Hsu Feng Lu

Chrysophanol induces necrosis through the production of ROS and alteration of ATP levels in J5 human liver cancer cells

Anthraquinone compounds have been shown to induce apoptosis in different cancer cell types. Effects of chrysophanol, an anthraquinone compound, on cancer cell death have not been well studied. The goal of this study was to examine if chrysophanol had cytotoxic effects and if such effects involved apoptosis or necrosis in J5 human liver cancer cells. Chrysophanol induced necrosis in J5 cells in a dose- and time-dependent manner. Non-apoptotic cell death was induced by chrysophanol in J5 cells and was characterized by caspase independence, delayed externalization of phosphatidylserine and plasma membrane disruption. Blockage of apoptotic induction by a general caspase inhibitor (z-VAD-fmk) failed to protect cells against chrysophanol-induced cell death. The levels of reactive oxygen species production and loss of mitochondrial membrane potential (DeltaPsi(m)) were also determined to assess the effects of chrysophanol. However, reductions in adenosine triphosphate levels and increases in lactate dehydrogenase activity indicated that chrysophanol stimulated necrotic cell death. In summary, human liver cancer cells treated with chrysophanol exhibited a cellular pattern associated with necrosis and not apoptosis.

Quercetin-mediated cell cycle arrest and apoptosis involving activation of a caspase cascade through the mitochondrial pathway in human breast cancer MCF-7 cells

Dietary polyphenols have been correlated with a reduced risk of developing cancer. Quercetin (a natural polyphenolic compound) induced apoptosis in many human cancer cell lines, including breast cancer MCF-7 cells. However, the involvement of possible signaling pathways and the roles of quercetin in apoptosis are still undefined. The purpose of this study was to investigate the effects of quercetin on the induction of the apoptotic pathway in human breast cancer MCF-7 cells. When MCF-7 cells were treated with quercetin for 24 and 48 h and at various doses (10–175 μM), cell viability decreased significantly in time- and dose-dependent manners. Exposure of MCF-7 cells to 10–175 μM quercetin resulted in an approximate 90.25% decrease in viable cells. To explicate the mechanism underlying the antiproliferative effect of quercetin, cell cycle distribution and apoptosis in MCF-7 cells was investigated after exposure to 150 μM quercetin for 6–48 h. Quercetin caused a remarkable increase in the number of S phase (14.56% to 61.35%) and sub-G1 phase cells (0.1% to 8.32%) in a dose- and time-dependent manner. Quercetin caused S phase arrest by decreasing the protein expression of CDK2, cyclins A and B while increasing the p53 and p57 proteins. Following incubation with quercetin for 48 h, MCF-7 cells showed apoptotic cell death by the decreased levels of Bcl-2 protein and ΔΨm and increased activations of caspase-6, -8 and -9. Moreover, quercetin increased the AIF protein released from mitochondria to nuclei and the GADD153 protein translocation from endoplasmic reticulum to the nuclei. These data suggested that quercetin may induce apoptosis by direct activation of the caspase cascade through the mitochondrial pathway in MCF-7 cells.

Quercetin-induced apoptosis acts through mitochondrial- and caspase-3-dependent pathways in human breast cancer MDA-MB-231 cells.

There has been considerable evidence recently demonstrating the anti-tumour effects of flavonols. Quercetin, an ubiquitous bioactive flavonol, inhibits cells proliferation, induces cell cycle arrest and apoptosis in different cancer cell types. The precise molecular mechanism of quercetin-induced apoptosis in human breast cancer cells is unclear. The purpose of this study was to investigate effects of quercetin on cell viability and to determine its underlying mechanism in human breast cancer MDA-MB-231 cells. Quercetin decreased the percentage of viable cells in a dose- and time-dependent manner, which was associated with cell cycle arrest and apoptosis. Quercetin did not increase reactive oxygen species generation but increased cytosolic Ca2+ levels and reduced the mitochondrial membrane potential (ΔΨm). Quercetin treatment promoted activation of caspase-3, -8 and -9 in MDA-MB-231 cells. Caspase inhibitors prevented the quercetin-induced loss of cell viability. Quercetin increased abundance of the pro-apoptotic protein Bax and decreased the levels of anti-apoptotic protein Bcl-2. Confocal laser microscope examination indicated that quercetin promoted apoptosis-inducing factor (AIF) release from mitochondria and stimulated translocation to the nucleus. Taken together, these findings suggest that quercetin results in human breast cancer MDA-MB-231 cell death through mitochondrial- and caspase-3-dependent pathways.

Kaempferol induced apoptosis via endoplasmic reticulum stress and mitochondria-dependent pathway in human osteosarcoma U-2 OS cells

Kaempferol is a natural flavonoid. Previous studies have reported that kaempferol has anti-proliferation activities and induces apoptosis in many cancer cell lines. However, there are no reports on human osteosarcoma. In this study, we investigate the anti-cancer effects and molecular mechanisms of kaempferol in human osteosarcoma cells. Our results demonstrate that kaempferol significantly reduces cell viabilities of U-2 OS, HOB and 143B cells, especially U-2 OS cells in a dose-dependent manner, but exerts low cytotoxicity on human fetal osteoblast progenitor hFOB cells. Comet assay, DAPI staining and DNA gel electrophoresis confirm the effects of DNA damage and apoptosis in U-2 OS cells. Flow cytometry detects the increase of cytoplasmic Ca(2+) levels and the decrease of mitochondria membrane potential. Western blotting and fluorogenic enzymatic assay show that kaempferol treatment influences the time-dependent expression of proteins involved in the endoplasmic reticulum stress pathway and mitochondrial signaling pathway. In addition, pretreating cells with caspase inhibitors, BAPTA or calpeptin before exposure to kaempferol increases cell viabilities. The anti-cancer effects of kaempferol in vivo are evaluated in BALB/c(nu/nu) mice inoculated with U-2 OS cells, and the results indicate inhibition of tumor growth. In conclusion, kaempferol inhibits human osteosarcoma cells in vivo and in vitro.

Benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC)-mediated generation of reactive oxygen species causes cell cycle arrest and induces apoptosis via activation of caspase-3, mitochondria dysfunction and nitric oxide (NO) in human osteogenic sarcoma U-2 OS cells†

Benzyl isothiocyanate (BITC) and phenethyl isothiocyanate (PEITC), a member of the isothiocyanate family, have been shown to exhibit antineoplastic ability against many human cancer cells. In this study, we found that exposure of human osteogenic sarcoma U‐2 OS cells to BITC and PEITC led to induce morphological changes and to decrease the percentage of viable cells in a time‐ and dose‐dependent manner. BITC and PEITC induced cell cycle arrest at G2/M phase at 48 h treatment and inhibited the levels of cell cycle regulatory proteins such as cyclin A and B1 in U‐2 OS cells but promoted the level of Chk1 and p53 that led to G2/M arrest. BITC and PEITC induced a marked increase in apoptosis (DNA fragmentation) and poly(ADP‐ribose)polymerase (PARP) cleavage, which was associated with mitochondrial dysfunction and the activation of caspase‐9 and ‐3. BITC and PEITC also promoted the ROS production in U‐2 OS cells and the N‐acetylcysteine (NAC, an antoxidant agent) was pretreated and then treated with both compounds which led to decrease the levels of ROS and increase the cell viability. Interestingly, BITC and PEITC promoted the levels of NO production and increased the iNOS enzyme. Confocal laser microscope also demonstrated that BITC and PEITC promoted the release of cytochrome c and AIF, suggesting that both compounds induced apoptosis through ROS, caspase‐3 and mitochondrial, and NO signaling pathways. Taken together, these molecular alterations and signaling pathways offer an insight into BITC and PEITC‐caused growth inhibition, G2/M arrest, and apoptotic death of U‐2 OS cells.

Antitumor Activity of Capsaicin on Human Colon Cancer Cells in Vitro and Colo 205 Tumor Xenografts in Vivo

Capsaicin was reported to inhibit cancer cell growth. The aim of this study was to evaluate the antitumor potential of capsaicin by studying antitumor activity in vitro as well as in vivo. The in vitro studies are to examine the effects of capsaicin on human colon cancer colo 205 cells after exposure to capsaicin. The results showed that capsaicin induced cytotoxic effects in a time- and dose-dependent manner and increased reactive oxygen species (ROS) and Ca(2+) but decreased the level of mitochondrial membrane potential (ΔΨ(m)) in colo 205 cells. Data from Western blotting analysis indicated that the levels of Fas, cytochrome c, and caspases were increased, leading to cell apoptosis. Capsaicin decreased the levels of anti-apoptotic proteins such as Bcl-2 and increased the levels of pro-apoptotic proteins such as Bax. Capsaicin-induced apoptosis in colo 205 cells was also done through the activations of caspase-8, -9 and -3. In vivo studies in immunodeficient nu/nu mice bearing colo 205 tumor xenografts showed that capsaicin effectively inhibited tumor growth. The potent in vitro and in vivo antitumor activities of capsaicin suggest that capsaicin might be developed for the treatment of human colon cancer.

Rutin inhibits human leukemia tumor growth in a murine xenograft model in vivo

Numerous studies have shown that rutin has anticancer effects. We have previously reported that rutin induced cell cycle arrest and apoptosis in murine leukemia WEHI‐3 cells in vitro and in vivo. However, there are no data showing that rutin inhibits human leukemia HL‐60 cells in vivo in a murine xenograft animal model. Human leukemia HL‐60 cells were implanted into mice and treated with vehicle (1% DMSO), rutin (120 mg/kg of body weight) or vinblastine (120 μg/kg of body weight). Compounds and agents were injected once every four days intraperitoneally (i.p.) for 36 days. Treatment with 120 mg/kg of rutin or with 120 μg/kg of vinblastine resulted in a reduction of tumor weight and volume when compared with the control groups. Tumor size in xenograft mice treated with 120 mg/kg of rutin was significantly smaller than that in the untreated‐control group. These novel findings indicate that rutin inhibits tumor growth in a xenograft animal model. Rutin may be useful in treating leukemia but certainly much more research is needed.

Diallyl sulfide, diallyl disulfide, and diallyl trisulfide inhibit migration and invasion in human colon cancer colo 205 cells through the inhibition of matrix metalloproteinase‐2, ‐7, and ‐9 expressions

Diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS) are major organosulfur compounds exiting in garlic (Allium sativum). These compounds are reported to exhibit various pharmacological properties such as antibacteria, antiangiogenesis, anticancer, and anticoagulation, and they also induce cytotoxicity and induction of apoptosis in human cancer cells. Although these compounds show wide spectrum of biological activities, there are no reports to show that DAS, DADS, and DATS affected migration and invasion of human colon cancer cells, and their exact molecular mechanisms are not well investigated. Therefore, the purpose of this study was to determine whether DAS, DADS, and DATS affected the invasion and migration abilities of colo 205 human colon cancer cells. The results indicate that DAS, DADS, and DATS at 10 and 25 μM inhibited the migration and invasion of colo 205 cells in the order of DATS < DADS < DAS. DATS is the highest for inhibition of migration and invasion of colo 205 cells. DAS, DADS, and DATS induce downregulation expression of PI3K, Ras, MEKK3, MKK7, ERK1/2, JNK1/2, and p38 and then lead to the inhibition of MMP‐2, ‐7, and ‐9. DAS, DADS, and DATS inhibited NF‐κB and COX‐2 for leading to the inhibition of cell proliferation. Taken together, these results demonstrated that application of DAS, DADS, and DATS might serve as potential antimetastatic drugs.

Capsaicin mediates apoptosis in human nasopharyngeal carcinoma NPC-TW 039 cells through mitochondrial depolarization and endoplasmic reticulum stress:

Capsaicin, a pungent compound found in hot chili peppers, has been reported to have antitumor activities in many human cancer cell lines, but the induction of precise apoptosis signaling pathway in human nasopharyngeal carcinoma (NPC) cells is unclear. Here, we investigated the molecular mechanisms of capsaicin-induced apoptosis in human NPC, NPC-TW 039, cells. Effects of capsaicin involved endoplasmic reticulum (ER) stress, caspase-3 activation and mitochondrial depolarization. Capsaicin-induced cytotoxic effects (cell death) through G0/G1 phase arrest and induction of apoptosis of NPC-TW 039 cells in a dose-dependent manner. Capsaicin treatment triggered ER stress by promoting the production of reactive oxygen species (ROS), increasing levels of inositol-requiring 1 enzyme (IRE1), growth arrest and DNA-damage-inducible 153 (GADD153) and glucose-regulated protein 78 (GRP78). Other effects included an increase in cytosolic Ca2+, loss of the mitochondrial transmembrane potential (ΔΨ m ), releases of cytochrome c and apoptosis-inducing factor (AIF), and activation of caspase-9 and -3. Furthermore, capsaicin induced increases in the ratio of Bax/Bcl-2 and abundance of apoptosis-related protein levels. These results suggest that ER stress- and mitochondria-mediated cell death is involved in capsaicin-induced apoptosis in NPC-TW 039 cells.

The roles of endoplasmic reticulum stress and mitochondrial apoptotic signaling pathway in quercetin-mediated cell death of human prostate cancer PC-3 cells

Prostate cancer has its highest incidence and is becoming a major concern. Many studies have shown that traditional Chinese medicine exhibited antitumor responses. Quercetin, a natural polyphenolic compound, has been shown to induce apoptosis in many human cancer cell lines. Although numerous evidences show multiple possible signaling pathways of quercetin in apoptosis, there is no report to address the role of endoplasmic reticulum (ER) stress in quercetin‐induced apoptosis in PC‐3 cells. The purpose of this study was to investigate the effects of quercetin on the induction of the apoptotic pathway in human prostate cancer PC‐3 cells. Cells were treated with quercetin for 24 and 48 h and at various doses (50–200 μM), and cell morphology and viability decreased significantly in dose‐dependent manners. Flow cytometric assay indicated that quercetin at 150 μM caused G0/G1 phase arrest (31.4–49.7%) and sub‐G1 phase cells (19.77%) for 36 h treatment and this effect is a time‐dependent manner. Western blotting analysis indicated that quercetin induces the G0/G1 phase arrest via decreasing the levels of CDK2, cyclins E, and D proteins. Quercetin also stimulated the protein expression of ATF, GRP78, and GADD153 which is a hall marker of ER stress. Furthermore, PC‐3 cells after incubation with quercetin for 48 h showed an apoptotic cell death and DNA damage which are confirmed by DAPI and Comet assays, leading to decrease the antiapoptotic Bcl‐2 protein and level of ΔΨm, and increase the proapoptotic Bax protein and the activations of caspase‐3, ‐8, and ‐9. Moreover, quercetin promoted the trafficking of AIF protein released from mitochondria to nuclei. These data suggest that quercetin may induce apoptosis by direct activation of caspase cascade through mitochondrial pathway and ER stress in PC‐3 cells.