Ethyl Acetate Extract of Halymenia durvillei Induced Apoptosis, Autophagy, and Cell Cycle Arrest in Colorectal Cancer Cells

Colorectal cancer is one of the most death-dealing cancers. However, conventional cancer treatments still have side effects. Therefore, novel chemotherapeutic agents with less side effects are still in search. A marine red seaweed, Halymenia durvillei, is recently interested in its anticancer effects. This study investigated the anticancer effect of ethyl acetate extract of H. durvillei (HDEA) on HT-29 colorectal cancer cells in association with the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway. HDEA-treated HT-29 and OUMS-36 cells were used for cell viability tests by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide assay. The effects of HDEA on apoptosis and cell cycle were evaluated. The nuclear morphology and mitochondrial membrane potential (ΔΨm) were observed by Hoechst 33342 and JC-1 staining, respectively. The gene expression of PI3K, AKT, and mTOR genes was evaluated using a real-time semiquantitative reverse transcription-polymerase chain reaction. The corresponding protein expressions were assessed by western blot analysis. The result revealed that the cell viability of treated HT-29 cells diminished while that of OUMS-36 cells was non-significant. By the down-regulation of cyclin-dependent ki-nase 4 and cyclin D1, HDEA-treated HT-29 cells were arrested in the G0/G1 phase. By the up-regulation of cleaved poly(adenosine diphosphate-ribose) polymerase, caspase-9, caspase-8, caspase-3, and Bax, HDEA-treated HT-29 cells underwent apoptosis, but suppressed Bcl-2, disrupted nuclear morphology and ΔΨm. Furthermore, treated HT-29 cells underwent autophagy by up-regulation of light chain 3-II and beclin-1. Lastly, HDEA suppressed the expression of PI3K, AKT, and mTOR. Therefore, HDEA exerts anticancer effects against HT-29 cells, confirmed by apoptosis, autophagy, and cell cycle arrest induction via regulation of the PI3K/AKT/mTOR signaling pathway.