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.

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.