9-PAN promotes tubulin- and ROS-mediated cell death in human triple-negative breast cancer cells.

OBJECTIVES: To examine the antiproliferative effect of a rationally designed, novel noscapine analogue, 9-((perfluorophenyl)methylene) aminonoscapine, '9-PAN') on MDA-MB-231 breast cancer cell line, and to elucidate the underlying mechanism of action. METHODS: The rationally designed Schiff base-containing compound, 9-PAN, was characterized using IR, NMR and mass spectra analysis. The effect of the compound on cell viability was studied using an MTT assay. Cell cycle and cell death analyses were performed using flow cytometry. Binding interactions of 9-PAN with tubulin were studied using spectrofluorometry. Reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP) were investigated using the probes, DCFDA and rhodamine-123, respectively. Immunofluorescence imaging was used to visualize cellular microtubules. KEY FINDINGS: 9-PAN inhibited cell proliferation (IC50 of 20 ± 0.3 µm) and colony formation (IC50 , 6.2 ± 0.3 µm) by arresting the cells at G2 /M phase of the cell cycle. It bound to tubulin in a concentration-dependent manner without considerably altering the tertiary conformation of the protein or the polymer mass of the microtubules in vitro. The noscapinoid substantially damaged cellular microtubule network and induced cell death, facilitated by elevated levels of ROS. CONCLUSIONS: 9-PAN exerts its antiproliferative effect by targeting tubulin and elevating ROS level in the cells.

Perturbation of tubulin structure by stellate gold nanoparticles retards MDA-MB-231 breast cancer cell viability.

Gold nanoparticles (GNPs) of different sizes and shapes have been investigated extensively for their therapeutic potential against several diseases including cancer. However, the mechanisms with which they affect the cells are yet to be fully comprehended. In this study, we report the strong antiproliferative potential of novel, star-shaped ("stellate") GNPs that target tubulin-the building-block protein of the cytoskeletal filaments called microtubules-and disrupt microtubule network integrity. The stellate GNPs ("sGNPs") were synthesized from tryptone-stabilized GNPs ("tGNPs") and characterized by various spectroscopy methods combined with high-resolution transmission electron microscopy. Among a panel of cancer cell lines tested, they showed strong antiproliferative and anti-clonogenic efficacy against MDA-MB-231 cells. The antiproliferative mechanism of the sGNPs involves perturbation of the secondary and tertiary conformation of tubulin as evidenced by far-UV circular dichroism and anilinonaphthalene sulphate-binding assays. The structural perturbation of tubulin retarded its assembly competence as evidenced by polymer mass analysis and electron microscopy imaging of tubulin assembled in vitro and by immunofluorescence visualization of the cellular microtubules. The treated cells also induced cell cycle arrest at G1 phase. Taken together, our data suggest that sGNPs are potent, tubulin-targeted antiproliferative particles that can be evaluated further for their anticancer potential.