Cantharidic acid induces apoptosis in human nasopharyngeal carcinoma cells through p38‐mediated upregulation of caspase activation

Cantharidic acid (CA) is the hydrolysis product of the acid anhydride cantharidin, which is a natural toxin secreted by several species of blister beetles. Several studies have indicated that as an inhibitor of protein phosphatase 2 (PP2A), CA induces apoptosis in various human cancer cells. However, the effect of CA on human nasopharyngeal carcinoma (NPC) cells and the underlying pathways have not been addressed. In our current study, we tested the hypothesis that CA treatment reduces the viability of human NPC cells (HONE‐1, NPC‐39, and NPC‐BM) by inducing apoptosis. Results indicated that CA markedly reduced cell viability, which was revealed by the upregulation of caspase activation in extrinsic and intrinsic apoptosis pathways as well as the upregulation of extracellular‐signal‐regulated kinase 1/2 (ERK1/2), p38, and c‐Jun N‐terminal kinase 1/2 (JNK1/2) pathways. Coadministration of a p38 inhibitor (SB203580) with CA abolished the activation of caspase proteins. These findings indicated that CA treatment leads to apoptosis in human NPC cells through the upregulation of caspase activation, mediated particularly by the p38 pathway. Hence, CA is a promising therapeutic agent for human NPC.     

Glabridin induces apoptosis and cell cycle arrest in oral cancer cells through the JNK1/2 signaling pathway

Glabridin, a flavonoid extracted from licorice (Glycyrrhiza glabra), possesses various biological properties, including anticancer activities. However, the effect of glabridin on oral cancer cell apoptosis and the underlying molecular mechanisms has not been elucidated. In this study, we demonstrated that glabridin treatment significantly inhibits cell proliferation in human oral cancer SCC‐9 and SAS cell lines. Flow cytometric assays demonstrated that glabridin induced several features of apoptosis, such as sub‐G1 phase cell increase and phosphatidylserine externalization. Furthermore, glabridin induced apoptosis dose‐dependently in SCC‐9 cells through caspase‐3, −8, and −9 activation and poly (ADP‐ribose) polymerase cleavage. Moreover, glabridin increased the phosphorylation of the extracellular signal–regulated kinase, p38, and c‐Jun N‐terminal kinase (JNK) pathways in a dose‐dependent manner. Moreover, the inhibition of the JNK1/2 inhibitor significantly reversed the glabridin‐induced activation of the caspase pathway. In conclusion, our findings suggest that glabridin induces oral cancer cell apoptosis through the JNK1/2 pathway and is a potential therapeutic agent for oral cancer.     

Guanylate cyclase activator YC-1 potentiates apoptotic effect of licochalcone A on human epithelial ovarian carcinoma cells via activation of death receptor and mitochondrial pathways

Natural phenol licorice compounds have been shown to induce apoptosis in cancer cells. 3-(5'-Hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) may enhance the sensitivity of cancer cells to anticancer drugs. However, the combined effect of licochalcone A and YC-1 on cell death in ovarian cancer cells has not been studied. We assessed the combined effect of licochalcone A and YC-1 on apoptosis in human epithelial ovarian carcinoma cell lines in relation to the cell death process. In the OVCAR-3 and SK-OV-3 cell lines, licochalocone A induced a decrease in Bid, Bcl-2, Bcl-xL and survivin protein levels; an increase in Bax levels; loss of the mitochondrial transmembrane potential; cytochrome c release; activation of caspases (-8, -9 and -3); cleavage of PARP-1; and an increase in the tumor suppressor p53 levels. YC-1 enhanced licochalcone A-induced apoptosis-related protein activation, nuclear damage and cell death. These results suggest that YC-1 may potentiate the apoptotic effect of licochalcone A on ovarian carcinoma cell lines by increasing the activation of the caspase-8- and Bid-dependent pathway and the mitochondria-mediated apoptotic pathway, leading to caspase activation. The combination of licochalcone A and YC-1 may confer a benefit in the treatment of human epithelial ovarian adenocarcinoma.     

Coronarin D induces human oral cancer cell apoptosis though upregulate JNK1/2 signaling pathway

The incidence of oral cancer is increasing all over the world, with rates particularly high in Southeast Asian countries, such as Taiwan. Coronarin D (CD) has been confirmed to have anti‐inflammatory, anti‐bacterial effects, and anti‐apoptotic effects in human hepatocellular carcinoma and nasopharyngeal carcinoma. The purpose of this study is to explore whether CD has a suppression effect on oral cancer cells and the mechanisms involved. The results of our study revealed the significantly decreased cancer cell viability and increased activation of apoptosis via increased loss of mitochondrial membrane potential, increased death receptors, leading to the activation of caspase‐8, ‐9, ‐3. Moreover, the rate of apoptosis of cells treated with CD plus JNK inhibitors was decreased compared to CD‐treated cells. This is the first study to demonstrate that CD induces apoptosis in human oral cancer cells and can be expected to be a promising anticancer agent for oral cancer treatment.     

Coronarin D induces apoptotic cell death through the JNK pathway in human hepatocellular carcinoma

Coronarin D, a diterpene derived from the rhizomes of Hedychium coronarium, has been used to treat inflammatory diseases. Coronarin D can exert strong anticancer effects through cell growth prevention and cell cycle arrest in many cancer cells. In this study, we investigated the molecular mechanism through which coronarin D suppresses cell proliferation and triggers cell death in human hepatocellular carcinoma (HCC) cells. Treatment of Huh7 and Sk‐hep‐1 cells with coronarin D resulted in a significantly increased loss of mitochondrial membrane potential, leading to the cleavage and activation of caspase‐9, caspase‐8, and caspase‐3 and changes in Bax, Bcl‐2, and Bcl‐xL protein levels. Coronarin D significantly induced autophagy by increasing the expression of Beclin‐1 and LC3‐II and reducing the expression of p62. Moreover, Huh7 and Sk‐hep‐1 cells exposed to coronarin D had decreased expression of phosphorylated AKT, p38, and ERK and increased expression of phosphorylated JNK. Exposure of cells to the JNK‐specific inhibitor SP600125 attenuated the apoptotic effects of coronarin D. Taken together, this is the first study to report that coronarin D may effectively inhibit cell growth through apoptosis. We have provided evidence indicating that coronarin D induces cell death through the upregulation of JNK mitogen‐activated protein kinases in human HCC cells.     

Proteasome inhibitor MG132-induced apoptosis via ER stress-mediated apoptotic pathway and its potentiation by protein tyrosine kinase p56lck in human Jurkat T cells

Exposure of human Jurkat T cells to MG132 caused apoptosis along with upregulation of Grp78/BiP and CHOP/GADD153, activation of JNK and p38MAPK, activation of Bak, mitochondrial membrane potential (Δψm) loss, cytochrome c release, activation of caspase-12, -9, -3, -7, and -8, cleavage of Bid and PARP, and DNA fragmentation. However, these MG132-induced apoptotic events, with the exceptions of upregulation of Grp78/BiP and CHOP/GADD153 and activation of JNK and p38MAPK, were abrogated by overexpression of Bcl-xL. Pretreatment with the pan-caspase inhibitor z-VAD-fmk prevented MG132-induced apoptotic caspase cascade, but allowed upregulation of Grp78/BiP and CHOP/GADD153 levels, activation of JNK and p38MAPK, Δψm loss, and cleavage of procaspase-9 (47kDa) to active form (35kDa). Further analysis using selective caspase inhibitors revealed that caspase-12 activation was required for activation of caspase-9 and -3 to the sufficient level for subsequent activation of caspase-7 and -8. MG132-induced cytotoxicity, apoptotic sub-G(1) peak, Bak activation, and Δψm loss were markedly reduced by p38MAPK inhibitor, but not by JNK inhibitor. MG132-induced apoptotic changes, including upregulation of Grp78/BiP and CHOP/GADD153 levels, activation of caspase-12, p38MAPK and Bak, and mitochondria-dependent activation of caspase cascade were more significant in p56(lck)-stable transfectant JCaM1.6/lck than in p56(lck)-deficient JCaM1.6/vector. The cytotoxicity of MG132 toward p56(lck)-positive Jurkat T cell clone was not affected by the Src-like kinase inhibitor PP2. These results demonstrated that MG132-induced apoptosis was caused by ER stress and subsequent activation of mitochondria-dependent caspase cascade, and that the presence of p56(lck) enhances MG132-induced apoptosis by augmenting ER stress-mediated apoptotic events in Jurkat T cells.     

Nimbolide induced apoptosis by activating ERK‐mediated inhibition of c‐IAP1 expression in human hepatocellular carcinoma cells

Nimbolide is one of the major compounds from the leaves and flowers of the neem tree and exhibits antitumor properties on various cancer cells. However, no report has shown that nimbolide induces apoptosis in vitro and in vivo in human hepatocellular carcinoma cells. Our results indicated that it inhibited cell growth in Huh‐7 and PLC/PRF/5 cells. We also found that nimbolide induced cell death through the induction of G2/M phase arrest and mitochondrial dysfunction, accompanied by the increased expression of cleaved caspase‐7, caspase‐9, caspase‐3, caspase‐PARP, and Bax and decreased expression of Mcl‐1 and Bcl‐2. A human apoptosis antibody array analysis demonstrated that inhibition of the apoptosis family proteins (XIAP, c‐IAP1, and c‐IAP2) was one of the major targets of nimbolide. Additionally, nimbolide sustained activation of ERK expression. Moreover, pretreatment with U0126 (MEK inhibitor) markedly abolished nimbolide‐inhibited cell viability, induced cell apoptosis, ERK phosphorylation, cleaved caspase‐9, caspase‐3, cleaved‐PARP activation, and increased c‐IAP1 expression in Huh‐7 cells. An in vivo study showed that nimbolide significantly reduced Huh‐7 tumor growth and weight in a xenograft mouse model. This study indicated the antitumor potential of nimbolide in human hepatocellular carcinoma cells.     

Cantharidic acid induces apoptosis of human leukemic HL‐60 cells via c‐Jun N‐terminal kinase‐regulated caspase‐8/‐9/‐3 activation pathway

Cantharidin, a natural toxin from blister beetles, has shown potent anticancer activities on many solid tumor cells. Recently, cantharidin and its analogue, norcantharidin, were also shown to suppress nonsolid tumors such as chronic myeloid leukemia, acute myeloid leukemia (AML), and leukemic stem cells. However, there is no available information to address the effects of cantharidic acid (CAC), a hydrolysis product of cantharidin, on human AML cells. The present study showed that CAC, at a range of concentrations (0‐20 μM), concentration‐dependently inhibited cell proliferation in the HL‐60 AML cell line. Western blot and flow cytometric assays demonstrated that CAC induced several features of apoptosis such as sub G1‐phase cell increase, phosphatidylserine (PS) externalization, and significantly activated proapoptotic signaling including caspase‐8, −9, and −3 activation and poly(ADP‐ribose) polymerase (PARP) cleavage in HL‐60 AML cells. Moreover, treatment of HL‐60 cells with CAC induced concentration‐ and time‐ dependent activation of p38 mitogen‐activated protein kinase (p38 MAPK) and c‐Jun N‐terminal kinase (JNK). Only JNK‐, but not p38 MAPK‐specific inhibitor can reverse the CAC‐induced activation of the caspase‐8, −9, and −3. We concluded that CAC can induce apoptosis in human leukemic HL‐60 cells via a caspases‐dependent pathway, and that the apoptosis‐inducing effect of CAC can be regulated by JNK activation signaling.     

Berberine induces apoptosis in SW620 human colonic carcinoma cells through generation of reactive oxygen species and activation of JNK/p38 MAPK and FasL

Berberine is the major constituent of Coptidis Rhizoma with multiple pharmacological activities, including anti-inflammation, promotion of apoptosis and anticancer potential effect. Mitogen-activated protein kinase (MAPK) and reactive oxygen species (ROS) may contribute to the causal relationship between tumorigenesis and pro-apoptotic function. Berberine is studied for the mechanism of its action in apoptotic pathway in human colonic carcinoma cell. Treatment of SW620 cells with 50 μM berberine resulted in activation of the caspase 3 and caspase 8, cleavage of poly ADP-ribose polymerase (PARP) and the release of cytochrome c; whereas, the expression of BID and anti-apoptosis factor c-IAP1, Bcl-2, and Bcl-_XL were decreased markedly. Berberine-induced, dose-dependent induction of apoptosis was accompanied by sustained phosphorylation of JNK and p38 MAPK, as well as generation of the ROS. Furthermore, the induction of apoptosis was alleviated by inhibitors specific for JNK and p38. In addition, there was an increase in the cellular levels of phospho-c-Jun, FasL and t-BID in the berberine-induced apoptosis via the activation of JNK and p38 signaling modules. NAC administration, a scavenger of ROS, reversed berberine-induced apoptosis effects via inhibition of JNK, p38 and c-jun activation, and FasL and t-BID expression. These results leads us to speculate that berberine may play an apoptotic cascade in SW620 cells by activation of the JNK/p38 pathway and induction of ROS production, providing a new mechanism for berberine-induced cell death in human colon cancer cells.     

Proteasome inhibitor MG132-induced apoptosis via ER stress-mediated apoptotic pathway and its potentiation by protein tyrosine kinase p56 in human Jurkat T cells

Exposure of human Jurkat T cells to MG132 caused apoptosis along with upregulation of Grp78/BiP and CHOP/GADD153, activation of JNK and p38MAPK, activation of Bak, mitochondrial membrane potential (Δψm) loss, cytochrome c release, activation of caspase-12, -9, -3, -7, and -8, cleavage of Bid and PARP, and DNA fragmentation. However, these MG132-induced apoptotic events, with the exceptions of upregulation of Grp78/BiP and CHOP/GADD153 and activation of JNK and p38MAPK, were abrogated by overexpression of Bcl-xL. Pretreatment with the pan-caspase inhibitor z-VAD-fmk prevented MG132-induced apoptotic caspase cascade, but allowed upregulation of Grp78/BiP and CHOP/GADD153 levels, activation of JNK and p38MAPK, Δψm loss, and cleavage of procaspase-9 (47 kDa) to active form (35 kDa). Further analysis using selective caspase inhibitors revealed that caspase-12 activation was required for activation of caspase-9 and -3 to the sufficient level for subsequent activation of caspase-7 and -8. MG132-induced cytotoxicity, apoptotic sub-G₁ peak, Bak activation, and Δψm loss were markedly reduced by p38MAPK inhibitor, but not by JNK inhibitor. MG132-induced apoptotic changes, including upregulation of Grp78/BiP and CHOP/GADD153 levels, activation of caspase-12, p38MAPK and Bak, and mitochondria-dependent activation of caspase cascade were more significant in p56^lck-stable transfectant JCaM1.6/lck than in p56^lck-deficient JCaM1.6/vector. The cytotoxicity of MG132 toward p56^lck-positive Jurkat T cell clone was not affected by the Src-like kinase inhibitor PP2. These results demonstrated that MG132-induced apoptosis was caused by ER stress and subsequent activation of mitochondria-dependent caspase cascade, and that the presence of p56^lck enhances MG132-induced apoptosis by augmenting ER stress-mediated apoptotic events in Jurkat T cells.     

Indomethacin induces apoptosis in 786-O renal cell carcinoma cells by activating mitogen-activated protein kinases and AKT

Studies on chemoprevention of cancer are generating increasing interest. The anti-neoplastic effect of nonsteroidal anti-inflammatory drugs (NSAIDs) involves cyclooxygenase (COX)-dependent and COX-independent mechanisms. Evidence suggests that mitogen-activated protein kinases (MAPKs) may mediate apoptotic signaling induced by anti-neoplastic agents. While many reports have revealed the existence of MAPK activation in apoptosis induced by various stimuli, the signaling transduction pathways used by NSAIDs to trigger apoptosis in human renal cell carcinoma (RCC) remain largely unknown. Treatment of RCC 786-O cells with indomethacin resulted in growth regression and apoptosis. Caspase-dependent apoptosis was evidenced by the detection of enzymatic activities of caspase-3, caspase-6, and caspase-9 and suppression of toxicity using a caspase inhibitor. Indomethacin treatment was associated with increased expression of glucose-regulated protein 78 (GRP78) and C/EBP homologus protein (CHOP) and activation of ATF-6, characteristics of endoplasmic reticulum stress. In addition, the concomitant induction of peroxisome proliferator-activated receptor (PPAR), especially PPAR-beta, was apparent in treated cells. Western blotting revealed the activation of extracellular signal-regulated kinase (ERK), p38 MAPK, and c-Jun N-terminal kinase (JNK) with indomethacin treatment. Selective inhibitors of ERK, p38 MAPK, and JNK suppressed the induction of GRP78, CHOP, and PPAR-beta, attenuated indomethacin-induced cytotoxicity and reduced increased caspase activity. LY294002, a phosphoinositide-3 kinase (PI3K)/AKT inhibitor, and Trolox, an antioxidant, suppressed indomethacin-induced cytotoxicity and caspase activation. Furthermore, Trolox attenuated indomethacin-induced increased phosphorylation in ERK, p38 MAPK, JNK, and AKT. In conclusion, our findings establish a mechanistic link between the oxidative stress, PI3K/AKT pathway, MAPK pathway and indomethacin-induced cellular alterations and apoptosis in 786-O cells.     

Desipramine-induced Ca-independent apoptosis in Mg63 human osteosarcoma cells: dependence on P38 mitogen-activated protein kinase-regulated activation of caspase 3

1. It has been shown that the antidepressant desipramine is able to induce increases in [Ca(2+)](i) and cell death in MG63 human osteosacroma cells, but whether apoptosis is involved is unclear. In the present study, the effect of desipramine on apoptosis and the underlying mechanisms were explored. It was demonstrated that desipramine induced cell death in a concentration- and time-dependent manner. 2. Cells treated with 100-800 mmol/L desipramine showed typical apoptotic features, including an increase in sub-diploid nuclei and activation of caspase 3, indicating that these cells underwent apoptosis. Immunoblotting revealed that 100 mmol/L desipramine activated extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Although pretreatment of cells with 20 mmol/L PD98059 (an ERK inhibitor) or 20 mmol/L SP600125 (an inhibitor of JNK) did not inhibit cell death, the addition of 20 mmol/L SB203580 (a p38 MAPK inhibitor) partially rescued cells from apoptosis. Desipramine-induced caspase 3 activation required p38 MAPK activation. 3. Pretreatment of cells with BAPTA/AM (20 mmol/L) to prevent desipramine-induced increases in [Ca(2+)](i) did not protect cells from death. 4. The results of the present study suggest that, in MG63 human osteosarcoma cells, desipramine causes Ca(2+)-independent apoptosis by inducing p38 MAPK-associated activation of caspase 3.     

Isoalantolactone induces apoptosis in human breast cancer cells via ROS-mediated mitochondrial pathway and downregulation of SIRT1

Isoalantolactone possessed various biological activities. However, whether it could treat breast cancer and its underlying mechanism remained largely unknown. This study was designed to evaluate the anticancer effects of isoalantolactone on breast cancer and explored the molecular mechanism. Two human breast cancer cell lines (MDA-MB-231 and MCF-7) and one normal breast cell line (MCF-10A) were applied. Our data suggested that isoalantolactone decreased breast cancer cell viability in a dose-dependent manner, but showed almost no toxicity to MCF-10A cells. The anticancer effects of isoalantolactone were related to the overexpression of reactive oxygen species. Isoalantolactone significantly induced breast cancer cell apoptosis by activating caspase cascade, cleaving poly (ADP-ribose) polymerase. Increase of Bax/Bcl-2 ratio, depolarization of mitochondrial membrane potential, release of cytochrome c from mitochondria to cytoplasm and cell cycle arrest at G2/M phase were associated to the apoptosis induction. Additionally, isoalantolactone increased the protein expression of p38 MAPK and JNK. The apoptosis-induction of isoalantolactone could be abrogated by co-treatment with SB203580 (inhibitor of p38 MAPK) or SP600125 (inhibitor of JNK). Furthermore, isoalantolactone induced breast cancer cells apoptosis in a caspase-independent pathway, which was downregulation of SIRT1. Therefore, isoalantolactone may serve as a chemotherapeutic agent for the treatment of human breast cancer.     

Dopamine D1 receptors induce apoptosis of osteosarcoma cells via changes of MAPK pathway

This study explored the effects and mechanisms of dopamine D1 receptors (DR1) activation on the apoptosis of osteosarcoma cells (OS732).The DR1 agonist SKF‐38393 decreased the viability of OS732 cells and increased their rate of apoptosis, whereas the DR1 antagonist SCH‐23390 abolished the effects of SKF‐38393. In OS732 cells, overexpression of DR1 increased the rate of apoptosis, caspase‐9 and ‐3 expression, and the release of cytochrome c (Cyt c), reduced Bcl‐2 expression, inhibited extracellular signal‐regulated kinase 1/2 (ERK1/2) phosphorylation, and induced phosphorylation of p38 mitogen‐activated protein kinase (p38 MAPK) and c‐Jun N‐terminal kinase (JNK). These results suggest that activation of DR1 induces osteosarcoma cell apoptosis via changes to the MAPK pathway.     

Irciniastatin A induces JNK activation that is involved in caspase-8-dependent apoptosis via the mitochondrial pathway

Irciniastatin A (ISA)/psymberin, a pederin-type natural product isolated from marine sponge, exhibits extremely potent and selective cytotoxicity against certain human cancer cell lines, but its molecular target and cytotoxic mechanisms are still unknown. Here we show that ISA is a potent inhibitor of protein translation, and induces apoptosis accompanied with activation of the stress-activated protein kinases via the mitochondrial pathway in human leukemia Jurkat cells. ISA potently inhibited protein translation, and induced a slow but prolonged activation of the stress-activated protein kinases, JNK and p38, at between 1h and 6h after treatment. In Bcl-x(L)-transfected cells, the activation of JNK and p38 by ISA was shortened. The same results were obtained in the cells treated with N-acetyl-L-cysteine, suggesting that the prolonged activation of JNK and p38 by ISA is mediated by reactive oxygen species generated from mitochondria. ISA strongly induced apoptosis, which was partially suppressed by the JNK inhibitor SP600125, but not by the p38 inhibitor SB202190. Apoptosis induction by ISA was partially reduced, but not suppressed by SP600125 in caspase-8-deficient Jurkat cells. These results suggest that ISA activates stress-activated kinases by a mitochondria-mediated mechanism, and that activation of JNK is required for caspase-8-dependent apoptosis.     

Suppression of reactive oxygen species‐mediated ERK and JNK activation sensitizes dihydromyricetin‐induced mitochondrial apoptosis in human non‐small cell lung cancer

Nonsmall cell lung cancer (NSCLC) is the most common type of lung cancer with a high mortality rate and still remains a therapeutic challenge. A strategy for targeting NSCLC is to identify agents that are effective against NSCLC cells while sparing normal cells. Dihydromyricetin (DHM) is the major flavonoid component derived from Ampelopsis grossedentata, which has a long history of use in medicine. Herein, the molecular mechanisms by which DHM exerts its anticancer effects against NSCLC cells were investigated. Results from MTS, colony formation, Western blot, flow cytometric, and JC‐1 mitochondrial membrane potential assays revealed that DHM showed a selective cytotoxic effect against NSCLC cells (A549 and H1975), but not against normal lung (WI‐38) fibroblasts, by inducing apoptosis. DHM‐induced cell apoptosis occurred through Bcl‐w suppression‐mediated mitochondrial membrane depolarization, caspase‐9/‐7/‐3 activation, and poly(ADP‐ribose) polymerase (PARP) cleavage in A549 and H1975 cells. Moreover, treatment of A549 and H1975 cells with DHM induced increase of intracellular peroxide and sustained activation of extracellular signal‐regulated kinase (ERK)1/2 and c‐Jun N‐terminal kinase (JNK)1/2, and the reactive oxygen species scavenger, N‐acetylcysteine (NAC), reversed DHM‐induced ERK and JNK activation. Furthermore, treatment of cells with specific inhibitors of ERK and JNK or NAC significantly promoted the DHM‐induced activation of caspase‐9/‐7/‐3 and PARP cleavage and also sensitized the antitumorigenic effect of DHM on NSCLC cells. These findings define and support a novel function of DHM of inducing mitochondrion‐derived apoptosis in human NSCLC cells, and a combination of DHM with ERK and JNK inhibitors should be a good strategy for preventing NSCLC proliferation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1426–1438, 2017.     

Ouabain induces apoptotic cell death in human prostate DU 145 cancer cells through DNA damage and TRAIL pathways

Ouabain, a cardiotonic steroid and specific Na⁺/K⁺‐ATPase inhibitor, has a potential to induce cancer cell apoptosis but the mechanisms of apoptosis induced by ouabain are not fully understand. The aim of this study was to investigate the cytotoxic effects of ouabain on human prostate cancer DU 145 cells in vitro. Cell morphological changes were examined by phase contrast microscopy. Cell viability, cell cycle distribution, cell apoptosis, DNA damage, the production of ROS and Ca²⁺, and mitochondrial membrane potential (ΔΨ_m) were measured by flow cytometry assay. Results indicated that ouabain induced cell morphological changes, decreased total cell viability, induced G0/G1 phase arrest, DNA damage, and cell apoptosis, increased ROS and Ca²⁺ production, but decreased the levels of ΔΨ_m in DU 145 cells. Ouabain also increased the activities of caspase‐3, ‐8, and ‐9. Western blotting was used for measuring the alterations of apoptosis‐associated protein expressions in DU 145 cells and results indicated that ouabain increased the expression of DNA damage associated proteins (pATM^Ser1981, p‐H2A.X^Ser139, and p‐p53^Ser15) and ER‐stress‐associated proteins (Grp78, ATF6β, p‐PERK^Thr981, PERK, eIF2A, GADD153, CaMKIIβ, and caspase‐4) in time‐dependently. Furthermore, ouabain increased apoptosis‐associated proteins (DR4, DR5, Fas, Fas Ligand, and FADD), TRAIL pathway, which related to extrinsic pathway, promoted the pro‐apoptotic protein Bax, increased apoptotic‐associated proteins, such as cytochrome c, AIF, Endo G, caspase‐3, ‐8, and ‐9, but reduced anti‐apoptotic protein Bcl‐2 and Bcl‐x in DU 145 cells. In conclusion, we may suggest that ouabain decreased cell viability and induced apoptotic cell death may via caspase‐dependent and mitochondria‐dependent pathways in human prostate cancer DU 145 cells.     

Dracorhodin perchlorate induces apoptosis in HL-60 cells

Dracorhodin perchlorate, an anthocyanin red pigment, induces human premyelocytic leukemia HL-60 cell death through apoptotic pathway. Caspase -1, -3, -8, -9, and -10 inhibitors partially reversed the cell death induced by dracorhodin perchlorate. Caspase-3 and -8 were activated followed to the degradation of caspase-3 substrates, inhibitor of caspase-activated DNase (ICAD) and poly-(ADP-ribose) polymerase (PARP). Dracorhodin perchlorate up-regulated the expression ratio of mitochondrial proteins, Bax/Bcl-X_L. The cell death was accompanied with phosphorylation of ERK, JNK and p38 MAPK and partially reduced by MEK inhibitor (PD98059), JNK MAPK inhibitor (SP600125) and p38 MAPK inhibitor (SB 203580). Taken together, dracorhodin perchlorate-induced apoptosis in HL-60 cells via up-regulation of Bax, activation of caspases and ERK/p38/JNK MAPKs.