Epigallocatechin Gallate (EGCG), an Active Phenolic Compound of Green Tea, Inhibits Tumor Growth of Head and Neck Cancer Cells by Targeting DNA Hypermethylation

Anshu Agarwal; Vikash Kansal; Humaira Farooqi; Ram Prasad; Vijay Kumar Singh

doi:10.3390/biomedicines11030789

Epigallocatechin Gallate (EGCG), an Active Phenolic Compound of Green Tea, Inhibits Tumor Growth of Head and Neck Cancer Cells by Targeting DNA Hypermethylation

Biomedicines. 2023 Mar 5;11(3):789. doi: 10.3390/biomedicines11030789.

Authors

Anshu Agarwal¹, Vikash Kansal², Humaira Farooqi³, Ram Prasad⁴, Vijay Kumar Singh^{1

5}

Affiliations

¹ Department of Zoology, Agra College, Dr. Bhimrao Ambedkar University, Agra 282004, India.
² Department of Otolaryngology, Emory University, Atlanta, GA 30322, USA.
³ Department of Biochemistry, Hamdard University, New Delhi 110062, India.
⁴ Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
⁵ Narain PG Degree College, Shikohabad, Dr. Bhimrao Ambedkar University, Agra 282004, India.

Abstract

Head and neck cancers are among the deadliest cancers, ranked sixth globally in rates of high mortality and poor patient prognoses. The prevalence of head and neck squamous cell carcinoma (HNSCC) is associated with smoking and excessive alcohol consumption. Despite several advances in diagnostic and interventional methods, the morbidity of subjects with HNSCC has remained unchanged over the last 30 years. Epigenetic alterations, such as DNA hypermethylation, are commonly associated with several cancers, including HNSCC. Thus, epigenetic changes are considered promising therapeutic targets for chemoprevention. Here, we investigated the effect of EGCG on DNA hypermethylation and the growth of HNSCC. First, we assessed the expression levels of global DNA methylation in HNSCC cells (FaDu and SCC-1) and observed enhanced methylation levels compared with normal human bronchial epithelial cells (NHBE). Treatment of EGCG to HNSCC cells significantly inhibited global DNA hypermethylation by up to 70-80% after 6 days. Inhibition of DNA hypermethylation in HNSCC cells was confirmed by the conversion of 5-methylcytosine (5-mc) into 5-hydroxy methylcytosine (5hmC). DNA methyltransferases regulate DNA methylation. Next, we checked the effect of EGCG on the expression levels of DNA methyltransferases (DNMTs) and DNMT activity. Treatment of EGCG to HNSCC cells significantly reduced DNMT activity to 60% in SCC-1 and 80% in FaDu cells. The protein levels of DNMT3a and DNMT3b were downregulated in both cell lines after EGCG treatment. EGCG treatment to HNSCC cells reactivated tumor suppressors and caused decreased cell proliferation. Our in vivo study demonstrated that administration of EGCG (0.5%, w/w) as a supplement within an AIN76A diet resulted in inhibition of tumor growth in FaDu xenografts in nude mice (80%; p < 0.01) compared with non-EGCG-treated controls. The growth inhibitory effect of dietary EGCG on the HNSCC xenograft tumors was associated with the inhibition of DNMTs and reactivation of silenced tumor suppressors. Together, our study provides evidence that EGCG acts as a DNA demethylating agent and can reactivate epigenetically silenced tumor suppressors to inhibit the growth of HNSCC cells.

Keywords: DNA methylation; EGCG; HNSCC; epigenetics; growth.

Grants and funding

This study was partially supported by the Vaikunthi Devi (VD-2020/01/06/21) educational trust, Agra, India, to A.A., and salary support to R.P. from NIH-funded research projects (R01EY025383, R01EY012601, R01EY028858, R01EY032753, and R01EY028037 awarded to Maria B. Grant).