induce apoptosis by inhibiting topoisomerase IIα in human non-small-cell lung cancer cells

BACKGROUND

Artemisia annua L. (A. annua) and its active components exhibit antitumour effects in many cancer cells. However, the biological processes and mechanisms involved are not well understood, especially for the treatment of non-small-cell lung cancer (NSCLC).

PURPOSE

This study aimed to comprehensively explore the biological processes of A. annua and its active components in NSCLC cells and to identify the mechanism by which these compounds induce apoptosis.

STUDY DESIGNS/METHODS

Cell viability and flow cytometry assays were used to evaluate the cytotoxicity of A. annua active components casticin (CAS) and chrysosplenol D (CHD) in A. annua in NSCLC cells. After treatment with CAS and CHD, A549 cells were subjected to RNA sequencing (RNA-seq) analysis, differentially expressed genes (DEGs) were screened and subjected to functional enrichment analysis (KEGG and GO analysis) as well as protein interaction network analysis. The key targets associated with apoptosis induction in A549 cells were screened by Cytoscape, and the screened DEGs were validated by qRT-PCR. Immunoblotting, immunofluorescence, and molecular docking assays were used to determine whether CAS and/or CHD could induce apoptosis in NSCLC cells by inducing DNA damage through down-regulation of topoisomerase IIα (topo IIα) expression. The same experiments were verified again in the H1299 lung cancer cell line.

RESULTS

CAS and CHD inhibited NSCLC cells proliferation in a time- and dose-dependent manner, and significantly induced apoptosis. A total of 115 co-upregulated DEGs and 277 co-downregulated DEGs were identified in A549 cells following treatment with CAS and CHD. Comprehensive and systematic data about biological processes and mechanisms were obtained. DNA damage pathways and topo IIα targets were screened to study the apoptosis effects of CAS and CHD on NSCLC cells. CAS and CHD may be able to induce DNA damage by binding to topo IIα-DNA and reducing topo IIα activity.

CONCLUSION

This study suggested that CAS and CHD may reduce topo IIα activity by binding to topo IIα-DNA, affecting the replication of DNA, triggering DNA damage, and inducing apoptosis. It described a novel mechanism associated with topo IIα inhibition to reveal a novel role for CAS and CHD in A. annua as potential anticancer agents and/or adjuvants in NSCLC cells.

Isolation and Characterization of Chemopreventive Agent from Sphaeranthus amaranthoides Burm F

Objective:

To investigate the in vitro cytotoxic effect and to isolate and characterize a chemopreventive secondary metabolite from Sphaeranthus amaranthoides Burm F (sivakaranthai).

Materials and Methods:

In vitro cytotoxic effect was carried out by 3 (4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide assay. Different concentrations of the extracts were tested on three different cell lines namely A549, HT29, and MCF7. The chloroform extract was subjected to column chromatography, and the isolated compound was characterized by various spectral methods and by single crystal X-ray crystallography.

Results:

The concentration that cause 50% growth inhibition value of chloroform extract was found to be 0.9 and 19 μg/mL against MCF7 and A549 cell lines, respectively. Chloroform extract was subjected to column chromatography for the isolation of phytoconstituent. The structure of the isolated compound was identified by spectroscopic techniques such as infrared, nuclear magnetic resonance, XRD, and mass spectroscopy. On comparison of complete spectral detail of the compound, the proposed structure was identified as chrysosplenol D (a flavonoid). Chrysosplenol D was isolated for the first time from this plant.

Conclusion:

The chloroform extract had higher cytotoxic effect, and the isolated chrysosplenol D may be responsible for the anti-proliferative effect of the plant.

SUMMARY

The plant Sphaeranthus amaranthoides Burm F was extracted with solvents of increasing polarity. The chloroform extract was found to have cell inhibition towards MCF 7 and HT 29 cell lines. This was subjected to fractionation. Chrysosplenol D was isolated from the chloroform extract