Sphingosine kinase 1 (SPHK1) is a newly discovered modulator of hypoxia inducible factor 1α (HIF-1α) with various biological activities such as cell growth, survival, invasion, angiogenesis, and carcinogenesis. Thus, in the present study, the biological mechanisms of melatonin were elucidated in association with SPHK1 pathway in PC-3 prostate cancer cells under hypoxia. Melatonin inhibited the stability of HIF-1α in a time- and concentration- dependent manners. Also, melatonin decreased SPHK1 activity in PC-3 cells during hypoxia. Furthermore, melatonin suppressed AKT/glycogen synthase kinase-3β (GSK-3β) signaling pathway, which stabilizes HIF-1α via inhibition of von Hippel-Lindau tumor suppressor protein. Consistently, siRNA-SPHK1 and sphingosine kinase inhibitor (SKI) effectively blocked the expression of HIF-1α, phospho-AKT and vascular endothelial growth factor (VEGF) production in PC-3 cells under hypoxia, suggesting the role of SPHK1 in melatonin-inhibited HIF-1α accumulation. Moreover, reactive oxygen species (ROS) scavenger N-acteylcysteine enhanced melatonin-inhibited HIF-1α expression and SPHK1 activity. Overall, our findings suggest that melatonin suppresses HIF-1α accumulation via inhibition of SPHK1 pathway and ROS generation in PC-3 cells under hypoxia.

No abstract

Here, antitumor mechanism of cinnamaldehyde derivative CB-PIC was elucidated in human SW620 colon cancer cells. CB-PIC significantly exerted cytotoxicity, increased sub-G1 accumulation, and cleaved PARP with apoptotic features, while it enhanced the phosphorylation of AMPK alpha and ACC as well as activated the ERK in hypoxic SW620 cells. Furthermore, CB-PIC suppressed the expression of HIF1 alpha, Akt, and mTOR and activated the AMPK phosphorylation in hypoxic SW620 cells. Conversely, silencing of AMPKα blocked PARP cleavage and ERK activation induced by CB-PIC, while ERK inhibitor PD 98059 attenuated the phosphorylation of AMPKα in hypoxic SW620 cells, implying cross-talk between ERK and AMPKα. Furthermore, cotreatment of CB-PIC and metformin enhanced the inhibition of HIF1α and Akt/mTOR and the activation of AMPKα and pACC in hypoxic SW620 cells. In addition, CB-PIC suppressed the growth of SW620 cells inoculated in BALB/c athymic nude mice, and immunohistochemistry revealed that CB-PIC treatment attenuated the expression of Ki-67, CD34, and CAIX and increased the expression of pAMPKα in CB-PIC-treated group. Interestingly, CP-PIC showed better antitumor activity in SW620 colon cancer cells under hypoxia than under normoxia, since it may be applied to chemoresistance. Overall, our findings suggest that activation of AMPKα and ERK mediates CB-PIC-induced apoptosis in hypoxic SW620 colon cancer cells.

BackgroundThough Mica, a thin and sheet like mineral, has been used as a mineral medicine for treatment of bleeding, dysentery and inflammation in traditional medicine including Ayurveda, the biological evidences of Mica were not clearly elucidated so far. Thus, in the present study, the antitumor mechanism of particled Mica (STB-HO) was examined in colorectal cancers.MethodsAthymic nude mice were inoculated with HCT116 colon cancer cells and orally administered STB-HO daily for 41 days, and HCT116 and human umbilical vein endothelial cells (HUVECs) were treated with STB-HO for 0 ~ 24 hours to perform immunoblotting, cytotoxicity assay, FACs analysis and measurement of matrix metalloproteinase 9 (MMP-9) secretion and other experiments. Significant differences of all date were evaluated using Student’s t-test and a Turkey-Kramer multiple-comparison post test.ResultsSTB-HO significantly suppressed the tumor volume and weight in athymic nude mice inoculated with HCT116 cells at a dose of 100 mg/kg. Thus, the in vivo antitumor mechanism of STB-HO was to elucidated in vitro as well. STB-HO exerted cytotoxicity in HCT116, SW620 and HCT15 colorectal cancer cells. Also, STB-HO increased G1 cell population in a time and concentration dependent manner, enhanced the expression of p21, p27, p53 as cyclin dependent kinase (CDK) inhibitors, attenuated the expression of proliferating cell nuclear antigen (PCNA) and cyclin D1 and also reduced the production of vascular endothelial growth factor (VEGF) and matrix metalloproteinase 9 (MMP-9) in HCT116 cells. Consistently, STB-HO suppressed the phosphorylation of VEGFR2 in HCT116, SW620 and HCT15 cells. Also, STB-HO inhibited the VEGF mediated proliferation and also attenuated the phosphorylation of VEGFR2 and Akt in human umbilical vein endothelial cells (HUVECs).ConclusionsCollectively, these findings suggest that STB-HO has chemopreventive potential via G1 arrest and inhibition of proliferation and VEGFR2 in HCT116 colorectal cancer cells.

No abstract