OSW-1 Induced Apoptosis in Hepatocellular Carcinoma through Generation of ROS, Cytochrome C and Noxa Activation Independent of p53 with Non-Activation of Caspase-3

Aim: To study the antitumor mechanism of OSW-1 in hepatocellular carcinoma. Materials and Methods: The expression profiling microarray was carried out to extract RNA from SK-Hep-1 which suffered from OSW-1. ρ0-SK-Hep-1 was maintained SK-Hep-1 in MEM containing 100 μg/L ethidium bromide (EB), 1 mM sodium pyruvate and 50 μg/ml uridine for 40 days. Then confirmed COX-I and COX-II of mitochondrial DNA were knocked out. Cells suffered from OSW-1 or doxorubicin. Then cells were washed twice with cold PBS and incubated with DCFH-DA. Fluorescent signal was recorded by using Infinite 200 Pro multimode Plate readers. Results: OSW-1 elevates generation of ROS and Cytochrome C which are associated with the induction of apoptosis in SK-Hep-1 cells. We also demonstrate that OSW-1 does not depend on p53 to up-regulate the BH3-only protein Noxa. What is more noteworthy that the Caspase-9 and FADD are down-regulated in above process. Conclusion: OSW-1 induced special apoptosis is different from the mitochondrial death pathway and the death receptor pathway and final result is not Caspase family’s activating. This provides a novel theory that nonmalignant cells are significantly less sensitive to OSW-1 than cancer cell lines.

Effects of Mitochondrial DNA Deletion and OSW-1 on PI3K-AKT Signaling Pathway PCR Array in SK-Hep1 Cells

To investigate the effect of mitochondrial DNA deletion and OSW-1 on PI3K-AKT signaling pathway PCR Array in SK-Hep1 hepatocellular carcinoma cells, we prepared SK-Hep1 cells with mtDNA deletion, that is, p0SK Hep. Then the OSW-1 of 100 ng/L was used to intervene SK-Hep1 and p0SK-Hep1. RT-qPCR was used to detect the difference of gene expression on PI3K-AKT signaling pathway PCR Array in four groups of cells. The gene expression of TLR4, FOS and TSC2 markers in SK-Hep1 cells treated with OSW-1 were significantly increased. The gene expressions of PDPK1, GJA1, TLR4 and TSC2 markers were significantly increased in p0SK-Hep1 cells, and the gene expressions of IRAK1 and GJA1 markers were significantly increased in p0SK-Hep1 cells treated with OSW-1. OSW-1 mainly affects the genes related to TLR4 pathway on PI3K-AKT signaling pathway PCR Array in SK-Hep1 HCC cells. P0SK-Hep1 mainly affects the upstream PDK1 gene and downstream TSC2 gene of Akt on PI3K-AKT signaling pathway PCR Array, and also affects the gene expression of gap junction at the same time.

TRAF6 Affects RAC1 Expression and Apoptosis in SK-Hep1 Cells

RAC1 is a small-molecule G protein that regulates multiple cell cycle, cytoskeletal reorganization, cell migration, and apoptosis. FADD-dependent TRAIL can promote tumor metastasis through RAC1 and PI3K, and down-regulating RAC1 expression can reduce FasL-induced apoptosis. In addition, RIP1 bound to GTP acts as an activating protein for RAC1 and is involved in cytoskeletal reorganization. TRAF6 promotes migration and metastasis by regulating the RAS pathway in tumors. Thus, it is necessary to understand the interaction between RAC1 and TRAF6 as well as FADD and RIP1. In this study, we cultured hepatoma SK-Hep1 cells in vitro, specifically blocked the necroptosis pathway with Nec-1, and silenced FADD, RIP1 and TRAF6 gene expression using RNAi technology. At the same time, the expression of RAC1 was evaluated separately using RT-PCR and Western blot. The hepatoma SK-Hep1 cells survival rate was highest when the concentration of Nec-1 was 60 μM and the concentration of Z-vad-fmk was 20 μM. And the apoptosis rate of the transfected RAC1 siRNA cells was 3.59% compared with transfected siRNA cells 10.01% which was significantly decreased (P < 0.01). RAC1 could promote the occurrence of apoptosis in SK-Hep1 cells. RAC1 expression was suppressed in both protein and gene level in SK-Hep1 cells when the TRAF6 gene was silenced, but there was no significant change in RAC1 gene and protein expression when FADD and RIP1 genes were silenced. TRAF6 affects RAC1 expression and apoptosis in SK-Hep1 cells, while the FADD and RIP1 genes do not affect the role of RAC1. The TRAF6 gene is an important target in liver cancer cells.

Effect of IRAK1 on Apoptosis and Necroptosis of Hepatoma Cell Line SK-Hep1

Interleukin I receptor associated kinase 1 (IRAK1) is a downstream signal molecule of activated MyD88 recruitment, which can activate Fas associated death domain protein (FADD) to induce apoptosis. IRAK1 can also activate tumor necrosis factor-related factor 6 (TRAF6) and induce the expression of a series of downstream specific genes. IRAK1 is an essential factor in the induction of mitochondrial division and necroptosis. In the current study, RNAi technique was used to silence IRAK1, and the apoptosis and necroptosis rate of SK-Hep1 cells were detected by flow cytometry. The apoptosis and the necroptosis pathway of hepatoma SK-Hep1 cells were blocked separately, and the expressions of FADD, RIP1 and TRAF6 genes were silenced separately. The results showed when the expression of IRAK1 was down-regulated, the apoptosis and necroptosis rate of SK-Hep1 cells were significantly increased. With silenced FADD, RIP1 and TRAF6, respectively, the expression of IRAK1 protein had no significant change. However, the expression of IRAK1 mRNA decreased significantly (p < 0.01) after the silencing of RIP1 and TRAF6 genes, while the IRAK1 mRNA did not change significantly after the silencing of FADD genes;when z-VAD-FMK was interfered, the expression of IRAK1 mRNA decreased significantly after the silencing of TRAF6 genes, while the IRAK1 mRNA did not change significantly after the silencing of FADD and RIP1genes. The study shows that RAK1 gene inhibits apoptosis and necroptosis in SK-Hep1 cells. TRAF6 gene affected the role of IRAK1 in apoptosis and necroptosis, RIP1 gene affected the role of IRAK1 in apoptosis, while FADD gene did not affect the role of IRAK1 in apoptosis and necroptosis.