Apoptosis In Human Colon Cancer Cells Research Articles

P4HB knockdown induces human HT29 colon cancer cell apoptosis through the generation of reactive oxygen species and inactivation of STAT3 signaling.

Colon cancer is the second most lethal malignancy worldwide. A better understanding of colon cancer at the molecular level may increase overall survival rates. Previous studies have indicated that prolyl 4-hydroxylase, β polypeptide (P4HB) is associated with tumorigenesis in colon cancer; however, its role and molecular mechanisms in colon cancer remain unclear. In the present study, the cellular responses to P4HB in human colon cancer cell lines were investigated by proliferation and apoptosis assays, western blotting, and immunohistochemistry. The results showed that expression of P4HB was higher in colon cancer tissues compared within adjacent normal tissues. P4HB knockdown increased the apoptosis of human HT29 cells. Furthermore, P4HB knockdown reduced the activation of signal transducer and activator of transcription 3 (STAT3) and promoted accumulation of reactive oxygen species (ROS). Inhibiting the accumulation of ROS abrogated the increased cell apoptosis induced by P4HB knockdown. Notably, decreased ROS levels effectively antagonized the effects of P4HB on STAT3 inactivation. In conclusion, these findings suggested that P4HB knockdown may induce HT29 human colon cancer cell apoptosis through the generation of ROS and inactivation of the STAT3 signaling pathway.

Combination of the histone deacetylase inhibitor depsipeptide and 5-fluorouracil upregulates major histocompatibility complex class II and p21 genes and activates caspase-3/7 in human colon cancer HCT-116 cells.

Epigenetic anticancer drugs such as histone deacetylase (HDAC) inhibitors have been combined with existing anticancer drugs for synergistic or additive effects. In the present study, we found that a very low concentration of depsipeptide, an HDAC inhibitor, potentiated the antitumor activity of 5-fluorouracil (5-FU) in a human colon cancer cell model using HCT-116, HT29, and SW48 cells via the inhibition of colony formation ability or cellular viability. Exposure to a combination of 5-FU (1.75 µM) and 1 nM depsipeptide for 24 and 48 h resulted in a 3- to 4-fold increase in activated caspase-3/7, while 5-FU alone failed to activate caspase-3/7. Microarray and subsequent gene ontology analyses revealed that compared to 5-FU or depsipeptide alone, the combination treatment of 5-FU and depsipeptide upregulated genes related to cell death and the apoptotic process consistent with the inhibition of colony formation and caspase-3/7 activation. These analyses indicated marked upregulation of antigen processing and presentation of peptide or polysaccharide antigen via major histocompatibility complex (MHC) class (GO:0002504) and MHC protein complex (GO:0042611). Compared with vehicle controls, the cells treated with the combination of 5-FU and depsipeptide showed marked induction (3- to 8.5-fold) of expression of MHC class II genes, but not of MHC class I genes. Furthermore, our global analysis of gene expression, which was focused on genes involved in the molecular regulation of MHC class II genes, showed enhancement of pro-apoptotic PCAF and CIITA after the combination of 5-FU and depsipeptide. These results may indicate a closer relationship between elevation of MHC class II expression and cellular apoptosis induced by the combination of depsipeptide and 5-FU. To the best of our knowledge, this is the first study to report that the combination of 5-FU and depsipeptide induces human colon cancer cell apoptosis in a concerted manner with the induction of MHC class II gene expression.

Inhibition of phospholipaseD2 increases hypoxia-induced human colon cancer cell apoptosis through inactivating of the PI3K/AKT signaling pathway.

Hypoxia is a common feature of solid tumor, and is a direct stress that triggers apoptosis in many human cell types. As one of solid cancer, hypoxia exists in the whole course of colon cancer occurrence and progression. Our previous studies shown that hypoxia induce high expression of phospholipase D2 (PLD2) and survivin in colon cancer cells. However, the correlation between PLD2 and survivin in hypoxic colon cancer cells remains unknown. In this study, we observed significantly elevated PLD2 and survivin expression levels in colon cancer tissues and cells. This is a positive correlation between of them, and co-expression of PLD2 and survivin has a positive correlation with the clinicpatholic features including tumor size, TNM stage, and lymph node metastasis. We also found that hypoxia induced the activity of PLD increased significant mainly caused by PLD2 in colon cancer cells. However, inhibition the activity of PLD2 induced by hypoxia promotes the apoptosis of human colon cancer cells, as well as decreased the expression of apoptosis markers including survivin and bcl2. Moreover, the pharmacological inhibition of PI3K/AKT supported the hypothesis that promotes the apoptosis of hypoxic colon cancer cells by PLD2 activity inhibition may through inactivation of the PI3K/AKT signaling pathway. Furthermore, interference the PLD2 gene expression leaded to the apoptosis of hypoxic colon cancer cells increased and also decreased the expression level of survivin and bcl2 may through inactivation of PI3K/AKT signaling pathway. These results indicated that PLD2 play antiapoptotic role in colon cancer under hypoxic conditions, inhibition of the activity, or interference of PLD2 gene expression will benefit for the treatment of colon cancer patients.

Implication of Akt, ERK1/2 and alternative p38MAPK signalling pathways in human colon cancer cell apoptosis induced by green tea EGCG

We investigated apoptosis induced by the green tea component the epigallocatechin-3-gallate (EGCG) and the pathways underlying its activity in a colon cancer cell line. A complete understanding of the mechanism(s) and molecules targeted by green tea polyphenols could be useful in developing novel therapeutic approaches for cancer treatment. EGCG, which is the major polyphenol in green tea, has cytotoxic effects and induced cell death in HT-29 cell death. In this study, we evaluated the effect EGCG on mitogen-activated protein kinase (MAPK) and Akt pathways. EGCG treatment increased phospho-ERK1/2, -JNK1/2 and -p38α, -p38γ and -p38δ, as well as phospho-Akt levels. Using a combination of kinase inhibitors, we found that EGCG-induced cell death is partially blocked by inhibiting Akt, ERK1/2 or alternative p38MAPK activity. Our data suggest that these kinase pathways are involved in the anti-cancer effects of EGCG and indicate potential use of this compound as chemotherapeutic agent for colon cancer treatment.

The Sirtuin Inhibitor Tenovin-6 Upregulates Death Receptor 5 and Enhances Cytotoxic Effects of 5-Fluorouracil and Oxaliplatin in Colon Cancer Cells

It has been reported that upregulated SIRT1 (NAD(+)-dependent class III histone deacetylase) deacetylates the p53 protein, represses its function, and allows for tumor cell growth in various cancers. Here we investigated antitumor effects of tenovin-6, a small-molecule inhibitor of SIRT1 and SIRT2, in various colon cancer cell lines. Tenovin-6 induced apoptosis in all five colon cancer cell lines investigated (two cell lines with wild-type p53 and three with mutant p53) regardless of the p53 mutation status. This effect was accompanied by accumulation of death receptor 5 (DR5) in most cell lines. DR5 silencing in HCT116 cells strongly attenuated tenovin-6-induced apoptosis. We investigated the effect of combining tenovin-6 with conventional anticancer agents 5-fluorouracil (5-FU), SN-38 (an active metabolite of irinotecan), and oxaliplatin. Synergistic antitumor effects of tenovin-6 were observed in combination with either 5-FU or oxaliplatin in vitro. The combination of tenovin-6 and oxaliplatin exhibited potent growth inhibition of HCT116 xenograft tumors in vivo. In conclusion, tenovin-6 induced apoptosis in human colon cancer cells through the activation of the DR5 signaling pathway and enhanced the antitumor properties of 5-FU and oxaliplatin. These results may help develop a novel treatment option for colorectal cancer using a SIRT inhibitor.

Aldose reductase inhibition enhances TRAIL-induced human colon cancer cell apoptosis through AKT/FOXO3a-dependent upregulation of death receptors

One of the major problems associated with the chemotherapy of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) that selectively kills tumor cells is decreased drug resistance. This warranted the development of safe novel pharmacological agents that could sensitize the tumor cells to TRAIL. Herein, we examined the role of aldose reductase (AR) in sensitizing cancer cells to TRAIL and potentiating TRAIL-induced apoptosis of human colon cancer cells. We demonstrate that AR inhibition potentiates TRAIL-induced cytotoxicity in cancer cells by upregulation of both death receptor (DR)-5 and DR4. Knockdown of DR5 and DR4 significantly (>85%) reduced the sensitizing effect of the AR inhibitor fidarestat on TRAIL-induced apoptosis. Further, AR inhibition also downregulates cell survival proteins (Bcl-xL, Bcl-2, survivin, XIAP, and FLIP) and upregulates the expression of proapoptotic proteins such as Bax and alters mitochondrial membrane potential, leading to cytochrome c release, caspases-3 activation, and PARP cleavage. We found that AR inhibition regulates AKT/PI3K-dependent activation of forkhead transcription factor FOXO3a. Knockdown of FOXO3a significantly (>80%) abolished AR inhibition-induced upregulation of DR5 and DR4 and apoptosis in colon cancer cells. Overall, our results show that fidarestat potentiates TRAIL-induced apoptosis through downregulation of cell survival proteins and upregulation of death receptors via activation of the AKT/FOXO3a pathway.

Phloroglucinol derivative MCPP induces cell apoptosis in human colon cancer

This study is the first to investigate the anticancer effects of the new phloroglucinol derivative (3,6-bis(3-chlorophenylacetyl)phloroglucinol; MCPP) in human colon cancer cells. MCPP induced cell death and antiproliferation in three human colon cancer, HCT-116, SW480, and Caco-2 cells, but not in primary human dermal fibroblast cells. MCPP-induced concentration-dependent apoptotic cell death in colon cancer cells was measured by fluorescence-activated cell sorter (FACS) analysis. Treatment of HCT-116 human colon cancer cells with MCPP was found to induce a number of signature endoplasmic reticulum (ER) stress markers; and up-regulation of CCAAT/enhancer-binding protein homologous protein (CHOP) and glucose-regulated protein (GRP)-78, phosphorylation of eukaryotic initiation factor-2α (eIF-2α), suggesting the induction of ER stress. MCPP also increased GSK3α/β(Tyr270/216) phosphorylation and reduced GSK3α/β(Ser21/9) phosphorylation time-dependently. Transfection of cells with GRP78 or CHOP siRNA, or treatment of GSK3 inhibitor SB216163 reduced MCPP-mediated cell apoptosis. Treatment of MCPP also increased caspase-7, caspase-9, and caspase-3 activity. The inhibition of caspase activity by z-DEVE-FMK or z-VAD-FMK significantly reduced MCPP-induced apoptosis. Furthermore, treatment of GSK3 inhibitor SB216763 also dramatically reversed MCPP-induced GRP and CHOP up-regulation, and pro-caspase-3 and pro-caspase-9 degradation. Taken together, the present study provides evidences to support that GRP78 and CHOP expression, and GSK3α/β activation in mediating the MCPP-induced human colon cancer cell apoptosis.

Resveratrol potentiates grape seed extract induced human colon cancer cell apoptosis

Colon cancer is the third leading cause of cancer deaths in men and women. Grape seed extract (GSE) and resveratrol (RSV) are potent chemopreventive agents against colon cancer both in vitro and in vivo, at relatively high concentrations. We hypothesized that RSV and GSE may act in concert with each other in potentiating their anti-cancer properties at sub-optimal doses, because they occur as complex mixtures in grapes. In this study, we showed that RSV (~25 micromolar) potentiated GSE (≤ 35 microg/mL) induced colon cancer cell apoptosis via activation of p53 dependent pathways. Elevation of apoptosis was much more pronounced in p53 +/+ cells compared to p53 -/- cells. Apoptosis was strongly correlated with pp53 levels and Bax:Bcl-2 ratio, key players in the mitochondrial apoptotic pathway. Caspase-3 inhibition and reactive oxygen species suppression attenuated apoptosis induced by the combination. RSV-GSE combination suppressed proliferation and induced apoptosis even in the presence of mitogenic growth factor IGF-1, suggesting the importance of understanding the potentiating effects of phytonutrients in combination as they would occur in nature rather than individually.

Abstract 1882: Resveratrol and grape seed extract synergistically elevate human colon cancer cell apoptosis and suppress cell proliferation via upregulation of p53 and suppression of Wnt/b-catenin signaling pathways

Abstract The health benefits of a diet rich in fruits and vegetables is partly due to the presence of a complex mixture of phytochemicals. The synergistic effect of phytochemicals may be responsible for chemopreventive/protective properties of fruits and vegetables. Resveratrol (RSV), a dietary stilbenoid and grape seed extract (GSE), rich in proanthocyanidins, are marketed as popular dietary supplements and have shown to suppress carcinogenesis in vivo. However, we and others have shown that both RSV (> 100 μM) and GSE (at or > 50 μg/ml) exert anti-cancer properties against human colon cancer cells only at very high doses. We hypothesized that RSV and GSE work together synergistically, at low doses (RSV < 50 μM and GSE < 50 μg/ml), against colon cancer cell proliferation and elevate apoptosis via suppression of Wnt/β-catenin pathway and activation of p53. To test this hypothesis, we used HCT-116 p53 +/+ and p53 -/- colon cancer cells to determine the anti-proliferative (WST-1 assay) and pro-apoptotic properties (cell death detection ELISA kit) of RSV and GSE, alone and in combination, and measured levels of critical proteins in p53 and Wnt pathway using immunoblotting. RSV (100-125 µM) and GSE (at or > 50 µM) suppressed (p < 0.05) proliferation in both p53 +/+ and -/- cell lines. RSV and GSE combination (RSV- 25 μM and GSE − 50 µg/ml - combination index value ∼ 0.7) synergistically suppressed (p < 0.05) colon cancer cell proliferation. RSV and GSE in combination also elevated (p < 0.05) apoptosis irrespective of p53 status in colon cancer cell lines, however the effect was more pronounced (p < 0.001) in p53 +/+ cells. RSV and GSE in combination suppressed (p < 0.05) nuclear translocation of β-catenin, a downstream effector of Wnt pathway, that plays a critical role in colon cancer cell proliferation in both p53 +/+ and -/- cell lines. Apoptosis strongly correlated (p < 0.001 in both cell lines) with pp53 levels and Bax/Bcl-2 ratio that play a crucial role in mitochondrial apoptotic pathway. For the first time, we report that addition of resveratrol to grape seed extract synergistically elevates apoptosis and suppresses human colon cancer cell proliferation via upregulation of p53 and suppression of Wnt/β-catenin pathways. This explains why no magic bullet approach can provide health benefits similar to the synergistic combination of numerous phytochemicals in fruits and vegetables. Focal adhesion kinase (Fak) mediated integrin signaling pathway lies upstream of the well studied p53, PI3K/Akt, Wnt/β-catenin and Ras signaling pathways, and might provide insight into how RSV and GSE combination governs colon cancer cell apoptosis and proliferation. We will examine this possibility in future studies using appropriate in vitro and in vivo models. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1882.

Resveratrol potentiates grape seed extract induced human colon cancer cell apoptosis

Resveratrol potentiates grape seed extract induced human colon cancer cell apoptosis

Inducing apoptosis of human colon cancer cells by an IGF-I D domain analogue peptide

BackgroundThe resistance of tumour cells to apoptosis is a major contributor to the limited effectiveness of chemotherapies. Insulin-like growth factor I (IGF-I) has potential to protect cancer cells from variety of apoptotic challenges. This study was carried out to investigate the effect of a novel IGF-I receptor antagonist on apoptosis in colon cancer cells.ResultsWe have designed and synthesised a novel antagonist of IGF-I receptor. The effect of this antagonist on human colon cancer cell proliferation was examined by a non-radioactive assay; the apoptosis was revealed by determining the activities of cellular caspases3/7, 8 and 9. The apoptosis pathways were investigated by examining the levels of pro-apoptosis proteins with Western blotting. Following 40 hours treatment with the novel antagonist peptide, colon cancer cell Caspase 3/7 activities increased 2–7 times; Caspase 8 activities increased 2–5 times and Caspase 9 increased 1.2–1.6 times. The proliferation of cancer cell was inhibited by 14–15%. The data showed that the antagonist induced colon cancer cell apoptosis and inhibited cancer cell proliferation. The different changes of Caspase 3/7, 8 and 9 activities suggested that the extrinsic pathways may play a major role in the antagonist peptide-induced apoptosis.ConclusionThis is the first report on this novel antagonist to induce human colon cancer cell apoptosis and inhibit cancer cell proliferation. These results suggest that IGF-I receptor antagonists may have the potential to be developed as a novel therapy for colon cancers in the future.

Chemotherapy enhances TNF-related apoptosis-inducing ligand DISC assembly in HT29 human colon cancer cells.

Cytokines such as Fas-ligand (Fas-L) and Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand (TRAIL) can induce human colon cancer cell apoptosis through engagement of their death domain receptors. All the cancer cells are not sensitive to these cytokines. We have shown recently that low doses of cytotoxic drugs could restore TRAIL-induced cell death in resistant colon cancer cell lines. The present work further explores the death pathway triggered by the cytotoxic drug/TRAIL combination in HT-29 colon cancer cells (www.alexis-corp.com). Clinically relevant concentrations of cisplatin, doxorubicin and 5-fluorouracil synergize with TRAIL to trigger HT-29 cell death. Activation of this pathway leads to apoptosis that involves both caspases and the mitochondria. An increased recruitment of Fas-associated death domain (FADD) and procaspase-8 to the TRAIL-induced death-inducing signaling complex (DISC) was shown in cells exposed to anticancer drugs. Following caspase-8 activation at the DISC level, the mitochondria-dependent death pathway is activated, as demonstrated by the cleavage of Bid, the dissipation of DeltaPsi(m), the release of mitochondrial proteins in the cytosol and the inhibitory effect of Bcl-2 expression. Importantly, besides mitochondrial potentiation, we show here that cytotoxic drugs sensitize HT-29 colon cancer cells to TRAIL-induced cell death by enhancing FADD and procaspase-8 recruitment to the DISC, a novel mechanism whose efficacy could depend partly on Bcl-2 expression level.