The major component of green tea is (-)-epigallocatechin-3-gallate(EGCG) which accounts for 5080% of catechin, representing 200300 mg in a brewed cup of green tea. EGCG has been known to possess growth inhibitory and pro-apoptotic effect on human cancer cell lines such as prostate, bladder and breast cancers. In contrast, several studies have suggested that EGCG could promote cell proliferation and/or survival instead of pro-apoptotic effect. Understanding how intracellular signaling pathways respond to EGCG may provide a clue to the difference of cell responses and basis for usefulness of EGCG as a chemopreventive and/or chemotherapeutic agent. To better understand the mechanisms responsible for the chemopreventive efficacy of EGCG, the authors tried to identify the key molecules that contributes to Akt activation and can inhibit this activation. In the present study, EGCG increased Akt phosphorylation, an activeform of Akt and negatively affect on direct upstream molecules of Akt including PTEN and EGFR, though Akt phosphorylation was increased.

I. Introduction
 II. Materials and Methods
  1. Cell cultures
  2. EGCG and/or kinase inhibitor treatment
  3. MTT assay
  4. Western Blot Analysis
 III. Results
  1. EGCG exhibits dual functions on cellsurvival depending on cell types
  2. EGCG promotes Akt activity of HaCat cellswhen other growth factors are deprived
  3. EGCG phosphorylates Akt although growthfactor signaling pathways are blocked
  4. EGCG activates Akt through a differentsignaling pathway depending cell types
 IV. Discussion
 V. References

• 김명진(부산대학교 치의학 전문대학원 치의학과 구강병리학 교실) | Myung Jin Kim
• 김형일(부산대학교 치의학 전문대학원 치의학과 치과재료학 교실) | Hyung Il Kim
• 김현철(부산대학교 치의학 전문대학원 치의학과 치과보존학 교실) | Hyeon Cheol Kim
• 정진(부산대학교 치의학 전문대학원 치의학과 구강미생물학 교실) | Jin Chung
• 박혜련(부산대학교 치의학 전문대학원 치의학과 구강병리학 교실) | Hae Ryoun Park correspondence