Abstract
DAMTC (7,8-diacetoxy-4-methylcoumarin) is a thioderivative of 4-methyl coumarin, and previously we have shown that DAMTC is a potent inhibitor of cell growth and an inducer of apoptosis in non-small cell lung cancer (A549) cells. It induces apoptosis through mitochondrial pathway by modulating NF-κB, mitogen-activated protein kinase (MAPK) and p53 pathways. Herein, we explored the genome-wide effects of DAMTC in A549 cells using the concerted approach of transcriptomics and proteomics. In addition to apoptotic pathways, which have been validated earlier, the bioinformatic analysis of microarray data identified small GTPase-mediated signal transduction among the significantly altered biological processes. Interestingly, we observed significant downregulation of some members of the Rho family GTPases in the proteomics data too. Downregulation of Rho GTPases (RhoGDIα (Rho GDP dissociation inhibitor-α, also known as ARHGDIA), Ras homolog family member A, Ras-related C3 botulinum toxin substrate 1 and cell division cycle 42) was validated by western blotting. The Rho protein family is implicated in maintaining the actin filament assembly and cell motility, and we also observed that DAMTC treatment causes actin cytoskeletal reorganization, promotes filopodia formation and inhibits cell motility in A549 cells. The effect of DAMTC treatment on cytoskeleton was reversed after the overexpression of RhoGDIα. In addition, DAMTC augmented the apoptotic effect of etoposide, a proapoptotic chemotherapeutic drug. This elucidation of the mechanism behind DAMTC-induced apoptosis and inhibition of cell motility in A549 cells may make it a potential therapeutic for lung cancer.
Highlights
Coumarins are polyphenolic compounds, which have been shown to possess various biological activities
Our previous results suggested that the inhibition of MAPK signaling pathway and the activation of NF-kB and p53 pathway may participate in the anti-proliferative activity of DAMTC in non-small cell lung cancer (NSCLC) (A549) cells.[7]
The changes in gene expression profile after DAMTC treatment in NSCLC (A549) cells were determined by a microarray experiment using Illumina human WG-6 v.3.0 beadchip (Illumina Inc., San Diego, CA, USA)
Summary
Coumarins are polyphenolic compounds, which have been shown to possess various biological activities. Studies from our own laboratory have shown that DAMTC (7,8-diacetoxy4-methylcoumarin) is a potent inhibitor of cell growth and an inducer of apoptotic cell death. Our previous results suggested that the inhibition of MAPK signaling pathway and the activation of NF-kB and p53 pathway may participate in the anti-proliferative activity of DAMTC in NSCLC (A549) cells.[7] the detailed molecular mechanism(s) by which DAMTC inhibits cell growth and induces apoptosis is still unknown. Transcriptional profiling of control and treated samples using oligonucleotide microarray allows the simultaneous analysis of the expression of thousands of genes in a high-throughput setting,[8,9] proteomic profiling using twodimensional gel electrophoresis allows identification of differentially expressed proteins in large sets of complex protein mixtures.[10] Using both transcriptome- and proteomebased approaches, we have shown that in addition to inducing apoptosis, DAMTC causes actin cytoskeletal reorganization, promotes filopodia formation and inhibits cell motility in A549 cells. The molecular effectors of signaling pathways leading to filopodia formation are yet to be completely defined
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