ginsenoside-m1 and Colonic-Neoplasms

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a potent cancer cell-specific apoptosis-inducing cytokine with little toxicity to most normal cells. However, acquired resistance of cancer cells to TRAIL is a roadblock. Agents that can either potentiate the effect of TRAIL or overcome resistance to TRAIL are urgently needed. This article reports that ginsenoside compound K (CK) potentiates TRAIL-induced apoptosis in HCT116 colon cancer cells and sensitizes TRAIL-resistant colon cancer HT-29 cells to TRAIL. On a cellular mechanistic level, CK downregulated cell survival proteins including Mcl-1, Bcl-2, surviving, X-linked inhibitor of apoptosis protein and Fas-associated death domain-like IL-1-converting enzyme-inhibitory protein, upregulated cell pro-apoptotic proteins including Bax, tBid and cytochrome c, and induced the cell surface expression of TRAIL death receptor DR5. Reduction of DR5 levels by siRNAs significantly decreases CK- and TRAIL-mediated apoptosis. Importantly, our results indicate, for the first time, that DR5 upregulation is mediated by autophagy, as blockade of CK-induced autophagy by 3-MA, LY294002 or Atg7 siRNAs substantially decreases DR5 upregulation and reduces the synergistic effect. Furthermore, CK-stimulated autophagy is mediated by the reactive oxygen species-c-Jun NH2-terminal kinase pathway. Moreover, we found that p53 and the C/EBP homologous (CHOP) protein is also required for DR5 upregulation but not related with autophagy. Our findings contribute significantly to the understanding of the mechanism accounted for the synergistic anticancer activity of CK and TRAIL, and showed a novel mechanism related with DR5 upregulation.

Topics: Apoptosis; Autophagy; Cell Survival; Colonic Neoplasms; Drug Resistance, Neoplasm; Ginsenosides; HCT116 Cells; HT29 Cells; Humans; JNK Mitogen-Activated Protein Kinases; Reactive Oxygen Species; Receptors, TNF-Related Apoptosis-Inducing Ligand; TNF-Related Apoptosis-Inducing Ligand; Transcription Factor CHOP; Tumor Suppressor Protein p53; Up-Regulation

Compound K (20-O-(β-D-glucopyranosyl)-20(S)-protopanaxadiol) is an active metabolite of ginsenosides and induces apoptosis in various types of cancer cells. This study investigated the role of autophagy in compound K-induced cell death of human HCT-116 colon cancer cells. Compound K activated an autophagy pathway characterized by the accumulation of vesicles, the increased positive acridine orange-stained cells, the accumulation of LC3-II, and the elevation of autophagic flux. Whereas blockade of compound K-induced autophagy by 3-methyladenein and bafilomycin A1 significantly increased cell viability. In addition, compound K augmented the time-dependent expression of the autophagy-related proteins Atg5, Atg6, and Atg7. However, knockdown of Atg5, Atg6, and Atg7 markedly inhibited the detrimental impact of compound K on LC3-II accumulation and cell vitality. Compound K-provoked autophagy was also linked to the generation of intracellular reactive oxygen species (ROS); both of these processes were mitigated by the pre-treatment of cells with the antioxidant N-acetylcysteine. Moreover, compound K activated the c-Jun NH2-terminal kinase (JNK) signaling pathway, whereas downregulation of JNK by its specific inhibitor SP600125 or by small interfering RNA against JNK attenuated autophagy-mediated cell death in response to compound K. Compound K also provoked apoptosis, as evidenced by an increased number of apoptotic bodies and sub-G1 hypodiploid cells, enhanced activation of caspase-3 and caspase-9, and modulation of Bcl-2 and Bcl-2-associated X protein expression. Notably, compound K-stimulated autophagy as well as apoptosis was induced by disrupting the interaction between Atg6 and Bcl-2. Taken together, these results indicate that the induction of autophagy and apoptosis by compound K is mediated through ROS generation and JNK activation in human colon cancer cells.

Topics: Adenine; Antineoplastic Agents; Apoptosis; Autophagy; Autophagy-Related Protein 5; Autophagy-Related Protein 7; Cell Survival; Colonic Neoplasms; Enzyme Activation; Ginsenosides; HCT116 Cells; Humans; JNK Mitogen-Activated Protein Kinases; Microtubule-Associated Proteins; Proto-Oncogene Proteins c-bcl-2; Reactive Oxygen Species; Ubiquitin-Activating Enzymes; Up-Regulation

Abnormal regulation of Ca(2+) mediates tumorigenesis and Ca(2+) channels are reportedly deregulated in cancers, indicating that regulating Ca(2+) signaling in cancer cells is considered as a promising strategy to treat cancer. However, little is known regarding the mechanism by which Ca(2+) affects cancer cell death. Here, we show that 20-O-β-d-glucopyranosyl-20(S)-protopanaxadiol (20-GPPD), a metabolite of ginseng saponin, causes apoptosis of colon cancer cells through the induction of cytoplasmic Ca(2+). 20-GPPD decreased cell viability, increased annexin V-positive early apoptosis and induced sub-G1 accumulation and nuclear condensation of CT-26 murine colon cancer cells. Although 20-GPPD-induced activation of AMP-activated protein kinase (AMPK) played a key role in the apoptotic death of CT-26 cells, LKB1, a well-known upstream kinase of AMPK, was not involved in this activation. To identify the upstream target of 20-GPPD for activating AMPK, we examined the effect of Ca(2+) on apoptosis of CT-26 cells. A calcium chelator recovered 20-GPPD-induced AMPK phosphorylation and CT-26 cell death. Confocal microscopy showed that 20-GPPD increased Ca(2+) entry into CT-26 cells, whereas a transient receptor potential canonical (TRPC) blocker suppressed Ca(2+) entry. When cells were treated with a TRPC blocker plus an endoplasmic reticulum (ER) calcium blocker, 20-GPPD-induced calcium influx was completely inhibited, suggesting that the ER calcium store, as well as TRPC, was involved. In vivo mouse CT-26 allografts showed that 20-GPPD significantly suppressed tumor growth, volume and weight in a dose-dependent manner. Collectively, 20-GPPD exerts potent anticarcinogenic effects on colon carcinogenesis by increasing Ca(2+) influx, mainly through TRPC channels, and by targeting AMPK.

Topics: AMP-Activated Protein Kinases; Animals; Antineoplastic Agents; Apoptosis; Calcium; Cell Death; Cell Survival; Colonic Neoplasms; Female; Ginsenosides; Mice; Mice, Inbred BALB C; Panax; Phosphorylation; Signal Transduction; TRPC Cation Channels

Previously, we reported that 20-O-(β-D-gluco-pyranosyl)-20(S)-protopanaxadiol (Compound K, a meta-bolite of ginseng saponin) induces mitochondria-dependent and caspase-dependent apoptosis in HT-29 human colon cancer cells via the generation of reactive oxygen species. The aim of the present study was to elucidate the mechanism underlying apoptosis induced by Compound K with respect to endoplasmic reticulum (ER) stress in HT-29 cells. In the present study, Compound K induced apoptotic cell death as confirmed by DNA fragmentation and apoptotic sub-G1 cell population. Compound K also induced ER stress as indicated by staining with ER tracker, cytosolic and mitochondrial Ca2+ overloading, phosphorylation of protein-kinase-like endoplasmic reticulum kinase (PERK), phosphorylation of eukaryotic initiation factor-2α (eIF-2α), phosphorylation of IRE-1, splicing of ER stress-specific X-box transcription factor-1 (XBP-1), cleavage of activating transcription factor-6 (ATF-6), upregulation of glucose-regulated protein-78 (GRP-78/BiP) and CCAAT/enhancer-binding protein-homologous protein (CHOP), and cleavage of caspase-12. Furthermore, downregulation of CHOP expression using siCHOP RNA attenuated Compound K-induced apoptosis. Taken together, these results support the important role of ER stress response in mediating Compound K-induced apoptosis in human colon cancer cells.

Topics: Apoptosis; Caspase 12; Colonic Neoplasms; DNA Fragmentation; DNA-Binding Proteins; Endoplasmic Reticulum Stress; Gene Expression Regulation, Neoplastic; HT29 Cells; Humans; Panax; Regulatory Factor X Transcription Factors; Sapogenins; Transcription Factor CHOP; Transcription Factors; X-Box Binding Protein 1

The objective of this study was to elucidate the cytotoxic mechanism of Compound K, with respect to the involvement of reactive oxygen species (ROS) and the mitochondrial involved apoptosis, in HT-29 human colon cancer cells. Compound K exhibited a concentration of 50% growth inhibition (IC(50)) at 20 μg/mL and cytotoxicity in a time dependent manner. Compound K produced intracellular ROS in a time dependent fashion; however, N-acetylcysteine (NAC) pretreatment resulted in the inhibition of this effect and the recovery of cell viability. Compound K induced a mitochondria-dependent apoptotic pathway via the modulation of Bax and Bcl-2 expressions, resulting in the disruption of the mitochondrial membrane potential (Δψ(m)). Loss of the Δψ(m) was followed by cytochrome c release from the mitochondria, resulting in the activation of caspase-9, -3, and concomitant poly ADP-ribosyl polymerase (PARP) cleavage, which are the indicators of caspase-dependent apoptosis. The apoptotic effect of Compound K, exerted via the activation of c-Jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), was abrogated by specific MAPK inhibitors. This study demonstrated that Compound K-mediated generation of ROS led to apoptosis through the modulation of a mitochondria-dependent apoptotic pathway and MAPK pathway.

Topics: Apoptosis; Caspases; Colonic Neoplasms; Drug Screening Assays, Antitumor; Ginsenosides; Humans; Mitochondria; Neoplasm Proteins; Panax; Reactive Oxygen Species; Saponins

Although compound K (CK), an intestinal metabolite of ginseng protopanaxadiol saponins, has been known to induce apoptosis in various cancer cells, association of AMP-activated protein kinase (AMPK) with apoptosis in HT-29 colon cancer cells remains unclear. We hypothesized that CK may exert an anticancer activity through modulating the AMPK pathway in HT-29 cells. CK-induced apoptosis was associated with the disruption of the mitochondrial membrane potential, release of apoptogenic factors (cytochrome c and apoptosis-inducing factor) from mitochondria, and cleavage of caspase-9, caspase-3, caspase-8, Bid, and PARP proteins. This apoptotic effect of CK on colon cancer cells was found to be initiated by AMPK activation, and AMPK was activated through phosphorylation by Ca2+/calmodulin-activated protein kinase-IV (CAMK-IV). Treatment of HT-29 cells with compound C (AMPK inhibitor) or siRNA for AMPK completely abolished the CK-induced apoptosis. STO-609, CAMKs inhibitor, also attenuated CK-induced AMPK activation and apoptosis. In conclusion, the present study demonstrates that CK-mediated cell death of HT-29 colon cancer cells is regulated by CAMK-IV/AMPK pathways, and these findings provide a molecular basis for the anticancer effect of CK.

Topics: AMP-Activated Protein Kinases; Apoptosis; Calcium-Calmodulin-Dependent Protein Kinase Type 4; Colonic Neoplasms; Enzyme Activation; Enzyme Inhibitors; Ginsenosides; HT29 Cells; Humans; Phosphorylation; RNA, Small Interfering; Signal Transduction

SC-514, an inhibitor of IkappaB kinase beta (IKKbeta), blocked the TNF-alpha-induced activation of nuclear factor-kappaB (NF-kappaB) as well as the TNF-alpha-promoted metastasis of murine colon adenocarcinoma cells. We investigated the effect of 20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol (M1), a main intestinal bacterial metabolite of ginseng, on the NF-kappaB-dependent metastasis. M1 was effective in suppressing the TNF-alpha-induced activation of NF-kappaB, expression of matrix metalloprotease-9 (MMP-9), migration and invasion. The TNF-alpha-evoked increase in lung and liver metastasis of colon carcinoma was also abrogated by treatment with M1 in vitro. These results suggest that ginseng has potential to suppress inflammation-related metastasis by downregulating the NF-kappaB signaling pathway.

Topics: Animals; Antineoplastic Agents, Phytogenic; Cell Movement; Colonic Neoplasms; Female; Ginsenosides; Liver Neoplasms; Lung Neoplasms; Mice; Mice, Inbred BALB C; Neoplasm Invasiveness; NF-kappa B; Signal Transduction; Tumor Necrosis Factor-alpha