Let-7a microRNA modulates caspase-3-dependent apoptosis in melanoma cells treated with dabrafenib and trametinib
1Department of Medical Oncology, Izmir Tepecik Education and Research Hospital, University of Health Sciences, Izmir, Türkiye.
Background:
Malignant melanoma is an aggressive tumor with high resistance to therapy. The emergence of RAS-driven secondary cancers and BRAF-inhibitor resistance has led to the development of combination therapies targeting both BRAF and MEK.
Aims:
This study explored the mechanisms underlying the synergistic effects of dabrafenib (DAB) and trametinib (TM) in drug-resistant A375 and RPMI 7951 melanoma cells.
Methods:
Cytotoxicity was assessed via MTT assay and combination effects were evaluated via combination index analysis. Apoptosis was analyzed by DNA fragmentation ELISA, while ectopic let-7a miRNA expression and inhibition were performed using lipofection. Gene expression levels were quantified by qRT-PCR, and protein expression was assessed via Western blot.
Results:
The combination of 0.7 μM DAB and 5.0 μM TM exhibited synergistic cytotoxicity by inhibiting the pERK1/2 signaling pathway and inducing MITF expression. This resulted in mitochondria-mediated apoptosis, characterized by a decrease in anti-apoptotic Bcl-2 and an increase in pro-apoptotic Bax, caspase-9, and caspase-3 levels. Additionally, Let-7a was identified as a crucial regulator of apoptosis sensitivity by targeting caspase-3, the key executor of apoptosis.
Conclusions:
These findings provide new insights into overcoming melanoma drug resistance through combined BRAF/MEK inhibition.
Insights
Combined dabrafenib (DAB) and trametinib (TM) therapy synergistically kills drug-resistant melanoma cells by inducing apoptosis. Let-7a microRNA is crucial for this sensitivity, targeting caspase-3 to enhance cell death.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Malignant melanoma exhibits high therapeutic resistance, necessitating novel treatment strategies.
- BRAF-inhibitor resistance and secondary cancers drive the need for combination therapies targeting BRAF and MEK pathways.
Purpose of the Study:
- To investigate the synergistic mechanisms of dabrafenib (DAB) and trametinib (TM) in drug-resistant melanoma cell lines.
- To elucidate the role of Let-7a microRNA in mediating apoptosis sensitivity to combined BRAF/MEK inhibition.
Main Methods:
- Cytotoxicity and combination effects assessed using MTT assays and combination index analysis.
- Apoptosis evaluated via DNA fragmentation ELISA, with gene and protein expression analyzed by qRT-PCR and Western blot.
- Ectopic Let-7a miRNA expression and inhibition performed using lipofection.
Main Results:
- The DAB and TM combination demonstrated synergistic cytotoxicity, inhibiting pERK1/2 signaling and upregulating MITF.
- Mitochondria-mediated apoptosis was induced, evidenced by altered Bcl-2, Bax, caspase-9, and caspase-3 levels.
- Let-7a was identified as a key regulator of apoptosis sensitivity by targeting caspase-3.
Conclusions:
- Combined BRAF/MEK inhibition offers a promising strategy to overcome melanoma drug resistance.
- Understanding the role of Let-7a provides new therapeutic targets for enhancing melanoma treatment efficacy.
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