Deoxyshikonin Isolated from Inhibits Colorectal Cancer by Down-regulating the PI3K/Akt/mTOR Pathway

Shikonins, a series of natural occurring naphthoquinones extracted from (Royle) Jonst. (Boraginaceae), have antitumor activities and low toxicity. To illuminate potential activity and mechanism of shikonins against colorectal cancer (CRC). Five shikonins were isolated from , and elucidated by extensive spectroscopic analysis. Anti-proliferative activities of shikonins (0-100 μg/mL) on human colorectal cells were evaluated by MTT and CCK-8 for 24 or 48 h. Cell apoptosis and cycle distribution were examined by FCM analysis. The expression of PI3K/Akt/mTOR pathway mRNAs and proteins was analysed by RT-PCR and Western blot, respectively. Cell viability, cell apoptosis, cell cycle and protein expression were measured, when co-treated with PI3K/Akt/mTOR pathway inhibitors. The activity of deoxyshikonin was evaluated using xenograft tumour model. Deoxyshikonin and another four shikonins were isolated and identified. Deoxyshikonin exhibited anti-proliferative activity with IC of 10.97 μM against HT29 cells. Moreover, the percentage of early apoptotic cells and G0/G1 cells increased from 1 to 29% and 44 to 67% with 0-50 μg/mL deoxyshikonin, respectively. Deoxyshikonin also down-regulated the expression of PI3K, p-PI3K, Akt, p-Akt308 and mTOR proteins in HT29 and DLD-1 cells. Moreover, LY294002, NVP-BEZ235 and MK-2206 can make deoxyshikonin more cell proliferation inhibited, cell cycle arrested at G0/G1 and apoptosis promoted. study, the weight of tumour tissues at deoxyshikonin groups was significantly reduced compared with the control group, and PI3K, p-PI3K, Akt, p-Akt308 and mTOR expression was decreased. We can conclude that deoxyshikonin isolated from inhibited CRC through the PI3K/Akt/mTOR pathway.