EGCG: A Metabolic Weapon Hidden in Green Tea

A Tier 1 anti-cancer drug

Epigallocatechin-3-gallate (EGCG), the main catechin in green tea, shows broad anticancer activity in preclinical models by affecting many cancer “hallmarks”. In addition, its anti-cancer activity is supported by clinical studies.

Figure 1. Epigallocatechin Gallate

Key anticancer actions

• Inhibits cancer cell growth by blocking proliferation and inducing cell cycle arrest, often at the G0/G1 or S phases in prostate, pancreatic, liver and other cancer cells.​

• Promotes apoptosis (programmed cell death) through mitochondrial pathways, including Bax activation, loss of mitochondrial membrane potential, cytochrome c release, caspase activation and downregulation of anti‑apoptotic proteins such as BCL‑2 and XIAP.​

• Suppresses angiogenesis, invasion and metastasis by inhibiting VEGF signaling, matrix metalloproteinases and cell adhesion/invasion in several tumor types, including hepatocellular carcinoma and lung cancer models.

Figure 2. Anticancer pathways of EGCG

Anticancer pathways and mechanisms

Green tea is a significant source of a type of flavonoid called catechin, which includes epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC). The most abundant individual catechin in fresh tea leaves is EGCG, which is more than 40% of the total content of catechins. (1) Green tea catechins (GTCs) have been proven to be effective in inhibiting cancer growth in several experimental models. (2-4) In addition, GTCs may have synergistic anticancer activity when combined with other phytochemicals, particularly resveratrol and curcumin. (5, 6) GTCs, particularly EGCG, may have a role in both the prevention and treatment of cancers, (7) specifically those dependent on the glutamate pathway as a source of energy. Mitochondrial glutamate dehydrogenase (GDH) catalyzes the oxidative deamination of L-glutamate. Activation of GDH is tightly correlated with increased glutaminolysis. Furthermore, glutamate serves as a mitochondrial intracellular messenger when glucose is being oxidized and the GDH participates in this process by synthesizing glutamate. (8) Li and colleagues demonstrated in vitro that EGCG allosterically inhibits GDH in nanomolar concentrations. (9, 10)

GTCs have an important anticarcinogenic role by promoting and/or inhibiting signal transmission through the targeted regulation of multiple links in the signal pathways that are activated or inhibited in cancer cells. (1) EGCG regulates signaling pathways by interacting with membrane receptors. EGCG significantly inhibited the expression of VEGF and reduced VEGF receptors. Inactivation of the VEGF signaling pathway suppresses angiogenesis, a common strategy for inhibiting carcinogenesis. EGCG activates PKA, which dephosphorylates related proteins such as the tumor suppressor Merlin and inhibits the proliferation of cancer cells. (11) EGCG inhibits STAT3 phosphorylation by blocking JAK2 phosphorylation. STAT3 suppresses anti-tumor immune responses and promotes the proliferation and migration of cancer cells. EGCG inhibits the MAPK signaling by competing for the phosphorylation sites of downstream proteins. EGCG inhibits the Wnt pathway by phosphorylating β-catenin and promoting its degradation. EGCG inhibits transcription factors involved in activating the Sonic hedgehog pathway. EGCG inhibited the activities of MMP2 and MMP9 and promoted the expression of tissue inhibitor of MMPs (TIMp1/2) to suppress the invasion and metastasis of tumor cells. (11) Green tea extract has been demonstrated to suppress cancer stem cells. (12, 13)

GTCs have anticancer effects via additional pathways. (1) GTCs exert potent and selective in vitro and in vivo pro-apoptotic activity in cancer cells via several pathways. (2, 3, 14) GTC inhibits A549 cells by regulating its cell cycle arrest, increasing the expressions of p21 and p27, and inhibiting the expressions of p-AKT and cyclin E1 in a dose-dependent manner in the cancer cells. (15) EGCG inhibited the proliferation of human lung cancer cells by targeting the epidermal growth factor receptor (EGFR) signaling pathway.

GTCs have been demonstrated to alter the tumor microenvironment (TME) thereby attenuating immunosuppression and the risk of metastases. (6) Flavonoids including GTCs (and resveratrol) are potent modulators of pro-inflammatory gene expression being, therefore, of great interest as agents selectively suppressing molecular targets within pro-inflammatory TME. GTCs have been demonstrated to increase the ratio of active cytotoxic T lymphocytes to Tregs in tumors, indicating a switch of “cold” tumors to “hot” with significantly improved anti-tumor immune therapeutics. (16) GTCs have anticancer effects by enhancing anticancer immunity via PD-1 axis and TLR4 pathways. (17, 18) In addition, GTCs repolarize tumor-associated macrophages (M2 to M1 macrophages), triggering an immune response and limiting metastases. (19) GTCs have been demonstrated to attenuate MDSC-mediated immunosuppression and increased the proportions of CD4+ and CD8+ T cells. (20)

Studies have shown that 20% of cancer-related deaths were directly due to TLR-induced cancer cachexia, in which cancer cells released heat shock proteins that acted as TLR-4 agonists in macrophages, skeletal muscle, and fat cells, causing downstream signal transduction. EGCG effectively downregulates the TLR-4 signal pathway. (18)

GTCs inhibit the accumulation of MDSCs, leading to restoration of the IFN-γ, enhancing the activity of CD8+ T-cells, and improvement of the ratio of CD4(+) to CD8(+) T-cells, which is beneficial to the improvement of the immune system’s attack on tumor cells. (1) In addition, a phytochemical mixture including GTCs exerted anti-tumor activity by repolarization of M2-polarized macrophages and induced the production of IL-12, which recruit cytotoxic T lymphocytes and natural killer cells (NK) with the tumor microenvironment. (19)

Figure 3: EGCG- Multitargeted anti-cancer activity

Synergy and resistance

In addition to all these beneficial effects, GTCs potentiate the effects of conventional chemotherapeutic agents. Due to their effects on the important signaling pathways in vivo, catechins are often used as sensitizing agents in combination with chemotherapeutic drugs. The combination of anticancer drugs with catechins, whether before or after drug administration, reduced the toxicity of these drugs and enhanced the clinical efficacy by accelerating apoptosis of cancer cells. (1) Importantly, the combination of a number of chemotherapeutic drugs with GTCs will improve the chemotherapeutic sensitivity of cells to the drug, allowing a reduction in the dose of the chemotherapeutic drug. (1)

EGCG enhances the activity of standard chemotherapeutics (for example doxorubicin) by increasing apoptosis and inhibiting migration and can help reverse multidrug resistance by modulating P‑glycoprotein and related transporters in some models.​ EGCG effectiveness can depend on tumor genotype; for instance, EGFR mutations in non‑small cell lung cancer lines are associated with resistance to EGCG’s EGFR‑blocking effects.

EGCG and Curcumin

EGCG and curcumin frequently show synergistic anticancer effects in preclinical models, enhancing growth inhibition, apoptosis, and anti‑angiogenic activity at lower doses than either agent alone. EGCG tends to arrest cells in G0/G1, while curcumin induces S and G2/M phase arrest; together they cause broader cell‑cycle blockade and stronger suppression of proliferation.​ The combination enhances apoptosis via mitochondrial pathways and convergent inhibition of survival signaling (for example NF‑κB, STAT3, and related prosurvival pathways), leading to greater caspase activation and PARP cleavage than either compound alone. In colorectal carcinoma models, EGCG plus curcumin blocked tumor‑conditioned medium–induced transition of normal endothelial cells to tumor endothelial cells by inhibiting JAK/STAT3/IL‑8 signaling, reducing migration, invasion and tube formation more than single agents. Prostate cancer PC3 cells, which are relatively resistant to apoptosis, show markedly improved growth inhibition and combined S and G2/M arrest when treated with EGCG plus curcumin compared with either agent alone.

Clinical studies

Numerous experimental models have explored the mechanistic anticancer effects of GTCs; this data is supported by epidemiologic data, a case series of patients with B cell malignancies,(21) several case reports,(22, 23) and a RCT. A meta-analysis including 18 prospective cohorts and 25 case-control studies showed a significant inverse association between intake of tea catechins and risk of various cancers, with a relative risk (RR) being 0.935 (95% CI = 0.891-0.981). (1) Similarly an umbrella review and meta-analysis by Kim et al, which included 64 observational studies (case-control or cohort) demonstrated that GTC significantly reduced the risk of gastrointestinal cancer (oral, gastric, colorectal, biliary tract, and liver), breast cancer, and gynecological cancer (endometrial and ovarian cancer) as well as leukemia, lung cancer, and thyroid cancer. (24) In a phase I dose finding study in patients with Chronic Lymphocytic Leukemia EGCG was well tolerated and a decline in the absolute lymphocyte count and/or lymphadenopathy was observed in the majority of patients. (25) Lemanne et al reported on a patient who demonstrated a complete and durable remission of chronic lymphocytic leukemia (CLL) following high dose EGCG. (23) In a randomized, double-blind, placebo-controlled study, treatment with 600 mg/day of green tea catechins reduced the risk of prostate cancer from 30% to 3% in men with high-grade prostate intraepithelial neoplasia. (26)

Types of cancers that green tea may be beneficial for

Green tea catechins may be effective against a range of tumors including cancers of the prostate, breast, uterus, ovary, colorectal, glioma, liver and gallbladder, melanoma, and lung cancers. (1) GTCs appear to be particularly beneficial for prostate cancer as well as breast cancer. (2-5, 20, 26-28)

Dosing and cautions

Green tea catechins should be taken in a dose of 500-1000 mg/day. Green tea extract should be taken during/after a meal rather than on an empty stomach. (29) Green tea extract has rarely been associated with liver toxicity. (30) The safety of green tea extract was evaluated by the US Pharmacopeia (USP) Dietary Supplement Information Expert Committee (DSIEC). (29) The DSIEC concluded that “when dietary supplement products containing green tea extracts are used and formulated appropriately the Committee is unaware of significant safety issues that would prohibit monograph development.” (29) Based on this data we suggest that green tea exacts be taken in the dosages recommended by the manufacturer. Regular liver function tests are suggested in patients taking green tea extract and green tea exact should be avoided/used cautiously in those with underlying liver disease.

Native EGCG has modest oral bioavailability, which has led to development of formulations such as nano‑EGCG that show stronger inhibition of proliferation, colony formation, migration and invasion in lung and breast cancer cells.​ These advanced formulations often work through the same core pathways (for example AMPK activation) but reach higher effective concentrations at the tumor site in experimental models.

Macha Tea

Matcha is a powdered form of green tea made from shade‑grown Camellia sinensis leaves, and it delivers higher concentrations of catechins and other polyphenols than typical brewed green tea per gram.​ The main catechin is epigallocatechin‑3‑gallate (EGCG).

In breast cancer models, matcha extract inhibited cancer stem cell propagation at low concentrations, partly by suppressing mitochondrial oxidative phosphorylation and glycolysis, shifting cells toward a metabolically quiescent state and reducing mammosphere formation.(13)

Green tea and matcha are generally considered safe as beverages, but high intakes or concentrated extracts have occasionally been associated with liver toxicity, so moderation and avoidance of high‑dose supplements without medical supervision are recommended.

Medical Disclaimer: The discussion of repurposed medications and nutraceuticals in this article is intended to review the scientific literature and does not constitute a recommendation for self-treatment. Decisions regarding the use of off-label therapies should be made in consultation with a qualified healthcare professional familiar with the patient’s medical history and current treatment plan. Please see the full Medical Disclaimer on the introductory page to Marik’s Cancer & Metabolic Healing Playbook.

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