Sulforaphene-Carboplatin Combination Synergistically Enhances Apoptosis by Disruption of Mitochondrial Membrane Potential and Cell Cycle Arrest in Human Non-Small Cell Lung Carcinoma

Worldwide non-small cell lung cancer (NSCLC) causes substantial morbidity and mortality among human populations. Due to the severe side effects and low survival rate of patients with the conventional drugs, implementation of new combination therapies is much needed. The aim of this study was to evaluate the efficacy of a combination therapy with a conventional drug and a natural medicine. We compared the combination of chemotherapy drug carboplatin and the radish-derived isothiocyanate compound sulforaphene, which synergistically induces higher apoptosis and growth inhibition in A549, to the drug alone in human NSCLC cells. We found that this combination group significantly induced higher depolarization of mitochondrial membrane potential (MMP) and intracellular reactive oxygen species generation than the single drug dose, followed by cell cycle arrest at the G0/G1 phase after 24 h of incubation. In addition to that, the Western blot assays showed that combination treatment inhibited the expression of Bcl-2 and successively upregulated the expression of Bax, cytochrome C, apoptosis-inducing factor, caspase-9 and -3, and cleaved poly ADP ribose polymerase. It also modulated the expression of PI3K, p-extracellular signal-regulated kinase (1/2), and p-c-Jun N-terminal kinase indicating the involvement of antiproliferative properties. Further pretreatment with pan-caspase inhibitor Z-VAD-fmk was carried out to confirm the effect of caspases in the combination therapy-induced apoptosis. To summarize, this is the first report that sulforaphene-carboplatin combination treatment synergistically promotes enhanced apoptosis and antiproliferative effect over single drug treatment against A549, human NSCLC cells through caspase activation, MMP disruption, and cell cycle arrest. This study demonstrates that the duel character of this combination therapy may be an effective replacement for conventional therapy alone against NSCLC.