Green tea catechin, epigallocatechin-3-gallate, attenuates the cell viability of human non-small-cell lung cancer A549 cells via reducing Bcl-xL expression

Abstract

Clinical and epidemiological studies have indicated that the consumption of green tea has a number of beneficial effects on health. Epigallocatechin-3-gallate (EGCg), the major polyphenolic compound present in green tea, has received much attention as an active ingredient. Among the numerous promising profiles of EGCg, the present study focused on the anticancer effects. Apoptosis induced by EGCg and subsequent cell growth suppression have been demonstrated in a number of cell culture studies. However, the underlying mechanism of apoptotic cell death remains unclear. Thus, the aim of the present study was to identify the major molecule that mediates proapoptotic cell death by EGCg. The effect of EGCg on cell proliferation and the induction of mRNA that modulates apoptotic cell death was evaluated in the A549 human non-small-cell lung cancer cell line. In addition, morphological changes were assessed by microscopy in A549 cells that had been treated with 100 μM EGCg for 24 h. The MTT assay revealed that cell proliferation was significantly reduced by EGCg in a dose-dependent manner (3-100 μM). The mRNA expression level of B-cell lymphoma-extra large (Bcl-xL) was decreased in A549 cells following 24 h incubation with 100 μM EGCg. Therefore, the results indicated that the inhibition of cell proliferation by EGCg may be achieved via suppressing the expression of the cell death-inhibiting gene, Bcl-xL.

Keywords: A549 cells; B-cell lymphoma-extra large; apoptosis; epigallocatechin-3-gallate.

Figure 1

Chemical structures of green tea catechins.

Figure 2

Effect of EGCg on the morphology of A549 cells. Representative morphology of A549 cells was microscopically observed in (A) control and following co-culture with (B) 25 μM and (C) 100 μM EGCg. EGCg, epigallocatechin-3-gallate.

Figure 3

Effect of EGCg on A549 cell survival in the absence or presence of EGCg (3–100 μM), as determined by an MTT assay. Points represent the mean of triplicate determination and the bars show the standard deviation. EGCg, epigallocatechin-3-gallate. *Significant reduction compared with control (0 mM EGCg).

Figure 4

Effect of EGCg on the expression of Bcl-xL in A549 cells, as determined by RT-PCR analysis. Representative image showing the Bcl-xL and GAPDH mRNA expression levels in the absence or presence of 100 μM EGCg. EGCg, epigallocatechin-3-gallate; Bcl-xL, B-cell lymphoma-extra large; RT-PCR, reverse transcription polymerase chain reaction.