BACKGROUND In developed countries,
colon cancer is a leading cause of
cancer-associated mortality. Dietary changes have resulted in an increased incidence of
colon cancer in Asia. This study aimed to investigate the effects of the structural analog of
endomorphin-2 (H-
Tyr-Pro-
Phe-Phe-NHâ‚‚) on human
colon cancer cells in vitro. MATERIAL AND METHODS Human DLD-1 and RKO
colon cancer cells and CCD-18Co normal human colonic fibroblasts were treated with increasing doses of the structural analog of
endomorphin-2. Cells underwent the MTT assay, fluorescence confocal flow cytometry, and
Hoechst 33258 staining to investigate cell proliferation, the cell cycle, and apoptosis. Western blot was used to measure the expression levels of
poly(ADP-ribose) polymerase-1 (PARP-1),
cytochrome c,
caspase-3, and
caspase-9. The
2',7'-dichlorofluorescein diacetate (
DCFH-DA) fluorescence method measured
reactive oxygen species (ROS). RESULTS Cell proliferation of DLD-1 and RKO cells was inhibited by the
endomorphin-2 analog in a dose-dependent manner, and a 100 µM dose reduced DLD-1 and RKO cell proliferation by 28% and 23%, respectively, at 72 h.
Endomorphin-2 analog induced cell apoptosis and the generation of ROS, activated
caspase-3 and
caspase-9, and increased the levels of p53 and
cytochrome c release, and down-regulated of Akt activation in DLD-1 and RKO cells in a dose-dependent manner. Treatment of the DLD-1 and RKO cells with the
endomorphin-2 analog increased the expression of Bax and reduced the expression of Bcl-2. CONCLUSIONS
Endomorphin-2 analog inhibited
colon cancer cell proliferation, activated apoptosis, and down-regulated Akt phosphorylation of human DLD-1 and RKO
colon cancer cells in vitro in a dose-dependent manner.