Pyrogallol inhibits the growth of human lung cancer Calu-6 cells via arresting the cell cycle arrest

Pyrogallol (PG) is a polyphenol compound and has been known to be an O₂^{{radical dot} -} generator. We evaluated the effects of PG on the growth of human pulmonary adenocarcinoma Calu-6 cells in relation to the cell cycle. DNA flow cytometric analysis indicated that PG induced a G2 phase arrest of the cell cycle in Calu-6 cells at 72 h. PG down-regulated the expression of CDKI (p27), CDK2, CDK4 and CDK6 as well as cyclin D1, and increased cyclin A and cyclin B1 proteins. In addition, O₂^{{radical dot} -} levels were significantly increased in PG-treated cells. Treatment with catalase rescued Calu-6 cells from PG-induced apoptosis, and also prevented the growth inhibition as well as a G2 phase arrest by PG, which were accompanied with the down-regulation of O₂^{{radical dot} -} levels. In conclusion, PG inhibited the growth of Calu-6 cells by inducing the cell cycle arrest, accompanied with an increase in O₂^{{radical dot} -} levels.