Sapphire used to Study Anti-cancer Effects in Green Tea

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Recent work published by Zhao et al in nature communications lends insight into a potential mechanism for the anti-cancer effects of green tea. The health benefits of drinking tea, particularly green tea, has been the subject of intense investigation. A large number of epidemiologic studies have examined whether tea consumption can reduce cancer risk, with a focus on a category of polyphenols called catechins, the most active and abundant of which in green tea is epigallocatechin-3-gallate (EGCG).

Zhao et al demonstrate how EGCG binds to the N-terminal domain of p53 in a recent study. They show that EGCG disrupts the interaction of p53 with MDM2 and inhibits ubiquitylation of p53 by MDM2.

In the publication, ubiquitylation assays were carried out using fluorescein-labeled p53 and varying amounts of EGCG. After incubation with MDM2 and ubiquitin, the amount of free and ubiquitinated p53 was detected on SDS-PAGE gels using the fluorescent channel from an Azure Sapphire Biomolecular Imager (Figure 6A). The amount of ubiquitin was quantified and concentration-dependent inhibition of ubiquitylation by EGCG was analyzed (Figure 6).

Since the release of this publication, the Azure Sapphire has been succeeded by the new Azure Sapphire FL, which was designed to be the flexible choice in bringing precise quantitation of nucleic acids and proteins. Learn more.

Potential anti-tumor properties from green tea

The authors propose the EGCG-induced reduction in ubiquitylation could stabilize p53 protein, making more p53 available and contributing to its anti-tumor activity. Additionally, the work suggests the N-terminal domain of p53 presents an attractive target for anti-cancer drug design.

Fig. 6: EGCG inhibits the MDM2-catalyzed ubiquitination of p53 in vitro.
Figure 6 from Zhao, J., Blayney, A., Liu, X. et al. Nat Commun 12, 986 (2021), licensed under CC BY 4.0. a. In-vitro ubiquitination of fluorescein-tagged p53 was carried out in the presence of up to 0.25 mM EGCG at 20 °C. The results were visualized by fluorescence SDS–PAGE. b. Plotting the fluorescence fraction of residual unmodified p53 as a function of EGCG concentration and fitting to a four-parameter sigmoid indicates that EGCG has an IC50 of ~100 μΜ for the MDM2-catalyzed ubiquitination of p53.

Health benefits of drinking green tea

According to the National Cancer Institute, EGCG and other polyphenols found in green tea have multiple biological activities including being potent antioxidants, inhibiting tumor cell proliferation, inducing tumor cell apoptosis, inhibiting angiogenesis, and activating detoxifying enzymes.

In in-vitro studies, EGCG has been shown to induce apoptosis in cancer cell lines. The transcription factor p53 plays a role in this activity of EGCG. P53 is an important tumor suppressor, promoting cell cycle arrest or apoptosis when a cell is stressed. Usually, cellular p53 levels are low, with p53 being ubiquitylated which targets the protein for degradation. The ubiquitylation is carried out by the protein MDM2, an E3 ligase. When cells are stressed, ubiquitylation is suppressed, p53 is not degraded, and p53 levels increase. The p53 protein then promotes apoptosis through interactions with other proteins and by inducing gene expression changes. Earlier studies have shown EGCG stabilizes p53 and may interfere with the interaction of p53 and MDM2.

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Next time you’re sipping on a cup of green tea with good company, share with them the findings of this study. Science is better shared with a friend! The Sapphire imager provides many imaging capabilities, in addition to multi-channel fluorescence, it can do white light, phosphor imaging, and chemiluminescence imaging of blots, tissues, microplates, and more.

Ready to learn more about the Sapphire imager and how it can support your research? Check out the capabilities of the Sapphire by clicking here.

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