Prodigiosin-induced apoptosis in human colon cancer cells

Prodigiosin is a red pigment produced by various bacteria including Serratia marcescens. Colorectal cancer is one of the most frequent malignancies and one of the most frequent causes of cancer death in the Western world. Its treatment is far from satisfactory and the challenge to oncologists is to find novel chemical entities with less toxicity and greater effectiveness than those used in current chemotherapy. Here we characterize the apoptotic action of prodigiosin in colon cancer cells. DLD-1 and SW-620 human colon adenocarcinoma cells, NRK and Swiss-3T3 nonmalignant cells were assayed by the MTT assay, fragmentation pattern of DNA, Hoechst 33342 staining and study of PARP cleavage by Western blot, in order to characterize the prodigiosin-induced apoptosis. Prodigiosin was purified and its structure was confirmed. Metastatic SW-620 cells were more sensitive to prodigiosin (IC50: 275 nM) than DLD-1. We did not observe a significant decrease in the viability of NRK cells. We confirmed that prodigiosin induces apoptosis in both cancer cell lines by the characteristic DNA laddering pattern and condensed nuclei or apoptotic bodies identified by fluorescence microscopy. These results indicate that prodigiosin induces apoptosis in colon cancer cells.     

Transcriptome analysis reveals GPNMB as a potential therapeutic target for gastric cancer

Gastric cancer has the fifth highest incidence of disease and is the third leading cause of cancer-associated mortality in the world. The etiology of gastric cancer is complex and needs to be fully elucidated. Thus, it is necessary to explore potential pathogenic genes and pathways that contribute to gastric cancer. Gene expression profiles of the GSE33335 and GSE54129 datasets were downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were compared and identified using R software. The DEGs were then subjected to gene set enrichment analysis and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses. Survival analyses based on The Cancer Genome Atlas database were used to further screen the essential DEGs. A knockdown assay was performed to determine the function of the candidate gene in gastric cancer. Finally, the association between the candidate gene and immune-related genes was investigated. We found that GPNMB serves as an essential gene, with a high expression level, and predicts a worse outcome of gastric cancer. Knockdown of GPNMB inhibited gastric cancer cell proliferation and migration. In addition, GPNMB may augment the immunosuppressive ability of gastric cancer by recruiting immunosuppressive cells and promoting immune cell exhaustion through PI3K/AKT/CCL4 signaling axis. Collectively, these data suggest that GPNMB acts as an important positive mediator of tumor progression in gastric cancer, and GPNMB could exert multimodality modulation of gastric cancer-mediated immune suppression.     

Mechanism of taurine-induced apoptosis in human colon cancer cells

Taurine （Tau） has been shown to possess cancer therapeutic effect through induction of apoptosis, while the underlying molecular mechanism of its anti-cancer effect is not well understood. PUMA （p53-upregulated modulator of apoptosis） plays an important role in the process of apoptosis induction in a variety of human tumor ceils in both p53- dependent and -independent manners. However, whether PUMA is involved in the process of Tau-induced apoptosis in cancer cells has not been well studied. In the present study, we treated human colorectal cancer cells HT-29 （mutant p53） and LoVo （wild-type p53） with different concentrations of Tau, which led to the repression of cell proliferation and induction of apoptosis in both cell fines. Meanwhile, we also observed the increased expression of PUMA and high Bax/Bcl-2 ratios. To determine the role of PUMA in Tau-induced apoptosis, we used small interfering RNA interference to suppress PUMA expression. As a result, apoptosis was decreased in response to Tau treatment. All these results indicated that PUMA plays a critical role in Tauinduced apoptosis pathway in human colorectal cancer ceils. Demonstration of the molecular mechanism involved in the anti-tumor effect of Tau may be useful in the therapeutic target selection for p53-deficient colorectal cancer.     

Dictyopteris undulata extract induces apoptosis in human colon cancer cells

The present study investigated the cytotoxic and apoptotic effects of an ethanol extract derived from the marine brown alga Dictyopteris undulata against human colon adenocarcinoma cells. The Dictyopteris undulata extract (DUE) showed cytotoxic activity against SW480 cells in a dose-dependent manner, with 50% inhibition of cell viability at a concentration of 40 μg/mL. DUE also induced programmed cell death in SW480 cells, as evidenced by apoptotic body formation, DNA fragmentation, an increase in the population of apoptotic sub-G1 phase cells, and mitochondrial membrane depolarization. Moreover, DUE significantly modulated the expression of apoptosisassociated proteins, resulting in a decrease in B cell lymphoma-2 expression and an increase in Bcl-2-associated X protein expression, as well as the activation of caspase-9 and caspase-3. Furthermore, DUE showed apoptotic cell death in two other colon cancer cell lines, SNU407 and HT29. These observations suggest that DUE may prove useful as a therapeutic agent for the attenuation of colon cancer.     

beta-lapachone induces cell cycle arrest and apoptosis in human colon cancer cells

BACKGROUND: Human colon cancers have a high frequency of p53 mutations, and cancer cells expressing mutant p53 tend to be resistant to current chemo- and radiation therapy. It is thus important to find therapeutic agents that can inhibit colon cancer cells with altered p53 status. beta-Lapachone, a novel topoisomerase inhibitor, has been shown to induce cell death in human promyelocytic leukemia and prostate cancer cells through a p53-independent pathway. Here we examined the effects of beta-lapachone on human colon cancer cells. MATERIALS AND METHODS: Several human colon cancer cell lines, SW480, SW620, and DLD1, with mutant or defective p53, were used. The antiproliferative effects of beta-lapachone were assessed by colony formation assays, cell cycle analysis, and apoptosis analysis, including annexin V staining and DNA laddering analysis. The effects on cell cycle and apoptosis regulatory proteins were examined by immunoblotting. RESULTS: All three cell lines, SW480, SW620, and DLD1, were sensitive to beta-lapachone, with an IC(50) of 2 to 3 microM in colony formation assays, a finding similar to that previously reported for prostate cancer cells. However, these cells were arrested in different stages of S phase. At 24 hr post-treatment, beta-lapachone induced S-, late S/G2-, and early S-phase arrest in SW480, SW620, and DLD1 cells, respectively. The cell cycle alterations induced by beta-lapachone were congruous with changes in cell cycle regulatory proteins such as cyclin A, cyclin B1, cdc2, and cyclin D1. Moreover, beta-lapachone induced apoptosis, as demonstrated by annexin V staining, flow cytometric analysis of DNA content, and DNA laddering analysis. Furthermore, down-regulation of mutant p53 and induction of p27 in SW480 cells, and induction of pro-apoptotic protein Bax in DLD1 cells may be pertinent to the anti-proliferative and apoptotic effects of beta-lapachone on these cells. CONCLUSIONS: beta-Lapachone induced cell cycle arrest and apoptosis in human colon cancer cells through a p53-independent pathway. For human colon cancers, which often contain p53 mutations, beta-lapachone may prove to be a promising anticancer agent that can target cancer cells, especially those with mutant p53.     

Alpha-tocopheryl succinate sensitizes human colon cancer cells to exisulind-induced apoptosis

Sulindac sulfone (also known as exisulind) and its chemical derivatives are promising anticancer agents capable of inducing apoptosis in a variety of malignant cell types with minimal toxicity to normal cells. Here, we tested the ability of alpha-tocopheryl succinate (TOS), another promising anticancer agent, to sensitize colon cancer cells to exisulind-induced apoptosis. We found that sub-apoptotic doses of TOS greatly enhanced exisulind-induced growth suppression and apoptosis in the HCT116, LoVo and SNU-C4 human colon cancer cell lines. Our results revealed that this was accounted for primarily by an augmented cleavage of poly(ADP-ribose) polymerase (PARP) and enhanced activation of caspase-8, -9 and -3. Pretreatment with z-VAD-FMK (a pan-caspase inhibitor), z-IETD-FMK (a caspase-8 inhibitor) or z-LEHD-FMK (a caspase-9 inhibitor) blocked TOS and exisulind cotreatment-induced PARP cleavage and apoptosis. Furthermore, TOS/exisulind cotreatment induced JNK phosphorylation, while pretreatment with SP600151 (a JNK inhibitor) partially blocked cotreatment-induced caspase-dependent PARP cleavage and apoptosis. Taken together, these findings indicate that TOS sensitizes human colon cancer cells to exisulind-induced apoptosis. Apoptotic synergy induced by exisulind plus TOS seems likely to be mediated through a mechanism involving activation of caspases and JNK. S.-J. Lim, Y.-J. Lee both authors are contributed equally to this study.     

PI3K/Akt pathway involving into apoptosis and invasion in human colon cancer cells LoVo

In this study we determined the effects of Curcumin on human colon cancer cells line LoVo. We found that Curcumin significantly inhibited the proliferation, migration and invasion, and clone formation of LoVo cells in a dose-dependent manner. Curcumin also dose-dependently reduced the phosphorylation of proteins Akt and increased expression levels of the genes caspase-3, cytochrome-c, Bax mRNA in LoVo cells. In addition, Curcumin dose-dependently decreased gene Bcl-2 mRNA expression. Similar results were observed in LoVo cells treated with LY294002. These in vitro studies suggest that Curcumin may play its anti-cancer actions partly via suppressing PI3K/Akt signal pathway in LoVo cells.     

Xanthones induce cell-cycle arrest and apoptosis in human colon cancer DLD-1 cells

We investigated the antiproliferative effects of four structurally similar prenylated xanthones, alpha-mangostin, beta-mangostin, gamma-mangostin, and methoxy-beta-mangostin, in human colon cancer DLD-1 cells. These xanthones differ in the number of hydroxyl and methoxy groups. Except for methoxy-beta-mangostin, the other three xanthones strongly inhibited cell growth at 20 microM and their antitumor efficacy was correlated with the number of hydroxyl groups. Hoechst 33342 nuclear staining and nucleosomal DNA-gel electrophoresis revealed that the antiproliferative effects of alpha- and gamma-mangostin, but not that of beta-mangostin, were associated with apoptosis. It was also shown that their antiproliferative effects were associated with cell-cycle arrest by affecting the expression of cyclins, cdc2, and p27; G1 arrest was by alpha-mangostin and beta-mangostin, and S arrest by gamma-mangostin. These findings provide a relevant basis for the development of xanthones as an agent for cancer prevention and combination therapy with anti-cancer drugs.     

Noscapine induces mitochondria-mediated apoptosis in human colon cancer cells in vivo and in vitro

Noscapine, a phthalide isoquinoline alkaloid derived from opium, has been widely used as a cough suppressant for decades. Noscapine has recently been shown to potentiate the anti-cancer effects of several therapies by inducing apoptosis in various malignant cells without any detectable toxicity in cells or tissues. However, the mechanism by which noscapine induces apoptosis in colon cancer cells remains unclear. The signaling pathways by which noscapine induces apoptosis were investigated in colon cancer cell lines treated with various noscapine concentrations for 72 h, and a dose-dependent inhibition of cell viability was observed. Noscapine effectively inhibited the proliferation of LoVo cells in vitro (IC(50)=75 μM). This cytotoxicity was reflected by cell cycle arrest at G(2)/M and subsequent apoptosis, as indicated by increased chromatin condensation and fragmentation, the upregulation of Bax and cytochrome c (Cyt-c), the downregulation of survivin and Bcl-2, and the activation of caspase-3 and caspase-9. Moreover, in a xenograft tumor model in mice, noscapine injection clearly inhibited tumor growth via the induction of apoptosis, which was demonstrated using a TUNEL assay. These results suggest that noscapine induces apoptosis in colon cancer cells via mitochondrial pathways. Noscapine may be a safe and effective chemotherapeutic agent for the treatment of human colon cancer.     

P38 MAP kinase functions as a switch in MS-275-induced reactive oxygen species-dependent autophagy and apoptosis in human colon cancer cells

MS-275 is a synthetic benzamide derivative of the histone deacetylase inhibitor and is currently in phase I/II clinical trials. Many reports have shown that the anti-tumor activity of MS-275 in several types of cancer is mainly attributable to its capacity to induce the apoptotic death of tumor cells. It remains unclear if autophagy is involved in MS-275 treatment of cancer cells. Here, we first show that MS-275 induces human colon cancer cell HCT116 autophagy as well as apoptosis. Short-term treatment (24h) induced HCT116 cells to undergo autophagy with dependence on intracellular reactive oxygen species production and ERK activation. The activated reactive oxygen species/ERK signal promoted Atg7 protein expression, which triggered MS-275-induced cancer cell autophagy. However, after prolonged treatment with MS-275 (over 48h), autophagic cells turned apoptotic, which was also dependent on reactive oxygen species generation. Interestingly, we found that p38 MAP kinase played a vital role in the switch from autophagy to apoptosis in MS-275-induced human colon cancer cells. High expression of p38 induced cell autophagy, but low expression resulted in apoptosis. In addition, observations in vivo are strongly consistent with the in vitro results. Therefore, these findings extend our understanding of the action of MS-275 in inducing cancer cell death and suggest that it may be a promising clinical chemotherapeutic agent with multiple effects.     

Detection of potassium currents and regulation of multidrug resistance by potassium channels in human gastric cancer cells

The present study aimed to investigate the potassium currents and further explore the role of potassium channels in drug response of gastric cancer cells. By patch-clamp technique, potassium currents of human gastric cancer cell SGC7901 were recorded in the mode of voltage clamp. Both 4-aminopyridine (4-AP) and tetraethylammonium (TEA) could almost completely block this current. The chemotherapeutic drugs, adriamycin or 5-fluorouracil could significantly increase the K(+) current density on SGC7901 cells in a dose-dependent manner. 4-AP or TEA was found to restrain adriamycin-induced apoptosis and enhance multidrug-resistant phenotype of SGC7901 cells. Up-regulation of Kv1.5, which has been found widely expressed in gastric cancer cells including SGC7901, increased the K(+) current density and sensitivity of SGC7901 cells to multiple chemotherapeutic drugs, whereas down-regulation of Kv1.5 enhanced the drug-resistant phenotype of SGC7901 cells. In conclusion, potassium channels may exert regulatory effects on multidrug resistance by regulating drug-induced apoptosis in gastric cancer cells.     

Transcriptome analysis reveals a role of interferon-gamma in human neointima formation

The most effective immediate cure for coronary stenosis is stent-supported angioplasty. Restenosis due to neointima proliferation represents a major limitation. We investigated the expression of 2435 genes in atherectomy specimens and blood cells of patients with restenosis, normal coronary artery specimens, and cultured human smooth muscle cells (SMCs). Of the 223 differentially expressed genes, 37 genes indicated activation of interferon-gamma (IFN-gamma) signaling in neointimal SMCs. In cultured SMCs, IFN-gamma inhibited apoptosis. Genetic disruption of IFN-gamma signaling in a mouse model of restenosis significantly reduced the vascular proliferative response. Our data suggest an important role of IFN-gamma in the control of neointima proliferation.     

ROS mediate selenite-induced apoptosis in colon cancer cells

Selenite-induced oxidative stress and its relationship to mitochondrial apoptosis was studied in human adenocarcinoma HT-29 cells. It is shown that selenite induces caspase-dependent apoptosis, which is mediated by mitochondria via released cytochrome c, apoptosis-inducing factor (AIF) and Smac/Diablo. Selenite activates stress kinases p38 and JNK while suppressing reduced glutathione (GSH) and thioredoxin reductase (TrxR) levels, transiently inducing heme oxygenase (HO-1) system as well as reducing Akt expression. Pre-treatment of cells with selected antioxidants and stress kinase inhibitors significantly prevented selenite-induced cell death, thereby implicating oxidative stress as a direct (Bax) as well as indirect (via kinases) cause of HT-29 cells demise. These results thus demonstrate for the first time active proapoptotic and anti-survival effects of selenite in colon cancer cells.