Green tea is now recognized as the most effective cancer preventive beverage. In one study, 10 Japanese-size cups of green tea daily supplemented with tablets of green tea extract limited the recurrence of colorectal polyps in humans to 50%. Thus, cancer patients who consume green tea and take anticancer drugs will have double prevention. We studied the effects of combining ())-epigallocatechin gallate (EGCG) and anticancer drugs, focusing on inhibition of cell growth and induction of apoptosis. Numerous anticancer drugs, such as tamoxifen, COX-2 inhibitors, and retinoids were used for the experiments, and the combination of EGCG and COX-2 inhibitors consistently induced the enhancement of apoptosis. To study the mechanism of the enhancement, we paid special attention to the enhanced expressions of DDIT3 (growth arrest and DNA damage-inducible 153, GADD153), GADD45A, and CDKN1A (p21 ⁄ WAF1 ⁄ CIP1) genes, based on our previous evidence that a combination of EGCG and sulindac specifically induced upregulated expression of GADD153 and p21 genes in PC-9 lung cancer cells. The synergistic enhancements of apoptosis and GADD153 gene expression in human non-small cell lung cancer cells by the combination of EGCG and celecoxib were mediated through the activation of the MAPK signaling pathway. This article reviews the synergistic enhancement of apoptosis, gene expression, and anticancer effects using various combinations of EGCG and anticancer drugs, including the combination of ())-epicatechin (EC) and curcumin. Based on the evidence, we present a new concept: green tea catechins as synergists with anticancer drugs. (Cancer Sci 2011; 102: 317-323) ''C ancer chemoprevention'' was defined in 1976,(1) and Michael Sporn (2) introduced the term ''combination cancer chemoprevention'' in the journal Nature in 1980. He defined the term as the combined use of several drugs with different mechanisms of action exerting marked synergistic preventive effects. In 1983, we began to study the cancer preventive activity of green tea catechins.(3,4) Green tea extract chemically contains at least four tea catechins: EGCG, ECG, EGC, and EC. The first three catechins induce cancer preventive activities, whereas EC is inactive.(5) We first reported that combinations with the active catechins and inactive EC induced synergistic effects on induction of apoptosis and inhibition of cell growth of human lung cancer cell line PC-9, and inhibition of TNF-a release from BALB ⁄ 3T3 cells treated with okadaic acid, a tumor promoter.(6) This suggests that whole green tea, which is a mixture of green tea catechins, is a more effective and practical cancer preventive than green tea catechins alone.(6) Using tritium ( 3 H)-EGCG we showed that EC induced the enhanced incorporation of 3 H-EGCG and other active green tea catechins into cells.(6) In addition, we recently showed that drinking 10 cups of green tea supplemented with green tea tablets significantly (50%) prevented recurrence of colorectal adenomas in patients who had received polypectomy 1 yea...