Characterization of LTr1 derived from cruciferous vegetables as a novel anti-glioma agent via inhibiting TrkA/PI3K/AKT pathway.

Malignant glioma is the most fatal, invasive brain cancer with limited treatment options. Our previous studies show that 2-(indol-3-ylmethyl)-3,3'-diindolylmethane (LTr1), a major metabolite of indole-3-carbinol (I3C) derived from cruciferous vegetables, produces anti-tumour effect against various tumour cell lines. In this study we characterized LTr1 as a novel anti-glioma agent. Based on screening 134 natural compounds and comparing the candidates' efficacy and toxicity, LTr1 was selected as the lead compound. We showed that LTr1 potently inhibited the viability of human glioma cell lines (SHG-44, U87, and U251) with IC50 values of 1.97, 1.84, and 2.03 µM, respectively. Furthermore, administration of LTr1 (100,300 mg· kg-1 ·d-1, i.g. for 18 days) dose-dependently suppressed the tumour growth in a U87 xenograft nude mouse model. We demonstrated that LTr1 directly bound with TrkA to inhibit its kinase activity and the downstream PI3K/AKT pathway thus inducing significant S-phase cell cycle arrest and apoptosis in SHG-44 and U87 cells by activating the mitochondrial pathway and inducing the production of reactive oxygen species (ROS). Importantly, LTr1 could cross the blood-brain barrier to achieve the therapeutic concentration in the brain. Taken together, LTr1 is a safe and promising therapeutic agent against glioma through inhibiting TrkA/PI3K/AKT pathway.

Standardized Saponin Extract from Baiye No.1 Tea (Camellia sinensis) Flowers Induced S Phase Cell Cycle Arrest and Apoptosis via AKT-MDM2-p53 Signaling Pathway in Ovarian Cancer Cells.

Ovarian cancer is considered to be one of the most serious malignant tumors in women. Natural compounds have been considered as important sources in the search for new anti-cancer agents. Saponins are characteristic components of tea (Camellia sinensis) flower and have various biological activities, including anti-tumor effects. In this study, a high purity standardized saponin extract, namely Baiye No.1 tea flower saponin (BTFS), which contained Floratheasaponin A and Floratheasaponin D, were isolated from tea (Camellia sinensis cv. Baiye 1) flowers by macroporous resin and preparative liquid chromatography. Then, the component and purity were detected by UPLC-Q-TOF/MS/MS. This high purity BTFS inhibited the proliferation of A2780/CP70 cancer cells dose-dependently, which is evidenced by the inhibition of cell viability, reduction of colony formation ability, and suppression of PCNA protein expression. Further research found BTFS induced S phase cell cycle arrest by up-regulating p21 proteins expression and down-regulating Cyclin A2, CDK2, and Cdc25A protein expression. Furthermore, BTFS caused DNA damage and activated the ATM-Chk2 signaling pathway to block cell cycle progression. Moreover, BTFS trigged both extrinsic and intrinsic apoptosis-BTFS up-regulated the expression of death receptor pathway-related proteins DR5, Fas, and FADD and increased the ratio of pro-apoptotic/anti-apoptotic proteins of the Bcl-2 family. BTFS-induced apoptosis seems to be related to the AKT-MDM2-p53 signaling pathway. In summary, our results demonstrate that BTFS has the potential to be used as a nutraceutical for the prevention and treatment of ovarian cancer.

The Effect of GADD45a on Furazolidone-Induced S-Phase Cell-Cycle Arrest in Human Hepatoma G2 Cells.

In this study, overexpression of GADD45a induced by furazolidone in HepG2 cells could arouse S-phase cell cycle arrest, suppress cell proliferation, and increase the activities of cyclin D1, cyclin D3, and cyclin-dependent kinase 6 (CDK6). To the opposite, GADD45a knockdown cells by RNAi could reduce furazolidone-induced S-phase cell cycle arrest, increase the cell viability, decrease the activities of cyclin D1, cyclin D3, and CDK6; however, cyclin-dependent kinase 4 (CDK4) showed no change. Moreover, data from our current studies show that cyclin D1, cyclin D3, and CDK6 are target genes functioning at the downstream of the GADD45a pathway induced by furazolidone. These results demonstrate that the GADD45a pathway is partially responsible for the furazolidone-induced S-phase cell cycle arrest. GADD45a influences furazolidone-induced S-phase cell cycle arrest in human hepatoma G2 cells via cyclin D1, cyclin D3, and CDK6, but not CDK4.

Opposite effects of JNK and p38 MAPK signaling pathways on furazolidone-stimulated S phase cell cycle arrest of human hepatoblastoma cell line.

Furazolidone (FZD), a synthetic nitrofuran with a broad spectrum of antimicrobial actions, is known to induce genotoxicity and potential carcinogenicity in several types of cells, but little is known about its p38 mitogen-activation protein kinase (p38 MAPK) and c-Jun N-terminal protein kinase (JNK) pathways in human hepatoblastoma cell line (HepG2). Given the previously described essential roles of p38 MAPK and JNK pathways in HepG2 cells, we undertook the present study to investigate the roles of p38 MAPK and JNK pathways in cell cycle arrest of HepG2 cells stimulated with FZD. Here we reported that FZD could obviously induce S phase cell cycle arrest, suppress cell growth, increase the activity of phosphorylated p38 (p-p38), and decrease the activity of phosphorylated JNK (p-JNK) in HepG2 cells. Simultaneously, inhibition of p38 MAPK pathway could significantly reduce FZD-stimulated S phase cell cycle arrest, active cell growth, decrease the activity of p-p38, and increase the activity of p-JNK. To the opposite, inhibition of JNK pathway could significantly increase FZD-stimulated S phase cell cycle arrest, suppress cell growth, decrease the activity of p-JNK, and increase the activity of p-p38. These results demonstrate that JNK and p38 MAPK pathways have opposite roles in FZD-stimulated S phase cell cycle arrest of HepG2 cells. FZD induces S phase cell cycle arrest and suppresses cell proliferation of HepG2 cells via activating the pathway from p38 to p-p38 and inhibiting the pathway from JNK to p-JNK.

Involvement of the p38 MAPK signaling pathway in S-phase cell-cycle arrest induced by Furazolidone in human hepatoma G2 cells.

Given the previously described essential role for the p38 mitogen-activation protein kinase (p38 MAPK) signaling pathway in human hepatoma G2 cells (HepG2), we undertook the present study to investigate the role of the p38 MAPK signaling pathway in cell-cycle arrest induced by Furazolidone (FZD). The aim of this study was to determine the effects of FZD on HepG2 cells by activating and inhibiting the p38 MAPK signaling pathway. The cell cycle and proliferation of HepG2 cells treated with FZD were detected by flow cytometry and MTT assay in the presence or absence of p38 MAPK inhibitors (SB203580), respectively. Cyclin D1, cyclin D3 and CDK6 were detected by quantitative real-time PCR and western blot analysis. Our data showed that p38 MAPK became phosphorylated after stimulation with FZD. Activation of p38 MAPK could arise S-phase cell-cycle arrest and suppress cell proliferation. Simultaneously, inhibition of the p38 MAPK signaling pathway significantly prevented S-phase cell-cycle arrest, increased the percentage of cell viability and decreased the expression of cyclin D1, cyclin D3 and CDK6. These results demonstrated that FZD arose S-phase cell-cycle arrest via activating the p38 MAPK signaling pathway in HepG2 cells. Cyclin D1, cyclin D3 and CDK6 are target genes functioning at the downstream of p38 MAPK in HepG2 cells induced by FZD.

Phytol isolated from watermelon (Citrullus lanatus) sprouts induces cell death in human T-lymphoid cell line Jurkat cells via S-phase cell cycle arrest.

The phytol isolated from watermelon (Citrullus lanatus) sprouts inhibited the growth of a human T-cell leukemia line Jurkat cell and suppressed tumor progression in a xenograft model of human lung adenocarcinoma epithelial cell line A549 in nude mice. To elucidate the mechanisms underlying the phytol-induced cell death in the present study, we examined the changes in cell morphology, DNA fragmentation, and intracellular reactive oxygen species (ROS) levels and performed flow cytometric analysis to evaluate cell cycle stage. There were no significant changes in apoptosis, autophagy, and necrosis marker in cells treated with the phytol. But, we found, for the first time, that phytol remarkably induced S-phase cell cycle arrest accompanied with intracellular ROS production. Western blot analyses showed that phytolinduced S-phase cell cycle arrest was mediated through the decreased expression of cyclins A and D and the downregulations of MAPK and PI3K/Akt. The tumor volume levels in mice treated with phytol were lower than those of non-treatment groups, and it showed very similar suppression compared with those of mice treated with cyclophosphamide. Based on the data of in vitro and in vivo studies and previous studies, we suggest phytol as a potential therapeutic compound for cancer.

Purification, partial characterization and antitumor effect of an exopolysaccharide from Rhizopus nigricans.

In this study, a homogeneous exopolysaccharide (EPS1-1) was purified from the fermentation broth of Rhizopus nigricans. EPS1-1 was composed of glucose, mannose, galactose and fructose in the molar ratio of 5.89:3.64:3.20:1.00 with weight average molecular weight of 9.7×10(3)g/mol. EPS1-1 could significantly inhibit proliferation of human colorectal carcinoma HCT-116 cells in vitro. EPS1-1 also induced S phase cell cycle arrest and increased sub-G0/G1 population, a hallmark of apoptosis. The results of morphological characterization and flow cytometry showed that EPS1-1 induced apoptotic cell death in HCT-116 cells. EPS1-1 caused dissipation of mitochondrial membrane potential, accumulation of reactive oxygen species, up-regulation of Bax and p53 mRNA expression and down-regulation of Bcl-2 mRNA expression, which suggested that mitochondrial pathway was involved in the EPS1-1-induced apoptosis. These findings bring new insights into the potential use of EPS1-1 as antitumor drug against human colorectal carcinoma.