Actinomycin D decreases Mcl-1 expression and acts synergistically with ABT-737 against small cell lung cancer cell
Haishan Xu1, Geoffrey W Krystal
1Department of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
Purpose:
ABT-737, which blocks the function of Bcl-2 and Bcl-X(L) but not Mcl-1, has shown single-agent 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 single-agent 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.
Insights
Actinomycin D synergizes with ABT-737 to overcome Mcl-1-mediated resistance in small cell lung cancer (SCLC) by reducing Mcl-1 expression. This combination therapy shows promise for treating SCLC patients.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- ABT-737 targets Bcl-2 and Bcl-X(L) but faces resistance in small cell lung cancer (SCLC) due to Mcl-1.
- Mcl-1's short mRNA and protein half-life suggests potential for targeted degradation.
Purpose of the Study:
- To investigate if actinomycin D can reverse Mcl-1-induced resistance to ABT-737 in SCLC.
- To evaluate the synergistic effect of combining actinomycin D and ABT-737 on SCLC cell viability and apoptosis.
Main Methods:
- Dose-response studies of actinomycin D and ABT-737 on SCLC cell lines.
- Assessment of Bcl-2 family protein expression and apoptosis markers via Western blot and flow cytometry.
- Viability and clonogenic assays to determine treatment efficacy.
Main Results:
- Actinomycin D reduced Mcl-1 expression and increased Noxa expression in SCLC cell lines.
- Clinically relevant actinomycin D concentrations showed single-agent activity.
- Combination therapy with ABT-737 resulted in near-complete loss of viability with synergistic effects.
Conclusions:
- Actinomycin D synergizes with ABT-737 to induce SCLC apoptosis, partly via Mcl-1 downregulation and Noxa upregulation.
- The combination of actinomycin D and BH3-mimetic drugs is feasible for clinical application in SCLC treatment.
Related Concept Videos
02:57Targeted Cancer Therapies
There are several types of targeted therapies against specific...
02:34Inhibition of Cdk Activity
02:50Combination Therapies and Personalized Medicine
The combination of the drug acetazolamide and sulforaphane is a good example of combination therapy to treat cancer. The cells in the interior of a large tumor often die due to the hypoxic and...
02:23Abnormal Proliferation