Barbigerone reverses multidrug resistance in breast MCF-7/ADR cells

Isoflavone Derivatives as Potential Anticancer Agents: Synthesis and Bioactivity Studies

Isoflavones are phenolic natural compounds with a C6C3C6 framework. They possess a plethora of biological activities that are associated with putative benefits to human health. In particular, the cancer chemopreventive and chemotherapeutic potential of isoflavones has attracted the interest of researchers. Several isoflavone derivatives have been synthesised and probed for their anticancer activities. The isoflavone analogues are mainly synthesised by molecular hybridisation and other strategies that enable diversification through early or late-stage functionalisation of A-, B- and C-rings of the isoflavones. This has resulted in the discovery of isoflavone analogues with improved antiproliferative activities against several cancer cells and different mechanisms of action. In this review, the synthesis of isoflavone derivatives and their anticancer activity studies are discussed.

Crystal structure of tubulin-barbigerone complex enables rational design of potent anticancer agents with isoflavone skeleton

BACKGROUND

Isoflavones possess many biological activities, including anti-inflammatory and anticancer effects. Microtubules (composed of αβ-tubulin heterodimers) are described as one possible cellular target of some of these isoflavones. However, the binding of tubulin to isoflavones has not been extensively studied, and until now, no crystal structure of the tubulin-isoflavone complex has been solved, and details of the isoflavone-tubulin interaction remain elusive.

PURPOSE

Barbigerone is an isoflavone mainly found in the genus Milletti, such as the edible leguminous plant Millettia ferruginea, with anticancer activity. This study aims to confirm the cellular target of barbigerone and to study its anticancer mechanism.

METHOD

Surface plasmon resonance assays and X-ray crystallography were used to study the interaction of barbigerone with tubulin protein. Immunofluorescence, in-cell and in vitro tubulin polymerization assays were employed to investigate the mechanism. MTT assays, cell clonal formation assays, wound healing assays, tube formation assays and H460 xenograft models were conducted to evaluate the in vitro and in vivo anticancer activities of barbigerone and one of its derivatives, 0412.

RESULTS

Here, we found that barbigerone binds to tubulin to inhibit tubulin polymerization. Moreover, we solved the X-ray crystal structure of the tubulin-barbigerone complex at 2.33 Å resolution, which unambiguously determined the orientation and position of barbigerone in the colchicine-binding site. Illuminated by the X-ray data, we synthetized and obtained a more active isoflavone, 0412. Both barbigerone and 0412 inhibit cancer cell proliferation, tubulin polymerization, migration of HeLa cells and capillary-like tube formation of HUVECs, induce G2/M phase cell cycle arrest and apoptosis, and exhibit anticancer activity in an H460 xenograft model.

CONCLUSION

In all, through biochemical and X-ray crystal structure results, we identified tubulin as the cellular target of one isoflavone, barbigerone, and proved that the tubulin-barbigerone complex plays a guiding role in obtaining a more active compound, 0412. These studies provide a crucial research basis for the development of isoflavones as anticancer candidate compounds.

Shenmai injection suppresses multidrug resistance in MCF-7/ADR cells through the MAPK/NF-κB signalling pathway

Context: Shenmai Injection (SMI) is usually used to treat atherosclerotic coronary heart disease and viral myocarditis in China. However, the effect of SMI on multidrug resistance has not been reported.Objective: To investigate the reversal effect of SMI in adriamycin (ADR) resistant breast cancer cell line (MCF-7/ADR) and explore the related molecular mechanisms.Materials and methods: The effect of SMI (0.25, 0.5, 1 mg/mL) to reverse chemoresistance in MCF-7/ADR cells was elucidated by MTT, HPLC-FLD, DAPI staining, flow cytometric analysis, western blotting. At the same time, in vivo test was conducted to probe into the effect of SMI on reversing ADR resistance, and verapamil (10 μM) was used as a positive control.Results: The results showed that the toxicity of ADR to MCF-7/ADR cells was strengthened significantly after treated with SMI (0.25, 0.5, 1 mg/mL), the IC₅₀ of ADR was decreased 54.4-fold. The intracellular concentrations of ADR were increased 2.2-fold (p < 0.05) and ADR accumulation was enhanced in the nuclei (p < 0.05). SMI could strongly enhance the ADR-induced apoptosis and increase intracellular rhodamine 123 accumulation in MCF-7/ADR cells. Additionally, a combination of ADR and SMI (5 mg/kg) could dramatically reduce the weight and volume of tumour (p < 0.05). Furthermore, the results revealed that SMI might reverse MDR via inhibiting ADR-induced activation of the mitogen-activated protein kinase/nuclear factor (NF)-κB pathway to down-regulated the expression of P-glycoprotein (P-gp).Discussion and conclusions: SMI could potentially be used to treat ADR-resistance. This suggests possibilities for future clinical research.

Berberine Reverses Doxorubicin Resistance by Inhibiting Autophagy Through the PTEN/Akt/mTOR Signaling Pathway in Breast Cancer

PURPOSE

Berberine (BBR), a traditional Chinese medicine, has been shown effects on inhibiting cancer development. Autophagy-mediated resistance plays an important role in cancer progression; therefore, regulation of autophagy is a novel therapeutic strategy for cancer treatment. However, effects of BBR on autophagy-mediated resistance have not been reported.

METHODS

MCF-7 breast cancer cells and the doxorubicin (ADR)-resistant MCF-7 cells (MCF-7/ADR) were used for analyses. Western blotting was conducted to evaluate protein expression; MTT, colony formation, and EdU assays were conducted to assess cell proliferation; transmission electron microscopy was used to monitor autophagy levels; and a xenograft tumor model was established to assess the effects of BBR on reversing doxorubicin resistance.

RESULTS

We confirmed that BBR, recently identified as a suppressor of autophagy, inhibits autophagosome formation in MCF-7/ADR cells. Treatment with BBR blocked the accumulation of the autophagy-associated protein LC3II, resulting in cellular accumulation of p62, reduced cell proliferation, and reversal of doxorubicin resistance. Mechanistically, we found that BBR inhibited autophagy by modulating the PTEN/Akt/mTOR signaling pathway. In vivo, our study showed that BBR exerts clear anti-tumor effects.

CONCLUSION

The results of this study suggest that BBR reverses doxorubicin resistance in breast cancer cells by inhibiting autophagy. This finding highlights the potential clinical application of BBR in the treatment of breast cancer.