of patients with refractory disease remains very poor. Combined therapies protocols have been emerging to improve treatment strategies to circumvent responseless BL patients. We evaluate the cell death effect of histone deacetylase inhibitor (HDACI) combined with etoposide (VP-16) and cisplatin (CDDP) on BL cell lines. METHODS: 3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT) assay was performed to assess drug toxicity. To establish the concentrations and time of incubation for the combined treatment, a kinetic analysis was performed for each drug on BL41 and Raji BL cell lines for 24, 48 and 72 h. Apoptosis was assessed by flow cytometry using Annexin V/propidium iodide (PI) and cleaved caspase 3 labeling assays. Caspase 9 activation and levels of Bcl-2 family proteins were analyzed by Western blot. RESULTS: The doses of NaB (1.0 mM), CDDP (1.0 and 2.5 ìM), and VP-16 (0.1 and 0.3 ìM) after 24 h of incubation were chosen for the evaluation of combined therapy. The apoptotic effects on BL cell lines of NaB/VP-16 and NaB/CDDP were followed by upregulation of Bim protein (P 0.05) and was accompanied by increase in Bax expression (P < 0.05). The combination effects of NaB/VP-16 and NaB/CDDP were found to be synergistic and additive, respectively, in both the cell lines. CONCLUSIONS: The study provides strong evidence for the synergistic effects of the association with HDCI and chemotherapy in BL cells

Modulation of reactive oxygen species by antioxidants in chronic myeloid leukemia cells enhances imatinib sensitivity through survivin downregulation.

Survivin, a member of the inhibitor of apoptosis protein family and a target for new drugs, is modulated by reactive oxygen species in several types of neoplasms including leukemias. The aim of this study is to find mechanisms to enhance sensitivity to imatinib in imatinib-responsive cells. In this study, we demonstrated through fluorescein isothiocyanate-labeled annexin V for apoptotic cells detection and western blotting that by inhibiting catalase activity, imatinib apoptosis induction was significantly enhanced (P<0.05) through diminishing survivin expression in K562 cells. These findings might be of clinical relevance and might help improve the chemotherapeutic use of imatinib mesylate.

Proliferação celular induzida por 8-oxoguanosina e 8-metilguanosina, dois produtos do ataque de radicais livres a ribonucleosídeos e RNA / Cell proliferation induced by 8-oxoguanosine and 8-methylguanosine, two products of free radical attack to ribonucleosides and RNA

Os efeitos de ribonucleosídeos de guanina substituídos na posição C-8 na proliferação de linfócitos B estão bem documentados na literatura. Esses compostos são análogos de adutos formados pela adição de radicais livres a ribonucleosídeos e a RNA. Neste trabalho, verificamos as propriedades proliferativas de dois desses adutos, 8-metilguanosina (8-MeGuo) e 8-oxo-7 ,8-di-hidroguanosina (8-OxoGuo) e comparamos com 8-bromoguanosina (8-BrGuo), o composto mais estudado como indutor da proliferação de linfócitos B. 8-MeGuo e 8-OxoGuo foram sintetisados em rendimentos de 28 e 55%, respectivamente, e foram caracterizados por UV, NMR e CG-massa. Seus efeitos sobre a incorporação de timidina radioativa ([3H] TdR) no DNA de células de baço, fibroblasto 3T3(A31) e melanoma B16F10 foram examinados. Os dois adutos foram mitogênicos para células de baço mas foram seletivos quanto as células imortalizadas. 8-MeGuo atuou sobre células 3T3(A31) e 8-OxoGuo sobre as células de melanoma B16F10. O análogo não fisiológico 8-BrGuo foi efetivo em todas as células testadas. Experimentos de contagem de células, citotoxicidade e citometria de fluxo, indicaram que a síntese de DNA induzida pelas guanosinas substituídas na posição C-8 refletia crescimento celular. Foi proposto que os compostos agem de dentro da célula uma vez que seus efeitos são bloqueados em presença de um inibidor de transporte de nucleosídeo, mas não foram inibidos por um antagonista de receptor purinérgico. Os resultados obtidos, junto com os descritos na literatura, sugerem que no caso dos fibroblastos 3T3(A31) e células de baço de camundongo os efeitos proliferativos dos compostos não são dependentes do metabolismo desses compostos via salvação das purinas. No caso das células de melanoma, entretanto, os compostos parecem fazer parte do "pool" de nucleosídeos. A demonstração de que adutos produzidos por ataques radicalares em ribonucleosídeos e RNA são capazes de induzir proliferação celular, abre novas perspectivas para a compreensão do papel de radicais livres em processos carcinogênicos

The ability of CS-substituted guanine ribonucleosides to induce B cell proliferation has been well documented in the literature. These compounds are analogues of adducts formed from free radical attack on ribonucleosides and RNA. Here we examined the proliferative properties of two of these radical adducts, 8-methylguanosine (8-MeGuo) and 8-oxo-7 ,8-dihydroguanosine (8-OxoGuo) and compared them with those of the well studied B cell mitogen, 8-bromoguanosine (8-BrGuo). 8-MeGuo and 8-OxoGuo were synthesized in yields of 28 and 55 %, respectively, and were characterized by UV, NMR and CG-MS. Their effects upon [3H] thymidine uptake by Swiss mice splenocytes, mouse embryo 3T3 (A31) fibroblasts and mouse B16F10 melanocytes were examined. Both guanosine radical adducts were shown to increase [3H] thymidine uptake by mice splenocytes but displayed selectivity in regard to continuous cell lines. 8-MeGuo acted upon 3T3(A31) fibroblasts whereas 8-OxoGuo acted upon B16F10 melanocytes. The non physiological analogue 8-BrGuo acted upon all tested cells. Parallel experiments of cell counting, cytotoxicity, and cell sorting indicated that DNA synthesis induced by the C8-substituted guanosines reflected cell growth. It is proposed that the compounds act intracellularly because their proliferative effects were blocked in the presence of a nucleoside transport inhibitor but were not inhibited by an antagonist of the A2 purine receptor. The obtained results, taken together with data from the literature suggest that in the case of 3T3 (A31) fibroblasts and mice splenocytes the proliferative effects of the compounds are not dependent on metabolism through purine salvage pathways. In the case of melanocytes, however, the compounds are likely to become part of the purine nucleoside pool. The demonstration that adducts produced by free radical attack on ribonucleosides and RNA are able to induce cell proliferation opens new perspectives for the understanding of free radical mediated carcinogenesis

Proliferaçäo celular induzida por 8-oxoguanosina e 8-metilguanosina, dois produtos do ataque de radicais livres a ribonucleosídeos e RNA / Cell proliferation induced by the 8-oxoguanosine and 8-methylguanosine, two products of the free radical attack on ribonucleosides and RNA

Os efeitos de ribonucleosídeos de guanina substituídos na posiçäo C-8 na proliferaçäo de linfócitos B estäo bem documentados na literatura. Esses compostos säo análogos de adutos formados pela adiçäo de radicais livres a ribonucleosídeos e a RNA. Neste trabalho, verificamos as propriedades proliferativas de dois desses adutos, 8-metilguanosina (8-MeGuo) e 8-oxo-7,8-di-hidroguanosina (8-OxoGuo) e comparamos com 8-bromoguanosina (8-BrGuo), o composto mais estudado como indutor da proliferaçäo de linfócitos B. 8-MeGuo e 8-OxoGuo foram sintetisados em rendimentos de 28 e 55 por cento, respectivamente, e foram caracterizados por UV, NMR e CG-massa. Seus efeitos sobre a incorporçäo de timidina radioativa ([üH] TdR) no DNA de células de baço, fibroblasto 3T3(A31) e melanoma B16F10 foram examinados. Os dois adutos foram mitogênicos para células de baço mas foram seletivos quanto as células imortalizadas...

Atividade superóxido dismutase em células de melanoma B16

Foi feita no presente trabalho a comparação das atividades da enzima superóxido dismutase (EC 1.15.1.1) em duas linhagens de células de melanoma - B16F1 e B16F10. A atividade da superóxido dismutase foi medida por um método indireto baseado na inibição da quimioluminescência do luminol ou por um método no qual o radical superóxido foi produzido por reação de NADH com fenazina metosulfato e detectado por sua reação com azul de nitrotetrazol. Usando homogeneizados de células foi constatado que a linhagem altamente metástatica -B16F10- possui atividades da superóxido dismutase menor do que a da linhagem B16F1, menos metastática. Eletroforese em gel de acrilamida dos homogeneizados mostrou em ambos os casos que as bandas com maior mobilidade tinham sua atividade enzimática inibida por cianeto 1mM e com o mesmo R da superóxido dismutase de hemácias (CuZn-SOD). Extratos de B16F1 apresentaram uma banda insensível ao cianeto, mais larga do que a dos extratos de B16F10 sugerindo que a atividade mangano-superóxido dismutase é maior nas células B16F1. A atividade enzimática total em B16F1 foi mais suscetível ao calor e menos sensível ao peróxido de hidrogênio do que a atividade em B16F10. Azida na concentração de 20m causou inibição de 35 (por cento)e 20 (por cento) da atividade enzimática nas células B16F10, respectivamente. O crescimento das células em meio ao qual foi adicionado sal de cobre (CuC1) resultou no aumento da atividade superóxido dismutase somente nas células B16F10.

The purpose of this study has been to compare superoxide dismutase (EC 1.15.1.1) activities in two variant lines of the B16 melanoma B16F1 and B16F10. The activity of superoxide dismutase was measured by an indirect method using inhibiton of the chemiluminescence of luminol or by a method in which superoxide radical was generated by NADH plus phenazine methosulfate and detected by its reaction with nitroblue tetrazolium. Using cell free extracts it was shown that the highly metastatic B16F10 mouse melanoma cell line has a superoxide dismutase activity lower that of the less metastatic B16F1 cell line. Acrylamide gel electrophoresis of the crude extracts showed in both cases that the more rapidly migrating activities were suppressed by 1.0mM cyanide and presented the same Rf of the erythrocyte cuprozinc superoxide dismutase. Extracts of B16F1 showed the cyanide-insensitive superoxicle dismutase band larger than that of the B16F10 extracts suggesting that mangano superoxide dismutase activity is higher in B16F1 cells. The enzymatic activity in B16F1 was more susceptible to heat and less sensitive to hydrogen peroxide than was the activity in B16F10. Azide at concentration of 20mM caused 35% and 20% inhibition of the superoxide dismutase activity of B16F1 and B16F10, respectively. Growth of cells in medium enriched with Cu2+ resulted in the elevation of the superoxide dismutase activity only in the B16F10 cells.