Caspase-dependent Mitochondrial Pathway Research Articles

Molecular mechanisms of hyperthermia-induced apoptosis enhanced by docosahexaenoic acid: Implication for cancer therapy

To develop a non-toxic enhancer for hyperthermia-induced cell death as a potential cancer treatment, we studied the effect and mechanism of docosahexaenoic acid (DHA) on hyperthermia-induced apoptosis. Treatment with 20μM DHA and 44°C for 10min induced significant apoptosis, increased intracellular reactive oxygen species (ROS), and caspase-3 activation in U937 cells, but heat or DHA alone did not induce notable apoptosis. Decreased mitochondrial transmembrane potentials were dramatically increased by the combined treatment, accompanied by increased pro-apoptotic Bcl-2 family protein tBid, and decreased anti-apoptotic Bcl-2 and Bcl-xL. Combined hyperthermia–DHA treatment induced significant phosphorylation of protein kinase C (PKC)-δ (p-PKC-δ), and apoptosis in a DHA dose-dependent manner. Using both 20μM DHA and 44°C for 10min induced significant PKC-δ cleavage and its translocation to mitochondria. These results were also seen in HeLa cells. However, MAPKs and Akt were not affected by the treatment. In conclusion, DHA enhances hyperthermia-induced apoptosis significantly via a mitochondria–caspase-dependent pathway; its underlying mechanism involves elevated intracellular ROS, mitochondria dysfunction, and PKC-δ activation.

Andrographolide sodium bisulfate-induced apoptosis and autophagy in human proximal tubular endothelial cells is a ROS-mediated pathway

Background and aimsThe nephrotoxic mechanisms of andrographolide sodium bisulfate (ASB) remain largely unknown. This study attempted to explore the mechanism of ASB-induced nephrotoxicity using human proximal tubular endothelial cells (HK-2). MethodsFor this study HK-2 cells were treated with rising concentrations of ASB. Their survival rate was detected using MTT assay and ultrastructure was observed with electron microscopy. l-Lactate dehydrogenase (LDH) assay was followed by examination of mitochondrial membrane potential (MMP). Reactive oxygen species (ROS) was detected using different methods and apoptosis/autophage related proteins were detected using immunoblotting. ResultsWe found that ASB inhibited HK-2 cell proliferation and decreased cell survival rate in a time and dose-dependent manner (P<0.05, P<0.01, respectively). With increasing ASB concentration, cell structure was variably damaged and evidence of apoptosis and autophagy were observed. MMP gradually decreased and ROS was induced. The expression of JNK and Beclin-1 increased and activation of the JNK signaling pathway were seen. Apoptosis was induced via the mitochondrial-dependent caspase-3 and caspase-9 pathway, and autophagy related protein Beclin-1 was enhanced by ASB. ConclusionThe data show that ASB induces high levels of ROS generation in HK-2 cells and activates JNK signaling. Furthermore, ASB induces cell apoptosis via the caspase-dependent mitochondrial pathway, and induces cellular autophagy, in part by enhancing Beclin-1 protein expression.

The Insulin-Like Growth Factor-I Receptor Inhibitor Picropodophyllin-Induced Selective Apoptosis of Hepatocellular Carcinoma Cell Through a Caspase-Dependent Mitochondrial Pathway

The insulin-like growth factor-I receptor (IGF-1R) and its ligands (IGF-I, IGF-II) have been shown to be important promoters of cancer development and are frequently overexpressed in most hepatocellular carcinomas (HCCs). The activation of IGF-1R signaling mediates tumorigenesis, proliferation, and metastasis and thus represents a potential target for innovative treatment strategies for HCC. We investigated the potential inhibitory effect and mechanism of the impact of a novel IGF-1R inhibitor, picropodophyllin (PPP), in HCC lines. It was found that PPP selectively induced cell apoptosis in a time- and dose-dependent manner in HCC cells compared to normal hepatocytes. The inhibitory effects had a positive correlation with the expression of IGF-1R. PPP exerted an apoptotic effect in HCC cells in a caspase-dependent manner through the mitochondrial pathway. The release of cytochrome C from the mitochondrion was coupled with activation of caspase-9 and caspase-3. Treatment of PPP in HepG2 cells resulted in a marked elevation of Bax protein, but decreased levels of phosphorylated Akt and Bcl-2 protein. The ratio of Bax/Bcl-2 was increased in a dose-dependent manner. Our study provides strong evidence that the IGF-1R inhibitor PPP selectively inhibits the growth of human hepatocellular cancer cells by inducing the caspase-dependent mitochondrial pathway cell apoptosis pathway with no observed cytotoxicity on normal cells.

Solena amplexicaulis induces cell cycle arrest, apoptosis and inhibits angiogenesis in hepatocarcinoma cells and HUVECs.

Solena amplexicaulis (Lam.) Gandhi (SA) has been used as a traditional medicine for the treatment of dysentery, multiple abscess, gastralgia, urethritis, and eczema in the minority area of China. This study was aimed to examine the cell proliferation inhibitory activity of the SA extract (SACE) and its mechanism of action in human hepatoma cell line (HepG2) and evaluate its anti-angiogenesis activity in human umbilical vein endothelial cell line (HUVEC). SACE could inhibit the growth of HepG2 cells in a dose- and time-dependent manner. FCM analysis showed that SACE could induce G2/M phase arrest, cell apoptosis, the mitochondrial membrane potential loss (ΔΨm) and increase the production of intracellular ROS of HepG2 cells. After treatment with SACE, topical morphological changes of apoptotic body formation, obvious increase of apoptosis-related protein expressions, such as Bax, cytochrome c, caspase-3, PARP-1, and decrease of Bcl-2, procaspase-9 protein expressions were observed at the same time. Moreover, SACE caused the significant inhibition of endothelial cell migration and tube formation in HUVEC cells. The results suggested that SACE could act as an angiogenesis inhibitor and induce cell apoptosis via a caspase-dependent mitochondrial pathway. Therefore, SACE could be a potent candidate for the prevention and treatment of liver cancer.

Molecular mechanisms of hyperthermia-induced apoptosis enhanced by withaferin A

Hyperthermia is a good therapeutic tool for non-invasive cancer therapy; however, its cytotoxic effects are not sufficient. In the present study, withaferin A (WA), a steroidal lactone derived from the plant Withania somnifera Dunal, has been investigated for its possible enhancing effects on hyperthermia-induced apoptosis. In HeLa cells, treatment with 0.5 or 1.0μM WA at 44°C for 30min induced significant apoptosis accompanied by decreased intracellular GSH/GSSG ratio and caspase-3 activation, while heat or WA alone did not induce such changes. The upregulation in apoptosis was significantly inhibited by glutathione monoethyl ester, a cell permeable glutathione precursor. Mitochondrial transmembrane potentials were dramatically decreased by the combined treatment, with increases in pro-apoptotic Bcl-2-family proteins tBid and Noxa, and downregulation of antiapoptotic Bcl-2 and Mcl-1. Combined treatment with hyperthermia and WA induced significant increases in JNK phosphorylation (p-JNK), and decreases in the phosphorylation of ERK (p-ERK) compared with either treatment alone. These results suggest that WA enhances hyperthermia-induced apoptosis via a mitochondria–caspase-dependent pathway; its underlying mechanism involves elevated intracellular oxidative stress, mitochondria dysfunction, and JNK activation.

DMPPQA, a novel angiogenesis inhibitor, induces apoptosis in human colon cancer HCT‐116 cells and HUVECs

Cytotoxic activity of 5,7-dimethoxy-2-phenyl-N-propylquinolin-4-amine (DMPPQA) was investigated in human colon cancer cells HCT-116 and umbilical vein endothelial cell line HUVEC. The IC(50) of DMPPQA on HCT-116 and HUVEC cells were respectively 1.26 and 7.43 µM after 72 h treatment. DMPPQA inhibited the growth of HCT-116 and HUVEC cells in concentration- and time-dependent manners. Typical morphological changes of apoptotic body formation were seen after DMPPQA with Hoechst 33258 staining. FCM analysis showed that DMPPQA induced apoptosis, mitochondrial membrane potential loss (ΔΨm) and increase in the production of intracellular reactive oxygen species (ROS) of HCT-116 cells. After treating with DMPPQA, apoptosis-related protein expression of Bax, cytochrome c, caspase-9, caspase-3, PARP-1 and P53 increased and Bcl-2 protein expression decreased. DMPPQA treatment of HUVECs reduced cell migration and microcapillary tube formation in a Matrigel matrix. It also decreased VEGF protein expression. Thus DMPPQA acts as an angiogenesis inhibitor and induces cell apoptosis by a caspase-dependent mitochondrial pathway.

Cd-Induced Apoptosis through the Mitochondrial Pathway in the Hepatopancreas of the Freshwater Crab Sinopotamon henanense

Cd is one of the most common pollutants in the environment that also induces the apoptosis. To explore the mechanism of apoptosis in the hepatopancreas, freshwater crab S . henanense were treated with 0, 3.56, 7.12, 14.25, 28.49 and 56.98 mg/L Cd for 72 h. Apoptosis was noticeable in every treatment group and necrosis was observed clearly in the high concentration Cd groups. Classical apoptotic bodies were found by transmission electronic microscopy, which revealed chromatin condensation under nuclear membrane and mitochondrial membrane rupture. An increasing number of autolysosomes, damaged rough endoplamic reticulum and Golgi complex were observed as the Cd concentration increase. Brown colored apoptotic cells were detected by the TUNEL test in all Cd-treatment groups. The apoptosis index increased following the elevation of Cd concentration and got 32.9% in the highest Cd group. Caspase-9 and caspase-3 activities increased in the lower Cd treatment groups but no changes in the higher Cd concentration groups (comparing to the control group). The activity of caspase-8 did not change significantly. No significant change in the content of mitochondrial cytochrome c (cyt c) in Cd exposed groups except the decrease in the 56.98 mg/L group. In crabs treated with 3.56, 7.12 and 14.25 mg/L Cd, hyperpolarization of mitochondrial membrane potential (Δψ m) significantly increased. These results implied that apoptosis in the hepatopancreas induced by Cd occurrs through the mitochondrial caspase-dependent pathway. However, whether there are other apoptotic pathways needs to be studied further.

Matrine inhibited the growth of rat osteosarcoma UMR-108 cells by inducing apoptosis in a mitochondrial–caspase-dependent pathway

Matrine, one of the main active components of the extracts from the dry roots of Sophora flavescens, has a potent antitumor activity in vitro and in vivo. However, the molecular mechanism of cell apoptosis induced by matrine remains elusive. Here, we investigated the apoptosis in matrine-treated rat osteosarcoma UMR-108 cells. The results showed that matrine could inhibit cell proliferation and induce apoptosis in a dose- and time-dependent manner. Further investigation revealed a disruption of mitochondrial transmembrane potential and an upregulation of reactive oxygen species in matrine-treated cells. By western blot analysis, we found the upregulation of cleaved poly(ADP-ribose) polymerase, cleaved caspase-3, and cleaved caspase-9 and the downregulation of Bax/Bcl-2 with different concentrations of matrine. These protein interactions may play a pivotal role in the regulation of apoptosis. Taken together, these results overall indicate that matrine could be used as an effective antitumor agent in therapy of osteosarcoma targets the caspase-dependent signaling pathway.

TCEA3 binds to TGF-beta receptor I and induces Smad-independent, JNK-dependent apoptosis in ovarian cancer cells

TFIIS is a transcription elongation factor conserved in frog, mouse and human. Recently, knockdown of TCEA1, the most well-characterized isoform of TFIIS, by RNA silencing was reported to inhibit cancer cell proliferation and induce apoptosis in breast, lung and pancreatic cancer cell lines through activation of p53 (Hubbard et al., 2008 [1]). However, the functions of other TFIIS isoforms are poorly defined. The present study shows that TCEA3, an isoform of TFIIS, can trigger ovarian cancer-specific cell death by activating the JNK signaling pathway. TCEA3 expression is low in ovarian cancer cell lines compared to noncancerous ovarian epithelial cells. Suppression of TCEA3 in noncancerous ovarian epithelial cells promotes cell growth whereas ectopic expression of TCEA3 in ovarian cancer cell lines induces the caspase-dependent mitochondrial cell death pathway. Molecular and chemical inhibition assays show that the interaction of TCEA3 with TGFβ receptor I induces cell death in ovarian cancer cell through Smad-independent activation of the JNK pathway. These results reveal that TCEA3 induces a novel apoptotic mechanism in OEC, which provides TCEA3 as a novel target to develop therapeutics of ovarian cancer.

Induction of Apoptosis by Low-Molecular-Weight Fucoidan through Calcium- and Caspase-Dependent Mitochondrial Pathways in MDA-MB-231 Breast Cancer Cells

Fucoidan, a fucose-rich polysaccharide extracted from brown seaweed, has antitumor, anticoagulant, antiviral, anti-inflammatory, and antibacterial activities. Several studies have shown that a fucoidan treatment of cancer cells induced cytotoxicity and apoptosis and inhibited angiogenesis and invasion. We investigated in the present study the effect of low-molecular-weight fucoidan (LMWF) on apoptosis in estrogen receptor-negative MDA-MB-231 human breast cancer cells. The LMWF treatment of MDA-MB-231 cells was associated with the activation of caspases and mitochondrial dysfunction, including dissipation of the mitochondrial membrane potential (ΔΨm), alteration of Ca(2+) homeostasis, cytochrome c release, and decreased expression of antiapoptotic Bcl-2 family proteins. Understanding the molecular events that mediated LMWF-induced MDA-MB-231 cell death will contribute to a more rational approach to cancer chemotherapy.

Gossypol acetic acid induces apoptosis in RAW264.7 cellsviaa caspase-dependent mitochondrial signaling pathway

To investigate the effects of gossypol acetic acid (GA) on proliferation and apoptosis of the macrophage cell line RAW264.7 and further understand the possible underlying mechanism responsible for GA-induced cell apoptosis, RAW264.7 cells were treated with GA (25~35 µmol/L) for 24 h and the cytotoxicity was determined by MTT assay, while apoptotic cells were identified by TUNEL assay, acridine orange/ethidium bromide staining and flow cytometry. Moreover, mitochondrial membrane potential (ΔΨm) with Rhodamine 123 and reactive oxygen species (ROS) with DCFH-DA were analyzed by fluorescence spectrofluorometry. In addition, the expression of caspase-3 and caspase-9 was assessed by Western Blot assay. Finally, the GA-induced cell apoptosis was evaluated by flow cytometry in the present of caspase inhibitors Z-VAD-FMK and Ac-LEHD-FMK, respectively. GA significantly inhibited the proliferation of RAW264.7 cells in a dose-dependent manner, and caused obvious cell apoptosis and a loss of ΔΨm in RAW264.7 cells. Moreover, the ROS production in cells was elevated, and the levels of activated caspase-3 and caspase-9 were up-regulated in a dose-dependent manner. Notably, GA-induced cell apoptosis was markedly inhibited by caspase inhibitors. These results suggest that GA-induced RAW264.7 cell apoptosis may be mediated via a caspase-dependent mitochondrial signaling pathway.

By improving regional cortical blood flow, attenuating mitochondrial dysfunction and sequential apoptosis galangin acts as a potential neuroprotective agent after acute ischemic stroke.

Ischemic stroke is a devastating disease with a complex pathophysiology. Galangin is a natural flavonoid isolated from the rhizome of Alpina officinarum Hance, which has been widely used as an antioxidant agent. However, its effects against ischemic stroke have not been reported and its related neuroprotective mechanism has not really been explored. In this study, neurological behavior, cerebral infarct volumes and the improvement of the regional cortical blood flow (rCBF) were used to evaluate the therapeutic effect of galangin in rats impaired by middle cerebral artery occlusion (MCAO)-induced focal cerebral ischemia. Furthermore, the determination of mitochondrial function and Western blot of apoptosis-related proteins were performed to interpret the neuroprotective mechanism of galangin. The results showed that galangin alleviated the neurologic impairments, reduced cerebral infarct at 24 h after MCAO and exerted a protective effect on the mitochondria with decreased production of mitochondrial reactive oxygen species (ROS). These effects were consistent with improvements in the membrane potential level (Δψm), membrane fluidity, and degree of mitochondrial swelling in a dose-dependent manner. Moreover, galangin significantly improved the reduced rCBF after MCAO. Western blot analysis revealed that galangin also inhibited apoptosis in a dose-dependent manner concomitant with the up-regulation of Bcl-2 expression, down-regulation of Bax expression and the Bax/Bcl-2 ratio, a reduction in cytochrome c release from the mitochondria to the cytosol, the reduced expression of activated caspase-3 and the cleavage of poly(ADP-ribose) polymerase (PARP). All these data in this study demonstrated that galangin might have therapeutic potential for ischemic stroke and play its protective role through the improvement in rCBF, mitochondrial protection and inhibiting caspase-dependent mitochondrial cell death pathway for the first time.

The BH3-only protein Noxa is stimulated during apoptosis of chronic lymphocytic leukemia cells triggered by M2YN, a new plant-derived extract.

Deficiency of apoptosis is a hallmark of chronic lymphocytic leukemia (CLL) cells. M2Yn is a natural extract from plants of central Asia, identified for its antiangiogenic properties and its ability to block the migration of malignant cells. Here, we report that in vitro treatment of cells derived from CLL patients with M2Yn results in internucleosomal DNA fragmentation, phosphatidylserine externalization, mitochondrial membrane depolarization, caspase-3 activation and cleavage of the caspase substrate PARP-1. The extents of these effects depend on the patients and are mostly comparable to those of flavopiridol or hyperforin, two known plant-derived apoptosis inducers of CLL cells. M2Yn does not modulate Mcl-1 expression, while downregulation of this antiapoptotic protein is involved in the action of flavopiridol. By contrast, M2Yn, like hyperforin, upregulates the Noxa protein, possibly by inhibiting proteasomal activity. This BH3-only protein is known to trigger the activation of the pro-apoptotic protein Bak through displacement of the Mcl-1/Bak complex at the mitochondrial membrane, as actually observed here in M2Yn-treated cells. Our data, therefore, show that M2Yn can induce the caspase-dependent mitochondrial pathway of apoptosis in CLL cells via a mechanism resembling that of hyperforin. Our data also confirm that the BH3-only protein Noxa is a relevant target for CLL therapy.

Apoptosis of Human Cholangiocarcinoma Cell Lines induced by β‐Escin through Mitochondrial Caspase‐dependent Pathway

The study aimed to evaluate the effects of β-escin on human cholangiocarcinoma cell lines (QBC939, Sk-ChA-1 and MZ-ChA-1) and to explore its mechanisms. Cell growth, cell cycle and apoptosis were investigated, respectively, by MTT assay, single PI and FITC/PI double-staining flow cytometry, and fluorescence microscopy. The protein expression was determined by western blotting. The study revealed that β-escin inhibited cholangiocarcinoma cell growth in a dose- and time-dependent manner, and the cell cycle of QBC939 and Sk-ChA-1 cells was arrested in the G2/M phase, and MZ-ChA-1 cells in G1 phase. Apoptosis of the three cholangiocarcinoma cell lines induced by β-escin was associated with the collapse of the mitochondrial membrane potential and the activation of caspase-3. The apoptotic effect of β-escin was suppressed by pancaspase inhibitor z-VAD-fmk. Molecular dissection revealed that the antiapoptotic protein bcl-2 was down-regulated after cholangiocarcinoma cell lines were treated with β-escin, while the protein levels of bax and p53 were unchanged. Apoptosis was accompanied by an increase in reactive oxygen species (ROS). These results suggest that β-escin induces apoptosis of cholangiocarcinoma cells through an intrinsic mitochondrial caspase-dependent pathway, and the increase in the bax/bcl-2 ratio and ROS may play important roles in β-escin-induced apoptosis of cholangiocarcinoma cells.

Daidzein induces MCF-7 breast cancer cell apoptosis via the mitochondrial pathway

BackgroundIn order to study the anticancer effects and cellular apoptosis pathways induced by daidzein. Materials and methodsWe used the human MCF-7 breast cancer cell line as a model and examined the apoptosis by Hoechst–propidium iodide staining fluorescence imaging and flow cytometry. ResultsOur data indicated that daidzein induces antiproliferative effects in a concentration- and time-dependent manner. We demonstrated that daidzein-induced apoptosis in MCF-7 cells was initiated by the generation of reactive oxygen species (ROS). Furthermore, we showed that this daidzein-induced ROS generation was accompanied by disruption of mitochondrial transmembrane potential, down-regulation of bcl-2, and up-regulation of bax, which led to the release of cytochrome C from the mitochondria into the cytosol, which, in turn, resulted in the activation of caspase-9 and caspase-7, and ultimately in cell death. The induction of the mitochondrial caspase-dependent pathway was confirmed by pretreatment with pan-caspase inhibitor z-VAD-fmk and antioxidant N-acetyl-L-cysteine. ConclusionAccordingly, daidzein could induce breast cancer cell apoptosis through the mitochondrial caspase-dependent cell death pathway.

Prolonged low‐dose administration of the cyclooxygenase‐2 inhibitor celecoxib enhances the antitumor activity of irinotecan against neuroblastoma xenografts

Cyclooxygenase (COX)-2 is overexpressed in many human tumors including neuroblastoma (NB) and promotes tumor progression. We evaluated the antitumor effect of irinotecan (CPT-11) treatment combined with prolonged very low-dose administration of celecoxib, a selective COX-2 inhibitor, against three human NB xenografts, TNB9, TS-N-2nu, and TS-N-5nu. In addition, the effects of the celecoxib-combined treatment were examined on tumor cell proliferation, apoptosis, angiogenesis, and expression of vascular endothelial growth factor and apoptosis-related proteins in xenografts. Celecoxib administered daily at 5 mg/kg body weight/day could not prevent the growth of any of the NB xenografts. However, the combination of daily low-dose CPT-11 (5.9 mg/kg body weight/day) and simultaneous very low-dose celecoxib resulted in highly significant suppression of tumor growth in all three xenografts (P < 0.001) compared not only with low-dose CPT-11 therapy alone but also with the combination therapy of intermittent conventional-dose CPT-11 (59 mg/kg body weight) and celecoxib accompanied by decreased proliferation and increased induction of apoptosis in tumor cells. Induction of apoptosis by CPT-11 with and without celecoxib was associated with the up-regulation of Bax expression and the down-regulation of Bcl-2 expression. The enhanced antitumor effect of the combination of the two drugs against the NB xenografts might be partially COX-2-independent and was probably mediated through multiple factors including diminished expression of VEGF and activation of the caspase-dependent mitochondrial apoptosis pathway. These findings demonstrate that prolonged low-dose CPT-11 treatment combined with very low-dose celecoxib shows promising antitumor activity through the blockage of multiple critical targets related to NB tumor cell survival and proliferation.

Octanoate and Decanoate Induce Apoptosis in 3T3-L1 Adipocytes

The effect of octanoate and decanoate, respectively, eight- and 10-carbon medium-chain fatty acids (MCFAs), on apoptotic signaling in 3T3-L1 adipocytes was investigated. 3T3-L1 adipocytes were treated with various concentrations of octanoate or decanoate. Cell viability, apoptosis, and expression of apoptosis-related proteins were investigated. Results indicated that both octanoate and decanoate decreased viability, increased apoptosis, and increased reactive oxygen species production. Immunoblotting analysis showed an increase in the levels of cytoplasmic cytochrome c and cleaved poly(ADP-ribose) polymerase by octanoate and decanoate. Concomitantly, we observed that pro-caspase-3 was decreased, resulting in the induced accumulation of the cleaved form of caspase-3 by both octanoate and decanoate. In addition, both octanoate and decanoate increased the expression of pro-apoptotic Bax with an accompanied decrease of anti-apoptotic Bcl-2. These results show that octanoate and decanoate mediate adipocyte apoptosis via a caspase-dependent mitochondrial pathway in 3T3-L1 adipocytes. MCFAs thus decrease adipocyte number by initiating the apoptotic process in 3T3-L1 adipocytes.

Siva1 is a XIAP-interacting protein that balances NFκB and JNK signalling to promote apoptosis

XIAP is known as a potent inhibitor of apoptosis, but in addition is involved in cellular signalling, including the NFkappaB, JNK and TGFbeta pathways. Our search for XIAP-interacting partners led us to Siva1, a proapoptotic protein that is known to play a role in T-cell apoptosis through a caspase-dependent mitochondrial pathway. The interaction sites between XIAP and Siva1 were mapped to the RING domain of XIAP and the N-terminal, SAH-containing and death-homology-region-containing domains of Siva1. Co-immunoprecipitation experiments showed that XIAP, Siva1 and TAK1 form a ternary complex in Jurkat T cells. Reporter-gene analysis revealed that Siva1 inhibits XIAP- and TAK1-TAB1-mediated NFkappaB activation. By contrast, Siva1 increased XIAP- and TNFalpha-mediated AP1 activity and prolonged TNFalpha-induced JNK activation, whereas knock down of Siva1 resulted in reduced JNK activation. This suggests that Siva1 differentially modulates signalling by JNK and NFkappaB and shifts the balance between these pathways towards enhanced JNK activation, a situation that promotes apoptosis. Ectopically expressed Siva1 increased caspase-3 activity, which was inhibited by XIAP in a ubiquitin-ligase-dependent manner. In line with this, Siva1 was lysine-48-linked polyubiquitylated by XIAP. Our findings suggest that, via physical interaction with XIAP and TAK1, Siva1 diminishes NFkappaB and enhances JNK activity to favour apoptosis.

Ocimum sanctum induces apoptosis in A549 lung cancer cells and suppresses the in vivo growth of lewis lung carcinoma cells

Although Ocimum sanctum has been used extensively for its medicinal values in India and China, its antitumor activity against human nonsmall cell lung carcinoma (NSCLC) A549 cells has not been investigated until now. Therefore, the antitumor mechanism of ethanol extracts of Ocimum sanctum (EEOS) was elucidated in A549 cells in vitro and the Lewis lung carcinoma (LLC) animal model. EEOS exerted cytotoxicity against A549 cells, increased the sub-G1 population and exhibited apoptotic bodies in A549 cells. Furthermore, EEOS cleaved poly(ADP-ribose)polymerase (PARP), released cytochrome C into cytosol and simultaneously activated caspase-9 and -3 proteins. Also, EEOS increased the ratio of proapoptotic protein Bax/antiapoptotic protein Bcl-2 and inhibited the phosphorylation of Akt and extracellular signal regulated kinase (ERK) in A549 cancer cells. In addition, it was found that EEOS can suppress the growth of LLC inoculated onto C57BL/6 mice in a dose-dependent manner. Overall, these results demonstrate that EEOS induces apoptosis in A549 cells via a mitochondria caspase dependent pathway and inhibits the in vivo growth of LLC, suggesting that EEOS can be applied to lung carcinoma as a chemopreventive candidate.

Cotreatment with apicidin overcomes TRAIL resistance via inhibition of Bcr-Abl signaling pathway in K562 leukemia cells

TNF-related apoptosis-inducing ligand (TRAIL) is a pro-apoptotic cytokine that is capable of inducing apoptosis in a wide variety of cancer cells but not in normal cells. Although many cancer cells are sensitive to TRAIL-induced apoptosis, chronic myeloid leukemia (CML) develops resistance to TRAIL. In this study, we investigated whether apicidin, a novel histone deacetylase inhibitor, could overcome the TRAIL resistance in CML-derived K562 cells. Compared to treatment with apicidin or TRAIL alone, cotreatment with apicidin and TRAIL-induced apoptosis synergistically in K562 cells. This combination led to activation of caspase-8 and Bcl-2 interacting domain (Bid), resulting in the cytosolic accumulation of cytochrome c from mitochondria as well as an activation of caspase-3. Treatment with apicidin resulted in down-regulation of Bcr-Abl and inhibition of its downstream target, PI3K/AKT-NF-κB pathway. In addition, apicidin decreased the level of NF-κB-dependent Bcl-x L, leading to caspase activation and Bid cleavage. These results suggest that apicidin may sensitize K562 cells to TRAIL-induced apoptosis through caspase-dependent mitochondrial pathway by regulating expression of Bcr-Abl and its related anti-apoptotic proteins. Therefore, the present study suggests that combination of apicidin and TRAIL may be an effective strategy for treating TRAIL-resistant Bcr-Abl expressing CML cells.