title: Stereoisomers of Astaxanthin Inhibit Human Colon Cancer Cell Growth by Inducing G2/M Cell Cycle Arrest and Apoptosis.
abstract: Astaxanthin (AST) is a xanthophyll carotenoid with potential protective effects against carcinogenesis. Different stereoisomers of AST (ASTs) exist in a variety of food sources. Due to limited information on the bioactivities of ASTs, the present study investigated the inhibitory effects of ASTs on HCT116 and HT29 human colon cancer cells. ASTs investigated herein included 3S,3'S (S) from Haematococcus pluvialis, 3R,3'R (R) from Phaffia rhodozyma, and a statistical mixture (S: meso: R = 1:2:1) (M) from synthetic AST. Cell viability assay showed that ASTs all inhibited colon cancer cell growth in a time-dependent (24-72 h) and dose-dependent (4-16 μM) manner, and there was no significant difference among the IC50values of ASTs (p > 0.05). Flow cytometry analysis indicated that ASTs induced G2/M cell cycle arrest and cellular apoptosis in cancer cells. The cell cycle arrest caused by ASTs was associated with increases in the expression levels of p21Cip1/Waf1, p27, and p53, as well as decreases in the levels of CDK4 and CDK6. Meanwhile, the apoptosis induced by ASTs was confirmed by activation of caspase-3 and PARP in the cancer cells. The results indicated that hydroxyl (OH) at C3 and C3' of terminal ring structure might not be the major factor that affects the anticancer activity of AST. This study revealed important information on the inhibitory effects of ASTs on human colon cancer cells, which provided a basis for using ASTs as chemopreventive agents for colon cancer.
authors.affiliation: Department of Food Science, College of Food Science, South China Agricultural University , Guangzhou 510642, China.|Department of Food Science, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Food Science, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: Mingyue
authors.initials: M
authors.lastname: Song
authors.affiliation: Department of Food Science, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: Zili
authors.initials: Z
authors.lastname: Gao
authors.affiliation: Department of Food Science, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: Xiaokun
authors.initials: X
authors.lastname: Cai
authors.affiliation: Department of Food Science, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: William
authors.initials: W
authors.lastname: Dixon
authors.affiliation: Department of Food Science, College of Food Science, South China Agricultural University , Guangzhou 510642, China.
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Food Science, College of Food Science, South China Agricultural University , Guangzhou 510642, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Food Science, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: Hang
authors.initials: H
authors.lastname: Xiao
keywords: apoptosis; astaxanthin; cell cycle; colon cancer; stereoisomer