Actinomycin D Decreases Mcl-1 Expression and Acts Synergistically with ABT-737 against Small Cell Lung Cancer Cell Lines

Abstract

Purpose: ABT-737, which blocks the function of Bcl-2 and Bcl-X L but not Mcl-1, has shown singleagent activity in preclinical models of small cell lung cancer (SCLC). Elevated expression of Mcl-1 induces resistance to ABT-737 in SCLC. Based on the short half-life of Mcl-1 mRNA and protein, we hypothesized that the actinomycin D could reverse Mcl-1-induced resistance to ABT-737.Experimental Design: The dose-response of multiple SCLC cell lines to actinomycin D in the absence and presence of ABT-737 was followed by the assessment of Bcl-2 family expression and poly ADP ribose polymerase cleavage by Western blot, viability by tetrazolium dye reduction and clonogenic assay, and cell cycle kinetics by flow cytometry.Results: Actinomycin D decreased Mcl-1 expression and resulted in a cell line-dependent increase in Noxa expression. Clinically relevant concentrations of actinomycin D from 0.4 to 4 ng/mL showed singleagent activity across a panel of SCLC cell lines. When combined with low micromolar doses of ABT-737, near complete loss of viability was seen with synergistic combination indices of 0.5 to 0.7. Exposure to 4 ng/mL actinomycin was only required for the first 24 hours of the combined incubation, mimicking a clinically achievable area under the curve, but the presence of ABT-737 was required for an additional 48 hours to obtain maximal effect.Conclusions: Clinically relevant concentrations of actinomycin D act synergistically with ABT-737 to induce SCLC apoptosis, which can be at least partially attributed to the actinomycin D-induced decrease in Mcl-1 and increase in Noxa expression. Taken together, these data suggest the feasibility of combining actinomycin D with BH3-mimetic drugs in the clinical setting. Clin Cancer Res; 16(17); 4392-400. ©2010 AACR.

ABT-737 Induces Apoptosis in Mantle Cell Lymphoma Cells with a Bcl-2high/Mcl-1low Profile and Synergizes with Other Antineoplastic Agents

“…Our investigation confirms that flavopiridol downregulates Mcl-1 at both the mRNA and protein levels in MCL cells and shows a highly synergistic apoptotic effect when combined with ABT-737 in ABT-737-resistant cell lines. The effectiveness of combining ABT-737 with compounds that inactivate Mcl-1 firmly establishes the validity of such a therapeutic approach in the treatment of MCL (12,(35)(36)(37). A similar synergistic effect is measured when ABT-737 is combined with ara-C, which is a heavily prescribed drug in the treatment of MCL (24,38,39).…”

Antioxidant, antimicrobial and wound healing properties ofStruthanthus vulgaris

“…In summary, 3T3 fibroblasts, Hepa-1c1c7, and OVCAR-3 cells were plated in 96-well flat-bottomed tissue culture plates with 6 Â 10 5 cells/ml, and after overnight incubation at 37 C (5% CO 2 and 95% air), cells were incubated for an additional 24 h in the presence or absence of increasing concentrations (1.0-200.0 mg/ml) of ethanol extract of the leaves and branches. Actinomycin D and camptothecin were used as positive controls (Ariyoshi-Kishino et al, 2010;Wu et al, 2011;Xu & Krystal, 2010). After incubation, 100 ml of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) [5 mg/ml in PBS:medium (1:3)] was added per well, and the plate incubated for 2 h to allow reaction of MTT by cellular mitochondrial dehydrogenases.…”

Genotoxicity and Cytotoxicity of novel 10B carrier ((2R)-4,5,6-trihydroxy-2-(hydroxymethyl)tetrahydro-2H-pyran-3-yl)boronic acid

“…To analyze the effects of 10 BDG on proliferation, NCI-H209 small lung carcinoma cells were used. Actinomycin D (ActD) inhibits DNAdependent RNA polymerases, may also induce apoptosis at high concentrations [21] (Fraschini et al, 2005), and inhibits proliferation [22] (Xu and Krystal, 2010). Even it does not seem to be statistically significant, the simultaneous exposure of H209 cells to 10 BDG and ActD demonstrates that 10 BDG may act synergistically with chemotherapeutics such as ActD and more effective results may be obtained with low dose chemotherapeutics (Fig.…”