Epigallocatechin gallate promotes p53 accumulation and activity via the inhibition of MDM2-mediated p53 ubiquitination in human lung cancer cells

Abstract

Abstract. Epigallocatechin gallate (EGCG), which is derived from green tea, is well known for its chemopreventive activity. Several studies have shown that p53 plays an important role in the activity of EGCG; however, the mechanism by which EGCG regulates p53 requires further investigation. In the present study, we showed that EGCG inhibits anchorage-independent growth of human lung cancer cells by upregulating p53 expression. EGCG treatment can substantially increase p53 stability, promote nuclear localization of p53 and decrease nuclear accumulation of MDM2. We also found that EGCG increases the phosphorylation of p53 at Ser15 and Ser20 and enhances its transcriptional activity. Although EGCG promotes MDM2 expression in a p53-dependent manner, the interaction between MDM2 and p53 was significantly inhibited following EGCG treatment, which resulted in the inhibition of MDM2-mediated p53 ubiquitination. Thus, our results suggest that the stabilization and activation of p53 may partly contribute to the anticancer activity of EGCG. IntroductionAccording to the results of epidemiologic studies, green tea consumption has a preventive effect on carcinogenesis (1-6). It is thought that polyphenols, also known as catechins, play an important role in the chemopreventive effects mediated by green tea. (-)-Epigallocatechin gallate (EGCG), a type of polyphenol, which is the most well known, abundant and active compound found in green tea, exerts its anticancer effects in a wide range of malignancies (2,7). Previous studies have suggested that multiple signaling pathways and mechanisms are involved in the antitumor activity of EGCG (1,8-10), including suppression of various protein kinases (11-13); disruption of the activation of transcription factors such as EGFR, NF-κB, AP-1 and STATs (14-16); induction of cell cycle arrest or apoptosis (17,18); and inhibition of cell migration and metastasis (19-24).p53, commonly referred to as the 'cellular gatekeeper' or 'the guardian of the genome', is a crucial tumor suppressor gene that is mutated in more than half of all types of human cancer. As a transcription factor, p53 functions to regulate cell fate following various types and levels of cellular stress through its downstream target genes. In addition to its canonical functions of inducing DNA repair, cell cycle arrest and apoptosis (25,26), recent studies have also revealed that p53 is involved in the regulation of various other cellular functions, such as senescence, metabolism and autophagy. Due to the importance of p53, its activation is regulated by complicated post-translational modifications, such as phosphorylation, acetylation, ubiquitination and sumoylation (8,(27)(28)(29). Previous studies have shown that the phosphorylation and acetylation of p53 promotes the expression of p53 target genes (28,30,31), whereas other modifications, such as ubiquitination and sumoylation, are considered to be associated with the suppression of p53-mediated transcription and nuclear export of p53 (32-34). MDM2, a Ring finger domain-con...

APE1/Ref-1 as an emerging therapeutic target for various human diseases: phytochemical modulation of its functions

“…215 EGCG has been shown to block the interaction between mouse double minute 2 homolog (MDM2) and p53, thus inhibiting MDM2-mediated p53 ubiquitination, which directly affects DNA damage repair. 216 EGCG exhibits significantly greater anti-invasive properties than other catechins. EGCG reverses the epithelial-to-mesenchymal transition in melanoma cells.…”

Neuroepithelial transforming gene 1 functions as a potential prognostic marker for patients with non-small cell lung cancer

“…RNA extraction and RT-qPCR. RT-qPCR was performed as described previously (20). Total RNA was extracted from tissue specimens using TRIzol reagent (Invitrogen Life Technologies, Inc., Carlsbad, CA, USA) according to the manufacturer's instructions.…”

Epigallocatechin gallate inhibits the growth of human lung cancer by directly targeting the EGFR signaling pathway

“…Epidemiological investigations and experimental studies have shown that green tea has chemopreventive effects for a wide range of malignancies, including lung, stomach, breast, prostate, pancreatic, ovarian, liver, colorectal and skin cancer (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). Mechanistic studies indicate that EGCG, the major component of green tea, appears to be the primary active ingredient responsible for its biological effects.…”