[Inhibition effect of active fraction from clove on PI3K/Akt/mTOR signaling pathway to induce apoptosis of human colon cancer HCT116 cells]

To screen the sensitive cell lines of active fraction from clove(AFC) on human colon cancer cells, investigate the effects of AFC on the cells proliferation and apoptosis as well as PI3 K/Akt/mTOR(phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin) signaling pathways involved, and reveal the mechanism of AFC for inducing apoptosis of human colorectal carcinoma cells. Cell counting kit-8(CCK-8) assay was used to detect the cytotoxic effect of different concentrations of AFC. AFC-induced apoptosis was detected by Hoechst 33258 fluorescence staining and Annexin V-FITC/PI double staining. HCT116 cells were treated with AFC with or without pretreatment with insulin-like growth factor-Ⅰ(IGF-Ⅰ), and then the protein expression levels of caspase-3, caspase-9, poly ADP-ribose polymerase(PARP), PI3 K, p-PI3 K, Akt, p-Akt, mTOR and p-mTOR in PI3 K/Akt/mTOR signaling pathway were detected by Western blot. RESULTS:: showed that the most obvious inhibitory effect of AFC was on human colon cancer HCT116 cells, and the optimal AFC treatment time was 48 hours. After AFC treatment, typical apoptotic features such as nuclear chromatin concentration, nuclear fragmentation and apoptotic bodies appeared in a dose-dependent manner. Annexin V-FITC/PI double staining showed that as compared with the control group, 50 and 100 μg·mL~(-1) AFC groups increased the apoptosis rate of HCT116 cells significantly(P<0.001); AFC activated caspase-9, cleaved caspase-3 and cleaved PARP in a concentration-dependent manner. The protein expression levels of cleaved caspase-3/procaspase-3, cleaved PARP/PARP and caspase-9/β-actin after treatment of AFC(100 μg·mL~(-1)) were significantly different from those in the control group(P<0.001). The relative protein expression of p-PI3 K, p-Akt and p-mTOR decreased in a concentration dependent manner, while Akt and mTOR showed no significant differences among groups. The ratios of p-PI3 K/PI3 K, p-Akt/Akt and p-mTOR/mTOR in the AFC groups(50 and 100 μg·mL~(-1)) were significantly lower than those in the control group(P<0.01). Its combination with IGF-Ⅰ weakened the effect of AFC in inhibiting PI3 K/Akt/mTOR signaling pathway. The ratios of p-Akt/Akt and p-mTOR/mTOR in the AFC+IGF-Ⅰ group were significantly enhanced as compared with the AFC group(P<0.05). Apoptosis-related protein expression levels(cleaved caspase-3 and cleaved PARP) in HCT116 cells treated with AFC+IGF-Ⅰ were also down regulated. As compared with the AFC group, the ratios of cleaved caspase-3/procaspase-3 and cleaved PARP/PARP in the AFC+IGF-Ⅰ group were significantly decreased(P<0.01). In summary, AFC activated caspase-mediated cascades and induced HCT116 cells apoptosis in a dose-dependent manner, which may be associated with the inhibition of the PI3 K/Akt/mTOR signaling pathway.